In an in vitromodel of human tuberculosis, monocyte-microglial networks regulate matrix metalloproteinase-1 and -3 gene expression and secretion via a p38 mitogen activated protein kinase-dependent pathway
© Green et al.; licensee BioMed Central Ltd. 2013
Received: 28 March 2013
Accepted: 10 August 2013
Published: 26 August 2013
Tuberculosis (TB) of the central nervous system (CNS) is characterized by extensive tissue inflammation, driven by molecules that cleave extracellular matrix such as matrix metalloproteinase (MMP)-1 and MMP-3. However, relatively little is known about the regulation of these MMPs in the CNS.
Using a cellular model of CNS TB, we stimulated a human microglial cell line (CHME3) with conditioned medium from Mycobacterium tuberculosis-infected primary human monocytes (CoMTb). MMP-1 and MMP-3 secretion was detected using ELISAs confirmed with casein zymography or western blotting. Key results of a phospho-array profile that detects a wide range of kinase activity were confirmed with phospho-Western blotting. Chemical inhibition (SB203580) of microglial cells allowed investigation of expression and secretion of MMP-1 and MMP-3. Finally we used promoter reporter assays employing full length and MMP-3 promoter deletion constructs. Student’s t-test was used for comparison of continuous variables and multiple intervention experiments were compared by one-way ANOVA with Tukey’s correction for multiple pairwise comparisons.
CoMTb up-regulated microglial MMP-1 and MMP-3 secretion in a dose- and time-dependent manner. The phospho-array profiling showed that the major increase in kinase activity due to CoMTb stimulation was in p38 mitogen activated protein kinase (MAPK), principally the α and γ subunits. p38 phosphorylation was detected at 15 minutes, with a second peak of activity at 120 minutes. High basal extracellular signal-regulated kinase activity was further increased by CoMTb. Secretion and expression of MMP-1 and MMP-3 were both p38 dependent. CoMTb stimulation of full length and MMP-3 promoter deletion constructs demonstrated up-regulation of activity in the wild type but a suppression site between -2183 and -1612 bp.
Monocyte-microglial network-dependent MMP-1 and MMP-3 gene expression and secretion are dependent upon p38 MAPK in tuberculosis. p38 is therefore a potential target for adjuvant therapy in CNS TB.
KeywordsTuberculosis Central nervous system Matrix metalloproteinase Immunopathology Mitogen-activated protein kinase
Tuberculosis (TB) remains a deadly disease responsible for approximately 1.5 million deaths a year, many caused by disseminated disease involving the central nervous system (CNS) . During active disease, infection of monocytic cells by Mycobacterium tuberculosis (M.tb) results in an intense host-driven inflammatory response that contributes not only to pathogen death, but also to local tissue destruction and immunopathology. In CNS TB, this inflammatory reaction is not well-tolerated and is responsible for infarction, hydrocephalus, neuronal damage and death.
Monocytic cell-derived matrix metalloproteinases (MMPs) are central mediators of TB-driven pulmonary tissue destruction due to their ability to degrade fibrillar collagens . Indeed this family of 23 proteases with differing, but overlapping, substrates can degrade all elements of the extracellular matrix at neutral pH, differentiating them from other proteases that might also be induced in inflammatory situations [3, 4]. MMPs perform multiple roles in development, reproduction and the normal immune response, such as facilitating leucocyte recruitment, processing cytokines and chemokines, activating defensins and remodelling matrix . In the CNS, MMPs are known to have a number of substrates, such as dystroglycan, a transmembrane receptor that anchors astrocyte endfeet to the basement membrane via laminin binding . Cleavage of these molecules contributes to blood-brain barrier breakdown. The resident CNS innate immune cell is the microglia, most likely of mesodermal monocyte-lineage origin . We and others have previously shown that microglia secrete high concentrations of MMPs in CNS TB [8–10]. MMP-1, MMP-3, MMP-8 and MMP-9 are found at high concentrations in the cerebral spinal fluid (CSF) of CNS TB patients . In addition, MMP-1, MMP-3 and -9, but not the specific tissue inhibitor of metalloproteinase (TIMP) -1, are present in CNS tuberculomas [9, 12]. Specifically MMP-1 is an interstitial collagenase able to digest aggrecan and collagen at neutral pH, and MMP-3 is a stromelysin with substrates such as fibronectin, laminin and type IV collagen . Finally dexamethasone, a specific and proven adjuvant to anti-tuberculous chemotherapy that improves patient outcomes, specifically suppresses MMPs, but not TIMPs, in CNS TB patients [11, 13].
