Young NOD mice show increased diabetes sensitivity to low doses of streptozotocin

VX-765 ameliorates renal injury and fibrosis in diabetes by regulating caspase-1-mediated pyroptosis and inflammation

INTRODUCTION

As a lytic inflammatory cell death, pyroptosis has been recently described but has not been unequivocally elucidated in diabetic nephropathy (DN). VX-765 is a safe and effective inhibitor of caspase-1, that was well tolerated in a phase II clinical trial in patients with epilepsy, but its application in DN is still undefined.

MATERIALS AND METHODS

Immunoblot, co-immunoprecipitation, confocal microscope and flow cytometry were used to analyze the effects of glucose on pyroptosis in renal tubular epithelia (HK-2). In vitro, selective caspase-1 inhibitors VX-765 and Z-YVAD-FMK were administered. Pyroptosis and fibrogenesis were determined by immunoblot, ELISA, cytotoxicity assay and flow cytometry. In vivo, diabetic mice were administered with 100 mg/kg VX-765. Renal function, pathological changes, and the expressions of NLRC4, GSDMD, IL-1β, collagen I, fibronectin and CD45 in renal cortex were evaluated.

RESULTS

We identified NLRC4 as a sensor for caspase-1 activation. Moreover, we provided morphological and molecular evidence for pyroptosis in glucose-stressed tubular cells, including ballooned cell membrane, caspase-1 immunoreactivity, GSDMD cleavage, and the release of inflammatory cytokine and cellular contents. All these effects were prevented by treatment with VX-765 or Z-YVAD-FMK, confirming that caspase-1 effectively regulates the occurrence of pyroptosis in HK-2 cells. In vivo, treatment of diabetic animals with VX-765 ameliorated renal function, suppressed inflammatory cell infiltration and pyroptosis-associated protein expression, and mitigated tubulointerstitial fibrosis.

CONCLUSIONS

This work revealed that caspase-1-mediated pyroptosis drives renal inflammation and fibrosis in diabetes. Our results are the first demonstration of VX-765 representing a promising therapeutic opportunity for alleviating the progression of DN.

Tolerogenic vaccine composited with islet-derived multipeptides and cyclosporin A induces pTreg and prevents Type 1 diabetes in murine model

Regulatory T cells (Tregs) play a crucial role in the control of the initiation and progression of type 1 diabetes (T1D). Various immunological interventions including those to ex vivo expansion Tregs transfer, in vivo induction of peripherally derived Treg (pTreg) have been considered as promising approaches for T1D therapy. In this study, we developed a novel tolerogenic vaccine using four autoantigenic peptides of islet-derived with cyclosporine A (CsA) as the pTreg inducer, designated as GAD-IN+CsA. This vaccine immunized into prediabetic NOD mice subcutaneously could induce IL-10 and TGF-β expressing pTregs and lead to suppressing autoreactive T cells responses, resulting in the prevention of T1D in these animals. Furthermore, we demonstrated that CsA with autoantigenic peptides modulates dendritic cells (DCs) to become immature IL-10^hiCD40^lo DCs. Such modulated DCs could foster naïve CD4⁺CD25⁻ T cell into Tregs when presenting antigen peptides in vitro. This novel approach offers an alternative strategy to induce pTregs to treat T1D.

Streptozotocin is equally diabetogenic whether administered to fed or fasted mice

