Persistent, unresolved inflammation in adipose tissue is a major contributor to obesity-associated metabolic complications. However, the molecular links between lipid-overloaded adipocytes and inflammatory immune cells in obese adipose tissues remain elusive. Here we identified adipocyte-secreted microRNA-34a (miR-34a) as a key mediator through its paracrine actions on adipose-resident macrophages. The expression of miR-34a in adipose tissues was progressively increased with the development of dietary obesity. Adipose-selective or adipocyte-specific miR-34a–KO mice were resistant to obesity-induced glucose intolerance, insulin resistance, and systemic inflammation, and this was accompanied by a significant shift in polarization of adipose-resident macrophages from proinflammatory M1 to antiinflammatory M2 phenotype. Mechanistically, mature adipocyte-secreted exosomes transported miR-34a into macrophages, thereby suppressing M2 polarization by repressing the expression of Krüppel-like factor 4 (Klf4). The suppressive effects of miR-34a on M2 polarization and its stimulation of inflammatory responses were reversed by ectopic expression of Klf4 in both bone marrow–derived macrophages and adipose depots of obese mice. Furthermore, increased miR-34a expression in visceral fat of overweight/obese subjects correlated negatively with reduced Klf4 expression, but positively with the parameters of insulin resistance and metabolic inflammation. In summary, miR-34a was a key component of adipocyte-secreted exosomal vesicles that transmitted the signal of nutrient overload to the adipose-resident macrophages for exacerbation of obesity-induced systemic inflammation and metabolic dysregulation.
Yong Pan, Xiaoyan Hui, Ruby Lai Chong Hoo, Dewei Ye, Cyrus Yuk Cheung Chan, Tianshi Feng, Yu Wang, Karen Siu Ling Lam, Aimin Xu
Goblet cell metaplasia, a disabling hallmark of chronic lung disease, lacks curative treatments at present. To identify novel therapeutic targets for goblet cell metaplasia, we studied the transcriptional response profile of IL-13–exposed primary human airway epithelia in vitro and asthmatic airway epithelia in vivo. A perturbation-response profile connectivity approach identified geldanamycin, an inhibitor of heat shock protein 90 (HSP90) as a candidate therapeutic target. Our experiments confirmed that geldanamycin and other HSP90 inhibitors prevented IL-13–induced goblet cell metaplasia in vitro and in vivo. Geldanamycin also reverted established goblet cell metaplasia. Geldanamycin did not induce goblet cell death, nor did it solely block mucin synthesis or IL-13 receptor–proximal signaling. Geldanamycin affected the transcriptome of airway cells when exposed to IL-13, but not when exposed to vehicle. We hypothesized that the mechanism of action probably involves TGF-β, ERBB, or EHF, which would predict that geldanamycin would also revert IL-17–induced goblet cell metaplasia, a prediction confirmed by our experiments. Our findings suggest that persistent airway goblet cell metaplasia requires HSP90 activity and that HSP90 inhibitors will revert goblet cell metaplasia, despite active upstream inflammatory signaling. Moreover, HSP90 inhibitors may be a therapeutic option for airway diseases with goblet cell metaplasia of an unknown mechanism of action.
Alejandro A. Pezzulo, Rosarie A. Tudas, Carley G. Stewart, Luis G. Vargas Buonfiglio, Brian D. Lindsay, Peter J. Taft, Nicholas D. Gansemer, Joseph Zabner
Neutrophil (PMN) infiltration of the intestinal mucosa is a hallmark of tissue injury associated with inflammatory bowel diseases (IBDs). The pathological effects of PMNs are largely attributed to the release of soluble mediators and reactive oxygen species (ROS). We identified what we believe is a new, ROS-independent mechanism whereby activated tissue-infiltrating PMNs release microparticles armed with proinflammatory microRNAs (miR-23a and miR-155). Using IBD clinical samples, and in vitro and in vivo injury models, we show that PMN-derived miR-23a and miR-155 promote accumulation of double-strand breaks (DSBs) by inducing lamin B1–dependent replication fork collapse and inhibition of homologous recombination (HR) by targeting HR-regulator RAD51. DSB accumulation in injured epithelium led to impaired colonic healing and genomic instability. Targeted inhibition of miR-23a and miR-155 in cultured intestinal epithelial cells and in acutely injured mucosa decreased the detrimental effects of PMNs and enhanced tissue healing responses, suggesting that this approach can be used in therapies aimed at resolution of inflammation, in wound healing, and potentially to prevent neoplasia.
