Preclinical evaluation of a novel SIRT1 modulator SRT1720 in multiple myeloma cells

SIRT1 belongs to the silent information regulator 2 (Sir2) protein family of enzymes and functions as a NAD(+) -dependent class III histone deacetylase. Here, we examined the anti-multiple myeloma (MM) activity of a novel oral agent, SRT1720, which targets SIRT1. Treatment of MM cells with SRT1720 inhibited growth and induced apoptosis in MM cells resistant to conventional and bortezomib therapies without significantly affecting the viability of normal cells. Mechanistic studies showed that anti-MM activity of SRT1720 is associated with: (i) activation of caspase-8, caspase-9, caspase-3, poly(ADP) ribose polymerase; (ii) increase in reactive oxygen species; (iii) induction of phosphorylated ataxia telangiectasia mutated/checkpoint kinase 2 signalling; (iv) decrease in vascular endothelial growth factor-induced migration of MM cells and associated angiogenesis; and (v) inhibition of nuclear factor-κB. Blockade of ATM attenuated SRT1720-induced MM cell death. In animal tumour model studies, SRT1720 inhibited MM tumour growth. Finally, SRT1720 enhanced the cytotoxic activity of bortezomib or dexamethasone. Our preclinical studies provide the rationale for novel therapeutics targeting SIRT1 in MM.     

Sirtuin 1 Activator SRT1720 Protects Against Lung Injury via Reduction of Type II Alveolar Epithelial Cells Apoptosis in Emphysema

In chronic obstructive pulmonary disease (COPD), two major pathological changes that occur are the loss of alveolar structure and airspace enlargement. Type II alveolar epithelial cells (AECII) play a vital role in maintaining alveolar homeostasis and lung tissue repair. Sirtuin 1 (SIRT1), a NAD⁺-dependent histone deacetylase, regulates many pathophysiological processes including inflammation, apoptosis, cellular senescence and stress resistance. The main aim of this study was to investigate whether SRT1720, a pharmacological SIRT1 activator, could protect against AECII apoptosis in rats with emphysema caused by cigarette smoke exposure and intratracheal lipopolysaccharide instillation in vivo. During the induction of emphysema in rats, administration of SRT1720 improved lung function including airway resistance and pulmonary dynamic compliance. SRT1720 treatment up-regulated the levels of surfactant protein (SP)A, SPC, SIRT1 and forkhead box O 3, increased SIRT1 activity, down-regulated the level of p53 and inhibited AECII apoptosis. Lung injury caused by emphysema was alleviated after SRT1720 treatment. SRT1720 could protect against AECII apoptosis in rats with emphysema and thus could be used in COPD treatment.     

中药清肠栓对溃疡性结肠炎大鼠结肠黏膜紧密连接蛋白ZO-1、occludin的影响

目的:探讨复方中药清肠栓对三硝基苯磺酸(TNBS)诱导的UC大鼠结肠黏膜上皮紧密连接相关蛋白-l(ZO-1)、闭锁蛋白(occludin)的修复作用.方法:清洁级♂SD大鼠36只,随机分为正常组、模型组、SASP组、清肠栓高、中、低剂量组,每组6只.选用TNBS诱导的UC大鼠模型.采用免疫荧光的方法观察各组大鼠结肠黏膜...     

Increase in the Tight Junction Protein Claudin-1 in Intestinal Inflammation

Background and Aims

Studies have shown a decrease in key tight junction (TJ) proteins such as ZO-1 and occludin in both inflammatory bowel disease (IBD) and experimental models of inflammation. Our group has also shown an increase in claudin-1 in experimental colitis.

Methods

IEC-18 cells were treated with increasing doses of tumor necrosis factor alpha (TNF??). The TJ was assessed by transepithelial resistance (TER), permeability, Western blot, PCR, and immunofluorescence. Mucosal samples from patients with ulcerative colitis (UC), Crohn??s disease (CD), and without IBD (normal) were assayed for TJ proteins occludin and claudin-1 by Western blot and a ratio of claudin-1 to occludin (C:O) was calculated.

