Regulation of Chronic and Acute Inflammatory Disease by microRNA and Microbiota

Inflammation is implicated in cancer development, degenerative diseases, allergies as well as artherosecelorsis. Dysregulated immune responses lead to chronic inflammation and tissue damage. Finding the ways to terminate inflammatory responses when no longer needed, demands further investigation. Herein, we investigated the modulation of acute and chronic inflammatory disease models by inducing antiinflammatory state. Acute inflammatory model was induced with SEB, an enterotoxin produced by a ubiquitous Gram-positive coccus, Staphylococcus aureus (S. aureus), which exerts profound toxic effects on the immune system, which leads to the cytokine storm and adverse immune response. SEB is the main cause of nosocomial infections, acute and fatal respiratory distress and toxic shock syndrome. Regulatory T cells (Tregs) are well characterized for their role in maintaining immunological tolerance and immune homeostasis. The immunosuppressive function of T regulatory cells correlates with the expression of the forkhead transcription factor (Foxp3) in these cells. However, the precise regulatory mechanisms which govern the expression of Foxp3 remain unclear. Herein, for the first time, we uncovered the complex interaction of DNA methyltransferase (DNMT) and/or histone deacetylase (HDAC) which leads to the reactivation of transcription of Foxp3 mRNA and induction of Tregs. More specifically, for the first time, we demonstrated the differential regulation of microRNA following administration of an immuno-suppressive environmental contaminant, 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) in SEB-primed mice. We identified the dual role of miR-31 in induction of Tregs by targeting Foxp3 and CYP-1A. Because there is a growing incidence of obesity in the last 25 years which defines it as an epidemic condition all over the world, we characterized the mechanism of chronic inflammatory disease in Diet-Induced Obesity (DIO) model. Chronic low-grade, systematic inflammation associated with obesity plays a major role in the development of various chronic disease states, including type 2 diabetes, metabolic syndrome and atherosclerotic cardiovascular disease, which contribute to high rates of mortality and morbidity. Endocannabinoid system consisting of exogenous and endogenous ligands as well as associated receptors, play a major role in diet intake, energy balance, and regulating of immune functions. In the current study, we offer a better understanding in the underlying mechanism of blockade of cannabinoid CB1 receptor with SR141761A in attenuation of DIO phenotype. We revealed that modulation of neuroimmune guidance cue (Netrin-1) and its related receptor (Unc5b), via blockade of cannabinoid CB1 receptor, leads to less retention of macrophages in adipose tissue, and subsequently causes improvement in metabolic functions. In the current study, we have attempted to investigate the impact of CB1 receptor antagonist, on gut microbial community in DIO phenotype. Herein, for the first time, we identified a rise in Akkermansia muciniphila bacterial community, following blockade of CB1 receptor. Interestingly, we uncovered that therapeutic properties of SR141716A at microbial level can be attributed to the suppression of immunogenic bacteria, Lanchnospiraceace and Erysipelotrichaceae community, in DIO phenotype. Furthermore, we found that SR141716A altered microRNA profile in adipose tissue macrophages and skewed the balance of adipose tissue macrophages to more anti-inflammatory M2 macrophages. These studies provide novel mechanistic information on how microbiota and microRNA can be modulated to suppress acute and chronic inflammation thereby providing new tools to prevent and treat inflammatory diseases

Cannabinoid Receptor 1 Blockade Attenuates Obesity and Adipose Tissue Type 1 Inflammation Through miR-30e-5p Regulation of Delta-Like-4 in Macrophages and Consequently Downregulation of Th1 Cells

