Vanillic acid attenuates paraquat-induced oxidative, mitochondrial, and acetylcholinesterase alterations in SH-SY5Y cells

Paraquat (PQ) is a widely used herbicide with well-documented neurotoxic potential, largely associated with redox cycling, oxidative stress, and mitochondrial dysfunction. Excessive reactive oxygen species (ROS) generation following PQ exposure disrupts cellular redox homeostasis and contributes to neuronal cell injury. Vanillic acid (VA), a naturally occurring phenolic compound, has antioxidant and cytoprotective properties. This study investigated whether VA attenuates PQ-induced cellular toxicity and associated changes in oxidative status, mitochondrial membrane potential, cell-cycle distribution, and acetylcholinesterase (AChE) activity in SH-SY5Y human neuroblastoma cells. SH-SY5Y cells were exposed to PQ (100 µM) in the presence or absence of VA (10, 25, and 50 µM). Cell viability and membrane integrity were assessed using MTT and LDH assays, respectively. Oxidative stress parameters were evaluated by measuring intracellular ROS production, total antioxidant capacity (TAC), and total oxidant status (TOS). Mitochondrial membrane potential (ΔΨm) was analyzed using JC-1 staining, and cell-cycle distribution was determined by flow cytometry. Acetylcholinesterase (AChE) activity was measured to assess PQ-associated cholinergic alterations. PQ exposure significantly reduced cell viability and TAC while increasing LDH release, ROS production, TOS, mitochondrial depolarization, and AChE activity. PQ exposure was also associated with an increased Sub-G1 population and altered cell-cycle distribution. Co-treatment with VA concentration-dependently improved viability and membrane integrity, reduced ROS and TOS, partially restored TAC, decreased mitochondrial depolarization, attenuated cell-cycle alterations, and reduced PQ-associated AChE elevation. In SH-SY5Y cells, VA attenuated PQ-induced cellular toxicity and was associated with improved redox indices, reduced mitochondrial depolarization, and modulation of AChE activity. These functional findings support a potential cytoprotective effect of VA, but the responsible molecular pathways, apoptosis, and direct cholinergic function require confirmation in differentiated neuronal models and by pathway-specific assays.