The significance of plasma ascorbic acid(AA)is underscored by its enzymatic and antioxidant properties as well as involvement in many aspects of health including the synthesis of biomolecules during acute illness,trau...The significance of plasma ascorbic acid(AA)is underscored by its enzymatic and antioxidant properties as well as involvement in many aspects of health including the synthesis of biomolecules during acute illness,trauma and chronic health conditions.Dietary intake supports maintenance of optimal levels with supplementation at higher doses more likely pursued.Transient increased intestinal paracellular permeability following high dose AA may be utilised to enhance delivery of other micronutrients across the intestinal lumen.The potential mechanism following dietary intake however needs further study but may provide an avenue to increase small intestinal nutrient co transport and absorption,including in acute and chronic illness.展开更多
The blood-brain barrier is the interface through which the brain interacts with the milieu and consists mainly of a sophisticated network of brain endothelial cells that forms blood vessels and selectively moves molec...The blood-brain barrier is the interface through which the brain interacts with the milieu and consists mainly of a sophisticated network of brain endothelial cells that forms blood vessels and selectively moves molecules inside and outside the brain through multiple mechanisms of transport.Although brain endothelial cell function is crucial for brain homeostasis,their role in neurodegenerative diseases has historically not been considered with the same importance as other brain cells such as microglia,astroglia,neurons,or even molecules such as amyloid beta,Tau,or alpha-synuclein.Alzheimer's disease is the most common neurodegenerative disease,and brain endothelial cell dysfunction has been reported by several groups.However,its impairment has barely been considered as a potential therapeutic target.Here we review the most recent advances in the relationship between Alzheimer's disease and brain endothelial cells commitment and analyze the possible mechanisms through which their alterations contribute to this neurodegenerative disease,highlighting their inflammatory phenotype and the possibility of an impaired secretory pattern of brain endothelial cells that could contribute to the progression of this ailment.Finally,we discuss why shall brain endothelial cells be appreciated as a therapeutic target instead of solely an obstacle for delivering treatments to the injured brain in Alzheimer's disease.展开更多
Intestinal Ca2+ absorption is a crucial physiological process for maintaining bone mineralization and Ca2+ homeostasis. It occurs through the transcellular and paracellular pathways. The first route comprises 3steps: ...Intestinal Ca2+ absorption is a crucial physiological process for maintaining bone mineralization and Ca2+ homeostasis. It occurs through the transcellular and paracellular pathways. The first route comprises 3steps: the entrance of Ca2+ across the brush border membranes(BBM) of enterocytes through epithelial Ca2+ channels TRPV6, TRPV5, and Cav1.3; Ca2+ movement from the BBM to the basolateral membranes by binding proteins with high Ca2+ affinity(such as CB9k); and Ca2+ extrusion into the blood. Plasma membrane Ca2+ ATPase(PMCA1b) and sodium calcium exchanger(NCX1) are mainly involved in the exit of Ca2+ from enterocytes. A novel molecule, the 4.1R protein, seems to be a partner of PMCA1 b, since both molecules colocalize and interact. The paracellular pathway consists of Ca2+ transport through transmembrane proteins of tight junction structures, such as claudins 2, 12, and 15. There is evidence of crosstalk between the transcellular and paracellular pathways in intestinal Ca2+ transport. When intestinal oxidative stress is triggered, there is a decrease in the expression of several molecules of both pathways that inhibit intestinal Ca2+ absorption. Normalization of redox status in the intestine with drugs such as quercetin, ursodeoxycholic acid, or melatonin return intestinal Ca2+ transport to control values. Calcitriol [1,25(OH)2D3] is the major controlling hormone of intestinal Ca2+ transport. It increases the gene and protein expression of most of the molecules involved in both pathways. PTH, thyroid hormones, estrogens, p ro l a c t i n, g ro w t h h o r m o n e, a n d g l u c o c o r t i c o i d s apparently also regulate Ca2+ transport by direct action, indirect mechanism mediated by the increase of renal 1,25(OH)2D3 production, or both. Different physiological conditions, such as growth, pregnancy, lactation, and aging, adjust intestinal Ca2+ absorption according to Ca2+ demands. Better knowledge of the molecular details of intestinal Ca2+ absorption could lead to the development of nutritional and medical strategies for optimizing the efficiency of intestinal Ca2+ absorption and preventing osteoporosis and other pathologies related to Ca2+ metabolism.展开更多
