PDGF-beta receptor and PKC have no effect on angiotensin II-induced JAK2 and STAT1 phosphorylation in vascular smooth muscle cells under high glucose condition

Abstract

Background: The mechanisms responsible for the accelerated cardiovascular disease in diabetes, as well as the increased hypertrophic effects of angiotensin II (Ang II) under hyperglycemic condition, are not very clear. Evidences show that platelet-derived growth factor (PDGF) and protein kinase C (PKC) play a critical role in this effect. In our study, we examined the role of PKC and PDGF receptor on JAK2 and STAT1 phosphorylation under high glucose (HG) condition (25 mmol/L) in response to Ang II in cultured vascular smooth muscle cells (VSMC). Methods: VSMCs were isolated from the thoracic aorta of male Wistar rats and were cultured. Growth-arrested VSMCs were placed in either normal glucose (NG) or HG condition for 48 h and then VSMCs were stimulated with agonists and antagonists. The tyrosine phosphorylation of JAK2 or STAT were determined by immunoblotting using specific antibodies. Results: High glucose markedly increased the phosphorylation of tyrosine residues of JAK2 and serine residues of STAT 1 compared with cells cultured in NG (5.5 mmol/L) with and without Ang II stimulation. Experiments made with specific PDGF-beta receptor inhibitor AG1295 and PKC inhibitor GF109203X showed that there were no changes in Ang II-stimulated JAK2 and STAT1 phosphorylation under NG and HG conditions compared with experiments without inhibitors. Conclusion: According to our findings, Ang II-stimulated JAK2 and STAT1 phosphorylation under either NG or HG condition do not proceed via a different pathway rather than PKC and PDGF-beta receptor.