In vivo gene transfer of the O2-sensitive potassium channel Kv1.5 reduces pulmonary hypertension and restores hypoxic pulmonary vasoconstriction in chronically hypoxic rats.
BACKGROUND
Alveolar hypoxia acutely elicits pulmonary vasoconstriction (HPV). Chronic hypoxia (CH), despite attenuating HPV, causes pulmonary hypertension (CH-PHT). HPV results, in part, from inhibition of O2-sensitive, voltage-gated potassium channels (Kv) in pulmonary artery smooth muscle cells (PASMCs). CH decreases Kv channel current/expression and depolarizes and causes Ca2+ overload in PASMCs. We hypothesize that Kv gene transfer would normalize the pulmonary circulation (restore HPV and reduce CH-PHT), despite ongoing hypoxia.


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 reporter+/-human 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 O2-sensitive K+ 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 O2-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+ channel gene therapy for a vascular disease.
Pozeg
Zlatko I
ZI
Vascular Biology Group, Cardiology, University of Alberta, Edmonton, Canada.
Michelakis
Evangelos D
ED
McMurtry
M Sean
MS
Thébaud
Bernard
B
Wu
Xi-Chen
XC
Dyck
Jason R B
JR
Hashimoto
Kyoko
K
Wang
Shaohua
S
Moudgil
Rohit
R
Harry
Gwyneth
G
Sultanian
Richard
R
Koshal
Arvind
A
Archer
Stephen L
SL
D000256:Adenoviridae / Q000235:genetics; D000280:Administration, Inhalation; D000818:Animals; D002302:Cardiac Output; D002908:Chronic Disease; D018014:Gene Transfer Techniques; D017930:Genes, Reporter; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000008:administration & dosage / Q000235:genetics; D006439:Hemodynamics / Q000187:drug effects; D006976:Hypertension, Pulmonary / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D000860:Hypoxia / Q000150:complications / Q000503:physiopathology; D066298:In Vitro Techniques; D051666:Kv1.5 Potassium Channel; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000503:physiopathology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011651:Pulmonary Artery / Q000187:drug effects / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014655:Vascular Resistance / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects
C496983:Kcna5 protein, rat; D051666:Kv1.5 Potassium Channel; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated