PPARα induced NOS1 phosphorylation via PI3K/Akt in guinea pig antral mucous cells: NO-enhancement in Ca(2+)-regulated exocytosis.

A PPAR alpha (peroxisome proliferation activation receptor alpha) agonist (GW7647) activates nitric oxide synthase 1 (NOS1) to produce NO leading to cGMP accumulation in antral mucous cells. In this study, we examined how PPARa activates NOS1. The NO production stimulated by GW7647 was suppressed by inhibitors of PI3K (wortmannin) and Akt (AKT 1/2 Kinase Inhibitor, AKT-inh), although it was also suppressed by the inhibitors of PPARa (GW6471) and NOS1 (N-PLA). GW7647 enhanced the ACh (acetylcholine)-stimulated exocytosis (Ca2+-regulated exocytosis) mediated via NO, which was abolished by GW6471, N-PLA, wortmannin, and AKT-inh. The Western blotting revealed that GW7647 phosphorylates NOS1 via phosphorylation of PI3K/Akt in antral mucous cells. The immunofluorescence examinations demonstrated that PPARa existing with NOS1 co-localizes with PI3K and Akt in the cytoplasm of antral mucous cells. ACh alone and AACOCF(3), an analogue of arachidonic acid (AA), induced the NOS1 phosphorylation via PI3K/Akt to produce NO, which was inhibited by GW6471. Since AA is a natural ligand for PPAR alpha, ACh stimulates PPARa probably via AA. In conclusion, PPAR alpha activates NOS1 via PI3K/Akt phosphorylation to produce NO in antral mucous cells during ACh stimulation.