Protective Effects of Melatonin and Misoprostol against Experimentally Induced Increases in Intestinal Permeability in Rats

Abstract

Intestinal mucosal barrier dysfunction caused by disease and/or chemotherapy lacks an effective treatment, which highlights a strong medical need. Our group has previously demonstrated the potential of melatonin and misoprostol to treat increases in intestinal mucosal permeability induced by 15-min luminal exposure to a surfactant, sodium dodecyl sulfate (SDS). However, it is not known which luminal melatonin and misoprostol concentrations are effective, and whether they are effective for a longer SDS exposure time. The objective of this single-pass intestinal perfusion study in rats was to investigate the concentration-dependent effect of melatonin and misoprostol on an increase in intestinal permeability induced by 60-min luminal SDS exposure. The cytoprotective effect was investigated by evaluating the intestinal clearance of ⁵¹Cr-labeled EDTA in response to luminal SDS as well as a histological evaluation of the exposed tissue. Melatonin at both 10 and 100 µM reduced SDS-induced increase in permeability by 50%. Misoprostol at 1 and 10 µM reduced the permeability by 50 and 75%, respectively. Combination of the two drugs at their respective highest concentrations had no additive protective effect. These in vivo results support further investigations of melatonin and misoprostol for oral treatments of a dysfunctional intestinal barrier.

Keywords: gastrointestinal physiology; intestinal barrier dysfunction; intestinal permeability; melatonin; misoprostol; single-pass intestinal perfusion.

Figure 1

Effect of 5 mg/mL sodium dodecyl sulfate (SDS) in the luminal perfusate between 45 and 105 min on mean (±SEM) jejunal permeability (blood-to-lumen ⁵¹Cr-EDTA clearance (CL_Cr-EDTA)). SDS induced a significant increase in permeability, an effect that was significantly reduced by the addition of luminal melatonin at concentrations of 10 µM and 100 µM. */** significantly (p < 0.05/p < 0.01) lower total CL_Cr-EDTA compared with the SDS group.

Figure 2

Effect of 5 mg/mL sodium dodecyl sulfate (SDS) in the luminal perfusate between 45 and 105 min on the mean (±SEM) jejunal permeability (blood-to-lumen ⁵¹Cr-EDTA clearance (CL_Cr-EDTA)). SDS induced a significant increase in permeability, an effect that was significantly reduced by the addition of luminal misoprostol at concentrations of 1 µM and 10 µM. */** significantly (p < 0.05/p < 0.01) lower total CL_Cr-EDTA compared with the SDS group.

Figure 3

Effect of 5 mg/mL sodium dodecyl sulfate (SDS) in the luminal perfusate between 45 and 105 min on jejunal permeability (blood-to-lumen ⁵¹Cr-EDTA clearance (CL_Cr-EDTA)). SDS induced a significant increase in permeability, an effect that was significantly reduced by the addition of a combination of luminal melatonin (100 µM) and misoprostol (10 µM). Values are means (±SEM). ** significantly (p < 0.01) lower total CL_Cr-EDTA compared with the SDS group.

Figure 4

Histological images of the jejunal tissue from three different treatment groups with two different stainings, hematoxylin-eosin (a,c,e,g,i) and Alcian blue-PAS (b,d,f,h,j). Control animals only perfused with an isotonic phosphate-buffer solution (a,b). Animals perfused with sodium dodecyl sulfate (SDS) from 45 to 105 min of the experiment (c,d). Animals perfused with SDS from 45 to 105 min and melatonin (100 µM, e,f), misoprostol (10 µM, g,h) or a combination of the two (i,j) from 30 to 165 min of the experiment. Bars represent 250 µm.

Figure 5

The luminal compositions, conditions, and treatments of the seven different experimental groups. The jejunal segment of rats (n = 6 in each group) was single-pass perfused with a pH 6.5 saline buffer solution without (a) or with (b–e) the addition of 5 mg/mL SDS between 45 and 105 min. Melatonin (10 or 100 µM, c), misoprostol (1 or 10 µM, d), or a combination of the two (100 and 10 µM, respectively, e), were supplemented from 30 min onward to investigate their effects on the increases in intestinal mucosal permeability induced by 60-min exposure of SDS.