Rutin as a potent antioxidant: implications for neurodegenerative disorders

A wide range of neurodegenerative diseases (NDs), including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and prion diseases, share common mechanisms such as neuronal loss, apoptosis, mitochondrial dysfunction, oxidative stress, and inflammation. Intervention strategies using plant-derived bioactive compounds have been offered as a form of treatment for these debilitating conditions, as there are currently no remedies to prevent, reverse, or halt the progression of neuronal loss. Rutin, a glycoside of the flavonoid quercetin, is found in many plants and fruits, especially buckwheat, apricots, cherries, grapes, grapefruit, plums, and oranges. Pharmacological studies have reported the beneficial effects of rutin in many disease conditions, and its therapeutic potential in several models of NDs has created considerable excitement. Here, we have summarized the current knowledge on the neuroprotective mechanisms of rutin in various experimental models of NDs. The mechanisms of action reviewed in this article include reduction of proinflammatory cytokines, improved antioxidant enzyme activities, activation of the mitogen-activated protein kinase cascade, downregulation of mRNA expression of PD-linked and proapoptotic genes, upregulation of the ion transport and antiapoptotic genes, and restoration of the activities of mitochondrial complex enzymes. Taken together, these findings suggest that rutin may be a promising neuroprotective compound for the treatment of NDs

Factors influencing the development of early- or late-onset Parkinson’s disease in a cohort of South African patients

Background. Neurodegenerative disorders such as Parkinson’s disease (PD) contribute significantly to global disease burden. PD can be categorised into early-onset PD (EOPD) with an age at onset (AAO) of ≤50 years and late-onset PD (LOPD) with an AAO of 50 years. Aims. To identify factors influencing EOPD and LOPD development in a group of patients in South Africa (SA). Methods. A total of 397 unrelated PD patients were recruited from the Movement Disorders Clinic at Tygerberg Hospital and via the Parkinson’s Association of SA. Patient demographic and environmental data were recorded and associations with PD onset (EOPD v. LOPD) were analysed with a Pearson’s Chi-squared test. The English- and Afrikaans-speaking (Afrikaner) white patients were analysed separately. Results. Logistic regression analysis showed that ethnicity (

Targeted next-generation sequencing identifies novel variants in candidate genes for Parkinson’s disease in Black South African and Nigerian patients

Background: The prevalence of Parkinson’s disease (PD) is increasing in sub-Saharan Africa, but little is known about the genetics of PD in these populations. Due to their unique ancestry and diversity, sub-Saharan African populations have the potential to reveal novel insights into the pathobiology of PD. In this study, we aimed to characterise the genetic variation in known and novel PD genes in a group of Black South African and Nigerian patients. Methods: We recruited 33 Black South African and 14 Nigerian PD patients, and screened them for sequence variants in 751 genes using an Ion AmpliSeq™ Neurological Research panel. We used bcftools to filter variants and annovar software for the annotation. Rare variants were prioritised using MetaLR and MetaSVM prediction scores. The effect of a variant on ATP13A2’s protein structure was investigated by molecular modelling. Results: We identified 14,655 rare variants with a minor allele frequency ≤ 0.01, which included 2448 missense variants. Notably, no common pathogenic mutations were identified in these patients. Also, none of the known PD-associated mutations were found highlighting the need for more studies in African populations. Altogether, 54 rare variants in 42 genes were considered deleterious and were prioritized, based on MetaLR and MetaSVM scores, for follow-up studies. Protein modelling showed that the S1004R variant in ATP13A2 possibly alters the conformation of the protein. Conclusions: We identified several rare variants predicted to be deleterious in sub-Saharan Africa PD patients; however, further studies are required to determine the biological effects of these variants and their possible role in PD. Studies such as these are important to elucidate the genetic aetiology of this disorder in patients of African ancestry

