Dr Maria Sukkar completed her PhD in Pharmacy at The University of Sydney in 2002. Dr Sukkar’s research expertise is focussed on understanding the cellular and molecular pathways that lead to chronic airway inflammation and airflow obstruction in asthma and chronic obstructive pulmonary disease. Dr Sukkar was a post doctoral research scientist at the National Heart and Lung Institute, Imperial College London for seven years (2001 – 2007) and has held a position as Lecturer in Pharmacy Practice at the Faculty of Pharmacy, The University of Sydney for the past four years (2008 – 2011). Dr Sukkar has principally been involved in developing, teaching and co-ordinating pharmacotherapeutics and professional practice courses for final year Pharmacy students in the Bachelor of Pharmacy at the University of Sydney. Dr Sukkar continues to pursue her research interests in airways disease and currently has several PhD students under her supervision. Dr Sukkar joined the UTS School of Pharmacy as Senior Lecturer in November 2011, and is also an Honorary Associate of the Woolcock Institute of Respiratory Medicine.Dr Sukkar is an experienced doctoral supervisor and welcomes research degree enquiries via a formal expression of interest (please do not email directly).
Can supervise: YES
Dr Sukkar is an experienced doctoral supervisor and welcomes research degree enquiries via a formal expression of interest (please do not email directly).
Allam, VSRR & Sukkar, MB 2020, 'Investigating MIF in Mouse Models of Severe Corticosteroid-Resistant Neutrophilic Asthma', Methods in molecular biology (Clifton, N.J.), vol. 2080, pp. 203-212.View/Download from: Publisher's site
Experimental mouse models of asthma are widely used to investigate the underlying mechanisms of this complex and heterogeneous disease. Using mouse models of ovalbumin-induced asthma, previous investigators have established a crucial role for MIF in the development of type 2-mediated eosinophilic asthma. Surprisingly, however, the role of MIF in other phenotypes of asthma has received little attention. MIF is an important mediator of neutrophilic inflammation, and also acts to antagonize the actions of corticosteroids. Thus, MIF may play a role in the development of severe forms of asthma in which airway neutrophilia and corticosteroid insensitivity are major features. In this chapter, we provide an experimental protocol that may be used to investigate the role of MIF in a mouse model of severe corticosteroid-resistant neutrophilic asthma.
Wong, SL, To, J, Santos, J, Allam, VSRR, Dalton, JP, Djordjevic, SP, Donnelly, S, Padula, MP & Sukkar, MB 2018, 'Proteomic Analysis of Extracellular HMGB1 Identifies Binding Partners and Exposes Its Potential Role in Airway Epithelial Cell Homeostasis.', Journal of Proteome Research, vol. 17, no. 1, pp. 33-45.View/Download from: Publisher's site
The release of damage-associated molecular patterns (DAMPs) by airway epithelial cells is believed to play a crucial role in the initiation and development of chronic airway conditions such as asthma and chronic obstructive pulmonary disease (COPD). Intriguingly, the classic DAMP high-mobility group box-1 (HMGB1) is detected in the culture supernatant of airway epithelial cells under basal conditions, indicating a role for HMGB1 in the regulation of epithelial cellular and immune homeostasis. To gain contextual insight into the potential role of HMGB1 in airway epithelial cell homeostasis, we used the orthogonal and complementary methods of high-resolution clear native electrophoresis, immunoprecipitation, and pull-downs coupled to liquid chromatography-tandem mass spectrometry (LC-MS/MS) to profile HMGB1 and its binding partners in the culture supernatant of unstimulated airway epithelial cells. We found that HMGB1 presents exclusively as a protein complex under basal conditions. Moreover, protein network analysis performed on 185 binding proteins revealed 14 that directly associate with HMGB1: amyloid precursor protein, F-actin-capping protein subunit alpha-1 (CAPZA1), glyceraldehyde-3 phosphate dehydrogenase (GAPDH), ubiquitin, several members of the heat shock protein family (HSPA8, HSP90B1, HSP90AA1), XRCC5 and XRCC6, high mobility group A1 (HMGA1), histone 3 (H3F3B), the FACT (facilitates chromatin transcription) complex constituents SUPT1H and SSRP1, and heterogeneous ribonucleoprotein K (HNRNPK). These studies provide a new understanding of the extracellular functions of HMGB1 in cellular and immune homeostasis at the airway mucosal surface and could have implications for therapeutic targeting.
Tanaka, A, Allam, VSRR, Simpson, J, Tiberti, N, Shiels, J, To, J, Lund, M, Combes, V, Weldon, S, Taggart, C, Dalton, JP, Phipps, S, Sukkar, MB & Donnelly, S 2018, 'The parasitic 68-mer peptide FhHDM-1 inhibits mixed granulocytic inflammation and airway hyperreactivity in experimental asthma', JOURNAL OF ALLERGY AND CLINICAL IMMUNOLOGY, vol. 141, no. 6, pp. 2316-2319.View/Download from: Publisher's site
Arikkatt, J, Ullah, MA, Short, KR, Zhang, V, Gan, WJ, Loh, Z, Werder, RB, Simpson, J, Sly, PD, Mazzone, SB, Spann, KM, Ferreira, MAR, Upham, JW, Sukkar, MB & Phipps, S 2017, 'RAGE deficiency predisposes mice to virus-induced paucigranulocytic asthma', eLife, vol. 6, pp. 1-25.View/Download from: Publisher's site
© 2017, eLife Sciences Publications Ltd. All rights reserved. Asthma is a chronic inflammatory disease. Although many patients with asthma develop type-2 dominated eosinophilic inflammation, a number of individuals develop paucigranulocytic asthma, which occurs in the absence of eosinophilia or neutrophilia. The aetiology of paucigranulocytic asthma is unknown. However, both respiratory syncytial virus (RSV) infection and mutations in the receptor for advanced glycation endproducts (RAGE) are risk factors for asthma development. Here, we show that RAGE deficiency impairs anti-viral immunity during an early-life infection with pneumonia virus of mice (PVM; a murine analogue of RSV). The elevated viral load was associated with the release of high mobility group box-1 (HMGB1) which triggered airway smooth muscle remodelling in early-life. Re-infection with PVM in later-life induced many of the cardinal features of asthma in the absence of eosinophilic or neutrophilic inflammation. Anti-HMGB1 mitigated both early-life viral disease and asthma-like features, highlighting HMGB1 as a possible novel therapeutic target.