Intracellular signalling is critical to control of MMP transcription and secretion. We have shown that nuclear factor-κB (NF-κB) and activator protein (AP)-1 pathways are activated both in vitro and in patients with CNS TB . Furthermore, the bacteriostatic TB drug para-aminosalicyclic acid exerts its anti-TB activity in part due to inhibition of the prostaglandin pathway, thereby reducing MMP-1 secretion and tissue destruction . Upstream of these signalling pathways are the mitogen-activated protein kinases (MAPKs). The three main pathways are p38, c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK)-1/2. The extracellular signal-regulated MAPK are involved in cell turnover and phosphorylation of transcription factors and microtubule-associated proteins, whereas the p38 MAP kinase subfamily regulates cell differentiation, apoptosis and cellular response to inflammation. p38 MAPK may be an important point of divergence in the regulation of MMP and TIMP secretion in pulmonary TB . In the CNS, MMP-9 secretion by astrocytes was dependent upon an IL-1β/MAP kinase/AP-1 pathway .
In this study, we tested the hypothesis that MAPK pathways are key factors in the control of microglial MMP gene expression and secretion using a cellular model of CNS TB. We present evidence that the p38 pathway is the principle regulator of MMP secretion in microglia, causing divergent secretion of MMP-1 and MMP-3 and their associated TIMPs.
Chemicals were from Sigma-Aldrich (Gillingham, UK), tissue culture materials from Invitrogen (Paisley, UK) and tissue culture plastic from TPP (Trasadingen, Switzerland) unless otherwise stated. Inhibition experiments were performed with a two-hour pre-incubation of the specific p38 chemical inhibitor SB203580 from Promega (Southampton, UK) at concentrations as shown.
The virulent M.tb strain H73Rv Pasteur was cultured in Middlebrook 7H9 broth (BD Biosciences, Oxford, UK) with 10% OADC enrichment medium, 0.2% glycerol and 0.02% Tween 80 with agitation. M.tb at optical density (OD) 0.6 (Biowave Cell Density Meter; WPA, Cambridge, UK), corresponding to 108 colony forming units/ml (cfu/ml) was used for infection. Endotoxin level was <0.03 ng/ml lipopolysaccharide (LPS) (Amoebocyte lysate assay, Associates of Cape Cod, Falmouth, MA, USA).
Cell culture and M.tbinfection
Monocytes were isolated from healthy blood donors (UK Blood Transfusion Service) by Ficoll-Paque (GE Healthcare, Little Chalfont, UK) density gradient centrifugation and adherence purification . Monocytes were infected with M.tb at a multiplicity of infection of 1. At 24 hours, cell culture medium was collected and 0.2 μm was sterile-filtered (Nalgene, Hereford, UK) to remove infectious particles but not MMPs . Conditioned medium from M.tb-infected monocytes was termed CoMTb and control medium from uninfected monocytes was CoMCont.
Human CHME3 microglial cells (used with permission of Marc Tardieu, Paris, France and kindly provided by Nicola Woodroofe, Sheffield Hallam University, UK) were maintained in DMEM with 10% FCS (Biosera, Ringmer, UK) and 3 mM glutamine. Cells were seeded at 35,000 to 50,000 cells/cm2 for experiments, which were performed in macrophage serum-free medium (MSFM).
