PPAR-γ Activation Inhibits Angiotensin II Synthesis, Apoptosis, and Proliferation of Mesangial Cells from Spontaneously Hypertensive Rats

BACKGROUND/AIM: The angiotensin II level is elevated in subjects genetically prone to develop hypertension, triggering renal hypercellularity, cytokine production, and matrix deposition. Angiotensin-converting enzyme inhibition and/or angiotensin II type 1 receptor blockade attenuate renal damage. Rosiglitazone, a peroxisome proliferator-activated receptor gamma agonist possessing antihypertensive and anti-inflammatory properties, was demonstrated to provide better renal protection than angiotensin-converting enzyme inhibitors. We studied the effects of in vivo peroxisome proliferator-activated receptor gamma activation by rosiglitazone on angiotensin II synthesis, proliferation, and apoptosis of mesangial cells of spontaneously hypertensive rats versus normotensive Sprague-Dawley rats. METHODS: The animals consumed either a high-sodium diet (8% Na) or a normal-sodium diet (0.5% Na). Half of each group received rosiglitazone at 5 mg/kg/day. After 3 weeks, all rats were sacrificed and the mesangial cells isolated and cultured. Angiotensin II was assessed by radioimmunoassay, apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay, and cell proliferation by [(3)H]thymidine incorporation. RESULTS: Only the spontaneously hypertensive rats which consumed the high-sodium diet developed hypertension (185 +/- 6 mm Hg vs. basal 128 +/- 5 mm Hg; p = 0.0007) which was attenuated by rosiglitazone (to 126 +/- 4 mm Hg; p = 0.34). Angiotensin II synthesis, proliferation, and apoptosis were exaggerated in mesangial cell cultures from Sprague-Dawley rats and, more so, spontaneously hypertensive rats fed the high-sodium diet, but were inhibited in cultures from rosiglitazone-treated animals. CONCLUSIONS: Peroxisome proliferator-activated receptor gamma activation, in addition to lowering blood pressure, suppresses angiotensin II synthesis and downregulates angiotensin-II-mediated proliferation and apoptosis of mesangial cells. In the context of hypertension-induced renal damage, this would mean that the renoprotective role of rosiglitazone extends beyond glycemic and lipidemic control.