CD11b maintains West Nile virus replication through modulation of immune response in human neuroblastoma cells.

BACKGROUND: West Nile virus (WNV) is a rapidly spreading mosquito-borne virus accounted for neuroinvasive diseases. An insight into WNV-host factors interaction is necessary for development of therapeutic approaches against WNV infection. CD11b has key biological functions and been identified as a therapeutic target for several human diseases. The purpose of this study was to determine whether CD11b was implicated in WNV infection. METHODS: SH-SY5Y cells with and without MEK1/2 inhibitor U0126 or AKT inhibitor MK-2206 treatment were infected with WNV. CD11b mRNA levels were assessed by real-time PCR. WNV replication and expression of stress (ATF6 and CHOP), pro-inflammatory (TNF-α), and antiviral (IFN-α, IFN-ß, and IFN-γ) factors were evaluated in WNV-infected SH-SY5Y cells with CD11b siRNA transfection. Cell viability was determined by MTS assay. RESULTS: CD11b mRNA expression was remarkably up-regulated by WNV in a time-dependent manner. U0126 but not MK-2206 treatment reduced the CD11b induction by WNV. CD11b knockdown significantly decreased WNV replication and protected the infected cells. CD11b knockdown markedly increased TNF-α, IFN-α, IFN-ß, and IFN-γ mRNA expression induced by WNV. ATF6 mRNA expression was reduced upon CD11b knockdown following WNV infection. CONCLUSION: These results demonstrate that CD11b is involved in maintaining WNV replication and modulating inflammatory as well as antiviral immune response, highlighting the potential of CD11b as a target for therapeutics for WNV infection.

Mechanisms underlying neutrophils adhesion to triple-negative breast cancer cells via CD11b-ICAM1 in promoting breast cancer progression.

BACKGROUND: Triple-negative breast cancer (TNBC) is recognized as the most aggressive and immunologically infiltrated subtype of breast cancer. A high circulating neutrophil-to-lymphocyte ratio (NLR) is strongly linked to a poor prognosis among patients with breast cancer, emphasizing the critical role of neutrophils. Although the involvement of neutrophils in tumor metastasis is well documented, their interactions with primary tumors and tumor cells are not yet fully understood. METHODS: Clinical data were analyzed to investigate the role of neutrophils in breast cancer. In vivo mouse model and in vitro co-culture system were used for mechanism researches. Blocking experiments were further performed to identify therapeutic agents against TNBC. RESULTS: TNBC cells secreted GM-CSF to sustain the survival of mature neutrophils and upregulated CD11b expression. Through CD11b, neutrophils specifically binded to ICAM1 on TNBC cells, facilitating adhesion. Transcriptomic sequencing combined with human and murine functional experiments revealed that neutrophils, through direct CD11b-ICAM1 interactions, activated the MAPK signaling pathway in TNBC cells, thereby enhancing tumor cell invasion and migration. Atorvastatin effectively inhibited ICAM1 expression in tumor cells, and tumor cells with ICAM1 knockout or treated with atorvastatin were unresponsive to neutrophil activation. The MAPK pathway and MMP9 expression were significantly inhibited in the tumor tissues of TNBC patients treated with atorvastatin. CONCLUSIONS: Targeting CD11b-ICAM1 with atorvastatin represented a potential clinical approach to reduce the malignant characteristics of TNBC.

Deletion of Tmem268 in mice suppresses anti-infectious immune responses by downregulating CD11b signaling.

Transmembrane protein 268 (TMEM268) is a novel, tumor growth-related protein first reported by our laboratory. It interacts with the integrin subunit ß4 (ITGB4) and plays a positive role in the regulation of the ITGB4/PLEC signaling pathway. Here, we investigated the effects and mechanism of TMEM268 in anti-infectious immune response in mice. Tmem268 knockout in mice aggravated cecal ligation and puncture-induced sepsis, as evidenced by higher bacterial burden in various tissues and organs, congestion, and apoptosis. Moreover, Tmem268 deficiency in mice inhibited phagocyte adhesion and migration, thus decreasing phagocyte infiltration at the site of infection and complement-dependent phagocytosis. Further findings indicated that TMEM268 interacts with CD11b and inhibits its degradation via the endosome-lysosome pathway. Our results reveal a positive regulatory role of TMEM268 in ß2 integrin-associated anti-infectious immune responses and signify the potential value of targeting the TMEM268-CD11b signaling axis for the maintenance of immune homeostasis and immunotherapy for sepsis and related immune disorders.

