title: Chronic inhibition of PPAR-γ signaling induces endothelial dysfunction in the juvenile lamb.
abstract: We have recently shown that the development of endothelial dysfunction in lambs with increased pulmonary blood flow (PBF) correlates with a decrease in peroxisome proliferator activated receptor-γ (PPAR-γ) signaling. Thus, in this study we determined if the loss of PPAR-γ signaling is necessary and sufficient to induce endothelial dysfunction by exposing lambs with normal PBF to the PPAR-γ antagonist, GW9662. Two-weeks of exposure to GW9662 significantly decreased both PPAR-γ protein and activity. In addition, although eNOS protein and nitric oxide metabolites (NO(x)) were significantly increased, endothelial dependent pulmonary vasodilation in response to acetylcholine was attenuated, indicative of endothelial dysfunction. To elucidate whether downstream mediators of vasodilation were impaired we examined soluble guanylate cyclase (sGC)-α and β subunit protein, cGMP levels, and phosphodiesterase 5 (PDE5) protein and activity, but we found no significant changes. However, we found that peroxynitrite levels were significantly increased in GW9662-treated lambs and this correlated with a significant increase in protein kinase G-1α (PKG-1α) nitration and a reduction in PKG activity. Peroxynitrite is formed by the interaction of NO with superoxide and we found that there was a significant increase in superoxide generation in GW9662-treated lambs. Further, we identified dysfunctional mitochondria as the primary source of the increased superoxide. Finally, we found that the mitochondrial dysfunction was due to a disruption in carnitine metabolism. We conclude that loss of PPAR-γ signaling is sufficient to induce endothelial dysfunction confirming its important role in maintaining a healthy vasculature.
authors.affiliation: Vascular Biology Center, Georgia Health Sciences University, 1459 Laney Walker Blvd, CB3210B, Augusta, GA 30912, USA.
authors.forename: Shruti
authors.initials: S
authors.lastname: Sharma
authors.forename: Jubilee
authors.initials: J
authors.lastname: Barton
authors.forename: Ruslan
authors.initials: R
authors.lastname: Rafikov
authors.forename: Saurabh
authors.initials: S
authors.lastname: Aggarwal
authors.forename: Hsuan-Chang
authors.initials: HC
authors.lastname: Kuo
authors.forename: Peter E
authors.initials: PE
authors.lastname: Oishi
authors.forename: Sanjeev A
authors.initials: SA
authors.lastname: Datar
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Fineman
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Black
mesh_terms: D000375:Aging; D000813:Anilides / Q000494:pharmacology; D000818:Animals; D002331:Carnitine / Q000378:metabolism; D006152:Cyclic GMP / Q000502:physiology; D062965:Cyclic GMP-Dependent Protein Kinase Type I / Q000037:antagonists & inhibitors; D004730:Endothelium, Vascular / Q000502:physiology*; D018841:HSP90 Heat-Shock Proteins / Q000502:physiology; D052250:Nitric Oxide Synthase Type III / Q000032:analysis; D047495:PPAR gamma / Q000037:antagonists & inhibitors / Q000502:physiology*; D012756:Sheep; D015398:Signal Transduction / Q000502:physiology*; D013481:Superoxides / Q000378:metabolism
chemical_list: C457499:2-chloro-5-nitrobenzanilide; D000813:Anilides; D018841:HSP90 Heat-Shock Proteins; D047495:PPAR gamma; D013481:Superoxides; D052250:Nitric Oxide Synthase Type III; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D006152:Cyclic GMP; D002331:Carnitine