Sphingosine-1-phosphate induces apoptosis of cultured hippocampal neurons that requires protein phosphatases and activator protein-1 complexes.

In this study, we report that mobilization of internal Ca2+ by sphingosine-1-phosphate, a metabolite of ceramide, induces apoptosis in cultured hippocampal neurons. This sphingosine-1-phosphate-induced apoptosis is dependent upon the activation of protein phosphatases, possibly calcineurin and phosphatase 2A (or a related phosphatase). In addition, pretreatment of neurons with double-stranded oligonucleotides containing the metallothionein phorbol-12-myristate-13-acetate response element sequence as transcription factor decoys suppressed apoptosis. In contrast, double-stranded oligonucleotides containing either the c-jun or SV40 phorbol-12-myristate-13-acetate response element sequences were ineffective. Electrophoretic mobility shift assays and supershift assays revealed that c-Fos-containing activator protein- complexes preferentially bound the metallothionein phorbol-12-myristate-13-acetate response element sequence-containing oligonucleotides. Furthermore, antisense oligonucleotides to c-fos and c-jun were also protective. The apoptotic death of hippocampal neurons has been hypothesized to contribute to the cognitive impairments observed following insults to the brain. While increases in intracellular calcium are thought to be key mediators of neuronal apoptosis, the biochemical cascade(s) activated as a result of increased Ca2+ which mediates apoptosis of hippocampal neurons is (are) not well understood. The findings presented in this study suggest that mobilization of internal calcium via prolonged exposure of sphingosine-1-phosphate induces apoptosis of hippocampal neurons in culture. Sustained increases in intracellular calcium activate a phosphatase cascade that includes calcineurin and a phosphatase 2A-like phosphatase, and leads to the expression of genes containing metallothionein phorbol-12-myristate-13-acetate response element (TGAGTCA)-type enhancer sequences. The expression of genes containing TGAGTCA-type enhancer sequences appears to be essential for sphingosine-1-phosphate-induced apoptosis of hippocampal neurons.

Isolated pontine lesion in algid cerebral malaria: clinical features, management, and magnetic resonance imaging findings.

Malaria, the most important of all tropical diseases, causes approximately one million deaths per year. In Plasmodium falciparum malaria, the organs most affected are the brain, kidneys, lungs, and liver. Cerebral involvement is the most important lethal complication with a mortality rate of up to 50%. We report a patient with malignant, tertian falciparum malaria with an initial parasitemia rate of 60% and severe cerebral, hepatorenal, and pulmonary involvement. In addition to the severe diffuse encephalopathy, an initial neurologic examination showed signs of a pontine lesion that was confirmed by cerebral magnetic resonance imaging. We therefore conclude that cerebral malaria may be responsible for focal neurologic lesions that can be demonstrated by this procedure.