Transcriptomic atlas reveals inflammation and complement as pathogenic factors in hemolysis-induced tissue damage

Intravascular hemolysis contributes to sickle cell disease (SCD) by releasing danger signals like hemoglobin and heme, which trigger inflammation and oxidative stress. Yet, the exact mechanisms behind organ damage remain unclear. Using bulk RNA sequencing in a phenylhydrazine-induced hemolysis model in mice, we mapped transcriptional changes across the spleen, liver, lung, and kidney. We identified common gene expression patterns tied to inflammation, oxidative stress, cell death, coagulation, and metabolic reprogramming. These signatures appeared consistently in SCD (HbSS Townes mice), heme-injected mice, and phenylhydrazine-treated mice, implicating heme as a shared driver of injury. Complement activation emerged as a central mechanism, marked by elevated plasma C5a and increased C5aR1 expression in all organs. Notably, C5 inhibition reduced inflammatory gene expression, especially in the lung. Our findings highlight inflammation and complement activation as key mediators of hemolysis-induced organ injury and point to complement inhibition as a potential therapy. This study sheds light on the broader impact of hemolysis in SCD, including complications like acute chest syndrome and organ dysfunction.