Expression Levels Of Tight Junction Proteins Research Articles

Curcumin modulated gut microbiota and alleviated renal fibrosis in 5/6 nephrectomy-induced chronic kidney disease rats.

Increasing evidence suggests that dysbiosis of gut microbiota exacerbates chronic kidney disease (CKD) progression. Curcumin (CUR) has been reported to alleviate renal fibrosis in animal models of CKD. However, the relationship between CUR and gut microbiome in CKD remains unclear. This study aims to investigate the potential anti-renal fibrosis effects of CUR from the gut microbiota perspective. A 5/6 nephrectomy (5/6Nx) rat model was used to explore the therapeutic effect of CUR on renal fibrosis. Tight junction protein expression levels were measured to assess intestinal barrier function. 16S rRNA sequencing was employed to evaluate changes in gut microbiota composition, and metabolomics was utilized to detect alterations in plasma metabolites. The administration of CUR significantly ameliorated renal fibrosis and inhibited inflammation in 5/6Nx rats. Additionally, CUR markedly improved the expression of tight junction proteins and local colon inflammation. CUR also positively reconstructed gut microbiota, significantly increasing the abundance of beneficial bacteria, such as Lachnospiraceae_NK4A136_group, Eubacterium_siraeum_group, and Muribaculaceae was significantly increased. Metabolomics revealed that CUR reduced uremic retention solutes and elevated Vitamin D and short-chain fatty acids (SCFAs). Spearman correlation analysis indicated that gut genera enriched by CUR were positively correlated with Vitamin D and SCFA and negatively correlated with chronic renal injury biomarkers. Mechanistically, we found inhibition of the LPS/TLR4/NF-κB and TGF-β1/Smads pathway in CUR-treated rats. Our study indicates that CUR has the potential to modulate gut microbiota composition, and that this modulation may contribute to the anti-fibrosis effects of CUR.

Maternal Intake of Laminarin Improves Infant Growth and Health by Fortifying Metabolite Profiles of Colostrum and Milk.

Laminarin mainly consists of fucoidan, a unique, naturally active sulfate polysaccharide. Laminarin is known for its outstanding multiple bioactives, but its role in lactation remains largely unknown. Therefore, this study aimed to explore the influence of maternal intake of laminarin on lactation and infant health in a porcine model. A total of 20 sows of parity 6.85 ± 0.88 with similar comprehensive scores were randomly allocated to two dietary treatments to receive a basal diet with/without supplementary laminarin. We showed that maternal intake of laminarin improved the antioxidant capacity and intestinal barrier function of the offspring, alleviated the inflammatory response, and facilitated infant growth and health. Mechanistically, maternal consumption of laminarin significantly modified the metabolite profiles of colostrum and milk. We also demonstrated in a vitro study that coniferyl aldehyde, a representative differential milk metabolite, enhanced antioxidant capacity and tight junction protein expression levels in intestinal epithelial cells. In summary, maternal intake of laminarin facilitated offspring health and growth by fortifying milk metabolites.

Effect of tegoprazan, a novel potassium-competitive acid blocker, on non-steroidal anti-inflammatory drug (NSAID)-induced enteropathy

As the non-steroidal anti-inflammatory drugs (NSAIDs) are typically used in the treatment of chronic conditions, the incidence of NSAID-induced enteropathy is increasing. Given the challenges associated with discontinuing NSAIDs, effective preventive and treatment strategies are crucial. We assessed the effect of tegoprazan on NSAID-induced enteropathy. Human epithelial cells (HIEC-6, HT-29, and Caco-2) were treated with indomethacin and tegoprazan. Cell viability, expression levels of tight-junction proteins, levels of proinflammatory cytokines, and apoptosis were assessed by conducting MTT assays, RT-PCR, western blotting, and immunofluorescence staining, respectively. Tegoprazan significantly ameliorated the inhibition of cell proliferation induced by indomethacin. Tegoprazan also mitigated the suppression of occludin and ZO-1 expression by indomethacin, thereby restoring intestinal permeability. Additionally, tegoprazan reversed the indomethacin-induced elevation of the levels of proinflammatory cytokines and the rate of apoptosis of small intestinal epithelial cells. Our findings indicate that tegoprazan exerts a protective effect against NSAID-induced injury to small intestinal epithelial cells. The effect involves enhancement of the expression levels of tight junction proteins and the suppression of inflammation and apoptosis.

