Pancreatic Stellate Cells Serve as a Brake Mechanism on Pancreatic Acinar Cell Calcium Signaling with Modulation by Methionine Sulfoxide Reductase Expression

Abstract

Although methionine sulfoxide reductase (Msr) is known to modulate activity of multiple functional proteins, roles of Msr in pancreatic stellate cell physiology have not been reported. In the present work we investigated expression and function of Msr in freshly isolated and cultured rat pancreatic stellate cells. Msr expression was determined by RT‐PCR, Western blot and immunocytochemistry. Msr over‐expression was achieved by transfection with adenovirus vectors. Pancreatic stellate cells were co‐cultured with pancreatic acinar cells AR4‐2J in monolayer culture. Pancreatic stellate and acinar cell function was monitored by Fura‐2 calcium imaging. Rat pancreatic stellate cells were found to express MsrA, B1, B2, their expressions diminished in culture. Over‐expressions of MsrA, B1, or B2 were found to enhance ATP‐stimulated calcium increase but decreased reactive oxygen species production and lipopolysaccharide‐elicited IL‐1 production. Pancreatic stellate cell‐co‐culture with AR4‐2J blunted cholecystokinin‐ and acetylcholine‐stimulated calcium increases in AR4‐2J, depending on acinar / stellate cell ratio, this inhibition was reversed by MsrA, B1 over‐expression in stellate cells or by Met supplementation in co‐culture medium. Different from the pancreatic acinar cells, although pancreatic stellate cells also express the cholecystokinin 1 receptor, the receptor is not coupled to calcium signaling. In addition, Msr‐overexpression only partially restored cholecystokinin 1 receptor coupling to the calcium signaling pathway in pancreatic stellate cells, whereas addition of free Met in the culture medium had no effect. These data suggest that Msr play important roles in pancreatic stellate cell function and the stellate cells may serve as a brake mechanism on pancreatic acinar cell calcium signaling modulated by stellate cell Msr expression. Pancreatic stellate cell cholecystokinin 1 receptor is de‐coupled from calcium signaling, Msr overexpression only partially restores cholecystokinin‐stimulation of calcium increases at high CCK concentrations in the stellate cells.Support or Funding InformationThis work was supported by grants from NSFC (31670856, 31971170).Figure 1