title: HIV protease inhibitors: suppression of insulin secretion by inhibition of voltage-dependent K+ currents and anion currents.
abstract: We have shown before that the human immunodeficiency virus (HIV) protease inhibitors ritonavir and nelfinavir, but not indinavir, suppress insulin secretion from mouse pancreatic B-cells via reduction of the cytosolic free calcium concentration ([Ca(2+)](c)). This was not because of an effect on ATP-dependent K(+) channels (K(ATP) channels) or L-type Ca(2+) channels. The study was intended to elucidate the mechanisms by which distinct HIV protease inhibitors decrease [Ca(2+)](c) and thus evoke their adverse side effect on insulin release. Membrane potential and whole-cell currents were measured with the patch-clamp technique, and [Ca(2+)](c) was determined with a fluorescence dye. Ritonavir and nelfinavir both inhibited the same component(s) of voltage-dependent K(+) currents with a concomitant change in action potential wave form, whereas indinavir was ineffective. Comparison with other blockers of voltage-dependent K(+) currents revealed that suppression of distinct noninactivating current component(s) altered action potential wave form and decreased [Ca(2+)](c) similar to ritonavir and nelfinavir, whereas blockage of inactivating component(s) was without effect. Complete inhibition of voltage-dependent K(+) currents by 80 mM TEA(+) drastically increased [Ca(2+)](c), demonstrating that voltage-dependent K(+) channels are not the sole target of ritonavir and nelfinavir. Accordingly, the Ca(2+)-lowering effect of ritonavir was preserved in the presence of 80 mM TEA(+). This effect was mimicked by the anion channel blocker 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). Consequentially, ritonavir and nelfinavir inhibited a DIDS-sensitive anion current in B-cells. We suggest that ritonavir and nelfinavir decrease insulin secretion by inhibition of voltage-dependent K(+) channels and anion channels, which are essential to provide counterion currents for Ca(2+) influx across the plasma membrane.
authors.affiliation: Pharmazeutisches Institut, Auf der Morgenstelle 8, D-72076 Tübingen, Germany.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Neye
authors.forename: Martina
authors.initials: M
authors.lastname: Düfer
authors.forename: Gisela
authors.initials: G
authors.lastname: Drews
authors.forename: Peter
authors.initials: P
authors.lastname: Krippeit-Drews
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000838:Anions / Q000378:metabolism; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003022:Clotrimazole / Q000494:pharmacology; D004594:Electrophysiology; D017320:HIV Protease Inhibitors / Q000494:pharmacology*; D019469:Indinavir / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D019888:Nelfinavir / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D019438:Ritonavir / Q000494:pharmacology; D019789:Tetraethylammonium / Q000494:pharmacology
chemical_list: D000838:Anions; D017320:HIV Protease Inhibitors; D007328:Insulin; D007473:Ion Channels; D026902:Potassium Channel Blockers; D019469:Indinavir; D019789:Tetraethylammonium; D003022:Clotrimazole; D019888:Nelfinavir; D019438:Ritonavir; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium