Large-Scale Screening: Phenotypic and Mutational Spectrum in Isolated and Combined Dystonia Genes.

BACKGROUND: Pathogenic variants in several genes have been linked to genetic forms of isolated or combined dystonia. The phenotypic and genetic spectrum and the frequency of pathogenic variants in these genes have not yet been fully elucidated, neither in patients with dystonia nor with other, sometimes co-occurring movement disorders such as Parkinson's disease (PD). OBJECTIVES: To screen >2000 patients with dystonia or PD for rare variants in known dystonia-causing genes. METHODS: We screened 1207 dystonia patients from Germany (DysTract consortium), Spain, and South Korea, and 1036 PD patients from Germany for pathogenic variants using a next-generation sequencing gene panel. The impact on DNA methylation of KMT2B variants was evaluated by analyzing the gene's characteristic episignature. RESULTS: We identified 171 carriers (109 with dystonia [9.0%]; 62 with PD [6.0%]) of 131 rare variants (minor allele frequency <0.005). A total of 52 patients (48 dystonia [4.0%]; four PD [0.4%, all with GCH1 variants]) carried 33 different (likely) pathogenic variants, of which 17 were not previously reported. Pathogenic biallelic variants in PRKRA were not found. Episignature analysis of 48 KMT2B variants revealed that only two of these should be considered (likely) pathogenic. CONCLUSION: This study confirms pathogenic variants in GCH1, GNAL, KMT2B, SGCE, THAP1, and TOR1A as relevant causes in dystonia and expands the mutational spectrum. Of note, likely pathogenic variants only in GCH1 were also found among PD patients. For DYT-KMT2B, the recently described episignature served as a reliable readout to determine the functional effect of newly identified variants. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Catecholamines and Parkinson's disease: tyrosine hydroxylase (TH) over tetrahydrobiopterin (BH4) and GTP cyclohydrolase I (GCH1) to cytokines, neuromelanin, and gene therapy: a historical overview.

The author identified the genes and proteins of human enzymes involved in the biosynthesis of catecholamines (dopamine, norepinephrine, epinephrine) and tetrahydrobiopterin (BH4): tyrosine hydroxylase (TH), aromatic L-amino acid decarboxylase (AADC), dopamine ß-hydroxylase (DBH), phenylethanolamine N-methyltransferase (PNMT), and GTP cyclohydrolase I (GCH1). In Parkinson's disease (PD), the activities and levels of mRNA and protein of all catecholamine-synthesizing enzymes are decreased, especially in dopamine neurons in the substantia nigra. Hereditary GCH1 deficiency results in reductions in the levels of BH4 and the activities of TH, causing decreases in dopamine levels. Severe deficiencies in GCH1 or TH cause severe decreases in dopamine levels leading to severe neurological symptoms, whereas mild decreases in TH activity in mild GCH1 deficiency or in mild TH deficiency result in only modest reductions in dopamine levels and symptoms of DOPA-responsive dystonia (DRD, Segawa disease) or juvenile Parkinsonism. DRD is a treatable disease and small doses of L-DOPA can halt progression. The death of dopamine neurons in PD in the substantia nigra may be related to (i) inflammatory effect of extra neuronal neuromelanin, (ii) inflammatory cytokines which are produced by activated microglia, (iii) decreased levels of BDNF, and/or (iv) increased levels of apoptosis-related factors. This review also discusses progress in gene therapies for the treatment of PD, and of GCH1, TH and AADC deficiencies, by transfection of TH, AADC, and GCH1 via adeno-associated virus (AAV) vectors.

GCH1 reduces LPS-induced alveolar macrophage polarization and inflammation by inhibition of ferroptosis.

