Monocyte-dependent oncostatin M and TNFa synergize to stimulate unopposed matrix metalloproteinase-1/3 secretion from human lung fibroblasts in tuberculosis

Leukocyte-derived matrix metalloproteinases (MMP) are implicated in the tissue destruction characteristic of tuberculosis (TB). The contribution of lung stromal cells to MMP activity in TB is unknown. Oncostatin M (OSM) is an important stimulus to extrapulmonary stromal MMP induction, but its role in regulation of pulmonary MMP secretion or pathophysiology of TB is unknown. We investigated OSM secretion from Mycobacterium tuberculosis (Mtb)-infected human monocytes/macrophages and the networking effects of such OSM on lung fibroblast MMP secretion. Mtb increased monocyte OSM secretion dose dependently in vitro. In vivo tuberculous granulomas immunostained positively for OSM. Further, conditioned media from Mtb-infected monocytes (CoMTb) induced monocyte OSM secretion (670 ± 55 versus 166 ± 14 pg/mL in controls), implicating an autocrine loop. Mtb-induced OSM secretion was prostaglandin (PG) sensitive, and required activation of surface G-protein coupled receptors. OSM induction was ERK MAP kinase dependent, p38-requiring but JNK-independent. OSM synergized with TNF-, a key cytokine in TB granuloma formation, to stimulate pulmonary fibroblast MMP-1/-3 secretion, while suppressing secretion of tissue inhibitors of metalloproteinases-1/-2. In summary, Mtb infection of monocytes results in PG-dependent OSM secretion, which synergizes with TNF- to drive functionally unopposed fibroblast MMP-1/-3 secretion, demonstrating a previously unrecognized role for OSM in TB.

STAT3, p38 MAP Kinase and NF-{kappa}B Drive Unopposed Monocyte-dependent Fibroblast MMP-1 Secretion in Tuberculosis.

Tissue destruction characterizes infection with Mycobacterium tuberculosis (Mtb). Type I collagen provides the lung's tensile strength, is extremely resistant to degradation, but is cleaved by matrix metalloproteinase (MMP)-1. Fibroblasts potentially secrete quantitatively more MMP-1 than other lung cells. We investigated mechanisms regulating Mtb-induced collagenolytic activity in fibroblasts in vitro and in patients. Lung fibroblasts were stimulated with conditioned media from Mtb-infected monocytes (CoMTb). CoMTb induced sustained increased MMP-1 (74 versus 16 ng/ml) and decreased tissue inhibitor of metalloproteinase (TIMP)-1 (8.6 versus 22.3 ng/ml) protein secretion. CoMTb induced a 2.7-fold increase in MMP-1 promoter activation and a 2.5-fold reduction in TIMP-1 promoter activation at 24 hours (P = 0.01). Consistent with this, TIMP-1 did not co-localize with fibroblasts in patient granulomas. MMP-1 up-regulation and TIMP-1 down-regulation were p38 (but not extracellular signal–regulated kinase or c-Jun N-terminal kinase) mitogen-activated protein kinase–dependent. STAT3 phosphorylation was detected in fibroblasts in vitro and in tuberculous granulomas.STAT3 inhibition reduced fibroblast MMP-1 secretion by 60% (P = 0.046). Deletion of the MMP-1 promoter NF-B–binding site abrogated promoter induction in response to CoMTb. TNF-, IL-1ß, or Oncostatin M inhibition in CoMTb decreased MMP-1 secretion by 65, 63, and 25%, respectively. This cytokine cocktail activated the same signaling pathways in fibroblasts and induced MMP-1 secretion similar to that induced by CoMTb. This study demonstrates in a cellular model and in patients with tuberculosis that in addition to p38 and NF-B, STAT3 has a key role in driving fibroblast-dependent unopposed MMP-1 production that may be key in tissue destruction in patients.

Linoleic acid increases monocyte chemotaxis and adhesion to human aortic endothelial cells through protein kinase C- and cyclooxygenase-2-dependent mechanisms

The effects of polyunsaturated n-6 linoleic acid on monocyte-endothelial interactions were investigated with particular emphasis on the expression of platelet/endothelial cell adhesion molecule (PECAM)-1 and the role of protein kinase C (PKC) and cyclooxygenase-2 (COX-2). As a diet rich in polyunsaturated fatty acids may favour atherosclerosis in hyperglycaemia, this study was performed in both normal and high-glucose media using human aortic endothelial cells (HAEC). The HAEC were preincubated with normal (5 mM) or high (25 mM) d-glucose for 3 days before addition of fatty acids (0.2 mM) for 3 days. Linoleic acid enhanced PECAM-1 expression independently of tumor necrosis factor (TNF)-a and significantly increased TNF-a-induced monocyte adhesion to HAEC in comparison to the monounsaturated n-9 oleic acid. Chronic glucose treatment (25 mM, 6 days) did not modify the TNF-a-induced or fatty acid-induced changes in monocyte binding. The increase in monocyte binding was accompanied by a significant increase in E-selectin and vascular cell adhesion molecule (VCAM)-1 expression and could be abrogated by an interleukin (IL)-8 neutralising antibody and by the PKC and COX inhibitors. Inhibition of PKC-d reduced VCAM-1 expression regardless of experimental condition and was accompanied by a significant decrease in monocyte binding. Conditioned medium from linoleic acid-treated HAEC grown in normal glucose conditions significantly increased THP-1 chemotaxis. These results suggest that linoleic acid-induced changes in monocyte chemotaxis and subsequent binding are not solely mediated by changes in adhesion molecule expression but may be due to secreted factors such as IL-8, monocyte chemoattractant protein-1 or prostaglandins (PGs) such as PGE2, as IL-8 neutralisation and COX-2 inhibition reduced monocyte binding without changes in adhesion molecule expression.