Evaluation of anti-amnesic effect of Conyza bonariensis in rats.

OBJECTIVE: Conyza bonariensis is an ornamental medicinal weed. This experiment was planned to explore the outcome of petroleum ether extract of C. bonariensis (PECB) leaves on scopolamine-induced amnesia in rats. MATERIALS AND METHODS: For impairing memory, 0.4 mg/kg (i. p.) of scopolamine was given. Fifty to 200 mg/kg of PECB was fed orally to rats and 3 mg/kg (i. p.) of tacrine was given as a standard drug. Anti-amnesic property was evaluated in Barnes maze using ANY-maze software. Following a behavioral study, acetylcholinesterase (AChE), ß-amyloid1-41, antioxidant enzymes, and cytokine levels were measured. Furthermore, reverse transcription-polymerase chain reaction was done for expression of the marker genes such as AChE, Nrf2, NF-κB, PP2A, and HO-1, whereas BDNF, TrkB, caspase-3, and Bax were measured by Western blotting. RESULTS: PECB and tacrine significantly improved memory dysfunction by decreasing escape latency in Barnes maze. At the highest dose, treatment with PECB altered the scopolamine-induced hyperactivation of AChE and ß-amyloid1-41 activity. PECB elevated the levels of superoxide dismutase, glutathione, and catalase and decreased lipid peroxidation and nitric oxide dose dependently. PECB attenuated scopolamine-induced increase of tumor necrosis factor-α and interleukin (IL)-1ß concentrations in the hippocampus with reversed diminished IL-10 level toward normal in the brain. Nrf2, HO-1, PP2A, BDNF, and TrkB were significantly upregulated with downregulation of AChE, NF-κB, Tau, Bax, and caspase-3. Different components such as beta-amyrin and alpha-amyrin were isolated from leaves of the plant. CONCLUSION: The results indicated that PECB might be a potential curative drug for the treatment of cognitive impairment.

Combined Therapy for Alzheimer's Disease: Tacrine and PAMAM Dendrimers Co-Administration Reduces the Side Effects of the Drug without Modifying its Activity.

Alzheimer's disease has become a public health priority, so an investigation of new therapies is required. Tacrine (TAC) was licensed for treatments; however, its oral administration caused hepatotoxicity, so it is essential to reduce the side effects. PAMAM dendrimer generation 4.0 and 4.5 (DG4.0 and DG4.5) can be used as drug delivery systems and as nanodrugs per se. Our work aims to propose a combined therapy based on TAC and PAMAM dendrimer co-administration. TAC and dendrimer interactions were studied by in vitro drug release, drug stability, and FTIR. The toxicity profile of co-administration was evaluated in human red blood cells, in Neuro-2a cell culture, and in zebrafish larvae. Also, the anti-acetylcholinesterase activity was studied in cell culture. It was possible to obtain DG4.0-TAC and DG4.5-TAC suspensions, without reducing the drug solubility and stability. FTIR and in vitro release studies confirmed that interaction between TAC and DG4.5 was of the electrostatic type. No toxicity effects on human red blood cells were observed, whereas the co-administration with DG4.5 reduced cytotoxicity of TAC on the Neuro-2a cell line. Moreover, in vivo co-administration of both DG4.0-TAC and DG4.5-TAC reduced the morphological and hepatotoxic effects of TAC in zebrafish larvae. The reduction of TAC toxicity was not accompanied by a reduction in its activity since the anti-acetylcholinesterase activity remains when it is co-administrated with dendrimers. In conclusion, the co-administration of TAC with both DG4.0 and DG4.5 is a novel therapy since it was less-toxic, was more biocompatible, and has the same effectiveness than the free drug. Graphical abstract.

Large-scale in silico identification of drugs exerting sex-specific effects in the heart.

