Is anti-cholinesterase therapy of Alzheimer's disease delaying progression?

CSF Cholinergic Index, a New Biomeasure of Treatment Effect in Patients With Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive disease with early degeneration of the central cholinergic neurons. Currently, three of four AD drugs act by inhibiting the acetylcholine (ACh) degrading enzyme, acetylcholinesterase (AChE). Efficacy of these drugs depends on available amount of ACh, which is biosynthesized by choline acetyltransferase (ChAT). We investigated whether treatment with a cholinesterase-inhibitor, galantamine, alters the relative levels of AChE to ChAT in cerebrospinal fluid (CSF) and whether levels of these CSF biomarkers correlate with in vivo AChE activity and nicotinic binding sites in the brain assessed by positron emission tomography (PET). Protein concentrations and activities of ChAT and AChE were measured in CSF of 18 patients with mild AD prior to and after 3 months of treatment with galantamine (n = 12) or placebo (n = 6), followed by nine additional months of galantamine treatment in all patients. A Cholinergic index was defined as the ratio of ChAT to AChE in CSF and was evaluated in relation to the in vivo AChE activity, the nicotinic binding sites and different measures of cognition. Besides an expected inhibition of AChE activity, galantamine treatment was accompanied by a mild increase in CSF ChAT activity. Thereby, the Cholinergic index was significantly increased in the Galantamine group (60% ± 14) after 3 months compared to baseline (p < 0.0023) or (p < 0.0004). This index remained high in the Galantamine group compared to baseline (54% ± 11) at 12 months follow-up, while it showed an increase in the Placebo group when they switched to active galantamine treatment (44% ± 14 vs. baseline, 61% ± 14 vs. 3 months, all p-values < 0.05). Furthermore, the in vivo brain AChE activity (assessed by PET) correlated with the CSF Cholinergic index at 12 months (r = 0.98, p < 0.001). The CSF Cholinergic index also correlated with ADAS-Cog and some other neuropsychological tests at 12 months. This is the first study assessing a CSF Cholinergic index in relation to treatment with a cholinesterase inhibitor. The treatment-specific increase in CSF ChAT activity suggests that cholinesterase-inhibitors may also increase the ACh-biosynthesis capacity in the patients. Additional studies are warranted to evaluate the utility of the CSF Cholinergic index as a biomeasure of therapeutic effect in AD.

The cholinergic system in the pathophysiology and treatment of Alzheimer's disease

Cholinergic synapses are ubiquitous in the human central nervous system. Their high density in the thalamus, striatum, limbic system, and neocortex suggest that cholinergic transmission is likely to be critically important for memory, learning, attention and other higher brain functions. Several lines of research suggest additional roles for cholinergic systems in overall brain homeostasis and plasticity. As such, the brain's cholinergic system occupies a central role in ongoing research related to normal cognition and age-related cognitive decline, including dementias such as Alzheimer's disease. The cholinergic hypothesis of Alzheimer's disease centres on the progressive loss of limbic and neocortical cholinergic innervation. Neurofibrillary degeneration in the basal forebrain is believed to be the primary cause for the dysfunction and death of forebrain cholinergic neurons, giving rise to a widespread presynaptic cholinergic denervation. Cholinesterase inhibitors increase the availability of acetylcholine at synapses in the brain and are one of the few drug therapies that have been proven clinically useful in the treatment of Alzheimer's disease dementia, thus validating the cholinergic system as an important therapeutic target in the disease. This review includes an overview of the role of the cholinergic system in cognition and an updated understanding of how cholinergic deficits in Alzheimer's disease interact with other aspects of disease pathophysiology, including plaques composed of amyloid-β proteins. This review also documents the benefits of cholinergic therapies at various stages of Alzheimer's disease and during long-term follow-up as visualized in novel imaging studies. The weight of the evidence supports the continued value of cholinergic drugs as a standard, cornerstone pharmacological approach in Alzheimer's disease, particularly as we look ahead to future combination therapies that address symptoms as well as disease progression.

