Induction Of Pro-inflammatory Factors Research Articles

SARS-CoV-2-triggered mast cell rapid degranulation induces alveolar epithelial inflammation and lung injury

SARS-CoV-2 infection-induced hyper-inflammation links to the acute lung injury and COVID-19 severity. Identifying the primary mediators that initiate the uncontrolled hypercytokinemia is essential for treatments. Mast cells (MCs) are strategically located at the mucosa and beneficially or detrimentally regulate immune inflammations. In this study, we showed that SARS-CoV-2-triggered MC degranulation initiated alveolar epithelial inflammation and lung injury. SARS-CoV-2 challenge induced MC degranulation in ACE-2 humanized mice and rhesus macaques, and a rapid MC degranulation could be recapitulated with Spike-RBD binding to ACE2 in cells; MC degranulation altered various signaling pathways in alveolar epithelial cells, particularly, the induction of pro-inflammatory factors and consequential disruption of tight junctions. Importantly, the administration of clinical MC stabilizers for blocking degranulation dampened SARS-CoV-2-induced production of pro-inflammatory factors and prevented lung injury. These findings uncover a novel mechanism for SARS-CoV-2 initiating lung inflammation, and suggest an off-label use of MC stabilizer as immunomodulators for COVID-19 treatments.

SNW1 interacts with IKKγ to positively regulate antiviral innate immune responses against influenza A virus infection

The Ski-interacting protein (SNW1) acts as a transcriptional co-regulator associated with mRNA splicing and transcription, cell cycle progression, acute and chronic inflammatory responses, however, its role involved in host antiviral innate immune responses remains to be explored. Here, for the first time, we demonstrated that SNW1 positively regulates the expression of pro-inflammatory cytokines and interferon (IFN) responses induced by influenza A virus (IAV) infection, and further inhibits virus replication by performing SNW1 depletion or overexpression approaches. Furthermore, we showed that reduced interferon beta (IFN-β) expression caused by interfering SNW1 impairs the activation of JAK-STAT pathway in response to IAV or poly I:C. Importantly, by interacting with IKKγ, the regulatory subunit of IκB kinase (IKK) complex, SNW1 promotes IAV-induced activation of NF-κB and phosphorylation of TBK1 kinase, leading to the increase of antiviral effectors interleukin 6 (IL-6), C-X-C motif chemokine 10 (CXCL10), IFN-β and myxovirus resistance protein 1 (MX1). Taken together, our study revealed that SNW1 is an important mediator of host defenses against IAV through the induction of pro-inflammatory factors and IFN signaling, providing novel insights in modulating innate immune responses to protect host from IAV infection.

