Effect of DEHP and DnOP on mitochondrial damage and related pathways of Nrf2 and SIRT1/PGC-1α in HepG2 cells

Di-2-ethylhexyl phthalate (DEHP) and Dioctyl phthalate (DnOP) are widely used as plasticizers in various industries for which the consequent health problems are of great concern. In this context, we treated HepG2 cells with DEHP or DnOP for 48 h. The results showed that DEHP and DnOP caused increase in oxygen species (ROS), malondialdehyde (MDA), Alanine aminotransferase (ALT) and Aspartate transaminase (AST). The proteins NF⁃E2-related factor 2 (Nrf2) and haemeoxygenase-1 (HO-1), were significantly down-regulated. Subsequently, the mitochondrial structure was disrupted, and the ATP content, the mitochondrial copy number as well as the expression of the corresponding mitochondrial genes were also reduced. The expression of sirtuin 1(SIRT1), PPAR gamma co-activator 1 alpha (PGC-1α), Nuclear respiratory factor 1(Nrf1), Mitochondrial transcription factor A (TFAM) on the SIRT1/PGC-1α pathway were significantly reduced. Finally, neither DEHP nor DnOP was found to induce apoptosis, but could significantly up-regulate Light chain 3 II (LC3II) levels. In conclusion, DEHP and DnOP could induce HepG2 cell damage via mitochondria, probably by causing oxidative stress, inhibiting the Nrf2 pathway and inhibiting the mitochondrial biogenesis pathway, which leads to excessive autophagy and cell death. DEHP and DnOP differ in the Nrf2 pathway, autophagic pathway and MAPK pathway, which may be structurally related.