Results

IEC-18 cells had increased permeability, decreased TER and an increase in claudin-1 with TNF?? treatment. In human specimens, there was a decrease in occludin and an increase in claudin-1 leading to a significant increase in the C:O ratio in diseased UC colon compared to non-diseased UC colon (P < 0.001) and normal colon (P < 0.01). In CD, the C:O ratio was similar in all CD tissue irrespective of disease status.

Conclusions

Treatment of IEC-18 cells with TNF??, a key inflammatory cytokine in IBD, led to a significant increase in claudin-1 expression. There was a significant increase in the C:O ratio in diseased colon in UC compared to the healthy appearing UC colon and normal controls. The C:O ratio was unchanged in CD despite presence or abscence of gross disease. This suggests that there may be an underlying difference in the TJ between UC and CD.     

Correlation of Intestinal Mucosal Healing and Tight Junction Protein Expression in Ulcerative Colitis Patients

Background

The aim of this study was to investigate the relationship between intestinal mucosal healing and tight junction (TJ) protein expression in patients with ulcerative colitis (UC).

β1-AR持久兴奋通过CaMKIIδ-内质网应激凋亡通路导致心力衰竭的机制

目的研究β1-AR持久兴奋通过CaMKIIδ内质网应激（ERS）凋亡通路导致心力衰竭的机制。方法30只SD大鼠随机分成三组，正常对照组（Control）、异丙肾上腺组（Iso）和、异丙肾上腺＋美托洛尔组（Iso＋Meto），每组10只，所有动物均自由进食进水。（1）Iso组大鼠背部皮下注射Iso5mg／（kg·d），连续10d；Control组背部皮下注射相同体积的生理盐水；Iso＋Meto组大鼠背部皮下注射Iso5mg／（kg·d），连续10d，在背部皮下注射Iso前一天开始Meto 10mg／（kg·d）灌胃，连续4周；（2）所有大鼠饲养4周后，采用美国Millar公司P—V Loop导管经颈动脉插管至左心室，使用Pow—erlab生理记录系统测量血流动力学相关指标；统计各组大鼠心脏重量和心脏重量／体重比值；（3）TUNEL法和Caspase-3活性检测心肌细胞凋亡；（4）Western blot分析CaMKIIδERS相关基因（GRP78、CHOP和caspase-12）和凋亡相关基因Bcl-2／Bax的表达水平。结果30只SD大鼠实验过程精神状态好，进食进水正常。（1）与Control组比较，Iso组SD大鼠心脏重塑和血流动力学指标有显著性差异（P〈0．05）；而Iso＋Meto组心脏重塑和血流动力学指标与Iso组相比明显改善（P〈0．05）；（2）TUNEL法原位检测各组大鼠心肌细胞凋亡示与Control组比较，Iso组TUNEL阳性细胞数明显增高（P〈0．05）；而Iso＋Met组明显低于Iso组（P〈0．05）。心肌细胞Caspase-3活性和TUNEL凋亡阳性细胞核指数各组变化一致。Western blot检测心肌细胞凋亡相关基因bcl-2／Bax蛋白表达。与Control组相比，Iso组bcl-2蛋白表达明显降低和Bax蛋白表达明显增加（P〈0．05）；而Iso＋Met组与Iso组相比,bcl-2明显增高和Bax明显降低（P〈0．05）；（3）Western blot分析CaMKIIδp-CaMKIIδ白表达显示，与Control组比较，Iso组CAMKII活性和p-CaMKIIδ蛋白表达明显增加；而Iso＋Meto组与Iso组相比，CAMKII活性和p-     