RNA extraction, cDNA synthesis and quantitative reverse-transcribed PCR (qRT-PCR)
Microglia were lysed with TRI reagent and total RNA was extracted. cDNA was prepared from 1 ug RNA and reverser transcribed using 2 μl of random primers and 200 units SuperScript III reverse transcriptase (both Invitrogen), according to supplier’s instructions. Quantitative PCR (qPCR) was performed as previously described . The cycle threshold (Ct) at which amplification entered the exponential phase was determined and this number was used to indicate the amount of target RNA in each sample. MMP Cts were normalized to ribosomal 18S mRNA.
We loaded 20 μl of cell culture medium with 5 μl of loading buffer (0.25 M Tris pH 6.8, 50% glycerol, 5% SDS and bromophenol blue crystals) on 12% casein gels (Invitrogen). Gels were run at 125 V for 2.5 hours (buffer 25 mM Tris, 190 mM glycine and 0.1% SDS). After one hour incubation in 2.5% Triton-X, gels were transferred to collagenase buffer (55 mM Tris base, 200 mM NaCl, 5 mM CaCl2 and 0.02% Brij; pH 7.6) for 40 hours at 37°C. Gels were stained with 0.2% Coomassie blue (Pharmacia Biotech, Sweden) for one hour before de-staining in acetic acid/methanol/water (1:3:6), and 5 ng of MMP-1 standard (Merck, Germany) was run on each gel. Gels were analyzed densitometrically by Scion Image Analysis (NIH Image version 1.61, Bethesda, MD, USA) normalized to standard.
Standard MMP-1 western blotting was performed as described . Overnight incubation in 1:1,000 MMP-1 primary antibody (The Binding Site, Birmingham, UK) in 5% milk protein was followed by washing and incubation with 1:2000 peroxidase-conjugate secondary antibody for an hour (The Binding Site). Bands were visualized by chemiluminescence with the ECL Plus system (GE Healthcare) according to manufacturer’s instructions. MMP-3 western blotting was performed using 1:5,000 rabbit anti-MMP-3 primary antibody (Chemicon, Millipore, Watford, UK) in 5% bovine serum albumin and 1:2,000 horseradish peroxidase (HRP)-linked anti-rabbit secondary (Cell Signalling Technology, Danvers, MA, US) in 5% milk protein. For MAPK experiments, cells were lysed using 200 μl of SDS sample buffer (62.5 mM Tris pH 6.8, 2% SDS, 10% glycerol, 50 mM DTT and 0.01% bromophenol blue) and immediately frozen at −80°C. Then, 40 μl aliquots were run on western gels as described and probed with 1:1,000 rabbit primary antibodies to both phosphorylated and unphosphorylated forms of p38 or ERK MAPK. 1:2,000 dilution of anti-rabbit HRP-linked secondary antibody was used (all Cell Signalling Technology).
MMP-1 and MMP-3 concentrations were analyzed by Fluorokine MAP profiling kit according to the manufacturer’s protocol (R&D systems) on the Luminex platform (Biorad, Hemel Hempstead, UK). The minimum level of detection for MMP-1 was 10 pg/ml and 15 pg/ml for MMP-3.
MMP-3, TIMP-1 and -2 ELISAs
MMP-3 and TIMP-1 and TIMP-2 concentrations in cell culture medium were measured by ELISA (R&D Systems) according to the manufacturer’s instructions. The lower limit of detection was 30 pg/ml.
The Proteome Profiler phospho-array (R&D systems) was used to investigate multiple kinase pathways. We stimulated 106 microglia with CoMCont or CoMTb for 30 minutes. The phospho-array was performed according to the manufacturer’s protocol and developed with the ECL system (GE Healthcare). Densitometric analysis of each array was performed using NIH Image version 1.61. The Proteome Profiler kit measured relative MAPK and related serine/threonine kinase phosphorylation status. Six positive controls are incorporated onto the membrane. Mean intensity was calculated for CoMCont and CoMTb. Data are presented as the difference between these mean intensities.
