Safinamide Differentially Modulates In Vivo Glutamate and GABA Release in the Rat Hippocampus and Basal Ganglia.

Safinamide has been recently approved as an add-on to levodopa therapy for Parkinson disease. In addition to inhibiting monoamine oxidase type B, it blocks sodium channels and modulates glutamate (Glu) release in vitro. Since this property might contribute to the therapeutic action of the drug, we undertook the present study to investigate whether safinamide inhibits Glu release also in vivo and whether this effect is consistent across different brain areas and is selective for glutamatergic neurons. To this aim, in vivo microdialysis was used to monitor the spontaneous and veratridine-induced Glu and GABA release in the hippocampus and basal ganglia of naive, awake rats. Brain levels of safinamide were measured as well. To shed light on the mechanisms underlying the effect of safinamide, sodium currents were measured by patch-clamp recording in rat cortical neurons. Safinamide maximally inhibited the veratridine-induced Glu and GABA release in hippocampus at 15 mg/kg, which reached free brain concentrations of 1.89-1.37 µM. This dose attenuated veratridine-stimulated Glu (but not GABA) release in subthalamic nucleus, globus pallidus, and substantia nigra reticulata, but not in striatum. Safinamide was ineffective on spontaneous neurotransmitter release. In vitro, safinamide inhibited sodium channels, showing a greater affinity at depolarized (IC50 = 8 µM) than at resting (IC50 = 262 µM) potentials. We conclude that safinamide inhibits in vivo Glu release from stimulated nerve terminals, likely via blockade of sodium channels at subpopulations of neurons with specific firing patterns. These data are consistent with the anticonvulsant and antiparkinsonian actions of safinamide and provide support for the nondopaminergic mechanism of its action.

The role of glutamatergic neurotransmission in the motor and non-motor symptoms in Parkinson's disease: Clinical cases and a review of the literature.

Glutamate is the major excitatory neurotransmitter in the central nervous system and, as such, many brain regions, including the basal ganglia, are rich in glutamatergic neurons. The importance of the basal ganglia in the control of voluntary movement has long been recognised, with the effect of dysfunction of the region exemplified by the motor symptoms seen in Parkinson's disease (PD). However, the basal ganglia and the associated glutamatergic system also play a role in the modulation of emotion, nociception and cognition, dysregulation of which result in some of the non-motor symptoms of PD (depression/anxiety, pain and cognitive deficits). Thus, while the treatment of PD has traditionally been approached from the perspective of dopaminergic replacement, using agents such as levodopa and dopamine receptor agonists, the glutamatergic system offers a novel treatment target for the disease. Safinamide has been approved in over 20 countries globally for fluctuating PD as add-on therapy to levodopa regimens for the management of 'off' episodes. The drug has both dopaminergic and non-dopaminergic pharmacological effects, the latter including inhibition of abnormal glutamate release. The effect of safinamide on the glutamatergic system might present some advantages over dopamine-based therapies for PD by providing efficacy for motor (levodopa-induced dyskinesia) as well as non-motor (anxiety, mood disorders, pain) symptoms. In this article, we discuss the potential role of glutamatergic inhibition on these symptoms, using illustrative real-world examples of patients we have treated with safinamide.

Safinamide inhibits in vivo glutamate release in a rat model of Parkinson's disease.

To investigate whether the reversible MAO-B inhibitor and sodium channel blocker safinamide impairs glutamate release under parkinsonian conditions in vivo, and this effect is dependent on MAO-B inhibition, safinamide (and rasagiline as a comparator) were administered to 6-hydroxydopamine hemilesioned rats, a model of Parkinson's disease, and haloperidol-treated rats, a model of neuroleptic-induced parkinsonism. A microdialysis probe was implanted in the dopamine-depleted dorsolateral striatum, globus pallidus, subthalamic nucleus or substantia nigra reticulata of 6-hydroxydopamine hemilesioned rats. Glutamate and GABA release was stimulated by reverse dialysis of veratridine, and safinamide or rasagiline were acutely administered before veratridine at doses inhibiting MAO-B >50%. A microdialysis probe was implanted in the substantia nigra reticulata of naïve rats to monitor glutamate and GABA release following acute haloperidol and safinamide administration. Safinamide inhibited the veratridine-evoked glutamate release in the globus pallidus and subthalamic nucleus but not in the striatum and substantia nigra. Moreover, it reduced pallidal and nigral GABA release. Conversely, rasagiline failed to modify the veratridine-induced glutamate and GABA release in the basal ganglia. Safinamide also inhibited the haloperidol-induced nigral glutamate release. MAO-B inhibitors safinamide and rasagiline differ in their abilities to inhibit depolarization-evoked glutamate release in the basal ganglia of parkinsonian rats. The ineffectiveness of rasagiline suggests that MAO-B inhibition does not contribute to the antiglutamatergic activity of safinamide. The glutamate-inhibiting action of safinamide within the subthalamo-external pallidal loop, which shows abnormal activity in Parkinson's disease, might contribute to its therapeutic actions of improving motor performance without provoking troublesome dyskinesia.

