Neurotoxic properties of cerebrospinal fluid from behaviorally impaired autoimmune mice

The chronic, lupus-like autoimmune disease in MRL-lpr mice is associated with leucocyte infiltration into the choroid plexus, brain cell death, and deficits in motivated behavior. The presence of lymphoid cells in the ventricular lumen and the increased number of TUNEL-positive cells in periventricular areas led to the hypothesis that immune cells enter into the cerebrospinal fluid (CSF) and induce primary neuronal damage in regions bordering the cerebral ventricles. Using an in vitro approach, we presently examine the possibility that CSF from autoimmune mice is neurotoxic and/or gliotoxic. The CSF and serum from diseased MRL-lpr mice, less symptomatic MRL +/+ controls, and healthy Swiss/Webster mice (non-autoimmune controls) were frozen until their effects on the viability of pyramidal neurons and astrocytes were assessed in a two-color fluorescence assay. Significant reduction in neuronal viability (in some cases as low as 67%) was observed in the co-cultures of hippocampal neurons and astrocytes incubated for 24 h with CSF from autoimmune MRL-lpr mice. The viability of astrocytes did not differ among the groups, and the CSF from autoimmune mice appeared more toxic than the serum. The behavior of MRL-lpr mice differed significantly from the control groups, as indicated by impaired exploration, reduced intake of palatable food, and excessive immobility in the forced swim test. The present results suggest that CSF from the behaviorally impaired lupus-prone mice is neurotoxic and are consistent with the hypothesis that neuroactive metabolites are produced intrathecally in neuropsychiatric lupus erythematosus.