OBJECTIVE: GTP cyclohydrolase 1(GCH1) was reported to protect against ferroptosis. However, it is not clear whether GCH1 reduced lipopolysaccharide (LPS)-induced macrophage polarization and inflammation by inhibition of ferroptosis. METHODS: Bioinformatics analysis was used to screen differential expression genes (DEGs) and obtain the different pathways and biological features. Lasso cox regression analysis with ferroptosis related DEGs was established to screen the most relevant genes for disease risk. LPS induced Raw264.7 macrophage polarization model and GCH1-specific siRNA oligos transfection were performed to confirm the function of GCH1. Immunofluorescence staining, western blot and quantitative real-time PCR were performed to detect the expression of iNOS, CD206, GCH1, IL6, SLC2A6, F4/80, IL1ß, TNFα, IL10, GPX4, ACSL4, AMPK and p-AMPK in macrophages. The levels of ROS, SOD, MDA and GSH were detected according to the instructions of the reagent kit, respectively. RESULTS: 542 DEGs were screened from GSE40885 microarray. GO and KEGG pathway enrichment analysis showed that the upregulated DEGs induced by LPS in alveolar macrophage were closely associated with inflammatory and immune responses, the downregulated DEGs were related to lipid metabolism, insulin resistance and AMPK signal pathway. Lasso cox regression analysis screened GCH1, IL6, and SLC2A6. Our experimental results showed that the expression of GCH1 and IL6 in the LPS group was higher than that in the control group, but there was no difference in the expression of SLC2A6. Bioinformatics analysis with GSE112720 observed that ferroptosis was enriched in GCHfl/fl + LPS group compared with GCHfl/flTie2cre + LPS group and GCHfl/fl + control group. Silence of GCH1 increased the levels of IL6, TNF-α and IL-1ß and decreased IL10 level. Silence of GCH1 increased iNOS level and decreased CD206 level. Moreover, silence of GCH1 raised ferroptosis induced by LPS in macrophages and suppressed the activity of AMPK pathway. CONCLUSIONS: GCH1 inhibited ferroptosis in LPS-stimulated macrophages, reduced macrophage toward to M1 polarization and inflammatory response.

Relationship of Genotype, Phenotype, and Treatment in Dopa-Responsive Dystonia: MDSGene Review.

BACKGROUND: Pathogenic variants in 5 genes (GCH1, TH, PTS, SPR, and QDPR), involved in dopamine/tetrahydrobiopterin biosynthesis or recycling, have been linked to Dopa-responsive dystonia (DRD). Diagnosis and treatment are often delayed due to high between- and within-group variability. OBJECTIVES: Comprehensively analyzed individual genotype, phenotype, treatment response, and biochemistry information. METHODS: 734 DRD patients and 151 asymptomatic GCH1 mutation carriers were included using an MDSGene systematic literature review and an automated classification approach to distinguish between different forms of monogenic DRDs. RESULTS: Whereas dystonia, L-Dopa responsiveness, early age at onset, and diurnal fluctuations were identified as red flags, parkinsonism without dystonia was rarely reported (11%) and combined with dystonia in only 18% of patients. While sex was equally distributed in autosomal recessive DRD, there was female predominance in autosomal dominant DYT/PARK-GCH1 patients accompanied by a lower median age at onset and more dystonia in females compared to males. Accordingly, the majority of asymptomatic heterozygous GCH1 mutation carriers (>8 years of age) were males. Multiple other subgroup-specific characteristics were identified, showing high accuracy in the automated classification approach: Seizures and microcephaly were mostly seen in DYT/PARK-PTS, autonomic symptoms appeared commonly in DYT/PARK-TH and DYT/PARK-PTS, and sleep disorders and oculogyric crises in DYT/PARK-SPR. Biochemically, homovanillic acid and 5-hydroxyindoleacetic acid in CSF were reduced in most DRDs, but neopterin and biopterin were increased only in DYT/PARK-PTS and DYT/PARK-SPR. Hyperphenylalaninemia was seen in DYT/PARK-PTS, DYT/PARK-QDPR, and rarely reported in autosomal recessive DYT/PARK-GCH1. CONCLUSIONS: Our indicators will help to specify diagnosis and accelerate start of treatment. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Influence of genetic variants on remifentanil sensitivity in Chinese women.

