Displaying publications 1 - 20 of 34 in total

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  1. Single strand dna breaks in human lymphocytes exposed to para-phenylenediamine and its derivatives
    Chye SM, Hseu YC, Liang SH, Chen CH, Chen SC
    Bull Environ Contam Toxicol, 2008 Jan;80(1):58-62.
    PMID: 18058049
    Para-Phenylenediamine (PPD), the main aromatic amines used in the hair dye formation, and its four derivatives (2-chloro-p-phenylenediamine, 4-chloro-o-phenylenediamine, 2-nitro-p-phenylenediamine, and 4-nitro-o-phenylenediamine) were examined for their potential to produce single strand DNA breaks in human lymphocytes using the alkaline comet assay. Results revealed that all the tested chemicals within the range of doses from 100 microM to 500 microM showed the genotoxicity in a dose-dependent manner after the incubation of lymphocytes with these chemicals for 2 h. In this study, we first reported that PPD and its four derivatives can elicit the type of single strand breaks in human lymphocytes.
  2. [Zn(phen)(O,N,O)(H2O)] and [Zn(phen)(O,N)(H2O)] with O,N,O is 2,6-dipicolinate and N,O is L-threoninate: synthesis, characterization, and biomedical properties
    Chin LF, Kong SM, Seng HL, Tiong YL, Neo KE, Maah MJ, et al.
    J Biol Inorg Chem, 2012 Oct;17(7):1093-105.
    PMID: 22825726 DOI: 10.1007/s00775-012-0923-y
    Two ternary Zn(II) complexes, with 1,10-phenanthroline (phen) as the main ligand and a carboxylate-containing ligand [dipicolinate (dipico) or L-threoninate (L-Thr)] as the subsidiary ligand, were prepared and characterized by elemental analysis, Fourier transform IR, UV, and fluorescence spectroscopy, X-ray diffraction, molar conductivity, and electrospray ionization mass spectrometry. X-ray structure analysis shows that both [Zn(phen)(dipico)(H(2)O)]·H(2)O (1) and [Zn(phen)(L-Thr)(H(2)O)Cl]·2H(2)O (2) have octahedral geometry about the Zn(II) atom. Both complexes can inhibit topoisomerase I, and have better anticancer activity than cisplatin against nasopharyngeal cancer cell lines, HK1 and HONE-1, with concentrations causing 50 % inhibition of cell proliferation (IC(50)) in the low micromolar range. Complex 2 has the highest therapeutic index for HK1. Both Zn(II) complexes can induce cell death by apoptosis. Changing the subsidiary ligand in the Zn(II) complexes affects the UV-fluorescence spectral properties of the coordinated phen ligand, the binding affinity for some DNA sequences, nucleobase sequence-selective binding, the phase at which cell cycle progression was arrested for treated cancer cells, and their therapeutic index.
  3. Fulltext Screening of anti-dengue activity in methanolic extracts of medicinal plants
    Tang LI, Ling AP, Koh RY, Chye SM, Voon KG
    BMC Complement Altern Med, 2012;12:3.
    PMID: 22244370 DOI: 10.1186/1472-6882-12-3
    Dengue fever regardless of its serotypes has been the most prevalent arthropod-borne viral diseases among the world population. The development of a dengue vaccine is complicated by the antibody-dependent enhancement effect. Thus, the development of a plant-based antiviral preparation promises a more potential alternative in combating dengue disease.
  4. Fulltext Anti-adipogenic effects of extracts of Ficus deltoidea var. deltoidea and var. angustifolia on 3T3-L1 adipocytes
    Woon SM, Seng YW, Ling AP, Chye SM, Koh RY
    J Zhejiang Univ Sci B, 2014 Mar;15(3):295-302.
    PMID: 24599694 DOI: 10.1631/jzus.B1300123
    This study examined the anti-adipogenic effects of extracts of Ficus deltoidea var. deltoidia and var. angustifolia, a natural slimming aid, on 3T3-L1 adipocytes.
