Protective Effect of Resveratrol against IL-1β-Induced Inflammatory Response on Human Osteoarthritic Chondrocytes Partly via the TLR4/MyD88/NF-κB Signaling Pathway: An “in Vitro Study”

Resveratrol is a natural polyphenolic compound that prevents inflammation in chondrocytes and animal models of osteoarthritis (OA) via yet to be defined mechanisms. The purpose of this study was to determine whether the protective effect of resveratrol on IL-1β-induced human articular chondrocytes was associated with the TLR4/MyD88/NF-κB signaling pathway by incubating human articular chondrocytes (harvested from osteoarthritis patients) with IL-1β before treatment with resveratrol. Cell viability was evaluated using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and TNFα levels in culture supernatants were measured by ELISA(Enzymelinked immunosorbent assay). The levels of TLR4 and its downstream signaling targets (MyD88 and TRAF6) and IL-1β were assessed by measuring the levels of mRNA and protein expression by real-time RT-PCR and western blot analysis, respectively, in addition to assessing NF-κB activation. In addition, TLR4 siRNA was used to block TLR4 expression in chondrocytes further demonstrating that resveratrol prevented IL-1β-mediated inflammation by TLR4 inhibition. We found that resveratrol prevented IL-1β-induced reduction in cell viability. Stimulation of chondrocytes with IL-1β caused a significant up-regulation of TLR4 and its downstream targets MyD88 and TRAF6 resulting in NF-κB activation associated with the synthesis of IL-1β and TNFα. These IL-1β-induced inflammatory responses were all effectively reversed by resveratrol. Furthermore, activation of NF-κB in chondrocytes treated with TLR4 siRNA was significantly attenuated, but not abolished, and exposure to resveratrol further reduced NF-κB translocation. These data suggested that resveratrol prevented IL-1β-induced inflammation in human articular chondrocytes at least in part by inhibiting the TLR4/MyD88/NF-κB signaling pathway suggesting that resveratrol has the potential to be used as a nutritional supplement to counteract OA symptoms.     

Natural Compound Resveratrol Attenuates TNF-Alpha-Induced Vascular Dysfunction in Mice and Human Endothelial Cells: The Involvement of the NF-κB Signaling Pathway

Resveratrol, a natural compound in grapes and red wine, has drawn attention due to potential cardiovascular-related health benefits. However, its effect on vascular inflammation at physiologically achievable concentrations is largely unknown. In this study, resveratrol in concentrations as low as 1 μm suppressed TNF-α-induced monocyte adhesion to human EA.hy926 endothelial cells (ECs), a key event in the initiation and development of atherosclerosis. Low concentrations of resveratrol (0.25–2 μm) also significantly attenuated TNF-α-stimulated mRNA expressions of MCP-1/CCL2 and ICAM-1, which are vital mediators of EC-monocyte adhesion molecules and cytokines for cardiovascular plaque formation. Additionally, resveratrol diminished TNF-α-induced IκB-α degradation and subsequent nuclear translocation of NF-κB p65 in ECs. In the animal study, resveratrol supplementation in diet significantly diminished TNF-α-induced increases in circulating levels of adhesion molecules and cytokines, monocyte adhesion to mouse aortic ECs, F4/80-positive macrophages and VCAM-1 expression in mice aortas and restored the disruption in aortic elastin fiber caused by TNF-α treatment. The animal study also confirmed that resveratrol blocks the activation of NF-κB In Vivo. In conclusion, resveratrol at physiologically achievable concentrations displayed protective effects against TNF-α-induced vascular endothelial inflammation in vitro and In Vivo. The ability of resveratrol in reducing inflammation may be associated with its role as a down-regulator of the NF-κB pathway.     