WHAT IS KNOWN AND OBJECTIVE: Significant individual differences have been observed in pain sensitivity and analgesic effect of opioids. Previous studies have shown that genetic factors contributed to analgesics requirement obviously. Therefore, we investigated the role of genetic polymorphisms in the sensitivity to the analgesic effect of remifentanil in this study. METHODS: One hundred thirty-seven patients undergoing gynaecological surgery were observed. Before procedures, we measured the basal pain threshold of each patient, including the pressure pain threshold and pressure pain tolerance threshold. Subsequently, patients received a continuous remifentanil infusion for 15 min at a constant rate of 0.2 µg/(kg min). The pain thresholds were measured again after the remifentanil infusion. Moreover, respiratory depression was estimated using oxygen saturation during infusion. DNA was extracted from peripheral venous blood and genotyped using SNaPshot technology. RESULTS AND DISCUSSION: Polymorphisms were found in genes associated with the individual variation in analgesia. Participants carrying OPRM1 rs9397685 AA, ADRB1 rs1801253 CC, and GCH1 rs8007267 CC polymorphisms showed higher sensitivity to analgesic effect induced by remifentanil, and the participants carrying the OPRD1 rs2234918 TT showed lower sensitivity to remifentanil-related respiratory depression. Moreover, individual susceptibility to remifentanil increases with age. WHAT IS NEW AND CONCLUSION: Gene variation in OPRM1 rs9397685 AA, ADRB1 rs1801253 CC, GCH1 rs8007267 CC, and OPRD1 rs2234918 TT were related to the conspicuous interindividual differences in the analgesia and respiratory depression of remifentanil, mainly by affecting the target protein receptors and relative metabolic enzymes.

Biophysical and structural investigation of the regulation of human GTP cyclohydrolase I by its regulatory protein GFRP.

GTP Cyclohydrolase I (GCH1) catalyses the conversion of guanosine triphosphate (GTP) to dihydroneopterin triphosphate (H2NTP), the initiating step in the biosynthesis of tetrahydrobiopterin (BH4). BH4 functions as co-factor in neurotransmitter biosynthesis. BH4 homeostasis is a promising target to treat pain disorders in patients. The function of mammalian GCH1s is regulated by a metabolic sensing mechanism involving a regulator protein, GCH1 feedback regulatory protein (GFRP). Dependent on the relative cellular concentrations of effector ligands, BH4 and phenylalanine, GFRP binds GCH1 to form inhibited or activated complexes, respectively. We determined high-resolution structures of the ligand-free and -bound human GFRP and GCH1-GFRP complexes by X-ray crystallography. Highly similar binding modes of the substrate analogue 7-deaza-GTP to active and inhibited GCH1-GFRP complexes confirm a novel, dissociation rate-controlled mechanism of non-competitive inhibition to be at work. Further, analysis of all structures shows that upon binding of the effector molecules, the conformations of GCH1 or GFRP are altered and form highly complementary surfaces triggering a picomolar interaction of GFRP and GCH1 with extremely slow koff values, while GCH1-GFRP complexes rapidly disintegrate in absence of BH4 or phenylalanine. Finally, comparing behavior of full-length and N-terminally truncated GCH1 we conclude that the disordered GCH1 N-terminus does not have impact on complex formation and enzymatic activity. In summary, this comprehensive and methodologically diverse study helps to provide a better understanding of the regulation of GCH1 by GFRP and could thus stimulate research on GCH1 modulating drugs.

GCH1 mutations in hereditary spastic paraplegia.

GCH1 mutations have been associated with dopa-responsive dystonia (DRD), Parkinson's disease (PD) and tetrahydrobiopterin (BH4 )-deficient hyperphenylalaninemia B. Recently, GCH1 mutations have been reported in five patients with hereditary spastic paraplegia (HSP). Here, we analyzed a total of 400 HSP patients (291 families) from different centers across Canada by whole exome sequencing (WES). Three patients with heterozygous GCH1 variants were identified: monozygotic twins with a p.(Ser77_Leu82del) variant, and a patient with a p.(Val205Glu) variant. The former variant is predicted to be likely pathogenic and the latter is pathogenic. The three patients presented with childhood-onset lower limb spasticity, hyperreflexia and abnormal plantar responses. One of the patients had diurnal fluctuations, and none had parkinsonism or dystonia. Phenotypic differences between the monozygotic twins were observed, who responded well to levodopa treatment. Pathway enrichment analysis suggested that GCH1 shares processes and pathways with other HSP-associated genes, and structural analysis of the variants indicated a disruptive effect. In conclusion, GCH1 mutations may cause HSP; therefore, we suggest a levodopa trial in HSP patients and including GCH1 in the screening panels of HSP genes. Clinical differences between monozygotic twins suggest that environmental factors, epigenetics, and stochasticity could play a role in the clinical presentation.

