T cells down-regulate macrophage TNF production by IRAK1-mediated IL-10 expression and control innate hyperinflammation

Effects of Zn-ZnO Core-Shell Nanoparticles on Antimicrobial Mechanisms and Immune Cell Activation

The deposition of zinc-zinc oxide nanoparticles (Zn-ZnO NPs) onto porous Ta2O5 surfaces enriched with calcium phosphate by DC magnetron sputtering was investigated to improve the surface antimicrobial activity without triggering an inflammatory response. Different sizes and amounts of Zn NPs obtained by two optimized different depositions and an additional thin carbon (C) layer deposited over the NPs were explored. The deposition of the Zn NPs and the C layer mitigates the surface porosity, increasing the surface hydrophobicity and decreasing the surface roughness. The possible antimicrobial effect and immune system activation of Zn-ZnO NPs were investigated in Candida albicans and macrophage cells, respectively. It was found that the developed surfaces displayed a fungistatic behavior, as they impair the growth of C. albicans between 5 and 24 h of culture. This behavior was more evident on the surfaces with bigger NPs and the highest amounts of Zn. The same trend was observed in both reactive oxygen species (ROS) generation and loss of C. albicans' membrane integrity. After 24 h of culture, cell toxicity was also dependent on the amount of the NPs. Cell toxicity was observed in surfaces with the highest amount of Zn NPs and with the C layer, while cells were able to grow without any signs of cytotoxicity in the porous surfaces with the lowest amount of NPs. The same Zn-dose-dependent behavior was noticed in the TNF-α production. The Zn-containing surfaces show a vastly inferior cytokine secretion than the lipopolysaccharide (LPS)-stimulated cells, indicating that the modified surfaces do not induce an inflammatory response from macrophage cells. This study provides insights for understanding the Zn amount threshold that allows a simultaneous inhibition of the fungi growth with no toxic effect and the main antimicrobial mechanisms of Zn-ZnO NPs, contributing to future clinical applications.

Soluble CD4 effectively prevents excessive TLR activation of resident macrophages in the onset of sepsis

T lymphopenia, occurring in the early phase of sepsis in response to systemic inflammation, is commonly associated with morbidity and mortality of septic infections. We have previously shown that a sufficient number of T cells is required to constrain Toll-like receptors (TLRs) mediated hyperinflammation. However, the underlying mechanisms remains unsolved. Herein, we unveil that CD4⁺ T cells engage with MHC II of macrophages to downregulate TLR pro-inflammatory signaling. We show further that the direct contact between CD4 molecule of CD4⁺ T cells or the ectodomain of CD4 (soluble CD4, sCD4), and MHC II of resident macrophages is necessary and sufficient to prevent TLR4 overactivation in LPS and cecal ligation puncture (CLP) sepsis. sCD4 serum concentrations increase after the onset of LPS sepsis, suggesting its compensatory inhibitive effects on hyperinflammation. sCD4 engagement enables the cytoplasmic domain of MHC II to recruit and activate STING and SHP2, which inhibits IRAK1/Erk and TRAF6/NF-κB activation required for TLR4 inflammation. Furthermore, sCD4 subverts pro-inflammatory plasma membrane anchorage of TLR4 by disruption of MHC II-TLR4 raft domains that promotes MHC II endocytosis. Finally, sCD4/MHCII reversal signaling specifically interferes with TLR4 but not TNFR hyperinflammation, and independent of the inhibitive signaling of CD40 ligand of CD4⁺ cells on macrophages. Therefore, a sufficient amount of soluble CD4 protein can prevent excessive inflammatory activation of macrophages via alternation of MHC II-TLR signaling complex, that might benefit for a new paradigm of preventive treatment of sepsis.

Osteopontin (OPN)/SPP1: from its biochemistry to biological functions in the innate immune system and the central nervous system (CNS)

Osteopontin (OPN) is a multifunctional protein, initially identified in osteosarcoma cells with its role of mediating osteoblast adhesion. Later studies revealed that OPN is associated with many inflammatory conditions caused by infections, allergic responses, autoimmunity and tissue damage. Many cell types in the peripheral immune system express OPN with various functions, which could be beneficial or detrimental. Also, more recent studies demonstrated that OPN is highly expressed in the central nervous system (CNS), particularly in microglia during CNS diseases and development. However, understanding of mechanisms underlying OPN's functions in the CNS is still limited. In this review, we focus on peripheral myeloid cells and CNS-resident cells to discuss the expression and functions of OPN.

Metformin inhibits the pathogenic functions of AChR-specific B and Th17 cells by targeting miR-146a

Myasthenia gravis (MG) is characterized by fatigable skeletal muscle weakness with a fluctuating and unpredictable disease course and is caused by circulating autoantibodies and pathological T helper cells. Regulation of B-cell function and the T-cell network may be a potential therapeutic strategy for MG. MicroRNAs (miRNAs) have emerged as potential biomarkers in immune disorders due to their critical roles in various immune cells and multiple inflammatory diseases. Aberrant miR-146a signal activation has been reported in autoimmune diseases, but a detailed exploration of the relationship between miR-146a and MG is still necessary. Using an experimental autoimmune myasthenia gravis (EAMG) rat model, we observed that miR-146a was highly expressed in the spleen but expressed at low levels in the thymus and lymph nodes in EAMG rats. Additionally, miR-146a expression in T and B cells was also quite different. EAMG-specific Th17 and Treg cells had lower miR-146a levels, while EAMG-specific B cells had higher miR-146a levels, indicating that targeted intervention against miR-146a might have diametrically opposite effects. Metformin, a drug that was recently demonstrated to alleviate EAMG, may rescue the functions of both Th17 cells and B cells by reversing the expression of miR-146a. We also investigated the downstream target genes of miR-146a in both T and B cells using bioinformatics screening and qPCR. Taken together, our study identifies a complex role of miR-146a in the EAMG rat model, suggesting that more caution should be paid in targeting miR-146a for the treatment of MG.

Alveolar macrophages protect mice from MERS-CoV-induced pneumonia and severe disease

Emerging and re-emerging human coronaviruses (hCoVs) cause severe respiratory illness in humans, but the basis for lethal pneumonia in these diseases is not well understood. Alveolar macrophages (AMs) are key orchestrators of host antiviral defense and tissue tolerance during a variety of respiratory infections, and AM dysfunction is associated with severe COVID-19. In this study, using a mouse model of Middle East respiratory syndrome coronavirus (MERS-CoV) infection, we examined the role of AMs in MERS pathogenesis. Our results show that depletion of AMs using clodronate (CL) liposomes significantly increased morbidity and mortality in human dipeptidyl peptidase 4 knock-in (hDPP4-KI) mice. Detailed examination of control and AM-depleted lungs at different days postinfection revealed increased neutrophil activity but a significantly reduced MERS-CoV-specific CD4 T-cell response in AM-deficient lungs during later stages of infection. Furthermore, enhanced MERS severity in AM-depleted mice correlated with lung inflammation and lesions. Collectively, these data demonstrate that AMs are critical for the development of an optimal virus-specific T-cell response and controlling excessive inflammation during MERS-CoV infection.

