Sex determines cardiac and renal Vulnerability to chronic hemoglobin toxicity

Hemolytic anemias are characterized by chronic intravascular hemolysis, leading to sustained release of acellular hemoglobin (Hb). Circulating Hb scavenges nitric oxide, releases redox-active heme, and promotes oxidative and inflammatory injury, contributing to progressive cardiac and renal dysfunction. Despite the known cardiopulmonary and renal complications in hemolytic disorders, the direct mechanisms of Hb-mediated injury and the influence of sex as a biological variable remain partially understood. In this study, we investigated the effects of chronic Hb exposure on cardiac and renal function in male and female mice. Animals received daily intraperitoneal injections of acellular Hb (320 mg/kg) for six weeks. Cardiac function was evaluated by echocardiography, renal function by transdermal glomerular filtration rate, and tissue injury biomarkers were quantified by ELISA. Mitochondrial respiratory function was also assessed in cardiac and renal tissues. Chronic Hb exposure induced significant cardiac dysfunction and renal impairment in male mice, evidenced by reduced ejection fraction, decreased stroke volume, diminished glomerular filtration rate, and elevated injury biomarkers. In contrast, female mice showed less impairment of cardiac and renal function and exhibited lower levels of biomarkers. Mitochondrial respiration revealed marked reductions in bioenergetics in males, whereas females maintained superior mitochondrial bioenergetics in both organs. These findings identify mitochondrial dysfunction as a mechanistic link between chronic Hb exposure and multi-organ injury and demonstrate sex-dependent bioenergetic adaptability as a key determinant of disease severity. Collectively, this work underscores the importance of incorporating sex as a biological variable and supports the development of Hb-neutralizing therapeutic strategies to mitigate Hb-induced organ damage.