CK2 Down-Regulation Increases the Expression of Senescence-Associated Secretory Phenotype Factors through NF-κB Activation

Senescent cells secrete pro-inflammatory factors, and a hallmark feature of senescence is senescence-associated secretory phenotype (SASP). The aim of this study is to investigate the protein kinase CK2 (CK2) effects on SASP factors expression in cellular senescence and organism aging. Here CK2 down-regulation induced the expression of SASP factors, including interleukin (IL)-1β, IL-6, and matrix metalloproteinase (MMP) 3, through the activation of nuclear factor-κB (NF-κB) signaling in MCF-7 and HCT116 cells. CK2 down-regulation-mediated SIRT1 inactivation promoted the degradation of inhibitors of NF-κB (IκB) by activating the AKT-IκB kinase (IKK) axis and increased the acetylation of lysine 310 on RelA/p65, an important site for the activity of NF-κB. kin-10 (the ortholog of CK2β) knockdown increased zmp-1, -2, and -3 (the orthologs of MMP) expression in nematodes, but AKT inhibitor triciribine and SIRT activator resveratrol significantly abrogated the increased expression of these genes. Finally, antisense inhibitors of miR-186, miR-216b, miR-337-3p, and miR-760 suppressed CK2α down-regulation, activation of the AKT-IKK-NF-κB axis, RelA/p65 acetylation, and expression of SASP genes in cells treated with lipopolysaccharide. Therefore, this study indicated that CK2 down-regulation induces the expression of SASP factors through NF-κB activation, which is mediated by both activation of the SIRT1-AKT-IKK axis and RelA/p65 acetylation, suggesting that the mixture of the four miRNA inhibitors can be used as anti-inflammatory agents.     

NLRP3 Inflammasome Activation Is Involved in LPA1-Mediated Brain Injury after Transient Focal Cerebral Ischemia

Lysophosphatidic acid receptor 1 (LPA₁) contributes to brain injury following transient focal cerebral ischemia. However, the mechanism remains unclear. Here, we investigated whether nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome activation might be an underlying mechanism involved in the pathogenesis of brain injury associated with LPA₁ following ischemic challenge with transient middle cerebral artery occlusion (tMCAO). Suppressing LPA₁ activity by its antagonist attenuated NLRP3 upregulation in the penumbra and ischemic core regions, particularly in ionized calcium-binding adapter molecule 1 (Iba1)-expressing cells like macrophages of mouse after tMCAO challenge. It also suppressed NLRP3 inflammasome activation, such as caspase-1 activation, interleukin 1β (IL-1β) maturation, and apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) speck formation, in a post-ischemic brain. The role of LPA₁ in NLRP3 inflammasome activation was confirmed in vitro using lipopolysaccharide-primed bone marrow-derived macrophages, followed by LPA exposure. Suppressing LPA₁ activity by either pharmacological antagonism or genetic knockdown attenuated NLRP3 upregulation, caspase-1 activation, IL-1β maturation, and IL-1β secretion in these cells. Furthermore, nuclear factor-κB (NF-κB), extracellular signal-regulated kinase 1/2 (ERK1/2), and p38 were found to be LPA₁-dependent effector pathways in these cells. Collectively, results of the current study first demonstrate that LPA₁ could contribute to ischemic brain injury by activating NLRP3 inflammasome with underlying effector mechanisms.     

Corilagin Attenuates Aerosol Bleomycin-Induced Experimental Lung Injury

Idiopathic pulmonary fibrosis (IPF) is a progressing lethal disease with few clinically effective therapies. Corilagin is a tannin derivative which shows anti-inflammatory and antifibrotics properties and is potentiated in treating IPF. Here, we investigated the effect of corilagin on lung injury following bleomycin exposure in an animal model of pulmonary fibrosis. Corilagin abrogated bleomycin-induced lung fibrosis as assessed by H&E; Masson’s trichrome staining and lung hydroxyproline content in lung tissue. Corilagin reduced the number of apoptotic lung cells and prevented lung epithelial cells from membrane breakdown, effluence of lamellar bodies and thickening of the respiratory membrane. Bleomycin exposure induced expression of MDA, IKKα, phosphorylated IKKα (p-IKKα), NF-κB P65, TNF-α and IL-1β, and reduced I-κB expression in mice lung tissue or in BALF. These changes were reversed by high-dose corilagin (100 mg/kg i.p) more dramatically than by low dose (10 mg/kg i.p). Last, corilagin inhibits TGF-β1 production and α-SMA expression in lung tissue samples. Taken together, these findings confirmed that corilagin attenuates bleomycin-induced epithelial injury and fibrosis via inactivation of oxidative stress, proinflammatory cytokine release and NF-κB and TGF-β1 signaling. Corilagin may serve as a promising therapeutic agent for pulmonary fibrosis.     

