Fig. 4

Effect of hemin on tumor necrosis factor-alpha (TNFα)-induced cytotoxicity. Villous fragments from term (A) and preeclamptic (B) placenta were exposed to vehicle (open column), 5 µM hemin (solid column), 50 ng/ml TNFα alone (crossed column) and TNFα added after 2 hr preincubation of villous fragments with 5 µM hemin (dotted column). The insert in (A) shows Western blots for HO-1 protein expression in villous explants exposed to hemin and/or TNFα for 24 hr. (C) Villous fragments were incubated with either vehicle (Veh), 5 µM hemin, 20 µM tin protoporphyri IX (SnPP), and 50 ng/ml TNFα. In addition, TNFα was added after 2 hr preincubation of villous fragments with 5 µM hemin, SnPP alone and SnPP incubated for 60 min prior to the addition of hemin. In the presence of SnPP, the protective effect of hemin on TNFα-induced damage was totally abolished. The cytotoxicity index is expressed as a percentage ratio of lactate dehydrogenase (LD) leakage into media/LD in tissue (LD_m/LD_t). A value of less then 5% was considered as viable tissue. Data represents the mean (± S.E.M.) of eight separate experiments performed in duplicate.