Abstract 15009: Increased Expression of TMEM16A May Lead to Depolarization of Human Pulmonary Arterial Smooth Muscle Cells in IPAH
Introduction: Depolarization of pulmonary arterial smooth muscle cells (PASMCs) and subsequent increase of intracellular calcium concentration are suggested to be crucial events in the pathomechanism of pulmonary hypertension. In animal models of PH the calcium activated chloride channel TMEM16A has been recently identified as a novel ion channel contributing to sustained pulmonary vasoconstriction.
Hypothesis: We hypothetised that TMEM16A is also upregulated in human pulmonary arteries obtained from patients with idiopathic pulmonary arterial hypertension (IPAH) and it is responsible for a relevant depolarizing current.
Methods: Laser capture microdissection (LCM) of the intima and media layers of pulmonary arteries from healthy donors (n=7) and IPAH patients (n=7) was performed in order to investigate the expression of several chloride channels by QPCR. These findings were confirmed on cultured PASMCs isolated from healthy donor and IPAH lungs. The membrane potential of PASMCs from both groups was measured with the patch-clamp technique and the effect of the specific TMEM16A inhibitor T16A-inh01 (10 μM) was studied.
Results: Our QPCR studies have shown marked upregulation of TMEM16A both in the LCM material and in the PASMCs isolated from IPAH patients. Measurement of the resting membrane potential showed that the PASMCs from IPAH patients were more depolarized compared to the PASMCs of healthy donors (-34 ± 2 mV vs -47 ± 2 mV, p< 0.05). Interestingly, treatment of the IPAH PASMCs with T16A-inh01 resulted in a significant hyperpolarization of the membrane potential (-41 ± 2 mV, p< 0.05 compared to untreated IPAH).
Conclusions: Our data suggest that TMEM16A is upregulated in the PASMCs of human IPAH patients and the resulting increase in chloride efflux indeed contributes to PASMC depolarization, which may lead to excess vasoconstriction and remodeling of pulmonary arteries.
Author Disclosures: R. Papp: None. C. Nagaraj: None. Z. Balint: None. B. Nagy: None. E. Stacher: None. B. Ghanim: None. W. Klepetko: None. A. Olschewski: None.
- © 2014 by American Heart Association, Inc.