HDAC9 and pulmonary arterial hypertension: Zhao et al. found that valproic acid (VPA) (an inhibitor to class I HDAC) and suberoylanilide hydroxamic (SAHA) (an inhibitor to classes I, II, and IV HDAC) are able to increase the acetylation of H3, reverse pulmonary hypertension, and reduce right ventricular hypertrophy with no effects to heart rate and systolic pressure (Zhao et al., 2012).