The gastrointestinal barrier is-with approximately 400 m^2-the human body's largest surface separating the external environment from the internal milieu. This barrier serves a dual function: permitting the absorpt...The gastrointestinal barrier is-with approximately 400 m^2-the human body's largest surface separating the external environment from the internal milieu. This barrier serves a dual function: permitting the absorption of nutrients, water and electrolytes on the one hand, while limiting host contact with noxious luminal antigens on the other hand. To maintain this selective barrier, junction protein complexes seal the intercellular space between adjacent epithelial cells and regulate the paracellular transport. Increased intestinal permeability is associated with and suggested as a player in the pathophysiology of various gastrointestinal and extraintestinal diseases such as inflammatory bowel disease, celiac disease and type 1 diabetes. The gastrointestinal tract is exposed to high levels of endogenous and exogenous proteases, both in the lumen and in the mucosa. There is increasing evidence to suggest that a dysregulation of the protease/antiprotease balance in the gut contributes to epithelial damage and increased permeability. Excessive proteolysis leads to direct cleavage of intercellular junction proteins, or to opening of the junction proteins via activation of protease activated receptors. In addition, proteases regulate the activity and availability of cytokines and growth factors, which are also known modulators of intestinal permeability. This review aims at outlining the mechanisms by which proteases alter the intestinal permeability. More knowledge on the role of proteases in mucosal homeostasis and gastrointestinal barrier function will definitely contribute to the identification of new therapeutic targets for permeability-related diseases.展开更多
The disequilibrium between the production of reactive oxygen(ROS) and nitrogen(RNS) species and their elimination by protective mechanisms leads to oxidative stress. Mitochondria are the main source of ROS as by-produ...The disequilibrium between the production of reactive oxygen(ROS) and nitrogen(RNS) species and their elimination by protective mechanisms leads to oxidative stress. Mitochondria are the main source of ROS as by-products of electron transport chain. Most of the time the intestine responds adequately against the oxidative stress, but with aging or under conditions that exacerbate the ROS and/or RNS production, the defenses are not enough and contribute to developing intestinal pathologies. The endogenous antioxidant defense system in gut includes glutathione(GSH) and GSH-dependent enzymes as major components. When the ROS and/or RNS production is exacerbated, oxidative stress occurs and the intestinal Ca2+ absorption is inhibited. GSH depleting drugs such as DLbuthionine-S,R-sulfoximine, menadione and sodium deoxycholate inhibit the Ca2+ transport from lumen to blood by alteration in the protein expression and/or activity of molecules involved in the Ca2+ transcellular and paracellular pathways through mechanisms of oxidative stress, apoptosis and/or autophagy. Quercetin, melatonin, lithocholic and ursodeoxycholic acids block the effect of those drugs in experimental animals by their antioxidant, anti-apoptotic and/or anti-autophagic properties. Therefore, they may become drugs of choice for treatment of deteriorated intestinal Ca2+ absorption under oxidant conditions such as aging, diabetes, gut inflammation and other intestinal disorders.展开更多
AIM:To elucidate the effect and underlying mechanisms of omeprazole action on Mg 2+ transport across the intestinal epithelium.METHODS:Caco-2 monolayers were cultured in various dose omeprazole-containing media for 14...AIM:To elucidate the effect and underlying mechanisms of omeprazole action on Mg 2+ transport across the intestinal epithelium.METHODS:Caco-2 monolayers were cultured in various dose omeprazole-containing media for 14 or 21 d before being inserted into a modified Ussing chamber apparatus to investigate the bi-directional Mg 2+ transport and electrical parameters.Paracellular permeability of the monolayer was also observed by the dilution potential technique and a cation permeability study.An Arrhenius plot was performed to elucidate the activation energy of passive Mg 2+ transport across the Caco-2 monolayers.RESULTS:Both apical to basolateral and basolateral to apical passive Mg 2+ fluxes of omeprazole-treated epithelium were decreased in a dose-and time-dependent manner.Omeprazole also decreased the paracellular cation selectivity and changed the paracellular selective permeability profile of Caco-2 epithelium to Li +,Na +,K +,Rb +,and Cs + from seriesⅦto seriesⅥof the Eisenman sequence.The Arrhenius plot revealed the higher activation energy for passive Mg 2+ transport in omeprazoletreated epithelium than that of control epithelium,indicating that omeprazole affected the paracellular channel of Caco-2 epithelium in such a way that Mg 2+ movement was impeded.CONCLUSION:Omeprazole decreased paracellular cation permeability and increased the activation energy for passive Mg 2+ transport of Caco-2 monolayers that led to the suppression of passive Mg 2+ absorption.展开更多