© 2017 Elsevier Ltd Autophagy is a ubiquitous cellular mechanism for the targeted lysosomal degradation of various cytosolic constituents, from proteins to organelles. As an ess ential homeostatic mechanism, autophagy is upregulated in response to numerous environmental and pharmacological stimuli, including starvation, where it facilitates the recycling of essential amino acids. In addition, autophagy plays specific roles within the immune system; it serves as a source of peptides for antigen presentation, a mechanism for the engulfment and degradation of intracellular pathogens and as a key regulator of inflammatory cytokines. In particular, autophagy has been shown to play a number of roles in regulating inflammasome activation, from the removal of inflammasome-activating endogenous signals, to the sequestration and degradation of inflammasome components. Autophagy also plays a role in determining the fate of IL-1β, which is concentrated in autophagosomes. This review discusses a growing body of literature that suggests autophagy is a critical regulator of inflammasome activation and the subsequent release of IL-1 family cytokines.
Pozzoli, M, Traini, D, Young, PM, Sukkar, MB & Sonvico, F 2017, 'Development of a Soluplus budesonide freeze-dried powder for nasal drug delivery.', Drug Development and Industrial Pharmacy, vol. 43, no. 9, pp. 1510-1518.View/Download from: Publisher's site
OBJECTIVE: The aim of this work was to develop an amorphous solid dispersions/solutions (ASD) of a poorly soluble drug, budesonide (BUD) with a novel polymer Soluplus(®) (BASF, Germany) using a freeze-drying technique, in order to improve dissolution and absorption through the nasal route. SIGNIFICANCE: The small volume of fluid present in the nasal cavity limits the absorption of a poorly soluble drug. Budesonide is a corticosteroid, practically insoluble and normally administered as a suspension-based nasal spray. METHODS: The formulation was prepared through freeze-drying of polymer-drug solution. The formulation was assessed for its physicochemical (specific surface area, calorimetric analysis and X-ray powder diffraction), release properties and aerodynamic properties as well as transport in vitro using RPMI 2650 nasal cells, in order to elucidate the efficacy of the Soluplus-BUD formulation. RESULTS: The freeze-dried Soluplus-BUD formulation (LYO) showed a porous structure with a specific surface area of 1.4334 ± 0.0178 m(2)/g. The calorimetric analysis confirmed an interaction between BUD and Soluplus and X-ray powder diffraction the amorphous status of the drug. The freeze-dried formulation (LYO) showed faster release compared to both water-based suspension and dry powder commercial products. Furthermore, a LYO formulation, bulked with calcium carbonate (LYO-Ca), showed suitable aerodynamic characteristics for nasal drug delivery. The permeation across RPMI 2650 nasal cell model was higher compared to a commercial water-based BUD suspension. CONCLUSIONS: Soluplus has been shown to be a promising polymer for the formulation of BUD amorphous solid suspension/solution. This opens up opportunities to develop new formulations of poorly soluble drug for nasal delivery.
Sukkar, MB & Harris, J 2017, 'Potential impact of oxidative stress induced growth inhibitor 1 (OSGIN1) on airway epithelial cell autophagy in chronic obstructive pulmonary disease (COPD)', Journal of Thoracic Disease, vol. 9, no. 12, pp. 4825-4827.View/Download from: Publisher's site
Wong, SLI & Sukkar, MB 2017, 'The SPARC protein: an overview of its role in lung cancer and pulmonary fibrosis and its potential role in chronic airways disease.', British Journal of Pharmacology, vol. 174, no. 1, pp. 3-14.View/Download from: Publisher's site
The SPARC (secreted protein acidic and rich in cysteine) protein is matricellular molecule regulating interactions between cells and their surrounding extracellular matrix (ECM). This protein thus governs fundamental cellular functions such as cell adhesion, proliferation and differentiation. SPARC also regulates the expression and activity of numerous growth factors and matrix metalloproteinases essential for ECM degradation and turnover. Studies in SPARC-null mice have revealed a critical role for SPARC in tissue development, injury and repair and in the regulation of the immune response. In the lung, SPARC drives pathological responses in non-small cell lung cancer and idiopathic pulmonary fibrosis by promoting microvascular remodelling and excessive deposition of ECM proteins. Remarkably, although chronic airway conditions such as asthma and chronic obstructive pulmonary disease (COPD) involve significant remodelling in both the airway and vascular compartments, the role of SPARC in these conditions has thus far been overlooked. In this review, we discuss the role of SPARC in lung cancer and pulmonary fibrosis, as well as potential mechanisms by which it may contribute to the disease process in asthma and COPD.
Clementino, A, Batger, M, Garrastazu, G, Pozzoli, M, Del Favero, E, Rondelli, V, Gutfilen, B, Barboza, T, Sukkar, MB, Souza, SAL, Cantu, L & Sonvico, F 2016, 'The nasal delivery of nanoencapsulated statins - an approach for brain delivery', INTERNATIONAL JOURNAL OF NANOMEDICINE, vol. 11, pp. 6575-6590.View/Download from: Publisher's site
Pozzoli, M, Ong, HX, Morgan, L, Sukkar, M, Traini, D, Young, PM & Sonvico, F 2016, 'Application of RPMI 2650 Nasal Cell Model to a 3D Printed Apparatus for the Testing of Drug Deposition and Permeation of Nasal Products.', European Journal of Pharmaceutics and Biopharmaceutics, vol. 107, pp. 223-233.View/Download from: Publisher's site
The aim of this study was to incorporate an optimized RPMI2650 nasal cell model into a 3D printed model of the nose to test deposition and permeation of drugs intended for use in the nose. The nasal cell model was optimized for barrier properties in terms of permeation marker and mucus production. RT-qPCR was used to determine the xenobiotic transporter gene expression of RPMI 2650 cells in comparison with primary nasal cells. After 14 days in culture, the cells were shown to produce mucus, and to express TEER (define) values and sodium fluorescein permeability consistent with values reported for excised human nasal mucosa. In addition, good correlation was found between RPMI 2650 and primary nasal cells transporters expression values. The purpose built 3D printed model of the nose takes the form of an expansion chamber with inserts for cells and an orifice for insertion of a spray drug delivery device. This model was validated against the FDA glass chamber with cascade impactors that is currently approved for studies of nasal products. No differences were found between the two apparatus. The apparatus including the nasal cell model was used to test a commercial nasal product containing budesonide (Rhinocort, AstraZeneca, Australia). Drug deposition and transport studies on RPMI 2650 were successfully performed. The new 3D printed apparatus that incorporate cells can be used as valid in vitro model to test nasal products in conditions that mimic the delivery from nasal devices in real life conditions.
