Recovery of thalamic microstructural damage after Shiga toxin 2-associated hemolytic-uremic syndrome

Cytokines expression from altered motor thalamus and behavior deficits following sublethal administration of Shiga toxin 2a involve the induction of the globotriaosylceramide receptor

Encephalopathy associated with hemolytic uremic syndrome is produced by enterohemorrhagic E. coli (EHEC) infection, which releases the virulence factors Shiga toxin (Stx) and lipopolysaccharide (LPS). Neurological compromise is a poor prognosis and mortality factor of the disease, and the thalamus is one of the brain areas most frequently affected. We have previously demonstrated the effectiveness of anti-inflammatory drugs to ameliorate the deleterious effects of these toxins. However, the thalamic production of cytokines involved in pro-inflammatory processes has not yet been acknowledged. The aim of this work attempts to determine whether systemic sublethal Stx2a or co-administration of Stx2a with LPS are able to rise a proinflammatory profile accompanying alterations of the neurovascular unit in anterior and lateral ventral nuclei of the thalamus (VA-VL) and motor behavior in mice. After 4 days of treatment, Stx2a affected the lectin-bound microvasculature distribution while increasing the expression of GFAP in reactive astrocytes and producing aberrant NeuN distribution in degenerative neurons. In addition, increased swimming latency was observed in a motor behavioral test. All these alterations were heightened when Stx2a was co-administered with LPS. The expression of pro-inflammatory cytokines TNFα, INF-γ and IL-2 was detected in VA-VL. All these effects were concomitant with increased expression of the Stx receptor globotriaosylceramide (Gb3), which hints at receptor involvement in the neuroinflammatory process as a key finding of this study. In conclusion, Stx2a to Gb3 may be determinant in triggering a neuroinflammatory event, which may resemble clinical outcomes and should thus be considered in the development of preventive strategies.

Behavioral sensitization induced by methamphetamine causes differential alterations in gene expression and histone acetylation of the prefrontal cortex in rats

Background

Methamphetamine (METH) is one of the most widely abused illicit substances worldwide; unfortunately, its addiction mechanism remains unclear. Based on accumulating evidence, changes in gene expression and chromatin modifications might be related to the persistent effects of METH on the brain. In the present study, we took advantage of METH-induced behavioral sensitization as an animal model that reflects some aspects of drug addiction and examined the changes in gene expression and histone acetylation in the prefrontal cortex (PFC) of adult rats.

Methods

We conducted mRNA microarray and chromatin immunoprecipitation (ChIP) coupled to DNA microarray (ChIP-chip) analyses to screen and identify changes in transcript levels and histone acetylation patterns. Functional enrichment analyses, including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, were performed to analyze the differentially expressed genes. We then further identified alterations in ANP32A (acidic leucine-rich nuclear phosphoprotein-32A) and POU3F2 (POU domain, class 3, transcription factor 2) using qPCR and ChIP-PCR assays.

Results

In the rat model of METH-induced behavioral sensitization, METH challenge caused 275 differentially expressed genes and a number of hyperacetylated genes (821 genes with H3 acetylation and 10 genes with H4 acetylation). Based on mRNA microarray and GO and KEGG enrichment analyses, 24 genes may be involved in METH-induced behavioral sensitization, and 7 genes were confirmed using qPCR. We further examined the alterations in the levels of the ANP32A and POU3F2 transcripts and histone acetylation at different periods of METH-induced behavioral sensitization. H4 hyperacetylation contributed to the increased levels of ANP32A mRNA and H3/H4 hyperacetylation contributed to the increased levels of POU3F2 mRNA induced by METH challenge-induced behavioral sensitization, but not by acute METH exposure.

Conclusions

The present results revealed alterations in transcription and histone acetylation in the rat PFC by METH exposure and provided evidence that modifications of histone acetylation contributed to the alterations in gene expression caused by METH-induced behavioral sensitization.

Therapeutic Strategies to Protect the Central Nervous System against Shiga Toxin from Enterohemorrhagic Escherichia coli

Infection with Shiga toxin-producing Escherichia coli (STEC) may cause hemorrhagic colitis, hemolytic uremic syndrome (HUS) and encephalopathy. The mortality rate derived from HUS adds up to 5% of the cases, and up to 40% when the central nervous system (CNS) is involved. In addition to the well-known deleterious effect of Stx, the gram-negative STEC releases lipopolysaccharides (LPS) and may induce a variety of inflammatory responses when released in the gut. Common clinical signs of severe CNS injury include sensorimotor, cognitive, emotional and/or autonomic alterations. In the last few years, a number of drugs have been experimentally employed to establish the pathogenesis of, prevent or treat CNS injury by STEC. The strategies in these approaches focus on: 1) inhibition of Stx production and release by STEC, 2) inhibition of Stx bloodstream transport, 3) inhibition of Stx entry into the CNS parenchyma, 4) blockade of deleterious Stx action in neural cells, and 5) inhibition of immune system activation and CNS inflammation. Fast diagnosis of STEC infection, as well as the establishment of early CNS biomarkers of damage, may be determinants of adequate neuropharmacological treatment in time.

Verotoxin Receptor-Based Pathology and Therapies

Verotoxin, VT (aka Shiga toxin,Stx) is produced by enterohemorrhagic E. coli (EHEC) and is the key pathogenic factor in EHEC-induced hemolytic uremic syndrome (eHUS-hemolytic anemia/thrombocytopenia/glomerular infarct) which can follow gastrointestinal EHEC infection, particularly in children. This AB5 subunit toxin family bind target cell globotriaosyl ceramide (Gb₃), a glycosphingolipid (GSL) (aka CD77, pk blood group antigen) of the globoseries of neutral GSLs, initiating lipid raft-dependent plasma membrane Gb₃ clustering, membrane curvature, invagination, scission, endosomal trafficking, and retrograde traffic via the TGN to the Golgi, and ER. In the ER, A/B subunits separate and the A subunit hijacks the ER reverse translocon (dislocon-used to eliminate misfolded proteins-ER associated degradation-ERAD) for cytosolic access. This property has been used to devise toxoid-based therapy to temporarily block ERAD and rescue the mutant phenotype of several genetic protein misfolding diseases. The A subunit avoids cytosolic proteosomal degradation, to block protein synthesis via its RNA glycanase activity. In humans, Gb₃ is primarily expressed in the kidney, particularly in the glomerular endothelial cells. Here, Gb₃ is in lipid rafts (more ordered membrane domains which accumulate GSLs/cholesterol) whereas renal tubular Gb₃ is in the non-raft membrane fraction, explaining the basic pathology of eHUS (glomerular endothelial infarct). Females are more susceptible and this correlates with higher renal Gb₃ expression. HUS can be associated with encephalopathy, more commonly following verotoxin 2 exposure. Gb₃ is expressed in the microvasculature of the brain. All members of the VT family bind Gb₃, but with varying affinity. VT2e (pig edema toxin) binds Gb₄ preferentially. Verotoxin-specific therapeutics based on chemical analogs of Gb₃, though effective in vitro, have failed in vivo. While some analogs are effective in animal models, there are no good rodent models of eHUS since Gb₃ is not expressed in rodent glomeruli. However, the mouse mimics the neurological symptoms more closely and provides an excellent tool to assess therapeutics. In addition to direct cytotoxicity, other factors including VT–induced cytokine release and aberrant complement cascade, are now appreciated as important in eHUS. Based on atypical HUS therapy, treatment of eHUS patients with anticomplement antibodies has proven effective in some cases. A recent switch using stem cells to try to reverse, rather than prevent VT induced pathology may prove a more effective methodology.