Effects of simulated weightlessness on tight junction protein occludin and Zonula Occluden-1 expression levels in the intestinal mucosa of rats

Abstract

This study investigated the tight junction (TJ) protein expression of the intestinal mucosa in a rat tail-suspension model under simulated weightlessness. Twenty-four Wistar rats were randomly divided into three groups: CON group (n=8), control; SUS-14 d group (n=8), tail-suspension for 14 days; SUS-21 d group (n=8), tail-suspension for 21 days. Occludin and Zonula Occluden-1 (ZO-1) expression levels were determined by immunohistochemical analysis and mRNA fluorescent quantitative PCR. Plasma levels of diamine oxidase (DAO) and d-lactate were determined using enzymatic spectrophotometry. Immunohistochemical results for occludin and ZO-1 showed disruption of the TJs in the intestinal mucosa in SUS-14 d and SUS-21 d groups. The expression levels of occludin and ZO-1 in SUS-21 d group were lower than those in SUS-14 d group, and significantly lower than those in CON group (Occldin: 0.86±0.02 vs 1.01±0.03 vs 1.63±0.03 and ZO-1: 0.82±0.01 vs 1.00±0.02 vs 1.55±0.01, P<0.01). Moreover, the levels of plasma DAO and d-lactate in SUS-21 d group were higher than those in SUS-14 d group, and significantly higher than those in CON group (DAO: 27.58±0.49 vs 20.74±0.49 vs 12.94±0.21 and d-lactate: 37.86±0.74 vs 28.26±1.01 vs 17.76±0.91, P<0.01). There were significant negative correlations between occludin or ZO-1 expression levels and DAO (r²=0.9014, r²=0.9355, P<0.01) or d-lactate levels (r²=0.8989, r²=0.9331, P<0.01). Occludin and Zo-1 were reduced in intestinal mucosa both in mRNA and protein levels in the rat tail-suspension model. The significant negative correlations between expression levels of TJs and plasma levels of DAO or d-lactate support the hypothesis that intestinal permeability is increased due to a decrease in TJ protein expression during tail-suspension from 14 days to 21 days.

Keywords

simulated weightlessness / tail-suspension / model / tight junction(TJ) protein / Wistar

References

[1] WilliamsD., KuipersA., MukaiC., et al.. Acclimation during space flight: effects on human physiology. CMAJ, 2009, 180(13): 1317-1323

[2] RabotS., SzylitO., Nugon-BaudonL., et al.. Variations in digestive physiology of rats after short duration flights aboard the US space shuttle. Dig Dis Sci, 2000, 45(9): 1687-1695

[3] DeitchE.A.. The role of intestinal barrier failure and bacterial translocation in the development of systemic infection and multiple organ failure. Arch Surg, 1990, 125(3): 403-404

[4] FanningA.S., MiticL.L., AndersonJ.M.. Transmembrane proteins in the tight junction barrier. J Am Soc Nephrol, 1999, 10(6): 1337-1345

[5] WittchenE.S., HaskinsJ., StevensonB.R.. Protein interactions at the tight junction. Actin has multiple binding partners, and ZO-1 forms independent complexes with ZO-2 and ZO-3. J Biol Chem, 1999, 274(49): 35 179-35 185

[6] VrolingA.B., FokkensW.J., van DrunenC.M.. How epithelial cells detect danger: aiding the immune response. Allergy, 2008, 63(9): 1110-1123

[7] BounousG., EchavéV., VobeckyS.J., et al.. Acute necrosis of the intestinal mucosa with high serum levels of diamine oxidase. Dig Dis Sci, 1984, 29(9): 872-874

[8] Morey-HoltonE.R., GlobusR.K.. Hindlimb unloading rodent model: technical aspects. J Appl Physiol, 2002, 92(4): 1367-1377

[9] FürstW., SchiesserA.. Test for stereospecifity of an automated Dd-lactate assay based on selective removal of Ll-lactate. Anal Biochem, 1999, 269(1): 214-215

[10] TakagiK., NakaoM., OguraY., et al.. Sensitive colorimetric assay of serum diamine oxidase. Clin Chim Acta, 1994, 226(1): 67-75

[11] Morey-HoltonE., GlobusR.K., KaplanskyA., et al.. The hindlimb unloading rat model: literature overview, technique update and comparison with space flight data. Adv Space Biol Med, 2005, 10: 7-40

[12] MoreyE.R., SabelmanE.E., TurnerR.T., et al.. A new rat model simulating some aspects of space flight. Physiologist, 1979, 22(6): S23-24

[13] ZhangL.F., YuZ.B., MaJ.. Functional alterations in cardiac muscle after medium- or long-term simulated weightlessness and related cellular mechanisms. J Gravit Physiol, 1995, 2(1): 5-8

[14] SchneebergerE.E., LynchR.D.. The tight junction: a multifunctional complex. Am J Physiol Cell Physiol, 2004, 286(6): C1213-1228

[15] NusratA., ParkosC.A., VerkadeP., et al.. Tight junctions are membrane microdomains. J Cell Sci, 2000, 113(Pt10): 1771-1781

[16] AlettiF., BaselliG.. Model study of the effects of interactions between systemic and peripheral circulation on interstitial fluid balance. J Gravit Physiol, 2007, 14(1): 51-52

[17] GandiaP., SaivinS., LavitM., et al.. Influence of simulated weightlessness on the pharmacokinetics of acetaminophen administered by the oral route: a study in the rat. Fundam Clin Pharmacol, 2004, 18(1): 57-64

[18] RiveraC.A., TcharmtchiM.H., MendozaL., et al.. Endotoxemia and hepatic injury in a rodent model of hindlimb unloading. J Appl Physiol, 2003, 95(4): 1656-1663

[19] MankertzJ., TavalaliS., SchmitzH., et al.. Expression from the human occludin promoter is affected by tumor necrosis factor alpha and interferon gamma. J Cell Sci, 2000, 113(Pt11): 2085-2090

[20] YeD., MaI., MaT.Y.. Molecular mechanism of tumor necrosis factor-alpha modulation of intestinal epithelial tight junction barrier. Am J Physiol Gastrointest Liver Physiol, 2006, 290(3): 496-504