  5. Neuroprotective effects of orientin on hydrogen peroxide‑induced apoptosis in SH‑SY5Y cells
    Law BN, Ling AP, Koh RY, Chye SM, Wong YP
    Mol Med Rep, 2014 Mar;9(3):947-54.
    PMID: 24366367 DOI: 10.3892/mmr.2013.1878
    Neurodegenerative diseases remain a global issue which affects the ageing population. Efforts towards determining their aetiologies to understand their pathogenic mechanisms are underway in order to identify a pathway through which therapeutic measures can be applied. One such pathogenic mechanism, oxidative stress (OS), is widely considered to be involved in neurodegenerative disease. Antioxidants, most notably flavonoids, have promising potential for therapeutic use as shown in in vitro and in vivo studies. In view of the importance of flavonoids for combating OS, this study investigated the neuroprotective effects of orientin, which has been reported to be capable of crossing the blood‑brain barrier. The maximum non‑toxic dose (MNTD) of orientin against SH‑SY5Y neuroblastoma cells was determined using a 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide (MTT) assay. The effects of the MNTD and the half MNTD (½MNTD) of orientin on cell cycle progression and intracellular reactive oxygen species (ROS) levels, as well as the activity of caspases 3/7, 8 and 9 after exposure to 150 µM of hydrogen peroxide (H2O2) were also determined using flow cytometry, a 2',7'‑dichlorodihydrofluorescein‑diacetate (DCFH‑DA) assay and caspase assay kits, respectively. The results revealed that orientin at ≤20 µM was not cytotoxic to SH‑SY5Y cells. After treatment with orientin at the MNTD, the percentage of apoptotic cells was significantly reduced compared with that in cells treated with 150 µM H2O2 alone. The results also showed that, although orientin at the MNTD and ½MNTD did not reduce intracellular ROS levels, it significantly inhibited the activity of caspases 3/7. Caspase 9 was significantly inactivated with orientin at the MNTD. Findings from this study suggest that the neuroprotection conferred by orientin was the result of the intracellular mediation of caspase activity.
  6. Apoptosis induced by para-phenylenediamine involves formation of ROS and activation of p38 and JNK in chang liver cells
    Chye SM, Tiong YL, Yip WK, Koh RY, Len YW, Seow HF, et al.
    Environ Toxicol, 2014 Sep;29(9):981-90.
    PMID: 23172806 DOI: 10.1002/tox.21828
    para-Phenylenediamine (p-PD) is a suspected carcinogen, but it has been widely used as a component in permanent hair dyes. In this study, the mechanism of p-PD-induced cell death in normal Chang liver cells was investigated. The results demonstrated that p-PD decreased cell viability in a dose-dependent manner. Cell death via apoptosis was confirmed by enhanced DNA damage and increased cell number in the sub-G1 phase of the cell cycle, using Hoechst 33258 dye staining and flow cytometry analysis. Apoptosis via reactive oxygen species generation was detected by the dichlorofluorescin diacetate staining method. Mitogen-activated protein kinase (MAPK) activation was assessed by western blot analysis and revealed that p-PD activated not only stress-activated protein kinase (SAPK)/c-Jun N-terminal kinases (JNK) and p38 MAPK but also extracellular signal-regulated kinase (ERK). Cytotoxicity and apoptosis induced by p-PD were markedly enhanced by ERK activation and selectively inhibited by ERK inhibitor PD98059, thus indicating a negative role of ERK. In contrast, inhibition of p38 MAPK activity with the p38-specific inhibitor SB203580 moderately inhibited cytotoxicity and apoptosis induction by p-PD. Similarly, SP600125, an inhibitor of SAPK/JNK, moderately inhibited cytotoxicity and apoptosis induced by p-PD, thus implying that p38 MAPK and SAPK/JNK had a partial role in p-PD-induced apoptosis. Western blot analysis revealed that p-PD significantly increased phosphorylation of p38 and SAPK/JNK and decreased phosphorylation of ERK. In conclusion, the results demonstrated that SAPK/JNK and p38 cooperatively participate in apoptosis induced by p-PD and that a decreased ERK signal contributes to growth inhibition or apoptosis.