Senolytic effects of exercise in human muscles require acute inflammation.

Higher intensity exercise, despite causing more tissue damage, improved aging conditions. We previously observed decreased p16INK4a mRNA in human skeletal muscle after high-intensity interval exercise (HIIE), with no change following equivalent work in moderate-intensity continuous exercise. This raises the question of whether the observed senolytic effect of exercise is mediated by inflammation, an immune response induced by muscle damage. In this study, inflammation was blocked using a multiple dose of ibuprofen (total dose: 1200 mg), a commonly consumed nonsteroidal anti-inflammatory drug (NSAID), in a placebo-controlled, counterbalanced crossover trial. Twelve men aged 20-26 consumed ibuprofen or placebo before and after HIIE at 120% maximum aerobic power. Multiple muscle biopsies were taken for tissue analysis before and after HIIE. p16INK4a+ cells were located surrounding myofibers in muscle tissues. The maximum decrease in p16INK4a mRNA levels within muscle tissues occurred at 3 h post-exercise (-82%, p < 0.01), gradually recovering over the next 3-24 h. A concurrent reduction pattern in CD11b mRNA (-87%, p < 0.01) was also found within the same time frame. Ibuprofen treatment attenuated the post-exercise reduction in both p16INK4a mRNA and CD11b mRNA. The strong correlation (r = 0.88, p < 0.01) between p16INK4a mRNA and CD11b mRNA in muscle tissues suggests a connection between the markers of tissue aging and pro-inflammatory myeloid differentiation. In conclusion, our results suggest that the senolytic effect of high-intensity exercise on human skeletal muscle is mediated by acute inflammation.

Immunophenotype of myeloid granulocytes in Chinese patients with BCR::ABL1-negative myeloproliferative neoplasms.

Typical BCR::ABL1-negative myeloproliferative neoplasms (MPN) are mainly referred to as polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofbrosis (PMF). Granulocytes in MPN patients are involved in their inflammation and form an important part of the pathophysiology of MPN patients. It has been shown that the immunophenotype of granulocytes in MPN patients is altered. We used flow cytometry to explore the immunophenotype of MPN patients and correlate it with clinical parameters. The results showed that PMF patients and PV patients had higher CD15+CD11b+ granulocytes than ET patients and normal controls. When grouped by gene mutation, changes in the granulocyte immunophenotype of MPN patients were independent of the JAK2V617F and CALR mutations. There was no significant heterogeneity in immunophenotype between ET patients and Pre-PMF, and between Overt-PMF and Pre-PMF patients. Granulocytes from some MPN patients showed an abnormal CD13/CD16 phenotype with a significant increase in mature granulocytes on molecular and cytomorphological grounds, and this abnormal pattern occurred significantly more frequently in PMF patients than in ET patients. CD15-CD11b- was negatively correlated with WBC and Hb and positively correlated with DIPSS score, whereas high CD10+ granulocytes were significantly and negatively associated with prognostic system IPSS and DIPSS scores in PMF patients. In conclusion, this study demonstrates the landscape of bone marrow granulocyte immunophenotypes in MPN patients. MPN patients, especially those with PMF, have a significant granulocyte developmental overmaturation phenotype. CD10+ granulocytes may be involved in the prognosis of PMF patients.

Identification of triciribine as a novel myeloid cell differentiation inducer.

