The helminth Fasciola hepatica is known as a master of immunomodulation. It suppresses antigen specific Th1 responses in concurrent bacterial infections while promoting the Th2/Treg regulatory responses, thus demonstrating its anti-inflammatory ability in vivo . We have recently demonstrated that a single intraperitoneal injection with native F. hepatica Glutathione S -Transferase (nFhGST), mostly comprised of mu-class isoforms, can suppresses the cytokine storm and increasing the survival rate in a mouse model of septic shock (1). Knowing that the peritoneal macrophages in response to microbial stimuli play essential roles in the defense, tissue repairment, and maintenance of homeostasis, the present study aimed to determine whether nFhGST could modulate the amount and dynamic of these cells concurrently to the suppression of pro-inflammatory cytokines. The remarkable findings described in this article are, (i) nFhGST suppresses serum IL-12, TNF-α, and IFN-γ in BALB/c mice challenged with a lethal dose of LPS, (ii) Although nFhGST does not elicit IL-10, it was able to significantly suppress the high levels of LPS-induced IL-10, which is considered a key cytokine in the pathophysiology of sepsis (2). iii) nFhGST prevent the disappearance of large peritoneal macrophages (LPM) whereas significantly increasing this population in the peritoneal cavity (PerC) of LPS treated animals, (iv) nFhGST promotes the alternative activation of macrophages whereas suppress the classical activation of macrophages in vitro by expressing high levels of Ym-1, a typical M2-type marker, secreting the production of IL-37, and preventing the production of TNF-α, iNOS2 and nitric oxide, which are typical markers of M1-type macrophages, (v) nFhGST suppress the bacterial phagocytosis of macrophages, a role that plays both, M1-and M2-macrophages, thus partially affecting the capacity of macrophages in destroying microbial pathogens. These findings present the first evidence that nFhGST is an excellent modulator of the PerC content in vivo, reinforcing the capacity of nFhGST as an anti-inflammatory drug against sepsis in animal models.
Importance: Sepsis is an infection that can lead to a life-threatening complication. Sepsis is the consequence of a systemic bacterial infection that exacerbates the immune cells' activation by bacterial products, resulting in the augmented release of inflammatory mediators. A critical factor in the pathogenesis of sepsis is the primary component of the outer membrane of Gram-negative bacteria known as lipopolysaccharide (LPS), which is sensed by toll-like receptor 4 (TLR4). For this reason, scientists aimed to develop antagonists able to block the cytokine storm by blocking TLR4. We report here that a mixture of mu-class isoforms from the F. hepatica glutathione S-transferase (nFhGST) protein family administered intraperitoneally 1 h after a lethal LPS injection, is capable of significantly suppressing the LPS-induced cytokine storm in a mouse model of septic shock whereas modulate the dynamic and abundance of large peritoneal macrophages in the peritoneal cavity of septic mice. These results suggest that nFhGST is a prominent candidate for drug development against endotoxemia and other inflammatory diseases.