阿托伐他汀对同型半胱氨酸诱导的心肌细胞MEK/ERK通路及心肌线粒体损伤的影响

目的探讨阿托伐他汀对同型半胱氨酸(Hcy)诱导的心肌细胞H9c2丝裂原细胞外信号调节激酶(MEK)/细胞外调节蛋白激酶(ERK)通路及心肌线粒体损伤的影响。方法细胞计数试剂盒8(CCK-8)检测不同浓度Hcy对H9c2细胞存活率的影响,筛选Hcy诱导浓度和时间。将诱导后的H9c2细胞分为模型组、5μmol/L阿托伐他汀组、10μmol/L阿托伐他汀组和15μmol/L阿托伐他汀组,另取正常H9c2细胞为对照组。流式细胞仪检测各组细胞凋亡率;JC-1法检测各组细胞线粒体膜电位的变化;DCFH-DA法检测各组细胞内活性氧(ROS)水平;酶联免疫吸附法(ELISA)检测各组细胞中丙二醛(MDA)、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)含量;Western blot检测各组细胞MEK1/2和ERK1/2磷酸化水平。结果与对照组相比,2μmol/L Hcy可显著降低H9c2细胞存活率(P0.05),本研究使用2μmol/L Hcy处理24 h诱导H9c2细胞。与对照组相比,模型组H9c2细胞凋亡率、ROS水平、MDA含量显著升高(P0.05),线粒体膜电位、SOD、CAT含量及MEK1/2、ERK1/2磷酸化水平显著降低(P0.05);与模型组相比,5μmol/L阿托伐他汀组、10μmol/L阿托伐他汀组和15μmol/L阿托伐他汀组H9c2细胞凋亡率、ROS水平、MDA含量依次降低(P0.05),线粒体膜电位、SOD、CAT含量及MEK1/2、ERK1/2磷酸化水平依次升高(P0.05)。结论阿托伐他汀可能通过激活MEK/ERK通路降低Hcy诱导的H9c2细胞氧化应激反应,减轻心肌线粒体损伤。     

Dual hereditary jaundice: simultaneous occurrence of mutations causing Gilbert's and Dubin-Johnson syndrome

BACKGROUND & AIMS: Dubin-Johnson syndrome is recessively inherited, conjugated hyperbilirubinemia induced by mutations in the ABCC2/MRP2 gene encoding the canalicular transporter for conjugated bilirubin. Gilbert's syndrome is recessively inherited, unconjugated hyperbilirubinemia caused by decreased conjugation rate of bilirubin associated mostly with homozygous A(TA) 7 TAA variant of the TATAA-box in the UGT1A1 gene promoter. Our aim was to establish the molecular diagnosis in a 3-year-old male with atypical, intermittent, predominantly unconjugated, hyperbilirubinemia. METHODS: 99m Tc-HIDA cholescintigraphy was used for imaging the biliary tree. Expression of ABCC2/MRP2 protein in hepatocytes was investigated immunohistochemically. UGT1A1 and ABCC2/MRP2 genes were sequenced from genomic DNA, and the mutations were verified by fragment analysis, sequencing the cloned exons, and restriction fragment length polymorphism. RESULTS: Cholescintigraphy revealed delayed visualization of the gallbladder. A brown granular lipopigment differing from melanin-like pigment reported in Dubin-Johnson syndrome was present in hepatocytes, but, otherwise, liver histology was normal. ABCC2/MRP2 protein was not detected on the canalicular membrane of hepatocytes, and 2 novel mutations were found in the ABCC2/MRP2 gene: a heterozygous in-frame insertion-deletion mutation 1256insCT/delAAACAGTGAACCTGATG in exon 10 inherited from the father and a heterozygous deletion 4292delCA in exon 30 inherited from the mother. In addition, the patient was homozygous for -3279T>G and A(TA) 7 TAA mutations in the UGT1A1 gene promoter. CONCLUSIONS: Our patient represents a case of digenic mixed hyperbilirubinemia-a distinct type of constitutive jaundice resulting from coinherited defects in ABCC2/MRP2 and UGT1A1 genes.     

