Ganciclovir as a potential treatment for glioma: a systematic review and meta-analysis.

BACKGROUND: Glioma is a challenging malignant tumor with a low survival rate and no effective treatment. Recently, ganciclovir, an antiviral drug, combined with gene therapy and its own antiviral ability, has been proposed as a potential treatment for glioma. However, there are differences in the results of various clinical trials. In this study, we conducted a systematic review and meta-analysis to evaluate the efficacy of ganciclovir in treating glioma. METHODS: We searched databases such as PubMed, EMBASE, and Cochrane Library before March 30, 2023. The search terms included glioma, ganciclovir, valganciclovir and treatment. Calculated 1, 2 and 4-year survival rate by risk difference (RD), and overall survival (OS) by odds ratio (OR). RESULTS: Five randomized controlled trials (RCTs) with a total of 606 high-grade glioma patients were included. The results showed that ganciclovir can improve 2-yeaer (RD = 0.179, 95% CI 0.012-0.346, P = 0.036) and 4-year survival rate (RD = 0.185, 95% CI 0.069-0.3, P = 0.002) and OS (OR 2.393, 95% CI 1.212-4.728, P = 0.012) compared with the control group. CONCLUSIONS: This meta-analysis showed that ganciclovir significantly improved the prognosis of glioma patients. Therefore, we suggest that more cases of ganciclovir as a glioma treatment can be conducted, or a large clinical trial can be designed.

Structure-Based Functional Analysis of a Hormone Belonging to an Ecdysozoan Peptide Superfamily: Revelation of a Common Molecular Architecture and Residues Possibly for Receptor Interaction.

A neuropeptide (Sco-CHH-L), belonging to the crustacean hyperglycemic hormone (CHH) superfamily and preferentially expressed in the pericardial organs (POs) of the mud crab Scylla olivacea, was functionally and structurally studied. Its expression levels were significantly higher than the alternative splice form (Sco-CHH) in the POs, and increased significantly after the animals were subjected to a hypo-osmotic stress. Sco-CHH-L, but not Sco-CHH, significantly stimulated in vitro the Na+, K+-ATPase activity in the posterior (6th) gills. Furthermore, the solution structure of Sco-CHH-L was resolved using nuclear magnetic resonance spectroscopy, revealing that it has an N-terminal tail, three α-helices (α2, Gly9-Asn28; α3, His34-Gly38; and α5, Glu62-Arg72), and a π-helix (π4, Cys43-Tyr54), and is structurally constrained by a pattern of disulfide bonds (Cys7-Cys43, Cys23-Cys39, and Cys26-Cys52), which is characteristic of the CHH superfamily-peptides. Sco-CHH-L is topologically most similar to the molt-inhibiting hormone from the Kuruma prawn Marsupenaeus japonicus with a backbone root-mean-square-deviation of 3.12 Å. Ten residues of Sco-CHH-L were chosen for alanine-substitution, and the resulting mutants were functionally tested using the gill Na+, K+-ATPase activity assay, showing that the functionally important residues (I2, F3, E45, D69, I71, and G73) are located at either end of the sequence, which are sterically close to each other and presumably constitute the receptor binding sites. Sco-CHH-L was compared with other members of the superfamily, revealing a folding pattern, which is suggested to be common for the crustacean members of the superfamily, with the properties of the residues constituting the presumed receptor binding sites being the major factors dictating the ligand-receptor binding specificity.

Comparative study between 3D-QSAR and Docking-Based Pharmacophore models for potent Plasomodium falciparum dihydroorotate dehydrogenase inhibitors.

