Effect of the knockdown of amyloid precursor protein on intracellular calcium increases in a neuronal cell line derived from the cerebral cortex of a trisomy 16 mouse Guillermo Rojas a,b , Ana María Cárdenas b , Paola Fernández-Olivares b , Takeshi Shimahara c , Juan Segura-Aguilar a , Raúl Caviedes a , Pablo Caviedes a, ⁎ a Program of Molecular & Clinical Pharmacology, ICBM, Faculty of Medicine, University of Chile, Santiago, Chile b Centro de Neurociencia de Valparaíso, University of Valparaíso, Chile c NBCM, CNRS, Gif-sur-Yvette, France Received 5 June 2007; revised 10 September 2007; accepted 25 September 2007 Available online 5 October 2007 Abstract Murine trisomy 16 (Ts16) is a useful model to study the deleterious effect of aneuploidy in neural pathophysiology. The CTb cell line derived from the cerebral cortex of a Ts16 mouse overexpresses the amyloid precursor protein (APP) and exhibits altered intracellular Ca 2+ homeostasis. In the present work, we induced knockdown of APP by transfecting specific mRNA antisense sequences into CTb cells. Forty-eight hours after transfection, the APP expression was knocked down by 40%, reaching levels comparable to those of the cortical line CNh, derived from a normal animal. Calcium measurements showed that the APP knockdown decreased intracellular Ca 2+ basal levels and accelerated the kinetics of the decay of Ca 2+ responses induced by glutamatergic agonists, nicotine, depolarization or ionomycin, to levels similar to those previously reported for CNh cells. The present results suggest that APP overexpression plays an important role on the altered intracellular Ca 2+ homeostasis in the trisomic cells. © 2007 Elsevier Inc. All rights reserved. Keywords: Calcium; Glutamate; Nicotine; Antisense; Down syndrome Introduction Trisomy 16 in the fetal mouse is a useful model in the study of the effect of gene dosage on cellular pathophysiology, and certain sinteny exists between mouse autosome 16 and human 21. Specific electrophysiological alterations exist in sensory neurons of both human and murine aneuploid conditions compared to normal controls and are essentially similar in both species. Further, cultured central neurons from trisomy 16 mice have cholinergic and glutamatergic defects, the latter expressed in abnormal intracellular Ca 2+ responses to neurotransmitter ago- nists (Schuchmann et al., 1998). Such abnormalities are probably related to imbalances induced by an increased and specific gene dosage effect. Indeed, several genes mapped to both human chromosome 21 and murine chromosome 16 may affect cell membrane composition and receptor/ion channel function when overexpressed, such as SOD-1 (Cu/Zn superoxide dismutase), IFRC (α and β interferon receptor), Slc5a3 (Na + /myoinositol cotransporter) and APP (amyloid precursor protein) (Cárdenas et al., 2002a,b). App, the gene that encodes for the amyloid precursor protein APP, merits attention. APP is an integral membrane protein (Sisodia and Price, 1995) and is reportedly overexpressed in human Down syndrome (DS), a condition that is represented by the trisomy of autosome 21 (Head and Lott, 2004). Relating its effects on membrane function, increased APP in DS neurons has also been linked to lipoperoxidation (Begni et al., 2003), to the formation of Ca 2+ channels by the Aß peptide that could dissipate the Ca 2+ gradient and alter intracellular homeostasis of the cation, thus deeply impairing cell function (Arispe et al., 1994; Kawahara et al., 2000). Also, altered APP metabolism in DS impairs mitochondrial function, which could Available online at www.sciencedirect.com Experimental Neurology 209 (2008) 234 – 242 www.elsevier.com/locate/yexnr ⁎ Corresponding author. Program of Molecular and Clinical Pharmacology, ICBM, Faculty of Medicine, University of Chile, Clasificador 7–Independencia, Independencia 1027, Santiago, Chile. Fax: +56 2 737 2783. E-mail address: pcaviede@med.uchile.cl (P. Caviedes). 0014-4886/$ - see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.expneurol.2007.09.024