Effects of 18β-glycyrrhetinic acid on intercellular junctions in neonatal rat cardiomyocytes: morphological and functional studies

• Main Authors: Yun-Jen Chang, 張芸潔
• Other Authors: Jiahn-Chun Wu
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/71986244514446017804

碩士 === 國立臺灣大學 === 解剖學研究所 === 88 === Gap junctions are intercellular channels between neighboring cells and are crucial for the coordinated cellular activity in cardiomyocytes. 18β-glycyrrhetinic acid (18β-GA), a compound isolated from licorice root which also functions as a potent gap junction inhibitor, has been shown to effectively block both electric and dye couplings in various cell types. The effect of 18β-GA on gap junctions in cardiomyocytes has not yet been examined. In this study, functional assays by Lucifer-yellow microinjection showed that dye coupling of cardiomyocytes was inhibited by 18β-GA and this inhibition of gap junction intercellular communication (GJIC) in cardiomyocytes is time- and dose-dependant. The IC50 of 18β-GA is 2 μM. 5 μM 18β-GA rapidly and completely inhibited GJIC in cardiomyocytes 30 min, and GJIC is completely restored 6 h after the removal of 18β-GA. Long-term treatment with 5 μM 18β-GA for 4 h caused an irreversible change of GJIC in 10% of cardiomyocytes. Dramatic morphological changes were observed by phase contrast microscopy in cardiomyocytes when treated with 5 μM 18β-GA. Separation of cardiomyocytes at cell-cell contact sites were occasionally detected 1 to 2 h after treatment. Immunofluorescence staining of connexin (Cx) 43, a gap junction integral membrane protein, changed from a sharp, discontinuous linear pattern to a diffuse speckle along the cell-cell contact sites 1 h after 5μM 18β-GA treatment. No significant change of the staining pattern of N-cadherin, the adherens junction integral membrane protein, was observed at the same concentration 3 h after treatment. However, when the concentration of 18β-GA was increased to 20 μM, staining of N-cadherin changed from a sharp continuous linear pattern to a discontinuous linear pattern 2 h after treatment. These results demonstrate a rapid, complete, and reversible inhibition of cardiomyocytes gap junctional function by 5 μM 18β-GA. The effect of 18β-GA on N-cadherin staining suggests a regulatory role of gap junction in the maintenance of adherens junction in cardiomyocytes.