Osteopontin-induced vascular hyperpermeability through tight junction disruption in diabetic retina

Diabetic retinopathy is a major cause of blindness in developed countries, and is characterized by deterioration of barrier function causing vascular hyperpermeability and retinal edema. Vascular endothelial growth factor (VEGF) is a major mediator of diabetic macular edema. Although anti-VEGF drugs are the first-line treatment for diabetic macular edema, some cases are refractory to anti-VEGF therapy. Osteopontin (OPN) is a phosphoglycoprotein with diverse functions and expressed in various cells and tissues. Elevated OPN level has been implicated in diabetic retinopathy, but whether OPN is involved in hyperpermeability remains unclear. Using streptozotocin-induced diabetic mice (STZ mice) and human retinal endothelial cells (HRECs), we tested the hypothesis that up-regulated OPN causes tight junction disruption, leading to vascular hyperpermeability. The serum and retinal OPN concentrations were elevated in STZ mice compared to controls. Intravitreal injection of anti-OPN neutralizing antibody (anti-OPN Ab) suppressed vascular hyperpermeability and prevented decreases in claudin-5 and ZO-1 gene expression levels in the retina of STZ mice. Immunohistochemical staining of retinal vessels in STZ mice revealed claudin-5 immunoreactivity with punctate distribution and attenuated ZO-1 immunoreactivity, and these changes were prevented by anti-OPN Ab. Intravitreal injection of anti-OPN Ab did not change VEGF gene expression or protein concentration in retina of STZ mice. In an in vitro study, HRECs were exposed to normal glucose or high glucose with or without OPN for 48 h, and barrier function was evaluated by transendothelial electrical resistance and Evans blue permeation. Barrier function deteriorated under high glucose condition, and was further exacerbated by the addition of OPN. Immunofluorescence localization of claudin-5 and ZO-1 demonstrated punctate appearance with discontinuous junction in HRECs exposed to high glucose and OPN. There were no changes in VEGF and VEGF receptor-2 expression levels in HRECs by exposure to OPN. Our results suggest that OPN induces tight junction disruption and vascular hyperpermeability under diabetic conditions. Targeting OPN may be an effective approach to manage diabetic retinopathy.

Mechanical model of steady-state and inflammatory conditions in patients with relapsing polychondritis: A review

Relapsing polychondritis (RP) is a multisystem inflammatory disorder, considered to associate with immune aberration.Increased T helper type-1 cell-related cytokines were reported in RP patients. mRNA expressions of a regulatory T cell cytokine interleukin (IL)-10 increased, whereas pro-inflammatory cytokines IL1β and IL6 mRNA expressions decreased in freshly isolated peripheral blood mononuclear cells of RP patients compared with those in healthy individuals. Upon in vitro stimulation with mitogen, IL10 mRNA expressions decreased, and IL1β and IL6 mRNA expressions increased in RP patients.This short-time dynamic change of gene expressions from anti-inflammatory to pro-inflammatory features of immune cells may be associated with the "relapsing" disease course of patients with RP. IL1β mRNA expressions of peripheral blood mononuclear cells exhibited positive correlations with serum matrix metalloproteinase (MMP)-3 concentrations in patients with respiratory involvement. Such positive correlation was not found in those without respiratory involvement.In a metagenomic analysis, an altered composition of gut microbes was found, suggesting that microbe metabolites such as short-chain fatty acids may affect T cell responses of the patients.In this review, the relationships among RP-related inflammatory molecules were summarized. The data support a hypothesis that the immune conditions are different between steady-state and inflammation in RP patients.

Secreted osteopontin from CD4+ T cells limits acute graft-versus-host disease

Osteopontin (OPN) has been considered a potential biomarker of graft-versus-host disease (GVHD). However, the function of OPN in GVHD is still elusive. Using a mouse model of acute GVHD (aGVHD), we report that OPN generated by CD4+ T cells is sufficient to exert a beneficial effect in controlling aGVHD through limiting gastrointestinal pathology, a major target organ of aGVHD. CD4+ T cell-derived OPN works on CD44 expressed in intestinal epithelial cells (IECs) and abates cell death of IECs. OPN also modulates gut microbiota with enhanced health-associated commensal bacteria Akkermansia. Importantly, we use our in vivo mouse mutant model to specifically express OPN isoforms and demonstrate that secreted OPN (sOPN), not intracellular OPN (iOPN), is solely responsible for the protective role of OPN. This study demonstrates that sOPN generated by CD4+ T cells is potent enough to limit aGVHD.

Lack of lymphocytes exacerbate heat stroke severity in male mice through enhanced inflammatory response

Though it has long been thought that the immune system is implicated in the pathophysiology of heat stroke, the underlying mechanisms are still poorly understood. As it has been reported in the literature that lymphocyte disturbance occurs in heat stroke patients or animals, we attempted to seek experimental evidence to define the role of lymphocytes in the pathophysiology of heat stroke. In our study, we used male Balb/c mice to establish a passive heat stroke model. We found that lymphocyte-deficient Severe combined immunodeficient (SCID) mice exposed to heat stress exhibited exacerbated heat stroke severity, which could be indicated by increased rates of mortality and serum levels of inflammatory cytokines compared to wildtype control mice. We further showed, through the depletion of T lymphocytes in wildtype mice and the transfer of wildtype lymphocytes into SCID mice, respectively, that T lymphocytes were both necessary and sufficient to alleviate the severity of heat stroke by inhibiting the early inflammatory response. Moreover, we found that the severity of heat injuries in heat-stressed wildtype mice showed great inter-individual variability, and the early number of T lymphocytes could be negatively associated with the severity of heat stroke. Our results suggest that lack of T lymphocytes could exacerbate the severity of heat stroke by augmenting inflammatory response, and the early circulating T lymphocytes may serve as a potential biomarker for the diagnosis of heat stroke.

Serum MMP3 Correlated With IL1β Messenger RNA Expressions of Peripheral Blood Mononuclear Cells in Patients with Relapsing Polychondritis With Respiratory Involvement

OBJECTIVE

Respiratory involvement was intimately associated with poorer prognosis in patients with relapsing polychondritis (RP). We previously reported that high serum matrix metalloproteinase-3 (MMP3) was frequently observed in patients with RP with respiratory involvement. Elevated MMP3 secreted through local inflammation may be associated with the development of airway lesions.

METHODS

We collected peripheral blood mononuclear cells (PBMCs) and sera from 30 patients with RP and 14 healthy individuals. Interleukin (IL) 1β, IL6, and tumor necrosis factor (TNF) α messenger RNA (mRNA) expressions were analyzed in freshly isolated and cultured PBMCs with phytohemagglutinin and phorbol myristate acetate stimulation by real-time reverse transcription polymerase chain reaction and serum MMP3 by enzyme-linked immunosorbent assay (ELISA).

RESULTS

We confirmed our previous finding that patients with respiratory involvements showed higher serum MMP3 compared with patients lacking respiratory involvement. IL1β mRNA expression was significantly higher in patients with RP than in healthy individuals after mitogenic stimulation. TNFα mRNA expression after stimulation was significantly lower in patients with RP compared with in healthy individuals. We performed correlation analyses between MMP3 and cytokine mRNA expressions in patients with RP. In patients with respiratory involvement, MMP3 correlated with IL1β and IL6 after stimulation. In patients without respiratory involvement, no positive correlations between MMP3 and cytokine mRNA expressions were observed regardless of culture condition. We did not find any positive correlations between MMP3 and TNFα mRNA expression in patients with RP.

CONCLUSION

It is possible that IL1β mRNA expression associates by some means with airway inflammation via the secretion of MMP3 in patients with RP. Involvement of proinflammatory cytokines, including IL1β, was suggested for the pathophysiology of airway lesions in patients with RP.