Increased quinolinic acid in peripheral mononuclear cells in Alzheimer's dementia

The role of monocytes and macrophages in the pathogenesis of neurodegenerative disorders such as Alzheimer's disease (AD) is poorly understood. Recently, we have shown that the number of CD14+ monocytes remained constant during healthy aging and in AD patients. Although only little is known about the function of activated macrophages and microglia in AD, one important mechanism involves the expression of quinolinic acid (QUIN), an endogenous N-methyl-D-aspartate glutamate receptor (NMDA-R) agonist which mediates excitotoxicity especially in the hippocampus. We used immunofluorescence stainings of PBMCs to determine the expression of quinolinic acid (QUIN) and the MHC class II molecule HLA-DR in peripheral monocytic cells in 51 healthy volunteers aged 22-87 years and 43 patients with AD at diagnosis (0 weeks) and during the course of rivastigmine treatment at 0.25 year (12 weeks), 0.5 year (30 weeks), 1 year, and 1.5 years. The number of QUIN+ HLA-DR+ cells rises in healthy persons aged 30-40 years compared to persons aged 60-70 years, indicating that this cell population increases with aging. AD patients at diagnosis had an increased frequency of QUIN+, QUIN+ HLA-DR+, and QUIN+ HLA-DR+/HLA-DR+ cells compared to aged-matched controls. These cell populations remained increased in AD for up to one year after initiation of treatment with rivastigmine; no alterations were detected in aged healthy persons. We conclude that the expression of the neurotoxic agent QUIN is increased in peripheral monocytes from AD patients. These cells could enter the brain and contribute to excitotoxicity.

Does Anticholinergic Activity Affect Neuropathology? Implication of Neuroinflammation in Alzheimer's Disease

One characteristic neuropathological feature of Alzheimer's disease (AD) is profound neuronal loss in the nucleus basalis of Meynert, the major source of cholinergic innervation of the cerebral cortex. Clinically, anticholinergic activity causes a decline in cognitive function and increases the risk of dementia, thus possibly enhancing AD pathologies and neurodegeneration. Until now there has been insufficient human neuropathological data to support this conclusion. Experimental studies using a tauopathy mouse model demonstrated anticholinergics enhanced tau pathology and neurodegeneration corresponding to central anticholinergic activity. Additionally, donepezil, a cholinesterase inhibitor, ameliorated tau pathology and neurodegeneration in the same mouse model. These results indicate the balance between cholinergic and anticholinergic activities might affect neurodegeneration. Importantly, neurodegeneration observed in the mouse model seemed to correspond to the distribution of microglial activation, and it was reported that neuroinflammation plays an important role in the pathomechanism of AD, while anticholinergic activity augments inflammatory responses. Moreover, some studies indicated β-amyloid itself depletes cholinergic function similarly to anticholinergic activity. Thus, anticholinergic activity might initiate and/or accelerate AD pathology. Limited human data support the conclusion that anticholinergic activity enhances AD-related neuropathology and neurodegeneration. However, experimental data from a tauopathy mouse model indicated anticholinergic activity might enhance neurodegeneration with enhanced neuroinflammation including microglial activation.

Maintenance treatment of depression in old age: a randomized, double-blind, placebo-controlled evaluation of the efficacy and safety of donepezil combined with antidepressant pharmacotherapy

CONTEXT

Cognitive impairment in late-life depression is a core feature of the illness.

OBJECTIVE

To test whether donepezil hydrochloride and antidepressant therapy is superior to placebo and antidepressant therapy in improving cognitive performance and instrumental activities of daily living and in reducing recurrences of depression over 2 years of maintenance treatment.

DESIGN

Randomized, double-blind, placebo-controlled maintenance trial.

SETTING

University clinic.

PARTICIPANTS

One hundred thirty older adults aged 65 years and older with recently remitted major depression.

INTERVENTIONS

Random assignment to maintenance antidepressant pharmacotherapy and donepezil or to maintenance antidepressant pharmacotherapy and placebo.

MAIN OUTCOME MEASURES

Global neuropsychological performance, cognitive instrumental activities of daily living, and recurrent depression.

