Stimulation of Erythrocyte Death by Phloretin

Abstract

Background: Phloretin, a natural component of apples, pears and strawberries, has previously been shown to stimulate apoptosis of nucleated cells. Erythrocytes may similarly enter suicidal death or eryptosis, which is characterized by cell shrinkage and phospholipid scrambling of the erythrocyte cell membrane with phosphatidylserine translocation to the erythrocyte surface. Stimulators of eryptosis include increase of cytosolic Ca²⁺-activity ([Ca²⁺]_i), ceramide, ATP depletion, and activation of protein kinase C (PKC) as well as p38 mitogen activated protein kinase (p38 kinase). Methods: Phosphatidylserine exposure at the cell surface was estimated from annexin V binding, cell volume from forward scatter, [Ca²⁺]_i from Fluo3-fluorescence, and ceramide abundance from binding of specific antibodies. Results: A 48 h exposure of human erythrocytes to phloretin significantly increased the percentage of annexin-V-binding cells (≥100 µM) without significantly influencing forward scatter. Phloretin did not significantly modify [Ca²⁺]_i and the stimulation of annexin-V-binding by phloretin (300 µM) did not require presence of extracellular Ca²⁺. Phloretin did not significantly modify erythrocyte ATP levels, and the effect of phloretin on annexin-V-binding was not significantly altered by PKC inhibitor staurosporine (1 µM) or p38 kinase inhibitor SB2203580 (2 µM). However, phloretin significantly increased the ceramide abundance at the cell surface. Conclusions: Phloretin stimulates phospholipid scrambling of the erythrocyte cell membrane, an effect at least partially due to up-regulation of ceramide abundance.

Enhanced suicidal erythrocyte death in acute cardiac failure

“…Eryptosis may be enhanced in young erythrocytes [35], and in erythrocytes generated under high erythropoietin concentrations [36]. Moreover, eryptosis is known to be triggered by a myriad of xenobiotics [29,[37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53]. If possible, eryptosis-inducing xenobiotics should therefore be avoided in the treatment of AHF patients.…”

Therapeutic potential of manipulating suicidal erythrocyte death

“…Nevertheless, any of the small molecules listed in Table 2 could, at least in theory, accelerate the eryptosis of plasmodium-infected erythrocytes and thus counteract the rise of parasitemia. It is noteworthy, that the malaria pathogen plasmodium is not expected to become resistant to therapeutic acceleration of eryptosis, which is accomplished by cell mechanisms and is Estramustine 75 --100 µM + + [67] Ferutinin 30 µM + [68] Fluoxetine 25 --50 µM + [69] FTY720 10 µM + [1,2] Fumagillin 10 --100 µM + + [70] Gambogic acid 100 --500 nM + + [1,2] Gedunin 12 µM + [71] Geldanamycin 5 --50 µM + + [72] Glycation 40 mM glucose + Honokiol 5 --15 µM + + [74] Indoxyl sulfate 50 --600 µM + + Lumefantrine 3 --24 µg/ml [76] Lysophosphatidic acid 2.5 µM + + [77] Mercury 1 µM + + [78] Methyldopa 6 µg/ml + + Mitoxantrone 10 µg/ml + + [55] Monensin 0.1 µg/ml + [1,2] Mushroom tyrosinase 7 U/mL + + [81] Naphthoquinone derivatives 10 µM + [82] Nitazoxanide 1 --50 µg/ml + [83] Novobiocin 500 µM + + [84] Nystatin 5 --15 µg/ml + [85] Ochratoxin A 2.5 --10 µM + + Patulin 2.5 --10 µM + [87] Penta-O-galloyl-b-D-glucose 10 --50 µM + + [88] Peptidoglycan 10 µg/ml + [89] Phloretin 100 µM + [90] Phorbol-12 myristate-13 acetate…”

Stimulation of Suicidal Erythrocyte Death by the Antimalarial Drug Mefloquine

“…Moreover, eryptosis is triggered by activated casein kinase 1α, Janus-activated kinase JAK3, protein kinase C, p38 kinase, and PAK2 kinase [25], as well as by inhibited or lacking AMP activated kinase AMPK, cGMP-dependent protein kinase, sorafenib sensitive kinases and sunitinib sensitive kinases [25]. Stimulators of eryptosis further include diverse xenobiotics [25,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57]. …”