Synergistic neurotoxic effects of combined treatments with cytokines in murine primary mixed neuron/glia cultures.

Activation of brain glial cells with the bacterial endotoxin lipopolysaccharide (LPS), the HIV-1 coat protein gp120, or beta-amyloid-derived peptides, stimulates the expression of several cytokines, including tumor necrosis factor-alpha (TNFalpha), interleukin-1 (IL-1) and IL-6. and nitric oxide (NO) which have been proposed as causes of neurodegeneration in the brain. In the present study, the neurotoxic effects of several cytokines, alone or in various combinations, and the correlations of the release of lactate dehydrogenase, the loss of neurons, and the secretion of NO in brain neuronal cell injury were investigated in murine primary mixed neuronal/glial cell cultures. A specific combination of cytokines, i.e., IL-1 (1 ng/ml)+ TNFalpha (10 ng/ml)/interferon-gamma (IFNgamma) (200 u/ml), induced a dramatic neuronal cell injury in the neuron/glia cultures, and its cytotoxic profile was very similar to that seen with the LPS/IFNgamma-induced neuron injury. This indicates that among the many toxic immune mediators secreted in response to LPS, IL-1 and TNFalpha can mimic LPS as the triggering signals and primary mediators for glia-mediated neuron injury in the presence of IFNgamma. This study provides new insights about the cytotoxic mechanism(s) for cytokine-mediated neuron injury.