CELL-SURFACE EXPRESSION OF HEAT-SHOCK PROTEINS IN DOG NEUTROPHILS INDUCED BY MITOCHONDRIAL BENZODIAZEPINE RECEPTOR LIGANDS

The effect of peripheral-type benzodiazepines on dog neutrophil stimulation was studied. Ro 5-4864 (a specific ligand of mitochondrial benzodiazepine receptor) and diazepam (which binds both to mitochondrial and central benzodiazepine receptors) did not show any direct toxic effect against neutrophils. PK 11195, a putative antagonist of the mitochondrial benzodiazepine receptor and an isoquinoline derivative, had a direct toxic effect at a concentration of 5 x 10(-5) M (72% of cells were viable). Ro 5-4864 (10(-6) - 10(-4) M) and diazepam (10(-6) - 2.5 x 10(-4) M) induced an intracellular oxidative stress in dog neutrophils. These compounds, in a micromolar range, also induced a concentration-dependent cell surface expression of heat shock protein (HSP) families. The percentages of positive cells that express these proteins were: 76.2% for HSP 27 kDa; 54.3% for HSP 72 kDa and 69.6% for HSP 90 kDa for Ro 5-4864 (10(-4) M), and 66.7% for HSP 27 kDa; 45.4% for HSP 72 kDa and 78.3 for HSP 90 kDa for diazepam (2.5 x 10(-4) M). It appears that this HSP expression, induced by peripheral-type benzodiazepines could be mediated by an intracellular oxidative stress.