Differentiation therapy using all-trans retinoic acid (ATRA) for acute promyelocytic leukemia (APL) is well established. However, because the narrow application and tolerance development of ATRA need to be improved, we searched for another efficient myeloid differentiation inducer. Kinase activation is involved in leukemia biology and differentiation block. To identify novel myeloid differentiation inducers, we used a Kinase Inhibitor Screening Library. Using a nitroblue tetrazolium dye reduction assay and real-time quantitative PCR using NB4 APL cells, we revealed that, PD169316, SB203580, SB202190 (p38 MAPK inhibitor), and triciribine (TCN) (Akt inhibitor) potently increased the expression of CD11b. We focused on TCN because it was reported to be well tolerated by patients with advanced hematological malignancies. Nuclear/cytoplasmic (N/C) ratio was significantly decreased, and myelomonocytic markers (CD11b and CD11c) were potently induced by TCN in both NB4 and acute myeloid leukemia (AML) M2 derived HL-60 cells. Western blot analysis using NB4 cells demonstrated that TCN promoted ERK1/2 phosphorylation, whereas p38 MAPK phosphorylation was not affected, suggesting that activation of the ERK pathway is involved in TCN-induced differentiation. We further examined that whether ATRA may affect phosphorylation of ERK and p38, and found that there was no obvious effect, suggesting that ATRA induced differentiation is different from TCN effect. To reveal the molecular mechanisms involved in TCN-induced differentiation, we performed microarray analysis. Pathway analysis using DAVID software indicated that "hematopoietic cell lineage" and "cytokine-cytokine receptor interaction" pathways were enriched with high significance. Real-time PCR analysis demonstrated that components of these pathways including IL1ß, CD3D, IL5RA, ITGA6, CD44, ITGA2B, CD37, CD9, CSF2RA, and IL3RA, were upregulated by TCN-induced differentiation. Collectively, we identified TCN as a novel myeloid cell differentiation inducer, and trials of TCN for APL and non-APL leukemia are worthy of exploration in the future.

TALEN-mediated intron editing of HSPCs enables transgene expression restricted to the myeloid lineage.

Gene therapy in hematopoietic stem and progenitor cells (HSPCs) shows great potential for the treatment of inborn metabolic diseases. Typical HSPC gene therapy approaches rely on constitutive promoters to express a therapeutic transgene, which is associated with multiple disadvantages. Here, we propose a novel promoterless intronic gene editing approach that triggers transgene expression only after cellular differentiation into the myeloid lineage. We integrated a splicing-competent eGFP cassette into the first intron of CD11b and observed expression of eGFP in the myeloid lineage but minimal to no expression in HSPCs or differentiated non-myeloid lineages. In vivo, edited HSPCs successfully engrafted in immunodeficient mice and displayed transgene expression in the myeloid compartment of multiple tissues. Using the same approach, we expressed alpha-L-iduronidase (IDUA), the defective enzyme in Mucopolysaccharidosis type I, and observed a 10-fold supraendogenous IDUA expression exclusively after myeloid differentiation. Edited cells efficiently populated bone marrow, blood, and spleen of immunodeficient mice, and retained the capacity to secrete IDUA ex vivo. Importantly, cells edited with the eGFP and IDUA transgenes were also found in the brain. This approach may unlock new therapeutic strategies for inborn metabolic and neurological diseases that require the delivery of therapeutics in brain.

ITGAM is a critical gene in ischemic stroke.

