RNAi Silencing of TNFα Attenuates Cold‐induced Pulmonary Hypertension (CIPH)

Abstract

BackgroundExposure to a moderate cold temperature (5ºC) causes pulmonary hypertension. Tumor necrosis factor‐alpha (TNF‐α) was increased in lungs and pulmonary arteries of rats prior to cold‐induced elevation of pulmonary arterial blood pressure (PABP). The purpose of this study was to investigate if the upregulation of TNFα plays a role in CIPH.Methods and ResultsThree groups of male SD rats (8 rats/group) received IV delivery of adeno‐associated virus (AAV)‐carrying TNFα small hairpin RNA (TNFαshRNA), AAV‐carrying scrambled shRNA, and PBS, respectively, 3 days before exposure to a cold environment (5°C). Three additional groups with the same treatments were housed in a warm chamber (25°C) and serve as controls. Eight weeks after injection, right ventricular (RV) systolic BP (equivalent of PABP) was recorded and PA smooth muscle cells were isolated for in vitro studies. TNFαshRNA significantly decreased cold‐induced elevation of RV BP but not RV hypertrophy. TNFαshRNA prevented cold‐induced upregulation of TNFα in lungs and PAs, confirming effective silencing of TNFα. TNFα inhibition decreased cold‐induced increases in intracellular levels of O2−, calcium, and cGMP in PA SMCs. RNAi silencing of TNFα also prevented the cold‐induced increase in PCNA, a marker of cell proliferation.ConclusionsThe upregulation of TNFα may play a key role in the development of CIPH and PASMC proliferation.