美沙拉嗪对溃疡性结肠炎患者肠黏膜紧密连接蛋白表达的影响

背景:溃疡性结肠炎(UC)是一种较常见的消化道疾病,其病因和发病机制尚未完全阐明,治疗缺乏特异性方法,导致病情迁延反复。目的:探讨美沙拉嗪治疗对UC肠道紧密连接蛋白的影响。方法:选取2010年12月～2011年6月南京医科大学附属南京医院收治的活动期UC患者30例,给予美沙拉嗪1.0 g tid治疗8周。治疗前后患者行结肠镜检查取活检,以免疫组化法检测治疗前后紧密连接蛋白occludin、ZO-1的表达。结果:美沙拉嗪治疗后UC患者内镜下均取得缓解。免疫组化结果显示,治疗后UC肠黏膜上皮细胞中occludin蛋白(7.20±1.55对1.60±0.55)、ZO-1蛋白表达(6.60±1.26对1.40±0.55)显著高于治疗前,差异均有统计学意义(P<0.05)。结论:美沙拉嗪可能通过上调紧密连接蛋白occludin、ZO-1的表达来保护肠黏膜屏障功能。     

Sirtuin 1 activator SRT1720 suppresses inflammation in an ovalbumin‐induced mouse model of asthma

Background and objective: In asthma, reduced histone deacetylase activity and enhanced histone acetyltransferase activity in the lungs have been reported. However, the precise function of Sirtuin 1 (Sirt1), a class III histone deacetylase, and the effect of the Sirt1 activator SRT1720 on allergic inflammation have not been fully elucidated. Methods: The effect of SRT1720, a synthetic activator of Sirt1, in an ovalbumin (OVA)‐induced asthma mouse model was investigated. The effect of SRT1720 and resveratrol on OVA stimulation in splenocytes from OVA‐sensitized and challenged mice was also examined. Results: In OVA‐sensitized and challenged mice (OVA mice) compared with saline‐sensitized and challenged mice (control mice), Sirt1 messenger RNA expression in the lungs was decreased (P = 0.02), while cellular infiltration, airway eosinophilia and bronchoalveolar lavage (BAL) fluid levels of interleukin (IL)‐4, IL‐5 and IL‐13 were increased (P < 0.01). In OVA mice, SRT1720 treatment decreased total and eosinophil cell counts and IL‐5 and IL‐13 levels in the BAL fluid compared with the vehicle treatment (P < 0.05). In OVA mice, SRT1720 treatment also decreased inflammatory cell lung infiltrates histologically (P = 0.002). Both SRT1720 and resveratrol suppressed OVA‐induced cell proliferation and IL‐6 (P < 0.05) and tumour necrosis factor‐α (TNF‐α) (P < 0.05) production in splenocytes (P < 0.01). Conclusions: The Sirt1 activator SRT1720 suppressed inflammatory cell infiltration and cytokine production in an OVA‐induced mouse model of asthma. SRT1720 and resveratrol suppressed OVA‐induced splenocyte proliferation and TNF‐α and IL‐6 production. Sirt1 activators might have beneficial effects in asthmatics by suppressing inflammation.     

Schistosoma japonicum ova maintains epithelial barrier function during experimental colitis

AIM: To evaluate the impacts of Schistosoma japonicum (S. japonicum) ova on the tight junction barriers in a trinitrobenzenesulfonic acid (TNBS)-induced colitis model.METHODS: Balb/c mice were randomly divided into three groups: control group; TNBS⁺ova^- group and TNBS⁺ova⁺ group. TNBS was used intracolonic to induce colitis and mice of the TNBS⁺ova⁺ group were pre-exposed to S. japonicum ova as a prophylactic intervention. Colon inflammation was quantified using following variables: mouse mortality, weight loss, colon extent and microscopic inflammation score. Serum expression of tumor necrosis factor-α and interferon-γ were assessed to evaluate the systemic inflammatory response. NOD2 and its mRNA were also tested. Bacterial translocations were tested by culturing blood and several tissues. ZO-1 and occludin were chosen as the representations of tight junction proteins. Both the proteins and mRNA were assessed.RESULTS: Ova pre-treatment contributed to the relief of colitis and decreased the mortality of the models. NOD2 expression was significantly downregulated when pretreated with the ova. The TNBS injection caused a significant downregulation of ZO-1 and occludin mRNA together with their proteins in the colon; ova pre-exposure reversed these alterations. Treatment with S. japonicum ova in the colitis model caused lower intestinal bacterial translocation frequency.CONCLUSION: S. japonicum ova can maintain epithelial barrier function through increasing tight junction proteins, thus causing less exposure of NOD2 to the luminal antigens which may activate a series of inflammatory factors and induce colitis.     