Veronika Butin-Israeli, Triet M. Bui, Hannah L. Wiesolek, Lorraine Mascarenhas, Joseph J. Lee, Lindsey C. Mehl, Kaitlyn R. Knutson, Stephen A. Adam, Robert D. Goldman, Arthur Beyder, Lisa Wiesmuller, Stephen B. Hanauer, Ronen Sumagin
In response to viral pathogens, the host upregulates antiviral genes that suppress translation of viral mRNAs. However, induction of such antiviral responses may not be exclusive to viruses, as the pathways lie at the intersection of broad inflammatory networks that can also be induced by bacterial pathogens. Using a model of Gram-negative sepsis, we show that propagation of kidney damage initiated by a bacterial origin ultimately involves antiviral responses that result in host translation shutdown. We determined that activation of the eukaryotic translation initiation factor 2-α kinase 2/eukaryotic translation initiation factor 2α (Eif2ak2/Eif2α) axis is the key mediator of translation initiation block in late-phase sepsis. Reversal of this axis mitigated kidney injury. Furthermore, temporal profiling of the kidney translatome revealed that multiple genes involved in formation of the initiation complex were translationally altered during bacterial sepsis. Collectively, our findings imply that translation shutdown is indifferent to the specific initiating pathogen and is an important determinant of tissue injury in sepsis.
Takashi Hato, Bernhard Maier, Farooq Syed, Jered Myslinski, Amy Zollman, Zoya Plotkin, Michael T. Eadon, Pierre C. Dagher
Pyrin is an inflammasome sensor that promotes caspase-1–mediated pyroptotic cell death and maturation of proinflammatory cytokines IL-1β and IL-18. Familial Mediterranean fever (FMF), an autoinflammatory disorder, is associated with mutations in the gene encoding pyrin (MEFV). FMF-knockin (FMF-KI) mice that express chimeric pyrin protein with FMF mutation (MefvV726A/V726A) exhibit an autoinflammatory disorder mediated by autoactivation of the pyrin inflammasome. Increase in the levels of TNF are observed in FMF-KI mice, and many features of FMF overlap with the autoinflammatory disorder associated with TNF receptor signaling. In this study, we assessed the contribution of TNF signaling to pyrin inflammasome activation and its consequent role in distinct FMF pathologies. TNF signaling promoted the expression of pyrin in response to multiple stimuli and was required for inflammasome activation in response to canonical pyrin stimuli and in myeloid cells from FMF-KI mice. TNF signaling promoted systemic wasting, anemia, and neutrophilia in the FMF-KI mice. Further, TNF-induced pathology was induced specifically through the TNFR1 receptor, while TNFR2-mediated signaling was distinctly protective in colitis and ankle joint inflammation. Overall, our data show that TNF is a critical modulator of pyrin expression, inflammasome activation, and pyrin-inflammasomopathy. Further, specific blockade of TNFR1 or activation of TNFR2 could provide substantial protection against FMF pathologies.
Deepika Sharma, Ankit Malik, Clifford Guy, Peter Vogel, Thirumala-Devi Kanneganti
NLRP3 inflammasome plays a critical spatiotemporal role in the pathogenesis of experimental autoimmune encephalomyelitis (EAE). This study reports a mechanistic insight into noncanonical NLRP3 inflammasome activation in microglia for the effector stage of EAE. Microglia-specific deficiency of ASC (apoptosis-associated speck-like protein containing a C-terminal caspase-activation and recruitment [CARD] domain) attenuated T cell expansion and neutrophil recruitment during EAE pathogenesis. Mechanistically, TLR stimulation led to IRAKM–caspase-8–ASC complex formation, resulting in the activation of caspase-8 and IL-1β release in microglia. Noncanonical inflammasome-derived IL-1β produced by microglia in the CNS helped to expand the microglia population in an autocrine manner and amplified the production of inflammatory cytokines/chemokines. Furthermore, active caspase-8 was markedly increased in the microglia in the brain tissue from patients with multiple sclerosis. Taken together, our study suggests that microglia-derived IL-1β via noncanonical caspase-8–dependent inflammasome is necessary for microglia to exert their pathogenic role during CNS inflammation.
