Xanthine or hypoxanthine or both may play therapeutical effect in Parkinson's disease through the endocannabinoid system

Abstract

Parkinson's disease (PD) is a common neurodegenerative disorder. The main neuropathological features of PD are the loss of dopaminergic neurons in the substantia nigra striata and the extensive accumulation of α-synuclein in different brain regions. The substantia nigra and striatum are brain regions with high expression of cannabinoid receptors, and the role of the endogenous cannabinoid system (ECS) has been explored in PD. The ECS may be a promising target for the treatment of PD. The correlation between PD and serum uric acid levels has been demonstrated in a large number of studies, but a causal relationship between the two has not been proven. Xanthine and hypoxanthine are upstream metabolite of uric acid, and they have been shown to be effective in relieving PD symptoms. Therefore, we hypothesized that xanthine or hypoxanthine or both may increase the inhibitory properties of GABAergic neurons by increasing the sensitivity of cannabinoid receptors on GABAergic neurons in the striatum, thereby activating the direct nigrostriatal pathway to ameliorate Parkinson's disease symptoms. The proposed hypothesis can be tested in animal and cellular intervention experiments. If this approach is found to be effective in improving PD symptoms with minimal adverse events, exogenous supplementation of xanthine/ hypoxanthine or the use of xanthine oxidase to block its metabolism to elevate hypoxanthine levels could potentially be an effective addition to PD therapy.