Promoter reporter analysis
Microglial cells were co-transfected with MMP-3 promoter constructs and a control reporter plasmid, constitutively expressing Renilla luciferase, with Fugene HD (Roche). Cells were stimulated after 18 hours, and luciferase activity analyzed 24 hours later by the Dual-Luciferase Reporter Assay System (Promega) on a luminometer (Medical Devices, Wokingham, UK). Renilla luciferase activity was used to normalize firefly luciferase activity to control for transfection efficiency.
Data are presented as means (± SD) of three samples and represent experiments performed in triplicate on at least two occasions, unless otherwise stated. Paired groups were compared with Student’s t-test. Multiple intervention experiments were compared by one-way analysis of variance (ANOVA) and Tukey’s correction for multiple pairwise comparisons with equal variance tested by Levene’s test. P <0.05 was taken as significant. All analysis was done using SPSS software (version 15.0, SPSS corp., Chicago, IL, USA).
Monocyte-microglial networks drive MMP-1 and MMP-3 secretion from human microglia
Phospho-array analysis of CoMTb-stimulated microglia
To investigate phospho-array findings further, kinetic Western blot analysis of CoM-stimulated p38 phosphorylation in microglia was performed over 120 minutes (Figure 2C). Minimal basal phosphorylation was seen. CoMTb stimulated p38 phosphorylation at 15 minutes, which waned by 60 minutes. However, a second peak of phosphorylation was detected at 2 hours. At 30 minutes, basal ERK phosphorylation was detected. Although CoMTb up-regulated ERK phosphorylation was blocked by PD98059 in a dose-dependent manner, the basal phosphorylation made subsequent interpretation of the effect of ERK hard to interpret, and so it was not studied further (Figure 2D).
Regulation of MMP-1 and MMP-3 secretion by p38
The MMP-3 promoter is up-regulated by CoMTb and has a suppression site between −2183 and −1612 bp
In this study, we have demonstrated that MMP-1 and MMP-3 secretion from monocyte-microglial networks are dependent on the p38, MAPK pathway in a cellular model of CNS TB. This control acts, at least in part, at the transcriptional level. We also defined that a key repressor element exists in the MMP-3 promoter upstream of −1612 from the transcriptional start site.
First, we delineated that CoMTb, but not CoMCont, drives dose-dependent MMP-1 and MMP-3 secretion. This effect peaked for MMP-3 at 72 hours, but MMP-1 secretion increased until 96 hours. Next, using phosphor-arrays, we demonstrated that the ERK and AKT pathways were active in CoMCont-stimulated cells. These pathways are responsible for cell turnover, and therefore, basal expression in cell lines is commonly found . Second, although there was increased phosphorylation of these pathways with CoMTb, the p38 pathway, and in particular the p38α and γ subunits, stood out as principle targets of CoMTb-activated signaling. This was confirmed in kinetic studies where biphasic phosphorylation of p38 was observed. Biphasic p38 activation is linked to the apoptotic pathway, which is activated only after the second peak in phosphorylation . No specific subunit analysis was performed in our experiments, because the antibody used recognizes epitopes common to all four p38 subunits. However, M.tb has also been shown to directly drive p38 phosphorylation in microglia. Yang et al. demonstrated that sonicated (therefore dead) M.tb stimulated p38 phosphorylation in a toll-like receptor (TLR)2-dependent manner . In our study, p38α activation was most marked. Conditional knockout of p38α in murine macrophages differentially affects bacterial phagocytosis and LPS-induced TNF-α, but not IL-6, secretion via the attenuation of the transcription factor cAMP response element-binding protein (CREB) but not the NF-κB pathway . There is emerging evidence that p38 inhibition may have a therapeutic role in the treatment of cerebral ischaemia, where it reduces neuronal death and microglial activation suggesting a possible translational application for our data . In addition, we found that MMP-3 was solely p38-dependent, and thus, p38 appears to be a central cellular control point for MMP-1 and MMP-3 secretion in microglial cells.
