The p38 MAPK pathway mediates both antiinflammatory and proinflammatory processes: comment on the article by Damjanov and the editorial by Genovese

Hepatoprotective effect of prenatal celecoxib in weaning preeclamptic rats: Role of HMGB1/MAPKs signaling

Preeclampsia (PE) is often associated with multiple organ damage that remains noticeable postnatally. Here, we tested the hypotheses that antenatal therapy with nonsteroidal antiinflammatory drugs (NSAIDs) refashions liver damage induced by PE in weaning rats and that the high mobility group box 1 (HMGB1) signaling modulates this interaction. PE was induced by pharmacologic nitric oxide deprivation during the last week of gestation (Nω-nitro-L-arginine methyl ester, L-NAME, 50 mg/kg/day, oral gavage). Compared with control rats, weaning PE rats revealed substantial rises in serum transaminases together with histopathological signs of hepatic cytoplasmic changes, portal inflammation, and central vein dilation. While gestational NSAIDs reversed the elevated transaminases, they had no effects (celecoxib, naproxen) or even worsened (diclofenac) the structural damage. Molecularly, celecoxib was the most effective NSAID in (i) reversing PE-evoked upregulation of hepatic HMGB1 gene expression and concomitant increments and decrements in mitogen-activated protein kinases MAPKERK and MAPKp38 expression, respectively, and (ii) elevating and suppressing serum interleukin-10 and tumor necrosis factor-α, respectively. Alternatively, rises in serum interleukin-1β and shifts in macrophage polarization towards an inflammatory phenotype caused by PE were comparably diminished by all NSAIDs. The data disclose an advantageous therapeutic potential for gestational celecoxib over diclofenac or naproxen in controlling hepatic dysfunction and HMGB1-interrelated inflammatory and oxidative sequels of PE.

The Prolyl Oligopeptidase Inhibitor KYP-2047 Is Cytoprotective and Anti-Inflammatory in Human Retinal Pigment Epithelial Cells with Defective Proteasomal Clearance

Increased oxidative stress, dysfunctional cellular clearance, and chronic inflammation are associated with age-related macular degeneration (AMD). Prolyl oligopeptidase (PREP) is a serine protease that has numerous cellular functions, including the regulation of oxidative stress, protein aggregation, and inflammation. PREP inhibition by KYP-2047 (4-phenylbutanoyl-L-prolyl1(S)-cyanopyrrolidine) has been associated with clearance of cellular protein aggregates and reduced oxidative stress and inflammation. Here, we studied the effects of KYP-2047 on inflammation, oxidative stress, cell viability, and autophagy in human retinal pigment epithelium (RPE) cells with reduced proteasomal clearance. MG-132-mediated proteasomal inhibition in ARPE-19 cells was used to model declined proteasomal clearance in the RPEs of AMD patients. Cell viability was assessed using LDH and MTT assays. The amounts of reactive oxygen species (ROS) were measured using 2',7'-dichlorofluorescin diacetate (H2DCFDA). ELISA was used to determine the levels of cytokines and activated mitogen-activated protein kinases. The autophagy markers p62/SQSTM1 and LC3 were measured with the western blot method. MG-132 induced LDH leakage and increased ROS production in the ARPE-19 cells, and KYP-2047 reduced MG-132-induced LDH leakage. Production of the proinflammatory cytokine IL-6 was concurrently alleviated by KYP-2047 when compared with cells treated only with MG-132. KYP-2047 had no effect on autophagy in the RPE cells, but the phosphorylation levels of p38 and ERK1/2 were elevated upon KYP-2047 exposure, and the inhibition of p38 prevented the anti-inflammatory actions of KYP-2047. KYP-2047 showed cytoprotective and anti-inflammatory effects on RPE cells suffering from MG-132-induced proteasomal inhibition.

Isoflavones daidzin and daidzein inhibit lipopolysaccharide-induced inflammation in RAW264.7 macrophages

Background

Inflammation contributes to various diseases and soybeans and legumes are shown to reduce inflammation. However, the bioactive ingredients involved and mechanisms are not completely known. We hypothesized that soy isoflavones daidzin and daidzein exhibit anti-inflammatory effect in lipopolysaccharides (LPS)-stimulated RAW264.7 macrophage cell model and that activation mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) signaling pathways may mediate the effect.

Methods

Cell viability and nitric oxide (NO) level were determined by 3-(4,5)-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Griess reagent respectively. ELISA kits and Western blotting respectively assessed the generations of pro-inflammatory cytokines and protein expressions of signaling molecules. p65 nuclear translocation was determined by immunofluorescence assay.

Results

The in vitro results showed that both isoflavones did not affect cell viability at the concentrations being tested and significantly reduced levels of NO, pro-inflammatory cytokines such as interleukin (IL)-6 and tumor necrosis factor-α (TNF-α), and inflammatory indicators such as cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in RAW264.7 cells. Daidzin and daidzein partially suppressed MAPK signaling pathways, reducing the phosphorylation of p38 and ERK; whilst phosphorylation of JNK was mildly but not significantly decreased. For the involvement of NF-κB signaling pathways, daidzin only reduced the phosphorylation of p65 whereas daidzein effectively inhibited the phosphorylation of IKKα/β, IκBα and p65. Daidzin and daidzein inhibited p65 nuclear translocation, comparable with dexamethasone (positive control).

Conclusion

This study supports the anti-inflammatory effects of isoflavones daidzin and daidzein, which were at least partially mediated through inactivation of MAPK and/or NF-κB signaling pathways in macrophages.

