Protein tyrosine kinase and p38 MAP kinase pathways are involved in stimulation of matrix metalloproteinase-9 by TNF-alpha in human monocytes

The Healing Capability of Clove Flower Extract (CFE) in Streptozotocin-Induced (STZ-Induced) Diabetic Rat Wounds Infected with Multidrug Resistant Bacteria

Treatment of diabetic foot ulcer (DFU) is of great challenge as it is shown to be infected by multidrug resistant bacteria (MDR bacteria). Sixty four bacterial isolates were isolated from DFU cases; antibiotic susceptibility tests were carried out for all of them. One bacterial isolate (number 11) was shown to resist the action of 8 out of 12 antibiotics used and was identified by both a Vitek-2 system and 16S rRNA fingerprints as belonging to Proteus mirabilis, and was designated Proteus mirabilis LC587231 (P. mirabilis). Clove flower extract (CFE) inhibited distinctively the P. mirabilis bacterium obtained. GC-MS spectroscopy showed that this CFE contained nine bioactive compounds. The effect of CFE on wound healing of Type 1 diabetic albino rats (Rattus norvegicus) was studied. The results indicated that topical application of CFE hydrogel improved wound size, wound index, mRNA expression of the wound healing markers (Coli1, MMP9, Fibronectin, PCNA, and TGFβ), growth factor signaling pathways (PPAR-α, PGC1-α, GLP-1, GLPr-1, EGF-β, EGF-βr, VEGF-β, and FGF-β), inflammatory cytokine expression (IL8, TNFα, NFKβ, IL1β, and MCP1), as well as anti-inflammatory cytokines (IL4 & IL10), pro-apoptotic markers (FAS, FAS-L, BAX, BAX/BCL-2, Caspase-3, P53, P38), as well as an antiapoptotic one (BCL2). Furthermore, it improved the wound oxidative state and reduced the wound microbial load, as the cefepime therapy improved the wound healing parameters. Based on the previous notions, it could be concluded that CFE represents a valid antibiotics alternative for DFU therapy since it improves diabetic wound healing and exerts antibacterial activity either in vitro or in vivo.

Tumor Necrosis Factor-alpha utilizes MAPK/NFκB pathways to induce cholesterol-25 hydroxylase for amplifying pro-inflammatory response via 25-hydroxycholesterol-integrin-FAK pathway

Exaggerated inflammatory response results in pathogenesis of various inflammatory diseases. Tumor Necrosis Factor-alpha (TNF) is a multi-functional pro-inflammatory cytokine regulating a wide spectrum of physiological, biological, and cellular processes. TNF induces Focal Adhesion Kinase (FAK) for various activities including induction of pro-inflammatory response. The mechanism of FAK activation by TNF is unknown and the involvement of cell surface integrins in modulating TNF response has not been determined. In the current study, we have identified an oxysterol 25-hydroxycholesterol (25HC) as a soluble extracellular lipid amplifying TNF mediated innate immune pro-inflammatory response. Our results demonstrated that 25HC-integrin-FAK pathway amplifies and optimizes TNF-mediated pro-inflammatory response. 25HC generating enzyme cholesterol 25-hydroxylase (C25H) was induced by TNF via NFκB and MAPK pathways. Specifically, chromatin immunoprecipitation assay identified binding of AP-1 (Activator Protein-1) transcription factor ATF2 (Activating Transcription Factor 2) to the C25H promoter following TNF stimulation. Furthermore, loss of C25H, FAK and α5 integrin expression and inhibition of FAK and α5β1 integrin with inhibitor and blocking antibody, respectively, led to diminished TNF-mediated pro-inflammatory response. Thus, our studies show extracellular 25HC linking TNF pathway with integrin-FAK signaling for optimal pro-inflammatory activity and MAPK/NFκB-C25H-25HC-integrin-FAK signaling network playing an essential role to amplify TNF dependent pro-inflammatory response. Thus, we have identified 25HC as the key factor involved in FAK activation during TNF mediated response and further demonstrated a role of cell surface integrins in positively regulating TNF dependent pro-inflammatory response.

TNF-α promotes human antibody-mediated complement-dependent cytotoxicity of porcine endothelial cells through downregulating P38-mediated Occludin expression

Background

The major limitation of organ transplantation is the shortage of available organs. Xenotransplantation is considered to be an effective way to resolve the problem. Immune rejection is a major hurdle for the successful survival of pig xenografts in primate recipients. Cytokines play important roles in inflammation and many diseases including allotransplantation, however, their roles in xenotransplantation have been less well investigated.

Methods

We assessed the role of several cytokines in xenotransplantation using an in vitro model of human antibody-mediated complement-dependent cytotoxicity (CDC). Porcine aortic endothelial cells (PAECs) and porcine iliac endothelial cells (PIECs) were selected as target cells. The complement regulators (CD46, CD55 and CD59) and junction protein genes were assessed by real-time PCR, flow cytometry, or western-blotting assay. Flow cytometry assay was also used to evaluate C3 and C5b-9 deposition, as well as the extent of human IgM and IgG binding to PIECs. Gene silencing was used to reduce genes expression in PIECs. Gene overexpression was mediated by adenovirus or retrovirus.

Results

Recombinant human TNF-α increased the cytotoxicity of PAECs and PIECs in a human antibody-mediated CDC model. Unexpectedly, we found that the expression of complement regulators (CD46, CD55 and CD59) increased in PIECs exposed to human TNF-α. Human TNF-α did not modify C3 or C5b-9 deposition on PIECs. The extent of human IgM and IgG binding to PIECs was not affected by human TNF-α. Human TNF-α decreased the expression of Occludin in PIECs. Gene silencing and overexpression assay suggested that Occludin was required for human TNF-α-mediated cytotoxicity of PIECs in this model. P38 gene silencing or inhibition of P38 signaling pathway with a specific inhibitor, SB203580, inhibited the reduction of Occludin expression induced by TNF-α, and suppressed TNF-α-augmented cytotoxicity of PIECs.

Conclusion

Our data suggest that human TNF-α increases the cytotoxicity of porcine endothelial cells in a human antibody-mediated CDC model by downregulating P38-dependent Occludin expression. Pharmacologic blockade of TNF-α is likely to increase xenograft survival in pig-to-primate organ xenotransplantation.

Graphical abstract

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0386-7) contains supplementary material, which is available to authorized users.

