ObjectiveTo observe the effect of Weichang'an prescription-containing serum on ferroptosis of human gastric cancer cells and explore the possible mechanism. MethodsSD rats were administrated with 18， 36， 72 g·kg^-1·d^-1 Weichang'an prescription by gavage for preparation of serum samples containing different doses of Weichang'an prescription， which were then used to treat MKN-45 cells. The cell proliferation was examined by the cell counting kit-8 （CCK-8）. In addition， inhibitors of apoptosis， necroptosis， and ferroptosis were added， and the survival of the cells treated with the serum samples was observed. The fluorescent probe dichlorodihydrofluorescein diacetate （DCF-DA） and the lipid peroxidation sensor C11-BODIPY were employed to detect the intracellular levels of reactive oxygen species （ROS） and lipid peroxidation， respectively. The levels of ferrous ion （Fe²⁺）， glutathione （GSH）， and malondialdehyde （MDA） were detected by enzyme-linked immunosorbent assay （ELISA）. Real-time PCR and Western blotting were employed to determine the expression of nuclear factor erythroid 2-related factor 2 （Nrf2）， aldo-keto reductase family 1 member B1 （AKR1B1）， glutathione peroxidase 4 （GPX4）， acyl-CoA synthetase long-chain family member 4 （ACSL4）， signal transducer and activator of transcription 3 （STAT3）， and mitogen-activated protein kinase （MAPK）. ResultsCompared with the blank group， Weichang'an prescription-containing serum decreased the viability of MKN-45 cells （P<0.05， P<0.01） in a time- and dose-dependent manner. Compared with the Weichang'an prescription group， the apoptosis inhibitor+Weichang'an prescription group and the ferroptosis inhibitor+Weichang'an prescription group showed increased cell viability （P<0.05， P<0.01）. Compared with the blank group， Weichang'an prescription elevated the levels of ROS， lipid peroxidation， and intracellular Fe²⁺ and MDA （P<0.05， P<0.01） and lowered the level of GSH （P<0.05， P<0.01） in a dose-dependent manner. Compared with the blank group， Weichang'an prescription down-regulated the mRNA and protein levels of Nrf2， AKR1B1， and GPX4 （P<0.05， P<0.01） and up-regulated the mRNA and protein levels of ACSL4 （P<0.05， P<0.01） in a dose-dependent manner. Compared with the blank group， Weichang'an prescription down-regulated the protein levels of p-STAT3 and p-ERK （P<0.05， P<0.01） in a dose-dependent manner. ConclusionThe Weichang'an prescription-containing serum can promote the ferroptosis and inhibit the proliferation of MKN-45 cells by regulating the STAT3 and MAPK pathways.

Cyclodipeptide (CDP) composed of two amino acids is the simplest cyclic peptide. These two amino acids form a typical diketopiperazine (DKP) ring by linking each other with peptide bonds. This characteristic stable ring skeleton is the foundation of CDP to display extensive and excellent bioactivities, which is beneficial for CDPs' pharmaceutical research and development. The natural CDP products are well isolated from actinomycetes. These bacteria can synthesize DKP backbones with nonribosomal peptide synthetase (NRPS) or cyclodipeptide synthase (CDPS). Moreover, actinomycetes could produce a variety of CDPs through different enzymatic modification. The presence of these abundant and diversified catalysis indicates that actinomycetes are promising microbial resource for exploring CDPs. This review summarized the pathways for DKP backbones biosynthesis and their post-modification mechanism in actinomycetes. The aim of this review was to accelerate the genome mining of CDPs and their isolation, purification and structure identification, and to facilitate revealing the biosynthesis mechanism of novel CDPs as well as their synthetic biology design.
Actinobacteria/metabolism* ; Actinomyces/metabolism* ; Biological Products/metabolism* ; Bacteria/metabolism* ; Diketopiperazines/metabolism* ; Amino Acids