BACKGROUND: Major differences exist between men and women in both physiology and pathophysiology. Dissecting the underlying processes and contributing mechanisms of sex differences in health and disease represents a crucial step towards precision medicine. Considering the significant differences between men and women in the response to pharmacotherapies, our aim was to develop an in silico model able to predict sex-specific drug responses in a large-scale. METHODS: For this purpose, we focused on cardiovascular effects because of their high morbidity and mortality. Our model predicted several drugs (including acebutolol and tacrine) with significant differences in the heart between men and women. To validate the sex-specific drug responses identified by our model, acebutolol was selected to lower blood pressure in spontaneous hypertensive rats (SHR), tacrine was used to assess cardiac injury in mice and metformin as control for a non-sex-specific response. RESULTS: As our model predicted, acebutolol exhibited a stronger decrease in heart rate and blood pressure in female than male SHRs. Tacrine lowered heart rate in male but not in female mice, induced higher plasma cTNI level and increased cardiac superoxide (DHE staining) generation in female than male mice, indicating stronger cardiac toxicity in female than male mice. To validate our model in humans, we employed two Chinese cohorts, which showed that among patients taking a beta-receptor blocker (metoprolol), women reached significantly lower diastolic blood pressure than men. CONCLUSIONS: We conclude that our in silico model could be translated into clinical practice to predict sex-specific drug responses, thereby contributing towards a more appropriate medical care for both men and women.

Tacrine-propargylamine derivatives with improved acetylcholinesterase inhibitory activity and lower hepatotoxicity as a potential lead compound for the treatment of Alzheimer's disease.

A series of tacrine-propargylamine derivatives were synthesised and evaluated as possible anti-Alzheimer's disease (AD) agents. Among these derivatives, compounds 3a and 3b exhibited superior activities and a favourable balance of AChE and BuChE activities (3a: IC50 values of 51.3 and 77.6 nM; 3b: IC50 values of 11.2 and 83.5 nM). Compounds 3a and 3b also exhibited increased hAChE inhibitory activity compared with tacrine by approximately 5- and 28-fold, respectively, and low neurotoxicity. Importantly, these compounds also had lower hepatotoxicity than tacrine. Based on these results, compounds 3a and 3b could be considered as potential lead compounds for the treatment of AD and other AChE related diseases, such as schizophrenia, glaucoma and myasthenia gravis.

Multifunctional tacrine-trolox hybrids for the treatment of Alzheimer's disease with cholinergic, antioxidant, neuroprotective and hepatoprotective properties.

Combining tacrine with trolox in a single molecule, novel multifunctional hybrids have been designed and synthesized. All these hybrids showed ChE inhibitory activity in nanomolar range and strong antioxidant activity close to the parent compound trolox. Among them, compound 6d was the most potent inhibitor against AChE (IC50 value of 9.8 nM for eeAChE and 23.5 nM for hAChE), and it was also a strong inhibitor to BuChE (IC50 value of 22.2 nM for eqBuChE and 20.5 nM for hBuChE). Molecular modeling and kinetic studies suggested that 6d was a mixed-type inhibitor, binding simultaneously to CAS and PAS of AChE. In vivo hepatotoxicity assays indicated that 6d was much less toxic than tacrine. In addition, it showed neuroprotective effect and good ability to penetrate the BBB. Overall, all these results highlighted 6d a promising multifunctional agent for AD treatment.

Effects of cabergoline and rotigotine on tacrine-induced tremulous jaw movements in rats.

OBJECTIVES: We examined the effects of two dopamine agonists, cabergoline and rotigotine, on tacrine-induced tremor and c-Fos expression in rats. METHODS: Rats received intraperitoneal injection of cabergoline (0.5, 1.0, or 5.0mg/kg), rotigotine (1.0, 2.5, or 10.0mg/kg), or vehicle 30min before intraperitoneal injection of tacrine (5.0mg/kg). The number of tremulous jaw movements (TJMs) after tacrine administration was counted for 5min. Animals were sacrificed 2h later under deep anesthesia, and the brain sections were immunostained in order to evaluate the c-Fos expression. RESULTS: Induction of TJMs by tacrine was dose-dependently reduced by pretreatment with cabergoline and rotigotine. The number of c-Fos-positive cells was significantly enhanced in the medial striatum, nucleus accumbens core, and nucleus accumbens shell after tacrine administration, and the enhanced expression of c-Fos in these three regions was significantly attenuated by cabergoline, while rotigotine suppressed c-Fos expression in two regions except the nucleus accumbens core. CONCLUSIONS: These results suggest that tacrine-induced TJMs would be relieved by either cabergoline or rotigotine and that anticholinesterase-induced TJMs and the ameliorating effects of dopamine agonists would relate to neuronal activation in the striatum and nucleus accumbens.

