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Abstract@#Alzheimer's disease (AD) is a neurodegenerative disease characterized by deposition of β-amyloid (Aβ). Liver X receptors (LXRs), a member of the nuclear receptor transcription factor superfamily, are widely expressed in brain, which may be involved in the development and progression of AD. Based on the international and national publications pertaining to the association between LXRs and AD from 2010 to 2022, this review summarizes the advances on the involvement of LXRs in the regulation of cholesterol metabolism, inflammatory response and synapse formation in the pathogenesis of AD was reviewed, so as to provide insights into the prevention and treatment of AD.
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Aim To examine the effect of peptide P3 on lipid accumulation in RAW264.7 cells and the underlying molecular mechanism. Methods MTT method was used to screen the concentration of peptide P3 and oxidized low density lipoprotein(ox-LDL),and RAW.264.7 cells were induced to form foam cells by ox-LDL with 80 mg·L
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ObjectiveTo study the effect of isoflavones from Sojae Semen Praeparatum （ISSP） on lipid metabolism in atherosclerotic mice， and decipher the underlying mechanism via the peroxisome proliferator-activated receptor gamma/liver X receptor alpha/ATP-binding cassette transporter A1 （PPARγ/LXRα/ABCA1） signaling pathway. MethodFifty ApoE-/- mice were randomly assigned into the model group， western medicine （atorvastatin calcium， 3.03 mg·kg-1） group， and low-， medium-， and high-dose ISSP （2.5， 5， 10 mg·kg-1， respectively） groups， with 10 rats in each group. Atherosclerosis model mice were established by bilateral ovariectomy and feeding high-fat diet. Another 10 ApoE-/- mice receiving ovariectomy and high-fat diet were taken as the sham group. Some mice died of postoperative infection， and finally 6 mice were included in each group. One week after operation， each group was administrated with corresponding drugs or equivalent amount of normal saline. After 12 weeks， the levels of triglyceride （TG）， total cholesterol （TC）， high-density lipoprotein cholesterol （HDL-C）， low-density lipoprotein cholesterol （LDL-C）， and non-esterified fatty acids （NEFAs） in serum and liver tissue were measured. The levels of tumor necrosis factor-α （TNF-α） and interleukin-6 （IL-6） in serum were detected by enzyme-linked immunosorbent assay （ELISA）. Hematoxylin-eosin （HE） staining and oil red O staining were used for observation of aortic plaque formation and liver lipid deposition. The mRNA and protein levels of PPARγ， LXRα， ABCA1， and ATP-binding cassette transporter G1 （ABCG1） in liver were determined by real-time fluorescence quantitative polymerase chain reaction （Real-time PCR） and Western blot. ResultCompared with the sham group， the modeling of atherosclerosis increased the aortic plaque area （P<0.01）， elevated the serum TC， TG， LDL-C， TNF-α， and IL-6 levels （P<0.01）， decreased the level of HDL-C （P<0.01）， increased the liver index （P<0.05） and the levels of TC， TG， and NEFAs in liver （P<0.01）， and caused obvious hepatic fat vacuoles and lipid deposition. In addition， the modeling down-regulated the mRNA levels of PPARγ， LXRα， ABCA1 in liver （P<0.05， P<0.01），and regulated the mRNA and protein levels of ABCG1（P<0.05， P<0.01）. Compared with the model group， atorvastatin calcium and middle-， high-dose ISSP reduced the serum TC， TG， LDL-C， TNF-α， and IL-6 levels （P<0.01）， decreased the liver index （P<0.01）， alleviated the liver fat vacuoles and lipid deposition， and increased the levels of TC， TG， and NEFAs in the liver （P<0.05， P<0.01）. Furthermore， they up-regulated the mRNA and protein levels of PPARγ， LXRα， ABCA1， and ABCG1 in the liver （P<0.05， P<0.01）. ConclusionISSP may regulate lipid metabolism through PPARγ/LXRα/ABCA1 signaling pathway to down-regulate the expression of inflammatory cytokines in serum and alleviate liver lipid deposition， thereby suppressing the formation of atherosclerotic plaque.