Ataxia-telangiectasia mutated activation mediates tumor necrosis factor-alpha induced MMP-13 up-regulation and metastasis in lung cancer cells

Despite that ataxia-telangiectasia mutated (ATM) is involved in IL-6 promoted lung cancer chemotherapeutic resistance and metastasis, the exact role of ATM in tumor necrosis factor-alpha (TNF-α) increasing tumor migration is still elusive. In the present study, we demonstrated that TNF-α promoted lung cancer cell migration by up-regulation of matrix metalloproteinase-13 (MMP-13). Notably, by gene silencing or kinase inhibition, we proposed for the first time that ATM is a key up-stream regulator of TNF-α activated ERK/p38-NF-κB pathway. The existence of TNF-α secreted in autocrine or paracrine manner by components of tumor microenvironment highlights the significance of TNF-α in inflammation-associated tumor metastasis. Importantly, in vivo lung cancer metastasis test showed that ATM depletion actually reduce the number of metastatic nodules and cancer nests in lung tissues, verifying the critical role of ATM in metastasis. In conclusion, our findings demonstrate that ATM, which could be activated by lung cancer-associated TNF-α, up-regulate MMP-13 expression and thereby augment tumor metastasis. Therefore, ATM might be a promising target for prevention of inflammation-associated lung cancer metastasis.

Effect of the herbal mixture composed of Aloe Vera, Henna, Adiantum capillus-veneris, and Myrrha on wound healing in streptozotocin-induced diabetic rats

BACKGROUND

Wound healing is often impaired in diabetic animals and humans. Matrix metalloproteases act as pro-inflammatory agents in physiological wound healing pathways by stimulating cytokines including the interleukins, IL6, IL1A and IL1B, and the tumor necrosis factor and transforming growth factor beta1. Botanicals are traditionally used to assist healing of different types of wounds, because they produce fewer side effects. Our specific aim here was to develop a plant-based recipe supporting effective wound healing in diabetic animals.

METHODS

Plant materials from Adiantum capillus-veneris, Commiphora molmol, Aloe Vera, and henna were collected for this study, and oven-dried at 60 °C. The dried leaves and resins were then crumbled into a powder and mixed in equal parts with Vaseline as a preservative. This mixture was used as an ointment on wounds induced in 60 diabetic and non-diabetic rats that were divided into 6 subgroups receiving agent or control treatments. Necrotic tissue surrounding the wound was periodically removed during wound healing. RNA was extracted from the healing region of the wound at days 7, 14 and 21 for cDNA synthesis to monitor changes in Tgfb1, Mmp3, Mmp9, Il6 and Tnf α expression using real-time PCR.

RESULTS

The expression of the Mmp3, the Tnf α, and the Tgfb1 genes from wound tissue were significantly different (p < 0.05) between diabetic and non-diabetic (control) rats treated with the herbal mixture after 14 and 21 days. There was no significant difference (p > 0.05) of the Mmp9 gene expression in diabetic and non-diabetic rats treated only with Vaseline after 7, 14, and 21 days. But, the expression of the Mmp9 gene decreased significantly (p < 0.05) in diabetic rats after 14 days in comparison to non-diabetic rats, when the herbal mixture was added to Vaseline.

CONCLUSIONS

Our study presents an herbal treatment that alters the gene expression signature at wounds induced in the rat model for type I diabetes in a manner consistent with accelerated healing, and demonstrates that this herbal treatment might be effective to treat wounds in diabetic patients.

Ion-Current-Based Temporal Proteomic Profiling of Influenza-A-Virus-Infected Mouse Lungs Revealed Underlying Mechanisms of Altered Integrity of the Lung Microvascular Barrier

Investigation of influenza-A-virus (IAV)-infected lung proteomes will greatly promote our understanding on the virus-host crosstalk. Using a detergent-cocktail extraction and digestion procedure and a reproducible ion-current-based method, we performed the first comprehensive temporal analysis of mouse IAV infection. Mouse lung tissues at three time points post-inoculation were compared with controls (n = 4/group), and >1600 proteins were quantified without missing value in any animal. Significantly changed proteins were identified at 4 days (n = 144), 7 days (n = 695), and 10 days (n = 396) after infection, with low false altered protein rates (1.73-8.39%). Functional annotation revealed several key biological processes involved in the systemic host responses. Intriguingly, decreased levels of several cell junction proteins as well as increased levels of tissue metalloproteinase MMP9 were observed, reflecting the IAV-induced structural breakdown of lung epithelial barrier. Supporting evidence of MMP9 activation came from immunoassays examining the abundance and phosphorylation states of all MAPKs and several relevant molecules. Importantly, IAV-induced MMP gelatinase expression was suggested to be specific to MMP9, and p38 MAPK may contribute predominantly to MMP9 elevation. These findings help to resolve the long-lasting debate regarding the signaling pathways of IAV-induced MMP9 expression and shed light on the molecular mechanisms underlying pulmonary capillary-alveolar leak syndrome that can occur during influenza infection.

A Network Approach to Wound Healing

OBJECTIVE

The wound healing process is well-understood on the cellular and tissue level; however, its complex molecular mechanisms are not yet uncovered in their entirety. Viewing wounds as perturbed molecular networks provides the tools for analyzing and optimizing the healing process. It helps to answer specific questions that lead to better understanding of the complexity of the process. What are the molecular pathways involved in wound healing? How do these pathways interact with each other during the different stages of wound healing? Is it possible to grasp the entire mechanism of regulatory interactions in the healing of a wound?

APPROACH

Networks are structures composed of nodes connected by links. A network describing the state of a cell taking part in the healing process may contain nodes representing genes, proteins, microRNAs, metabolites, and drug molecules. The links connecting nodes represent interactions such as binding, regulation, co-expression, chemical reaction, and others. Both nodes and links can be weighted by numbers related to molecular concentration and the intensity of intermolecular interactions. Proceeding from data and from molecular profiling experiments, different types of networks are built to characterize the stages of the healing process. Network nodes having a higher degree of connectivity and centrality usually play more important roles for the functioning of the system they describe.

RESULTS

We describe here the algorithms and software packages for building, manipulating and analyzing networks proceeding from information available from a literature or database search or directly extracted from experimental gene expression, metabolic, and proteomic data. Network analysis identifies genes/proteins most differentiated during the healing process, and their organization in functional pathways or modules, and their distribution into gene ontology categories of biological processes, molecular functions, and cellular localization. We provide an example of how network analysis can be used to reach better understanding of regulation of key wound healing mediators and microRNAs that regulate them.

INNOVATION

Univariate statistical tests widely used in clinical studies are not enough to improve understanding and optimize the processes of wound healing. Network methods of analysis of patients "omics" data, such as transcriptoms, proteomes, and others can provide a better insight into the healing processes and help in development of better treatment practices. We review several articles that are examples of this emergent approach to the study of wound healing.

