Protective effects of ouabain conjugated peptide from Ph. D.-7 Library on vascular endothelial cell / 细胞与分子免疫学杂志

AIM: To find one kind of peptide that will conjugate with ouabain and inhibit its biological function, and provide a new treatment strategy for primary hypertension. METHODS: In this study, ouabain was used as a target to screen ouabain conjugated peptide (OCP) from Ph. D. -7 phage display peptide library. After 3 rounds of bio-panning, the products were identified by ELISA and DNA electrophoresis analysis and sequencing. Peptide was synthesized and analyzed the activity by radioligand binding assay. The inhibitory ratio of cell proliferation was measured by MTT and the cell morphology changing was measured by Hoechst 33342/PI staining. The expression of Na~+-K~+-ATPase α1-subunit and β1-subunit were detected by RT-PCR and immunocytochemistry. The levels of the free intracellular Na~+ in EAhy926 cells were measured by laser confocal microscope. RESULTS: The ouabain conjugated peptide was found out, and it was occupied in 0.64(9/14). The analysis of protein showed that the obtained peptides had no homology with Na~+-K~+-ATPase. The amino acid sequence of synthesized peptide was Arg-Cys-Met-Thr-Ser-Arg-Ser. There was binding activity between OCP and ~3H-ouabain. The MTT assay showed that OCP could reverse the inhibition action of ouabain on vascular endothelial EAhy926 cells in a dose and time-dependent manner. The number of apoptotic cells had significantly decreased detected by Hoechst 33342/PI staining. The results of RT-PCR and immunocytochemistry showed that OCP could inhibit the up-regulated expression of Na~+-K~+-ATPase α1-subunit and down-regulated expression of Na~+-K~+-ATPase β1-subunit induced by ouabain in EAhy926 cells. CONCLUSION: The OCP could reverse the growth inhibition and death induction of ouabain in EAhy926 cells, which would provide the basis for studying the interaction between ouabain and Na~+-K~+-ATPase and explore novel anti-ouabain agents.

Immunohistochemical Localization of Na/K-APTase Subunit Isoforms in Rat Inner Ear / 대한해부학회지

The endolymph and perilymph of the inner ear have unique ionic composition and electrical potential. It is widely accepted that normal auditory function depends on them and Na/K-ATPase plays a central role in production and maintenance of them. The distribution of five Na/K-ATPase subunit isoform (alpha1, alpha2, alpha3, beta1, and beta2) in rat inner ear was determined by immunohistochemistry after decalcifying the temporal bone with Gooding and Stewart's solution. In the cochlear regions, Na/K-ATPase alpha1beta1 isozyme was abundantly expressed in the infrastrial fibrocytes, suprastrial fibrocytes, spiral prominence, outer sulcus cells and spiral ganglion, and also detected in cochlear nerve and interdental cells. alpha1beta2 isozyme was abundantly expressed in all layers of stria vascularis and alpha3beta1 isozyme was detected in cochlear nerve and spiral ganglion. alpha3beta2 isozyme was expressed in spiral ganglion. In vestibular regions, Na/K-ATPase alpha1b1 isozyme was expressed in macular sacculi hair cell, transitional cells of ampulla, and vestibular ganglion, and alpha1b2 isozyme was abundantly expressed in ampullary dark cells and transitional cells and vestibular ganglion. a3b1 isozyme was abundantly expressed in crista ampularis, macula utriculi, and macula sacculi hair cells, and also moderately detected in ampullary, utricular, and saccular nerves, and vestibular ganglion. alpha3beta2 isozyme also detected in ampullary, utricular, and saccular nerves, and vestibular ganglion. But, alpha2beta1 and alpha2beta2 isozymes were not detected in any regions of inner ear. These findings suggest the possibility of four unique Na/K-ATPase isozymes deferentially expressed among the various cell types of the inner ear. This structural diversity imparts considerable biological versatility to the Na/K-ATPase and would be provided the explanations for the differences in fluid and ion transport and its regulation among the inner ear regions.

Renal Adaptive Responses of Na+-K+-APTase Subunit Isoforms to Chronic Hypokalemia / 대한해부학회지

Chronic hypokalemia alters Na+-K+-ATPase gene expression in several tissues. While it is established that Na+-K+-ATPase activity and alpha1 and beta1 subunit protein levels increase during K depletion in the outer medullary collecting duct (OMCD) and do not significantly change in the cortical collecting duct (CCD), little is known about the adaptive responses of the other isoforms in these other nephron segments. Accordingly, this study was performed to characterize the relative levels of expression and cellular distribution of mRNAs encoding the Na+-K+-ATPase subunit isoforms in normal and K-deprived (2 weeks) rats using the Northern analysis and in situ hybridization (ISH). Isoform specific 32P-labeled cDNA (for Northerns) or digoxigenin labeled cRNA (for ISH) probes were used. In normal rats, the order of expression amounts of all isoforms mRNAs from highest was outer medulla > cortex > inner medulla, and that of K-deprived rats was outer medulla > inner medulla > cortex. alpha1 mRNA levels were much greater than those of alpha2 or alpha3 in cortex, outer and inner medulla. mRNA levels for all isoforms were 2~3 folds greater in inner medulla of K-deprived rats compared to controls. In contrasts, the levels of all isoforms mRNAs in cortex and outer medulla were comparable between the two gruops. By ISH, mRNAs for all isoforms were observed in the S3 segment of proximal tubule, the cortical thick ascending limb (CTAL), medullary thick ascending limb (MTAL), distal convoluted tubule (DCT), connecting tuble (CNT), and the entire collecting duct. Both groups exhibited comparable cellular patterns of labeling, but the signal intensity of K-deprived rats was much greater in the proximal portion of the inner stripe of outer medullary collecting duct (OMCDi) and proximal portion of the inner medullary collecting duct (IMCD), and less in the MTAL compared to controls. The signal intensity of alpha1, alpha3, and beta1 isoforms was less in the CTAL, DCT, and CCD of K-deprived rats, but alpha2 isoform was slightly increased. These results suggest that chronic hypokalemia enhances expression of Na+-K+-ATPase subunit isoforms in the proximal portion of OMCDi and proximal IMCD, but not other nephron segments, and that these isoforms may participate in potassium conservation by these segments during potassium deprivation.