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Evaluation of Dimebon in cellular model of Huntington's disease.

Wu J, Li Q, Bezprozvanny I - Mol Neurodegener (2008)

Bottom Line: Lower concentrations of Dimebon (5 muM and 10 muM) did not stabilize glutamate-induced Ca2+ signals and did not exert neuroprotective effects in experiments with YAC128 MSN.Dimebon also had significant effect on a number of additional receptors.Our results suggest that Ca2+ and mitochondria stabilizing effects may, in part, be responsible for beneficial clinical effects of Dimebon.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physiology, UT Southwestern Medical Center at Dallas, TX 75390, USA. Ilya.Bezprozvanny@UTSouthwestern.edu.

ABSTRACT

Background: Dimebon is an antihistamine compound with a long history of clinical use in Russia. Recently, Dimebon has been proposed to be useful for treating neurodegenerative disorders. It has demonstrated efficacy in phase II Alzheimer's disease (AD) and Huntington's disease (HD) clinical trials. The mechanisms responsible for the beneficial actions of Dimebon in AD and HD remain unclear. It has been suggested that Dimebon may act by blocking NMDA receptors or voltage-gated Ca2+ channels and by preventing mitochondrial permeability pore transition.

Results: We evaluated the effects of Dimebon in experiments with primary striatal neuronal cultures (MSN) from wild type (WT) mice and YAC128 HD transgenic mice. We found that Dimebon acts as an inhibitor of NMDA receptors (IC50 = 10 muM) and voltage-gated calcium channels (IC50 = 50 muM) in WT and YAC128 MSN. We further found that application of 50 muM Dimebon stabilized glutamate-induced Ca2+ signals in YAC128 MSN and protected cultured YAC128 MSN from glutamate-induced apoptosis. Lower concentrations of Dimebon (5 muM and 10 muM) did not stabilize glutamate-induced Ca2+ signals and did not exert neuroprotective effects in experiments with YAC128 MSN. Evaluation of Dimebon against a set of biochemical targets indicated that Dimebon inhibits alpha-Adrenergic receptors (alpha1A, alpha1B, alpha1D, and alpha2A), Histamine H1 and H2 receptors and Serotonin 5-HT2c, 5-HT5A, 5-HT6 receptors with high affinity. Dimebon also had significant effect on a number of additional receptors.

Conclusion: Our results suggest that Ca2+ and mitochondria stabilizing effects may, in part, be responsible for beneficial clinical effects of Dimebon. However, the high concentrations of Dimebon required to achieve Ca2+ stabilizing and neuroprotective effects in our in vitro studies (50 muM) indicate that properties of Dimebon as cognitive enhancer are most likely due to potent inhibition of H1 histamine receptors. It is also possible that Dimebon acts on novel high affinity targets not present in cultured MSN preparation. Unbiased evaluation of Dimebon against a set of biochemical targets indicated that Dimebon efficiently inhibited a number of additional receptors. Potential interactions with these receptors need to be considered in interpretation of results obtained with Dimebon in clinical trials.

No MeSH data available.


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Evaluation of Dimebon in in vitro HD assay. Glutamate-induced apoptosis of WT and YAC128 MSN treated with Dimebon at different concentrations. WT and YAC128 MSN at 14 DIV were exposed to 250 μM glutamate for 7 h, fixed, permeabilized and analyzed by TUNEL staining and PI counterstaining. The Dimebon was added 30 min before the application of glutamate. The fraction of TUNEL-positive is plotted against glutamate concentration for WT (open circle) and YAC128 (YAC, filled circles) mice. The data are shown as mean ± SE (n = 6–8 microscopic fields, 100–300 MSN per field). The results in the absence (black symbols) and presence (red symbols) obtained in the presence of 5 μM of Dimebon (A) 10 μM Dimebon (B) and 50 μM Dimebon (C) are compared.
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Figure 5: Evaluation of Dimebon in in vitro HD assay. Glutamate-induced apoptosis of WT and YAC128 MSN treated with Dimebon at different concentrations. WT and YAC128 MSN at 14 DIV were exposed to 250 μM glutamate for 7 h, fixed, permeabilized and analyzed by TUNEL staining and PI counterstaining. The Dimebon was added 30 min before the application of glutamate. The fraction of TUNEL-positive is plotted against glutamate concentration for WT (open circle) and YAC128 (YAC, filled circles) mice. The data are shown as mean ± SE (n = 6–8 microscopic fields, 100–300 MSN per field). The results in the absence (black symbols) and presence (red symbols) obtained in the presence of 5 μM of Dimebon (A) 10 μM Dimebon (B) and 50 μM Dimebon (C) are compared.