BACKGROUND: Globally, ischemic stroke (IS) is ranked as the second most prevailing cause of mortality and is considered lethal to human health. This study aimed to identify genes and pathways involved in the onset and progression of IS. METHODS: GSE16561 and GSE22255 were downloaded from the Gene Expression Omnibus (GEO) database, merged, and subjected to batch effect removal using the ComBat method. The limma package was employed to identify the differentially expressed genes (DEGs), followed by enrichment analysis and protein-protein interaction (PPI) network construction. Afterward, the cytoHubba plugin was utilized to screen the hub genes. Finally, a ROC curve was generated to investigate the diagnostic value of hub genes. Validation analysis through a series of experiments including qPCR, Western blotting, TUNEL, and flow cytometry was performed. RESULTS: The analysis incorporated 59 IS samples and 44 control samples, revealing 226 DEGs, of which 152 were up-regulated and 74 were down-regulated. These DEGs were revealed to be linked with the inflammatory and immune responses through enrichment analyses. Overall, the ROC analysis revealed the remarkable diagnostic potential of ITGAM and MMP9 for IS. Quantitative assessment of these genes showed significant overexpression in IS patients. ITGAM modulation influenced the secretion of critical inflammatory cytokines, such as IL-1ß, IL-6, and TNF-α, and had a distinct impact on neuronal apoptosis. CONCLUSIONS: The inflammation and immune response were identified as potential pathological mechanisms of IS by bioinformatics and experiments. In addition, ITGAM may be considered a potential therapeutic target for IS.

Alteration of functionality and differentiation directed by changing gene expression patterns in myeloid-derived suppressor cells (MDSCs) in tumor microenvironment and bone marrow through early to terminal phase of tumor progression.

Myeloid-derived suppressor cells are heterogenous immature myeloid lineage cells that can differentiate into neutrophils, monocytes, and dendritic cells as well. These cells have been characterized to have potent immunosuppressive capacity in neoplasia and a neoplastic chronic inflammatory microenvironment. Increased accumulation of myeloid-derived suppressor cells was reported with poor clinical outcomes in patients. They support neoplastic progression by abrogating antitumor immunity through inhibition of lymphocyte functions and directly by facilitating tumor development. Yet the shifting genetic signatures of this myeloid lineage cell toward immunosuppressive functionality in progressive tumor development remain elusive. We have attempted to identify the gene expression profile using lineage-specific markers of these unique myeloid lineage cells in a tumor microenvironment and bone marrow using a liquid transplantable mice tumor model to trace the changing influence of the tumor microenvironment on myeloid-derived suppressor cells. We analyzed the phenotype, functional shift, suppressive activity, differentiation status, and microarray-based gene expression profile of CD11b+Gr1+ lineage-specific cells isolated from the tumor microenvironment and bone marrow of 4 stages of tumor-bearing mice and compared them with control counterparts. Our analysis of differentially expressed genes of myeloid-derived suppressor cells isolated from bone marrow and the tumor microenvironment reveals unique gene expression patterns in the bone marrow and tumor microenvironment-derived myeloid-derived suppressor cells. It also suggests T-cell suppressive activity of myeloid-derived suppressor cells progressively increases toward the mid-to-late phase of the tumor and a significant differentiation bias of tumor site myeloid-derived suppressor cells toward macrophages, even in the presence of differentiating agents, indicating potential molecular characteristics of myeloid-derived suppressor cells in different stages of the tumor that can emerge as an intervention target.

CD11b Deficiency Favors Cartilage Calcification via Increased Matrix Vesicles, Apoptosis, and Lysyl Oxidase Activity.

Pathological cartilage calcification is a hallmark feature of osteoarthritis, a common degenerative joint disease, characterized by cartilage damage, progressively causing pain and loss of movement. The integrin subunit CD11b was shown to play a protective role against cartilage calcification in a mouse model of surgery-induced OA. Here, we investigated the possible mechanism by which CD11b deficiency could favor cartilage calcification by using naïve mice. First, we found by transmission electron microscopy (TEM) that CD11b KO cartilage from young mice presented early calcification spots compared with WT. CD11b KO cartilage from old mice showed progression of calcification areas. Mechanistically, we found more calcification-competent matrix vesicles and more apoptosis in both cartilage and chondrocytes isolated from CD11b-deficient mice. Additionally, the extracellular matrix from cartilage lacking the integrin was dysregulated with increased collagen fibrils with smaller diameters. Moreover, we revealed by TEM that CD11b KO cartilage had increased expression of lysyl oxidase (LOX), the enzyme that catalyzes matrix crosslinks. We confirmed this in murine primary CD11b KO chondrocytes, where Lox gene expression and crosslinking activity were increased. Overall, our results suggest that CD11b integrin regulates cartilage calcification through reduced MV release, apoptosis, LOX activity, and matrix crosslinking. As such, CD11b activation might be a key pathway for maintaining cartilage integrity.

