Early manifestations in multiple-low-dose streptozotocin-induced diabetes in mice

Macrophage inflammatory state in Type 1 diabetes: triggered by NLRP3/iNOS pathway and attenuated by docosahexaenoic acid

Type 1 diabetes mellitus (T1D) is a chronic autoimmune disease characterized by insulin-producing pancreatic β-cell destruction and hyperglycemia. While monocytes and NOD-like receptor family-pyrin domain containing 3 (NLRP3) are associated with T1D onset and development, the specific receptors and factors involved in NLRP3 inflammasome activation remain unknown. Herein, we evaluated the inflammatory state of resident peritoneal macrophages (PMs) from genetically modified non-obese diabetic (NOD), NLRP3-KO, wild-type (WT) mice and in peripheral blood mononuclear cells (PBMCs) from human T1D patients. We also assessed the effect of docosahexaenoic acid (DHA) on the inflammatory status. Macrophages from STZ-induced T1D mice exhibited increased inflammatory cytokine/chemokine levels, nitric oxide (NO) secretion, NLRP3 and iNOS protein levels, and augmented glycolytic activity compared to control animals. In PMs from NOD and STZ-induced T1D mice, DHA reduced NO production and attenuated the inflammatory state. Furthermore, iNOS and IL-1β protein expression levels and NO production were lower in the PMs from diabetic NLRP3-KO mice than from WT mice. We also observed increased IL-1β secretion in PBMCs from T1D patients and immortalized murine macrophages treated with advanced glycation end products and palmitic acid. The present study demonstrated that the resident PMs are in a proinflammatory state characterized by increased NLRP3/iNOS pathway-mediated NO production, up-regulated proinflammatory cytokine/chemokine receptor expression and altered glycolytic activity. Notably, ex vivo treatment with DHA reverted the diabetes-induced changes and attenuated the macrophage inflammatory state. It is plausible that DHA supplementation could be employed as adjuvant therapy for treating individuals with T1D.

Ethanolic extracts of Pluchea indica (L.) leaf pretreatment attenuates cytokine-induced β-cell apoptosis in multiple low-dose streptozotocin-induced diabetic mice

Loss of β-cell mass and function is a fundamental feature of pathogenesis for type 1 and type 2 diabetes. Increasing evidence indicates that apoptosis is one of the main mechanisms of β-cell death in both types. Ethanolic extracts of Pluchea indica leaf (PILE) have been reported to possess blood glucose lowering actions in vivo. Nevertheless, further study is required to determine the underlying mechanisms. In this report, we have investigated the preventive effects of PILE on multiple low doses of streptozotocin (MLDS)-induced β-cell apoptosis. Mice were pre-treated with PILE at 50 mg/kg (PILE 50) or 100 mg/kg (PILE 100) for 2 weeks before streptozotocin (STZ) stimulation, and the treatment continued for 4 or 8 weeks. Results revealed that PILE 100 mice exhibited improved blood biochemistry, maintained a higher body weight, had decreased hyperglycemia, and restored islet architectures compared to non-treated STZ mice. Significantly, PILE 100 decreased levels of inflammatory response markers interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), and interlukin1-β (IL-1β), concomitant with the inhibition of caspase-3, caspase-8, capsepase-9, phosphorylation of signal transducer and activator of transcription 1 (pSTAT1), nuclear factor-κBp65 (NF-κBp65), and inducible nitric oxide synthase (iNOS). Additionally, survival and proliferative ability of β-cells was mediated by up-regulated Bcl-2 and Ki67, respectively. These results provide strong evidence that pretreatment with PILE 100 effectively attenuated STZ-induced diabetes-related symptoms and these effects could be associated with the inhibition of cytokine-induced β-cell apoptosis.

Rodent models of diet-induced type 2 diabetes mellitus: A literature review and selection guide

Several research teams have focused on finding the "ideal" animal model that reflects the pathophysiological changes and closely simulates the metabolic characteristics of patients with type 2 diabetes. However, the multitude of studies on this topic has resulted in large variations, making the models difficult to compare, as the measured parameters vary significantly. Additionally, selecting the appropriate animal model for a new study has become more difficult due to the increasing number of background variables. This article gives a detailed overview of the literature, covering the entire range of animal models and model characteristics, and most importantly, provides guidance for selecting the most suitable model for specific research goals in the future.

