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Objective: To investigate apoptotic effects of berberine, a significant alkaloids component existing in Rhizoma coptidis, and its possible acting mechanism in insulinoma cells., Methods: Different concentrations of berberine were used to treat mouse insulinoma (MIN6) cells for various period of time. The viability and apoptosis of the cells were analyzed using methylthiazolyldiphenvl-tetrazolium bromide assay, flow cytometry and enzyme-linked immuno sorbent assay. Changes in the relating pro- and anti-apoptosis proteins were detected by western-blotting., Results: The half-maximal inhibitory concentration (IC 50 ) of berberine was 5.7 μmol/L on MIN6 cells viability for 16 h. Berberine caused a 20% reduction (P<0.05) in cell number after only 4-h incubation; which reached 50% after 24 h (P<0.01). Berberine treatment for 16 h significantly increased the level of DNA fragmentation. The flow cytometry showed the apoptotic rate increased 2.9- and 4.6-fold after treating with berberine (5 μmol/L) for 8 and 16 h, while 3- and 8.7-fold after 10 μmol/L treatment for 8 and 16 h (P<0.01). Berberine treatment dramatically elevated the expression ratio of Bax to Bcl-2. Meanwhile, berberine notably increased the apoptosis-inducing factors and cytochrome C transforming from the mitochondria to the cytoplasm. Apoptotic protease-activating factor 1 (Apaf-1) was subsequently activated after cytochrome C release. Furthermore, caspase-3 and poly adenosine diphosphate-ribose polymerase were also activated to trigger apoptosis cascade., Conclusion: High concentration (5 and 10 μmol/L) of berberine could induce the apoptosis of MIN6 cells through cytochrome C/Apaf-1/caspase-3 and apoptosis inducing factor (AIF) pathway.

IGF-I is normally produced from hepatocytes and other sources, stimulates protein synthesis, cell survival, and proliferation through receptor-mediated activation of phosphatidylinositol 3-kinase and MAPK, and targets specific molecules within the pancreatic islet cells. The current study was designed to identify novel targets that may mediate its pro-islet actions. Whole-genome cDNA microarray analysis in IGF-I-overexpressing islets identified 82 genes specifically up- or down-regulated. Prominent among them was CCN5/WISP2 whose expression was increased 3- and 2-fold at the mRNA and protein levels. Dual-labeled immunofluorescence revealed that CCN5 expression was low in the β-cells of wild-type islets but was significantly induced in response to IGF-I overexpression. In vitro treatment of mouse islets with IGF-I increased both CCN5 mRNA and protein levels significantly. To define the role of CCN5 in islet cell biology, we stably overexpressed its cDNA in insulinoma MIN6 cells and detected a 2-fold increase in the proliferation of MIN6-CCN5 compared with that in control cells, which correlated with significant elevations in the levels of cyclin D1 and the phosphorylation of Akt and Erk2. Moreover, MIN6-CCN5 cells were found to be resistant to streptozotocin-induced cell death. Using confocal microscopy and subcellular fractionation, we found that overexpressed CCN5 exhibited cytoplasmic accumulation upon stimulation by high glucose. Our results indicate that CCN5, which is minimally expressed in islet β-cells, is strongly and directly induced by IGF-I. CCN5 overexpression stimulates the proliferation of insulinoma cells, activates Akt kinase, and inhibits streptozotocin-induced apoptosis, suggesting that increased CCN5 expression contributes to IGF-I-stimulated islet cell growth and/or survival.

We reported previously that pancreas-specific ablation of IGF-I in mice induced an increased expression of regenerating family proteins Reg2 and Reg3&#x03B2; in the pancreas and protected them from streptozotocin (Stz)-induced &#x03B2;-cell damage. We, therefore, assessed the effect of ectopically introduced Reg2 on Stz-induced apoptosis in MIN6 mouse insulinoma cells and report here that Reg2 protects MIN6 cells from Stz-induced apoptosis by attenuating its ability to disrupt mitochondrial membrane integrity, activate caspase-3 and promote poly-ADP ribose polymerase cleavage, and induce apoptosis. These changes correlated with suppression of c-jun N-terminal kinase (JNK) phosphorylation by Stz. Reg2 inhibited Stz-induced proapoptotic events as well as the inactivation of JNK. Inclusion of chemical inhibitor of JNK to Reg2 expressing cells rendered them sensitive to Stz. These data demonstrate that Reg2 protects insulin-producing cells against Stz-induced apoptosis by interfering with its cytotoxic signaling upstream of the intrinsic proapoptotic events by preventing its ability to inactivate JNK.