Glutathione （GSH） is a tripeptide that constitutes one of the main intracellular reducing compounds. The normal content of GSH in the intestine is essential to optimize the intestinal Ca2＋ absorption. The use of GS...Glutathione （GSH） is a tripeptide that constitutes one of the main intracellular reducing compounds. The normal content of GSH in the intestine is essential to optimize the intestinal Ca2＋ absorption. The use of GSH depleting drugs such as DL-buthionine-S,R-sulfoximine, menadione or vitamin K3, sodium deoxycholate or diets enriched in fructose, which induce several features of the metabolic syndrome, produce inhibition of the intestinal Ca2＋ ab-sorption. The GSH depleting drugs switch the redox state towards an oxidant condition provoking oxida-tive/nitrosative stress and inflammation, which lead to apoptosis and/or autophagy of the enterocytes. Either the transcellular Ca transport or the paracellular Ca route are altered by GSH depleting drugs. The gene and/or protein expression of transporters involved in the transcellular Ca2＋ pathway are decreased. The favonoids quercetin and naringin highly abrogate the inhibition of intestinal Ca2＋ absorption, not only by restoration of the GSH levels in the intestine but also by their anti-apoptotic properties. Ursodeoxycholic acid, melatonin and glutamine also block the inhibition of Ca2＋ transport caused by GSH depleting drugs. The use of any of these antioxidants to ameliorate the intestinal Ca2＋ absorption under oxidant conditions associated with different pathologies in humans requires more investigation with regards to the safety,pharmacokinetics and pharmacodynamics of them.展开更多
AIM:To investigate the effect of emodin on pancreatic claudin-5 and occludin expression,and pancreatic paracellular permeability in acute pancreatitis(AP).METHODS:Experimental pancreatitis was induced by retrograde in...AIM:To investigate the effect of emodin on pancreatic claudin-5 and occludin expression,and pancreatic paracellular permeability in acute pancreatitis(AP).METHODS:Experimental pancreatitis was induced by retrograde injection of 5% sodium taurocholate into the biliopancreatic duct.Emodin was injected via the external jugular vein 0 or 6 h after induction of AP.Rats from sham operation and AP groups were injected with normal saline at the same time.Samples of pancreas were obtained 6 or 12 h after drug administration.Pancreatic morphology was examined with hematoxylin and eosin staining.Pancreatic edema was estimated by measuring tissue water content.Tumor necrosis factor(TNF)-α and interleukin(IL)-6 level were measured by enzyme-linked immunosorbent assay.Pancreatic paracellular permeability was assessed by tissue dye extravasation.Expression of pancreatic claudin-5 and occludin was examined by immunohistology,quantitative real-time reverse transcriptase polymerase chain reaction and western blotting.RESULTS:Pancreatic TNF-α and IL-6 levels,wet/dry ratio,dye extravasation,and histological score were significantly elevated at 3,6 and 12 h following sodium taurocholate infusion;treatment with emodin prevented these changes at all time points.Immunostaining of claudin-5 and occludin was detected in rat pancreas,which was distributed in pancreatic acinar cells,ductal cells and vascular endothelial cells,respectively.Sodium taurocholate infusion significantly decreased pancreatic claudin-5 and occludin mRNA and protein levels at 3,6 and 12 h,and that could be promoted by intravenous administration of emodin at all time points.CONCLUSION:These results demonstrate that emodin could promote pancreatic claudin-5 and occludin expression,and reduce pancreatic paracellular permeability.展开更多
AIM:To investigate omeprazole-induced transepithelial gastric leak and its effects on the permeability of the peptides bradykinin and oxytocin.METHODS:Rat gastric corpus tissue was isolated and mounted in an Ussing ch...AIM:To investigate omeprazole-induced transepithelial gastric leak and its effects on the permeability of the peptides bradykinin and oxytocin.METHODS:Rat gastric corpus tissue was isolated and mounted in an Ussing chamber apparatus to evaluate the permeability of 3H-bradykinin,3H-oxytocin,and 14CEDTA in the presence or absence of omeprazole.Thinlayer chromatography was performed to identify any metabolic breakdown products of the peptides resulting from permeation through the gastric tissue,and thereby calculate the true flux of the peptide.RESULTS:The flux rate ofintact 3H-bradykinin increased substantially after omeprazole addition (109.5%) compared to the DMSO vehicle control (14%).No corresponding change in flux ofintact 3H-oxytocin was observed under the same conditions (11.9% and 6.4% in the DMSO-and omeprazole-treated conditions,respectively).After exposure to omeprazole,the flux rate of 14C-EDTA also increased dramatically (122.3%) compared to the DMSO condition (36.3%).CONCLUSION:The omeprazole-induced gastric leak allows for transmucosal permeability to charged molecules as well as non-electrolytes.This induced leak will allow certain peptides to permeate.展开更多
