TY - JOUR
T1 - Acute dosing of latrepirdine (Dimebon), a possible Alzheimer therapeutic, elevates extracellular amyloid- levels in vitro and in vivo
AU - Steele, John W.
AU - Kim, Soong H.
AU - Cirrito, John R.
AU - Verges, Deborah K.
AU - Restivo, Jessica L.
AU - Westaway, David
AU - Fraser, Paul
AU - Hyslop, Peter St George
AU - Sano, Mary
AU - Bezprozvanny, Ilya
AU - Ehrlich, Michelle E.
AU - Holtzman, David M.
AU - Gandy, Sam
N1 - Funding Information:
Support: JWS is a trainee in the Integrated Pharmacological Sciences Training Program supported by grant T32GM062754 from the National Institute of General Medical Sciences. JWS, SHK, and SG; and JRC (National Institute on Aging grant P01 AG10491 and K01 AG29524, respectively); JWS, SHK, and SG; and JRC and DMH (Cure Alzheimer's Fund); DMH [Zenith Award] and IB (Alzheimer's Association); IB (NINDS R01 NS056224); PF (Canadian Institutes for Health Research and the Alzheimer's Society of Ontario). Swedish APP N2a cell line was the generous gift of Dr. Gopal Thinakaran (University of Chicago). The authors would like to thank Loren E. Khan- Vaughan and Justine Bonet for their assistance with animal colony management.
PY - 2009
Y1 - 2009
N2 - Background. Recent reports suggest that latrepirdine (Dimebon, dimebolin), a retired Russian antihistamine, improves cognitive function in aged rodents and in patients with mild to moderate Alzheimer's disease (AD). However, the mechanism(s) underlying this benefit remain elusive. AD is characterized by extracellular accumulation of the amyloid- (A) peptide in the brain, and A-lowering drugs are currently among the most popular anti-amyloid agents under development for the treatment of AD. In the current study, we assessed the effect of acute dosing of latrepirdine on levels of extracellular A using in vitro and in vivo experimental systems. Results. We evaluated extracellular levels of A in three experimental systems, under basal conditions and after treatment with latrepirdine. Mouse N2a neuroblastoma cells overexpressing Swedish APP were incubated for 6 hr in the presence of either vehicle or vehicle + latrepirdine (500pM-5 M). Synaptoneurosomes were isolated from TgCRND8 mutant APP-overexpressing transgenic mice and incubated for 0 to 10 min in the absence or presence of latrepirdine (1 M or 10 M). Drug-nave Tg2576 Swedish mutant APP overexpressing transgenic mice received a single intraperitoneal injection of either vehicle or vehicle + latrepirdine (3.5 mg/kg). Picomolar to nanomolar concentrations of acutely administered latrepirdine increased the extracellular concentration of A in the conditioned media from Swedish mutant APP-overexpressing N2a cells by up to 64% (p = 0.01), while a clinically relevant acute dose of latrepirdine administered i.p. led to an increase in the interstitial fluid of freely moving APP transgenic mice by up to 40% (p = 0.01). Reconstitution of membrane protein trafficking and processing is frequently inefficient, and, consistent with this interpretation, latrepirdine treatment of isolated TgCRND8 synaptoneurosomes involved higher concentrations of drug (1-10 M) and led to more modest increases in extracellular Ax-42levels (+10%; p = 0.001); of note, however, was the observation that extracellular Ax-40levels did not change. Conclusions. Here, we report the surprising association of acute latrepirdine dosing with elevated levels of extracellular A as measured in three independent neuron-related or neuron-derived systems, including the hippocampus of freely moving Tg2576 mice. Given the reported association of chronic latrepirdine treatment with improvement in cognitive function, the effects of chronic latrepirdine treatment on extracellular A levels must now be determined.
AB - Background. Recent reports suggest that latrepirdine (Dimebon, dimebolin), a retired Russian antihistamine, improves cognitive function in aged rodents and in patients with mild to moderate Alzheimer's disease (AD). However, the mechanism(s) underlying this benefit remain elusive. AD is characterized by extracellular accumulation of the amyloid- (A) peptide in the brain, and A-lowering drugs are currently among the most popular anti-amyloid agents under development for the treatment of AD. In the current study, we assessed the effect of acute dosing of latrepirdine on levels of extracellular A using in vitro and in vivo experimental systems. Results. We evaluated extracellular levels of A in three experimental systems, under basal conditions and after treatment with latrepirdine. Mouse N2a neuroblastoma cells overexpressing Swedish APP were incubated for 6 hr in the presence of either vehicle or vehicle + latrepirdine (500pM-5 M). Synaptoneurosomes were isolated from TgCRND8 mutant APP-overexpressing transgenic mice and incubated for 0 to 10 min in the absence or presence of latrepirdine (1 M or 10 M). Drug-nave Tg2576 Swedish mutant APP overexpressing transgenic mice received a single intraperitoneal injection of either vehicle or vehicle + latrepirdine (3.5 mg/kg). Picomolar to nanomolar concentrations of acutely administered latrepirdine increased the extracellular concentration of A in the conditioned media from Swedish mutant APP-overexpressing N2a cells by up to 64% (p = 0.01), while a clinically relevant acute dose of latrepirdine administered i.p. led to an increase in the interstitial fluid of freely moving APP transgenic mice by up to 40% (p = 0.01). Reconstitution of membrane protein trafficking and processing is frequently inefficient, and, consistent with this interpretation, latrepirdine treatment of isolated TgCRND8 synaptoneurosomes involved higher concentrations of drug (1-10 M) and led to more modest increases in extracellular Ax-42levels (+10%; p = 0.001); of note, however, was the observation that extracellular Ax-40levels did not change. Conclusions. Here, we report the surprising association of acute latrepirdine dosing with elevated levels of extracellular A as measured in three independent neuron-related or neuron-derived systems, including the hippocampus of freely moving Tg2576 mice. Given the reported association of chronic latrepirdine treatment with improvement in cognitive function, the effects of chronic latrepirdine treatment on extracellular A levels must now be determined.
UR - http://www.scopus.com/inward/record.url?scp=76249083708&partnerID=8YFLogxK
U2 - 10.1186/1750-1326-4-51
DO - 10.1186/1750-1326-4-51
M3 - Article
C2 - 20017949
AN - SCOPUS:76249083708
SN - 1750-1326
VL - 4
JO - Molecular neurodegeneration
JF - Molecular neurodegeneration
IS - 1
M1 - 51
ER -