Dysfunction of Microglial STAT3 Alleviates Depressive Behavior via Neuron-Microglia Interactions.
ABSTRACT: Neuron-microglia interactions have a crucial role in maintaining the neuroimmune system. The balance of neuroimmune system has emerged as an important process in the pathophysiology of depression. However, how neuron-microglia interactions contribute to major depressive disorders has been poorly understood. Herein, we demonstrated that microglia-derived synaptic changes induced antidepressive-like behavior by using microglia-specific signal transducer and activator of transcription 3 (STAT3) knockout (KO) (STAT3fl/fl;LysM-Cre+/-) mice. We found that microglia-specific STAT3 KO mice showed antidepressive-like behavior in the forced swim, tail suspension, sucrose preference, and open-field tests. Surprisingly, the secretion of macrophage colony-stimulating factor (M-CSF) was increased from neuronal cells in the brains of STAT3fl/fl;LysM-Cre+/- mice. Moreover, the phosphorylation of antidepressant-targeting mediators and brain-derived neurotrophic factor expression were increased in the brains of STAT3fl/fl;LysM-Cre+/- mice as well as in neuronal cells in response to M-CSF stimulation. Importantly, the miniature excitatory postsynaptic current frequency in the medial prefrontal cortex was increased in STAT3fl/fl;LysM-Cre+/- mice and in the M-CSF treatment group. Collectively, microglial STAT3 regulates depression-related behaviors via neuronal M-CSF-mediated synaptic activity, suggesting that inhibition of microglial STAT3 might be a new therapeutic strategy for depression.
Project description:STAT3 is a master regulator of the immune responses. Here we show that M. tuberculosis-infected stat3fl/fl lysm cre mice, defective for STAT3 in myeloid cells, contained lower bacterial load in lungs and spleens, reduced granuloma extension but higher levels of pulmonary neutrophils. STAT3-deficient macrophages showed no improved control of intracellular mycobacterial growth. Instead, protection associated to elevated ability of stat3fl/fl lysm cre antigen-presenting cells (APCs) to release IL-6 and IL-23 and to stimulate IL-17 secretion by mycobacteria-specific T cells. The increased IL-17 secretion accounted for the improved control of infection since neutralization of IL-17 receptor A in stat3fl/fl lysm cre mice hampered bacterial control. APCs lacking SOCS3, which inhibits STAT3 activation via several cytokine receptors, were poor inducers of priming and of the IL-17 production by mycobacteria-specific T cells. In agreement, socs3fl/fl cd11c cre mice deficient of SOCS3 in DCs showed increased susceptibility to M. tuberculosis infection. While STAT3 in APCs hampered IL-17 responses, STAT3 in mycobacteria-specific T cells was critical for IL-17 secretion, while SOCS3 in T cells impeded IL-17 secretion. Altogether, STAT3 signalling in myeloid cells is deleterious in the control of infection with M. tuberculosis.
Project description:Zn plays a key role in controlling macrophage function during an inflammatory event. Cellular Zn homeostasis is regulated by two families of metal transporters, the SLC39A family of importers and the SLC30A family of exporters; however, the precise role of these transporters in maintaining macrophage function is poorly understood. Using macrophage-specific Slc39a10-knockout (Slc39a10fl/fl;LysM-Cre+ ) mice, we found that Slc39a10 plays an essential role in macrophage survival by mediating Zn homeostasis in response to LPS stimulation. Compared with Slc39a10fl/fl mice, Slc39a10fl/fl;LysM-Cre+ mice had significantly lower mortality following LPS stimulation as well as reduced liver damage and lower levels of circulating inflammatory cytokines. Moreover, reduced intracellular Zn concentration in Slc39a10fl/fl;LysM-Cre+ macrophages led to the stabilization of p53, which increased apoptosis upon LPS stimulation. Concomitant knockout of p53 largely rescued the phenotype of Slc39a10fl/fl;LysM-Cre+ mice. Finally, the phenotype in Slc39a10fl/fl;LysM-Cre+ mice was mimicked in wild-type mice using the Zn chelator TPEN and was reversed with Zn supplementation. Taken together, these results suggest that Slc39a10 plays a role in promoting the survival of macrophages through a Zn/p53-dependent axis in response to inflammatory stimuli.
