Autor:innen:
L. Calvier (Hannover, DE)
E. Legchenko (Hannover, DE)
P. Chouvarine (Hannover, DE)
J. Geldner (Hannover, DE)
G. Hansmann (Hannover, DE)
Background. Bone morphogenetic protein 2 (BMP2) and transforming growth factor beta (TGFβ1) are members of the TGFβ superfamily and functional antagonists of pathological remodeling in the arteries, heart and lung. However, the underlying mechanisms in vascular smooth muscle cells (SMC) and cardiomyocytes (CM), and their disturbance in PAH and right ventricular (RV) failure are unclear.
Hypothesis. The metabolic master regulator PPARγ counterbalances BMP and TGFβ pathways in human pulmonary artery SMC (HPASMC), and normalizes dysfunctional metabolism in PAH-PAs and the failing RV.
Methods. Mice overexpressing circulating TGFβ1 (TG-TGFβ1). Male SD rats were divided in 4 groups: control normoxia (ConNx); control/hypoxia (ConHx, 1xs.c. DMSO, 3wks hypoxia, 6wks room air); SU5416/hypoxia (SuHx, VEGFR2 inhibitor SU5416 s.c. x1, 3wks Hx, 6wks Nx); SU5416/hypoxia treated with PPARγ agonist pioglitazone (SuHx+Pio, SU5416 s.c.x1, 3wks Hx, 6wks Nx, including 5wks of Pio treatment p.o.). ChiPSeq (HAPSMC), mRNASeq (rat RV, LV), miRNA/mRNA qPCR on rodent tissue and on laser-microdissected explanted heart-lung tissue of IPAH HLTx patients and healthy donors (N=7-10). Pio-regulated miRNA, mRNA, protein expression, glucose/lipid metabolism by qPCR, WB, Seahorse assays in HPASMC and rat neonatal ventricular CM.
Results. TG-TGFβ1 mice and SuHx rats had PAH, and the latter also RV failure (RVF). PAH and RVF was fully inhibited by Pio. We found a pro-proliferative TGFβ1-Stat3-FoxO1 axis in HPASMC, and PPARγ as inhibitory regulator of TGFβ1-Stat3-FoxO1 and TGFβ1-Smad3/4, by physically interacting with Stat3 and Smad3. TGFβ1 induced fibrosis-related genes and miR130a/301b, suppressing PPARγ. Conversely, PPARγ inhibited TGFβ1-induced mitochondrial activation and PASMC proliferation, and regulated two glucose metabolism-related enzymes, phosphofructokinase (PFKP, a PPARγ target) via miR-331-5p and protein phosphatase 1 regulatory subunit 3G (PPP1R3G, a Smad3 target). PPARγ knockdown/deletion in PASMC activated TGFβ1 signaling. SuHx rats had cardiac dysregulation of all, specific miRNA/mRNA expression, fatty acid oxidation (FAO), and TGFβ signaling in the failing RV; these alterations were modulated by Pio through miRNA/mRNAs networks previously not known to be involved in PAH/RV dysfunction.
Conclusion. In PAH, detrimental epigenetic and transcriptional regulation related to disturbed glucose metabolism and altered lipid metabolism, occur in HPASMC and in cardiomyocytes, respectively. These novel PAH events, including a novel TGFβ1-Stat3-FoxO1 axis in vascular SMC, and a previously unknown shutdown of FAO in the stressed right heart, drive the fatal mechanisms in both the hypertensive pulmonary vasculature and the failing RV. PPARγ activation can normalize such abnormal signaling and metabolism, thus representing a novel therapeutic approach in PAH, other cardiovascular/pulmonary diseases (heart failure, Marfan’s syndrome, BPD, pulmonary fibrosis), and cancer.