THE ROLE OF MATRIX METALLOPROTEINASE-28 IN HEALTH AND DISEASE

Matrix Metalloproteinase-28 (MMP-28) is the newest and least characterized member of MMP family. To date several potential substrate candidates for MMP-28 have been proposed but no in vivo substrates for this enzyme were confirmed. In the central nervous system (CNS) MMP-28 is believed to be important factor during myelination of the developing nervous system as well as during remyelination that follows neuronal injury. On the other hand, MMP-28 has been found in actively demyelinating lesions in both experimental autoimmune encephalopathy (EAE) and multiple sclerosis patients suggesting its possible role in pathological events associated with autoimmune neurodegenerative processes. In addition, MMP-28 has been linked to modulation of immune response and activation of macrophages which presents another role of this enzyme in autoimmune pathologies. In the study described herein, MMP-28 has been shown to affect myelin composition and appearance, mitochondrial protein content, and vesicular transport proteins. Moreover, the decrease in myelin basic protein quantity observed in healthy MMP-28KO animals affected the myelin staining intensity in various brain regions including corpus callous. Cellular energetic studies did not reveal differences in mitochondrial function in MMP-28KO animals and no difference in reactive oxygen species was observed. In the EAE model, MMP-28 deletion increased the occurrence of atypical form of EAE characterized by increased inflammation of arbor vitae of the brain. In addition, MMP-28 deletion decreased the inflammatory infiltrates present in brains obtained from EAE animals. Lastly, MMP-28 has been shown to affect cellular energetics and activation of bone marrow derived macrophages during the initial stages and after 24 h activation. In addition, MMP-28 deletion increased proinflammatory cytokines and receptors CD86 and iNOS found in M1 polarized macrophages.