ORMDL orosomucoid-like proteins are degraded by free-cholesterol-loading–induced autophagy

Eukaryotic cells have evolved robust mechanisms to counter excess cholesterol including redistribution of lipids into different compartments and compensatory up-regulation of phospholipid biosynthesis. We demonstrate here that excess cellular cholesterol increased the activity of the endoplasmic reticulum (ER) enzyme serine palmitoyl-CoA transferase (SPT), the rate-limiting enzyme in sphingomyelin synthesis. This increased SPT activity was not due to altered levels of SPTLC1 or SPTLC2, the major subunits of SPT. Instead, cholesterol loading decreased the levels of ORMDL1, a negative regulator of SPT activity, due to its increased turnover. Several lines of evidence demonstrated that free-cholesterol–induced autophagy, which led to increased turnover of ORMDL1. Cholesterol loading induced ORMDL1 redistribution from the ER to cytoplasmic p62 positive autophagosomes. Coimmunoprecipitation analysis of cholesterol-loaded cells showed increased association between ORMDL1 and p62. The lysosomal inhibitor chloroquine or siRNA knockdown of Atg7 inhibited ORMDL1 degradation by cholesterol, whereas proteasome inhibitors showed no effect. ORMDL1 degradation was specific to free-cholesterol loading as autophagy induced by serum starvation or general ER stress did not lead to ORMDL1 degradation. ORMDL proteins are thus previously unidentified responders to excess cholesterol, exiting the ER to activate SPT and increase sphingomyelin biosynthesis, which may buffer excess cellular cholesterol.Human atheroma macrophages accumulate large amounts of free cholesterol (FC), cholesterol esters (CEs), oxidized lipids, and oxysterols (1). Recent studies have established that accumulation of FC, oxidized phospholipids (PLs), and oxysterols in atherosclerotic plaques leads to endoplasmic reticulum (ER) stress, which in turn triggers the induction of autophagy to clear these toxic lipids (2–6). In addition, autophagy has been implicated as a key player in the clearance of cholesterol esters from foam cells and the regression of atherosclerotic lesions (2, 7, 8).Sphingomyelin (SM) levels are inversely correlated with HDL function and are higher in atherosclerotic aorta compared with healthy aorta (9–13). Myriocin, a potent inhibitor of SM biosynthesis, decreases atherosclerosis in mouse models, which may be accounted by its effects on increasing reverse cholesterol transport (RCT) and decreasing cholesterol absorption (14–21).The rate-limiting step in sphingomyelin biosynthesis is catalyzed by the ER resident serine palmitoyl-CoA transferase (SPT) enzyme complex, a heterodimer of serine palmitoyltransferase long-chain subunit (SPTLC)1 with either SPTLC2 or SPTLC3 (22). In yeast, the activity of SPT complex is posttranslationally inhibited by the orosomucoid-like (ORM) proteins. Under conditions of high sphingolipids, ORM proteins directly bind to the SPT complex and inhibit its activity, thus preventing further synthesis of sphingolipids (23, 24). When sphingolipid levels are low, ORM proteins are phosphorylated in N-terminal serine residues and dissociate from SPT complex (25), leading to increased sphingolipid biosynthesis (24, 25). However, no information is available about the mechanism by which mammalian ORM-like proteins (ORMDL1–3) regulate SPT activity. Recently, all three mammalian ORMDL proteins were shown to be involved in mediating a negative feedback response of ceramide biosynthesis upon addition of sphingosine (26). ORMDL3 has also been implicated in childhood asthma (27) and in promoting eosinophil trafficking and activation (28). Because mammalian ORMDL proteins have a truncated N-terminal domain and lack the phosphorylated serine residues found in yeast (29), the regulated binding to and inhibition of SPT by these ORMDL proteins must occur by a different mechanism than characterized in yeast.Here, we show that FC loading in macrophages induced SPT activity without altering the levels of SPT complex enzymes. The molecular mechanism of this up-regulation was increased turnover of ORMDL proteins via autophagy upon FC loading. Our finding that ORMDL proteins are degraded by FC-induced autophagy provides insights into molecular pathways and mechanisms regulating lipid homeostasis upon the accumulation of excess cholesterol. We propose that ORMDL proteins play a previously unidentified role in mediating cross-talk between cholesterol and sphingolipid biosynthesis.     

