Metabolic Reprogramming and Redox Signaling in Pulmonary Hypertension.

Abstract

Pulmonary hypertension is a complex disease of the pulmonary vasculature, which in severe cases terminates in right heart failure. Complex remodeling of pulmonary arteries comprises the central issue of its pathology. This includes extensive proliferation, apoptotic resistance and inflammation. As such, the molecular and cellular features of pulmonary hypertension resemble hallmark characteristics of cancer cell behavior. The vascular remodeling derives from significant metabolic changes in resident cells, which we describe in detail. It affects not only cells of pulmonary artery wall, but also its immediate microenvironment involving cells of immune system (i.e., macrophages). Thus aberrant metabolism constitutes principle component of the cancer-like theory of pulmonary hypertension. The metabolic changes in pulmonary artery cells resemble the cancer associated Warburg effect, involving incomplete glucose oxidation through aerobic glycolysis with depressed mitochondrial catabolism enabling the fueling of anabolic reactions with amino acids, nucleotides and lipids to sustain proliferation. Macrophages also undergo overlapping but distinct metabolic reprogramming inducing specific activation or polarization states that enable their participation in the vascular remodeling process. Such metabolic synergy drives chronic inflammation further contributing to remodeling. Enhanced glycolytic flux together with suppressed mitochondrial bioenergetics promotes the accumulation of reducing equivalents, NAD(P)H. We discuss the enzymes and reactions involved. The reducing equivalents modulate the regulation of proteins using NAD(P)H as the transcriptional co-repressor C-terminal binding protein 1 cofactor and significantly impact redox status (through GSH, NAD(P)H oxidases, etc.), which together act to control the phenotype of the cells of pulmonary arteries. The altered mitochondrial metabolism changes its redox poise, which together with enhanced NAD(P)H oxidase activity and reduced enzymatic antioxidant activity promotes a pro-oxidative cellular status. Herein we discuss all described metabolic changes along with resultant alterations in redox status, which result in excessive proliferation, apoptotic resistance, and inflammation, further leading to pulmonary arterial wall remodeling and thus establishing pulmonary artery hypertension pathology.