Bromodomain and extra‐terminal protein mimic JQ1 decreases inflammation in human vascular endothelial cells: Implications for pulmonary arterial hypertension

Background and objective Nuclear factor kappa B ( NF‐kB )‐mediated inflammatory gene expression and vascular endothelial cell proliferation/remodelling are implicated in the pathophysiology of the fatal disease, pulmonary arterial hypertension ( PAH ). Bromodomain and extra‐terminal ( BET ) proteins are essential for the expression of a subset of NF‐kB ‐induced inflammatory genes. BET mimics including JQ1 + prevent binding of BETs to acetylated histones and down‐regulate the expression of selected genes. Methods The effects of JQ1 + on the proliferation of primary human pulmonary microvascular endothelial cells ( HPMECs ) from healthy subjects were measured by bromodeoxyuridine ( BrdU ) incorporation. Cell cycle progression was assessed by flow cytometry; mRNA and protein levels of cyclin‐dependent kinases ( CDKs ), inhibitors and cytokines were determined by reverse transcription‐quantitative PCR ( RT‐qPCR ), Western blotting or ELISA . Histone acetyltransferase ( HAT ) and deacetylase ( HDAC ) activities were determined in nuclear extracts from whole lung of PAH and control patients. Results JQ1 + significantly inhibited IL 6 and IL 8 ( IL 6 and CXCL8 ) mRNA and protein in HPMECs compared with its inactive enantiomer JQ1 −. JQ1 + decreased NF‐kB p65 recruitment to native IL6 and IL8 promoters. JQ1 + showed a concentration‐dependent decrease in HPMEC proliferation compared with JQ1 −‐treated cells. JQ1 + induced G1 cell cycle arrest by increasing the expression of the CDK inhibitors (CDKN) 1A (p21 cip ) and CDKN2D ( p19 INK4D ) and decreasing that of CDK2 , CDK4 and CDK6 . JQ1 + also inhibited serum‐stimulated migration of HPMECs . Finally, HAT activity was significantly increased in the lung of PAH patients. Conclusion Inhibition of BETs in primary HPMECs decreases inflammation and remodelling. BET proteins could be a target for future therapies for PAH .