Phellinus linteus mushroom protects against tacrine-induced mitochondrial impairment and oxidative stress in HepG2 cells.

Tacrine (THA) was the first drug licensed for the treatment of Alzheimer's disease. Unfortunately, reversible hepatotoxicity is evident in about 30% of patients and limits its clinical use. The intracellular mechanisms have not yet been elucidated. Phellinus linteus (PL) is a mushroom that has long been used as a folk medicine. In our previous study, we found that PL could decrease the reactive oxygen species (ROS) formation in HepG2 cells. Presently, protective effects of PL on tacrine-induced ROS formation and mitochondria dysfunction were evaluated. The results showed that PL significantly reduced tacrine-induced ROS production, disruption of ΔΨm, 8-OHdG formation in mitochondrial DNA, and cytotoxicity in HepG2 cells. These data suggest that PL could attenuate the cytotoxicity and mitochondria dysfunction induced by tacrine in HepG2 cells. The protection is probably mediated by an antioxidant protective mechanism. Consumption of PL may be a plausible way to prevent tacrine-induced hepatotoxicity.

Cytoprotective effects of phlorofucofuroeckol A isolated from Ecklonia stolonifera against tacrine-treated HepG2 cells.

We have recently reported that phlorofucofuroeckol A isolated from Ecklonia stolonifera showed potential antioxidative and anti-inflammatory properties in LPS-stimulated macrophages. This study aims to investigate the cytoprotective effect of phlorofucofuroeckol A and to characterize its molecular mechanisms using tacrine-treated HepG2 cells. Phlorofucofuroeckol A showed a cytoprotective effect against tacrine-treated HepG2 cells in a dose-dependent manner (EC(50): 5.7±0.5 µM). Increased intracellular reactive oxygen species (ROS) by tacrine were decreased by phlorofucofuroeckol A. The cytotoxicity of tacrine to HepG2 cells was associated with upregulations of Fas and JNK phosphorylation resulted in the caspase activations and apoptosis. Phlorofucofuroeckol A inhibited the phosphorylation of JNK and the expression of Fas-mediated apoptotic proteins including Fas ligand, cleaved caspase-8, cleaved caspase-3, and poly (ADP-ribose) polymerase. In addition, treatment of phlorofucofuroeckol A regulated the release of cytochrome c from mitochondria to cytosol in a dose-dependent manner in tacrine-treated HepG2 cells. Furthermore, pretreatment of an inhibitor of JNK, SP600125, downregulated Fas and cleaved caspase-3 without change of ROS productions in tacrine-treated HepG2 cells. In conclusion, our study demonstrated that phlorofucofuroeckol A regulates Fas-mediated apoptosis via inhibition of ROS productions and inhibition of JNK phosphorylation in tacrine-treated HepG2 cells.

Tacrine and its analogues impair mitochondrial function and bioenergetics: a lipidomic analysis in rat brain.