ITGAM rs1143679 Variant in Systemic Lupus Erythematosus Is Associated with Increased Serum Calcification Propensity.

OBJECTIVES: CD11B/ITGAM (Integrin Subunit α M) mediates the adhesion of monocytes, macrophages, and granulocytes and promotes the phagocytosis of complement-coated particles. Variants of the ITGAM gene are candidates for genetic susceptibility to systemic lupus erythematosus (SLE). SNP rs1143679 (R77H) of CD11B particularly increases the risk of developing SLE. Deficiency of CD11B is linked to premature extra-osseous calcification, as seen in the cartilage of animals with osteoarthritis. Serum calcification propensity measured by the T50 test is a surrogate marker for systemic calcification and reflects increased cardiovascular (CV) risk. We aimed to assess whether the CD11B R77H gene variant is associated with a higher serum calcification propensity (i.e., a lower T50 value) in SLE patients compared to the wild-type allele (WT). METHODS: Cross-sectional study incorporating adults with SLE genotyped for the CD11B variant R77H and assessed for serum calcification propensity with the T50 method. Participants were included in a multicenter trans-disciplinary cohort and fulfilled the 1997 revised American College of Rheumatology (ACR) criteria for SLE. We used descriptive statistics for comparing baseline characteristics and sequential T50 measurements in subjects with the R77H variant vs. WT CD11B. RESULTS: Of the 167 patients, 108 (65%) were G/G (WT), 53 (32%) were G/A heterozygous, and 6 (3%) were A/A homozygous for the R77H variant. A/A patients cumulated more ACR criteria upon inclusion (7 ± 2 vs. 5 ± 1 in G/G and G/A; p = 0.02). There were no differences between the groups in terms of global disease activity, kidney involvement, and chronic renal failure. Complement C3 levels were lower in A/A individuals compared to others (0.6 ± 0.08 vs. 0.9 ± 0.25 g/L; p = 0.02). Baseline T50 did not differ between the groups (A/A 278 ± 42' vs. 297 ± 50' in G/G and G/A; p = 0.28). Considering all sequential T50 test results, serum calcification propensity was significantly increased in A/A individuals compared to others (253 ± 50 vs. 290 ± 54; p = 0.008). CONCLUSIONS: SLE patients with homozygosity for the R77H variant and repeated T50 assessment displayed an increased serum calcification propensity (i.e., a lower T50) and lower C3 levels compared to heterozygous and WT CD11B, without differing with respect to global disease activity and kidney involvement. This suggests an increased CV risk in SLE patients homozygous for the R77H variant of CD11B.

Daytime Light Deficiency Leads to Sex- and Brain Region-Specific Neuroinflammatory Responses in a Diurnal Rodent.

Seasonal changes in peripheral inflammation are well documented in both humans and animal models, but seasonal changes in neuroinflammation, especially the impact of seasonal lighting environment on neuroinflammation remain unclear. To address this question, the present study examined the effects of environmental lighting conditions on neuroinflammation in a diurnal rodent model, Nile grass rats (Arvicanthis niloticus). Male and female grass rats were housed in either bright (brLD) or dim (dimLD) light during the day to simulate a summer or winter light condition, respectively. After 4 weeks, microglia markers Iba-1 and CD11b, as well as pro-inflammatory cytokines TNF-α and IL-6, were examined in the anterior cingulate cortex (ACC), basolateral amygdala (BLA), and dorsal hippocampus (dHipp). The results revealed that winter-like dim light during the day leads to indicators of increased neuroinflammation in a brain site- and sex-specific manner. Specifically, relatively few changes in the neuroinflammatory markers were observed in the ACC, while numerous changes were found in the BLA and dHipp. In the BLA, winter-like dimLD resulted in hyper-ramified microglia morphology and increased expression of the pro-inflammatory cytokine IL-6, but only in males. In the dHipp, dimLD led to a higher number and hyper-ramified morphology of microglia as well as increased expression of CD11b and TNF-α, but only in females. Neuroinflammatory state is thus influenced by environmental light, differently in males and females, and could play a role in sex differences in the prevalence and symptoms of psychiatric or neurological disorders that are influenced by season or other environmental light conditions. Diurnal Nile grass rats were housed under bright or dim light during the day for 4 weeks, simulating seasonal fluctuations in daytime lighting environment. Dim light housing resulted in hyper-ramified morphology of microglia (scale bar, 15 µm) and altered expression of pro-inflammatory cytokines (TNF-α) in a sex- and brain region-specific manner.

