Glutamate mediated signaling in the pathophysiology of autism spectrum disorders.

Autism spectrum disorder (ASD) is a childhood neurodevelopmental disorder. During fetal and neonatal brain development, the cues for neurodevelopment are regulated in a well orchestrated manner. Generally, neurotransmitters play a major role in the formation of central nervous system (CNS) and peripheral nervous system (PNS). Glutamate, the excitatory neurotransmitter actively participates in various neurodevelopmental processes through complex regulatory events. Excitatory neurotransmitter signaling via glutamate receptors modulates cognitive functions such as memory and learning, which are usually impaired in ASD. Therefore, glutamate and its regulatory molecules are considered as potential targets for these disorders. Pharmacological, biochemical and behavioral studies reveal possible involvement of glutamatergic system in ASD pathology. An abnormal increase in electrical activity resulting from excessive glutamate signaling causes prolonged alterations in behavior, as commonly seen in ASDs. On the contrary, reports on animal models of hypoglutamatergia demonstrate phenotypes that overlap with features seen in autism. So controversies prevail whether to regard autism as hyper- or hypo-glutamatergic disorder. This paper reviews the role of glutamate and its regulatory proteins such as different receptors, transporters and metabolizing enzymes in the pathophysiology of ASD based on evidences gathered through multidisciplinary approaches. All these information raise the possibility of exploiting glutamatergic neurotransmitter system for future therapeutic interventions for ASD.

Culture of human breast cancer cell line (MDA-MB-231) on fibronectin-coated surface induces pro-matrix metalloproteinase-9 expression and activity.

Interaction between cell surface integrin receptors with extracellular matrix (ECM) plays an important role in cell survival, proliferation, and migration including tumor development and invasion. Binding of ECM to integrins initiates intracellular signaling cascades, modulating expression and activity of different matrix metalloproteinases (MMPs) which is important in ECM degradation. The present study investigates fibronectin-integrin-mediated signaling and thereby modulation of MMPs expression and activity in human breast cancer cell line, MDA-MB-231. Culture of MDA-MB-231 cells on fibronectin (FN) induced expression and activity of pro-matrixmetalloproteinase-9 (MMP-9). Appreciable reduction of FN-induced pro-MMP-9 activity was observed in anti-α5 antibody treated cells. Inhibitor studies revealed that inhibitors of phosphatidyl inositiol-3-kinase (PI-3K), and nuclear factor kappa B (NF-κB) inhibited FN-induced pro-MMP-9 activity. FN increased tyrosine phosphorylation of focal adhesion kinase (FAK), integrin linked kinase (ILK), and PI-3K in MDA-MB-231 cells. FN-induced the transactivation of MMP-9 promoter by enhancing DNA binding activity of NF-κB and Sp1. Wound healing assay showed faster migration of MDA-MB-231cells grown on fibronectin-coated as surface as compared to control. Our findings indicated that culture of MDA-MB-231 on fibronectin perhaps send signals via fibronectin-integrin-mediated signaling pathways recruiting FAK, PI-3K, ILK, NF-κB, and modulate expression and activation of pro-MMP-9. These observations may enrich fundamental aspects of cancer biology especially role of α5ß1 integrin in regulation of MMPs expression and activity.

Multifunctional effect of epigallocatechin-3-gallate (EGCG) in downregulation of gelatinase-A (MMP-2) in human breast cancer cell line MCF-7.

AIMS: The tumor inhibiting property of green tea polyphenol epigallocatechin-3-gallate (EGCG) is well documented. Studies reveal that matrix-metalloproteinases (MMPs) play pivotal roles in tumor invasion through degradation of basement membranes and extracellular matrix (ECM). We studied the effect of EGCG on matrixmetalloproteinases-2 (MMP-2), the factors involved in activation, secretion and signaling molecules that might be involved in the regulation of MMP-2 in human breast cancer cell line, MCF-7. MAIN METHODS: MCF-7 was treated with EGCG (20 muM, 24 h), the effect of EGCG on MMP-2 expression, activity and its regulatory molecules were studied by gelatin zymography, Western blot, quantitative and semi-quantitative real time RT-PCR, immunoflourescence and cell adhesion assay. KEY FINDINGS: EGCG treatment reduced the activity, protein expression and mRNA expression level of MMP-2. EGCG treatment reduced the expression of focal adhesion kinase (FAK), membrane type-1-matrix metalloproteinase (MT1-MMP), nuclear factor-kappa B (NF-kB), vascular endothelial growth factor (VEGF) and reduced the adhesion of MCF-7 cells to ECM, fibronectin and vitronectin. Real time RT-PCR revealed a reduced expression of integrin receptors alpha5, beta1, alphav and beta3 due to EGCG treatment. SIGNIFICANCE: Down regulation of expression of MT1-MMP, NF-kB, VEGF and disruption of functional status of integrin receptors may indicate decreased MMP-2 activation; low levels of FAK expression might indicate disruption in FAK-induced MMP-2 secretion and decrease in activation of phosphatidyl-inositol-3-kinase (PI-3K), extracellular regulated kinase (ERK) indicates probable hindrance in MMP-2 regulation and induction. We propose EGCG as potential inhibitor of expression and activity of pro-MMP-2 by a process involving multiple regulatory molecules in MCF-7.