PIWIL1 governs the crosstalk of cancer cell metabolism and immunosuppressive microenvironment in hepatocellular carcinoma

Altered energy metabolism of cancer cells shapes the immune cell response in the tumor microenvironment that facilitates tumor progression. Herein, we reported the novel of tumor cell-expressed Piwi Like RNA-Mediated Gene Silencing 1 (PIWIL1) in mediating the crosstalk of fatty acid metabolism and immune response of human hepatocellular carcinoma (HCC). PIWIL1 expression in HCC was increased compared to normal hepatic tissues and was positively correlated with the proliferation rate of HCC cell lines. PIWIL1 overexpression accelerated in vitro proliferation and in vivo growth of HCC tumors, while PIWIL1 knockdown showed opposite effects. PIWIL1 increased oxygen consumption and energy production via fatty acid metabolism without altering aerobic glycolysis. Inhibition of fatty acid metabolism abolished PIWIL1-induced HCC proliferation and growth. RNA-seq analysis revealed that immune system regulation might be involved, which was echoed by the experimental observation that PIWIL1-overexpressing HCC cells attracted myeloid-derived suppressor cells (MDSCs) into the tumor microenvironment. MDSCs depletion reduced the proliferation and growth of PIWIL1-overexpressing HCC tumors. Complement C3, whose secretion was induced by PIWIL1 in HCC cells, mediates the interaction of HCC cells with MDSCs by activated p38 MAPK signaling in MDSCs, which in turn initiated expression of immunosuppressive cytokine IL10. Neutralizing IL10 secretion reduced the immunosuppressive activity of MDSCs in the microenvironment of PIWIL1-overexpressing HCC. Taken together, our study unraveled the critical role of PIWIL1 in initiating the interaction of cancer cell metabolism and immune cell response in HCC. Tumor cells-expressed PIWIL1 may be a potential target for the development of novel HCC treatment.

Toll-Like Receptor 7 Mediates Inflammation Resolution and Inhibition of Angiogenesis in Non-Small Cell Lung Cancer

Simple Summary

The progression of cancer is strictly linked to the formation of new blood vessels responsible for nutrition supply of the tumor. We identified TLR7 as an inhibitor of lung cancer vascularization. TLR7 is part of a large family of immune receptors that function as “sensors” of pathogen- and damage-derived signals. We found that TLR7 exerts antitumor functions in non-small cell lung cancer by inducing the production of specific molecules with inhibitory properties against new blood vessel formation. These molecules are known as specialized pro-resolving mediators (SPMs) and are derived from ω-3 and ω-6 fatty acids. We believe that the results obtained suggest novel potential targets and strategies to treat lung cancer.

Abstract

Pattern recognition receptors (PRR) promote inflammation but also its resolution. We demonstrated that a specific PRR—formyl peptide receptor 1 (FPR1)—sustains an inflammation resolution response with anti-angiogenic and antitumor potential in gastric cancer. Since toll-like receptor 7 (TLR7) is crucial in the physiologic resolution of airway inflammation, we asked whether it could be responsible for pro-resolving and anti-angiogenic responses in non-small cell lung cancer (NSCLC). TLR7 correlated directly with pro-resolving and inversely with angiogenic mediators in NSCLC patients, as revealed by a publicly available RNAseq analysis. In NSCLC cells, depletion of TLR7 caused an upregulation of angiogenic mediators and a stronger vasculogenic response of endothelial cells compared to controls, assessed by qPCR, ELISA, protein array, and endothelial cell responses. TLR7 activation induced the opposite effects. TLR7 silencing reduced, while its activation increased, the pro-resolving potential of NSCLC cells, evaluated by qPCR, flow cytometry, and EIA. The increased angiogenic potential of TLR7-silenced NSCLC cells is due to the lack of pro-resolving mediators. MAPK and STAT3 signaling are responsible for these activities, as demonstrated through Western blotting and inhibitors. Our data indicate that TLR7 sustains a pro-resolving signaling in lung cancer that inhibits angiogenesis. This opens new possibilities to be exploited for cancer treatment.

Biochanin A impedes STAT3 activation by upregulating p38δ MAPK phosphorylation in IL-6-stimulated macrophages

OBJECTIVE

IL-6-induced STAT3 activation is associated with various chronic inflammatory diseases. In this study, we investigated the anti-STAT3 mechanism of the dietary polyphenol, biochanin A (BCA), in IL-6-treated macrophages.

METHODS

The effect of BCA on STAT3 and p38 MAPK was analyzed by immunoblot. The localization of both these transcription factors was determined by immunofluorescence and fractionation studies. The impact on DNA-binding activity of STAT3 was studied by luciferase assay. To understand which of the isoforms of p38 MAPK was responsible for BCA-mediated regulation of STAT3, overexpression of the proteins, site-directed mutagenesis, pull-down assays and computational analysis were performed. Finally, adhesion-migration assays and semi-quantitative PCR were employed to understand the biological effects of BCA-mediated regulation of STAT3.

RESULTS

BCA prevented STAT3 phosphorylation (Tyr⁷⁰⁵) and increased p38 MAPK phosphorylation (Thr¹⁸⁰/Tyr¹⁸²) in IL-6-stimulated differentiated macrophages. This opposing modulatory effect of BCA was not observed in cells treated with other stress-inducing stimuli that activate p38 MAPK. BCA abrogated IL-6-induced nuclear translocation of phospho-STAT3 and its transcriptional activity, while increasing the cellular abundance of phospho-p38 MAPK. BCA-induced phosphorylation of p38δ, but not α, β, or γ was responsible for impeding IL-6-induced STAT3 phosphorylation. Interestingly, interaction with phospho-p38δ masked the Tyr⁷⁰⁵ residue of STAT3, preventing its phosphorylation. BCA significantly reduced STAT3-dependent expression of icam-1 and mcp-1 diminishing IL-6-mediated monocyte adhesion and migration.

CONCLUSION

This differential regulation of STAT3 and p38 MAPK in macrophages establishes a novel anti-inflammatory mechanism of BCA which could be important for the prevention of IL-6-associated chronic inflammatory diseases.

Bromosulfophthalein suppresses inflammatory effects in lipopolysaccharide-stimulated RAW264.7 macrophages

OBJECTIVE

It has been reported that glutathione (GSH), the most abundant cellular antioxidant, can inhibit production of pro-inflammatory cytokines by activated macrophages. Bromosulfophthalein (BSP) has been recognized as an inhibitor of the efflux of reduced GSH from cells, leading to an increase in the intracellular GSH level. In this study, we evaluated, for the first time, whether BSP possessed anti-inflammatory effects in lipopolysaccharide (LPS)-stimulated macrophages.

