Direct Effect of Septic Plasma in Human Cell Lines Viability

Abstract

Background: Sepsis is a life-threatening condition often associated with a high incidence of multiple organs injury. Several papers suggested the immune response by itself, with the production of humoral inflammatory mediators, is crucial in determining organ injury. However, little is known of how sepsis directly induces organ injury at the cellular levels. To assess this point, we set up an in vitro study to investigate the response of renal tubular cells (RTCs), monocytes (U937) and hepatocytes (HepG2) after 24 h-incubation with septic patients’ plasma. Methods: We enrolled 26 septic patients (“test” group). We evaluated cell viability, apoptosis and necrosis by flow cytometer. Caspase-3,-8,-9 and cytochrome-c concentrations have been analyzed using the Human enzyme-linked immunosorbent assay kit. Results: We found that a decrease of cell viability in all cell lines tested was associated to the increase of apoptosis in RTCs and U937 (p < 0.0001) and increase of necrosis in HepG2 (p < 0.5). The increase of apoptosis in RTCs and U937 cells was confirmed by higher levels of caspase-3 (p < 0.0001). We showed that apoptosis in both RTCs and U937 was triggered by the activation of the intrinsic pathway, as caspase-9 and cytochrome-c levels significantly increased (p < 0.0001), while caspase-8 did not change. This assumption was strengthened by the significant correlation of caspase-9 with both cytochrome-c (r = 0.73 for RTCs and r = 0.69 for U937) and caspase-3 (r = 0.69 for RTCs and r = 0.63 for U937). Conclusion: Humoral mediators in septic patients’ plasma induce apoptosis. This fact suggests that apoptosis inhibitors should be investigated as future strategy to reduce sepsis-induced organ damages.