P-glycoprotein (P-gp/MDR1) is a multispecific efflux transporter regulating the pharmacokinetics of various drugs. Although P-gp expression in the small intestine is elevated after liver ischemiareperfusion (I/R) injury, the regulatory mechanism remains to be clarified. MicroRNAs (miRNAs) play an important role in the posttranscriptional regulation of the expression of drug transporters. Here, we investigated the intestinal expression profile of miRNAs after liver I/R and the role of miRNAs in the post-transcriptional regulation of P-gp in intestinal epithelial cells. Microarray analysis showed that microRNA-145 (miR-145) level was decreased in the small intestine of I/R rats. This downregulation of miR-145 was further confirmed by real-time polymerase chain reaction. In silico analysis revealed that 39-untranslated regions (UTRs) of rat Mdr1a, mouse Mdr1a, and human MDR1 mRNA retain binding sites for miR-145. Luciferase assays using MDR1 39-UTR reporter plasmid in HEK293 cells showed that luciferase activity was decreased by the overexpression of miR-145, and the deletion of miR-145 binding site within MDR1 39-UTR abolished this decreased luciferase activity. The downregulation of miR-145 in Caco-2 cells, an epithelial cell line derived from human colon, increased P-gp expression and efflux activity of rhodamine 123, but not MDR1 mRNA level. These findings demonstrated that miR-145 negatively regulates the expression and function of P-gp through the repression of mRNA by direct interaction on the 39-UTR of MDR1 mRNA. In addition, the downregulation of miR-145 should significantly contribute to the elevated intestinal P-gp expression after liver I/R. Our results provide new insight into the post-transcriptional regulation of intestinal P-gp.
Highly sensitive, fast responsive, and highly reversible sensing of nitrogen dioxide, nitric oxide, and nitrous oxide at a ppm-to-sub-ppm level has been achieved by fluorescence measurements upon excitation of various dye-doped deoxyribonucleic acid (DNA) or hydrophobic DNA thin films spincoated on a thin silver film by electric-field-enhanced evanescent light at surface plasmon resonance. The response time, sensitivity, or selectivity was controlled by combination of dyes and matrices. The present result will make a great many contributions to environmental and medical applications.
The
relationship between dehydration of polymer chains
and the
nanodroplet formation through the macroscopic liquid–liquid
phase separation (LLPS) has been investigated for the aqueous solution
of stereocontrolled poly(N-isopropylacrylamide) (PNiPAm)
and poly(N-diethylacrylamide) (PNdEAm). The fluorescent
probe method reveals that the temperature range of dehydration for
PNiPAm chains is much narrower than that for PNdEAm. The sharp dehydration
of polymer chains may give rise to the characteristic thermoresponsive
behavior of PNiPAm in water. For meso-rich PNiPAms, the dehydration
point (T
dh), which is defined as the temperature
where the single chains start assembling in the solution, locates
far from the cloud point (T
c). That is,
the dehydration of the chain occurs antecedently before the system
undergoes a macroscopic LLPS. For PNdEAm, however, the dissociation
between T
dh and T
c is not found. For the aqueous solution of PNiPAm with 52%
of the meso content, the fluorescence correlation spectroscopy has
revealed that nano-order droplets (ca. 45 nm of the hydration radius)
are stabilized in the intermediate state between T
dh and T
c. The sharp dehydration
of PNiPAm chains may enable an acute condensation of polymers in droplets,
causing a viscoelastic hindrance in the coalescence of droplets.
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