CONCLUSION

Network analysis has the potential to considerably contribute to the better understanding of the molecular mechanisms of wound healing and to the discovery of means to control and optimize that process.

Natural haemozoin induces expression and release of human monocyte tissue inhibitor of metalloproteinase-1

Recently matrix metalloproteinase-9 (MMP-9) and its endogenous inhibitor (tissue inhibitor of metalloproteinase-1, TIMP-1) have been implicated in complicated malaria. In vivo, mice with cerebral malaria (CM) display high levels of both MMP-9 and TIMP-1, and in human patients TIMP-1 serum levels directly correlate with disease severity. In vitro, natural haemozoin (nHZ, malarial pigment) enhances monocyte MMP-9 expression and release. The present study analyses the effects of nHZ on TIMP-1 regulation in human adherent monocytes. nHZ induced TIMP-1 mRNA expression and protein release, and promoted TNF-α, IL-1β, and MIP-1α/CCL3 production. Blocking antibodies or recombinant cytokines abrogated or mimicked nHZ effects on TIMP-1, respectively. p38 MAPK and NF-κB inhibitors blocked all nHZ effects on TIMP-1 and pro-inflammatory molecules. Still, total gelatinolytic activity was enhanced by nHZ despite TIMP-1 induction. Collectively, these data indicate that nHZ induces inflammation-mediated expression and release of human monocyte TIMP-1 through p38 MAPK- and NF-κB-dependent mechanisms. However, TIMP-1 induction is not sufficient to counterbalance nHZ-dependent MMP-9 enhancement. Future investigation on proteinase-independent functions of TIMP-1 (i.e. cell survival promotion and growth/differentiation inhibition) is needed to clarify the role of TIMP-1 in malaria pathogenesis.

Involvement of p38 MAPK in haemozoin-dependent MMP-9 enhancement in human monocytes

The lipid moiety of natural haemozoin (nHZ, malarial pigment) was previously shown to enhance expression and release of human monocyte matrix metalloproteinase-9 (MMP-9), and a major role for 15-(S,R)-hydroxy-6,8,11,13-eicosatetraenoic acid (15-HETE), a nHZ lipoperoxidation product, was proposed. Here, the underlying mechanisms were investigated, focusing on the involvement of mitogen-activated protein kinases (MAPKs). Results showed that nHZ promoted either early or late p38 MAPK phosphorylation; however, nHZ did not modify basal phosphorylation/expression ratios of extracellular signal-regulated kinase-1/2 and c-jun N-terminal kinase-1/2. 15-HETE mimicked nHZ effects on p38 MAPK, whereas lipid-free synthetic (s)HZ and delipidized (d)HZ did not. Consistently, both nHZ and 15-HETE also promoted phosphorylation of MAPK-activated protein kinase-2, a known p38 MAPK substrate; such an effect was abolished by SB203580, a synthetic p38 MAPK inhibitor. SB203580 also abrogated nHZ-dependent and 15-HETE-dependent enhancement of MMP-9 mRNA and protein (latent and activated forms) levels in cell lysates and supernatants. Collectively, these data suggest that in human monocytes, nHZ and 15-HETE upregulate MMP-9 expression and secretion through activation of p38 MAPK pathway. The present work provides new evidence on mechanisms underlying MMP-9 deregulation in malaria, which might be helpful to design new specific drugs for adjuvant therapy in complicated malaria.

Clinical significance of expression of fascin and MMP-9 in hilar cholangiocarcinoma

AIM: To detect the expression of fascin and matrix metalloproteinase-9 (MMP-9) in hilar cholangiocarcinoma and to analyze their clinical significance.

METHODS: The expression of fascin and MMP-9 was examined by immunohistochemistry in 56 cases of hilar cholangiocarcinoma and 14 cases of normal tissue of the bile duct.

RESULTS: The positive rates of fascin and MMP-9 expression in hilar cholangiocarcinoma were obviously higher than those in normal tissue of the bile duct (58.9% vs 0%, 73.2% vs 14.3%, both P < 0.05). Both fascin and MMP-9 expression were associated with histological grade, lymph node metastasis, and portal vein invasion (all P < 0.05). In hair cholangiocarcinoma, the expression of fascin was positively correlative with that of MMP-9 (P < 0.05).

CONCLUSION: The expression of fascin and MMP-9 in hilar cholangiocarcinoma plays important roles in tumor progression and metastasis.

Suppression of matrix metalloproteinase-9 expression by andrographolide in human monocytic THP-1 cells via inhibition of NF-κB activation

There is much evidence indicating that human leukemic cells and monocytes/macrophages synthesize, and secrete, several matrix metalloproteinases (MMPs), and participate in the degradation of extracellular matrix components in tissue lesions. In this study, we investigated the effects and mechanisms of andrographolide, extracted from the herb Andrographis paniculata, on human monocytic MMPs expression and activation. Andrographolide (1-50 μM) exhibited concentration-dependent inhibition of MMP-9 activation, induced by either tumor necrosis factor-α (TNF-α), or lipopolysaccharide (LPS), in THP-1cells. In addition, andrographolide did not present an inhibitory effect on MMP-9 enzymatic activity at a concentration of 50 μM. By contrast, enzyme-linked immunosorbent assay (ELISA) showed that andrographolide partially affect TIMP-1 levels. Western blot analysis showed that both TNF-α, and LPS stimulators attenuated MMP-9 protein expression in a concentration-dependent manner. Using reverse transcription polymerase chain reaction (RT-PCR), we found that andrographolide suppressed expression of MMP-9 messenger RNA. Furthermore, we also found that andrographolide could significantly inhibit the degradation of inhibitor-κB-α (IκB-α) induced by TNF-α. We used electrophoretic mobility shift assay and reporter gene detection to show that andrographolide also markedly inhibited NF-κB signaling, anti-translocation and anti-activation. In conclusion, we demonstrate that andrographolide attenuates MMP-9 expression, and its main mechanism might involve the NF-κB signal pathway. These results provide new opportunities for the development of new anti-inflammatory and leukemic therapies.

