Haptoglobin attenuates Hb+Hpx neurotoxicity and nonheme chelatable iron increase. (A) Percentage neuron loss, measured by LDH release assay, in cultures treated for 24 h with Hb 10 μM alone (n = 15 cultures) or with Hpx 1 mg/ml (n = 15 cultures), Hpx 1 mg/ml+Hp 1 mg/ml (n = 8 cultures), or Hp 1 mg/ml without Hpx (n = 8 cultures); (B) nonheme iron content of cultures (n = 7-8) subjected to same treatment, as detected by ferrozine assay; (C) cultures (10/condition) treated with Hb alone or with Hpx as in B, but with addition of 10 μM ferrostatin-1 (F) to prevent cell lysis and neuron iron loss. *p < 0.05, ***p < 0.001 versus Hb alone or Hb + ferrostatin-1 condition, ###p < 0.001 versus Hb+Hpx condition.