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Hydrogen sulfide (H 2 S) has been identified as a novel gasotransmitter and a substantial antioxidant that can activate various cellular targets to regulate physiological and pathological processes in mammals. However, under physiological conditions, it remains unclear whether it is involved in regulating cardiomyocyte (CM) proliferation during postnatal development in mice. This study mainly aimed to evaluate the role of H 2 S in postnatal CM proliferation and its regulating molecular mechanisms. We found that sodium hydrosulfide (NaHS, the most widely used H 2 S donor, 50-200 μM) increased neonatal mouse primary CM proliferation in a dose-dependent manner in vitro. Consistently, exogenous administration of H 2 S also promoted CM proliferation and increased the total number of CMs at postnatal 7 and 14 days in vivo. Moreover, we observed that the protein expression of SIRT1 was significantly upregulated after NaHS treatment. Inhibition of SIRT1 with EX-527 or si-SIRT1 decreased CM proliferation, while enhancement of the activation of SIRT1 with SRT1720 promoted CM proliferation. Meanwhile, pharmacological and genetic blocking of SIRT1 repressed the effect of NaHS on CM proliferation. Taken together, these results reveal that H 2 S plays a promotional role in proliferation of CMs in vivo and in vitro and SIRT1 is required for H 2 S-mediated CM proliferation, which indicates that H 2 S may be a potential modulator for heart development in postnatal time window.

Adult mammalian cardiomyocytes (CMs) lose their proliferative potential due to cell-cycle withdrawal and polyploidization and fail to mount a proliferative response to regenerate new CMs after cardiac injury. The decline in the proliferative potential of mammalian CMs occurs in the neonatal period when the endocrine system undergoes drastic changes for adaptation to extra-uterine life. There is an increase in circulating glucocorticoid (GC) levels shortly after birth in mammals, and thus, we sought to determine the roles and mechanisms of GCs in regulating CM proliferation. Here, we showed that GCs suppressed CM proliferation in vitro and in vivo , decreased the total number of CMs, and increased the cross-sectional area of CMs. However, the glucocorticoid receptor antagonist had no effect on CM proliferation. Agonists of adenylate cyclase and protein kinase A (PKA) inhibited CM proliferation, while PKA antagonists or knockdown of PKA alleviated the inhibitory effect of GCs on CM proliferation. GCs and the activation of the cyclic adenosine monophosphate (cAMP)/PKA signaling pathway facilitated yes-associated protein (YAP) phosphorylation in mouse CMs and promoted YAP protein translocation from the nucleus to the cytoplasm. Meanwhile, blocking the cAMP/PKA signaling pathway partially blocked the effect of GCs on YAP protein phosphorylation and YAP protein translocation. Thus, our findings suggest that GCs suppress mouse CM proliferation in vitro and in vivo , through a mechanism that involves targeting the cAMP-PKA-YAP signaling pathway. •GCs inhibited neonatal mouse CM proliferation in vivo and in vitro. •cAMP/PKA pathway is involved in the regulation of GCs on neonatal mouse CM proliferative potential. •GCs promoted YAP phosphorylation by activating the cAMP-PKA pathway. •GCs regulated neonatal mouse CM proliferative potential through cAMP-PKA-YAP pathway partially. [ABSTRACT FROM AUTHOR]