Related Experiment Video
Updated: Jul 14, 2025

Functional Assessment of Intestinal Tight Junction Barrier and Ion Permeability in Native Tissue by Ussing Chamber Technique
Published on: May 26, 2021
Increase in Paracellular Leakage of Amino Acids Mediated by Aging-Induced Reduction of Claudin-4 Expression
Ema Okamoto1, Shunsuke Matsuda1, Yuta Yoshino1
1Laboratory of Biochemistry, Department of Biopharmaceutical Sciences, Gifu Pharmaceutical University, Gifu, Japan.
Background:
Claudins (CLDNs), major components of tight junctions, control paracellular permeabilities of mineral ions and wastes. The absorption of nutrients including glucose and amino acids (AAs) is regulated by intestinal epithelial cells. However, the role of CLDNs is not fully understood.
Objectives:
The purpose of this study was to clarify the effect of AA deprivation on the expression of AA transporters and CLDNs, as well as the role of CLDNs in the regulation of paracellular AA fluxes.
Methods:
The messenger RNA and protein expression of various CLDNs were examined by real-time quantitative polymerase chain reaction and Western blot analyses, respectively. The AA selectivity of CLDNs was estimated using liquid chromatography-tandem mass spectrometry (LC-MS) analysis.
Results:
The expression levels of some AA transporters, CLDN4, and CLDN15 were increased by AA deprivation in normal mouse colon-derived MCE301 cells. The expression of AA transporters and CLDN15 in the mouse colon was positively correlated with aging but the expression of CLDN4 was not. The AA deprivation-induced elevation of CLDN4 expression was inhibited by MHY1485, a mammalian target of rapamycin (mTOR) activator. Furthermore, CLDN4 expression was increased by rapamycin, an mTOR inhibitor. mTOR may be involved in the transcriptional activation of CLDN4. The fluxes of AAs from the basal to apical compartments were decreased and increased by CLDN4 overexpression and silencing, respectively. LC-MS analysis showed that the fluxes of all AAs, especially Lys, His, and Arg, were enhanced by CLDN4 silencing.
Conclusions:
CLDN4 is suggested to form a paracellular barrier to AAs, especially alkaline AAs, which is attenuated with aging.
Related Concept Videos
The Effect of Aging on Tissues
Tight Junctions
Type IV Collagen of Basal Lamina
A type IV collagen molecule has six alpha chains which can...
Bone Disorders
Bone deposition is also affected by the levels of sex hormones like estrogen and testosterone that promote osteoblast activity and bone matrix synthesis. When the level of these hormones decreases due to aging, it causes a reduction in bone deposition. As a result, bone resorption by osteoclasts...
Factors Affecting Protein-Drug Binding: Patient-Related Factors
Age stands as a key determinant in protein-drug binding. Neonates, characterized by low albumin content, experience heightened concentrations of unbound drugs such as phenytoin and...
Nephrotic Syndrome I : Introduction