Combined dystonias: clinical and genetic updates.

The genetic combined dystonias are a clinically and genetically heterogeneous group of neurologic disorders defined by the overlap of dystonia and other movement disorders such as parkinsonism or myoclonus. The number of genes associated with combined dystonia syndromes has been increasing due to the wider recognition of clinical features and broader use of genetic testing. Nevertheless, these diseases are still rare and represent only a small subgroup among all dystonias. Dopa-responsive dystonia (DYT/PARK-GCH1), rapid-onset dystonia-parkinsonism (DYT/PARK-ATP1A3), X-linked dystonia-parkinsonism (XDP, DYT/PARK-TAF1), and young-onset dystonia-parkinsonism (DYT/PARK-PRKRA) are monogenic combined dystonias accompanied by parkinsonian features. Meanwhile, MYC/DYT-SGCE and MYC/DYT-KCTD17 are characterized by dystonia in combination with myoclonus. In the past, common molecular pathways between these syndromes were the center of interest. Although the encoded proteins rather affect diverse cellular functions, recent neurophysiological evidence suggests similarities in the underlying mechanism in a subset. This review summarizes recent developments in the combined dystonias, focusing on clinico-genetic features and neurophysiologic findings. Disease-modifying therapies remain unavailable to date; an overview of symptomatic therapies for these disorders is also presented.

Identification of candidate genes associated with fibromyalgia susceptibility in southern Spanish women: the al-Ándalus project.

BACKGROUND: Candidate-gene studies on fibromyalgia susceptibility often include a small number of single nucleotide polymorphisms (SNPs), which is a limitation. Moreover, there is a paucity of evidence in Europe. Therefore, we compared genotype frequencies of candidate SNPs in a well-characterised sample of Spanish women with fibromyalgia and healthy non-fibromyalgia women. METHODS: A total of 314 women with a diagnosis of fibromyalgia (cases) and 112 non-fibromyalgia healthy (controls) women participated in this candidate-gene study. Buccal swabs were collected for DNA extraction. Using TaqMan™ OpenArray™, we analysed 61 SNPs of 33 genes related to fibromyalgia susceptibility, symptoms, or potential mechanisms. RESULTS: We observed that the rs841 and rs1799971 GG genotype was more frequently observed in fibromyalgia than in controls (p = 0.04 and p = 0.02, respectively). The rs2097903 AT/TT genotypes were also more often present in the fibromyalgia participants than in their control peers (p = 0.04). There were no differences for the remaining SNPs. CONCLUSIONS: We identified, for the first time, associations of the rs841 (guanosine triphosphate cyclohydrolase 1 gene) and rs2097903 (catechol-O-methyltransferase gene) SNPs with higher risk of fibromyalgia susceptibility. We also confirmed that the rs1799971 SNP (opioid receptor µ1 gene) might confer genetic risk of fibromyalgia. We did not adjust for multiple comparisons, which would be too stringent and yield to non-significant differences in the genotype frequencies between cases and controls. Our findings may be biologically meaningful and informative, and should be further investigated in other populations. Of particular interest is to replicate the present study in a larger independent sample to confirm or refute our findings. On the other hand, by including 61 SNPs of 33 candidate-genes with a strong rationale (they were previously investigated in relation to fibromyalgia susceptibility, symptoms or potential mechanisms), the present research is the most comprehensive candidate-gene study on fibromyalgia susceptibility to date.

