Abstract 11711: Valproic Acid, a Class [[Unable to Display Character: І]] Histone Deacetylase Inhibitor, Suppresses the Development of Severe Pulmonary Hypertension in Rats

Abstract

Introduction: Pulmonary hypertension (PH) is a progressive vascular remodeling disease characterized by exuberant cell proliferation, apoptosis resistance, and inflammation that contributes to increased pulmonary arterial resistance. Histone deacetylases (HDACs) and histone acetyltransferases shift acetyl groups from histone and non-histone proteins and enhance gene transcription by post-translational modifications. Valproic acid, a class I HDAC inhibitor, is a widely used antiepileptic drug with low toxicity and also shows supportive efficacy in cancer treatment by inhibiting cancer cell proliferation and inflammation. Hypothesis: We assessed the hypothesis that HDAC inhibition may attenuate excessive cell proliferation and inflammation and improve vascular remodeling in a severe PH rat model. Methods: To compare the development of vascular remodeling, we assessed 6 rats that underwent a single monocrotaline injection, chronic hypoxic exposure, or a combination of both treatments. Valproic acid or vehicle was administered in rats with severe PH induced by the combination method to assess whether valproic acid has the ability to prevent severe PH development in the first 3 weeks or to reverse disease progression at 3-5 weeks. Results: The combination method induced PH of greater severity than that induced by any single stimulation in rats after 3 weeks. Compared with the vehicle-treated rats, valproic acid treatment blocked the elevation of right ventricular systolic pressure and right ventricle hypertrophy index (from 57 ± 3 to 49 ± 3 mmHg and from 46 ± 4 to 37 ± 3 %) in both the first 3 weeks and in the late treatment group (from 75 ± 2 to 61 ± 5mmHg and from 61 ± 7 to 48 ± 3 %, respectively; P < 0.01). Valproic acid attenuated the muscularization ratio of peripheral pulmonary vascular, repressed proliferation and inflammation marker expression (PCNA and ED1), and enhanced apoptosis (cleaved caspase 3) in severe PH rats. Conclusions: These data indicate that a selective HDAC inhibitor may be effective in the treatment of PH.