Post-transcriptional regulation of gene expression by mitogen-activated protein kinase p38

Nimbolide Targets Multiple Signalling Pathways to Reduce Neuroinflammation in BV-2 Microglia

Nimbolide, a limonoid compound found in the neem plant, was investigated for effects on neuroinflammation in BV-2 microglia activated with lipopolysaccharide (LPS). Cultured BV-2 cells were treated with nimbolide (125, 250 and 500 nM) followed by stimulation with LPS (100 ng/ml). Results showed that nimbolide caused a significant reduction in the levels of TNFα, IL-6, IFNγ, NO/iNOS and PGE2/COX-2 in LPS-activated BV-2 cells. Further experiments revealed that LPS-induced increased expression of phospho-p65 and phospho-IκBα proteins were reduced in the presence of nimbolide. Also, LPS-induced NF-κB acetylation, increased binding to consensus sites and transactivation, as well as phosphorylation of p38 and JNK MAPKs were reduced by nimbolide. Reduction of cellular ROS generation by nimbolide was accompanied by a reduction in gp91phox protein levels, while antioxidant effects were also observed through elevation in protein levels of HO-1 and NQO-1. It was observed that treatment of BV-2 microglia with nimbolide resulted in reduced levels of cytoplasmic Nrf2, which was accompanied by increased levels in the nucleus. Furthermore, treatment with this compound resulted in increased binding of Nrf2 to antioxidant responsive element (ARE) consensus sites accompanied by enhanced ARE luciferase activity. Knockdown experiments revealed a loss of anti-inflammatory activity by nimbolide in cells transfected with Nrf2 siRNA. Treatment with nimbolide resulted in nuclear accumulation of SIRT-1, while siRNA knockdown of SIRT-1 resulted in the reversal of anti-inflammatory activity of nimbolide. It is proposed that nimbolide reduces neuroinflammation in BV-2 microglia through mechanisms resulting in dual inhibition of NF-κB and MAPK pathways. It is also proposed that activation of Nrf2 antioxidant mechanisms may be contributing to its anti-inflammatory activity.

The Formulation of the N-Acetylglucosamine as Nanoparticles Increases Its Anti-Inflammatory Activities: An In Vitro Study

Nanomedicine can represent a new strategy to treat several types of diseases such as those with inflammatory aetiology. Through this strategy, it is possible to obtain nanoparticles with controlled shape, size, and eventually surface charge. Moreover, the use of molecules in nanoform may allow more effective delivery into the diseased cells and tissues, reducing toxicity and side effects of the used compounds. The aim of the present manuscript was the evaluation of the effects of N-acetylglucosamine in nanoform (GlcNAc NP) in an in vitro model of osteoarthritis (OA). Human primary chondrocytes were treated with Tumor Necrosis Factor (TNF)-α to simulate a low-grade inflammation and then treated with both GlcNAc and GlcNAc NP, in order to find the lowest concentrations able to counteract the inflammatory state of the cells and ensure a chondroprotective action. The findings showed that GlcNAc NP was able to decrease the pro-inflammatory mediators, IL-6 and IL-8, which are among the main effectors of inflammation; moreover, the nanoparticles downregulated the production of metalloprotease enzymes. GlcNAc NP was effective at a very low concentration compared to GlcNAc in its native form. Furthermore, GlcNAc NP stimulated an increase in collagen type II synthesis. In conclusion, the GlcNAc in nanoform showed better performance than GlcNAc, at concentrations lower than those reached in the joints after oral administration to patients of 1.5 g/die of glucosamine.

Regulation of mRNA stability contributes to the function of innate lymphoid cells in various diseases

Innate lymphoid cells (ILCs) are important subsets of innate immune cells that regulate mucosal immunity. ILCs include natural killer cells, innate lymphoid cells-1 (ILC1s), ILC2s, and ILC3s, which have extremely important roles in the immune system. In this review, we summarize the regulation of mRNA stability mediated through various factors in ILCs (e.g., cytokines, RNA-binding proteins, non-coding RNAs) and their roles in mediating functions in different ILC subsets. In addition, we discuss potential therapeutic targets for diseases such as chronic obstructive pulmonary disease, cancer, and pulmonary fibrosis by regulation of mRNA stability in ILCs, which may provide novel directions for future clinical research.

MicroRNA-181a restricts human γδ T cell differentiation by targeting Map3k2 and Notch2

γδ T cells are a conserved population of lymphocytes that contributes to anti-tumor responses through its overt type 1 inflammatory and cytotoxic properties. We have previously shown that human γδ T cells acquire this profile upon stimulation with IL-2 or IL-15, in a differentiation process dependent on MAPK/ERK signaling. Here, we identify microRNA-181a as a key modulator of human γδ T cell differentiation. We observe that miR-181a is highly expressed in patients with prostate cancer and that this pattern associates with lower expression of NKG2D, a critical mediator of cancer surveillance. Interestingly, miR-181a expression negatively correlates with an activated type 1 effector profile obtained from in vitro differentiated γδ T cells and miR-181a overexpression restricts their levels of NKG2D and TNF-α. Upon in silico analysis, we identify two miR-181a candidate targets, Map3k2 and Notch2, which we validate via overexpression coupled with luciferase assays. These results reveal a novel role for miR-181a as critical regulator of human γδ T cell differentiation and highlight its potential for manipulation of γδ T cells in next-generation immunotherapies.

Discovery of Phenolic Glycoside from Hyssopus cuspidatus Attenuates LPS-Induced Inflammatory Responses by Inhibition of iNOS and COX-2 Expression through Suppression of NF-κB Activation

It seems quite necessary to obtain effective substances from natural products against inflammatory response (IR) as there are presently clinical problems regarding accompanying side effects and lowered quality of life. This work aimed to investigate the abilities of hyssopuside (HY), a novel phenolic glycoside isolated from Hyssopus cuspidatus (H. cuspidatus), against IR in lipopolysaccharide (LPS)-induced RAW 264.7 cells and mouse peritoneal macrophages. The results indicated that HY could reduce nitric oxide (NO) production and inhibit the production and secretion of pro-inflammatory mediators including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) in LPS-stimulated macrophages. Moreover, data from the immunofluorescence study showed that HY suppressed nuclear translocation of nuclear factor-kappa B (NF-κB) upon LPS induction. The Western blot results suggested that HY reversed the LPS-induced degradation of IκB (inhibitor of NF-κB), which is normally required for the activation of NF-κB. Meanwhile, the overexpression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) diminished significantly with the presence of HY in response to LPS stimulation. On the other hand, HY had a negligible impact on the activation of mitogen-activated protein kinase (MAPK) pathways. Moreover, an in silico study of HY against four essential proteins/enzymes revealed that COX-2 was the most efficient enzyme for the interaction, and binding of residues Phe179, Asn351, and Ser424 with HY played crucial roles in the observed activity. The structure analysis indicated the typical characterizations with phenylethanoid glycoside contributed to the anti-inflammatory effects of HY. These results indicated that HY manipulated its anti-inflammatory effects mainly through blocking the NF-κB signal transduction pathways. Collectively, we believe that HY could be a potential alternative phenolic agent for alleviating excessive inflammation in many inflammation-associated diseases.

Experimental Pulmonary Tuberculosis in the Absence of Detectable Brain Infection Induces Neuroinflammation and Behavioural Abnormalities in Male BALB/c Mice

Tuberculosis (TB) is a chronic infectious disease in which prolonged, non-resolutive inflammation of the lung may lead to metabolic and neuroendocrine dysfunction. Previous studies have reported that individuals coursing pulmonary TB experience cognitive or behavioural changes; however, the pathogenic substrate of such manifestations have remained unknown. Here, using a mouse model of progressive pulmonary TB, we report that, even in the absence of brain infection, TB is associated with marked increased synthesis of both inflammatory and anti-inflammatory cytokines in discrete brain areas such as the hypothalamus, the hippocampal formation and cerebellum accompanied by substantial changes in the synthesis of neurotransmitters. Moreover, histopathological findings of neurodegeneration and neuronal death were found as infection progressed with activation of p38, JNK and reduction in the BDNF levels. Finally, we perform behavioural analysis in infected mice throughout the infection, and our data show that the cytokine and neurochemical changes were associated with a marked onset of cognitive impairment as well as depressive- and anxiety-like behaviour. Altogether, our results suggest that besides pulmonary damage, TB is accompanied by an extensive neuroinflammatory and neurodegenerative state which explains some of the behavioural abnormalities found in TB patients.