MATERIALS AND METHODS

RAW 264.7 cells were treated with BSP and the levels of proinflammatory cytokines, GSH, and nitrite were assessed. Gene expression of inducible nitric oxide synthase (iNOS), tumor necrosis factor alpha (TNF α), interleukin-1beta (IL-1β), and interleukin-6 (IL-6) was analyzed via quantitative RT-PCR. We also examined various inflammatory signaling pathways including Akt/forkhead box protein O1 (FoxO1)/toll-like receptor 4 (TLR4), mitogen-activated protein kinases (MAPKs), and Fas protein by Western blot and flow cytometry analysis.

RESULTS

Our study demonstrated that BSP induced an increase in intracellular GSH level in LPS-stimulated macrophages. BSP inhibited production of nitric oxide and proinflammatory cytokines. BSP increased phosphorylation of Akt and nuclear exclusion of FoxO1 and suppressed TLR4 expression. Additionally, BSP decreased MAPKs activation and Fas expression.

DISCUSSION AND CONCLUSION

Taken together, these data suggest that BSP can attenuate inflammation through multiple signaling pathways. These findings highlight the potential of BSP as a new anti-inflammatory agent.

Tropisetron ameliorates cyclophosphamide-induced hemorrhagic cystitis in rats

Hemorrhagic cystitis is one of the most important complications of cyclophosphamide, a drug widely used in cancer chemotherapy and bone marrow transplantation. 5-HT₃ antagonists are anti-emetic agents and have been shown to have notable anti-inflammatory and antioxidant properties. This study was designed to investigate the possible protective effects of tropisetron against cyclophosphamide-induced hemorrhagic cystitis in rats. Hemorrhagic cystitis was induced in female rats by cyclophosphamide (270 mg/kg). Tropisetron (2.5, 5 and 7.5 mg/kg), granisetron (2.5 and 5 mg/kg), and ondansetron (5 mg/kg) were injected 15 min before, 4 and 8 h after cyclophosphamide. To evaluate the role of alpha7 nicotinic acetylcholine receptor (α7nAChR), its antagonist, methyllycaconitine (5 mg/kg) was administered 30 min before tropisetron. After 24 h, animals were killed under anesthesia. Macroscopic and histological changes were evaluated. Malondialdehyde (MDA), glutathione (GSH) and Evans blue were measured spectrophotometrically. Furthermore, the protein levels of p38 mitogen-activated protein kinases (P38 MAPK), p-P38, signal transducer and activator of transcription 3 (STAT3), p-STAT3 and Poly (ADP-ribose) polymerase (PARP) were determined using Western blot. Cyclophosphamide administration significantly induced histopathological damages and increased MDA, p-p38/p38, p-STAT3/STAT3, and PARP levels compared with the saline group. Tropisetron treatment diminished histopathological injuries as well as MDA level, and STAT3 activity compared to cyclophosphamide treated rats. Co-administration of methyllycaconitine with tropisetron, partially or completely reversed the protective effects of tropisetron. Our results showed that prophylactic administration of tropisetron markedly ameliorated the cyclophosphamide-induced bladder hemorrhage and inflammation in rats. These effects of tropisetron were α7nAChR dependent.

Oxymatrine exhibits anti-neuroinflammatory effects on Aβ1-42-induced primary microglia cells by inhibiting NF-κB and MAPK signaling pathways

Oxymatrine (OMT), isolated from Sophora flavescens or Sophora alopecuroides, possesses various pharmacological and biological activities, including anti-inflammatory, anti-oxidant, and anti-diabetic properties. Microglia cells, the resident immune cells in the central nervous system (CNS), play a key role in neurodegenerative diseases. In this study, the neuroinflammatory effects of OMT and its mechanisms were investigated by Aβ_1-42-induced rat brain tissue model and primary microglia cells model. The hematoxylin-eosin (HE) staining and immunohistochemistry results showed that OMT could reduce neuronal damage and inhibit microglia activation in the model tissue. The in vitro experiments revealed that OMT could decrease the levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and nitric oxide (NO), and down-regulate the expression of iNOS and COX-2 in a dose-dependent manner. Furthermore, OMT inhibited phosphorylation of JNK, ERK 1/2, P-p38 and NF-κB in Aβ_1-42-induced microglia cells. In summary, OMT exhibits anti-neuroinflammatory effects and the anti-inflammatory activity of OMT is related to the regulation of MAPK and NF-κB signaling pathways.

Crocin attenuates cigarette smoke-induced lung injury and cardiac dysfunction by anti-oxidative effects: the role of Nrf2 antioxidant system in preventing oxidative stress

BACKGROUND

Chronic obstructive pulmonary disease (COPD) has been emerging as a great health problem in world. Cigarette smoke is known to cause oxidative stress and deplete glutathione (GSH) levels. Nuclear erythroid-related factor 2 (Nrf2) is involved in transcriptional regulation of glutamate-cysteine ligase catalytic subunit (GCLc). Antioxidant compounds may be of therapeutic value in monitoring disease progression. Crocin demonstrates antioxidant and anti-inflammatory functions. The aim of this study was to investigate the protective role of crocin against CSE-mediated oxidative stress, inflammatory process, Nrf2 modifications and impairment of cardiac function in rats with COPD.

METHODS

Eighty rats were divided into four groups: Control, Cigarette smoke exposure (CSE), Crocin, Crocin+CS. Each group was divided into the two parts: 1) to evaluate lung inflammatory and oxidative process, 2) to evaluate the effect of Cigarette smoke induced-lung injuries on cardiac electrocardiogram (such as heart rate and QRS complex) and hemodynamic parameters (such as perfusion pressure and left ventricular developed pressure).

RESULTS

CSE rats showed a significant increase in cotinine concentration (17.24 ng/ml), and inflammatory parameters and a decrease in PO2 (75.87 mmHg) and expression of PKC (0.86 fold), PI3K (0.79 fold), MAPK (0.87 fold), Nrf2 (0.8 fold) and GCLc (0.75 fold) genes, antioxidant activity, and finally cardiac abnormalities in electrocardiogram and hemodynamic parameters. Co-treatment whit crocin could restore all these values to normal levels.

CONCLUSIONS

CS induced-COPD in rat model provides evidence that chronic CS exposure leads to lung injury and mediated cardiac dysfunction. Crocin co-treatment by modulating of Nrf2 pathway protected lung injury caused by COPD and its related cardiac dysfunction. In this study, we showed the importance of Nrf2 activators as a therapeutic target for the development of novel therapy for lung oxidative injuries.