  7. Fulltext Edible bird's nest ameliorates oxidative stress-induced apoptosis in SH-SY5Y human neuroblastoma cells
    Yew MY, Koh RY, Chye SM, Othman I, Ng KY
    BMC Complement Altern Med, 2014;14:391.
    PMID: 25308934 DOI: 10.1186/1472-6882-14-391
    Parkinson's disease (PD) is the second most common neurodegenerative disorder affecting the senile population with manifestation of motor disability and cognitive impairment. Reactive oxygen species (ROS) is implicated in the progression of oxidative stress-related apoptosis and cell death of the midbrain dopaminergic neurons. Its interplay with mitochondrial functionality constitutes an important aspect of neuronal survival in the perspective of PD. Edible bird's nest (EBN) is an animal-derived natural food product made of saliva secreted by swiftlets from the Aerodamus genus. It contains bioactive compounds which might confer neuroprotective effects to the neurons. Hence this study aims to investigate the neuroprotective effect of EBN extracts in the neurotoxin-induced in vitro PD model.
  8. Cytotoxic and apoptogenic effects of Strobilanthes crispa Blume extracts on nasopharyngeal cancer cells
    Koh RY, Sim YC, Toh HJ, Liam LK, Ong RS, Yew MY, et al.
    Mol Med Rep, 2015 Oct;12(4):6293-9.
    PMID: 26239257 DOI: 10.3892/mmr.2015.4152
    The chemotherapeutic agents used to treat nasopharyngeal cancer (NPC) exhibit low efficacy. Strobilanthes crispa Blume is widely used for its anticancer, diuretic and anti‑diabetic properties. The present study aimed to determine the cytotoxic and apoptogenic effects of S. crispa on CNE‑1 NPC cells. A 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5 diphenyl tetrazolium bromide assay was used to evaluate the cytotoxic effects of S. crispa against CNE‑1 cells. The rate of apoptosis was determined using propidium iodide staining and caspase assays. Ethyl acetate, hexane and chloroform extracts of S. crispa leaves all exhibited cytotoxic effects on CNE‑1 cells, at a half maximal inhibitory concentration (IC50) of 119, 123.5 and 161.7 µg/ml, respectively. In addition, hexane, chloroform and ethyl acetate extracts of S. crispa stems inhibited CNE‑1 cell proliferation, at a IC50 of 49.4, 148.3 and 163.5 µg/ml, respectively. Flow cytometric analysis revealed an increased proportion of cells in the sub G1 phase and a decreased proportion of cells in the G2/M phase, following treatment with the extracts. However, the extracts did not alter the activities of caspase ‑3/7, ‑8 and ‑9. No cytotoxic effect was observed when the cells were treated with the methanol and water extracts of S. crispa stems and leaves. In conclusion, the S. crispa extracts were cytotoxic against CNE‑1 cells and these extracts were able to induce apoptosis, independent of caspase activation.
  9. para-Phenylenediamine induces apoptosis through activation of reactive oxygen species-mediated mitochondrial pathway, and inhibition of the NF-κB, mTOR, and Wnt pathways in human urothelial cells
    Reena K, Ng KY, Koh RY, Gnanajothy P, Chye SM
    Environ Toxicol, 2017 Jan;32(1):265-277.
    PMID: 26784575 DOI: 10.1002/tox.22233
    para-Phenylenediamine (PPD) has long been used in two-thirds of permanent oxidative hair dye formulations. Epidemiological studies and in vivo studies have shown that hair dye is a suspected carcinogen of bladder cancer. However, the toxicity effects of PPD to human bladder remains elusive. In this study, the effects of PPD and its involvement in the apoptosis pathways in human urothelial cells (UROtsa) was investigated. It was demonstrated that PPD decreased cell viability and increased the number of sub-G1 hypodiploid cells in UROtsa cells. Cell death due to apoptosis was detected using Annexin V binding assay. Further analysis showed PPD generated reactive oxygen species (ROS), induced mitochondrial dysfunction through the loss of mitochondrial membrane potential and increased caspase-3 level in UROtsa cells. Western blot analysis of PPD-treated UROtsa cells showed down-regulation of phosphorylated proteins from NF-κB, mTOR, and Wnt pathways. In conclusion, PPD induced apoptosis via activation of ROS-mediated mitochondrial pathway, and possibly through inhibition of NF-κB, mTOR, and Wnt pathways. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 265-277, 2017.