Effect of the p38 MAPK inhibitor doramapimod on the systemic inflammatory response to intravenous lipopolysaccharide in horses

Background

Doramapimod, a p38 MAPK inhibitor, is a potent anti‐inflammatory drug that decreases inflammatory cytokine production in equine whole blood in vitro. It may have benefits for treating systemic inflammation in horses.

Objective

To determine whether doramapimod is well tolerated when administered IV to horses, and whether it has anti‐inflammatory effects in horses in a low‐dose endotoxemia model.

Animals

Six Standardbred horses.

Methods

Tolerability study, followed by a blinded, randomized, placebo‐controlled cross‐over study. Horses were given doramapimod, and clinical and clinicopathological variables were monitored for 24 hours. Horses then were treated with doramapimod or placebo, followed by a low dose infusion of lipopolysaccharide (LPS). Clinical variables (heart rate, rectal temperature, noninvasive blood pressure), leukocyte count and tumor necrosis factor alpha (TNF‐α) and interleukin‐1 beta (IL‐1β) concentrations were measured at multiple time points until 6 hours post‐LPS infusion.

Results

No adverse effects or clinicopathological changes were seen in the safety study. When treated with doramapimod as compared to placebo, horses had significantly lower heart rates (P = .03), rectal temperatures (P = .03), and cytokine concentrations (P = .03 for TNF‐α and IL‐1β), and a significantly higher white blood cell count (P = .03) after LPS infusion.

Conclusions and Clinical Importance

Doramapimod has clinically relevant anti‐inflammatory effects in horses, likely mediated by a decrease in leukocyte activation and decrease in the release of pro‐inflammatory cytokines. To evaluate its potential as a novel treatment for systemic inflammatory response syndrome in horses, clinical trials will be necessary to determine its efficacy in naturally occurring disease.

ROS induced by spring viraemia of carp virus activate the inflammatory response via the MAPK/AP-1 and PI3K signaling pathways

Spring viraemia of carp virus (SVCV) can cause a high mortality in common carp (Cyprinus carpio), and its main pathological processes include the inflammatory response. However, the detailed mechanism is still unclear. Reactive oxygen species (ROS) have been shown to play critical roles in the immune response, including inflammation, in different models. Our previous studies have demonstrated that SVCV infection results in the accumulation of ROS, including H₂O₂, in epithelioma papulosum cyprini (EPC) cells. In this study, we aimed to explore the relationship between H₂O₂ accumulation and inflammation during SVCV infection. After EPC cells were infected with SVCV, the expression levels of the inflammatory factors tumor necrosis factor (TNF)-α, cyclooxygenase (COX)-2, and interleukin (IL)-8 were up-regulated, while the expression of the anti-inflammatory factor interleukin (IL)-10 was down-regulated, compared with that in mock-infected EPC cells. The antioxidant N-acetyl-l-cysteine (NAC) could dampen the increased TNF-ɑ and COX-2 expression induced by SVCV and H₂O₂, suggesting a relationship between ROS accumulation and inflammation during SVCV infection. Dual luciferase reporter assays demonstrated that SVCV could not activate the NF-κB pathway. In addition, inhibition of NF-κB by pyrrolidine dithiocarbamate (PDTC) treatment had no effect on the expression of inflammatory factors. Furthermore, inhibition of the ERK, JNK, and p38MAPK signaling pathways by U0126, SP600125, and SB203580, respectively, reduced the expression of TNF-ɑ, COX-2, and IL-8, indicating that these three signaling pathways were all involved in the inflammatory response after SVCV infection. In addition, the PI3K signaling pathway was involved in the expression of the chemokine IL-8 in the SVCV-induced inflammatory response. We also showed that inhibition of the MAPK or PI3K signaling pathway facilitated the expression of SVCV-G as well as increased the SVCV viral titer. Altogether these results reveal the mechanism of the SVCV-mediated inflammatory response. Thus, targeting these signaling pathways may provide novel treatment strategies for SVCV-mediated diseases.

Post-Transcriptional Inflammatory Response to Intracellular Bacterial c-di-AMP

Cyclic-di-AMP (c-di-AMP) is a bacterial second messenger that is produced by intracellular bacterial pathogens in mammalian host macrophages. Previous reports have shown that c-di-AMP is recognized by intracellular pattern recognition receptors of the innate immune system and stimulate type I interferon response. Here we report that the response to c-di-AMP includes a post-transcriptional component that is involved in the induction of additional inflammatory cytokines including IL-6, CXCL2, CCL3, and CCL4. Their mRNAs contain AU-rich elements (AREs) in their 3' UTR that promote decay and repress translation. We show that c-di-AMP leads to the phosphorylation of p38 MAPK as well as the induction of the ARE-binding protein TTP, both of which are components of a signaling pathway that modulate the expression of ARE-containing mRNAs at the post-transcriptional level. Pharmacological inhibition of p38 reduces the c-di-AMP-dependent release of induced cytokines, while TTP knockdown increases their release and mRNA stability. C-di-AMP can specifically increase the expression of a nano-Luciferase reporter that contains AREs. We propose a non-canonical intracellular mode of activation of the p38 MAPK pathway with the subsequent enhancement in the expression of inflammatory cytokines. C-di-AMP is widely distributed in bacteria, including infectious intracellular pathogens; hence, understanding of its post-transcriptional gene regulatory effect on the host response may provide novel approaches for therapy.

Discovery of a potent p38α/MAPK14 kinase inhibitor: Synthesis, in vitro/in vivo biological evaluation, and docking studies

This article reports the synthesis of new triarylpyrazole derivatives possessing urea or amide linker, and their biological activities at molecular, cellular, and in vivo levels. Compound 2b was the most potent inhibitor of p38α/MAPK14 kinase (IC₅₀ = 22 nM) among this series. Molecular docking studies were conducted to understand the kinase inhibitory variations and the basis of selectivity. Compound 2b was able to inhibit p38α/MAPK14 kinase inside HEK293 cells in nanoBRET cellular kinase assay with EC₅₀ value of 0.55 μM, comparable to the potency of dasatinib. Compound 2b inhibited TNF-α production in lipopolysaccharide-induced THP-1 cells with IC₅₀ value of 58 nM. In addition, compound 2b showed low potency against hERG. It is 622.38 times less potent than E-4031 against hERG, so the risk of cardiotoxicity of the compound is very minimal. Compound 2b showed also high plasma stability in vitro in human and rat plasmas. The in vivo PK profile of compound 2b is acceptable, and its antiinflammatory effect was comparable to diclofenac with no ulcerogenic side effect on stomach.

BML-111 alleviates acute lung injury through regulating the expression of lncRNA MALAT1

BML-111 is a lipoxin receptor agonist that plays a vital role on inflammation. MALAT1 is reported to mediate lung injury. ALI rat model was established using the method of venous cannula. Pulmonary microvascular endothelial cells (PMVEC) of rats were isolated using immunomagnetic separation method. Hematoxylin-eosin (HE) staining was performed to observe the lung injury degree. Real-time PCR and western blot were performed to detect the genes expression. ELIAS was used to determine the level of TNF-α and IL-6. RNA pull-down and RIP were carried out to affirm the relationship between MALAT1 and TLR4. The lung injury score and lung wet/dry weight ratio was significantly increased in ALI rats, while BML-111 treatment significantly decreased it, the HE staining directly revealed the lung injury. The expression of MALAT1 was decreased, while TLR4 was increased in ALI rats, BML-111 stimulation significantly reversed it. MALAT1 targets TLR4 to regulate its expression. TLR4 regulated the inflammation and cell apoptosis of PMVEC via NF-κB and p38 MAPK signaling pathway. The down-regulated MALAT1 mediates the mechanism of ALI by regulating of NF-κB and p38 MAPK signaling pathways via TLR4, while BML-111 stimulation significantly alleviated the ALI by regulating the expression of MALAT1.

