SIRT1 and pulmonary arterial hypertension: SIRT1 expression was downregulated in PH models in lungs [7,63,106,111,157,167], PA [110], PASMCs [7,16,63,105,108,109,156,157,159,160,161,167,168], and with tendency in the RV [45]; surprisingly, it was not altered in PASMCs from humans with PAH, but pharmacological and genetic inhibitions of SIRT1 promoted cell proliferation via the alteration of the acetylation/deacetylation balance [7].