RESULTS

Donepezil and antidepressant therapy temporarily improved global cognition (treatment × time interaction, F₂,₂₁₆ = 3.78; P = .03), but effect sizes were small (Cohen d = 0.27, group difference at 1 year). A marginal benefit to cognitive instrumental activities of daily living was also observed (treatment × time interaction, F₂,₁₃₇ = 2.94; P = .06). The donepezil group was more likely than the placebo group to experience recurrent major depression (35% [95% confidence interval {CI}, 24%-46%] vs 19% [95% CI, 9%-29%], respectively; log-rank χ² = 3.97; P = .05; hazard ratio = 2.09 [95% CI, 1.00-4.41]). Post hoc subgroup analyses showed that of 57 participants with mild cognitive impairment, 3 of 30 participants (10% [95% CI, 0%-21%]) receiving donepezil and 9 of 27 participants (33% [95% CI, 16%-51%]) receiving placebo had a conversion to dementia over 2 years (Fisher exact test, P = .05). The mild cognitive impairment subgroup had recurrence rates of major depression of 44% with donepezil vs 12% with placebo (likelihood ratio = 4.91; P = .03). The subgroup with normal cognition (n = 73) showed no benefit with donepezil and no increase in recurrence of major depression.

CONCLUSIONS

Whether a cholinesterase inhibitor should be used as augmentation in the maintenance treatment of late-life depression depends on a careful weighing of risks and benefits in those with mild cognitive impairment. In cognitively intact patients, donepezil appears to have no clear benefit for preventing progression to mild cognitive impairment or dementia or for preventing recurrence of depression.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00177671.

Comparison of persistence rates of acetylcholine-esterase inhibitors in a state Medicaid program

OBJECTIVE

To compare levels of persistency between cholinesterase inhibitors (ChEIs) among a Medicaid patient population of older adults.

METHODS

Survival analysis was used to assess differences in discontinuation between ChEIs (donepezil versus rivastigmine and galantamine), and for difference in patient gender, age, race, and care setting.

RESULTS

Rates of discontinuation increased from 42.7% (95% CI = 39.9-45.5) at 12 months to 84.8% (95% CI = 82.3-87.3) at 24 months. In multivariate models, no significant difference in discontinuation existed prior to 365 days. However, patients dispensed donepezil were less likely to discontinue as compared with users of the other two ChEIs after the first year (RR = 0.70; CI = 0.499-0.983; p < 0.04). Patients of white race were less likely to discontinue (RR = 0.549; 95% CI = 0.43-0.82; p = 0.0015), while gender, care setting, and age were not associated with discontinuation.

CONCLUSIONS

One-year persistence rates were similar between different ChEIs. Among patients persisting with ChEI medication for at least 12 months, users of donepezil were slightly more likely to continue to persist at 24 months. Nearly half of patients failed to persist with ChEI therapy for at least 12 months. Our findings underscore the limitations of the ChEI medications and the urgent need for effective and tolerable therapeutic options for patients having dementia.

Alzheimer patients treated with an AchE inhibitor show higher IL-4 and lower IL-1 beta levels and expression in peripheral blood mononuclear cells

The study evaluates the expression and production of cytokines in peripheral blood mononuclear cells of patients with Alzheimer disease treated or not treated with acetylcholinesterase inhibitor, which enhances neuronal transmission. Cytokines associated with brain inflammation such as interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha have been implicated in the regulation of amyloid peptide protein synthesis. The anti-inflammatory cytokine, IL-4, may suppress the activity of IL-1beta. Patients were assessed for clinical and immunologic features at baseline and after 1 month of treatment with Donepezil, an acetylcholinesterase inhibitor. Peripheral blood mononuclear cells were cultured with and without phytohemagglutinin stimulation. IL-1beta and IL-4 levels were measured by enzyme-linked immunosorbent assay. Reverse transcriptase-polymerase chain reaction was used to determine the expression of cytokines in peripheral mononuclear cells. Compared with untreated patients and healthy control subjects, IL-1beta levels and expression decreased in Alzheimer disease patients treated with Donepezil (P < 0.001). In contrast, IL-4 levels and expression were significantly higher in Alzheimer patients treated with the acetylcholinesterase inhibitor. This increment was observed in both unstimulated and phytohemagglutinin-stimulated peripheral blood mononuclear cells.

