Advanced Glycation End Products Inhibit Distal Colon Contraction In Rats Via Protein Kinase C-Dependent Modulation Of Intracellular Calcium

Aims: To investigate the effect of advanced glycation end products (AGEs) on contractile activity of rat distal colon and its possible mechanisms. Methods: Contractile responses of colonic smooth muscle strips from male SD rats were recorded using a polyphysiograph. Colonic smooth muscle cells were isolated and identified by immunofluorescence. Changes in [Ca2+] i in response to AGEs were measured by confocal laser scanning microscopy. Immunoprecipitation and Western blotting were used to examine the phosphorylation of type 3 InsP3 receptors (InsP3R3) in colonic smooth muscle cells. The PKC inhibitor chelerythrine and the PKC activator phorbol 12-myristate 13-acetate (PMA) was used to examine the role of PKC in the responses to AGEs. Results: Carbachol-induced contractions of colonic smooth muscle strips were relaxed following the administration of 150 mu g/mL and 200 mu g/mL AGEs compared to control, and this was significantly counteracted by prior administration of chelerythrine and decreased more significantly by prior administration of PMA before exposure to AGEs. AGEs at the concentration of 150 mu g/mL or 200 mu g/mL significantly inhibited [Ca2+] i compared with the control group. AGEs at 150 mu g/mL was considered as the most effective concentration in vitro, but this effect was less marked in the presence of chelerythrine. PMA (1 mu M) significantly enhanced AGEs-mediated effect on the decrease of [Ca2+] i. AGEs increased PKC activity compared to controls, and increased phosphorylation of InsP3R3. The latter effect was prevented by chelerythrine. Conclusions: AGEs inhibit contraction of colonic smooth muscle strips and reduce [Ca2+] i in colonic smooth muscle cells. The mechanism involves the release of InsP3R3-operated Ca2+ stores, regulated by the PKC signaling pathway.