Prednisolone inhibits hyperosmolarity-induced expression of MCP-1 via NF-κB in peritoneal mesothelial cells

Abstract

The mechanism of peritoneal fibrosis in patients on continuous ambulatory peritoneal dialysis (CAPD) is poorly elucidated. We investigated the cellular mechanism of high-glucose-induced expression of monocyte chemoattractant protein-1 (MCP-1), which is important in recruiting monocytes into the peritoneum and progression of peritoneal fibrosis, and examined the inhibitory mechanism of glucocorticoids. Rat peritoneal mesothelial cells were cultured in high-glucose-containing medium and then analyzed for phosphorylation levels of p42/44 and p38 mitogen-activated protein (MAP) kinases (MAPK), MAPK or extracellular signal-regulated kinase kinase (MEK)1/2, c-Jun N-terminal kinase (JNK)1/2, and protein kinase C (PKC) by Western blotting. Expression of MCP-1 was examined by reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. DNA-binding activity of nuclear factor (NF)-kappaB was measured by electrophoretic mobility shift assay. High glucose increased MCP-1 mRNA and MCP-1 protein expression. Although glucose increased phosphorylation of MEK1/2, p42/44 MAPK, p38 MAPK, JNK1/2, and PKC, and DNA-binding activity of NF-kappaB, its effect on MCP-1 expression was suppressed only by PKC and NF-kappaB inhibitors. Mannitol caused a similar increase in PKC and NF-kappaB activation and MCP-1 synthesis. Prednisolone increased I-kappaB-alpha expression and inhibited glucose/mannitol-induced NF-kappaB DNA binding and MCP-1 expression without affecting PKC phosphorylation. The inhibitory effects of prednisolone on MCP-1 expression were reversed by mifepristone, a glucocorticoid receptor antagonist. Our results indicate that glucose induces MCP-1 mainly through hyperosmolarity by activating PKC and its downstream NF-kappaB, and that such effect was inhibited by prednisolone, suggesting the efficacy of prednisolone in preventing peritoneal fibrosis in patients on CAPD.

Hypertonicity-Induced Expression of Monocyte Chemoattractant Protein-1 through a Novel Cis-Acting Element and MAPK Signaling Pathways

“…These results thus indicate that, PKC, NADPH oxidase, and H 2 O 2 , which are related to NF-kB activation, may not be involved in the signaling pathways underlying MCP1 induction in response to hyperosmolar NaCl or mannitol in NRK52 E cells. This finding differs from the previous findings of Matsuo et al (6) using peritoneal mesothelial cells, and it might be due to the difference in cell types used in this study, although further study is needed for clarification.…”

“…Matsuo et al (6) reported that hyperosmolar mannitol induced MCP1 mRNA and protein through the activation of PKC and NF-kB in peritoneal mesothelial cells. PKC activates NADPH-oxidase, leading to the production of reactive oxygen species, and in turn the reactive oxygen species activate NF-kB transcription factor through the phosphorylation of Ik-B, followed by proteasome degradation, which induces expression of NF-kB-regulated genes (8,40).…”

“…Recently, Matsuo et al (6) reported that in peritoneal mesothelial cells, mannitol at a dose of 140 mM induced expression of MCP1 mRNA and protein through PKC activation and a NF-kB cisacting element localized in the distal region of the MCP1 gene. However, previous studies on the molecular mechanisms of protective adaptation to hyperosmolality identified a hypertonicity-sensitive cisacting element, TonE/ORE, localized in the BGT1 (11) and aldose reductase (AR) genes (12).…”

“…In addition to renal fibrosis, MCP1 is also implicated in the pathogenesis of peritoneal fibrosis. In peritoneal fibrosis, it has been suggested that high glucose concentration in conventional peritoneal dialysis solutions, which are used for continuous ambulatory peritoneal dialysis, plays a role in fibrotic lesions by increasing MCP1 gene expression (5,6).…”

“…High glucose, for instance, stimulates MCP1 gene expression by activating AP1 (5), or protein kinase C (PKC) and NF-kB (6), in peritoneal mesothelial cells. High glucose also increases MCP1 mRNA levels in renal mesangial cells through NF-kB activation (7), which provides insight into understanding the development of diabetic nephropathy.…”