Receptor-interacting protein kinase 3 deficiency inhibits immune cell infiltration and attenuates organ injury in sepsis

Introduction: Sepsis is defined as a systemic hyper-inflammatory immune response, with a subsequent immune-suppressive phase, which leads to multiple organ dysfunction and late lethality. Receptor-interacting protein kinase 3 (RIPK3)-dependent necrosis is implicated in driving tumor necrosis factor alpha (TNF-alpha)- and sepsis-induced mortality in mice. However, it is unknown if RIPK3 deficiency has any impact on immune cell trafficking, which contributes to organ damage in sepsis. Methods: To study this, male wild-type (WT) and RIPK3-deficient (Ripk3(-/-) mice on C57BL/6 background were subjected to sham operation or cecal ligation and puncture (CLP)-induced sepsis. Blood and tissue samples were collected 20 hours post-CLP for various measurements. Results: In our severe sepsis model, the mean survival time of Ripk3(-/-) mice was significantly extended to 68 hours compared to 41 hours for WT mice. Ripk3(-/-) mice had significantly decreased plasma levels of TNF-alpha and IL-6 and organ injury markers compared to WT mice post-CLP. In the lungs, Ripk3(-/-) mice preserved better integrity of microscopic structure with reduced apoptosis, and decreased levels of IL-6, macrophage inflammatory protein (MIP)-2 and keratinocyte-derived chemokine (KC), compared to WT. In the liver, the levels of MIP-1, MIP-2 and KC were also decreased in septic Ripk3(-/-) mice. Particularly, the total number of neutrophils in the lungs and liver of Ripk3(-/-) mice decreased by 59.9% and 66.7%, respectively, compared to WT mice post-CLP. In addition, the number of natural killer (NK) and CD8T cells in the liver decreased by 64.8% and 53.4%, respectively, in Ripk3(-/-) mice compared to WT mice post-sepsis. Conclusions: Our data suggest that RIPK3 deficiency modestly protected from CLP-induced severe sepsis and altered the immune cell trafficking in an organ-specific manner attenuating organ injury. Thus, RIPK3 acts as a detrimental factor in contributing to the organ deterioration in sepsis.