Intracellular TLR22 acts as an inflammation equalizer via suppression of NF-κB and selective activation of MAPK pathway in fish

TLR22, a typical member of the fish-specific TLRs, is a crucial sensor in virally triggered innate immune signalling retained from natural selection. To elucidate the role of the TLR22-specific signalling cascade mechanism, we provide evidence that the double-stranded (ds) RNA-sensor TLR22 positively regulates the ERK pathway and negatively regulates the JNK, p38 MAP kinase and NF-κB pathway. Here, we show that TLR22 restrains NF-κB activation and IFN (interferon) β and AP-1 (activator protein-1) promoter binding (impairing "primary response" genes (TNF and IL-1)), induces "secondary response" genes (IL-12 and IL-6) and mediates the irregular expression of inflammatory genes. Therefore, TLR22 promotes ERK phosphorylation but impairs the JNK and p38 MAP kinases and IκB phosphorylation. Additionally, TLR22 controls the excessive generation of reactive oxygen species (ROS) to avoid damaging the organism. The specific kinetics of TLR22 depends on its distinct cellular localization. We demonstrate that TLR22 is an intracellular receptor localized in the endosome, and the TLR22-TIR domain is the functional structure inducing the signalling cascade post-viral replication in the body. As mentioned above, our data reveal a novel mechanism whereby TLR22-induced positive adjustment and negative regulation evolved independently to avoid harmful and inappropriate inflammatory responses.

Deficiency of MAPK-activated protein kinase 2 (MK2) prevents adverse remodelling and promotes endothelial healing after arterial injury

Maladaptive remodelling of the arterial wall after mechanical injury (e. g. angioplasty) is characterised by inflammation, neointima formation and media hypertrophy, resulting in narrowing of the affected artery. Moreover, mechanical injury of the arterial wall causes loss of the vessel protecting endothelial cell monolayer. Mitogen-activated protein kinase (MAPK)-activated protein kinase 2 (MK2), a major downstream target of p38 MAPK, regulates inflammation, cell migration and proliferation, essential processes for vascular remodelling and reendothelialisation. Therefore, we investigated the role of MK2 in remodelling and reendothelialisation after arterial injury in genetically modified mice in vivo. Hypercholesterolaemic low-densitylipoprotein- receptor-deficient mice (ldlr-/- ) were subjected to wire injury of the common carotid artery. MK2-deficiency (ldlr-/-/mk2-/- ) nearly completely prevented neointima formation, media hypertrophy, and lumen loss after injury. This was accompanied by reduced proliferation and migration of MK2-deficient smooth muscle cells. In addition, MK2-deficiency severely reduced monocyte adhesion to the arterial wall (day 3 after injury, intravital microscopy), which may be attributed to reduced expression of the chemokine ligands CCL2 and CCL5. In line, MK2-deficiency significantly reduced the content of monocytes, neutrophiles and lymphocytes of the arterial wall (day 7 after injury, flow cytometry). In conclusion, in a model of endothelial injury (electric injury), MK2-deficiency strongly increased proliferation of endothelial cells and improved reendothelialisation of the arterial wall after injury. Deficiency of MK2 prevents adverse remodelling and promotes endothelial healing of the arterial wall after injury, suggesting that MK2-inhibition is a very attractive intervention to prevent restenosis after percutaneous therapeutic angioplasty.

Role and regulation of MKP-1 in airway inflammation

Mitogen-activated protein kinase (MAPK) phosphatase 1 (MKP-1) is a protein with anti-inflammatory properties and the archetypal member of the dual-specificity phosphatases (DUSPs) family that have emerged over the past decade as playing an instrumental role in the regulation of airway inflammation. Not only does MKP-1 serve a critical role as a negative feedback effector, controlling the extent and duration of pro-inflammatory MAPK signalling in airway cells, upregulation of this endogenous phosphatase has also emerged as being one of the key cellular mechanism responsible for the beneficial actions of clinically-used respiratory medicines, including β₂-agonists, phosphodiesterase inhibitors and corticosteroids. Herein, we review the role and regulation of MKP-1 in the context of airway inflammation. We initially outline the structure and biochemistry of MKP-1 and summarise the multi-layered molecular mechanisms responsible for MKP-1 production more generally. We then focus in on some of the key in vitro studies in cell types relevant to airway disease that explain how MKP-1 can be regulated in airway inflammation at the transcriptional, post-translation and post-translational level. And finally, we address some of the potential challenges with MKP-1 upregulation that need to be explored further to fully exploit the potential of MKP-1 to repress airway inflammation in chronic respiratory disease.

The control of inflammation via the phosphorylation and dephosphorylation of tristetraprolin: a tale of two phosphatases

Twenty years ago, the first description of a tristetraprolin (TTP) knockout mouse highlighted the fundamental role of TTP in the restraint of inflammation. Since then, work from several groups has generated a detailed picture of the expression and function of TTP. It is a sequence-specific RNA-binding protein that orchestrates the deadenylation and degradation of several mRNAs encoding inflammatory mediators. It is very extensively post-translationally modified, with more than 30 phosphorylations that are supported by at least two independent lines of evidence. The phosphorylation of two particular residues, serines 52 and 178 of mouse TTP (serines 60 and 186 of the human orthologue), has profound effects on the expression, function and localisation of TTP. Here, we discuss the control of TTP biology via its phosphorylation and dephosphorylation, with a particular focus on recent advances and on questions that remain unanswered.

Macrophage responses to lipopolysaccharide are modulated by a feedback loop involving prostaglandin E2, dual specificity phosphatase 1 and tristetraprolin

In many different cell types, pro-inflammatory agonists induce the expression of cyclooxygenase 2 (COX-2), an enzyme that catalyzes rate-limiting steps in the conversion of arachidonic acid to a variety of lipid signaling molecules, including prostaglandin E₂ (PGE₂). PGE₂ has key roles in many early inflammatory events, such as the changes of vascular function that promote or facilitate leukocyte recruitment to sites of inflammation. Depending on context, it also exerts many important anti-inflammatory effects, for example increasing the expression of the anti-inflammatory cytokine interleukin 10 (IL-10), and decreasing that of the pro-inflammatory cytokine tumor necrosis factor (TNF). The tight control of both biosynthesis of, and cellular responses to, PGE₂ are critical for the precise orchestration of the initiation and resolution of inflammatory responses. Here we describe evidence of a negative feedback loop, in which PGE₂ augments the expression of dual specificity phosphatase 1, impairs the activity of mitogen-activated protein kinase p38, increases the activity of the mRNA-destabilizing factor tristetraprolin, and thereby inhibits the expression of COX-2. The same feedback mechanism contributes to PGE₂-mediated suppression of TNF release. Engagement of the DUSP1-TTP regulatory axis by PGE₂ is likely to contribute to the switch between initiation and resolution phases of inflammation.

Endothelial MAPKs Direct ICAM-1 Signaling to Divergent Inflammatory Functions

Lymphocyte transendothelial migration (TEM) is critically dependent on intraendothelial signaling triggered by adhesion to ICAM-1. Here we show that endothelial MAPKs ERK, p38, and JNK mediate diapedesis-related and diapedesis-unrelated functions of ICAM-1 in cerebral and dermal microvascular endothelial cells (MVECs). All three MAPKs were activated by ICAM-1 engagement, either through lymphocyte adhesion or Ab-mediated clustering. MAPKs were involved in ICAM-1-dependent expression of TNF-α in cerebral and dermal MVECs, and CXCL8, CCL3, CCL4, VCAM-1, and cyclooxygenase 2 (COX-2) in cerebral MVECs. Endothelial JNK and to a much lesser degree p38 were the principal MAPKs involved in facilitating diapedesis of CD4⁺ lymphocytes across both types of MVECs, whereas ERK was additionally required for TEM across dermal MVECs. JNK activity was critical for ICAM-1-induced F-actin rearrangements. Furthermore, activation of endothelial ICAM-1/JNK led to phosphorylation of paxillin, its association with VE-cadherin, and internalization of the latter. Importantly ICAM-1-induced phosphorylation of paxillin was required for lymphocyte TEM and converged functionally with VE-cadherin phosphorylation. Taken together we conclude that during lymphocyte TEM, ICAM-1 signaling diverges into pathways regulating lymphocyte diapedesis, and other pathways modulating gene expression thereby contributing to the long-term inflammatory response of the endothelium.

