MyMedR

Displaying all 11 publications

Abstract:

Sort:

Fulltext Development of peptides inhibitor against human papillomavirus E7 protein

Tan Wan Chein, Nurshamimi Nor Rashid, Heh Choon Han, Lim See Khai, Shatrah Othman

Malaysian Journal of Medicine and Health Sciences, 2019;15(102):28-28.
MyJurnal

Introduction: Human papillomavirus (HPV) is a small, non-enveloped double-stranded circular DNA virus. The high risk types of HPV are claimed to be responsible for over 99% of cervical cancers while the most common oncogenic genotypes 16 and 18, implicated in approximately 70% of all cervical cancers. HPV has six early genes (E1, E2, E4, E5, E6 and E7) that code for regulatory proteins involved in viral DNA replication, transcription control and cellular transformation. The E7 protein is responsible for the escape from cell cycle arrest in HPV infected cells by binding to the retinoblastoma protein (pRB) through its LXCXE binding motif. This inhibits the tumour suppressor protein from regulating the cell cycle progression from G1 to S phase. In this study, the pocket domain of pRB which is targeted by LXCXE is used as a target to design peptide inhibitors using in silico methods. Methods: Biovia Discovery Studio Visualizer and UCSF Chimera softwares were used in designing the peptides. Results: Two crystal structures: 1GUX and 4YOZ were superimposed and studied. The similar amino acid sequences which bind to LXCXE were cut to form the potential peptide inhibitors. Based on this, peptide 1 was selected for further in vitro analysis. The cytotoxicity of the peptide 1 was analysed on three cell lines: CaSki (HPV16+ cervical cancer cell), C33a (cervical cancer cell), and HaCaT (normal keratinocyte). As a result, the IC50 of one of the designed peptide inhibitor – peptide 1, on CaSki cell line was 180 μM. The inhibitory effect of the peptide 1 was also analysed validated using Western Blot using antibodies from the B-Myb and pRB family. The changes in cell cycle before and after treatment of the peptide inhibitor will be further monitored using a cell analyser. Conclusion: Peptide 1 had shown potential as an inhibitor of the HPV E7 protein based on the in silico analysis, but further functional studies are needed to validate its potential.
Fulltext Development of MTH1-Binding Nucleotide Analogs Based on 7,8-Dihalogenated 7-Deaza-dG Derivatives

Shi H, Ishikawa R, Heh CH, Sasaki S, Taniguchi Y

Int J Mol Sci, 2021 Jan 28;22(3).
PMID: 33525366 DOI: 10.3390/ijms22031274

MTH1 is an enzyme that hydrolyzes 8-oxo-dGTP, which is an oxidatively damaged nucleobase, into 8-oxo-dGMP in nucleotide pools to prevent its mis-incorporation into genomic DNA. Selective and potent MTH1-binding molecules have potential as biological tools and drug candidates. We recently developed 8-halogenated 7-deaza-dGTP as an 8-oxo-dGTP mimic and found that it was not hydrolyzed, but inhibited enzyme activity. To further increase MTH1 binding, we herein designed and synthesized 7,8-dihalogenated 7-deaza-dG derivatives. We successfully synthesized multiple derivatives, including substituted nucleosides and nucleotides, using 7-deaza-dG as a starting material. Evaluations of the inhibition of MTH1 activity revealed the strong inhibitory effects on enzyme activity of the 7,8-dihalogenated 7-deaza-dG derivatives, particularly 7,8-dibromo 7-daza-dGTP. Based on the results obtained on kinetic parameters and from computational docking simulating studies, these nucleotide analogs interacted with the active site of MTH1 and competitively inhibited the substrate 8-oxodGTP. Therefore, novel properties of repair enzymes in cells may be elucidated using new compounds.
Rational drug discovery: Ellagic acid as a potent dual-target inhibitor against hepatitis C virus genotype 3 (HCV G3) NS3 enzymes