Effects of safinamide on the glutamatergic striatal network in experimental Parkinson's disease.

OBJECTIVE: The aim of the study was to evaluate electrophysiological effects of safinamide on the intrinsic and synaptic properties of striatal spiny projection neurons (SPNs) and to characterize the possible therapeutic antiparkinsonian effect of this drug in dopamine (DA) denervated rats before and during levodopa (l-DOPA) treatment. BACKGROUND: Current therapeutic options in Parkinson's disease (PD) are primarily DA replacement strategies that usually cause progressive motor fluctuations and l-DOPA-induced dyskinesia (LIDs) as a consequence of SPNs glutamate-induced hyperactivity. As a reversible and use-dependent inhibitor of voltage-gated sodium channels, safinamide reduces the release of glutamate and possibly optimize the effect of l-DOPA therapy in PD. METHODS: Electrophysiological effects of safinamide (1-100 µM) were investigated by patch-clamp recordings in striatal slices of naïve, 6-hydroxydopamine (6-OHDA)-lesioned DA-denervated rats and DA-denervated animals chronically treated with l-DOPA. LIDs were assessed in vivo with and without chronic safinamide treatment and measured by scoring the l-DOPA-induced abnormal involuntary movements (AIMs). Motor deficit was evaluated with the stepping test. RESULTS: Safinamide reduced the SPNs firing rate and glutamatergic synaptic transmission in all groups, showing a dose-dependent effect with half maximal inhibitory concentration (IC50) values in the therapeutic range (3-5 µM). Chronic co-administration of safinamide plus l-DOPA in DA-denervated animals favored the recovery of corticostriatal long-term synaptic potentiation (LTP) and depotentiation of excitatory synaptic transmission also reducing motor deficits before the onset of LIDs. CONCLUSIONS: Safinamide, at a clinically relevant dose, optimizes the effect of l-DOPA therapy in experimental PD reducing SPNs excitability and modulating synaptic transmission. Co-administration of safinamide and l-DOPA ameliorates motor deficits.

Safinamide's potential in treating nondystrophic myotonias: Inhibition of skeletal muscle voltage-gated sodium channels and skeletal muscle hyperexcitability in vitro and in vivo.

The antiarrhythmic sodium-channel blocker mexiletine is used to treat patients with myotonia. However, around 30% of patients do not benefit from mexiletine due to poor tolerability or suboptimal response. Safinamide is an add-on therapy to levodopa for Parkinson's disease. In addition to MAOB inhibition, safinamide inhibits neuronal sodium channels, conferring anticonvulsant activity in models of epilepsy. Here, we investigated the effects of safinamide on skeletal muscle hNav1.4 sodium channels and in models of myotonia, in-vitro and in-vivo. Using patch-clamp, we showed that safinamide reversibly inhibited sodium currents in HEK293T cells transfected with hNav1.4. At the holding potential (hp) of -120 mV, the half-maximum inhibitory concentrations (IC50) were 160 and 33 µM at stimulation frequencies of 0.1 and 10 Hz, respectively. The calculated affinity constants of safinamide were dependent on channel state: 420 µM for closed channels and 9 µM for fast-inactivated channels. The p.F1586C mutation in hNav1.4 greatly impaired safinamide inhibition, suggesting that the drug binds to the local anesthetic receptor site in the channel pore. In a condition mimicking myotonia, i.e. hp. of -90 mV and 50-Hz stimulation, safinamide inhibited INa with an IC50 of 6 µM, being two-fold more potent than mexiletine. Using the two-intracellular microelectrodes current-clamp method, action potential firing was recorded in vitro in rat skeletal muscle fibers in presence of the chloride channel blocker, 9-anthracene carboxylic acid (9-AC), to increase excitability. Safinamide counteracted muscle fiber hyperexcitability with an IC50 of 13 µM. In vivo, oral safinamide was tested in the rat model of myotonia. In this model, intraperitoneal injection of 9-AC greatly increased the time of righting reflex (TRR) due to development of muscle stiffness. Safinamide counteracted 9-AC induced TRR increase with an ED50 of 1.2 mg/kg, which is 7 times lower than that previously determined for mexiletine. In conclusion, safinamide is a potent voltage and frequency dependent blocker of skeletal muscle sodium channels. Accordingly, the drug was able to counteract abnormal muscle hyperexcitability induced by 9-AC, both in vitro and in vivo. Thus, this study suggests that safinamide may have potential in treating myotonia and warrants further preclinical and human studies to fully evaluate this possibility.