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The function of ATP binding cassette protein A1 (ABCA1) is central to cholesterol mobilization. Reduced ABCA1 expression or activity is implicated in Alzheimer's disease (AD) and other disorders. Therapeutic approaches to boost ABCA1 activity have yet to be translated successfully to the clinic. The risk factors for AD development and progression, including comorbid disorders such as type 2 diabetes and cardiovascular disease, highlight the intersection of cholesterol transport and inflammation. Upregulation of ABCA1 can positively impact APOE lipidation, insulin sensitivity, peripheral vascular and blood-brain barrier integrity, and anti-inflammatory signaling. Various strategies towards ABCA1-boosting compounds have been described, with a bias toward nuclear hormone receptor (NHR) agonists. These agonists display beneficial preclinical effects; however, important side effects have limited development. In particular, ligands that bind liver X receptor (LXR), the primary NHR that controls ABCA1 expression, have shown positive effects in AD mouse models; however, lipogenesis and unwanted increases in triglyceride production are often observed. The longstanding approach, focusing on LXRβ vs. LXRα selectivity, is over-simplistic and has failed. Novel approaches such as phenotypic screening may lead to small molecule NHR modulators that elevate ABCA1 function without inducing lipogenesis and are clinically translatable.
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Aim To investigate the molecular mechanism of metformin inhibiting atherosclerosis in ApoE 1_ mice by reverse cholesterol transport. Methods Eighteen ApoE -/ _ mice were randomly divided into three groups, control group, model group and metformin group, and body weight changes were monitored weekly. Blood samples were taken to measure serum lipid levels; animal ultrasound was used to measure abdominal aortic wall thickness; HE and oil red 0 staining were used to evaluate the degree of liver steatosis; Western blot was used to detect the expression of liver cholesterol reverse transport-related proteins LXRa and ABCA1. Results Compared with control group, the body weight, serum T C, T G, and LDL in model group increased, HDL decreased(P <0. 05), abdominal aortic wall thickened (P <0. 05), liver fat deposition increased, and L X R a, ABCA1 expression was reduced. In metformin group, body weight, serum T C, T G, LDL decreased, HDL increased (P <0. 05), liver fat deposition and abdominal aortic wall thickness were significandy reduced (P <0. 05), and LXRa and ABCA1 expressions markedly increased (P <0. 0 5). Conclusions Metformin can delay the progression of atherosclerosis by up-regulating the expression of liver cholesterol reverse transport related proteins LXRa and ABCA1, enhancing liver reverse cholesterol transport, regulating blood lipid metabolism and reducing liver lipid deposition.
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OBJECTIVE: To investigate the effect of liver X receptor(LXR)-adenosine triphosphate-binding cassette transporter A1(ABCA1) signaling pathway on the free silica(SiO_2)-induced foaming of macrophages. METHODS: Human histiocytic lymphoma U937 cells were induced to differentiate into macrophages by phorbol myristate acetate. The macrophages at logarithmic growth phase were randomly divided into 4 groups: the cells in the control group received no treatment, the cells in the SiO_2 stimulation group were stimulated with SiO_2 suspension at a dose of 50 mg/L, and the cells in the oxidized low-density lipoprotein(ox-LDL) group were treated with ox-LDL at the dosed 50 mg/L, the cells in the combination group were simultaneously stimulated with SiO_2 suspension and ox-LDL at a dose of 50 mg/L. Cells were collected after 48 hours of culture. Macrophage foaming was observed by oil red O staining. The levels of total cholesterol(TC), free cholesterol(FC), cholesteryl ester(CE) and CE specific gravity(CE%) in macrophages were detected using a microplate reader. The expression of LXR and ABCA1 was detected using Western blotting. RESULTS: The results of the oil red O staining showed that all the macrophages in the SiO_2 stimulation group, ox-LDL group and the combination group had foaming changes. The degree of foaming in the macrophages in the combination group was higher than that in the other two groups. The levels of TC, FC, CE and CE% in macrophages increased(P<0.05), and the protein relative expression of LXR and ABCA1 decreased(P<0.05), in SiO_2 stimulation group, ox-LDL group and combination group compared with the control group. The macrophages in the combination group were transformed into foam cells. The levels of TC, FC, CE and CE% in macrophages of the combination group increased(P<0.05), and the protein relative expression of LXR and ABCA1 decreased(P<0.05), compared with the SiO_2 stimulation group and the ox-LDL group. CONCLUSION:sFree SiO_2 can induce foaming of macrophages, and ox-LDL in combination with SiO_2 has a synergistic effect on the formation of foaming of macrophages.The process of macrophage foaming may be achieved by inhibiting the LXR-ABCA1 signaling pathway.