AIM： To determine if the observed paracellular sucrose leak in Barrett＇s esophagus patients is due to their pro- ton pump inhibitor （PPI） use. METHODS： The in vivo sucrose permeability test was administered to he...AIM： To determine if the observed paracellular sucrose leak in Barrett＇s esophagus patients is due to their pro- ton pump inhibitor （PPI） use. METHODS： The in vivo sucrose permeability test was administered to healthy controls, to Barrett＇s patients and to non-Barrett＇s patients on continuous PPI thera- py. Degree of leak was tested for correlation with pres- ence of Barrett＇s, use of PPIs, and length of Barrett＇s segment and duration of PPI use. RESULTS： Barrett＇s patients manifested a near 3-fold greater, upper gastrointestinal sucrose leak than healthy controls. A decrease of sucrose leak was ob- served in Barrett＇s patients who ceased PPI use for 7 d.Although initial introduction of PPI use （in a PPI-na＇ive population） results in dramatic increase in sucrose leak, long-term, continuous PPI use manifested a slow spon- taneous decline in leak. The sucrose leak observed in Barrett＇s patients showed no correlation to the amount of Barrett＇s tissue present in the esophagus. CONCLUSION： Although future research is needed to determine the degree of paracellular leak in actual Barrett＇s mucosa, the relatively high degree of leak ob- served with in vivo sucrose permeability measurement of Barrett＇s patients reflects their PPI use and not their Barrett＇s tissue perse.展开更多
Ca2+has an important role in the maintenance of the skeleton and is involved in the main physiological processes.Its homeostasis is controlled by the intestine,kidney,bone and parathyroid glands.The intestinal Ca2+abs...Ca2+has an important role in the maintenance of the skeleton and is involved in the main physiological processes.Its homeostasis is controlled by the intestine,kidney,bone and parathyroid glands.The intestinal Ca2+absorption occurs mainly via the paracellular and the transcellular pathways.The proteins involved in both ways are regulated by calcitriol and other hormones as well as dietary factors.Fibroblast growth factor 23(FGF-23)is a strong antagonist of vitamin D action.Part of the intestinal Ca2+movement seems to be vitamin D independent.Intestinal Ca2+absorption changes according to different physiological conditions.It is promoted under high Ca2+demands such as growth,pregnancy,lactation,dietary Ca2+deficiency and high physical activity.In contrast,the intestinal Ca2+transport decreases with aging.Oxidative stress inhibits the intestinal Ca2+absorption whereas the antioxidants counteract the effects of prooxidants leading to the normalization of this physiological process.Several pathologies such as celiac disease,inflammatory bowel diseases,Turner syndrome and others occur with inhibition of intestinal Ca2+absorption,some hypercalciurias show Ca2+hyperabsorption,most of these alterations are related to the vitamin D endocrine system.Further research work should be accomplished in order not only to know more molecular details but also to detect possible therapeutic targets to ameliorate or avoid the consequences of altered intestinal Ca2+absorption.展开更多
We aimed to examine paracellular barrier function in cultured mouse lung microvascular endothelial cells (LMECs). The transcellular resistance of LMEC monolayers yielded an electrical resistance of approximately 19 Ω...We aimed to examine paracellular barrier function in cultured mouse lung microvascular endothelial cells (LMECs). The transcellular resistance of LMEC monolayers yielded an electrical resistance of approximately 19 Ω × cm<sup>2</sup> at days 6 - 7 in culture when the cells reached confluence, and paracellular permeable clearance of sodium fluorescein was the lowest on day 6 in culture, suggesting the formation of tight junctions (TJs) in cultured LMECs. Moreover, the expression of TJ-associated proteins, occludin, claudin-1 and -4 and zonula occludents 1 (ZO-1) was detected in LMECs at day 6 in culture. However, mRNAs of occludin, claudin-1 and -4 and ZO-1 were already expressed on day 1 after culture, and large variations were absent in the mRNA levels of occludin, claudin-4 and ZO-1 between days 1 and 7 in culture, when the level of each mRNA on day 1 in culture was used as a basal level. However, the claudin-1 mRNA level gradually increased up to approximately 7-fold on day 7 in culture over the basal level. These results indicate that the drastic increase in the mRNA expression level of claudin-1 leads to the strong formation of TJs.展开更多
