The Cyclooxygenase 2 Inhibitor Etoricoxib as Adjunctive Therapy in Tuberculosis Impairs Macrophage Control of Mycobacterial Growth.

BACKGROUND: Current tuberculosis treatment regimens could be improved by adjunct host-directed therapies (HDT) targeting host responses. We investigated the antimycobacterial capacity of macrophages from patients with tuberculosis in a phase 1/2 randomized clinical trial (TBCOX2) of the cyclooxygenase-2 inhibitor etoricoxib. METHODS: Peripheral blood mononuclear cells from 15 patients with tuberculosis treated with adjunctive COX-2i and 18 controls (standard therapy) were collected on day 56 after treatment initiation. The ex vivo capacity of macrophages to control mycobacterial infection was assessed by challenge with Mycobacterium avium, using an in vitro culture model. Macrophage inflammatory responses were analyzed by gene expression signatures, and concentrations of cytokines were analyzed in supernatants by multiplex. RESULTS: Macrophages from patients receiving adjunctive COX-2i treatment had higher M. avium loads than controls after 6 days, suggesting an impaired capacity to control mycobacterial infection compared to macrophages from the control group. Macrophages from the COX-2i group had lower gene expression of TNF, IL-1B, CCL4, CXCL9, and CXCL10 and lowered production of cytokines IFN-ß and S100A8/A9 than controls. CONCLUSIONS: Our data suggest potential unfavorable effects with impaired macrophage capacity to control mycobacterial growth in patients with tuberculosis receiving COX-2i treatment. Larger clinical trials are required to analyze the safety of COX-2i as HDT in patients with tuberculosis. CLINICAL TRIALS REGISTRATION: NCT02503839.

Surface Toll-like receptor 3 expression in metastatic intestinal epithelial cells induces inflammatory cytokine production and promotes invasiveness.

Toll-like receptors (TLRs) are innate immune receptors for sensing microbial molecules and damage-associated molecular patterns released from host cells. Double-stranded RNA and the synthetic analog polyinosinic:polycytidylic acid (poly(I:C)) bind and activate TLR3. This stimulation leads to recruitment of the adaptor molecule TRIF (Toll/IL-1 resistance (TIR) domain-containing adapter-inducing interferon ß) and activation of the transcription factors nuclear factor κB (NF-κB) and interferon regulatory factor 3 (IRF-3), classically inducing IFNß production. Here we report that, unlike non-metastatic intestinal epithelial cells (IECs), metastatic IECs express TLR3 and that TLR3 promotes invasiveness of these cells. In response to poly(I:C) addition, the metastatic IECs also induced the chemokine CXCL10 in a TLR3-, TRIF-, and IRF3-dependent manner but failed to produce IFNß. This was in contrast to healthy and non-metastatic IECs, which did not respond to poly(I:C) stimulation. Endolysosomal acidification and the endosomal transporter protein UNC93B1 was required for poly(I:C)-induced CXCL10 production. However, TLR3-induced CXCL10 was triggered by immobilized poly(I:C), was only modestly affected by inhibition of endocytosis, and could be blocked with an anti-TLR3 antibody, indicating that TLR3 can still signal from the cell surface of these cells. Furthermore, plasma membrane fractions from metastatic IECs contained both full-length and cleaved TLR3, demonstrating surface expression of both forms of TLR3. Our results imply that metastatic IECs express surface TLR3, allowing it to sense extracellular stimuli that trigger chemokine responses and promote invasiveness in these cells. We conclude that altered TLR3 expression and localization may have implications for cancer progression.

A role for the adaptor proteins TRAM and TRIF in toll-like receptor 2 signaling.

Toll-like receptors (TLRs) are involved in sensing invading microbes by host innate immunity. TLR2 recognizes bacterial lipoproteins/lipopeptides, and lipopolysaccharide activates TLR4. TLR2 and TLR4 signal via the Toll/interleukin-1 receptor adaptors MyD88 and MAL, leading to NF-κB activation. TLR4 also utilizes the adaptors TRAM and TRIF, resulting in activation of interferon regulatory factor (IRF) 3. Here, we report a new role for TRAM and TRIF in TLR2 regulation and signaling. Interestingly, we observed that TLR2-mediated induction of the chemokine Ccl5 was impaired in TRAM or TRIF deficient macrophages. Inhibition of endocytosis reduced Ccl5 release, and the data also suggested that TRAM and TLR2 co-localize in early endosomes, supporting the hypothesis that signaling may occur from an intracellular compartment. Ccl5 release following lipoprotein challenge additionally involved the kinase Tbk-1 and Irf3, as well as MyD88 and Irf1. Induction of Interferon-ß and Ccl4 by lipoproteins was also partially impaired in cells lacking TRIF cells. Our results show a novel function of TRAM and TRIF in TLR2-mediated signal transduction, and the findings broaden our understanding of how Toll/interleukin-1 receptor adaptor proteins may participate in signaling downstream from TLR2.

Glycine inhibits NINJ1 membrane clustering to suppress plasma membrane rupture in cell death.

