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Polystyrene Nanoplastics Induce Early Mitochondrial Dysfunction in H9c2 Cardiomyoblasts Without Substantial Cell Damage
Summary
Scientists exposed heart muscle cells to nanoplastics (tiny plastic particles similar to those found in human blood and heart tissue) and found that even without killing the cells or causing obvious damage, the plastics quietly disrupted the cells' mitochondria — the "power plants" that generate energy. This means the heart cells' ability to produce extra energy during stress or exertion may be weakened, even though everything looks normal on the surface. While this was a lab study on cells (not people), it raises concern that everyday plastic exposure could be subtly straining our hearts' energy reserves over time.
Global plastic production has led to widespread contamination by micro- and nanoplastics, with polystyrene nanoplastics (PSNPs) increasingly being detected in human biological samples, including blood and cardiac tissue. Given the critical role of mitochondria in cardiac energy metabolism, this study investigated whether 100 nm PSNPs interact with mitochondria and affect mitochondrial function in H9c2 cardiomyoblasts. Cellular uptake and intracellular distribution were examined, followed by an evaluation of mitochondrial ultrastructure, intracellular and mitochondrial reactive oxygen species (ROS) production, mitochondrial membrane potential, mitochondrial dynamics and mitophagy-related gene expression, mitochondrial DNA copy number, and metabolic function. PSNPs were internalized but did not directly localize to mitochondria within 24 h. No significant cytotoxicity, increase in intracellular or mitochondrial ROS production, or alteration in basal metabolic activity was observed. However, PSNP exposure resulted in intracellular accumulation, an altered mitochondrial ultrastructure characterized by crista loosening and vacuole-like structural changes. These changes were accompanied by reduced mitochondrial membrane potential; the upregulation of mitochondrial dynamics-related genes, including optic atrophy 1 (Opa1) and dynamin-related protein 1 (Drp1); the suppression of PTEN-induced kinase 1 (PINK1)/Parkin RBR E3 ubiquitin protein ligase (Parkin)-mediated mitophagy-related genes; and decreased maximal respiratory capacity. Lactate production and the extracellular acidification rate remained unchanged, suggesting that compensatory glycolysis was not activated. These findings indicate that PSNP exposure induces early mitochondrial structural and functional alterations without substantial cell damage, suggesting a potential reduction in cardiac adaptive capacity under PSNP-induced stress conditions.