The role of heme in sepsis induced Kupffer cell PANoptosis and senescence

Elevated heme levels, a consequence of hemolysis, are strongly associated with increased susceptibility to bacterial infections and adverse sepsis outcomes, particularly in older populations. However, the underlying mechanisms remain poorly understood. Using a cecal ligation and puncture (CLP) model of sepsis, we demonstrate that elevated heme levels correlate with Kupffer cell loss, increased bacterial burden, and heightened mortality. Mechanistically, we identify mitochondrial damage as a key driver of heme- and bacterial-induced Kupffer cell PANoptosis, a form of cell death integrating pyroptosis, apoptosis, and necroptosis, as well as cellular senescence. Specifically, heme activates phospholipase C gamma (PLC-γ), facilitating the translocation of cleaved gasdermin D (c-GSDMD) to mitochondria, resulting in GSDMD pore formation, mitochondrial dysfunction, and the release of mitochondrial DNA (mtDNA) during bacterial infection. This mitochondrial damage amplifies PANoptosis and triggers the cGAS-STING signaling pathway, further driving immune senescence. Notably, PLC-γ inhibition significantly reduces mitochondrial damage, cell death, and senescence caused by heme and bacterial infection. Furthermore, we show that hemopexin, a heme scavenger, effectively mitigates sepsis-induced Kupffer cell death and senescence, enhances bacterial clearance, and improves survival outcomes in both young and aged mice. These findings establish mitochondrial damage as a central mediator of heme induced Kupffer cell loss and highlight PLC-γ inhibition and hemopexin administration as promising therapeutic strategies for combating sepsis associated immune dysfunction.