Safer topical treatment for inflammation using 5α-tetrahydrocorticosterone in mouse models

Use of topical glucocorticoid for inflammatory skin conditions is limited by systemic and local side-effects. This investigation addressed the hypothesis that topical 5α-tetrahydrocorticosterone (5αTHB, a corticosterone metabolite) inhibits dermal inflammation without affecting processes responsible for skin thinning and impaired wound healing. The topical anti-inflammatory properties of 5αTHB were compared with those of corticosterone in C57Bl/6 male mice with irritant dermatitis induced by croton oil, whereas its effects on angiogenesis, inflammation, and collagen deposition were investigated by subcutaneous sponge implantation. 5αTHB decreased dermal swelling and total cell infiltration associated with dermatitis similarly to corticosterone after 24 h, although at a five fold higher dose, but in contrast did not have any effects after 6 h. Pre-treatment with the glucocorticoid receptor antagonist RU486 attenuated the effect of corticosterone on swelling at 24 h, but not that of 5αTHB. After 24 h 5αTHB reduced myeloperoxidase activity (representative of neutrophil infiltration) to a greater extent than corticosterone. At equipotent anti-inflammatory doses 5αTHB suppressed angiogenesis to a limited extent, unlike corticosterone which substantially decreased angiogenesis compared to vehicle. Furthermore, 5αTHB reduced only endothelial cell recruitment in sponges whereas corticosterone also inhibited smooth muscle cell recruitment and decreased transcripts of angiogenic and inflammatory genes. Strikingly, corticosterone, but not 5αTHB, reduced collagen deposition. However, both 5αTHB and corticosterone attenuated macrophage infiltration into sponges. In conclusion, 5αTHB displays the profile of a safer topical anti-inflammatory compound. With limited effects on angiogenesis and extracellular matrix, it is less likely to impair wound healing or cause skin thinning.

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.

Cyclooxygenase-2 and microRNA-155 expression are elevated in asthmatic airway smooth muscle cells

Cyclooxygenase-2 (COX-2) expression and PGE2 secretion from human airway smooth muscle cells (hASMCs) may contribute to β2-adrenoceptor hyporesponsiveness, a clinical feature observed in some patients with asthma. hASMCs from patients with asthma exhibit elevated expression of cytokine-responsive genes, and in some instances this is attributable to an altered histone code and/or microRNA expression. We hypothesized that COX-2 expression and PGE2 secretion might be elevated in asthmatic hASMCs in response to proinflammatory signals in part due to altered histone acetylation and/or microRNA expression. hASMCs obtained from nonasthmatic and asthmatic human subjects were treated with cytomix (IL-1β, TNF-α, and IFN-γ). A greater elevation of COX-2 mRNA, COX-2 protein, and PGE2 secretion was observed in the asthmatic cells. We investigated histone H3/H4-acetylation, transcription factor binding, mRNA stability, p38 mitogen-activated protein kinase signaling, and microRNA (miR)-155 expression as potential mechanisms responsible for the differential elevation of COX-2 expression. We found that histone H3/H4-acetylation and transcription factor binding to the COX-2 promoter were similar in both groups, and histone H3/H4-acetylation did not increase after cytomix treatment. Cytomix treatment elevated NF-κB and RNA polymerase II binding to similar levels in both groups. COX-2 mRNA stability was increased in asthmatic cells. MiR-155 expression was higher in cytomix-treated asthmatic cells, and we show it enhances COX-2 expression and PGE2 secretion in asthmatic and nonasthmatic hASMCs. Thus, miR-155 expression positively correlates with COX-2 expression in the asthmatic hASMCs and may contribute to the elevated expression observed in these cells. These findings may explain, at least in part, β2-adrenoceptor hyporesponsiveness in patients with asthma.

IFNλ Stimulates MxA Production in Human Dermal Fibroblasts via a MAPK-Dependent STAT1-Independent Mechanism

IFNλ is important for epidermal defense against viruses. It is produced by, and acts on, keratinocytes, whereas fibroblasts were previously considered to be unresponsive to this type III IFN. Herein we report findings revealing cell type-specific differences in IFNλ signaling and function in skin resident cells. In dermal fibroblasts, IFNλ induced the expression of myxovirus protein A (MxA), a potent antiviral factor, but not other IFN signature genes as it does in primary keratinocytes. In contrast to its effect on keratinocytes, IFNλ did not phosphorylate signal transducer and activator of transcription 1 in fibroblasts, but instead activated mitogen activated protein kinases (MAPK). Accordingly, inhibition of MAPK activation (p38 and p42/44) blocked the expression of MxA protein in fibroblasts but not in keratinocytes. Functionally, IFNλ inhibited proliferation in keratinocytes but not in fibroblasts. Moreover, IFNλ upregulated the expression of Tumor growth factor beta 1 (TGFβ1)-induced collagens in fibroblasts. Taken together, our findings identify primary human dermal fibroblasts as responder cells to IFNλ. Our study shows cutaneous cell type-specific IFN signaling and suggests that IFNλ, although important for epidermal antiviral competence, may also have a regulatory role in the dermal compartment balancing type I IFN-induced inhibition of tissue repair processes.

p38 MAPK mediates glial P2X7R-neuronal P2Y1R inhibitory control of P2X3R expression in dorsal root ganglion neurons

Background

We have previously shown that endogenously active purinergic P2X7 receptors (P2X7Rs) in satellite glial cells of dorsal root ganglia (DRGs) stimulate ATP release. The ATP activates P2Y1Rs located in the enwrapped neuronal somata, resulting in down-regulation of P2X3Rs. This P2X7R-P2Y1-P2X3R inhibitory control significantly reduces P2X3R-mediated nociceptive responses. The underlying mechanism by which the activation of P2Y1Rs inhibits the expression of P2X3Rs remains unexplored.

Results

Examining the effect of the activation of p38 mitogen-activated protein kinase on the expression of P2X3Rs in DRGs, we found that the p38 activator, anisomycin (Anis), reduced the expression of P2X3Rs. Blocking the activity of SGCs by the glial Krebs cycle inhibitor, fluorocitrate, did not change the effect of Anis. These results suggest that neuronal p38 plays a major role in the inhibition of P2X3R expression. Western blotting analyses showed that inhibiting P2Y1Rs by MRS2179 (MRS) or blocking P2X7Rs by either oxATP or A740003 reduced pp38 and increased P2X3R expression in DRGs. These results are further supported by the immunohistochemical study showing that P2X7R and P2Y1R antagonists reduce the percentage of pp38-positive neurons. These observations suggest that activation of P2X7Rs and P2Y1Rs promotes p38 activity to exert inhibitory control on P2X3R expression. Since activation of p38 by Anis in the presence of either A740003 or MRS could overcome the block of P2X7R-P2Y1R inhibitory control, p38 in DRG neurons is downstream of P2Y1Rs. In addition, inhibition of p38 by SB202190 was found to prevent the P2X7R and P2Y1R block of P2X3R expression and increase P2X3R-mediated nociceptive flinch behaviors.

Conclusions

p38 in DRG neurons downstream of P2Y1R is necessary and sufficient for the P2X7R-P2Y1R inhibitory control of P2X3R expression.

Interleukin-1 Acts via the JNK-2 Signaling Pathway to Induce Aggrecan Degradation by Human Chondrocytes

OBJECTIVE

Aggrecan enables articular cartilage to bear load and resist compression. Aggrecan loss occurs early in osteoarthritis and rheumatoid arthritis and can be induced by inflammatory cytokines such as interleukin-1 (IL-1). IL-1 induces cleavage of specific aggrecans characteristic of the ADAMTS proteinases. The aim of this study was to identify the intracellular signaling pathways by which IL-1 causes aggrecan degradation by human chondrocytes and to investigate how aggrecanase activity is controlled by chondrocytes.