目的通过研究P-糖蛋白(P-gp)底物罗丹明123(R123)在空肠、回肠和结肠转运时辣椒素的作用,探究辣椒素对肠粘膜上P-gp功能的影响。方法使用体外扩散池法技术,分别取SD雄性大鼠的空肠、回肠和结肠肠段标本,计算各肠段中吸收方向(mucosa to ...目的通过研究P-糖蛋白(P-gp)底物罗丹明123(R123)在空肠、回肠和结肠转运时辣椒素的作用,探究辣椒素对肠粘膜上P-gp功能的影响。方法使用体外扩散池法技术,分别取SD雄性大鼠的空肠、回肠和结肠肠段标本,计算各肠段中吸收方向(mucosa to serosa,M-S)和分泌方向(serosa to mucosa,S-M)R123的表观渗透速率(Papp)。用荧光分光光度计测定R123和荧光素钠(CF)在接收室中的浓度。结果在辣椒素作用下,R123经空肠粘膜透过时,吸收方向与空白组相比显著增高,分泌方向显著降低,但其在回肠及结肠M-S组及S-M组表观渗透系数Papp与空白组相比均没有显著性差异。CF经空肠粘膜透过时,MS组及S-M组Papp与空白组相比均显著增高;经回肠和结肠粘膜透过与空白组相比没有显著性差异。结论辣椒素影响P-gp底物R123和细胞旁转运药物CF经肠粘膜透过的作用具有肠段差异性,对R123和CF的影响仅存在于空肠,表明辣椒素是一种较弱的P-gp抑制剂和粘膜通道改善剂。可能与P-gp和紧密连接在肠粘膜上的逐渐变化的分布有关。展开更多
文摘The significance of plasma ascorbic acid(AA)is underscored by its enzymatic and antioxidant properties as well as involvement in many aspects of health including the synthesis of biomolecules during acute illness,trauma and chronic health conditions.Dietary intake supports maintenance of optimal levels with supplementation at higher doses more likely pursued.Transient increased intestinal paracellular permeability following high dose AA may be utilised to enhance delivery of other micronutrients across the intestinal lumen.The potential mechanism following dietary intake however needs further study but may provide an avenue to increase small intestinal nutrient co transport and absorption,including in acute and chronic illness.
文摘The blood-brain barrier is the interface through which the brain interacts with the milieu and consists mainly of a sophisticated network of brain endothelial cells that forms blood vessels and selectively moves molecules inside and outside the brain through multiple mechanisms of transport.Although brain endothelial cell function is crucial for brain homeostasis,their role in neurodegenerative diseases has historically not been considered with the same importance as other brain cells such as microglia,astroglia,neurons,or even molecules such as amyloid beta,Tau,or alpha-synuclein.Alzheimer's disease is the most common neurodegenerative disease,and brain endothelial cell dysfunction has been reported by several groups.However,its impairment has barely been considered as a potential therapeutic target.Here we review the most recent advances in the relationship between Alzheimer's disease and brain endothelial cells commitment and analyze the possible mechanisms through which their alterations contribute to this neurodegenerative disease,highlighting their inflammatory phenotype and the possibility of an impaired secretory pattern of brain endothelial cells that could contribute to the progression of this ailment.Finally,we discuss why shall brain endothelial cells be appreciated as a therapeutic target instead of solely an obstacle for delivering treatments to the injured brain in Alzheimer's disease.
文摘Intestinal Ca2+ absorption is a crucial physiological process for maintaining bone mineralization and Ca2+ homeostasis. It occurs through the transcellular and paracellular pathways. The first route comprises 3steps: the entrance of Ca2+ across the brush border membranes(BBM) of enterocytes through epithelial Ca2+ channels TRPV6, TRPV5, and Cav1.3; Ca2+ movement from the BBM to the basolateral membranes by binding proteins with high Ca2+ affinity(such as CB9k); and Ca2+ extrusion into the blood. Plasma membrane Ca2+ ATPase(PMCA1b) and sodium calcium exchanger(NCX1) are mainly involved in the exit of Ca2+ from enterocytes. A novel molecule, the 4.1R protein, seems to be a partner of PMCA1 b, since both molecules colocalize and interact. The paracellular pathway consists of Ca2+ transport through transmembrane proteins of tight junction structures, such as claudins 2, 12, and 15. There is evidence of crosstalk between the transcellular and paracellular pathways in intestinal Ca2+ transport. When intestinal oxidative stress is triggered, there is a decrease in the expression of several molecules of both pathways that inhibit intestinal Ca2+ absorption. Normalization of redox status in the intestine with drugs such as quercetin, ursodeoxycholic acid, or melatonin return intestinal Ca2+ transport to control values. Calcitriol [1,25(OH)2D3] is the major controlling hormone of intestinal Ca2+ transport. It increases the gene and protein expression of most of the molecules involved in both pathways. PTH, thyroid hormones, estrogens, p ro l a c t i n, g ro w t h h o r m o n e, a n d g l u c o c o r t i c o i d s apparently also regulate Ca2+ transport by direct action, indirect mechanism mediated by the increase of renal 1,25(OH)2D3 production, or both. Different physiological conditions, such as growth, pregnancy, lactation, and aging, adjust intestinal Ca2+ absorption according to Ca2+ demands. Better knowledge of the molecular details of intestinal Ca2+ absorption could lead to the development of nutritional and medical strategies for optimizing the efficiency of intestinal Ca2+ absorption and preventing osteoporosis and other pathologies related to Ca2+ metabolism.