The high ERK basal phosphorylation up-regulated by CoMTb observed in the MAP kinase array was confirmed by western blotting. However, since in cell lines, high basal ERK activity is driven by the immortalization process, we chose not to study this pathway further. However, ERK activation is known to contribute to the control of MMP secretion in the CNS, macrophages and other cells, suggesting a ubiquitous, rather than specific, cellular role for this MAPK [16, 25, 26]. Specifically, further experiments in primary cells are warranted to confirm these preliminary findings. Gene expression data exactly reflected secretion data although the extent of any post-transcriptional effect on MMP-1 regulated by p38 was not investigated in the present study.
Finally promoter-reporter studies demonstrated CoMTb-specific up-regulation of promoter activity, and also indicated that a repressor element exists in the upstream part of the promoter (−1612 to −2183). The exact repressor element demonstrated to be acting here is as yet undefined. Tantalizingly the 1612 bp construct exactly disrupts a previously reported SIRE binding site, a transcription factor associated with down-regulation of MMP-3 secretion in fibroblasts . In microglial cells, we have previously proven that the observed CoMTb effect involves synergy between TNF-α and IL-1β for MMP-3 but not MMP-1 secretion, supporting the role of this latter cytokine . However, unlike in respiratory epithelial cells and macrophages, we have been unable to demonstrate an additional effect of M. tb-derived antigens on secretion of MMPs or p38 MAPK signalling via TLR2, respectively, in this model system [14, 15].
We have demonstrated that in CNS TB, MMP-1 and MMP-3 secretion from monocyte-microglial networks are critically dependent upon the p38 MAP kinase pathway, and this pathway may warrant further investigation as a therapeutic target in CNS TB.
Analysis of variance
Colony forming units
Conditioned media from control monocytes
Conditioned media from tuberculosis-infected monocytes
Central nervous system
cAMP response element-binding protein
Dulbecco’s modified Eagle’s medium
Enzyme-linked immunosorbent assay
Extracellular signal-regulated mitogen-activated protein kinase
Fetal calf serum
Mitogen-activated protein kinase
Macrophage serum-free medium
Quantitative polymerase chain reaction
Stromelysin IL-1 responsive element
Tissue inhibitor of metalloproteinase
Tumour necrosis factor.
JAG was supported by the Mason Medical Foundation and by a Medical Research Council (UK) Clinical Training Fellowship (G0500385). RM is supported by a Wellcome Trust Clinical Research Training Fellowship. SD was supported by a vacation grant from The Pathology Society, UK. JSF and PTE are grateful for support from the National Institute for Health Research (NIHR) Biomedical Research Centre funding scheme. JSF acknowledges the support of the Imperial College Wellcome Centre for Clinical Tropical Medicine. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
- World Health Organization: Global Tuberculosis Control. 2010, GenevaGoogle Scholar
- Elkington P, Shiomi T, Breen R, Nuttall RK, Ugarte-Gil CA, Walker NF, Saraiva L, Pedersen B, Mauri F, Lipman M, Edwards DR, Robertson BD, D'Armiento J, Friedland JS: MMP-1 drives immunopathology in human tuberculosis and transgenic mice. J Clin Invest. 2011, 121: 1827-1833. 10.1172/JCI45666.PubMed CentralView ArticlePubMedGoogle Scholar