Structures of human monoamine oxidase B complexes with selective noncovalent inhibitors: safinamide and coumarin analogs.

Structures of human monoamine oxidase B (MAO B) in complex with safinamide and two coumarin derivatives, all sharing a common benzyloxy substituent, were determined by X-ray crystallography. These compounds competitively inhibit MAO B with Ki values in the 0.1-0.5 microM range that are 30-700-fold lower than those observed with MAO A. The inhibitors bind noncovalently to MAO B, occupying both the entrance and the substrate cavities and showing a similarly oriented benzyloxy substituent.

Solid-phase synthesis and insights into structure-activity relationships of safinamide analogues as potent and selective inhibitors of type B monoamine oxidase.

Safinamide, (S)-N2-{4-[(3-fluorobenzyl)oxy]benzyl}alaninamide methanesulfonate, which is in phase III clinical trials as an anti-Parkinson drug, and a library of alkanamidic analogues were prepared through an expeditious solid-phase synthesis and evaluated for their monoamine oxidase B (MAO-B) and monoamine oxidase A (MAO-A) inhibitory activity and selectivity. (S)-3-Chlorobenzyloxyalaninamide (8) and (S)-3-chlorobenzyloxyserinamide (13) derivatives proved to be more potent MAO-B inhibitors than safinamide (IC50 = 33 and 43 nM, respectively, vs 98 nM) but with a lower MAO-B selectivity (SI = 3455 and 1967, respectively, vs 5918). The highest MAO-B inhibitory potency (IC50 = 17 nM) and a good selectivity (SI = 2941) were displayed by (R)-21, a tetrahydroisoquinoline analogue of safinamide. Structure-affinity relationships and docking simulations pointed out strong negative steric effects of alpha-aminoamide side chains and para substituents of the benzyloxy groups and favorable hydrophobic interactions of meta substituents. The significantly diverse MAO-B affinities of a number of R and S alpha-aminoamide enantiomers, including the two rigid analogues (21) of safinamide, indicated likely enantioselective interactions at the enzymatic binding sites.

Pressor response to intravenous tyramine in healthy subjects after safinamide, a novel neuroprotectant with selective, reversible monoamine oxidase B inhibition.

Safinamide is a novel neuroprotectant combining sodium and calcium channel blocking properties with selective, reversible monoamine oxidase type B (MAO B) inhibition. Phase 1 studies have demonstrated that in healthy volunteers, the ED50 (a dose that inhibits enzyme activity by 50% in 50% of treated subjects) for MAO B inhibition is 87.5 microg/kg/day orally, and that no MAO A inhibition occurs after 10-mg/kg oral dosing. To assess the risk of inducing the "cheese effect," the effect of safinamide and placebo on the pressor response to tyramine was investigated in a group of healthy male volunteers. The study was an open, single-dose placebo-controlled trial with the 2 treatments in sequence. An increase of 30 mm Hg systolic blood pressure was obtained by intravenous tyramine administered by 0.5-mg incremental boluses injected at 15-minute intervals. The amount of tyramine necessary to achieve such a blood pressure increase was the same after the safinamide 2-mg/kg oral load compared with placebo. These results suggest that dietary restrictions for food with high tyramine content should not be required under safinamide treatment.

