Despite their protective antimicrobial function, neutrophil extracellular traps (NETs) have been implicated in propagation of inflammatory responses in several disease conditions including sepsis. Highly diffusible exogenous ROS produced under such inflammatory conditions, can induce exuberant NETs, thus making inhibition of NETs desirable in inflammatory diseases. Here we report that helminth parasite excretory/secretory factors termed as parasitic ligands (PL) inhibit ROS-induced NETs by blocking the activation of nonselective calcium permeable channel Transient Receptor Potential Melastatin 2 (TRPM2). Therapeutic implication of PL mediated blockage of NET formation was tested in preclinical model of septic peritonitis, where PL treatment regulated neutrophil cell death modalities including NET formation and mitigated neutrophil mediated inflammatory response. This translated into improved survival and reduced systemic and local bacterial load in infected mice. Overall, our results posit PL as an important biological regulator of neutrophil functions with implications to a variety of inflammatory diseases including peritonitis.

Neutrophil extracellular traps (NETs) are implicated in host defense and inflammatory pathologies alike. A wide range of pathogen- and host-derived factors are known to induce NETs, yet the knowledge about specific receptor–ligand interactions in this response is limited. We previously reported that macrophage-inducible C-type lectin (Mincle) regulates NET formation. In this article, we identify glycosphingolipid β-glucosylceramide (β-GlcCer) as a specific NET-inducing ligand of Mincle. We found that purified β-GlcCer induced NETs in mouse primary neutrophils in vitro and in vivo, and this effect was abrogated in Mincle deficiency. Cell-free β-GlcCer accumulated in the lungs of pneumonic mice, which correlated with pulmonary NET formation in wild-type, but not in Mincle^−/−, mice infected intranasally with Klebsiella pneumoniae. Although leukocyte infiltration by β-GlcCer administration in vivo did not require Mincle, NETs induced by this sphingolipid were important for bacterial clearance during Klebsiella infection. Mechanistically, β-GlcCer did not activate reactive oxygen species formation in neutrophils but required autophagy and glycolysis for NET formation, because ATG4 inhibitor NSC185058, as well as glycolysis inhibitor 2-deoxy-d-glucose, abrogated β-GlcCer–induced NETs. Forced autophagy activation by tamoxifen could overcome the inhibitory effect of glycolysis blockage on β-GlcCer–mediated NET formation, suggesting that autophagy activation is sufficient to induce NETs in response to this metabolite in the absence of glycolysis. Finally, β-GlcCer accumulated in the plasma of patients with systemic inflammatory response syndrome, and its levels correlated with the extent of systemic NET formation in these patients. Overall, our results posit β-GlcCer as a potent NET-inducing ligand of Mincle with diagnostic and therapeutic potential in inflammatory disease settings. Key Points Endogenous β-glucosylceramide (β-GlcCer) is a specific NET-inducing ligand of Mincle. β-GlcCer–induced NETs are antimicrobial and require glycolysis and autophagy. Cell-free β-GlcCer in infection and inflammation may have diagnostic potential.

All biological processes, from embryonic development to cancer, are tightly controlled by the interactions between genetics and epigenetics. An array of epigenetic modifications, such as DNA methylation, histone/chromatin modifications, and noncoding RNA-mediated targeting, are essential to regulate the heritable changes that occur during multiple cellular processes. A failure in proper regulation results in inappropriate gene expression that ultimately leads to pathological states. Groundbreaking advances in genomics and transcriptomics have revealed the potential involvement of epigenetics in various physiological and pathological states. The promising clinical and preclinical results shown by epigenetics drugs further underscore the central role of epigenetics in multiple human diseases, including cancer. AT rich interaction domain (ARID)-containing proteins are a family of evolutionarily conserved DNA binding proteins that regulate epigenetic modifications. Genome sequencing has revealed the existence of 15 ARID family proteins that are divided into 7 subfamilies based on their sequence and domain homology. Although the ARID family of proteins are implicated in cell growth, development, differentiation, and cancer, the diverse biological functions of many family members remain to be elucidated. Here, we focus on ARID4B to summarize its prominent role in embryonic stem cell differentiation and human malignancies.