Associate Professor Bronwyn O'Brien

Biography

Bronwyn is a Senior Lecturer of Immunology and Associate Head in the Department of Medical & Molecular Biosciences. She is a core member of the Centre for Health Technologies (Key University Research Strength).

Bronwyn's major research interest is investigating the role of macrophages in the development of autoimmunity. She is currently conducting expression and functional studies of SLC11A1, a gene specifically expressed in antigen-presenting cells (macrophages and dendritic cells) that modulates the immune cell balance to influence the development of autoimmune disease. A greater understanding of the expression and function of this gene may provide novel avenues for modulating macrophage and dendritic cell function and consequently stop the development of autoimmune disease.

With funding from the Juvenile Diabetes Research Foundation (JDRF) Bronwyn is currently investigating the use of novel parasite antigens to prevent the initiation of autoimmunity. This work was prompted by epidemiological observations that in regions where parasitic worm infections are endemic there is a very low incidence of autoimmune disease. Our group has been able to prevent autoimmune diabetes in a rodent model using parasite secretions and we are now planning to test individual molecules within the secretions for their efficacy in preventing autoimmune disease. This project may ultimately lead to novel therapeutic strategies to prevent diabetes, and perhaps more broadly, autoimmunity per se.

Bronwyn is also conducting preliminary research to identify novel biomarkers of hypoglycaemia in exhaled air with the objective of developing a reliable, noninvasive means of detecting impending hypoglycaemia. This work was prompted by anecdotal evidence that some dogs owned by Type 1 diabetics can alert there owners to impending hypoglycaemia even when the dogs cannot see their owners. The stimulus for the dog’s behaviour is likely compounds that transit from the blood into exhaled air to provide a breath signature of hypoglycaemia.

Professional

Australasian Society for Immunology
Australian Diabetes Society
Transplantation Society of Australia and New Zealand

Image of Bronwyn O'Brien
Associate Professor, School of Medical and Molecular Biosciences
Core Member, Centre for Health Technologies
DipT (QUT), BAppSc (Hons) (QUT), PhD (QUT)
 
Phone
+61 2 9514 4104
Fax
+61 2 9514 8206
Room
CB04.06.37B

Research Interests

Bronwyn’s research area is the immunology of autoimmune disease.

Bronwyn is investigating the role of macrophages in the development of autoimmune disease, specifically type 1 (juvenile-onset, insulin-dependent) diabetes.

She is also involved in NHMRC-funded research investigating the liver-directed gene therapy of diabetes.

With funding from JDRF Bronwyn is currently investigating the use of novel parasite antigens to prevent the initiation of autoimmunity in Type 1 diabetes.

Bronwyn is also conducting preliminary research to identify novel biomarkers of hypoglycaemia in exhaled air with the objective of developing a reliable, noninvasive means of detecting impending hypoglycaemia.

Can supervise: Yes
Nicholas Archer Promoter studies of SLC11A1, a gene that modulates macrophage function Stephanie Dowdell Functional studies of SLC11A1, a gene that modulates macrophage function Katrina Norial Macrophage phayocytic defects in Type 1 Diabetes

Bronwyn coordinates the Immunology subjects offered by the Faculty of Science, namely Introductory Haematology & Immunology (subject number 91351) and Advanced Immunology (subject number 91401).

Book Chapters

Simpson, A.M., Swan, M.A., Liu, G.J., Tao, C.Z., O'Brien, B., Ch'ng, E., Castro, L.M., Ting, H.J., Elgundi, Z., An, T., Lutherborrow, M., Torpy, F.R., Martin, D.K., Tuch, B.E. & Nicholson, G.M. 2013, 'Insulin trafficking in a glucose responsive engineered human liver cell line is regulated by the interaction of ATP-sensitive potassium channels and voltage- gated calcium channels' in Molina, Francisco Martin (eds), Gene Therapy - Tools and Potential Applications, InTech, Rijeka, Croatia, pp. 703-726.
View/Download from: UTSePress |
Type I diabetes is caused by the autoimmune destruction of pancreatic beta () cells [1]. Current treatment requires multiple daily injections of insulin to control blood glucose levels. Tight glucose control lowers, but does not eliminate, the onset of diabetic complications, which greatly reduce the quality and longevity of life for patients. Transplantation of pancreatic tissue as a treatment is restricted by the scarcity of donors and the requirement for lifelong immunosuppression to preserve the graft, which carries adverse side-effects. This is of particular concern as Type 1 diabetes predominantly affects children. Lack of glucose control could be overcome by genetically engineering "an artificial -cell" that is capable of synthesising, storing and secreting insulin in response to metabolic signals. The donor cell type must be readily accessible and capable of being engineered to synthesise, process, store and secrete insulin under physiological conditions.

