Induction of nuclear factor κB but not κB-responsive cytokine expression during myocardial reperfusion injury after neutropenia

Neutrophils may contribute to myocardial ischemia/reperfusion (I/R) injury by generating reactive oxygen intermediates (ROIs). ROIs activate nuclear factor (NF)-κB, which regulates genes for cytokines with negative inotropic effects (interleukin [IL]-1β, IL-6, and tumor necrosis factor [TNF]-α). We investigated the impact of neutrophil depletion on NF-κB DNA binding activity, and expression of these cytokines during myocardial I/R injury. Male WKY rats (n = 28) received a single dose of antineutrophil antiserum (i/v). Twenty two hours later, when the peripheral blood neutrophil counts were profoundly decreased (94% reduction), the animals underwent 15 min of left anterior descending coronary artery ligation followed by reperfusion for 0.25, 0.5, 1, 2, 3, and 6 h (n = 4/group). Saline-treated animals underwent a similar protocol, and served as controls (n = 28, 4/group). Neutrophil accumulation, defined by myeloperoxidase activity, was present in controls, but not in anti-PMN antisera-treated animals (at least p <0.05 at 1, 2, 3, and 6 h R). Despite this difference, in both saline- and antiserum-treated animals, the GSH levels were very similar and fell significantly (p < 0.0001) at 15 min R; the levels increased gradually over time. In contrast, GSSG levels rose at 15 and 30 min R (p < 0.05), and declined thereafter. NF-κB DNA binding activity increased in both groups at 15 min and again at 3 h of R. Both NF-κBp50 and p65 subunits were detected by supershift assay. In saline-injected controls both mRNA and protein for IL-1β, IL-6, and TNF-α were detected at 1 h R; levels remained high until 3 h, then fell (except IL-6, which was elevated at 6 h). In neutropenic animals, however, a significant decrease in mRNA (at least 1.7-fold, p < 0.05) as well as protein levels (at least 2.3-fold, p < 0.01) for all three cytokines was observed. Thus, while neutrophils had minimal effects on oxidative stress (GSH/GSSG) and oxidative stress-responsive NF-κB activity, they contributed significantly to myocardial cytokine expression.