文摘The gastrointestinal barrier is-with approximately 400 m^2-the human body's largest surface separating the external environment from the internal milieu. This barrier serves a dual function: permitting the absorption of nutrients, water and electrolytes on the one hand, while limiting host contact with noxious luminal antigens on the other hand. To maintain this selective barrier, junction protein complexes seal the intercellular space between adjacent epithelial cells and regulate the paracellular transport. Increased intestinal permeability is associated with and suggested as a player in the pathophysiology of various gastrointestinal and extraintestinal diseases such as inflammatory bowel disease, celiac disease and type 1 diabetes. The gastrointestinal tract is exposed to high levels of endogenous and exogenous proteases, both in the lumen and in the mucosa. There is increasing evidence to suggest that a dysregulation of the protease/antiprotease balance in the gut contributes to epithelial damage and increased permeability. Excessive proteolysis leads to direct cleavage of intercellular junction proteins, or to opening of the junction proteins via activation of protease activated receptors. In addition, proteases regulate the activity and availability of cytokines and growth factors, which are also known modulators of intestinal permeability. This review aims at outlining the mechanisms by which proteases alter the intestinal permeability. More knowledge on the role of proteases in mucosal homeostasis and gastrointestinal barrier function will definitely contribute to the identification of new therapeutic targets for permeability-related diseases.
基金Supported by Dr.Nori Tolosa de Talamoni from CONICET,No.PIP 2013-2015 and No.SECYT(UNC)2016,Argentina
文摘The disequilibrium between the production of reactive oxygen(ROS) and nitrogen(RNS) species and their elimination by protective mechanisms leads to oxidative stress. Mitochondria are the main source of ROS as by-products of electron transport chain. Most of the time the intestine responds adequately against the oxidative stress, but with aging or under conditions that exacerbate the ROS and/or RNS production, the defenses are not enough and contribute to developing intestinal pathologies. The endogenous antioxidant defense system in gut includes glutathione(GSH) and GSH-dependent enzymes as major components. When the ROS and/or RNS production is exacerbated, oxidative stress occurs and the intestinal Ca2+ absorption is inhibited. GSH depleting drugs such as DLbuthionine-S,R-sulfoximine, menadione and sodium deoxycholate inhibit the Ca2+ transport from lumen to blood by alteration in the protein expression and/or activity of molecules involved in the Ca2+ transcellular and paracellular pathways through mechanisms of oxidative stress, apoptosis and/or autophagy. Quercetin, melatonin, lithocholic and ursodeoxycholic acids block the effect of those drugs in experimental animals by their antioxidant, anti-apoptotic and/or anti-autophagic properties. Therefore, they may become drugs of choice for treatment of deteriorated intestinal Ca2+ absorption under oxidant conditions such as aging, diabetes, gut inflammation and other intestinal disorders.
基金Supported by The Thailand Research Fund(to Thongon N),No.MRG5380003
文摘AIM:To elucidate the effect and underlying mechanisms of omeprazole action on Mg 2+ transport across the intestinal epithelium.METHODS:Caco-2 monolayers were cultured in various dose omeprazole-containing media for 14 or 21 d before being inserted into a modified Ussing chamber apparatus to investigate the bi-directional Mg 2+ transport and electrical parameters.Paracellular permeability of the monolayer was also observed by the dilution potential technique and a cation permeability study.An Arrhenius plot was performed to elucidate the activation energy of passive Mg 2+ transport across the Caco-2 monolayers.RESULTS:Both apical to basolateral and basolateral to apical passive Mg 2+ fluxes of omeprazole-treated epithelium were decreased in a dose-and time-dependent manner.Omeprazole also decreased the paracellular cation selectivity and changed the paracellular selective permeability profile of Caco-2 epithelium to Li +,Na +,K +,Rb +,and Cs + from seriesⅦto seriesⅥof the Eisenman sequence.The Arrhenius plot revealed the higher activation energy for passive Mg 2+ transport in omeprazoletreated epithelium than that of control epithelium,indicating that omeprazole affected the paracellular channel of Caco-2 epithelium in such a way that Mg 2+ movement was impeded.CONCLUSION:Omeprazole decreased paracellular cation permeability and increased the activation energy for passive Mg 2+ transport of Caco-2 monolayers that led to the suppression of passive Mg 2+ absorption.