Anti-inflammatory roles of p38α MAPK in macrophages are context dependent and require IL-10

The p38 MAPK pathway was originally identified as a master regulator of proinflammatory cytokine production by myeloid cells. Numerous drugs targeting this kinase showed promise in preclinical models of inflammatory disease, but so far, none have shown efficacy in clinical trials. The reasons behind this are unclear, but may, in part, be explained by emerging anti-inflammatory functions of this kinase or overly refined selectivity of second-generation pharmacologic inhibitors. Here, we show that p38α signaling in macrophages plays pro- and anti-inflammatory functions in vivo and in vitro, with the outcome depending on the stimulus, output, kinetics, or mode of kinase inhibition (genetic vs. pharmacologic). Different pharmacologic inhibitors of p38 exhibit opposing effects, with second-generation inhibitors acting more specifically but inhibiting anti-inflammatory functions. Functionally, we show that the anti-inflammatory functions of p38α in macrophages are critically dependent on production of IL-10. Accordingly, in the absence of IL-10, inhibition of p38α signaling in macrophages is protective in a spontaneous model of colitis. Taken together, our results shed light on the limited clinical efficacy of drugs targeting p38 and suggest that their therapeutic efficacy can be significantly enhanced by simultaneous modulation of p38-dependent anti-inflammatory mediators, such as IL-10.

Hydroxychloroquine in the primary thrombosis prophylaxis of antiphospholipid antibody positive patients without systemic autoimmune disease

Objective The objective of this study was to determine the efficacy of hydroxychloroquine (HCQ) in the primary thrombosis prevention of antiphospholipid antibody (aPL)-positive patients with no other systemic autoimmune diseases. Methods Under the auspices of Antiphospholipid Syndrome Alliance for Clinical Trials and International Networking, a multicenter, international, randomized controlled trial (RCT) was initiated, in which persistently aPL-positive but thrombosis-free patients without systemic autoimmune diseases were randomized to receive HCQ or no treatment in addition to their standard regimen. The primary objective was the efficacy of HCQ in preventing the first thrombosis. The secondary objectives were the thrombosis incidence rate, and the effects of HCQ on aPL profile and mortality rate. Patients were risk-stratified based on antiplatelet agent use. The goal was to follow patients every 6 months for 5 years. Results We recruited 20 persistently aPL-positive patients (female: 19, mean age: 46.6 ± 9.9 years, and baseline antiplatelet medication: 14); 9/20 were randomized to HCQ. During the mean follow-up of 1.7 years, no patients developed thrombosis or a serious adverse event. The study was terminated early due to the low recruitment rate, exacerbated by the prolonged manufacturing shortage and significant price increase of HCQ in the United States. Conclusion Given that a small number of patients with a relatively short follow-up were enrolled in our RCT, and no patients developed thrombosis, we cannot accurately assess the effectiveness of HCQ for primary thrombosis prevention in persistently aPL-positive patients with no other systemic autoimmune diseases. Our experience suggests that conducting an international RCT, especially without pharmaceutical support, is an extremely challenging undertaking.

Protective effects of tropisetron on cerulein-induced acute pancreatitis in mice

Acute pancreatitis (AP) causes morbidity and mortality. The aim of the present study was to investigate the protective effect of tropisetron against AP induced by cerulein. Cerulein (50μg/kg, 5 doses) was used to induce AP in mice. Six hours after final cerulein injection, animals were decapitated. Hepatic/pancreatic enzymes in the serum, pancreatic content of malondialdehyde (MDA), pro-inflammatory cytokines and myeloperoxidase (MPO) activity were measured. Tropisetron significantly attenuated pancreatic injury markers and decreased the amount of elevated serum amylase, lipase, alanine aminotransferase (ALT), aspartate aminotransferase (AST), MPO activities and pro-inflammatory cytokines levels caused by AP in mice. Tropisetron didn't affect the pancreatic levels of MDA. Our results suggest that tropisetron could attenuate cerulein-induced AP by combating inflammatory signaling. Further clinical studies are needed to confirm its efficacy in patients with AP.

Cytokine-Regulation of Na+-K+-Cl- Cotransporter 1 and Cystic Fibrosis Transmembrane Conductance Regulator-Potential Role in Pulmonary Inflammation and Edema Formation

Pulmonary edema, a major complication of lung injury and inflammation, is defined as accumulation of extravascular fluid in the lungs leading to impaired diffusion of respiratory gases. Lung fluid balance across the alveolar epithelial barrier protects the distal airspace from excess fluid accumulation and is mainly regulated by active sodium transport and Cl^- absorption. Increased hydrostatic pressure as seen in cardiogenic edema or increased vascular permeability as present in inflammatory lung diseases such as the acute respiratory distress syndrome (ARDS) causes a reversal of transepithelial fluid transport resulting in the formation of pulmonary edema. The basolateral expressed Na⁺-K⁺-2Cl^- cotransporter 1 (NKCC1) and the apical Cl^- channel cystic fibrosis transmembrane conductance regulator (CFTR) are considered to be critically involved in the pathogenesis of pulmonary edema and have also been implicated in the inflammatory response in ARDS. Expression and function of both NKCC1 and CFTR can be modulated by released cytokines; however, the relevance of this modulation in the context of ARDS and pulmonary edema is so far unclear. Here, we review the existing literature on the regulation of NKCC1 and CFTR by cytokines, and-based on the known involvement of NKCC1 and CFTR in lung edema and inflammation-speculate on the role of cytokine-dependent NKCC1/CFTR regulation for the pathogenesis and potential treatment of pulmonary inflammation and edema formation.

Treatment of inflammatory arthritis via targeting of tristetraprolin, a master regulator of pro-inflammatory gene expression

OBJECTIVES

Tristetraprolin (TTP), a negative regulator of many pro-inflammatory genes, is strongly expressed in rheumatoid synovial cells. The mitogen-activated protein kinase (MAPK) p38 pathway mediates the inactivation of TTP via phosphorylation of two serine residues. We wished to test the hypothesis that these phosphorylations contribute to the development of inflammatory arthritis, and that, conversely, joint inflammation may be inhibited by promoting the dephosphorylation and activation of TTP.