T Cell-Intrinsic IRF5 Regulates T Cell Signaling, Migration, and Differentiation and Promotes Intestinal Inflammation

IRF5 polymorphisms are associated with multiple immune-mediated diseases, including ulcerative colitis. IRF5 contributions are attributed to its role in myeloid lineages. How T cell-intrinsic IRF5 contributes to inflammatory outcomes is not well understood. We identify a previously undefined key role for T cell-intrinsic IRF5. In mice, IRF5 in CD4⁺ T cells promotes Th1- and Th17-associated cytokines and decreases Th2-associated cytokines. IRF5 is required for the optimal assembly of the TCR-initiated signaling complex and downstream signaling at early times, and at later times binds to promoters of Th1- and Th17-associated transcription factors and cytokines. IRF5 also regulates chemokine receptor-initiated signaling and, in turn, T cell migration. In vivo, IRF5 in CD4⁺ T cells enhances the severity of experimental colitis. Importantly, human CD4⁺ T cells from high IRF5-expressing disease-risk genetic carriers demonstrate increased chemokine-induced migration and Th1/Th17 cytokines and reduced Th2-associated and anti-inflammatory cytokines. These data demonstrate key roles for T cell-intrinsic IRF5 in inflammatory outcomes.

Involvement of Interleukin-1 Receptor-Associated Kinase 4 and Interferon Regulatory Factor 5 in the Immunopathogenesis of SARS-CoV-2 Infection: Implications for the Treatment of COVID-19

Interleukin-1 receptor-associated kinase 4 (IRAK4) and interferon regulatory factor 5 (IRF5) lie sequentially on a signaling pathway activated by ligands of the IL-1 receptor and/or multiple TLRs located either on plasma or endosomal membranes. Activated IRF5, in conjunction with other synergistic transcription factors, notably NF-κB, is crucially required for the production of proinflammatory cytokines in the innate immune response to microbial infection. The IRAK4-IRF5 axis could therefore have a major role in the induction of the signature cytokines and chemokines of the hyperinflammatory state associated with severe morbidity and mortality in COVID-19. Here a case is made for considering IRAK4 or IRF5 inhibitors as potential therapies for the "cytokine storm" of COVID-19.

Development and Characterization of Monoolein-Based Liposomes of Carvacrol, Cinnamaldehyde, Citral, or Thymol with Anti-Candida Activities

There is an increasing need for novel drugs and new strategies for the therapy of invasive candidiasis. This study aimed to develop and characterize liposome-based nanoparticles of carvacrol, cinnamaldehyde, citral, and thymol with anti-Candida activities. Dioctadecyldimethylammonium bromide- and monoolein-based liposomes in a 1:2 molar ratio were prepared using a lipid-film hydration method. Liposomes were assembled with equal volumes of liposomal stock dispersion and stock solutions of carvacrol, cinnamaldehyde, citral, or thymol in dimethyl sulfoxide. Cytotoxicity was tested on RAW 264.7 macrophages. In vitro antifungal activity of liposomes with phytocompounds was evaluated according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) methodology using clinical isolates of Candida albicans, Candida auris, Candida dubliniensis, and Candida tropicalis Finally, the ability of macrophage cells to kill Candida isolates after addition of phytocompounds and their nanoparticles was determined. Nanoparticles with 64 μg/ml of cinnamaldehyde, 256 μg/ml of citral, and 128 μg/ml of thymol had the best characteristics among the formulations tested. The highest encapsulation efficiencies were achieved with citral (78% to 83%) and carvacrol (66% to 71%) liposomes. Carvacrol and thymol in liposome-based nanoparticles were nontoxic regardless of the concentration. Moreover, carvacrol and thymol maintained their antifungal activity after encapsulation, and there was a significant reduction (∼41%) of yeast survival when macrophages were incubated with carvacrol or thymol liposomes. In conclusion, carvacrol and thymol liposomes possess high stability, low cytotoxicity, and antifungal activity that act synergistically with macrophages.

Immunoregulatory Effects of Porcine Plasma Protein Concentrates on Rat Intestinal Epithelial Cells and Splenocytes

Simple Summary

Blood contains proteins which have interest as products that may regulate immune function. For this reason some protein-based products are currently used as nutritional supplements for animals, for instance two porcine concentrates, spray dried serum (SDS), and an immunoglobulin concentrate (IC). These products have shown to protect against colonic inflammation in rodents. In the present study we characterize the ability of these products to modulate immune function in isolated cells, namely intestinal epithelial cells (IEC18 cells) and rat spleen cells. Our data indicate that both porcine protein concentrates indeed alter immune cell function, based on the secretion of the modulators known as cytokines. In intestinal epithelial IEC18 cells they promoted the secretion of GROα and MCP-1 cytokines. In spleen cells they mainly inhibited the production of TNF, a key proinflammatory cytokine. In addition, the IC product augmented the release of IL-10, an anti-inflammatory cytokine. Taken together, our data indicate that the immunomodulatory effects observed in vivo are consistent with the direct actions of the protein concentrates on epithelial cells, T lymphocytes, and monocytes.

Abstract

Serum protein concentrates have been shown to exert in vivo anti-inflammatory effects. Specific effects on different cell types and their mechanism of action remain unraveled. We aimed to characterize the immunomodulatory effect of two porcine plasma protein concentrates, spray dried serum (SDS) and an immunoglobulin concentrate (IC), currently used as animal nutritional supplements with established in vivo immunomodulatory properties. Cytokine production by the intestinal epithelial cell line IEC18 and by primary cultures of rat splenocytes was studied. The molecular pathways involved were explored with specific inhibitors and gene knockdown. Our results indicate that both products induced GROα and MCP-1 production in IEC18 cells by a MyD88/NF-κB-dependent mechanism. Inhibition of TNF production was observed in rat primary splenocyte cultures. The immunoglobulin concentrate induced IL-10 expression in primary splenocytes and lymphocytes. The effect on TNF was independent of IL-10 production or the stimulation of NF-kB, MAPKs, AKT, or RAGE. In conclusion, SDS and IC directly regulate intestinal and systemic immune response in murine intestinal epithelial cells and in T lymphocytes and monocytes.

Splenic erythroid progenitors decrease TNF-α production by macrophages and reduce systemic inflammation in a mouse model of T cell-induced colitis

In inflammatory bowel disease (IBD), inflammation can occur beyond the intestine and spread systemically causing complications such as arthritis, cachexia, and anemia. Here, we determine the impact of CD45, a pan-leukocyte marker and tyrosine phosphatase, on IBD. Using a mouse model of T cell transfer colitis, CD25^- CD45RB^high CD4⁺ T cells were transferred into Rag1-deficient mice (RAGKO) and CD45-deficient RAGKO mice (CD45RAGKO). Weight loss and systemic wasting syndrome were delayed in CD45RAGKO mice compared to RAGKO mice, despite equivalent inflammation in the colon. CD45RAGKO mice had reduced serum levels of TNF-α, and reduced TNF-α production by splenic myeloid cells. CD45RAGKO mice also had increased numbers of erythroid progenitors in the spleen, which had previously been shown to be immunosuppressive. Adoptive transfer of these erythroid progenitors into RAGKO mice reduced their weight loss and TNF-α expression by splenic red pulp macrophages. In vitro, erythroid cells suppressed TNF-α expression in red pulp macrophages in a phagocytosis-dependent manner. These findings show a novel role for erythroid progenitors in suppressing the pro-inflammatory function of splenic macrophages and cachexia associated with IBD.