GCH1 attenuates cardiac autonomic nervous remodeling in canines with atrial-tachypacing via tetrahydrobiopterin pathway regulated by microRNA-206.

BACKGROUND/AIMS: Cardiac autonomic nerve remodeling (ANR) is an important mechanism of atrial fibrillation (AF). GTP cyclohydrolase I, encoded by GCH1, is the rate-limiting enzyme in de novo synthesis of tetrahydrobiopterin (BH4), an essential cofactor for nitric oxide (NO) synthesis. Previous studies reported that increased BH4 and NO content negatively regulated nerve regeneration. This study investigated the effects of GCH1 on ANR via BH4 pathway, regulated by microRNA-206 (miR-206). METHODS AND RESULTS: In canines, atrial tachypacing (A-TP), together with miR-206 overexpression, increased PGP9.5 level and inhibited GCH1 expression by quantitative real-time polymerase chain reaction and western blot analysis. GCH1 was validated to be a direct target of miR-206 by luciferase assays. Meanwhile, miR-206 overexpression by lentiviruses infection into right superior pulmonary vein fat pad decreased GCH1 expression to ∼40% and further reduced BH4 and NO content compared with the control canines. After infection of GCH1 overexpression lentiviruses for two weeks, atrial effective refractory period was increased compared with the control group (105.8 ± 1.537 ms vs 99.17 ± 2.007 ms, P < 0.05). Moreover, GCH1 overexpression attenuated canines' atrial PGP9.5 level to ∼56% of the controls. In myocardial cells, transfection of GCH1 overexpression lentiviruses also decreased PGP9.5 expression to 26% of the control group. In patients, plasma was collected and miR-206 expression was upregulated in AF patients (n = 18) than the controls (n = 12). CONCLUSIONS: Our findings suggested that GCH1 downregulation exacerbated ANR by decreasing atrial BH4 and NO content modulated by miR-206 in A-TP canines. This indicates that GCH1 may prevent the initiation of AF through inhibiting ANR.

A novel tyrosine hydroxylase variant in a group of Chinese patients with dopa-responsive dystonia.

Dopa-responsive dystonia (DRD) comprises a heterogeneous group of movement disorders. A limited number of studies of Chinese patients with DRD have been reported. In the present study, we investigated the clinical and genetic features of 12 Chinese DRD families. Point mutation analysis of the GTP-cyclohydrolase I (GCH1), tyrosine hydroxylase (TH) and sepiapterin reductase (SPR) genes was conducted by direct sequencing. In addition, multiplex ligation-dependent probe amplification targeting GCH1 and TH was performed in "mutation-free" patients. Three reported mutations (IVS2-2A>G, c.293C>T, c.550C>T) were detected in GCH1, whereas two compound heterozygous variants were identified in TH, one of which was novel (c.1083C>A). Furthermore, this novel variant was not detected in any of the 250 ethnicity-matched, healthy controls. No exon deletions or duplicate mutations in the two genes were found in patients with DRD. No mutation in SPR was found. In addition, one patient with the IVS2-2A>G mutation in GCH1 showed signs of Parkinsonism. In conclusion, we here identified a novel heterozygous variant in TH (c.1083C>A). It is important to perform routine screening of GCH1 and TH for patients with DRD. While for patients with Parkinsonism, GCH1 mutation analysis should be performed after screening of genes like PARKIN, PARK7 (DJ-1) and PINK1.

Dopa-responsive dystonia or early-onset Parkinson disease - Genotype-phenotype correlation.