Conference Papers

Biady, J., O'Brien, B. & Simpson, A.M. 2007, 'An insulin secreting liver cell line, TAO, is resistant to the cytotoxic effects of pro-inflammatory cytokines via NF-KB-dependent pathways', Canberra, April 2007 in Journal of Gene Medicine, ed Asano s, Wiley, UK, pp. 527-527.
Ren, B., O'Brien, B., Swan, M.A., Koina, M.E., Nassif, N. & Wei, M.Q. 2007, 'Delivery of furin-cleavable insulin to diabetic rat livers resulted in long-term correction of diabetes and partial pancreatic transdifferentiation of the liver', Canberra, April 2007 in Journal of Gene Medicine, ed Asano s, Wiley, UK, pp. 532-532.
Lawandi, J., Tao, C.Z., O'Brien, B. & Simpson, A.M. 2005, 'Susceptibility of an insulin-secreting liver cell line to the toxic effects of cytokines involved in the autoimmune destruction of pancreatic beta cells', 4th Meeting of the Australasian-Gene-Therapy-Society, Melbourne, Australia, April 2005 in Journal Of Gene Medicine, ed N/A, Unknown, Unknown, pp. 1124-1124.
N/A
Biady, J., Tao, C.Z., O'Brien, B. & Simpson, A.M. 2005, 'Susceptibility of an insulin-secreting liver cell line to the toxic effects of cytokines involved in the autoimmune destruction of pancreatic beta cells', Melbourne, April 2005 in Journal of Medicine, ed Asano s, Wiley, UK, pp. 1124-1124.
O'Brien, B. 2005, 'Effect of pro-inflammaton cytokines on an insulin-secreting liver cell line', San Diego CA, June 2011 in Diabetes, ed Butler PC, Amer Diabetes Assoc, USA, pp. A101-A101.