Lentinan protects pancreatic β cells from STZ-induced damage

Pancreatic β‐cell death or dysfunction mediated by oxidative stress underlies the development and progression of diabetes mellitus (DM). In this study, we evaluated the effect of lentinan (LNT), an active ingredient purified from the bodies of Lentinus edodes, on pancreatic β‐cell apoptosis and dysfunction caused by streptozotocin (STZ) and the possible mechanisms implicated. The rat insulinoma cell line INS‐1 were pre‐treated with the indicated concentration of LNT for 30 min. and then incubated for 24 hrs with or without 0.5 mM STZ. We found that STZ treatment causes apoptosis of INS‐1 cells by enhancement of intracellular reactive oxygen species (ROS) accumulation, inducible nitric oxide synthase (iNOS) expression and nitric oxide release and activation of the c‐jun N‐terminal kinase (JNK) and p38 mitogen‐activated protein kinase (MAPK) signalling pathways. However, LNT significantly increased cell viability and effectively attenuated STZ‐induced ROS production, iNOS expression and nitric oxide release and the activation of JNK and p38 MAPK in a dose‐dependent manner in vitro. Moreover, LNT dose‐dependently prevented STZ‐induced inhibition of insulin synthesis by blocking the activation of nuclear factor kappa beta and increasing the level of Pdx‐1 in INS‐1 cells. Together these findings suggest that LNT could protect against pancreatic β‐cell apoptosis and dysfunction caused by STZ and therefore may be a potential pharmacological agent for preventing pancreatic β‐cell damage caused by oxidative stress associated with diabetes.

Generation of insulin-producing cells from C3H10T1/2 mesenchymal progenitor cells

Mesenchymal stem cells (MSCs) have been reported to be an attractive source for the generation of transplantable surrogate β cells. A murine embryonic mesenchymal progenitor cell line C3H10T1/2 has been recognized as a model for MSCs, because of its multi-lineage differentiation potential. The purpose of this study was to explore whether C3H/10T1/2 cells have the potential to differentiate into insulin-producing cells (IPCs). Here, we investigated and compared the in vitro differentiation of rat MSCs and C3H10T1/2 cells into IPCs. After the cells underwent IPC differentiation, the expression of differentiation markers were detected by immunocytochemistry, reverse transcription-polymerase chain reaction (RT-PCR), quantitative real-time RT-PCR (qRT-PCR) and Western blotting. The insulin secretion was evaluated by enzyme-linked immunosorbent assay (ELISA). Furthermore, these differentiated cells were transplanted into streptozotocin-induced diabetic mice and their biological functions were tested in vivo. This study reports a 2-stage method to generate IPCs from C3H10T1/2 cells. Under specific induction conditions for 7-8 days, C3H10T1/2 cells formed three-dimensional spheroid bodies (SBs) and secreted insulin, while generation of IPCs derived from rat MSCs required a long time (more than 2 weeks). Furthermore, these IPCs derived from C3H10T1/2 cells were injected into diabetic mice and improves basal glucose, body weight and exhibited normal glucose tolerance test. The present study provided a simple and faithful in vitro model for further investigating the mechanism underlying IPC differentiation of MSCs and cell replacement therapy for diabetes.

The antidiabetic effect of mesenchymal stem cells is unrelated to their transdifferentiation potential but to their capability to restore Th1/Th2 balance and to modify the pancreatic microenvironment

Type 1 diabetes mellitus (T1DM) is a chronic metabolic disease that results from cell-mediated autoimmune destruction of insulin-producing cells. In T1DM animal models, it has been shown that the systemic administration of multipotent mesenchymal stromal cells, also referred as to mesenchymal stem cells (MSCs), results in the regeneration of pancreatic islets. Mechanisms underlying this effect are still poorly understood. Our aims were to assess whether donor MSCs (a) differentiate into pancreatic β-cells and (b) modify systemic and pancreatic pathophysiologic markers of T1DM. After the intravenous administration of 5 × 10(5) syngeneic MSCs, we observed that mice with T1DM reverted their hyperglycemia and presented no donor-derived insulin-producing cells. In contrast, 7 and 65 days post-transplantation, MSCs were engrafted into secondary lymphoid organs. This correlated with a systemic and local reduction in the abundance of autoaggressive T cells together with an increase in regulatory T cells. Additionally, in the pancreas of mice with T1DM treated with MSCs, we observed a cytokine profile shift from proinflammatory to antinflammatory. MSC transplantation did not reduce pancreatic cell apoptosis but recovered local expression and increased the circulating levels of epidermal growth factor, a pancreatic trophic factor. Therefore, the antidiabetic effect of MSCs intravenously administered is unrelated to their transdifferentiation potential but to their capability to restore the balance between Th1 and Th2 immunological responses along with the modification of the pancreatic microenvironment. Our data should be taken into account when designing clinical trials aimed to evaluate MSC transplantation in patients with T1DM since the presence of endogenous precursors seems to be critical in order to restore glycemic control.

