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
Inflammation occurs in all tissues in response to injury or stress and is the key process underlying hepatic fibrogenesis. Targeting chronic and uncontrolled inflammation is one strategy to prevent liver injury and fibrosis progression. Here, we demonstrate that triggering receptor expressed on myeloid cells-1 (TREM-1), an amplifier of inflammation, promotes liver disease by intensifying hepatic inflammation and fibrosis. In the liver, TREM-1 expression is limited to liver macrophages and monocytes and is highly upregulated on Kupffer cells, circulating monocytes, and monocyte-derived macrophages in a mouse model of chronic liver injury and fibrosis induced by carbon tetrachloride (CCl4) administration. TREM-1 signaling promotes pro-inflammatory cytokine production and mobilization of inflammatory cells to the site of injury. Deletion of Trem1 reduced liver injury, inflammatory cell infiltration, and fibrogenesis. Reconstitution of Trem1-deficient mice with Trem1-sufficient Kupffer cells restored recruitment of inflammatory monocytes and severity of liver injury. Markedly increased infiltration of liver fibrotic areas with TREM-1-positive Kupffer cells and monocytes/macrophages was found in patients with hepatic fibrosis. Our data support a role of TREM-1 in liver injury and hepatic fibrogenesis and suggests that TREM-1 is a master regulator of Kupffer cell activation, which escalates chronic liver inflammatory responses, activates hepatic stellate cells, and reveals a novel mechanism of promotion of liver fibrosis.
Anh Thu Nguyen-Lefebvre, Ashwin Ajith, Vera Portik-Dobos, Daniel David Horuzsko, Ali Syed Arbab, Amiran Dzutsev, Ramses Sadek, Giorgio Trinchieri, Anatolij Horuzsko
The mechanisms of pain induction by inflammation have been extensively studied. However, the mechanisms of pain resolution are not fully understood. Here, we report that GPR37, expressed by macrophages (MΦs) but not microglia, contributes to the resolution of inflammatory pain. Neuroprotectin D1 (NPD1) and prosaptide TX14 increase intracellular Ca2+ (iCa2+) levels in GPR37-transfected HEK293 cells. NPD1 and TX14 also bind to GPR37 and cause GPR37-dependent iCa2+ increases in peritoneal MΦs. Activation of GPR37 by NPD1 and TX14 triggers MΦ phagocytosis of zymosan particles via calcium signaling. Hind paw injection of pH-sensitive zymosan particles not only induces inflammatory pain and infiltration of neutrophils and MΦs, but also causes GPR37 upregulation in MΦs, phagocytosis of zymosan particles and neutrophils by MΦs in inflamed paws, and resolution of inflammatory pain in WT mice. Mice lacking Gpr37 display deficits in MΦ phagocytic activity and delayed resolution of inflammatory pain. Gpr37-deficient MΦs also show dysregulations of proinflammatory and antiinflammatory cytokines. MΦ depletion delays the resolution of inflammatory pain. Adoptive transfer of WT but not Gpr37-deficient MΦs promotes the resolution of inflammatory pain. Our findings reveal a previously unrecognized role of GPR37 in regulating MΦ phagocytosis and inflammatory pain resolution.
Sangsu Bang, Ya-Kai Xie, Zhi-Jun Zhang, Zilong Wang, Zhen-Zhong Xu, Ru-Rong Ji
Induction of TLR2 activation depends on its association with adapter protein MyD88. We have found that levels of TLR2 and MyD88 are elevated in the hippocampus and cortex of Alzheimer’s disease (AD) patients and 5XFAD mouse model of AD. Since there is no specific inhibitor of TLR2, to target induced TLR2 from therapeutic angle, we engineered a peptide corresponding to the TLR2-interacting domain of MyD88 (TIDM) that binds to the BB loop of only TLR2, but not other TLRs. Interestingly, wild type (wt) TIDM peptide inhibited microglial activation induced by fibrillar Aβ1-42 and lipoteichoic acid, but not 1-methyl-4-phenylpyridinium, double-stranded RNA, bacterial lipopolysaccharide, flagellin, and CpG DNA. After intranasal administration, wtTIDM peptide reached the hippocampus, reduced hippocampal glial activation, lowered Aβ burden, attenuated neuronal apoptosis, and improved memory and learning in 5XFAD mice. However, wtTIDM peptide was not effective in 5XFAD mice lacking TLR2. In addition to 5XFAD mice, wtTIDM peptide also suppressed the disease process in mice with experimental allergic encephalomyelitis and collagen-induced arthritis. Therefore, selective targeting of activated status of one component of the innate immune system by wtTIDM peptide may be beneficial in AD as well as other disorders in which TLR2-MyD88 signaling plays a role in disease pathogenesis.
