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Epigenetic processes have emerged as important modulators of kidney health and disease. Here, we studied the role of KDM6A (a histone demethylase that escapes X-chromosome inactivation) in kidney tubule epithelial cells. We initially observed an increase in tubule cell Kdm6a mRNA in male mice with unilateral ureteral obstruction (UUO). However, tubule cell knockout of KDM6A had relatively minor consequences, characterized by a small reduction in apoptosis, increase in inflammation and downregulation of the peroxisome proliferator-activated receptor (PPAR) signaling pathway. In proximal tubule lineage HK-2 cells, KDM6A knockdown decreased PPARγ coactivator-1α (PGC-1α) protein levels and mRNA levels of the encoding gene, PPARGC1A. Tubule cell Kdm6a mRNA levels were approximately 2-fold higher in female mice than in male mice, both under sham and UUO conditions. However, kidney fibrosis after UUO was similar in both sexes. The findings demonstrate Kdm6a to be a dynamically regulated gene in the kidney tubule, varying in expression levels by sex and in response to injury. Despite the context-dependent variation in Kdm6a expression, knockout of tubule cell KDM6A has subtle (albeit non-negligible) effects in the adult kidney, at least in males.

Introduction:Inflammation promotes adverse ventricular remodeling, a common antecedent of heart failure. Here, we set out to determine how cardiomyocytes respond to accumulating inflammatory cells within the remodeling heart and how this response, in turn, affects heart function.Methods:Experiments were performed in mouse and rat models of pressure overload, cultured mouse and human cardiomyocytes and human heart failure tissue.Results:CCR2+ monocyte-derived macrophages from Ccr2gfp/+mice accumulated early in mouse hearts after transverse aortic constriction (TAC) and Ccr2knockout attenuated cardiac function decline (ejection fraction, fractional shortening, cardiac output and stroke volume). Cardiomyocyte RNA sequencing revealed that the secretome of CCR2+ cells isolated from TAC hearts induced an interferon response in cardiomyocytes, characterized by upregulation of interferon-stimulated gene 15 (ISG15), which post-translationally modifies actively translated proteins through a process termed ISGylation. ISG15 upregulation or protein ISGylation were also observed in the hearts of mice infused with angiotensin II, uninephrectomized rats treated with DOCA-salt, rats after pulmonary artery banding; mouse and human cardiomyocytes exposed to recombinant interferons; and ventricular tissue of humans with non-ischemic cardiomyopathy. ISG15 accumulated at, or close to, cardiomyocyte intercalated discs and Nano LC-MS/MS, co-immunoprecipitation and co-localization experiments identified the myofibrillar protein filamin-C to be an ISGylation target at these sites. Lastly, knockout of Isg15attenuated cardiac function decline in mice following TAC, accompanied by a transcriptional profile indicative of preserved cardiac energetics.Conclusions:Collectively, these studies reveal that ISG15 induction is a characteristic of non-ischemic ventricular remodeling and they identify protein ISGylation as an inflammation-induced post-translational modification that may contribute to heart failure development. Strategies that prevent the ISGylation of cardiomyocyte proteins occurring during ventricular remodeling may improve heart failure outcomes.