Study On The Mechanism And Therapy Of Lipid Droplets In Gallbladder Cholesterolosis

Background:Gallbladder cholesterosis is a local disorder of lipid metabolism. A lot of macrophages swallowing lipid droplet destroy lymphatic vessel, leading to the obstruction to reverse cholesterol transport and the accumulation of lipid droplets. The pathology of cholesterosis is divided into two subtypes:diffuse cholesterosis and cholesterol polyps. For the former, there are channel to return in submucosa, so reverse cholesterol transport could be used and drug intervention could achieve the purpose of treatment. For the latter the return channel in submucosa was damaged, the only treatment should be the resection of gallbladder polyps and preservation of gallbladder. The histopathology of cholesterolosis is due to excessive lipid droplet accumulation in epithelial and subcutaneous tissues. The main components of lipid droplets are cholesterol esters (CEs). Removal of CEs from gallbladder epithelial cells (GBECs) is very important for maintaining intracellular cholesterol homeostasis and for treating cholesterol-related diseases. Several lines of evidence have indicated that the activation of either peroxisome proliferator-activated receptors y (PPARy) or liver X receptor a (LXRa) relates to cholesterol efflux. While pioglitazone can regulate the activation of PPARγ,22(R)-hydroxycholesterol can activate LXRa and is a metabolic intermediate in the biosynthesis of steroid hormones. In this study, pioglitazone was used to reduce intracellular CEs and the effect of 22(R)-hydroxycholesterol in combination with pioglitazone on cholesterosis of the gallbladder was tested. For gallbladder polyps are most commonly treated with cholecystectomy, which is associated with various complications. Preserving the gallbladder is preferable. This study reports a new endoscopic-laparoscopic (Endolap) technique for the removal of polyps and the preservation of the gallbladder.Methods:Gallbladder epithelial cells were treated with pioglitazone, 22(R)-hydroxycholesterol (a liver X receptor a (LXRa) agonist), or PPARy siRNA. Western blotting for PPARy, LXRa, ATP-binding cassette transporter A1 (ABCA1) and neutral cholesteryl ester hydrolase 1 (NCEH1) was performed, and cholesterol efflux to apoA-I was measured. Oil Red O staining was used to visualize lipid variations in cells. In the clinical cases,60 patients with gallbladder polyps were studied. Under general anesthesia, each polyp stem was coagulated, and then, the polyp was removed. A retrospective analysis was conducted to assess the recovery of gallbladder function.Results:In GBECs,1 uM pioglitazone significantly induced the expression of NCEH 1 and ABCA1. After PPARy siRNA was introduced into GBECs, the NCEH 1 and ABCAl proteins were significantly reduced to 22.15% and 23.62%, respectively. Furthermore,10 μM 22(R)-hydroxycholesterol was introduced into GBECs transfected with PPARy siRNA. Following this treatment, ABCAl protein expression increased 1.77-fold; however, NCEH 1 protein expression was not altered. In GBECs treated with pioglitazone, cholesterol efflux increased in a drug dose- and time-dependent fashion. Treatment of cholesterosis GBECs with 1 μM pioglitazone followed by Oil Red O staining revealed a marked decrease in lipid content.22(R)-hydroxycholesterol can modestly up-regulate LXRa while simultaneously increasing ABCA1 by 56%. The combination of 22(R)-hydroxycholesterol and pioglitazone resulted in a 3.64-fold increase in ABCAl expression and a high rate of cholesterol efflux. Oil Red O staining showed an obvious reduction in the lipid droplets associated with cholesterosis in GBECs. In conclusion, the present findings indicate that the anti-lipid deposition action of 22(R)-hydroxycholesterol combined with pioglitazone involves the activation of the PPARγ- LXRα-ABCA1 pathway, increased ABCAl expression and the efflux of cholesterol from GBECs. In the clinical cases, all procedures were successful between 60 and 135 min. The success rate was 93.33% (56/60). All patients were followed up and symptom-free, without recurrence of the polyps; 3 months after the operation, the volume and contraction of the gallbladder recovered to the preoperative levels. Even till to 6 months, the values are a little better.Conclusions:(1). Pioglitazone increased ABCA1 expression in an LXRa-dependent pathway and increased NCEH 1 expression in an LXRa-independent pathway.(2). Pioglitazone enhanced cholesterol efflux and decreased CE in cholesterosis GBECs.(3).22(R)-hydroxycholesterol synergistically combined with pioglitazone to produce a remarkable effect on lipid deposition in cholesterosis GBECs.(4). The Endolap technique is reliable for removing benign gallbladder polyps and is applicable to a wider range of clinical situations than percutaneous polypectomy.