Journal Articles

Robinson, M.W., Dalton, J.P., O'Brien, B. & Donnelly, S.M. 2013, 'Fasciola hepatica: The therapeutic potential of a worm secretome', International Journal For Parasitology, vol. 43, no. 3-4, pp. 283-291.
View/Download from: UTSePress | Publisher's site
The success of helminth parasites is partly related to their ability to modulate host immune responses towards an anti-inflammatory/regulatory phenotype. This ability resides with the molecules contained in the secretome of various helminths that have been shown to interact with host immune cells and influence their function. Consequently, there exists a unique opportunity to exploit these molecules for the prophylactic and therapeutic treatment of human pro- and auto-inflammatory disorders (for example septic shock, transplant rejection and autoimmune disease). In this review, we describe the mechanisms used by the trematode parasite, Fasciola hepatica, to modulate the immune responses of its host and discuss the potent immune-modulatory effects of three individual molecules within the secretome; namely cathepsin L1, peroxiredoxin and helminth defence molecule. With a focus on the requirements from industry, we discuss the strategies by which these molecules may be clinically developed to control human immune responses in a way that is conducive to the prevention of immune-mediated diseases.
Ren, B., O'Brien, B., Byrne, M., Ch'ng, E., Gatt, P.N., Swan, M.A., Nassif, N., Wei, M., Gijsbers, R., Debyser, Z. & Simpson, A.M. 2013, 'Long-term reversal of diabetes in non-obese diabetic mice by liver-directed gene therapy.', The Journal of gene Medicine, vol. 15, no. 1, pp. 28-41.
View/Download from: Publisher's site
Background Type 1 diabetes (T1D) results from an autoimmune attack against the insulin-producing -cells of the pancreas. The present study aimed to reverse T1D by gene therapy. Methods We used a novel surgical technique, which involves isolating the liver from the circulation before the delivery of a lentiviral vector carrying furin-cleavable human insulin (INS-FUR) or empty vector to the livers of diabetic non-obese diabetic mice (NOD). This was compared with the direct injection of the vector into the portal circulation. Mice were monitored for body weight and blood glucose. Intravenous glucose tolerance tests were performed. Expression of insulin and pancreatic transcription factors was determined by the reverse transcriptase-polymerase chain reaction and immunohistochemistry and immunoelectron microscopy was used to localise insulin. Results Using the novel surgical technique, we achieved long-term transduction (42% efficiency) of hepatocytes, restored normoglycaemia for 150 days (experimental endpoint) and re-established normal glucose tolerance. We showed the expression of -cell transcription factors, murine insulin, glucagon and somatostatin, and hepatic storage of insulin in granules. The expression of hepatic markers, C/EBP-, G6PC, AAT and GLUI was down-regulated in INS-FUR-treated livers. Liver function tests remained normal, with no evidence of intrahepatic inflammation or autoimmune destruction of the insulin-secreting liver tissue. By comparison, direct injection of INS-FUR reduced blood glucose levels, and no pancreatic transdifferentiation or normal glucose tolerance was observed.
Gerace, D., Ren, B., Hawthorne, W., Byrne, M., Phillips, P., O'Brien, B., Nassif, N., Alexander, I. & Simpson, A.M. 2013, 'Pancreatic transdifferentiation in porcine liver following lentiviral delivery of human furin-cleavable insulin', Transplantation Proceedings, vol. 45, no. 5, pp. 1869-1874.
View/Download from: UTSePress | Publisher's site
Type I diabetes mellitus (TID) results from the autoimmune destruction of the insulin-producing pancreatic -cells. Gene therapy is one strategy being actively explored to cure TID by affording non--cells the ability to secrete insulin in response to physiologic stimuli. In previous studies, we used a novel surgical technique to express furin-cleavable human insulin (INS-FUR) in the livers of streptozotocin (STZ)-diabetic Wistar rats and nonobese diabetic (NOD) mice with the use of the HMD lentiviral vector. Normoglycemia was observed for 500 and 150 days, respectively (experimental end points). Additionally, some endocrine transdifferentiation of the liver, with storage of insulin in granules, and expression of some -cell transcription factors (eg, Pdx1, Neurod1, Neurog3, Nkx2-2, Pax4) and pancreatic hormones in both studies. The aim of this study was to determine if this novel approach could induce liver to pancreatic transdifferentiation to reverse diabetes in pancreatectomized Westran pigs. Nine pigs were used in the study, however only one pig maintained normal fasting blood glucose levels for the period from 10 to 44 days (experimental end point). This animal was given 2.8 10(9) transducing units/kg of the lentiviral vector expressing INS-FUR. A normal intravenous glucose tolerance test was achieved at 30 days. Reverse-transcription polymerase chain reaction analysis of the liver tissue revealed expression of several -cell transcription factors, including the key factors, Pdx-1 and Neurod1, pancreatic hormones, glucagon, and somatostatin; however, endogenous pig insulin was not expressed.
