College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, Republic of Korea.
Rationale: While some non-steroidal anti-inflammatory drugs (NSAIDs) are reported to induce hepatic steatosis, the molecular mechanisms are poorly understood. This study presented the mechanism by which NSAIDs induce hepatic lipid accumulation.
Methods: Mouse primary hepatocytes and HepG2 cells were used to examine the underlying mechanism of NSAID-induced hepatic steatosis. Lipid accumulation was measured using Nile-red assay and BODIPY 493/503. The activity of chaperone-mediated autophagy (CMA) was determined by western blotting, qRT-PCR, and confocal imaging. The effect of NSAID on CMA inhibition was evaluated in vivo using diclofenac and CMA activator (AR7) administered mice.
Results: All tested NSAIDs in this study accumulated neutral lipids in hepatocytes, diclofenac having demonstrated the most potency in that regard. Diclofenac-induced lipid accumulation was confirmed in both mouse primary hepatocytes and the liver of mice. NSAIDs inhibited CMA, as reflected by the decreased expression of lysosome-associated membrane glycoprotein 2 isoform A (LAMP2A) protein, the increased expression of CMA substrate proteins such as PLIN2, and the decreased activity of photoactivatable KFERQ-PAmCherry reporter. Reactivation of CMA by treatment with AR7 or overexpression of LAMP2A inhibited diclofenac-induced lipid accumulation and hepatotoxicity. Upregulation of sorting nexin 10 (SNX10) via the CHOP-dependent endoplasmic reticulum stress response and thus maturation of cathepsin A (CTSA) was shown to be responsible for the lysosomal degradation of LAMP2A by diclofenac.
Conclusion: We demonstrated that NSAIDs induced SNX10- and CTSA-dependent degradation of LAMP2A, thereby leading to the suppression of CMA. In turn, impaired CMA failed to degrade PLIN2 and disrupted cellular lipid homeostasis, thus leading to NSAID-induced steatosis and hepatotoxicity.
Keywords: Chaperone-mediated autophagy, Diclofenac, NSAIDs, Perilipin 2, Sorting nexin 10