Showing papers by "Tzi Bun Ng published in 2021"

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

Abstract: In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Study on the Biocontrol Potential of Antifungal Peptides Produced by Bacillus velezensis against Fusarium solani That Infects the Passion Fruit Passiflora edulis

Abstract: A bacterium identified as Bacillus velezensis with a growth inhibitory effect against Fusarium solani, a pathogen that caused basal stem rot in the passion fruit Passiflora edulis, was isolated in this study From the fermentation broth of B velezensis, a type of antifungal peptide (named BVAP) with a molecular weight of ca 15 kDa was purified and found to be fengycin BVAP suppressed mycelial growth in F solani with an IC50 of 558 μg/mL, which was superior to those of the chemical fungicides thiram (4124 μg/mL) and hymexazol (34331 μg/mL) The antifungal activity remained stable after exposure to 50-100 °C or following incubation with solutions at pH 1-3 Further research revealed that BVAP increased the permeability of the F solani mycelial membrane, brought about swelling at the tips of hyphae, and elicited abnormal accumulation of nucleic acids and chitin at the sites of swelling These findings indicate that BVAP possessed a remarkable biocontrol potential toward F solani

Purification and properties of a laccase from the mushroom Agaricus sinodeliciosus.

Abstract: A homogeneous monomeric laccase (ASL) from Agaricus sinodeliciosus, with a molecular mass of 65 kDa, was isolated using ion-exchange chromatography (CM-cellulose and Q-Sepharose) and gel-filtration chromatography (Superdex 75). This laccase exhibited maximum activity at 50 °C and pH 5.0. Hg2+ and Cd2+ significantly inhibited its activity. The laccase displayed a Km value of 0.9 mM toward 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS). In addition to ABTS, ASL exhibited higher affinity toward o-toluidine and benzidine than other substrates. ASL is able to decolorize malachite green and Eriochrome black T.

Purified antioxidant from the medicinal mushroom Phellinus pini protects rat H9c2 cell against H 2 O 2 -induced oxidative stress.

Abstract: In this study, through the combination of AB-8 macroporous resin, Sephadex LH-20 column chromatography and semi-preparative HPLC, an antioxidant component was purified from the crude extract of Phellinus pini, thereby evaluating the cardioprotective effect of the fraction. As a result, total phenolic content of the 60% ethanol elution was increased by 4.8-fold after one run treatment on Sephadex LH-20 chromatography with gradient elution. After semi-preparative HPLC separation, the first peak (PP-S4-1) showed that inhibition ratio of erythrocyte hemolysis was 91.9%, and inhibition ratio of lipid peroxidation was also increased by 87.6%, at 50 μg/ml (p < .01). Based on the results of ESI-MS, 1 HNMR, 13 CNMR, and RP-HPLC compared to many published results, PP-S4-1was identified as catechin (MW 290.015, C15 H14 O6 ). The results showed that PP-S4-1 pretreatment made cell viability increased, and the generation of reactive oxygen species (ROS) inhibited. Meanwhile, PP-S4-1 remarkably decreased the fluorescence intensity of Ca2+ , and increased mitochondrial membrane potential (MMP; ΔΨm). In addition, PP-S4-1 could significantly inhibit the decrease of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activity as well as the increase of MDA content in H9c2 cells induced by H2 O2 . Moreover, pretreatment with PP-S4-1 significantly improved the morphological changes and prevented H2 O2 -induced DNA damage. Therefore, this study clarifies the ability of PP-S4-1 to treat H9c2 cell oxidative stress damage induced by H2 O2 through its antioxidant effect. PRACTICAL APPLICATIONS: This research is not only helpful to elaborate the cardioprotective effect of Phellinus pini but also can contribute to the development of health foods or drug supplements for heart disease in the future. This is the first report dealing with phenolic component and cardioprotective activity of a medicinal mushroom P. pini belonging to the genus Phellinus.