Macrophage p38α promotes nutritional steatohepatitis through M1 polarization

p38 mitogen-activated protein kinases are important inflammatory factors. p38α alteration has been implicated in both human and mouse inflammatory disease models. Therefore, we aimed to characterize the cell type-specific role of p38α in non-alcoholic steatohepatitis (NASH). Human liver tissues were obtained from 27 patients with non-alcoholic fatty liver disease (NAFLD) and 20 control individuals. NASH was established and compared between hepatocyte-specific p38α knockout (p38αΔHep), macrophage-specific p38α knockout (p38αΔMΦ) and wild-type (p38αfl/fl) mice fed with high-fat diet (HFD), high-fat/high-cholesterol diet (HFHC), or methionine-and choline-deficient diet (MCD). p38 inhibitors were administered to HFHC-fed wild-type mice for disease treatment. p38α was significantly upregulated in the liver tissues of patients with NAFLD. Compared to p38αfl/fl littermates, p38αΔHep mice developed significant nutritional steatohepatitis induced by HFD, HFHC or MCD. Meanwhile, p38αΔMΦ mice exhibited less severe steatohepatitis and insulin resistance than p38αfl/fl mice in response to a HFHC or MCD. The effect of macrophage p38α in promoting steatohepatitis was mediated by the induction of pro-inflammatory factors (CXCL2, IL-1β, CXCL10 and IL-6) secreted by M1 macrophages and associated signaling pathways. p38αΔMΦ mice exhibited M2 anti-inflammatory polarization as demonstrated by increased CD45+F4/80+CD11b+CD206+ M2 macrophages and enhanced arginase activity in liver tissues. Primary hepatocytes from p38αΔMΦ mice showed decreased steatosis and inflammatory damage. In a co-culture system, p38α deleted macrophages attenuated steatohepatitic changes in hepatocytes through decreased secretion of pro-inflammatory cytokines (TNF-α, CXCL10 and IL-6), which mediate M1 macrophage polarization in p38αΔMΦ mice. Restoration of TNF-α, CXCL10 or IL-6 induced lipid accumulation and inflammatory responses in p38αfl/fl hepatocytes co-cultured with p38αΔMΦ macrophages. Moreover, pharmacological p38 inhibitors suppressed HFHC-induced steatohepatitis. Macrophage p38α promotes the progression of steatohepatitis by inducing pro-inflammatory cytokine secretion and M1 polarization. p38 inhibition protects against steatohepatitis. LAY SUMMARY: p38 mitogen-activated protein kinases are important inflammatory factors. In the present study, we demonstrated that p38α is upregulated in liver tissues of patients with non-alcoholic fatty liver diseases. Genetic deletion of p38α in macrophages led to ameliorated nutritional steatohepatitis in mice through decreased pro-inflammatory cytokine secretion and increased M2 macrophage polarization.

Visfatin alters the cytokine and matrix-degrading enzyme profile during osteogenic and adipogenic MSC differentiation

Age-related bone loss is associated with bone marrow adiposity. Adipokines (e.g., visfatin, resistin, leptin) are adipocyte-derived factors with immunomodulatory properties and might influence differentiation of bone marrow-derived mesenchymal stem cells (MSC) in osteoarthritis (OA) and osteoporosis (OP). Thus, the presence of adipokines and MMPs in bone marrow and their effects on MSC differentiation were analyzed. MSC and ribonucleic acid (RNA) were isolated from femoral heads after hip replacement surgery of OA or osteoporotic femoral neck fracture (FF) patients. Bone structural parameters were evaluated by microcomputed tomography (μCT). MSC were differentiated towards adipocytes or osteoblasts with/without adipokines. Gene expression (adipokines, bone marker genes, MMPs, TIMPs) and cytokine production was evaluated by realtime-polymerase chain reaction (realtime-PCR) and enzyme-linked immunosorbent assay (ELISA). Matrix mineralization was quantified using Alizarin red S staining. μCT showed an osteoporotic phenotype of FF compared to OA bone (reduced trabecular thickness and increased ratio of bone surface vs volume of solid bone). Visfatin and leptin were increased in FF vs OA. Visfatin induced the secretion of IL-6, IL-8, and MCP-1 during osteogenic and adipogenic differentiation. In contrast to resistin and leptin, visfatin increased MMP2 and MMP13 during adipogenesis. In osteogenically differentiated cells, MMPs and TIMPs were reduced by visfatin. Visfatin significantly increased matrix mineralization during osteogenesis, whereas collagen type I expression was reduced. Visfatin-mediated increase of matrix mineralization and reduced collagen type I expression could contribute to bone fragility. Visfatin is involved in impaired bone remodeling at the adipose tissue/bone interface through induction of proinflammatory factors and dysregulated MMP/TIMP balance during MSC differentiation.

