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Updated: Mar 13, 2026
In Vitro and In Vivo Approaches to Determine Intestinal Epithelial Cell Permeability
Published on: October 19, 2018
Characterization of in vitro effects of microcystin-LR on intestinal epithelial cells
Yuan Zhou1, Xiaoping Xu2, Beibei Yu3
1College of Medicine and Life Sciences, Nanjing University of Chinese Medicine, Nanjing, 210023, Jiangsu, China.
Abstract:
The intestinal epithelium is a single-cell layer that provides an important barrier against natural toxins. Microcystin-LR (MC-LR), a cyclic heptapeptide, is one of the best known toxins able to alter the functions of intestine. This study evaluated the toxic effects and the possible mechanisms of MC-LR on barrier function of the intestinal epithelial cells. Intestinal epithelial cells (IEC-6) were exposed to 0, 6.25, 12.5, 25 and 50 μM MC-LR. Cell viability significantly decreased, while the ratio of apoptotic cells increased after exposure to 12.5μM and higer concentration of MC-LR. As expected, the integrity of a polarized IEC-6 monolayer was affected by MC-LR exposure, as demonstrated by a decrease in the transepithelial electrical resistance (TEER) values, becoming most pronounced at 50μM, 24 h. No effects were detected on the protein expression levels of the tight junction protein claudin at 50μM. However, the expression of occludin and zonula occludens-1 (ZO-1) declined. Furthermore, MC-LR can immigrate into IEC-6 cells. The activity of protein phosphatases 2A (PP2A) decreased from the concentration of 12.5 μM, showing a dose-dependent decline. These results provide new information that strengthens the concept that the intestinal epithelium is important targets for toxic effects of water contaminants like MC-LR. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1539-1547, 2017.
Insights
Microcystin-LR (MC-LR) harms intestinal barrier function by decreasing cell viability and increasing apoptosis. This toxin also disrupts tight junctions and inhibits protein phosphatase 2A activity in intestinal epithelial cells.
Area of Science:
- Environmental Toxicology
- Cell Biology
- Gastroenterology
Background:
- The intestinal epithelium forms a critical barrier against ingested toxins.
- Microcystin-LR (MC-LR) is a prevalent cyanobacterial toxin known to affect various organs.
- Understanding MC-LR's impact on intestinal health is crucial for public health.
Purpose of the Study:
- To investigate the toxic effects of MC-LR on intestinal epithelial cells (IEC-6).
- To elucidate the mechanisms underlying MC-LR-induced damage to intestinal barrier function.
- To assess MC-LR's impact on cell viability, apoptosis, tight junctions, and protein phosphatase activity.
Main Methods:
- IEC-6 cells were exposed to varying concentrations of MC-LR (0-50 μM).
- Cell viability and apoptosis were quantified.
- Transepithelial electrical resistance (TEER) was measured to assess barrier integrity.
- Expression of tight junction proteins (claudin, occludin, ZO-1) was analyzed.
- MC-LR cellular uptake and protein phosphatase 2A (PP2A) activity were evaluated.
Main Results:
- MC-LR exposure (≥12.5 μM) reduced cell viability and increased apoptosis in IEC-6 cells.
- A significant decrease in TEER indicated compromised barrier integrity, most pronounced at 50 μM.
- MC-LR exposure led to a decline in occludin and ZO-1 expression, but not claudin.
- MC-LR was found to permeate IEC-6 cells.
- PP2A activity decreased in a dose-dependent manner starting from 12.5 μM MC-LR.
Conclusions:
- MC-LR exerts toxic effects on the intestinal epithelium, compromising barrier function.
- Mechanisms include reduced cell viability, increased apoptosis, disrupted tight junctions (occludin, ZO-1), and inhibited PP2A activity.
- The intestinal epithelium is a significant target for MC-LR toxicity, highlighting risks associated with contaminated water.
