Complex regulation of neutrophil-derived MMP-9 secretion in central nervous system tuberculosis.
BACKGROUND
Central nervous system tuberculosis (CNS-TB) may be fatal even with treatment. Neutrophils are the key mediators of TB immunopathology, and raised CSF matrix metalloproteinase-9 (MMP-9) which correlates to neutrophil count in CNS-TB is associated with neurological deficit and death. The mechanisms by which neutrophils drive TB-associated CNS matrix destruction are not clearly defined.


METHODS
Human brain biopsies with histologically proven CNS-TB were stained for neutrophils, neutrophil elastase, and MMP-9. Neutrophil MMP-9 secretion and gene expression were analyzed using Luminex and real-time PCR. Type IV collagen degradation was evaluated using confocal microscopy and quantitative fluorescent assays. Intracellular signaling pathways were investigated by immunoblotting and chemical inhibitors.


RESULTS
MMP-9-expressing neutrophils were present in tuberculous granulomas in CNS-TB and neutrophil-derived MMP-9 secretion was upregulated by Mycobacterium tuberculosis (M.tb). Concurrent direct stimulation by M.tb and activation via monocyte-dependent networks had an additive effect on neutrophil MMP-9 secretion. Destruction of type IV collagen, a key component of the blood-brain barrier, was inhibited by neutralizing neutrophil MMP-9. Monocyte-neutrophil networks driving MMP-9 secretion in TB were regulated by MAP-kinase and Akt-PI3kinase pathways and the transcription factor NF-kB. TNFα neutralization suppressed MMP-9 secretion to baseline while dexamethasone did not.


CONCLUSIONS
Multiple signaling paths regulate neutrophil-derived MMP-9 secretion, which is increased in CNS-TB. These paths may be better targets for host-directed therapies than steroids currently used in CNS-TB.
Section of Infectious Diseases and Immunity, Hammersmith Campus, Imperial College London, 8th floor Commonwealth Building, Du Cane Road, London, W12 0NN, UK.|Division of Infectious Diseases, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
Catherine W M
CW
Ong
Section of Infectious Diseases and Immunity, Hammersmith Campus, Imperial College London, 8th floor Commonwealth Building, Du Cane Road, London, W12 0NN, UK.
Przemyslaw J
PJ
Pabisiak
Section of Infectious Diseases and Immunity, Hammersmith Campus, Imperial College London, 8th floor Commonwealth Building, Du Cane Road, London, W12 0NN, UK.
Sara
S
Brilha
Department of Histopathology, Hammersmith Campus, Imperial College London, London, UK.
Poonam
P
Singh
Division of Neuroscience and Experimental Psychology, University of Manchester, Manchester, UK.
Federico
F
Roncaroli
Section of Infectious Diseases and Immunity, Hammersmith Campus, Imperial College London, 8th floor Commonwealth Building, Du Cane Road, London, W12 0NN, UK.|NIHR Respiratory Biomedical Research Unit, Faculty of Medicine, University of Southampton, Southampton, UK.
Paul T
PT
Elkington
Section of Infectious Diseases and Immunity, Hammersmith Campus, Imperial College London, 8th floor Commonwealth Building, Du Cane Road, London, W12 0NN, UK. j.friedland@imperial.ac.uk.
Jon S
JS
Friedland
D000906:Antibodies / Q000494:pharmacology; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D024141:Collagen Type IV / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D006801:Humans; D007962:Leukocytes / Q000378:metabolism*; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D009169:Mycobacterium tuberculosis / Q000502:physiology; D016328:NF-kappa B / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D051058:Oncogene Protein v-akt / Q000235:genetics / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D020306:Tuberculosis, Central Nervous System / Q000473:pathology*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D000906:Antibodies; D002867:Chromones; D024141:Collagen Type IV; D004791:Enzyme Inhibitors; D009025:Morpholines; D016328:NF-kappa B; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D009195:Peroxidase; D051058:Oncogene Protein v-akt; D020780:Matrix Metalloproteinase 9
Immunopathology; Matrix metalloproteinase; Neutrophils; Tuberculosis