OBJECTIVE: Dopa-responsive dystonia (DRD) is a rare form of hereditary movement disorder with onset in childhood, characterized by gait difficulties due to postural dystonia with marked improvement after low doses of levodopa. Mutations in the GCH1 gene are the most common cause of DRD, however, in some cases when the disease is associated with parkinsonism mutations in the PARK2 gene may be identified. The aim of this study was to analyze and compare genotype-phenotype correlation. MATERIAL/PARTICIPANTS: Four families with inter- and intrafamilial variability of progressive gait dysfunction due to lower limb dystonia occurring in childhood or adolescence were included in the analysis. METHODS: General and neurological examination was performed for all affected family members and asymptomatic mutation carriers. The molecular analysis encompassed GCH1 and PARK2 genes. RESULTS: All probands were clinically diagnosed with DRD. The molecular analysis revealed, however, that the dopa-responsive dystonia phenotype was caused by a mutation in the GCH1 gene in three families and in the PARK2 gene in one family. Obtained results allowed to establish the final diagnosis for all families as DYT5a or early-onset Parkinson disease (EO-PD). CONCLUSIONS: Reported cases confirm that the DRD phenotype may have heterogeneous genetic background and may be caused by point mutations or rearrangements in the GCH1 gene as well as in the PARK2 gene. Differential diagnosis and genetic tests covering the analysis of genes causative for DRD and EO-PD should be obligatory in both disorders diagnostics as DRD, mainly adolescent onset dystonia, may be associated with parkinsonism.

Depressed mood, anxiety, and the use of labor analgesia.

Relatively little is known about mental health and labor pain. The aim of this study was to assess if self-rated antenatal depressed mood and anxiety are associated with pain-related behaviors and self-reported labor pain. We also wanted to replicate our previous finding of altered labor pain behavior in carriers of a specific guanosine triphosphate cyclohydrolase 1 gene (GCH1) haplotype. Ninety-nine women in gestational weeks 37 to 40 filled out questionnaires on depression and anxiety symptoms and later rated their labor pain by use of visual analog scales. Each subject was also genotyped for GCH1. Following adjustment for relevant confounders, women who arrived early to the delivery unit (cervical dilation <5 cm) had a significantly higher antenatal Montgomery-Åsberg Depression Rating Scale (MADRS-S) score, p < 0.05, than late arrivers (cervical dilation >5 cm). Women with increased Spielberger State-Trait Anxiety Inventory (STAI-T) scores reported higher self-rated pain prior to labor analgesia, p < 0.05, than women with low STAI-T scores. No association between the GCH1 pain-protective haplotype and cervical dilation was found, but a previously demonstrated association with increased use of second-line analgesia was confirmed. Depressed mood during pregnancy is associated with early arrival to the delivery department, whereas antenatal anxiety is associated with increased self-rated pain prior to labor analgesia.

Association of four new candidate genetic variants with Parkinson's disease in a Han Chinese population.

Large-scale meta-analysis of genome-wide association data has identified six new risk loci (SIPA1L2, INPP5F, MIR4697, GCH1, VPS13C, and DDRGK1) for Parkinson's disease (PD). However, the characteristics of those loci in a Han Chinese population from mainland China are unknown. We examined genetic associations of VPS13C rs2414739, MIR4697 rs329648, GCH1 rs11158026, and SIPA1L2 rs10797576 with PD susceptibility in a Han Chinese population of 1028 sporadic PD patients and 1109 healthy controls. All subjects were genotyped for these loci using the Sequenom iPLEX Assay. We also conducted further stratified analysis according to age at onset and compared the clinical characteristics between minor allele carriers and non-carriers for each locus. However, we did not observe any significant difference in genotype distribution between PD patients and controls for the four loci, even after being stratified by age at onset. Besides, minor allele carriers cannot be distinguished from non-carriers based on their clinical features. Our findings first demonstrated that VPS13C rs2414739, MIR4697 rs329648, GCH1 rs11158026, and SIPA1L2 rs10797576 do not confer a significant risk for PD in Chinese population. Additional replication studies in other populations and functional studies are warranted to better validate the role of the four new loci in PD risk.

Coffee extracts suppress tryptophan breakdown in mitogen-stimulated peripheral blood mononuclear cells.