p38 mitogen-activated protein kinase pathways in asthma and COPD

The mitogen-activated protein kinase (MAPK) family includes the p38 kinases, which consist of highly conserved proline-directed serine-threonine protein kinases that are activated in response to inflammatory signals. Of the four isoforms, p38α is the most abundant in inflammatory cells and has been the most studied through mainly the availability of small molecule inhibitors. The p38 substrates include transcription factors; other protein kinases, which in turn phosphorylate transcription factors; cytoskeletal proteins and translational components; and other enzymes. Both asthma and COPD are characterized by chronic airflow obstruction, airway and lung remodeling, and chronic inflammation. p38 is involved in the inflammatory responses induced by cigarette smoke exposure, endotoxin, and oxidative stress through activation and release of proinflammatory cytokines/chemokines, posttranslational regulation of these genes, and activation of inflammatory cell migration. Inhibition of p38 MAPK prevented allergen-induced pulmonary eosinophilia, mucus hypersecretion, and airway hyperresponsiveness, effects that may partly result from p38 activation on eosinophil apoptosis and on airway smooth muscle cell production of cytokines/chemokines. In addition, p38 regulates the augmented contractile response induced by oxidative stress. The activation of p38 observed in epithelial cells and macrophages also may underlie corticosteroid insensitivity of severe asthma and COPD. Therefore, p38 inhibitors present a potential attractive treatment of these conditions. Second-generation p38 inhibitors have been disappointing in the treatment of rheumatoid arthritis. In two 6-week studies in patients with COPD, the results were encouraging. Side effects such as liver toxicity remain a possibility, and whether the beneficial effects of p38 inhibitors are clinically significant and sustained need to be determined.

Engineered blood vessel networks connect to host vasculature via wrapping-and-tapping anastomosis

Rapid blood perfusion is critical for postimplantation survival of thick, prevascularized bioartificial tissues. Yet the mechanism by which implanted vascular networks inosculate, or anastomose, with the host vasculature has been unknown, making it difficult to develop optimized strategies for facilitating perfusion. Here we show that implanted vascular networks anastomose with host vessels through a previously unidentified process of "wrapping and tapping" between the engrafted endothelial cells (ECs) and the host vasculature. At the host-implant interface, implanted ECs first wrap around nearby host vessels and then cause basement membrane and pericyte reorganization and localized displacement of the underlying host endothelium. In this way, the implanted ECs replace segments of host vessels to divert blood flow to the developing implanted vascular network. The process is facilitated by high levels of matrix metalloproteinase-14 and matrix metalloproteinase-9 expressed by the wrapping ECs. These findings open the door to new strategies for improving perfusion of tissue grafts and may have implications for other physiologic and pathologic processes involving postnatal vasculogenesis.

Matrix Metalloproteinase-9 and Haemozoin: Wedding Rings for Human Host and Plasmodium falciparum Parasite in Complicated Malaria

It is generally accepted that the combination of both Plasmodium falciparum parasite and human host factors is involved in the pathogenesis of complicated severe malaria, including cerebral malaria (CM). Among parasite products, the malarial pigment haemozoin (HZ) has been shown to impair the functions of mononuclear and endothelial cells. Different CM models were associated with enhanced levels of matrix metalloproteinases (MMPs), a family of proteolytic enzymes able to disrupt subendothelial basement membrane and tight junctions and shed, activate, or inactivate cytokines, chemokines, and other MMPs through cleavage from their precursors. Among MMPs, a good candidate for targeted therapy might be MMP-9, whose mRNA and protein expression enhancement as well as direct proenzyme activation by HZ have been recently investigated in a series of studies by our group and others. In the present paper the role of HZ and MMP-9 in complicated malaria, as well as their interactions, will be discussed.

Aminopeptidase-N/CD13 is a potential proapoptotic target in human myeloid tumor cells

The transmembrane metalloprotease aminopeptidase‐N (APN)/CD13 is overexpressed in various solid and hematological malignancies in humans, including acute myeloid leukemia (AML) and is thought to influence tumor progression. Here, we investigated the contribution of APN/CD13 to the regulation of growth and survival processes in AML cells in vitro. Anti‐CD13 monoclonal antibodies MY7 and SJ1D1 (which do not inhibit APN activity) and WM15 (an APN‐blocking antibody) inhibited the growth of the AML cell line U937 and induced apoptosis, as evidenced by cell accumulation in the sub‐G₁ phase, DNA fragmentation, and phosphatidylserine externalization. Isotype‐matched IgG1 and the APN/CD13 enzymatic inhibitors bestatin and 2' ,3‐dinitroflavone‐8‐acetic acid, were ineffective. Internalization of CD13‐MY7 complex into cells was followed by mitochondrial membrane depolarization, Bcl‐2 and Mcl‐1 down‐regulation, Bax up‐regulation, caspase‐9, caspase‐8, and caspase‐3 activation, and cleavage of the caspase substrate PARP‐1. The broad‐spectrum caspase inhibitor Z‐VAD‐fmk and the caspase‐9‐ and caspase‐8‐specific inhibitors significantly attenuated apoptosis. CD13 ligation also induced apoptosis and PARP‐1 cleavage in primary AML blasts, whereas normal blood cells were not affected. Overall, these data provide new evidence that CD13 can serve as a target for inducing caspase‐dependent apoptosis in AML (independently of its APN activity). These findings may have implications for tumor biology and treatment.—Piedfer, M., Dauzonne, D., Tang, R., N'Guyen, J., Billard, C., Bauvois, B. Aminopeptidase‐N/CD13 is a potential proapoptotic target in human myeloid tumor cells. FASEB J. 25, 2831‐2842 (2011). http://www.fasebj.org

Role of the NF-κB transcription pathway in the haemozoin- and 15-HETE-mediated activation of matrix metalloproteinase-9 in human adherent monocytes

Haemozoin (HZ, malarial pigment) is a crystalline ferriprotoporphyrin IX polymer derived from undigested host haemoglobin haem, present in late stages of Plasmodium falciparum-parasitized RBCs and in residual bodies shed after schizogony. It was shown previously that phagocytosed HZ or HZ-containing trophozoites increased monocyte matrix metalloproteinase-9 (MMP-9) activity and enhanced production of MMP-9-related cytokines TNF and IL-1beta. Here we show that in human monocytes the HZ/trophozoite phagocytosis effects and their recapitulation by 15(S,R)-hydroxy-6,8,11,13-eicosatetraenoic acid (15-HETE), a potent lipoperoxidation derivative generated by HZ from arachidonic acid via haem catalysis, were mediated via activation of NF-κB transcription pathway. After phagocytosis of HZ/trophozoites or treatment with 15-HETE, the NF-κB complex migrated to the nuclear fraction while the inhibitory cytosolic IκBalpha protein was phosphorylated and degraded. All HZ/trophozoite/15-HETE effects on MMP-9 activity and TNF/IL-1beta production were abrogated by quercetin, artemisinin and parthenolide, inhibitors of IκBalpha phosphorylation and subsequent degradation, NF-κB nuclear translocation, and NF-κB-p65 binding to DNA respectively. In conclusion, enhanced activation of MMP-9, and release of pro-inflammatory cytokines TNF and IL-1beta, a triad of effects involved in malaria pathogenesis, elicited in human monocytes by trophozoite and HZ phagocytosis and recapitulated by 15-HETE, appear to be causally connected to persisting activation of the NF-κB system.