METHODS

The expression of TTP and its relationship with MAPK p38 activity were examined in non-inflamed and rheumatoid arthritis (RA) synovial tissue. Experimental arthritis was induced in a genetically modified mouse strain, in which endogenous TTP cannot be phosphorylated and inactivated. In vitro and in vivo experiments were performed to test anti-inflammatory effects of compounds that activate the protein phosphatase 2A (PP2A) and promote dephosphorylation of TTP.

RESULTS

TTP expression was significantly higher in RA than non-inflamed synovium, detected in macrophages, vascular endothelial cells and some fibroblasts and co-localised with MAPK p38 activation. Substitution of TTP phosphorylation sites conferred dramatic protection against inflammatory arthritis in mice. Two distinct PP2A agonists also reduced inflammation and prevented bone erosion. In vitro anti-inflammatory effects of PP2A agonism were mediated by TTP activation.

CONCLUSIONS

The phosphorylation state of TTP is a critical determinant of inflammatory responses, and a tractable target for novel anti-inflammatory treatments.

Cleome rutidosperma and Euphorbia thymifolia Suppress Inflammatory Response via Upregulation of Phase II Enzymes and Modulation of NF-κB and JNK Activation in LPS-Stimulated BV2 Microglia

Cleome rutidosperma DC. and Euphorbia thymifolia L. are herbal medicines used in traditional Indian and Chinese medicine to treat various illnesses. Reports document that they have antioxidant and anti-inflammatory activities; nonetheless, the molecular mechanisms involved in their anti-inflammatory actions have not yet been elucidated. The anti-neuroinflammatory activities and underlying mechanisms of ethanol extracts of Cleome rutidosperma (CR) and Euphorbia thymifolia (ET) were studied using lipopolysaccharide (LPS)-stimulated microglial cell line BV2. The morphology changes and production of pro-inflammatory mediators were assayed. Gene expression of inflammatory genes such as inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, interleukin (IL)-1β, and CC chemokine ligand (CCL)-2, as well as phase II enzymes such as heme oxygenase (HO)-1, the modifier subunit of glutamate cysteine ligase (GCLM) and NAD(P)H quinone dehydrogenase 1 (NQO1), were further investigated using reverse transcription quantitative-PCR (RT-Q-PCR) and Western blotting. The effects of CR and ET on mitogen activated protein kinases (MAPKs) and nuclear factor (NF)-κB signaling pathways were examined using Western blotting and specific inhibitors. CR and ET suppressed BV2 activation, down-regulated iNOS and COX-2 expression and inhibited nitric oxide (NO) overproduction without affecting cell viability. They reduced LPS-mediated tumor necrosis factor (TNF) and IL-6 production, attenuated IL-1β and CCL2 expression, but upregulated HO-1, GCLM and NQO1 expression. They also inhibited p65 NF-κB phosphorylation and modulated Jun-N terminal kinase (JNK) activation in BV2 cells. SP600125, the JNK inhibitor, significantly augmented the anti-IL-6 activity of ET. NF-κB inhibitor, Bay 11-7082, enhanced the anti-IL-6 effects of both CR and ET. Znpp, a competitive inhibitor of HO-1, attenuated the anti-NO effects of CR and ET. Our results show that CR and ET exhibit anti-neuroinflammatory activities by inhibiting pro-inflammatory mediator expression and production, upregulating HO-1, GCLM and NQO1, blocking NF-κB and modulating JNK signaling pathways. They may offer therapeutic potential for suppressing overactivated microglia and alleviating neurodegeneration.

Cry1Ac toxin induces macrophage activation via ERK1/2, JNK and p38 mitogen-activated protein kinases

The Cry1Ac toxin from Bacillus thuringiensis is used commercially as a bio-insecticide and is expressed in transgenic plants that are used for human and animal consumption. Although it was originally considered innocuous for mammals, the Cry1Ac toxin is not inert and has the ability to induce mucosal and systemic immunogenicity. Herein, we examined whether the Cry1Ac toxin promotes macrophage activation and explored the signalling pathways that may mediate this effect. Treatment of primary and RAW264.7 macrophages with the Cry1Ac toxin resulted in upregulation of the costimulatory molecules CD80, CD86 and ICOS-L and enhanced production of nitric oxide, the chemokine MCP-1 and the proinflammatory cytokines TNF-α and IL-6. Remarkably, the Cry1Ac toxin induced phosphorylation of the mitogen-activated protein kinases (MAPKs) ERK1/2, JNK and p38 and promoted nuclear translocation of nuclear factor-kappa B (NF-κB) p50 and p65. p38 and ERK1/2 MAPKs were involved in this effect, as indicated by the Cry1Ac-induced upregulation of CD80 and IL-6 and TNF-α abrogation by the p38 MAPK inhibitor SB203580. Furthermore, treatment the MEK1/2 kinase inhibitor PD98059 blocked increases in MCP-1 secretion and augmented Cry1Ac-induced ICOS-L upregulation. These data demonstrate the capacity of the Cry1Ac toxin to induce macrophage activation via the MAPK and NF-κB pathways.

Role of mitogen- and stress-activated kinases in inflammatory arthritis

Lysophosphatidic acid (LPA) is a pleiotropic lipid mediator that promotes motility, survival, and the synthesis of chemokines/cytokines in human fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis. LPA activates several proteins within the mitogen activated protein (MAP) kinase signaling network, including extracellular signal-regulated kinases (ERK) 1/2 and p38 MAP kinase (MAPK). Upon docking to mitogen- and stress-activated kinases (MSKs), ERK1/2 and p38 MAPK phosphorylate serine and threonine residues within its C-terminal domain and cause autophosphorylation of MSKs. Activated MSKs can then directly phosphorylate cAMP response element-binding protein (CREB) at Ser133 in FLS. Phosphorylation of CREB by MSKs is essential for the production of pro-inflammatory and anti-inflammatory cytokines. However, other downstream effectors of MSK1/2 such as nuclear factor-kappa B, histone H3, and high mobility group nucleosome binding domain 1 may also regulate gene expression in immune cells involved in disease pathogenesis. MSKs are master regulators of cell function that integrate signals induced by growth factors, pro-inflammatory cytokines, and cellular stresses, as well as those induced by LPA.