Lim SK, Othman R, Yusof R, Heh CH

Chem Biol Drug Des, 2021 01;97(1):28-40.
PMID: 32657543 DOI: 10.1111/cbdd.13756

Structure-based virtual screening (SBVS) has served as a popular strategy for rational drug discovery. In this study, we aimed to discover novel benzopyran-based inhibitors that targeted the NS3 enzymes (NS3/4A protease and NS3 helicase) of HCV G3 using a combination of in silico and in vitro approaches. With the aid of SBVS, six novel compounds were discovered to inhibit HCV G3 NS3/4A protease and two phytochemicals (ellagic acid and myricetin) were identified as dual-target inhibitors that inhibited both NS3/4A protease and NS3 helicase in vitro (IC50 = 40.37 ± 5.47 nm and 6.58 ± 0.99 µm, respectively). Inhibitory activities against the replication of HCV G3 replicons were further assessed in a cell-based system with four compounds showed dose-dependent inhibition. Compound P8 was determined to be the most potent compound from the cell-based assay with an EC50 of 19.05 µm. The dual-target inhibitor, ellagic acid, was determined as the second most potent (EC50 = 32.37 µm) and the most selective in its inhibitory activity against the replication of HCV replicons, without severely affecting the viability of the host cells (selectivity index > 6.18).
Fulltext Prevalence of c.2268dup and detection of two novel alterations, c.670_672del and c.1186C>T, in the TPO gene in a cohort of Malaysian-Chinese with thyroid dyshormonogenesis

Lee CC, Harun F, Jalaludin MY, Heh CH, Othman R, Junit SM

BMJ Open, 2015 Jan 05;5(1):e006121.
PMID: 25564141 DOI: 10.1136/bmjopen-2014-006121

OBJECTIVES: The c.2268dup mutation in the thyroid peroxidase (TPO) gene is the most common TPO alteration reported in Taiwanese patients with thyroid dyshormonogenesis. The ancestors of these patients are believed to originate from the southern province of China. Our previous study showed that this mutation leads to reduced abundance of the TPO protein and loss of TPO enzyme activity in a Malaysian-Chinese family with goitrous hypothyroidism. The aim of our study was to provide further data on the incidence of the c.2268dup mutation in a cohort of Malaysian-Chinese and its possible phenotypic effects.
SETTING: Cohort study.
PARTICIPANTS: Twelve biologically unrelated Malaysian-Chinese patients with congenital hypothyroidism were recruited in this study. All patients showed high thyrotropin and low free thyroxine levels at the time of diagnosis with proven presence of a thyroid gland.
PRIMARY OUTCOME MEASURE: Screening of the c.2268dup mutation in the TPO gene in all patients was carried out using a PCR-direct DNA sequencing method.
SECONDARY OUTCOME MEASURE: Further screening for mutations in other exonic regions of the TPO gene was carried out if the patient was a carrier of the c.2268dup mutation.
RESULTS: The c.2268dup mutation was detected in 4 of the 12 patients. Apart from the c.2268dup and a previously documented mutation (c.2647C>T), two novel TPO alterations, c.670_672del and c.1186C>T, were also detected in our patients. In silico analyses predicted that the novel alterations affect the structure/function of the TPO protein.
CONCLUSIONS: The c.2268dup mutation was detected in approximately one-third of the Malaysian-Chinese patients with thyroid dyshormonogenesis. The detection of the novel c.670_672del and c.1186C>T alterations expand the mutation spectrum of TPO associated with thyroid dyshormonogenesis.
Variable clinical phenotypes in a family with homozygous c.1159G>A mutation in the thyroid peroxidase gene

Lee CC, Harun F, Jalaludin MY, Heh CH, Othman R, Kang IN, et al.