Dietary supplementation of probiotic Lactobacillus modulates metabolic dysfunction-associated steatotic liver disease and intestinal barrier integrity in obesity-induced mice.

The impact of Lacticaseibacillus paracasei NWAFU334 and Limosilactobacillus fermentum NWAFU0035 on the amelioration of liver function, oxidative stress reduction, and lipid metabolism modulation in mice subjected to an obesity-inducing high-fat diet (HFD) model was investigated. L. paracasei NWAFU334 and L. fermentum NWAFU0035 supplementations over 12weeks have been shown to have numerous beneficial effects in mice with induced obesity. These effects comprise the restoration of liver function and the reduction of oxidative stress within the liver. Furthermore, the supplementation led to a decreased content of fat accumulation in the liver, mitigation of the expression of inflammatory cytokines in the liver and colon, and a decrease in the expression levels of tight-junction proteins, for example, claudin-1, PPARγ, occludin, and ZO-1. Additionally, a notable improvement in the colonic expression proteins, including IL-6, TNF-α, IL-1β, Muc-2, Muc-3, Zo-1, claudin-1, and occludin. These proposed strains considerably decreased proinflammatory cytokines and influenced the regulation of lipid metabolism in the liver. These findings indicate that the potential mechanisms, primarily the impact of L. paracasei NWAFU334 and L. fermentum NWAFU0035 on obesity-induced liver function in mice, involve two regulated pathways: downregulation of lipogenesis and upregulation of gene expression related to fatty acid oxidation and lipolysis. In other words, these probiotic bacterial strains might be beneficial in reducing fat production and increasing fat breakdown in the liver. They may serve as effective therapeutic supplements for alleviating abnormalities induced by an HFD.

Intraocular fatty acids induce reinforcement of barrier functions on the outer blood-retinal barrier

The aim of the present study was to elucidate unknown effects of intraocular fatty acids (ioFAs) including palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2), arachidonic acid (C20:4), eicosapentaenoic acid (EPA, C20:5) and docosahexaenoic acid (DHA, C22:6) on the outer blood-retinal barrier (oBRB). For this purpose, human retinal pigment epithelium cell line ARPE19 was subjected to analyses for evaluating the following biological phenotypes: (1) cell viability, (2) cellular metabolic functions, (3) barrier functions by trans-epithelial electrical resistance (TEER), and (4) expression of tight junction (TJ) molecules. In the presence of 100 nM ioFAs, no significant effects on cell viability of ARPE19 cells was observed. While treatment with EPA or DHA tended to reduce non-mitochondrial oxygen consumption, most indices in mitochondrial functions were not markedly affected by treatment with ioFAs in ARPE19 cells. On the other hand, ioFAs except for palmitic acid and stearic acid significantly increased basal extracellular acidification rates, suggesting activated glycolysis or increased lactate production. Interestingly, TEER values of planar ARPE19 monolayer were significantly increased by treatment any ioFAs. Consistently, gene expression levels of TJ proteins were increased by treatment with ioFAs. Collectively, the findings presented herein suggest that ioFAs may contribute to reinforcement of barrier functions of the oBRB albeit there are some differences in biological effects depending on the type of ioFAs.

Eucommia ulmoides Leaves Alleviate Cognitive Dysfunction in Dextran Sulfate Sodium (DSS)-Induced Colitis Mice through Regulating JNK/TLR4 Signaling Pathway.