Negative Feed-forward Control of Tumor Necrosis Factor (TNF) by Tristetraprolin (ZFP36) Is Limited by the Mitogen-activated Protein Kinase Phosphatase, Dual-specificity Phosphatase 1 (DUSP1): IMPLICATIONS FOR REGULATION BY GLUCOCORTICOIDS

TNF is central to inflammation and may play a role in the pathogenesis of asthma. The 3'-untranslated region of the TNF transcript contains AU-rich elements (AREs) that are targeted by the RNA-binding protein, tristetraprolin (also known as zinc finger protein 36 (ZFP36)), which is itself up-regulated by inflammatory stimuli, to promote mRNA degradation. Using primary human bronchial epithelial and pulmonary epithelial A549 cells, we confirm that interleukin-1β (IL1B) induces expression of dual-specificity phosphatase 1 (DUSP1), ZFP36, and TNF. Whereas IL1B-induced DUSP1 is involved in feedback control of MAPK pathways, ZFP36 exerts negative (incoherent) feed-forward control of TNF mRNA and protein expression. DUSP1 silencing increased IL1B-induced ZFP36 expression at 2 h and profoundly repressed TNF mRNA at 6 h. This was partly due to increased TNF mRNA degradation, an effect that was reduced by ZFP36 silencing. This confirms a regulatory network, whereby DUSP1-dependent negative feedback control reduces feed-forward control by ZFP36. Conversely, whereas DUSP1 overexpression and inhibition of MAPKs prevented IL1B-induced expression of ZFP36, this was associated with increased TNF mRNA expression at 6 h, an effect that was predominantly due to elevated transcription. This points to MAPK-dependent feed-forward control of TNF involving ZFP36-dependent and -independent mechanisms. In terms of repression by dexamethasone, neither silencing of DUSP1, silencing of ZFP36, nor silencing of both together prevented the repression of IL1B-induced TNF expression, thereby demonstrating the need for further repressive mechanisms by anti-inflammatory glucocorticoids. In summary, these data illustrate why understanding the competing effects of feedback and feed-forward control is relevant to the development of novel anti-inflammatory therapies.

Camptothecin promotes the production of nitric oxide that triggers subsequent S-nitrosoproteome-mediated signaling cascades in endothelial cells

Camptothecin (CPT) has been used for colorectal cancer therapy. At low concentration of 10^-9M, CPT modulates endothelial nitric oxide production following the phosphorylation of LKB1 Ser431, AMPK-α Thr172, eNOS Ser633 and Ser1177. Elevated nitric oxide (NO) was observed by FA-OMe fluorescent probe. 726 S-nitrosoproteins were identified by iTRAQ quantitative proteomics. IPA analysis indicated that ERK/MAPK was closely linked in the signaling network. Further studies showed that CPT phosphorylated p38 MAPK Thr180/Tyr182 and dephosphorylated Tau Ser199/202. CPT also suppressed the TNF-α-induced expression of the inflammasome and cyclooxygenase 2. All this suggests that in addition to the original character of CPT in attenuating the binding of topoisomerase I and DNA in cancer cells, the role of CPT in triggering NO production and the subsequent S-nitrosylated signaling including anti-inflammatory effects in endothelial cells are proposed here. CPT, therefore, provides a potential application addition in preventing vascular disorders.

Dual-Specificity Phosphatase 1 and Tristetraprolin Cooperate To Regulate Macrophage Responses to Lipopolysaccharide

Dual-specificity phosphatase (DUSP) 1 dephosphorylates and inactivates members of the MAPK superfamily, in particular, JNKs, p38α, and p38β MAPKs. It functions as an essential negative regulator of innate immune responses, hence disruption of the Dusp1 gene renders mice extremely sensitive to a wide variety of experimental inflammatory challenges. The principal mechanisms behind the overexpression of inflammatory mediators by Dusp1(-/-) cells are not known. In this study, we use a genetic approach to identify an important mechanism of action of DUSP1, involving the modulation of the activity of the mRNA-destabilizing protein tristetraprolin. This mechanism is key to the control of essential early mediators of inflammation, TNF, CXCL1, and CXCL2, as well as the anti-inflammatory cytokine IL-10. The same mechanism also contributes to the regulation of a large number of transcripts induced by treatment of macrophages with LPS. These findings demonstrate that modulation of the phosphorylation status of tristetraprolin is an important physiological mechanism by which innate immune responses can be controlled.

Regulation of IL-10 by chondroitinase ABC promotes a distinct immune response following spinal cord injury

Chondroitinase ABC (ChABC) has striking effects on promoting neuronal plasticity after spinal cord injury (SCI), but little is known about its involvement in other pathological mechanisms. Recent work showed that ChABC might also modulate the immune response by promoting M2 macrophage polarization. Here we investigate in detail the immunoregulatory effects of ChABC after SCI in rats. Initially, we examined the expression profile of 16 M1/M2 macrophage polarization markers at 3 h and 7 d postinjury. ChABC treatment had a clear effect on the immune signature after SCI. More specifically, ChABC increased the expression of the anti-inflammatory cytokine IL-10, accompanied by a reduction in the proinflammatory cytokine IL-12B in injured spinal tissue. These effects were associated with a distinct, IL-10-mediated anti-inflammatory response in ChABC-treated spinal cords. Mechanistically, we show that IL-10 expression is driven by tissue injury and macrophage infiltration, while the p38 MAPK is the central regulator of IL-10 expression in vivo. These findings provide novel insights into the effects of ChABC in the injured spinal cord and explain its immunoregulatory activity.

Dual-specificity phosphatase 1-null mice exhibit spontaneous osteolytic disease and enhanced inflammatory osteolysis in experimental arthritis

OBJECTIVE

Bone formation and destruction are usually tightly linked; however, in disorders such as rheumatoid arthritis, periodontal disease, and osteoporosis, elevated osteoclast activity leads to bone destruction. Osteoclast formation and activation are controlled by many signaling pathways, including p38 MAPK. Dual-specificity phosphatase 1 (DUSP-1) is a factor involved in the negative regulation of p38 MAPK. The purpose of this study was to examine the effect of Dusp1 deficiency on bone destruction.