Unraveling pancreatic islet biology by quantitative proteomics

The pancreatic islets of Langerhans play a critical role in maintaining blood glucose homeostasis by secreting insulin and several other important peptide hormones. Impaired insulin secretion due to islet dysfunction is linked to the pathogenesis underlying both Type 1 and Type 2 diabetes. Over the past 5 years, emerging proteomic technologies have been applied to dissect the signaling pathways that regulate islet functions and gain an understanding of the mechanisms of islet dysfunction relevant to diabetes. Herein, we briefly review some of the recent quantitative proteomic studies involving pancreatic islets geared towards gaining a better understanding of islet biology relevant to metabolic diseases.

Prevention of experimental diabetes by Uncaria tomentosa extract: Th2 polarization, regulatory T cell preservation or both?

ETHNOPHARMACOLOGICAL RELEVANCE

Uncaria tomentosa (Willd.) DC (Rubiaceae) is a species native to the Amazon rainforest and surrounding tropical areas that is endowed with immunomodulatory properties and widely used around the world. In this study we investigated the immunomodulatory potential of Uncaria tomentosa (UT) aqueous-ethanol extract on the progression of immune-mediated diabetes.

MATERIALS AND METHODS

C57BL/6 male mice were injected with MLDS (40 mg/kg) and orally treated with UT at 10-400mg/kg during 21 days. Control groups received MLDS alone or the respective dilution vehicle. Pancreatic mononuclear infiltrate and β-cell insulin content were analyzed by HE and immunohistochemical staining, respectively, and measured by digital morphometry. Lymphocyte immunophenotyping and cytokine production were determined by flow cytometry analysis.

RESULTS

Treating the animals with 50-400mg/kg of UT caused a significant reduction in the glycemic levels, as well as in the incidence of diabetes. The morphometric analysis of insulitis revealed a clear protective effect. Animals treated with UT at 400mg/kg presented a higher number of intact islets and a significant inhibition of destructive insulitis. Furthermore, a significant protection against the loss of insulin-secreting presented β-cells was achieved, as observed by a careful immunohistochemical evaluation. The phenotypic analysis indicated that the groups treated with higher doses (100-400mg/kg) presented CD4(+) and CD8(+) T-cell values similar to those observed in healthy animals. These same higher doses also increased the number of CD4(+)CD25(+)Foxp3(+) regulatory T-cells. Moreover, the extract modulated the production of Th1 and Th2, with increased levels of IL-4 and IL-5.

CONCLUSIONS

The extract was effective to prevent the progression of immune-mediated diabetes by distinct pathways.

High pancreatic n-3 fatty acids prevent STZ-induced diabetes in fat-1 mice: inflammatory pathway inhibition

OBJECTIVE

Because of confounding factors, the effects of dietary n-3 polyunsaturated fatty acids (PUFA) on type 1 diabetes remain to be clarified. We therefore evaluated whether fat-1 transgenic mice, a well-controlled experimental model endogenously synthesizing n-3 PUFA, were protected against streptozotocin (STZ)-induced diabetes. We then aimed to elucidate the in vivo response at the pancreatic level.

RESEARCH DESIGN AND METHODS

β-Cell destruction was produced by multiple low-doses STZ (MLD-STZ). Blood glucose level, plasma insulin level, and plasma lipid analysis were then performed. Pancreatic mRNA expression of cytokines, the monocyte chemoattractant protein, and GLUT2 were evaluated as well as pancreas nuclear factor (NF)-κB p65 and inhibitor of κB (IκB) protein expression. Insulin and cleaved caspase-3 immunostaining and lipidomic analysis were performed in the pancreas.

RESULTS

STZ-induced fat-1 mice did not develop hyperglycemia compared with wild-type mice, and β-cell destruction was prevented as evidenced by lack of histological pancreatic damage or reduced insulin level. The prevention of β-cell destruction was associated with no proinflammatory cytokine induction (tumor necrosis factor-α, interleukin-1β, inducible nitric oxide synthase) in the pancreas, a decreased NF-κB, and increased IκB pancreatic protein expression. In the fat-1-treated mice, proinflammatory arachidonic-derived mediators as prostaglandin E₂ and 12-hydroxyeicosatetraenoic acid were decreased and the anti-inflammatory lipoxin A₄ was detected. Moreover, the 18-hydroxyeicosapentaenoic acid, precursor of the anti-inflammatory resolvin E1, was highly increased.