Gold, MJ, Hiebert, PR, Park, HY, Stefanowicz, D, Le, A, Starkey, MR, Deane, A, Brown, AC, Liu, G, Horvat, JC, Ibrahim, ZA, Sukkar, MB, Hansbro, PM, Carlsten, C, VanEeden, S, Sin, DD, McNagny, KM, Knight, DA & Hirota, JA 2016, 'Mucosal production of uric acid by airway epithelial cells contributes to particulate matter-induced allergic sensitization.', Mucosal Immunology, vol. 9, no. 3, pp. 809-820.View/Download from: Publisher's site
Exposure to particulate matter (PM), a major component of air pollution, contributes to increased morbidity and mortality worldwide. PM induces innate immune responses and contributes to allergic sensitization, although the mechanisms governing this process remain unclear. Lung mucosal uric acid has also been linked to allergic sensitization. The links among PM exposure, uric acid, and allergic sensitization remain unexplored. We therefore investigated the mechanisms behind PM-induced allergic sensitization in the context of lung mucosal uric acid. PM10 and house dust mite exposure selectively induced lung mucosal uric acid production and secretion in vivo, which did not occur with other challenges (lipopolysaccharide, virus, bacteria, or inflammatory/fibrotic stimuli). PM10-induced uric acid mediates allergic sensitization and augments antigen-specific T-cell proliferation, which is inhibited by uricase. We then demonstrate that human airway epithelial cells secrete uric acid basally and after stimulation through a previously unidentified mucosal secretion system. Our work discovers a previously unknown mechanism of air pollution-induced, uric acid-mediated, allergic sensitization that may be important in the pathogenesis of asthma.
Ullah, MA, Revez, JA, Loh, Z, Simpson, J, Zhang, V, Bain, L, Varelias, A, Rose-John, S, Blumenthal, A, Smyth, MJ, Hill, GR, Sukkar, MB, Ferreira, MAR & Phipps, S 2015, 'Allergen-induced IL-6 trans-signaling activates gamma delta T cells to promote type 2 and type 17 airway inflammation', JOURNAL OF ALLERGY AND CLINICAL IMMUNOLOGY, vol. 136, no. 4, pp. 1065-1073.View/Download from: Publisher's site
Ullah, MA, Loh, Z, Gan, WJ, Zhang, V, Yang, H, Li, JH, Yamamoto, Y, Schmidt, AM, Armour, CL, Hughes, JM, Phipps, S & Sukkar, MB 2014, 'Receptor for advanced glycation end products and its ligand high-mobility group box-1 mediate allergic airway sensitization and airway inflammation', JOURNAL OF ALLERGY AND CLINICAL IMMUNOLOGY, vol. 134, no. 2, pp. 440-+.View/Download from: Publisher's site
The innate immune system forms the first line of protection against infectious and non-infectious tissue injury. Cells of the innate immune system detect pathogen-associated molecular patterns or endogenous molecules released as a result of tissue injury or inflammation through various innate immune receptors, collectively termed pattern-recognition receptors. Members of the Toll-like receptor (TLR) family of pattern-recognition receptors have well established roles in the host immune response to infection, while the receptor for advanced glycation end products (RAGE) is a pattern-recognition receptor predominantly involved in the recognition of endogenous molecules released in the context of infection, physiological stress or chronic inflammation. RAGE and TLRs share common ligands and signaling pathways, and accumulating evidence points towards their co-operative interaction in the host immune response. At present however, little is known about the mechanisms that result in TLR versus RAGE signalling or RAGETLR cross-talk in response to their shared ligands. Here we review what is known in relation to the physicochemical basis of ligand interactions between TLRs and RAGE, focusing on three shared ligands of these receptors: HMGB1, S100A8/A9 and LPS. Our aim is to discuss what is known about differential ligand interactions with RAGE and TLRs and to highlight important areas for further investigation so that we may better understand the role of these receptors and their relationship in host defense.
Sukkar, M & Postma, DS 2013, 'Receptor for advanced glycation end products and soluble receptor for advanced glycation end products: A balancing act in chronic obstructive pulmonary disease?', American Journal of Respiratory and Critical Care Medicine, vol. 188, no. 8, pp. 893-894.View/Download from: Publisher's site
The receptor for advanced glycation end products (RAGE) is a pattern-recognition receptor implicated in immune/inflammatory and tissue remodeling responses in numerous pathological states. RAGE plays an important role in lung development during embryogenesis and homeostatic maintenance of the adult lung, where its expression is high relative to other organ tissues (1, 2). RAGE exists primarily in two forms, a transmembrane protein consisting of a cytoplasmic signaling domain and an extracellular ligand-binding domain, and a soluble protein that lacks the transmembrane and cytoplasmic domains. Soluble RAGE (sRAGE) circulates in blood under physiological conditions and is an endogenous inhibitor of RAGE signaling. Although sRAGE is primarily generated through alternative RNA splicing, soluble isoforms are also produced via proteolytic ectodomain shedding of the cell-bound receptor (1). Recent evidence suggests that levels of RAGE expression and sRAGE isoforms are altered in chronic obstructive pulmonary disease (COPD) (1). Higher RAGE expression is observed in epithelial and smooth muscle layers of the airway wall in subjects with COPD than in smokers and never-smokers without COPD (1). In addition, RAGE expression is higher in alveolar walls of resection tissue samples of subjects with than without COPD (3). On the other hand, we and others have demonstrated reduced airway and systemic levels of sRAGE in subjects with COPD, and shown this to be associated with the degree of lung function impairment, predominance of neutrophilic lung inflammation, and both the presence and progression of emphysema (1, 4-6). Boschetto and colleagues did not observe reduced plasma sRAGE in subjects with mild-to-moderate COPD, further suggesting that sRAGE deficiency is associated with more severe disease and/ or disease progression (7).
