Therapy with oral clotrimazole induces inhibition of the Gardos channel and reduction of erythrocyte dehydration in patients with sickle cell disease.

Abstract

Pathologic water loss from sickle erythrocytes concentrates the abnormal hemoglobin and promotes sickling. The Ca 2 ϩ -activated K ϩ channel (Gardos channel) contributes to this deleterious dehydration in vitro, and blockade of K ϩ and water loss via this channel could be a potential therapy in vivo. We treated five subjects who have sickle cell anemia with oral clotrimazole, a specific Gardos channel inhibitor. Patients were started on a dose of 10 mg clotrimazole/kg/d for one week. Protocol design allowed the daily dose to be escalated by 10 mg/kg each week until significant changes in erythrocyte density and K ϩ transport were achieved. Blood was sampled three times a week for hematological and chemical assays, erythrocyte density, cation content, and K ϩ transport. At dosages of 20 mg clotrimazole/kg/d, all subjects showed Gardos channel inhibition, reduced erythrocyte dehydration, increased cell K ϩ content, and somewhat increased hemoglobin levels. Adverse effects were limited to mild/moderate dysuria in all subjects, and a reversible increase in plasma alanine transaminase and aspartic transaminase levels in two subjects treated with 30 mg clotrimazole/kg/d. This is the first in vivo evidence that the Gardos channel causes dehydration of sickle erythrocytes, and that its pharmacologic inhibition provides a realistic antisickling strategy. ( J. Clin. Invest. 1996. 97:1227-1234.)

Clotrimazole Binds to Heme and Enhances Heme-dependent Hemolysis

“…The remaining non-polymerized free heme passes through the membrane of food vacuoles and also reaches the cytosol of the parasite (39 -42), where free heme may be efficiently decomposed by reaction with GSH (10,11). It is reported that oral CLT (single dose of 1 g) was absorbed rather efficiently, reaching a concentration in plasma of 2 M within 2-4 h of administration (43) without serious side effects, and easily diffused into erythrocytes (43,44). Therefore, CLT should be able to reach the parasite compartment, enabling production of stable heme-CLT complexes in both erythrocytes and parasites.…”

The antifungal antibiotic clotrimazole alters calcium homeostasis of leukemic lymphoblasts and induces apoptosis

“…[3][4][5][6][7][8][9] Clotrimazole disrupts cellular Ca 2+ homeostasis by releasing Ca 2+ from intracellular stores while inhibiting Ca 2+ influx and blocking IK channels. 7,[10][11][12][13][14][15] It is being evaluated clinically for the treatment of IK channel-driven erythrocyte dehydration in sickle cell dis- ease 16,17 and the treatment of secretory diarrheas that involve chloride secretion through IK channels. 18 Interest in clotrimazole as a potential antileukemic compound derives from the following observations.…”

Delineation of the Clotrimazole/TRAM-34 Binding Site on the Intermediate Conductance Calcium-activated Potassium Channel, IKCa1

“…Erythrocyte dehydration in sickle cell disease can be attributed partly to excessive K ϩ loss through IKCa1 channels that are activated by a rise in intracellular Ca 2ϩ during sickling (10). Clotrimazole and ICA-15451, two potent triarylmethane (TRAM) blockers of this channel, are in clinical trials for the treatment of sickle cell disease (11,12). In intestinal and airway epithelium cells, basolateral expression of the IKCa1 channel modulates apical water and Cl Ϫ secretion (13,14), and blockade of this channel by clotrimazole has been reported to ameliorate secretory diarrhea (15).…”

“…In intestinal and airway epithelium cells, basolateral expression of the IKCa1 channel modulates apical water and Cl Ϫ secretion (13,14), and blockade of this channel by clotrimazole has been reported to ameliorate secretory diarrhea (15). However, the therapeutic usefulness of clotrimazole is seriously limited by its nanomolar affinity for cytochrome P450-dependent enzymes, especially CYP3A4 (the major xenobiotic metabolizing enzyme in human liver), which leads to a high incidence of side effects (11,16).…”