BACE1 inhibitory activity of fungal endophytic extracts from Malaysian medicinal plants

Microorganism-Derived Molecules as Enzyme Inhibitors to Target Alzheimer's Diseases Pathways

Alzheimer's disease (AD) is the most common form of dementia. It increases the risk of other serious diseases and causes a huge impact on individuals, families, and socioeconomics. AD is a complex multifactorial disease, and current pharmacological therapies are largely based on the inhibition of enzymes involved in the pathogenesis of AD. Natural enzyme inhibitors are the potential sources for targeting AD treatment and are mainly collected from plants, marine organisms, or microorganisms. In particular, microbial sources have many advantages compared to other sources. While several reviews on AD have been reported, most of these previous reviews focused on presenting and discussing the general theory of AD or overviewing enzyme inhibitors from various sources, such as chemical synthesis, plants, and marine organisms, while only a few reviews regarding microbial sources of enzyme inhibitors against AD are available. Currently, multi-targeted drug investigation is a new trend for the potential treatment of AD. However, there is no review that has comprehensively discussed the various kinds of enzyme inhibitors from the microbial source. This review extensively addresses the above-mentioned aspect and simultaneously updates and provides a more comprehensive view of the enzyme targets involved in the pathogenesis of AD. The emerging trend of using in silico studies to discover drugs concerning AD inhibitors from microorganisms and perspectives for further experimental studies are also covered here.

The Neuroprotective Potential of Endophytic Fungi and Proposed Molecular Mechanism: A Current Update

Millions of people are affected by neuronal disorders that are emerging as a principal cause of death after cancer. Alzheimer's disease, ataxia, Parkinson's disease, multiple system atrophy, and autism comprise the most common ones, being accompanied by loss of cognitive power, impaired balance, and movement. In past decades, natural polyphenols obtained from different sources including bacteria, fungi, and plants have been utilized in the traditional system of medicine for the treatment of several ailments. Endophytes are one such natural producer of secondary metabolites, namely, polyphenols, which exhibit strong abilities to assist in the management of such affections, through modifying multiple therapeutic targets and weaken their complex physiology. Limited research has been conducted in detail on bioactive compounds present in the endophytic fungi and their neuroprotective effects. Therefore, this review aims to provide an update on scientific evidences related to the pharmacological and clinical potential along with proposed molecular mechanism of action of endophytes for neuronal protection.

Bioprospecting of endophytic microorganisms for bioactive compounds of therapeutic importance

Presently, several drug discovery investigations on therapeutic management of human health are aimed at bioprospecting for microorganisms, especially endophytic microbes of biotechnological importance. This review investigates the benefits of endophytes, especially in producing bioactive compounds useful in modern medicine by systematically reviewing published data from 12 databases. Only experimental studies investigating either or both bacterial and fungal endophytes and within the scope of this review were selected. The published data from the last 2 decades (2000-2019) revealed diverse endophytes associated with different plants produce a broad spectrum of bioactive compounds with therapeutic benefits. Notably, antibacterial, followed by anticancer and antifungal activities, were mostly reported. Only three studies investigated the anti-plasmodial activity. The variation observed in the synthesis of bioactive compounds amongst endophytes varied with host type, endophyte species, and cultivation medium. Fungal endophytes were more investigated than bacterial endophytes, with both endophytes having species diversity amongst literature. The endophytes were predominantly from medicinal plants and belonged to either Ascomycota (fungi) or Proteobacteria and Firmicutes (bacteria). This review presents excellent prospects of harnessing endophytes and their unique bioactive compounds in developing novel and effective compounds of medicinal importance.

Biochemical Constituents of Phaleria macrocarpa (Leaf) Methanolic Extract Inhibit ROS Production in SH-SY5Y Cells Model

Background. Reactive oxygen species generation in mammalian cells profoundly affects several critical cellular functions, and the lack of efficient cellular detoxification mechanisms which remove these radicals may lead to several human diseases. Several studies show that ROS is incriminated as destructive agents in the context of the nervous system especially with advance in age leading to neurodegeneration. Current treatments of this disease are not effective and result in several side effects. Thus, the search for alternative medicines is in high demand. Therefore, the aim of this study is to evaluate the reactive oxygen inhibitory effect of Phaleria macrocarpa 80% (leaf) extract. Methods. The leaf was extracted with 80% methanol. Cytotoxicity studies were carried out using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and ROS inhibitory activities were evaluated using dichlorofluorescein diacetate (DCF-DA) assay in the SH-SY5Y cells model. Results. The result revealed ROS inhibitory activities of the crude extract with highly significant differences at $p<0.001$ between the group that were treated with crude extract only, the group treated with crude extract and exposed to H2O2, and the group exposed to H2O2 only as well as the group that were maintained in complete media. Bioactive compounds show the presence of vitexin and isovitexin following the HPLC method. Conclusion. High antioxidant activities and low toxicity effect of this crude revealed its high benefit to be used as natural medicine/supplements.