A novel ZsGreen knock-in melanoma cell line reveals the function of CD11b in tumor phagocytosis.

Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) is an efficient tool for establishing genetic models including cellular models, and has facilitated unprecedented advancements in biomedical research. In both patients and cancer animal models, immune cells infiltrate the tumor microenvironment and some of them migrate to draining lymph nodes to exert antitumor effects. Among these immune cells, phagocytes such as macrophages and dendritic cells engulf tumor antigens prior to their crosstalk with T cells and elicit adaptive immune response against tumors. Melanoma cells are frequently used as a tumor model because of their relatively high level of somatic mutations and antigenicity. However, few genetic models have been developed using melanoma cell lines to track tumor cell phagocytosis, which is essential for understanding protective immune response in vivo. In this study, we used CRISPR/Cas9-mediated DNA cleavage and homologous recombination to develop a novel knock-in tool which expresses the ultra-bright fluorescent probe ZsGreen in YUMM1.7 melanoma cells. Using this novel tool, we measured the macrophagic engulfment of melanoma cells inside the tumor microenvironment. We also found that in tumor-grafted mice, a subset of dendritic cells efficiently engulfed YUMM1.7 cells and was preferentially trafficking tumor antigens to draining lymph nodes. In addition, we used this knock-in tool to assess the impact of a point mutation of CD11b on phagocytosis in the tumor microenvironment. Our results demonstrate that the ZsGreen-expressing YUMM1.7 melanoma model provides a valuable tool for the study of phagocytosis in vivo.

Human Neutrophil Antigen Genotype and Allele Frequencies in Iranian Blood Donors.

OBJECTIVE: Human neutrophil antigens (HNAs) can be targeted by HNA-allo antibodies and cause a variety of clinical conditions such as transfusion-related acute lung injury (TRALI) and neonatal alloimmune neutropenia (NAIN). The current study is aimed at identifying the genotype and allele frequencies of HNAs in Iranian blood donors. METHODS: A total of 150 blood samples were obtained from healthy blood donors. HNA-1, HNA-3, HNA-4, and HNA-5 were genotyped, using the polymerase chain reaction sequence-specific primer (PCR-SSP) technique. The expression of the HNA-2 antigen on the neutrophil surface was evaluated by flow cytometry. RESULTS: The allele frequencies of FCGR3B∗1 (encoding HNA-1a), FCGR3B∗2 (encoding HNA-1b), and FCGR3B∗3 (encoding HNA-1c) were 0.34, 0.63, and 0.03, respectively. For HNA-3, the allele frequencies for SLC44A2∗1 (encoding HNA-3a) and SLC44A2∗2 (encoding HNA-3b) were 0.63 and 0.37, respectively. The frequencies of ITGAM∗1 (encoding HNA-4a) and ITGAM∗2 (encoding HNA-4b) alleles were 0.85 and 0.15, respectively. Furthermore, the frequencies of ITGAL∗1 (encoding HNA-5a) and ITGAL∗2 (encoding HNA-5b) alleles were 0.72 and 0.28, respectively. In the studied population, HNA-2 antigen was present on the neutrophil surface in 97.3% of the individuals, while no detectable HNA-2 expression was observed in 2.7% of the individuals. However, no significant difference in HNA-2 expression between different age groups was found. CONCLUSION: The present study provides the first report of the HNA allele and genotype frequencies among the Iranian population. All HNAs (HNA-1 to HNA-5) were typed using the PCR-SSP and flow cytometer. In the current cohort study, the determined HNA allele frequencies were similar to the previous reports from British, German, and Danish populations. Considering the presence of different Iranian ethnic groups, further studies with a larger sample size are needed to draw a total picture for HNA allele frequencies.