- Yong VW, Power C, Forsyth P, Edwards DR: Metalloproteinases in biology and pathology of the nervous system. Nat Rev Neurosci. 2001, 2: 502-511. 10.1038/35081571.View ArticlePubMedGoogle Scholar
- Parks WC, Mecham RP: Matrix metalloproteinases. 1998, San Diego: Academic PressGoogle Scholar
- Nagase H, Visse R, Murphy G: Structure and function of matrix metalloproteinases and TIMPs. Cardiovasc Res. 2006, 69: 562-573. 10.1016/j.cardiores.2005.12.002.View ArticlePubMedGoogle Scholar
- Agrawal S, Anderson P, Durbeej M, van Rooijen N, Ivars F, Opdenakker G, Sorokin LM: Dystroglycan is selectively cleaved at the parenchymal basement membrane at sites of leukocyte extravasation in experimental autoimmune encephalomyelitis. J Exp Med. 2006, 203: 1007-1019. 10.1084/jem.20051342.PubMed CentralView ArticlePubMedGoogle Scholar
- Prinz M, Mildner A: Microglia in the CNS: immigrants from another world. Glia. 2011, 59: 177-187. 10.1002/glia.21104.View ArticlePubMedGoogle Scholar
- Green JA, Dholakia S, Janczar K, Ong CW, Moores R, Fry J, Elkington PT, Roncaroli F, Friedland JS: Mycobacterium tuberculosis-infected human monocytes down-regulate microglial MMP-2 secretion in CNS tuberculosis via TNFalpha, NFkappaB, p38 and caspase 8 dependent pathways. J Neuroinflammation. 2011, 8: 46-10.1186/1742-2094-8-46.PubMed CentralView ArticlePubMedGoogle Scholar
- Green JA, Elkington PT, Pennington CJ, Roncaroli F, Dholakia S, Moores RC, Bullen A, Porter JC, Agranoff D, Edwards DR, Friedland JS: Mycobacterium tuberculosis upregulates microglial matrix metalloproteinase-1 and −3 expression and secretion via NF-kappaB- and Activator Protein-1-dependent monocyte networks. J Immunol. 2010, 184: 6492-6503. 10.4049/jimmunol.0903811.View ArticlePubMedGoogle Scholar
- Nuttall RK, Silva C, Hader W, Bar-Or A, Patel KD, Edwards DR, Yong VW: Metalloproteinases are enriched in microglia compared with leukocytes and they regulate cytokine levels in activated microglia. Glia. 2007, 55: 516-526. 10.1002/glia.20478.View ArticlePubMedGoogle Scholar
- Green JA, Tran CT, Farrar JJ, Nguyen MT, Nguyen PH, Dinh SX, Ho ND, Ly CV, Tran HT, Friedland JS, Thwaites GE: Dexamethasone, cerebrospinal fluid matrix metalloproteinase concentrations and clinical outcomes in tuberculous meningitis. PLoS One. 2009, 4: e7277-10.1371/journal.pone.0007277.PubMed CentralView ArticlePubMedGoogle Scholar
- Harris JE, Nuttall RK, Elkington PT, Green JA, Horncastle DE, Graeber MB, Edwards DR, Friedland JS: Monocyte-astrocyte networks regulate matrix metalloproteinase gene expression and secretion in central nervous system tuberculosis in vitro and in vivo. J Immunol. 2007, 178: 1199-1207.View ArticlePubMedGoogle Scholar
- Thwaites GE, Nguyen DB, Nguyen HD, Hoang TQ, Do TT, Nguyen TC, Nguyen QH, Nguyen TT, Nguyen NH, Nguyen TN, Nguyen NL, Nguyen HD, Vu NT, Cao HH, Tran TH, Pham PM, Nguyen TD, Stepniewska K, White NJ, Tran TH, Farrar JJ: Dexamethasone for the treatment of tuberculous meningitis in adolescents and adults. N Engl J Med. 2004, 351: 1741-1751. 10.1056/NEJMoa040573.View ArticlePubMedGoogle Scholar
- Rand L, Green JA, Saraiva L, Friedland JS TEP: Matrix metalloproteinase-1 is regulated in tuberculosis by a paraminosalicylic acid-sensitive cascade. J Immunol. 2009, 182: 5865-5872. 10.4049/jimmunol.0801935.View ArticlePubMedGoogle Scholar
- Elkington PT, Green JA, Emerson JE, Lopez-Pascua LD, Boyle JJ, O'Kane CM, Friedland JS: Synergistic up-regulation of epithelial cell matrix metalloproteinase-9 secretion in tuberculosis. Am J Respir Cell Mol Biol. 2007, 37: 431-437. 10.1165/rcmb.2007-0011OC.View ArticlePubMedGoogle Scholar
