globotriaosylceramide and Central-Nervous-System-Diseases

Hemolytic uremic syndrome (HUS) is caused by endothelial cell damages. Ninety percent of children with HUS have verotoxin-producing E.coli infection. Verotoxin binds to glycolipid receptors globotriaosyl ceramide (Gb3), and the difference of Gb3 expression level in each organ would lead to specific organ involvement. The receptors are expressed in human renal cortex and medulla. The expression level of Gb3 in normal human brain has not been characterized completely. However involvement of central nervous system is a severe complication of HUS. Spreading of microvascular thrombosis caused by combined effects of lipopolysaccharide, cytokine, enhanced shear stress, and verotoxin would play a major role in the development of central nervous dysfunction.

Topics: Bacterial Toxins; Central Nervous System Diseases; Escherichia coli Infections; Escherichia coli O157; Gastrointestinal Hemorrhage; Hemolytic-Uremic Syndrome; Humans; Purpura, Thrombotic Thrombocytopenic; Shiga Toxin 1; Trihexosylceramides

Shiga toxins (Stxs) are the major agents responsible for hemorrhagic colitis and hemolytic-uremic syndrome (HUS) during infections caused by Stx-producing Escherichia coli (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.. 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.. 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)-alpha and interleukin (IL)-1beta mRNA in the CNS parenchyma was significantly up-regulated. There was significant overexpression of TNF-alpha transcripts in the brain.. 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.

Topics: Animals; Apoptosis; Central Nervous System Diseases; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelium, Vascular; Inflammation; Interleukin-1beta; Male; Neuroglia; Neurons; Rabbits; RNA, Messenger; Shiga Toxin 2; Trihexosylceramides; Tumor Necrosis Factor-alpha; Up-Regulation