l-Carnitine therapy improves right heart dysfunction through Cpt1-dependent fatty acid oxidation.

Pulmonary arterial hypertension (PAH) is a fatal vasculopathy that ultimately leads to elevated pulmonary pressure and death by right ventricular (RV) failure, which occurs in part due to decreased fatty acid oxidation and cytotoxic lipid accumulation. In this study, we tested the hypothesis that decreased fatty acid oxidation and increased lipid accumulation in the failing RV is driven, in part, by a relative carnitine deficiency. We then tested whether supplementation of l-carnitine can reverse lipotoxic RV failure through augmentation of fatty acid oxidation. In vivo in transgenic mice harboring a human BMPR2 mutation, l-carnitine supplementation reversed RV failure by increasing RV cardiac output, improving RV ejection fraction, and decreasing RV lipid accumulation through increased PPARγ expression and augmented fatty acid oxidation of long chain fatty acids. These findings were confirmed in a second model of pulmonary artery banding-induced RV dysfunction. In vitro, l-carnitine supplementation selectively increased fatty acid oxidation in mitochondria and decreased lipid accumulation through a Cpt1-dependent pathway. l-Carnitine supplementation improves right ventricular contractility in the stressed RV through augmentation of fatty acid oxidation and decreases lipid accumulation. Correction of carnitine deficiency through l-carnitine supplementation in PAH may reverse RV failure.

Prostate-specific membrane antigen (PSMA)-mediated laminin proteolysis generates a pro-angiogenic peptide.

Prostate-specific membrane antigen (PSMA) is a membrane-bound glutamate carboxypeptidase expressed in a number of tissues. PSMA participates in various biological functions depending on the substrate available in the particular tissue; in the brain, PSMA cleaves the abundant neuropeptide N-acetyl-aspartyl-glutamate to regulate release of key neurotransmitters, while intestinal PSMA cleaves polyglutamated peptides to supply dietary folate. PSMA expression is also progressively upregulated in prostate cancer where it correlates with tumor progression as well as in tumor vasculature, where it regulates angiogenesis. The previous research determined that PSMA cleavage of small peptides generated via matrix metalloprotease-mediated proteolysis of the extracellular matrix protein laminin potently activated endothelial cells, integrin signaling and angiogenesis, although the specific peptide substrates were not identified. Herein, using enzymatic analyses and LC/MS, we unequivocally demonstrate that several laminin-derived peptides containing carboxy-terminal glutamate moieties (LQE, IEE, LNE) are bona fide substrates for PSMA. Subsequently, the peptide products were tested for their effects on angiogenesis in various models. We report that LQ, the dipeptide product of PSMA cleavage of LQE, efficiently activates endothelial cells in vitro and enhances angiogenesis in vivo. Importantly, LQE is not cleaved by an inactive PSMA enzyme containing an active site mutation (E424S). Endothelial cell activation by LQ was dependent on integrin beta-1-induced activation of focal adhesion kinase. These results characterize a novel PSMA substrate, provide a functional rationale for the upregulation of PSMA in cancer cells and tumor vasculature and suggest that inhibition of PSMA could lead to the development of new angiogenic therapies.