Sukkar, M, Ullah, MA, Gan, WJ, Wark, PA, Chung, KF, Hughes, MJ, Armour, CL & Phipps, S 2012, 'RAGE: a new frontier in chronic airways disease', British Journal of Pharmacology, vol. 167, no. 6, pp. 1161-1176.View/Download from: Publisher's site
Asthma and chronic obstructive pulmonary disease (COPD) are heterogeneous inflammatory disorders of the respiratory tract characterized by airflow obstruction. It is now clear that the environmental factors that drive airway pathology in asthma and COPD, including allergens, viruses, ozone and cigarette smoke, activate innate immune receptors known as pattern-recognition receptors, either directly or indirectly by causing the release of endogenous ligands. Thus, there is now intense research activity focused around understanding the mechanisms by which pattern-recognition receptors sustain the airway inflammatory response, and how these mechanisms might be targeted therapeutically. One pattern-recognition receptor that has recently come to attention in chronic airways disease is the receptor for advanced glycation end products (RAGE). RAGE is a member of the immunoglobulin superfamily of cell surface receptors that recognizes pathogen- and host-derived endogenous ligands to initiate the immune response to tissue injury, infection and inflammation. Although the role of RAGE in lung physiology and pathophysiology is not well understood, recent genome-wide association studies have linked RAGE gene polymorphisms with airflow obstruction. In addition, accumulating data from animal and clinical investigations reveal increased expression of RAGE and its ligands, together with reduced expression of soluble RAGE, an endogenous inhibitor of RAGE signalling, in chronic airways disease. In this review, we discuss recent studies of the ligandRAGE axis in asthma and COPD, highlight important areas for future research and discuss how this axis might potentially be harnessed for therapeutic benefit in these conditions.
Sukkar, M, Wood, L, Tooze, M, Simpson, J, McDonald, V, Gibson, P & Wark, P 2012, 'Soluble RAGE is deficient in neutrophilic asthma and COPD', European Respiratory Journal, vol. 39, pp. 721-729.View/Download from: Publisher's site
The receptor for advanced glycation end-products (RAGE) is a pattern-recognition receptor involved in the host response to injury, infection and inflammation. It is a membrane receptor, but also has soluble forms (sRAGE). Deficiencies in sRAGE are linked to heightened inflammation in various chronic conditions. We determined whether airway and systemic levels of sRAGE and the RAGE ligands HMGB1 (high-mobility group box-1) and serum amyloid A (SAA) are related to neutrophilic inflammation in asthma and chronic obstructive pulmonary disease (COPD).
Manetsch, M, Seidel, P, Heintz, U, Che, W, Hughes, JM, Ge, Q, Sukkar, MB & Ammit, AJ 2012, 'TLR2 ligand engagement upregulates airway smooth muscle TNF alpha-induced cytokine production', AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY, vol. 302, no. 9, pp. L838-L845.View/Download from: Publisher's site
Kritikos, V, Woulfe, J, Sukkar, M & Saini, B 2011, 'Intergroup Peer Assessment in Problem-Based Learning Tutorials for Undergraduate Pharmacy Students', American Journal of Pharmaceutical Education, vol. 75, no. 4, pp. Article 73-Article 73.View/Download from: Publisher's site
Objective: To develop, implement, and evaluate a process of intergroup peer assessment and feedback using problem-based learning (PBL) tutorials. A peer-assessment process was used in a PBL tutorial setting for an integrated pharmacy practice course in which small groups of students graded each others' PBL case presentations and provided feedback in conjunction with facilitator assessment.
Michaeloudes, C, Sukkar, MB, Khorasani, NM, Bhavsar, PK & Chung, KF 2011, 'TGF-B regulates Nox4, MnSOD and catalase expression, and IL-6 release in airway smooth muscle cells', American Journal of Physiology: Lung Cellular and Molecular Physiology, vol. 300, pp. 295-304.View/Download from: Publisher's site
Reactive oxygen species (ROS) are generated as a result of normal cellular metabolism, mainly through the mitochondria and peroxisomes, but their release is enhanced by the activation of oxidant enzymes such as NADPH oxidases or downregulation of endogenous antioxidant enzymes such as manganese-superoxide dismutase (MnSOD) and catalase. Transforming growth factor-B (TGF-B), found to be overexpressed in airway smooth muscle (ASM) from asthmatic and chronic obstructive pulmonary disease patients, may be a pivotal regulator of abnormal ASM cell (ASMC) function in these diseases. An important effect of TGF-B on ASMC inflammatory responses is the induction of IL-6 release. TGF-B also triggers intracellular ROS release in ASMCs by upregulation of NADPH oxidase 4 (Nox4). However, the effect of TGF-B on the expression of key antioxidant enzymes and subsequently on oxidant/antioxidant balance is unknown. Moreover, the role of redoxdependent pathways in the mediation of the proinflammatory effects of TGF-B in ASMCs is unclear. In this study, we show that TGF-B induced the expression of Nox4 while at the same time inhibiting the expression of MnSOD and catalase. This change in oxidant/antioxidant enzymes was accompanied by elevated ROS levels and IL-6 release. Further studies revealed a role for Smad3 and phosphatidylinositol kinase-mediated pathways in the induction of oxidant/antioxidant imbalance and IL-6 release. The changes in oxidant/antioxidant enzymes and IL-6 release were reversed by the antioxidants N-acetylcysteine (NAC) and ebselen through inhibition of Smad3 phosphorylation, indicating redox-dependent activation of Smad3 by TGF-B. Moreover, these findings suggest a potential role for NAC in preventing TGF-B-mediated pro-oxidant and proinflammatory responses in ASMCs. Knockdown of Nox4 using small interfering RNA partially prevented the inhibition of MnSOD but had no effect on catalase and IL-6 expression. These findings provide novel insights into redo regul...
Clarke, D, Damera, G, Sukkar, M & Tliba, O 2009, 'Transcriptional regulation of cytokine function in airway smooth muscle cells', Pulmonary Pharmacology and Therapeutics, vol. 22, no. 5, pp. 436-445.View/Download from: Publisher's site
Despite numerous studies of the cellular effects of cytokines on cultured ASM, few have identified intracellular signaling pathways by which cytokines modulate or induce these cellular responses. In this review we provide an overview of the transcriptional mechanisms as well as intracellular signaling pathways regulating cytokine functions in ASM cells. The recent discovery of toll-like receptors in ASM cells represents a significant development in our understanding of the immuno-modulatory capabilities of ASM cells. Thus, we also review emerging evidence of the inflammatory response to toll-like receptor activation in ASM cells.
