Stimulation of Suicidal Erythrocyte Death by Benzethonium

Abstract

Benzethonium, an antimicrobial surfactant widely used as preservative of pharmaceuticals, topical wound care product and oral disinfectant, triggers apoptosis of several cell types. The apoptosis is preceded and possibly triggered by mitochondrial depolarization. Even though lacking mitochondria, erythrocytes may similarly undergo suicidal cell death or eryptosis. Hallmarks of eryptosis include cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the cell surface. Eryptosis may be triggered by energy depletion, which leads to increase of cytosolic Ca²⁺-activity with subsequent Ca²⁺-sensitive cell shrinkage and cell membrane scrambling. Ca²⁺-sensitivity is enhanced by ceramide. The present study explored the effect of benzethonium on eryptosis. Cell membrane scrambling was estimated from binding of fluorescent annexin V to phosphatidylserine, cell volume from forward scatter in FACS analysis, cytosolic Ca²⁺-concentration from Fluo3-fluorescence, hemolysis from hemoglobin release, lactate formation by colorimetry and ceramide utilizing fluorescent antibodies. A 48 hours exposure to benzethonium (=5µM) significantly increased cytosolic Ca²⁺-concentration, decreased forward scatter and triggered annexin V-binding affecting some 30% of the erythrocytes at 5 µM benzethonium. Only 5% of treated erythrocytes were hemolytic. The effects of benzethonium on annexin V binding were blunted in the nominal absence of Ca²⁺ and in the presence of amiloride (1 mM) but not in the presence of the pancaspase inhibitor zVAD (10 µM). Benzethonium further significantly enhanced the effect of glucose depletion on cytosolic Ca²⁺-concentration and annexin V-binding, but significantly blunted the effect of glucose depletion on forward scatter. Benzethonium (5 µM) significantly enhanced lactic acid formation but not ceramide abundance. The present observations disclose a novel effect of benzethonium, i.e. triggering of suicidal death of erythrocytes.

The Uremic Toxin Acrolein Promotes Suicidal Erythrocyte Death

“…Accelerated suicidal erythrocyte death may contribute to the anemia of several clinical disorders and eryptosis may be triggered by a wide variety of xenobiotics [22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45]. …”

Stimulation of Suicidal Erythrocyte Death by Increased Extracellular Phosphate Concentrations

“…Eryptosis is further triggered by a wide variety of xenobiotics and is enhanced in a variety of clinical disorders [9,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43]. …”

Mitoxantrone-Induced Suicidal Erythrocyte Death

“…The mitoxantrone concentrations required for the stimulation of eryptosis are within the range of mitoxantrone concentrations required for the antineoplastic activity of the substance [46]. At least in theory, the erythrocytes could be sensitized to the effect of mitoxantrone by parallel exposure to further eryptosis triggering xenobiotics [28,39,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73]. Moreover, the sensitivity to mitoxantrone may be increased in patients suffering from disorders with enhanced eryptosis [28], such as diabetes [34,74,75], dehydration [76], renal insufficiency [77,78], hemolytic uremic syndrome [79], sepsis [80], malaria [81], sickle cell disease [81], Wilson's disease [82], iron deficiency [83], malignancy [84], phosphate depletion [85], and metabolic syndrome [65].…”