PAD4 inhibitor GSK484 alleviates doxorubicin-induced myocardial fibrosis by modulating profibrotic, inflammatory and apoptotic signaling pathways in mice

BACKGROUND: The therapeutic potential of selective PAD4 inhibitors such as GSK484 in mitigating adverse cardiac remodeling remains to be established. This study tested the hypothesis that PAD4 inhibition by GSK484 alleviates doxorubicin (DOX)-induced myocardial fibrosis in mice by modulating the expression of fibrosis-related biomarkers. METHODS: Male BALB/c mice were injected intraperitoneally with DOX (6 mg/kg/day) or saline (control) for three days, followed by intraperitoneal injection of GSK484 (0.5 mg/kg/day) for seven days. Blood analytes were determined. Left ventricular tissues were analyzed for PAD4 protein expression, fibrotic content by Masson's staining, as well as mRNA expression of inflammatory, fibrotic, proliferation and apoptosis biomarkers by quantitative PCR. RESULTS: Significant elevation of fibrotic content and PAD4 protein expression was evidenced in the heart of DOX-induced cardiomyopathic mice relative to controls, together with significantly lower serum high-density lipoprotein. These alterations were prevented in DOX-induced cardiomyopathic mice treated with GSK484. Likewise, GSK484 alleviated the upregulation of biomarkers of inflammation (IL-6), fibrosis (fibronectin, MMP-2, MMP-9, SMAD1, SMAD6, SMAD7, BMP-2) and apoptosis (caspase 9, BAX, BCL-2) in this model. Moreover, GSK484 modified the significance and direction of the correlations between PAD4 transcription levels and several other biomarkers. CONCLUSION: Findings show that PAD4 inhibition by GSK484 is associated with reduced fibrosis in DOX-induced cardiomyopathy, accompanied by changes in key inflammatory and profibrotic signaling markers. While the underlying mechanisms remain unclear, findings support further investigation of PAD4 inhibition as a potential therapeutic strategy for fibrotic cardiac diseases.