Aim: To investigate the effect of saturated fatty acid palmitate (PA) on cell viability of MIN6 beta-cell and the possible cell cycle pathways affected by PA., Methods: MIN6 cells were synchronized at G(0); phase by serum deprivation for 36 h, and further MIN6 cells were exposed to different concentrations of PA(0.25-1.0 mmol/L, 45 min-24 h)compared with control cell treated with BSA.Cell viability was assessed by MTT colorimetric assay. The cell cycle was measured by FACS analysis, and cell cycle proteins were further detected using Western blot., Results: (1)PA significantly affected the cell viability of MIN6 cells. (2)The G(0);/G(1); cell cycle arrest (n=6, P<0.05) also induced by PA, whereas MIN6 cells in S and G(2);/M phase were decreased. (3) For cell cycle proteins, PA treatment caused significant reductions in cyclin D1 and CDK4 levels, which was consistent to the cell cycle delay., Conclusion: The findings thus suggest that increased PA directly affects pancreatic beta-cell proliferation, possibly by reducing the levels of cyclin D1/CDK4 in the cells, which results in arresting in progression through the G(1); phase to the S phase of the cell cycle.

Aims: The potential effect of regenerating (Reg) proteins in the treatment of diabetes has been indicated in the past decade, but the clinical use of Reg proteins requires more advances in translational medicine. In the present study, we produced recombinant regenerating protein 2 (rReg2), to prove its protective effect against streptozocin (STZ)‐induced diabetes in BALB/c mice. Materials and Methods: rReg2 was administrated in STZ‐induced diabetic mice. Blood glucose, body weight, serum insulin and islet β‐cell loss were determined. However, Reg2 has also been reported to serve as an autoantigen that induces autoimmune attacks on islets and aggravates diabetic development in non‐obese diabetic mice. To address this contradiction, complete Freund's adjuvant was injected to generate a model that was hypersensitive to Reg2. In this model, islet CD8 T‐cell infiltration, serum Reg2 antibody and interleukin (IL)‐4 and IL‐10, and splenic CD4+/interferon (IFN)‐γ+ T cells were determined. Results: Direct rReg2 pretreatment preserved islet β‐cell mass against STZ and improved glycaemia, body weight and serum insulin content. The protection against cell death was further confirmed in cultured mouse islets and MIN6 cells. On the other hand, significant elevations of serum Reg2 antibody and splenic CD4+/IFN‐γ+ T cells, and decreases in serum IL‐4 and IL‐10 were detected in rReg2‐vaccinated mice, which may contribute to the accelerated diabetes. Interestingly, these mice, upon further rReg2 treatment, exhibited alleviated diabetic conditions with less islet CD8+ T‐cell infiltration. Conclusion: rReg2 treatment ameliorated STZ‐induced diabetes in normal BALB/c mice. By contrast, rReg2 vaccination exacerbated, but further rReg2 treatment alleviated, the severity of STZ‐induced diabetes. Thus, the protective effect of rReg2 is predominant over the autoantigenic β‐cell destruction, supporting the potential of rReg2 in the clinical treatment of diabetes. [ABSTRACT FROM AUTHOR]

The bioactive, signaling lipid, sphingosine-1-phosphate (S1P), and its analog, fingolimod (FTY720), have previously shown neuroprotective effects against ischemic brain injury. However, the underlying mechanisms have not yet been fully clarified. The roles of autophagy in ischemic stroke are being increasingly recognized. In the present study, we sought to determine whether the S1P pathway is involved in neuronal autophagy and investigate its possible mechanisms following stroke. Interestingly, we found that FTY720 significantly attenuates infarct volumes and reduces neuronal apoptosis on days 1 and 3 post stroke, accompanied by amelioration of functional deficits. Additionally, FTY720 was found to decrease the induction of autophagosome proteins, microtubule-associated protein 1 light chain 3(LC3-II) and Beclin1, following ischemic stroke in a dose-dependent manner. Meanwhile, protein levels of the mammalian target of rapamycin (mTOR) and the 70-kDa ribosomal protein, S6 kinase1 (p70S6K), were also up-regulated in FTY720-treated animals, and the nonspecific SphK inhibitor, N,N-dimethylsphingosine (DMS), was found to cause a reverse effect. Our results indicate that modulation of the S1P signaling pathway by FTY720 could effectively decrease neuronal autophagy through the mTOR/p70S6K pathway and attenuate ischemic brain injury in mice. [ABSTRACT FROM AUTHOR]

