The unique metabolic profile of cancer (aerobic glycolysis) might confer apoptosis resistance and be therapeutically targeted. Compared to normal cells, several human cancers have high mitochondrial membrane potential (DeltaPsim) and low expression of the K+ channel Kv1.5, both contributing to apoptosis resistance. Dichloroacetate (DCA) inhibits mitochondrial pyruvate dehydrogenase kinase (PDK), shifts metabolism from glycolysis to glucose oxidation, decreases DeltaPsim, increases mitochondrial H2O2, and activates Kv channels in all cancer, but not normal, cells; DCA upregulates Kv1.5 by an NFAT1-dependent mechanism. DCA induces apoptosis, decreases proliferation, and inhibits tumor growth, without apparent toxicity. Molecular inhibition of PDK2 by siRNA mimics DCA. The mitochondria-NFAT-Kv axis and PDK are important therapeutic targets in cancer; the orally available DCA is a promising selective anticancer agent.

Background-The cause of pulmonary arterial hypertension (PAH) was investigated in humans and fawn hooded rats (FHR), a spontaneously pulmonary hypertensive strain. Methods and Results-Serial Doppler echocardiograms and cardiac catheterizations were performed in FHR and FHR/BN1, a consomic control that is genetically identical except for introgression of chromosome 1. PAH began after 20 weeks of age, causing death by Ϸ60 weeks. FHR/BN1 did not develop PAH. FHR pulmonary arterial smooth muscle cells (PASMCs) had a rarified reticulum of hyperpolarized mitochondria with reduced expression of electron transport chain components and superoxide dismutase-2. These mitochondrial abnormalities preceded PAH and persisted in culture. Depressed mitochondrial reactive oxygen species (ROS) production caused normoxic activation of hypoxia inducible factor (HIF-1␣), which then inhibited expression of oxygen-sensitive, voltage-gated K ϩ channels (eg, Kv1.5). Disruption of this mitochondrial-HIF-Kv pathway impaired oxygen sensing (reducing hypoxic pulmonary vasoconstriction, causing polycythemia), analogous to the pathophysiology of chronically hypoxic Sprague-Dawley rats. Restoring ROS (exogenous H 2 O 2 ) or blocking HIF-1␣ activation (dominant-negative HIF-1␣) restored Kv1.5 expression/function. Dichloroacetate, a mitochondrial pyruvate dehydrogenase kinase inhibitor, corrected the mitochondrial-HIF-Kv pathway in FHR-PAH and human PAH PASMCs. Oral dichloroacetate regressed FHR-PAH and polycythemia, increasing survival. Chromosome 1 genes that were dysregulated in FHRs and relevant to the mitochondria-HIF-Kv pathway included HIF-3␣ (an HIF-1␣ repressor), mitochondrial cytochrome c oxidase, and superoxide dismutase-2. Like FHRs, human PAH-PASMCs had dysmorphic, hyperpolarized mitochondria; normoxic HIF-1␣ activation; and reduced expression/activity of HIF-3␣, cytochrome c oxidase, and superoxide dismutase-2. Conclusions-FHRs

In pulmonary arterial hypertension (PAH), antiapoptotic, proliferative, and inflammatory diatheses converge to create an obstructive vasculopathy. A selective down-regulation of the Kv channel Kv1.5 has been described in human and animal PAH. The resultant increase in intracellular free Ca 2؉ ([Ca 2؉ ]i) and K ؉ ([K ؉ ]i) concentrations explains the pulmonary artery smooth muscle cell (PASMC) contraction, proliferation and resistance to apoptosis. The recently described PASMC hyperpolarized mitochondria and increased bcl-2 levels also contribute to apoptosis resistance in PAH. The cause of the Kv1.5, mitochondrial, and inflammatory abnormalities remains unknown. We hypothesized that these abnormalities can be explained in part by an activation of NFAT (nuclear factor of activated T cells), a Ca 2؉ / calcineurin-sensitive transcription factor. We studied PASMC and lungs from six patients with and four without PAH and blood from 23 PAH patients and 10 healthy volunteers.

Background-Constriction of the ductus arteriosus (DA) is initiated at birth by inhibition of O 2 -sensitive K ϩ channels in DA smooth muscle cells. Subsequent membrane depolarization and calcium influx through L-type calcium channels initiates functional closure. We hypothesize that Rho-kinase activation is an additional mechanism that sustains DA constriction. Methods and Results-The effect of increased PO 2 on the activity and expression of Rho-kinase was assessed in DAs from neonates with hypoplastic left-heart syndrome (nϭ15) and rabbits (339 term and 99 preterm rabbits). Rho-kinase inhibitors (Y-27632 and fasudil) prevent and reverse O 2 constriction. Heterogeneity exists in the sensitivity of constrictors (PO 2 ϭendothelinϭphenylephrineϾKCl) and of fetal vessels (DAϭpulmonary arteryϾaorta) to Rho-kinase inhibition. Inhibition of L-type calcium channels (nifedipine) or removal of extracellular calcium inhibits approximately two thirds of O 2 constriction. Residual DA constriction reflects calcium sensitization, which persists after removal of extracellular calcium and blocking of sarcoplasmic reticulum Ca 2ϩ -ATPase. In term DA, an increase in PO 2 activates Rho-kinase and thereby increases RhoB and ROCK-1 expression. Activation of Rho-kinase in DA smooth muscle cells is initiated by a PO 2 -dependent, rotenone-sensitive increase in mitochondrion-derived reactive O 2 species. O 2 effects on Rho-kinase are mimicked by exogenous H 2 O 2 . In preterm DAs, immaturity of mitochondrial reactive oxygen species generation is associated with reduced and delayed O 2 constriction and lack of PO 2 -dependent upregulation of Rho-kinase expression. Conclusions-O 2 activates Rho-kinase and increases Rho-kinase expression in term DA smooth muscle cells by a redox-regulated, positive-feedback mechanism that promotes sustained vasoconstriction. Conversely, Rho-kinase inhibitors may be useful in maintaining DA patency, as a bridge to congenital heart surgery.