Activation of PPARβ/δ prevents the high glucose-induced impairment of cAMP-mediated relaxation in rat coronary arteries

Laura Moreno1,3, Bianca Barreira1,3, Javier Moral-Sanz1,3, Enrique Moreno1,3, Carmen Menendez1,3, Rosario Jimenez2, Juan Duarte2, Francisco Perez-Vizcaino1,3, Angel Cogolludo1,3. 1Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid, Spain, 2Department of Pharmacology, School of Pharmacy, Universidad de Garanada, Granada, Spain, 3Ciber Enfermedades Respiratorias, Madrid, Spain.

Activation of peroxisome proliferator-activated receptor β/δ (PPARβ/δ) causes protective effects on obesity, insulin sensitivity and metabolic syndrome. Very recently, the PPARβ/δ agonist GW0742 has been shown to reduce endothelial dysfunction in spontaneously hypertensive rats (Zarzuelo et al., 2011). Besides endothelial dysfunction, coronary arteries show a reduced cAMP-mediated dilation in experimental models of diabetes. We hypothesized that activation of PPARβ/δ may exert protective effects in the diabetic vascular dysfunction. Thus, the aim of the present study was to analyze the effects of PPARβ/δ activation on the altered relaxation to cAMP in coronary arteries following short term exposure to high glucose.

Male Wistar rats (250-280g) were killed by cervical dislocation. Coronary and pulmonary arteries (250-400 μm internal diameter) were incubated for 20 hours in medium containing normal (5x10-3 M) or high (30x10-3 M) glucose in the absence (DMSO, final concentration 0.1-0.2%) or the presence of the PPARβ/δ agonist GW0742 (10-6 M or 10-5 M) or GW0742 (10-5 M) plus the PPARβ/δ antagonist GSK0660 (10-6 M). Vascular reactivity was assessed using isometric wire myographs and potassium currents were recorded with the patch clamp technique. Statistical analysis for multiple comparisons was carried out by two-way ANOVA followed by Bonferroni post hoc test.

The relaxant response induced by the adenylate cyclase activator forskolin (3x10-9 - 3x10-7 M) in arteries pretreated with serotonin (10-6 M) was reduced in high glucose-incubated vs low glucose-incubated coronary arteries (60.5 ± 7.6% vs 94.6 ± 3.7% relaxation at 3x10-7 M p<0.01). Treatment with GW0742 (10-5 M) improved the relaxation to forskolin in high glucose-incubated coronary arteries (93.9 ± 8.5% relaxation at 3x10-6 M p>0.05 vs low glucose). This effect was prevented in arteries co-incubated with GSK0660 (57.9 ± 7.2% relaxation at 3x10-6 M p<0.01 vs low glucose). The Kv1 channel blocker DPO-1 (10-6 M) inhibited the relaxation induced by forskolin in coronary arteries incubated with low glucose or with high glucose + GW0742. However, this drug did not affect the relaxation induced by forskolin in coronary arteries incubated with high glucose (45.1 ± 6.6%). Accordingly, DPO inhibited Kv currents in coronary arteries incubated with low glucose but not in those incubated with high glucose (41 ± 9% and 1.4 ± 11% inhibition at +40mV, respectively). In pulmonary arteries. The relaxation induced by forskolin was similar after incubation with low glucose, high glucose or high glucose + GW0742 (82.5 ± 5%, 93 ± 12% and 80± 6% relaxation at 3x10-7 M, respectively). Moreover, DPO-1 did not affect the relaxant response induced by forskolin in these arteries.

In conclusion, activation of PPARβ/δ prevents high glucose-induced alteration of cAMP relaxation in coronary arteries. This improvement appears to be partly due to the ability of the PPARβ/δ agonist to restore a relaxant component which depends on Kv1 channel function.

Zarzuelo MJ et al., (2011). Hypertension 58:733-43.

Supported by SAF2010-22066.