Tacrine is an acetylcholinesterase (AChE) inhibitor used as a cognitive enhancer in the treatment of Alzheimer's disease (AD). However, its low therapeutic efficiency and a high incidence of side effects have limited its clinical use. In this study, the molecular mechanisms underlying the impact on brain activity of tacrine and two novel tacrine analogues (T1, T2) were approached by focusing on three aspects: (i) their effects on brain cholinesterase activity; (ii) perturbations on electron transport chain enzymes activities of non-synaptic brain mitochondria; and (iii) the role of mitochondrial lipidome changes induced by these compounds on mitochondrial bioenergetics. Brain effects were evaluated 18 h after the administration of a single dose (75.6 µmol/kg) of tacrine or tacrine analogues. The three compounds promoted a significant reduction in brain AChE and butyrylcholinesterase (BuChE) activities. Additionally, tacrine was shown to be more efficient in brain AChE inhibition than T2 tacrine analogue and less active than T1 tacrine analogue, whereas BuChE inhibition followed the order: T1 > T2 > tacrine. The studies using non-synaptic brain mitochondria show that all the compounds studied disturbed brain mitochondrial bioenergetics mainly via the inhibition of complex I activity. Furthermore, the activity of complex IV is also affected by tacrine and T1 treatments while FoF(1) -ATPase is only affected by tacrine. Therefore, the compounds' toxicity as regards brain mitochondria, which follows the order: tacrine >> T1 > T2, does not correlate with their ability to inhibit brain cholinesterase enzymes. Lipidomics approaches show that phosphatidylethanolamine (PE) is the most abundant phospholipids (PL) class in non-synaptic brain mitochondria and cardiolipin (CL) present the greatest diversity of molecular species. Tacrine induced significant perturbations in the mitochondrial PL profile, which were detected by means of changes in the relative abundance of phosphatidylcholine (PC), PE, phosphatidylinositol (PI) and CL and by the presence of oxidized phosphatidylserines. Additionally, in both the T1 and T2 groups, the lipid content and molecular composition of brain mitochondria PL are perturbed to a lesser extent than in the tacrine group. Abnormalities in CL content and the amount of oxidized phosphatidylserines were associated with significant reductions in mitochondrial enzymes activities, mainly complex I. These results indicate that tacrine and its analogues impair mitochondrial function and bioenergetics, thus compromising the activity of brain cells.

Cognitive dysfunctions induced by a cholinergic blockade and Aß 25-35 peptide are attenuated by salvianolic acid B.

Alzheimer's disease (AD) is a neurodegenerative disorder associated with progressive cognitive and memory loss and neuronal cell death. Current therapeutic strategies for AD are very limited; thus, traditional herbal medicines or their active constituents receive much attention. The aim of this study was to investigate the cognitive enhancing effects of salvianolic acid B (SalB) isolated from Salvia miltiorrhiza and its ameliorating effects on various drug-induced amnesic models using the passive avoidance, Y-maze, and Morris water maze tasks. Drug-induced amnesia was induced by administering scopolamine, diazepam, muscimol, or amyloid-ß (Aß)(25-35) peptide. SalB (10 mg/kg, p.o.) was found to significantly reverse the cognitive impairments induced by scopolamine (1 mg/kg, i.p.) or Aß(25-35) (10 nmol/5 µl, i.c.v.) injection. This ameliorating effect of SalB was antagonized by the GABA(A) receptor agonists, muscimol or diazepam, respectively. In addition, SalB alone was capable of improving cognitive performances. Furthermore, SalB (100 µM) was found to inhibit GABA-induced outward Cl(-) currents in single hippocampal CA1 neuron. These results suggest that the observed ameliorations of cholinergic dysfunction- or Aß(25-35)-induced memory impairment by SalB were mediated, in part, via the GABAergic neurotransmitter system after a single administration.

Pharmacokinetic and pharmacodynamic properties of cholinesterase inhibitors donepezil, tacrine, and galantamine in aged and young Lister hooded rats.

Physiological alterations that may change pharmacological response accompany aging. Pharmacokinetic/pharmacodynamic properties of cholinesterase inhibitors (ChEIs) used in the treatment of Alzheimer's disease, donepezil, tacrine, and galantamine, were investigated in an aged Lister hooded rat model. Intravenous and oral 6-h blood sampling profiles in old (30 months old) and young (7 months old) rats revealed pharmacokinetic changes similar to those in humans with an approximately 40% increase in C(max) of galantamine and prolonged t(1/2) (1.4-fold) and mean residence time (1.5-fold) of donepezil. Tacrine disposition was maintained with age, and area under the concentration-time curve and clearance in old rats were similar to those in young rats for all drugs tested as was bioavailability. Old rats showed a trend of increased pharmacodynamic sensitivity (<20%) to ChEIs in cholinesterase activity assays, which was attributed to pharmacokinetic effects because a trend of higher blood and brain concentrations was seen in the old rats although brain/blood ratios remained unaffected. Enhanced cholinergic-mediated behaviors such as tremor, hypothermia, salivation, and lacrimation were also observed in the old rats, which could not be accounted for by a similar magnitude of change in pharmacokinetics. A decrease in expression of muscarinic acetylcholine receptor subtype 2 detected in old rat brains was postulated to play a role. Greater age effects in both pharmacokinetics and pharmacodynamics of donepezil and tacrine were seen in previous studies with Fischer 344 rats, indicating a potential risk in overreliance on this rat strain for aging studies.