Robinson, M.W., Alvarado, R., To, J., Hutchinson, A.T., Dowdell, S.N., Lund, M.E., Turnbull, L., Whitchurch, C.B., O'Brien, B., Dalton, J.P. & Donnelly, S.M. 2012, 'A helminth cathelicidin-like protein suppresses antigen processing and presentation in macrophages via inhibition of lysosomal vATPase', Faseb Journal, vol. 26, no. 11, pp. 4614-4627.
View/Download from: UTSePress | Publisher's site
We previously reported the identification of a novel family of immunomodulatory proteins, termed helminth defense molecules (HDMs), that are secreted by medically important trematode parasites. Since HDMs share biochemical, structural, and functional characteristics with mammalian cathelicidin-like host defense peptides (HDPs), we proposed that HDMs modulate the immune response via molecular mimicry of host molecules. In the present study, we report the mechanism by which HDMs influence the function of macrophages. We show that the HDM secreted by Fasciola hepatica (FhHDM-1) binds to macrophage plasma membrane lipid rafts via selective interaction with phospholipids and/or cholesterol before being internalized by endocytosis. Following internalization, FhHDM-1 is rapidly processed by lysosomal cathepsin L to release a short C-terminal peptide (containing a conserved amphipathic helix that is a key to HDM function), which then prevents the acidification of the endolysosomal compartments by inhibiting vacuolar ATPase activity. The resulting endolysosomal alkalization impedes macrophage antigen processing and prevents the transport of peptides to the cell surface in conjunction with MHC class II for presentation to CD4(+) T cells. Thus, we have elucidated a novel mechanism by which helminth pathogens alter innate immune cell function to assist their survival in the host.-Robinson, M. W., Alvarado, R., To, J., Hutchinson, A. T., Dowdell, S. N., Lund, M., Turnbull, L., Whitchurch, C. B., O'Brien, B. A., Dalton, J. P., Donnelly, S. A helminth cathelicidin-like protein suppresses antigen processing and presentation in macrophages via inhibition of lysosomal vATPase
Feller, J.M., Simpson, A.M., Nelson, M., Swan, M.A., O'Connell, P.J., Hawthorne, W.J., Tao, C.Z. & O'Brien, B. 2008, 'Growth-promoting effect of Rh(D) antibody on human pancreatic islet cells', Journal of Clinical Endocrinology and Metabolism, vol. 93, no. 9, pp. 3560-3567.
View/Download from: UTSePress | Publisher's site
Context/Objective: Hyperinsulinism with islet cell hyperplasia is a frequent complication, of unknown cause, in hemolytic disease of the newborn, occurring in Rh(D)-positive infants of Rh-isoimmunized Rh(D)-negative mothers, but not in infants with other hemolytic disorders. We investigated the possibility that trans-placentally acquired anti-D Ig is the cause of both conditions. Design: Monolayer cultures of human islet cells were exposed to sera from Rh-isoimmunized mothers and newborns, where jaundice, hyperinsulinism, and hypoglycemia in the infant had ensued. Parallel cultures with anti-D, specific anti-D monoclonal antibodies, normal human Ig (15 ++g/ml), and serum controls were also undertaken. Islet cell proliferation was determined by [ 3H]thymidine incorporation. Insulin storage and chronic and acute insulin secretion to glucose were analyzed by RIA. Rh(D) surface antigen expression was determined on islet cells by flow cytometric analysis. Results: Islet cell proliferation and insulin secretion were significantly greater in coculture with test sera (P < 0.01; n = 8) and with anti-D (P < 0.001; n = 8), compared with either controls or Ig. After 8 d of growth, the static incubation experiment showed a 3.5-fold response to glucose stimulus in all sera. Rh(D) antigen expression was detected on the islet cell surface by flow cytometry, and islet cell morphology was normal. Colocalization of the proliferation marker Ki67 with insulin by immunofluorescent staining further indicated that Rh(D) antibody promoted islet growth. Conclusions: The anti-Rh(D) islet cell proliferative effect generates neonatal hyperinsulinism in Rh isoimmunization. Anti-Rh(D) may have application for islet cell proliferation in diabetes mellitus treatment for Rh(D)-positive subjects. Further analysis is required. Copyright 2008 by The Endocrine Society.
O'Brien, B., Archer, N.S., Simpson, A.M., Torpy, F.R. & Nassif, N. 2008, 'Association of SLC11A1 promoter polymorphisms with the incidence of autoimmune and inflammatory diseases: A meta-analysis', Journal Of Autoimmunity, vol. 31, no. 1, pp. 42-51.
