Exploring the chemical components of Kuanchang-Shu granule and its protective effects of postoperative ileus in rats by regulating AKT/HSP90AA1/eNOS pathway.

BACKGROUND: Postoperative ileus (POI) is a common obstruction of intestinal content passage caused by almost all abdominal operations that seriously strokes the quality of life of patients. Kuanchang-Shu granule (KCSG), a classic modified prescription based on "Da-Cheng-Qi Decoction", has obtained satisfactory efficacy in the clinical therapeutics of POI. However, its material basis and holistic molecular mechanism against POI have not been revealed. METHODS: The chemical ingredients of KCSG were first characterized by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS). Subsequently, an integration strategy of the network pharmacology and molecular docking based on above identified ingredients was performed to unveil the potential targets involved in the treatment of KCSG on POI. Finally, intestinal manipulation induced rat POI model was constructed to verify the efficacy and predicted mechanism of KCSG against POI. RESULTS: In total, 246 ingredients mainly including organic acids, flavonoids, quinones, alkaloids, terpenoids, phenylpropanoids and phenols were identified. 41 essential ingredients, 24 crucial targets as well as 15 relevant signaling pathways were acquired based on network pharmacology analysis. Pharmacodynamic research showed that KCSG treatment could protect intestinal histological damage, promote the recovery of measurement of gastrointestinal transit disorder and inhibit the secretion of myeloperoxidase in the distal ileum tissues. The up-regulated expression of p-AKT and down-regulated expression of p-eNOS and HSP9OAA1 predicted by molecular docking and validated by western blotting showed that AKT/eNOS/HSP90AA1 pathway may be one of the crucial mechanisms that mediates the protective effect of KCSG.

Control of transcription elongation and DNA repair by alarmone ppGpp.

Second messenger (p)ppGpp (collectively guanosine tetraphosphate and guanosine pentaphosphate) mediates bacterial adaptation to nutritional stress by modulating transcription initiation. More recently, ppGpp has been implicated in coupling transcription and DNA repair; however, the mechanism of ppGpp engagement remained elusive. Here we present structural, biochemical and genetic evidence that ppGpp controls Escherichia coli RNA polymerase (RNAP) during elongation via a specific site that is nonfunctional during initiation. Structure-guided mutagenesis renders the elongation (but not initiation) complex unresponsive to ppGpp and increases bacterial sensitivity to genotoxic agents and ultraviolet radiation. Thus, ppGpp binds RNAP at sites with distinct functions in initiation and elongation, with the latter being important for promoting DNA repair. Our data provide insights on the molecular mechanism of ppGpp-mediated adaptation during stress, and further highlight the intricate relationships between genome stability, stress responses and transcription.

Plant polysaccharides with anti-lung injury effects as a potential therapeutic strategy for COVID-19.

When coronavirus disease 2019 (COVID-19) develops into the severe phase, lung injury, acute respiratory distress syndrome, and/or respiratory failure could develop within a few days. As a result of pulmonary tissue injury, pathomorphological changes usually present endothelial dysfunction, inflammatory cell infiltration of the lung interstitium, defective gas exchange, and wall leakage. Consequently, COVID-19 may progress to tremendous lung injury, ongoing lung failure, and death. Exploring the treatment drugs has important implications. Recently, the application of traditional Chinese medicine had better performance in reducing fatalities, relieving symptoms, and curtailing hospitalization. Through constant research and study, plant polysaccharides may emerge as a crucial resource against lung injury with high potency and low side effects. However, the absence of a comprehensive understanding of lung-protective mechanisms impedes further investigation of polysaccharides. In the present article, a comprehensive review of research into plant polysaccharides in the past 5 years was performed. In total, 30 types of polysaccharides from 19 kinds of plants have shown lung-protective effects through the pathological processes of inflammation, oxidative stress, apoptosis, autophagy, epithelial-mesenchymal transition, and immunomodulation by mediating mucin and aquaporins, macrophage, endoplasmic reticulum stress, neutrophil, TGF-ß1 pathways, Nrf2 pathway, and other mechanisms. Moreover, the deficiencies of the current studies and the future research direction are also tentatively discussed. This research provides a comprehensive perspective for better understanding the mechanism and development of polysaccharides against lung injury for the treatment of COVID-19.

Principles of RNA and nucleotide discrimination by the RNA processing enzyme RppH.

All enzymes face a challenge of discriminating cognate substrates from similar cellular compounds. Finding a correct substrate is especially difficult for the Escherichia coli Nudix hydrolase RppH, which triggers 5'-end-dependent RNA degradation by removing orthophosphate from the 5'-diphosphorylated transcripts. Here we show that RppH binds and slowly hydrolyzes NTPs, NDPs and (p)ppGpp, which each resemble the 5'-end of RNA. A series of X-ray crystal structures of RppH-nucleotide complexes, trapped in conformations either compatible or incompatible with hydrolysis, explain the low reaction rates of mononucleotides and suggest two distinct mechanisms for their hydrolysis. While RppH adopts the same catalytic arrangement with 5'-diphosphorylated nucleotides as with RNA, the enzyme hydrolyzes 5'-triphosphorylated nucleotides by extending the active site with an additional Mg2+ cation, which coordinates another reactive nucleophile. Although the average intracellular pH minimizes the hydrolysis of nucleotides by slowing their reaction with RppH, they nevertheless compete with RNA for binding and differentially inhibit the reactivity of RppH with triphosphorylated and diphosphorylated RNAs. Thus, E. coli RppH integrates various signals, such as competing non-cognate substrates and a stimulatory protein factor DapF, to achieve the differential degradation of transcripts involved in cellular processes important for the adaptation of bacteria to different growth conditions.

The crystal structure of Zika virus NS5 reveals conserved drug targets.

Zika virus (ZIKV) has emerged as major health concern, as ZIKV infection has been shown to be associated with microcephaly, severe neurological disease and possibly male sterility. As the largest protein component within the ZIKV replication complex, NS5 plays key roles in the life cycle and survival of the virus through its N-terminal methyltransferase (MTase) and C-terminal RNA-dependent RNA polymerase (RdRp) domains. Here, we present the crystal structures of ZIKV NS5 MTase in complex with an RNA cap analogue (m7GpppA) and the free NS5 RdRp. We have identified the conserved features of ZIKV NS5 MTase and RdRp structures that could lead to development of current antiviral inhibitors being used against flaviviruses, including dengue virus and West Nile virus, to treat ZIKV infection. These results should inform and accelerate the structure-based design of antiviral compounds against ZIKV.