A marked contrast between serotonergic and dopaminergic changes in dopa-responsive dystonia

Abstract

Dopa-responsive dystonia (DRD) is a clinical syndrome characterized by childhood-onset dystonia and a dramatic and sustained response to low doses of levodopa.1 Autosomal dominant DRD is caused by mutations in GCH1, which encodes GTP cyclohydrolase 1 (GTPCH), the rate-limiting enzyme in the biosynthesis of tetrahydrobiopterin (BH4; the cofactor for phenylalanine and tyrosine and tryptophan hydroxylases [TH and TPH]).1 Recently, the phenotype of this major form of DRD (GTPCH-deficient DRD) was expanded to include nonmotor symptoms, such as depression, anxiety, and obsessive-compulsive disorder, and these psychiatric symptoms were attributed to serotonin deficiency.2,3 However, the actual status of brain serotonergic involvement in GTPCH-deficient DRD is unknown. To evaluate possible serotonin deficiency, we measured levels of serotonin markers in the striatum (one of the serotonin-and dopamine-rich brain regions) 4 in a 19-year-old woman with DRD and a GCH1 nonsense mutation. 5 Her dystonia (onset at 5 years of age) was well controlled by levodopa (without a decarboxylase inhibitor) 750 mg/d for 11 years (no psychiatric symptoms and residual motor signs) until her automobile accidental death. Neuropathologic studies revealed a normal population of cells with reduced melanin in the substantia nigra and also no evidence of degeneration in other brain areas. 1,5 This study was approved by the institutional review board of the Centre for Addiction and Mental Health.Results. In the putamen and caudate nucleus of the patient with GTPCH-deficient DRD, protein concentrations of serotonin transporter, TPH, and "control" neuron-specific enolase were within the age-matched normal control range (table). Normal dopamine transporter, dopa decarboxylase protein, and vesicular monoamine transporter 2 levels and severely reduced TH protein content in the putamen were reported previously in this patient. 5In the striatum of the patient, we found normal concentrations of serotonin and confirmed very low levels of dopamine. The most remarkable contrast between serotonergic and dopaminergic findings in this patient was preserved TPH protein and serotonin concentrations (118% and 79% of the age-matched normal control means) vs severely decreased TH protein and dopamine levels (less than 1.5% 5 and 8%) in the putamen.Discussion. Biochemical findings in GTPCH-deficient DRD have suggested that severe striatal dopamine reduction (confirmed in the present study) is caused not only by decreased TH activity due to low cofactor content but also by actual loss of TH protein without nerve terminal loss. No dopaminergic terminal reduction was indicated by the normal striatal dopamine transporter, dopa decarboxylase protein, and vesicular monoamine transporter 2 levels. 1,5 In this autosomal dominant DRD, as BH4 is also the cofactor for TPH, it has been assumed that partial BH4 deficiency results in lowering of serotonin and that there is an increased frequency of nonmotor symptoms relating to a deficit in serotonin. 2,3 However, the present inve...

Enhanced pseudotargeted analysis using a segment data dependent acquisition strategy by liquid chromatography–tandem mass spectrometry for a metabolomics study of liquiritin in the treatment of depression

“…Therefore, the decline of retinol metabolism might be closely correlated with immune dysregulation in depression [4]. Phenylalanine, tyrosine, and tryptophan were involved in the biosynthesis of serotonin, whose depletion caused the anhedonia symptom of depression [24]. Phenylalanine was an important precursor molecule for neurotransmitter biosynthesis, and the reduction of phenylalanine triggered off a depression in mood [25].…”

Serotonergic system in vivo with [11C]DASB PET scans in GTP-cyclohydrolase deficient dopa-responsive dystonia patients

“…As we know that other neurotransmitters, such as dopamine and acetylcholine, are also involved in dystonia, it is very likely that the non-motor symptoms, in a similar way, can be the result of an imbalance between multiple neurotransmitters, rather than a disruption in the pathway of only serotonin. Other neurotransmitters such as dopamine, noradrenaline and acetylcholine are extensively studied with regard to psychiatric disorders and sleep disorders 23 – 25 and are likely involved in non-motor symptoms in dystonia as well. Further studies assessing not only the serotonergic system, but combined with other neurotransmitter systems are necessary.…”

Doparesponsive dystonier

“…Klassisk doparesponsiv dystoni debuterer typisk i barne-eller ungdomsårene, oftest med gangvansker. Symptomene forverres mot kveld og bedres på morgenen etter søvn og har en dramatisk positiv og vedvarende respons på levodopabehandling (2)(3)(4).…”