METHODS

We developed a cell-based assay combining small interfering RNA (siRNA)-induced knockdown with aggrecan degradation assays. Human articular chondrocytes were overlaid with bovine aggrecan after transfection with siRNAs against molecules of the IL-1 signaling pathway. After IL-1 stimulation, released aggrecan fragments were detected with AGEG and ARGS neoepitope antibodies. Aggrecanase activity and tissue inhibitor of metalloproteinases 3 levels were measured by enzyme-linked immunosorbent assay. Low-density lipoprotein receptor-related protein 1 (LRP-1) shedding was analyzed by Western blotting.

RESULTS

ADAMTS-5 is a major aggrecanase in human chondrocytes, regulating aggrecan degradation in response to IL-1. The tumor necrosis factor receptor-associated 6 (TRAF-6)/transforming growth factor β-activated kinase 1 (TAK-1)/MKK-4 signaling axis is essential for IL-1-induced aggrecan degradation, while NF-κB is not. Of the 3 MAPKs (ERK, p38, and JNK), only JNK-2 showed a significant role in aggrecan degradation. Chondrocytes constitutively secreted aggrecanase, which was continuously endocytosed by LRP-1, keeping the extracellular level of aggrecanase low. IL-1 induced aggrecanase activity in the medium in a JNK-2-dependent manner, possibly by reducing aggrecanase endocytosis, because IL-1 caused JNK-2-dependent shedding of LRP-1.

CONCLUSION

The signaling axis TRAF-6/TAK-1/MKK-4/JNK-2 mediates IL-1-induced aggrecanolysis. The level of aggrecanase is controlled by its endocytosis, which may be reduced upon IL-1 stimulation because of LRP-1 shedding.

Functional regulation of Zfp36l1 and Zfp36l2 in response to lipopolysaccharide in mouse RAW264.7 macrophages

Background

The tristetraprolin (TTP) family of mRNA-binding proteins contains three major members, Ttp, Zfp36l1, and Zfp36l2. Ttp down-regulates the stability of AU-rich element–containing mRNAs and functions as an anti-inflammation regulator.

Methods

To examine whether other TTP family proteins also play roles in the inflammatory response, their expression profiles and the possible mRNA targets were determined in the knockdown cells.

Results

Ttp mRNA and protein were highly induced by lipopolysaccharide (LPS), whereas Zfp36l1 and Zfp36l2 mRNAs were down-regulated and their proteins were phosphorylated during early lipopolysaccharide stimulation. Biochemical and functional analyses exhibited that the decrease of Zfp36l2 mRNA was cross-regulated by Ttp. Knockdown of Zfp36l1 and Zfp36l2 increased the basal level of Mkp-1 mRNAs by prolonging its half-life. Increasing the expression of Mkp-1 inhibited the activation of p38 MAPK under lipopolysaccharide stimulation and down-regulated Tnfα, and Ttp mRNA. In addition, hyper-phosphorylation of Zfp36l1 might stabilize Mkp-1 expression by forming a complex with the adapter protein 14-3-3 and decreasing the interaction with deadenylase Caf1a.

Conclusions

Our findings imply that the expression and phosphorylation of Zfp36l1 and Zfp36l2 may modulate the basal level of Mkp-1 mRNA to control p38 MAPK activity during lipopolysaccharide stimulation, which would affect the inflammatory mediators production. Zfp36l1 and Zfp36l2 are important regulators of the innate immune response.

Electronic supplementary material

The online version of this article (doi:10.1186/s12950-015-0088-x) contains supplementary material, which is available to authorized users.

Coordinated post-transcriptional regulation of the chemokine system: messages from CCL2

The molecular cross-talk between epithelium and immune cells in the airway mucosa is a key regulator of homeostatic immune surveillance and is crucially involved in the development of chronic lung inflammatory diseases. The patterns of gene expression that follow the sensitization process occurring in allergic asthma and chronic rhinosinusitis and those present in the neutrophilic response of other chronic inflammatory lung diseases such as chronic obstructive pulmonary disease (COPD) are tightly regulated in their specificity. Studies exploring the global transcript profiles associated with determinants of post-transcriptional gene regulation (PTR) such as RNA-binding proteins (RBP) and microRNAs identified several of these factors as being crucially involved in controlling the expression of chemokines upon airway epithelial cell stimulation with cytokines prototypic of Th1- or Th2-driven responses. These studies also uncovered the participation of these pathways to glucocorticoids' inhibitory effect on the epithelial chemokine network. Unmasking the molecular mechanisms of chemokine PTR may likely uncover novel therapeutic strategies for the blockade of proinflammatory pathways that are pathogenetic for asthma, COPD, and other lung inflammatory diseases.

Tubulin-binding agents down-regulate matrix metalloproteinase-2 and -9 in human hormone-refractory prostate cancer cells – a critical role of Cdk1 in mitotic entry

Tubulin is an important target for anticancer therapy. Taxanes and vinca alkaloids are two groups of tubulin-binding agents in cancer chemotherapy. Besides tubulin binding, these groups of agents can also down-regulate protein levels of matrix metalloproteinase (MMP)-2 and -9, two important cancer-associated zinc-dependent endopeptidases in invasion and metastasis. However, the mechanism of action waits to be explored. In this study, protein levels but not mRNA expressions of MMP-2 and -9 were down-regulated by paclitaxel (a microtubule-stabilization agent), vincristine and evodiamine (two tubulin-depolymerization agents). These agents induced an increase of protein expression of cyclin B1, MPM2 (mitosis-specific phosphoprotein) and polo-like kinase (PLK) 1 phosphorylation. The data showed a negative relationship between the levels of mitotic proteins and MMP-2 and -9 expressions. MG132 (a specific cell-permeable proteasome inhibitor) blocked mitotic entry and arrested cell cycle at G2 phase, preventing down-regulation of MMP-2 and -9. Cell cycle synchronization experiments by thymidine block or nocodazole treatment showed that mitotic exit inhibited the down-regulation of MMP-2 and -9, confirming negative relationship between cell mitosis and protein levels of MMP-2 and -9 expressions. Cyclin-dependent kinase (Cdk) 1 is a key kinase in mitotic entry. Knockdown of Cdk1 almost completely inhibited the down-regulation of MMP-2 and -9 induced by tubulin-binding agents. In conclusion, the data suggest that mitotic entry and Cdk1 plays a central role in down-regulation of MMP-2 and -9 protein expressions. Tubulin-binding agents cause mitotic arrest and Cdk1 activation, which may contribute largely to the down-regulation of both MMP-2 and -9 expressions.

A new IRAK-M-mediated mechanism implicated in the anti-inflammatory effect of nicotine via α7 nicotinic receptors in human macrophages

Nicotine stimulation of α7 nicotinic acetylcholine receptor (α7 nAChR) powerfully inhibits pro-inflammatory cytokine production in lipopolysaccharide (LPS)-stimulated macrophages and in experimental models of endotoxemia. A signaling pathway downstream from the α7 nAChRs, which involves the collaboration of JAK2/STAT3 and NF-κB to interfere with signaling by Toll-like receptors (TLRs), has been implicated in this anti-inflammatory effect of nicotine. Here, we identifiy an alternative mechanism involving interleukin-1 receptor-associated kinase M (IRAK-M), a negative regulator of innate TLR-mediated immune responses. Our data show that nicotine up-regulates IRAK-M expression at the mRNA and protein level in human macrophages, and that this effect is secondary to α7 nAChR activation. By using selective inhibitors of different signaling molecules downstream from the receptor, we provide evidence that activation of STAT3, via either JAK2 and/or PI3K, through a single (JAK2/PI3K/STAT3) or two convergent cascades (JAK2/STAT3 and PI3K/STAT3), is necessary for nicotine-induced IRAK-M expression. Moreover, down-regulation of this expression by small interfering RNAs specific to the IRAK-M gene significantly reverses the anti-inflammatory effect of nicotine on LPS-induced TNF-α production. Interestingly, macrophages pre-exposed to nicotine exhibit higher IRAK-M levels and reduced TNF-α response to an additional LPS challenge, a behavior reminiscent of the ‘endotoxin tolerant’ phenotype identified in monocytes either pre-exposed to LPS or from immunocompromised septic patients. Since nicotine is a major component of tobacco smoke and increased IRAK-M expression has been considered one of the molecular determinants for the induction of the tolerant phenotype, our findings showing IRAK-M overexpression could partially explain the known influence of smoking on the onset and progression of inflammatory and infectious diseases.

