Diclofenac Prolongs Repolarization in Ventricular Muscle with Impaired Repolarization Reserve

Background: The aim of the present work was to characterize the electrophysiological effects of the non-steroidal anti- inflammatory drug diclofenac and to study the possible proarrhythmic potency of the drug in ventricular muscle. Methods: Ion currents were recorded using voltage clamp technique in canine single ventricular cells and action potentials were obtained from canine ventricular preparations using microelectrodes. The proarrhythmic potency of the drug was investigated in an anaesthetized rabbit proarrhythmia model. Results: Action potentials were slightly lengthened in ventricular muscle but were shortened in Purkinje fibers by diclofenac (20 mM). The maximum upstroke velocity was decreased in both preparations. Larger repolarization prolongation was observed when repolarization reserve was impaired by previous BaCl 2 application. Diclofenac (3 mg/kg) did not prolong while dofetilide (25 mg/kg) significantly lengthened the QT c interval in anaesthetized rabbits. The addition of diclofenac following reduction of repolarization reserve by dofetilide further prolonged QT c . Diclofenac alone did not induce Torsades de Pointes ventricular tachycardia (TdP) while TdP incidence following dofetilide was 20%. However, the combination of diclofenac and dofetilide significantly increased TdP incidence (62%). In single ventricular cells diclofenac (30 mM) decreased the amplitude of rapid (I Kr ) and slow (I Ks ) delayed rectifier currents thereby attenuating repolarization reserve. L-type calcium current (I Ca ) was slightly diminished, but the transient outward (I to ) and inward rectifier (I K1 ) potassium currents were not influenced. Conclusions: Diclofenac at therapeutic concentrations and even at high dose does not prolong repolarization markedly and does not increase the risk of arrhythmia in normal heart. However, high dose diclofenac treatment may lengthen repolarization and enhance proarrhythmic risk in hearts with reduced repolarization reserve

Mutations in VPS13D lead to a new recessive ataxia with spasticity and mitochondrial defects

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Brain-derived neurotrophic factor--a major player in stimulation-induced homeostatic metaplasticity of human motor cortex?

Repetitive transcranial magnetic stimulation (rTMS) of the human motor hand area (M1HAND) can induce lasting changes in corticospinal excitability as indexed by a change in amplitude of the motor-evoked potential. The plasticity-inducing effects of rTMS in M1HAND show substantial inter-individual variability which has been partially attributed to the val(66)met polymorphism in the brain-derived neurotrophic factor (BDNF) gene. Here we used theta burst stimulation (TBS) to examine whether the BDNF val(66)met genotype can be used to predict the expression of TBS-induced homeostatic metaplasticity in human M1HAND. TBS is a patterned rTMS protocol with intermittent TBS (iTBS) usually inducing a lasting increase and continuous TBS (cTBS) a lasting decrease in corticospinal excitability. In three separate sessions, healthy val(66)met (n = 12) and val(66)val (n = 17) carriers received neuronavigated cTBS followed by cTBS (n = 27), cTBS followed by iTBS (n = 29), and iTBS followed by iTBS (n = 28). Participants and examiner were blinded to the genotype at the time of examination. As expected, the first TBS intervention induced a decrease (cTBS) and increase (iTBS) in corticospinal excitability, respectively, at the same time priming the after effects caused by the second TBS intervention in a homeostatic fashion. Critically, val(66)met carriers and val(66)val carriers showed very similar response patterns to cTBS and iTBS regardless of the order of TBS interventions. Since none of the observed TBS effects was modulated by the BDNF val(66)met polymorphism, our results do not support the notion that the BDNF val(66)met genotype is a major player with regard to TBS-induced plasticity and metaplasticity in the human M1HAND

Exome sequencing in a family with restless legs syndrome

Background: Restless legs syndrome (RLS) has a high familial aggregation. To date, several loci and genetic risk factors have been identified, but no causative gene mutation has been found

Effects of the three TBS-TBS protocols and BDNF polymorphism on corticospinal excitability over time: (A) MEP_bi amplitude independent of polymorphism, (B) MEP_bi amplitude divided by polymorphism, (C) MEP_mo amplitude independent of polymorphism, (D) MEP_mo amplitude divided by polymorphism.

<p>Asterisks indicate significant changes from baseline in the expected direction as revealed by one-sided one-sample t-tests (^#P<0.05, *P<0.01, **P<0.001, ***P<0.0001, ****P<0.00001, *****P<0.000001; please note that p-values indicated by one or more asterisks are also significant when applying two-sided t-tests).</p

Effect of preconditioning on the after-effects of cTBS: (A) MEP_bi amplitude independent of polymorphism, (B) MEP_bi amplitude divided by polymorphism, (C) MEP_mo amplitude independent of polymorphism, (D) MEP_mo amplitude divided by polymorphism.

<p>Asterisks indicate significant changes from baseline in the expected direction as revealed by one-sided one-sample t-tests (^#P<0.05, *P<0.01, **P<0.001; please note that p-values indicated by one or more asterisks are also significant when applying two-sided t-tests). Actual p-values are given for post-hoc two-sided paired t-tests comparing different conditions.</p

Time line of an experimental session.