Exploring the potential of marine microbes in clinical management of Alzheimer's disease: A road map for bioprospecting and identifying promising isolates

Pervasiveness of Alzheimer's disease (AD) across the globe is on rise, devitalizing the essential brain functions of the afflicted individual. Multiple neurological pathways viz., cholinergic, amyloidogenic and tau protein pathways underlying the disease and interdependence make it more complex to develop effective treatment strategies. Existing drug treatments for Alzheimer's disease majorly belong to the class of cholinergic inhibitors which improve the behavioral symptoms. But there are no drugs that could arrest the disease progression. Inhibition of beta secretase enzyme could prevent the deposition of amyloid plaques in the neurons, thereby arresting the disease progression. Search for novel drugs to treat the underlying pathogenesis of the disease is pivotal in this day and age. The source of most active lead molecules discovered recently is from the nature. Marine ecosystem provides a plethora of pharmacologically lead molecules from various living organisms inhabiting the sea. Among all, marine microbes are the most under-explored and indispensable source of many bioactive metabolites. Studies have been reported on potent metabolites from marine microbes which could inhibit the key enzymes involved in the AD pathogenesis. The advancement in microbial bioprospecting and molecular biology techniques have eased the process of cultivation and identification of microbes, isolation of novel bioactive metabolites of clinical use. Exploring such marine natural resources for pharmacological lead molecules could give a breakthrough in the drug discovery domain for treating AD such debilitating diseases. In this review, a comprehensive account of bioprospecting methods and reports of marine microbial isolates are discussed.

Morphological and phylogenetic characterisation of novel Cytospora species associated with mangroves

Mangroves are relatively unexplored habitats and have been shown to harbour a number of novel species of fungi. In this study, samples of microfungi were collected from symptomatic branches, stem and leaves of the mangrove species Xylocarpusgranatum, X.moluccensis and Lumnitzeraracemosa and examined morphologically. The phylogeny recovered supports our morphological data to introduce three new species, Cytosporalumnitzericola, C.thailandica and C.xylocarpi. In addition, a combined multi-gene DNA sequence dataset (ITS, LSU, ACT and RPB2) was analysed to investigate phylogenetic relationships of isolates and help in a more reliable species identification.

Ciproxifan improves cholinergic transmission, attenuates neuroinflammation and oxidative stress but does not reduce amyloid level in transgenic mice

AIM

The present study is aimed to investigate the ability of ciproxifan, a histamine H₃ receptor antagonist to inhibit β-amyloid (Aβ)-induced neurotoxicity in SK-N-SH cells and APP transgenic mouse model.

MATERIALS AND METHODS

In vitro studies was designed to evaluate the neuroprotective effects of ciproxifan in Aβ_25-35 - induced SK-N-SH cells. For the in vivo study, ciproxifan (1 and 3mg/kg, i.p.) was administrated to transgenic mice for 15days and behaviour was assessed using the radial arm maze (RAM). Brain tissues were collected to measure Aβ levels (Aβ_1-40 and Aβ_1-42), acetylcholine (ACh), acetylcholinesterase (AChE), nitric oxide (NO), lipid peroxidation (LPO), antioxidant activities, cyclooxygenases (COX) and cytokines (IL-1α, IL-1β and IL-6), while plasma was collected to measure TGF-1β.

RESULTS

The in vitro studies demonstrated neuroprotective effect of ciproxifan by increasing cell viability and inhibiting reactive oxygen species (ROS) in Aβ_25-35-induced SK-N-SH cells. Ciproxifan significantly improved the behavioural parameters in RAM. Ciproxifan however, did not alter the Aβ levels in APP transgenic mice. Ciproxifan increased ACh and showed anti-oxidant properties by reducing NO and LPO levels as well as enhancing antioxidant levels. The neuroinflammatory analysis showed that ciproxifan reduced both COX-1 and COX-2 activities, decreased the level of pro-inflammatory cytokines IL-1α, IL-1β and IL-6 and increased the level of anti-inflammatory cytokine TGF-1β.

CONCLUSION

This present study provides scientific evidence of the use of ciproxifan via antioxidant and cholinergic pathways in the management of AD.