The two-hit hypothesis for neuroinflammation: role of exogenous ATP in modulating inflammation in the brain

Brain inflammation is a common occurrence following responses to varied insults such as bacterial infections, stroke, traumatic brain injury and neurodegenerative disorders. A common mediator for these varied inflammatory responses is prostaglandin E₂ (PGE₂), produced by the enzymatic activity of cyclooxygenases (COX) 1 and 2. Previous attempts to reduce neuronal inflammation through COX inhibition, by use of nonsteroidal anti-inflammatory drugs (NSAIDs), have met with limited success. We are proposing the two-hit model for neuronal injury—an initial localized inflammation mediated by PGE₂ (first hit) and the simultaneous release of adenosine triphosphate (ATP) by injured cells (second hit), which significantly enhances the inflammatory response through increased synthesis of PGE₂. Several evidences on the role of exogenous ATP in inflammation have been reported, including contrary instances where extracellular ATP reduces inflammatory events. In this review, we will examine the current literature on the role of P2 receptors, to which ATP binds, in modulating inflammatory reactions during neurodegeneration. Targeting the P2 receptors, therefore, provides a therapeutic alternative to reduce inflammation in the brain. P2 receptor-based anti-inflammatory drugs (PBAIDs) will retain the activities of essential COX enzymes, yet will significantly reduce neuroinflammation by decreasing the enhanced production of PGE₂ by extracellular ATP.

Role of p38 MAP Kinase Signal Transduction in Solid Tumors

Mitogen-activated protein kinases (MAPKs) mediate a wide variety of cellular behaviors in response to extracellular stimuli. One of the main subgroups, the p38 MAP kinases, has been implicated in a wide range of complex biologic processes, such as cell proliferation, cell differentiation, cell death, cell migration, and invasion. Dysregulation of p38 MAPK levels in patients are associated with advanced stages and short survival in cancer patients (e.g., prostate, breast, bladder, liver, and lung cancer). p38 MAPK plays a dual role as a regulator of cell death, and it can either mediate cell survival or cell death depending not only on the type of stimulus but also in a cell type specific manner. In addition to modulating cell survival, an essential role of p38 MAPK in modulation of cell migration and invasion offers a distinct opportunity to target this pathway with respect to tumor metastasis. The specific function of p38 MAPK appears to depend not only on the cell type but also on the stimuli and/or the isoform that is activated. p38 MAPK signaling pathway is activated in response to diverse stimuli and mediates its function by components downstream of p38. Extrapolation of the knowledge gained from laboratory findings is essential to address the clinical significance of p38 MAPK signaling pathways. The goal of this review is to provide an overview on recent progress made in defining the functions of p38 MAPK pathways with respect to solid tumor biology and generate testable hypothesis with respect to the role of p38 MAPK as an attractive target for intervention of solid tumors.

Proteomic profiling of chikungunya virus-infected human muscle cells: reveal the role of cytoskeleton network in CHIKV replication

Chikungunya virus (CHIKV) is an arthropod-borne, positive-sense, single-stranded RNA virus belonging to genus Alphavirus and family Togaviridae. The clinical manifestations developed upon CHIKV-infection include fever, myositis, arthralgia and maculopapular rash. Thus, the re-emergence of CHIKV has posed serious health threats worldwide. Due to the fact that myositis is induced upon CHIKV-infection, we sought to understand the dynamic proteomic regulation in SJCRH30, a human rhabdomyosarcoma cell line, to gain insights on CHIKV pathogenesis. Two-dimensional gel electrophoresis (2DE) in combination of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to profile differential cellular proteins expression in CHIKV-infected SJCRH30 cells. 2DE analysis on CHIKV-infected cells has revealed 44 protein spots. These spots are found to be involved in various biological pathways such as biomolecules synthesis and metabolism, cell signaling and cellular reorganization. siRNA-mediated gene silencing on selected genes has elucidated the biological significance of these gene-translated host proteins involved in CHIKV-infection. More importantly, the interaction of vimentin with non-structural protein (nsP3) of CHIKV was shown, suggesting the role played by vimentin during CHIKV replication by forming an anchorage network with the CHIKV replication complexes (RCs).

BIOLOGICAL SIGNIFICANCE

Chikungunya virus (CHIKV) is a re-emerging virus that has caused various disease outbreaks in Africa and Asia. The clinical symptoms of CHIKV-infection include fever, skin rash, recurrent joint paint, and myositis. Neuronal implications and death may be resulted from the severe viral infection. Up to date, there are no effective treatments and vaccines against CHIKV-infection. More importantly, little is known about the differential regulation of host proteins upon CHIKV infection, hence deciphering the viral-host cell interactions during viral infection provide critical information on our understanding on the mechanisms of virus infection and its dependency of host proteins for replication. In light of the muscle-related clinical manifestations of myositis resulting from CHIKV-infection, human rhabdomyosarcoma cells, SJCRH30 were utilized in this protein profiling study, in order to decipher the pathogenesis of CHIKV. This study has identified an arrays of host proteins that are differentially regulated upon CHIKV infection including that of the cytoskeletal protein, vimentin that plays significant role in aiding the replication of CHIKV within the host cells through 2DE assay. Immunofluorescence assay further shows that the novel interaction between cytoskeleton structure and CHIKV replication complex by forming an intercalating network around the replication complexes and facilitating various stages of the virus life cycle. This novel finding has inevitably led to a deeper understanding of CHIKV pathogenesis in revealing the importance of host proteins during CHIKV replication, as well as contributing to the development of specific antiviral strategies against this medically important viral pathogen.

The TLR signaling adaptor TRAM interacts with TRAF6 to mediate activation of the inflammatory response by TLR4

TLRs act as sentinels in professional immune cells to detect and initiate the innate immune response to pathogen challenge. TLR4 is a widely expressed TLR, responsible for initiating potent immune responses to LPS. TRAM acts to bridge TLR4 with TRIF, orchestrating the inflammatory response to pathogen challenge. We have identified a putative TRAF6-binding motif in TRAM that could mediate a novel signaling function for TRAM in TLR4 signaling. TRAM and TRAF6 association was confirmed by immunoprecipitation of endogenous, ectopically expressed and recombinant proteins, which was ablated upon mutation of a key Glu residue in TRAM (TRAM E183A). TRAF6 and TRAM were observed colocalizing using confocal microscopy following ectopic expression in cells and the ability of TRAM and TRAM E183A to activate luciferase-linked reporter assays was determined in HEK293 and TRAF6-deficient cells. Importantly, TRAM-deficient macrophages reconstituted with TRAM E183A display significantly reduced inflammatory TNF-α, IL-6, and RANTES protein production compared with WT TRAM. These results demonstrate a novel role for TRAM in TLR4-mediated signaling in regulating inflammatory responses via its interaction with TRAF6, distinct from its role as a bridging adaptor between TLR4 and TRIF.

Sex-specific control of central nervous system autoimmunity by p38 mitogen-activated protein kinase signaling in myeloid cells

OBJECTIVE

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS), characterized by a global increasing incidence driven by relapsing-remitting disease in females. Investigators have described p38 mitogen-activated protein kinase (MAPK) as a key regulator of inflammatory responses in autoimmunity, but its role in the sexual dimorphism in MS or MS models remains unexplored.

METHODS

Toward this end, we used experimental autoimmune encephalomyelitis (EAE), the principal animal model of MS, combined with pharmacologic and genetic inhibition of p38 MAPK activity and transcriptomic analyses.