Specific Silencing of Microglial Gene Expression in the Rat Brain by Nanoparticle-Based Small Interfering RNA Delivery.

Microglia are the major innate immune cells in the brain and are essential for maintaining homeostasis in a neuronal microenvironment. Currently, a genetic tool to modify microglial gene expression in specific brain regions is not available. In this report, we introduce a tailor-designed method that uses lipid and polymer hybridized nanoparticles (LPNPs) for the local delivery of small interfering RNAs (siRNAs), allowing the silencing of specific microglial genes in the hypothalamus. Our physical characterization proved that this LPNP-siRNA was uniform and stable. We demonstrated that, due to their natural phagocytic behavior, microglial cells are the dominant cell type taking up these LPNPs in the hypothalamus of rats. We then tested the silencing efficiency of LPNPs carrying a cluster of differentiation molecule 11b (CD11b) or Toll-like receptor 4 (TLR4) siRNA using different in vivo and in vitro approaches. In cultured microglial cells treated with LPNP-CD11b siRNA or LPNP-TLR4 siRNA, we found a silencing efficiency at protein expression levels of 65 or 77%, respectively. In line with this finding, immunohistochemistry and western blotting results from in vivo experiments showed that LPNP-CD11b siRNA significantly inhibited microglial CD11b protein expression in the hypothalamus. Furthermore, following lipopolysaccharide (LPS) stimulation of cultured microglial cells, gene expression of the TLR4 downstream signaling component myeloid differentiation factor 88 and its associated cytokines was significantly inhibited in LPNP-TLR4 siRNA-treated microglial cells compared with cells treated with LPNP-scrambled siRNA. Finally, after LPNP-TLR4 siRNA injection into the rat hypothalamus, we observed a significant reduction in microglial activation in response to LPS compared with the control rats injected with LPNP-scrambled siRNA. Our results indicate that LPNP-siRNA is a promising tool to manipulate microglial activity locally in the brain and may serve as a prophylactic approach to prevent microglial dysfunction-associated diseases.

Association between complement gene polymorphisms and systemic lupus erythematosus: a systematic review and meta-analysis.

Complement dysfunction results in impaired ability in clearing apoptotic cell debris that may stimulate autoantibody production in systemic lupus erythematosus (SLE). Herein, we provided a comprehensive search to find and meta-analyze any complement gene polymorphisms associated with SLE. The ITGAM, C1q, and MBL gene polymorphisms were included in this meta-analysis to reveal the exact association with SLE risk. Electronic databases, including Scopus, PubMed, and Google Scholar, were searched to find studies investigating the ITGAM, C1q, and MBL gene polymorphisms and SLE risk in different populations. The pooled odds ratio (OR) and its corresponding 95% confidence interval (CI) were used to analyze the association between ITGAM, C1q, and MBL gene polymorphisms and susceptibility to SLE. According to inclusion criteria, a total of 24 studies, comprising 4 studies for C1QA rs292001, 5 studies for C1QA rs172378, 9 studies for ITGAM rs1143679, 8 studies for MBL rs1800450, 3 studies for MBL2 rs1800451, and 3 studies for MBL2 rs5030737, were included in the final meta-analysis. A significant positive association was found between rs1143679 and SLE risk, while rs1800451 significantly associated with decreased SLE susceptibility. In summary, ITGAM gene rs1143679 SNP and MBL gene rs1800451 SNP were positively and negatively associated with SLE risk, respectively.

Carbon Monoxide Regulates Macrophage Differentiation and Polarization toward the M2 Phenotype through Upregulation of Heme Oxygenase 1.

