Augmenting hemopexin-mediated heme scavenging mitigates sepsis-induced acute kidney injury in humanized sickle cell mice.

Sickle cell disease (SCD) is characterized by chronic intravascular hemolysis and depletion of the heme scavenger hemopexin (HPX), generating a high-heme milieu that may increase susceptibility to inflammatory organ injury. Sepsis is a leading cause of acute kidney injury (AKI), yet the contribution of hemolysis-derived free heme to polymicrobial sepsis-associated AKI in SCD remains poorly defined. Using humanized SCD mice, we tested whether augmenting heme clearance via HPX mitigates septic AKI. Low-grade cecal ligation and puncture induced exaggerated systemic inflammation, elevated circulating heme and ferritin, and marked reductions in glomerular filtration rate (GFR) in sickling (hemoglobin SS [HbSS]) mice compared with nonsickling (HbAA) control mice. Septic SS mice also exhibited enhanced renal nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 inflammasome activation, increased oxidative stress, and tubular injury, consistent with heme-driven inflammatory and cytotoxic signaling. Acute administration of purified human HPX reduced circulating heme and ferritin, attenuated cytokine responses, and preserved GFR, indicating that restoration of heme buffering in SCD interrupts kidney injury pathways during septic stress. To achieve sustained heme control, we restored HPX expression using liver-directed delivery of adeno-associated virus serotype 8 (AAV8). AAV8-HPX restored hepatic HPX, reduced basal and sepsis-induced plasma heme levels, conferred protection against kidney dysfunction and tubular stress, and improved survival without evidence of hepatotoxicity. Collectively, these findings identify free heme as a central mediator linking hemolysis to sepsis-associated AKI in SCD, and establish that HPX augmentation via protein replacement or gene therapy is a mechanistically targeted, potentially translatable therapeutic strategy to mitigate heme-driven tissue injury and improve outcomes in SCD-associated sepsis.