RESULTS

Pharmacologic inhibition of p38 MAPK selectively ameliorated EAE in female mice. Conditional deletion studies demonstrated that p38α signaling in macrophages/myeloid cells, but not T cells or dendritic cells, mediated this sexual dimorphism, which was dependent on the presence of adult sex hormones. Analysis of CNS inflammatory infiltrates showed that female but not male mice lacking p38α in myeloid cells exhibited reduced immune cell activation compared with controls, whereas peripheral T-cell priming was unaffected in both sexes. Transcriptomic analyses of myeloid cells revealed differences in p38α-controlled transcripts comprising female- and male-specific gene modules, with greater p38α dependence of proinflammatory gene expression in females.

INTERPRETATION

Our findings demonstrate a key role for p38α in myeloid cells in CNS autoimmunity and uncover important molecular mechanisms underlying sex differences in disease pathogenesis. Taken together, our results suggest that the p38 MAPK signaling pathway represents a novel target for much needed disease-modifying therapies for MS.

Sustained stabilization of Interleukin-8 mRNA in human macrophages

The mRNAs of most inflammatory mediators are short-lived due to AU-rich elements (AREs) in their 3'-untranslated regions. AREs ensure a low basal level of expression during homeostasis and a transient nature of expression during the inflammatory response. Here, we report that the mRNA of the pro-inflammatory chemokine IL-8, which contains an archetypal ARE, is unexpectedly constitutively abundant and highly stable in primary human monocytes and macrophages. Using the pre-monocyte-like THP-1 cell line that can differentiate into macrophage-like cells, we show that a low level of unstable IL-8 mRNA in undifferentiated cells (half-life<30 min) becomes constitutively elevated and the mRNA is dramatically stabilized in differentiated THP-1 cells with a half-life of more than 15 h similar to primary monocytes and macrophages. In contrast, the level and stability of TNF-α mRNA also containing an ARE is only slightly affected by differentiation; it remains low and unstable in primary macrophages and differentiated THP-1 cells with an estimated half-life of less than 20 min. This differentiation-dependent stabilization of IL-8 mRNA is p38 MAPK-independent and is probably coupled with reduced protein translation. Reporter assays in THP-1 cells suggest that the ARE alone is not sufficient for the constitutive stabilization in macrophage-like cells and imply an effect of the natural biogenesis of the transcript on the stabilization of the mature form. We present a novel, cell type-dependent sustained stabilization of an ARE-containing mRNA with similarities to situations found in disease.

Expression of p38 MAPK in Acute Lung Injury Induced by LPS in Mice

Objective To investigate the expression and roles of p38 mitogen-activated protein kinase (p38 MAPK) in LPS-induced acute lung injury (ALI) in mice. Methods The ALI mice models were set up by intraperineal injection of lipopolysaccharide (LPS). The expressions of p38 MAPK in lung tissues were detected by immunohistochemistry and Western-blot. Results The positive expressions of p38 MAPK distribute mainly in infiltrative inflammatory cells, epithelial cells and endothelial cells. And the level of expression of phosphated p38 MAPK in ALI group were higher obviously than that in the control group, and it reached a peak after two hours. Conclusion p38 MAPK signaling pathway was triggered by ALI induced by endotoxin.

Sulforaphane pretreatment prevents systemic inflammation and renal injury in response to cardiopulmonary bypass

OBJECTIVES

Systemic inflammatory responses are a major cause of morbidity and mortality in patients undergoing cardiac surgery with cardiopulmonary bypass. However, the underlying molecular mechanisms for systemic inflammation in response to cardiopulmonary bypass are poorly understood.

METHODS

A porcine model was established to study the signaling pathways that promote systemic inflammation in response to cardiac surgery with cardiopulmonary bypass under well-controlled experimental conditions. The influence of sulforaphane, an anti-inflammatory compound derived from green vegetables, on inflammation and injury in response to cardiopulmonary bypass was also studied. Intracellular staining and flow cytometry were performed to measure phosphorylation of p38 mitogen-activated protein kinase and the transcription factor nuclear factor-κB in granulocytes and mononuclear cells.

RESULTS

Surgery with cardiopulmonary bypass for 1 to 2 hours enhanced phosphorylation of p38 (2.5-fold) and nuclear factor-κB (1.6-fold) in circulating mononuclear cells. Cardiopulmonary bypass also modified granulocytes by activating nuclear factor-κB (1.6-fold), whereas p38 was not altered. Histologic analyses revealed that cardiopulmonary bypass promoted acute tubular necrosis. Pretreatment of animals with sulforaphane reduced p38 (90% reduction) and nuclear factor-κB (50% reduction) phosphorylation in leukocytes and protected kidneys from injury.

CONCLUSIONS

Systemic inflammatory responses after cardiopulmonary bypass were associated with activation of p38 and nuclear factor-κB pathways in circulating leukocytes. Inflammatory responses to cardiopulmonary bypass can be reduced by sulforaphane, which reduced leukocyte activation and protected against renal injury.

Comparative amino acid decomposition analysis of potent type I p38α inhibitors

Background and purpose of the study

p38α is a member of mitogen-activated protein kinases (MAPK) considered as a prominent target in development of anti-inflammatory agents. Any abnormality in the phosphorylation process leads to the different human diseases such as cancer, diabetes and inflammatory diseases. Several small molecule p38α inhibitors have been developed up to now. In this regard, structural elucidation of p38 inhibitors needs to be done enabling us in rational lead development strategies.

Methods

Various interactions of three potent inhibitors with p38α active site have been evaluated in terms of binding energies and bond lengths via density function theory and MD simulations.

Results

Our comparative study showed that both ab initio and MD simulation led to the relatively similar results in pharmacophore discrimination of p38α inhibitors.

Conclusion

The results of the present study may find their usefulness in pharmacophore based modification of p38α inhibitors.

Vitamin D enhances glucocorticoid action in human monocytes: involvement of granulocyte-macrophage colony-stimulating factor and mediator complex subunit 14

Vitamin D (VitD) is now recognized for its pleiotrophic roles in regulating immune function. VitD interaction with other steroid receptor superfamily receptors in peripheral blood mononuclear cells is poorly understood. In the current study, we demonstrate that VitD enhanced glucocorticoid (GC) responses in human peripheral blood mononuclear cells because it stimulated GC induction of mitogen-activated protein kinase phosphatase-1 (MKP-1) and enhanced GC inhibition of LPS-induced IL-6. These VitD effects were abolished in purified CD14(+) and CD14(-) cells but were recovered in CD14(+) cells co-cultured with CD14(-) cells separated by tissue culture inserts. GM-CSF, found in culture supernatants from CD14(-) cells, was shown to mediate VitD enhancement of GC-induced MKP-1 production in monocytes via increased production of mediator complex subunit 14 (MED14). Recruitment of VitD receptor and MED14, 4.7 kbp upstream of the human MKP-1 gene transcription start site, enhanced binding of glucocorticoid receptor and histone H4 acetylation at the 4.6-kbp glucocorticoid response element of the MKP-1 promoter in the presence of GM-CSF in U937 cells. Knockdown of MED14 abolished VitD-mediated enhancement of GC-induced MKP-1 production. These data demonstrate VitD-mediated stimulation of GC anti-inflammatory effects in human monocytes and identify a role for GM-CSF and MED14 as mediators of this process.

Molecular and expression characterizations of interleukin-8 gene in large yellow croaker (Larimichthys crocea)

IL-8 plays a crucial role in acute inflammation by recruiting and mediating neutrophils and other cells and in initiating the oxidative burst in neutrophils and inducing wound healing by promoting angiogenesis. In the present study, the full-length cDNA and genome sequence of interleukin-8 (LcIL-8) were cloned from large yellow croaker Larimichthys crocea. The LcIL-8 cDNA sequence was 931 bp, containing a 118-bp 5'-untranslated region (UTR), a 528-bp 3'-UTR and a 285-bp open reading frame (ORF) which encoded 94 amino acids. A putative signal peptide including 20 amino acid residues was found at N-terminal in LcIL-8 protein. And a small cytokine (SCY) domain showing a typical CXC chemokine gene organization was predicted in LcIL-8. The genome sequence of LcIL-8 gene was composed of 1930 nucleotides, including four exons and three introns. Quantitative real-time PCR analysis indicated a broad expression of LcIL-8 in most detected tissues, with the most predominant expression in liver. After injection with LPS, Vibrio parahaemolyticus and poly I:C, LcIL-8 expression levels showed up-regulation in head-kidney and spleen. The peak value was in the spleen with 6 times (at 6 h) greater expression than in the control after LPS injection (p < 0.05). However, LcIL-8 transcripts showed down-regulation in the liver after all the three stimulants injection. Recombinant LcIL-8 mature peptide was produced by Escherichia coli, which enhanced the production of superoxide anion in PCK cells. In addition, 5 single-nucleotide polymorphisms (SNPs) were identified in LcIL-8 gene. The results suggested that LcIL-8 might play an important role in fish's immune response, and the SNPs might be used as potential candidate molecular markers for selection for disease-resistant large yellow croaker.