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Objective:To investigate the mechanism of Shugan Wendan decoction in treating atherosclerosis based on liver X receptor α(LXRα)/nuclear factor-κB(NF-κB) signal. Method:A New Zealand rabbit model of atherosclerosis with liver-Qi stagnation was established by using calf serum albumin immune injury, high fat feeding and bondage emotional stress method. Theses rabbits are randomly divided into 6 groups, control group,model group, atorvastatin group, Shugan Wendan decoction low, medium and high dose group(2.18,6.54,19.62 g·kg-1·d-1). After successful modeling, the rabbits were treated by injecting drugs with Atorvastatin and low, middle and high dose Shugan Wendan decoction to gastric.The control group and the model group were given intragastric administration of saline in the same volume. The period of gavage is 6 weeks. The pathological changes of the rabbits were detected by hematoxylin-eosin(HE) staining.Serum levels of totalcholesterol(TC), triglyceride(TG),low density extremityprotein(LDL-C), high density extremity protein(HDL-C), nitric oxide(NO), and endothelin-1(ET-1) of the rabbits were detected by enzyme method, nitrate reductase method, and enzyme-linked immunosorbent assay(ELISA), respectively.The gene expression of CRP, IL-1β, IL-6 and MMP-9 in the aorta was detected by Real-time fluorescent quantitative polymerase chain reaction(Real-time PCR) method.The protein expression of LXRα/NF-κB signaling pathway wasdetected by Western blot. Result:Compared with normal control group, in model group, the lumen of the blood vessels was significantly narrowed, atheromatous plaques were formed, and a large number of intracellular foam-like changes were seen. In atorvastatin group and Shugan Wendan decoction group, the blood vessels in high, middle, and low concentration groups were narrowed. Atherosclerotic plaques and foam-like changes were all lower than the model group.Compared with the normal control group, the TG, TC, and LDL-C levels in the model groupincreased(PPPPβ, IL-6 and MMP-9 all increased(Pα protein in the model group was decreased(PκB was increased(PPPβ, IL-6 and MMP-9 in the atorvastatin group,the low, middle and high dose Shugan Wendan decoction groups all decreased(Pα protein in the group was increased(PκB was decreased(PConclusion:Shugan Wendan decoction can inhance the function of vascular endothelial cells and the stability of atherosclerotic plaque by regulating LXRα/NF-κB signaling pathway.
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Objective:To observe the expression levels of niemann-pick C1-like 1 (NPC1L1) and adenosine triphosphate-binding cassette transporters G8 (ABCG8) in intestine of hyperlipidemic model rats, in order to investigate the therapeutic mechanism of Shuangyu Tiaozhi decoction on hyperlipidemia. Method:A total of 40 SD rats were selected, including 8 for normal control group. The remaining 32 rats were used to establish hyperlipemic model. After modeling, the rats were randomly divided into the model group (equivalent normal saline), the high and low-dose Shuangyu Tiaozhi groups (15.6, 7.8 g·kg-1), and the Simvastatin group (4 mg·kg-1), with 8 in each group. They were given drugs by gavage for 8 weeks. The levels of total cholesterol (TC), triglyceride (TG) in serum and total cholesterol (TTC), free cholesterol (FTC) in liver of rats in each group were determined by biochemical and enzymatic methods. The morphological changes of liver were observed by hematoxylin-eosin (HE) staining, and the levels of expressions of NPC1L1, ABCG8 and liver X receptor-α (LXR-α) in intestine were detected by Real-time fluorescence quantitative polymerase chain reaction (Real-time PCR) and Western blot. The expression of ABCG8 protein was determined by immunohistochemistry. Result:After successful replication of the hyperlipidemia model, the blood lipid level was abnormally increased, and the liver steatosis became obvious in the model group compared with the normal control group. The expression levels of NPC1L1, LXR-α and ABCG8 increased significantly (PPα were significantly down-regulated, but ABCG8 was obviously up-regulated in a dose-dependent manner (PPPPPPConclusion:Shuangyu Tiaozhi decoction can reduce the blood lipid level of hyperlipemic rat model by reducing the absorption of cholesterol. Its mechanism may be correlated with the down-regulation of NPC1L1 expression and the up-regulation of ABCG8 expression.