Granulocyte-macrophage colony-stimulating factor- and tumor necrosis factor alpha-mediated matrix metalloproteinase production by human osteoblasts and monocytes after infection with Brucella abortus

Osteoarticular complications are common in human brucellosis, but the pathogenic mechanisms involved are largely unknown. Since matrix metalloproteinases (MMPs) are involved in joint and bone damage in inflammatory and infectious diseases, we investigated the production of MMPs by human osteoblasts and monocytes, either upon Brucella abortus infection or upon reciprocal stimulation with factors produced by each infected cell type. B. abortus infection of the normal human osteoblastic cell line hFOB 1.19 triggered a significant release of MMP-2, which was mediated in part by granulocyte-macrophage colony-stimulating factor (GM-CSF) acting on these same cells. Supernatants from infected osteoblasts exhibited increased levels of monocyte chemoattractant protein 1 and induced the migration of human monocytes (THP-1 cell line). Infection with B. abortus induced a high MMP-9 secretion in monocytes, which was also induced by heat-killed B. abortus and by the Omp19 lipoprotein from B. abortus. These effects were mediated by Toll-like receptor 2 and by the action of tumor necrosis factor alpha (TNF-α) produced by these same cells. Supernatants from B. abortus-infected monocytes induced MMP-2 secretion in uninfected osteoblasts, and this effect was mediated by TNF-α. Similarly, supernatants from infected osteoblasts induced MMP-9 secretion in uninfected monocytes. This effect was mediated by GM-CSF, which induced TNF-α production by monocytes, which in turn induced MMP-9 in these cells. These results suggest that MMPs could be potentially involved in the tissue damage observed in osteoarticular brucellosis.

Mechanisms of non-opioid analgesics beyond cyclooxygenase enzyme inhibition

Non-opioid analgesics including both selective and non-selective cyclooxygenase (COX) inhibitors and acetaminophen are the most widely used treatments for pain. Inhibition of COX is thought to be largely responsible for both the therapeutic and adverse effects of this class of drugs. Accumulating evidence over the past two decades has demonstrated effects of non-opioids beyond the inhibition of COX and prostaglandin synthesis that might also explain their therapeutic and adverse effects. These include their interaction with endocannabinoids, nitric oxide, monoaminergic, and cholinergic systems. Moreover, the recent development of microarray technology that allows the study of human gene expression suggests multiple pathways that may be related to the analgesic and anti-inflammatory effects of non-opioids. The present review will discuss the multiple actions of non-opioids and their interactions with these systems during inflammation and pain, suggesting that COX inhibition is an incomplete explanation for the actions of non-opioids and proposes the involvement of multiple selective targets for their analgesic, as well as, their adverse effects.

NFAT1 mediates placental growth factor-induced myelomonocytic cell recruitment via the induction of TNF-alpha

Recruitment of bone marrow-derived myelomonocytic cells plays a fundamental role in tumor angiogenesis and metastasis. Placental growth factor (PlGF) is a potent cytokine that can attract myelomonocytic cells to the tumor. However, the underlying mechanism remains obscure. In this study, we demonstrate that tumor-derived PlGF activates NFAT1 via vascular endothelial growth factor receptor 1 in both murine and human myelomonocytic cells. Activation of NFAT1 is crucial for PlGF-induced myelomonocytic cell recruitment as shown by the in vitro transwell migration assay, transendothelial migration assay, and PlGF-overexpressing tumor models in mice, respectively. TNF-alpha is upregulated by PlGF in myelomonocytic cells in an NFAT1-dependent manner, which in turn contributes to PlGF-induced myelomonocytic cell recruitment. Blockade of TNF-alpha expression by RNA interference or neutralization of secreted TNF-alpha with its Ab attenuates PlGF-induced myelomonocytic cell migration and transendothelial migration. Furthermore, the inhibitory effect of NFAT1 RNA interference on PlGF function is rescued by exogenously added TNF-alpha. Taken together, we demonstrate that NFAT1 mediates PlGF-induced myelomonocytic cell recruitment via the induction of TNF-alpha. Our present studies discover a novel role of the NFAT1-TNF-alpha pathway in tumor inflammation, which may provide potential targets to diversify current cancer therapy.

High matrix metalloproteinase production correlates with immune activation and leukocyte migration in leprosy reactional lesions

Gelatinases A and B (matrix metalloproteinase 2 [MMP-2] and MMP-9, respectively) can induce basal membrane breakdown and leukocyte migration, but their role in leprosy skin inflammation remains unclear. In this study, we analyzed clinical specimens from leprosy patients taken from stable, untreated skin lesions and during reactional episodes (reversal reaction [RR] and erythema nodosum leprosum [ENL]). The participation of MMPs in disease was suggested by (i) increased MMP mRNA expression levels in skin biopsy specimens correlating with the expression of gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha), (ii) the detection of the MMP protein and enzymatic activity within the inflammatory infiltrate, (iii) increased MMP levels in patient sera, and (iv) the in vitro induction of MMP-9 by Mycobacterium leprae and/or TNF-alpha. It was observed that IFN-gamma, TNF-alpha, MMP-2, and MMP-9 mRNA levels were higher in tuberculoid than lepromatous lesions. In contrast, interleukin-10 and tissue inhibitor of MMP (TIMP-1) message were not differentially modulated. These data correlated with the detection of the MMP protein evidenced by immunohistochemistry and confocal microscopy. When RR and ENL lesions were analyzed, an increase in TNF-alpha, MMP-2, and MMP-9, but not TIMP-1, mRNA levels was observed together with stronger MMP activity (zymography/in situ zymography). Moreover, following in vitro stimulation of peripheral blood cells, M. leprae induced the expression of MMP-9 (mRNA and protein) in cultured cells. Overall, the present data demonstrate an enhanced MMP/TIMP-1 ratio in the inflammatory states of leprosy and point to potential mechanisms for tissue damage. These results pave the way toward the application of new therapeutic interventions for leprosy reactions.

