Multiple sclerosis (MS) is a demyelinating autoimmune disease in which peripheral immune cells infiltrate the CNS and damage the insulating myelin sheaths surrounding neurons, creating demyelinated lesions in the spinal cord and the brain. MS is an incurable, life-long disease which causes a range of symptoms resulting from CNS degeneration. Current treatments mostly focus on preventing autoimmune attacks and the formation of lesions, but do not reduce the damage caused by the attacks, or impact the gradual degeneration of the axons of MS patients. This study aimed to establish the potential of MANF (mesencephalic astrocyte-derived neurotrophic factor) and CDNF (cerebral dopamine neurotrophic factor) as treatments for MS. MANF and CDNF are endoplasmic reticulum (ER) located proteins with unique structure and mode of action. UPR is a cellular stress response that, when triggered by inflammation in MS, can cause the apoptosis of myelinating oligodendrocytes and neurodegeneration. MANF and CDNF are also capable of modulating immune responses and improving regenerative processes in damaged tissues. The capability of these two molecules to protect CNS tissue was tested on mice induced with experimental autoimmune encephalomyelitis (EAE), a disease model for MS. Intravenous injections of MANF or CDNF in two doses were performed every 2nd day for 28 days after disease induction. Behavioral testing (rotarod and open field tests) indicated that both proteins improved motor function before the onset of paralysis. Daily clinical scoring showed a brief therapeutic window after the onset of paralysis, during which MANF and CDNF were able to halt disease progression. Flow cytometry analysis of mice spleens and brains showed no effect on immune cell populations at the end of the 28-day testing period. Immunohistological staining at the end of the experiment showed no differences in levels of neuroinflammation between treatment groups and control mice but showed that treatment with MANF and CDNF clearly reduced the formation of demyelinated lesions over the duration of the disease. These findings suggest the improved motor performances and protection from paralysis provided by treatment by MANF and CDNF may be due to their ability to protect CNS tissue from UPR caused by autoimmune demyelinating attacks. Further research is required to elucidate the mechanics behind this neuroprotective ability, and lead to more effective use of MANF and CDNF.