Horm Res Paediatr, 2014;81(5):356-60.
PMID: 24717978 DOI: 10.1159/000359922

Defects in the thyroid peroxidase (TPO) gene have been associated with goitrous congenital hypothyroidism (CH).
Phosphodiesterase-5 inhibitors and their analogues as adulterants of herbal and food products: analysis of the Malaysian market, 2014-16

Bujang NB, Chee CF, Heh CH, Rahman NA, Buckle MJC

Food Addit Contam Part A Chem Anal Control Expo Risk Assess, 2017 Jul;34(7):1101-1109.
PMID: 28580889 DOI: 10.1080/19440049.2017.1336674

Adulteration of herbal health supplements with phosphodiesterase-5 (PDE-5) inhibitors and their analogues is becoming a worldwide problem. The aim of this study was to investigate herbal and food products sold in the Malaysian market for the presence of these adulterants. Sixty-two products that claim to enhance men's sexual health were sampled between April 2014 and April 2016. These products included unregistered products seized by the Pharmacy Enforcement Division of the Ministry of Health (n = 39), products sent to the National Pharmaceutical Regulatory Agency for pre-registration testing (n = 9) and products investigated under the post-registration market surveillance programme (n = 14). The products were tested against an in-house spectral library consisting of 61 PDE-5 inhibitors and analogues using a validated liquid chromatography-mass spectrometry ion-trap-time-of-flight (LC-MS IT-TOF) method. Thirty-two (82%) of the unregistered products and two (14%) of the registered products were found to be adulterated with at least one PDE-5 inhibitor or analogue, while none of the pre-registration products contained adulterants. A total of 16 different adulterants were detected and 36% of the adulterated products contained a mixture of two or more adulterants. This study has demonstrated that the adulteration of unregistered herbal products in the Malaysian market is an alarming issue that needs to be urgently addressed by the relevant authorities.
Synthesis of γ-N-modified 8-oxo-2'-deoxyguanosine triphosphate and its characterization

Thavoncharoensub N, Maruyama K, Heh CH, Hoong Leong K, Shi H, Shigematsu Y, et al.

Nucleosides Nucleotides Nucleic Acids, 2019;38(8):578-589.
PMID: 30929604 DOI: 10.1080/15257770.2019.1586919

8-OxodGTP is generated by the reaction between dGTP and reactive oxygen species and a considered mutagenic nucleotide. It can be incorporated into the duplex DNA during replication processes by the DNA polymerase, and thus the repair enzyme removes oxodGTP from the nucleotide pools in living cells. On the other hand, the γ-modified triphosphates show interesting properties for use as biological tools. Therefore, the γ-N-pyrenylalkyl-oxodGTP derivatives were synthesized and their effect on the enzymatic reactions were evaluated. The γ-N-pyrenylmethyl-oxodGTP was found to be accepted by the DNA polymerase just like oxodGTP, but showed a competitive inhibition property for the human oxodGTPase.
Sofosbuvir as treatment against dengue?

Gan CS, Lim SK, Chee CF, Yusof R, Heh CH

Chem Biol Drug Des, 2018 02;91(2):448-455.
PMID: 28834304 DOI: 10.1111/cbdd.13091

Dengvaxia® (CTD-TDV), the only licensed tetravalent dengue vaccine by Sanofi Pasteur, was made available since 2015. However, administration of CTD-TDV, in general, has not received the prequalification recommendation from the World Health Organization. Having a universal antidengue agent for treatment will therefore beneficial. Accordingly, the development of nucleoside inhibitors specific to dengue viral polymerase that perturb dengue infection has been studied by many. Alternatively, we have used a marketed anti-HCV prodrug sofosbuvir to study its in silico and in vitro effects against dengue. As a result, the active metabolite of sofosbuvir (GS-461203) was predicted to bind to the catalytic motif (Gly-Asp-Asp) of dengue viral polymerase with binding affinity of -6.9 kcal/mol. Furthermore, sofosbuvir demonstrated excellent in vitro viral inhibition with an EC90 of 0.4 μm. In addition, this study demonstrated the requirement of specific liver enzymes to activate the prodrug into GS-461203 to exert its antidengue potential. All in all, sofosbuvir should be subjected to in-depth studies to provide information of its efficacy toward dengue and its lead potential as DENV polymerase inhibitor in human subjects. In conclusion, we have expended the potential of the clinically available drug sofosbuvir as treatment for dengue.
Fulltext A Novel, Homozygous c.1502T>G (p.Val501Gly) Mutation in the Thyroid peroxidase Gene in Malaysian Sisters with Congenital Hypothyroidism and Multinodular Goiter

