Pulmonary arterial hypertension (PAH) is a syndrome characterized by a multiorgan metabolic dysfunction, with a cancer-like glycolytic shift seen in pulmonary arterial (PA) cells, and extra-pulmonary tissues. Because metabolic homeostasis relies on accurate and collaborative circadian timing within individual cells and tissues of the body, we hypothesized that human and experimental PAH are characterized by an arrhythmic clock machinery.
Methods and Results:
In PASMCs isolated from PAH patients and healthy controls, we synchronized the circadian rhythms by giving a 50% horse serum shock (called Zeitgerber time zero ZT0) and cells were harvested at ZT4, 8, 12, 16 and ZT20. The nuclear receptor Rev-Erbα (a core clock protein) was expressed at ZT0,16 and 20 in control but was significantly decreased in PAH-PASMCs (n=4/group, p<0.05). The Rev-Erbα agonist SR9011 (10uM) given to PAHPASMCs at ZT12, was able to restore Rev-Erb expression at ZT20 and to reduce PAH-PASMCs proliferation and resistance to apoptosis 24h after treatment. In rats, the circadian rhythms are synchronised by the light on from 6am (ZT0) to 6pm (ZT12). In vivo, we found that Rev-Erbα was expressed at ZT12 in control rats, but not in the monocrotaline (MCT) rats. Moreover, Actograms and Periodograms of their recorded activity showed that MCT rats failed to behave with a 24h period in constant darkness like control rats do. SR9011 injected daily at 4pm (100mg/kg, i.p.), 2 weeks post MCT injection for 2 weeks, increased Rev-Erbα expression at 6pm (ZT12), decreased mean Pulmonary arterial pressures (24.37mmHg vs 43.18mmHg, n=5/group, p=0.002) and decreased the Fulton index (0.40 vs 0.54, n=6/group, p=0.09) compared to vehicle treated rats.
We describe for the time evidences of the implication of the core clock protein Rev-Erb in the pathogenesis of PAH, and the use of selective circadian clock modulators, including Rev-Erb agonists, for the treatment of PAH.