Selective blockade by nicergoline of vascular responses elicited by stimulation of alpha 1A-adrenoceptor subtype in the rat

Phosphodiesterase Inhibitors for Alzheimer's Disease: A Systematic Review of Clinical Trials and Epidemiology with a Mechanistic Rationale

BACKGROUND

Preclinical studies, clinical trials, and reviews suggest increasing 3',5'-cyclic adenosine monophosphate (cAMP) and 3',5'-cyclic guanosine monophosphate (cGMP) with phosphodiesterase inhibitors is disease-modifying in Alzheimer's disease (AD). cAMP/protein kinase A (PKA) and cGMP/protein kinase G (PKG) signaling are disrupted in AD. cAMP/PKA and cGMP/PKG activate cAMP response element binding protein (CREB). CREB binds mitochondrial and nuclear DNA, inducing synaptogenesis, memory, and neuronal survival gene (e.g., brain-derived neurotrophic factor) and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α). cAMP/PKA and cGMP/PKG activate Sirtuin-1, which activates PGC1α. PGC1α induces mitochondrial biogenesis and antioxidant genes (e.g.,Nrf2) and represses BACE1. cAMP and cGMP inhibit BACE1-inducing NFκB and tau-phosphorylating GSK3β.

OBJECTIVE AND METHODS

We review efficacy-testing clinical trials, epidemiology, and meta-analyses to critically investigate whether phosphodiesteraseinhibitors prevent or treat AD.

RESULTS

Caffeine and cilostazol may lower AD risk. Denbufylline and sildenafil clinical trials are promising but preliminary and inconclusive. PF-04447943 and BI 409,306 are ineffective. Vinpocetine, cilostazol, and nicergoline trials are mixed. Deprenyl/selegiline trials show only short-term benefits. Broad-spectrum phosphodiesterase inhibitor propentofylline has been shown in five phase III trials to improve cognition, dementia severity, activities of daily living, and global assessment in mild-to-moderate AD patients on multiple scales, including the ADAS-Cogand the CIBIC-Plus in an 18-month phase III clinical trial. However, two books claimed based on a MedScape article an 18-month phase III trial failed, so propentofylline was discontinued. Now, propentofylline is used to treat canine cognitive dysfunction, which, like AD, involves age-associated wild-type Aβ deposition.

CONCLUSION

Phosphodiesterase inhibitors may prevent and treat AD.

Neurotransmitter signaling pathways required for normal development in Xenopus laevis embryos: a pharmacological survey screen

Neurotransmitters are not only involved in brain function but are also important signaling molecules for many diverse cell types. Neurotransmitters are widely conserved, from evolutionarily ancient organisms lacking nervous systems through man. Here, results are reported from a loss- and gain-of-function survey, using pharmacological modulators of several neurotransmitter pathways to examine possible roles for these pathways in normal embryogenesis. Applying reagents targeting the glutamatergic, adrenergic and dopaminergic pathways to embryos of Xenopus laevis from gastrulation to organogenesis stages, we observed and quantified numerous malformations, including craniofacial defects, hyperpigmentation, muscle mispatterning and miscoiling of the gut. These data implicate several key neurotransmitters in new embryonic patterning roles, reveal novel earlier stages for processes involved in eye development, suggest new targets for subsequent molecular-genetic investigation, and highlight the necessity for in-depth toxicology studies of psychoactive compounds to which human embryos might be exposed during pregnancy.

Ergotamine and nicergoline - facts and myths

Ergotamine, being a representative of naturally occurring ergoline alkaloids, derived from d-lysergic acid, and nicergoline, a d-lumilysergic acid derivative belonging to semi-synthetic ergot-derived alkaloids, display diversified affinity for adrenergic, serotoninergic, and dopamine receptors. Although introduction of triptans marginalized use of ergotamine, nicergoline is used in cerebral metabolic-vascular disorders, and dementia. Additionally, nicergoline exhibits a safety profile comparable to that of placebo, and none of the reviewed studies reported any incidence of fibrosis or ergotism with nicergoline treatment. In line with the recent data, activation of 5-HT2B receptor by ergot derivatives i.e. ergotamine, methysergide, pergolide, and carbegoline is involved in pathogenesis of drug-induced valvulopathy. In contrary structurally related drugs - lisuride and terguride do not increase the risk of valvular heart disease. It seems, that more detailed mechanistic studies on nicergoline and ergotamine might be beneficial for determining structural requirements related to activation of G-protein as well as alternative signal transduction pathways e.g. β-arrestins or different kinases, and responsible for drug liabilities.