Malaria, caused by infections of the human malaria parasites Plasmodium falciparum, is a global infectious parasitic disease. Each year, about three million people died from malaria and the majority of whom are pregnant women and young children. Recently, a number of research attempt to reduce malaria parasite resistance and the toxicity of anti-malarial drugs. Nowadays, Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) was validated as a potent drug target to inhibit malarial activity by blocking pyrimidine biosynthesis. In this study, we employed 3D-QSAR Pharmacophore Generation and Docking-Based Pharmacophore Development to build the pharmacophore by using the collected 67 effective inhibitors against PfDHODH. 3D-QSAR Pharmacophore model, Hypo1, shows the high correlation coefficient (0.935), the lowest RMS deviation (2.15), the predicting accuracy of successful rates to training set (89.4%) and test set compounds (72.4%), respectively, revealing favorable predictive ability and is a reliable for further study. Additionally, Docking-Based Pharmacophore model, DBP-All255, exhibits comparable predictive capability to that of Hypo1, while DBP-Top1 shows poor statistical significance. This study reveals pharmacophore features of Hypo1, built by 3D-QSAR Pharmacophore Generation, are well-complementary to the functional residues in the active site of PfDHODH and is of great reliable for database screening.

Phage display-mediated discovery of novel tyrosinase-targeting tetrapeptide inhibitors reveals the significance of N-terminal preference of cysteine residues and their functional sulfur atom.

Tyrosinase, a key copper-containing enzyme involved in melanin biosynthesis, is closely associated with hyperpigmentation disorders, cancer, and neurodegenerative diseases, and as such, it is an essential target in medicine and cosmetics. Known tyrosinase inhibitors possess adverse side effects, and there are no safety regulations; therefore, it is necessary to develop new inhibitors with fewer side effects and less toxicity. Peptides are exquisitely specific to their in vivo targets, with high potencies and relatively few off-target side effects. Thus, we systematically and comprehensively investigated the tyrosinase-inhibitory abilities of N- and C-terminal cysteine/tyrosine-containing tetrapeptides by constructing a phage-display random tetrapeptide library and conducting computational molecular docking studies on novel tyrosinase tetrapeptide inhibitors. We found that N-terminal cysteine-containing tetrapeptides exhibited the most potent tyrosinase-inhibitory abilities. The positional preference of cysteine residues at the N terminus in the tetrapeptides significantly contributed to their tyrosinase-inhibitory function. The sulfur atom in cysteine moieties of N- and C-terminal cysteine-containing tetrapeptides coordinated with copper ions, which then tightly blocked substrate-binding sites. N- and C-terminal tyrosine-containing tetrapeptides functioned as competitive inhibitors against mushroom tyrosinase by using the phenol ring of tyrosine to stack with the imidazole ring of His263, thus competing for the substrate-binding site. The N-terminal cysteine-containing tetrapeptide CRVI exhibited the strongest tyrosinase-inhibitory potency (with an IC50 of 2.7 ± 0.5 µM), which was superior to those of the known tyrosinase inhibitors (arbutin and kojic acid) and outperformed kojic acid-tripeptides, mimosine-FFY, and short-sequence oligopeptides at inhibiting mushroom tyrosinase.

Antiviral treatment for hepatitis C virus infection is associated with improved renal and cardiovascular outcomes in diabetic patients.

UNLABELLED: Hepatitis C virus (HCV) infection is causally associated with insulin resistance and diabetes mellitus. This population-based cohort study aimed to investigate whether antiviral therapy for HCV infection was associated with improved clinical outcomes related to diabetes. From the Taiwan National Health Insurance Research Database, 2,267,270 Taiwanese residents diagnosed with diabetes mellitus were screened for eligibility. HCV infection was defined by a specific diagnosis code and measurement of serum antibody. After excluding patients with serious comorbidity, we enrolled a total of 1,411 eligible patients who received pegylated interferon plus ribavirin (treated cohort), and matched them 1:1 with 1,411 untreated controls by propensity scores (untreated cohort). We also matched the treated cohort 1:4 with 5,644 diabetic patients without HCV infection (uninfected cohort). Participants were followed up for the occurrence of endstage renal disease (ESRD), ischemic stroke, and acute coronary syndrome (ACS) after receiving antiviral treatment or the corresponding calendar date. From 2003 to 2011, the 8-year cumulative incidences of ESRD in the treated, untreated, and uninfected cohorts were 1.1% (95% confidence interval [CI], 0.3-2.0%), 9.3% (95% CI, 5.9-12.7%), and 3.3% (95% CI, 2.3-4.3%), respectively (P < 0.001); those of stroke were 3.1% (95% CI, 1.1-5.0%), 5.3% (95% CI, 3.0-7.5%), and 6.1% (95% CI, 4.8-7.4%), respectively (P = 0.01); and those for ACS were 4.1% (95% CI, 2.1-6.1%), 6.6% (95% CI, 3.7-9.5%), and 7.4% (95% CI, 5.9-9.0%), respectively (P = 0.05). As compared with the untreated cohort, antiviral treatment was associated with multivariate-adjusted hazard ratios of 0.16 (95% CI, 0.07-0.33%) for ESRD, 0.53 (95% CI, 0.30-0.93) for ischemic stroke, and 0.64 (95% CI, 0.39-1.06) for ACS. CONCLUSION: Antiviral treatment for HCV infection is associated with improved renal and cardiovascular outcomes in diabetic patients.

