Quercetin and phenylpropanoids are well known chemoprotective compounds identified in many plants. This study was aimed at determining their effects on activation of Nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant response element (Nrf2-ARE) signalling pathway and expression of its important downstream effector phase II detoxification enzyme glutathione-S-transferase P1 (GSTP1) in BJ foreskin fibroblasts and skin HaCaT keratinocytes. Cell lines and their corresponding Nrf2-ARE luciferase reporter cells were treated by ginger phenylpropanoids and quercetin for 10 h and the level of Nrf2 activity was subsequently determined. Both, ginger phenylpropanoids and quercetin, significantly increased the level of Nrf2 activity. Subsequent western blot analyses of proteins showed the increased expression level of glutathione-S-transferase P1 (GSTP1) in BJ cells but not in HaCaT cells. Such phenomenon of unresponsive downstream target expression in HaCaT cells was consistent with previous studies showing a constitutive expression of their GSTP1. Thus, while both ginger phenylpropanoids and quercetin have the property of increasing the level of Nrf2 both in HaCaT and in BJ cells, their effects on its downstream signalling were mediated only in BJ cells.

No abstract

This study presents the very first report on the in vitro antiviral activity of selected essential oils of Lamiaceae plant species and their monoterpenes against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Nineteen essential oils were obtained by hydrodistillation of dried plant material, and their monoterpene profiles were determined. In addition, the exact concentrations of each monoterpene that were found at a significant level were defined. Both essential oils and their monoterpene components were tested for cytotoxic and antiviral activity against SARS-CoV-2 in infected Vero 76 cells. The results showed that the essential oils of four Mentha species, i.e., M. aquatica L. cv. Veronica, M. pulegium L., M. microphylla K.Koch, and M. x villosa Huds., but also Micromeria thymifolia (Scop.) Fritsch and Ziziphora clinopodioides Lam., and five different monoterpenes, i.e., carvacrol, carvone, 1,8-cineol, menthofuran, and pulegone, inhibited the SARS-CoV-2 replication in the infected cells. However, the antiviral activity varied both among essential oils and monoterpenes. Carvone and carvacrol exhibited moderate antiviral activity with IC50 concentrations of 80.23 ± 6.07 μM and 86.55 ± 12.73 μM, respectively, while the other monoterpenes were less active (IC50 > 100.00 μM). Structure-activity relations of related monoterpenes showed that the presence of keto and hydroxyl groups is associated with the activity of carvone and carvacrol, respectively. Furthermore, the carvone-rich essential oil of M. x villosa had the greatest activity among all active essential oils (IC50 127.00 ± 4.63 ppm) while the other active oils exhibited mild (140 ppm < IC50 < 200 ppm) to weak antiviral activity (IC50 > 200 ppm). Both essential oils and monoterpenes showed limited or no cytotoxicity against Vero 76 cells. Hierarchical cluster analysis showed that the differences in the antiviral activity of essential oils were directly attributed to the antiviral efficacies of their particular single monoterpenes. The findings presented here on the novel antiviral property of plant essential oils and monoterpenes might be used in the development of different measures against SARS-CoV-2.

In frogs, an important mechanism of skin innate immunity against invading microbial pathogens is secretion of antimicrobial peptides from the specialized granular glands. Since these glands develop fully in skin dermis after completion of metamorphosis, they are small and immature in skin of larvae (tadpoles). Skin secretions vary among different life stages. Antimicrobial activity and peptide composition of natural mixture of skin peptides of three different life stages of New Zealand Ewing's Tree Frog (Litoria ewingii), tadpoles, metamorphs and adults were analyzed. The peptide mixtures were collected from skin secretions and analyzed for activity against the standard reference bacterium, Escherichia coli (ATCC 25922). Their peptide components were analyzed using liquid chromatography mass spectrometry (LC-MS). The peptide mixture from adults and metamorphs contained the species-specific antimicrobial peptide uperin 7.1 and inhibited the growth of E. coli (ATCC 25922). In contrast, the peptide mixture of tadpoles did not inhibit the growth of E. coli (ATCC 25922). This peptide mixture did not contain uperin 7.1 but had peptides whose molecular masses did not correspond to molecular masses of any known frog antimicrobial peptides.

