In Vivo Gene Transfer of the O ₂ -Sensitive Potassium Channel Kv1.5 Reduces Pulmonary Hypertension and Restores Hypoxic Pulmonary Vasoconstriction in Chronically Hypoxic Rats

Abstract

Background-Alveolar hypoxia acutely elicits pulmonary vasoconstriction (HPV). Chronic hypoxia (CH), despiteattenuating HPV, causes pulmonary hypertension (CH-PHT). HPV results, in part, from inhibition of O 2 -sensitive, voltage-gated potassium channels (Kv) in pulmonary artery smooth muscle cells (PASMCs). CH decreases Kv channel current/expression and depolarizes and causes Ca 2ϩ overload in PASMCs. We hypothesize that Kv gene transfer would normalize the pulmonary circulation (restore HPV and reduce CH-PHT), despite ongoing hypoxia. Methods and Results-Adult male Sprague-Dawley rats were exposed to normoxia or CH for 3 to 4 weeks and then nebulized orotracheally with saline or adenovirus (Ad5) carrying genes for the reporter, green fluorescent protein reporterϮhuman Kv1.5 (cloned from normal PA). HPV was assessed in isolated lungs. Hemodynamics, including Fick and thermodilution cardiac output, were measured in vivo 3 and 14 days after gene therapy by use of micromanometer-tipped catheters. Transgene expression, measured by quantitative RT-PCR, was confined to the lung, persisted for 2 to 3 weeks, and did not alter endogenous Kv1.5 levels. Ad5-Kv1.5 caused no mortality or morbidity, except for sporadic, mild elevation of liver transaminases. Ad5-Kv1.5 restored the O 2 -sensitive K ϩ current of PASMCs, normalized HPV, and reduced pulmonary vascular resistance. Pulmonary vascular resistance decreased at day 2 because of increased cardiac output, and remained reduced at day 14, at which time there was concomitant regression of right ventricular hypertrophy and PA medial hypertrophy. Conclusions-Kv1.5 is an important O 2 -sensitive channel and potential therapeutic target in PHT. Kv1.5 gene therapy restores HPV and improves PHT. This is, to the best of our knowledge, the first example of K ϩ channel gene therapy for a vascular disease.

Potassium channels in pulmonary arterial hypertension

“…Reduced expression of K V 1.5 is a common denominator of human and experimental PAH suggesting an important role of this channel in the pathogenesis of various forms of PH [16][17][18][19]. Accordingly, in vivo gene transfer of K V 1.5 was shown to reduce PH and to restore hypoxic pulmonary vasoconstriction in chronically hypoxic rats, adding further weight to its implication in PAH [20]. Although K V 1.5 is considered as a potential therapeutic target, the molecular mechanisms leading to its reduced expression in this disease are not clear.…”

Characterization of a rat model of right-sided heart failure induced by pulmonary trunk banding

“…Few animal models exist that are able to induce HF (whereas several models have been employed to induce RV hypertrophy, including monocrotaline (MCT) treatment (Jones et al, 2002;Jones et al, 2004;Kato et al, 2003), hypoxia (Bonnet et al, 2004;Pozeg et al, 2003), infarction (Nahrendorf et al, 2003) and also mild pulmonary trunk banding (PTB) (Adachi et al, 1995;Bar et al, 2003;Braun et al, 2003;Ikeda et al, 1999;Kuroha et al, 1991;Olivetti et al, 1988;Zierhut et al, 1990)). MCT treatment has been used to induce pulmonary hypertension resulting in RV hypertrophy and eventually HF (Chen et al, 2001;Doggrell and Brown, 1998).…”

The nuclear factor of activated T cells in pulmonary arterial hypertension can be therapeutically targeted

“…A selective down-regulation of PASMC Kv channels, like Kv1.5, has been described both in human (7) and animal models of PAH (6,(8)(9)(10). This causes depolarization, opening of the voltage-gated Ca 2ϩ channels, and increase in intracellular free Ca 2ϩ concentration ([Ca 2ϩ ] i ).…”