Th1-Dependent Cryptococcus-Associated Immune Reconstitution Inflammatory Syndrome Model With Brain Damage

Cryptococcus-associated immune reconstitution inflammatory syndrome (C-IRIS) is identified upon immune reconstitution in immunocompromised patients, who have previously contracted an infection of Cryptococcus neoformans (Cn). C-IRIS can be lethal but how the immune system triggers life-threatening outcomes in patients is still poorly understood. Here, we establish a mouse model for C-IRIS with Cn serotype A strain H99, which is highly virulent and the most intensively studied. C-IRIS in mice is induced by the adoptive transfer of CD4+ T cells in immunocompromised Rag1-deficient mice infected with a low inoculum of Cn. The mice with C-IRIS exhibit symptoms which mimic clinical presentations of C-IRIS. This C-IRIS model is Th1-dependent and shows host mortality. This model is characterized with minimal lung injury, but infiltration of Th1 cells in the brain. C-IRIS mice also exhibited brain swelling with resemblance to edema and upregulation of aquaporin-4, a critical protein that regulates water flux in the brain in a Th1-dependent fashion. Our C-IRIS model may be used to advance our understanding of the paradoxical inflammatory phenomenon of C-IRIS in the context of neuroinflammation.

Overexpression of miR-146b-5p Ameliorates Neonatal Hypoxic Ischemic Encephalopathy by Inhibiting IRAK1/TRAF6/TAK1/NF-αB Signaling

PURPOSE

Neonatal hypoxic ischemic encephalopathy (HIE) is an essential factor underlying neonatal death and disability. This study sought to explore the role of miR-146b-5p in regulating neonatal HIE.

MATERIALS AND METHODS

In vitro and in vivo HIE models were established in PC12 cells and 10-day neonatal Sprague Dawley rats, respectively. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to assess miR-146b-5p expression and inflammatory factors [interleukin (IL)-6 and tumor necrosis factor (TNF)-α] in brain lesions and PC12 cells, while enzyme-linked immunosorbent assay was employed to detect the expression of oxidative stress factors (SOD and GSH-Px). Gain- and loss-assays of miR-146b-5p were conducted to verify its role in modulating the viability and apoptosis of PC12 cells under oxygen-glucose deprivation (OGD) treatment. Expression of TLR4, IRAK1, TRAF6, TAK1, and NF-κB were examined by qRT-PCR and/or Western blot. Dual luciferase activity assay was conducted to identify relationships between miR-146b-5p and IRAK1.

RESULTS

In the HIE models, significant oxidative stress and inflammatory responses emerged upon upregulation of TLR4/IRAK1/TRAF6/TAK1/NF-κB signaling. Overexpression of miR-146b-5p greatly inhibited OGD-induced PC12 cell injury, inflammatory responses, and oxidative stress. Inhibiting miR-146b-5p, however, had the opposite effects. IRAK1 was found to be a target of miR-146b-5p, and miR-146b-5p overexpression suppressed the activation of IRAK1/TRAF6/TAK1/NF-κB signaling.

CONCLUSION

This study demonstrated that miR-146b-5p overexpression alleviates HIE-induced neuron injury by inhibiting the IRAK1/TRAF6/TAK1/NF-κB pathway.

Myeloid Cell-Intrinsic IRF5 Promotes T Cell Responses through Multiple Distinct Checkpoints In Vivo, and IRF5 Immune-Mediated Disease Risk Variants Modulate These Myeloid Cell Functions

Common IRF5 genetic risk variants associated with multiple immune-mediated diseases are a major determinant of interindividual variability in pattern-recognition receptor (PRR)-induced cytokines in myeloid cells. However, how myeloid cell-intrinsic IRF5 regulates the multiple distinct checkpoints mediating T cell outcomes in vivo and IRF5-dependent mechanisms contributing to these distinct checkpoints are not well defined. Using an in vivo Ag-specific adoptive T cell transfer approach into Irf5^-/- mice, we found that T cell-extrinsic IRF5 regulated T cell outcomes at multiple critical checkpoints, including chemokine-mediated T cell trafficking into lymph nodes and PDK1-dependent soluble Ag uptake, costimulatory molecule upregulation, and secretion of Th1 (IL-12)- and Th17 (IL-23, IL-1β, and IL-6)-conditioning cytokines by myeloid cells, which then cross-regulated Th2 and regulatory T cells. IRF5 was required for PRR-induced MAPK and NF-κB activation, which, in turn, regulated these key outcomes in myeloid cells. Importantly, mice with IRF5 deleted from myeloid cells demonstrated T cell outcomes similar to those observed in Irf5^-/- mice. Complementation of IL-12 and IL-23 was able to restore T cell differentiation both in vitro and in vivo in the context of myeloid cell-deficient IRF5. Finally, human monocyte-derived dendritic cells from IRF5 disease-associated genetic risk carriers leading to increased IRF5 expression demonstrated increased Ag uptake and increased PRR-induced costimulatory molecule expression and chemokine and cytokine secretion compared with monocyte-derived dendritic cells from low-expressing IRF5 genetic variant carriers. These data establish that myeloid cell-intrinsic IRF5 regulates multiple distinct checkpoints in T cell activation and differentiation and that these are modulated by IRF5 disease risk variants.

AAV-Mediated Combination Gene Therapy for Neuropathic Pain: GAD65, GDNF, and IL-10

Neuropathic pain is a chronic pain state characterized by nerve damage, inflammation, and nociceptive neuron hyperactivity. As the underlying pathophysiology is complex, a more effective therapy for neuropathic pain would be one that targets multiple elements. Here, we generated recombinant adeno-associated viruses (AAVs) encoding three therapeutic genes, namely, glutamate decarboxylase 65, glial cell-derived neurotrophic factor, and interleukin-10, with various combinations. The efficacy for pain relief was evaluated in a rat spared nerve injury model of neuropathic pain. The maximal analgesic effect was achieved when the AAVs expressing all three genes were administered to rats with neuropathic pain. The combination of two virus constructs expressing the three genes was named KLS-2031 and evaluated as a potential novel therapeutic for neuropathic pain. Single transforaminal epidural injections of KLS-2031 into the intervertebral foramen to target the appropriate dorsal root ganglion produced notable long-term analgesic effects in female and male rats. Furthermore, KLS-2031 mitigated the neuroinflammation, neuronal cell death, and dorsal root ganglion hyperexcitability induced by the spared nerve injury. These results suggest that KLS-2031 represents a promising therapeutic option for refractory neuropathic pain.

TLR4 mediates alveolar bone resorption in experimental peri-implantitis through regulation of CD45+ cell infiltration, RANKL/OPG ratio, and inflammatory cytokine production

BACKGROUND

The present study was to determine the role of Toll-like receptor 4 (TLR4) signaling in inflammation and alveolar bone resorption using a murine model of Porphyromonas gingivalis-associated ligature-induced peri-implantitis.

METHODS

Smooth surface titanium implants were placed in the left maxilla alveolar bone 6 weeks after extraction of first and second molars in Wild-type (WT) and TLR4^-/- (TLR4 KO) mice. Silk ligatures immersed with P. gingivalis were tied around the implants 4 weeks after the implant placement and confirmation of osteointegration. Two weeks after the ligation, bone resorption, osteoclastogenesis, cellular inflammatory responses, and gingival mRNA expression levels of cytokines were assessed by micro-computed tomography, tartrate-resistant acid phosphatase (TRAP) staining, immunobiological examination and Real-time quantitative polymerase chain reaction, respectively.