Assessment of symptomatic and neuroprotective efficacy of Mucuna pruriens seed extract in rodent model of Parkinson's disease.

Mucuna pruriens (MP) has long been used in Indian traditional medicine as support in the treatment of Parkinson's disease. However, no systematic preclinical studies that aimed at evaluating the efficacy of this substance are available to date. This study undertook an extensive evaluation of the antiparkinsonian effects of an extract of MP seeds known to contain, among other components, 12.5% L: -dihydroxyphenylalanine (L: -DOPA), as compared to equivalent doses of L: -DOPA. Moreover, the neuroprotective efficacy of MP and its potential rewarding effects were evaluated. The results obtained reveal how an acute administration of MP extract at a dose of 16 mg/kg (containing 2 mg/kg of L: -DOPA) consistently antagonized the deficit in latency of step initiation and adjusting step induced by a unilateral 6-hydroxydopamine lesion, whereas L: -DOPA was equally effective only at the doses of 6 mg/kg. At the same dosage, MP significantly improved the placement of the forelimb in vibrissae-evoked forelimb placing, suggesting a significant antagonistic activity on both motor and sensory-motor deficits. The effects of MP extract were moreover investigated by means of the turning behavior test and in the induction of abnormal involuntary movements (AIMs) after either acute or subchronic administration. MP extract acutely induced a significantly higher contralateral turning behavior than L: -DOPA (6 mg/kg) when administered at a dose of 48 mg/kg containing 6 mg/kg of L: -DOPA. On subchronic administration, both MP extract (48 mg/kg) and L: -DOPA (6 mg/kg) induced sensitization of contralateral turning behavior; however, L: -DOPA alone induced a concomitant sensitization in AIMs suggesting that the dyskinetic potential of MP is lower than that of L: -DOPA. MP (48 mg/kg) was also effective in antagonizing tremulous jaw movements induced by tacrine, a validated test reproducing parkinsonian tremor. Furthermore, MP induced no compartment preference in the place preference test, indicating the lack of components characterized by rewarding effects in the extract. Finally, in a subchronic mice model of 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine hydrochloride (MPTP)-induced dopamine neuron degeneration, MP extract did not prove capable of preventing either tyrosine hydroxylase decrease induced by MPTP or astroglial or microglial activation as assessed by means of GFAP and CD11b immunohistochemistry, supporting the absence of neuroprotective effects by MP. Characterization MP extract strongly supports its antiparkinsonian activity.

Delayed evacuatory function due to specific smooth muscle reactivity in the gastrointestinal tracts of tacrine-treated rats.

Most of the side effects induced by tacrine are associated with the gastrointestinal (GI) tract. The aim of the study was to analyze the nature of radiographically registered, tacrine-induced changes in evacuatory function, as well as to find a possible correlation with the immediate in vitro action of the drug on smooth muscles from the GI tracts of rats. The tacrine dose we used reliably delayed GI passage: contrast matter was not fully evacuated, predominantly from the stomach and cecum. The delay resulted from changes in tone and peristaltic activity, specific for the various regions of the tract. These changes were associated with a superposing of the responses due to the anticholinesterase and noncholinergic action of tacrine.

Tacrine-induced liver damage: an analysis of 19 candidate genes.

OBJECTIVES: Tacrine, the first acetylcholinesterase inhibitor used in the treatment of Alzheimer's disease, is associated with transaminase elevation in up to 50% of patients. The mechanism of tacrine-induced liver damage is not fully understood, but earlier studies have suggested that genetic factors may play a role. Our aim was to investigate whether single-nucleotide polymorphisms (SNPs) in 19 candidate genes were associated with tacrine-induced liver damage. METHODS: Sixty-nine patients of Caucasian origin treated with tacrine for Alzheimer's disease were investigated by genotyping 241 SNPs in 19 candidate genes potentially related to hepatotoxicity. The association with ABCB4 [which encodes MultiDrug Resistance Protein 3 (MDR3)] was explored in transepithelial transport studies using the ABCB4-transfected pig kidney epithelial cell line (LLC-PK1). RESULTS: The strongest association between alanine aminotransferase levels and three SNPs within ATP-binding cassette, subfamily B (MDR/TAP), member 4 (ABCB4) (uncorrected P=0.0005) was not significant after adjusting for multiple testing. No association was demonstrated with ATP-binding cassette, subfamily B (MDR/TAP), member 1 (ABCB1) or carnitine O-octanoyltransferase (CROT) which are located adjacent to ABCB4. Using the transepithelial transport system we failed to show a difference in tacrine accumulation between ABCB4-transfected and parental cell lines. The association with ABCB4 warrants further testing using either another population and/or functional studies.