Project description:Suppressor of cytokine signalling 3 (SOCS3) negatively regulates STAT3 activation in response to several cytokines such as those in the gp130-containing IL-6 receptor family. Thus, SOCS3 may play a major role in immune responses to pathogens. In the present study, the role of SOCS3 in M. tuberculosis infection was examined. All Socs3(fl/fl) LysM cre, Socs3(fl/fl) lck cre (with SOCS3-deficient myeloid and lymphoid cells, respectively) and gp130(F/F) mice, with a mutation in gp130 that impedes binding to SOCS3, showed increased susceptibility to infection with M. tuberculosis. SOCS3 binding to gp130 in myeloid cells conveyed resistance to M. tuberculosis infection via the regulation of IL-6/STAT3 signalling. SOCS3 was redundant for mycobacterial control by macrophages in vitro. Instead, SOCS3 expression in infected macrophages and DCs prevented the IL-6-mediated inhibition of TNF and IL-12 secretion and contributed to a timely CD4+ cell-dependent IFN-? expression in vivo. In T cells, SOCS3 expression was essential for a gp130-independent control of infection with M. tuberculosis, but was neither required for the control of infection with attenuated M. bovis BCG nor for M. tuberculosis in BCG-vaccinated mice. Socs3(fl/fl) lck cre mice showed an increased frequency of ??+ T cells in different organs and an enhanced secretion of IL-17 by ??+ T cells in response to infection. Socs3(fl/fl) lck cre ??+ T cells impaired the control of infection with M. tuberculosis. Thus, SOCS3 expression in either lymphoid or myeloid cells is essential for resistance against M. tuberculosis via discrete mechanisms.
Project description:Professional antigen-presenting cells (APCs) are important modulators of acute graft-versus-host disease (GVHD). Although dendritic cells (DCs) are the most potent APC subset, other myeloid cells, especially macrophages (MFs) and neutrophils, recently have been shown to play a role in the severity of GVHD. The critical molecular mechanisms that determine the functions of myeloid cells in GVHD are unclear, however. Signal transducer and activator of transcription 3 (STAT3) is a master transcription factor that plays a crucial role in regulating immunity, but its role in MF biology and in acute GVHD remains unknown. To determine the impact of myeloid cell-specific expression of STAT3 on the severity of acute GVHD, we used myeloid cell-specific STAT3-deficient LysM-Cre/STAT3fl/- animals as recipients and donors in well-characterized experimental models of acute GVHD. We found that reduced expression of STAT3 in myeloid cells from the hosts, but not the donors, increased inflammation, increased donor T cell activation, and exacerbated GVHD. Our data demonstrate that STAT3 in host myeloid cells, such as MFs, dampens acute GVHD.