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Sterol regulatory element binding proteins (SREBPs) are the major transcription factors regulating cholesterol, fatty acid and triglyceride biosynthesis and control the expression of key genes such as lipogenesis and uptake. In this review, we summarize the processing of SREBPs and their interactions with insulin, cyclic adenosine monophosphate (cAMP), and liver X receptor (LXR) for the synthesis and metabolism of lipid, and combine the latest researches to illustrate the function of SREBPs. These findings suggest that inhibition of SREBPs can be a new strategy for the treatment of metabolic diseases, such as type Ⅱ diabetes, insulin resistance, fatty liver, atherosclerosis and tumors.
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A large number of epidemiological data have shown that the high-density lipoprotein cholesterol level is negatively related to atherosclerotic cardiovascular disease, suggesting that high-density lipoprotein may have the effect of anti-atherosclerosis. It may play the role of anti-atherosclerosis, through the promotion of cholesterol reverse transport, anti-inflammatory, antioxidant, and against thrombosis and fibrinolysis and so on. Among them, reverse cholesterol transport which is mainly regulated by apolipoprotein A-I, ATP-binding cassette transporter 1, liver X receptor and cholesteryl ester transfer protein, may play a major role in the maintenance of cholesterol homeostasis and reversing the course of atherosclerosis. These regulatory factors may be potential targets in high density lipoprotein-based drug discovery. In this review, these key proteins are discussed for the current status of small molecule drugs against atherosclerosis.
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Aim To investigate the effect of liver X receptor (LXR) activation on the proliferation of hippocampal neural stem cells in global cerebral ischemia/reperfusion (I/R) mice,and its mechanisms.Methods A total of 75 C57BL/6 mice were randomly divided into three groups,namely the sham operation group,the cerebral I/R group and the cerebral I/R with TO901317 treatment (I/R + TO90) group.The I/R mouse model was induced via the bilateral common carotid artery occlusion.HE staining was used to detect the pathological changes in hippocampal CA1 region.Immunohistochemistry was executed to detect hippocampus DCX + cells.Immunofluorescence of BrdU was implemented to detect the proliferation neural stem cell.Morris water maze test was used to assess spatial learning and memory in mice.Western blot was used to detect the expression of hippocampus LXRα,LXRβ,ABCA1,p-ERK1/2,t-ERK1/2,p-CREB,t-CREB,BDNF.Results LXR activation improved cognitive recovery(P ＜0.01),and induced the proliferation of neural stem cells (P ＜ 0.01) in I/R mice.The expressions of hippocampal ABCA1,p-ERK1/2,p-CREB,BDNF in I/R + TO90 group mice also increased (P ＜ 0.01).Conclusions LXR activation can induce the proliferation of hippocampal neural stem cells and facilitate cognitive recovery following global cerebral I/R in mice,which may be related to the activation of hippocampal ERK1/2-CREB-BDNF pathway and then promoting endogenous neurogenesis in the hippocampus DG region of I/R mice.
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OBJECTIVE:To investigate the effect and mechanism of Allii macrostemonis bulbus on blood lipid levels in hyperlipidemia model rats,and to provide reference for clinical use of Allii macrostemonis bulbus to reduce blood lipid. METHODS:A total of 10 normal rats were included in normal control group and given common diet. Other 50 rats were given hyperlipid diet to induce hyperlipidemia rat model. 40 model rats were randomly divided into model group(hyperlipid diet),Allii macrostemonis bulbus low-dose,medium-dose and high-dose groups(0.83,1.67,2.50 g/kg,fed by hyperlipid diet which containing 10%Allii macrostemonis bulbus 8.3,16.7,25.0 g/kg,fill with hyperlipid feed in patients with insufficient food intake). After fed for 45 d,the contents of TC,TG,LDL-C and HDL-C in serum of rats were detected. Liver,spleen,renal and cardiac indexes of rats were calculated. mRNA expression of low density lipoprotein receptor(LDLR)and liver X-receptor α(LXRα)were detected in liver tissue of rats. RESULTS:Compared with normal control group,the contents of TC and LDL-C in serum and liver index of rats were increased significantly in model group,while the content of HDL-C in serum and mRNA expressions of LDLR and LXR α in liver tissue were decreased significantly,with statistical significance(P<0.01). Compared with model group,the contents of TC and LDL-C in serum were decreased significantly in Allii macrostemonis bulbus groups,while the content of HDL-C was increased significantly. mRNA expressions of LDLR and LXR α in liver tissue were increased significantly in Allii macrostemonis bulbus medium-dose and high-dose groups,while liver and spleen indexes were decreased significantly,with statistical significance(P<0.05 or P<0.01). CONCLUSIONS:Allii macrostemonis bulbus shows good blood-lipid lowering effect,the mechanism of which may be associated with up-regulating mRNA expressions of LDLR and LXRα in liver tissue.
