a(CHEBI:galanthamine)
Surprisingly, however, activation of nAChRs by galantamine or physostigmine was insensitive to blockade by competitive nAChR antagonists, was detected even when the receptors were desensitized by high agonist concentrations, and was inhibited by the monoclonal antibody FK1 (350, 370, 372, 413, 428, 429). PubMed:19126755
Surprisingly, however, activation of nAChRs by galantamine or physostigmine was insensitive to blockade by competitive nAChR antagonists, was detected even when the receptors were desensitized by high agonist concentrations, and was inhibited by the monoclonal antibody FK1 (350, 370, 372, 413, 428, 429). PubMed:19126755
In SHSY5Y cells, RNA interference (RNAi) knockdown of alpha7 enhanced Abeta toxicity (Qi et al., 2007), and alpha7 antagonists, but not alpha4beta2 antagonists, block galantamine protection of cultured rat neurons (Kihara et al., 2004). Donepezil protects cultured rat cortical neurons against Abeta toxicity through both alpha7 and non-alpha7 nAChRs (Takada et al., 2003). It is therefore likely that alpha7 nAChRs are the primary mediators of nicotine neuroprotection, but in some cells, non-alpha7 subtypes are also likely to contribute. PubMed:19293145
Notably, PHA could completely block the Ab-impaired task acquisition and reduce escape-latency to the normal level. Furthermore, the effect of PHA against the Ab-impaired task acquisition could be abolished by the pre-treatment of the a7 nAChR antagonist MLA (p<0.001). It was also noted that blockade of a7 nAChR by MLA in the Gal-treated group resulted in a significant prolongation of the escape-latency on comparing with the Gal group (p<0.001) (Fig. 2). PubMed:25881725
MLA could completely block the PHA-induced spatial memory improvement (p<0.001). Furthermore, the effect of Gal against the Ab-impaired reference memory could be abolished by the pre-treatment of the a7 nAChR antagonist MLA (p<0.001). However, a7 nAChR blockage in the Gal group has a lesser effect on reference memory in comparison of blockage of that receptor in the PHA group (p<0.05) (Fig. 4). PubMed:25881725
Inter-group analysis showed that the protein level decreased by pretreatment with selective a7 nAChR antagonist MLA (p<0.001). PHA and Gal prevent receptor destroying in AD animals, but this effect is completely abolished by MLA (p<0.001) (Fig. 9). The groups showed results in the cortex similar to those observed in the hippocampus (data not shown). PubMed:25881725
An alternative means to increase nicotinic functions in the brain is to sensitize the nAChRs to activation by the endogenous agonist(s) using the so-called nicotinic allosteric potentiating ligands (APLs), which include drugs such as physostigmine and galantamine, a drug currently approved for the treatment of AD. PubMed:19126755
In the early 1990s, galantamine, an alkaloid originally extracted from the bulbs and flowers of the wild Caucasian snowdrop Galanthus nivalis and other related Amaryllidacea species, was found to act like physostigmine on muscle and neuronal nAChRs (370, 372). PubMed:19126755
Surprisingly, however, activation of nAChRs by galantamine or physostigmine was insensitive to blockade by competitive nAChR antagonists, was detected even when the receptors were desensitized by high agonist concentrations, and was inhibited by the monoclonal antibody FK1 (350, 370, 372, 413, 428, 429). PubMed:19126755
The nicotinic APL action of galantamine appears to be an important determinant of its clinical effectiveness (reviewed in Refs. 98, 291, 371). Acting primarily as a nicotinic APL, galantamine improves synaptic transmission and decreases neurodegeneration, two effects essential for its cognitive-enhancing properties (40, 108, 241, 409, 521). PubMed:19126755
The nicotinic APL action of galantamine appears to be an important determinant of its clinical effectiveness (reviewed in Refs. 98, 291, 371). Acting primarily as a nicotinic APL, galantamine improves synaptic transmission and decreases neurodegeneration, two effects essential for its cognitive-enhancing properties (40, 108, 241, 409, 521). PubMed:19126755
