Effect of GFAP and MMP9 expressions on tight junction proteins in experimental autoimmune encephalomyelitis rats

Abstract

Objective To observe the expressions of tight junctional proteins in rats with experimental autoimmune encephalomyelitis (EAE), and to explore their relevant pathological mechanism. Methods Twenty-four Sprague Dawley rats were selected and randomly divided into a control group and a EAE group, and rats in the EAE group were subcutaneously injected at the footpad with autoimmune antigens to induce EAE models. The clinical behavioral scale scores of the rats 12 d after immunization were observed and recorded daily. The rats were sacrificed 23 d after immunization, and the histopathological changes of the brain tissues were observed by hematoxylin-eosin (HE) staining and fast blue (LFB) staining; the expressions of tight junction proteins Occludin, ZO-1 and Claudin-5 in the brain tissues were evaluated by immunofluorescence staining; the mRNA and protein levels of glial fibrillary acidic protein (GFAP, surface marker of astrocytes) and matrix metalloproteinase-9 (MMP9) in brain tissues were detected by reverse transiption-PCR (RT-PCR) and Western blotting, respectively. Results As compared with those in the control group, the clinical behavioral scale scores from 15 to 23 d of immunization and histopathological scale scores in the EAE group were significantly increased (P< 0.05). In EAE group, a lot of inflammatory cell infiltration and myelin loss in the cerebellar white matter were noted. As compared with those in the control group, the expressions of Occludin, ZO-1, and Claudin-5 in EAE group were significantly decreased (P<0.05), and the mRNA and protein expressions of GFAP and MMP9 were significantly up-regulated (P<0.05). Conclusion The activation of astrocytes and increased expression of MMP9 may reduce expressions of Occludin, ZO-1 and Claudin-5, disrupt blood-brain barrier, promote inflammatory cell infiltration, and increase myelin loss during EAE. Key words: Multiple sclerosis; Experimental autoimmune encephalomyelitis; Blood-brain barrier; Tight junction; Astrocyte; Matrix metalloproteinase-9