14-3-3γ Regulates Lipopolysaccharide-Induced Inflammatory Responses and Lactation in Dairy Cow Mammary Epithelial Cells by Inhibiting NF-κB and MAPKs and Up-Regulating mTOR Signaling

As a protective factor for lipopolysaccharide (LPS)-induced injury, 14-3-3γ has been the subject of recent research. Nevertheless, whether 14-3-3γ can regulate lactation in dairy cow mammary epithelial cells (DCMECs) induced by LPS remains unknown. Here, the anti-inflammatory effect and lactation regulating ability of 14-3-3γ in LPS-induced DCMECs are investigated for the first time, and the molecular mechanisms responsible for their effects are explored. The results of qRT-PCR showed that 14-3-3γ overexpression significantly inhibited the mRNA expression of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β) and inducible nitric oxide synthase (iNOS). Enzyme-linked immunosorbent assay (ELISA) analysis revealed that 14-3-3γ overexpression also suppressed the production of TNF-α and IL-6 in cell culture supernatants. Meanwhile, CASY-TT Analyser System showed that 14-3-3γ overexpression clearly increased the viability and proliferation of cells. The results of kit methods and western blot analysis showed that 14-3-3γ overexpression promoted the secretion of triglycerides and lactose and the synthesis of β-casein. Furthermore, the expression of genes relevant to nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPKs) and lactation-associated proteins were assessed by western blot, and the results suggested that 14-3-3γ overexpression inactivated the NF-κB and MAPK signaling pathways by down-regulating extracellular signal regulated protein kinase (ERK), p38 mitogen-activated protein kinase (p38MAPK) and inhibitor of NF-κB (IκB) phosphorylation levels, as well as by inhibiting NF-κB translocation. Meanwhile, 14-3-3γ overexpression enhanced the expression levels of β-casein, mammalian target of rapamycin (mTOR), ribosomal protein S6 kinase 1 (S6K1), serine/threonine protein kinase Akt 1 (AKT1), sterol regulatory element binding protein 1 (SREBP1) and peroxisome proliferator-activated receptor gamma (PPARγ). These results suggest that 14-3-3γ was able to attenuate the LPS-induced inflammatory responses and promote proliferation and lactation in LPS-induced DCMECs by inhibiting the activation of the NF-κB and MAPK signaling pathways and up-regulating mTOR signaling pathways to protect against LPS-induced injury.     

Benzyl Isothiocyanate Attenuates Inflammasome Activation in Pseudomonas aeruginosa LPS-Stimulated THP-1 Cells and Exerts Regulation through the MAPKs/NF-κB Pathway

Inflammasomes are a group of intracellular multiprotein platforms that play important roles in immune systems. Benzyl isothiocyanate (BITC) is a constituent of cruciferous plants and has been confirmed to exhibit various biological activities. The modulatory effects of BITC on inflammasome-mediated interleukin (IL)-1β expression and its regulatory mechanisms in Pseudomonas aeruginosa (P. aeruginosa) LPS/ATP-stimulated THP-1 cells was investigated. Monocytic THP-1 cells were treated with phorbol myristate acetate (PMA) to induce differentiation into macrophages. Enzyme-linked immunosorbent assays (ELISA) were performed to measure the levels of IL-1β produced in P. aeruginosa LPS/ATP-exposed THP-1 cells. Western blotting was performed to examine the BITC modulatory mechanisms in inflammasome-mediated signaling pathways. BITC inhibited IL-1β production in P. aeruginosa LPS/ATP-induced THP-1 cells. BITC also inhibited activation of leucine-rich repeat protein-3 (NLRP3) and caspase-1 in P. aeruginosa LPS/ATP-induced THP-1 cells. Furthermore, we show that mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) activation in P. aeruginosa LPS was attenuated by BITC. These BITC-mediated modulatory effects on IL-1β production may have therapeutic potential for inflammasome-mediated disorders such as a nasal polyp.     

