TTP protects against 6-OHDA-induced dopaminergic neurodegeneration via astrocytic Nrf2/HO-1 activation in cellular and rat models of Parkinson's disease

Parkinson's disease (PD) is characterized by progressive dopaminergic neuronal loss driven by oxidative stress, mitochondrial dysfunction, and Apoptosis. Adenosine A_2A receptor (A_2AR) antagonism is clinically validated for symptomatic relief; however, its potential disease-modifying mechanisms remain incompletely defined. We hypothesized that TTP, a novel and highly selective A_2AR antagonist, would confer neuroprotection against 6-hydroxydopamine (6-OHDA)-induced toxicity by modulating oxidative stress and activating astrocytic Nrf2/HO-1 antioxidant signaling. In primary midbrain dopaminergic neurons, TTP significantly restored cell viability, reduced ROS accumulation, preserved mitochondrial membrane potential, and attenuated Caspase-3 mediated Apoptosis following 6-OHDA exposure. TTP also reinstated Tyrosine Hydroxylase, DJ-1, and dopamine levels. In primary astrocytes, TTP robustly upregulated Nrf2 and its downstream targets HO-1 and NQO1. In a unilateral 6-OHDA rat model, TTP improved apomorphine-induced rotational behavior and depression-like symptoms, restored striatal dopamine and antioxidant enzyme activities, and elevated Nrf2/HO-1 signaling in vivo. These findings indicate that TTP exerts neuroprotective effects through combined antioxidant, anti-apoptotic, and glia-associated mechanisms, supporting its potential as a disease-modifying A_2AR antagonist. However, the mechanistic involvement of Nrf2 was not confirmed using loss-of-function approaches, and astrocyte-neuron interactions were not directly examined. Future studies employing targeted Nrf2 inhibition, cell-type specific models, and comprehensive pharmacokinetic profiling will be essential to establish causality and translational feasibility. Collectively, this study provides strong preclinical evidence supporting TTP as a promising therapeutic candidate for modifying PD progression beyond symptomatic control.