ABSTRACT
Enterocyte apoptosis induced by lipid emulsions is a key cause of intestinal atrophy under total parenteral nutrition (TPN) support, and our previous work demonstrated that olive oil lipid emulsion (OOLE) could induce enterocyte apoptosis via CUGBP, Elav-like family member 1 (CELF1)/ apoptosis-inducing factor (AIF) pathway. As TPN-associated complications are partially related to choline deficiency, we aimed to address whether choline supplementation could attenuate OOLE-induced enterocyte apoptosis. Herein we present evidence that supplementary choline exhibits protective effect against OOLE-induced enterocyte apoptosis both in vivo and in vitro. In a rat model of TPN, substantial reduction in apoptotic rate along with decreased expression of CELF1 was observed when supplementary choline was added to OOLE. In cultured Caco-2 cells, supplementary choline attenuated OOLE-induced apoptosis and mitochondria dysfunction by suppressing CELF1/AIF pathway. Compared to OOLE alone, the expression of CELF1 and AIF was significantly decreased by supplementary choline, whereas the expression of Bcl-2 was evidently increased. No obvious alterations were observed in Bax expression and caspase-3 activation. Mechanistically, supplementary choline repressed the expression of CELF1 by increasing the recruitment of CELF1 mRNA to processing bodies, thus resulting in suppression of its protein translation. Taken together, our data suggest that supplementary choline exhibits effective protection against OOLE-induced enterocyte apoptosis, and thus, it has the potential to be used for the prevention and treatment of TPN-induced intestinal atrophy.
Subject(s)
Apoptosis Inducing Factor/genetics , Atrophy/prevention & control , CELF1 Protein/genetics , Choline Deficiency/prevention & control , Choline/administration & dosage , Olive Oil/adverse effects , Parenteral Nutrition, Total/adverse effects , Animals , Apoptosis/drug effects , Apoptosis/genetics , Apoptosis Inducing Factor/metabolism , Atrophy/chemically induced , Atrophy/genetics , Atrophy/physiopathology , CELF1 Protein/metabolism , Caco-2 Cells , Caspase 3/genetics , Caspase 3/metabolism , Choline Deficiency/genetics , Choline Deficiency/physiopathology , Disease Models, Animal , Emulsions , Enterocytes/drug effects , Enterocytes/metabolism , Enterocytes/pathology , Gene Expression Regulation , Humans , Intestines/drug effects , Intestines/physiopathology , Male , Mitochondria/drug effects , Mitochondria/metabolism , Olive Oil/administration & dosage , Proto-Oncogene Proteins c-bcl-2/genetics , Proto-Oncogene Proteins c-bcl-2/metabolism , Rats , Rats, Sprague-Dawley , Signal Transduction , bcl-2-Associated X Protein/genetics , bcl-2-Associated X Protein/metabolismABSTRACT
BACKGROUND AND AIMS: Parenterally-administered lipid emulsion (LE) is a key cause of enterocyte apoptosis under total parenteral nutrition, yet the pathogenesis has not been fully understood. CUGBP, Elav-like family member 1 (CELF1) has been recently identified as a crucial modulator of apoptosis, and thus this study sought to investigate its role in the LE-induced apoptosis in vitro. METHODS: Caco-2 cells were used as an in vitro model. The cells were treated with varying LEs derived from soybean oil, olive oil or fish oil, and changes in the apoptosis and CELF1 expression were assessed. Rescue study was performed using transient knockdown of CELF1 with specific siRNA prior to LE treatment. Regulation of CELF1 by LE treatment was studied using quantitative real-time PCR and Western blotting. RESULTS: All the LEs up-regulated CELF1expression and induced apoptosis, but only olive oil-supplemented lipid emulsion (OOLE)-induced apoptosis was attenuated by depletion of CELF1. Up-regulation of apoptosis-inducing factor (AIF) was involved in OOLE-induced CELF1 dependent apoptosis. The protein expression of CELF1 was up-regulated by OOLE in a dose- and time-dependent manner, but the mRNA expression of CELF1 was unchanged. Analysis by polysomal profiling and nascent protein synthesis revealed that the regulation of CELF1 by OOLE treatment was mediated by directly accelerating its protein translation. CONCLUSION: OOLE-induces apoptosis in Caco-2 cells partially through up-regulation of CELF1.