The effect of carbohydrate moieties on immunoregulatory activity of yolkin polypeptides naturally occurring in egg yolk

Substances isolated from natural sources showing a character of endogenous regulators may have a circular meaning. One example is yolkin, which can be useful as a natural therapeutic agent for treating immunological disorders. In the present work we studied the effect of degree of deglycosylation on the biological activity of yolkin polypeptides. For this purpose, yolkin from hen egg yolk was fractionated by gel permeation chromatography (Sephacryl S 100 - HR and Zorbax GF- 250 columns) and enzymatically deglycosylated. The immunoregulatory activity of yolkin fractions (ysec, y4 and y9) were estimated by their induction of proinflammatory factors. The induction of cytokines IL-6, IL-10, and TNF-α in human whole blood cell cultures and nitric oxide from bone-marrow mouse macrophages BMDM were measured. The obtained results showed that all of the yolkin polypeptides, irrespective of size, exerted a strong cytokine and nitric oxide induction, indicating that all of the yolkin constituents possess these activities. The results indicated that the presence of carbohydrate in yolkin polypeptides is unnecessary to preserve cytokine inducing activity and NO generation. Furthermore the removal of carbohydrates from the yolkin by PNGase F led to a significant increase in the level of secretion of nitric oxide from the macrophages.

Myeloid-Related Protein-14/MRP-14/S100A9/Calgranulin B is Associated with Inflammation in Proliferative Diabetic Retinopathy

ABSTRACTPurpose: To investigate the expression of the leukocyte proteins myeloid-related protein (MRP)-8 and MRP-14 in proliferative diabetic retinopathy (PDR) and the effect of MRP-8/MRP-14 (calprotectin) heterodimer on induction of proinflammatory factors in human retinal microvascular endothelial cells (HRMEC).Methods: Epiretinal membranes from 20 patients with PDR and 10 patients with proliferative vitreoretinopathy (PVR), vitreous fluid samples from PDR and non-diabetic subjects and HRMEC were studied by immunohistochemistry and Western blot analysis.Results: MRP-14 expression was localized in endothelial cells, leukocytes and myofibroblasts in all PDR membranes. MRP-8 expression was limited to intravascular leukocytes in 42% of the studied membranes. In PVR membranes, MRP-14 was expressed in leukocytes and myofibroblasts, whereas MRP-8 immunoreactivity was limited to leukocytes. MRP-14 was significantly upregulated in vitreous from PDR patients. MRP-8/MRP-14 (calprotectin) increased expression of intercellular adhesion molecule-1, but attenuated vascular cell adhesion molecule-1 expression in HRMEC.Conclusions: Increased MRP-14 levels are associated with inflammation in PDR.

Ligation of TLR7 by rheumatoid arthritis synovial fluid single strand RNA induces transcription of TNFα in monocytes

ObjectiveThe aim of the study was to characterise the expression, regulation and pathogenic role of toll-like receptor 7 (TLR7) and TLR8 in rheumatoid arthritis (RA).MethodsExpression of TLR7 and TLR8 was...

Regional difference in inflammatory response to LPS-injection in the brain: Role of microglia cell density

To elucidate whether density of cells could contribute to the extent of microglial activation, we performed in vitro assays using three different densities of N13 microglia stimulated with LPS. Our results showed that induction of pro-inflammatory factors as TNF-α and iNOS was directly related to cell density, meanwhile the induction of the anti-inflammatory IL-10 was inversely related to cell density. Accordingly, in vivo assays showed that after LPS-injection, iNOS expression was more intense in substantia nigra, a brain area showing specific susceptibility to neurodegeneration after microglia activation, whereas IL-10 expression was more sustained in striatum, an area resistant to damage. These results support that microglia density is pivotal to control the balance between pro- and anti-inflammatory factors release.

TLR3 signaling in a hepatoma cell line is skewed towards apoptosis

Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPS) leading to the activation of the innate immune response and subsequently to the shaping of the adaptive immune response. Of the known human TLRs, TLR3, 7, 8, and 9 were shown to recognize nucleic acid ligands. TLR3 signaling is induced by double-stranded (ds)RNA, a molecular signature of viruses, and is mediated by the TRIF (TIR domain-containing adaptor-inducing IFNbeta) adaptor molecule. Thus, TLR3 plays an important role in the host response to viral infections. The liver is constantly exposed to a large variety of foreign substances, including pathogens such as HBV (hepatitis B virus) and HCV (hepatitis C virus), which frequently establish persistent liver infections. In this work, we investigated the expression and signaling pathway of TLR3 in different hepatoma cell lines. We show that hepatocyte lineage cells express relatively low levels of TLR3 mRNA. TLR3 signaling in HEK293 cells (human embryonic kidney cells) activated NF-kappaB and IRF3 (interferon regulatory factor 3) and induced IFNbeta (interferon beta) promoter expression, which are known to lead to pro-inflammatory cytokine secretion. In Huh7 cells, there was only a short-term IRF3 activation, and a very low level of IFNbeta expression. In HepG2 cells on the other hand, while no induction of pro-inflammatory factors was observed, signaling by TLR3 was skewed towards the induction of apoptosis. These results indicate preferential induction of the apoptotic pathway over the cytokine induction pathway by TLR3 signaling in hepatocellular carcinoma cells with potential implications for therapeutic strategies.

