cis-Element clustering correlates with dose-dependent pro- and antisignaling effects of IL18

The IL-18/IL-18R1 signalling axis: Diagnostic and therapeutic potential in hypertension and chronic kidney disease

Chronic kidney disease (CKD) is inherently an inflammatory condition, which ultimately results in the development of end stage renal disease or cardiovascular events. Low-grade inflammatory diseases such as hypertension and diabetes are leading causes of CKD. Declines in renal function correlate with elevated circulating pro-inflammatory cytokines in patients with these conditions. The inflammasome is an important inflammatory signalling platform that has been associated with low-grade chronic inflammatory diseases. Notably, activation and assembly of the inflammasome causes the auto cleavage of pro-caspase-1 into its active form, which then processes the pro-inflammatory cytokines pro-interleukin (IL)-1β and pro-IL-18 into their active forms. Currently, the nod-like receptor protein 3 (NLRP3) inflammasome has been implicated in the development of CKD in pre-clinical and clinical settings, and the ablation or inhibition of inflammasome components have been shown to be reno-protective in models of CKD. While clinical trials have demonstrated that neutralisation of IL-1β signalling by the drug anakinra lowers inflammation markers in haemodialysis patients, ongoing preclinical studies are showing that this ability to attenuate disease is limited in progressive models of kidney disease. These results suggest a potential predominant role for IL-18 in the development of CKD. This review will discuss the role of the inflammasome and its pro-inflammatory product IL-18 in the development of renal fibrosis and inflammation that contribute to the pathophysiology of CKD. Furthermore, we will examine the potential of the IL-18 signalling axis as an anti-inflammatory target in CKD and its usefulness as diagnostic biomarker to predict acute kidney injury.

A comprehensive pathway map of IL-18-mediated signalling

Interleukin-18 (IL-18) is a member of the IL-1 family of cytokines and was initially described as an IFN-γ-inducing factor derived from anti-CD3-stimulated T-helper (Th)1 cells. IL-18 plays a significant role in the activation of hematopoietic cell types mediating both Th1 and Th2 responses and is the primary inducer of interferon-γ in these cells. The biological activity of IL-18 is mediated through its binding to the IL-18 receptor complex and activation of nuclear factor-κB (NF-κB), culminating in the production and release of several cytokines, chemokines, and cellular adhesion molecules. In certain cell types, IL-18 also activates mitogen-activated protein kinases (MAPKs) and phosphoinositide 3-kinase/ AKT serine/threonine kinase (PI3K/AKT) signaling modules leading to the production and release of proinflammatory cytokines. IL-18-mediated signaling acts as one of the vital components of the immunomodulatory cytokine networks involved in host defense, inflammation, and tissue regeneration. Albeit its biomedical importance, a comprehensive resource of IL-18 mediated signaling pathway is currently lacking. In this study, we report on the development of an integrated pathway map of IL-18/IL-18R signaling. The pathway map was developed through literature mining from published literature based on manual curation guidelines adapted from NetPath and includes information on 16 protein-protein interaction events, 38 enzyme-catalysis events, 12 protein translocation events, 26 activations/inhibition events, transcriptional regulators, 230 gene regulation events and 84 induced protein expression events. The IL-18 signaling pathway can be freely accessed through the WikiPathways database (https://www.wikipathways.org/index.php/Pathway:WP4754).

Effect of strontium-substituted biphasic calcium phosphate on inflammatory mediators production by human monocytes

Calcium phosphate materials are widely used as bone substitutes because of their properties close to those of the mineral phase of bones. Nevertheless, after several months, calcium phosphate-based materials release particles that may be phagocytosed by monocytes, leading to an inflammatory reaction. Strontium is well known to counteract the osteoporosis process, but little is known about its effect on inflammatory processes. The purpose of this work was to study the effect of biphasic calcium phosphate (BCP) particles substituted with strontium on the inflammatory reaction. Human primary monocytes stimulated or not by lipopolysaccharide (LPS) were exposed to BCP particles containing strontium for 6 and 24 h. Inflammatory mediators (cytokines and matrix metalloproteinases (MMPs)) production was then quantified by ELISA and zymography. We observed that the presence of strontium had few effects on unstimulated cells, but it decreased the production of pro-inflammatory cytokines and the chemokine interleukin 8 in LPS-stimulated cell-conditioned medium. This work suggests for the first time that strontium may be involved in the control of inflammatory processes following BCP phagocytosis by human monocytes.