Novel interactions between the 5‐HT transporter, 5‐HT 1B receptors and Rho kinase in vivo and in pulmonary fibroblasts

• Published in: British journal of pharmacology Vol. 155; no. 4; pp. 606 - 616
• Main Authors: Mair, K M, MacLean, M R, Morecroft, I, Dempsie, Y, Palmer, T M
• Format: Journal Article
• Language: English
• Published: 29.01.2009
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/bjp.2008.310

Background and purpose: While the 5‐HT and Rho‐kinase (ROCK) pathways have been implicated in the development of pulmonary arterial hypertension (PAH), the nature of any interactions between them remain unclear. This study investigated a role for ROCK in 5‐HT‐regulated proliferative responses in lung fibroblasts in vivo and in vitro . Experimental approach: PAH was examined in mice over‐expressing human 5‐HT transporters (SERT+), from which pulmonary artery fibroblasts (PFs) were isolated to assess ROCK expression. In vitro analysis of 5‐HT signalling employed CCL39 hamster lung fibroblasts. Key results: ROCK inhibition ablated increased pulmonary remodelling and hypertension observed in SERT+ mice, and ROCK1/2 protein levels were elevated in SERT+ PFs. ROCK inhibition also reduced 5‐HT‐stimulated proliferation by suppressing MEK‐stimulated ERK phosphorylation. While optimal 5‐HT‐stimulated proliferation required 5‐HT 1B and 5‐HT 2A receptors and SERT, receptor sensitivity to Y27632 was restricted to the 5‐HT 1B receptor. Also, while hypoxia‐induced pulmonary vascular remodelling and hypertension were sensitive to Y27632 in WT and SERT+ animals, the proportions sensitive to ROCK inhibition were increased by SERT over‐expression. Conclusions and implications: SERT over‐expression increased ROCK‐dependent pulmonary remodelling in normoxia and hypoxia and SERT over‐expression was associated with elevated ROCK1/2 levels. ROCK also potentiated 5‐HT 1B receptor‐stimulated ERK activation and proliferation in vitro by facilitating MEK‐ERK interaction. British Journal of Pharmacology (2008) 155 , 606–616; doi: 10.1038/bjp.2008.310 ; published online 11 August 2008