Cholesterol influences potassium currents in inner hair cells isolated from guinea pig cochlea

Objective: There is a correlation between serum hyperlipidemia and hearing loss. Cholesterol is an integral component of the cell membrane and regulates the activity of ion channels in the lipid bilayer. The aim of this study was to investigate the effects of Cholesterol on the potassium currents in IHCs by using the cholesterol-depleting drug, MβCD, and water-soluble Cholesterol.

Methods: IHCs were acutely isolated from a mature guinea-pig cochlea and potassium currents were recorded. MβCD and water-soluble Cholesterol were applied to IHCs under pressure puff pipettes.

Results: IHCs showed outwardly rectifying currents (I_K,f and I_K,s) in response to depolarizing voltage pulses, with only a slight inward current (I_K,n) when hyperpolarized. In 10mM MβCD solutions, the amplitude of outward K currents reversely decreased; however, fast activation kinetics was preserved. In contrast, in solution of 1mM water-soluble Cholesterol, the amplitude of outward K currents reversely increased. At the membrane potential of +110mV, relative conductances were 0.87±0.07 and 1.18±0.11 in MβCD solutions and Cholesterol solutions, respectively.

Conclusion: The amplitude of K currents in isolated IHCs was reversely changed by cholesterol-depleting drug and water-soluble Cholesterol. These results demonstrated the possibility of the involvement of IHC function in hyperlipidemia-induced inner ear disorders.