OBJECTIVES: Coffee consumption is considered to exert an influence on mood, the immune system, cardiovascular disease, and cancer development, but the mechanisms of action of coffee and its compounds are only partly known and understood. METHODS: Immunomodulatory effects of filtered extracts of coffee and decaffeinated coffee as well as coffee compounds were investigated in human peripheral blood mononuclear cells (PBMCs) stimulated with mitogen phytohemagglutinin (PHA). The activation of PBMCs was monitored by the breakdown of tryptophan to kynurenine via enzyme indoleamine 2,3-dioxygenase (IDO) and the production of the immune activation marker neopterin by GTP-cyclohydrolase I (GCH1). Both of these biochemical pathways are induced during cellular immune activation in response to the Th1-type cytokine interferon-γ (IFN-γ). RESULTS: Filtered extracts of coffee and decaffeinated coffee both suppressed tryptophan breakdown and neopterin formation in mitogen-stimulated PBMCs efficiently and in a dose-dependent manner. Of 4 coffee compounds tested individually, only gallic acid and less strong also caffeic acid had a consistent suppressive influence but also affected cell viability, whereas pure caffeine and chlorogenic acid exerted no relevant effect in the PBMC assay. CONCLUSION: The parallel influence of extracts on tryptophan breakdown and neopterin production shows an anti-inflammatory and immunosuppressive property of coffee extracts and some of its compounds. When extrapolating the in vitro results to in vivo, IFN-γ-mediated breakdown of tryptophan could be counteracted by the consumption of coffee or decaffeinated coffee. This may increase tryptophan availability for the biosynthesis of the neurotransmitter 5-hydroxytryptamine (serotonin) and thereby improve mood and quality of life.

Parkinson's disease in GTP cyclohydrolase 1 mutation carriers.

GTP cyclohydrolase 1, encoded by the GCH1 gene, is an essential enzyme for dopamine production in nigrostriatal cells. Loss-of-function mutations in GCH1 result in severe reduction of dopamine synthesis in nigrostriatal cells and are the most common cause of DOPA-responsive dystonia, a rare disease that classically presents in childhood with generalized dystonia and a dramatic long-lasting response to levodopa. We describe clinical, genetic and nigrostriatal dopaminergic imaging ([(123)I]N-ω-fluoropropyl-2ß-carbomethoxy-3ß-(4-iodophenyl) tropane single photon computed tomography) findings of four unrelated pedigrees with DOPA-responsive dystonia in which pathogenic GCH1 variants were identified in family members with adult-onset parkinsonism. Dopamine transporter imaging was abnormal in all parkinsonian patients, indicating Parkinson's disease-like nigrostriatal dopaminergic denervation. We subsequently explored the possibility that pathogenic GCH1 variants could contribute to the risk of developing Parkinson's disease, even in the absence of a family history for DOPA-responsive dystonia. The frequency of GCH1 variants was evaluated in whole-exome sequencing data of 1318 cases with Parkinson's disease and 5935 control subjects. Combining cases and controls, we identified a total of 11 different heterozygous GCH1 variants, all at low frequency. This list includes four pathogenic variants previously associated with DOPA-responsive dystonia (Q110X, V204I, K224R and M230I) and seven of undetermined clinical relevance (Q110E, T112A, A120S, D134G, I154V, R198Q and G217V). The frequency of GCH1 variants was significantly higher (Fisher's exact test P-value 0.0001) in cases (10/1318 = 0.75%) than in controls (6/5935 = 0.1%; odds ratio 7.5; 95% confidence interval 2.4-25.3). Our results show that rare GCH1 variants are associated with an increased risk for Parkinson's disease. These findings expand the clinical and biological relevance of GTP cycloydrolase 1 deficiency, suggesting that it not only leads to biochemical striatal dopamine depletion and DOPA-responsive dystonia, but also predisposes to nigrostriatal cell loss. Further insight into GCH1-associated pathogenetic mechanisms will shed light on the role of dopamine metabolism in nigral degeneration and Parkinson's disease.

Calcium-sensing receptor antagonist (calcilytic) NPS 2143 specifically blocks the increased secretion of endogenous Aß42 prompted by exogenous fibrillary or soluble Aß25-35 in human cortical astrocytes and neurons-therapeutic relevance to Alzheimer's disease.

