Factors influencing the expression of interleukin-1 beta in cultured rainbow trout (Oncorhynchus mykiss) leucocytes

The dose dependency and kinetics of lipopolysaccharide (LPS) induced interl eukin-1 beta (IL-1 beta) mRNA expression in rainbow trout leucocytes has be en studied. Northern blot analysis revealed weak hybridisation of a trout I L-1 beta probe to RNA from head kidney leucocytes stimulated with 0.1 mu g LPS/ml, with a large increase in IL-1 beta transcript level seen between 0. 1 and 1.5 mu g LPS/ml. Using 5 mu g LPS/ml expression was first detectable 1-2 h post-stimulation. By 4 h post-stimulation maximal induction was seen but by 24-48 h the level had fallen and by 72 h no transcript was detectabl e. Culture temperature had a marked effect on IL-1 beta expression, with lo w temperatures inhibiting transcription. Indeed, an eight-fold increase in IL-1 beta transcript level was seen between cells cultured at 4 degrees C a nd 22 degrees C. Preincubation with cortisol was also shown to inhibit LPS- induced IL-1 beta expression. (C) 2000 Elsevier Science Ltd. All rights res erved.