Weight loss intervention for young adults using mobile technology: design and rationale of a randomized controlled trial - Cell Phone Intervention for You (CITY).

BACKGROUND: The obesity epidemic has spread to young adults, leading to significant public health implications later in adulthood. Intervention in early adulthood may be an effective public health strategy for reducing the long-term health impact of the epidemic. Few weight loss trials have been conducted in young adults. It is unclear what weight loss strategies are beneficial in this population. PURPOSE: To describe the design and rationale of the NHLBI-sponsored Cell Phone Intervention for You (CITY) study, which is a single center, randomized three-arm trial that compares the impact on weight loss of 1) a behavioral intervention that is delivered almost entirely via cell phone technology (Cell Phone group); and 2) a behavioral intervention delivered mainly through monthly personal coaching calls enhanced by self-monitoring via cell phone (Personal Coaching group), each compared to 3) a usual care, advice-only control condition. METHODS: A total of 365 community-dwelling overweight/obese adults aged 18-35 years were randomized to receive one of these three interventions for 24 months in parallel group design. Study personnel assessing outcomes were blinded to group assignment. The primary outcome is weight change at 24 [corrected] months. We hypothesize that each active intervention will cause more weight loss than the usual care condition. Study completion is anticipated in 2014. CONCLUSIONS: If effective, implementation of the CITY interventions could mitigate the alarming rates of obesity in young adults through promotion of weight loss. ClinicalTrial.gov: NCT01092364.

Determinants and consequences of adherence to the dietary approaches to stop hypertension diet in African-American and white adults with high blood pressure: results from the ENCORE trial.

BACKGROUND: Although the Dietary Approaches to Stop Hypertension (DASH) diet is an accepted nonpharmacologic treatment for hypertension, little is known about what patient characteristics affect dietary adherence and what level of adherence is needed to reduce blood pressure (BP). OBJECTIVE: Our aim was to determine what factors predict dietary adherence and the extent to which dietary adherence is necessary to produce clinically meaningful BP reductions. DESIGN: Ancillary study of the ENCORE (Exercise and Nutrition Interventions for Cardiovascular Health) trial--a 16-week randomized clinical trial of diet and exercise. PARTICIPANTS/SETTING: Participants included 144 sedentary, overweight, or obese adults (body mass index 25 to 39.9) with high BP (systolic 130 to 159 mm Hg and/or diastolic 85 to 99 mm Hg). INTERVENTION: Patients were randomized to one of three groups: DASH diet alone, DASH diet plus weight management, and Usual Diet Controls. MAIN OUTCOMES MEASURES: Our primary outcomes were a composite index of adherence to the DASH diet and clinic BP. STATISTICAL ANALYSES PERFORMED: General linear models were used to compare treatment groups on post-treatment adherence to the DASH diet. Linear regression was used to examine potential predictors of post-treatment DASH adherence. Analysis of covariance was used to examine the relation of adherence to the DASH diet and BP. RESULTS: Participants in the DASH diet plus weight management (16.1 systolic BP [SBP]; 95% CI 13.0 to 19.2 mm Hg and 9.9 diastolic BP [DBP]; 95% CI 8.1 to 11.6 mm Hg) and DASH diet alone (11.2 SBP; 95% CI 8.1 to 14.3 mm Hg and 7.5 DBP; 95% CI 5.8 to 9.3 mm Hg) groups showed significant reductions in BP in comparison with Usual Diet Controls participants (3.4 SBP; 95% CI 0.4 to 6.4 mm Hg and DBP 3.8; 95% CI 2.2 to 5.5 mm Hg). Greater post-treatment consumption of DASH foods was noted in both the DASH diet alone (mean = 6.20; 95% CI 5.83 to 6.57) and DASH diet plus weight management groups (mean = 6.23; 95% CI 5.88 to 6.59) compared with Usual Diet Controls (mean = 3.66; 95% CI 3.30 to 4.01; P<0.0001), and greater adherence to the DASH diet was associated with larger reductions in clinic SBP and DBP (P ≤ 0.01). Only ethnicity predicted dietary adherence, with African Americans less adherent to the DASH diet compared with whites (4.68; 95% CI 4.34 to 5.03 vs 5.83; 95% CI 5.50 to 6.11; P<0.001). CONCLUSIONS: Greater adherence to the DASH diet was associated with larger BP reductions independent of weight loss. African Americans were less likely to be adherent to the DASH dietary eating plan compared with whites, suggesting that culturally sensitive dietary strategies might be needed to improve adherence to the DASH diet.