Mentions: To evaluate neuroprotective effects of Dimebon, we performed a series of glutamate toxicity experiments with WT and YAC128 MSN DIV14 cultures. In the absence of glutamate approximately 5–10% of neurons are apoptotic in both wild type (WT) and YAC128 MSN cultures. Following exposure to 250 μM glutamate, the fraction of apoptotic WT MSN is increased to 25–40% and the fraction of apoptotic YAC128 MSN is increased to 55–70% (Table 1). The difference between the glutamate-induced apoptosis of YAC128 and WT MSN is highly significant and constitutes a quantitative basis for the in vitro HD assay we have previously described [12,13,15]. The neuroprotective effects of Dimebon were evaluated at 5 μM, 10 μM and 50 μM concentrations using the in vitro HD assay (Table 1, Fig 5). In these experiments, Dimebon was added 30 minutes prior to the exposure of MSN cultures to glutamate. We found that 5 μM and 10 μM Dimebon had no significant effects on the glutamate-induced apoptosis of YAC128 MSN (Table 1, Figs 5A, B). At 50 μM concentration, Dimebon showed significant protective effects in the in vitro HD assay (Table 1, Fig 5C).


Evaluation of Dimebon in cellular model of Huntington's disease.

Wu J, Li Q, Bezprozvanny I - Mol Neurodegener (2008)

Evaluation of Dimebon in in vitro HD assay. Glutamate-induced apoptosis of WT and YAC128 MSN treated with Dimebon at different concentrations. WT and YAC128 MSN at 14 DIV were exposed to 250 μM glutamate for 7 h, fixed, permeabilized and analyzed by TUNEL staining and PI counterstaining. The Dimebon was added 30 min before the application of glutamate. The fraction of TUNEL-positive is plotted against glutamate concentration for WT (open circle) and YAC128 (YAC, filled circles) mice. The data are shown as mean ± SE (n = 6–8 microscopic fields, 100–300 MSN per field). The results in the absence (black symbols) and presence (red symbols) obtained in the presence of 5 μM of Dimebon (A) 10 μM Dimebon (B) and 50 μM Dimebon (C) are compared.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 5: Evaluation of Dimebon in in vitro HD assay. Glutamate-induced apoptosis of WT and YAC128 MSN treated with Dimebon at different concentrations. WT and YAC128 MSN at 14 DIV were exposed to 250 μM glutamate for 7 h, fixed, permeabilized and analyzed by TUNEL staining and PI counterstaining. The Dimebon was added 30 min before the application of glutamate. The fraction of TUNEL-positive is plotted against glutamate concentration for WT (open circle) and YAC128 (YAC, filled circles) mice. The data are shown as mean ± SE (n = 6–8 microscopic fields, 100–300 MSN per field). The results in the absence (black symbols) and presence (red symbols) obtained in the presence of 5 μM of Dimebon (A) 10 μM Dimebon (B) and 50 μM Dimebon (C) are compared.
Mentions: To evaluate neuroprotective effects of Dimebon, we performed a series of glutamate toxicity experiments with WT and YAC128 MSN DIV14 cultures. In the absence of glutamate approximately 5–10% of neurons are apoptotic in both wild type (WT) and YAC128 MSN cultures. Following exposure to 250 μM glutamate, the fraction of apoptotic WT MSN is increased to 25–40% and the fraction of apoptotic YAC128 MSN is increased to 55–70% (Table 1). The difference between the glutamate-induced apoptosis of YAC128 and WT MSN is highly significant and constitutes a quantitative basis for the in vitro HD assay we have previously described [12,13,15]. The neuroprotective effects of Dimebon were evaluated at 5 μM, 10 μM and 50 μM concentrations using the in vitro HD assay (Table 1, Fig 5). In these experiments, Dimebon was added 30 minutes prior to the exposure of MSN cultures to glutamate. We found that 5 μM and 10 μM Dimebon had no significant effects on the glutamate-induced apoptosis of YAC128 MSN (Table 1, Figs 5A, B). At 50 μM concentration, Dimebon showed significant protective effects in the in vitro HD assay (Table 1, Fig 5C).