RESULTS

In both WT and TLR4 KO mice, the bone resorption around implants was significantly increased in the P. gingivalis/ligation group compared with control group. In P. gingivalis/ligation group, the levels of bone resorption, TRAP+ cell formation, and gingival CD3+ and CD45+ cell infiltration were significantly decreased in TLR4 KO mice compared with that in WT mice. Receptor activator of nuclear factor-kappa B ligand /osteoprotegerin (RANKL/OPG) ratio was significantly increased after P. gingivalis/ligation treatment in WT mice not in TLR4 KO mice. When comparing the P. gingivalis/ligation group with the respective control group, gingival mRNA expressions of IL-1β, IFN-γ, and 1L-17 were significantly increased in TLR4 KO mice.

CONCLUSION

This study suggests that TLR4 mediates alveolar bone resorption in P. gingivalis associated ligature-induced peri-implantitis through regulation of immune B cell infiltration, RANKL/OPG expression ratio, and differential inflammatory cytokine production.

Osteopontin as a Link between Inflammation and Cancer: The Thorax in the Spotlight

The glycoprotein osteopontin (OPN) possesses multiple functions in health and disease. To this end, osteopontin has beneficial roles in wound healing, bone homeostasis, and extracellular matrix (ECM) function. On the contrary, osteopontin can be deleterious for the human body during disease. Indeed, osteopontin is a cardinal mediator of tumor-associated inflammation and facilitates metastasis. The purpose of this review is to highlight the importance of osteopontin in malignant processes, focusing on lung and pleural tumors as examples.

Reducing IRF5 expression attenuates colitis in mice, but impairs the clearance of intestinal pathogens

IRF5 genetic variants leading to decreased IRF5 expression reduce risk for ulcerative colitis. However, how IRF5 regulates intestinal inflammation and contributes to the balance between defenses against intestinal pathogens and inflammation in vivo, and the cells mediating this balance, are not known. We found that deleting IRF5 in mice led to reduced intestinal inflammation in the T cell transfer colitis model, with reduced Th1 and Th17, and increased Th2 cytokines. However, with orally-administered invasive S. Typhimurium, IRF5^-/- mice demonstrated an increased bacterial burden in the context of reduced Th1 and Th17 cytokines. IRF5 in macrophages was required for PDK1-dependent phagocytosis and for NFκB-dependent pathways mediating intracellular bacterial clearance. Despite reduced bacterial clearance pathways, in IRF5^-/- mice exposed to high levels of resident intestinal bacteria after DSS-induced injury, the lower levels of inflammatory cytokines were associated with reduced intestinal permeability, and in turn, reduced bacterial translocation and intestinal inflammation. Consistent with the myeloid cell-intrinsic roles for IRF5 in vitro, mice with IRF5 deleted from myeloid cells demonstrated outcomes similar to those observed in IRF5^-/- mice. While these data suggest that inhibition of IRF5 may be therapeutic in colitis, this needs to be balanced with the identified IRF5 role in protecting against intestinal pathogens.

Leukocyte integrin signaling regulates FOXP1 gene expression via FOXP1-IT1 long non-coding RNA-mediated IRAK1 pathway

Leukocyte integrin-dependent downregulation of the transcription factor FOXP1 is required for monocyte differentiation and macrophage functions, but the precise gene regulatory mechanism is unknown. Here, we identify multi-promoter structure (P1, P2, and P3) of the human FOXP1 gene. Clustering of the β₂-leukocyte integrin Mac-1 downregulated transcription from these promoters. We extend our prior observation that IL-1 receptor-associated kinase 1 (IRAK1) is physically associated with Mac-1 and provide evidence that IRAK1 is a potent suppressor of human FOXP1 promoter. IRAK1 reduced phosphorylation of histone deacetylase 4 (HDAC4) via inhibiting phosphorylation of calcium/calmodulin dependent protein kinase II delta (CaMKIIδ), thereby promoting recruitment of HDAC4 to P1 chromatin. A novel human FOXP1 intronic transcript 1 (FOXP1-IT1) long non-coding RNA (lncRNA), whose gene is embedded within that of FOXP1, has been cloned and found to bind directly to HDAC4 and regulate FOXP1 in cis manner. Overexpression of FOXP1-IT1 counteracted Mac-1 clustering-dependent downregulation of FOXP1, reduced IRAK1 downregulation of HDAC4 phosphorylation, and attenuated differentiation of THP-1 monocytic cells. In contrast, Mac-1 clustering inhibited FOXP1-IT1 expression with reduced binding to HDAC4 as well as phosphorylation of CaMKIIδ to activate the IRAK1 signaling pathway. Importantly, both IRAK1 and HDAC4 inhibitors significantly reduced integrin clustering-triggered downregulation of FOXP1 expression in purified human blood monocytes. Identification of this Mac-1/IRAK-1/FOXP1-IT1/HDAC4 signaling network featuring crosstalk between lncRNA and epigenetic factor for the regulation of FOXP1 expression provides new targets for anti-inflammatory therapeutics.

IRF5 Is Required for Bacterial Clearance in Human M1-Polarized Macrophages, and IRF5 Immune-Mediated Disease Risk Variants Modulate This Outcome

Common IFN regulatory factor 5 (IRF5) variants associated with multiple immune-mediated diseases are a major determinant of interindividual variability in pattern recognition receptor (PRR)-induced cytokines in macrophages. PRR-initiated pathways also contribute to bacterial clearance, and dysregulation of bacterial clearance can contribute to immune-mediated diseases. However, the role of IRF5 in macrophage-mediated bacterial clearance is not well defined. Furthermore, it is unclear if macrophages from individuals who are carriers of low IRF5-expressing genetic variants associated with protection for immune-mediated diseases might be at a disadvantage in bacterial clearance. We found that IRF5 was required for optimal bacterial clearance in PRR-stimulated, M1-differentiated human macrophages. Mechanisms regulated by IRF5 included inducing reactive oxygen species through p40phox, p47phox and p67phox, NOS2, and autophagy through ATG5. Complementing these pathways in IRF5-deficient M1 macrophages restored bacterial clearance. Further, these antimicrobial pathways required the activation of IRF5-dependent MAPK, NF-κB, and Akt2 pathways. Importantly, relative to high IRF5-expressing rs2004640/rs2280714 TT/TT immune-mediated disease risk-carrier human macrophages, M1-differentiated GG/CC carrier macrophages demonstrated less reactive oxygen species, NOS2, and autophagy pathway induction and, consequently, reduced bacterial clearance. Increasing IRF5 expression to the rs2004640/rs2280714 TT/TT levels restored these antimicrobial pathways. We define mechanisms wherein common IRF5 genetic variants modulate bacterial clearance, thereby highlighting that immune-mediated disease risk IRF5 carriers might be relatively protected from microbial-associated diseases.

3,4,5-Trihydroxycinnamic acid attenuates lipopolysaccharide (LPS)-induced acute lung injury via downregulating inflammatory molecules and upregulating HO-1/AMPK activation

The increase in inflammatory cytokines and chemokines is a common denominator in the pathogenesis of acute lung injury (ALI) which are involved in the influx of inflammatory cells and lung damage. The aim of the present study was to evaluate the protective effect of 3,4,5-trihydroxycinnamic acid (THC) in lipopolysaccharide (LPS)-induced ALI. THC efficiently decreased the mRNA expression of interleukin-8 (IL-8) in LPS-stimulated A549 airway epithelial cells. THC induced heme oxygenase-1 (HO-1) expression in A549 cells. THC also increased the activation of AMP-activated protein kinase (AMPK) in A549 cells and RAW264.7 macrophages. In LPS-induced ALI in mice, THC significantly suppressed neutrophil influx and monocyte chemoattractant protein-1 (MCP-1) production in the bronchoalveolar lavage fluid (BALF). THC also attenuated the levels of neutrophil elastase (NE), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the BALF and serum. In addition, THC inhibited the expressions of inducible nitric oxide synthase (iNOS) and the activation of nuclear factor-kappa B (NF-κB) in the lung. These protective effects of THC were accompanied with HO-1 induction and AMPK activation. Taken together, the present study clearly demonstrates that THC significantly attenuates the LPS-induced ALI, suggesting that THC might be a valuable therapeutic adjuvant in airway inflammatory disorders.

