Abstracts

Rationale: Pre-natal exposure to methylazoxymethanoic acid (MAM) and thalidomide (THAL) has been demonstrated to impede brain vasculogenesis and neurogenesis. MAM and THAL combined cause time dependent changes in vascular integrity and synaptic organization. We studied the molecular mechanisms of MAM and THAL-induced neuro-vascular dysplasia. Methods: We evaluated the pattern of gene expression by cDNA microarray (Illumina Ratref-12 beadchips) in rat brains harvested from early postnatal (PN 1) and adult (PN 28) stages. A total of about 21900 genes were detected and included in the statistical analysis. Western blot was used to confirm brain expression of selected genes. Results: At PN 1, expression of of 536 genes was significantly changed (P <0.01, 296 upregulated and 220 downregulated) in MAM-THAL compared to control rats. At PN 28, expression of 56 genes was significantly changed (P <0.01, 34 upregulated and 22 downregulated). 20 genes were affected at both developmental stages. Among these, we identified: gap junction protein alpha 1 (GJA-1) expressed in astrocytes; gap junction protein beta 2 (GJB-2) expressed in neuronal cells; tight junction protein claudin-5 (CLDN-5) expressed in brain endothelial cells. Expression of these genes is under the control of anti-inflammatory molecules such as corticosteroids. CLDN-5 is also under transcriptional control by AKT. AKT mRNA and protein expression were affected similar to CLDN-5 confirming a possible role in mediating the effects of MAM-THAL. Expression of CLDN-5 at the protein level confirmed the cDNA data showing significant downregulation in PN 1 MAM-THAL treated rats. This may account for the early blood-brain barrier impairment described in this model. Conclusions: Brain gene expression is significantly altered in response to pre-natal exposure to toxins that affect vasculogenesis. We have unveiled specific genes that may be involved in this pathological process, possibly leading to malformation of cortical development and neurodegenerative diseases. In addition, since steroidal treatment has been shown to improve both BBB function and ameliorate seizures, these genes may be exploited as targets for improved therapy for epilepsy and acute seizures.