Ulcerative colitis (UC) is one of the inflammatory bowel diseases (IBD) that is characterized by systemic immune system activation. This study was performed to assess the alleviative effect of administering an aqueous extract of Eucommia ulmoides leaves (AEEL) on cognitive dysfunction in mice with dextran sulfate sodium (DSS)-induced colitis. The major bioactive compounds of AEEL were identified as a quinic acid derivative, caffeic acid-O-hexoside, and 3-O-caffeoylquinic acid using UPLC Q-TOF/MSE. AEEL administration alleviated colitis symptoms, which are bodyweight change and colon shortening. Moreover, AEEL administration protected intestinal barrier integrity by increasing the tight junction protein expression levels in colon tissues. Likewise, AEEL improved behavioral dysfunction in the Y-maze, passive avoidance, and Morris water maze tests. Additionally, AEEL improved short-chain fatty acid (SCFA) content in the feces of DSS-induced mice. In addition, AEEL improved damaged cholinergic systems in brain tissue and damaged mitochondrial and antioxidant functions in colon and brain tissues caused by DSS. Also, AEEL protected against DSS-induced cytotoxicity and inflammation in colon and brain tissues by c-Jun N-terminal kinase (JNK) and the toll-like receptor 4 (TLR4) signaling pathway. Therefore, these results suggest that AEEL is a natural material that alleviates DSS-induced cognitive dysfunction with the modulation of gut-brain interaction.

Kinase PIM1 governs ferroptosis to reduce retinal microvascular endothelial cell dysfunction triggered by high glucose.

Previous studies have implicated targeting Pim-1 proto-oncogene, serine/threonine kinase (PIM1) as a preventive measure against high glucose-induced cellular stress and apoptosis. This study aimed to reveal the potential role and regulatory mechanism of PIM1 in diabetic retinopathy. Human retinal microvascular endothelial cells (hRMECs) underwent high glucose induction, and fluctuations in PIM1 levels were assessed. By overexpressing PIM1, its effects on the levels of inflammatory factors, oxidative stress indicators, migration and tube formation abilities, tight junction protein expression levels, and ferroptosis in hRMECs were identified. Afterwards, hRMECs were treated with the ferroptosis-inducing agent erastin, and the effect of erastin on the above PIM1 regulatory functions was focused on. PIM1 was downregulated upon high glucose, and its overexpression inhibited the inflammatory response, oxidative stress, cell migration, and tube formation potential in hRMECs, whereas elevated tight junction protein levels. Furthermore, PIM1 overexpression reduced intracellular iron ion levels, lipid peroxidation, and levels of proteins actively involved in ferroptosis. Erastin treatment reversed the impacts of PIM1 on hRMECs, suggesting the mediation of ferroptosis in PIM1 regulation. The current study has yielded critical insights into the role of PIM1 in ameliorating high glucose-induced hRMEC dysfunction through the inhibition of ferroptosis.

Changes in Tight Junction Protein Expression Levels but Not Distribution in Commercial White and Brown Laying Hens Supplemented with Chondrus crispus or Ascophyllum nodosum Seaweed.

It is proposed that prebiotic diet supplements improve intestinal function, in part by improving the barrier function of the intestinal epithelium with an associated increase in the expression of tight junction proteins, including occludin and zonula occludens-1 (ZO-1). We examined the expression of these proteins in two strains of laying hens (Lohman LSL-lite (White) and Lohman Brown-lite (Brown)) who were supplemented or not with 3% Chondrus crispus or 0.5% Ascophyllum nodosum seaweeds from 31 to 72 weeks of age. Occludin was localized to the lateral surfaces and across the intestinal epithelium in all animals. Reactivity for ZO-1 was concentrated at the apicolateral epithelial cell membrane border. Mood's median test indicated that White hens may express more occludin in villus epithelium (median intensity 3.5 vs. 2.5 in Brown hens, p = 0.06) but less ZO-1 in the deep cryptal epithelium (median intensity 1.5 vs. 2.5 in Brown hens, p = 0.06). Western blotting also showed higher levels of occludin in White than Brown hens (p < 0.05). A decrease in ZO-1 Western blot expression was associated with Chondrus crispus supplementation in comparison to controls (p < 0.05), but not with Ascophyllum nodosum supplementation (p > 0.05). In conclusion, genetic strain and dietary seaweed supplements affect tight junction regulatory protein expression levels but do not impact the anatomical distribution, as seen in cryosections.

Substance P Alleviates Retinal Pigment Epithelium Dysfunction Caused by High Glucose-Induced Stress.