Inhibition of carbachol stimulated acid secretion by interleukin 1beta in rabbit parietal cells requires protein kinase C

BACKGROUND: Interleukin 1beta (IL-1beta) is a potent inhibitor of gastric acid secretion. Regulatory actions at several levels have previously been demonstrated, including direct inhibition of parietal cell acid secretion. Although IL-1beta may activate several intracellular signalling pathways, the mechanisms responsible for inhibition of carbachol stimulated acid secretion have not been determined. AIMS: To investigate the roles of protein kinase C (PKC) and the sphingomyelinase signalling pathways in the regulation of acid secretion by IL-1beta. METHODS: Rabbit parietal cells were obtained by collagenase-EDTA digestion and centrifugal elutriation. Acid secretion stimulated by carbachol and A23187 (to mimic elevations in intracellular calcium) was assessed by 14C aminopyrine uptake in response to IL-1beta, PKC, and sphingomyelinase manipulation. RESULTS: IL-1beta inhibited carbachol and A23187 stimulated acid secretion in a dose dependent manner. The inhibitory actions were completely reversed by each of three different PKC inhibitors, staurosporine, H-7, and chelerythrine, as well as by PKC depletion with high dose phorbol ester pretreatment. IL-1beta did not downregulate parietal cell muscarinic receptor. IL-1beta significantly increased membrane PKC activity. Activation of the sphingomyelinase/ceramide pathway had no effect on basal or stimulated acid secretion. The inhibitory action of IL-1beta was independent of protein kinase A and protein kinase G activity. CONCLUSIONS: IL-1beta directly inhibits parietal cell carbachol stimulated acid secretion. This action occurs distal to muscarinic receptor activation and elevations in intracellular calcium and requires PKC.     

Effect of folic acid and betaine on fasting and postmethionine-loading plasma homocysteine and methionine levels in chronic haemodialysis patients

OBJECTIVES: To study fasting and postmethionine-loading (increment and decrement) plasma homocysteine levels in end-stage renal disease (ESRD) patients in relation to B-vitamin status and after folic acid treatment without or with betaine. DESIGN: Plasma total homocysteine (tHcy) and methionine levels were measured in chronic haemodialysis patients after an overnight fast, and 6 and 24 h after an oral methionine load (0.1 g kg-1). The patients were subsequently randomized to treatment with folic acid 5 mg daily with or without betaine 4 g daily, and the loading test was repeated after 12 weeks. The patients were then re-randomized to treatment with 1 or 5 mg folic acid daily for 40 weeks, after which a third loading test was performed. SETTING: Haemodialysis unit of university hospital and centre for haemodialysis. SUBJECTS: Twenty-nine consecutive maintenance (> 3 months) haemodialysis patients, not on folic acid supplementation, 26 of whom completed the study. RESULTS: At baseline, the mean fasting, the 6 h postload and the 6 h postload increment plasma tHcy levels were increased as compared with those in healthy controls (46.8 +/- 6.9 (SEM), 92.8 +/- 9.1 and 46.0 +/- 4.2 mumol L-1, respectively) and correlated with serum folate (r = -0.42, P = 0.02; r = -0.61, P = 0.001 and r = -0.54, P = 0.003, respectively), but not with vitamin B6 or vitamin B12. At week 12, these variables had all decreased significantly. Betaine did not have additional homocysteine-lowering effects. At week 52, fasting and postload tHcy levels did not differ significantly between patients on 1 or 5 mg folic acid daily. Plasma tHcy half-life and plasma methionine levels after methionine loading were not altered by folic acid treatment. CONCLUSIONS: In chronic haemodialysis patients, fasting as well as postmethionine-loading plasma tHcy levels depend on folate status and decrease after folic acid therapy. Increased postload homocysteine levels in these patients therefore do not necessarily indicate an impaired transsulphuration capacity only; alternatively, folate may indirectly influence transsulphuration. The elucidation of the complex pathogenesis of hyperhomocysteinaemia in chronic renal failure requires further investigation.     