Identification of parkin interactions: implications for Parkinson’s disease

Thesis (PhD)--Stellenbosch University, 2015.ENGLISH ABSTRACT: Parkinson’s disease (PD) is a progressive and debilitating neurodegenerative disorder, characterized by a distinct motor phenotype and the selective loss of dopaminergic neurons in the substantia nigra. While the etiology of PD is not fully understood, it is thought to involve a combination of different genetic, cellular and environmental factors that independently or concurrently contribute to neurodegeneration. To date, several PD-causing genes have been identified, and investigations of their function have provided novel insights into the pathobiology of disease. Particularly interesting among the known PD genes is parkin, mutations in which are the most common genetic cause of early onset PD. Parkin is an E3 ligase that ubiquitinates protein substrates and targets such substrates for degradation via the ubiquitin proteasome system (UPS). Therefore, the loss of parkin may result in the deleterious accumulation or dysregulation of parkin substrates and neurotoxicity. Parkin’s enzymatic activity has also been implicated in the maintenance of mitochondrial health, and mitochondrial dysfunction is commonly reported in cellular and animal models of parkin deficiency. This study aimed to investigate parkin and its role in PD on various levels. Initially, genetic screening approaches were used to assess the contribution of parkin mutations to PD in a group of 229 South African patients. It was concluded that parkin mutations are rare in the South African PD population, being present in only seven (3.1%) patients in the study group. Interestingly, this study identified two of only three Black African PD patients with mutations in a known PD-causing gene to date. The low frequency of known PD genes raises the interesting possibility that the unique South African ethnic groups may harbor mutations in novel PD-causing genes. Although many parkin-interacting proteins have been identified in the literature, it is anticipated that novel, pathologically-relevant parkin substrates remain to be discovered. Hence, this study used a yeast two-hybrid (Y2H) approach to identify novel parkin interactions. This yielded 29 putative parkin interactors, of which four, namely ATPAF1, SEPT9, actin and 14-3-3η, were prioritized for verification by co-localization and co-immunoprecipitation experiments. Interestingly, two of the parkin interactors (ATPAF1 and SEPT9) were found to accumulate in the absence of parkin, supporting their role as authentic parkin substrates. The identification of these two intriguing proteins implicates parkin in the regulation of mitochondrial ATP synthase assembly and septin filament dynamics, which may be of significant relevance to our understanding of processes underlying neurodegeneration. Moreover, it was aimed to assess various markers of mitochondrial function in a parkin-deficient cellular model, as previous studies had reported conflicting results regarding mitochondrial impairments in patient-derived cells with parkin mutations. Hence, dermal fibroblasts were obtained from PD patients with homozygous parkin mutations, after which cell growth and viability, mitochondrial membrane potential, respiratory rates and the integrity of the mitochondrial network were assessed. Surprisingly, it was found that cell growth was significantly higher in the parkin-mutant fibroblasts compared to wild-type controls fibroblasts under basal conditions (p=0.0001), while exhibiting a greater inhibition of cell growth in the presence of the mitochondrial toxin CCCP (p=0.0013). Furthermore, whereas the mitochondrial networks of patient-derived fibroblasts were more fragmented than controls (p=0.0306), it was found that mitochondrial respiratory rates were paradoxically higher in the patients (p=0.0355). These unanticipated findings are suggestive of a compensatory response to the absence of parkin. The parkin-deficient cellular model was also used in a pilot study of the functional effects of vitamin K2 treatment, which has recently been identified as a promising PD therapeutic modality. It was found that treatment with vitamin K2 resulted in more interconnected mitochondrial networks (p=0.0001) and enhanced respiratory rates (p=0.0459) in both parkin-mutant and wild-type control cells. While these results need to be studied further, it suggests that vitamin K2 supplementation may be of use as a general promoter of mitochondrial integrity and function. In conclusion, this dissertation highlights some novel interactions of the parkin protein and some interesting phenotypes of parkin deficiency. It is hoped that further investigation of parkin and its role in PD will, ultimately, aid in the development of therapeutic strategies to treat this debilitating and poorly-understood disorder.AFRIKAANSE OPSOMMING: Parkinson se siekte (PS) is 'n progressiewe en aftakelende neurodegeneratiewe kondisie, wat