Anacardic acid, a histone acetyltransferase inhibitor, stimulates hemolysis and eryptosis through energy depletion and calcium accumulation

Histone acetyltransferase (HAT) inhibitors are promising epigenetic anticancer therapeutics. However, challenges remain regarding tissue specificity and off-target toxicity. This study presents a preclinical safety assessment of the HAT inhibitor anacardic acid (AA) in erythrocytes, given that anaemia is a clinically significant complication of chemotherapy. Freshly isolated erythrocytes were cultured in vitro with and without 1–10 µmol L^–1 of AA, then markers and mechanisms of cell death were examined by fluorescence-activated cell sorting, spectrophotometry, and potentiometry. AA treatment induced marked hemolysis independently of oxidative stress, which was paralleled by Ca²⁺ accumulation and phosphatidylserine (PS) trans location. Morphological abnormalities were also observed upon AA treatment, including eryptotic loss of volume and elliptocyte phenotype. Co-treatment of AA with ATP, acetylsalicylic acid, NSC23766, or polyethylene glycol conferred significant cytoprotective effects. AA is cytotoxic to erythrocytes, causing both hemolysis and eryptosis, through non-genomic mechanisms involving Ca²⁺ signalling, metabolic exhaustion, K⁺ depletion, shrinkage and elliptocytic morphological aberrations. This toxic effect is sensitive to cyclooxygenase and Rac1 GTPase inhibition.