Ca²⁺ Signaling and Proliferation via Ca²⁺-Sensing Receptors in Human Hepatic Stellate LX-2 Cells

Abstract

Hepatic stellate cells (HSCs) play a significant role in the development of chronic liver diseases. Hepatic damage activates HSCs and results in hepatic fibrosis. The functions of activated HSCs require an increase in the cytosolic Ca²⁺ concentration ([Ca²⁺]_cyt). However, the regulatory mechanisms underlying Ca²⁺ signaling in activated HSCs remain largely unknown. In the present study, functional analyses of Ca²⁺-sensing receptors (CaSRs) were performed using activated human HSCs, LX-2. Expression analyses revealed that CaSR proteins were expressed in α-smooth muscle actin-positive LX-2 cells. Extracellular Ca²⁺ restoration (from 0 to 2.2 mM) increased [Ca²⁺]_cyt in these cells. The extracellular Ca²⁺-induced increase in [Ca²⁺]_cyt was reduced by the CaSR antagonists, NPS2143 and Calhex 231. Furthermore, the growth of LX-2 cells was blocked by NPS2143 and Calhex 231 in concentration-dependent manners (IC₅₀ = 6.0 and 9.5 μM, respectively). LX-2 cell proliferation was also attenuated by NPS2143 and Calhex 231. In conclusion, CaSRs are functionally expressed in activated HSCs and regulate Ca²⁺ signaling and cell proliferation. The present results provide insights into the molecular mechanisms underlying hepatic fibrosis and will contribute to the development of potential therapeutic targets.