A shear stress-responsive pathway in monocytes drives cardiopulmonary bypass-induced inflammation via spectrin/RAF1/store-operated calcium entry.

Cardiopulmonary bypass (CPB) during cardiac surgery triggers inflammation that increases morbidity and mortality, though its molecular mechanisms remain unknown. To address this gap, we conducted single-nucleus RNA/ATAC sequencing (snRNA-seq/snATAC-seq) to profile transcriptional- and chromatin-level changes in circulating leukocytes from neonatal patients who underwent CPB. Classical monocytes increase after CPB, show dysregulated inflammatory genes, and exhibit altered chromatin accessibility, underscoring their role in CPB-associated inflammation. Expression of the proinflammatory cytokine interleukin-8 (IL-8/CXCL8) is significantly upregulated after CPB exposure, accompanied by increased accessibility of its promoter to AP-1 transcription factors. A genome-wide CRISPR screen in THP-1 cells identified SPTAN1 and RAF1 as novel effectors of hemodynamic stress. We further found that SPTAN1 and RAF1 activate store-operated calcium entry under CPB conditions, leading to elevated IL8 expression. We identify a shear stress-responsive SPTAN1/RAF1/store-operated calcium entry (SOCE) pathway and show that targeting it may alleviate CPB-induced inflammation, providing new insights into sterile inflammation and shear sensing in non-adherent cells.