When the retina is constantly affected by high glucose (HG) due to diabetes, the barrier function of the retinal pigment epithelium (RPE) is impaired, accompanied by unnecessary vascularization. This eventually leads to the development of diabetic retinopathy (DR). This study investigated the recovery effect of substance P (SP) on RPE injured by HG. RPE was treated with HG for 24 h, and HG-induced cellular injuries were confirmed. SP was added to the dysfunctional RPE. Compared to RPE in low glucose (LG) conditions, HG-damaged RPE had large, fibrotic cell shapes, and its cellular viability decreased. HG treatment reduced tight junction protein expression levels and caused oxidative stress by interrupting the antioxidant system; this was followed by inflammatory factor intracellular adhesion molecule-1 (ICAM-1), Monocyte chemotactic protein-1 (MCP-1), and angiogenesis factor vascular endothelial growth factor (VEGF) expression. SP treatment contributed to RPE recovery by enhancing cell viability, tight junction protein expression, and RPE function under HG conditions, possibly by activating the Akt signaling pathway. Importantly, SP treatment reduced ICAM-1, MCP-1, and VEGF expression. Collectively, SP activated survival signals to suppress oxidative stress and improve retinal barrier function in RPE, accompanied by immune suppression. This suggests the possible application of SP to diabetic retinal injuries.

Fructo-oligosaccharides Ameliorate Intestinal Mechanical Barrier Injury in Piglets Induced by Soybean Antigen in vitro and in vivo.

Fructose oligosaccharides (FOS) have been shown to reduce soybean antigeninduced hypersensitivity in piglets, but their effects on intestinal epithelial barrier function have not been characterized. Therefore, this study aimed to determine the effects of FOS on intestinal barrier injury induced by soybean antigen in piglets in vitro and in vivo. We studied the protective effects of FOS against mechanical barrier dysfunction induced using β-conglycinin or glycinin in porcine intestinal epithelial cells (IPEC-J2), and measured the serum concentrations of diamine oxidase (DAO), D-lactic acid, and endotoxin, and the expression of tight junction (TJ) proteins, in piglets. We found that FOS concentration dependently increases cell activity, trans-epithelial electrical resistance, and TJ protein expression (P < 0.05) and reduces alkaline phosphatase (AP) activity (P < 0.05) in vitro. In addition, the serum DAO, D-lactic acid, and endotoxin concentrations were reduced by FOS administration in piglets (P < 0.05). Both in vitro and in vivo, the expression levels of TJ proteins (zona occludens 1 and occludin) were increased significantly by FOS (P < 0.05). Therefore, FOS protect against intestinal injury induced by soybean antigen in piglets, which may provide a basis for the prevention of allergy.

Selenium deficiency increased duodenal permeability and decreased expression of antimicrobial peptides by activating ROS/NF-κB signal pathway in chickens.

Selenium (Se) is an essential trace element for the body. Various organs of the body, including the intestine, are affected by its deficiency. Se deficiency can induce oxidative stress and inflammatory responses in the intestine. It can also increase intestinal permeability and decrease intestinal immune function in mammals. However, the detailed studies, conducted on the intestinal molecular mechanisms of Se deficiency-induced injury in poultry, are limited. This study explored the adverse effects of Se deficiency on intestinal permeability and its mechanism. A Se-deficient chicken model was established, and the morphological changes in the chicken duodenum tissues were observed using a light microscope and transmission electron microscope (TEM). Western blotting, qRT-PCR, and other methods were used to detect the expression levels of selenoproteins, oxidative stress indicators, inflammatory factors, tight junction (TJ) proteins, antimicrobial peptides, and other related indicators in intestinal tissues. The results showed that Se deficiency could decrease the expression levels of selenoproteins and antioxidant capacity, activate the nuclear factor kappa-B (NF-κB) pathway, cause inflammation, and decrease the expression levels of TJ proteins and antimicrobial peptides in the duodenum tissues. The study also demonstrated that Se deficiency could increase intestinal permeability and decrease antimicrobial peptides via reactive oxygen species (ROS)/NF-κB. This study provided a theoretical basis for the scientific prevention and control of Se deficiency in poultry. Se deficiency decreased the expression levels of selenoproteins and increased ROS levels to activate the NF-κB pathway, resulting in the production of pro-inflammatory cytokines, reducing the expression levels of TJ protein, and weakening the expression of antimicrobial peptides, which contributed to the higher intestinal permeability. Oxidative stress weakened the expression of antimicrobial peptides.