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Objective To explore the effect and mechanism of liver X receptor agonist T0901317 on angiogenesis phenotype of liver cancer.Methods The experimental study was conducted.Hepatocellular carcinoma MHCC97-H and Huh7 cells and human umbilical vein endothelial cells (HUVEC) were cultured in vitro.Each cell line was divided into 3 groups:control group (non-treated),low concentration group (treated using 1 μmot/L T0901317) and high concentration group (treated using 3 μmol/L T0901317).Cell proliferation was counted with a CCK-8 assay.Quantitative real-time polymerase chain reaction (PCR) was applied to confirm the relative mRNA expression of fatty acid synthetase (FAS) of liver X receptor target genes in 3 groups.Subcutaneous xenograft tumor volume and body mass were measured in MHCC97-H nude mice model.Then mice were sacrificed and tumor tissues were analyzed for CD31 relative expression by immunohistochemistry (IHC) staining.Migration and vessel angiogenesis of HUVEC were determined by Transwell method.Observation indicators:(1) effects of T0901317 on MHCC97-H,Huh7 and HUVEC cells proliferation,(2) effects of T0901317 on liver X receptor with MHCC97-H,Huh7 and HUVEC cells,(3) effects of T0901317 on subcutaneous xenograft tumor growth in MHCC97-H nude mice model,(4) effects of T0901317 on CD31 relative expression in subcutaneous xenograft tumor tissues of MHCC97-H nude mice model,(5) effects of T0901317 on migration of HUVEC,(6) effects of T0901317 on vessel angiogenesis of HUVEC.Measurement data with normal distribution were represented as x±s,and comparisons between groups were analyzed by the t test.Results (1)Effects of T0901317 on MHCC97-H,Huh7 and HUVEC cells proliferation:results of CCK-8 assay showed that percentage of living cells was respectively 100.0％± 1.7％,101.0％±0.7％ and 104.6％± 1.9％ in MHCC97-H control,low concentration and high concentration groups,with no statistically significant difference (F =2.632,P＞0.05).Percentage of living cells was respectively 100.0％ ± 2.7％,97.6％ ± 2.4％ and 103.7％ ± 2.8％ in Huh7 control,low concentration and high concentration groups,with no statistically significant difference (F =1.404,P＞0.05).Percentage of living cells was respectively 100.0％ ±0.7％,100.7％± 1.2％ and 101.3％ ±0.8％ in HUVEC control,low concentration and high concentration groups,with no statistically significant difference (F=0.471,P＞0.05).(2) Effects of T0901317 on liver X receptor with MHCC97-H,Huh7 and HUVEC cells:results of quantitative real-time PCR showed that relative mRNA expressions of FAS in MHCC97-H control,low concentration and high concentration groups were respectively 100.0 ％±2.2％,658.5％±7.7％ and 1 241.0％± 106.8％,with a statistically significant difference among groups (F=46.227,P＜0.05),and with a statistically significant difference between MHCC97-H control group and MHCC97-H low concentration and high concentration groups (t =70.025,8.274,P ＜ 0.05) and between MHCC97-H low concentration and high concentration groups (t =4.222,P ＜ 0.05).Relative mRNA expressions of FAS in Huh7 control,low concentration and high concentration groups were respectively 100.0％ ± 15.8％,1 225.0％ ± 26.7 ％ and 2 015.0％ ± 215.1％,with a statistically significant difference among groups (F =49.402,P＜ 0.05),and with a statistically significant difference between Huh7 control group and Huh7 low concentration and high concentration groups (t=39.460,8.879,P＜0.05) and between Huh7 low concentration and high concentration groups (t =2.836,P ＜ 0.05).Relative mRNA expressions of FAS in HUVEC control,low concentration and high concentration groups were respectively 100.0％ ± 19.6％,790.8％ ± 116.5％ and 1 756.0％ ± 55.0％,with a statistically significant difference among groups (F=185.395,P＜0.05),and with a statistically significant difference between HUVEC control group and HUVEC low concentration and high concentration groups (t =7.639,34.375,P＜0.05) and between HUVEC low concentration and high concentration groups (t =7.488,P＜0.05).