Su1719 Effectiveness and Safety of Baclofen Treatment in Alcohol-Dependent Patients With or Without Liver Cirrhosis: Results of an Open Study in True Life

Background and Aims: The endoplasmic reticulum (ER) is a multifunctional organelle involved in synthesis, processing and folding of proteins, lipid biosynthesis, and regulation of calcium and redox homeostasis. Altered ER-function due to accumulation of misfolded/unfolded proteins, oxidative stress or depletion of ER calcium, lead to a condition called “ER-stress”, particularly important in cells with a high burden of protein synthesis as hepatocytes. Efavirenz, a non-nucleoside analog reverse transcriptase inhibitor, is a cornerstone in the combined therapy of HIV1 infection. Despite being considered generally safe, it has been related to development of adverse events such as hepatic toxicity. Here we report the presence of specific ER-stress in human hepatic cells. Methods: Hep3B cells and primary human hepatocytes were exposed to short-term treatment (24h) with clinically relevant concentrations of Efavirenz. General cell biology methods were employed (RNA interference, RT-PCR, Western blot and fluorescence microscopy). Results: ER-stress markers indicative of several ER-stress pathways were up-regulated concentration-dependently by Efavirenz, including the expression of CHOP and GRP78, at protein and mRNA level, and the phosphorylated form of eIF-2a. Furthermore, we also detected an increase in the transcription of ATF4 and XBP-1, and presence of the spliced form s-XBP-1. Efavirenz also induced morphological changes in ER with enhanced ER-content and dilatation of its cisternae, and led to an increase in the cytosolic calcium level. All these changes were similar to those produced by the standard pharmacological ER-stressor, Thapsigargin. On the contrary, while Thapsigargin induced an increment in the mitochondrial calcium level, Efavirenz provoked a decrease. A differential effect was also observed with transient silencing of CHOP. The stimulating effect of Thapsigargin on the generation of reactive oxygen species and the increment in the ER-content was more pronounced in CHOP-depleted cells, but this exacerbated action was not observed when cells were treated with Efavirenz. Conclusions: Clinical concentrations of Efavirenz induce ER-stress in hepatic cells in a compound-specific manner. Given the lifelong and widespread use of Efavirenz in the multidrug therapy of HIV, this novel mechanism of cellular response to drug-induced stress could help to understand the frequent hepatic toxicities that accompany the treatment of HIV1 infection.