Glucocorticoid insensitivity as a source of drug targets for respiratory disease

Glucocorticoids (corticosteroids) are effective and clinically useful medicines for repressing inflammation in lung disease; however, the number of respiratory conditions that have been recognized to be refractory or insensitive to glucocorticoids is on the rise--either due to an inherent difference in the glucocorticoid sensitivity as part of the disease process or due to exogenous stressors such as cigarette smoke and other oxidative insults. Independent of causality, the aim of future therapeutic advances to conquer this frontier will no doubt be based on our growing knowledge of molecular mechanisms underlying glucocorticoid insensitivity in respiratory diseases. The current article aims to highlight the key molecular mechanisms responsible for glucocorticoid insensitivity in asthma and COPD. This new knowledge will ultimately allow us to enhance lung health by restoring glucocorticoid responsiveness in respiratory disease. In this way, our increased understanding of corticosteroid insensitivity can be exploited as a source of drug targets for respiratory disease in the future.

Regulation of ARE-mRNA Stability by Cellular Signaling: Implications for Human Cancer

During recent years, it has become clear that regulation of mRNA stability is an important event in the control of gene expression. The stability of a large class of mammalian mRNAs is regulated by AU-rich elements (AREs) located in the mRNA 3' UTRs. mRNAs with AREs are inherently labile but as a response to different cellular cues they can become either stabilized, allowing expression of a given gene, or further destabilized to silence their expression. These tightly regulated mRNAs include many that encode growth factors, proto-oncogenes, cytokines, and cell cycle regulators. Failure to properly regulate their stability can therefore lead to uncontrolled expression of factors associated with cell proliferation and has been implicated in several human cancers. A number of transfactors that recognize AREs and regulate the translation and degradation of ARE-mRNAs have been identified. These transfactors are regulated by signal transduction pathways, which are often misregulated in cancers. This chapter focuses on the function of ARE-binding proteins with an emphasis on their regulation by signaling pathways and the implications for human cancer.

Identification and expression analysis of two Toll-like receptor genes from sea cucumber (Apostichopus japonicus)

Toll-like receptors (TLRs) are a family of type I integral membrane glycoproteins which play pivotal roles in innate immunity. In this study, two TLRs named AjTLR3 and AjToll were cloned from sea cucumber (Apostichopus japonicus). The full-length cDNA sequences of AjTLR3 and AjToll are 3484 bp and 4211 bp, with an open reading frame (ORF) of 2679 bp and 2853 bp, encoding 892 and 950 amino acids, respectively. Both AjTLR3 and AjToll are composed of a leucine-rich repeat (LRR) domain, a transmembrane (TM) domain and an intracellular Toll/interleukin-1 receptor (TIR) domain. Evolution analysis revealed that AjTLR3 and AjToll were clustered with the vertebrate-like TLRs (V-TLRs) and the protostome-like TLRs (P-TLRs), respectively. These two genes were widely expressed in all five tested tissues (body wall, coelomocytes, tube feet, intestine and respiratory tree), but showed different expression patterns. The significantly up-regulated expressions of AjTLR3 and AjToll after peptidoglycan (PGN), lipopolysaccharides (LPS), Zymosan A and polyinosinic-polycytidylic acid (PolyI:C) challenges suggested that they were functionally involved in the immune responses to the Cram-positive bacteria, Gram-negative bacteria, fungi and double-stranded RNA (dsRNA) viruses, respectively.

Impaired cytokine production and decreased TLR2-mediated signaling in mouse infant macrophages

Infants are known to be more susceptible to pathogens. This might be due in part to the impaired function of macrophage. In the present study, we observed that macrophages from infant mice produced decreased levels of TNF-α and IL-6, but increased IL-10 after stimulation with toll-like receptor 2 (TLR2) agonist zymosan. Moreover, zymosan-stimulated activation of mitogen-activated protein kinase (MAPK) p38 and ERK1/2 was significantly reduced in mouse infant macrophages. These effects could be reversed by using MAPK modulators. The findings suggest that the impaired cytokine production and decreased TLR2-mediated signaling in infant macrophages may contribute to the susceptibility of infants to bacterial infection.

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.

Zinc deficiency induces production of the proinflammatory cytokines IL-1β and TNFα in promyeloid cells via epigenetic and redox-dependent mechanisms

The deprivation of zinc, caused by malnutrition or as a consequence of aging or disease, strongly affects immune cell functions, causing higher frequency of infections. Among other effects, an increased production of reactive oxygen species (ROS) and proinflammatory cytokines has been observed in zinc-deficient patients, but the underlying mechanisms were unknown. The aim of the current study was to define mechanisms explaining the increase in proinflammatory cytokine production during zinc deficiency, focusing on the role of epigenetic and redox-mediated mechanisms. Interleukin (IL)-1β and tumor necrosis factor (TNF)α production was increased in HL-60 cells under zinc deficiency. Analyses of the chromatin structure demonstrated that the elevated cytokine production was due to increased accessibilities of IL-1β and TNFα promoters in zinc-deficient cells. Moreover, the level of nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) oxidase-produced ROS was elevated under zinc deficiency, subsequently leading to p38 mitogen-activated protein kinase (MAPK) phosphorylation. The increased activation of p38 MAPK appeared to be necessary for posttranscriptional processes in IL-1β and TNFα synthesis. These data demonstrate that IL-1β and TNFα expression under zinc deficiency is regulated via epigenetic and redox-mediated mechanisms. Assuming an important role of zinc in proinflammatory cytokine regulation, this should encourage research in the use of zinc supplementation for treatment of inflammatory diseases.

Restoration of corticosteroid sensitivity by p38 mitogen activated protein kinase inhibition in peripheral blood mononuclear cells from severe asthma

BACKGROUND

Severe asthma accounts for a small number of asthmatics but represents a disproportionate cost to health care systems. The underlying mechanism in severe asthma remains unknown but several mechanisms are likely to be involved because of a very heterogeneous profile. We investigated the effects of a p38MAPK inhibitor in corticosteroid sensitivity in peripheral blood mononuclear cells (PBMCs) from severe asthmatics and the profile of its responders.

METHODOLOGY/PRINCIPAL FINDINGS

Corticosteroid sensitivity was determined by measuring dexamethasone inhibition of CD3/28 and TNF-α induced IL-8 production in PBMCs by using ELISA. PBMCs from severe asthmatics were relatively less sensitive to dexamethasone (Dex) as compared to those of non-severe asthmatics and healthy volunteers. The IC(50) values of Dex negatively correlated with decreased glucocorticoid receptor (GR) nuclear translocation assessed using immunocytochemistry (r = -0.65; p<0.0005) and with decreased FEV(1) (% predicted) (r = 0.6; p<0.0005). A p38α/β inhibitor (SB203580) restored Dex-sensitivity in a subpopulation of severe asthma that was characterized by a defective GR nuclear translocation, clinically by lower FEV(1) and higher use of oral prednisolone. We also found that SB203580 partially inhibited GR phosphorylation at serine 226, resulting in increased GR nuclear translocation in IL-2/IL-4 treated corticosteroid insensitive U937s.

CONCLUSIONS/SIGNIFICANCE

p38MAPKα/β is involved in defective GR nuclear translocation due to phosphorylation at Ser226 and this will be a useful biomarker to identify responders to p38MAPKα/β inhibitor in the future.