MICS-1 interacts with mitochondrial ATAD-3 and modulates lifespan in C. elegans

Caenorhabditis elegans open reading frame T21C9.1 encodes an uncharacterized protein, which is here named MICS-1 (mitochondrial scaffolding protein-1). It is predicted to be the homolog of human outer mitochondrial membrane protein 25 (OMP25 or synaptojanin-2-binding protein), which is a PDZ domain containing protein with a putative role in cellular stress response pathways. Here, we provide evidence that MICS-1 is an interacting partner of mitochondrial protein ATAD-3 (homologue of human ATAD3), which is essential for C. elegans development. We demonstrate that mics-1(RNAi) animals or mics-1 mutants display enhanced longevity with an increased mean lifespan of up to 54% compared to control animals. Of note, also atad-3(RNAi) promoted longevity, although to a lesser extend (29% compared to controls). In addition, thermal stress of mics-1 mutants induced low reactive oxygen species (ROS) production, whereas atad-3(RNAi) animals were highly sensitive to this assay, displaying drastically increased ROS levels. Further studies revealed that MICS-1 and ATAD-3 associated longevity was partially dependent on the presence of DAF-16. However, for both conditions, we also found a DAF-16 independent extension of lifespan. Finally, we observed an additional lifespan extension in mics-1 mutants when subjected to atad-3(RNAi) whereas heat induced ROS production was even aggravated under this condition. This suggests (partially) independent effects of MICS-1 and ATAD-3 on lifespan and ROS production in vivo.     

Elevated dimethylglycine in blood of children with congenital heart defects and their mothers

Objective

Congenital Heart Defects (CHD) may be related to nutritional deficiencies affecting the methylation cycle. We aimed to study the metabolic markers of the betaine homocysteine methyl transferase (BHMT) pathway in children with CHD and their mothers compared to children without CHD and their mothers.

Materials and Methods

Children with CHD (n = 105, age < 3 years) and mothers of 80 of the affected children were studied. The controls were non-CHDs children of comparable age as the CHD group (n = 52) and their mothers (n = 50). We measured serum or plasma concentrations of the metabolites of the methylation cycle homocysteine (HCY), methylmalonic acid (MMA), cystathionine, S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), betaine, choline, and dimethylglycine (DMG).

Results

Children with CHD had higher plasma SAM (131 vs. 100 nmol/L) and DMG (8.7 vs. 6.0 μmol/L) and lower betaine/DMG ratio (7.5 vs. 10.2) compared to the controls. Mothers of CHD children showed also higher DMG (6.1 vs. 4.1 µmol/L) and lower betaine/DMG ratio compared with the mothers of the controls. Higher SAM levels were related to higher cystathionine, MMA, betaine, choline, and DMG. MMA elevation in the patients was related to higher HCY, SAM, betaine and DMG.

Conclusions

Elevated DMG in CHD children and their mothers compared to the controls can indicate upregulation of the BHMT pathway in this disease group. Nutritional factors are related to metabolic imbalance during pregnancy that may be related to worse birth outcome.     

Vitamin B6 intake, alcohol consumption, and colorectal cancer: a longitudinal population-based cohort of women

BACKGROUND & AIMS: Vitamin B6 has a crucial role in 1-carbon metabolism, which involves DNA synthesis and DNA methylation. Aberrations in these processes have been implicated in colorectal carcinogenesis. We examined the association between long-term dietary vitamin B6 intake and risk of colorectal cancer and whether this association is modified by consumption of alcohol, which may disrupt 1-carbon metabolism. METHODS: Our study population comprised 61,433 women in the population-based Swedish Mammography Cohort. The women were aged 40 to 76 years, had no history of cancer, and completed a food-frequency questionnaire at baseline in 1987-1990. Dietary information was updated in 1997. During a mean follow-up of 14.8 years, 805 incident colorectal cancer cases were diagnosed. RESULTS: After controlling for age and other potential confounders, long-term intake of dietary vitamin B6 was significantly inversely associated with risk of colorectal cancer (P value for trend = .002). Compared with women in the lowest quintile of vitamin B6 intake, those in the highest quintile had a 34% lower risk (multivariate rate ratio, 0.66; 95% confidence interval, 0.50-0.86). The association was most pronounced among women with moderate to high alcohol consumption. The multivariate rate ratio of colorectal cancer comparing extreme quintiles of vitamin B6 intake was 0.28 (95% confidence interval, 0.13-0.59) among women who consumed > or = 30 g/wk of alcohol (approximately equivalent to 2 drinks per week). CONCLUSIONS: Findings of this study suggest that vitamin B6 may play a role in the prevention of colorectal cancer, particularly among women who drink alcohol.     

