Regulation of matrix metalloproteinase-1, -3, and -9 in Mycobacterium tuberculosis-dependent respiratory networks by the rapamycin-sensitive PI3K/p70S6K cascade

This study was designed to investigate the role of the phosphatidyl inositol 3-kinase (PI3K)/AKT/p70S6K signaling path on regulation of primary normal human bronchial epithelial cell-derived matrix metalloproteinase (MMP)-1, -3, and -9 expression in tuberculosis (TB). These MMPs are key in pathological extracellular matrix degradation in TB. Normal human bronchial epithelials were stimulated with conditioned medium from monocytes infected with virulent TB (CoMTb) and components of the PI3K/AKT signaling pathway blocked using specific chemical inhibitors and siRNA. MMP gene expression was measured by RT-PCR and secretion by ELISA, luminex, or zymography. Phospho-p70 S6K was detected by Western blot analysis and activity blocked by rapamycin. Chemical blockade of the proximal catalytic PI3K p110 subunit augmented MMP-1 and MMP-9 in a dose-dependent manner (all P<0.001) but suppressed MMP-3 (P<0.01). Targeted siRNA studies identified the p110? isoform as key causing 5-fold increase in TB network-dependent MMP-1 secretion to 4900 ± 1100 pg/ml. Specific inhibition of the AKT node suppressed all 3 MMPs. Phospho-p70S6K was identified in the cellular model, and rapamycin, a p70S6K inhibitor, inhibited MMP-1 (P<0.001) and MMP-3 (P<0.01) but not MMP-9. Controls were epithelial cells that were unstimulated or exposed to conditioned medium from monocytes not exposed to TB. In summary, blockade of the proximal PI3K catalytic subunit increases MMP-1 and MMP-9, whereas rapamycin decreased both MMP-1 and MMP-3. The regulation of the PI3K path in TB is complex, MMP specific, and a potential immunotherapeutic target in diseases characterized by tissue destruction.—Singh, S., Saraiva, L., Elkington, P. T. G., Friedland, J. S. Regulation of matrix metalloproteinase-1, -3, and -9 in Mycobacterium tuberculosis-dependent respiratory networks by the rapamycin-sensitive PI 3-kinase/p70S6K cascad

Tuberculosis and TNF-inhibitors: history of exposure should outweigh investigations

A 39-year-old Indian man was diagnosed with ulcerative colitis on colonic biopsy and started on mesalazine, prednisolone and azathioprine. However, the colitis remained active and required antitumour necrosis factor (TNF) treatment with infliximab. Prior to starting infliximab, his chest X-ray was normal and QuantiFERON interferon ? release assay for tuberculosis (TB) was negative. However, his wife had been treated for pulmonary TB 11 years previously when they were cohabiting. On attending for his third dose of infliximab, he was feverish and tachycardic, and was admitted for investigation. Chest X-ray on admission showed changes consistent with miliary TB, and thoracic CT confirmed extensive miliary nodules with supraclavicular and mediastinal lymphadenopathy. Abdominal CT showed multiple mesenteric lymph nodes. Subsequent bronchoalveolar lavage, neck lymph node aspirate and colonic biopsies all cultured Mycobacterium tuberculosis. In retrospect, a clear history of close household TB exposure should have precipitated consideration of TB chemoprophylaxis prior to anti-TNF treatment

Extremes of age are associated with indeterminate QuantiFERON-TB Gold assay results

Results from 3263 QuantiFERON-TB Gold-in-Tube (QFT-GIT) assays were analyzed to determine the impact of age on test performance. The proportion of indeterminate results was significantly higher in pediatric and elderly (9.1% and 7.4%, respectively), than in adult patients (2.6%; chi-quare p&lt;0.0001). A detailed analysis of indeterminate QFT-GIT results is presented.<br/

Matrix metalloproteinases and tissue damage in HIV-tuberculosis immune reconstitution inflammatory syndrome

