Dynamic Brain Imaging during Parkinson's disease and L-DOPA-induced dyskinesia: Investigation of commitment level of the blood-brain barrier and activation of glial cells (microglia and astrocytes)

Abstract

The loss of dopaminergic neurons in Parkinson's disease (PD) is accompanied by neuroinflammation, which is mediated by glial cells, mainly microglia. However, the cause of origin and development of neuroinflammation was not elucidated and probably it is perpetuating and amplifying the progression of this disease. The dopamine precursor, L-DOPA, is the most efficient treatment for PD motor symptoms. However, chronic treatment with L-DOPA induces several motor complications, including L-DOPA-induced dyskinesia (LID). As inflammatory mechanisms are also responsible for LID, our hypothesis is that there is blood-brain barrier (BBB) breakdown, possibiliting the activation of surrounding glial cells, such as microglia and astrocytes, which present an important role in DP and LID. These cells acquire a characteristic phenotypic profile that could be bennefic or cause damage locally. Despite of there are several studies in the literature proposing new approaches for LID treatment, the effectiveness of new pharmacological target is still limited. Moreover, the participation of microglia and astrocytes in DP and LID and the effect of pharmacs in these cells is still incipient. A recent study of our group found out doxicicline as a new possible therapeutic target in the treatment of DP, possibiliting a new researcher approache in the pharmacological area. Furthermore, recent data indicate that treatment with cannabinoid drugs (CBD) + capsazepine reduced the LID by decreasing inflammatory mediators. In this context, the use of state-of-the-art fluorescent and functional immunoimaging techniques is a very valuable tool. Based on this, the main aims of the proposal are: 1) to characterize the commitment level of the BBB, 2) to evaluate the impact of BBB breakdown in the dynamic behavior of microglia and astrocytes in DP and LID, 3) to evaluate the influence of the CBD and doxicicline treatment in the neuroinflammation and neurodegeneration, and 4) to investigate the influence of fractalkine receptor gene deletion (CX3CR1) in the dynamic behavior of microglia and in the neurodegenerative and neuroinflammatory response. The animal model used in this project will be C57BL/6 wild type mice, as well as transgenic mice with the insertion of green fluorescent protein (GFP) in the CX3CR1 gene (obtained recently by collaboration with a German team). Transgenic mice will be heterozygotes (CX3CR1+/GFP) and homozygotes (CX3CR1GFP/GFP), which present green fluorescence in microglia. Together, these results will provide the first comprehensive study of phenotypic characterization of glial cells in DP and LID using innovative techniques. Findings obtained here can provide new insight related to the neuroinflammation and the pharmacological treatment in LID.