Safety of nicergoline as an agent for management of cognitive function disorders

Nicergoline is a semisynthetic ergot derivative and has a selective alpha-1A adrenergic receptor blocking property and also other additional mechanisms of actions, both in the brain and in the periphery. It is in clinical use for over three decades in over fifty countries for conditions such as cerebral infarction, acute and chronic peripheral circulation disorders, vascular dementia, and Alzheimer's disease and has been found to be beneficial in a variety of other conditions. However, concerns about its safety have been raised, especially after the European medicines agency's (EMEA's) restriction in the use of all ergot derivatives including nicergoline. But, most of the available literature and data suggest that the adverse events with nicergoline are mild and transient. Further, none of the available treatment options for cognitive disorders afford definitive resolution of symptoms. In this backdrop, we discuss the pharmacology of nicergoline with special emphasis on the safety of this compound, especially when used in patients suffering from cognitive function disorders.

A systematic review and meta-analysis assessing adverse event profile and tolerability of nicergoline

OBJECTIVE

To evaluate the safety profile of nicergoline compared with placebo and other active agents from published randomised controlled trials.

DESIGN

Systematic review and meta-analysis of nicergoline compared with placebo and other active agents across various indications.

DATA SOURCES

MEDLINE, Medline-in-process, Cochrane, EMBASE, EMBASE alerts, Cochrane Central Register of Controlled Trials (CENTRAL), Cochrane Database of Systematic Reviews (CDSR) and Cochrane Methodology Register (CMR) for all the randomised controlled trials, open-label or blinded, in adults treated with nicergoline. Studies published until August 2013 were included.

REVIEW METHOD

29 studies were included for data extraction. The studies included in this review were majorly from European countries and mostly in cerebrovascular disease (n=15) and dementia (n=8).

RESULTS

The treatment withdrawals were comparatively lower in the nicergoline group as compared with the placebo group (RR=0.92; 95% CI 0.7 to 1.21) and other active comparators (RR=0.45; 95% CI 0.10 to 1.95), but the difference was non-significant. Incidence of any adverse events (AEs) was slightly higher (RR=1.05; 95% CI 0.93 to 1.2) while incidence of serious AEs was lower (RR=0.85; 95% CI 0.50 to 1.45) in the nicergoline compared with placebo group. Frequency of anxiety was significantly lower in nicergoline as compared with placebo (p=0.01). Other AEs including diarrhoea, gastric upset, dizziness and drowsiness were less frequent in the nicergoline group when compared with placebo/active drugs, but the difference was non-significant. Frequency of hypotension and hot flushes was slightly higher in the nicergoline group but the difference was non-significant. None of the studies reported any incidence of fibrosis or ergotism with nicergoline treatment.

CONCLUSIONS

Nicergoline is an ergot derivative, but its safety profile is better than other ergot derivatives like ergotamine and ergotoxine. This systematic review and meta-analysis suggests that nicergoline has a good safety profile. None of the studies included in this systematic review reported any incidence of fibrosis or ergotism with nicergoline.

Therapeutic use of nicergoline

The ergot alkaloid derivative nicergoline became clinically available about 35 years ago in the 1970s. Nicergoline has a broad spectrum of action: (i) as an alpha(1)-adrenoceptor antagonist, it induces vasodilation and increases arterial blood flow; (ii) it enhances cholinergic and catecholaminergic neurotransmitter function; (iii) it inhibits platelet aggregation; (iv) it promotes metabolic activity, resulting in increased utilization of oxygen and glucose; and (v) it has neurotrophic and antioxidant properties. Acting on several basic pathophysiological mechanisms, nicergoline has therapeutic potential in a number of disorders. This article provides an overview of the published clinical evidence relating to the efficacy and safety of nicergoline (30 mg twice daily) in the treatment of dementia (including Alzheimer's disease and vascular dementia) and vascular and balance disorders. For dementia of different aetiologies, the therapeutic benefit of nicergoline has been established, with up to 89% of patients showing improvements in cognition and behaviour. After as little as 2 months of treatment, symptom improvement is apparent compared with placebo, and most patients are still improved or stable after 12 months. Concomitant neurophysiological changes in the brain indicate (after only 4-8 weeks' treatment) improved vigilance and information processing. In patients with balance disorders, mean improvements of 44-78% in symptom severity and quality of life have been observed with nicergoline. Although clinical experience with nicergoline in vascular disorders is limited to relatively short-term, small-scale studies, it has been successfully used in rehabilitation therapy of patients with chronic ischaemic stroke. Open-label evaluations suggest that nicergoline may also be valuable in glaucoma, depression and peripheral arterio-pathy. Adverse events of nicergoline, if any, are related to the central nervous system, the metabolic system and the overall body. Most are considered typical symptoms of ergot derivatives. Because of their generally mild and transient nature, treatment discontinuations occur relatively infrequently. The efficacy of nicergoline combined with a favourable safety and tolerability profile at commonly applied doses (60 mg/day) make this agent a valuable therapy in patients with mild to moderate dementia, vascular diseases and balance disorders.