Cun-Jin Zhang, Meiling Jiang, Hao Zhou, Weiwei Liu, Chenhui Wang, Zizhen Kang, Bing Han, Quanri Zhang, Xing Chen, Jianxin Xiao, Amanda Fisher, William J. Kaiser, Masanori A. Murayama, Yoichiro Iwakura, Ji Gao, Julie Carman, Ashok Dongre, George Dubyak, Derek W. Abbott, Fu-Dong Shi, Richard M. Ransohoff, Xiaoxia Li
Dysregulated intestinal epithelial apoptosis initiates gut injury, alters the intestinal barrier, and can facilitate bacterial translocation leading to a systemic inflammatory response syndrome (SIRS) and/or multi-organ dysfunction syndrome (MODS). A variety of gastrointestinal disorders, including inflammatory bowel disease, have been linked to intestinal apoptosis. Similarly, intestinal hyperpermeability and gut failure occur in critically ill patients, putting the gut at the center of SIRS pathology. Regulation of apoptosis and immune-modulatory functions have been ascribed to Thirty-eight-negative kinase 1 (TNK1), whose activity is regulated merely by expression. We investigated the effect of TNK1 on intestinal integrity and its role in MODS. TNK1 expression induced crypt-specific apoptosis, leading to bacterial translocation, subsequent septic shock, and early death. Mechanistically, TNK1 expression in vivo resulted in STAT3 phosphorylation, nuclear translocation of p65, and release of IL-6 and TNF-α. A TNF-α neutralizing antibody partially blocked development of intestinal damage. Conversely, gut-specific deletion of TNK1 protected the intestinal mucosa from experimental colitis and prevented cytokine release in the gut. Finally, TNK1 was found to be deregulated in the gut in murine and porcine trauma models and human inflammatory bowel disease. Thus, TNK1 might be a target during MODS to prevent damage in several organs, notably the gut.
Milena Armacki, Anna Katharina Trugenberger, Ann K. Ellwanger, Tim Eiseler, Christiane Schwerdt, Lucas Bettac, Dominik Langgartner, Ninel Azoitei, Rebecca Halbgebauer, Rüdiger Groß, Tabea Barth, André Lechel, Benjamin M. Walter, Johann M. Kraus, Christoph Wiegreffe, Johannes Grimm, Annika Scheffold, Marlon R. Schneider, Kenneth Peuker, Sebastian Zeißig, Stefan Britsch, Stefan Rose-John, Sabine Vettorazzi, Eckhart Wolf, Andrea Tannapfel, Konrad Steinestel, Stefan O. Reber, Paul Walther, Hans A. Kestler, Peter Radermacher, Thomas F.E. Barth, Markus Huber-Lang, Alexander Kleger, Thomas Seufferlein
Allergic asthma is characterized by airway hyperresponsiveness, inflammation, and a cellular infiltrate dominated by eosinophils. Numerous epidemiological studies have related the exacerbation of allergic asthma with an increase in ambient inhalable particulate matter from air pollutants. This is because inhalable particles efficiently deliver airborne allergens deep into the airways, where they can aggravate allergic asthma symptoms. However, the cellular mechanisms by which inhalable particulate allergens (pAgs) potentiate asthmatic symptoms remain unknown, in part because most in vivo and in vitro studies exploring the pathogenesis of allergic asthma use soluble allergens (sAgs). Using a mouse model of allergic asthma, we found that, compared with their sAg counterparts, pAgs triggered markedly heightened pulmonary eosinophilia in allergen-sensitized mice. Mast cells (MCs) were implicated in this divergent response, as the differences in airway inflammatory responses provoked by the physical nature of the allergens were attenuated in MC-deficient mice. The pAgs were found to mediate MC-dependent responses by enhancing retention of pAg/IgE/FcεRI complexes within lipid raft–enriched, CD63+ endocytic compartments, which prolonged IgE/FcεRI-initiated signaling and resulted in heightened cytokine responses. These results reveal how the physical attributes of allergens can co-opt MC endocytic circuitry and signaling responses to aggravate pathological responses of allergic asthma in mice.