灭活血吸虫卵对实验性结肠炎肠黏膜的影响

目的 研究灭活血吸虫卵对2,4,6一三硝基苯磺酸(tinitrobenzene sulfonic acid,TNBS)诱导小鼠结肠炎肠黏膜紧密连接蛋白ZO-1和Occludin基因及蛋白表达影响及其机制.方法 清洁级BALB/C雌性小鼠50只分成对照组(10只)、TNBS+0.9%氯化钠溶液组(20只)和TNBS+血吸虫卵组(20只).TNBS+血吸虫卵组在造模前第3、14天分别给予腹腔注射冰冻灭活血吸虫卵10 000个(1 ml冰0.9%氯化钠溶液混悬液);TNBS+0.9%氯化钠溶液组给予相同体积的冰0.9%氯化钠溶液腹腔注射.后两组予TNBS溶液灌肠(100 mg/kg)建立结肠炎模型,建模后第7天处死存活小鼠,观察各组小鼠结肠的大体形态和HE染色光镜下病理特征;荧光实时定量PCR法测定结肠组织的Occludin和ZO-1基因表达;Western印迹法检测蛋白表达;免疫组化法测定结肠组织紧密连接蛋白表达分布.结果 TNBS+血吸虫卵组小鼠死亡率较TNBS+0.9%氯化钠溶液组明显下降(15%比30%).TNBS+0.9%氯化钠溶液组组织学评分为(4.21±0.40)分,较TNBS+血吸虫卵组和对照组高[(1.74±0.10)和(1.06±0.20)分,P<0.05].TNBS+0.9%氯化钠溶液组ZO-1和Occludin mRNA表达量较对照组显著下降(P<0.01),而TNBS+血吸虫卵组较TNBS+0.9%氯化钠溶液组显著增加(P<0.05).TNBs+0.9%氯化钠溶液组ZO-1蛋白相对灰度值较正常对照组降低50.3%(P<0.05),而TNBS+血吸虫卵组较TNBS+0.9%氯化钠溶液增加41.1%(P<0.05);TNBS+0.9%氯化钠溶液组Occludin相对灰度值较对照组下降48.7%(P<0.05),而血吸虫卵组较TNBS+0.9%氯化钠溶液组增加23.6%(P<0.05).ZO-1、Occludin蛋白染色强度TNBS+0.9%氯化钠溶液组分布均较对照组间增强(P<0.01),而TNBS+血吸虫卵组染色强度信号分布较TNBS+0.9%氯化钠溶液组显著增加(P<0.05).结论 灭活血吸虫卵能在细胞水平加强紧密连接蛋白ZO-1、Occludin聚集及表达,通过稳定紧密连接蛋白,增加肠道黏膜屏障功能,显著改善实验性结肠炎的肠道炎症反应.     

Nicotinamide prohibits proliferation and enhances chemosensitivity of pancreatic cancer cells through deregulating SIRT1 and Ras/Akt pathways