Obesity is characterized by chronic low-grade inflammation that contributes to development of cardiometabolic disorders. Cannabinoid receptor 1 (CB1) antagonists attenuate diet-induced obesity (DIO) and related inflammation, although the precise anti-inflammatory mechanisms involved have not been fully explored. In the current study we used a mouse model of DIO intervention to determine the microRNA (miRNA, miR)-mediated anti-obesity and anti-inflammatory effects of the CB1 antagonist, AM251. DIO mice that were fed high-fat diet (HFD) for 12 weeks were treated with AM251 (10 mg/kg) for an additional 4 weeks. HFD + AM251 mice experienced rapid and prolonged weight loss and reduced inflammatory M1 adipose tissue macrophage (ATM) infiltration. To investigate miRNA-mediated regulation of ATMs, F4/80+ cells from stromal vascular fractions (SVF) of epididymal fat were subjected to miR microarray analysis. Several miRs were differentially expressed in AM251-treated mice that were independent of calorie restriction. Prominently, miR-30e-5p was upregulated in ATMs from HFD + AM251 mice while the miR-30e-5p target, DLL4, was downregulated. Consistent with a decrease in DLL4-Notch signaling, fat storage and pro-inflammatory cytokine/chemokine expression was reduced following AM251 treatment. Furthermore, we found that AM251-treated macrophages can suppress DLL4-mediated Th1 polarization in CD4+ T cells. Together these data demonstrate that blocking CB1 receptors leads to upregulation of miR-30e-5p and down regulation of DLL4 in ATMs, which in turn suppress DLL4-Notch signaling-induced polarization of inflammatory Th1 cells and adipocyte energy storage. This combined effect of ATMs and T cells leads to an anti-inflammatory state and attenuation of DIO. These data support therapeutic potential of miR-30 in the treatment of cardiometabolic disorders

STAT4 is expressed in neutrophils and promotes antimicrobial immunity

Signal transducer and activator of transcription 4 (STAT4) is expressed in hematopoietic cells and plays a key role in the differentiation of T helper 1 cells. Although STAT4 is required for immunity to intracellular pathogens, the T cell-independent protective mechanisms of STAT4 are not clearly defined. In this report, we demonstrate that STAT4-deficient mice were acutely sensitive to methicillin-resistant Staphylococcus aureus (MRSA) infection. We show that STAT4 was expressed in neutrophils and activated by IL-12 via a JAK2-dependent pathway. We demonstrate that STAT4 was required for multiple neutrophil functions, including IL-12-induced ROS production, chemotaxis, and production of the neutrophil extracellular traps. Importantly, myeloid-specific and neutrophil-specific deletion of STAT4 resulted in enhanced susceptibility to MRSA, demonstrating the key role of STAT4 in the in vivo function of these cells. Thus, these studies identify STAT4 as an essential regulator of neutrophil functions and a component of innate immune responses in vivo

Blockade of CB1 cannabinoid receptor alters gut microbiota and attenuates inflammation and diet-induced obesity

Abstract Obesity is characterized by chronic low-grade, systemic inflammation, altered gut microbiota, and gut barrier disruption. Additionally, obesity is associated with increased activity of endocannabinoid system (eCB). However, the clear connection between gut microbiota and the eCB system in the regulation of energy homeostasis and adipose tissue inflammation and metabolism, remains to be established. We investigated the effect of treatment of mice with a cannabinoid receptor 1 (CB1) antagonist on Diet-Induced Obesity (DIO), specifically whether such a treatment that blocks endocannabinoid activity can induce changes in gut microbiota and anti-inflammatory state in adipose tissue. Blockade of CB1 attenuated DIO, inflammatory cytokines and trafficking of M1 macrophages into adipose tissue. Decreased inflammatory tone was associated with a lower intestinal permeability and decreased metabolic endotoxemia as evidenced by reduced plasma LPS level, and improved hyperglycemia and insulin resistance. 16S rRNA metagenomics sequencing revealed that CB1 blockade dramatically increased relative abundance of Akkermansia muciniphila and decreased Lanchnospiraceae and Erysipelotrichaceae in the gut. Together, the current study suggests that blocking of CB1 ameliorates Diet-Induced Obesity and metabolic disorder by modulating macrophage inflammatory mediators, and that this effect is associated with alterations in gut microbiota and their metabolites