Streptozotocin (STZ) is a selective pancreatic β cell toxin used to generate experimental hyperglycemia in rodent models. Several laboratory animal protocols suggest that STZ be administered to fasted rodents to minimize competition between STZ and glucose for low affinity GLUT2 transporters on β cells. However, whether the diabetogenic effects of multiple low dose (MLD)-STZ administration are enhanced by fasting has not been addressed. Given that repeated bouts of fasting can cause undue metabolic stress in mice, we compared the efficacy of MLD-STZ injections (50 mg/kg body weight daily for 5 days) to induce experimental hyperglycemia in both NOD/SCID/γchain(null) and C57BL/6J mice that were either ad libitum fed (STZ-Fed) or that had been fasted for 6 h (STZ-Fasted) prior to the time of STZ administration. Both STZ-Fed and STZ-Fasted mice had significantly worse glucose tolerance than vehicle-treated control mice 10 days after initiation of the MLD-STZ regimen. In C57BL/6J mice, fasting glucose levels, serum insulin levels, β cell mass, and glucose disposal during intraperitoneal glucose tolerance tests (IPGTTs) were indistinguishable between STZ-Fed and STZ-Fasted mice 20 days after MLD-STZ. The glucose intolerant phenotypes persisted for 20 weeks thereafter, irrespective of whether C57BL/6J mice were fed or fasted at the time of STZ injections. However, STZ-Fasted C57BL/6J mice experienced significant weight loss during the repeated bouts of fasting/re-feeding that were required to complete the MLD-STZ protocol. In summary, induction of experimental hyperglycemia can be achieved using the MLD-STZ protocol without repeated bouts of fasting, which have the potential to cause metabolic stress in laboratory mice.

TRAIL and DcR1 expressions are differentially regulated in the pancreatic islets of STZ- versus CY-applied NOD mice

TNF-related apoptosis-inducing ligand (TRAIL) is an important component of the immune system. Although it is well acknowledged that it also has an important role in Type 1 Diabetes (T1D) development, this presumed role has not yet been clearly revealed. Streptozotocin (STZ) and Cyclophosphamide (CY) are frequently used agents for establishment or acceleration of T1D disease in experimental models, including the non-obese diabetic (NOD) mice. Although such disease models are very suitable for diabetes research, different expression patterns for various T1D-related molecules may be expected, depending on the action mechanism of the applied agent. We accelerated diabetes in female NOD mice using STZ or CY and analyzed the expression profiles of TRAIL ligand and receptors throughout disease development. TRAIL ligand expression followed a completely different pattern in STZ- versus CY-accelerated disease, displaying a prominent increase in the former, while appearing at reduced levels in the latter. Decoy receptor 1 (DcR1) expression also increased significantly in the pancreatic islets in STZ-induced disease. Specific increases observed in TRAIL ligand and DcR1 expressions may be part of a defensive strategy of the beta islets against the infiltrating leukocytes, while the immune-suppressive agent CY may partly hold down this defense, contributing further to diabetes development.

Newly weaned nonobese diabetic mice show heightened early diabetes sensitivity to multiple low doses of streptozotocin than nondiabetes-prone CD-1 mice: initial beta-cell damage a key trigger for type 1 diabetes?

OBJECTIVES

We determined if newly weaned female nonobese diabetic (NOD) mice show greater diabetes sensitivity to dose-adjusted regimens of multiple low doses of streptozotocin (Stz) than nondiabetes-prone CD-1 mice.

METHODS

Female NOD mice received 5 daily doses of Stz from day 21 (0, 5, 10, 15, 20, 30, and 40 mg/kg body weight) and CD-1 mice 20, 30, and 40 mg.

RESULTS

: Streptozotocin, at the 15-, 20-, 30-, and 40-mg dose, induced rapid diabetes in NOD mice. By day 100, 90% to 95% of NOD mice became diabetic after the 40- and 30-mg dose and 33% to 40% with the 15- and 20-mg dose. In comparison, only about 50% and 33% of CD-1 mice developed diabetes with the 40- and 30-mg dose, respectively, and 5.5% with the 20-mg dose. In NOD mice, the 20-mg dose also partially suppressed spontaneous diabetes. All diabetic mice displayed insulitis, variable immunostaining for insulin, and redistribution of glucagon and somatostatin cells. Glucose transporter-2 was markedly attenuated in selective beta cells.

CONCLUSIONS

Newly weaned female NOD mice show heightened early sensitivity to low doses of Stz than CD-1 mice. At diabetes, several beta cells remain and show variable immunostaining for insulin and an attenuated expression for glucose transporter-2. Specific low doses of Stz may also suppress spontaneous diabetes.