Published online before print September 16, 2004, doi: 10.1161/01.RES.0000145360.16770.9f
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© 2004 American Heart Association, Inc.
Integrative Physiology |
Dichloroacetate Prevents and Reverses Pulmonary Hypertension by Inducing Pulmonary Artery Smooth Muscle Cell Apoptosis
From the Department of Medicine and Pediatrics (J.R.B.D.) and the Vascular Biology Group (M.S.M., S.B., X.W., J.R.B.D., A.H., K.H., E.D.M.), University of Alberta, Edmonton, Canada.
Correspondence to Evangelos D. Michelakis, MD, FACC, University of Alberta Hospitals, Edmonton, Alberta T6G2B7, Canada. E-mail emichela{at}cha.ab.ca
The pulmonary arteries (PA) in pulmonary arterial hypertension (PAH) are constricted and remodeled;. They have suppressed apoptosis, partly attributable to suppression of the bone morphogenetic protein axis and selective downregulation of PA smooth muscle cell (PASMC) voltage-gated K+ channels, including Kv1.5. The Kv downregulation-induced increase in [K+]i, tonically inhibits caspases, further suppressing apoptosis. Mitochondria control apoptosis and produce activated oxygen species like H2O2, which regulate vascular tone by activating K+ channels, but their role in PAH is unknown. We show that dichloroacetate (DCA), a metabolic modulator that increases mitochondrial oxidative phosphorylation, prevents and reverses established monocrotaline-induced PAH (MCT-PAH), significantly improving mortality. Compared with MCT-PAH, DCA-treated rats (80 mg/kg per day in drinking water on day 14 after MCT, studied on day 21) have decreased pulmonary, but not systemic, vascular resistance (63% decrease, P<0.002), PA medial thickness (28% decrease, P<0.0001), and right ventricular hypertrophy (34% decrease, P<0.001). DCA is similarly effective when given at day 1 or day 21 after MCT (studied day 28) but has no effect on normal rats. DCA depolarizes MCT-PAH PASMC mitochondria and causes release of H2O2 and cytochrome c, inducing a 10-fold increase in apoptosis within the PA media (TUNEL and caspase 3 activity) and decreasing proliferation (proliferating-cell nuclear antigen and BrdU assays). Immunoblots, immunohistochemistry, laser-captured microdissection-quantitative reverse-transcription polymerase chain reaction and patch-clamping show that DCA reverses the Kv1.5 downregulation in resistance PAs. In summary, DCA reverses PA remodeling by increasing the mitochondria-dependent apoptosis/proliferation ratio and upregulating Kv1.5 in the media. We identify mitochondria-dependent apoptosis as a potential target for therapy and DCA as an effective and selective treatment for PAH.
Key Words: apoptosis • proliferation • smooth muscle • vascular remodeling
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