Bhavsar, PK, Sukkar, M, Khorasani, NM, Lee, K & Chung, KF 2008, 'Glucocorticoid suppression of CX3CL1 (fractalkine) by reduced gene promoter recruitment of NF-kB', The Journal of the Federation of American Societies for Experimental Biology, vol. 22, pp. 1807-1816.View/Download from: Publisher's site
Respiratory epithelial cells are a source of CX3CL1 (fractalkine), which mediates cell adhesion and acts as a chemoattractant for monocytes, T cells, and mast cells. We show, in lung A549 epithelial cells, that the tumor necrosis factor-Î± (TNF-Î±) and IFNÎ³ synergistically induced protein release and mRNA expression of CX3CL1 is inhibited by dexamethasone, without interfering with cytokine-induced nuclear translocation of NF-ÎºB, and by an inhibitor of IÎºB kinase 2, AS602868. DNA binding assays confirmed the ability of NF-ÎºB to bind to the proximal CX3CL1 promoter. Chromatin immunoprecipitation assays showed a 5-fold increase in the recruitment of NF-ÎºB to the CX3CL1 gene promoter in response to IFNÎ³/TNF-Î±; this too was reversed by dexamethasone. In contrast, dexamethasone did not displace NF-ÎºB from the granulocyte-macrophage colony-stimulating factor gene promoter. We conclude that CX3CL1 expression is regulated through the NF-ÎºB pathway and that dexamethasone inhibits CX3CL1 expression through a glucocorticoid receptor-dependent (RU486 sensitive) mechanism. This study also provides support for the action of glucocorticoids mediating their suppressive effects on expression by interfering with the binding of transcriptional activators at native gene promoters.
Issa, R, Sorrentino, R, Sukkar, M, Sriskandan, S, Chung, KF & Mitchell, J 2008, 'Differential regulation of CCL-11/eotaxin-1 and CXCL-8/IL-8 by Gram-positive and Gram-negative bacteria in human airway smooth muscle cells', Respiratory Research, vol. 9, no. 30, pp. 1-8.View/Download from: Publisher's site
Bacterial infections are a cause of exacerbation of airway disease. Airway smooth muscle cells (ASMC) are a source of inflammatory cytokines/chemokines that may propagate local airway inflammatory responses. We hypothesize that bacteria and bacterial products could induce cytokine/chemokine release from ASMC. Our findings that ASMC can respond directly to Gram-negative and Gram-positive bacteria by releasing the neutrophil selective chemokine, CXCL-8, is consistent with what we know about the role of neutrophil recruitment in bacterial infections in the lung. Our findings that bacteria inhibit the release of the eosinophil selective chemokine, eotaxin-1 may help to explain the mechanisms by which bacterial immunotherapy reduces allergic inflammation in the lung.
Kaur, M, Holden, NS, Wilson, SM, Sukkar, MB, Chung, KF, Barnes, PJ, Newton, R & Giembycz, MA 2008, 'Effect of beta(2)-adrenoceptor agonists and other cAMP-elevating agents on inflammatory gene expression in human ASM cells: a role for protein kinase A', AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY, vol. 295, no. 3, pp. L505-L514.View/Download from: Publisher's site
Oltmanns, U, Walters, M, Sukkar, M, Xie, S, Issa, R, Mitchell, J, Johnson, M & Chung, K 2008, 'Fluticasone, But Not Salmeterol, Reduces Cigarette Smoke-induced Production Of Interleukin-8 In Human Airway Smooth Muscle', Pulmonary Pharmacology & Therapeutics, vol. 21, no. 2, pp. 292-297.View/Download from: Publisher's site
Cigarette smoke is the leading risk factor for the development of chronic obstructive pulmonary disease. We have recently shown that cigarette smoke extract synergises with tumour necrosis factor alpha (TNF alpha) in the induction of interleukin-8 (IL-8)
Zuyderduyn, S, Sukkar, M, Fust, A, Dhaliwal, S & Burgess, JK 2008, 'Treating asthma means treating airway smooth muscle cells', European Respiratory Journal, vol. 32, no. 2, pp. 265-274.View/Download from: Publisher's site
Asthma is characterised by airway hyperresponsiveness, airway inflammation and airway remodelling. Airway smooth muscle cells are known to be the main effector cells of airway narrowing. In the present paper, studies will be discussed that have led to a novel view of the role of airway smooth muscle in the pathogenesis of asthma in which airway hyperresponsiveness, remodelling and inflammation are, at least in part, attributable to airway smooth muscle. Furthermore, how this new view may lead to a change in the phenotyping and treatment of patients with asthma will be discussed.
Issa, R, Xie, S, Khorasani, N, Sukkar, M, Adcock, I, Lee, K & Chung, K 2007, 'Corticosteroid Inhibition Of Growth-related Oncogene Protein-alpha Via Mitogen-activated Kinase Phosphatase-1 In Airway Smooth Muscle Cells', Journal Of Immunology, vol. 178, no. 11, pp. 7366-7375.View/Download from: Publisher's site
Expression of the inflammatory chemokine, growth-related oncogene protein-alpha (GRO-alpha), from airway smooth muscle cells (ASMC) is regulated by pathways involving NF-kappa B and MAPK activation. We determined the effects of dexamethasone on GRO-alpha
Lu, D, Xie, S, Sukkar, M, Lu, X, Scully, M & Chung, KF 2007, 'Inhibition of Airway Smooth Muscle Adhesion and Migration by the Disintegrin Domain of ADAM-15', American Journal of Respiratory Cell and Molecular Biology, vol. 37, no. 4, pp. 494-500.View/Download from: Publisher's site
Disintegrin and metalloprotease proteins (ADAMs) are membrane anchored glycoproteins involved in cell adhesion, cell fusion, protein ecto-domain shedding, and intracellular signaling. We examined whether the disintegrin domain of ADAM-15 (named ddADAM-15) containing an Asp-Gly Asp (RGD) integrin-binding motif could interfere with airway smooth muscle cell (ASMC) adhesion and migration.
