Figure 12

Quantification of apoptotic cell death by DNA fragmentation in TNFα-transgenic and non-transgenic rat brain after focal ischemia. The bar graph shows DNA fragmentation representing apoptotic cell death in brain sampled from TNFα-transgenic (TNFα-Tg) and non-Tg rats (n = 6 – 7 per group and sampling time) after one hour of unilateral middle cerebral artery occlusion (MCAO). Tissue samples were obtained from the developing infarct core and the border zone approximating the ischemic penumbra in both groups of animals after 3 or 24 hours of post-ischemic reperfusion. Neural cell death represented by DNA fragmentation is presented as mU/mg protein (mean ± SE). Cell death represented by DNA fragmentation was present at only negligible levels in non-ischemic TNFα-Tg and non-Tg controls (n = 12 per group) and after MCAO followed by 3 hours of post-ischemic reperfusion (p = NS for all pairwise comparisons). However, DNA fragmentation increased markedly after 24 hours of post-ischemic reperfusion in both TNFα-Tg and non-Tg rats. In the border zone approximating the ischemic penumbra in TNFα-Tg brain sampled at 24 hours, mean DNA fragmentation was increased by almost 200-fold compared to the respective non-ischemic control (p ≤ 0.0001; ANOVA/Fisher's test) and over 60-fold compared to border zone tissue sampled from TNFα-Tg brain at 3 hours (p ≤ 0.001; ANOVA/Fisher's test). DNA fragmentation in this region sampled from TNFα-Tg brain was almost 4-fold higher than that observed in non-Tg brain after 24 hours of post-ischemic reperfusion (p ≤ 0.01; ANOVA/Fisher's test). Within the infarct zone of TNFα-Tg brain sampled at 24 hours, mean DNA fragmentation was again increased by almost 200-fold compared to the respective non-ischemic control (p ≤ 0.0001; ANOVA/Fisher's test) and 60-fold compared to infarct zone tissue sampled from TNFα-Tg brain at 3 hours (p ≤ 0.001; ANOVA/Fisher's test). There was no significant difference observed between the elevated mean levels of DNA fragmentation within the infarct zone in TNFα-Tg and non-Tg rat brain after 24 hours of post-ischemic reperfusion (p = NS). **p ≤ 0.01; ***p ≤ 0.001; †p ≤ 0.0001