CONCLUSIONS

Collectively, these findings indicate that fat-1 mice were protected against MLD-STZ-induced diabetes and pointed out for the first time in vivo the beneficial effects of n-3 PUFA at the pancreatic level, on each step of the development of the pathology-inflammation, β-cell damage-through cytokine response and lipid mediator production.

The antidiabetic effect of MSCs is not impaired by insulin prophylaxis and is not improved by a second dose of cells

Type 1 diabetes mellitus (T1D) is due to autoimmune destruction of pancreatic beta-cells. Previously, we have shown that intravenously administered bone marrow-derived multipotent mesenchymal stromal cells (MSCs) allows pancreatic islet recovery, improves insulin secretion and reverts hyperglycemia in low doses streptozotocin (STZ)-induced diabetic mice. Here we evaluate whether insulin prophylaxis and the administration of a second dose of cells affect the antidiabetic therapeutic effect of MSC transplantation. Insulitis and subsequent elimination of pancreatic beta-cells was promoted in C57BL/6 mice by the injection of 40 mg/kg/day STZ for five days. Twenty-four days later, diabetic mice were distributed into experimental groups according to if they received or not insulin and/or one or two doses of healthy donor-derived MSCs. Three and half months later: glycemia, pancreatic islets number, insulinemia, glycated hemoglobin level and glucose tolerance were determined in animals that did not received exogenous insulin for the last 1.5 months. Also, we characterized MSCs isolated from mice healthy or diabetic. The therapeutic effect of MSC transplantation was observed in diabetic mice that received or not insulin prophylaxis. Improvements were similar irrespective if they received one or two doses of cells. Compared to MSCs from healthy mice, MSCs from diabetic mice had the same proliferation and adipogenic potentials, but were less abundant, with altered immunophenotype and no osteogenic potential.

Our preclinical results should be taken into account when designing phase II clinical trials aimed to evaluate MSC transplantation in patients with T1D. Cells should be isolated form healthy donor, insulin prophylaxis could be maintained and a second dose, after an elapse of two months, appears unnecessary in the medium-term.

Improvement of inflammatory and toxic stress biomarkers by silymarin in a murine model of type one diabetes mellitus

Type 1 diabetes mellitus (T1DM) is characterized by an impairment of the insulin-secreting beta cells with an immunologic base. Inflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β, and free radicals are believed to play key roles in destruction of pancreatic β cells. The present study was designed to investigate the effect of Silybum marianum seed extract (silymarin), a combination of several flavonolignans with immunomodulatory, anti-oxidant, and anti-inflammatory potential on streptozotocin (STZ)-induced T1DM in mouse. Experimental T1DM was induced in male albino mice by IV injection of multiplelow- doses of STZ for 5 days. Seventy-two male mice in separate groups received various doses of silymarin (20, 40, and 80 mg/kg) concomitant or after induction of diabetes for 21 days. Blood glucose and pancreatic biomarkers of inflammation and toxic stress (IL-1β, TNF-α, myeloperoxidase, lipid peroxidation, protein oxidation, thiol molecules, and total antioxidant capacity) were determined. Silymarin treatment reduced levels of inflammatory cytokines such as TNF-α and IL-1β and oxidative stress mediators like myeloperoxidase activity, lipid peroxidation, carbonyl and thiol content of pancreatic tissue in an almost dose dependent manner. No marked difference between the prevention of T1DM and the reversion of this disease by silymarin was found. Use of silymarin seems to be helpful in T1DM when used as pretreatment or treatment. Benefit of silymarin in human T1DM remains to be elucidated by clinical trials.

A novel steroid from Elephantopus scaber L. an ethnomedicinal plant with antidiabetic activity

Acetone extract of Elephantopus scaber, an ethnomedicnal plant, reduced the blood glucose levels in streptozotocin-induced diabetic rats significantly. Acute toxicity studies revealed the non-toxic nature of the crude extract. Fractionation of the acetone extract yielded a new steroid, 28Nor-22(R)Witha 2,6,23-trienolide. Biological testing of the compound demonstrated a significant antidiabetic activity by reducing the elevated blood glucose levels and restoring the insulin levels in streptozotocin-induced diabetic rats. This compound can be a useful candidate to treat diabetes.