FOSL1 knockdown ameliorates DSS-induced inflammation and barrier damage in ulcerative colitis via MMP13 downregulation.

Ulcerative colitis (UC) is a chronic inflammatory disease of the colon. Fos-related antigen 1 is highly expressed in mild UC and affects the maintenance and delayed recurrence of inflammatory bowel disease. Therefore the present study aimed to investigate the role of Fos-like antigen-1 (FOSL1) in UC. Use of the JASPAR database predicted the possible interaction of FOSL1 and the MMP13 promoter. FOSL1 and MMP13 mRNA and protein expression levels in dextran sodium sulfate (DSS)-induced HT29 cells and colon tissues of a UC mice model were determined using reverse transcription-quantitative PCR and western blotting, respectively. MMP13 promoter activity was determined using the dual-luciferase reporter assay, the relationship between FOSL1 and MMP13 promoter was determined using chromatin immunoprecipitation, inflammatory factor levels were quantified using ELISA, cell monolayer permeability analysis was performed using transepithelial electrical resistance measurements and tight junction protein expression levels were determined by western blotting. After constructing a UC mice model, mice colonic injury was determined with the quantification of colon length, H&E staining and disease activity index. The results demonstrated that FOSL1 and MMP13 were upregulated in DSS-induced HT29 cells and tissues. FOSL1 was also determined to be bound to the MMP13 promoter region and was demonstrated to upregulate MMP13 expression levels. Furthermore, FOSL1 knockdown inhibited DSS-induced inflammation and barrier damage in HT29 cells via MMP13 downregulation. FOSL1 knockdown also ameliorated colonic injury, inflammation and barrier damage in the tissues of the UC mice model via MMP13 downregulation. Overall, FOSL1 knockdown was demonstrated to potentially ameliorate DSS-induced inflammatory injury and protect the intestinal barrier integrity in the UC mice model via MMP13 downregulation.

Sufentanil ameliorates oxygen-glucose deprivation/reoxygenation-induced endothelial barrier dysfunction in HCMECs via the PI3K/Akt signaling pathway.

Ischemic heart disease, a chronic myocardial damage disease caused by coronary artery ischemia, is the leading cause of death worldwide. The aim of the present study was to explore the efficacy of sufentanil in myocardial ischemia/reperfusion (I/R) injury. Oxygen and glucose deprivation/reoxygenation (OGD/R) was utilized to induce human cardiac microvascular endothelial cells (HCMECs) to simulate myocardial I/R injury in vitro. The Cell Counting Kit-8 assay was used to detect the effects of sufentanil on HCMECs and OGD/R-induced HCMECs. The TUNEL, lactate dehydrogenase (LDH) activity, immunofluorescence and in vitro permeability assays, were used to assess apoptosis, LDH activity, VE-cadherin protein expression levels and endothelial barrier function in OGD/R-induced HCMECs, respectively. Moreover, western blotting was performed to assess the protein expression levels of apoptosis, endothelial barrier function and phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)-related proteins. The results demonstrated that sufentanil had no significant influence on the viability of HCMECs but increased the viability of OGD/R-induced HCMECs in a dose-dependent manner. Furthermore, sufentanil inhibited cell apoptosis and permeability of OGD/R-induced HCMECs but enhanced the protein expression levels of tight junction proteins, including ZO-1, Occludin, VE-cadherin and Claudin-5. Sufentanil was also demonstrated to activate the PI3K/Akt signaling pathway. In addition, the use of LY294002, an inhibitor of the PI3K/Akt signaling pathway, partially abolished the protective effects of sufentanil on apoptosis, permeability and tight junction protein expression levels. These results indicated that sufentanil ameliorated OGD/R-induced endothelial barrier dysfunction in HCMECs, potentially via the PI3K/Akt signaling pathway. The present study therefore suggested that sufentanil may serve as a novel therapeutic option for the improvement of myocardial I/R injury.