Bottom Line: Lower concentrations of Dimebon (5 muM and 10 muM) did not stabilize glutamate-induced Ca2+ signals and did not exert neuroprotective effects in experiments with YAC128 MSN.Dimebon also had significant effect on a number of additional receptors.Our results suggest that Ca2+ and mitochondria stabilizing effects may, in part, be responsible for beneficial clinical effects of Dimebon.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physiology, UT Southwestern Medical Center at Dallas, TX 75390, USA. Ilya.Bezprozvanny@UTSouthwestern.edu.

ABSTRACT

Background: Dimebon is an antihistamine compound with a long history of clinical use in Russia. Recently, Dimebon has been proposed to be useful for treating neurodegenerative disorders. It has demonstrated efficacy in phase II Alzheimer's disease (AD) and Huntington's disease (HD) clinical trials. The mechanisms responsible for the beneficial actions of Dimebon in AD and HD remain unclear. It has been suggested that Dimebon may act by blocking NMDA receptors or voltage-gated Ca2+ channels and by preventing mitochondrial permeability pore transition.

Results: We evaluated the effects of Dimebon in experiments with primary striatal neuronal cultures (MSN) from wild type (WT) mice and YAC128 HD transgenic mice. We found that Dimebon acts as an inhibitor of NMDA receptors (IC50 = 10 muM) and voltage-gated calcium channels (IC50 = 50 muM) in WT and YAC128 MSN. We further found that application of 50 muM Dimebon stabilized glutamate-induced Ca2+ signals in YAC128 MSN and protected cultured YAC128 MSN from glutamate-induced apoptosis. Lower concentrations of Dimebon (5 muM and 10 muM) did not stabilize glutamate-induced Ca2+ signals and did not exert neuroprotective effects in experiments with YAC128 MSN. Evaluation of Dimebon against a set of biochemical targets indicated that Dimebon inhibits alpha-Adrenergic receptors (alpha1A, alpha1B, alpha1D, and alpha2A), Histamine H1 and H2 receptors and Serotonin 5-HT2c, 5-HT5A, 5-HT6 receptors with high affinity. Dimebon also had significant effect on a number of additional receptors.

Conclusion: Our results suggest that Ca2+ and mitochondria stabilizing effects may, in part, be responsible for beneficial clinical effects of Dimebon. However, the high concentrations of Dimebon required to achieve Ca2+ stabilizing and neuroprotective effects in our in vitro studies (50 muM) indicate that properties of Dimebon as cognitive enhancer are most likely due to potent inhibition of H1 histamine receptors. It is also possible that Dimebon acts on novel high affinity targets not present in cultured MSN preparation. Unbiased evaluation of Dimebon against a set of biochemical targets indicated that Dimebon efficiently inhibited a number of additional receptors. Potential interactions with these receptors need to be considered in interpretation of results obtained with Dimebon in clinical trials.

No MeSH data available.


Related in: MedlinePlus