  10. Clinacanthus Nutans Hexane Extracts Induce Apoptosis Through a Caspase-Dependent Pathway in Human Cancer Cell Lines
    Ng PY, Chye SM, Ng ChH, Koh RY, Tiong YL, Pui LP, et al.
    Asian Pac J Cancer Prev, 2017 04 01;18(4):917-926.
    PMID: 28545188
    Background: Clinacanthus nutans (C.nutans) is a plant consumed as a cancer treatment in tropical Asia. Despite
    the availability of numerous anecdotal reports, evaluation of active anticancer effects has remained elusive. Therefore
    we here examined antiproliferative, reactive oxygen species (ROS)-inducing and apoptosis mechanisms of whole plant
    extracts in different cancer cell lines. Methods: Antiproliferative actions of five solvent extracts (hexane, chloroform,
    ethyl acetate, methanol and water) of C.nutans were tested on non-small cell lung cancer (A549), nasopharygeal cancer
    (CNE1) and liver cancer (HepG2) cells using MTT assay. The most potent anticancer extract was then assessed by flow
    cytometry to study cell cycle changes . Intracellular levels of ROS were quantified by DCFH-DA assay. Involvement of
    the caspase pathway in induction of apoptosis was assessed using caspase assay kits. GC-MS analysis was performed
    to identify phytoconstituents in the extracts. Results: Hexane and chloroform extracts were antiproliferative against
    all three cell lines, while the ethyl acetate extract, at 300 μg/mL, was antiproliferative in the CNE1 but not A549 and
    HepG2 cases. Methanol and water extracts did not inhibit cancer cell proliferation. The most potent anticancer hexane
    extract was selected for further testing. It induced apoptosis in all three cell lines as shown by an increase in the
    percentage of cell in sub-G1 phase. Dose-dependent increase in ROS levels in all three cell lines indicated apoptosis to
    be possibly modulated by oxidative stress. At high concentrations (>100 μg/mL), hexane extracts upregulated caspases
    8, 9 and 3/7 across all three cell lines. GC-MS analysis of the hexane extract revealed abundance of 31 compounds.
    Conclusion : Among the five extracts of C.nutans, that with hexane extract demonstrated the highest antiproliferative
    activity against all three cancer cell lines tested. Action appeared to be via ion of intracellular ROS, and induction of
    apoptosis via intrinsic and extrinsic caspase pathways.
  11. Fulltext Anticancer mechanisms of Strobilanthes crispa Blume hexane extract on liver and breast cancer cell lines
    Koh RY, Lim FP, Ling LSY, Ng CPL, Liew SF, Yew MY, et al.
    Oncol Lett, 2017 Oct;14(4):4957-4964.
    PMID: 29085507 DOI: 10.3892/ol.2017.6821
    Cancer is a major public health concern not only in developed countries, but also in developing countries. It is one of the leading causes of mortality worldwide. However, current treatments may cause severe side effects and harm. Therefore, recent research has been focused on identifying alternative therapeutic agents extracted from plant-based sources in order to develop novel treatment options for cancer. Strobilanthes crispa Blume is a plant native to countries including Madagascar and Indonesia. It has been used as an anti-diabetic, diuretic and laxative in traditional folk medicine. Furthermore, S. crispa has potential in treating cancer, as evidenced in previous studies. In the present study, the cytotoxic and apoptotic activities of S. crispa crude extracts were investigated in liver and breast cancer cell lines. Hexane, ethyl acetate, chloroform, methanol and water extracts prepared from the leaves, and stems of S. crispa were evaluated for their cytotoxicity on HepG-2 and MDA-MB-231 cells using an MTT assay. The anti-proliferative properties of stem hexane (SH) extract on both cell lines were analysed using cell doubling time determination and cell cycle analysis, while the apoptogenic properties was determined through the detection of caspase-8. Among the extracts tested, SH extract exhibited the lowest half maximal inhibitory concentrations in both the cell lines. The SH extract induced morphological changes in HepG-2 and MDA-MB-231 cells, and significantly delayed cell population doubling time. Furthermore, it altered cell cycle profile and significantly increased caspase-8 activity in HepG-2 cells, but not in MDA-MB-231 cells. In conclusion, the SH extract of S. crispa possesses potent anticancer properties and may be a suitable chemotherapeutic target.
