Elucidating Molecular Interactions of Ten Natural Compounds Targeting E6 HPV High Risk Oncoproteins Using Microsecond Molecular Dynamics Simulations

BACKGROUND

Cervical cancer is a major public health issue worldwide, occurring in the vast majority of cases (85%) in low-income countries. Human papillomavirus (HPV) mainly infects the mucosal epithelium, and a small portion causes over 600,000 cases every year worldwide at various anatomical spots, mainly leading to anogenital and head and neck.

INTRODUCTION

The E6 oncoprotein encoded by cancer-associated alpha HPV can transform epithelial cells into tumorigenic tissue. Therapy for this infection and blocking of the HPV E6 oncoprotein could be provided with cost-effective and abundant natural products which are an exponentially growing topic in the literature. Finding an active natural compound that readily blocks HPV E6 oncoprotein which could be available for developing countries without expensive extraction processes or costly synthetic pathways is of major interest.

METHODS

Molecular dynamics simulation was performed using the most up-to-date AMBER protein force field ff14SB and a GPU enabled high performance computing cluster.

RESULTS

In this research, we present a study of the binding properties between 10 selected natural compounds that are readily available with two variants of the E6 oncoprotein types (HPV-16 and HPV-18) using 10+ microsecond molecular dynamics simulations.

CONCLUSION

Our results suggest that crocetin, ergosterol peroxide and κ-carrageenan natural products bind strongly to both HPV-16 and HPV-18 and could potentially serve as a scaffolding for further drug development.

Ergosterol exerts a differential effect on AR-dependent LNCaP and AR-independent DU-145 cancer cells

Androgen-dependent LNCaP and androgen-independent DU-145 cells, were treated with different concentrations of ergosterol (15 µM and 25 µM) and its respective cell viability was measured by MTT bioassay. While ergosterol showed an antiproliferative effect on LNCaP, on DU-145 promoted cell proliferation. This differential effect suggests that the effect of ergosterol might be related to its ability to act as an Androgen Receptor ligand. In silico Molecular Dynamics simulations were performed to analyze the interaction mechanism between androgen receptor and ergosterol, in comparison with natural ligands, 5α-dihydrotestosterone and testosterone. Our model suggests that the binding of androgen receptor with ergosterol is thermodinamically feasible, which is concordant with our experimental results.

In Vitro Expression of Toll-Like Receptors and Proinflammatory Molecules Induced by Ergosta- 7,22-Dien-3-One Isolated from a Wild Mexican Strain of Ganoderma oerstedii (Agaricomycetes)

Compounds showing pharmacological activity on the immune system are of interest because of their therapeutic potential in the treatment of many diseases. However, data from primary human immune cells and in vivo studies are limited. The aim of this study was to analyze the ability to induce the expression of Toll-like receptors (TLRs) and proinflammatory molecules on cells involved in the immune system using the compound ergosta-7,22-dien-3- one, isolated from a wild Mexican strain of Ganoderma oerstedii. According to our study, ergosta-7,22-dien-3-one did not present any cytotoxic effect on HeLa or J774A.1 cells, and it was able to stimulate nitric oxide production, induce the expression of genes, and induce the production of TLRs, cytokines, chemokines, and cellular adhesion molecules in J774A.1 cells, based on reverse-transcriptase polymerase chain reaction and enzyme-linked immunosorbent assay. Here we report a new pro-inflammatory property of ergosta-7,22-dien-3-one, which should be considered as a possible adjuvant property in view of its biological activity.

Molecular Dynamics and Virtual Screening Analysis of Lanosterol Derivatives from Ganoderma Medicinal Mushrooms (Agaricomycetes) as Selective Ligands of Human Androgen Receptor

Male sex hormones such as testosterone and dihydrotestosterone play important roles in several physiological and pathological processes. The biological activities of the aforementioned metabolites are mediated by the multidomain androgen receptor (AR), which is therefore a well-studied drug target. Ganoderma mushroom lanostanoid extracts have previously been shown to exert antiandrogenic activity; therefore, this work aims to identify which lanostane derivatives might act as selective ligands for AR. Because protein flexibility is of paramount importance for ligand binding, different conformations of AR were sampled to account for binding modes within a ligand binding site, then subjected to virtual screening against a metabolite library. Fifteen Ganoderma lanostanoids were selected as AR ligands, according to their calculated binding affinity to this nuclear receptor. The results show the relevance of certain structural and chemical aspects of our ligands, such as the presence of a ketonic group on C-3, which influences the process through which they bind to AR.

Antiproliferative activity of epi-cercosporin in human solid tumor cell lines

From cultures of Cercospora piaropi, a phytopathogenic fungus isolated from symptomatic leaves of water hyacinth was obtained a red compound, which, according to the spectroscopic data, was epi-cercosporin. It showed in vitro antiproliferative activity against the panel of human solid tumor cells HBL-100, HeLa, SW1573 and WiDr. Cell cycle studies revealed that epi-cercosporin induces accumulation of cells in G2/M phase.