Suresh B. Rangasamy, Malabendu Jana, Avik Roy, Grant T. Corbett, Madhuchhanda Kundu, Sujyoti Chandra, Susanta Mondal, Sridevi Dasarathi, Elliott J. Mufson, Rama K. Mishra, Chi-Hao Luan, David A. Bennett, Kalipada Pahan
Myocardial infarction (MI) arising from obstruction of the coronary circulation engenders massive cardiomyocyte loss and replacement by non-contractile scar tissue, leading to pathological remodeling, dysfunction, and ultimately heart failure. This is presently a global health problem for which there is no effective cure. Following MI, the innate immune system directs the phagocytosis of dead cell debris in an effort to stimulate cell repopulation and tissue renewal. In the mammalian adult heart, however, the persistent influx of immune cells, coupled with the lack of an inherent regenerative capacity, results in cardiac fibrosis. Here, we reveal that stimulation of cardiac lymphangiogenesis with VEGF-C improves clearance of the acute inflammatory response after MI by trafficking immune cells to draining mediastinal lymph nodes (MLNs) in a process dependent on lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1). Deletion of Lyve1 in mice, preventing docking and transit of leukocytes through the lymphatic endothelium, results in exacerbation of chronic inflammation and long-term deterioration of cardiac function. Our findings support targeting of the lymphatic/immune cell axis as a therapeutic paradigm to promote immune modulation and heart repair.
Joaquim Miguel Vieira, Sophie Norman, Cristina Villa del Campo, Thomas J. Cahill, Damien N. Barnette, Mala Gunadasa-Rohling, Louise A. Johnson, David R. Greaves, Carolyn A. Carr, David G. Jackson, Paul R. Riley
It is critical for survival to assign positive or negative valence to salient stimuli in a correct manner. Accordingly, harmful stimuli and internal states characterized by perturbed homeostasis are accompanied by discomfort, unease, and aversion. Aversive signaling causes extensive suffering during chronic diseases, including inflammatory conditions, cancer, and depression. Here, we investigated the role of melanocortin 4 receptors (MC4Rs) in aversive processing using genetically modified mice and a behavioral test in which mice avoid an environment that they have learned to associate with aversive stimuli. In normal mice, robust aversions were induced by systemic inflammation, nausea, pain, and κ opioid receptor–induced dysphoria. In sharp contrast, mice lacking MC4Rs displayed preference or indifference toward the aversive stimuli. The unusual flip from aversion to reward in mice lacking MC4Rs was dopamine dependent and associated with a change from decreased to increased activity of the dopamine system. The responses to aversive stimuli were normalized when MC4Rs were reexpressed on dopamine D1 receptor–expressing cells or in the striatum of mice otherwise lacking MC4Rs. Furthermore, activation of arcuate nucleus proopiomelanocortin neurons projecting to the ventral striatum increased the activity of striatal neurons in an MC4R-dependent manner and elicited aversion. Our findings demonstrate that melanocortin signaling through striatal MC4Rs is critical for assigning negative motivational valence to harmful stimuli.
Anna Mathia Klawonn, Michael Fritz, Anna Nilsson, Jordi Bonaventura, Kiseko Shionoya, Elahe Mirrasekhian, Urban Karlsson, Maarit Jaarola, Björn Granseth, Anders Blomqvist, Michael Michaelides, David Engblom
Radiographic contrast agents cause acute kidney injury (AKI), yet the underlying pathogenesis is poorly understood. Nod-like receptor pyrin containing 3–deficient (Nlrp3-deficient) mice displayed reduced epithelial cell injury and inflammation in the kidney in a model of contrast-induced AKI (CI-AKI). Unexpectedly, contrast agents directly induced tubular epithelial cell death in vitro that was not dependent on Nlrp3. Rather, contrast agents activated the canonical Nlrp3 inflammasome in macrophages. Intravital microscopy revealed diatrizoate (DTA) uptake within minutes in perivascular CX3CR1+ resident phagocytes in the kidney. Following rapid filtration into the tubular luminal space, DTA was reabsorbed and concentrated in tubular epithelial cells via the brush border enzyme dipeptidase-1 in volume-depleted but not euvolemic mice. LysM-GFP+ macrophages recruited to the kidney interstitial space ingested contrast material transported from the urine via direct interactions with tubules. CI-AKI was dependent on resident renal phagocytes, IL-1, leukocyte recruitment, and dipeptidase-1. Levels of the inflammasome-related urinary biomarkers IL-18 and caspase-1 were increased immediately following contrast administration in patients undergoing coronary angiography, consistent with the acute renal effects observed in mice. Taken together, these data show that CI-AKI is a multistep process that involves immune surveillance by resident and infiltrating renal phagocytes, Nlrp3-dependent inflammation, and the tubular reabsorption of contrast via dipeptidase-1.