  12. Tau Proteins and Tauopathies in Alzheimer's Disease
    Chong FP, Ng KY, Koh RY, Chye SM
    Cell Mol Neurobiol, 2018 Jul;38(5):965-980.
    PMID: 29299792 DOI: 10.1007/s10571-017-0574-1
    Alzheimer's disease (AD) is characterized by progressive memory loss and cognitive function deficits. There are two major pathological hallmarks that contribute to the pathogenesis of AD which are the presence of extracellular amyloid plaques composed of amyloid-β (Aβ) and intracellular neurofibrillary tangles composed of hyperphosphorylated tau. Despite extensive research that has been done on Aβ in the last two decades, therapies targeting Aβ were not very fruitful at treating AD as the efficacy of Aβ therapies observed in animal models is not reflected in human clinical trials. Hence, tau-directed therapies have received tremendous attention as the potential treatments for AD. Tauopathies are closely correlated with dementia and immunotherapy has been effective at reducing tau pathology and improving cognitive deficits in animal models. Thus, in this review article, we discussed the pathological mechanism of tau proteins, the key factors contributing to tauopathies, and therapeutic approaches for tauopathies in AD based on the recent progress in tau-based research.
  13. Single-chain Fv Antibodies for Targeting Neurodegenerative Diseases
    Chia KY, Ng KY, Koh RY, Chye SM
    CNS Neurol Disord Drug Targets, 2018;17(9):671-679.
    PMID: 29546836 DOI: 10.2174/1871527317666180315161626
    BACKGROUND & OBJECTIVE: Protein misfolding and aggregation have been considered the common pathological hallmarks for a number of neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD). These abnormal proteins aggregates damage mitochondria and induce oxidative stress, resulting in neuronal cell death. Prolonged neuronal damage activates microglia and astrocytes, development of inflammation reaction and further promotes neurodegeneration. Thus, elimination of abnormal protein aggregates without eliciting any adverse effects are the main treatment strategies. To overcome this, recent studies have deployed single- chain fragment variable antibodies (scFvs) to target the pathological protein aggregates, such as amyloid-beta (Aβ) peptides, α-synuclein (α-syn) and Huntingtin (Htt). To date scFv has been effective at inhibiting abnormal protein aggregates formation in both in vitro and in vivo model system of AD, PD and HD.

    CONCLUSION: Currently active research is still ongoing to improve the scFv gene delivery technology, to further enhance brain penetration, intracellular stability, solubility and efficacy of scFv intrabody.

  14. Anticancer Potential of Syzygium Species: a Review
    Chua LK, Lim CL, Ling APK, Chye SM, Koh RY
    Plant Foods Hum Nutr, 2019 Mar;74(1):18-27.
    PMID: 30535971 DOI: 10.1007/s11130-018-0704-z
    Cancer is a preventable and treatable disease, however, the incidence rates are on the rise. Classical treatment modalities for cancer include surgery, radiotherapy and chemotherapy. However, these are associated with detrimental side effects such as nausea and emesis. Therefore, researchers currently vest interest in complementary and alternative medicines for cancer treatment and prevention. Plants such as Syzygium sp. are a common basis of complementary medicines due to its abundance of bioactive phytochemicals. Numerous natural compounds derived from Syzygium sp., such as phenolics, oleanolic acids, and betulinic acids, and dimethyl cardamonins, were reported to have anticancer effects. Many possess the ability to inhibit cell proliferation and induce apoptosis. In this review, we discuss the vast potential Syzygium sp. harbours as a source of anticancer natural compounds due to its abundance, easy acceptability, affordability and safety for regular consumption.