Malaysian endophytic fungal extracts-induced anti-inflammation in Lipopolysaccharide-activated BV-2 microglia is associated with attenuation of NO production and, IL-6 and TNF-α expression

BACKGROUND

Excessive production of inflammatory mediators such as nitric oxide (NO) and proinflammatory cytokines like tumour necrosis factor-alpha (TNF-α) from activated microglia contributes to uncontrolled inflammation in neurodegenerative diseases. This study investigated the protective role of five endophytic extracts (HAB16R12, HAB16R13, HAB16R14, HAB16R18 and HAB8R24) against LPS-induced inflammatory events in vitro. These endophytic extracts were previously found to exhibit potent neuroprotective effect against LPS-challenged microglial cells.

METHODS

The effects of these fungal endophytic extracts against nitric oxide (NO), CD40 phenotype and, pro- and anti-inflammatory cytokine production in lipopolysaccharide (LPS)-stimulated BV2 microglia cells were examined using commercially available assay kits, immunophenotyping and flow cytometry, respectively.

RESULTS

Microglia pre-treated with the five endophytic extracts (0.1 mg/mL) reduced NO production without compromising cell viability. Whilst CD40 expression in LPS-stimulated microglia was not significantly different with or without the influence of endophytic extracts, expression of the proinflammatory cytokines, IL-6 and TNF-α in LPS-stimulated microglia was significantly (P < 0.05) inhibited by these endophytic extracts.

CONCLUSIONS

The outcomes suggest that the neuroprotective effect of the fungal endophytic extracts is likely mediated through supression of neuroinflammation. To our knowledge, this is the first report of the effect of a fungal endophytic extract in controlling inflammation in BV2 microglia cells.

Effects of secondary metabolite extract from Phomopsis occulta on β-amyloid aggregation

Inhibition of β-amyloid (Aβ) aggregation is an attractive therapeutic and preventive strategy for the discovery of disease-modifying agents in Alzheimer's disease (AD). Phomopsis occulta is a new, salt-tolerant fungus isolated from mangrove Pongamia pinnata (L.) Pierre. We report here the inhibitory effects of secondary metabolites from Ph. occulta on the aggregation of Aβ42. It was found that mycelia extracts (MEs) from Ph. occulta cultured with 0, 2, and 3 M NaCl exhibited inhibitory activity in an E. coli model of Aβ aggregation. A water-soluble fraction, ME0-W-F1, composed of mainly small peptides, was able to reduce aggregation of an Aβ42-EGFP fusion protein and an early onset familial mutation Aβ42E22G-mCherry fusion protein in transfected HEK293 cells. ME0-W-F1 also antagonized the cytotoxicity of Aβ42 in the neural cell line SH-SY5Y in dose-dependent manner. Moreover, SDS-PAGE and FT-IR analysis confirmed an inhibitory effect of ME0-W-F1 on the aggregation of Aβ42 in vitro. ME0-W-F1 blocked the conformational transition of Aβ42 from α-helix/random coil to β-sheet, and thereby inhibited formation of Aβ42 tetramers and high molecular weight oligomers. ME0-W-F1 and other water-soluble secondary metabolites from Ph. occulta therefore represent new candidate natural products against aggregation of Aβ42, and illustrate the potential of salt tolerant fungi from mangrove as resources for the treatment of AD and other diseases.

Endophytic fungi: expanding the arsenal of industrial enzyme producers

Endophytic fungi, mostly belonging to the Ascomycota, are found in the intercellular spaces of the aerial plant parts, particularly in leaf sheaths, sometimes even within the bark and root system without inducing any visual symptoms of their presence. These fungi appear to have a capacity to produce a wide range of enzymes and secondary metabolites exhibiting a variety of biological activities. However, they have been only barely exploited as sources of enzymes of industrial interest. This review emphasizes the suitability and possible advantages of including the endophytic fungi in the screening of new enzyme producing organisms as well as in studies aiming to optimize the production of enzymes through well-known culture processes. Apparently endophytic fungi possess the two types of extracellular enzymatic systems necessary to degrade the vegetal biomass: (1) the hydrolytic system responsible for polysaccharide degradation consisting mainly in xylanases and cellulases; and (2) the unique oxidative ligninolytic system, which degrades lignin and opens phenyl rings, comprises mainly laccases, ligninases and peroxidases. The obvious ability of endophytic fungi to degrade the complex structure of lignocellulose makes them useful in the exploration of the lignocellulosic biomass for the production of fuel ethanol and other value-added commodity chemicals. In addition to this, endophytic fungi may become new sources of industrially useful enzymes such as lipases, amylases and proteases.