[The influence of patatin-like phospholipase domain-containing protein 3 on palmitic acid-induced hepatocyte apoptosis]

Abstract

Objective: To explore the influence of patatin-like phospholipase domain-containing protein 3 (PNPLA3) on palmitic acid (PA)-induced hepatocyte apoptosis and its mechanism.

Methods: Human hepatocarcinoma cell line HepG2 cells were transfected with PNPLA3(WT)-pcDNA3.1 (PNPLA3(WT) group) and PNPLA3(I148M)-pcDNA3.1 (PNPLA3(I148M) group) plasmids respectively to overexpress wild type or mutant type PNPLA3, and cells transfected with empty vector pcDNA3.1 (NC group) were set as control group.After 24 h PA incubation, Oil red staining was used to determine lipid deposition, and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL) was used to measure apoptosis.Western blot was used to detect the protein level of endoplasmic reticulum (ER) stress and associated apoptosis.Enzyme-linked immunosorbent assay (ELISA) was used to test lysolecithin (LPC) levels in the cellular supernatant.

Results: After 24 h PA incubation, there was no significant difference in lipid deposition among three groups.Compared to NC group, the cell apoptosis rates of PNPLA3(WT) and PNPLA3(I148M) groups were increased by 2 times and 3 times respectively.The levels of ER stress PRKR-like endoplasmic reticulum kinase (PERK) pathway associated proteins, immunoglobulin-binding protein (BIP), p-PERK, p-eIF2α, and ER stress associated apoptosis pathway proteins, CCAAT/enhancer binding homologous protein (CHOP), p53 upregulated modulator of apoptosis (PUMA), Bax, caspase-3 were higher, and were more significant in PNPLA3(I148M) group.The LPC level in the supernatant of PNPLA3(WT) and PNPLA3(I148M) groups were about 5 times and 1.5 times of NC group respectively after PA incubation.

Conclusion: PNPLA3 may be involved in palmitic acid-induced apoptosis mediated by hepatocyte ER stress through regulating LPC metabolism.