Effects of the DASH diet alone and in combination with exercise and weight loss on blood pressure and cardiovascular biomarkers in men and women with high blood pressure: the ENCORE study.

BACKGROUND: Although the DASH (Dietary Approaches to Stop Hypertension) diet has been shown to lower blood pressure (BP) in short-term feeding studies, it has not been shown to lower BP among free-living individuals, nor has it been shown to alter cardiovascular biomarkers of risk. OBJECTIVE: To compare the DASH diet alone or combined with a weight management program with usual diet controls among participants with prehypertension or stage 1 hypertension (systolic BP, 130-159 mm Hg; or diastolic BP, 85-99 mm Hg). DESIGN AND SETTING: Randomized, controlled trial in a tertiary care medical center with assessments at baseline and 4 months. Enrollment began October 29, 2003, and ended July 28, 2008. PARTICIPANTS: Overweight or obese, unmedicated outpatients with high BP (N = 144). INTERVENTIONS: Usual diet controls, DASH diet alone, and DASH diet plus weight management. OUTCOME MEASURES: The main outcome measure is BP measured in the clinic and by ambulatory BP monitoring. Secondary outcomes included pulse wave velocity, flow-mediated dilation of the brachial artery, baroreflex sensitivity, and left ventricular mass. RESULTS: Clinic-measured BP was reduced by 16.1/9.9 mm Hg (DASH plus weight management); 11.2/7.5 mm (DASH alone); and 3.4/3.8 mm (usual diet controls) (P < .001). A similar pattern was observed for ambulatory BP (P < .05). Greater improvement was noted for DASH plus weight management compared with DASH alone for pulse wave velocity, baroreflex sensitivity, and left ventricular mass (all P < .05). CONCLUSION: For overweight or obese persons with above-normal BP, the addition of exercise and weight loss to the DASH diet resulted in even larger BP reductions, greater improvements in vascular and autonomic function, and reduced left ventricular mass. CLINICAL TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00571844.

Discovery of a novel class of potent coumarin monoamine oxidase B inhibitors: development and biopharmacological profiling of 7-[(3-chlorobenzyl)oxy]-4-[(methylamino)methyl]-2H-chromen-2-one methanesulfonate (NW-1772) as a highly potent, selective, reversible, and orally active monoamine oxidase B inhibitor.

In an effort to discover novel selective monoamine oxidase (MAO) B inhibitors with favorable physicochemical and pharmacokinetic profiles, 7-[(m-halogeno)benzyloxy]coumarins bearing properly selected polar substituents at position 4 were designed, synthesized, and evaluated as MAO inhibitors. Several compounds with MAO-B inhibitory activity in the nanomolar range and excellent MAO-B selectivity (selectivity index SI > 400) were identified. Structure-affinity relationships and docking simulations provided valuable insights into the enzyme-inhibitor binding interactions at position 4, which has been poorly explored. Furthermore, computational and experimental studies led to the identification and biopharmacological characterization of 7-[(3-chlorobenzyl)oxy]-4-[(methylamino)methyl]-2H-chromen-2-one methanesulfonate 22b (NW-1772) as an in vitro and in vivo potent and selective MAO-B inhibitor, with rapid blood-brain barrier penetration, short-acting and reversible inhibitory activity, slight inhibition of selected cytochrome P450s, and low in vitro toxicity. On the basis of this preliminary preclinical profile, inhibitor 22b might be viewed as a promising clinical candidate for the treatment of neurodegenerative diseases.

Hormonal induction of adipogenesis induces Skp2 expression through PI3K and MAPK pathways.

