Novel interactions between the 5-HT transporter, 5-HT1B receptors and Rho kinase in vivo and in pulmonary fibroblasts.
OBJECTIVE
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.


METHODS
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.


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
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.
Mair
K M
KM
Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, University of Glasgow, Glasgow, Scotland, UK.
MacLean
M R
MR
Morecroft
I
I
Dempsie
Y
Y
Palmer
T M
TM
D000577:Amides / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D049109:Cell Proliferation; D006224:Cricetinae; D003412:Cricetulus; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D006976:Hypertension, Pulmonary / Q000503:physiopathology; D000860:Hypoxia / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D011651:Pulmonary Artery / Q000166:cytology / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D044302:Receptor, Serotonin, 5-HT1B / Q000187:drug effects / Q000378:metabolism*; D044402:Receptor, Serotonin, 5-HT2A / Q000378:metabolism; D050486:Serotonin Plasma Membrane Transport Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D054460:rho-Associated Kinases / Q000378:metabolism
D000577:Amides; D000959:Antihypertensive Agents; D011725:Pyridines; D044302:Receptor, Serotonin, 5-HT1B; D044402:Receptor, Serotonin, 5-HT2A; D050486:Serotonin Plasma Membrane Transport Proteins; C108830:Y 27632; C515854:Rock1 protein, mouse; C515855:Rock2 protein, mouse; D054460:rho-Associated Kinases; D048049:Extracellular Signal-Regulated MAP Kinases