Antidepressant-like effect of Ganoderma lucidum spore polysaccharide-peptide mediated by upregulation of prefrontal cortex brain-derived neurotrophic factor

Abstract: A 28-kDa polysaccharide-peptide (PGL) with antidepressant-like activities was isolated from spores of the mushroom Ganoderma lucidum. It was unadsorbed on DEAE-cellulose. Its internal amino acid sequences manifested pronounced similarity with proteins from the mushrooms Lentinula edodes and Agaricus bisporus. The monosaccharides present in 28-kDa PGL comprised predominantly of glucose (over 90%) and much fewer galactose, mannose residues, and other residues. PGL manifested antidepressant-like activities as follows. It enhanced viability and DNA content in corticosterone-injured PC12 cells(a cell line derived from a pheochromocytoma of the rat adrenal medulla with an embryonic origin from the neural crest containing a mixture of neuroblastic cells and eosinophilic cells) and reduced LDH release. A single acute PGL treatment shortened the duration of immobility of mice in both tail suspension and forced swimming tests. PGL treatment enhanced sucrose preference and shortened the duration of immobility in mice exposed to chronic unpredictable mild stress (CUMS). Chronic PGL treatment reversed the decline in mouse brain serotonin and norepinephrine levels but did not affect dopamine levels. PGL decreased serum corticosterone levels and increased BDNF mRNA and protein levels and increased synapsin I and PSD95 levels in the prefrontal cortex. This effect was completely blocked by pretreatment with the BDNF antagonist K252a, indicating that PGL increased synaptic proteins in a BDNF-dependent manner.Key points• An antidepressive polysaccharide-peptide PGL was isolated from G. lucidum spores.• PGL protected PC12 nerve cells from the toxicity of corticosterone.• PGL upregulated BDNF expression and influenced key factors in the prefrontal cortex.

A thermophilic chitinase 1602 from the marine bacterium Microbulbifer sp. BN3 and its high-level expression in Pichia pastoris

Abstract: Chitinases play an important role in many industrial processes, including the preparation of oligosaccharides with potential applications. In the present study, a 1,713 bp gene of Chi1602, derived from a marine bacterium Microbulbifer sp. BN3, encoding a GH18 family chitinase, was expressed at high levels in Pichia pastoris. Distinct from most of the marine chitinases, the recombinant chitinase 1602 exhibited maximal activity at 60 °C and over a broad pH range between 5.0 and 9.0, and was stable at 50 °C and over the pH range 4.0-9.0. The hydrolytic products derived from colloidal chitins comprised mainly (GlcNAc)2 and GlcNAc, indicating that rChi1602 is a GH18 processive chitinase in conformity with its hypothetical structure. However, rChi1602 showed traces of β-N-acetylglucosaminidase activity on substrates such as powder chitin, chitosan, and ethylene glycol chitin. The thermophilic rChi1602, which manifests adaptation to a wide pH range and can be expressed at a high level in P. pastoris, is advantageous for applications in industrial processes.

Review of the therapeutic effects of the traditional Chinese medicine yuye decoction on diabetes mellitus and its complications

Abstract: Ethnopharmacological relevance: Diabetes is a serious metabolic disease which imposes a heavy burden on the society. It may also bring about a variety of complications if the blood glucose level is not well controlled. Yuye Decoction (YYD) is an ancient herbal medicinal formulation of China and has been widely used in Traditional Chinese medicine to treat patients with diabetes for thousands of years. There are seven medicinal herbs in YYD. Aim of the study: The aim of the present review is to summarize and critically appraise data concerning medicinal plants used in YYD, its main active constituents and signaling pathways mediating its therapeutic effects on diabetes and diabetic complications. Materials and methods: The search of papers published in the period 2009 to 2019 and recorded in PubMed was conducted using specific search terms. Results: After screening, 88 studies were included. Among seven medicinal herbs in YYD formulation, six of them exhibited therapeutic effects on diabetes and its complications through different signaling pathways. Most (55.7%) of the studies were animal studies. Type 2 diabetes was studied in most (37.5%) of the research papers and diabetic nephropathy was the most (19.3%) studied diabetic complication. Focus was placed on Astragalus membranaceus (Fisch.) Bge. and Pueraria lobata (Willd.) Ohwi in the largest number of research papers. Conclusion: YYD exerted a therapeutic effect on diabetes and a preventive effect on diabetic complications. *Correspondence to: Kalin Y.B. Zhang, School of Chinese Medicine, LKS Faculty of Medicine, The University of Hong Kong,10 Sassoon Road, Hong Kong, E-mail: ybzhang@hku.hk Jack Hei Wan, School of Chinese Medicine, LKS Faculty of Medicine, The University of Hong Kong,10 Sassoon Road, Hong Kong, E-mail: jack_wan88@ hotmail.com Sydney Chi-Wai TANG, Department of Medicine, LKS Faculty of Medicine, The University of Hong Kong, 102 Pok Fu Lam Road, Hong Kong, E-mail: scwtang@ hku.hk