Role of ferroptosis in Porphyromonas gingivalis-induced impairment of epithelial junction

Objectives

This study aims to clarify the effect of ferroptosis by P. gingivalis on periodontal epithelium impairment and potential mechanisms.

Materials and methods

The expression of epithelial junction proteins (CDH1, OCLN, ZO-1), FTL and GPX4 in healthy and periodontitis tissues was analyzed using bioinformatics analysis and validated in vivo. An in vitro model was constructed to evaluate ferroptosis by mitochondria morphology, content of iron and GSH, and level of lipid peroxidation, FTL, GPX4 and SLC7A11. The iron concentration was changed with iron chelator DFO and iron supplementation FAC. The epithelial impairment was assessed by protein expression. To investigate the mechanism, si-MYB (a negative transcription factor of SLC7A11) and GPX4 inhibitor RSL3 were employed.

Results

CDH1, OCLN, ZO-1 and GPX4 expression was decreased, while FTL expression was elevated in periodontitis tissues. Infected cells showed ferroptosis change of the mitochondria with higher level of lipid peroxidation, iron, FTL and lower level of GPX4, GSH, SLC7A11. FAC augmented ferroptosis and weakened epithelial junction, while DFO exhibited a counteractive effect. Silencing MYB rescued SLC7A11, GPX4 and epithelial junction proteins, which was hindered by RSL3.

Conclusions

Our study demonstrated that P. gingivalis weakened the oral epithelial barrier by causing ferroptosis via inhibiting SLC7A11/GSH/GPX4 axis.

RAB11A-mediated YAP localization to adherens and tight junctions is essential for colonic epithelial integrity

Within the intestinal epithelium, regulation of intracellular protein and vesicular trafficking is of utmost importance for barrier maintenance, immune responses, and tissue polarity. RAB11A is a small GTPase that mediates the anterograde transport of protein cargos to the plasma membrane. Loss of RAB11A-dependent trafficking in mature intestinal epithelial cells results in increased epithelial proliferation and nuclear accumulation of Yes-associated protein (YAP), a key Hippo-signaling transducer that senses cell–cell contacts and regulates tissue growth. However, it is unclear how RAB11A regulates YAP intracellular localizations. In this report, we examined the relationship of RAB11A to epithelial junctional complexes, YAP, and the associated consequences on colonic epithelial tissue repair. We found that RAB11A controls the biochemical associations of YAP with multiple components of adherens and tight junctions, including α-catenin, β-catenin, and Merlin, a tumor suppressor. In the absence of RAB11A and Merlin, we observed enhanced YAP–β-catenin complex formation and nuclear translocation. Upon chemical injury to the intestine, mice deficient in RAB11A were found to have reduced epithelial integrity, decreased YAP localization to adherens and tight junctions, and increased nuclear YAP accumulation in the colon epithelium. Thus, RAB11A-regulated trafficking regulates the Hippo–YAP signaling pathway for rapid reparative response after tissue injury.

Congenital biliary atresia is correlated with disrupted cell junctions and polarity caused by Cdc42 insufficiency in the liver

Rationale: Congenital biliary atresia (BA) is a destructive obliterative cholangiopathy of neonates that affects both intrahepatic and extrahepatic bile ducts. However, the cause of BA is largely unknown.

Methods: We explored the cell junctions and polarity complexes in early biopsy BA livers by immunofluorescence staining and western blot. Cdc42, as a key cell junction and polarity regulator, was found dramatically decreased in BA livers. Therefore, in order to investigate the role of Cdc42 in BA development, we constructed liver-specific and tamoxifen induced cholangiocyte-specific Cdc42 deleted transgenic mice. We further evaluated the role of bile acid in aggravating biliary damage in Cdc42 insufficient mouse liver.

Results: We found a dramatic defect in the assembly of cell junctions and polarity complexes in both cholangiocytes and hepatocytes in BA livers. This defect was characterized by the disordered location of cell junction proteins, including ZO1, β-catenin, E-cadherin and claudin-3. Cdc42 and its active form, Cdc42-GTP, which serves as a small Rho GTPase to orchestrate the assembly of polarity complexes with Par6/Par3/αPKC, were substantially reduced in BA livers. Selective Cdc42 deficiency in fetal mouse cholangiocytes resulted in histological changes similar to those found in human BA livers, including obstruction in both the intra- and extrahepatic bile ducts, epithelial atrophy, and the disruption of cell junction and polarity complexes. A reduction in bile acids notably improved the histology and serological indices in Cdc42-mutant mice.

Conclusion: Our results illustrate that BA is closely correlated with the impaired assembly of cell junction and polarity complexes in liver cells, which is likely caused by Cdc42 insufficiency and aggravated by bile acid corrosion.

Synthesis, activity and mechanism of alkoxy-, carbamato-, sulfonamido-, thioureido-, and ureido-derivatives of 2,4,5-trimethylpyridin-3-ol against inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic immuno-inflammation in gastrointestinal tract. We have evaluated the activity of the compounds to inhibit the adhesion of monocytes to colon epithelial cells is triggered by a pro-inflammatory cytokine, tumour necrosis factor (TNF)-α. The in vitro activity of the compounds, 13b (an ureido-derivative), 14c, 14j, 14k, 14n (thioureido-), 18c and 18d (sulfonamido-), was in correlation with in vivo anti-colitis activity revealed as significant recovery in body- and colon-weights and colon myeloperoxidase level, a biochemical marker of inflammation reflecting neutrophil infiltration. In vivo, TNBS-induced changes in the expression of inflammatory cytokines (TNF-α, IL-6, IL-1β, IL-10, and TGF-β), NLRP3 inflammasome components (NLRP-3, Caspase-1, and IL-18), and epithelial junction molecules (E-cadherin, claudin2/3, and ZO-1) were blocked and recovered by oral administration of the compounds (1 mg/kg). Compound 14n which showed the best efficacy can be a promising lead for orally available therapeutics for pathology of IBD.

Galectin-3 as a regulator of the epithelial junction: Implications to wound repair and cancer

Epithelial cells are closely connected to each other and to the extracellular matrix by a set of adhesive contacts that provide tissues with unique barrier properties and play a prominent role in cell morphology, tissue physiology, and cell signaling. This review highlights advances made in understanding the contributions of galectin-3, a carbohydrate-binding protein with affinity toward β-galactosides, as a modulator of epithelial junction assembly and function. The interactions of galectin-3 within adhesive structures are discussed in relation to wound healing and tumor progression.