Matrix-degrading metalloproteinases and cytokines in multiple sclerosis and ischemic stroke

Abstract

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system characterized by blood-brain barrier breakdown, perivascular inflammation and demyelination. In ischemic stroke, an inflammatory reaction develops shortly after arterial occlusion. Inflammatory processes, therefore, may play an important role in the clinical outcome of both MS and stroke. Professional antigen presenting cells (APC) like dendritic cells (DC) and monocytes are critical in initiation and perpetuation of inflammatory responses. Efficient functioning of APC requires the shuttling of antigen in tissues to lymphoid organs. Local secretion of matrix-degrading metalloproteinases (MMP), a group of enzymes capable of degrading virtually all components of the extracellular matrix (ECM), may provide APC with a powerful tool to cross the various barriers between tissues and lymph nodes. Cytokines encompass a group of immunomodulatory proteins secreted by a variety of cells that regulate extent, nature and duration of immune responses. MMP and cytokines are two interdependent immune variables regulating production and activation of each other. In this study, the involvement of APC in MS and stroke was examined by evaluating their MMP and cytokine production capacities.

We observed that MS is associated with high levels of monocytes secreting IL-6 and IL-12 and expressing mRNA of MMP-1, -2, -7 and -9 and of TIMP-1 compared to healthy subjects (HC). MS is also associated with high levels of immature DC expressing MMP-1, -2 and -9 and mature DC expressing MMP-2 and -3 and of TIMP- 1 In parallel, we observed high enzymatic activity in culture supernatants and a higher migratory capacity over ECM-coated filters of DC generated from MS patients' blood compared to DC from HC. Treatment with IFN-beta is beneficial for MS. When patients with MS were examined before vs. during IFN-beta treatment, lower levels of IL-6 and TNIF-alpha secreting and of MMP-3 and -9 mRNA expressing mononuclear cells (MNC) compared to pre-treatment levels were observed. On the contrary, numbers of IL-10 secreting MNC and TIMP-1 mRNA expressing MNC were augmented during IFN-beta treatment. We conclude that MS is associated with altered levels of MMP, TIMP and cytokines. When studied separately, APC such as monocytes and DC partly mirror the systemic imbalances in MMP and cytokine profiles observed in MS suggesting their involvement in MS pathogenesis. MMP, TIMP and cytokine alterations in MS were normalized by IFN- beta treatment.

Examining patients with ischemic stroke within 4 days and 1 month after onset of symptoms, we observed higher levels of blood monocytes and MNC secreting TNFalpha, IL-12 and IL-6 in the acute phase of stroke compared to convalescence and to HC. Levels of monocytes expressing MMP-1, and -7, and TIMP-1 mRNA were also elevated in the acute phase of stroke, as were levels of MMP-1, -2, -7, and -9, and of TIMP-1 mRNA expressing MNC. MMP activity as measured by zymography was also higher in MNC supernatants in the acute phase of stroke compared to convalescence. The acute phase of ischemic stroke is associated with elevated levels of MMP and cytokine expressing monocytes and MNC that are normalized in convalescence. Our data suggest that monocytes are involved in the transient systemic immune alterations observed in stroke.