METHODS

Penetrance, onset, and severity of collagen-induced arthritis were recorded in DUSP-1+/+ and DUSP-1-/- mice. Bone destruction was assessed by histologic and micro-computed tomographic examination of the joints. The in vitro formation and activation of osteoclasts from DUSP-1+/+ and DUSP-1-/- precursors were assessed in the absence or presence of tumor necrosis factor (TNF).

RESULTS

The formation and activation of osteoclasts in vitro in the presence of TNF were enhanced by Dusp1 gene disruption. DUSP-1-/- mice exhibited higher penetrance, earlier onset, and increased severity of experimental arthritis, accompanied by greater numbers of osteoclasts in inflamed joints and more extensive loss of bone. A DUSP-1-/- mouse colony of mixed genetic background also demonstrated striking spontaneous osteolytic destruction of distal phalanges.

CONCLUSION

DUSP-1 is a critical regulator of osteoclast activity and limits bone destruction in an experimental model of rheumatoid arthritis. Defects in the expression or activity of DUSP1 in humans may correlate with a propensity to develop osteolytic lesions in arthritis.

The p38 MAPK Pathway in Rheumatoid Arthritis: A Sideways Look

The p38 mitogen-activated protein kinase (MAPK) signaling pathway has been strongly implicated in many of the processes that underlie the pathology of rheumatoid arthritis (RA). For many years it has been considered a promising target for development of new anti-inflammatory drugs with which to treat RA and other chronic immune-mediated inflammatory diseases. However, several recent clinical trials have concluded in a disappointing manner. Why is this so, if p38 MAPK clearly contributes to the excessive production of inflammatory mediators, the destruction of bone and cartilage? We argue that, to explain the apparent failure of p38 inhibitors in the rheumatology clinic, we need to understand better the complexities of the p38 pathway and its many levels of communication with other cellular signaling pathways. In this review we look at the p38 MAPK pathway from a slightly different perspective, emphasising its role in post-transcriptional rather than transcriptional control of gene expression, and its contribution to the off-phase rather than the on-phase of the inflammatory response.

Circulating microRNAs as candidate biomarkers in patients with systemic lupus erythematosus

Aberrant expression of microRNAs (miRNAs) has been identified in various diseases. Recent studies demonstrated that miRNAs can be detected in the circulation and serve as potential biomarkers of various diseases. Moreover, the detection of circulating miRNAs can provide important novel information concerning diseases. In this study, a miRNA profile was used to determine the aberrantly expressed circulating miRNAs in patients with systemic lupus erythematosus (SLE) compared with patients with rheumatoid arthritis (RA) and healthy controls (HCs). To further confirm the microarray data, we identified 8 miRNAs (miR-126, miR-21, miR-451, miR-223, miR-16, miR-125a-3p, miR-155, and miR-146a) by real-time quantitative PCR (qRT-PCR) in 20 healthy controls and in 55 patients, of whom 30 patients were diagnosed with SLE and 25 were diagnosed with RA. Consistent with the microarray data, miR-126 was specifically enriched only in the blood of the SLE patients, but 4 other miRNAs (miR-21, miR-451, miR-223, and miR-16) were upregulated in the patients with SLE and were also significantly increased in the patients with RA. In contrast, miR-125a-3p, miR-155, and miR-146a showed a trend toward significantly reduced levels in the patients with SLE. In addition, to further estimate the potential roles of these differentially expressed circulating miRNAs in the pathogenesis of SLE, we used a bioinformatics exploratory analysis and identified a number of significantly enriched pathways, which implied that most dysregulated circulating miRNAs might be involved in various signal transduction pathways and cell interactions, particularly the mitogen-activated protein kinase signaling pathway. Based on these findings, we postulate that aberrantly expressed plasma miRNAs could be attractive as candidates for putative biomarkers of SLE and may help elucidate the possible pathogenesis of SLE.

Mitogen-activated protein kinase-activated protein kinase 2 (MAPKAP-K2) as an antiinflammatory target: discovery and in vivo activity of selective pyrazolo[1,5-a]pyrimidine inhibitors using a focused library and structure-based optimization approach

A novel class of mitogen-activated protein kinase-activated protein kinase 2 (MAPKAP-K2) inhibitors was discovered through screening a kinase-focused library. A homology model of MAPKAP-K2 was generated and used to guide the initial SAR studies and to rationalize the observed selectivity over CDK2. An X-ray crystal structure of a compound from the active series bound to crystalline MAPKAP-K2 confirmed the predicted binding mode. This has enabled the discovery of a series of pyrazolo[1,5-a]pyrimidine derivatives showing good in vitro cellular potency as anti-TNF-α agents and in vivo efficacy in a mouse model of endotoxin shock.

Selective involvement of ERK and JNK mitogen-activated protein kinases in early rheumatoid arthritis (1987 ACR criteria compared to 2010 ACR/EULAR criteria): a prospective study aimed at identification of diagnostic and prognostic biomarkers as well as therapeutic targets

Objectives

To investigate the expression and activation of mitogen-activated protein kinases in patients with early arthritis who are disease-modifying antirheumatic drug (DMARD) naïve.

Methods

A total of 50 patients with early arthritis who were DMARD naïve (disease duration <1 year) were prospectively followed and diagnosed at baseline and after 2 years for undifferentiated arthritis (UA), rheumatoid arthritis (RA) (1987 American College of Rheumatology (ACR) and 2010 ACR/European League Against Rheumatism (EULAR) criteria), or spondyloarthritis (SpA). Synovial biopsies obtained at baseline were examined for expression and phosphorylation of p38, extracellular signal regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) by immunohistochemistry and digital analysis. Synovial tissue mRNA expression was measured by quantitative PCR (qPCR).

Results

ERK and JNK activation was enhanced at inclusion in patients meeting RA criteria compared to other diagnoses. JNK activation was enhanced in patients diagnosed as having UA at baseline who eventually fulfilled 1987 ACR RA criteria compared to those who remained UA, and in patients with RA fulfilling 2010 ACR/EULAR criteria at baseline. ERK and JNK activation was enhanced in patients with RA developing progressive joint destruction. JNK activation in UA predicted 1987 ACR RA classification criteria fulfilment (R²=0.59, p=0.02) after follow-up, and disease progression in early arthritis (R²=0.16, p<0.05). Enhanced JNK activation in patients with persistent disease was associated with altered synovial expression of extracellular matrix components and CD44.