CCR7-specific migration to CCL19 and CCL21 is induced by PGE(2) stimulation in human monocytes: Involvement of EP(2)/EP(4) receptors activation

The recent demonstration that newly recruited monocytes do not die at the site of inflammation, but migrate to draining lymph nodes, raises the question on the mechanism involved in this process. In this study, we demonstrate for the first time that prostaglandin E(2) (PGE(2)) regulates the expression and the activity of CCR7 in human blood-isolated monocytes as well as in the MONO-MAC-1 cell lineage. PGE(2) induces intracellular cAMP formation through engagement of the E-prostanoid 2/E-prostanoid 4 (EP(2)/EP(4)) receptors present on monocytes. Migration to chemokines CCL19 and CCL21 in the PGE(2)-stimulated monocytes is mediated through the augmentation of cAMP concentration and furthermore, the cAMP/PKA pathway appears to act as the major inducer of CCR7 transcription in MONO-MAC-1. While p38 MAPK was induced by PGE(2), we observed that PGE(2) can downregulate p42/p44 MAPK phosphorylation. At the transcription level, inhibition of p38 MAPK inhibits CCR7 mRNA expression. Finally, we demonstrated that transcription factors CREB-1 and C/EBPalpha and C/EBPbeta are translocated to the nucleus following PGE(2) stimulation and bind the potent CCR7 promoter region. Our findings may have important implication for HIV-1 migration to the lymph nodes since macrophages and monocytes, particularly CD16 positive subset, are susceptible to HIV-1 infection.

Endurance exercise activates matrix metalloproteinases in human skeletal muscle

In the present study, the effect of exercise training on the expression and activity of matrix metalloproteinases (MMPs) in the human skeletal muscle was investigated. Ten subjects exercised one leg for 45 min with restricted blood flow and then exercised the other leg at the same absolute workload with unrestricted blood flow. The exercises were conducted four times per week for 5 wk. Biopsies were taken from the vastus lateralis muscles of both legs at rest before the training period, after 10 days and 5 wk of training, and 2 h after the first exercise bout for analysis of MMP and tissue inhibitor of metalloproteinase-1 (TIMP-1) mRNA, enzyme activity, and protein expression. Levels of MMP-2, MMP-14, and TIMP-1 mRNA in muscle tissue increased after 10 days of training regardless of blood flow condition. MMP-2 mRNA level in laser-dissected myofibers and MMP-2 activity in whole muscle increased with training. The level of MMP-9 mRNA and activity increased after the first bout of exercise. Although MMP-9 mRNA levels appeared to be very low, the activity of MMP-9 after a single bout of exercise was similar to that of MMP-2 after 10 days of exercise. MMP-2 and MMP-9 protein was both present throughout the extracellular matrix of the muscle, both around fibers and capillaries, but MMP-2 was also present within the skeletal muscle fibers. These results show that MMPs are activated in skeletal muscle in nonpathological conditions such as voluntary exercise. The expression and time pattern indicate differences between the MMPs in regards of production sites as well as in the regulating mechanism.

Reduced limb length and worsened osteoarthritis in adult mice after genetic inhibition of p38 MAP kinase activity in cartilage

OBJECTIVE

MAP kinase p38 is part of an intracellular signaling pathway activated by environmental stress and inflammatory factors. Since in vitro studies show that inhibiting p38 activity leads to a reduction in the release of degenerative metalloproteinase from chondrocytes, we speculated that inactivation of p38 in vivo may be chondroprotective. To test this hypothesis, we examined the morphology of adult mice that express a dominant-negative (DN) p38 MAPK transgene in a cartilage-specific manner.

METHODS

The in vivo effects of the genetic inhibition of p38 MAPK activity in cartilage were investigated in 1-year-old heterozygous DN p38-transgenic mice (n = 10) using morphologic measurements, microfocal computed tomography scanning, biomechanical testing, and histologic analysis. Results were compared with those in wild-type (WT) littermates (n = 9).

RESULTS

Adult DN p38 MAPK+/- -transgenic mice exhibited 50% p38 MAPK activity in articular chondrocytes as compared with WT mice. They were significantly shorter in overall body length as well as in the femur and tibia lengths. There were no differences in bone material or mechanical properties between the transgenic and WT mice. Surprisingly, the transgenic mice had higher grades of osteoarthritis of the knee joint.

CONCLUSION

Genetic inhibition of p38 MAPK activity in cartilage results in shortened limb length and defects in the articular cartilage of the knee joints of adult mice. Our findings demonstrate that chronic life-long reduction of p38 MAPK activity may be harmful to joint health and suggest that the timing of p38 inhibition for chondroprotection in vivo is an important variable that warrants further investigation.

Therapeutic potential of inhaled p38 mitogen-activated protein kinase inhibitors for inflammatory pulmonary diseases

BACKGROUND

Over the past two decades, p38 MAPK (mitogen-activated protein kinase) has been the subject of intense multidisciplinary research. p38 MAPK inhibitors have been shown to be efficacious in several disease models, including rheumatoid arthritis, psoriasis, Crohn's disease, and stroke. Recent studies support a role for p38 MAPK in the development, maintenance, and/or exacerbation of a number of pulmonary diseases, such as asthma, cystic fibrosis, idiopathic pulmonary fibrosis, and chronic obstructive pulmonary disease (COPD).

OBJECTIVE

Many previous attempts to develop p38 MAPK inhibitors have failed as a result of unacceptable safety profiles. These toxicities have been varied and are believed to derive from different off-target effects.

METHOD

The above concerns can be overcome by delivering the compound locally to minimize whole-body burden, resulting in low exposure to the gastrointestinal, liver, and CNS. This review discusses the role of p38 MAPK in various inflammatory diseases, followed by the toxicity concerns associated with p38 MAPK inhibition. It also highlights the possible beneficial effect of delivering drugs via the inhalation route.

CONCLUSION

We present proof-of-principle confirming the therapeutic potential of inhaled p38 inhibitors for asthma and other inflammatory pulmonary diseases.

Type I collagen induces tissue factor expression and matrix metalloproteinase 9 production in human primary monocytes through a redox-sensitive pathway

BACKGROUND

Tissue factor (TF), the main trigger of coagulation cascade, is a major component of the atherosclerotic plaque. Matrix metalloproteinases (MMPs) are recognized as key mediators of extracellular matrix remodeling during inflammation. It was recently emphasized that both TF and MMP-9 were overexpressed in atherosclerotic plaques, suggesting a role of both molecules in plaque instability and thrombogenicity.

OBJECTIVE

The present study was designed to determine whether human monocytes could co-express TF and MMP-9 when the cells interact with type I collagen, a major component of the extracellular matrix and atherosclerotic plaque.