Donepezil use in US nursing homes

BACKGROUND AND AIMS

Donepezil is effective in slowing the progression of Alzheimer's disease (AD). No data are available on the patterns of donepezil use among nursing home residents. We estimate the prevalence of the use of donepezil and the frequency of its initiation, and describe the demographic and clinical characteristics of residents taking this drug.

METHODS

We used data from the Minimum Data Set (N=174659). We compared users and non-users of donepezil with respect to demographic, clinical and functional variables. We estimated the 6-month incidence of donepezil use. All analyses were stratified by the admission status of the residents (newly admitted/long-stay).

RESULTS

Among those meeting the manufacturer's indication for donepezil (mild to moderate AD), the prevalence of use was 30% among newly admitted, and 19% among long-stay residents. About 3% of residents not meeting the manufacturer's indication for donepezil were taking it. The proportion of people with AD still taking donepezil after six months was 44.8% among newly admitted, and 59.5% among long-stay residents. Donepezil use was associated with cognitive impairment, behavioral problems and the use of psychotropic drugs including anti-psychotics and anti-depressants. In people without a diagnosis of AD, there seems to be an association between behavioral problems and use of donepezil.

CONCLUSIONS

Donepezil is frequently used in the nursing home setting for the management of AD. Off-label use of donepezil is also relatively frequent. This may reflect an empirical perception of effectiveness on outcomes different from cognitive impairment, such as behavioral problems, although evidence is lacking.

The protective effect of ganstigmine against amyloid beta 25-35 neurotoxicity on chicken cortical neurons is independent from the cholinesterase inhibition

Ganstigmine (CHF2819), a novel genserine derived acetylcholinesterase inhibitor and its enantiomer CHF3360 have been investigated for neuroprotective activity in two different in vitro assay systems using isolated cortical neurons from 9 day old chicken embryos. In the first in vitro model cells were lesioned by growth factor deprivation for 8 days achieved by reduced serum supplementation (2%) to the tissue culture medium. In the second lesion model neurodegeneration due to the addition of pre-aggregated beta-amyloid(25-35) has been achieved. Neuronal viability of treated neurons evaluated with the 3-(4,5-dimethylthiazol-2-yl)-2,5,diphenyl tetrazolium bromid reduction assay was compared to that of untreated control cells. In a dose range between 1.0 and 10.0 microM both compounds significantly prevent progressive neuronal cell death due to growth factor deprivation. Furthermore Ganstigmine and its enantiomer in concentrations between 0.1 and 3 microM also significantly decrease neurodegeneration achieved by the addition of beta-amyloid(25-35) by approximately 50%. Dose response curves of both substances were identical concerning effect size and concentration. Because CHF3360 does not show any acetylcholine inhibitor activity in the applied dose range it is concluded that Ganstigmine provides significant neuroprotection independent from its cholinergic activity.

Progress in clinical neurosciences: Treatment of Alzheimer's disease and other dementias--review and comparison of the cholinesterase inhibitors

BACKGROUND

Alzheimer's disease (AD) is the most common cause of dementia in older adults. Acceptance of the cholinergic hypothesis led to a search for medications which could enhance central cholinergic activity in this condition. There are now three cholinesterase inhibitors available for the treatment of AD in Canada.

OBJECTIVES

To review the currently available cholinesterase inhibitors approved for the treatment of AD in Canada and to provide guidance on who and how to treat with these agents.

RESULTS

Donepezil, rivastigmine, and galantamine are approved for the treatment of AD in Canada. In clinical trails, patients with mild to moderate AD treated with these agents experienced modest improvements in cognition, function, behaviour, and/or global clinical state. The magnitude of benefits seen with each agent appeared to be similar. While to date, there is no convincing evidence that one is more efficacious or effective, they do differ in their pharmacokinetics, additional mechanisms of action, and side effect profiles. Therefore, the selection of agent will be based on considerations such as side effect profiles, ease of administration, personal familiarity/experience, and beliefs about the importance of the noted differences in their pharmacokinetics and additional mechanisms of action.

CONCLUSION

We believe that these agents should be offered to all individuals with a mild to moderate dementia where Alzheimer's pathology is felt to be a contributing factor. We view all three available cholinesterase inhibitors as first-line drugs.