Differential Reactivity of Airborne Quinones on Human Red Blood Cells: Insights into Their Biochemical and Morphological Alterations

Airborne fine particulate matter (PM_2.5) exposure has been epidemiologically linked to increased risk of cardiovascular complications, thrombosis, and hypoxia-related disorders. Quinones, prevalent constituents of PM_2.5, are suspected mediators of these health effects. Yet, the molecular mechanisms underpinning these associations remain poorly understood. Red blood cells (RBCs) have a central role in oxygen transport and vascular physiology. Thus, we investigated the effects of four environmentally relevant quinones (70 μg/mL), such as methyl-p-benzoquinone (MBQ), 1,4-naphthoquinone (NQ), 9,10-phenanthrenequinone (9,10-PQ), and 9,10-anthraquinone (9,10-AQ), on human RBCs. MBQ, NQ, and PQ significantly depleted intracellular glutathione, subsequently elevated reactive oxygen species, and triggered lipid peroxidation. Morphological analysis revealed membrane blebbing and surface protrusions of RBCs, indicative of impaired deformability and altered rheology. MBQ and NQ exposure further disrupted membrane proteins, impairing membrane fluidity and compromising membrane integrity. Tandem mass spectrometry confirmed covalent binding of MBQ and NQ to the βCys93 residue of hemoglobin via Michael addition. Native mass spectrometry revealed reduced stability of the α₂β₂ tetramer of hemoglobin. These findings were further corroborated by altered hemoglobin structure, methemoglobin formation, and hemoglobin aggregation. Mechanistically, MBQ and NQ induce RBC damage via both one-electron redox reaction and Michael addition to thiol groups, while PQ acts primarily through redox cycling without direct thiol binding. In contrast, AQ exhibited negligible effects, likely due to its low electrophilicity and steric hindrance. Our findings reveal distinct mechanistic pathways by which environmental quinones compromise RBC structure and function. This study offers a novel molecular link between airborne quinone exposure and pollution-driven health pathologies.