BackgroundNicotinamide (NAM), the precursor for the synthesis of NAD⁺ and also an inhibitor of SIRT1, has been discovered to inhibit some types of cancer. However, little is known about the effects of NAM on pancreatic cancer cells. Since previous research showed that SIRT1 and K-Ras/Akt signaling acted as a promoter in tumorigenesis of pancreatic cancer, our present research set out to explore whether NAM inhibits proliferation and facilitates chemosensitivity in pancreatic cancer cells as well as the potential mechanisms involving SIRT1 and K-Ras/Akt pathway.MethodsCell viability was assessed by MTT assay, and apoptosis and cell cycle were measured by flow cytometry. Cell invasive ability was evaluated by matrigel invasion assays. The activity of SIRT1 was measured by the Fluor de Lys deacetylation assay. Expression levels of SIRT1, K-Ras, Phosphated Akt (P-Akt, Ser-473) and Akt were measured using western blot. In vivo tumor growth was performed in pancreatic cancer cells xenografts.ResultsNAM inhibited the proliferation of pancreatic cancer cells in a dose-dependent manner, and significantly induced apoptosis and cell cycle arrest in G2/M phase. Moreover, NAM obviously restrained cell invasive ability and increased the chemosensitivity. NAM significantly inhibited the activity of SIRT1 and decreased expression of SIRT1, K-Ras and P-Akt. Further, NAM prohibited proliferation and enhanced GEM antitumor activity in vivo.ConclusionsOur results implied that NAM might be a potential therapeutic agent for human pancreatic cancer treatment through downregulating SIRT1, K-Ras and P-Akt expression.     

Fatty acids and epithelial permeability: effect of conjugated linoleic acid in Caco-2 cells

Conjugated linoleic acid (CLA) is a collective term referring to the positional and geometric isomers of linoleic acid. This novel fatty acid has been shown to have a number of beneficial actions, including immunomodulatory, anticarcinogenic, and antiatherogenic effects. Tight junctions of epithelial cells determine epithelial membrane integrity and selective paracellular permeability to ions and macromolecules. Occludin and ZO-1 are integral structural components of the tight junction, which are involved in the biogenesis and functional integrity of the epithelial monolayer. This study investigated the effects of two isomers of CLA (cis-9 and trans-10 isomers) on Caco-2 cell transepithelial resistance (TER) development, paracellular epithelial permeability, and occludin and ZO-1 expression. Caco-2 cells were grown in media supplemented with 0.05 mM linoleic acid, cis-9 CLA, or trans-10 CLA for 21 days. The trans-10 CLA isomer delayed Caco-2 cell TER development, which is an in vitro measure of epithelial cell integrity, and increased paracellular epithelial permeability. Immunofluorescent staining of Caco-2 cell epithelial monolayers grown in media supplemented trans-10 CLA showed that the trans-10 CLA isomer altered distribution of occludin and ZO-1. The trans-10 CLA isomer delayed the acquisition of transepithelial resistance and altered the cellular distribution of occludin, which have important implications in relation to epithelial permeability.     

阿托伐他汀减轻巨噬细胞内质网应激及其介导的细胞凋亡

目的 探讨阿托伐他汀对7-酮胆固醇（7-KC）诱导的巨噬细胞内质网应激及细胞凋亡的影响。方法 AopE-/-小鼠左肾动脉和左颈总动脉联合部分结扎建立颈动脉易损斑块模型。采用HE染色方法观察斑块病理学改变,用免疫荧光结合激光扫描共聚焦显微镜技术检测斑块中内质网应激(ER stress)相关蛋白CHOP及磷酸化PERK（p-PERK）的表达。体外培养小鼠巨噬细胞RAW264.7,给予7-KC、H2O2或联合阿托伐他汀处理后,蛋白质免疫印迹方法（Western blot）测定ER stress相关蛋白CHOP、p-PERK 、XBP-1s及凋亡相关蛋白cleaved caspase-3的表达。结果 AopE-/-小鼠颈动脉易损斑块局部ER stress相关蛋白CHOP的表达及PERK磷酸化水平明显上调;7-KC可诱导小鼠巨噬细胞ER stress,进而诱导细胞凋亡;同时,氧化应激诱导剂H2O2也可通过诱导小鼠巨噬细胞ER stress介导细胞凋亡;而阿托伐他汀可抑制7-KC和H2O2诱导的巨噬细胞ER stress及其介导的细胞凋亡。结论 ER stress可能参与AS易损斑块的形成;阿托伐他汀可通过减少细胞内氧化应激的水平,减轻巨噬细胞ER stress,从而抑制细胞凋亡。     