Arthur Lau, Hyunjae Chung, Takanori Komada, Jaye M. Platnich, Christina F. Sandall, Saurav Roy Choudhury, Justin Chun, Victor Naumenko, Bas G.J. Surewaard, Michelle C. Nelson, Annegret Ulke-Lemée, Paul L. Beck, Hallgrimur Benediktsson, Anthony M. Jevnikar, Sarah L. Snelgrove, Michael J. Hickey, Donna L. Senger, Matthew T. James, Justin A. Macdonald, Paul Kubes, Craig N. Jenne, Daniel A. Muruve
Many Toll-like receptors (TLRs) signal through TNF receptor–associated factor 6 (TRAF6) to activate innate immune responses. Here, we show that somatic nuclear autoantigenic sperm protein (sNASP) binds to TRAF6 to prevent TRAF6 autoubiquitination in unstimulated macrophages. Following LPS stimulation, a complex consisting of sNASP, TRAF6, IRAK4, and casein kinase 2 (CK2) is formed. CK2 phosphorylates sNASP at serine 158, allowing sNASP to dissociate from TRAF6. Free TRAF6 is then autoubiquitinated, followed by activation of downstream signaling pathways. In sNasp S158A knockin (S158A-KI) mice, LPS-treated macrophages could not phosphorylate sNASP, which remained bound to TRAF6. S158A-KI mice were more susceptible to sepsis due to a marked reduction in IL-1β, TNF-α, and IFN-γ production accompanied by an inability to clear bacteria and recruit leukocytes. Furthermore, phosphorylation-regulated release of sNASP from TRAF6 is observed following activation of TLR-1, -2, -4, -5, and -6. Thus, sNASP is a negative regulator of TLR signaling to modulate the innate immune response.
Feng-Ming Yang, Yong Zuo, Wei Zhou, Chuan Xia, Bumsuk Hahm, Mark Sullivan, Jinke Cheng, Hui-Ming Chang, Edward T.H. Yeh
Chronic obstructive pulmonary disease (COPD) is an incurable inflammatory lung disease that afflicts millions of people worldwide, and it is the fourth leading cause of death. Systemic comorbidities affecting the heart, skeletal muscle, bone, and metabolism are major contributors to morbidity and mortality. Given the surprising finding in large prospective clinical biomarker studies that peripheral white blood cell count is more closely associated with disease than inflammatory biomarkers, we probed the role of blood growth factors. Using the SHIP-1–deficient COPD mouse model, which manifests a syndrome of destructive lung disease and a complex of comorbid pathologies, we have identified a critical and unexpected role for granulocyte-CSF (G-CSF) in linking these conditions. Deletion of G-CSF greatly reduced airway inflammation and lung tissue destruction, and attenuated systemic inflammation, right heart hypertrophy, loss of fat reserves, and bone osteoporosis. In human clinical translational studies, bronchoalveolar lavage fluid of patients with COPD demonstrated elevated G-CSF levels. These studies suggest that G-CSF may play a central and unforeseen pathogenic role in COPD and its complex comorbidities, and identify G-CSF and its regulators as potential therapeutic targets.
Evelyn Tsantikos, Maverick Lau, Cassandra M.N. Castelino, Mhairi J. Maxwell, Samantha L. Passey, Michelle J. Hansen, Narelle E. McGregor, Natalie A. Sims, Daniel P. Steinfort, Louis B. Irving, Gary P. Anderson, Margaret L. Hibbs
Receptor interacting protein kinase 1 (RIPK1) has important kinase-dependent and kinase-independent scaffolding functions that activate or prevent apoptosis or necroptosis in a cell context–dependent manner. The kinase activity of RIPK1 mediates hypothermia and lethality in a mouse model of TNF-induced shock, reflecting the hyperinflammatory state of systemic inflammatory response syndrome (SIRS), where the proinflammatory “cytokine storm” has long been viewed as detrimental. Here, we demonstrate that cytokine and chemokine levels did not predict survival and, importantly, that kinase-inactive Ripk1D138N/D138N hematopoietic cells afforded little protection from TNF- or TNF/zVAD-induced shock in reconstituted mice. Unexpectedly, RIPK1 kinase–inactive mice transplanted with WT hematopoietic cells remained resistant to TNF-induced shock, revealing that a nonhematopoietic lineage mediated protection. TNF-treated Ripk1D138N/D138N mice exhibited no significant increases in intestinal or vascular permeability, nor did they activate the clotting cascade. We show that TNF administration damaged the liver vascular endothelium and induced phosphorylated mixed lineage kinase domain-like (phospho-MLKL) reactivity in endothelial cells isolated from TNF/zVAD-treated WT, but not Ripk1D138N/D138N, mice. These data reveal that the tissue damage present in this SIRS model is reflected, in part, by breaks in the vasculature due to endothelial cell necroptosis and thereby predict that RIPK1 kinase inhibitors may provide clinical benefit to shock and/or sepsis patients.
Matija Zelic, Justine E. Roderick, Joanne A. O’Donnell, Jesse Lehman, Sung Eun Lim, Harish P. Janardhan, Chinmay M. Trivedi, Manolis Pasparakis, Michelle A. Kelliher
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