Project description:Macrophages regulate innate immunity to maintain intestinal homeostasis and play pathological roles in intestinal inflammation. Activation of the epidermal growth factor receptor (EGFR) promotes cellular proliferation, differentiation, survival, and wound closure in several cell types. However, the impact of EGFR in macrophages remains unclear. This study was to investigate whether EGFR activation in macrophages regulates cytokine production and intestinal inflammation. We found that EGFR was activated in colonic macrophages in mice with dextran sulfate sodium (DSS)-induced colitis and in patients with ulcerative colitis. DSS-induced acute colitis was ameliorated, and recovery from colitis was promoted in Egfr(fl/fl)LysM-Cre mice with myeloid cell-specific deletion of EGFR, compared with LysM-Cre mice. DSS treatment increased IL-10 and TNF levels during the acute phase of colitis, and increased IL-10 but reduced TNF levels during the recovery phase in Egfr(fl/fl)LysM-Cre mice. An anti-IL-10 neutralizing Ab abolished these effects of macrophage-specific EGFR deletion on DSS-induced colitis in Egfr(fl/fl)LysM-Cre mice. LPS stimulated EGFR activation and inhibition of EGFR kinase activity enhanced LPS-stimulated NF-?B activation in RAW 264.7 macrophages. Furthermore, induction of IL-10 production by EGFR kinase-blocked RAW 264.7 cells, in response to LPS plus IFN-?, correlated with decreased TNF production. Thus, although selective deletion of EGFR in macrophages leads to increases in both pro- and anti-inflammatory cytokines in response to inflammatory stimuli, the increase in the IL-10 level plays a role in suppressing proinflammatory cytokine production, resulting in protection of mice from intestinal inflammation. These results reveal an integrated response of macrophages regulated by EGFR in intestinal inflammatory disorders.
Project description:Macrophages form an important component of the innate immune system and serve as first responders against invading pathogens. While pathways critical for initiation of inflammatory responses between macrophages and other LysM+ myeloid cells are largely similar, it remains unknown whether a specific pathway has differential effects on inflammatory responses mediated between these cells. Recent studies demonstrated that depletion of SAG (Sensitive to Apoptosis Gene), an E3 ubiquitin ligase, blocked inflammatory responses generated by macrophages and dendritic cells in response to LPS in cell culture settings. However, the in vivo role of Sag on modulation of macrophages and neutrophil is not known. Here we generated LysM-Cre/Sag fl/fl mice with selective Sag deletion in myeloid lineage, and found that in contrast to in vitro observations, LysM-Cre/Sag fl/fl mice showed increased serum levels of proinflammatory cytokines and enhanced mortality in response to LPS. Interestingly, while Sag -/- macrophages released less proinflammatory cytokines, Sag -/- neutrophils released more. Mechanistically, expression of a list of genes response to LPS was significantly altered in bone marrow cells from LysM-Cre +/Sag fl/fl mice after LPS challenge. Specifically, induction by LPS of myeloperoxidase (Mpo), a key neutrophil enzyme, and Elane, neutrophil expressed elastase, was significantly decreased upon Sag depletion. Collectively, our study revealed that Sag plays a differential role in the activation of macrophages and neutrophils.
Project description:Although uncontrolled inflammatory response plays a central role in the pathogenesis of acute lung injury (ALI), the precise molecular mechanisms underlying the development of this disorder remain poorly understood. SOCS3 is an important negative regulator of IL-6-type cytokine signaling. SOCS3 is induced in lung during LPS-induced lung injury, suggesting that generation of SOCS3 may represent a regulatory product during ALI. In the current study, we created mice lacking SOCS3 expression in macrophages and neutrophils (LysM-cre SOCS3(fl/fl)). We evaluated the lung inflammatory response to LPS in both LysM-cre SOCS3(fl/fl) mice and the wild-type (WT) mice (SOCS3(fl/fl)). LysM-cre SOCS3(fl/fl) mice displayed significant increase of the lung permeability index (lung vascular leak of albumin), neutrophils, lung neutrophil accumulation (myeloperoxidase activity), and proinflammatory cytokines/chemokines in bronchial alveolar lavage fluids compared to WT mice. These phenotypes were consistent with morphological evaluation of lung, which showed enhanced inflammatory cell influx and intra-alveolar hemorrhage. We further identify the transcription factor, CCAAT/enhancer-binding protein (C/EBP) ? as a critical downstream target of SOCS3 in LPS-induced ALI. These results indicate that SOCS3 has a protective role in LPS-induced ALI by suppressing C/EBP? activity in the lung. Elucidating the function of SOCS3 would represent prospective targets for a new generation of drugs needed to treat ALI.
