Pancreatic acinar-specific overexpression of Reg2 gene offered no protection against either experimental diabetes or pancreatitis in mice

Abstract

Reg proteins are normally expressed in pancreatic acinar cells, and the level of several of these proteins was significantly induced upon damage to the endocrine or exocrine pancreas. It has been established that Reg1 and pancreatic islet neogenesis-associated protein [INGAP, Reg3␦] promote the growth or regeneration of the endocrine islet cells. Recent reports suggest that Reg2 is an autoantigen normally expressed in islet ␤-cells. Reg2 overexpression in vitro offered protection to insulinoma cells. Overexpressed Reg3␣ increased cyclin D1 and CDK4 levels and the rate of proliferation in insulinoma cells. Acinar-specific overexpression of INGAP increased ␤-cell mass and protected the animals from streptozotocin-induced diabetes. Moreover, Reg2 gene expression was induced during pancreatitis. We hypothesized that Reg2 is a secreted protein that promotes the growth, survival, and/or regeneration of pancreatic endocrine and exocrine cells. To test its effectiveness, we used elastase-1 promoter (Ela-Reg2) to develop an acinar cell-specific overexpression of the Reg2 gene. Western blot analysis, real-time PCR, and immunohistochemistry revealed barely detectable levels of endogenous Reg2 in the pancreas of normal wild-type mice and increased Reg2 levels in the pancreas of Ela-Reg2 mice that were similar to or higher than Reg2 levels induced in experimental diabetes or pancreatitis. Compared with wild-type littermates, growth, blood glucose and insulin levels, and glucose tolerance were normal in Ela-Reg2 mice; pancreatic histology revealed no change in endocrine or exocrine tissues. Acinar-specific overexpression of the Reg2 gene offered no protection against streptozotocin-induced ␤-cell damage and diabetes, in hyperglycemia and weight loss, and no advantage in restoring glucose homeostasis and islet function within 3 mo. Furthermore, serum amylase level and pancreatic histochemistry showed that Reg2 overexpression did not protect acinar cells against caerulein-induced acute pancreatitis. In contrast to INGAP or Reg3␤, exocrine overexpression of Reg2 offered no protection to the endocrine or exocrine pancreas, indicating clear subtype specificities of the Reg family of proteins.caerulein; immunohistochemistry; pancreatic islets; streptozotocin; transgenic mice REG PROTEINS CONSTITUTE a conserved family of seven members (Reg1, Reg2, Reg3␣, Reg3␤, Reg3␦, Reg3␥, and Reg4) in rodents; their production in the pancreas (including the islets of Langerhans) was induced upon endocrine ␤-cell or exocrine acinar cell damage (2,11,14,15). While some of these proteins [Reg1 and islet neogenesis-associated protein (INGAP or Reg3␦)] have been implicated in promoting ␤-cell replication and/or neogenesis in in vivo studies in transgenic and knockout mice (24 -26, 32), the roles of the other five proteins have not been well characterized. A unique seven-amino acid insertion (QVAEEDE) near its NH 2 terminus distinguishes Reg2 (found only in mice and hamsters) from other Reg proteins (4, 29). Results from a recent dual-labeled immunohi...

Four Decades After the Discovery of Regenerating Islet-Derived (Reg) Proteins: Current Understanding and Challenges

“…In contrast, transgenic non-obese diabetic (NOD) mice expressing Reg from the rat insulin II promoter (Ins-Reg) show increased β-cell regeneration and diminished hyperglycemia. Such findings and the reported mitogenic effects on β-cells (Michael et al, 1996; Borelli et al, 2005; Cox et al, 2015) support the notion that Reg proteins may serve as biomarkers (Astorri et al, 2010) and treatment targets for diabetes (Watanabe et al, 1994; Gross et al, 1998; Gurr et al, 2002; Li et al, 2010; Hou et al, 2011). For instance, administration of Reg protein induces β-cell mass expansion in female NOD mice (Gross et al, 1998) and rats with surgical diabetes (Watanabe et al, 1994).…”

Karyopherin Alpha 2-Expressing Pancreatic Duct Glands and Intra-Islet Ducts in Aged Diabetic C414A-Mutant-CRY1 Transgenic Mice

“…We focused REG2 and REG3 β , because the proteins are known to be abundantly expressed in pancreatic acinar cells in the normal condition [26] and induced in response to various pathological conditions such as diabetes and pancreatitis in mice. As to protective effects of the REGs in the endocrine and exocrine cells in the pancreas against the generation of diabetes and acute pancreatitis, its roles in the pancreas are still not decisive in spite of extensive studies using gene-manipulated mice [27–29]. Our result suggests the possibility that the reduced expression of Reg2 and Reg3 β genes in the pancreas might have some roles in accelerating the pathophysiological conditions of the pancreas in TGs (Figure 8).…”

Recombinant Reg3β protein protects against streptozotocin-induced β-cell damage and diabetes

“…DNA damage and some particular feedback mechanism can further interact with Reg gene transcription 24 . Nevertheless, the auto-induced Reg gene expression is unfortunately insufficient to achieve a protective outcome that will defend against islet β-cell destruction, even in Reg2-overexpressed transgenic mice 11 . Thus, we questioned whether there was any distinction between endogenous overexpression and exogenous administration of Reg protein affecting its bioactivities.…”

“…To reveal their possible contribution to the protective effect, we thereafter developed two mouse models with pancreatic-specific overexpressed Reg2 and Reg3β. Interestingly, acinar overexpression of Reg2 offered no protection while islet-specific Reg3β predominantly ameliorated the hyperglycemia and body weight reduction caused by Stz 11 12 . Given this result, Reg3β was chosen for the preparation of recombinant protein and its effectiveness in treating diabetes was assessed in the present study.…”