(3) Effects of T0901317 on subcutaneous xenograft tumor growth in MHCC97-H nude mice model:results of assay showed that subcutaneous xenograft tumor volume in MHCC97-H control group and MHCC97-H T0901317 group were respectively (935±72)mm3 and (552 ± 47)mm3,with a statistically significant difference between groups (t=4.449,P＜0.05).Body masses of nude mice model in MHCC97-H control group and MHCC97-H T0901317 group were respectively (23.8±0.8) g and (21.7± 1.7) g,with no statistically significant difference between groups (t =1.059,P＞0.05).(4) Effects of T0901317 on CD31 relative expression in subcutaneous xenograft tumor tissues of MHCC97-H nude mice model:results of IHC staining showed that CD31 relative expression in subcutaneous xenograft tumor tissues of MHCC97-H nude mice model was 100％±11％ and 35％±7％ in MHCC97-H control group and MHCC97-H T0901317 group,with a statistically significant difference between groups (t =4.919,P＜0.05).(5) Effects of T0901317 on migration of HUVEC:results of Transwell method showed that percentages of membrane cells in HUVEC control,low concentration and high concentration groups were respectively 100.0％±4.0％,57.3％±1.5％ and 32.7％± 1.7％,with a statistically significant difference among groups (F=163.944,P＜0.05),and with statistically significant differences between HUVEC control group and HUVEC low concentration and high concentration groups (t =9.998,15.434,P＜0.05) and between HUVEC low concentration and high concentration groups (t =10.801,P ＜ 0.05).(6) Effects of T0901317 on vessel angiogenesis of HUVEC:results of vessel angiogenesis assay showed that length of vessel angiogenesis in HUVEC control,low concentration and high concentration groups were respectively 100.0％±3.4％,68.4％ ±3.5％ and 44.7％± 0.5％,with a statistically significant difference among groups (F =38.964,P ＜ 0.05),and with statistically significant differences between HUVEC control group and HUVEC low concentration and high concentration groups (t=6.268,9.831,P＜0.05) and between HUVEC low concentration and high concentration groups (t =3.460,P＜0.05).Conclusion Liver X receptor agonist T0901317 can inhibit vessel angiogenesis of liver cancer.
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Objective · To investigate the effects of ox-LDL on the proliferation of rat theca cells and expression of LXR-α and StAR, two genes associated with androgen biosynthesis. Methods · The expression of LXR-α in the ovarian tissue of rats was determined by immunohistochemistry. Primary theca cells were isolated and collected from rat ovary and cultured in vitro. Furthermore, the theca cells were treated with 25, 50, 100, 150, 200, 300 and 400 mg/L ox-LDL, respectively. The variations in LXR-α mRNA were identified using real-time PCR. MTT assay was performed to detect cell viability. The expression of LXR-α and StAR was measured by Western blotting analysis. Results · The effect of ox-LDL on the proliferation of rat theca cells and the levels of LXR-α and StAR in theca cells was in a concentration-dependent manner. Following exposure to various concentration of ox-LDL for 24 h, the proliferation of theca cells was induced by low concentration of ox-LDL (25-150 mg/L), and 100 mg/L ox-LDL showed the most significant inducing effect. Moreover, the cell survival rate was diminished considerably following with ox-LDL concentration increasing, especially lowered by 400 mg/L ox-LDL. The mRNA level of LXR-α was increased with low concentration of ox-LDL (25-150 mg/L) and the impact of ox-LDL on the induced expression of LXR-α mRNA was considerably distinct at the concentration of 150 mg/L. On the other hand, the expression of LXR-α mRNA was reduced with high concentration of ox-LDL, and the impact of 400 mg/L ox-LDLwas substantially distinct. The protein expression levels of LXR-α and StAR were increased with 150 mg/L ox-LDL, but StAR protein level in 150 mg/L ox-LDL group revealed no significant difference when compared with control group. The expression of LXR-α and StAR protein was significantly inhibited with 400 mg/L ox-LDL in the rat theca cells. Conclusion · Low concentrations of ox-LDL can induce the proliferation of theca cells, and promote the expression of StAR and LXR-α. Whereas, high concentrations of ox-LDL can reduce the cell viability and inhibit the expression of StAR and LXR-α.