View/Download from: UTSePress | Publisher's site
Solute carrier family 11 member a1 (SLC11A1) exerts pleiotropic effects on macrophage function. Expression of SLC11A1 is regulated by a (GT)(n) microsatellite promoter repeat polymorphism of which nine alleles have been described. Enhanced activation of
Simpson, A.M. & O'Brien, B. 2008, 'Diabetes therapy by lentiviral hepatic insulin gene expression without transofrmation of liver. Reply to Elsner M, Jorns A, Lenzen S (letter)', Diabetologia, vol. 51, pp. 696-696.
Ren, B., O'Brien, B., Swan, M.A., Koina, M.E., Nassif, N., Wei, M.Q. & Simpson, A.M. 2007, 'Long-term Correction Of Diabetes In Rats After Lentiviral Hepatic Insulin Gene Therapy', Diabetologia, vol. 50, no. 9, pp. 1910-1920.
View/Download from: UTSePress | Publisher's site
Aims/hypothesis Type 1 diabetes results from the autoimmune destruction of pancreatic beta cells. Exogenous insulin therapy cannot achieve precise physiological control of blood glucose concentrations, and debilitating complications develop. Lentiviral v
O'Brien, B., Geng, X., Orteu, C.H., Huang, Y., Ghoreishi, M., Zhang, Y., Bush, J.A., Li, G., Finegood, D.T. & Dutz, J.P. 2006, 'A deficiency in the in vivo clearance of apopototic cells is a feature of the NOD mouse', Journal of Autoimmunity, vol. 26, no. 2, pp. 104-115.
View/Download from: UTSePress | Publisher's site
Deficiencies in apoptotic cell clearance have been linked to autoimmunity. Here we examined the time-course of peritoneal macrophage phagocytosis of dying cells following the direct injection of apoptotic thymocytes into the peritoneum of NOD mice and BALB/c controls. Macrophages from NOD mice demonstrated a profound defect in the phagocytosis of apoptotic thymocytes as compared to control macrophages. Nonobese diabetic mice also demonstrated a decrease in the clearance of apoptotic cell loads following an apoptotic stimulus to thymocytes (dexamethasone) when compared to BALB/c or NOR controls. Further, NOD mice demonstrated an increase in apoptotic cell load following an apoptotic stimulus to keratinocytes (ultraviolet light, UVB) when compared to control strains. Animals deficient in macrophage phagocytosis of apoptotic debris often manifest an autoimmune phenotype characterized by the production of antinuclear autoantibodies (ANA). We determined whether increased apoptotic cell loads (through repeated exposure to UVB irradiation) could accelerate such autoimmune phenomena in young NOD mice. Following repeated UVB irradiation, NOD mice, but not BALB/c or NOR controls, developed ANA. We propose that abnormalities in apoptotic cell clearance by macrophages predispose NOD mice to autoimmunity.
Ren, B., O'Brien, B., Swan, M.A. & Simpson, A.M. 2005, 'In vivo delivery of the human insulin gene results in long-term reversal of streptozotocin-induced type 1 diabetes in rats', Journal Of Gene Medicine, vol. 7, no. 8, pp. 1124-1124.
N/A
Ren, B., O'Brien, B. & Simpson, A.M. 2004, 'Long-term Reversal Of Type 1 Diabetes In Rats After In Vivo Delivery Of The Human Insulin Gene', Immunology And Cell Biology, vol. 82, no. 2, pp. 1-1.
NA
Zhang, Y., O'Brien, B., Trudeau, J., Tan, R., Santamaria, P. & Dutz, J.P. 2002, 'In situ beta cell death promotes priming of diabetogenic CD8 T lymphocytes', Journal of Immunology, vol. 168, no. 3, pp. 1466-1472.
View/Download from: UTSePress
This paper was the first to report that increased beta cell death can lead to the priming of diabetogenic T cells, and hence, the initiation of autoimmunity in Type 1 diabetes. The Journal of Immunology is the top-ranked immunology journal.
O'Brien, B., Huang, Y., Geng, X., Dutz, J.P. & Finegood, D.T. 2002, 'Phagocytosis of apoptotic cells by macrophages from NOD mice is reduced', Diabetes, vol. 51, no. 8, pp. 2481-2488.
View/Download from: UTSePress |
Macrophages limit inflammatory responses by clearing apoptotic cells. Deficiencies in apoptotic cell phagocytosis have been linked to autoimmunity. In this study, we determined the efficiency with which macrophages from diabetes-prone NOD and diabetes-resistant NOR, Idd5, Balb/c, and C57BL/6 mice phagocytose apoptotic thymocytes and NIT-1 insulinoma cells. Peritoneal and bone marrow-derived macrophages from NOD mice engulfed fewer apoptotic thymocytes than macrophages from Balb/c mice (P < 0.05). Peritoneal macrophages from NOR and Idd5 NOD congenic mice were more proficient at engulfment than their NOD counterparts. Annexin V blockade diminished apoptotic thymocyte clearance and heat-labile serum factors augmented clearance. Binding of apoptotic thymocytes to NOD macrophages was also reduced, suggesting that the deficiency in phagocytosis may be partly attributable to a recognition defect. Peritoneal macrophages from female Balb/c and NOD mice were equally efficient in the engulfment of microspheres, suggesting that the phagocytic deficiency observed in NOD mice was specific for apoptotic cells. In summary, we have demonstrated a deficiency in phagocytic function of macrophages from NOD mice. Normal and diabetes-prone neonatal rodents have a wave of -cell apoptosis coincident with the onset of target organ inflammation. A constitutive defect in the clearance of apoptotic -cells may be contributory to the initiation of autoimmunity.
