NOD2 up-regulates TLR2-mediated IL-23p19 expression via NF-κB subunit c-Rel in Paneth cell-like cells

NOD2 silencing promotes cell apoptosis and inhibits drug resistance in chronic lymphocytic leukemia by inhibiting the NF-κB signaling pathway

Recent years have witnessed increasing studies on the effect of epigenetic silencing of genes in the progression of chronic lymphocytic leukemia (CLL). This study investigates whether the nucleotide binding oligomerization domain containing 2 (NOD2) participates in the cell apoptosis and drug resistance of CLL cells. Cells were treated with adriamycin (ADR), etoposide, aclacinomycin and daunorubicin. After treatment, drug resistance and cell proliferation were examined to detect the inhibitory effect of ADR on cell proliferation; flow cytometry to identify ADR accumulation, the cell cycle distribution and apoptosis after transfection, and rhodamine 123 accumulation and efflux tests to assess P-glycoprotein (P-gp) function. NOD2 silencing or inhibition of the nuclear factor kappa-B (NF-κB) signaling pathway suppressed the multidrug resistance level in CLL, the inhibition rate, and cell proliferation caused by ADR at concentrations of approximately 0.25-1.5 μmol/L. Greater accumulation of ADR was observed in the CLL-AAT cell line than in the CLL-AAT/A02 cell line, but NOD2 silencing or inhibition of the NF-κB signaling pathway further increased the accumulation of ADR drugs in the CLL-AAT cell line and inhibited the drug efflux pump function of P-gp. Additionally, NOD2 silencing or NF-κB signaling pathway inhibition increased the apoptotic rate. The results of this study indicate that NOD2 promotes cell apoptosis and reduces the drug resistance of CLL by inhibiting the NF-κB signaling pathway.

NF-κB: At the Borders of Autoimmunity and Inflammation

The transcription factor NF-κB regulates multiple aspects of innate and adaptive immune functions and serves as a pivotal mediator of inflammatory response. In the first part of this review, we discuss the NF-κB inducers, signaling pathways, and regulators involved in immune homeostasis as well as detail the importance of post-translational regulation by ubiquitination in NF-κB function. We also indicate the stages of central and peripheral tolerance where NF-κB plays a fundamental role. With respect to central tolerance, we detail how NF-κB regulates medullary thymic epithelial cell (mTEC) development, homeostasis, and function. Moreover, we elaborate on its role in the migration of double-positive (DP) thymocytes from the thymic cortex to the medulla. With respect to peripheral tolerance, we outline how NF-κB contributes to the inactivation and destruction of autoreactive T and B lymphocytes as well as the differentiation of CD4⁺-T cell subsets that are implicated in immune tolerance. In the latter half of the review, we describe the contribution of NF-κB to the pathogenesis of autoimmunity and autoinflammation. The recent discovery of mutations involving components of the pathway has both deepened our understanding of autoimmune disease and informed new therapeutic approaches to treat these illnesses.

Absence of neurotensin attenuates intestinal dysbiosis and inflammation by maintaining Mmp7/α-defensin axis in diet-induced obese mice

We previously reported that high levels of plasma neurotensin (NT), a gut hormone released from enteroendocrine cells of the small bowel, contribute to obesity and comorbid conditions. Gut microbiota has been implicated in the obesity development. Paneth cells are critical in maintaining gut microbiota composition and homeostasis by releasing antimicrobial proteins including α-defensins. The purpose of our current study was to determine the possible role of NT in gut microbiota composition and α-defensin gene expression associated with obesity. Here we show that the ratio of Firmicutes/Bacteroidetes (F/B ratio) and intestinal proinflammatory cytokines is significantly increased in NT+/+ mice fed with a high-fat diet (HFD) which were improved in NT-deficient mice. HFD disrupted the intestinal Mmp7/α-defensin axis, which was completely prevented in NT-/- mice. In addition, NT treatment inhibited DEFA5 expression and concurrent NF-κB activity, which was blocked by a pan PKC inhibitor (Gö6983) or an inhibitor for atypical PKCs (CRT0066854). More importantly, the shRNA-mediated knockdown of atypical PKCτ reversed NT-attenuated DEFA5 expression and increased NF-κB activity. NT contributes to the HFD-induced disruption of gut microbiota composition and α-defensin expression. PKCτ/λ plays a central role in NT-mediated α-defensin gene expression which might be mediated through the inhibition of NF-κB signaling pathways in Paneth cells.