文摘Glutathione （GSH） is a tripeptide that constitutes one of the main intracellular reducing compounds. The normal content of GSH in the intestine is essential to optimize the intestinal Ca2＋ absorption. The use of GSH depleting drugs such as DL-buthionine-S,R-sulfoximine, menadione or vitamin K3, sodium deoxycholate or diets enriched in fructose, which induce several features of the metabolic syndrome, produce inhibition of the intestinal Ca2＋ ab-sorption. The GSH depleting drugs switch the redox state towards an oxidant condition provoking oxida-tive/nitrosative stress and inflammation, which lead to apoptosis and/or autophagy of the enterocytes. Either the transcellular Ca transport or the paracellular Ca route are altered by GSH depleting drugs. The gene and/or protein expression of transporters involved in the transcellular Ca2＋ pathway are decreased. The favonoids quercetin and naringin highly abrogate the inhibition of intestinal Ca2＋ absorption, not only by restoration of the GSH levels in the intestine but also by their anti-apoptotic properties. Ursodeoxycholic acid, melatonin and glutamine also block the inhibition of Ca2＋ transport caused by GSH depleting drugs. The use of any of these antioxidants to ameliorate the intestinal Ca2＋ absorption under oxidant conditions associated with different pathologies in humans requires more investigation with regards to the safety,pharmacokinetics and pharmacodynamics of them.
基金Supported by National Natural Science Foundation of China,No.30500688
文摘AIM:To investigate the effect of emodin on pancreatic claudin-5 and occludin expression,and pancreatic paracellular permeability in acute pancreatitis(AP).METHODS:Experimental pancreatitis was induced by retrograde injection of 5% sodium taurocholate into the biliopancreatic duct.Emodin was injected via the external jugular vein 0 or 6 h after induction of AP.Rats from sham operation and AP groups were injected with normal saline at the same time.Samples of pancreas were obtained 6 or 12 h after drug administration.Pancreatic morphology was examined with hematoxylin and eosin staining.Pancreatic edema was estimated by measuring tissue water content.Tumor necrosis factor(TNF)-α and interleukin(IL)-6 level were measured by enzyme-linked immunosorbent assay.Pancreatic paracellular permeability was assessed by tissue dye extravasation.Expression of pancreatic claudin-5 and occludin was examined by immunohistology,quantitative real-time reverse transcriptase polymerase chain reaction and western blotting.RESULTS:Pancreatic TNF-α and IL-6 levels,wet/dry ratio,dye extravasation,and histological score were significantly elevated at 3,6 and 12 h following sodium taurocholate infusion;treatment with emodin prevented these changes at all time points.Immunostaining of claudin-5 and occludin was detected in rat pancreas,which was distributed in pancreatic acinar cells,ductal cells and vascular endothelial cells,respectively.Sodium taurocholate infusion significantly decreased pancreatic claudin-5 and occludin mRNA and protein levels at 3,6 and 12 h,and that could be promoted by intravenous administration of emodin at all time points.CONCLUSION:These results demonstrate that emodin could promote pancreatic claudin-5 and occludin expression,and reduce pancreatic paracellular permeability.
文摘AIM:To investigate omeprazole-induced transepithelial gastric leak and its effects on the permeability of the peptides bradykinin and oxytocin.METHODS:Rat gastric corpus tissue was isolated and mounted in an Ussing chamber apparatus to evaluate the permeability of 3H-bradykinin,3H-oxytocin,and 14CEDTA in the presence or absence of omeprazole.Thinlayer chromatography was performed to identify any metabolic breakdown products of the peptides resulting from permeation through the gastric tissue,and thereby calculate the true flux of the peptide.RESULTS:The flux rate ofintact 3H-bradykinin increased substantially after omeprazole addition (109.5%) compared to the DMSO vehicle control (14%).No corresponding change in flux ofintact 3H-oxytocin was observed under the same conditions (11.9% and 6.4% in the DMSO-and omeprazole-treated conditions,respectively).After exposure to omeprazole,the flux rate of 14C-EDTA also increased dramatically (122.3%) compared to the DMSO condition (36.3%).CONCLUSION:The omeprazole-induced gastric leak allows for transmucosal permeability to charged molecules as well as non-electrolytes.This induced leak will allow certain peptides to permeate.