O'Brien, B., Finegood, D.T., Fieldus, W.E. & Field, C.J. 2002, 'Clearance of apoptotic beta-cells is reduced in neonatal autoimmune diabetes-prone rats', Cell Death and Differentiation, vol. 9, no. 4, pp. 457-464.
View/Download from: UTSePress | Publisher's site
The kinetics of -cell death in neonatal diabetes-prone (BBdp) and diabetes-resistant (BBdr) BioBreeding rats was investigated using both direct (histochemical) and indirect (mathematical modelling) techniques. In both BBdp and BBdr rats, the incidence of TUNEL positive -cells increased until 10 days of age before declining. The number of apoptotic -cells was significantly higher in BBdp as compared to BBdr neonates from birth until 20 days of age (P < 0.05). Using a mathematical model applied to the time course of -cell mass and replication rate, a wave of net -cell loss was detected between 10 and 20 days of age in both strains. In contrast to the observed difference in the incidence of TUNEL positive cells, with the model-based approach we found no difference in the rate of -cell apoptosis between BBdp and BBdr rats prior to weaning. As the number of apoptotic cells present in a tissue depends on the rate at which cells die and the rate at which the apoptotic cell debris is cleared, we compared in vitro phagocytosis of apoptotic thymocytes by peritoneal macrophages from 2-week-old BBdp and BBdr rats. Macrophages from BBdp neonates engulfed significantly less apoptotic cells as compared to BBdr neonates (P < 0.0005). Taken together, these findings suggest that there is impaired clearance of apoptotic -cells in diabetes-prone BB rats during the neonatal period
Heczko, U., Carthy, C.M., O'Brien, B. & Finlay, B.B. 2001, 'Decreased apoptosis in the ileum and ileal Peyer's patches after infection with rabbit enteropathogenic Escherichia coli O103', Infection And Immunity, vol. 69, no. 7, pp. 4580-4589.
View/Download from: UTSePress | Publisher's site
Significant changes occur in intestinal epithelial cells after infection with enteropathogenic Escherichia coli (EPEC), However, it is unclear whether this pathogen alters rates of apoptosis, By using: a naturally occurring weaned rabbit infection model, we determined physiological levels of apoptosis in rabbit ileum and ileal Peyer's patches (PP) and compared them to those found after infection with adherent rabbit EPEC (REPEC O103), Various REPEC O103 strains were first tested in vitro for characteristic virulence features. Rabbits were then inoculated with the REPEC O103 strains that infected cultured cells the most efficiently. After experimental infection, intestinal samples were examined by light and electron microscopy, Simultaneously, ileal apoptosis was assessed by using terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) and caspase 3 assays and by apoptotic cell counts based on morphology (hematoxylin-and-eosin staining). The highest physiological apoptotic indices were measured in PP germinal centers (median = 14.7%), followed by PP domed villi (8.1%), tips of absorptive villi (3.8%), and ileal crypt regions (0.5%), Severe infection with REPEC O103 resulted in a significant decrease in apoptosis in PP germinal centers (determined by TUNEL assay; P = 0.01), in the tips of ileal absorptive villi (determined by H&E staining; P = 0.04), and in whole ileal cell lysates (determined by caspase 3 assay; P = 0.001). We concluded that REPEC O103 does not promote apoptosis, Furthermore, we cannot rule out the possibility that REPEC O103, in fact, decreases apoptotic levels in the rabbit ileum.
O'Brien, B., Harmon, B.V., Cameron, D.P. & Allan, D.J. 2000, 'Nicotinamide prevents the development of diabetes in the cyclophosphamide-induced NOD mouse model by blocking beta cell apoptosis', Journal of Pathology, vol. 191, no. 1, pp. 86-92.
View/Download from: UTSePress