CD4+ and CD8+ T Cells Exert Regulatory Properties During Experimental Acute Aristolochic Acid Nephropathy

Experimental aristolochic acid nephropathy is characterized by transient acute proximal tubule necrosis and inflammatory cell infiltrates followed by interstitial fibrosis and tubular atrophy. The respective role of T-cell subpopulations has never been studied in the acute phase of the mouse model, and was heretofore exclusively investigated by the use of several depletion protocols. As compared to mice injected with aristolochic acids alone, more severe acute kidney injury was observed after CD4⁺ or CD8⁺ T-cells depletion. TNF-alpha and MCP-1 mRNA renal expressions were also increased. In contrast, regulatory T-cells depletion did not modify the severity of the aristolochic acids induced acute kidney injury, suggesting an independent mechanism. Aristolochic acids nephropathy was also associated with an increased proportion of myeloid CD11b^highF4/80^mid and a decreased proportion of their counterpart CD11b^lowF4/80^high population. After CD4⁺ T-cell depletion the increase in the CD11b^highF4/80^mid population was even higher whereas the decrease in the CD11b^lowF4/80^high population was more marked after CD8+ T cells depletion. Our results suggest that CD4⁺ and CD8⁺ T-cells provide protection against AA-induced acute tubular necrosis. Interestingly, T-cell depletion was associated with an imbalance of the CD11b^highF4/80^mid and CD11b^lowF4/80^high populations.

Skewing of the population balance of lymphoid and myeloid cells by secreted and intracellular osteopontin

The balance of myeloid populations and lymphoid populations must be well controlled. Here we found that osteopontin (OPN) skewed this balance during pathogenic conditions such as infection and autoimmunity. Notably, two isoforms of OPN exerted distinct effects in shifting this balance through cell-type-specific regulation of apoptosis. Intracellular OPN (iOPN) diminished the population size of myeloid progenitor cells and myeloid cells, and secreted OPN (sOPN) increase the population size of lymphoid cells. The total effect of OPN on skewing the leukocyte population balance was observed as host sensitivity to early systemic infection with Candida albicans and T cell-mediated colitis. Our study suggests previously unknown detrimental roles for two OPN isoforms in causing the imbalance of leukocyte populations.

An AAAG-Rich Oligodeoxynucleotide Rescues Mice from Bacterial Septic Peritonitis by Interfering Interferon Regulatory Factor 5

A previous study found that an AAAG-rich Oligodeoxynucleotide (ODN), designated as MS19, could lessen the acute lung inflammatory injury (ALII) in mice infected by influenza viruses. Bioinformatics analysis found that MS19 is consensus with the binding site of interferon regulatory factor 5 (IRF5) in the regulatory elements of pro-inflammatory genes. This study established a septic peritonitis model in Institute of Cancer Research (ICR) mice infected with Escherichia coli (E. coli), and found that MS19 prolonged the survival of the mice and down-regulated the expression of inducible nitric oxide synthase (iNOS), interleukin-6 (IL-6), and tumor necrosis factor α (TNF-α). In cultured RAW264.7 cells, MS19 significantly reduced the expression of iNOS, IRF5, IL-6, and TNF-α and inhibited the nuclear translocation of IRF5. This data may provide a new insight for understanding how MS19 reduces the excessive inflammatory responses in sepsis.

MiR-146a promotes remyelination in a cuprizone model of demyelinating injury

The death of mature oligodendrocytes (OLs) which are the sole myelinating cells of the central nervous system (CNS), leads to demyelination and functional deficits. Currently, there is lack of effective remyelination therapies for patients with demyelinating diseases. MicroRNAs (miRNAs) mediate OL function. We hypothesized that miR-146a, by inactivating interleukin-1 receptor-associated kinase 1 (IRAK1), promotes differentiation of oligodendrocyte progenitor cells (OPCs) and thereby enhances remyelination. To test this hypothesis, a demyelination model induced by a cuprizone (CPZ) diet was employed, in which C57BL/6J mice were fed with a CPZ diet for 5weeks. After termination of CPZ diet, the mice were randomly treated with continuous infusion of miR-146a mimics or mimic controls into the corpus callosum for 7days. Compared to the mimic control, infusion of miR-146a mimics facilitated remyelination assessed by increased myelin basic proteins in the corpus callosum, which was associated with augmentation of newly generated mature OLs. Infusion of miR-146a mimics also substantially elevated miR-146a levels in the corpus callosum and fluorescently tagged miR-146a mimics were mainly detected in OPCs. Western blot and double immmunofluorescent staining analysis showed that the miR-146a treatment considerably reduced IRAK1 protein levels and the number of IRAK1-positive cells, respectively. Collectively, these data indicate that exogenous miR-146a enhances remyelination, possibly by promoting OPCs to differentiate into myelinated OLs via targeting IRAK1.

Osteopontin has a protective role in prostate tumor development in mice

Osteopontin (OPN) is a protein, generally considered to play a pro-tumorigenic role, whereas several reports have demonstrated the anti-tumorigenic function of OPN during tumor development. These opposing anti- and pro-tumorigenic functions are not fully understood. Here, we report that host-derived OPN plays an anti-tumorigenic role in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model and a TRAMP tumor transplant model. Tumor suppression mediated by OPN in Rag2^-/- mice suggests that OPN is dispensable in the adaptive immune response. We found that host-derived OPN enhanced infiltration of natural killer (NK) cells into TRAMP tumors. The requirement of OPN in NK cell migration towards TRAMP cells was confirmed by an ex vivo cell migration assay. In contrast to TRAMP cells, in vivo B16 tumor development was not inhibited by OPN, and B16 tumors did not show OPN-mediated cell recruitment. It is possible that low levels of chemokine expression by B16 cells do not allow OPN to enhance immune cell recruitment. In addition to demonstrating the anti-tumorigenic role of OPN in TRAMP tumor development, this study also suggests that the contribution of OPN to tumor development depends on the type of tumor as well as the source and isoform of OPN.

IRF5 and IRF5 Disease-Risk Variants Increase Glycolysis and Human M1 Macrophage Polarization by Regulating Proximal Signaling and Akt2 Activation

Interferon regulatory factor 5 (IRF5) regulates inflammatory M1 macrophage polarization, and disease-associated IRF5 genetic variants regulate pattern-recognition-receptor (PRR)-induced cytokines. PRR-stimulated macrophages and M1 macrophages exhibit enhanced glycolysis, a central mediator of inflammation. We find that IRF5 is needed for PRR-enhanced glycolysis in human macrophages and in mice in vivo. Upon stimulation of the PRR nucleotide binding oligomerization domain containing 2 (NOD2) in human macrophages, IRF5 binds RIP2, IRAK1, and TRAF6. IRF5, in turn, is required for optimal Akt2 activation, which increases expression of glycolytic pathway genes and HIF1A as well as pro-inflammatory cytokines and M1 polarization. Furthermore, pro-inflammatory cytokines and glycolytic pathways co-regulate each other. Rs2004640/rs2280714 TT/TT IRF5 disease-risk-carrier cells demonstrate increased IRF5 expression and increased PRR-induced Akt2 activation, glycolysis, pro-inflammatory cytokines, and M1 polarization relative to GG/CC carrier macrophages. Our findings identify that IRF5 disease-associated polymorphisms regulate diverse immunological and metabolic outcomes and provide further insight into mechanisms contributing to the increasingly recognized important role for glycolysis in inflammation.

