Pharmacological inhibition of SUMO-1 with ginkgolic acid alleviates cardiac fibrosis induced by myocardial infarction in mice

Background and purpose: Protein modification by small ubiquitin-like modifier (SUMO) plays a critical role in the pathogenesis of heart diseases. The present study was designed to determine whether ginkgolic acid (GA) as a SUMO-1 inhibitor exerts an inhibitory effect on cardiac fibrosis induced by myocardial infarction (MI).

Experimental approach: GA was delivered by osmotic pumps in MI mice. Masson staining, electron microscopy (EM) and echocardiography were used to assess cardiac fibrosis, ultrastructure and function. Expression of SUMO-1, PML, TGF-β1 and PIN1 was measured with Western blot or Real-Time PCR. Collagen content, cell viability and myofibroblast transformation were measured in neonatal mouse cardiac fibroblasts (NMCFs). Promyelocytic leukemia (PML) protein was over-expressed by plasmid transfection.

Key results: GA improved cardiac fibrosis and dysfunction, and decreased SUMO-1 expression in MI mice. GA (>20 μM) inhibited NMCF viability in a dose-dependent manner. Nontoxic GA (10 μM) restrained angiotensin II (Ang II)-induced myofibroblast transformation and collagen production. GA also inhibited expression of TGF-β1 mRNA and protein in vitro and in vivo. GA suppressed PML SUMOylation and PML nuclear body (PML-NB) organization, and disrupted expression and recruitment of PIN1 (a positive regulator of TGF-β1 mRNA), whereas over-expression of PML reversed that.

Conclusions and implications: Inhibition of SUMO-1 by GA alleviated MI-induced heart dysfunction and fibrosis, and the SUMOylated PML/PIN1/TGF-β1 pathway is crucial for GA-inhibited cardiac fibrosis.