Transformation-dependent calcium influx by voltage-operated calcium channels in stellate cells of rat liver

• Published in: Journal of hepatology 1999-04, Vol.30 (4), p.612-620
• Main Authors: Roth-Eichhorn, Sylke, Eberheim, Andreas, Bode, Hans-Peter, Gressner, Axel M
• Format: Article
• Language: English
• Subjects: Actins - metabolism; Animals; Biological and medical sciences; Calcium - metabolism; Calcium Channels - physiology; Calcium Channels, L-Type; Cell Differentiation - drug effects; Cells, Cultured; Cytosol - metabolism; Fibroblasts - cytology; Fibroblasts - physiology; Fura-2; Gastroenterology. Liver. Pancreas. Abdomen; Hepatic stellate cell; Hyaluronic Acid - metabolism; Interferon-gamma - pharmacology; Kinetics; Liver - cytology; Liver - drug effects; Liver - physiology; Liver. Biliary tract. Portal circulation. Exocrine pancreas; Male; Medical sciences; Membrane Potentials; Microscopy, Fluorescence; Muscle, Smooth - cytology; Muscle, Smooth - physiology; Other diseases. Semiology; Potassium - pharmacology; Rats; Rats, Sprague-Dawley; Recombinant Proteins - pharmacology; TGF- β; Transformation; Transforming Growth Factor beta - pharmacology; Voltage-operated calcium channels
• ISSN: 0168-8278; 1600-0641
• DOI: 10.1016/S0168-8278(99)80191-3

Background/Aims: The transformation of hepatic stellate cells into myofibroblasts is a key step in the pathogenesis of fibrotic liver diseases. The intracellular signaling associated with hepatic stellate cell transformation becomes a point of interest, especially the role of cytosolic free calcium concentration ([Ca 2+] i). The aim of the study was to investigate possible differences between various transformation phenotypes of hepatic stellate cells with regard to the calcium influx mediated by L-type voltage-operated calcium channels (L-type VOC). Methods: Hepatic stellate cells were isolated from rat liver by pronase-collagenase reperfusion and cultured under standard conditions. The transformation of hepatic stellate cells was stimulated by treatment with transforming growth factor-beta (TGF- β) or inhibited with interferon-gamma (IFN- γ) and characterized by immunocytochemistry for smooth muscle α-actin and determination of hyaluronan in the culture media with a ligand binding assay. [Ca 2+] i was measured in individual cells with fluorescence microscopy using fura-2. VOCs were activated by the standard procedure of extracellular potassium elevation, to achieve depolarization, and identified by various controls. Results: In transformed myofibroblasts the activation of VOCs by potassium elevation from 5.4 mmol/l to 50.4 mmol/l led to a 19% increase in [Ca 2+] i in contrast to 0.2% in hepatic stellate cells cultured for 3 days. In 7-day old hepatic stellate cells, after stimulation of cell transformation with TGF- β-1, an enhanced [Ca 2+] i response to potassium elevation was detected, while inhibition of transformation with IFN- γ for the same time caused a decreased calcium signal compared with untreated control cultures. Short-term treatment with the cytokines (1 day) did not influence depolarization-dependent calcium signals. Conclusion: The results show the [Ca 2+] i increase via L-type VOCs to be dependent on the transformation level of hepatic stellate cells into myofibroblasts which can be influenced by the long-term treatment of hepatic stellate cells with TGF- β or IFN- γ. In contrast, there is no evidence for direct regulation of VOC activity by TGF- β or IFN- γ after short-term exposure.