Serendipitous discovery of short peptides from natural products as tyrosinase inhibitors.

Tyrosinase, which is the crucial copper-containing enzyme involved in melanin synthesis, is strongly associated with hyperpigmentation disorders, cancer, and neurodegenerative disease; thus, it has attracted considerable interest in the fields of medicine and cosmetics. The known tyrosinase inhibitors show numerous adverse side effects, and there is a lack of safety regulations governing their use. As a result, there is a need to develop novel inhibitors with no toxicity and long-term stability. In this study, we use molecular docking and pharmacophore modeling to construct a reasonable and reliable pharmacophore model, called Hypo 1, that could be used for identifying potent natural products with crucial complementary functional groups for mushroom tyrosinase inhibition. It was observed that, out of 47,263 natural compounds, A5 structurally resembles a dipeptide (WY) and natural compound B16 is the equivalent of a tripeptide (KFY), revealing that the C-terminus tyrosine residues play a key role in tyrosinase inhibition. Tripeptides RCY and CRY, which show high tyrosinase inhibitory potency, revealed a positional and functional preference for the cysteine residue at the N-terminus of the tripeptides, essentially determining the capacity of tyrosinase inhibition. CRY and RCY used the thiol group of cysteine residues to coordinate with the Cu ions in the active site of tyrosinase and showed reduced tyrosinase activity. We discovered the novel tripeptide CRY that shows the most striking inhibitory potency against mushroom tyrosinase (IC50 = 6.16 µM); this tripeptide is more potent than the known oligopeptides and comparable with kojic acid-tripeptides. Our study provides an insight into the structural and functional roles of key amino acids of tripeptides derived from the natural compound B16, and the results are expected to be useful for the development of tyrosinase inhibitors.

Design of novel FLT-3 inhibitors based on dual-layer 3D-QSAR model and fragment-based compounds in silico.

FMS-like tyrosine kinase 3 (FLT-3) is strongly correlated with acute myeloid leukemia, but no FLT-3-inhibitor cocomplex structure is available to assist the design of therapeutic inhibitors. Hence, we propose a dual-layer 3D-QSAR model for FLT-3 that integrates the pharmacophore, CoMFA, and CoMSIA. We then coupled the model with the fragment-based design strategy to identify novel FLT-3 inhibitors. In the first layer, the previously established model, Hypo02, was evaluated in terms of its correlation coefficient (r), RMS, cost difference, and configuration cost, with values of 0.930, 1.24, 106.45, and 16.44, respectively. Moreover, Fischer's cross-validation test of data generated by Hypo02 yielded a 98% confidence level, and the validation of the testing set yielded a best r value of 0.87. The features of Hypo02 were separated into two parts and then used to screen the MiniMaybridge fragment compound database. Nine novel FLT-3 inhibitors were generated in this layer. In the second layer, Hypo02 was subjected to an alignment rule to generate CoMFA- and CoMSIA-based models, for which the partial least-squares validation method was utilized. The values of q(2), r(2), and predictive r(2) were 0.58, 0.98, and 0.76, respectively, derived from the CoMFA model with steric and electrostatic fields. The CoMSIA model with five different fields yielded values of 0.54, 0.97, and 0.76 for q(2), r(2), and predictive r(2), respectively. The CoMFA and CoMSIA models were used to constrain 3D structures of the nine novel FLT-3 inhibitors. This dual-layer 3D-QSAR model constitutes a valuable tool to easily and quickly screen and optimize novel potential FLT-3 inhibitors for the treatment of acute myeloid leukemia.

