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 A2A receptor (A2AR) 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 A2AR 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 A2AR 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.