CENTRAL NERVOUS SYSTEM TUBERCULOSIS IMMUNOPATHOLOGY IS DRIVEN BY MATRIX DESTRUCTION WITH MATRIX METALLOPROTEINASES INHIBITION REDUCING INFLAMMATION AND IMPROVING SURVIVAL

Abstract

Intro: Central nervous system tuberculosis (CNS-TB) patients may suffer permanent neurological complications and death despite receiving antituberculous treatment (ATT). Matrix metalloproteinases (MMPs) and neutrophil extracellular traps (NETs) potentially drive tissue destruction in CNS-TB. We aim to determine MMPs, NETs and inflammatory mediators expression in CNS-TB patients and a murine model, and evaluate adjunctive MMP inhibition as host directed therapy. Methods: The cerebrospinal fluid (CSF) of 72 TB meningitis (TBM) and non-TBM patients were analysed for MMPs by luminex array and NETs by quantitative fluorometry and ELISA. Four human CNS-TB tissue sections were stained with hematoxylin and eosin for histopathological observation. C57/BL6 Nos2-/- mice were infected intra-cerebroventricularly with H37Rv Mycobacterium tuberculosis (M.tb) and treated with MMP inhibitors SB-3CT or doxycycline with ATT or ATT alone. Brain homogenates were profiled for MMPs, NETs, inflammatory cytokines and chemokines expression. Histopathological evaluation was performed by a pathologist blinded to the treatment received. Findings: CNS-TB human and murine histology showed similar necrotising granuloma formation, tissue necrosis and inflammation. MMP-9 expression correlated with NETs concentration and gelatinase activity in CSF of TBM patients (r=0.85, p<0.001; r=0.31, p<0.01) and brain homogenates of CNS-TB mice (r=0.70, p<0.0001; r=0.90, p<0.0001). Mtb-infected mice treated with MMP inhibitor doxycycline or SB-3CT plus ATT showed significantly improved survival with decreasing trend in brain concentration of MMPs (MMP-9, -8, -3, -12), inflammatory cytokines (TNF-α, IFN-ɣ) and chemokines (CXCL2, CXCL10, CCL3, CCL7) compared with ATT alone. Furthermore, their decreased expression is significantly associated with improved survival. Discussion: Functionally active gelatinase MMP-9 degrades the brain matrix in CNS-TB patients. Neutrophils release NETs which exacerbates tissue destruction with pro-inflammatory mediators causing overt inflammation. Adjunctive MMP inhibition with doxycycline or SB-3CT together with ATT reduced MMPs and inflammatory mediators, improving CNS-TB murine survival. Conclusion: MMPs and NETs may contribute to CNS-TB immunopathology. MMP inhibition is a potential adjunctive therapy to improve CNS-TB outcomes.