The "amyloid-ß (Aß) hypothesis" posits that accumulating Aß peptides (Aßs) produced by neurons cause Alzheimer's disease (AD). However, the Aßs contribution by the more numerous astrocytes remains undetermined. Previously we showed that fibrillar (f)Aß25-35, an Aß42 proxy, evokes a surplus endogenous Aß42 production/accumulation in cortical adult human astrocytes. Here, by using immunocytochemistry, immunoblotting, enzymatic assays, and highly sensitive sandwich ELISA kits, we investigated the effects of fAß25-35 and soluble (s)Aß25-35 on Aß42 and Aß40 accumulation/secretion by human cortical astrocytes and HCN-1A neurons and, since the calcium-sensing receptor (CaSR) binds Aßs, their modulation by NPS 2143, a CaSR allosteric antagonist (calcilytic). The fAß25-35-exposed astrocytes and surviving neurons produced, accumulated, and secreted increased amounts of Aß42, while Aß40 also accrued but its secretion was unchanged. Accordingly, secreted Aß42/Aß40 ratio values rose for astrocytes and neurons. While slightly enhancing Aß40 secretion by fAß25-35-treated astrocytes, NPS 2143 specifically suppressed the fAß25-35-elicited surges of endogenous Aß42 secretion by astrocytes and neurons. Therefore, NPS 2143 addition always kept Aß42/Aß40 values to baseline or lower levels. Mechanistically, NPS 2143 decreased total CaSR protein complement, transiently raised proteasomal chymotrypsin activity, and blocked excess NO production without affecting the ongoing increases in BACE1/ß-secretase and γ-secretase activity in fAß25-35-treated astrocytes. Compared to fAß25-35, sAß25-35 also stimulated Aß42 secretion by astrocytes and neurons and NPS 2143 specifically and wholly suppressed this effect. Therefore, since NPS 2143 thwarts any Aß/CaSR-induced surplus secretion of endogenous Aß42 and hence further vicious cycles of Aß self-induction/secretion/spreading, calcilytics might effectively prevent/stop the progression to full-blown AD.

Exploring the therapeutic potential of tetrahydrobiopterin for heart failure with preserved ejection fraction: A path forward.

A large number of patients are affected by classical heart failure (HF) symptomatology with preserved ejection fraction (HFpEF) and multiorgan syndrome. Due to high morbidity and mortality rate, hospitalization and mortality remain serious socioeconomic problems, while the lack of effective pharmacological or device treatment means that HFpEF presents a major unmet medical need. Evidence from clinical and basic studies demonstrates that systemic inflammation, increased oxidative stress, and impaired mitochondrial function are the common pathological mechanisms in HFpEF. Tetrahydrobiopterin (BH4), beyond being an endogenous co-factor for catalyzing the conversion of some essential biomolecules, has the capacity to prevent systemic inflammation, enhance antioxidant resistance, and modulate mitochondrial energy production. Therefore, BH4 has emerged in the last decade as a promising agent to prevent or reverse the progression of disorders such as cardiovascular disease. In this review, we cover the clinical progress and limitations of using downstream targets of nitric oxide (NO) through NO donors, soluble guanylate cyclase activators, phosphodiesterase inhibitors, and sodium-glucose co-transporter 2 inhibitors in treating cardiovascular diseases, including HFpEF. We discuss the use of BH4 in association with HFpEF, providing new evidence for its potential use as a pharmacological option for treating HFpEF.

De novo p.Glu61Ter mutation in GCH1 in a Moroccan patient with dopa-responsive dystonia: a case report.

Dopa-responsive dystonia (DRD) is a hereditary movement disorder due to a selective nigrostriatal dopamine deficiency. It is characterized by onset in childhood or adolescence with marked diurnal fluctuation with or without Parkinsonian features, and is caused by mutations in GCH1 gene. We report in this study the clinical and genetic features of the first DRD Moroccan patient. Using a gene panel sequencing, we identified a heterozygous nonsense variant p. Glu61Ter in GCH1. A subsequent targeted segregation analysis by Sanger sequencing validated the presence of the mutation in the patient, which was found to have occurred de novo. The objective of this study is to report the first description of DRD in Morocco, and highlights the importance of new generation sequencing technology in the reduction of medical wandering and the management of hereditary diseases.