Crotoxin modulates inflammation and macrophages' functions in a murine sepsis model

Sepsis is a syndrome of physiological and biochemical abnormalities induced by an infection that represents a major public health concern. It involves the early activation of inflammatory responses. Crotoxin (CTX), the major toxin of the South American rattlesnake Crotalus durissus terrificus venom, presents longstanding anti-inflammatory properties. Since immune system modulation may be a strategic target in sepsis management, and macrophages' functional and secretory activities are related to the disease's progression, we evaluated the effects of CTX on macrophages from septic animals. Balb/c male mice submitted to cecal ligation and puncture (CLP) were treated with CTX (0.9 μg/animal, subcutaneously) 1 h after the procedure and euthanized after 6 h. We used plasma samples to quantify circulating cytokines and eicosanoids. Bone marrow differentiated macrophages (BMDM) were used to evaluate the CTX effect on macrophages' functions. Our data show that CTX administration increased the survival rate of the animals from 40% to 80%. Septic mice presented lower plasma concentrations of IL-6 and TNF-α after CTX treatment, and higher concentrations of LXA₄, PGE_2, and IL-1β. No effect was observed in IL-10, IFN-γ, and RD1 concentrations. BMDM from septic mice treated with CTX presented decreased capacity of E. coli phagocytosis, but sustained NO and H₂O₂ production. We also observed higher IL-6 concentration in the culture medium of BMDM from septic mice, and CTX induced a significant reduction. CTX treatment increased IL-10 production by macrophages as well. Our data show that the protective effect of CTX in sepsis mortality involves modulation of macrophage functions and inflammatory mediators' production.