METHODS

Human monocytes were isolated by elutriation and incubated in collagen I-coated plates. Tissue factor and MMP-9 expression were examined using real-time reverse transcription-polymerase chain reaction, flow cytometry, western blot and zymography. The activation of nuclear factor-kappa B (NF-kappaB) and the role of reactive oxygen species (ROS) in TF and MMP-9 production was studied using gel shift experiments, antioxidants pyrrolidine dithiocarbamate (PDTC) and N-acetyl-cysteine (NAC), and apocynin (a specific inhibitor of the NADPH oxidase).

RESULTS

Type I collagen induced TF expression and increased MMP-9 production. In addition, the pro-inflammatory tumor necrosis factor-alpha (TNF-alpha), produced in response to collagen I, increased MMP-9 production. PDTC and NAC inhibited NF-kappaB activation during monocyte interaction with collagen I. Finally, both antioxidants and apocynin decreased the expression of TF, TNF-alpha, and MMP-9.

CONCLUSIONS

These results indicate a new mechanism in the monocyte expression of TF and MMP-9 in response to collagen I involving a ROS-dependent pathway linked to the activation of the NADPH oxidase.

Inhibition of monocyte chemoattractant protein-1 ameliorates rat adjuvant-induced arthritis

Chemokines, including RANTES/CCL5 and MCP-1/CCL2, are highly expressed in the joints of patients with rheumatoid arthritis, and they promote leukocyte migration into the synovial tissue. This study was conducted to determine whether the inhibition of RANTES and MCP-1 therapeutically was capable of ameliorating rat of adjuvant-induced arthritis (AIA). Postonset treatment of AIA using a novel inhibitor for endogenous MCP-1 (P8A-MCP-1) improved clinical signs of arthritis and histological scores measuring joint destruction, synovial lining, macrophage infiltration, and bone erosion. Using immunohistochemistry, ELISA, real-time RT-PCR, and Western blot analysis, we defined joint inflammation, bony erosion, monocyte migration, proinflammatory cytokines, and bone markers, and p-p38 levels were reduced in rat AIA treated with P8A-MCP-1. In contrast, neither the dominant-negative inhibitor for endogenous RANTES (44AANA47-RANTES) nor the CCR1/CCR5 receptor antagonist, methionylated-RANTES, had an effect on clinical signs of arthritis when administered after disease onset. Additionally, therapy with the combination of 44AANA47-RANTES plus P8A-MCP-1 did not ameliorate AIA beyond the effect observed using P8A-MCP-1 alone. Treatment with P8A-MCP-1 reduced joint TNF-alpha, IL-1beta, and vascular endothelial growth factor levels. P8A-MCP-1 also decreased p38 MAPK activation in the joint. Our results indicate that inhibition of MCP-1 with P8A-MCP-1 after the onset of clinically detectable disease ameliorates AIA and decreases macrophage accumulation, cytokine expression, and p38 MAPK activation within the joint.

Regulation of neutral sphingomyelinase-2 (nSMase2) by tumor necrosis factor-alpha involves protein kinase C-delta in lung epithelial cells

Neutral sphingomyelinases (N-SMases) are major candidates for stress-induced ceramide production, but there is still limited knowledge of the regulatory mechanisms of the cloned N-SMase enzyme-nSMase2. We have reported that p38 mitogen-activated protein kinase (MAPK) was upstream of nSMase2 in tumor necrosis-alpha (TNF-alpha)-stimulated A549 cells ( J Biol Chem 282: 1384-1396, 2007 ). Here, we report a role for protein kinase C (PKC) in mediating TNF-induced translocation of nSMase2 from the Golgi to the plasma membrane (PM). Pharmacological inhibition of PKCs prevented TNF-stimulated nSMase2 translocation to the PM in A549 cells. Using phorbol 12-myristate 13-acetate (PMA) as a tool to dissect PKC responses, we found that PMA induced nSMase2 translocation to the PM in a time- and dose-dependent manner. Pharmacological inhibitors and specific siRNA implicated the novel PKCs, specifically PKC-delta, in both TNF and PMA-stimulated nSMase2 translocation. However, PMA did not increase in vitro N-SMase activity and PKC-delta did not regulate TNF-induced N-SMase activity. Furthermore, PKC-delta and nSMase2 did not coimmunoprecipitate, suggesting that other signaling proteins may be involved. PMA-stimulated nSMase2 translocation was independent of p38 MAPK, and neither PKC inhibitors nor small interfering RNA had significant effects on TNF-stimulated p38 MAPK activation, indicating that PKC-delta does not act through p38 MAPK in regulating nSMase2. Finally, down-regulation of PKC-delta inhibited induction of vascular cell and intercellular adhesion molecules, previously identified as downstream of nSMase2 in A549 cells. Taken together, these data implicate PKC-delta as a regulator of nSMase2 and, for the first time, identify nSMase2 as a point of cross-talk between the PKC and sphingolipid pathways.

Desflurane preconditioning inhibits endothelial nuclear factor-kappa-B activation by targeting the proximal end of tumor necrosis factor-alpha signaling

BACKGROUND

Volatile anesthetics interfere with inflammatory cytokine production and expression of adhesion molecules which are critical for ischemia reperfusion induced injury. Nuclear factor (NF)-kappaB has been reported to be suppressed in this process, but the detailed molecular mechanism is still unclear.

METHODS

In this study, ECV304 (a human umbilical vein endothelial cell line) was preconditioned with 30 min desflurane (1 minimal alveolar concentration), after 15 min washout, 30 min anoxia, and 60 min reoxygenation was performed. ECV304 was finally stimulated with tumor necrosis factor (TNF)-alpha (10 ng/mL). Control groups, which were not preconditioned and/or not stimulated, were also included in the protocol. IkappaB-alpha, phospho-IkappaB-alpha, phospho-IkappaB kinase (IKKalpha)/IKKbeta, and phospho-p38 were detected by Western blotting. The nuclear NF-kappaB p65 subunit was measured by subcellular fractionation and Western blotting. The surface expression of TNF-R1 was measured by flow cytometry. Receptor-associated signaling adaptors, e.g., TNF receptor-associated factor 2 (TRAF2) and IKK-alpha, were evaluated by immunoprecipitation by TNF-R1 antibody and subsequent Western blotting.

RESULTS

Desflurane preconditioning inhibits IkappaB-alpha phosphorylation, degradation, and p65 nuclear localization. Desflurane also affects p38 phosphorylation, which is needed for optimal inflammatory response. The phosphorylation of IKKalpha/IKKbeta was suppressed by preconditioning while the surface abundance of TNF-R1 was not affected. The association of TRAF2 and IKK-alpha with TNF-R1 was compromised by desflurane.

