Blocking swelling-activated chloride current inhibits mouse liver cell proliferation

Area of Science:

• Cell Biology
• Physiology
• Molecular Biology

Background:

• Hepatocyte proliferation is essential for liver function and regeneration.
• Swelling-activated chloride currents play a role in cell volume regulation.
• The specific role of these currents in liver cell growth remains to be fully elucidated.

Purpose of the Study:

• To investigate the role of swelling-activated membrane chloride currents in hepatocyte proliferation.
• To identify specific chloride channels involved in liver cell growth.
• To determine the effects of channel blockers on hepatocyte proliferation and metabolism.

Main Methods:

• Utilized the AML12 mouse liver cell line.
• Applied hypotonic stress to induce cell swelling and activate chloride currents.
• Measured whole-cell chloride currents using electrophysiology.
• Assessed cell proliferation via cell counts and protein accumulation.
• Investigated the effects of various chloride channel blockers (DIDS, NPPB, tamoxifen, mibefradil) and hyperosmolarity on cell growth and ATP levels.

Main Results:

• Hypotonic stress activated an ATP-dependent, outwardly rectifying chloride current in dividing AML12 cells.
• This current exhibited a specific halide permeability sequence (SCN(-) > I(-) > Br(-) > Cl(-) > gluconate).
• Chloride channel blockers (NPPB, DIDS, tamoxifen, mibefradil) and hyperosmolarity inhibited both swelling-activated currents and hepatocyte proliferation.
• NPPB and mibefradil showed reversible inhibition, while DIDS reduced cellular ATP levels.

Conclusions:

• Swelling-activated membrane chloride currents are implicated in the control of liver cell proliferation.
• Specific chloride channel blockers effectively inhibit hepatocyte growth.
• NPPB, tamoxifen, and mibefradil inhibit proliferation without suppressing hepatocyte metabolism at their effective concentrations.