Ceramide inhibits Kv currents and contributes to TP-receptor-induced vasoconstriction in rat and human pulmonary arteries

et al.

Neutral sphingomyelinase (nSMase)-derived ceramide has been proposed as a mediator of hypoxic pulmonary vasoconstriction (HPV), a specific response of the pulmonary circulation. Voltage-gated K+ (Kv) channels are modulated by numerous vasoactive factors, including hypoxia, and their inhibition has been involved in HPV. Herein, we have analyzed the effects of ceramide on Kv currents and contractility in rat pulmonary arteries (PA) and in mesenteric arteries (MA). The ceramide analog C6-ceramide inhibited Kv currents in PA smooth muscle cells (PASMC). Similar effects were obtained after the addition of bacterial sphingomyelinase (SMase), indicating a role for endogenous ceramide in Kv channel regulation. Kv current was reduced by stromatoxin and diphenylphosphine oxide-1 (DPO-1), selective inhibitors of Kv2.1 and Kv1.5 channels, respectively. The inhibitory effect of ceramide was still present in the presence of stromatoxin or DPO-1, suggesting that this sphingolipid inhibited both components of the native Kv current. Accordingly, ceramide inhibited Kv1.5 and Kv2.1 channels expressed in Ltk- cells. Ceramide-induced effects were reduced in human embryonic kidney 293 cells expressing Kv1.5 channels but not the regulatory subunit Kvβ2.1. The nSMase inhibitor GW4869 reduced the thromboxane-endoperoxide receptor agonist U46619-induced, but not endothelin-1-induced pulmonary vasoconstriction that was partly restored after addition of exogenous ceramide. The PKC-ζ pseudosubstrate inhibitor (PKCζ-PI) inhibited the Kv inhibitory and contractileé effects of ceramide. In MA ceramide had no effect on Kv currents and GW4869 did not affect U46619-induced contraction. The effects of SMase were also observed in human PA. These results suggest that ceramide represents a crucial signaling mediator in the pulmonary vasculature. © 2011 the American Physiological Society.

This work was supported by Fundación Mutua Madrileña to A. Cogolludo, by the Spanish Ministerio de Ciencia e Innovación (Research Grants SAF2010-22066-C02-02 to A. Cogolludo; SAF2008-03948, AGL2007-66108 to F. Perez-Vizcaino; SAF2007-65868, SAF2010-14916, and FIS RD06/0014/0006 to C. Valenzuela; JAE-Doc contract to T. Gonzalez; RECAVA contract to M. David; SAF2008-03113 to J. Cortijo; Juan de la Cierva contract to L. Moreno and predoctoral FPI grant to C. Menendez) the Spanish Ministerio de Educación (predoctoral FPU grant to J. Moral-Sanz), and European Union FP7-PEOPLE (AOR-PERG05-GA-2009-249165) to F. Perez-Vizcaino and L. Moreno.