DNA repair proteins as the targets for paroxetine to induce cytotoxicity in gastric cancer cell AGS.

To evaluate the potential anticancer effects of 1175 FDA-approved drugs, cell viability screening was performed using 25 human cancer cell lines covering 14 human cancer types. Here, we focus on the action of paroxetine, which demonstrated greater toxicity toward human gastric adenocarcinoma cell-line AGS cells compared with the other FDA-approved drugs, exhibiting an IC50 value lower than 10 µM. Evaluation of the underlying novel mechanisms revealed that paroxetine can enhance DNA damage in gastric cancer cells and involves downregulation of Rad51, HR23B and ERCC1 expression and function, as well as nucleotide shortage. Enhancement of autophagy counteracted paroxetine-induced apoptosis but did not affect paroxetine-induced DNA damage. Paroxetine also enhanced ROS generation in AGS cells, but a ROS scavenger did not improve paroxetine-mediated DNA damage, apoptosis, or autophagy, suggesting ROS might play a minor role in paroxetine-induced cell toxicity. In contrast, paroxetine did not enhance DNA damage, apoptosis, or autophagy in another insensitive gastric adenocarcinoma cell-line MKN-45 cells. Interestingly, co-administration of paroxetine with conventional anticancer agents sensitized MKN-45 cells to these agents: co-treated cells showed increased apoptosis relative to MKN-45 cells treated with the anticancer agent alone. Unequivocally, these data suggest that for the first time that paroxetine triggers cytotoxicity and DNA damage in AGS cells at least partly by reducing the gene expression of Rad51, HR23B, and ERCC1. Our findings also suggest that paroxetine is a promising candidate anticancer agent and/or chemosensitizing agent for use in combination with other anticancer drugs in cancer therapy. The molecular mechanisms underlying the anticancer activity of co-treatment with paroxetine and chemotherapy appear to be complex and are worthy of further investigation.

Production of Active Nonglycosylated Recombinant B-Chain of Type-2 Ribosome-Inactivating Protein from Viscum articulatum and Its Biological Effects on Peripheral Blood Mononuclear Cells.

Type-2 ribosome-inactivating proteins, composed of a toxic A-chain and lectin-like B-chain, display various biological functions, including cytotoxicity and immunomodulation. We here cloned the lectin-like B-chain encoding fragment of a newly identified type-2 RIP gene, articulatin gene, from Viscum articulatum, into a bacterial expression vector to obtain nonglycosylated recombinant protein expressed in inclusion bodies. After purification and protein refolding, soluble refolded recombinant articulatin B-chain (rATB) showed lectin activity specific toward galactoside moiety and was stably maintained while stored in low ionic strength solution. Despite lacking glycosylation, rATB actively bound leukocytes with preferential binding to monocytes and in vitro stimulated PBMCs to release cytokines without obvious cytotoxicity. These results implicated such a B-chain fragment as a potential immunomodulator.

A Closer Look at Dexamethasone and the SARS-CoV-2-Induced Cytokine Storm: In Silico Insights of the First Life-Saving COVID-19 Drug.

The term cytokine storm refers to an uncontrolled overproduction of soluble inflammatory markers known as cytokines and chemokines. Autoimmune destruction of the lungs triggered by the release of these inflammatory markers often induces acute respiratory distress syndrome (ARDS). ARDS is an emergency condition with a high mortality rate in COVID-19 patients. Dexamethasone is the first repurposed corticosteroid with life-saving efficacy in patients with severe SARS-CoV-2 infection. Dexamethasone has traditionally been known to suppress the production of inflammatory markers at the transcriptional level, but its role as a direct therapeutic to neutralize cytokines, chemokines, their receptors, and functionally critical SARS-CoV-2 proteins has not yet been explored. Herein, we demonstrated that dexamethasone binds with high affinity to interlukin-1 (IL-1), IL-6, IL-8, IL-12, IL-21, INF2, TGFß-1, INF-γ, CXCL8, some of the receptors, IL-1R, IL-21R, IFNGR, INFAR, IL-6αR-gp130, ST2 and the SARS-CoV-2 protein NSP macro X, and 3CLpro, forming stable drug-protein complexes. Our work implied that dexamethasone has the potential to directly neutralize inflammatory markers, further supporting its life-saving potential in patients with severe manifestations of COVID-19.