Torrego, A, Hew, M, Oates, T, Sukkar, M & Chung, KF 2007, 'Expression and activation of TGF-b isoforms in acute allergen-induced remodelling in asthma', Thorax, vol. 62, no. 4, pp. 307-313.View/Download from: Publisher's site
Aim: To determine the effect of allergen challenge on airway inflammation and remodelling and whether TGF-b isoforms and the Smad signalling pathways are involved. Thirteen patients with atopic asthma underwent inhalational challenge with 0.9% saline, followed by allergen 3-4 weeks later. After both challenges, fibreoptic bronchoscopy was undertaken to obtain bronchial biopsies and tissue samples were processed for immunohistochemistry and examined by microscopy. Conclusions: TGF-b2 may contribute to the remodelling changes in allergic asthma following single allergen exposure.
Xie, S, Sukkar, MB, Issa, R, Khorasani, NM & Chung, KF 2007, 'Mechanisms of induction of airway smooth muscle hyperplasia by transforming growth factor-beta', AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY, vol. 293, no. 1, pp. L245-L253.View/Download from: Publisher's site
Bayram, H, Ito, K, Issa, R, Ito, M, Sukkar, M & Chung, KF 2006, 'Regulation of human lung epithelial cell numbers by diesel exhaust particles', European Respiratory Journal, vol. 27, no. 4, pp. 705-713.View/Download from: Publisher's site
Catley, MC, Sukkar, M, Chung, K, Jaffee, BD, Liao, SM, Coyle, AJ, Haddad, E, Barnes, PJ & Newton, R 2006, 'Validation of the anti-inflammatory properties of small molecule I kappa B kinase (IKK)-2 inhibitors by comparison with adenoviral-mediated delivery of dominant-negative IKK1 and IKK2 in human airways smooth muscle', Molecular Pharmacology, vol. 70, no. 2, pp. 697-705.View/Download from: Publisher's site
Issa, R, Xie, S, Lee, K, Standbridge, RD, Bhavsar, P, Sukkar, M & Chung, K 2006, 'GRO-alpha regulation in airway smooth muscle by IL-1 beta and TNF-alpha: role of NF-kappa B and MAP kinases', American Journal of Physiology: Lung Cellular and Molecular Physiology, vol. 291, no. 1, pp. 66-74.View/Download from: Publisher's site
growth-related oncogene protein-alpha; extracellular signal kinase; NH2-regulated kinase; Jun NH2; terminal kinase; nuclear factor-kappaB
Sukkar, M, Xie, S, Khorasani, NM, Kon, OM, Stanbridge, RD, Issa, R & Chung, K 2006, 'Toll-like receptor 2, 3, and 4 expression and function in human airway smooth muscle', Journal of Allergy and Clinical Immunology, vol. 118, no. 3, pp. 641-648.View/Download from: Publisher's site
oltmanns, U, Sukkar, M, Xie, S, John, M & Chung, KF 2005, 'Induction of Human Airway Smooth Muscle Apoptosis by Neutrophils and Neutrophil Elastase', American Journal of Respiratory Cell and Molecular Biology, vol. 32, pp. 334-341.View/Download from: Publisher's site
Xie, S, Issa, R, Sukkar, M, Oltmanns, U, Bhavsar, PK, Papi, A, Caramori, G, Adcock, I & Chung, KF 2005, 'Induction and regulation of matrix metalloproteinase-12 in human airway smooth muscle cells', Respiratory Research, vol. 6, no. 148, pp. 1-11.
Xie, S, Sukkar, M, Issa, R, Oltmanns, U, Nicholson, AG & Chung, K 2005, 'Regulation of TGF-beta 1-induced connective tissue growth factor expression in airway smooth muscle cells', American Journal of Physiology: Lung Cellular and Molecular Physiology, vol. 288, no. 1, pp. 68-76.View/Download from: Publisher's site
Jarai, G, Sukkar, M, Garrett, S, Duroudier, N, Westwick, J, Adcock, I & Chung, K 2004, 'Effects Of Interleukin-1 Beta, Interleukin-13 And Transforming Growth Factor-beta On Gene Expression In Human Airway Smooth Muscle Using Gene Microarrays', European Journal Of Pharmacology, vol. 497, no. 3, pp. 255-265.View/Download from: Publisher's site
Inflammatory gene expression in airway smooth muscle may be influenced by its inflammatory milieu. We analysed the gene expression profile of airway smooth muscle cells cultured from human airways exposed to a pro-inflammatory cytokine, interleukin-1beta
Sukkar, M, Issa, R, Xie, S, Oltmanns, U, Newton, R & Chung, K 2004, 'Fractalkine/CX(3)CL1 production by human airway smooth muscle cells: induction by IFN-gamma and TNF-alpha and regulation by TGF-beta and corticosteroids', American Journal of Physiology: Lung Cellular and Molecular Physiology, vol. 287, no. 6, pp. 1230-1240.View/Download from: Publisher's site
Sukkar, M, Stanley, AJ, Blake, AE, Hodgkin, PD, Johnson, PR, Armour, CL & Hughes, MJ 2004, ''Proliferative' and 'synthetic' airway smooth muscle cells are overlapping populations', Immunology And Cell Biology, vol. 82, no. 5, pp. 471-478.View/Download from: Publisher's site
Oltmanns, U, Issa, R, Sukkar, M, John, M & Chung, K 2003, 'Role of c-jun N-terminal kinase in the induced release of GM-CSF, RANTES and IL-8 from human airway smooth muscle cells', British Journal Of Pharmacology, vol. 139, no. 6, pp. 1228-1234.View/Download from: Publisher's site
Sukkar, M, Hughes, MJ, Armour, CL & Johnson, PR 2001, 'Tumour necrosis factor-a potentiates contraction of human bronchus in vitro', Respirology, vol. 6, no. 3, pp. 199-203.
