Gut-derived bacterial lipopolysaccharides (LPS) play an essential role in inducing intestinal and systemic inflammatory responses and have been implicated as a pathogenic factor of necrotizing enterocolitis (NEC) and inflammatory bowel disease (IBD). The defective intestinal tight junction (TJ) barrier has been shown to be an important factor contributing to the development of intestinal inflammation. LPS, at physiological concentrations, cause an increase in intestinal tight junction permeability (TJP) via a TLR-4 dependent process; however the intracellular mechanisms that mediate LPS regulation of intestinal TJP remain unclear. The aim of this study was to investigate the adaptor proteins and the signaling interactions that mediate LPS modulation of intestinal TJ barrier using an in-vitro and in-vivo model system. LPS caused a TLR-4 dependent activation of membrane-associated adaptor protein FAK in Caco-2 monolayers. LPS caused an activation of both MyD88-dependent and –independent pathways. SiRNA silencing of MyD88 prevented LPS-induced increase in TJP. LPS caused a MyD88-dependent activation of IRAK4. TLR-4, FAK and MyD88 were co-localized. SiRNA silencing of TLR-4 inhibited TLR-4 associated FAK activation; and FAK knockdown prevented MyD88 activation. In-vivo studies also confirmed that LPS-induced increase in mouse intestinal permeability was associated with FAK and MyD88 activation; knockdown of intestinal epithelial FAK prevented LPS-induced increase in intestinal permeability. Additionally, high dose LPS-induced intestinal inflammation was also dependent on TLR-4/FAK/MyD88 signal-transduction axis. Our data show for the first time that LPS-induced increase in intestinal TJP and intestinal inflammation was regulated by TLR-4 dependent activation of FAK-MyD88-IRAK4 signaling pathway.

The defective intestinal epithelial tight junction (TJ) barrier has been postulated to be an important pathogenic factor contributing to intestinal inflammation. It has been shown that the proinflammatory cytokine IL-1β causes an increase in intestinal permeability; however, the signaling pathways and the molecular mechanisms involved remain unclear. The major purpose of this study was to investigate the role of the p38 kinase pathway and the molecular processes involved. In these studies, the in vitro intestinal epithelial model system (Caco-2 monolayers) was used to delineate the cellular and molecular mechanisms, and a complementary in vivo mouse model system (intestinal perfusion) was used to assess the in vivo relevance of the in vitro findings. Our data indicated that the IL-1β increase in Caco-2 TJ permeability correlated with an activation of p38 kinase. The activation of p38 kinase caused phosphorylation and activation of p38 kinase substrate, activating transcription factor (ATF)-2. The activated ATF-2 translocated to the nucleus where it attached to its binding motif on the myosin L chain kinase (MLCK) promoter region, leading to the activation of MLCK promoter activity and gene transcription. Small interfering RNA induced silencing of ATF-2, or mutation of the ATF-2 binding motif prevented the activation of MLCK promoter and MLCK mRNA transcription. Additionally, in vivo intestinal perfusion studies also indicated that the IL-1β increase in mouse intestinal permeability required p38 kinase–dependent activation of ATF-2. In conclusion, these studies show that the IL-1β–induced increase in intestinal TJ permeability in vitro and in vivo was regulated by p38 kinase activation of ATF-2 and by ATF-2 regulation of MLCK gene activity.

EOGE is an underdiagnosed condition. In contrast to eosinophilic esophagitis; the disease might be female-predominant in adults. High index of clinical suspicion is required for diagnosis. Further studies about the long-term outcomes and the efficacy of restriction diet in adult patients are required.

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BackgroundInflammatory bowel disease (IBD) is characterised by acute intestinal mucosal inflammation with chronic inflammatory features. Various degrees of mucosal eosinophilia are present along with the typical acute (neutrophil-predominant) inflammation. The effect of intestinal eosinophils on IBD outcomes remains unclear.MethodsThis is a retrospective study. Archived intestinal mucosal biopsy specimens of treatment-naïve IBD patients were examined by two pathologists. The number of eosinophils per high-power field was counted, and the mucosal inflammation was classified according to the eosinophilic inflammatory patterns. Clinical outcomes during the follow-up period were recorded.Results142 treatment-naïve IBD patients were included. Mean age was 39 years. 83% of patients had ulcerative colitis, and median follow-up was 3 years. 41% of patients had disease flare(s) and 24% required hospitalisation. Eosinophil count was not associated with risk of disease flare or hospitalisation. Patients with neutrophil-predominant inflammation (>70% neutrophils) had greater risk of disease flare(s): 27(55%) versus 24(36%) and 7(28%) in patients with mixed and eosinophil-predominant inflammation, respectively (p=0.04). Overall, patients with neutrophil-predominant inflammation were more likely to have a disease flare; HR: 2.49, 95% CI (1.0 to 5.6). Hospitalisation rate was higher in patients with neutrophil-predominant inflammation: 17(35%) compared to 17(19%) in patients with eosinophil-rich inflammation (p=0.04). Kaplan–Meier analysis showed higher flare-free survival in patients with eosinophil-predominant inflammation compared to mixed and neutrophil-predominant inflammation.ConclusionIBD patients with eosinophil-predominant inflammation phenotype might have reduced risk of disease flares and hospitalisation. Larger prospective studies to assess IBD outcomes in this subpopulation are warranted.