Cong Jin, Christopher P. Shelburne, Guojie Li, Kristina J. Riebe, Gregory D. Sempowski, W. Michael Foster, Soman N. Abraham
The E3 ubiquitin ligase Pellino 1 (Peli1) is a microglia-specific mediator of autoimmune encephalomyelitis. Its role in neurotropic flavivirus infection is largely unknown. Here, we report that mice deficient in Peli1 (Peli1–/–) were more resistant to lethal West Nile virus (WNV) infection and exhibited reduced viral loads in tissues and attenuated brain inflammation. Peli1 mediates chemokine and proinflammatory cytokine production in microglia and promotes T cell and macrophage infiltration into the CNS. Unexpectedly, Peli1 was required for WNV entry and replication in mouse macrophages and mouse and human neurons and microglia. It was also highly expressed on WNV-infected neurons and adjacent inflammatory cells from postmortem patients who died of acute WNV encephalitis. WNV passaged in Peli1–/– macrophages or neurons induced a lower viral load and impaired activation in WT microglia and thereby reduced lethality in mice. Smaducin-6, which blocks interactions between Peli1 and IRAK1, RIP1, and IKKε, did not inhibit WNV-triggered microglia activation. Collectively, our findings suggest a nonimmune regulatory role for Peli1 in promoting microglia activation during WNV infection and identify a potentially novel host factor for flavivirus cell entry and replication.
Huanle Luo, Evandro R. Winkelmann, Shuang Zhu, Wenjuan Ru, Elizabeth Mays, Jesus A. Silvas, Lauren L. Vollmer, Junling Gao, Bi-Hung Peng, Nathen E. Bopp, Courtney Cromer, Chao Shan, Guorui Xie, Guangyu Li, Robert Tesh, Vsevolod L. Popov, Pei-Yong Shi, Shao-Cong Sun, Ping Wu, Robyn S. Klein, Shao-Jun Tang, Wenbo Zhang, Patricia V. Aguilar, Tian Wang
The resolution of inflammation is an active process that is coordinated by endogenous mediators. Previous studies have demonstrated the immunomodulatory properties of the axonal guidance proteins in the initial phase of acute inflammation. We hypothesized that the neuronal guidance protein neogenin (Neo1) modulates mechanisms of inflammation resolution. In murine peritonitis, Neo1 deficiency (Neo1–/–) resulted in higher efficacies in reducing neutrophil migration into injury sites, increasing neutrophil apoptosis, actuating PMN phagocytosis, and increasing the endogenous biosynthesis of specialized proresolving mediators, such as lipoxin A4, maresin-1, and protectin DX. Neo1 expression was limited to Neo1-expressing Ly6Chi monocytes, and Neo1 deficiency induced monocyte polarization toward an antiinflammatory and proresolving phenotype. Signaling network analysis revealed that Neo1–/– monocytes mediate their immunomodulatory effects specifically by activating the PI3K/AKT pathway and suppressing the TGF-β pathway. In a cohort of 59 critically ill, intensive care unit (ICU) pediatric patients, we found a strong correlation between Neo1 blood plasma levels and abdominal compartment syndrome, Pediatric Risk of Mortality III (PRISM-III) score, and ICU length of stay and mortality. Together, these findings identify a crucial role for Neo1 in regulating tissue regeneration and resolution of inflammation, and determined Neo1 to be a predictor of morbidity and mortality in critically ill children affected by clinical inflammation.
Martin Schlegel, Andreas Körner, Torsten Kaussen, Urs Knausberg, Carmen Gerber, Georg Hansmann, Hulda Soffia Jónasdóttir, Martin Giera, Valbona Mirakaj
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