The nicotinic APL action of galantamine appears to be an important determinant of its clinical effectiveness (reviewed in Refs. 98, 291, 371). Acting primarily as a nicotinic APL, galantamine improves synaptic transmission and decreases neurodegeneration, two effects essential for its cognitive-enhancing properties (40, 108, 241, 409, 521). PubMed:19126755
Drugs currently approved to treat mild-to-moderate AD, including galantamine, donepezil, and rivastigmine, all inhibit AChE, the enzyme that hydrolyzes ACh (462). PubMed:19126755
Current licensed pharmacological treatments for AD consist largely of three acetylcholinesterase (AChE) inhibitors: rivastigmine, galantamine, and donepezil (Aguglia et al., 2004; Ritchie et al., 2004), although memantine, a blocker of L-glutamate receptors of the Nmethyl- D-aspartate (NMDA) subtype, is also deployed in late stages of the disease PubMed:19293145
In SHSY5Y cells, RNA interference (RNAi) knockdown of alpha7 enhanced Abeta toxicity (Qi et al., 2007), and alpha7 antagonists, but not alpha4beta2 antagonists, block galantamine protection of cultured rat neurons (Kihara et al., 2004). Donepezil protects cultured rat cortical neurons against Abeta toxicity through both alpha7 and non-alpha7 nAChRs (Takada et al., 2003). It is therefore likely that alpha7 nAChRs are the primary mediators of nicotine neuroprotection, but in some cells, non-alpha7 subtypes are also likely to contribute. PubMed:19293145
The AD therapeutic AChE inhibitors donepezil, galantamine, and tacrine increase BCL2 expression when applied to cultured neuronal cells (Arias et al., 2004; Takada-Takatori et al., 2006). In these cells, nicotine promotes cell survival and causes the phosphorylation of the proapoptotic protein Bcl2-associated X protein (BAX), through the PI3K/AKT pathway, reducing the movement of BAX from the cytosol to the mitochondria and inhibiting its apoptotic activity (Xin and Deng, 2005). PubMed:19293145
Nicotine stimulates the secretion of betaAPP, which is trophic and neuroprotective against Abeta, from PC12 cells through an alpha7 and calcium-dependent pathway (Kim et al., 1997) as well as increasing the secretion of soluble APP and lowering the Abeta-containing sAPP-gamma in rats (Lahiri et al., 2002), again through nAChR-dependent mechanisms. Galantamine, a nAChR potentiator and AChE inhibitor, also increases the secretion of sAPP from human SH-SY5Y neuroblastoma cells (Lenzken et al., 2007) through the activation of nAChRs. It therefore seems that activation of nAChRs shifts the balance of APP processing away from beta-amyloidogenic to soluble APP production. PubMed:19293145
The most commonly prescribed treatments for AD are acetylcholinesterase inhibitors, which decrease the hydrolysis rate of ACh and, thereby, enhance cholinergic signaling. One such drug, galantamine (Reminyl), also potentiates nAChRs (66). PubMed:17009926
In a double-blind study designed to assess patients survival with mild to moderately severe AD, the long-term treatment (2 years) with galantamine significantly reduced mortality and cognition decline, besides improving daily live activities in mild to moderate AD patients PubMed:26813123
In a double-blind study designed to assess patients survival with mild to moderately severe AD, the long-term treatment (2 years) with galantamine significantly reduced mortality and cognition decline, besides improving daily live activities in mild to moderate AD patients PubMed:26813123
It is likely that the therapeutic benefit of cholinesterase inhibitors occurs at least in part through activation of the nAChRs, by the direct action of increased levels and/or through a direct activation of the allosteric site on the nAChR (Maelicke et al 1995, 2000) PubMed:11230871
Moreover in Ab-received mice, treatment with PHA and Gal improved the acquisition performance on comparing with the normal saline group (p<0.001) PubMed:25881725
Moreover in Ab-received mice, treatment with PHA and Gal improved the acquisition performance on comparing with the normal saline group (p<0.001) PubMed:25881725
The analysis also showed significant enhancing effects of PHA and Gal on the time spent in the target quadrant on comparing with the normal saline in AD mice (p<0.001). Also, in comparison with the control group, PHA-treated AD animals did not have a significant difference (p>0.05) on the time spent in the target quadrant, but in the Gal group it was significantly lower (p<0.001) (Fig. 3). PubMed:25881725
