Introduction:
Ultrafine particles (UFP,
d
< 0.1 μm), a major sub-fraction of particulate matter (PM
2.5
,
d
< 2.5μm) in air pollutant, have been reported to increase cardiovascular morbidity. UFP promote endothelial dysfunction/permeability associated with Notch inhibition and degradation of tight junction protein. Gut vascular barrier (GVB) is a distinct protective barrier that inhibits translocations of antigens across the gut lumen, preventing infections by oral digestions. Here, we hypothesized UFP impair GVB by attenuating Notch signaling and disrupting tight junction protein.
Method:
The transgenic Tg(
flk1:mCherry
) zebrafish embryos were immobilized in neutralized tricaine solution and mounted in 2% low melting agarose to perform micro-gavage at 5 days post fertilizations (5dpf). A mA mixture of 10 kD FITC conjugated dextran and phenol red dye wasere micro-gavaged on the intestinal bulb with or without UFP at 25 μg/mL. Anterior trunk and posterior cardinal vein (PCV) post micro-gavage were imaged under a confocal microscope. Notch signaling related genes including the Notch ligand, Dll4, and the target, HES1, and the level of tight junction protein genes zonula occludens-1 (ZO-1) and Occludin (OCLN) mRNA expression following different courses of exposure to UFP were assessed in Human Aortic Endothelial Cells (HAEC) with quantitative RT-PCR.,
Result:
In the control group, the majority of FITC-dextran remained inside the gastrointestinal system. On the other hand, UFP exposure developed a significant accumulation of FITC-dextran in the intersomatic spaces (ISS) between the dorsal aorta (DA) and the PCV. This finding supports evidence of UFP exposure disrupted both the epithelial boundary and the endothelial vascular layer of the gut. In addition, Notch signaling related gene (HES1, DLL4) and the tight junction proteins genes (ZO-1, OCLN) expressions in HAEC were downregulated in concentration and time-course dependent manner by the exposure to UFP.
Conclusion:
The UFP exposure affected GVB homeostasis and increased endothelial permeability. This finding supports the link between ambient air pollutant exposure to the impairment in the gastrointestinal system.
Chronic stress and intestinal barrier dysfunction: Glucocorticoid receptor and transcription repressor HES1 regulate tight junction protein Claudin-1 promoter