Fibrosis is a basic connective tissue lesion defined by the increase in the fibrillar extracellular matrix (ECM) components in tissue or organ. Matrix metalloproteinases (MMPs) are a major group of proteases known to regulate the turn-over of ECM and so they are suggested to be important in tissue remodelling observed during fibrogenic process associated with chronic inflammation. Tissue remodelling is the result of an imbalance in the equilibrium of the normal processes of synthesis and degradation of ECM components markedly controlled by the MMPs/TIMP imbalance. We previously showed an association of the differences in collagen deposition in the lungs of bleomycin-treated mice with a reduced molar pro-MMP-9/TIMP-1 ratio. Using the carbon tetrachloride (CCl4) preclinical model of liver fibrosis in mice, we observed a significant increase in collagen deposition with increased expression and release of tissue inhibitors of metalloproteinase (TIMP)-1 both at 24 h and 3 weeks later. This suggests an early altered regulation of matrix turnover involved in the development of fibrosis. We also demonstrated an activation of NLRP3-inflammasome pathway associated with the IL-1R/MyD88 signalling in the development of experimental fibrosis both in lung and liver. This was also associated with an increased expression of purinergic receptors mainly P2X7. Finally, these observations emphasize those effective therapies for these disorders must be given early in the natural history of the disease, prior to the development of tissue remodelling and fibrosis.

The Nod-like receptor family protein 3 (NLRP3)-inflammasome pathway is known to be activated by danger signals such as monosodium urate (MSU). We investigated the role of P2 purinergic receptors in the activation of NLRP3-inflammasome pathway after MSU treatment of primary human monocyte-derived macrophages (MDMs). After initial stimulation with a low concentration of LPS (0.1 µg/ml), a 6 h treatment with MSU crystals (250, 500, and 1000 µg/ml) induced the MDMs to release IL-1β, IL-1α, and IL-6 in a dose-dependent manner. Moreover, the caspase 1 inhibitor Z-YVAD-FMK and the cathepsin B inhibitor CA-074Me reduced production of IL-1β in a dose-dependent manner after LPS + MSU treatment. We used real-time reverse transcription-quantitative PCR to show that treatment with LPS and MSU (500 µg/ml) induced significantly greater expression of NLRP3 and IL-1β than after treatment with LPS. We also found that MSU treatment induced P2X purinergic receptor 7 (P2X7R) mRNA and protein expression. Furthermore, addition of the P2X7 purinergic receptor antagonist A-740003 significantly impeded IL-1β production and pro-IL-1β cleavage after treatment with LPS + MSU. Remarkably, RNA silencing of P2X7R (but not P2X4R) inhibited the release of IL-1β and other M1 macrophage cytokines (such as IL-1α, IL-6, and TNF-α) from MDMs stimulated with LPS + MSU. Taken as a whole, our results show that P2 purinergic receptors and the NLRP3 inflammasome pathway are involved in the secretion of IL-1β from MSU-stimulated human macrophages. This pathway may constitute a novel therapeutic target for controlling the inflammatory process in several associated pathologies.

Sepsis is a systemic inflammatory response resulting from the inability of the host to contain the infection locally. Previously, we demonstrated that during severe sepsis there is a marked failure of neutrophil migration to the infection site, which contributes to dissemination of infection, resulting in high mortality. IL-17 plays an important role in neutrophil recruitment. Herein, we investigated the role of IL-17R signaling in polymicrobial sepsis induced by cecal ligation and puncture (CLP). It was observed that IL-17R-deficient mice, subjected to CLP-induced non-severe sepsis, show reduced neutrophil recruitment into the peritoneal cavity, spread of infection, and increased systemic inflammatory response as compared with C57BL/6 littermates. As a consequence, the mice showed an increased mortality rate. The ability of IL-17 to induce neutrophil migration was demonstrated in vivo and in vitro. Beside its role in neutrophil recruitment to the infection focus, IL-17 enhanced the microbicidal activity of the migrating neutrophils by a mechanism dependent on NO. Therefore, IL-17 plays a critical role in host protection during polymicrobial sepsis.

Innate immune responses against microorganisms may be mediated by Toll-like receptors (TLRs). Intestinal ischemia-reperfusion (i-I/R) leads to the translocation of bacteria and/or bacterial products such as endotoxin, which activate TLRs leading to acute intestinal and lung injury and inflammation observed upon gut trauma. Here, we investigated the role of TLR activation by using mice deficient for the common TLR adaptor protein myeloid differentiation factor 88 (MyD88) on local and remote inflammation following intestinal ischemia. Balb/c and MyD88(-/-) mice were subjected to occlusion of the superior mesenteric artery (45 min) followed by intestinal reperfusion (4 h). Acute neutrophil recruitment into the intestinal wall and the lung was significantly diminished in MyD88(-/-) after i-I/R, which was confirmed microscopically. Diminished neutrophil recruitment was accompanied with reduced concentration of TNF-alpha and IL-1beta level. Furthermore, diminished microvascular leak and bacteremia were associated with enhanced survival of MyD88(-/-) mice. However, neither TNF-alpha nor IL-1beta neutralization prevented neutrophil recruitment into the lung but attenuated intestinal inflammation upon i-I/R. In conclusion, our data demonstrate that disruption of the TLR/MyD88 pathway in mice attenuates acute intestinal and lung injury, inflammation, and endothelial damage allowing enhanced survival.