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Objective To investigate the effects of liver X receptor (LXR) agonist on the proliferation of mouse pancreatic β cell line MIN6 cells.Methods The viability,changes of cell cycle,mRNA levels of S phase kinase associated protein 2 (Skp2) and p27,and protein levels of Skp2 and p27 in MIN6 cells treated with LXR agonist T0901317 were determined by the CCK-8 method,flow cytometry,real-time RT-PCR and western blot,respectively.Results The viability of MIN6 cells treated with 1 μmol/L,5 μmol/L and 10 μnol/L of T0901317 were (98.54 ±0.94)％,(87.03 ±0.93)％ and (75.57 ± 1.85)％ of the controls,respectively,and there was significant difference among them (F =301.90,P ＜ 0.01).The percentages of G1 phase cells in the MIN6 cells treated with 0 μmol/L,1 μmol/L,5 μmol/L and 10 μmol/L of T0901317 were (35.93 ±2.25)％,(38.45 ±0.91)％,(45.46±1.34)％ and (53.28 ± 1.14) ％,respectively,and there was significant difference among them (F =80.83,P ＜ 0.01).Similarly,the percentages of S phase cells in the MIN6 cells treated with 0 μmol/L,1 μmol/L,5 μmol/L and 10 μmoi/L of T0901317 were (52.87 ± 1.19) ％,(48.65 ± 0.85) ％,(36.31 ± 1.37) ％ and (31.45 ± 1.22) ％,respectively,and there was also significant difference among them (F =221.30,P ＜ 0.01).The protein levels of p27 in the MIN6 cells treated with 10 μmol/L of T0901317 (2.84 ± 0.14) were significantly higher than that in the controls (2.28 ± 0.10) (t =4.54,P ＜ 0.05),while there was no significant difference in the mRNA levels of p27 between them (t =0.28,P ＞ 0.05).However,10 μmol/L of T0901317 significantly decreased mRNA (0.52 ± 0.02,t =29.22,P ＜ 0.01) and protein levels (0.98 ± 0.12 vs 1.89 ± 0.01,t =10.98,P ＜ 0.01) of Skp2 in MIN6 cells.Based on the control siRNA transfection group as a reference (100％),the cell survival rates of the p27 siRNA transfection group,10 μmol/L of T0901317 treatment group and the intervention group (p27 siRNA transfection + T0901317 treatment) were (100.97 ± 1.08) ％,(75.03 ± 1.83) ％ and (86.67 ± 2.45) ％,respectively.There was no significant difference between the control siRNA and p27 siR-NA transfection groups (t =1.542,P ＞ 0.05).Compared with the control siRNA transfection group,the cell survival rates of the T0901317 treatment group decreased (t =23.58,P ＜ 0.01).There was also significant difference in the cell survival rates between the T0901317 treatment group and the intervention group (t =7.77,P ＜ 0.01).Conclusion The activation of LXR may induce pancreatic β cell cycle arrest by up-regulating the expression of p27 and down-regulating the expression of Skp2.
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Cholesterol is a component of cell membrane and plays a vital role in maintaining metabolism and normal functions in human body. Liver X receptor (LXR) is a nuclear receptor expressed in abundance in the liver. It influences the process of cholesterol metabolism through regulating the synthesis, transformation, and transportation of cholesterol and bile acid at the level of hepatocytes, and therefore, it plays an important role in maintaining cholesterol homeostasis in human body. In addition, LXR can inhibit the intestinal absorption of dietary cholesterol, reduce exogenous cholesterol level and total cholesterol level in human body, and prevent hypercholesterolemia and formation of gallstones. This article summarizes the mechanism of action of LXR in regulating cholesterol metabolism at both liver and intestinal levels.