gekarakteriseer word deur 'n kenmerkende bewegingsfenotipe en die selektiewe afsterwing van dopaminergiese neurone in die substantia nigra. Terwyl die etiologie van PS nie ten volle verstaan is nie, behels dit waarskynlik 'n kombinasie van verskillende genetiese, sellulêre en omgewings-faktore wat onafhanklik of gelyktydig lei tot senuwee-afsterwing. Tot op hede is daar al verskeie PS-veroorsakende gene geïdentifiseer, en die bestudering van hul funksie het nuwe insigte in die patobiologie van hierdie siekte verskaf. Onder meer hierdie PS gene is parkin van besondere belang, aangesien mutasies in parkin die mees algemene genetiese oorsaak van vroeë-aanvang PS is. Parkin is 'n E3 ligase-ensiem wat proteïen substrate ubiquitineer en teiken vir degradasie via die ubiquitien proteasoomstelsel (UPS). Dus kan die verlies van parkin lei tot die beskadigende opeenhoping of wanregulasie van parkin substrate en senuwee-afsterwing. Parkin se ensiematiese aktiwiteit is ook betrokke by die instandhouding van mitokondriale gesondheid, en mitokondriale afwykings word dikwels gerapporteer in sellulêre en diermodelle van parkin tekort. Hierdie studie het gepoog om parkin en sy rol in PS op verskillende vlakke te ondersoek. Aanvanklik is genetiese siftingsbenaderinge gebruik om die bydrae van parkin mutasies tot PS in 'n groep van 229 Suid-Afrikaanse pasiënte te evalueer. Die gevolgtrekking is bereik dat parkin mutasies skaars is in die Suid-Afrikaanse PS bevolking, aangesien dit teenwoordig is in net sewe (3.1%) pasiënte in die studie groep. Interessant genoeg, hierdie studie het twee van slegs drie gevalle van Swart Afrika-pasiënte met mutasies in 'n bekende PS geen to op datum geïdentifiseer. Die lae frekwensie van bekende PS gene versterk die stimulerende moontlikheid dat die unieke Suid-Afrikaanse sub-populasies dalk mutasies in nuwe PS-veroorsakende gene mag koester. Alhoewel baie parkin proteïen-interaksies reeds in die literatuur geïdentifiseer is, word daar verwag dat nuwe, patologies-relevante parkin substrate nog wag om ontdek te word. Dus het hierdie studie 'n gis twee-hibried (G2H) benadering gebruik om nuwe parkin interaksies te identifiseer. Hierdie het 29 vermeende parkin interaktors opgelewer, waarvan vier, naamlik ATPAF1, SEPT9, aktien en 14-3-3η, geprioritiseer is vir verifikasie deur mede-lokalisering en mede-immunopresipitasie eksperimente. Interessant genoeg, daar is gevind dat twee van die parkin interaktors (ATPAF1 en SEPT9) ophoop in die afwesigheid van parkin, wat hul rol as werklike parkin substrate ondersteun. Die identifisering van hierdie twee interessante proteïene impliseer parkin in die regulering van mitokondriale ATP sintase vervaardiging en septienfilament dinamika, wat moontlik van beduidende belang is vir ons begrip van die onderliggende prosesse wat senuwee-afsterwing veroorsaak. Verder is daar daarop gemik om verskeie aanwysigings van mitokondriale funksie in 'n parkin-gebrekkige sellulêre model te evalueer, aangesien vorige studies teenstrydige resultate rapporteer rakende mitokondriale afwykings in pasiënt-selle met parkin mutasies. Dus is daar dermale fibroblaste verkry van PS pasiënte met homosigotiese parkin mutasies, waarna sel-groei en lewensvatbaarheid, mitokondriale membraanpotensiaal, respiratoriese tempo en die integriteit van die mitokondriale netwerk geëvalueer is. Daar is verbasend gevind dat sel-groei aansienlik hoër is die parkin-mutante fibroblaste in vergelyking met wilde-tipe kontrole fibroblaste onder basale kondisies (p=0.0001), terwyl hulle 'n groter inhibisie van sel-groei in die teenwoordigheid van die mitokondriale toksien CCCP ondergaan (p=0.0013). Verder, terwyl die mitokondriale netwerke van pasiënt fibroblaste meer gefragmenteer is as die van kontroles (p=0.0306), is daar gevind dat mitokondriale respiratoriese tempo’s, paradoksaal-gewys, hoër is in die pasiënte (p=0.0355). Hierdie onverwagte bevindinge is suggestief van die aanskakeling van 'n vergoedende respons-proses in die afwesigheid van parkin. Die parkin-gebrekkige sellulêre model is ook gebruik in 'n voorlopige studie van die funksionele effekte van vitamiene K2 behandeling, wat onlangs geïdentifiseer is as 'n belowende terapeutiese moontlikheid vir PS. Daar is gevind dat sel-behandeling met vitamiene K2 lei tot meer geïnterkonnekteerde mitokondriale netwerke (p=0.0001) en verbeterde respiratoriese fuksie (p=0.0459) in beide parkin-mutante en wilde-tipe kontrole selle. Terwyl hierdie resultate verder bestudeer sal moet word, dui dit daarop dat vitamiene K2-aanvulling moontlik gebruik kan word as 'n algehele promotor van mitochondriale integriteit en funksie. Ten slotte, hierdie verhandeling beklemtoon ‘n paar nuwe interaksies van die parkin proteïen en 'n paar interessante fenotipes van parkin tekort. Daar word gehoop dat verdere ondersoek van parkin en parkin se rol in PS sal, uiteindelik, steun in die ontwikkeling van terapeutiese strategieë om hierdie aftakelende en swak-verstaande wanorde beter te behandel