Structural and functional comparisons and production of recombinant crustacean hyperglycemic hormone (CHH) and CHH-like peptides from the mud crab Scylla olivacea.

Sco-CHH and Sco-CHH-L (CHH-like peptide), two structural variants of the crustacean hyperglycemic hormone family identified in the mud crab (Scylla olivacea), are presumably alternatively spliced gene products. In this study, Sco-CHH and Sco-CHH-L were isolated from the tissues using high performance liquid chromatography. Identity of the native peptides was confirmed using mass spectrometric (MS) analyses of purified materials and of trypsin-digested peptide fragments. Additionally, characterizations using circular dichroism (CD) spectrometry revealed that the 2 peptides have similar CD spectral profiles, showing they are composed mainly of alpha-helices, and are similarly thermo-stable with a melting temperature of 74-75 degrees C. Results of bioassays indicated that Sco-CHH exerted hyperglycemic and molt-inhibiting activity, whereas Sco-CHH-L did not. Further, recombinant Sco-CHH-Gly (rSco-CHH-Gly, a glycine extended Sco-CHH) and Sco-CHH-L (rSco-CHH-L) were produced using an Escherichia coli expression system, refolded, and purified. rSco-CHH-Gly was further alpha-amidated at the C-terminal end to produce rSco-CHH. MS analyses of enzyme-digested peptide fragments of rSco-CHH-Gly and rSco-CHH-L showed that the two peptides share a common disulfide bond pattern: C7-C43, C23-C39, and C26-C52. Circular dichroism analyses and hyperglycemic assay revealed that rSco-CHH and rSco-CHH-L resemble their native counterparts, in terms of CD spectral profiles, melting curve profiles, and biological activity. rSco-CHH-Gly has a lower alpha-helical content (32%) than rSco-CHH (47%), a structural deviation that may be responsible for the significant decrease in the biological activity of rSco-CHH-Gly. Finally, modeled structure of Sco-CHH and Sco-CHH-L indicated that they are similarly folded, each with an N-terminal tail region and 4 alpha-helices. Putative surface residues located in corresponding positions of Sco-CHH and Sco-CHH-L but with side chains of different properties were identified. The combined results support the notion that Sco-CHH and Sco-CHH-L are functionally different, but resemble each other at higher-level structures. Functional diversity between the 2 peptides is probably due to critical residues located in the C-terminus. The availability of large amounts of recombinant proteins will permit additional functional and structural studies of these CHH family peptides.

The first pharmacophore model for potent NF-kappaB inhibitors.

As an important transcription factor of the Ral family, nuclear factor-kappa B (NF-kappaB) is involved in numerous cellular processes, such as the responses to cellular stress and to inflammation. For better elucidating the quantitative structure-activity relationship of NF-kappaB inhibitors and determining possible ligand-protein interaction, a pharmacophore model, Hypo1, was built based on 35 training molecules by Catalyst/HypoGen algorithm. The five pharmacophore features of Hypo1, including three hydrophobic groups, one hydrogen-bond acceptor, and one hydrophobic aromatic group, were correctly mapped onto NF-kappaB surface. This model has strong capability to identify NF-kappaB inhibitors and to predict the activities of structurally diverse molecules, thus to provide a valuable tool in the design of new leads with desired biological activity by virtual screening.

Characterization, molecular modelling and developmental expression of zebrafish manganese superoxide dismutase.

A 977 bp cDNA containing an open reading frame encoding 224 amino acid residues of manganese superoxide dismutase was cloned from zebrafish (zMn-SOD). The deduced amino acid sequence showed high identity with the sequences of Mn-SODs from human (85.1%) to nematode (61.6%). The 3-D structure model was superimposed on the relative domains of human Mn-SOD with the root mean square (rms) deviation of 0.0919 A. The recombinant mature zMn-SOD with enzyme activity was purified using His-tag technique. The half-life of the enzyme is approximately 48 min and its thermal inactivation rate constant k(d) is 0.0154 min(-1)at 70 degrees C. The enzyme was active under a broad pH (2.2-11.2) and in the presence of up to 4% SDS. Real-time RT-PCR assay was used to detect the zMn-SOD mRNA expression during the developmental stages following a challenge with paraquat. A high level expression of Mn-SOD mRNA was detected at the cleavage stage, but decreased significantly under paraquat treatment. The results indicated that Mn-SOD plays an important role during embryonic development.

