Retinoid X Receptor as a Therapeutic Target to Treat Neurological Disorders Associated with alpha-Synucleinopathy

Abstract

This study investigated the therapeutic potential of the nuclear retinoid X receptor (RXR) in mitigating the progression of alpha-synucleinopathies (SNPs), particularly in Parkinsons disease (PD). PD-like pathology in mice was successfully induced through the co-delivery of AAV expressing human -synuclein (S) and S preformed fibrils (PFFs) into the substantia nigra pars compacta (SNpc). Significant increases in Lewy body (LB)-like inclusions, loss of tyrosine hydroxylase-positive (TH+) neurons, and reductions in dopamine (DA) levels in the striatum were observed. Additionally, diminished levels of PPAR and NURR1, along with elevated GFAP and Iba1, markers of neuroinflammation, microglial activation, and astrocytic gliosis were associated with PD pathogenesis. AAV-mediated overexpression of human RXR demonstrated preservation of TH+ neurons, prevention of DA decline and attenuation of S accumulation. Furthermore, RXR-treated PD brains showed a reduced number of GFAP+ and Iba1+ cells, decreased GFAP+ and Iba1+ immunoreactivity, and fewer and less widespread LB-like aggregates. RXR overexpression also enhanced the production of PPAR and NURR1, proteins critical for neuronal survival. These findings suggest that RXR activation promotes neuroprotection by mitigating SNPs and chronic neuroinflammation, a major contributor to PD progression. This research underscores the therapeutic potential of targeting nuclear receptors, such as RXR, in neurodegenerative diseases like PD