Expression of nonclassical class I molecules by intestinal epithelial cells

It is well recognized that the nature of the immune response is different in the intestinal tract than in peripheral lymphoid organs. The immunologic tone of the gut-associated lymphoid tissue is one of suppression rather than active immunity, distinguishing pathogens from normal flora. Failure to control mucosal immune responses may lead to inflammatory diseases such as Crohn's disease (CD) and ulcerative colitis (UC) and celiac disease. It has been suggested that this normally immunosuppressed state may relate to unique antigen-presenting cells and unique T-cell populations. The intestinal epithelial cell (IEC) has been proposed to act as a nonprofessional antigen-presenting cell (APC). Previous studies have suggested that antigens presented by IECs result in the activation a CD8(+) regulatory T-cell subset in a nonclassical MHC I molecule restricted manner. We therefore analyzed the expression of nonclassical MHC I molecules by normal IECs and compared this to those expressed by inflammatory bowel disease (IBD) IECs. Normal surface IEC from the colon and, to a much lesser extent, the small bowel express nonclassical MHC I molecules on their surface. In contrast, mRNA is expressed in all intestinal epithelial cells. Surface IEC express CD1d, MICA/B, and HLA-E protein. In contrast, crypt IECs express less or no nonclassical MHC I molecules but do express mRNA for these molecules. Furthermore, the regulation of expression of distinct nonclassical class I molecules is different depending on the molecule analyzed. Interestingly, IECs derived from patients with UC fail to express any nonclassical MHC I molecules (protein and HLA-E mRNA). IECs from CD patients express HLA-E and MICA/B comparable to that seen in normal controls but fail to express CD1d. Thus, in UC there may be a failure to activate any nonclassical MHC I molecule restricted regulatory T cells that may result in unopposed active inflammatory responses. In CD only the CD1d-regulated T cells would be affected.     

番茄红素减轻H9C2心肌细胞缺氧/复氧致内质网应激的相关机制

目的 探讨番茄红素减轻H9C2心肌细胞缺氧/复氧(H/R)致内质网应激(ERS)的相关机制。方法 H9C2心肌细胞随机分为:①空白对照组、②番茄红素组、③H/R组、④番茄红素+H/R组、⑤4-苯基丁酸（4-phenyl butyric acid,4-PBA）+H/R组、⑥毒胡萝卜素内酯（thapsigargin,TG）组、⑦番茄红素+TG组。流式细胞术检测H9C2心肌细胞凋亡比例;Western blot检测葡萄糖调节蛋白(glucose-regulated proteins,GRP)78、C/EBP环磷酸腺苷反应元件结合转录因子同源蛋白(C/EBP homologous protein,CHOP)、c-Jun氨基末端激酶(c-Jun-N-terminal protein kinase,JNK)、磷酸化JNK（p-JNK）及半胱氨酸天冬氨酸蛋白酶(Casepase)-12的表达。结果 与对照组相比,H/R组及TG组细胞的细胞凋亡比例、GRP78、CHOP、p-JNK和Caspase-12蛋白表达量明显增加（P<0.01）;与H/R组相比,细胞凋亡比例及上述蛋白表达在番茄红素+H/R组与4-PBA+H/R组明显下降（P<0.01）;与TG组相比,细胞凋亡比例及上述蛋白表达在番茄红素+TG组也明显下降（P<0.01）;而番茄红素+H/R组与4-PBA+H/R组相比差异不具有统计学意义。JNK蛋白总量表达无明显变化。结论 番茄红素通过抑制ERS致凋亡的相关信号通路CHOP、p-JNK和Caspase-12对H/R H9C2心肌细胞起到保护作用。     

Oral treatment with plecanatide or dolcanatide attenuates visceral hypersensitivity via activation of guanylate cyclase-C in rat models