Harris, J, Lang, T & Sukkar, MB 2017, 'Autophagy regulates inflammatory responses in antigen-presenting cells: Underlying mechanisms' in Autophagy: Cancer, Other Pathologies, Inflammation, Immunity, Infection, and Aging Volume 12, pp. 325-341.View/Download from: Publisher's site
© 2018 Elsevier Inc. All rights reserved. Autophagy is a highly conserved homeostatic mechanism for the lysosomal degradation of cytosolic constituents, including proteins and organelles. Studies over the past 10 years have demonstrated a number of specific roles for autophagy in the regulation of host immune responses, host-microbe interactions, and inflammation. This chapter presents some of the known and proposed mechanisms through which autophagy impacts on inflammatory responses elicited by antigen-presenting cells, with a particular emphasis on the modulation of cytokine expression, production, and release. Through regulation of the IL-1 family cytokines, IL-1a, IL-1Β, and IL-18, autophagy has far-reaching impacts on numerous immune cell types, in particular by influencing the secretion of IL-23 and IL-17. Autophagy intersects with IL-1Β both directly, through sequestration of the cytokine in autophagosomes, and indirectly, through regulation of inflammasome activation in response to inflammatory stimuli. Perturbations in autophagic activity can also affect the secretion of other cytokines, including macrophage migration inhibitory factor. A better understanding of how autophagy exerts its effects on inflammation has the potential to open new therapeutic avenues for the treatment of diseases with inflammatory pathologies.
Allam, VSRR, Adcock, I, Chung, KF, Morand, E, Harris, J & Sukkar, M 2018, 'MIF antagonism restores corticosteroid sensitivity in a murine model of severe asthma', EUROPEAN RESPIRATORY JOURNAL, 28th International Congress of the European-Respiratory-Society (ERS), EUROPEAN RESPIRATORY SOC JOURNALS LTD, Paris, FRANCE.View/Download from: Publisher's site
Fin, NASH, Sukkar, M & Golzan, M 2018, 'Receptor for advanced glycation end product (RAGE) mediates retinal ganglion cell loss in experimental glaucoma', INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE, Annual Meeting of the Association-for-Research-in-Vision-and-Ophthalmology (ARVO), ASSOC RESEARCH VISION OPHTHALMOLOGY INC, Honolulu, HI.
Allam, V, Lam, M, Sukkar, M & Bourke, JE 2017, 'Role Of Pattern Recognition Receptors In The Regulation Of Intrapulmonary Airway Contraction Following Short-Term Cigarette Smoke Exposure In Mice', AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE, International Conference of the American-Thoracic-Society (ATS), AMER THORACIC SOC, Washington, DC.
Allam, VSRR, Tanaka, A, Dalton, J, Sukkar, M & Donnelly, S 2017, 'A NOVEL PEPTIDE FROM THE LIVER FLUKE FASCIOLA HEPATICA INHIBITS THE MIXED GRANULOCYTIC AIRWAY INFLAMMATION IN A MOUSE MODEL OF ALLERGIC ASTHMA', RESPIROLOGY, WILEY, pp. 81-81.
Lam, M, Allam, V, Sukkar, M & Bourke, J 2017, 'ACUTE CIGARETTE SMOKE EXPOSURE IMPAIRS AIRWAY CONTRACTION BUT NOT RELAXATION IN MOUSE PRECISION CUT LUNG SLICES', RESPIROLOGY, WILEY, pp. 26-26.
Raju, RAVS, Lam, M, Sukkar, M & Bourke, JE 2017, 'ROLE OF RAGE AND TLR4 IN THE REGULATION OF INTRAPULMONARY AIRWAY CONTRACTION FOLLOWING SHORT-TERM CIGARETTE SMOKE EXPOSURE IN MICE', RESPIROLOGY, WILEY, pp. 140-140.
Wong, S, Chen, L, Oliver, B, Padula, M & Sukkar, M 2017, 'SPARC EXPRESSION IN AIRWAY SMOOTH MUSCLE CELLS IS REGULATED BY THE UNFOLDED PROTEIN RESPONSE AND MAY BE DIMINISHED IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE', RESPIROLOGY, WILEY, pp. 31-32.
Ullah, AM, Pharm, M, Revez, J, Loh, Z, Simpson, J, Zhang, V, Bain, L, Varelias, A, Rose-John, S, Blumenthal, A, Smyth, M, Hill, G, Sukkar, M, Ferreira, M & Phipps, S 2015, 'IL-6R BLOCKADE ATTENUATES EXPERIMENTAL ALLERGIC ASTHMA ASSOCIATED WITH ACTIVATION OF THE IL-6 TRANS-SIGNALLING PATHWAY', RESPIROLOGY, pp. 32-32.
Ullah, MA, Revez, J, Loh, Z, Simpson, J, Zhang, V, Bain, L, Varelias, A, Rose-John, S, Blumenthal, A, Smyth, M, Hill, G, Sukkar, M, Ferreira, MA & Phipps, S 2015, 'IL-6R blockade attenuates experimental allergic asthma associated with activation of the IL-6 trans-signalling pathway', ALLERGY, Congress of the European-Academy-of-Allergy-and-Clinical-Immunology, WILEY-BLACKWELL, Barcelona, SPAIN, pp. 43-44.
Wong, S, Ibrahim, Z, Wark, P & Sukkar, M 2015, 'Potential role of SPARC, a downstream mediator of TGF-b in chronic airways disease', EUROPEAN RESPIRATORY JOURNAL, EUROPEAN RESPIRATORY SOC JOURNALS LTD.View/Download from: Publisher's site
Wong, S, Ibrahim, Z, Wark, P & Sukkar, M 2015, 'SPARC: A DOWN-STREAM MEDIATOR OF TGF-BETA; WHICH MAY POTENTIALLY PLAY A ROLE IN CHRONIC AIRWAYS DISEASE', RESPIROLOGY, Thoracic Society Australia New Zealand Australian New Zealand Society Respiratory Science Annual Scientific Meeting 2015, WILEY-BLACKWELL, Queensland, AUSTRALIA, pp. 144-144.
Ibrahim, ZA, Wong, S, Phipps, S, Armour, C & Sukkar, M 2014, 'HMGBi expression and function in the allergic airway immune response', EUROPEAN RESPIRATORY JOURNAL, EUROPEAN RESPIRATORY SOC JOURNALS LTD.