Also, no alterations in the expression of a7 nAChR mRNA were observed in pretreatment with normal saline or MLA in PHA- or Gal-treated groups (p>0.05). In the same way, the pattern of mRNA expression in the cortex (data not shown) was similar to the hippocampus (Fig. 7). PubMed:25881725
The analysis also showed significant effects of PHA and Gal on the protein levels on comparing with normal saline in AD mice (p<0.001). Moreover, Gal could not completely protect the a7 nAChR protein level in AD animals. This group has a lesser a7 nAChR protein level in comparison with the control group (p<0.001) (Fig. 8). The groups showed results in the cortex similar to those observed in the hippocampus (data not shown) PubMed:25881725
Inter-group analysis showed that the protein level decreased by pretreatment with selective a7 nAChR antagonist MLA (p<0.001). PHA and Gal prevent receptor destroying in AD animals, but this effect is completely abolished by MLA (p<0.001) (Fig. 9). The groups showed results in the cortex similar to those observed in the hippocampus (data not shown). PubMed:25881725
Two compounds that are currently in clinical use might have direct effects on the alpha7 nAChR. The anticholinesterase inhibitor galantamine has modulatory effects on alpha7 nAChR and was reportedly beneficial for patients with schizophrenia in a case study184 PubMed:19721446
Two compounds that are currently in clinical use might have direct effects on the alpha7 nAChR. The anticholinesterase inhibitor galantamine has modulatory effects on alpha7 nAChR and was reportedly beneficial for patients with schizophrenia in a case study184 PubMed:19721446
Only five drugs (Figure 1) have been approved by the U. S. Food and Drug Administration (FDA), four of which are cholinesterase inhibitors (tacrine, 15 donepezil, 16 rivastigmine 17 and galantamine 18 ) and one of which is a N-methyl-D-aspartate (NMDA) receptor antagonist (memantine 19 ). a N-methyl-D-aspartate (NMDA) receptor antagonist (memantine 19 ). These pharmacological agents have had limited effect in improving the cognitive function of AD patients and do not slow the progression of the disease. Clinical studies have shown that these agents temporarily stabilize cognitive impairment and help to maintain global function, delaying the need for patient palliative care by only a few month PubMed:30444369
Only five drugs (Figure 1) have been approved by the U. S. Food and Drug Administration (FDA), four of which are cholinesterase inhibitors (tacrine, 15 donepezil, 16 rivastigmine 17 and galantamine 18 ) and one of which is a N-methyl-D-aspartate (NMDA) receptor antagonist (memantine 19 ). a N-methyl-D-aspartate (NMDA) receptor antagonist (memantine 19 ). These pharmacological agents have had limited effect in improving the cognitive function of AD patients and do not slow the progression of the disease. Clinical studies have shown that these agents temporarily stabilize cognitive impairment and help to maintain global function, delaying the need for patient palliative care by only a few month PubMed:30444369
It inhibits AChE competitively and reversibly, causing elevated cerebral concen-trations of ACh, and thus, enhancing cholinergic activity. PubMed:29179999
It inhibits AChE competitively and reversibly, causing elevated cerebral concen-trations of ACh, and thus, enhancing cholinergic activity. PubMed:29179999
Besides, galantamine allosterically interacted with nicotinic ACh receptors to increase the agonistic activity of these receptors and amplified the ACh reaction through stimulating ACh release [165–167]. PubMed:29179999
The protective effects of galantamine in brain microvascular endothelial cells were mediated via protective gene, heme oxygenase-1 induction through NF-B activation [168] PubMed:29179999
The protective effects of galantamine in brain microvascular endothelial cells were mediated via protective gene, heme oxygenase-1 induction through NF-B activation [168] PubMed:29179999
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