Cultured rat mesothelial cells generate hydrogen peroxide: a new player in peritoneal defense?

This study was designed to examine whether rat peritoneal mesothelial cells in culture could generate hydrogen peroxide in different experimental conditions. Mesothelial cells, incubated in M-199, spontaneously released hydrogen peroxide. This process was significantly increased by addition of phorbol myristate acetate, as well as of superoxide dismutase to the medium, whereas it was substantially inhibited by catalase. Exposure of mesothelial cells to modified M-199 medium with 1.5% glucose concentration-lactated peritoneal dialysis solution did not seem to interfere either with the spontaneous release of hydrogen peroxide, or with that induced by phorbol myristate acetate. Furthermore, exposure of mesothelial cells to the glucose (4.25%) peritoneal dialysis solution in Medium M-199, was coincident with increased hydrogen peroxide generation, which was significantly higher than the spontaneous release, and not far from that observed with phorbol myristate acetate and superoxide dismutase. So far, it can be inferred from this evidence that peritoneal mesothelial cells in culture are not only endowed with the capability of producing hydrogen peroxide, but they can also be activated to do so in a way comparable to that observed in neutrophils and macrophages. This attribute is one more indication that mesothelial cells play a relevant role in the peritoneal mechanism of defense against infection. On the other hand, continuous exposure of mesothelial cells to glucose-enriched fluids, as occurs in clinical continuous ambulatory peritoneal dialysis, may well also be at the origin of a process of continuous injury, resulting from an increased hydrogen peroxide generation.