Reprogramming of TIMP-1 and TIMP-3 expression profiles in brain microvascular endothelial cells and astrocytes in response to proinflammatory cytokines

Effects of oncostatin M on human cerebral endothelial cells and expression in inflammatory brain lesions

Oncostatin M (OSM) is a member of the interleukin (IL)-6 cytokine family and modulates inflammatory responses. Here we investigated the role of OSM as an immunoregulatory factor for human cerebral endothelial cells (HCEC). Using RT-PCR we detected transcripts of the receptor components involved in OSM signaling, gp130, OSM receptor (OSMR)-beta, and leukemia inhibitory factor receptor (LIFR), in HCEC. A parallel FACS analysis revealed surface expression of gp130 and OSMR-beta, but not of LIFR on these cells. Functionally, OSM upregulated intercellular adhesion molecule-1, but did not induce vascular cell adhesion molecule-1 in HCEC. Further, OSM upregulated IL-6 and monocyte chemoattractant protein (MCP)-1, whereas IL-8 was unaffected. Combined application of tumor necrosis factor (TNF)-alpha and OSM synergistically enhanced IL-6 and MCP-1 production, but downregulated TNF-alpha-induced IL-8. As OSM regulated molecules relevant in inflammatory brain diseases, we investigated its expression in normal and pathological human brains. OSM was detected by immunohistochemistry in brains from multiple sclerosis patients in microglia, reactive astrocytes, and infiltrating leukocytes, whereas in normal brains and noninflammatory neurological diseases. immunoreactivity was absent from the parenchyma. These data suggest that immunoregulatory functions in human cerebral endothelial cells may be a mechanism by which OSM participates in the pathophysiology of inflammatory brain disease.

Ultrastructural changes of the vascular endothelium after intra-arterial administration of tumor necrosis factor-alpha (TNFalpha) in rat gliomas

The ensuing ultrastructural changes in tumor vascular endothelial cells following intra-arterial administration of tumor necrosis factor-alpha (TNFalpha) were studied in an experimental rat glioma model. C6 glioma cells were implanted in Wistar rats and then after 14 days, 5 x 10(3) U of human natural-type TNFalpha (1.7 x 10(5) U/m2) was administered through the carotid artery. The animals were sacrificed at 3 or 24 h after TNFalpha treatment. A detailed examination with transmission electron microscope revealed swelling of the tumor vascular endothelial cell nuclei and mitochondria with matrix densities at 3 h. At 24 h, these cells demonstrated the presence of high amplitude mitochondrial swelling or the violent blebbing characteristic of damaged mitochondria; the cytoplasm was swollen enormously and there were dissolution of cytoplasmic organelles and rupture of the plasma membrane. The observed findings were typical of cell necrosis and confirms yet another mechanism by which TNFalpha exerts its anti-tumor effects, that is, necrotizing effects on tumor vascular endothelium. The information appears to be important in the context of clinical application of intra-arterial TNFalpha in the treatment of malignant gliomas.

Elevated expression of membrane type 1 metalloproteinase (MT1-MMP) in reactive astrocytes following neurodegeneration in mouse central nervous system

Reactive astrocytes occurring in response to neurodegeneration are thought to play an important role in neuronal regeneration by upregulating the expression of extracellular matrix (ECM) components as well as the ECM degrading metalloproteinases (MMPs). We examined the mRNA levels and cellular distribution of membrane type matrix metalloproteinase 1 (MT1-MMP) and tissue inhibitors 1-4 of MMPs (TIMPs) in brain stem and spinal cord of wobbler (WR) mutant mice affected by progressive neurodegeneration and astrogliosis. MT1-MMP, TIMP-1 and TIMP-3 mRNA levels were elevated, whereas TIMP-2 and TIMP-4 expression was not affected. MT1-MMP was expressed in reactive astrocytes of WR. In primary astrocyte cultures, MT1-MMP mRNA was upregulated by exogeneous tumor necrosis factor alpha. Increased plasma membrane and secreted MMP activities were found in primary WR astrocytes.

Differential regulation of tissue inhibitor of metalloproteinase mRNA expression in response to intracranial injury

Injury to the CNS induces complex cellular and molecular interactions referred to as reactive gliosis. Alterations in the extracellular microenvironment associated with the gliotic response are believed to be the primary cause of regenerative failure of the mature CNS. For injured neurons to reestablish severed connections their processes must explore the extracellular milieu. Thus far, experiments have focused on extracellular matrix (ECM) proteins whose expression is upregulated after CNS injury and that exert inhibitory effects on neurite outgrowth. An intricate balance between ECM synthesis and degradation must be maintained during the tissue remodeling associated with injury. Matrix metalloproteinases (MMPs) are believed to be the main mediators of ECM degradation. MMP activity is tightly regulated by interaction with tissue inhibitors of metalloproteinases (TIMPs). To determine whether TIMPs are expressed during injury-induced matrix remodeling, TIMP expression was examined during reactive gliosis. A stab injury to the mature rat brain leads to the differential regulation of TIMP mRNA expression. Timp-1 and Timp-2 mRNA are significantly upregulated after injury, while the expression of Timp-3 and Timp-4 is unaltered. The expression of Timp-1 in reactive astrocytes and Timp-2 in microglia and neurons suggests these TIMPs may serve distinct functions in response to injury.