Critical Involvement of Calcium-Dependent Cytosolic Phospholipase A2α in Aortic Valve Interstitial Cell Calcification

The involvement of calcium-dependent cytosolic phospholipase A2 alpha (cPLA2 alpha) in aortic valve calcification is not exhaustively elucidated. Here, cPLA2 alpha expression in aortic valve interstitial cell (AVIC) pro-calcific cultures simulating either metastatic or dystrophic calcification was estimated by qPCR, Western blotting, and counting of cPLA2 alpha-immunoreactive cells, with parallel ultrastructural examination of AVIC calcific degeneration. These evaluations also involved pro-calcific AVIC cultures treated with cPLA2 alpha inhibitor dexamethasone. cPLA2 alpha over-expression resulted for both types of pro-calcific AVIC cultures. Compared to controls, enzyme content was found to increase by up to 300% and 186% in metastatic and dystrophic calcification-like cultures, respectively. Increases in mRNA amounts were also observed, although they were not as striking as those in enzyme content. Moreover, cPLA2 alpha increases were time-dependent and strictly associated with mineralization progression. Conversely, drastically lower levels of enzyme content resulted for the pro-calcific AVIC cultures supplemented with dexamethasone. In particular, cPLA2 alpha amounts were found to decrease by almost 88% and 48% in metastatic and dystrophic calcification-like cultures, respectively, with mRNA amounts showing a similar trend. Interestingly, these drastic decreases in cPLA2 alpha amounts were paralleled by drastic decreases in mineralization degrees, as revealed ultrastructurally. In conclusion, cPLA2 alpha may be regarded as a crucial co-factor contributing to AVIC mineralization in vitro, thus being an attractive potential target for designing novel therapeutic strategies aimed to counteract onset or progression of calcific aortic valve diseases.