Maf1 Ameliorates Sepsis-Associated Encephalopathy by Suppressing the NF-kB/NLRP3 Inflammasome Signaling Pathway.

BackgroundThe NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome has been identified as an important mediator of blood–brain-barrier disruption in sepsis-associated encephalopathy (SAE). However, no information is available concerning the critical upstream regulators of SAE.MethodsLipopolysaccharide (LPS) was used to establish an in vitro model of blood–brain barrier (BBB) disruption and an in vivo model of SAE. Disruption of BBB integrity was assessed by measuring the expression levels of tight-junction proteins. NLRP3 inflammasome activation, pro-inflammatory cytokines levels, and neuroapoptosis were measured using biochemical assays. Finally, the FITC-dextran Transwell assay and Evan’s blue dye assay were used to assess the effect of Maf1 on LPS-induced endothelial permeability in vitro and in vivo. ResultsWe found that Maf1 significantly suppressed the brain inflammatory response and neuroapoptosis induced by LPS in vivo and in vitro. Notably, Maf1 downregulated activation of the NF-κB/p65-induced NLRP3 inflammasome and the expression of pro-inflammatory cytokines. In addition, we found that Maf1 and p65 directly bound to the NLRP3 gene promoter region and competitively regulated the function of NLRP3 in inflammations. Moreover, overexpression of NLRP3 reversed the effects of p65 on BBB integrity, apoptosis, and inflammation in response to LPS. Our study revealed novel role for Maf1 in regulating NF-κB-mediated inflammasome formation, which plays a prominent role in SAE.ConclusionsRegulation of Maf1 might be a therapeutic strategy for SAE and other neurodegenerative diseases associated with inflammation.

Effects of treadmill exercise on the regulation of tight junction proteins in aged mice.

Tight junction protein is representative regulator of gut permeability. Also, it has been noted for controlling inflammatory responses through tight junction. Therefore, in this study, we examined that whether tight junction protein is changed in aged mice, and to further, confirmed the effect of treadmill exercise on the tight junction protein. In in vitro study, doxorubicin that induces cell senescence was treated to Caco2 cells (colon cell) to mimic aging effect. After that, 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR), exercise mimic chemical that stimulates AMPK level, was also administered to Caco2 cells. In animal study, 2months and 21months C57BL/6J mouse were treated with treadmill exercise for 4weeks (YE=5, OE=5). Then, the tight junction protein expression level was examined by western blot. Also, serum lipopolysaccharide (LPS) and zonulin level were analyzed to identify gut permeability. In vitro studies showed that doxorubicin downregulates tight junction protein expression levels in Caco2 cell, and also AICAR treatment upregulates tight junction protein expression levels. In animal study, 4weeks treadmill exercise upregulated claudin-1 (p<0.05) and occludin (p<0.01) protein expression level in 21months old mice. Also, zonula occluden-1 (ZO-1) protein expression level was not significant difference among all mice group. In addition, old mice group had higher level of serum LPS compared to young mice group, but the level was downregulated in both 2months and 21months mice group after four weeks of treadmill exercise. Zonulin, which is known as degrading tight junction protein, is not significantly changed by both age and exercise. This study compared that tight junction protein expression level in old mice compared to its level in young mice, and also clarified that the effect of treadmill exercise on tight junction protein in both young and old mice.

Alterations in intestinal microbiota by alginate oligosaccharide improve intestinal barrier integrity in weaned pigs