Hydrostatic Pressure Influences HIF-2 Alpha Expression in Chondrocytes

Hypoxia-inducible factor (HIF)-2α is considered to play a major role in the progression of osteoarthritis. Recently, it was reported that pressure amplitude influences HIF-2α expression in murine endothelial cells. We examined whether hydrostatic pressure is involved in expression of HIF-2α in articular chondrocytes. Chondrocytes were cultured and stimulated by inflammation or hydrostatic pressure of 0, 5, 10, or 50 MPa. After stimulation, heat shock protein (HSP) 70, HIF-2α, nuclear factor kappa B (NF-κB), matrix metalloproteinase (MMP)-13, MMP-3, and vascular endothelial growth factor (VEGF) gene expression were evaluated. The levels of all gene expression were increased by inflammatory stress. When chondrocytes were exposed to a hydrostatic pressure of 5 MPa, HIF-2α, MMP-13, and MMP-3 gene expression increased significantly although those of HSP70 and NF-κB were not significantly different from the control group. In contrast, HIF-2α gene expression did not increase under a hydrostatic pressure of 50 MPa although HSP70 and NF-κB expression increased significantly compared to control. We considered that hydrostatic pressure of 5 MPa could regulate HIF-2α independent of NF-κB, because the level of HIF-2α gene expression increased significantly without upregulation of NF-κB expression at 5 MPa. Hydrostatic pressure may influence cartilage degeneration, inducing MMP-13 and MMP-3 expression through HIF-2α.     

Acute Glucose Shift Induces the Activation of the NLRP3 Inflammasome in THP-1 Cells

We aimed to investigate the effect of acute glucose shift on the activation of the NLRP3 inflammasome, IL-1β secretion, and underlying signaling pathways in THP-1 cells. THP-1 cells were divided into four groups and exposed to the following glucose concentrations for 24 h: constant normal glucose (NG, 5.5 mM), constant high glucose (HG, 25 mM), normal to high glucose shift (NG-to-HG, 5.5 to 25 mM), and high to normal glucose shift (HG-to-NG, 25 to 5.5 mM). Cell viability, oxidative stress, and the levels of NLRP3 inflammasome components were assessed. Both directions of the acute glucose shift increased the activation of the NLRP3 inflammasome, generation of reactive oxygen species (ROS), and expression of phosphorylated p38 MAPK, JNK, and NF-κB compared with either constant NG or HG. Treatment with N-acetylcysteine, a pharmacological antioxidant, inhibited the acute glucose shift-induced generation of ROS, activation of NLRP3 inflammasome, and upregulation of MAPK-NF-κB. Further analysis using inhibitors of p38 MAPK, JNK, and NF-κB indicated that acute glucose shifts promoted IL-1β secretion by activating the signaling pathway in a ROS-MAPK-NF-κB-NLRP3 inflammasome in THP-1 cells. These findings suggested that acute changes in glucose concentration might cause monocyte inflammation, which is associated with diabetic complications.     

