Increased I kappa B expression and diminished nuclear NF-kappa B in human mononuclear cells following hydrocortisone injection

We have recently demonstrated that hydrocortisone and other glucocorticoids inhibit reactive oxygen species (ROS) generation by mononuclear (MNC) and polymorphonuclear leucocytes (PMNL). Since NF-kappa B/I kappa B system regu lates the transcription of proinflammatory genes, including those responsib le for ROS generation, we tested the hypothesis that hydrocortisone may sti mulate I kappa B production thus inhibiting NF-kappa B translocation from t he cytosol into the nucleus in MNC, in vivo. One hundred milligram of hydro cortisone was injected intravenously into 4 normal subjects. Blood samples were obtained prior to the injection and at 1, 2, 4, 8 and 24 hr after the injection. Nuclear extracts and total cell lysates were prepared from MNC b y standard techniques. I kappa B levels in MNC homogenates increased at 1 h r, peaked at 2-4 hr, started to decrease at 8 hr, and returned to baseline levels at 24 hr. NF-kappa B in MNC nuclear extracts decreased at 1 hr, reac hed a nadir at 4 hr, gradually increased at 8 hr and returned back to basel ine levels at 24 hr. The total protein content of NF-kappa B subunit (P65) in MNC lysates also showed a decrease following hydrocortisone injection. T his decrease was observed at 2 hr, reached a nadir at 4 hr, and returned to baseline levels at 24 hr.ROS generation inhibition paralleled NF-kappa B l evels in the nucleus. It was inhibited at 1 hr,reached a nadir at 2-4 hr, s tarted to increase at 8 hr, and returned to basal levels at 24 hr. Our data demonstrate that hydrocortisone induces I kappa B and suppresses NF-kappa B expression in MNC in parallel. I kappa B further reduces the translocatio n of NF-kappa B into the nucleus thus preventing the expression of proinfla mmatory genes.