• AOS enhances the intestinal barrier integrity by activating the AMPK pathway. • AOS attenuates intestinal inflammatory reactions by inhibiting the NF-κB pathway. • These changes are associated with alterations in intestinal microbiota and microbial metabolites caused by AOS. In this study, we investigated the effects of alginate oligosaccharide (AOS) on the intestinal microbiota and intestinal barrier integrity in weaned pigs. Twenty-four weaned pigs were equally assigned to either a control group (fed the basal diet) or an AOS group (fed the basal diet supplemented with 100 mg/kg AOS). AOS upregulated caecal and colonic tight junction protein expression levels but downregulated caecal pro-inflammatory cytokine expression levels. AOS increased the caecal and colonic abundance of phospho-adenosine 5′-monophosphate-activated protein kinase α (p-AMPKα) and decreased the abundance of caecal intra-nuclear nuclear factor-κB (NF-κB) p65. Furthermore, AOS increased the caecal prevalence of several bacteria belonging to Bacteroidetes and Firmicutes as well as the caecal and colonic concentrations of short-chain fatty acids (SCFAs). Thus, AOS alters the intestinal microbiota composition and SCFA concentrations in weaned pigs, thereby influencing the intestinal inflammatory responses and barrier integrity by regulating NF-κB and AMPK pathways.

Arsenic induces autophagy in developmental mouse cerebral cortex and hippocampus by inhibiting PI3K/Akt/mTOR signaling pathway: involvement of blood-brain barrier's tight junction proteins.

For the past decade, there has been an increased concern about the health risks from arsenic (As) exposure, because of its neurotoxic effects on the developing brain. The exact mechanism underlying As-induced neurotoxicity during sensitive periods of brain development remains unclear, especially the role of blood-brain barrier's (BBB) tight junction (TJ) proteins during As-induced neurotoxicity. Here, we highlight the involvement of TJ proteins in As-induced autophagy in cerebral cortex and hippocampus during developmental periods [postnatal day (PND) 21, 28, 35 and 42]. Here, the administration of arsenic trioxide (As2O3) at doses of 0.15mg or 1.5mg or 15mg As2O3/L in drinking water from gestational to lactational and continued to the pups till PND42 resulted in a significant decrease in the mRNA expression levels of TJ proteins (Occludin, Claudin, ZO-1 and ZO-2) and Occludin protein expression level. In addition, As exposure significantly decreased PI3K, Akt, mTOR, and p62 with a concomitant increase in Beclin1, LC3I, LC3II, Atg5 and Atg12. Moreover, As exposure also significantly downregulated the protein expression levels of mTOR with a concomitant upregulation of Beclin 1, LC3 and Atg12 in all the developmental age points. However, no significant alterations were observed in low and medium dose-exposed groups of PND42. Histopathological analysis in As-exposed mice revealed decreased number of pyramidal neurons in hippocampus; and neurons with degenerating axons, shrinkage of cells, remarkable vacuolar degeneration in cytoplasm, karyolysis and pyknosis in cerebral cortex. Ultrastructural analysis by transmission electron microscopy revealed the occurrence of autophagosomes and vacuolated axons in the cerebral cortex and hippocampus of the mice exposed to high dose As at PND21 and 42. The severities of changes were found to more persist in the cerebral cortex than in the hippocampus of As-exposed mice. Finally, we conclude that the leaky BBB in cerebral cortex and hippocampus may facilitate the transfer of As and induces autophagy by inhibiting PI3K/Akt/mTOR signaling pathway in an age-dependent manner, i.e., among the four different developmental age points, PND21 animals were found to be more vulnerable to the As-induced neurotoxicity than the other three age points.

Glutamine alleviates heat stress-induced impairment of intestinal morphology, intestinal inflammatory response, and barrier integrity in broilers

