Nitric oxide-induced reduction of lung cell and whole lung thioredoxin expression is regulated by NF-kappa B

We examined whether nitric oxide (NO)-induced inhibition of thioredoxin (Th x) expression is regulated by a mechanism mediated by a transcription facto r, i.e., nuclear factor-kappa B (NF-kappa B), in cultured porcine pulmonary artery endothelial cells (PAEC) and in mouse lungs. Western blot analysis revealed that I kappa B-alpha content was reduced by 20 and 60% in PAEC exp osed to 8.5 ppm NO for 2 and 24 h, respectively. NO exposure also caused si gnificant reductions of cytosol fraction p65 and p52 content in PAEC. The n uclear fraction p65 and p52 contents were significantly reduced only in PAE C exposed to NO for 24 h. Exposure to NO resulted in a 50% reduction of p52 mRNA but not of the I kappa B-alpha subunit. DNA binding activity of the o ligonucleotide encoding the NF-kappa B sequence in the Thx gene was signifi cantly reduced in PAEC exposed to NO for 24 h. Exposure of mice to 10 ppm N O for 24 h resulted in a significant reduction of lung Thx and I kappa B-al pha mRNA and protein expression and in the oligonucleotide encoding Thx and NF-kappa B/DNA binding. These results 1) demonstrate that the effects of N O exposure on Thx expression in PAEC are comparable to those observed in in tact lung and 2) suggest that reduced expression of the NF-kappa B subunit, leading to reduced NF-kappa B/DNA binding, is associated with the loss of Thx expression in PAEC and in intact mouse lungs.