Selective destruction of microscopic fungi through photo-oxidation of ergosterol

Ergosterol is an important component of fungal membranes. This sterol can be easily transformed to peroxide of ergosterol by photo-oxidation with singlet oxygen. Cultures of Papalauspora immersa were grown on Czapeck agar medium, and subjected to the following conditions: 1) irradiation with daylight and quartz light (excluding UV light), 2) addition by diffusion of yellowish eosine (0.1 mg/mL), and 3) the control (no yellowish eosine, under darkness conditions). Fungal growth was completely inhibited after the treatment with quartz light (3 h) and yellow eosine, and no growth was observed in subsequent subcultures. These results suggested that plasma membrane components changed significantly by the transformation of ergosterol to peroxide of ergosterol leading to fungal death. To confirm this, a second experiment on a larger scale was carried out in which the fungus was grown on liquid medium in test tubes, treated, irradiated, and tested for peroxide of ergosterol by (1)HNMR. This peroxide was only found in treated samples. These findings represent a new strategy for developing antifungal agents, based on ergosterol photo-oxidation which might probably be related to the disruption of the plasma membrane, instead of only preventing the ergosterol biosynthesis. The potential application of this strategy for the selective control or prevention of pathogenic fungi is considerable.

Ganoderma oerstedii (Fr.) murrill (higher Basidiomycetes), a tree parasite species in Mexico: taxonomic description, rDNA study, and review of its medical applications

We present a description of macro- and microscopic taxonomical features of a medicinal mushroom, Ganoderma oerstedii, based on Mexican specimens from the states of Chiapas, Morelos, Sinaloa, and Veracruz, and discuss its relationships with species of the G. lucidum complex. A phylogenetic study based in rDNA sequences of a specimen of G. oerstedii from Veracruz is presented, as well as a review of traditional and modern uses in medicine.

Isolation, characterization, and production of red pigment from Cercospora piaropi a biocontrol agent for waterhyacinth

A red pigment produced by a Mexican isolate of Cercospora piaropi (waterhyacinth pathogen) has been isolated and identified as cercosporin. The kinetic of cercosporin production in culture media during dark/light regimes was evaluated. When C. piaropi was cultivated in continuous light and potato dextrose broth culture, a maximum of cercosporin production was observed (72.59 mg/l). Despite other reports, C piaropi Mexican isolate produce cercosporin in dark conditions (25.70 mg/l). The results suggest that production of cercosporin in C. piaropi-waterhyacinth pathogenesis is an important factor to take into account in biocontrol strategies.

Phosphopantetheinyl transferase CfwA/NpgA is required for Aspergillus nidulans secondary metabolism and asexual development

Polyketide synthases (PKSs) and/or nonribosomal peptide synthetases (NRPSs) are central components of secondary metabolism in bacteria, plants, and fungi. In filamentous fungi, diverse PKSs and NRPSs participate in the biosynthesis of secondary metabolites such as pigments, antibiotics, siderophores, and mycotoxins. However, many secondary metabolites as well as the enzymes involved in their production are yet to be discovered. Both PKSs and NRPSs require activation by enzyme members of the 4'-phosphopantetheinyl transferase (PPTase) family. Here, we report the isolation and characterization of Aspergillus nidulans strains carrying conditional (cfwA2) and null (DeltacfwA) mutant alleles of the cfwA gene, encoding an essential PPTase. We identify the polyketides shamixanthone, emericellin, and dehydroaustinol as well as the sterols ergosterol, peroxiergosterol, and cerevisterol in extracts from A. nidulans large-scale cultures. The PPTase CfwA/NpgA was required for the production of these polyketide compounds but dispensable for ergosterol and cerevisterol and for fatty acid biosynthesis. The asexual sporulation defects of cfwA, DeltafluG, and DeltatmpA mutants were not rescued by the cfwA-dependent compounds identified here. However, a cfwA2 mutation enhanced the sporulation defects of both DeltatmpA and DeltafluG single mutants, suggesting that unidentified CfwA-dependent PKSs and/or NRPSs are involved in the production of hitherto-unknown compounds required for sporulation. Our results expand the number of known and predicted secondary metabolites requiring CfwA/NpgA for their biosynthesis and, together with the phylogenetic analysis of fungal PPTases, suggest that a single PPTase is responsible for the activation of all PKSs and NRPSs in A. nidulans.

Ergosterol from Phytophthora drechsleri, a unusual metabolite of a member of this genus

Ergosterol was isolated from the plant pathogenic pseudofungus Phytophthora drechsleri grown on clarified V8 booth (CV8-B). Its structure was confirmed by comparison to an authentic sample. The species was identified by morphological analysis and molecular characterization by PCR: ITS (Internal transcribed spaces). This is the first report of this sterol in Phytophthora. This result is unusual because Phytophthora fungi were previously thought to be unable to synthesize sterols and the Oomycetes in general do not produce ergosterol.