  15. Pharmacological Effects of Melatonin as Neuroprotectant in Rodent Model: A Review on the Current Biological Evidence
    Tan HY, Ng KY, Koh RY, Chye SM
    Cell Mol Neurobiol, 2020 Jan;40(1):25-51.
    PMID: 31435851 DOI: 10.1007/s10571-019-00724-1
    The progressive loss of structure and functions of neurons, including neuronal death, is one of the main factors leading to poor quality of life. Promotion of functional recovery of neuron after injury is a great challenge in neuroregenerative studies. Melatonin, a hormone is secreted by pineal gland and has antioxidative, anti-inflammatory, and anti-apoptotic properties. Besides that, melatonin has high cell permeability and is able to cross the blood-brain barrier. Apart from that, there are no reported side effects associated with long-term usage of melatonin at both physiological and pharmacological doses. Thus, in this review article, we summarize the pharmacological effects of melatonin as neuroprotectant in central nervous system injury, ischemic-reperfusion injury, optic nerve injury, peripheral nerve injury, neurotmesis, axonotmesis, scar formation, cell degeneration, and apoptosis in rodent models.
  16. Mechanisms of action of amyloid-beta and its precursor protein in neuronal cell death
    Leong YQ, Ng KY, Chye SM, Ling APK, Koh RY
    Metab Brain Dis, 2020 01;35(1):11-30.
    PMID: 31811496 DOI: 10.1007/s11011-019-00516-y
    Extracellular senile plaques and intracellular neurofibrillary tangles are the neuropathological findings of the Alzheimer's disease (AD). Based on the amyloid cascade hypothesis, the main component of senile plaques, the amyloid-beta (Aβ) peptide, and its derivative called amyloid precursor protein (APP) both have been found to place their central roles in AD development for years. However, the recent therapeutics have yet to reverse or halt this disease. Previous evidence demonstrates that the accumulation of Aβ peptides and APP can exert neurotoxicity and ultimately neuronal cell death. Hence, we discuss the mechanisms of excessive production of Aβ peptides and APP serving as pathophysiologic stimuli for the initiation of various cell signalling pathways including apoptosis, necrosis, necroptosis and autophagy which lead to neuronal cell death. Conversely, the activation of such pathways could also result in the abnormal generation of APP and Aβ peptides. An elucidation of actions of APP and its metabolite, Aβ, could be vital in suggesting novel therapeutic opportunities.
  17. Melatonin inhibits high glucose-induced ox-LDL/LDL expression and apoptosis in human umbilical endothelial cells
    Tiong YL, Ng KY, Koh RY, Ponnudurai G, Chye SM
    Horm Mol Biol Clin Investig, 2020 Jun 29;41(4).
    PMID: 32598308 DOI: 10.1515/hmbci-2020-0009
    BACKGROUND: Cardiovascular disease (CVD) is one of the major cause of mortality in diabetic patients. Evidence suggests that hyperglycemia in diabetic patients contributes to increased risk of CVD. This study is to investigate the therapeutic effects of melatonin on glucose-treated human umbilical vein endothelial cells (HUVEC) and provide insights on the underlying mechanisms.

    MATERIALS AND METHODS: Cell viability was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Reactive oxygen species (ROS) and membrane potential was detected using 2',7'-dichlorofluorescein diacetate and 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine iodide (JC-1) dye staining, respectively. While, cell apoptosis was determined by Annexin-V staining and protein expression was measured using Western blot.

    RESULTS: Our results suggested that melatonin inhibited glucose-induced ROS elevation, mitochondria dysfunction and apoptosis on HUVEC. Melatonin inhibited glucose-induced HUVEC apoptosis via PI3K/Akt signaling pathway. Activation of Akt further activated BcL-2 pathway through upregulation of Mcl-1 expression and downregulation Bax expression in order to inhibit glucose-induced HUVEC apoptosis. Besides that, melatonin promoted downregulation of oxLDL/LOX-1 in order to inhibit glucose-induced HUVEC apoptosis.

    CONCLUSIONS: In conclusion, our results suggested that melatonin exerted vasculoprotective effects against glucose-induced apoptosis in HUVEC through PI3K/Akt, Bcl-2 and oxLDL/LOX-1 signaling pathways.