The aim of this study was to investigate the protective effect of glutamine (Gln) on the intestinal morphology, intestinal inflammatory response, and barrier integrity in broilers exposed to high ambient temperature. Three-hundred-sixty 21-d-old Arbor Acres broilers (half male and half female) were randomly allocated to 4 treatment groups in a completely randomized design, each of which included 6 replicates with 15 birds per replicate, for 21 d. The 4 treatment groups were as follows: the control group, in which birds were kept in a thermoneutral room at 22 ± 1°C (no stress, NS; fed a basal diet); the heat stress group (36 ± 1°C for 10 h/d from 08:00 to 18:00 h and 22 ± 1°C for the remaining time, heat stress (HT); fed a basal diet); and heat stress + Gln group (0.5 and 1.0% Gln, respectively). Compared to the NS group, broilers in the HT group had lower villus height (P < 0.05), higher crypt depth (P < 0.05), higher D-lactic acid and diamine oxidase (DAO) activity (P < 0.05), higher soluble intercellular adhesion molecule-1 (sICAM-1) concentration (P < 0.05), higher tumor necrosis factor (TNF)-α/interleukin (IL)-10 (P < 0.05), and lower tight junction protein expression levels (P < 0.05). Compared with birds in the HT, birds in the HT + Gln group exhibited increased villus height (P < 0.05), decreased D-lactate and DAO activity (P < 0.05), decreased sICAM-1 concentration (P < 0.05), and mediate the secretion of cytokines (P < 0.05), as well as increased zonula occludens-1 (ZO-1), claudin-1, and occludin mRNA expression levels (P < 0.05). In conclusion, these results indicate that supplementation with Gln was effective in partially ameliorating the adverse effects of heat stress on intestinal barrier function in broilers by promoting epithelial cell proliferation and renewal, modifying the function of the intestinal mucosa barrier, and regulating the secretion of cytokines.

Matrix Metalloproteinase-Mediated Blood-Brain Barrier Dysfunction in Epilepsy.

The blood-brain barrier is dysfunctional in epilepsy, thereby contributing to seizure genesis and resistance to antiseizure drugs. Previously, several groups reported that seizures increase brain glutamate levels, which leads to barrier dysfunction. One critical component of barrier dysfunction is brain capillary leakage. Based on our preliminary data, we hypothesized that glutamate released during seizures mediates an increase in matrix-metalloproteinase (MMP) expression and activity levels, thereby contributing to barrier leakage. To test this hypothesis, we exposed isolated brain capillaries from male Sprague Dawley rats to glutamate ex vivo and used an in vivo/ex vivo approach of isolated brain capillaries from female Wistar rats that experienced status epilepticus as an acute seizure model. We found that exposing isolated rat brain capillaries to glutamate increased MMP-2 and MMP-9 protein and activity levels, and decreased tight junction protein levels, which resulted in barrier leakage. We confirmed these findings in vivo in rats after status epilepticus and in brain capillaries from male mice lacking cytosolic phospholipase A2 Together, our data support the hypothesis that glutamate released during seizures signals an increase in MMP-2 and MMP-9 protein expression and activity levels, resulting in blood-brain barrier leakage.SIGNIFICANCE STATEMENT The mechanism leading to seizure-mediated blood-brain barrier dysfunction in epilepsy is poorly understood. In the present study, we focused on defining this mechanism in the brain capillary endothelium. We demonstrate that seizures trigger a pathway that involves glutamate signaling through cytosolic phospholipase A2, which increases MMP levels and decreases tight junction protein expression levels, resulting in barrier leakage. These findings may provide potential therapeutic avenues within the blood-brain barrier to limit barrier dysfunction in epilepsy and decrease seizure burden.

The effect of phytic acid on tight junctions in the human intestinal Caco-2 cell line and its mechanism

This study investigated the effect of phytic acid (IP6), a potential absorption enhancer of flavonoid components, on tight junction (TJ) integrity in Caco-2 cell monolayers and its possible mechanisms. Transepithelial electrical resistance (TEER) across the monolayers decreased rapidly, and the flux of fluorescein sodium (a paracellular marker) increased after treating with IP6 in a concentration-dependent manner. Confocal microscopy results showed that IP6 produced a concentration-dependent attenuation in the distribution of occludin, ZO-1, and claudin-1. Immunoblot analysis revealed that IP6 could down-regulate the expression level of these TJ proteins, which resulted in the opening of TJ. Additionally, the divalent cations Ca2+ and Mg2+ influenced the IP6-induced distribution of occludin, ZO-1, and claudin-1 in different directions, which enhanced barrier function. In conclusion, IP6 can decrease the integrity of Caco-2 cell monolayers by modulating the TJ proteins' localization and down-regulating the expression levels of TJ proteins including claudin-1, occludin, and ZO-1; the reduction effects of divalent cations such as Ca2+ and Mg2+ on the regulation of TJ induced by IP6 should be addressed. The present work will offer some useful guidance for the application of IP6 in drug delivery area.