IL-1α and IL-1β promote NOD2-induced immune responses by enhancing MAPK signaling

Both toll-like receptors (TLRs) and nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) induce a tightly regulated inflammatory response at risk of causing tissue damage, depending on the effectiveness of ensuing negative feedback regulatory mechanisms. Cross-regulation between TLRs, NLRs, and cytokine receptors has been observed. However, the cross-regulation between interleukin-1 (IL-1) receptors and NOD2 is not completely understood. In this study, we found that IL-1α/β increased NOD2-induced inflammatory response in human monocytic THP1 cells, peripheral blood mononuclear cells (PBMCs), mouse macrophage RWA264.7 cells and spleen cells, and in an in vivo experiment. IL-1α/β pre-treatment induced the production of CXC chemokines, including growth-regulated oncogene (GRO)-α, GRO-β, and IL-8, and proinflammatory cytokines, including IL-1β, IL-6, and TNFα, which are induced by the activation of NOD2, in a dose- and time-dependent manner. However, pre-treatment with the NOD2 ligand muramyl dipeptide (MDP) did not up-regulate the expression of cytokines induced by IL-1α/β re-treatment. IL-1β treatment increased the expression of A20, which is an important inhibitor of the innate immune response. However, the overexpression of A20 failed to inhibit MDP-induced cytokine production, suggesting that A20 had no effects on the NOD2-induced immune response. In addition, IL-1α/β increased the expression of NOD2 and its downstream adaptor RIP2, and IL-1α/β pre-treatment increased MDP-induced activation of mitogen-activated protein kinases (MAPKs), including ERK, JNK, and P38, which contributed to MDP-induced cytokine production. Based on these results, IL-1α/β promote the NOD2-induced immune responses by enhancing MDP-induced activation of MAPK signaling pathways.

Sublytic C5b-9 Induces IL-23 and IL-36a Production by Glomerular Mesangial Cells via PCAF-Mediated KLF4 Acetylation in Rat Thy-1 Nephritis

Sublytic C5b-9 formation on glomerular mesangial cells in rat Thy-1 nephritis (Thy-1N), a model of human mesangioproliferative glomerulonephritis, is accompanied by the production of proinflammatory cytokines, but the relationship between sublytic C5b-9 and cytokine synthesis and the underlying mechanism remains unclear. To explore the problems mentioned above, in this study, we first examined the levels of proinflammatory ILs (e.g., IL-23 and IL-36a) as well as transcription factor (KLF4) and coactivator (PCAF) in the renal tissues of Thy-1N rats and in the glomerular mesangial cell line (HBZY-1) stimulated by sublytic C5b-9. Then, we further determined the role of KLF4 and PCAF in sublytic C5b-9-induced IL-23 and IL-36a production as well as the related mechanism. Our results showed that the levels of KLF4, PCAF, IL-23, and IL-36a were obviously elevated. Mechanistic investigation revealed that sublytic C5b-9 stimulation could increase IL-23 and IL-36a synthesis through KLF4 and PCAF upregulation, and KLF4 and PCAF could form a complex, binding to the IL-23 or IL-36a promoter in a KLF4-dependent manner, causing gene transcription. Importantly, KLF4 acetylation by PCAF contributed to sublytic C5b-9-induced IL-23 and IL-36a transcription. Besides, the KLF4 binding regions on IL-23 or IL-36a promoters and the KLF4 lysine site acetylated by PCAF were identified. Furthermore, silencing renal KLF4 or PCAF gene could significantly inhibit IL-23 or IL-36a secretion and tissue damage of Thy-1N rats. Collectively, these findings implicate that the KLF4/PCAF interaction and KLF4 acetylation by PCAF play a pivotal role in the sublytic C5b-9-mediated IL-23 and IL-36a production of Thy-1N rats.

NOD2 Expression in Intestinal Epithelial Cells Protects Toward the Development of Inflammation and Associated Carcinogenesis

Nucleotide-binding oligomerization domain 2 (NOD2) is an intracellular pattern recognition receptor that senses bacterial peptidoglycan-conserved motifs in cytosol and stimulates host immune response including epithelial and immune cells. The association of NOD2 mutations with a number of inflammatory pathologies including Crohn's disease (CD), graft-versus-host diseases, or Blau syndrome, highlights its pivotal role in inflammatory response and the associated-carcinogenesis development. Since its identification in 2001 and its association with CD, the role of NOD2 in epithelial cells and immune cells has been investigated extensively but the precise mechanism by which NOD2 mutations lead to CD and the associated carcinogenesis development is largely unknown. In this review, we present and discuss recent developments about the role of NOD2 inside epithelial cells on the control of the inflammatory process and its linked carcinogenesis development.

ICG-001 affects DRP1 activity and ER stress correlative with its anti-proliferative effect

Mitochondria form a highly dynamic network driven by opposing scission and fusion events. DRP1 is an essential modulator of mitochondrial fission and dynamics within mammalian cells. Its fission activity is regulated by posttranslational modifications such as activating phosphorylation at serine 616. DRP1 activity has recently been implicated as being dysregulated in numerous human disorders such as cancer and neurodegenerative diseases. Here we describe the development of a cell-based screening assay to detect DRP1 activation. We utilized this to undertake focused compound library screening and identified potent modulators that affected DRP1 activity including ICG-001, which is described as WNT/β-catenin signaling inhibitor. Our findings elucidate novel details about ICG-001’s mechanism of action (MOA) in mediating anti-proliferative activity. We show ICG-001 both inhibits mitochondrial fission and activates an early endoplasmic reticulum (ER) stress response to induce cell death in susceptible colorectal cancer cell lines.