Gitelman syndrome in a South African family presenting with hypokalaemia and unusual food cravings

Abstract Background Gitelman syndrome (GS) is an autosomal recessive renal tubular disorder characterised by renal salt wasting with hypokalaemia, metabolic alkalosis, hypomagnesaemia and hypocalciuria. It is caused by mutations in SLC12A3 encoding the sodium-chloride cotransporter on the apical membrane of the distal convoluted tubule. We report a South African family with five affected individuals presenting with hypokalaemia and unusual food cravings. Methods The affected individuals and two unaffected first degree relatives were enrolled into the study. Phenotypes were evaluated through history, physical examination and biochemical analysis of blood and urine. Mutation screening was performed by sequencing of SLC12A3 , and determining the allele frequencies of the sequence variants found in this family in 117 ethnically matched controls. Results The index patient, her sister, father and two aunts had a history of severe salt cravings, fatigue and tetanic episodes, leading to consumption of large quantities of salt and vinegar. All affected individuals demonstrated hypokalaemia with renal potassium wasting. Genetic analysis revealed that the pseudo-dominant pattern of inheritance was due to compound heterozygosity with two novel mutations: a S546G substitution in exon 13, and insertion of AGCCCC at c.1930 in exon 16. These variants were present in the five affected individuals, but only one variant each in the unaffected family members. Neither variant was found in any of the controls. Conclusions The diagnosis of GS was established in five members of a South African family through clinical assessment, biochemical analysis and mutation screening of the SLC12A3 gene, which identified two novel putative pathogenic mutations

Factors influencing the development of early- or late-onset Parkinson's disease in a cohort of South African patients

CITATION: Van der Merwe, C. et al. 2012. Factors influencing the development of early- or late-onset Parkinson's disease in a cohort of South African patients. South African Medical Journal, 102(11):848-851, doi:10.7196/SAMJ.5879.The original publication is available at http://www.samj.org.zaBackground. Neurodegenerative disorders such as Parkinson’s disease (PD) contribute significantly to global disease burden. PD can be categorised into early-onset PD (EOPD) with an age at onset (AAO) of ≤50 years and late-onset PD (LOPD) with an AAO of 50 years. Aims. To identify factors influencing EOPD and LOPD development in a group of patients in South Africa (SA). Methods. A total of 397 unrelated PD patients were recruited from the Movement Disorders Clinic at Tygerberg Hospital and via the Parkinson’s Association of SA. Patient demographic and environmental data were recorded and associations with PD onset (EOPD v. LOPD) were analysed with a Pearson’s Chi-squared test. The English- and Afrikaans-speaking (Afrikaner) white patients were analysed separately. Results. Logistic regression analysis showed that ethnicity (p<0.001) and family history (p=0.004) were independently associated with AAO of PD. Average AAO was younger in black, coloured and Afrikaner patients than English-speaking white patients. A positive family history of PD, seen in 31.1% of LOPD patients, was associated with a younger AAO in the study population. Conclusions. These associations may be attributed to specific genetic and/or environmental risk factors that increase PD susceptibility and influence the clinical course of the disorder. More studies on PD in the unique SA populations are required to provide novel insights into mechanisms underlying this debilitating condition.http://www.samj.org.za/index.php/samj/article/view/5879Publisher's versio

Mutations in the parkin gene are a minor cause of Parkinson's disease in the South African population

The molecular basis of Parkinson's disease (PD) has been extensively studied in numerous population groups over the past decade. However, very little is known of the molecular etiology of PD in the South African population. We aimed to assess the genetic contribution of parkin mutations to PD pathology by determining the frequency of both point mutations and exon rearrangements in all 12 exons of the parkin gene in a group of 229 South African patients diagnosed with PD. This was done by performing high resolution melt (HRM) as well as multiplex ligation-dependent probe amplification (MLPA) analyses. In total, seven patients (3.1%; 7/229) had either compound heterozygous or homozygous mutations in parkin, and seven patients (3.1%) had heterozygous sequence variants. Two of the patients with parkin mutations are of Black African ancestry. Reverse-transcription PCR on lymphocytes obtained from two patients verified the presence of parkin mutations on both alleles. In conclusion, the present study reveals that mutations in the parkin gene are not a major contributor to PD in the South African population. Further investigations of the molecular etiology of PD in the unique South African population, particularly the Black African and mixed ancestry sub-populations, are warranted. (C) 2011 Elsevier Ltd. All rights reserved