Evaluation of centrally acting cholinesterase inhibitor exposures in adults.

BACKGROUND: There are 4 centrally acting cholinesterase inhibitors (CA-ChEI) available in the US: tacrine, galantamine, rivastigmine, and donepezil. Documented clinical experience involving exposure to these agents is limited. The lack of information makes decisions involving excessive or unintended CA-ChEI exposure difficult. OBJECTIVE: To assess the effects, demographics, and outcomes of CA-ChEI exposures reported to US poison centers. METHODS: A retrospective review of the Toxic Exposure Surveillance System of the American Association of Poison Control Centers data of acute and acute-onchronic exposures involving only a CA-ChEI in patients 19 years of age or older with documented medical outcomes from 2000-2005 was performed. RESULTS: There were 1026 records that met criteria for this study. Patients aged 70-89 years made up 73% of reports; 69% of the patients were female. Moderate (197) and major outcomes (20) accounted for 21% of exposures. There were no deaths. Clinical effects that occurred in 5% or more of patients included vomiting (34%), nausea (28%), diarrhea (12%), dizziness/vertigo (9.9%), drowsiness/lethargy (7.7%), diaphoresis (7.4%), tremor (5.2%), and bradycardia (5%). Patients were admitted to the hospital in 19% of all exposures. Of those patients, 42% were admitted to a critical care unit. The majority (65%) of exposures were attributed to unintentional therapeutic error. Patients received at least one form of therapy in 47% of exposures, including intravenous fluid (111), antiemetic (48), atropine (17), benzodiazepine (15), oxygen (14), antihypertensive (4), pralidoxime (4), intubation (3), antihistamine (2), antiarrhythmic (1), anticonvulsant (1), and pacemaker (1). CONCLUSIONS: The majority of patients evaluated in this retrospective study experienced no or mild effect; however, significant or life-threatening effects were observed in a small group of patients and an appreciable number of patients were admitted to a healthcare facility.

The acetylcholinesterase inhibitors for treatment of cognitive and behavioral symptoms in dementia with Lewy bodies.

Dementia with Lewy bodies (DLB) is a common cause of dementia with effects on cognition, mood, behavior, and function. Changes in the acetylcholine system have been reported in brains of patients with DLB, which provides a rationale for trials of acetylcholinesterase inhibitors in DLB. This review includes all English-language publications found via Medline and related to the efficacy and/or safety of these compounds in DLB. Preliminary data suggest that these compounds may be efficacious in DLB and that future randomized clinical trials are strongly needed. Methodological limitations of the existing data include small sample sizes, and the paucity of standardized psychometric measures.

Five-year outcome of cholinergic treatment of Alzheimer's disease: early response predicts prolonged time until nursing home placement, but does not alter life expectancy.

Fifty consecutive outpatients with Alzheimer's disease (AD) received treatment with the cholinesterase inhibitor tacrine in an open longitudinal study. Assessments using Mini-Mental State Examination, Alzheimer's Disease Assessment Scale - cognitive subscale, and a global rating were made at baseline and at 6, 12, 24, 36, 48 and 60 months. Three outcome groups were characterized: responders, unchanged and deteriorated. Additional outcome measures were time until nursing home placement, and mortality rate. At 6 months -75%, at 12 months -42%, at 24 months -20%, and after that 10% of the patients still on medication had improved or remained stable. The mortality rate did not differ between the outcome groups. Response to tacrine treatment at 6 or 12 months was found to predict a prolonged time until nursing home placement. No predictors for a positive treatment response could be identified at baseline.