<p>The experiment consisted of three of these sessions in each of which two different TBS protocols were subsequently applied: iTBS followed by iTBS (i-iTBS), cTBS followed by iTBS (c-iTBS), and cTBS followed by cTBS (c-cTBS).Motor evoked potentials (MEPs) were recorded at the contralateral FDI muscle both with biphasic pulses (MEP_bi) at baseline as well as 5 and 25 minutes after the end of each TBS intervention and with monophasic pulses (MEP_mo) at baseline, and 10 min after the end of each TBS intervention. Session were randomized in order across subjects and were conducted at least five days apart.</p

Clinical Spectrum of Kufor-Rakeb Syndrome in the Chilean Kindred with ATP13A2 Mutations

We report the clinical features of the original Chilean family with Kufor-Rakeb syndrome (KRS) that led to the discovery of the ATP13A2 gene at the PARK9 locus. KRS is a rare juvenile-onset autosomal recessive disease characterized by progressive Parkinsonism, pyramidal signs, and cognitive decline in addition to vertical gaze palsy and facial-faucial-finger minimyoclonus. Neurological and neuropsychological examination during a 10-year period, videotaping, neuroimaging, and measurement of DNA methylation of the ATP13A2 promoter region were performed. The youngest 5 of 17 children of nonconsanguineous parents, carrying compound-heterozygous ATP13A2 mutations, had normal development until ages similar to 10 to 12 years, when school performance deteriorated and slowness, rigidity, and frequent falls developed. Examination revealed bradykinesia, subtle postural/action tremor, cogwheel rigidity, spasticity, upward gaze palsy, smooth pursuit with saccadic intrusions, and dementia. Additional signs included facial-faucial-finger minimyoclonus, absent postural reflexes, visual/auditory hallucinations, and insomnia. Levodopa response could not be fully judged in this family. T2* magnetic resonance imaging sequences revealed marked diffuse hypointensity of the caudate (head and body) and lenticular nucleus bilaterally. Disease progression was slow including epilepsy, cachexia, and anarthria. Four affected members died after 28.5 +/- 5.5 (mean +/- SD) years of disease. Two heterozygous carriers, the mother and eldest sibling, showed jerky perioral muscle contractions and clumsiness of hand movements. There was no significant correlation between DNA methylation of the ATP13A2 promoter region and disease progression. The marked caudate and lenticular nucleus T2*-hypointensity suggests that KRS might belong to the family of neurodegenerative diseases associated with brain iron accumulation. (C) 2010 Movement Disorder Societ

Mitochondrial damage-associated inflammation highlights biomarkers in PRKN/PINK1 parkinsonism

There is increasing evidence for a role of inflammation in Parkinson’s disease. Recent research in murine models suggests that parkin and PINK1 deficiency leads to impaired mitophagy, which causes the release of mitochondrial DNA (mtDNA), thereby triggering inflammation. Specifically, the CGAS (cyclic GMP-AMP synthase)-STING (stimulator of interferon genes) pathway mitigates activation of the innate immune system, quantifiable as increased interleukin-6 (IL6) levels. However, the role of IL6 and circulating cell-free mtDNA in unaffected and affected individuals harbouring mutations in PRKN/PINK1 and idiopathic Parkinson’s disease patients remain elusive. We investigated IL6, C-reactive protein, and circulating cell-free mtDNA in serum of 245 participants in two cohorts from tertiary movement disorder centres. We performed a hypothesis-driven rank-based statistical approach adjusting for multiple testing. We detected (i) elevated IL6 levels in patients with biallelic PRKN/PINK1 mutations compared to healthy control subjects in a German cohort, supporting the concept of a role for inflammation in PRKN/PINK1-linked Parkinson’s disease. In addition, the comparison of patients with biallelic and heterozygous mutations in PRKN/PINK1 suggests a gene dosage effect. The differences in IL6 levels were validated in a second independent Italian cohort; (ii) a correlation between IL6 levels and disease duration in carriers of PRKN/PINK1 mutations, while no such association was observed for idiopathic Parkinson’s disease patients. These results highlight the potential of IL6 as progression marker in Parkinson’s disease due to PRKN/PINK1 mutations; (iii) increased circulating cell-free mtDNA serum levels in both patients with biallelic or with heterozygous PRKN/PINK1 mutations compared to idiopathic Parkinson’s disease, which is in line with previous findings in murine models. By contrast, circulating cell-free mtDNA concentrations in unaffected heterozygous carriers of PRKN/PINK1 mutations were comparable to control levels; and (iv) that circulating cell-free mtDNA levels have good predictive potential to discriminate between idiopathic Parkinson’s disease and Parkinson’s disease linked to heterozygous PRKN/PINK1 mutations, providing functional evidence for a role of heterozygous mutations in PRKN or PINK1 as Parkinson’s disease risk factor. Taken together, our study further implicates inflammation due to impaired mitophagy and subsequent mtDNA release in the pathogenesis of PRKN/PINK1-linked Parkinson’s disease. In individuals carrying mutations in PRKN/PINK1, IL6 and circulating cell-free mtDNA levels may serve as markers of Parkinson’s disease state and progression, respectively. Finally, our study suggests that targeting the immune system with anti-inflammatory medication holds the potential to influence the disease course of Parkinson’s disease, at least in this subset of patients