人类真核延伸因子1A2对胰腺癌细胞侵袭、转移能力的影响

目的 探讨外源性人类真核延伸因子(EEF)1A2基因导入人胰腺癌SW1990细胞株后.细胞侵袭转移能力的改变.方法 应用腺病毒载体将EEF1A2基因导入人胰腺癌SW1990细胞中,采用划痕实验、Transwell小室、细胞粘附实验检测转染前后细胞运动、侵袭、转移及粘附能力的改变.结果 Ad5/F35-EEF1A2转染后继续培养48 h的SW1990细胞,可见预期大小的特异性条带.实验组24 h后细胞迁移率为(74.43±2.12)%,与阴性对照组和空白对照组比较差异有统计学意义[(44.08±5.92)%和(48.09±3.54)%,P＜0.05].实验组48 h后穿膜细胞数为(65.42±8.24)个,与阴性对照组和空白对照组相比差异有统计学意义[(20.10±5.82)个和(23.25±5.23)个,P＜0.05].实验组48 h后穿膜细胞数为(61.30±5.68)个,与阴性对照组和空白对照组相比差异有统计学意义[(32.04±3.60)个和(32.33±2.51)个,P＜0.05],且对Ⅰ型、Ⅱ型、Ⅳ型胶原、纤维结合蛋白、粘蛋白的粘附力增强(P＜0.05).结论 腺病毒介导的EEF1A2高表达能明显增强胰腺癌SW1990细胞的运动、侵袭、转移及粘附能力.提示EEF1A2可能通过改变胰腺癌细胞的生物学特性影响胰腺癌的发生发展.     

Challenges in diagnosing adhesive small bowel obstruction

Adhesive small bowel obstruction(ASBO)is the most frequently encountered surgical disorder of the small intestine.Up to 80%of ASBO cases resolve spontaneously and do not require invasive treatment.It is important to identify such patients that will benefit from conservative treatment in order to prevent unnecessarily exposing them to the risks associated with surgical intervention,such as morbidity and further adhesion formation.For the remaining ASBO patients,timely surgical intervention is necessary to prevent small bowel strangulation,which may cause intestinal ischemia and bowel necrosis.While early identification of these patients is key to decreasing ASBO-related morbidity and mortality,the non-specific signs and laboratory findings upon clinic presentation limit timely diagnosis and implementation of appropriate clinical management.Combining the clinical presentation findings with those from other diagnostic imaging modalities,such as abdominal X-ray,computed tomography-scan and water-soluble contrast studies,will improve diagnosis of ASBO and help clinicians to better evaluate the potential of conservative management as a safe strategy for a particular patient.Nonetheless,patients who present with moderate findings by all these approaches continue to represent a challenge.A new diagnostic strategy is urgently needed to further improve our ability to identify early signs of strangulated bowel,and this diagnostic modality should be able to indicate when surgical management is required.A number of potential serum markers have been proposed for this purpose,including intestinal fatty acid binding protein andα-glutathione S transferase.On-going research is attempting to clearly define their diagnostic utility and to optimize their potential role in determining which patients should be managed surgically.     

Resveratrol and fenofibrate ameliorate fructose-induced nonalcoholic steatohepatitis by modulation of genes expression

