Heterogenous Gene Expression of Bicellular and Tricellular Tight Junction-Sealing Components in the Human Intestinal Tract.

A major site for the absorption of orally administered drugs is the intestinal tract, where the mucosal epithelium functions as a barrier separating the inside body from the outer environment. The intercellular spaces between adjacent epithelial cells are sealed by bicellular and tricellular tight junctions (TJs). Although one strategy for enhancing intestinal drug absorption is to modulate these TJs, comprehensive gene (mRNA) expression analysis of the TJs components has never been fully carried out in humans. In this study, we used human biopsy samples of normal-appearing mucosa showing no endoscopically visible inflammation collected from the duodenum, jejunum, ileum, colon, and rectum to examine the mRNA expression profiles of TJ components, including occludin and tricellulin and members of the claudin family, zonula occludens family, junctional adhesion molecule (JAM) family, and angulin family. Levels of claudin-3, -4, -7, -8, and -23 expression became more elevated in each segment along the intestinal tract from the upper segments to the lower segments, as did levels of angulin-1 and -2 expression. In contrast, expression of claudin-2 and -15 was decreased in the large intestine compared to the small intestine. Levels of occludin, tricellulin, and JAM-B and -C expression were unchanged throughout the intestine. Considering their segment specificity, claudin-8, claudin-15, and angulin-2 appear to be targets for the development of permeation enhancers in the rectum, small intestine, and large intestine, respectively. These data on heterogenous expression profiles of intestinal TJ components will be useful for the development of safe and efficient intestinal permeation enhancers.

Quantitative Analysis of mRNA and Protein Expression Levels of Aldo-Keto Reductase and Short-Chain Dehydrogenase/Reductase Isoforms in the Human Intestine.

Enzymes catalyzing the reduction reaction of xenobiotics are mainly members of the aldo-keto reductase (AKR) and short-chain dehydrogenase/reductase (SDR) superfamilies. The intestine, together with the liver, is responsible for first-pass effects and is an organ that determines the bioavailability of orally administered drugs. In this study, we evaluated the mRNA and protein expression levels of 12 AKR isoforms (AKR1A1, AKR1B1, AKR1B10, AKR1B15, AKR1C1, AKR1C2, AKR1C3, AKR1C4, AKR1D1, AKR1E2, AKR7A2, and AKR7A3) and 7 SDR isoforms (CBR1, CBR3, CBR4, DCXR, DHRS4, HSD11B1, and HSD17B12) in each region of the human intestine using next-generation sequencing and data-independent acquisition proteomics. At both the mRNA and protein levels, most AKR isoforms were highly expressed in the upper regions of the intestine, namely the duodenum and jejunum, and then declined toward the rectum. Among the members in the SDR superfamily, CBR1 and DHRS4 were highly expressed in the upper regions, whereas the expression levels of the other isoforms were almost uniform in all regions. Significant positive correlations between mRNA and protein levels were observed in AKR1A1, AKR1B1, AKR1B10, AKR1C3, AKR7A2, AKR7A3, CBR1, and CBR3. The mRNA level of AKR1B10 was highest, followed by AKR7A3 and CBR1, each accounting for more than 10% of the sum of all AKR and SDR levels in the small intestine. This expression profile in the human intestine was greatly different from that in the human liver, where AKR1C isoforms are predominantly expressed. SIGNIFICANCE STATEMENT: In this study comprehensively determined the mRNA and protein expression profiles of aldo-keto reductase (AKR) and short-chain dehydrogenase/reductase isoforms involved in xenobiotic metabolism in the human intestine and found that most of them are highly expressed in the upper region, where AKR1B10, AKR7A3, and CBR1 are predominantly expressed. Since the intestine is significantly involved in the metabolism of orally administered drugs, the information provided here is valuable for pharmacokinetic studies in drug development.

Regional Transcriptomics and Proteomics of Pharmacokinetics-Related Genes in Human Intestine.

The intestine is an organ responsible for the absorption and metabolism of orally administered drugs. To predict pharmacokinetics behavior in the small intestine, it is necessary to examine the human intestinal expression profiles of the genes related to drug absorption, distribution, metabolism, and excretion (ADME). In this study, to obtain more accurate expression profiles in various regions of the human intestine, biopsy samples were collected from endoscopically noninflamed mucosa of the duodenum, jejunum, ileum, colon, and rectum from Japanese including Crohn's disease or ulcerative colitis patients, and both RNA-seq and quantitative proteomics analyses were performed. We also analyzed the expression of drug-metabolizing enzymes (cytochromes P450 (CYPs) and non-CYP enzymes), drug transporters, and nuclear receptors. Overall, the mRNA expression levels of these ADME-related genes correlated highly with the protein expression levels. The characteristics of the expression of ADME-related genes differed significantly between the small and large intestines, including the expression levels of CYP enzymes, which were higher and lower in the small and large intestines, respectively. Most CYPs were expressed dominantly in the small intestine, especially the jejunum, but were rarely expressed in the large intestine. On the other hand, non-CYP enzymes were expressed in the large intestine but at lower expression levels than in the small intestine. Moreover, the expression levels of drug metabolizing enzyme genes differed even between the proximal and distal small intestine. Transporters were expressed most highly in the ileum. The data in the present study will enhance understanding of the intestinal ADME of drug candidates and would be useful for drug discovery research.

How does Striga hermonthica Bewitch its hosts?

The common name witchweed synonymous with the Latin name Striga befits the bewitching effects, viz wilting and chlorosis, the parasite inflicts on its hosts long before it emerges and becomes visible above the ground. However, interactions in the rhizosphere between host roots and Striga seedlings are concealed and inscrutable. In vitro experiments revealed that abscisic acid was produced by S. hermonthica seedlings and a considerable portion of the phytohormone was exuded. The phytohormone in the rhizosphere could, at least in part, contribute to the bewitching effects, disrupt host immunity and promote commencement of parasitism.

Aberrant protein phosphatase 2C leads to abscisic acid insensitivity and high transpiration in parasitic Striga.

Striga parasitizes major crops in arid regions, depriving the host crop of nutrients through the transpiration stream and causing vast agricultural damage. Here, we report on the mechanism underlying how Striga maintains high transpiration under drought conditions. We found that Striga did not respond to abscisic acid, the phytohormone responsible for controlling stomatal closure. Protein phosphatase 2C of Striga (ShPP2C1) is not regulated by abscisic acid receptors, and this feature is attributable to specific mutations in its amino acid sequence. Moreover, Arabidopsis transformed with ShPP2C1 showed an abscisic acid-insensitive phenotype, indicating that ShPP2C1 functions as a dominant negative regulator of abscisic acid signal transduction. These findings suggest that ShPP2C1 interrupts abscisic acid signalling in Striga, resulting in high transpiration and subsequent efficient absorption of host nutrients under drought conditions.