The HIV-TB-associated immune reconstitution inflammatory syndrome (TB-IRIS) can complicate combined treatments for HIV-1 and TB. Little is known about tissue damage in TB-IRIS. Matrix metalloproteinases (MMPs) degrade components of the extracellular matrix and consequently may play a role in such immunopathology. Here we investigated the involvement of MMPs in TB-IRIS. We determined MMP transcript abundance and secreted protein in Mycobacterium tuberculosis stimulated PBMCs from 22 TB-IRIS patients and 22 non-IRIS controls. We also measured MMP protein levels in corresponding serum and the effect of prednisone — which reduces the duration of symptoms in IRIS patients — or placebo treatment on MMP transcript and circulating MMP protein levels. PBMCs from TB-IRIS had increased MMP-1, -3, -7, and -10 transcript levels when compared with those of controls at either 6 or 24 h. Similarly, MMP-1, -3, -7, and -10 protein secretion in stimulated cultures was higher in TB-IRIS than in controls. Serum MMP-7 concentration was elevated in TB-IRIS and 2 weeks of corticosteroid therapy decreased this level, although not significantly. TB-IRIS is associated with a distinct pattern of MMP gene and protein activation. Modulation of dysregulated MMP activity may represent a novel therapeutic approach to alleviate TB-IRIS in HIV-TB patients undergoing treatmen

HIV-1 infection of macrophages dysregulates innate immune responses to Mycobacterium tuberculosis by inhibition of interleukin 10

Human immunodeficiency virus (HIV)–1 and Mycobacterium tuberculosis (Mtb) both target macrophages, which are key cells in inflammatory responses and their resolution. Therefore, we tested the hypothesis that HIV-1 may modulate macrophage responses to coinfection with Mtb. HIV-1 caused exaggerated proinflammatory responses to Mtb that supported enhanced virus replication, and were associated with deficient stimulus-specific induction of anti-inflammatory interleukin (IL)–10 and attenuation of mitogen-activated kinase signaling downstream of Toll-like receptor 2 and dectin-1 stimulation. Our in vitro data were mirrored by lower IL-10 and higher proinflammatory IL-1? in airway samples from HIV-1–infected patients with pulmonary tuberculosis compared with those with non-tuberculous respiratory tract infections. Single-round infection of macrophages with HIV-1 was sufficient to attenuate IL-10 responses, and antiretroviral treatment of replicative virus did not affect this phenotype. We propose that deficient homeostatic IL-10 responses may contribute to the immunopathogenesis of active tuberculosis and propagation of virus infection in HIV-1/Mtb coinfection. <br/

Mycobacterium tuberculosis dysregulates MMP/TIMP balance to drive rapid cavitation and unrestrained bacterial proliferation.

Active tuberculosis (TB) often presents with advanced pulmonary disease, including irreversible lung damage and cavities. Cavitary pathology contributes to antibiotic failure, transmission, morbidity and mortality. Matrix metalloproteinases (MMPs), in particular MMP-1 are implicated in TB pathogenesis. We explored the mechanisms relating MMP/TIMP imbalance to cavity formation in a modified rabbit model of cavitary TB. Our model results in consistent progression of consolidation to human-like cavities (100% by day 28) with resultant bacillary burdens (&gt;107 CFU/g) far greater than those found in matched granulomatous tissue (105 CFU/g). Using a novel, breath-hold computerized tomography scanning and image analysis protocol. We show that cavities develop rapidly from areas of densely consolidated tissue. Radiological change correlated with a decrease in functional lung tissue as estimated by changes in lung density during controlled pulmonary expansion (R2=0.6356, p?&lt;?0.0001). We demonstrated that the expression of interstitial collagenase (MMP-1) is specifically greater in cavitary compared to granulomatous lesions (p?&lt;?0.01), and that TIMP-3 significantly decreases at the cavity surface. Our findings demonstrate that an MMP-1/TIMP imbalance, is associated with the progression of consolidated regions to cavities containing very high bacterial burdens. Our model provided mechanistic insight, correlating with human disease at the pathological, microbiological and molecular levels,. It also provides a strategy to investigate therapeutics in the context of complex TB pathology. We used these findings to predict a MMP/TIMP balance in active TB; and confirmed this in human plasma, revealing the potential of MMP/TIMP levels as key components of a diagnostic matrix aimed at distinguishing active from latent TB (PPV=92.9%; 95%CI 66.1-99.8%, NPV=85.6%; 95%CI 77.0-91.9%)