Long-Term Environmental Exposure to Polystyrene Microplastics Induces Mitochondrial Dysfunction and Apoptosis in Human Renal Tubular Epithelial Cells

The ubiquitous presence of microplastics (MPs) in various environmental matrices has raised significant concerns regarding their potential impacts on human health. This study investigates the long-term effects of polystyrene microplastics (PS-MPs) exposure on human renal tubular epithelial cells (HK-2 cells), focusing on cellular viability, mitochondrial function, and apoptosis induction. HK-2 cells were exposed to environmentally relevant concentrations (10 and 100 µg/mL) of 5 µm PS-MPs for durations of 7, 14, and 21 days. Our findings demonstrate a significant dose- and time-dependent decrease in cell viability, accompanied by marked morphological alterations. Mechanistically, PS-MP exposure led to severe mitochondrial dysfunction, characterized by a substantial reduction in ATP production, decreased mitochondrial membrane potential, and a significant increase in intracellular reactive oxygen species (ROS) levels. Furthermore, long-term exposure to PS-MPs significantly induced apoptosis, evidenced by increased caspase-3/7 activity and elevated levels of pro-apoptotic markers. These results suggest that chronic exposure to PS-MPs can compromise renal cellular integrity and function through the induction of mitochondrial damage and subsequent activation of apoptotic pathways. This study provides crucial insights into the nephrotoxic potential of environmental microplastic pollution and underscores the need for further research into the long-term health consequences of human exposure.