Metabolomics Reveal Nanoplastic-Induced Mitochondrial Damage in Human Liver and Lung Cells

Abstract

Plastic debris in the global biosphere is an increasing concern, and nanoplastic (NPs) toxicity in humans is far from being understood. Studies have indicated that NPs can affect mitochondria, but the underlying mechanisms remain unclear. The liver and lungs have important metabolic functions and are vulnerable to NP exposure. In this study, we investigated the effects of 80 nm NPs on mitochondrial functions and metabolic pathways in normal human hepatic (L02) cells and lung (BEAS-2B) cells. NP exposure did not induce mass cell death; however, transmission electron microscopy analysis showed that the NPs could enter the cells and cause mitochondrial damage, as evidenced by overproduction of mitochondrial reactive oxygen species, alterations in the mitochondrial membrane potential, and suppression of mitochondrial respiration. These alterations were observed at NP concentrations as low as 0.0125 mg/mL, which might be comparable to the environmental levels. Nontarget metabolomics confirmed that the most significantly impacted processes were mitochondrial-related. The metabolic function of L02 cells was more vulnerable to NP exposure than that of BEAS-2B cells, especially at low NP concentrations. This study identifies NP-induced mitochondrial dysfunction and metabolic toxicity pathways in target human cells, providing insight into the possibility of adverse outcomes in human health.

Keywords: cytotoxicity; electron transport chain; energy metabolism; mitochondria; plastic particles.

Figure 1

Uptake of 80 nm NPs by normal human hepatic L02 and lung BEAS-2B cell lines and their cell viability at a series of concentrations: the internalization of fluorescent NPs (F-NPs) (A, C) and nonfluorescent NPs via TEM analysis (B,D). Data of cell viability are presented as the mean ± standard deviation of n = 6, *p < 0.05.

Figure 2

NP-induced mROS production in the normal human hepatic L02 cell line (A) and lung BEAS-2B cell line (B) (in 5 μM MitoSOX Red); n = 3.

Figure 3

NP-induced MMP alterations in the normal human hepatic L02 cell line (A) and lung BEAS-2B cell line (B); n = 3.

Figure 4

NP-induced mitochondrial stress responses in the normal human hepatic L02 cell line (A) and lung BEAS-2B cell line (B) through the mitochondrial respiration chain. Relative changes in key parameters of mitochondrial function were measured: basal respiration (C), maximal respiration (D), mitochondrial ATP production (E), and proton (H+) leakage (F); n = 3; *p < 0.05, **p < 0.01.

Figure 5

Metabolic pathway analysis and enrichment analysis of the most relevant metabolite sets in the NP-treated normal human hepatic L02 cell line (A, C) and lung BEAS-2B cell line (B, D).

Figure 6

NP perturbed metabolic pathways of the TCA cycle, GSH metabolism, and purine metabolism (A). Relative changes in identified endogenous biomarkers in the normal human hepatic L02 cell line (B) and lung BEAS-2B cell line-2B (C), n = 9; for XOD activity, n = 6; *p < 0.05, **p < 0.01.