Carbon monoxide (CO) is generated by heme oxygenase (HO), and HO-1 is highly induced in monocytes and macrophages upon stimulation. Monocytes differentiate into macrophages, including pro-inflammatory (M1) and anti-inflammatory (M2) cells, in response to environmental signals. The present study investigated whether CO modulates macrophage differentiation and polarization, by applying the CO-releasing molecule-3 (CORM-3). Results showed that murine bone marrow cells are differentiated into macrophages by CORM-3 in the presence of macrophage colony-stimulating factor. CORM-3 increases expressions of macrophage markers, including F4/80 and CD11b, and alters the cell morphology into elongated spindle-shaped cells, which is a typical morphology of M2 cells. CORM-3 upregulates the expressions of genes and molecules involved in M2 polarization and M2 phenotype markers, such as STAT6, PPARγ, Ym1, Fizz1, arginase-1, and IL-10. However, exposure to CORM-3 inhibits the iNOS expression, suggesting that CO enhances macrophage differentiation and polarization toward M2. Increased HO-1 expression is observed in differentiated macrophages, and CORM-3 further increases this expression. Hemin, an HO-1 inducer, results in increased macrophage differentiation, whereas the HO-1 inhibitor zinc protoporphyrin IX inhibits differentiation. In addition, CORM-3 increases the proportion of macrophages in peritoneal exudate cells and enhances the expression of HO-1 and arginase-1 but inhibits iNOS. Taken together, these results suggest that the abundantly produced CO in activated macrophages enhances proliferation, differentiation, and polarization toward M2. It will probably help clear apoptotic cells, resolve inflammation, and promote wound healing and tissue remodeling.

Intestinal CD11b+ B Cells Ameliorate Colitis by Secreting Immunoglobulin A.

The intestinal mucosal immune environment requires multiple immune cells to maintain homeostasis. Although intestinal B cells are among the most important immune cells, little is known about the mechanism that they employ to regulate immune homeostasis. In this study, we found that CD11b+ B cells significantly accumulated in the gut lamina propria and Peyer's patches in dextran sulfate sodium-induced colitis mouse models and patients with ulcerative colitis. Adoptive transfer of CD11b+ B cells, but not CD11b-/- B cells, effectively ameliorated colitis and exhibited therapeutic effects. Furthermore, CD11b+ B cells were found to produce higher levels of IgA than CD11b- B cells. CD11b deficiency in B cells dampened IgA production, resulting in the loss of their ability to ameliorate colitis. Mechanistically, CD11b+ B cells expressed abundant TGF-ß and TGF-ß receptor II, as well as highly activate phosphorylated Smad2/3 signaling pathway, consequently promoting the class switch to IgA. Collectively, our findings demonstrate that CD11b+ B cells are essential intestinal suppressive immune cells and the primary source of intestinal IgA, which plays an indispensable role in maintaining intestinal homeostasis.

Homeostatic IL-13 in healthy skin directs dendritic cell differentiation to promote TH2 and inhibit TH17 cell polarization.

The signals driving the adaptation of type 2 dendritic cells (DC2s) to diverse peripheral environments remain mostly undefined. We show that differentiation of CD11blo migratory DC2s-a DC2 population unique to the dermis-required IL-13 signaling dependent on the transcription factors STAT6 and KLF4, whereas DC2s in lung and small intestine were STAT6-independent. Similarly, human DC2s in skin expressed an IL-4 and IL-13 gene signature that was not found in blood, spleen and lung DCs. In mice, IL-13 was secreted homeostatically by dermal innate lymphoid cells and was independent of microbiota, TSLP or IL-33. In the absence of IL-13 signaling, dermal DC2s were stable in number but remained CD11bhi and showed defective activation in response to allergens, with diminished ability to support the development of IL-4+GATA3+ helper T cells (TH), whereas antifungal IL-17+RORγt+ TH cells were increased. Therefore, homeostatic IL-13 fosters a noninflammatory skin environment that supports allergic sensitization.