Inhibition of Vascular Permeability Factor/Vascular Endothelial Growth Factor-mediated Angiogenesis by the Kruppel-like Factor KLF2

The Kruppel-like factor KLF2 was recently identified as a novel regulator of endothelial pro-inflammatory and pro-thrombotic function. Here it is shown that overexpression of KLF2 potently inhibits vascular permeability factor/vascular endothelial growth factor (VEGF-A)-mediated angiogenesis and tissue edema in the nude ear mouse model of angiogenesis. In vitro, KLF2 expression retards VEGF-mediated calcium flux, proliferation and induction of pro-inflammatory factors in endothelial cells. This effect is due to a potent inhibition of VEGFR2/KDR expression and promoter activity. These observations identify KLF2 as a regulator of VEGFR2/KDR and provide a foundation for novel approaches to regulate angiogenesis.

ＴＡＫ１が関与する新しいＮＦ‐κＢ活性化機構

The transcription factor NF-κB plays an important role in the induction of proinflammatory factors. NF-κB is sequestered in the cytoplasm by its inhibitory protein, IκB. Agents that stimulate NF-κB activation induce the phosphorylation of IκB by two IκB kinase (IKK) subunits, IKKα and IKKβ. The phosphorylation targets it for rapid degradation through ubiquitin-proteasome pathway, thereby releasing NF-κB to enter the nucleus. Several mitogen-activated protein kinase kinase kinases (MAP3Ks) play critical roles in NF-κB activation mediated through IKK pathway. We have found that TGFβ activated kinase 1 (TAK1), a member of the MAP3K family, stimulates NF-κB activation. TAK1 interacts with and activates IKKα and IKKβ. Furthermore, TNFα, but not TGFβ, activates TAK1 and the kinase negative TAK1 acts as a dominant negative inhibitor against TNFα-induced NF-κB activation. These results demonstrated a novel signaling pathway to NF-κB activation through TAK1, in which TAK1 may act as a regulatory kinase of IKKs.

Activation of transcription factor NF-κB in experimental glomerulonephritis in rats

NF-κB plays a pivotal role in cells of the immune system as an inducible transcriptional activator. NF-κB regulates the transcription of many genes of pro-inflammatory cytokines and cell adhesion molecules, which could be involved in the pathogenesis of glomerulonephritis. Using a gel shift assay, we investigated NF-κB DNA-binding activity in glomeruli of WKY rats injected with nephrotoxic serum (NTS). Kinetic analysis indicated that the NF-κB DNA-binding activity in glomeruli, composed of p50 subunit determined by a supershift assay, increased on day 1 after NTS injection and the maximal activation was observed on day 3 to 5. NF-κB activation persisted at least until day 14. Pyrrolidine dithiocarbamate (PDTC), a potent inhibitor of NF-κB activation, inhibited the NTS-induced increase of glomerular NF-κB DNA-binding activity, followed by the inhibition of mRNA expression of IL-1β, MCP-1, ICAM-1 and iNOS, which are known to be regulated by NF-κB. PDTC also prevented urinary protein excretion which is a pathophysiological parameter for glomerulonephritis. These results suggest that NF-κB activation causes the induction of pro-inflammatory factors in nephritic glomeruli, which may play significant roles in the pathogenesis of glomerulonephritis.