First recognized more than 30 years ago, glycine protects cells against rupture from diverse types of injury. This robust and widely observed effect has been speculated to target a late downstream process common to multiple modes of tissue injury. The molecular target of glycine that mediates cytoprotection, however, remains elusive. Here, we show that glycine works at the level of NINJ1, a newly identified executioner of plasma membrane rupture in pyroptosis, necrosis, and post-apoptosis lysis. NINJ1 is thought to cluster within the plasma membrane to cause cell rupture. We demonstrate that the execution of pyroptotic cell rupture is similar for human and mouse NINJ1 and that NINJ1 knockout functionally and morphologically phenocopies glycine cytoprotection in macrophages undergoing lytic cell death. Next, we show that glycine prevents NINJ1 clustering by either direct or indirect mechanisms. In pyroptosis, glycine preserves cellular integrity but does not affect upstream inflammasome activities or accompanying energetic cell death. By positioning NINJ1 clustering as a glycine target, our data resolve a long-standing mechanism for glycine-mediated cytoprotection. This new understanding will inform the development of cell preservation strategies to counter pathologic lytic cell death.

Chemical, Physical and Biological Triggers of Evolutionary Conserved Bcl-xL-Mediated Apoptosis.

BACKGROUND: The evidence that pan-Bcl-2 or Bcl-xL-specific inhibitors prematurely kill virus-infected or RNA/DNA-transfected cells provides rationale for investigating these apoptotic inducers further. We hypothesized that not only invasive RNA or DNA (biological factors) but also DNA/RNA-damaging chemical or physical factors could trigger apoptosis that have been sensitized with pan-Bcl-2 or Bcl-xL-specific agents; Methods: We tested chemical and physical factors plus Bcl-xL-specific inhibitor A-1155463 in cells of various origins and the small roundworms (C. elegans); Results: We show that combination of a A-1155463 along with a DNA-damaging agent, 4-nitroquinoline-1-oxide (4NQO), prematurely kills cells of various origins as well as C. elegans. The synergistic effect is p53-dependent and associated with the release of Bad and Bax from Bcl-xL, which trigger mitochondrial outer membrane permeabilization. Furthermore, we found that combining Bcl-xL-specific inhibitors with various chemical compounds or physical insults also induced cell death; Conclusions: Thus, we were able to identify several biological, chemical and physical triggers of the evolutionarily conserved Bcl-xL-mediated apoptotic pathway, shedding light on strategies and targets for novel drug development.

Coactivation of TLR2 and TLR8 in Primary Human Monocytes Triggers a Distinct Inflammatory Signaling Response.

Innate immune signaling is essential to mount a fast and specific immune response to pathogens. Monocytes and macrophages are essential cells in the early response in their capacity as ubiquitous phagocytic cells. They phagocytose microorganisms or damaged cells and sense pathogen/damage-associated molecular patterns (PAMPs/DAMPs) through innate receptors such as Toll-like receptors (TLRs). We investigated a phenomenon where co-signaling from TLR2 and TLR8 in human primary monocytes provides a distinct immune activation profile compared to signaling from either TLR alone. We compare gene signatures induced by either stimulus alone or together and show that co-signaling results in downstream differences in regulation of signaling and gene transcription. We demonstrate that these differences result in altered cytokine profiles between single and multi-receptor signaling, and show how it can influence both T-cell and neutrophil responses. The end response is tailored to combat extracellular pathogens, possibly by modifying the regulation of IFNß and IL12-family cytokines.

Enhanced expression of CXCL10 in inflammatory bowel disease: potential role of mucosal Toll-like receptor 3 stimulation.

BACKGROUND: We explored the gene expression in colonic biopsies of active and inactive inflammatory bowel disease (IBD) in an extensive material of ulcerative colitis (UC) and Crohn's disease (CD). The chemokine CXCL10 and its receptor CXCR3 were among the upregulated genes. This study examined the expression of CXCL10 and the mechanisms for its release in patients with UC or CD and in intestinal epithelial cell (IEC) lines. METHODS: A microarray gene expression analysis was done on colonic biopsies (n = 133) from patients with IBD. Biopsies were studied with immunohistochemistry for CXCL10 and CXCR3 expression. Mechanisms for CXCL10 release in peripheral blood mononuclear cells (PBMCs) and in the colonic epithelial cell lines HT-29 and SW620 were studied upon pattern recognition receptor (PRR) stimulation. RESULTS: CXCL10 and CXCR3 mRNA abundances were increased in biopsies from active UC and CD compared to inactive disease and controls. CXCL10 was mainly localized to mucosal epithelial cells, with increased immunostaining in active IBD. CXCR3-positive cells were scattered in the lamina propria. CXCL10 was secreted from the colonic epithelial cell lines in response to the Toll-like receptor 3 (TLR3) ligand polyinosinic: polycytidylic acid (poly(I:C)). This ligand also induced a marked release of CXCL10 in PBMCs from IBD patients and controls. CONCLUSIONS: We identified CXCL10 and CXCR3 as upregulated genes in colonic mucosa in active IBD. The TLR3-ligand poly(I:C) markedly increased release of CXCL10 in colonic epithelial cell lines, suggesting a TLR3-mediated CXCL10 release from mucosal epithelial cells in IBD patients.