Methadone ameliorates multiple-low-dose streptozotocin-induced type 1 diabetes in mice

Type 1 diabetes is an autoimmune disease characterized by inflammation of pancreatic islets and destruction of beta cells by the immune system. Opioids have been shown to modulate a number of immune functions, including T helper 1 (Th1) and T helper 2 (Th2) cytokines. The immunosuppressive effect of long-term administration of opioids has been demonstrated both in animal models and humans. The aim of this study was to determine the effect of methadone, a mu-opioid receptor agonist, on type 1 diabetes. Administration of multiple low doses of streptozotocin (STZ) (MLDS) (40 mg/kg intraperitoneally for 5 consecutive days) to mice resulted in autoimmune diabetes. Mice were treated with methadone (10 mg/kg/day subcutaneously) for 24 days. Blood glucose, insulin and pancreatic cytokine levels were measured. Chronic methadone treatment significantly reduced hyperglycemia and incidence of diabetes, and restored pancreatic insulin secretion in the MLDS model. The protective effect of methadone can be overcome by pretreatment with naltrexone, an opioid receptor antagonist. Also, methadone treatment decreased the proinflammatory Th1 cytokines [interleukin (IL)-1beta, tumor necrosis factor-alpha and interferon-gamma] and increased anti-inflammatory Th2 cytokines (IL-4 and IL-10). Histopathological observations indicated that STZ-mediated destruction of beta cells was attenuated by methadone treatment. It seems that methadone as an opioid agonist may have a protective effect against destruction of beta cells and insulitis in the MLDS model of type 1 diabetes.

Systemic administration of multipotent mesenchymal stromal cells reverts hyperglycemia and prevents nephropathy in type 1 diabetic mice

Multipotent mesenchymal stromal cells (MSCs), often labeled mesenchymal stem cells, contribute to tissue regeneration in injured bone and cartilage, as well as in the infarcted heart, brain, and kidney. We hypothesize that MSCs might also contribute to pancreas and kidney regeneration in diabetic individuals. Therefore, in streptozotocin (STZ)-induced type 1 diabetes C57BL/6 mice, we tested whether a single intravenous dose of MSCs led to recovery of pancreatic and renal function and structure. When hyperglycemia, glycosuria, massive beta-pancreatic islets destruction, and mild albuminuria were evident (but still without renal histopathologic changes), mice were randomly separated in 2 groups: 1 received 0.5 x 10(6) MSCs that have been ex vivo expanded (and characterized according to their mesenchymal differentiation potential), and the other group received the vehicle. Within a week, only MSC-treated diabetic mice exhibited significant reduction in their blood glucose levels, reaching nearly euglycemic values a month later. Reversion of hyperglycemia and glycosuria remained for 2 months at least. An increase in morphologically normal beta-pancreatic islets was observed only in MSC-treated diabetic mice. Furthermore, in those animals albuminuria was reduced and glomeruli were histologically normal. On the other side, untreated diabetic mice presented glomerular hyalinosis and mesangial expansion. Thus, MSC administration resulted in beta-pancreatic islets regeneration and prevented renal damage in diabetic animals. Our preclinical results suggest bone marrow-derived MSC transplantation as a cell therapy strategy to treat type 1 diabetes and prevent diabetic nephropathy, its main complication.

The radical scavenger edaravone counteracts diabetes in multiple low-dose streptozotocin-treated mice

Edaravone is a potent scavenger of hydroxyl radicals and attenuates oxidative damage-related neurodegenerative diseases. Previous studies suggest that oxidative stress plays a key role in the pathogenesis of diabetes. The present study examined the effect of edaravone on diabetes in multiple low-dose streptozotocin-treated mice. Mice treated with low-doses of streptozotocin for five consecutive days showed progressive hyperglycemia and an increased incidence of diabetes. Daily treatment with edaravone during the streptozotocin injections counteracted the multiple low-dose streptozotocin-induced hyperglycemia in a dose-dependent manner. Edaravone protected against the multiple low-dose streptozotocin-induced reduction in pancreatic insulin. The suppressive effects of edaravone were also observed when it was administered after the last injection of streptozotocin. Histochemical examination showed that multiple low-dose streptozotocin treatment caused mononuclear cell infiltration in pancreatic islets, followed by hyperglycemia, and that edaravone significantly inhibited the multiple low-dose streptozotocin-induced insulitis. Multiple low-dose streptozotocin treatment also increased the lipid peroxidation product thiobarbituric acid reactive substance in pancreatic tissues of mice, and this effect was completely inhibited by edaravone. These findings suggest that edaravone, even after streptozotocin treatment, counteracts the development of multiple low-dose streptozotocin-induced diabetes by scavenging free radicals, which are possible mediators of the immune destruction of islet beta cells.

