7th International Symposium on Shiga Toxin (V - LOCAL ADMINISTRATION OF SHIGA TOXIN 2 INDUCES THE EXPRESSION OF THE GLOBOTRIAOSYLCERAMIDE (GB3) RECEPTOR IN THE RAT BRAIN

Congreso

Summary *

Shiga toxin-producing Escherichia coli (STEC) causes hemorrhagic diarrhea, hemolytic uremic syndrome (HUS) and various encephalopathies, one of the major risk factors of children mortality. Shiga toxin (Stx) binds to its receptor, the glycolipid globotriaosylceramide (Gb3) and produces cell death. At present, the cerebral distribution of Gb3 is a matter of controversy. We previously published that the intracerebroventricular (ICV) administration of Stx2 in the rat brain causes neuronal and glial alterations that included neuronal death (1,2). The aim of this work is to demonstrate the presence of the receptor GB3 on normal rat brains and the changes in its expression after the ICV administration of Stx2. Methods After 8 days of treatment, SD male rats were anesthetized, perfused and their brains were processed to perform double immunofluorescence confocal microscopy studies using commercial antibodies targeting Gb3, Stx2, Map2 (neuronal marker) and GFAP (astrocytic marker). Results The immunodetection of the Gb3 receptor was observed in neurons and microvessels of striatum, hippocampus, cerebral cortex and hypothalamus of rat brains after ICV administration of a vehicle. The increase in the expression of Gb3 receptor after Stx2 microinfusion were observed in neurons, microvessels and astrocytes of the same brain regions but mainly located next to the ventricle (p<0,01). The presence of Gb3 in astrocytes of the subfornical area was also detected. The areas where Gb3 was located coincided with the topographical distribution of Stx2. Subcell Stx2 distribution colocalized with Gb3 in neurons. We also analyzed the kidneys in the Stx2 treated animals to observe whether the ICV administration of the toxin could alterate the organ histology, produced as a secondary event. Strikingly, histological renal changes, consisting in thickening of the glomerular basement membrane and abundant protein deposits in the cytoplasm of tubular renal cells were observed in treated animals. Conclusions In this work we reported for first time the normal distribution of the Gb3 receptor in different cell types of rat brains. We concluded that the local administration of Stx2 in the rat brain increased the expression of Gb3 receptor in neurons, astrocytes and endothelial cells in particular regions close to the ventricles, in coincidence with the topographical Stx2 immunodetection. It is suggestive the presence of Gb3 in the brain microvasculature, that would allow the diffusion of the toxin or related subproducts from the brain to the periphery.  The renal alterations observed demonstrate the peripheric action of the toxin. The induction of the Gb3 receptor after Stx2 administration may explain some of the neuropathogenic mechanisms in acute encephalopaties triggered by STEC intoxications in patients. Information provided by the agent in SIGEVA