Bacterial Melanin Ameliorates Symptoms of Experimental Autoimmune Encephalomyelitis in Rats

Abstract

Experimental autoimmune encephalomyelitis (EAE) is a T cell autoimmune inflammatory disease of the central nervous system (CNS) that is a widely used animal model for the human demyelinating disease, multiple sclerosis. Bacterial melanin has proved to be a potent neuroprotector. It supports regeneration and motor recovery after CNS lesions. It is established that bacterial melanin can induce suppression of inflammatory process. Studies have revealed the negative correlation between skin pigmentation, vitamin D and the prevalence of autoimmune disease. Therefore we analyzed the anti-inflammatory effects of bacterial melanin in a rat EAE model. EAE was induced in adult albino male rats by immunizing with a rat spinal cord encephalitogenic emulsion. The development of EAE and neurological signs were evaluated by a standard protocol. Walking track analysis was conducted to evaluate motor recovery. Histomorphological analysis was applied to show cell infiltration into the spinal cord and effects of BM on the EAE pathomorphology. Pretreatment of EAE rats with bacterial melanin inhibited the development of disease, providing significant protective effect compared to control rats. BM treated rats showed lower degree of neurological deficit and higher level of motor recovery than controls. In treated rats histomorphological analysis demonstrated that brain infiltration with mononuclears was less expressed in bacterial melanin treated rats. Results show that bacterial melanin has protective effects in EAE and ameliorates symptoms of EAE.