  18. Recent advances in tau-directed immunotherapy against Alzheimer's disease: an overview of pre-clinical and clinical development
    Ng PY, Chang IS, Koh RY, Chye SM
    Metab Brain Dis, 2020 10;35(7):1049-1066.
    PMID: 32632666 DOI: 10.1007/s11011-020-00591-6
    Alzheimer's disease (AD) has been a worldwide concern for many years now. This is due to the fact that AD is an irreversible and progressive neurodegenerative disease that affects quality of life. Failure of some Phase II/III clinical trials in AD targeting accumulation of β-amyloid in the brain has led to an increase in interest in studying alternative treatments against tubulin-associated unit (Tau) pathology. These alternative treatments include active and passive immunisation. Based on numerous studies, Tau is reported as a potential immunotherapeutic target for tauopathy-related diseases including AD. Accumulation and aggregation of hyperphosphorylated Tau as neuropil threads and neurofibrillary tangles (NFT) are pathological hallmarks of AD. Both active and passive immunisation targeting Tau protein have shown the capabilities to decrease or prevent Tau pathology and improve either motor or cognitive impairment in various animal models. In this review, we summarise recent advances in active and passive immunisation targeting pathological Tau protein, and will discuss with data obtained from both animal and human trials. Together, we give a brief overview about problems being encountered in these immunotherapies.
  19. Fulltext Melatonin promotes Schwann cell dedifferentiation and proliferation through the Ras/Raf/ERK and MAPK pathways, and glial cell-derived neurotrophic factor expression
    Tiong YL, Ng KY, Koh RY, Ponnudurai G, Chye SM
    Exp Ther Med, 2020 Nov;20(5):16.
    PMID: 32934681 DOI: 10.3892/etm.2020.9143
    Upon peripheral nerve injury (PNI), continuous proliferation of Schwann cells is critical for axon regeneration and tubular reconstruction for nerve regeneration. Melatonin is a hormone that is able to induce proliferation in various cell types. In the present study, the effects of melatonin on promoting Schwann cell proliferation and the molecular mechanism involved were investigated. The present results showed that melatonin enhanced the melatonin receptors (MT1 and MT2) expression in Schwann cells. Melatonin induced Schwann cell dedifferentiation into progenitor-like Schwann cells, as observed by immunofluorescence staining, which showed Sox2 marker expression. In addition, melatonin enhanced Schwann cell proliferation, mediated by the upregulation of glial cell-derived neurotropic factor (GNDF) and protein kinase C (PKC). Furthermore, the Ras/Raf/ERK and MAPK signaling pathways were also involved in Schwann cell dedifferentiation and proliferation. In conclusion, melatonin induced Schwann cell dedifferentiation and proliferation via the Ras/Raf/ERK, MAPK and GDNF/PKC pathways. The present results suggested that melatonin could be used to enhance the recovery of PNI.
  20. The Mechanism of Action of Salsolinol in Brain: Implications in Parkinson's Disease
    Voon SM, Ng KY, Chye SM, Ling APK, Voon KGL, Yap YJ, et al.
    CNS Neurol Disord Drug Targets, 2020;19(10):725-740.
    PMID: 32881676 DOI: 10.2174/1871527319666200902134129
    1-Methyl-1,2,3,4-tetrahydroisoquinoline-6,7-diol, commonly known as salsolinol, is a compound derived from dopamine. It was first discovered in 1973 and has gained attention for its role in Parkinson's disease. Salsolinol and its derivatives were claimed to play a role in the pathogenesis of Parkinson's disease as a neurotoxin that induces apoptosis of dopaminergic neurons due to its structural similarity to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its ability to induce Parkinsonism. In this article, we discussed the biosynthesis, distribution and blood-brain barrier permeability of salsolinol. The roles of salsolinol in a healthy brain, particularly the interactions with enzymes, hormone and catecholamine, were reviewed. Finally, we discussed the involvement of salsolinol and its derivatives in the pathogenesis of Parkinson's disease.
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