Neuronal apoptosis and inflammatory responses in the central nervous system of a rabbit treated with Shiga toxin-2

<p>Abstract</p> <p>Background</p> <p>Shiga toxins (Stxs) are the major agents responsible for hemorrhagic colitis and hemolytic-uremic syndrome (HUS) during infections caused by Stx-producing <it>Escherichia coli </it>(STEC) such as serotype O157:H7. Central nervous system (CNS) involvement is an important determinant of mortality in diarrhea associated-HUS. It has been suggested that vascular endothelial injuries caused by Stxs play a crucial role in the development of the disease. The current study investigates the relationship between the cytotoxic effects of Stxs and inflammatory responses in a rabbit brain treated with Stx2.</p> <p>Methods</p> <p>In a rabbit model treated with purified Stx2 or PBS(-), we examined the expression of the Stx receptor globotriaosylceramide (Gb3)/CD77 in the CNS and microglial activation using immunohistochemistry. The relationship between inflammatory responses and neuronal cell death was analyzed by the following methods: real time quantitative reverse transcriptase (RT)-polymerase chain reaction (PCR) to determine the expression levels of pro-inflammatory cytokines, and the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) method to detect apoptotic changes.</p> <p>Results</p> <p>Gb3/CD77 expression was detected in endothelial cells but not in neurons or glial cells. In the spinal cord gray matter, significant levels of Gb3/CD77 expression were observed. Severe endothelial injury and microvascular thrombosis resulted in extensive necrotic infarction, which led to acute neuronal damage. Conversely, in the brain, Stx receptor expression was much lower. The observed neuropathology was less severe. However, neuronal apoptosis was observed at the onset of neurological symptoms, and the number of apoptotic cells significantly increased in the brain at a later stage, several days after onset. Microglial activation was observed, and tumor necrosis factor (TNF)-α and interleukin (IL)-1β mRNA in the CNS parenchyma was significantly up-regulated. There was significant overexpression of TNF-α transcripts in the brain.</p> <p>Conclusion</p> <p>This study indicates that Stx2 may not directly damage neural cells, but rather inflammatory responses occur in the brain parenchyma in response to primary injury by Stx2 in vascular endothelial cells expressing Gb3/CD77. These findings suggest that neuroinflammation may play a critical role in neurodegenerative processes during STEC infection and that anti-inflammatory intervention may have therapeutic potential.</p

Neuronal apoptosis and inflammatory responses in the central nervous system of a rabbit treated with Shiga toxin-2-0

Ositive neurons showing shrunken cytoplasm, pycnotic nuclei, and/or apoptotic bodies increased at a later stage in the following other regions: CA1 of the hippocampus and cerebral cortex . Apoptotic glial cells in pons and small vessels with condensed cytoplasm and apoptotic bodies were also observed at a later stage. TUNEL assay without TdT showed no positive staining. Quantitative evaluation of TUNEL-positive cells per 10 fields in the hippocampus, cerebellum, and other cerebral regions, including the basal ganglia, thalamus, and cerebral cortex, and TUNEL-positive vessels per 100 fields in the cerebral parenchyma at the onset of neurological symptoms and at a later stage when compared with control rabbits treated with PBS(-) (n = 2 in each group). The number of apoptotic cells significantly increased in the hippocampus at both onset and a later stage, and in granular layers of the cerebellum and other cerebral regions at a late stage. TUNEL-positive vessels were significantly elevated at a later stage. *: < 0.01 and **: < 0.05. (Original magnification: and 200×, 800×, and 600×, 400×)<p><b>Copyright information:</b></p><p>Taken from "Neuronal apoptosis and inflammatory responses in the central nervous system of a rabbit treated with Shiga toxin-2"</p><p>http://www.jneuroinflammation.com/content/5/1/11</p><p>Journal of Neuroinflammation 2008;5():11-11.</p><p>Published online 21 Mar 2008</p><p>PMCID:PMC2330034.</p><p></p