Emodin Ameliorates LPS-Induced Acute Lung Injury,Involving the Inactivation of NF-κB in Mice

Acute lung injury (ALI) and its severe manifestation of acute respiratory distress syndrome (ARDS) are well-known illnesses. Uncontrolled and self-amplified pulmonary inflammation lies at the center of the pathology of this disease. Emodin, the bio-active coxund of herb Radix rhizoma Rhei, shows potent anti-inflammatory properties through inactivation of nuclear factor-κB (NF-κB). The aim of this study was to evaluate the effect of emodin on lipopolysaccharide (LPS)-induced ALI in mice, and its potential bio-mechanism. In our study, BALB/c mice were stimulated with LPS to induce ALI. After 72 h of LPS stimulation, pulmonary pathological changes, lung injury scores, pulmonary edema, myeloperoxidase (MPO) activity, total cells, neutrophils, macrophages, TNF-α, IL-6 and IL-1β in bronchoalveolar lavage fluid (BALF), and MCP-1 and E-selectin expression were notably attenuated by emodin in mice. Meanwhile, our data also revealed that emodin significantly inhibited the LPS-enhanced the phosphorylation of NF-κB p65 and NF-κB p65 DNA binding activity in lung. Our data indicates that emodin potently inhibits LPS-induced pulmonary inflammation, pulmonary edema and MCP-1 and E-selectin expression, and that these effects were very likely mediated by inactivation of NF-κB in mice. These results suggest a therapeutic potential of emodin as an anti-inflammatory agent for ALI/ARDS treatment.     

Short Chain Fatty Acid Acetate Increases TNFα-Induced MCP-1 Production in Monocytic Cells via ACSL1/MAPK/NF-κB Axis

Short-chain fatty acid (SCFA) acetate, a byproduct of dietary fiber metabolism by gut bacteria, has multiple immunomodulatory functions. The anti-inflammatory role of acetate is well documented; however, its effect on monocyte chemoattractant protein-1 (MCP-1) production is unknown. Similarly, the comparative effect of SCFA on MCP-1 expression in monocytes and macrophages remains unclear. We investigated whether acetate modulates TNFα-mediated MCP-1/CCL2 production in monocytes/macrophages and, if so, by which mechanism(s). Monocytic cells were exposed to acetate with/without TNFα for 24 h, and MCP-1 expression was measured. Monocytes treated with acetate in combination with TNFα resulted in significantly greater MCP-1 production compared to TNFα treatment alone, indicating a synergistic effect. On the contrary, treatment with acetate in combination with TNFα suppressed MCP-1 production in macrophages. The synergistic upregulation of MCP-1 was mediated through the activation of long-chain fatty acyl-CoA synthetase 1 (ACSL1). However, the inhibition of other bioactive lipid enzymes [carnitine palmitoyltransferase I (CPT I) or serine palmitoyltransferase (SPT)] did not affect this synergy. Moreover, MCP-1 expression was significantly reduced by the inhibition of p38 MAPK, ERK1/2, and NF-κB signaling. The inhibition of ACSL1 attenuated the acetate/TNFα-mediated phosphorylation of p38 MAPK, ERK1/2, and NF-κB. Increased NF-κB/AP-1 activity, resulting from acetate/TNFα co-stimulation, was decreased by ACSL1 inhibition. In conclusion, this study demonstrates the proinflammatory effects of acetate on TNF-α-mediated MCP-1 production via the ACSL1/MAPK/NF-κB axis in monocytic cells, while a paradoxical effect was observed in THP-1-derived macrophages.     

Pantoprazole Attenuates MAPK (ERK1/2, JNK,p38)–NF-κB and Apoptosis Signaling Pathways after Renal Ischemia/Reperfusion Injury in Rats

