Histone deacetylase inhibition disturbs the balance between ACE and chymase expression in endothelial cells: a potential mechanism of chymase activation in preeclampsia

Chymase is a major angiotensin-converting enzyme (ACE)-independent angiotensin convertase, and its expression is upregulated in the maternal vascular endothelium in preeclampsia, a hypertensive disorder in human pregnancy. Increased chymase-dependent angiotensin II generation has been reported in several cardiovascular diseases, including atherosclerosis and aneurysmal lesions. However, it remains unclear how chymase is activated. Histone modification is an important regulatory mechanism that controls gene expression. In this study, using a chymase overexpression cell model, we investigated the mechanisms of chymase activation to test our hypothesis that histone acetylation could promote endothelial chymase expression. Human umbilical vein endothelial cells were transfected with the chymase gene. Trichostatin A was used to inhibit histone deacetylases (HDACs). The expression levels of chymase, ACE, and HDACs were determined by western blotting. Our results showed that ACE was strongly expressed in control cells, but was significantly downregulated in cells transfected to express chymase. Strikingly, we also found that HDAC inhibition resulted in a dose-dependent increase in chymase expression but a dose-dependent decrease in ACE expression in cells transfected with the chymase gene. HDAC inhibition was confirmed by the decreased expression of HDAC1 and HDAC6 in cells treated with trichostatin A. Increased chymase expression associated with reduced histone deacetylase expression was further confirmed by immunostaining of subcutaneous adipose sections from women with preeclampsia. We conclude that aberrant HDAC expression/activity could disturb the balance between ACE and chymase expression in endothelial cells. Our results support the clinical importance of chymase as a new pharmacological target for cardiovascular disorders.