AIM To investigate the effects of plecanatide and dolcanatide on maintenance of paracellular permeability, integrity of tight junctions and on suppression of visceral hypersensitivity. METHODS Transport of fluorescein isothiocyanate(FITC)-dextran was measured to assess permeability across cell monolayers and rat colon tissues. Effects of plecanatide and dolcanatide on the integrity of tight junctions in Caco-2 and T84 monolayers and on the expression and localization of occludin and zonula occludens-1(ZO-1) were examined by immunofluorescence microscopy. Anti-nociceptive activity of these agonists was evaluated in trinitrobenzene sulfonic acid(TNBS)-induced inflammatory as well as in non-inflammatory partial restraint stress(PRS) rat models. Statistical significance between the treatment groups in the permeability studies were evaluated using unpaired t-tests.RESULTS Treatment of T84 and Caco-2 monolayers with lipopolysaccharide(LPS) rapidly increased permeability, which was effectively suppressed when monolayers were also treated with plecanatide or dolcanatide. Similarly, when T84 and Caco-2 monolayers were treated with LPS, cell surface localization of tight junction proteins occludin and ZO-1 was severely disrupted. When cell monolayers were treated with LPS in the presence of plecanatide or dolcanatide, occludin and ZO-1 were localized at the cell surface of adjoining cells, similar to that observed for vehicle treated cells. Treatment of cell monolayers with plecanatide or dolcanatide without LPS did not alter permeability, integrity of tight junctions and cell surface localization of either of the tight junction proteins. In rat visceral hypersensitivity models, both agonists suppressed the TNBS-induced increase in abdominal contractions in response to colorectal distension without affecting the colonic wall elasticity, and both agonists also reduced colonic hypersensitivity in the PRS model. CONCLUSION Our results suggest that activation of GC-C signaling might be involved in maintenance of barrier function, possibly through regulating normal localization of tight junction proteins. Consistent with these findings, plecanatide and dolcanatide showed potent antinociceptive activity in rat visceral hypersensitivity models. These results imply that activation of GC-C signaling may be an attractive therapeutic approach to treat functional constipation disorders and inflammatory gastrointestinal conditions.     

Epidermal growth factor prevents acetaldehyde-induced paracellular permeability in Caco-2 cell monolayer

BACKGROUND: Intestinal permeability and endotoxemia play a crucial role in the pathogenesis of alcoholic liver disease. Previous studies showed that acetaldehyde disrupts intestinal epithelial barrier function and increases paracellular permeability by a tyrosine kinase-dependent mechanism. In the present study, the role of epidermal growth factor (EGF) in protection of epithelial barrier function from acetaldehyde was evaluated in Caco-2 intestinal epithelial cell monolayer. METHODS: Caco-2 cells on Transwell inserts were exposed to acetaldehyde in the absence or presence of EGF, and the paracellular permeability was evaluated by measuring transepithelial electrical resistance and unidirectional flux of inulin. Integrity of epithelial tight junctions and adherens junctions was analyzed by confocal immunofluorescence microscopy and immunoblot analysis of occludin, zonula occludens (ZO)-1, E-cadherin, and beta-catenin in the actin cytoskeleton. Reorganization of actin cytoskeletal architecture was examined by confocal microscopy. RESULTS: Acetaldehyde increased paracellular permeability to inulin and lipopolysaccharide, and EGF significantly reduced these effects of acetaldehyde in a time- and dose-dependent manner. EGF prevented acetaldehyde-induced reorganization of occludin, ZO-1, E-cadherin, and beta-catenin from the cellular junctions to the intracellular compartments. Acetaldehyde treatment induced a reorganization of actin cytoskeletal network and reduced the levels of occludin, ZO-1, E-cadherin, and beta-catenin associated with the actin cytoskeleton. EGF effectively prevented acetaldehyde-induced reorganization of actin cytoskeleton and the interaction of occludin, ZO-1, E-cadherin, and beta-catenin with the actin cytoskeleton. CONCLUSION: These results indicate that EGF attenuates acetaldehyde-induced disruption of tight junctions and adherens junctions and prevents acetaldehyde-induced reorganization of actin cytoskeleton and its interaction with occludin, ZO-1, E-cadherin, and beta-catenin.