Late-stage cascade of oxidation reactions during the biosynthesis of oxalicine B in Penicillium oxalicum

Oxalicine B ( 1) is an α-pyrone meroterpenoid with a unique bispirocyclic ring system derived from Penicillium oxalicum. The biosynthetic pathway of 15-deoxyoxalicine B ( 4) was preliminarily reported in Penicillium canescens, however, the genetic base and biochemical characterization of tailoring reactions for oxalicine B ( 1) has remained enigmatic. In this study, we characterized three oxygenases from the metabolic pathway of oxalicine B ( 1), including a cytochrome P450 hydroxylase OxaL, a hydroxylating Fe(II)/α-KG-dependent dioxygenase OxaK, and a multifunctional cytochrome P450 OxaB. Intriguingly, OxaK can catalyze various multicyclic intermediates or shunt products of oxalicines with impressive substrate promiscuity. OxaB was further proven via biochemical assays to have the ability to convert 15-hydroxdecaturin A ( 3) to 1 with a spiro-lactone core skeleton through oxidative rearrangement. We also solved the mystery of OxaL that controls C-15 hydroxylation. Chemical investigation of the wild-type strain and deletants enabled us to identify 10 metabolites including three new compounds, and the isolated compounds displayed potent anti-influenza A virus bioactivities exhibiting IC50 values in the range of 4.0-19.9 μmol/L. Our studies have allowed us to propose a late-stage biosynthetic pathway for oxalicine B ( 1) and create downstream derivatizations of oxalicines by employing enzymatic strategies.

Molecular Mechanism of "Transmission Between Lung and Brain" of Influenza and Intervention Effect of Maxing Shigantang Based on JAK1/STAT1 Signaling Pathway / 中国实验方剂学杂志

ObjectiveTo explore the molecular mechanism of "transmission between the lung and brain" of influenza based on Janus kinase 1/signal transducer and activator of transcription 1（JAK1/STAT1） signaling pathway and further investigate the intervention effect of Maxing Shigantang （MXSGT）. MethodA total of 100 SPF BALB/c mice were randomly divided into a normal group，a model group，an oseltamivir group （21.63 mg·kg-1·d-1），an antiviral granules group（3.9 g·kg-1·d-1）， and an MXSGT group（6.05 g·kg-1·d-1）， with 20 mice in each group. The pneumonia model was induced in mice except for those in the normal group by intranasal infection of influenza A virus（IAV）. Twenty-four hours after modeling，mice were treated with corresponding drugs， while those in the normal group and the model group received the same amount of normal saline by gavage， once a day for 3 and 7 days. The pathological changes in the lung and brain were observed by hematoxylin-eosin（HE）staining. The mRNA expression of IAV nucleoprotein（NP），JAK1， and STAT1 in the lung and brain was detected by real-time quantitative polymerase chain reaction（Real-time PCR）， and the protein expression of JAK1 and STAT1 in the lung and brain was detected by Western blot. Immunohistochemical method was used to detect the expression of phosphorylated（p）-STAT1 in the lung and brain tissues， and enzyme-linked immunosorbent assay（ELISA） was used to detect the serum levels of interleukin-1β（IL-1β） and interleukin-10（IL-10）. ResultCompared with the normal group， the model group showed obvious pathological changes in the lung tissues and cerebral cortex， increased relative mRNA expression of IAV NP in the lung （P<0.01）， elevated mRNA and protein expression of JAK1 and STAT1 in the lung and brain tissues （P<0.05，P<0.01），up-regulated expression level of p-STAT1 in lung tissues and cerebral cortex （P<0.05，P<0.01）， and increased serum level of IL-1β （P<0.05）. Compared with the model group， the MXSGT group showed alleviated pathological damage to lung tissues and cerebral cortex， decreased relative mRNA expression of IAV NP in lung tissues（P<0.01），reduced mRNA and protein expression levels of JAK1 and STAT1 in lung tissues and brain tissues（P<0.05，P<0.01）， and increased serum level of IL-10（P<0.01）. ConclusionThe abnormal activation of the JAK1-STAT1 signaling pathway may be one of the molecular mechanisms of "transmission between the lung and brain" of influenza. As an effective compound prescription against the influenza virus，MXSGT can alleviate the pathological damage of brain tissues in mice infected with IAV by regulating the level of cytokines mediated by this pathway.

In vitro validation of self designed “universal human Influenza A siRNA”.

The genomic variability of Influenza A virus (IAV) makes it difficult for the existing vaccines or anti-influenza drugs to control. The siRNA targeting viral gene induces RNAi mechanism in the host and silent the gene by cleaving mRNA. In this study, we developed an universal siRNA and validated its efficiency in vitro. The siRNA was designed rationally, targeting the most conserved region (delineated with the help of multiple sequence alignment) of M gene of IAV strains. Three level screening method was adopted, and the most efficient one was selected on the basis of its unique position in the conserved region. The siRNA efficacy was confirmed in vitro with the Madin Darby Canine Kidney (MDCK) cell line for IAV propagation using two clinical isolates i.e., Influenza A/H3N2 and Influenza A/pdmH1N1. Of the total 168 strains worldwide and 33 strains from India, 97 bp long (position 137-233) conserved region was identified. The longest ORF of matrix gene was targeted by the selected siRNA, which showed 73.6% inhibition in replication of Influenza A/pdmH1N1 and 62.1% inhibition in replication of Influenza A/H3N2 at 48 h post infection on MDCK cell line. This study provides a basis for the development of siRNA which can be used as universal anti-IAV therapeutic agent.

Anti-Influenza A Virus Effect of Hypericum perforatum L. Extract / 中国病毒学·英文版

To study the antiviral effect of Hypericum perforatum L. extract (HPE) on influenza A virus (IAV) (H1N1) in vitro and in vivo. Cytopathic effect (CPE) and neutral red (NR) dye uptake were used to examine the antiviral effect of HPE on Madin Darby Canine Kidney (MDCK) cells which were infected with IAV in vitro. HPE was effective against influenza A virus (IAV) in vitro, with a 50% effective concentration (EC50) of 40 μg/mL. The mean 50% cytotoxic concentration (CC50) in the MDCK used in these experiments was 1.5 mg/mL. Ribavirin was run in parallel with EC50 values of 5.0 μg/mL; the mean CC50 for ribavirin was 520 μg/mL. Oral gavage administrations of HPE or ribavirin to mice infected with the IAV were highly effective in preventing death, slowing the decline of arterial oxygen saturation, inhibiting lung consolidation and reducing lung virus titers. The minimum effective dose of HPE in these studies was 31.25 mg/kg/day, which was administered twice daily for 5 d beginning 4 h prior to virus exposure. Below a dosage of 2000 mg/kg/day, almost all treated mice survived, which suggests that HPE is of low toxicity. Ribavirin's minimum effective dose was 40 mg/kg/day with the LD50 determined to be 200 mg/kg/day. Delay of the initiation of either HPE or ribavirin therapy, using approximately 1/3 LD50 dose each time, could still be protective as late as 48 h after exposure to the IAV. While both agents appeared to have similar efficacy against IAV infections, HPE was considered to be less toxic and may warrant further evaluation as a possible therapy for influenza.