Ullah, MA, Sukkar, M, Ferreira, M & Phipps, S 2014, 'IL-6R blockade: A new personalised treatment for asthma?', CYTOKINE, 2nd Annual Meeting of the International-Cytokine-and-Interferon-Society (ICIS), ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, Melbourne, AUSTRALIA, pp. 40-40.View/Download from: Publisher's site
Ullah, MA, Loh, Z, Gan, WJ, Zhang, V, Lynch, J, Eacharath, J, Hughes, JM, Armour, CL, Phipps, S & Sukkar, MB 2013, 'HMGB1-RAGE AXIS MEDIATES HOUSE DUST MITE INDUCED ALLERGIC SENSITIZATION AND AIRWAY INFLAMMATION', RESPIROLOGY, WILEY-BLACKWELL, pp. 25-25.
Sukkar, MB, Wood, LG, Tooze, M, Simpson, JL, McDonald, VM, Gibson, P & Wark, PA 2011, 'Deficiency Of Srage In Asthma And COPD Is Selectively Associated With Neutrophilic Airway Inflammation', AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE, AMER THORACIC SOC.
Manetsch, M, Seidel, P, Che, W, Ge, Q, Sukkar, M & Ammit, AJ 2011, 'Effect Of H202 On The Synergistic Upregulation Of TnfAlpha-Induced Cytokines By TLR2 Ligand Engagement', AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE, AMER THORACIC SOC.
Michaeloudes, C, Sukkar, MB, Johnson, M & Chung, KF 2009, 'Regulation of Oxidant and Antioxidant Enzyme Expression by TGF-beta in Human Airway Smooth Muscle Cells', AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE, AMER THORACIC SOC.
Sukkar, MB, Yeo, CY, Ge, Q, Armour, CL, Michaeloudes, C & Chung, KF 2009, 'Is Oxidative Stress an Important Determinant of Airway Smooth Muscle Cytokine and Chemokin Production?', AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE, AMER THORACIC SOC.
Sukkar, MB & Hughes, JM 2001, 'Flow-cytometr1c detection of intracellular gm-csf in human airway smooth muscle cells (asmc)', Respirology.
Rationale: ASMC synthesise many inflammatory mediators and so may be imolved in the regulation of airway inflammation in asthma. Recently, we reported that IL-l and TNF-a prime ASMC to release GM-CSF in response to human serum (Sukkar et al., Med Inflamm 2000;9:173180). ASMC in culture represent a heterogenous population of cells \vith regard to their contractile, proliferative and synthetic functions. The purpose of this study was to develop a methodology for flow-cytometric detection of intracellular GM-CSF in ASMC in order to determine whether cytokine synthesis is a function of all or only a distinct phenotypic subset of cells. Methods: Induction of GM-CSF synthesis: ASMC were pre-treated with IL-l and TNF-a (5-25ng/tnl each) for 24hrs before being incubated in 10% human serum for 24hrs. Brefeldin A ( 10(ig/ml), an inhibitor of intracellular protein transport, was added to the cells for the final 20hrs of the incubation period with human serum. GM-CSF staining: ASMC were fixed in 4% formalin and then incubated with a GM-CSF antibody (Ab) conjugated to R-phycoerythrin (0.2mg/ml) or its isotype control diluted (1;2-1;80) in a solution containing 0.5% saponin (permeabilizing agent). ASMC were w-ashed thoroughly prior to flow-cytometric analysis. Results and Conclusions: Preliminary results indicate that 50% of ASMC synthesise GM-CSF. In ASMC obtained from any given donor, the proportion of cells staining for GM-CSF was dependent on the Ab concentration as well as the amount of GM-CSF production. This is the first study to utilise flott-cytometric techniques for intracellular cytokine detection in ASMC. This methodology will be invaluable for further phenotypic characterisation of synthetic ASMC in culture.
Sukkar, M, Johnson, P, Hughes, JM & Armour, C 1999, 'Responsiveness of human airways in vitro is increased by IL-1 beta and TNF alpha.', AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE, AMER LUNG ASSOC, pp. A124-A124.
Sukkar, MB, Hughes, JM, Johnson, PRA & Armour, CL 1999, 'Human serum increases human airway smooth muscle cell (ASMC) cytokine synthesis', Respirology.
Chronic inflammation of the airways is a major factor contributing to abnormal airway function in asthma. We have demonstrated that the inflammatory cytokines IL-1β and TNF-α induce human ASMC to synthesize GM-CSF, a cytokine involved in the survival and activation of airway inflammatory cells, such as the eosinophil. It was recently demonstrated that IL-1β and TNF-α induce the expression of the IgE receptor on human ASMC (Allakhverdiet ai, Am J Respir Crit Care Med 157;A658 1998). These observations prompted us to investigate whether allergen challenge of passively sensitized human ASMC that had been previously treated with IL-1β and TNF-α, would result in GM-CSF production by ASMC. Methods: ASMC were stimulated with IL-1β and TNF-α in combination (5,10,25ng/ml each) for 24h followed by medium with 10% serum from either an atopic asthmatic allergic to house dust mite (HDM) or a non-atopic non-asthmatic or Monomed A™ (defined serum substitute), for a further 24h. Following this, ASMC were challenged with HDM for 24h. GM-CSF was measured in supernatants collected after each treatment step by ELISA. Results: HDM challenge did not induce GM-CSF release from human ASMC. However, stimulation of ASMC with atopic asthmatic serum (AAS) or non-atopic non-asthmatic serum (NAS) significantly increased GM-CSF release from ASMC that had been previously exposed to IL-1β and TNF-α, but not from those that had not been exposed to cytokines (see table). GM-CSF (pg/ml) (±SEM) IL-1β/TNF-α (ng/ml) AAS (n=5) NAS (n=5) Monomed A™ (n=3) 0 4.6 (±3.2) 6.44 (±4.2) 0 (±O) 5 268.8 (±81.1) 331.2 (±54.2) 75.8 (±28.8) 10 407.2 (±99.0) 410 (±40.3) 145.1 (±48.6) 25 603.8(±118.3) 665.2 (±55.0)~~ 244.3 (±111.5) Conclusions: These findings suggest that ASMC, in addition to their contractile function, may play an active role in airway inflammation, particularly during periods of vascular leakage. However, the role of IgE in this is minimal.
Sukkar, M 2008, 'The toll on the road to allergic airways disease', pp. 71-73.
The discovery of human toll-like receptors that help defend against microbial infection has led to significant advances in our understanding of the interplay between microbial exposure, immune system development and allergic disease at multiple levels.