Role of leptin in coronary vascular dysfunction and proliferation

Abstract

The purpose of this investigation was to test the hypothesis that leptin augments vasoconstriction and impairs dilation via a Rho kinase‐dependent pathway and promotes proliferation of coronary smooth muscle. Coronary arteries from domestic swine were cleaned of surrounding tissue and incubated with/without leptin (30 ng/mL) for 30 min. Leptin administration significantly augmented contractile responses to KCl (10 – 60 mM), with active tension development increased by ~1.3 g at doses >40mM, and reduced maximal vasodilation to adenosine (30 μM) ~18% compared to untreated controls. To examine the extent to which longer‐term exposure to leptin influences coronary vascular reactivity, arteries were placed in organ culture for 3 days. Following incubation in serum‐free media, leptin treatment significantly augmented overall active tension development to KCl (10 – 60 mM), with an average increase of ~2.0 g at doses >40 mM, and reduced maximal vasodilation to adenosine (30 μM) ~50% compared to untreated controls. The acute and chronic effects of leptin administration on maximal KCl (60 mM) contractions were essentially abolished in the presence of the Rho kinase inhibitor, fasudil (1 μM). Short‐term leptin exposure significantly increased the level of Rho kinase activity, while no difference in Rho kinase (Rock‐2) protein abundance was detected. In contrast, long‐term leptin administration in cultured arteries significantly increased the abundance of Rock‐2 protein, while no difference in Rho kinase activity level was detected. Global proteomic assessment of arteries cultured (3 days) in the presence or absence of leptin (30 ng/mL) revealed significant alterations in the coronary artery proteome and Ingenuity Pathway Analysis identified associations between leptin treatment and numerous cellular processes, namely cellular growth and proliferation (35 proteins). To assess the effects of leptin on vascular smooth muscle proliferation, additional studies were conducted in which coronary arteries were cultured in serum‐containing media with/without leptin (30 ng/mL) for 2 or 8 days. 5‐Bromo‐2′‐deoxyuridine (BrdU) staining revealed a significantly higher percentage of BrdU‐positive nuclei in leptin treated arteries (~10%) compared to untreated controls at both time points. Taken together, data from this investigation indicate that leptin alters coronary smooth muscle reactivity and potentiates contraction via a Rho kinase‐dependent pathway. Additionally, these findings support the potential for leptin to modulate a key network of pathways that promote vascular smooth muscle proliferation.Support or Funding InformationIndiana University Health, Indiana University School of Medicine Strategic Research Initiative (CECARE); HL117620 (J.D. Tune‐Mather); TL1 TR001107 and UL TR001108 (A. Shekhar).