The development of diabetes in non-obese diabetic (NOD) mice, which normally takes between 3 and 7 months, can be accelerated by cyclophosphamide (CY) injections, with rapid progression to diabetes within only 23 weeks. This insulin-dependent diabetes mellitus (IDDM) can be prevented or delayed in CY-treated NOD mice by nicotinamide (NA). The present study was undertaken to determine the mode of cell death responsible for the development of IDDM in CYtreated male NOD mice and to investigate the effect of NA on beta-cell death. Apoptotic beta cells were present within the islets of Langerhans in haematoxylin and eosin-stained sections of the pancreata harvested from 3- and 12-week-old male NOD mice, from 8 h until 14 days after a single intraperitoneal injection of CY (150 mg/kg body weight). The maximum amount of betacell apoptosis in 3-week-old animals occurred 12 days after CY treatment (20 apoptotic cells per 100 islets), after which time levels of apoptosis declined steadily throughout the 14-day period studied. The incidence of beta-cell apoptosis in 12-week-old male NOD mice occurred in two peaks; the rst was recorded 824 h after CY treatment (30 apoptotic cells/100 islets), while the second, at 7 days (36 apoptotic cells per 100 islets), coincided with increased insulitis. Administration of NA 15 min before CY treatment, and thereafter daily, substantially reduced the amount of apoptosis and effectively eliminated (4 apoptotic cells per 100 islets) the second wave of beta-cell apoptosis seen at day 7 in 12-week-old animals given CY alone. These results show that apoptosis is the mode of beta-cell death responsible for the development of CY-induced IDDM and that prevention of IDDM by NA is associated with a reduction in beta-cell apoptosis.
Allan, D.J., Cameron, D.P., Harmon, B.V. & O'Brien, B. 1997, 'Apoptosis is the mode of beta-cell death responsible for the development of IDDM in the nonobese diabetic (NOD) mouse', Diabetes, vol. 46, no. 5, pp. 750-757.
View/Download from: UTSePress |
The NOD/Lt mouse, a widely used model of human autoimmune IDDM, was used to establish the mode of beta-cell death responsible for the development of IDDM. Apoptotic cells were present within the islets of Langerhans in hematoxylin and eosin-stained sections of pancreases harvested from 3- to 18-week-old female NOD/Lt mice (a range of 11-50 apoptotic cells per 100 islets). Immunohistochemical localization of insulin to the dying cells confirmed the beta-cell origin of the apoptosis. Although some islets from age-matched control female NOD/scid mice contained apoptotic cells, virtually all of these cells were insulin negative as determined by immunohistochemistry. The small number of apoptotic insulin-positive cells identified in islets from NOD/scid mice (a range of 0-1 apoptotic cells per 100 islets) was not statistically significant, compared with the numbers recorded in NOD/Lt mice. All dying cells showed the morphological changes characteristic of cell death by apoptosis and stained positively with the TUNEL method for end-labeling DNA strand breaks. The maximum mean amount of beta-cell apoptosis occurring in NOD/Lt mice was at week 15 (50 apoptotic cells per 100 islets), which coincided with the earliest onset of diabetes as determined by blood glucose, urine glucose, and pancreatic immunoreactive insulin measurements. While there was no peak incidence of beta-cell apoptosis throughout the time period studied (weeks 3-18), the incidence of apoptosis decreased at week 18, by which time 50% of the animals had overt diabetes. The low levels of beta-cell apoptosis observed is indicative of a gradual deletion of the beta-cell population throughout the extensive preclinical period seen in this model and would be sufficient to account for the beta-cell loss resulting in IDDM. Apoptosis of beta-cells preceded the appearance of T-cells (CD3-positive by immunohistochemistry) in islets.
O'Brien, B., Harmon, B.V., Cameron, D.P. & Allan, D.J. 1996, 'Beta cell apoptosis is responsible for the development of IDDM in the multiple low-dose streptozotocin model', Journal Of Pathology, vol. 178, pp. 176-181.
View/Download from: UTSePress
Although insulin-dependent diabetes mellitus (IDDM) results from irreversible loss of beta cells, the mode of cell death responsible for this loss has not previously been categorized. In this study, the multiple low-dose streptozotocin (stz) model (intraperitoneal injection of stz at a concentration of 40 mglkg body weight per day for five consecutive days) was used to investigate beta-cell death during the development of IDDM in male C57B116 mice. Apoptotic cells were evident by light microscopy within the islets of Langerhans of treated animals from day 2 (the day of the second stz injection) until day 17. Immunohistochemical localization of insulin to the dying cells confirmed the beta-cell origin of the apoptosis. Two peaks in the incidence of beta-cell apoptosis occurred: the first at day 5, which corresponded to an increase in blood glucose concentration, and the second at day 11, when lymphocytic infiltration of the islets (insulitis) was maximal. Insulitis did not begin until day 9, by which time treated animals had developed overt diabetes as revealed by blood glucose and pancreatic immunoreactive insulin (IRI) measurements. Beta-cell apoptosis preceded the appearance of T-cells in the islets and continued throughout the period of insulitis. Thus, whether induced by stz or a subsequent immune response, apoptosis is the mode of cell death responsible for beta-cell loss in the multiple low-dose stz model of IDDM.