基金Supported by Sharpe-Strumia Research Foundation of the Bryn Mawr Hospital
文摘AIM： To determine if the observed paracellular sucrose leak in Barrett＇s esophagus patients is due to their pro- ton pump inhibitor （PPI） use. METHODS： The in vivo sucrose permeability test was administered to healthy controls, to Barrett＇s patients and to non-Barrett＇s patients on continuous PPI thera- py. Degree of leak was tested for correlation with pres- ence of Barrett＇s, use of PPIs, and length of Barrett＇s segment and duration of PPI use. RESULTS： Barrett＇s patients manifested a near 3-fold greater, upper gastrointestinal sucrose leak than healthy controls. A decrease of sucrose leak was ob- served in Barrett＇s patients who ceased PPI use for 7 d.Although initial introduction of PPI use （in a PPI-na＇ive population） results in dramatic increase in sucrose leak, long-term, continuous PPI use manifested a slow spon- taneous decline in leak. The sucrose leak observed in Barrett＇s patients showed no correlation to the amount of Barrett＇s tissue present in the esophagus. CONCLUSION： Although future research is needed to determine the degree of paracellular leak in actual Barrett＇s mucosa, the relatively high degree of leak ob- served with in vivo sucrose permeability measurement of Barrett＇s patients reflects their PPI use and not their Barrett＇s tissue perse.
基金Supported by Consejo Nacional de Investigaciones Científicas y Tecnológicas,Argentina PIP 2017-2019,No.11220170100012COSecretaría de Ciencia y Técnica de la Universidad Nacional de Córdoba,Argentina(Programa 2018-2019),No.30920180100056CB。
文摘Ca2+has an important role in the maintenance of the skeleton and is involved in the main physiological processes.Its homeostasis is controlled by the intestine,kidney,bone and parathyroid glands.The intestinal Ca2+absorption occurs mainly via the paracellular and the transcellular pathways.The proteins involved in both ways are regulated by calcitriol and other hormones as well as dietary factors.Fibroblast growth factor 23(FGF-23)is a strong antagonist of vitamin D action.Part of the intestinal Ca2+movement seems to be vitamin D independent.Intestinal Ca2+absorption changes according to different physiological conditions.It is promoted under high Ca2+demands such as growth,pregnancy,lactation,dietary Ca2+deficiency and high physical activity.In contrast,the intestinal Ca2+transport decreases with aging.Oxidative stress inhibits the intestinal Ca2+absorption whereas the antioxidants counteract the effects of prooxidants leading to the normalization of this physiological process.Several pathologies such as celiac disease,inflammatory bowel diseases,Turner syndrome and others occur with inhibition of intestinal Ca2+absorption,some hypercalciurias show Ca2+hyperabsorption,most of these alterations are related to the vitamin D endocrine system.Further research work should be accomplished in order not only to know more molecular details but also to detect possible therapeutic targets to ameliorate or avoid the consequences of altered intestinal Ca2+absorption.
文摘We aimed to examine paracellular barrier function in cultured mouse lung microvascular endothelial cells (LMECs). The transcellular resistance of LMEC monolayers yielded an electrical resistance of approximately 19 Ω × cm<sup>2</sup> at days 6 - 7 in culture when the cells reached confluence, and paracellular permeable clearance of sodium fluorescein was the lowest on day 6 in culture, suggesting the formation of tight junctions (TJs) in cultured LMECs. Moreover, the expression of TJ-associated proteins, occludin, claudin-1 and -4 and zonula occludents 1 (ZO-1) was detected in LMECs at day 6 in culture. However, mRNAs of occludin, claudin-1 and -4 and ZO-1 were already expressed on day 1 after culture, and large variations were absent in the mRNA levels of occludin, claudin-4 and ZO-1 between days 1 and 7 in culture, when the level of each mRNA on day 1 in culture was used as a basal level. However, the claudin-1 mRNA level gradually increased up to approximately 7-fold on day 7 in culture over the basal level. These results indicate that the drastic increase in the mRNA expression level of claudin-1 leads to the strong formation of TJs.
文摘目的通过研究P-糖蛋白(P-gp)底物罗丹明123(R123)在空肠、回肠和结肠转运时辣椒素的作用,探究辣椒素对肠粘膜上P-gp功能的影响。方法使用体外扩散池法技术,分别取SD雄性大鼠的空肠、回肠和结肠肠段标本,计算各肠段中吸收方向(mucosa to serosa,M-S)和分泌方向(serosa to mucosa,S-M)R123的表观渗透速率(Papp)。用荧光分光光度计测定R123和荧光素钠(CF)在接收室中的浓度。结果在辣椒素作用下,R123经空肠粘膜透过时,吸收方向与空白组相比显著增高,分泌方向显著降低,但其在回肠及结肠M-S组及S-M组表观渗透系数Papp与空白组相比均没有显著性差异。CF经空肠粘膜透过时,MS组及S-M组Papp与空白组相比均显著增高;经回肠和结肠粘膜透过与空白组相比没有显著性差异。结论辣椒素影响P-gp底物R123和细胞旁转运药物CF经肠粘膜透过的作用具有肠段差异性,对R123和CF的影响仅存在于空肠,表明辣椒素是一种较弱的P-gp抑制剂和粘膜通道改善剂。可能与P-gp和紧密连接在肠粘膜上的逐渐变化的分布有关。
