Betulin attenuates pneumolysin-induced cell injury and DNA damage

Therapeutic potential of kaempferol on Streptococcus pneumoniae infection

Co-infections with pathogens and secondary bacterial infections play significant roles during the pandemic coronavirus disease 2019 (COVID-19) pathogenetic process, caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Notably, co-infections with Streptococcus pneumoniae (S. pneumoniae), as a major Gram-positive pathogen causing pneumonia or meningitis, severely threaten the diagnosis, therapy, and prognosis of COVID-19 worldwide. Accumulating evidences have emerged indicating that S. pneumoniae evolves multiple virulence factors, including pneumolysin (PLY) and sortase A (SrtA), which have been extensively explored as alternative anti-infection targets. In our study, natural flavonoid kaempferol was identified as a potential candidate drug for infection therapeutics via anti-virulence mechanisms. We found that kaempferol could interfere with the pore-forming activity of PLY by engaging with catalytic active sites and consequently inhibit PLY-mediated cytotoxicity. Additionally, exposed to kaempferol significantly reduced the SrtA peptidase activity by occupying the active sites of SrtA. Further, the biofilms formation and bacterial adhesion to the host cells could be significantly thwarted by kaempferol incubation. In vivo infection model by S. pneumoniae highlighted that kaempferol oral administration exhibited notable treatment benefits, as evidenced by decreased bacterial burden, suggesting that kaempferol has tremendous potential to attenuate S. pneumoniae pathogenicity. Scientifically, our study implies that kaempferol is a promising therapeutic option by targeting bacterial virulence factors.

The regular pattern of metabolite changes in mushroom Inonotus hispidus in different growth periods and exploration of their indicator compounds

Inonotus hispidus is a valuable and rare edible and medicinal mushroom with extremely high nutritional and medicinal value. However, there is no holistic insight to elucidate the molecular basis of the differentiated usage and accurate annotation of physiological maturity to fluctuating yields and quality. This study aimed to figure out the fruiting bodies' metabolites change regulation and potential maturating indicators to distinguish different quality I. hispidus. We applied non-targeted ultra-high performance liquid chromatography and high-resolution mass spectrometry combined and with multivariate analysis and analyzed cultivated and wild mushroom I. hispidus in different growth periods (budding, mature and aging). With the fruiting bodies maturating, 1358 metabolites were annotated, 822 and 833 metabolites abundances changed greater than or equal to 1 time from the budding period to the aging period in abundance in cultivated and wild, the total polysaccharides, crude fat, total flavonoids, and total terpenes increased at first and then decreased. Total amino acids, crude protein, and total polyphenols decreased, while the total steroids increased linearly. The change of metabolites showed certain regularity. Metabolic pathways enrichment analysis showed that these metabolites are involved in glycolysis, biosynthesis of amino acids, organic acid metabolism, glycine-serine-and-threonine metabolism, tricarboxylic acid cycle, purine metabolism, and pyrimidine metabolism. In addition, ergosterol peroxide and (22E)-ergosta-4,6,8(14),22-tetraen-3-one can be used as indicator compounds, and their contents increase linearly with the fruiting bodies of I. hispidus' physiological maturation. This comprehensive analysis will help to evaluate the edible values and facilitate exploitation in mushroom I. hispidus.

Inhibitory effect of hederagenin on Streptococcus pneumoniae pneumolysin in vitro

Streptococcus pneumoniae is an important pathogen that causes otitis media, pneumonia, meningitis and bacteremia. As an important virulence factors of S. pneumoniae, pneumolysin (PLY) can penetrate cell membranes and lead to cell lysis and inflammation, which is one of the main causes of infection and damage of S. pneumoniae. Therefore, using pneumolysin as a target to study its inhibitors can provide a new treatment strategy for pneumococcal disease. This study analyzed the inhibitory effect of the natural compound hederagenin on PLY in vitro. The results show that hederagenin has great potential as a new strategy for the treatment of pneumococcal diseases.