Aloe-emodin is an interferon-inducing agent with antiviral activity against Japanese encephalitis virus and enterovirus 71.

In this study, aloe-emodin was identified as a potential interferon (IFN)-inducer by screening compounds from Chinese herbal medicine. Aloe-emodin showed low cytotoxicity to human HL-CZ promonocyte cells and TE-671 medulloblastoma cells and significantly activated interferon-stimulated response element (ISRE) and gamma-activated sequence (GAS)-driven cis-reporting systems. Moreover, aloe-emodin upregulated expression of IFN-stimulated genes such as dsRNA-activated protein kinase and 2',5'-oligoisoadenylate synthase. Aloe-emodin resulted in significant activation of nitric oxide production. The antiviral activity of aloe-emodin against Japanese encephalitis virus (JEV) and enterovirus 71 (EV71) was evaluated using dose- and time-dependent plaque reduction assays in HL-CZ cells and TE-671 cells. The 50% inhibitory concentration (IC(50)) of aloe-emodin ranged from 0.50microg/mL to 1.51microg/mL for JEV and from 0.14microg/mL to 0.52microg/mL for EV71. Aloe-emodin showed clearly potent virus inhibitory abilities and achieved high therapeutic indices, in particular for HL-CZ cells. Therefore, the study demonstrated dose- and time-dependent actions of aloe-emodin on the inhibition of JEV and EV71 replication via IFN signalling responses.

The effect of different electrostatic potentials on docking accuracy: a case study using DOCK5.4.

As a commonly used structure-based approach for virtual screening, molecular design and lead optimization, molecular docking can search the preferred orientation and conformation of a ligand for its optimal binding to a receptor or enzyme active site. In doing so, selecting an appropriate method to calculate the electrostatic potentials is critical. In the current report, nine different semi-empirical and empirical methods, including AM1, AM1-BCC, Del-Re, MMFF, Gasteiger, Hückel, Gasteiger-Hückel, Pullman and formal charges were investigated for their performance on the prediction of docking poses using the DOCK5.4 program. The results demonstrated that the AM1-BCC charges had the highest success rate.

Identification of a novel septin 4 protein binding to human herpesvirus 8 kaposin A protein using a phage display cDNA library.

Human herpesvirus 8 (HHV-8) is associated with the development of Kaposi's sarcoma and several other human malignancies. Kaposin A protein of HHV-8 has been demonstrated as inducing tumorigenic transformation, being responsible for nuclear receptor coactivators in the transforming activity. In this study, a kaposin A-interacting septin 4 variant that contained the unique GDR at the N-terminus and AAALE at the C-terminus was identified using affinity selection of a phage display library. Co-immunoprecipitation and confocal imaging revealed in vitro binding specificity and in vivo co-localization of HHV-8 kaposin A protein to the septin 4 variant. The kaposin A-interacting septin 4 variant induced cell rounding up, activated caspase-3, and up-regulated transcriptional factor NF-kappaB. By contrast, kaposin A protein showed an antagonistic effect on the biological functions of the septin 4 variant. Therefore, the interaction of kaposin A protein and the septin 4 variant was suggested as playing a possible role in the development of HHV-8-associated malignancies. This study provides insights into the mechanism of the kaposin A protein pathology, in which the interactions of kaposin A protein with cellular proteins might allow alteration of fundamental cellular processes.

Discovery of a potent cyclooxygenase-2 inhibitor, S4, through docking-based pharmacophore screening, in vivo and in vitro estimations.

