Adenosine A(2A) receptor activation reverses hypoxia­induced rat pulmonary artery smooth muscle cell proliferation via cyclic AMP­mediated inhibition of the SDF1­CXC4 signaling pathway.

ABSTRACT

The occurrence and the subsequent development of pulmonary arterial hypertension (PAH) involve complicated mechanisms. Of these, the proliferation of pulmonary artery smooth muscle cells (PASMCs) has been indicated to be closely associated with its progression. Therefore, therapeutic methods targeting PASMCs to inhibit proliferation is an effective method for alleviating PAH. The present study was designed to determine the role of the adenosine A(2A) receptor (A2A receptor) in hypoxia­induced rat PASMC (RPASMC) proliferation. Primary RPASMCs were isolated from the pulmonary artery of adult male SD rats, cultured and used for the following experiments. The mRNA level and protein expression of CXCR4 were measured by reverse transcription­quantitative polymerase chain reaction and western blot analysis, respectively. The cell proliferation of RPASMCs was measured using a cell proliferation assay kit. In the present study, it was demonstrated that the proliferation of RPASMCs was partially mediated by activation of the stromal cell­derived factor 1 (SDF1)­CXC chemokine receptor 4 (CXCR4) axis under hypoxic conditions. In addition, SDF1­α alone upregulated the mRNA and protein expression levels of CXCR4, and stimulated the proliferation of RPASMCs. The protein expression of CXCR4 and the cell proliferation were markedly inhibited by application of A2A receptor agonist CGS21680 or cyclic adenosine monophosphate (cAMP) under hypoxic conditions or treatment with SDF1­α and was reversed by the A2A receptor antagonist SCH58261 or 8­bromoadenosine­3',5'­cyclic monophosphorothioate. These results demonstrated that the inhibition of SDF1­CXC4 signaling by the activation of A2A receptor and subsequent increase in the level of cAMP may be a potential method to ameliorate PAH.