Conclusions

JNK activation is elevated in RA before 1987 ACR RA classification criteria are met and predicts development of erosive disease in early arthritis, suggesting JNK may represent an attractive target in treating RA early in the disease process.

IL-1R-associated kinase-1 mediates protein kinase Cδ-induced IL-1β production in monocytes

The role of IL-1R-associated kinase (IRAK)1 and its interaction with protein kinase C (PKC)δ in monocytes to regulate IL-1β production has not been reported so far. The present study thus investigates such mechanisms in the THP1 cell line and human monocytes. PMA treatment to THP1 cells induced CD11b, TLR2, TLR4, CD36, IRAK1, IRAK3, and IRAK4 expression, IRAK1 kinase activity, PKCδ and JNK phosphorylation, AP-1 and NF-κB activation, and secretory IL-1β production. Moreover, PMA-induced IL-1β production was significantly reduced in the presence of TLR2, TLR4, and CD11b Abs. Rottlerin, a PKCδ-specific inhibitor, significantly reduced PMA-induced IL-1β production as well as CD11b, TLR2 expression, and IRAK1-JNK activation. In PKCδ wild-type overexpressing THP1 cells, IRAK1 kinase activity and IL-1β production were significantly augmented, whereas recombinant inactive PKCδ and PKCδ small interfering RNA significantly inhibited basal and PMA-induced IRAK1 activation and IL-1β production. Endogenous PKCδ-IRAK1 interaction was observed in quiescent cells, and this interaction was regulated by PMA. IRAK1/4 inhibitors, their small interfering RNAs, and JNK inhibitor also attenuated PMA-induced IL-1β production. NF-κB activation inhibitor and SN50 peptide inhibitor, however, failed to affect PMA-induced IL-1β production. A similar role of IRAK1 in IL-1β production and its regulation by PKCδ was evident in the primary human monocytes, thus signifying the importance of our finding. To our knowledge, the results obtained demonstrate for the first time that IRAK1 and PKCδ functionally interact to regulate IL-1β production in monocytic cells. A novel mechanism of IL-1β production that involves TLR2, CD11b, and the PKCδ/IRAK1/JNK/AP-1 axis is thus being proposed.

Intracellular localization and interaction of mRNA binding proteins as detected by FRET

Background

A number of RNA binding proteins (BPs) bind to A+U rich elements (AREs), commonly present within 3'UTRs of highly regulated RNAs. Individual RNA-BPs proteins can modulate RNA stability, RNA localization, and/or translational efficiency. Although biochemical studies have demonstrated selectivity of ARE-BPs for individual RNAs, less certain is the in vivo composition of RNA-BP multiprotein complexes and how their composition is affected by signaling events and intracellular localization. Using FRET, we previously demonstrated that two ARE-BPs, HuR and AUF1, form stable homomeric and heteromeric associations in the nucleus and cytoplasm. In the current study, we use immuno-FRET of endogenous proteins to examine the intracellular localization and interactions of HuR and AUF1 as well as KSRP, TIA-1, and Hedls. These results were compared to those obtained with their exogenously expressed, fluorescently labeled counterparts.

Results

All ARE-BPs examined were found to colocalize and to form stable associations with selected other RNA-BPs in one or more cellular locations variably including the nucleus, cytoplasm (in general), or in stress granules or P bodies. Interestingly, FRET based interaction of the translational suppressor, TIA-1, and the decapping protein, Hedls, was found to occur at the interface of stress granules and P bodies, dynamic sites of intracellular RNA storage and/or turnover. To explore the physical interactions of RNA-BPs with ARE containing RNAs, in vitro transcribed Cy3-labeled RNA was transfected into cells. Interestingly, Cy3-RNA was found to coalesce in P body like punctate structures and, by FRET, was found to interact with the RNA decapping proteins, Hedls and Dcp1.

Conclusions

Biochemical methodologies, such as co-immunoprecipitation, and cell biological approaches such as standard confocal microscopy are useful in demonstrating the possibility of proteins and/or proteins and RNAs interacting. However, as demonstrated herein, colocalization of proteins and proteins and RNA is not always indicative of interaction. To this point, using FRET and immuno-FRET, we have demonstrated that RNA-BPs can visually colocalize without producing a FRET signal. In contrast, proteins that appear to be delimited to one or another intracellular compartment can be shown to interact when those compartments are juxtaposed.

MAPKAP kinase 2 blocks tristetraprolin-directed mRNA decay by inhibiting CAF1 deadenylase recruitment

Tristetraprolin (TTP) directs its target AU-rich element (ARE)-containing mRNAs for degradation by promoting removal of the poly(A) tail. The p38 MAPK pathway regulates mRNA stability via the downstream kinase MAPK-activated protein kinase 2 (MAPKAP kinase 2 or MK2), which phosphorylates and prevents the mRNA-destabilizing function of TTP. We show that deadenylation of endogenous ARE-containing tumor necrosis factor mRNA is inhibited by p38 MAPK. To investigate whether phosphorylation of TTP by MK2 regulates TTP-directed deadenylation of ARE-containing mRNAs, we used a cell-free assay that reconstitutes the mechanism in vitro. We find that phosphorylation of Ser-52 and Ser-178 of TTP by MK2 results in inhibition of TTP-directed deadenylation of ARE-containing RNA. The use of 14-3-3 protein antagonists showed that regulation of TTP-directed deadenylation by MK2 is independent of 14-3-3 binding to TTP. To investigate the mechanism whereby TTP promotes deadenylation, it was necessary to identify the deadenylases involved. The carbon catabolite repressor protein (CCR)4.CCR4-associated factor (CAF)1 complex was identified as the major source of deadenylase activity in HeLa cells responsible for TTP-directed deadenylation. CAF1a and CAF1b were found to interact with TTP in an RNA-independent fashion. We find that MK2 phosphorylation reduces the ability of TTP to promote deadenylation by inhibiting the recruitment of CAF1 deadenylase in a mechanism that does not involve sequestration of TTP by 14-3-3. Cyclooxygenase-2 mRNA stability is increased in CAF1-depleted cells in which it is no longer p38 MAPK/MK2-regulated.