Aims:  To determine whether the extracellular products (ECPs) from Aeromonas hydrophila, a frog bacterial pathogen that is resistant to skin antimicrobial peptides of three different frog species Xenopus laevis, Litoria aurea and Litoria raniformis, can modulate the activity of these peptides. Methods and Results:  ECPs were collected from cultures of Klebsiella pneumoniae, a pathogen susceptible to skin antimicrobial peptides of all three tested frog species, and from cultures of Aer. hydrophila. They were tested for protease activity and for inhibition of the antimicrobial activity of natural peptide mixtures and single peptides of all three frog species against Escherichia coli ATCC 25922. ECPs from cultures of Aer. hydrophila grown for 16, 24 and 36 h showed protease activity and inhibited the antibacterial activity of all peptides against E. coli ATCC 25922. In contrast, the ECPs from cultures of Kl. pneumoniae neither had protease activity nor inhibited the activity of any peptides. Conclusion:  The proteolytic ECPs of Aer. hydrophila have the ability to inhibit the skin antimicrobial peptides of frogs. Significance and Impact of the Study:  The results of this study provide new information on the association of ECPs with the resistance of Aer. hydrophila to frog antimicrobial peptides.

No abstract

A truncated haemoglobin (tHb) has been identified in an acidophilic and thermophilic methanotroph Methylacidiphilium infernorum. Hell's Gate Globin IV (HGbIV) and its related tHbs differ from all other bacterial tHbs due to their distinctively large sequence and polar distal haem pocket residues. Here we report the crystal structure of HGbIV determined at 1.96 Å resolution. The HGbIV structure has the distinctive 2/2 α-helical structure with extensions at both termini. It has a large distal site cavity in the haem pocket surrounded by four polar residues: His70(B9), His71(B10), Ser97(E11) and Trp137(G8). This cavity can bind bulky ligands such as a phosphate ion. Conformational shifts of His71(B10), Leu90(E4) and Leu93(E7) can also provide more space to accommodate larger ligands than the phosphate ion. The entrance/exit of such bulky ligands might be facilitated by positional flexibility in the CD1 loop, E helix and haem-propionate A. Therefore, the large cavity in HGbIV with polar His70(B9) and His71(B10), in contrast to the distal sites of other bacterial tHbs surrounded by non-polar residues, suggests its distinct physiological functions.

Virulence capsular polysaccharide (Vi antigen) and Salmonella`s Pathogenicity Island type 1 and 2 TTSS (SPI-1 and SPI-2 TTSS) are important membrane virulence factors of human restricted pathogen S. Typhi. The Vi antigen modulates different proinflammatory signaling pathways in infected macrophages, microfold epithelial and dendritic cells. SPI-2 TTSS and its effectors are required for promoting bacterial intracellular survival, replication and apoptosis while SPI-1 and its effectors are associated with invasion of microfold epithelial cells. The purified Vi-antigen has been used as a vaccine against disease. It is a T cell independent antigen that induces moderate efficacy ( ̴ 55%) in adults and no efficacy in children bellow two years of age. Carrier protein conjugation of the Vi antigen has been successfully used to confer T cell dependency and to develop Vi conjugate vaccines with high efficacy, around 89% in three years, in all age groups. So far, the attenuated live vaccine with constitutive expression of Vi antigen and the SPI-2 TTSS mutant vaccine, progressed to phase 3 clinical tests. Particularly, the live attenuated vaccine with constitutive expression of Vi antigen might be also used to optimize the efficacies of other vaccines. The current preclinical studies consider also development of novel T cell independent vaccines from recombinant proteins and generalized modules for membrane antigens. An approach for future antivirulence therapy against disease might also consider the bioactive compounds with ability to inhibit TTSS secretions. It is concluded that combined approaches my successfully reduce S. Typhi infection in this new globalized era.