A potent immunomodulatory compound, (S,R)-3-Phenyl-4,5-dihydro-5-isoxazole acetic acid, prevents spontaneous and accelerated forms of autoimmune diabetes in NOD mice and inhibits the immunoinflammatory diabetes induced by multiple low doses of streptozotocin in CBA/H mice

(S,R)-3-Phenyl-4,5-dihydro-5-isoxasole acetic acid (VGX-1027) is an isoxazole compound that exhibits various immunomodulatory properties. The capacity of VGX-1027 to prevent interleukin (IL)-1beta plus interferon-gamma-induced pancreatic islet death in vitro prompted us to evaluate its effects on the development of autoimmune diabetes in preclinical models of human type 1 diabetes mellitus (T1D). Administration of VGX-1027 to NOD mice with spontaneous or accelerated forms of diabetes induced either by injection of cyclophosphamide or by transfer of spleen cells from acutely diabetic syngeneic donors markedly reduced the cumulative incidence of diabetes and insulitis. In addition, VGX-1027 given either i.p. or p.o. to CBA/H mice made diabetic with multiple low doses of streptozotocin successfully counteracted the development of destructive insulitis and hyperglycemia. The animals receiving VGX-1027 exhibited reduced production of the proinflammatory mediators tumor necrosis factor-alpha, IL-1beta, macrophage migration inhibitory factor, and inducible nitric-oxide synthase-mediated nitric oxide generation in both pancreatic islets and peripheral compartments. These results indicate that VGX-1027 probably exerts its antidiabetogenic effects by limiting cytokine-mediated immunoinflammatory events, leading to inflammation and destruction of pancreatic islets. VGX-1027 seems worthy of being considered as a candidate drug in the development of new therapeutic strategies for the prevention and early treatment of T1D.

Transplantation of rat islets transduced with human heme oxygenase-1 gene using adenovirus vector

OBJECTIVE

To investigate whether human heme oxygenase-1 (HO-1) gene has protective action on islets cultured in vitro, and to explore whether transduction of HO-1 gene to donor islets could enhance engrafted islets survival and suppress local lymphocytic infiltration in islet grafts.

METHODS

Newly isolated rat islets were isolated from the Sprague-Dawley rats and were divided into 3 groups in vitro study as follows: enhanced green fluorescent protein (EGFP) group, islets transduced with adenovirus vectors containing EGFP gene using multiplicities of infection (MOI) = 2, 5, 10, and 20 to determine the transduction efficacy; HO-1 group, islets transduced with adenovirus vectors containing human HO-1 gene using MOI = 20; and control group, mock transduced islets. Flow cytometry was used to detect apoptotic cells after induction by recombinant human tumor necrosis factor-alpha (rTNF-alpha) and cycloheximide (CHX) for 48 hours. Diabetic recipients were randomly divided into the following groups: HO-1 group (n = 9), receiving islets transduced with recombinant adenovirus-HO-1; control group (n = 9), receiving mock transduced islets; and phosphate buffer solution (PBS) group (n = 6), receiving only 0.8 mL PBS. About 1200 rat islet equivalents were transplanted into each recipient rendered by streptozotocin using the portal vein as transplant site. Allograft survival, apoptosis, and the state of lymphocytic infiltration were analyzed.

RESULTS

After treatment with rTNF-alpha and CHX, the apoptotic ratio of islet cells was 4.22% +/- 2.38% in the HO-1 group (MOI = 20), significantly lower than 23.81% +/- 8.51% in the control group (P < 0.05), and 28.76% +/- 14.76% in the EGFP group (MOI = 20; P < 0.05). Maintenance of normoglycemia was prolonged in the HO-1 group, indicated by results that islet survival time was 10.56 +/- 4.33 days significantly longer than that of untreated islets which was 5.33 +/- 4.18 days (P < 0.05). The lymphocytic infiltration degree in engrafted islets treated with HO-1 gene was lower than that in the control group.

CONCLUSIONS

HO-1 gene overexpression in rat islets by adenovirus transduction can protect cultured islets against rTNF-alpha and CHX-mediated cytotoxicity. HO-1 gene has cytoprotective effects on engrafted islets, which could prolong engrafted islets survival in allogenic transplantation model, and diminish the degree of lymphocytic infiltration in islet grafts. These findings suggest a potential therapeutic application for HO-1 gene in improving islet survival/function in human islet transplantation.