CONCLUSIONS

Our results suggest that the molecular target of desflurane in the NF-kappaB pathway is upstream of IKK activation. The abundance of TNF-R1 on the cell membrane is not affected by anesthetic preconditioning. We suggest that desflurane preconditioning targets the proximal end of TNF-alpha signaling.

Multiple effects of acetaminophen and p38 inhibitors: towards pathway toxicology

The majority of drug-related toxicities are idiosyncratic, with little pathophysiological insight and mechanistic understanding. Pathway toxicology is an emerging field of toxicology in the post-genomic era that studies the molecular interactions between toxicants and biological pathways as a way to bridge this knowledge gap. Using two case studies--acetaminophen and p38 MAPK inhibitors--this review illustrates how a pathway-based perspective has advanced our understanding of compound and target-based toxicities. The advancement of pathway toxicology will be dependent on integrated applications of techniques from basic sciences and a fundamental understanding of the interdependence of multiple biological pathways in living organisms.

Activation of human monocytes after infection by human coronavirus 229E

Human coronaviruses (HCoV) are recognized respiratory pathogens that may be involved in other pathologies such as central nervous system (CNS) diseases. To investigate whether leukocytes could participate in respiratory pathologies and serve as vector for viral spread towards other tissues, the susceptibility of human leukocytic cell lines and peripheral blood mononuclear cells (PBMC) to HCoV-229E and HCoV-OC43 infection was investigated. Human primary monocytes/macrophages were susceptible to HCoV-229E infection, but strongly restricted HCoV-OC43 replication. Moreover, productive HCoV-229E infection of primary monocytes and of the THP-1 monocytic cell line led to their activation, as indicated by the production of pro-inflammatory mediators, including TNF-alpha, CCL5, CXCL10 and CXCL11 and MMP-9. Moreover, an in vitro chemotaxis assay showed that motility towards chemokines of THP-1 cells and primary monocytes was increased following an acute or persistent HCoV-229E infection. Taken together, these results suggest that infected monocytes could serve as a reservoir for HCoV-229E, become activated, participate in the exacerbation of pulmonary pathologies, as well as serve as potential vectors for viral dissemination to host tissues, where it could be associated with other pathologies.

Cathepsins B, K, and L are regulated by a defined collagen type II peptide via activation of classical protein kinase C and p38 MAP kinase in articular chondrocytes

Degradation of the extracellular matrix (ECM) is a prominent feature in osteoarthritis (OA), which is mainly because of the imbalance between anabolic and catabolic processes in chondrocytes resulting in cartilage and bone destruction. Various proteases act in concert to degrade matrix components, e.g. type II collagen, MMPs, ADAMTS, and cathepsins. Protease-generated collagen fragments may foster the destructive process. However, the signaling pathways associated with the action of collagen fragments on chondrocytes have not been clearly defined. The present data demonstrate that the N-terminal telopeptide of collagen type II enhances expression of cathepsins B, K, and L in articular chondrocytes at mRNA, protein, and activity levels, mediated at least in part through extracellular calcium. We also demonstrate that the induction is associated with the activation of protein kinase C and p38 MAP kinase.

Metalloproteinases and their inhibitors: regulators of wound healing

Wound healing is a dynamic process that involves a coordinated response of many cell types representing distinct tissue compartments and is fundamentally similar among tissue types. Among the many gene products that are essential for restoration of normal tissue architecture, several members of the matrix metalloproteinase (MMP) family function as positive and, at times, negative regulators of repair processes. MMPs were initially thought to only function in the resolution phase of wound healing, particularly during scar resorption; however, recent evidence suggests that they also influence other wound-healing responses, such as inflammation and re-epithelialization. In this review, we discuss what is currently known about the function of MMPs in wound healing and will provide suggestions for future research directions.

Involvement of p38MAPK on the antinociceptive action of myricitrin in mice

Previous studies from our group investigated the analgesic and anti-inflammatory properties of the flavonoid myricitrin. Here, we demonstrated the role of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha) and mitogen-activated protein kinases (MAPKs) on the antinociceptive action of myricitrin. The nociceptive response was evaluated by monitoring biting behaviour following intratecal (i.t.) administration of IL-1beta and TNF-alpha in mice. Western blot analyses of total and phosphorylated MAPKs: p38(MAPK), extracellular-signal regulated kinase (ERK1/2) and c-Jun amino-terminal kinases (JNK1/2) from the spinal cord of mice injected with cytokines were measured. Myricitrin (0.03-30mg/kg) or vehicle (control) was administered 30 min beforehand by intraperitoneal (i.p.) injection. Myricitrin pre-treatment prevented cytokine-induced biting behaviour. The calculated ID(50) of myricitrin were 6.8 (4.6-9.0) and 2.6 (0.3-4.9) mg/kg and maximal inhibition of 83+/-9 and 100+/-0% for IL-1beta and TNF-alpha, respectively. Intrathecal injection of IL-1beta and TNF-alpha significantly increased p38(MAPK) phosphorylation and this was inhibited by myricitrin treatment. Cytokines administration did not alter ERK1/2 and JNK1/2 phosphorylation. Myricitrin prevented cytokine-induced biting behaviour and inhibited p38(MAPK) phosphorylation in response to cytokines stimulation. Taken together, it suggests that the mechanism for antinociceptive action of myricitrin in response to cytokines may involve a blockage on p38(MAPK) pathway. This finding could explain, at least in part, the antinociceptive action of this flavonoid in process like neuropathic and inflammatory chronic pain.

p38 MAP-kinases pathway regulation, function and role in human diseases

Mammalian p38 mitogen-activated protein kinases (MAPKs) are activated by a wide range of cellular stresses as well as in response to inflammatory cytokines. There are four members of the p38MAPK family (p38alpha, p38beta, p38gamma and p38delta) which are about 60% identical in their amino acid sequence but differ in their expression patterns, substrate specificities and sensitivities to chemical inhibitors such as SB203580. A large body of evidences indicates that p38MAPK activity is critical for normal immune and inflammatory response. The p38MAPK pathway is a key regulator of pro-inflammatory cytokines biosynthesis at the transcriptional and translational levels, which makes different components of this pathway potential targets for the treatment of autoimmune and inflammatory diseases. However, recent studies have shed light on the broad effect of p38MAPK activation in the control of many other aspects of the physiology of the cell, such as control of cell cycle or cytoskeleton remodelling. Here we focus on these emergent roles of p38MAPKs and their implication in different pathologies.