AIM: To evaluate the effect of resveratrol, alone and in combination with fenofibrate, on fructose-induced metabolic genes abnormalities in rats. METHODS: Giving a fructose-enriched diet(FED) to rats for 12 wk was used as a model for inducing hepatic dyslipidemia and insulin resistance. Adult male albino rats(150-200 g) were divided into a control group and a FED group which was subdivided into 4 groups, a control FED, fenofibrate(FENO)(100 mg/kg), resveratrol(RES)(70 mg/kg) and combined treatment( FENO + RES)( half the doses). A l l treatments were given orally from the 9th week till the end of experimental period. Body weight, oral glucose tolerance test(OGTT), liver index, glucose, insulin, insulin resistance(HOMA), serum and liver triglycerides(TGs), oxidative stress(liver MDA, GSH and SOD),serum AST, ALT, AST/ALT ratio and tumor necrosis factor-α(TNF-α) were measured. Additionally, hepatic gene expression of suppressor of cytokine signaling-3(SOCS-3), sterol regulatory element binding protein-1c(SREBP-1c), fatty acid synthase(FAS), malonyl Co A decarboxylase(MCD), transforming growth factor-β1(TGF-β1) and adipose tissue genes expression of leptin and adiponectin were investigated. Liver sections were taken for histopathological examination and steatosis area were determined.RESULTS: Rats fed FED showed damaged liver, impairment of glucose tolerance, insulin resistance, ox ida t ive s t re s s a nd dy s l ipide m ia. As fo r ge ne expression, there was a change in favor of dyslipidemia and nonalcoholic steatohepatitis(NASH) development. All treatment regimens showed some benefit in reversing the described deviations. Fructose caused deterioration in hepatic gene expression of SOCS-3, SREBP-1c, FAS, MDA and TGF-β1 and in adipose tissue gene expression of leptin and adiponectin. Fructose showed also an increase in body weight, insulin resistance(OGTT, HOMA), serum and liver TGs, hepatic MDA, serum AST, AST/ALT ratio and TNF-α compared to control. All treatments improved SOCS-3, FAS, MCD, TGF-β1 and leptin genes expression while only RES and FENO + RES groups showed an improvement in SREBP-1c expression. Adiponectin gene expression was improved only by RES. A decrease in body weight, HOMA, liver TGs, AST/ALT ratio and TNF-α were observed in all treatment groups. Liver index was increased in FENO and FENO + RES groups. Serum TGs was improved only by FENO treatment. Liver MDA was improved by RES and FENO + RES treatments. FENO + RES group showed an increase in liver GSH content.CONCLUSION: When resveratrol was given with half the dose of fenofibrate it improved NASH-related fructose-induced disturbances in gene expression similar to a full dose of fenofibrate.     

The cell biology of the unfolded protein response

The unfolded protein response (UPR) is an ensemble of signal transduction pathways that respond to perturbations in the oxidative, pro-folding environment of the endoplasmic reticulum. During the past decade, ongoing research implicated these pathways in maintaining homeostasis of cells and organisms exposed to various stresses. Herein, we highlight recent findings regarding the functional role of the UPR in both normal and pathophysiologic processes.     

Cyclodextrin overcomes deficient lysosome-to-endoplasmic reticulum transport of cholesterol in Niemann-Pick type C cells

A handoff model has been proposed to explain the egress from lysosomes of cholesterol derived from receptor-mediated endocytosis of LDL. Cholesterol is first bound by soluble Niemann-Pick C2 (NPC2) protein, which hands off the cholesterol to the N-terminal domain of membrane-bound NPC1. Cells lacking NPC1 or NPC2 accumulate LDL-derived cholesterol in lysosomes and fail to deliver LDL cholesterol to the endoplasmic reticulum (ER) for esterification by acyl-CoA acyltransferase (ACAT) and for inhibition of sterol regulatory element-binding protein cleavage. Here, we support this model by showing that the cholesterol transport defect in NPC1 mutant cells is restricted to lysosomal export. Other cholesterol transport pathways appear normal, including the movement of cholesterol from the plasma membrane to the ER after treatment of cells with 25-hydroxycholesterol or sphingomyelinase. The NPC1 or NPC2 block in cholesterol delivery to the ER can be overcome by 2-hydroxypropyl-β-cyclodextrin, which leads to a marked increase in ACAT-mediated cholesterol esterification. The buildup of cholesteryl esters in the cytosol is expected to be much less toxic than the buildup of free cholesterol in the lysosomes of patients with mutations in NPC1 or NPC2.     

The immunosuppressive agents rapamycin,cyclosporin A and tacrolimus increase lipolysis,inhibit lipid storage and alter expression of genes involved in lipid metabolism in human adipose tissue

Cyclosporin A (CsA), tacrolimus and rapamycin are immunosuppressive agents (IAs) associated with insulin resistance and dyslipidemia, although their molecular effects on lipid metabolism in adipose tissue are unknown.