Search

We studied activity of lysosomal cysteine proteases, cathepsins B and L, in brain structures (frontal cortex, caudate nucleus, hippocampus, and hypothalamus) of C57Bl/6J mice with aggressive and depressive-like behavior formed under conditions of chronic social stress (repeated experience of victories and defeats within 20 days). Mice with depressive-like behavior showed increased activity of cathepsin В in the hypothalamus and nucleus caudatus and increased activity of cathepsin L in the hippocampus compared to control animals not subjected to agonistic confrontations. In mice with aggressive behavior, protease activity in the studied brain structures was not changed. In 4 h after immune system activation with LPS (250 μg/kg), cathepsin L activity in the hippocampus of control mice increased in comparison with mice receiving saline. In contrast to control animals, LPS caused a decrease in activity of the enzyme in the caudate nucleus and frontal cortex of aggressive mice and in the hippocampus of mice with depressive-like behavior.

The effect of aggressive behavior shaped under social stress of various durations on the production of proinflammatory cytokines by splenic cells was examined on C57BL/6J mice. Aggressive mice were characterized by enhanced production of IL-2 and IFN-γ (released by T helper type 1 cells) and reduced secretion of TNF-α, whose major producers are monocytes and macrophages. Elevation of IL-2 and IFN-γ in aggressive mice resulted from enhancement of spontaneous and Con A-stimulated production, the most pronounced effect was demonstrated by the with a longer period (20 days) of victories. In contrast, spontaneous production of TNF-α was similar in control and aggressive mice, although LPS-stimulated production of this cytokine decreased after 10- and 20-day stress. The possible mechanisms of the changes in cytokine production are discussed.