Synthetic neuromelanin as a trigger of inflammation in the brain, new mouse model of Parkinson's disease

Parkinsons disease (PD) is a neurodegenerative disease that is an increasing threat to an aging society. The idiopathic form of PD accounts for over 90% of all cases, and the current etiology is still unknown. One of the reasons hindering research on this form of PD is the lack of an appropriate animal models. Among mouse models of the disease, those based on the administration of neurotoxins such as 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP) or 6-hydroxydopamine (6-OHDA) to the substantia nigra pars compacta (SNpc) or striatum are predominantly used. In these models, there are metabolic disturbances causing oxidative stress in the SNpc or striatum, which ultimately leads to the death of dopaminergic neurons. However, the models used so far have serious limitations, most of all they do not fully reflect the processes occurring in the course of the disease and do not consider the involvement of inflammation in the etiology and pathogenesis of PD. In this study we show that the administration of synthetic neuromelanin, which activates astrocytes and microglia, induces the inflammation and may be involved in degeneration of dopaminergic neurons. Neuromelanin under physiological conditions acts as a neuroprotector, however, released from dying dopaminergic neurons is an important factor activating astrocytes, microglia and causing neuroinflammation. Since one of the causes of Parkinsons appear to be the death of dopaminergic neurons overloaded with neuromelanin and consequent pathological activation of microglia, the use of synthetic neuromelanin reflect the natural pathological processes occurring during the development of the disease.