Project description:Junctional adhesion molecule-A (JAM-A) is a transmembrane glycoprotein expressed on leukocytes, endothelia, and epithelia that regulates biological processes including barrier function and immune responses. While JAM-A has been reported to facilitate tissue infiltration of leukocytes under inflammatory conditions, the contributions of leukocyte-expressed JAM-A in vivo remain unresolved. We investigated the role of leukocyte-expressed JAM-A in acute peritonitis induced by zymosan, lipopolysaccharide (LPS), or TNF? using mice with selective loss of JAM-A in myelomonocytic cells (LysM-Cre;Jam-afl/fl). Surprisingly, in LysM-Cre;Jam-afl/fl mice, loss of JAM-A did not affect neutrophil (PMN) recruitment into the peritoneum in response to zymosan, LPS, or TNF? although it was significantly reduced in Jam-aKO mice. In parallel, Jam-aKO peritoneal macrophages exhibited diminished CXCL1 chemokine production and decreased activation of NF-kB, whereas those from LysM-Cre;Jam-afl/fl mice were unaffected. Using Villin-Cre;Jam-afl/fl mice, targeted loss of JAM-A on intestinal epithelial cells resulted in increased intestinal permeability along with reduced peritoneal PMN migration as well as lower levels of CXCL1 and active NF-kB similar to that observed in Jam-aKO animals. Interestingly, in germ-free Villin-Cre;Jam-afl/fl mice, PMN recruitment was unaffected suggesting dependence on gut microbiota. Such observations highlight the functional link between a leaky gut and regulation of innate immune responses.
Project description:Autophagy is a cell biological pathway affecting immune responses. In vitro, autophagy acts as a cell-autonomous defense against Mycobacterium tuberculosis, but its role in vivo is unknown. Here we show that autophagy plays a dual role against tuberculosis: antibacterial and anti-inflammatory. M. tuberculosis infection of Atg5(fl/fl) LysM-Cre(+) mice relative to autophagy-proficient littermates resulted in increased bacillary burden and excessive pulmonary inflammation characterized by neutrophil infiltration and IL-17 response with increased IL-1? levels. Macrophages from uninfected Atg5(fl/fl) LysM-Cre(+) mice displayed a cell-autonomous IL-1? hypersecretion phenotype, whereas T cells showed propensity toward IL-17 polarization during nonspecific activation or upon restimulation with mycobacterial antigens. Thus, autophagy acts in vivo by suppressing both M. tuberculosis growth and damaging inflammation.
Project description:Why ocular mucosa is paucibacterial is unknown. Many different mechanisms have been suggested but the comprehensive experimental studies are sparse. We found that a deficiency in L-plastin (LCP1), an actin bundling protein, resulted in an ocular commensal overgrowth, characterized with increased presence of conjunctival Streptococcal spp. The commensal overgrowth correlated with susceptibility to P. aeruginosa-induced keratitis. L-plastin knock-out (KO) mice displayed elevated bacterial burden in the P. aeruginosa-infected corneas, altered inflammatory responses, and compromised bactericidal activity. Mice with ablation of LPL under the LysM Cre (LysM. Cre pos LPL fl/fl ) and S100A8 Cre (S100A8.Cre pos LPL fl/fl ) promoters had a similar phenotype to the LPL KOs mice. In contrast, infected CD11c.Cre pos LPL fl/fl mice did not display elevated susceptibility to infection, implicating the myeloid L-plastin-sufficient cells (e.g., macrophages and neutrophils) in maintaining ocular homeostasis. Mechanistically, the elevated commensal burden and the susceptibility to infection were linked to defects in neutrophil frequencies at steady state and during infection and compromised bactericidal activities upon priming. Macrophage exposure to commensal organisms primed neutrophil responses to P. aeruginosa, augmenting PMN bactericidal capacity in an L-plastin dependent manner. Cumulatively, our data highlight the importance of neutrophils in controlling ocular paucibacteriality, reveal molecular and cellular events involved in the process, and suggest a link between commensal exposure and resistance to infection.