Ischemia/reperfusion injury (IRI) in the kidney is the most common cause of acute renal dysfunction through different cell damage mechanisms. This study aimed to investigate, on molecular basics for the first time, the effect of pantoprazole on renal IRI in rats. Different biochemical parameters and oxidative stress markers were assessed. ELISA was used to estimate proinflammatory cytokines. qRT-PCR and western blot were used to investigate the gene and protein expression. Renal histopathological examination was also performed. IRI resulted in tissue damage, elevation of serum levels of creatinine, urea nitrogen, malondialdehyde, TNF-α, IL-6, IL-1β, up-regulation of NF-κB, JNK1/2, ERK1/2, p38, and cleaved caspase-3 proteins. Furthermore, it up-regulated the expression of the Bax gene and down-regulated the expression of the Bcl-2 gene. Treatment of the injured rats with pantoprazole, either single dose or multiple doses, significantly alleviated IRI-induced biochemical and histopathological changes, attenuated the levels of proinflammatory cytokines, down-regulated the expression of NF-κB, JNK1/2, ERK1/2, p38, and cleaved caspase-3 proteins, and the Bax gene, and up-regulated Bcl-2 gene expression. Moreover, treatment with pantoprazole multiple doses has an ameliorative effect that is greater than pantoprazole single-dose. In conclusion, pantoprazole diminished renal IRI via suppression of apoptosis, attenuation of the pro-inflammatory cytokines’ levels, and inhibition of the intracellular signaling pathway MAPK (ERK1/2, JNK, p38)–NF-κB.     

Human Caspase 12 Enhances NF-κB Activity through Activation of IKK in Nasopharyngeal Carcinoma Cells

Human nasopharyngeal carcinoma (NPC) is a highly invasive cancer associated with proinflammation. Caspase-12 (Casp12), an inflammatory caspase, is implicated in the regulation of NF-κB-mediated cellular invasion via the modulation of the IκBα protein in NPC cells. However, the effect mechanisms of Casp12 need to be elucidated. NPC cells were transfected with the full length of human Casp12 cDNA (pC12) and the effect of human Casp12 (hCasp12) on the NF-κB activity was investigated. We found ectopic expression of hCasp12 increased the NF-κB activity accompanied by an increased p-IκBα expression and a decreased IκBα expression. Treatment of BMS, a specific IKK inhibitor, and pC12-transfected cells markedly decreased the NF-κB activity and ameliorated the expression level of IκBα reduced by hCasp12. Co-immunoprecipitation assays validated the physical interaction of hCasp12 with IKKα/β, but not with NEMO. Furthermore, the NF-κB activity of ΔCasp12-Q (a mutated catalytic of hCasp12) transfected cells was concentration-dependently induced, but lower than that of hCasp12-transfected cells. Importantly, the hCasp12-mediated NF-kB activity was enhanced by TNFα stimulation. That indicated a role of the catalytic motif of hCasp12 in the regulation of the NF-κB activity. This study indicated hCasp12 activated the NF-κB pathway through the activation of IKK in human NPC cells.     

NLRP2 Is Overexpressed in Spinal Astrocytes at the Peak of Mechanical Pain Sensitivity during Complete Freund Adjuvant-Induced Persistent Pain

Our earlier findings revealed that interleukin-1 receptor type-1 (IL-1R1) was overexpressed in spinal neurons, and IL-1R1-deficient mice showed significant attenuation of thermal and mechanical allodynia during the course of the Complete Freund adjuvant (CFA)-induced persistent pain model. In the present study, we found that a ligand of IL-1R1, termed interleukin-1β (IL-1β), is also significantly overexpressed at the peak of mechanical pain sensitivity in the CFA-evoked pain model. Analysis of cellular distribution and modeling using IMARIS software showed that in the lumbar spinal dorsal horn, IL-1β is significantly elevated by astrocytic expression. Maturation of IL-1β to its active form is facilitated by the formation of the multiprotein complex called inflammasome; thus, we tested the expression of NOD-like receptor proteins (NLRPs) in astrocytes. At the peak of mechanical allodynia, we found expression of the NLRP2 inflammasome sensor and its significantly elevated co-localization with the GFAP astrocytic marker, while NLRP3 was moderately present and NLRP1 showed total segregation from the astrocytic profiles. Our results indicate that peripheral CFA injection induces NLRP2 inflammasome and IL-1β expression in spinal astrocytes. The release of mature IL-1β can contribute to the maintenance of persistent pain by acting on its neuronally expressed receptor, which can lead to altered neuronal excitability.     

