| Summary: | 碩士 === 台北醫學院 === 生物醫學技術研究所 === 89 === Advanced glycosylation end products (AGEs) have been implicated in the structural and functional alterations of proteins that occur during aging and long-term diabetes. Previously, we have demonstrated that p38 MAPK is involved in the AGEs-induced iNOS expression in C6 glioma cells. In the present study, roles of cAMP dependent protein kinase in AGEs-induced iNOS expression in RAW 264.7 macrophages were investigated. AGEs caused a dose- and time-dependent increase of nitric oxide (NO) accumulation and iNOS expression in murine RAW 264.7 macrophages. The AGEs-simulated NO production and iNOS expression was dose-dependently inhibited by the PKA inhibitor, KT 5720 (1 M) and H8 (10 M). Consistently, treatment of RAW264.7 macrophages with dibutyryl cAMP results in concentration-dependent NO release and iNOS induction. On the other hand, AGEs-stimulated cAMP production in RAW 264.7 cells was seen in 1 h and persisted for at least 24 h. The NO production was not affected by polymyxin B, a lipopolysaccharide (LPS) inhibitor, suggesting the NO production is not due to LPS contamination in the BSA-AGEs (AGEs) preparation. AGEs actived p38 MAP kinase in RAW 264.7 cells and this effect was blocked by KT 5720 (1 M), H8 (10 M) and SB 203580 (10 M). The p38 MAPK inhibitor (SB 203580) did not inhibit AGEs-induced cAMP accumulation. In conclusion, our data suggest that AGEs may increase intracellular cAMP, which in turn activates PKA and results in p38 MAPK activation, iNOS induction and NO production in RAW 264.7 macrophages.
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