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Gallstone disease is highly prevalent in clinic,particularly in women and some specific ethnic groups.The formation of water-insoluble cholesterol crystals is due to a misbalance between the three major lipids present in the bile:cholesterol,bile salts,and phospholipids.Many proteins implicated in biliary lipid secretion in the liver are regulated by several transcription factors,including nuclear receptors LXR and FXR.Human and murine genetic,pathophysiological evidence is consistent with the relevance of these nuclear receptors in gallstone formation.In addition,there is emerging data that also suggests a role for estrogen receptor ESR1 in abnormal cholesterol metabolism leading to gallstone disease.A better comprehension of the role of nuclear receptor function in gallstone formation may help doctors to design new and more effective therapeutic strategies for this highly prevalent disease condition.
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Objective To investigate the effect and mechanism of liver X receptor ( LXR ) agonist on expression of fatty acid synthase( FAS) in diabetic kidney. Methods In the part of in vivo study, immunostaining was used to detect the FAS protein expression in kidney. 16-week-old male db/db mice on C57BL/6 background were administered via gavage a LXR synthetic agonist, TO901317, at a dose of 3 mg · kg-1 · d-1 or vehicle ( 0. 5%Carboxymethyl Cellulose Sodium, CMC-Na) alone for 7 d;Quantitative RT-PCR and Western blot were used to detect mRNA and protein levels of FAS and SREBP-1. In the part of in vitro study, MCT cell(a mouse murine proximal tubule cell line)was treated with 10μmol/L TO901317 for 24 h or transfected with active SREBP-1c expression vector (SREBP-1cN). HEK293 cells(a human renal tubule cell line)were transfected with mFAS-(1. 7 kb)-luc, LXR expression vector or SREBP-1cN for 12 h. Quantitative RT-PCR and luciferase reproter assay were utilized to examine FAS mRNA level and FAS promoter activity. Results FAS was abundantly expressed in renal cortex, with low expresson in renal glomeruli. The mRNA and protein expressious of FAS in kidney of db/db mice were lowered compared with db/m mice. TO90137 treatment increased FAS mRNA expression by 1. 3-fold. TO901317 increased expression of SREBP-1 in kidneys of db/m and db/db mice by 5. 1-fold and 17-fold, respectively. TO901317 and overexpression of SREBP-1c increased expression of FAS in MCT cells by 1. 5-fold and 1. 8-fold. Transcription activity of FAS were induced by TO901317, LXR, and SREBP-1cN overexpressions in HEK293 cells. Conclusions Both direct(LXRE)and indirect(SREBP-1c)mechanisms may contribute to the up-regulation of FAS expression by LXR in renal proximal tubule cells.
ABSTRACT
The term 'inflammation' was first introduced by Celsus almost 2000 years ago. Biological and medical researchers have shown increasing interest in inflammation over the past few decades, in part due to the emerging burden of chronic and degenerative diseases resulting from the increased longevity that has arisen thanks to modern medicine. Inflammation is believed to play critical roles in the pathogenesis of degenerative brain diseases, including Alzheimer's disease and Parkinson's disease. Accordingly, researchers have sought to combat such diseases by controlling inflammatory responses. In this review, we describe the endogenous inflammatory stimulators and signaling pathways in the brain. In particular, our group has focused on the JAK-STAT pathway, identifying anti-inflammatory targets and testing the effects of various anti-inflammatory drugs. This work has shown that the JAK-STAT pathway and its downstream are negatively regulated by phosphatases (SHP2 and MKP-1), inhibitory proteins (SOCS1 and SOCS3) and a nuclear receptor (LXR). These negative regulators are controlled at various levels (e.g. transcriptional, post-transcriptional and post-translational). Future study of these proteins could facilitate the manipulation of the inflammatory response, which plays ubiquitous, diverse and ambivalent roles under physiological and pathological conditions.
Subject(s)
Alzheimer Disease , Brain , Brain Diseases , History, Modern 1601- , Inflammation , Longevity , Neurons , Parkinson Disease , Phosphoric Monoester HydrolasesABSTRACT
EGFR-TKI plays an important role in the treatment of non-small-cell lung cancer. However, some researchers find that there are still some patients with primary or acquired resistance to EGFR-TKI. The present known mechanisms of acquired drug resistance finally lead to the re-activation EGFR downstream signa-ling pathways. Liver X receptor agonist has inhibition function to several critical steps of EGFR downstream sig-naling pathways PI3K-Akt-NF-κB,which makes it possible to overcome the drug resistance.