We have previously shown that the F-box protein, S-phase kinase-associated protein (Skp2) plays a mechanistic role in targeting the cell-cycle inhibitor, p27 for degradation by the 26S proteasome during early stages of 3T3-L1 adipocyte differentiation. Here, we demonstrate that protein levels of Skp2 and its accessory protein, Cks1 increased as density-arrested preadipocytes re-entered the cell cycle during clonal expansion, decreased with differentiation-induced growth arrest, and became refractory to hormonal stimulation following the onset of terminal adipocyte differentiation. Component analysis revealed that while maximal Skp2/Cks1 protein accumulation required the complete differentiation cocktail, that insulin was principally involved. Skp2 mRNA accumulation was found to precede the increase in Skp2 protein and succeed the activation of Akt and Erk1/2, mediators of phosphatidylinositol-3 kinase (PI3K) and mitogen-activated protein kinase (MAPK) signal transduction pathways, respectively. Using specific inhibitors, we found that while activation of both pathways was required for maximal expression, PI3K signaling was primarily responsible for the increase in Skp2/Cks1 accumulation. The increase in Skp2 mRNA was notable 4 h following hormonal stimulation, plateaued by 12 h during mid-G1 phase progression, and occurred without change to mRNA stability. We further demonstrate that luciferase activity, originating from a pGL3 vector containing 2.4 kb of the Skp2 promoter, increased 2.5-fold with hormonal stimulation. This increase in promoter activity was markedly suppressed following PI3K and MAPK blockade. Deletion studies indicate that responsive elements were located within the proximal Skp2 promoter. These data demonstrate that Skp2 is transcriptionally regulated by PI3K and MAPK pathways as 3T3-L1 preadipocytes transition from quiescence to proliferation during adipocyte hyperplasia.

Pharmacokinetics and pharmacodynamics of safinamide, a neuroprotectant with antiparkinsonian and anticonvulsant activity.

OBJECTIVE: This paper describes the pharmacokinetics and the pharmacodynamics, in terms of monoamino oxidase type B (MAO-B) inhibition, in male healthy volunteers of orally administered safinamide, a new neuroprotectant that in experimental models has demonstrated strong anticonvulsant and antiparkinson activities. METHODS: Four clinical trials covering the dose range of 25-10,000 microg/kg were carried out to describe pharmacokinetics, pharmacodynamics and tolerability of safinamide, administered in single or repeated dose regimen to steady state, including a food interaction trial. All the above trials were carried out after the Ethics Committee's approval and signature of the consent form by the volunteers. In single dose trials blood sampling covered a 24 h-period in pharmacodynamic trials, 48 h-period in pharmacokinetic trials. In the case of repeated dose regimen to steady state a pre-dose sample was drawn on the first six study days, whereas the curve was explored on the 7th study day, prolonging blood sampling over a 48 h-period after the last dosing. Safinamide level was determined in plasma by a very sensitive and specific LC-MS-MS method, with a low limit of quantification of 0.5 ng/ml of plasma. Pharmacokinetic analysis was carried out with non-compartmental method and, in one case, also with the two-compartmental method. Monoamine oxidase activity of both types A and B (MAO-A and MAO-B) was determined in plasma at different times (MAO-B) and correlated to safinamide levels, or in urine (MAO-A). RESULTS: Pharmacokinetics of safinamide proved to be linearly and proportionally related to the administered doses. The absorption of safinamide was rapid with peak plasma concentrations ranging from 2 to 4 h. Food prolonged the rate and did not affect the extent of absorption of safinamide. In repeat dose regimen once daily, the steady state was reached on the 5th study day with a marginal accumulation factor of 1.5-1.7. The drug was cleared with a t(1/2) of about 22 h. Safinamide reversibly inhibited MAO-B enzyme. Full inhibition was observed with single doses >/= 600 microg/kg, and a relevant, dose dependent, progressive inhibition was encountered with doses starting from 25 microg/kg. Even at the highest single dose of 10 mg/kg no evidence of MAO-A inhibition was observed. CONCLUSION: Enteral absorption of the drug is linear and proportional to the doses administered. The drug is cleared from the body with a t(1/2) of approximately equal to 22 h, without producing any clinically relevant accumulation at steady state. The MAO-B inhibitory activity, without affecting MAO-A, is useful to prevent a dopamine bioinactivation in patients suffering from Parkinson's disease. Safinamide tolerability in the four clinical trials proved to be good.