Figure 4

Increased myocardial TLR4 levels in aging hearts is associated with enhanced TLR4-mediated NF-κB activation. A) Left ventricular tissue was collected from hearts of untreated 5 adult and 4 aging mice. A representative immunoblot shows higher myocardial TLR4 protein levels in aging hearts. B) Hearts isolated from adult and aging TLR4-competent (WT) and TLR4-deficient (TLR4d) mice were perfused with recombinant HSP27 (1.0 or 2.0 µg/mL) for 30 min followed by 20 min washout. Aging WT hearts exhibited greater myocardial NF-κB activation in comparison to adult WT hearts. TLR4 deficiency abrogated the effect of HSP27 on myocardial NF-κB DNA-binding activity in both adult and aging hearts. Data are expressed as mean ± SE. n = 6 in each group, ^aP < 0.05 versus age/genotype-matched control, ^bP < 0.05 versus adult WT treated with the same dose of HSP27; ^cP < 0.05 versus age-matched WT treated with a lower dose of HSP27. C) Hearts isolated from adult and aging TLR4-competent (WT) and TLR4-deficient (TLR4d) mice were subjected to 20 min of ischemia followed by 20 min of reperfusion. Aging WT hearts exhibited greater myocardial NF-κB activation following I/R in comparison to adult WT hearts. TLR4 deficiency greatly reduced myocardial NF-κB DNA-binding activity in aging hearts and abrogated the age-related difference in postischemic NF-κB activity. Data are expressed as mean ± SE. n = 6 in each group, ^aP < 0.05 versus age/genotype-matched control, ^bP < 0.05 versus adult WT I/R; ^cP < 0.05 versus aging WT I/R.