Altered mitochondrial respiration and other features of mitochondrial function in parkin-mutant fibroblasts from parkinson’s disease patients

CITATION: Haylett, W., et al. 2016. Altered mitochondrial respiration and other features of mitochondrial function in parkin-mutant fibroblasts from parkinson’s disease patients. Parkinson’s Disease, 2016 (Article ID 1819209), doi:10.1155/2016/1819209.The original publication is available at https://www.hindawi.comMutations in the parkin gene are the most common cause of early-onset Parkinson’s disease (PD). Parkin, an E3 ubiquitin ligase, is involved in respiratory chain function, mitophagy, and mitochondrial dynamics. Human cellular models with parkin null mutations are particularly valuable for investigating the mitochondrial functions of parkin. However, published results reporting on patient-derived parkin-mutant fibroblasts have been inconsistent. This study aimed to functionally compare parkin-mutant fibroblasts from PD patients with wild-type control fibroblasts using a variety of assays to gain a better understanding of the role of mitochondrial dysfunction in PD. To this end, dermal fibroblasts were obtained from three PD patients with homozygous whole exon deletions in parkin and three unaffected controls. Assays of mitochondrial respiration, mitochondrial network integrity, mitochondrial membrane potential, and cell growth were performed as informative markers of mitochondrial function. Surprisingly, it was found that mitochondrial respiratory rates were markedly higher in the parkin-mutant fibroblasts compared to control fibroblasts (p = 0.0093), while exhibiting more fragmented mitochondrial networks (). Moreover, cell growth of the parkin-mutant fibroblasts was significantly higher than that of controls (). These unanticipated findings are suggestive of a compensatory mechanism to preserve mitochondrial function and quality control in the absence of parkin in fibroblasts, which warrants further investigation.https://www.hindawi.com/journals/pd/2016/1819209/Publisher's versio

Targeted next-generation sequencing identifies novel variants in candidate genes for Parkinson’s disease in Black South African and Nigerian patients

CITATION: Oluwole, O. G., et al. 2020. Targeted next-generation sequencing identifies novel variants in candidate genes for Parkinson’s disease in Black South African and Nigerian patients. BMC Medical Genetics, 21:23, doi:10.1186/s12881-020-0953-1.The original publication is available at https://bmcmedgenet.biomedcentral.comBackground: The prevalence of Parkinson’s disease (PD) is increasing in sub-Saharan Africa, but little is known about the genetics of PD in these populations. Due to their unique ancestry and diversity, sub-Saharan African populations have the potential to reveal novel insights into the pathobiology of PD. In this study, we aimed to characterise the genetic variation in known and novel PD genes in a group of Black South African and Nigerian patients. Methods: We recruited 33 Black South African and 14 Nigerian PD patients, and screened them for sequence variants in 751 genes using an Ion AmpliSeq™ Neurological Research panel. We used bcftools to filter variants and annovar software for the annotation. Rare variants were prioritised using MetaLR and MetaSVM prediction scores. The effect of a variant on ATP13A2’s protein structure was investigated by molecular modelling. Results: We identified 14,655 rare variants with a minor allele frequency ≤ 0.01, which included 2448 missense variants. Notably, no common pathogenic mutations were identified in these patients. Also, none of the known PD-associated mutations were found highlighting the need for more studies in African populations. Altogether, 54 rare variants in 42 genes were considered deleterious and were prioritized, based on MetaLR and MetaSVM scores, for follow-up studies. Protein modelling showed that the S1004R variant in ATP13A2 possibly alters the conformation of the protein. Conclusions: We identified several rare variants predicted to be deleterious in sub-Saharan Africa PD patients; however, further studies are required to determine the biological effects of these variants and their possible role in PD. Studies such as these are important to elucidate the genetic aetiology of this disorder in patients of African ancestry.https://bmcmedgenet.biomedcentral.com/articles/10.1186/s12881-020-0953-1Publisher's versio