Pulmonary cavitation is vital to the persistence and spread of Mycobacterium tuberculosis (MTb), but mechanisms underlying this lung destruction are poorly understood. Fibrillar type I collagen provides the lung’s tensile strength, and only matrix metalloproteinases (MMPs) can degrade it at neutral pH. We investigated MTb-infected lung tissue and found that airway epithelial cells adjacent to tuberculosis (Tb) granulomas expressed a high level of MMP-1 (interstitial collagenase). Conditioned media from MTb-infected monocytes (CoMTb) up-regulated epithelial cell MMP-1 promoter activity, gene expression, and secretion, whereas direct MTb infection did not. CoMTb concurrently suppressed tissue inhibitor of metalloprotease-1 (TIMP-1) secretion, further promoting matrix degradation, and in Tb patients very low TIMP-1 expression was detected. MMP-1 up-regulation required synergy between TNF-α and G protein-coupled receptor signaling pathways. CoMTb stimulated p38 MAPK phosphorylation, and this is the point of TNF-α synergy with G protein-coupled receptor activation. Furthermore, p38 phosphorylation was the switch up-regulating MMP-1 activity and decreasing TIMP-1 secretion. Activated p38 localized to MMP-1-secreting airway epithelial cells in Tb patients. These data reveal a monocyte-epithelial cell network whereby MTb may drive tissue destruction, and they demonstrate that p38 phosphorylation is a key regulatory point in the generation of a matrix-degrading phenotype.

M. tuberculosis specifically upregulates MMP-1 in a cellular model of human infection and in patients with tuberculosis. In contrast, vaccine BCG, which does not cause lung cavitation, does not upregulate prostaglandin E2-dependent MMP-1 secretion.

CXCL8 is a chemokine that is implicated in the formation of tuberculous (TB) granulomas and in immunity to Mycobacterium tuberculosis (Mtb). Fibroblast chemokine secretion is important for modulating inflammatory responses in chronic lung disease and inflammatory arthritis but has not been investigated in the pathophysiology of TB. In this study, we used a cellular model to examine monocyte/macrophage-dependent stimulation of fibroblasts by Mtb in the regulation of chemokine secretion, particularly that of CXCL8. Human lung fibroblasts grown in collagen were stimulated with conditioned medium from Mtb-infected monocytes (CoMTb). CoMTb-induced prolonged dose-dependent, p38-mediated expression of stable CXCL8 mRNA by fibroblasts accompanied by a >10-fold increase in CXCL8 secretion (487 ± 88 ng/ml vs 48.6 ± 34 ng/ml in controls) at 120 h. Fibroblasts strongly expressed CXCL8 in vivo in human TB granulomas. Inhibition of TNF-α or IL-1 in CoMTb abrogated the induction of CXCL8 at a pretranscriptional level. CXCL8 secretion was NF-κB, C/EBP, and JNK dependent. Sustained NF-κB activation was demonstrated beyond 24 h in response to CoMTb. Exogenous CXCL8 reduced the survival of Mtb within macrophages, and inhibition of CXCL8 was associated with intracellular mycobacterial proliferation. These data show that fibroblasts have a previously unrecognized role in modulating inflammation in TB by their CXCL8-dependent contribution to cell recruitment and mycobacterial killing within the granuloma.

Solid pseudopapillary tumor (SPT) of the pancreas is an uncommon neoplasm of uncertain lineage. They have been shown to express nuclear beta-catenin believed to be due to mutations of the beta-catenin gene. The aim of this study was to investigate the status of the E-cadherin/catenin complex in SPTs. We studied the expression of 4 principal members of the E-cadherin/catenin complex using immunohistochemistry and the E-cadherin gene status by screening all exons of the gene for mutations, in 6 cases of SPT. In addition to the nuclear localization of beta-catenin, we found nuclear localization of E-cadherin in all tumors with complete absence of membranous and cytoplasmic localization. Nuclear localization of E-cadherin was independent of beta-catenin. No mutations were identified in the E-cadherin gene in any of the tumors. Ten cases of pancreatic adenocarcinomas and 15 neuroendocrine tumors were studied as well for comparison. The reported changes in the expression of the principal members of the E-cadherin/catenin complex were unique to SPTs. Our study shows abnormalities in the expression of 4 principal members of the E-cadherin/catenin complex in SPTs, which may help to explain the discohesive nature of the cells and the cystic changes in these tumors, and provide additional diagnostic features.

CNS tuberculosis (CNS-TB) is the most deadly form of tuberculous disease accounting for 10% of clinical cases. CNS-TB is characterized by extensive tissue destruction, in which matrix metalloproteinases (MMPs) may play a critical role. We investigated the hypothesis that Mycobacterium tuberculosis activates monocyte-astrocyte networks increasing the activity of key MMPs. We examined the expression of all human MMPs and the tissue inhibitors of metalloproteinases (TIMPs) in human astrocytes stimulated by conditioned medium from M. tuberculosis-infected monocytes (CoMTB). Real-time RT-PCR showed that gene expression of MMP-1, -2, -3, -7, and -9 was increased (p < 0.05). MMP-9 secretion was significantly up-regulated at 24 h and increased over 120 h (p < 0.01). MMP-1, -3, and -7 secretion was not detected. Secretion of MMP-2 was constitutive and unaffected by CoMTB. Astrocyte gene expression and secretion of TIMP-1 was not affected by CoMTB although TIMP-2 secretion increased 3-fold at 120 h. Immunohistochemical analysis of human brain biopsies confirmed that astrocyte MMP-9 secretion is a predominant feature in CNS-TB in vivo. Dexamethasone inhibited astrocyte MMP-9, but not TIMP-1/2 secretion in response to CoMTB. CoMTB stimulated the nuclear translocation of NF-κB, inducing a 6-fold increase in nuclear p65 and a 2-fold increase in nuclear p50. This was associated with degradation of IκBα and β within 30 min, persisting for 24 h. In summary, networks active between monocytes and astrocytes regulate MMP-9 activity in tuberculosis and astrocytes are a major source of MMP-9 in CNS-TB. Astrocytes may contribute to a matrix degrading environment within the CNS and subsequent morbidity and mortality.