- Harris JE, Green JA, Elkington PT, Friedland JS: Monocytes infected with Mycobacterium tuberculosis regulate MAP kinase-dependent astrocyte MMP-9 secretion. J Leukoc Biol. 2006, 81: 548-556.View ArticlePubMedGoogle Scholar
- Elkington PT, Emerson JE, Lopez-Pascua LD, O'Kane CM, Horncastle DE, Boyle JJ, Friedland JS: Mycobacterium tuberculosis up-regulates matrix metalloproteinase-1 secretion from human airway epithelial cells via a p38 MAPK switch. J Immunol. 2005, 175: 5333-5340.View ArticlePubMedGoogle Scholar
- Elkington PT, Green JA, Friedland JS: Filter sterilization of highly infectious samples to prevent false negative analysis of matrix metalloproteinase activity. J Immunol Methods. 2006, 309: 115-119. 10.1016/j.jim.2005.11.010.View ArticlePubMedGoogle Scholar
- Elkington PT, Nuttall RK, Boyle JJ, O'Kane CM, Horncastle DE, Edwards DR, Friedland JS: Mycobacterium tuberculosis but not vaccine BCG specifically up-regulates matrix metalloproteinase-1. Am J Respir Crit Care Med. 2005, 172: 1596-1604. 10.1164/rccm.200505-753OC.View ArticlePubMedGoogle Scholar
- Tommasi S, Zheng A, Weninger A, Bates SE, Li XA, Wu X, Hollstein M, Besaratinia A: Mammalian cells acquire epigenetic hallmarks of human cancer during immortalization. Nucleic Acids Res. 2013, 41: 182-195. 10.1093/nar/gks1051.PubMed CentralView ArticlePubMedGoogle Scholar
- Lee HE, Berkowitz P, Jolly PS, Diaz LA, Chua MP, Rubenstein DS: Biphasic activation of p38MAPK suggests that apoptosis is a downstream event in pemphigus acantholysis. J Biol Chem. 2009, 284: 12524-12532. 10.1074/jbc.M808204200.PubMed CentralView ArticlePubMedGoogle Scholar
- Yang CS, Shin DM, Lee HM, Son JW, Lee SJ, Akira S, Gougerot-Pocidalo MA, El-Benna J, Ichijo H, Jo EK: ASK1-p38 MAPK-p47phox activation is essential for inflammatory responses during tuberculosis via TLR2-ROS signalling. Cell Microbiol. 2008, 10: 741-754. 10.1111/j.1462-5822.2007.01081.x.View ArticlePubMedGoogle Scholar
- Kang YJ, Chen J, Otsuka M, Mols J, Ren S, Wang Y, Han J: Macrophage deletion of p38alpha partially impairs lipopolysaccharide-induced cellular activation. J Immunol. 2008, 180: 5075-5082.View ArticlePubMedGoogle Scholar
- Strassburger M, Braun H, Reymann KG: Anti-inflammatory treatment with the p38 mitogen-activated protein kinase inhibitor SB239063 is neuroprotective, decreases the number of activated microglia and facilitates neurogenesis in oxygen-glucose-deprived hippocampal slice cultures. Eur J Pharmacol. 2008, 592: 55-61. 10.1016/j.ejphar.2008.06.099.View ArticlePubMedGoogle Scholar
- Kim JY, Kim WJ, Kim H, Suk K, Lee WH: The Stimulation of CD147 induces MMP-9 expression through ERK and NF-kappaB in macrophages: implication for atherosclerosis. Immune Netw. 2009, 9: 90-97. 10.4110/in.2009.9.3.90.PubMed CentralView ArticlePubMedGoogle Scholar
- Park S, Jung HH, Park YH, Ahn JS, Im YH: ERK/MAPK pathways play critical roles in EGFR ligands-induced MMP1 expression. Biochem Biophys Res Commun. 2011, 407: 680-686. 10.1016/j.bbrc.2011.03.075.View ArticlePubMedGoogle Scholar
- Borghaei RC, Rawlings PL, Javadi M, Woloshin J: NF-kappaB binds to a polymorphic repressor element in the MMP-3 promoter. Biochem Biophys Res Commun. 2004, 316: 182-188. 10.1016/j.bbrc.2004.02.030.View ArticlePubMedGoogle Scholar
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