Lee CC, Harun F, Jalaludin MY, Heh CH, Othman R, Mat Junit S

Int J Endocrinol, 2013;2013:987186.
PMID: 23737781 DOI: 10.1155/2013/987186

Congenital hypothyroidism (CH) with multinodular goiter (MNG) is uncommonly seen in children. However, CH associated with goiter is often caused by defective Thyroid peroxidase (TPO) gene. In this study, we screened for mutation(s) in the TPO gene in two siblings with CH and MNG and their healthy family members. The two sisters, born to consanguineous parents, were diagnosed with CH during infancy and received treatment since then. They developed MNG during childhood despite adequate L-thyroxine replacement and negative thyroid antibody screening. PCR-amplification of all exons using flanking primers followed by DNA sequencing revealed that the two sisters were homozygous for a novel c.1502T>G mutation. The mutation is predicted to substitute valine for glycine at a highly conserved amino acid residue 501 (p.Val501Gly). Other healthy family members were either heterozygotes or mutation-free. The mutation was not detected in 50 healthy unrelated individuals. In silico analyses using PolyPhen-2 and SIFT predicted that the p.Val501Gly mutation is functionally "damaging." Tertiary modeling showed structural alterations in the active site of the mutant TPO. In conclusion, a novel mutation, p.Val501Gly, in the TPO gene was detected expanding the mutation spectrum of TPO associated with CH and MNG.
Discovery of Dengue Virus Inhibitors

Abdullah AA, Lee YK, Chin SP, Lim SK, Lee VS, Othman R, et al.

Curr Med Chem, 2020;27(30):4945-5036.
PMID: 30514185 DOI: 10.2174/0929867326666181204155336

To date, there is still no approved anti-dengue agent to treat dengue infection in the market. Although the only licensed dengue vaccine, Dengvaxia is available, its protective efficacy against serotypes 1 and 2 of dengue virus was reported to be lower than serotypes 3 and 4. Moreover, according to WHO, the risk of being hospitalized and having severe dengue increased in seronegative individuals after they received Dengvaxia vaccination. Nevertheless, various studies had been carried out in search of dengue virus inhibitors. These studies focused on the structural (C, prM, E) and non-structural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B and NS5) of dengue virus as well as host factors as drug targets. Hence, this article provides an overall up-to-date review of the discovery of dengue virus inhibitors that are only targeting the structural and non-structural viral proteins as drug targets.
Fulltext Development of flexible electrochemical impedance spectroscopy-based biosensing platform for rapid screening of SARS-CoV-2 inhibitors

Kiew LV, Chang CY, Huang SY, Wang PW, Heh CH, Liu CT, et al.

Biosens Bioelectron, 2021 Jul 01;183:113213.
PMID: 33857754 DOI: 10.1016/j.bios.2021.113213

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters the cells through the binding of its spike protein (S-protein) to the cell surface-expressing angiotensin-converting enzyme 2 (ACE2). Thus, inhibition of S-protein-ACE2 binding may impede SARS-CoV-2 cell entry and attenuate the progression of Coronavirus disease 2019 (COVID-19). In this study, an electrochemical impedance spectroscopy-based biosensing platform consisting of a recombinant ACE2-coated palladium nano-thin-film electrode as the core sensing element was fabricated for the screening of potential inhibitors against S-protein-ACE2 binding. The platform could detect interference of small analytes against S-protein-ACE2 binding at low analyte concentration and small volume (0.1 μg/mL and ~1 μL, estimated total analyte consumption