CD40 in coronary artery disease: a matter of macrophages?

Coronary artery disease (CAD), also known as ischemic heart disease (IHD), is the leading cause of mortality in the western world, with developing countries showing a similar trend. With the increased understanding of the role of the immune system and inflammation in coronary artery disease, it was shown that macrophages play a major role in this disease. Costimulatory molecules are important regulators of inflammation, and especially, the CD40L-CD40 axis is of importance in the pathogenesis of cardiovascular disease. Although it was shown that CD40 can mediate macrophage function, its exact role in macrophage biology has not gained much attention in cardiovascular disease. Therefore, the goal of this review is to give an overview on the role of macrophage-specific CD40 in cardiovascular disease, with a focus on coronary artery disease. We will discuss the function of CD40 on the macrophage and its (proposed) role in the reduction of atherosclerosis, the reduction of neointima formation, and the stimulation of arteriogenesis.

TLR-mediated albuminuria needs TNFα-mediated cooperativity between TLRs present in hematopoietic tissues and CD80 present on non-hematopoietic tissues in mice

Transient albuminuria induced by pathogen-associated molecular patterns (PAMPs) in mice through engagement of Toll-like receptors (TLRs) is widely studied as a partial model for some forms of human nephrotic syndrome (NS). In addition to TLRs, CD80 has been shown to be essential for PAMP-mediated albuminuria. However, the mechanistic relationships between TLRs, CD80 and albuminuria remain unclear. Here, we show that albuminuria and CD80-uria induced in mice by many TLR ligands are dependent on the expression of TLRs and their downstream signalling intermediate MyD88 exclusively in hematopoietic cells and, conversely, on CD80 expression exclusively in non-hematopoietic cells. TNFα is crucial for TLR-mediated albuminuria and CD80-uria, and induces CD80 expression in cultured renal podocytes. IL-10 from hematopoietic cells ameliorates TNFα production, albuminuria and CD80-uria but does not prevent TNFα-mediated induction of podocyte CD80 expression. Chitohexaose, a small molecule originally of parasite origin, mediates TLR4-dependent anti-inflammatory responses, and blocks TLR-mediated albuminuria and CD80-uria through IL-10. Thus, TNFα is a prominent mediator of renal CD80 induction and resultant albuminuria in this model, and small molecules modulating TLR-mediated inflammatory activation might have contributory or adjunct therapeutic potential in some contexts of NS development.

Summary: Systemic TNFα mediates myeloid cell and podocyte cross-talk to cause LPS-induced mouse microalbuminuria, a partial model of human nephrotic syndrome, pointing to potential adjunct therapeutic approaches.

Intracellular osteopontin stabilizes TRAF3 to positively regulate innate antiviral response

Osteopontin (OPN) is a multifunctional protein involved in both innate immunity and adaptive immunity. However, the function of OPN, especially the intracellular form OPN (iOPN) on innate antiviral immune response remains elusive. Here, we demonstrated that iOPN is an essential positive regulator to protect the host from virus infection. OPN deficiency or knockdown significantly attenuated virus-induced IRF3 activation, IFN-β production and antiviral response. Consistently, OPN-deficient mice were more susceptible to VSV infection than WT mice. Mechanistically, iOPN was found to interact with tumor necrosis factor receptor (TNFR)-associated factor 3 (TRAF3) and inhibit Triad3A-mediated K48-linked polyubiquitination and degradation of TRAF3 through the C-terminal fragment of iOPN. Therefore, our findings delineated a new function for iOPN to act as a positive regulator in innate antiviral immunity through stabilization of TRAF3.

Inflammation-Induced Changes in Circulating T-Cell Subsets and Cytokine Production During Human Endotoxemia

Observational clinical studies suggest the initial phase of sepsis may involve impaired cellular immunity. In the present study, we investigated temporal changes in T-cell subsets and T-cell cytokine production during human endotoxemia. Endotoxin (Escherichia coli lipopolysaccharide 4 ng/kg) was administered intravenously in 15 healthy volunteers. Peripheral blood and bronchoalveolar lavage fluid (BALF) were collected at baseline and after 2, 4, 6, 8, and 24 hours for flow cytometry. CD4⁺CD25⁺CD127lowFoxp3⁺ regulatory T cells (Tregs), CD4⁺CD161⁺ cells, and activated Human leukocyte antigen, HLA-DR⁺CD38⁺ T cells were determined. Ex vivo whole-blood cytokine production and Toll-like receptor (TLR)-4 expression on Tregs were measured. Absolute number of CD3⁺CD4⁺ (P = .026), CD3⁺CD8⁺ (P = .046), Tregs (P = .023), and CD4⁺CD161⁺ cells (P = .042) decreased after endotoxin administration. The frequency of anti-inflammatory Tregs increased (P = .033), whereas the frequency of proinflammatory CD4⁺CD161⁺ cells decreased (P = .034). Endotoxemia was associated with impaired whole-blood production of tumor necrosis factor-α, interleukin-10, IL-6, IL-17, IL-2, and interferon-γ in response to phytohaemagglutinin but did not affect TLR4 expression on Tregs. No changes in the absolute count or frequency of BALF T cells were observed. Systemic inflammation is associated with lymphopenia, a relative increase in the frequency of anti-inflammatory Tregs, and a functional impairment of T-cell cytokine production.

Cutting edge: Role of osteopontin and integrin αv in T cell-mediated anti-inflammatory responses in endotoxemia

The immune system is equipped with mechanisms that downregulate hyperinflammation to avoid collateral damage. We demonstrated recently that unprimed T cells downregulate macrophage TNF production through direct interaction with macrophages in the spleen during LPS endotoxemia. How T cell migration toward macrophages occurs upon LPS injection is still not clear. In this study, we demonstrate that secreted osteopontin (sOPN) plays a role in the T cell migration to initiate the suppression of hyperinflammation during endotoxemia. Osteopontin levels in splenic macrophages were upregulated 2 h after LPS treatment, whereas T cell migration toward macrophages was observed 3 h after treatment. Neutralization of sOPN and blockade of its receptor, integrin αv, significantly inhibited CD4(+) T cell migration and increased susceptibility to endotoxemia. Our study demonstrates that the sOPN/integrin αv axis, which induces T cell chemotaxis toward macrophages, is critical for suppressing hyperinflammation during the first 3 h of endotoxemia.