Cyclooxygenase (COX; EC: 1.14.99.1), the key enzyme in prostaglandin production in the human body, is a major pharmacological target for developing anti-inflammatory agents. Nonsteroidal anti-inflammatory drugs exhibit anti-inflammatory and analgesic activities when inhibiting COX-2 but cause gastrointestinal toxicity and other side effects because of concurrent inhibition of COX-1. Thus, potent and safe inhibitors against COX-2 are urgently required. We constructed a novel docking-based pharmacophore model for screening selective COX-2 inhibitors and discovered compounds S1, S2, S3, and S4, which apparently inhibit COX-2. Particularly, S4 inhibits COX-2 in vitro and shows a potent anti-inflammatory effect in vivo without cytotoxicity. Molecular docking analyses revealed that S4 interacted satisfactorily with the active site of COX-2 but not with that of COX-1. This reveals that S4 more specifically inhibits COX-2 and has potential for application in developing anti-inflammatory and anticancer agents.

Discovery of highly potent tyrosinase inhibitor, T1, with significant anti-melanogenesis ability by zebrafish in vivo assay and computational molecular modeling.

Tyrosinase is involved in melanin biosynthesis and the abnormal accumulation of melanin pigments leading to hyperpigmentation disorders that can be treated with depigmenting agents. A natural product T1, bis(4-hydroxybenzyl)sulfide, isolated from the Chinese herbal plant, Gastrodia elata, is a strong competitive inhibitor against mushroom tyrosinase (IC50 = 0.53 µM, Ki = 58 ± 6 nM), outperforms than kojic acid. The cell viability and melanin quantification assay demonstrate that 50 µM of T1 apparently attenuates 20% melanin content of human normal melanocytes without significant cell toxicity. Moreover, the zebrafish in vivo assay reveals that T1 effectively reduces melanogenesis with no adverse side effects. The acute oral toxicity study evidently confirms that T1 molecule is free of discernable cytotoxicity in mice. Furthermore, the molecular modeling demonstrates that the sulfur atom of T1 coordinating with the copper ions in the active site of tyrosinase is essential for mushroom tyrosinase inhibition and the ability of diminishing the human melanin synthesis. These results evident that T1 isolated from Gastrodia elata is a promising candidate in developing pharmacological and cosmetic agents of great potency in skin-whitening.

Discovery of Potent Cysteine-Containing Dipeptide Inhibitors against Tyrosinase: A Comprehensive Investigation of 20 × 20 Dipeptides in Inhibiting Dopachrome Formation.

Tyrosinase is an essential copper-containing enzyme required for melanin synthesis. The overproduction and abnormal accumulation of melanin cause hyperpigmentation and neurodegenerative diseases. Thus, tyrosinase is promising for use in medicine and cosmetics. Our previous study identified a natural product, A5, resembling the structure of the dipeptide WY and apparently inhibiting tyrosinase. Here, we comprehensively estimated the inhibitory capability of 20 × 20 dipeptides against mushroom tyrosinase. We found that cysteine-containing dipeptides, directly blocking the active site of tyrosinase, are highly potent in inhibition; in particular, N-terminal cysteine-containing dipeptides markedly outperform the C-terminal-containing ones. The cysteine-containing dipeptides, CE, CS, CY, and CW, show comparative bioactivities, and tyrosine-containing dipeptides are substrate-like inhibitors. The dipeptide PD attenuates 16.5% melanin content without any significant cytotoxicity. This study reveals the functional role of cysteine residue positional preference and the selectivity of specific amino acids in cysteine-containing dipeptides against tyrosinase, aiding in developing skin-whitening products.

Relationship between local structural entropy and protein thermostability.

We developed a technique to compute structural entropy directly from protein sequences. We explored the possibility of using structural entropy to identify residues involved in thermal stabilization of various protein families. Examples include methanococcal adenylate kinase, Ribonuclease HI and holocytochrome c(551). Our results show that the positions of the largest structural entropy differences between wild type and mutant usually coincide with the residues relevant to thermostability. We also observed a good linear relationship between the average structural entropy and the melting temperatures for adenylate kinase and its chimeric constructs. To validate this linear relationship, we compiled a large dataset comprised of 1153 sequences and found that most protein families still display similar linear relationships. Our results suggest that the multitude of interactions involved in thermal stabilization may be generalized into the tendency of proteins to maintain local structural conservation. The linear relationship between structural entropy and protein thermostability should be useful in the study of protein thermal stabilization.