We have reported earlier that murine-regenerating gene mReg2 protects MIN6 mouse insulinoma cells from ER stress and caspase-mediated apoptosis. In apoptotic cells, DNA damage is induced by the nuclear translocation of mitochondrial apoptosis-inducing factor (AIF). Here we tested the hypothesis that mReg2 may regulate Scythe and/or hsp70 which influence the nuclear import of AIF. Treatment with thapsigargin (Tg) or doxorubicin induced an increase in nuclear AIF in MIN6 cells carrying the empty transfection vector (MIN6-VC) but not in cells overexpressing mReg2 (MIN6-mReg2). On one hand, nuclear Scythe was higher in the nucleus of MIN6-mReg2 compared with that in MIN6-VC cells. mReg2 did not alter the expression of AIF or Scythe. On the other hand, mReg2 induced the expression of hsp70 which is known to promote cytosolic retention of AIF. We conclude that mReg2 inhibits AIF-mediated apoptosis by promoting the nuclear presence of Scythe and inducing hsp70. [ABSTRACT FROM AUTHOR]

Highlights: [•] mReg2 inhibits ER stress-induced unfolded protein response in MIN6 cells. [•] mReg2 increases basal expression of GRP78 via Akt–mTORC1 signaling axis. [•] mReg2 attenuates ER stress-induced apoptosis. [•] si-RNA mediated knockdown of GRP78 blunts the protective effect of mReg2. [ABSTRACT FROM AUTHOR]

The dogma that IGF-I stimulates pancreatic islet growth has been challenged by combinational targeting of IGF or IGF-IR (IGF receptor) genes as well as beta-cell-specific IGF-IR gene deficiency, which caused no defect in islet cell growth. To assess the physiological role of locally produced IGF-I, we have developed pancreatic-specific IGF-I gene deficiency (PID) by crossing Pdx1-Cre and IGF-I/loxP mice. PID mice are normal except for decreased blood glucose level and a 2.3-fold enlarged islet cell mass. When challenged with low doses of streptozotocin, control mice developed hyperglycemia after 6 days that was maintained at high levels for at least 2 months. In contrast, PID mice only exhibited marginal hyperglycemia after 12 days, maintained throughout the experiment. Fifteen days after streptozotocin, PID mice demonstrated significantly higher levels of insulin production. Furthermore, streptozotocin-induced beta-cell apoptosis (transferase-mediated dUTP nick-end labeling [TUNEL] assay) was significantly prevented in PID mice. Finally, PID mice exhibited a delayed onset of type 2 diabetes induced by a high-fat diet, accompanied by super enlarged pancreatic islets, increased insulin mRNA levels, and preserved sensitivity to insulin. Our results suggest that locally produced IGF-I within the pancreas inhibits islet cell growth; its deficiency provides a protective environment to the beta-cells and potential in combating diabetes. [ABSTRACT FROM AUTHOR]

Regenerating gene 3α (Reg3α) protein is a trophic factor that stimulates cell and tissue proliferation, neogenesis and also acts against apoptosis and necrosis. In order to explore the potential roles of recombinant Reg3α (rReg3α), we produced a mature rReg3α polypeptide for direct administration in l -arginine (L-Arg) induced acute pancreatitis (AP) in mice. Our results showed that rReg3α stimulated cell proliferation through Erk1/2 and p38 phosphorylation and also cyclin D1 upregulation mediated by Akt/ATF-2 signaling. Moreover, rReg3α administration significantly reduced the pancreatic damage caused by L-Arg injection, as shown in histological examination and serum amylase, lipase and C-reactive protein (CRP) assays. Not only acinar cell necrosis but also apoptosis found in the pancreas of AP mice were alleviated by rReg3α. Finally, upregulated Bcl-2 and Bcl-xL and suppressed poly (ADP-ribose) synthetase/polymerase (PARP) levels were detected as being relevant to the mechanism of rReg3α protection. We therefore conclude that rReg3α acts as a protective polypeptide against AP in mice by enhancing Bcl-2 and Bcl-xL expressions and suppressing PARP level. [ABSTRACT FROM AUTHOR]