Interleukin-10 limits intense acute swimming-induced muscle mechanical hyperalgesia in mice

NEW FINDINGS

What is the central question of this study? This study investigated the role of the endogenous anti-inflammatory cytokine interleukin-10 in intense acute swimming-induced muscle mechanical hyperalgesia in mice. What is the main finding and its importance? Endogenous interleukin-10 has a key role in limiting exercise-induced muscle pain in a model presenting similarities to delayed-onset muscle soreness in mice. Interleukin-10 reduced muscle pain by diminishing leucocyte recruitment, hyperalgesic cytokine production, oxidative stress and myocyte damage. Interleukin-10 (IL-10) is an antihyperalgesic cytokine. In this study, IL-10-deficient (IL-10(-/-) ) mice were used to investigate the role of endogenous IL-10 in intense acute swimming-induced muscle mechanical hyperalgesia, which presents similarities with delayed-onset muscle soreness. An intense acute swimming session of 1 or 2 h induced significant muscle mechanical hyperalgesia in a time-dependent manner in wild-type mice compared with the sham group 24 h after the session, which was further increased in IL-10(-/-) mice (P ˂ 0.05). Intraperitoneal treatment of wild-type mice with IL-10 (1-10 ng) reduced muscle mechanical hyperalgesia in a dose-dependent manner and reversed the enhanced muscle hyperalgesia in IL-10(-/-) mice (P ˂ 0.05). The 2 h swimming session induced increases in tumour necrosis factor-α, interleukin-1β and IL-10 production in the soleus muscle. However, tumour necrosis factor-α and interleukin-1β production in the soleus muscle were even higher in IL-10(-/-) mice between 2 and 6 h after the stimulus (P ˂ 0.05). There was no statistical difference in the levels of the antihyperalgesic cytokines interleukin-4, interleukin-5, interleukin-13 and transforming growth factor-β between wild-type and IL-10(-/-) mice (P ˃ 0.05). Interleukin-10 deficiency also resulted in increased myeloperoxidase activity, greater depletion of reduced glutathione levels, increased superoxide anion production and the maintenance of high plasma concentrations of creatine kinase (until 24 h after the swimming session) in soleus muscle (P ˂ 0.05). These results demonstrate that endogenous IL-10 controls intense acute swimming-induced muscle mechanical hyperalgesia by limiting oxidative stress and cytokine production.

Autophagy enhances NFκB activity in specific tissue macrophages by sequestering A20 to boost antifungal immunity

Immune responses must be well restrained in a steady state to avoid excessive inflammation. However, such restraints are quickly removed to exert antimicrobial responses. Here we report a role of autophagy in an early host antifungal response by enhancing NFκB activity through A20 sequestration. Enhancement of NFκB activation is achieved by autophagic depletion of A20, an NFκB inhibitor, in F4/80(hi) macrophages in the spleen, peritoneum and kidney. We show that p62, an autophagic adaptor protein, captures A20 to sequester it in the autophagosome. This allows the macrophages to release chemokines to recruit neutrophils. Indeed, mice lacking autophagy in myeloid cells show higher susceptibility to Candida albicans infection due to impairment in neutrophil recruitment. Thus, at least in the specific aforementioned tissues, autophagy appears to break A20-dependent suppression in F4/80(hi) macrophages, which express abundant A20 and contribute to the initiation of efficient innate immune responses.

Granulocyte-colony stimulating factor (G-CSF)-induced mechanical hyperalgesia in mice: Role for peripheral TNFα, IL-1β and IL-10

Granulocyte-colony stimulating factor (G-CSF) is a therapeutic approach to increase peripheral neutrophil counts after anti-tumor therapies. Pain is the major side effect of G-CSF. Intraplantar administration of G-CSF in mice induces mechanical hyperalgesia. However, the peripheral mechanisms involved in this effect were not elucidated. Therefore, the participation of pronociceptive cytokines tumor necrosis factor (TNF) alpha (TNFα), interleukin (IL)-1 beta (IL-1β) and antinociceptive cytokine IL-10 in G-CSF-induced mechanical hyperalgesia in mice was investigated. G-CSF-induced mechanical hyperalgesia was inhibited by systemic and local treatment with etanercept and IL-1 receptor antagonist (IL-1ra) or TNF receptor 1 (TNFR1) deficiency and increased in IL-10 deficient mice. In agreement, G-CSF injection induced significant TNFα, IL-1β and IL-10 production in paw tissue. G-CSF-induced hyperalgesia was dose-dependently inhibited by thalidomide (5-45mg/kg) and pentoxifylline (0.5-13.5mg/kg), and treatment with these drugs inhibited G-CSF-induced TNFα, IL-1β and IL-10 production. The combined treatment with pentoxifylline or thalidomide with morphine, at doses that are ineffective as single treatment, diminished G-CSF-induced hyperalgesia through inhibiting cytokine production. Indomethacin also reduces G-CSF hyperalgesia alone or combined with pentoxifylline or thalidomide. Thus, G-CSF-induced hyperalgesia might be mediate by peripheral production of pronociceptive cytokines TNFα and IL-1β and down-regulated by IL-10. Systemic IL-1ra reduced G-CSF-induced increase of peripheral neutrophil counts. However, local treatment with morphine, IL-1ra or etanercept, and systemic treatment with indomethacin, etanercept, thalidomide and pentoxifylline did not alter G-CSF-induced mobilization of neutrophils. Therefore, this study advances in the understanding of G-CSF-induced hyperalgesia and suggests therapeutic approaches for its control.

New insights into the anti-obesity activity of xanthones from Garcinia mangostana

This article reviews the anti-adipogenic, anti-inflammatory and antioxidant activities of xanthones from Garcinia mangostana.

T cell-macrophage interactions and granuloma formation in vasculitis

Granuloma formation, bringing into close proximity highly activated macrophages and T cells, is a typical event in inflammatory blood vessel diseases, and is noted in the name of several of the vasculitides. It is not known whether specific properties of the microenvironment in the blood vessel wall or the immediate surroundings of blood vessels contribute to granuloma formation and, in some cases, generation of multinucleated giant cells. Granulomas provide a specialized niche to optimize macrophage-T cell interactions, strongly activating both cell types. This is mirrored by the intensity of the systemic inflammation encountered in patients with vasculitis, often presenting with malaise, weight loss, fever, and strongly upregulated acute phase responses. As a sophisticated and highly organized structure, granulomas can serve as an ideal site to induce differentiation and maturation of T cells. The granulomas possibly seed aberrant Th1 and Th17 cells into the circulation, which are known to be the main pathogenic cells in vasculitis. Through the induction of memory T cells, aberrant innate immune responses can imprint the host immune system for decades to come and promote chronicity of the disease process. Improved understanding of T cell-macrophage interactions will redefine pathogenic models in the vasculitides and provide new avenues for immunomodulatory therapy.

The promotion of functional urinary bladder regeneration using anti-inflammatory nanofibers

Current attempts at tissue regeneration utilizing synthetic and decellularized biologic-based materials have typically been met in part by innate immune responses in the form of a robust inflammatory reaction at the site of implantation or grafting. This can ultimately lead to tissue fibrosis with direct negative impact on tissue growth, development, and function. In order to temper the innate inflammatory response, anti-inflammatory signals were incorporated through display on self-assembling peptide nanofibers to promote tissue healing and subsequent graft compliance throughout the regenerative process. Utilizing an established urinary bladder augmentation model, the highly pro-inflammatory biologic scaffold (decellularized small intestinal submucosa) was treated with anti-inflammatory peptide amphiphiles (AIF-PAs) or control peptide amphiphiles and used for augmentation. Significant regenerative advantages of the AIF-PAs were observed including potent angiogenic responses, limited tissue collagen accumulation, and the modulation of macrophage and neutrophil responses in regenerated bladder tissue. Upon further characterization, a reduction in the levels of M2 macrophages was observed, but not in M1 macrophages in control groups, while treatment groups exhibited decreased levels of M1 macrophages and stabilized levels of M2 macrophages. Pro-inflammatory cytokine production was decreased while anti-inflammatory cytokines were up-regulated in treatment groups. This resulted in far fewer incidences of tissue granuloma and bladder stone formation. Finally, functional urinary bladder testing revealed greater bladder compliance and similar capacities in groups treated with AIF-PAs. Data demonstrate that AIF-PAs can alleviate galvanic innate immune responses and provide a highly conducive regenerative milieu that may be applicable in a variety of clinical settings.