ROS/TNF-α Crosstalk Triggers the Expression of IL-8 and MCP-1 in Human Monocytic THP-1 Cells via the NF-κB and ERK1/2 Mediated Signaling

IL-8/MCP-1 act as neutrophil/monocyte chemoattractants, respectively. Oxidative stress emerges as a key player in the pathophysiology of obesity. However, it remains unclear whether the TNF-α/oxidative stress interplay can trigger IL-8/MCP-1 expression and, if so, by which mechanism(s). IL-8/MCP-1 adipose expression was detected in lean, overweight, and obese individuals, 15 each, using immunohistochemistry. To detect the role of reactive oxygen species (ROS)/TNF-α synergy as a chemokine driver, THP-1 cells were stimulated with TNF-α, with/without H₂O₂ or hypoxia. Target gene expression was measured by qRT-PCR, proteins by flow cytometry/confocal microscopy, ROS by DCFH-DA assay, and signaling pathways by immunoblotting. IL-8/MCP-1 adipose expression was significantly higher in obese/overweight. Furthermore, IL-8/MCP-1 mRNA/protein was amplified in monocytic cells following stimulation with TNF-α in the presence of H₂O₂ or hypoxia (p ˂ 0.0001). Synergistic chemokine upregulation was related to the ROS levels, while pre-treatments with NAC suppressed this chemokine elevation (p ≤ 0.01). The ROS/TNF-α crosstalk involved upregulation of CHOP, ERN1, HIF1A, and NF-κB/ERK-1,2 mediated signaling. In conclusion, IL-8/MCP-1 adipose expression is elevated in obesity. Mechanistically, ROS/TNF-α crosstalk may drive expression of these chemokines in monocytic cells by inducing ER stress, HIF1A stabilization, and signaling via NF-κB/ERK-1,2. NAC had inhibitory effect on oxidative stress-driven IL-8/MCP-1 expression, which may have therapeutic significance regarding meta-inflammation.     

IL-33 Is Involved in the Anti-Inflammatory Effects of Butyrate and Propionate on TNFα-Activated Endothelial Cells

Short-chain fatty acids (e.g., butyrate and propionate) are able to diminish endothelial cell activation. The aim of this study was to investigate whether intracellular IL-33 mediates the effects of butyrate and propionate on TNFα-induced IL-8 production and vascular cell adhesion molecule-1 (VCAM-1) expression. In addition, it was investigated whether regulating NF-κB and MAPK signaling pathways are involved. Intracellular IL-33 was measured in human endothelial cells (HUVECs) pre-incubated for 24 h with butyrate (0.1 mM or 5 mM), propionate (0.3 mM or 10 mM), or trichostatin A (TSA, 0.5 μM) prior to TNFα (1 ng/mL) stimulation (24 h). The effects of butyrate, propionate, and TSA on TNFα-induced IL-8, vascular cell adhesion molecule-1 (VCAM-1), NF-κB, and MAPK signaling pathways in normal HUVECs and IL-33 siRNA (siIL-33)-transfected HUVECs were compared to study the role of IL-33 in the protective effects of butyrate and propionate. Endogenous IL-33 was highly expressed in the perinuclear in HUVECs, which was significantly reduced by TNFα stimulation. The TNFα-induced reduction in IL-33 was prevented by pre-incubation with butyrate or propionate. Butyrate (0.1 mM), propionate (0.3 mM), and TSA inhibited the IL-8 production and activation of NF-κB. Interestingly, this effect was not observed in siIL-33-transfected HUVECs. The effects of butyrate (5 mM), propionate (10 mM), and TSA (0.5 μM) on VCAM-1 expression and activation of MAPK signaling pathways were not affected by siIL-33 transfection. In conclusion, we showed that the inhibitory effects of butyrate and propionate on TNFα-induced IL-8 production were mediated by the HDACs/IL-33/NF-κB pathway, while their effects on VCAM-1 expression might be associated with the HDACs/MAPK signaling pathway, independently of IL-33.