Dynamic changes of inflammatory response and oxidative stress induced by methicillin-resistant Staphylococcus aureus in mice

Ferroptosis is involved in Staphylococcus aureus-induced mastitis through autophagy activation by endoplasmic reticulum stress

Cell death caused by severe Staphylococcus aureus (S. aureus) infection is a fatal threat to humans and animals. However, whether ferroptosis, an iron-dependent form of cell death, is involved in S. aureus-induced cell death and its role in S. aureus-induced diseases are unclear. Using a mouse mastitis model and mammary epithelial cells (MMECs), we investigated the role of ferroptosis in the pathogenesis of S. aureus infection. The results revealed that S. aureus-induced ferroptosis in vivo and in vitro as demonstrated by dose-dependent increases in cell death; the level of malondialdehyde (MDA), the final product of lipid peroxidation; and dose-dependent decrease the production of the antioxidant glutathione (GSH). Treatment with typical inhibitors of ferroptosis, including ferrostatin-1 (Fer-1) and deferiprone (DFO), significantly inhibited S. aureus-induced death in MMECs. Mechanistically, treatment with S. aureus activated the protein kinase RNA-like ER kinase (PERK)-eukaryotic initiation factor 2, α subunit (eIF2α)-activating transcription factor 4 (ATF4)-C/EBP homologous protein (CHOP) pathway, which subsequently upregulated autophagy and promoted S. aureus-induced ferroptosis. The activation of autophagy degraded ferritin, resulting in iron dysregulation and ferroptosis. In addition, we found that excessive reactive oxygen species (ROS) production induced ferroptosis and activated endoplasmic reticulum (ER) stress, manifesting as elevated p-PERK-p-eIF2α-ATF4-CHOP pathway protein levels. Collectively, our findings indicate that ferroptosis is involved in S. aureus-induced mastitis via ER stress-mediated autophagy activation, implying a potential strategy for the prevention of S. aureus-associated diseases by targeting ferroptosis. In conclusion, the ROS-ER stress-autophagy axis is involved in regulating S. aureus-induced ferroptosis in MMECs. These findings not only provide a new potential mechanism for mastitis induced by S. aureus but also provide a basis for the treatment of other ferroptotic-related diseases.

Propolis Alleviates Acute Lung Injury Induced by Heat-Inactivated Methicillin-Resistant Staphylococcus aureus via Regulating Inflammatory Mediators, Gut Microbiota and Serum Metabolites

Propolis has potential anti-inflammatory properties, but little is known about its efficacy against inflammatory reactions caused by drug-resistant bacteria, and the difference in efficacy between propolis and tree gum is also unclear. Here, an in vivo study was performed to study the effects of ethanol extract from poplar propolis (EEP) and poplar tree gum (EEG) against heat-inactivated methicillin-resistant Staphylococcus aureus (MRSA)-induced acute lung injury (ALI) in mice. Pre-treatment with EEP and EEG (100 mg/kg, p.o.) resulted in significant protective effects on ALI in mice, and EEP exerted stronger activity to alleviate lung tissue lesions and ALI scores compared with that of EEG. Furthermore, EEP significantly suppressed the levels of pro-inflammatory mediators in the lung, including TNF-α, IL-1β, IL-6, and IFN-γ. Gut microbiota analysis revealed that both EEP and EEG could modulate the composition of the gut microbiota, enhance the abundance of beneficial microbiota and reduce the harmful ones, and partly restore the levels of short-chain fatty acids. EEP could modulate more serum metabolites and showed a more robust correlation between serum metabolites and gut microbiota. Overall, these results support the anti-inflammatory effects of propolis in the treatment of ALI, and the necessity of the quality control of propolis.

Geraniol-a potential alternative to antibiotics for bovine mastitis treatment without disturbing the host microbial community or causing drug residues and resistance

Mastitis is one of the most prevalent diseases of dairy cows. Currently, mastitis treatment in dairy cows is mainly based on antibiotics. However, the use of antibiotics causes adverse effects, including drug resistance, drug residues, host-microbiome destruction, and environmental pollution. The present study sought to investigate the potentiality of geraniol as an alternative to antibiotics for bovine mastitis treatment in dairy cows. Additionally, the effectiveness of treatment, improvement in inflammatory factors, the influence on microbiome, presence of drug residues, and drug resistance induction were compared and analyzed comprehensively.Geraniol showed an equivalent therapeutic rate as antibiotics in the mouse infection model and cows with mastitis. Moreover, geraniol significantly inhibited the pathogenic bacteria and restored the microbial community while increasing the abundance of probiotics in milk. Notably, geraniol did not destroy the gut microbial communities in cows and mice, whereas antibiotics significantly reduced the diversity and destroyed the gut microbial community structure. Additionally, no geraniol residue was detected in milk four days after treatment discontinuation, but, antibiotic residues were detected in milk at the 7th day after drug withdrawal. In vitro experiments revealed that geraniol did not induce drug resistance in the Escherichia coli strain ATCC25922 and Staphylococcus aureus strain ATCC25923 after 150 generations of culturing, while antibiotics induced resistance after 10 generations. These results suggest that geraniol has antibacterial and anti-inflammatory effects similar to antibiotics without affecting the host-microbial community structure or causing drug residues and resistance. Therefore, geraniol can be a potential substitute for antibiotics to treat mastitis or other infectious diseases and be widely used in the dairy industry.

Altitude patterns of seed C, N, and P concentrations and their stoichiometry in an alpine meadow on the eastern Tibetan Plateau

Understanding the altitudinal patterns of plant stoichiometry in seeds is critical for characterizing important germination and dormancy strategies, soil seed bank composition, seed predation probability, efficiency of seed dispersal and seedling performance, and to predict how biodiversity might be influenced by climate change. However, our understanding of the altitudinal patterns of seed stoichiometry is extremely limited. In this study, we measured the concentrations of carbon (C), nitrogen (N) and phosphorus (P) in the seeds of 253 herbaceous species along an altitudinal transect (2,000–4,200 m) on the eastern Tibetan Plateau, China, and further to characterize seed C:N:P stoichiometry. The geometric means of C, N, and P concentrations were 569.75 mg/g, 34.76 mg/g, and 5.03 mg/g, respectively. The C:N, C:P, and N:P ratios were 16.39, 113.31, and 6.91, respectively. The seed C, N, and P concentrations and C:N:P ratios varied widely among major plant groups and showed significant altitudinal trends. In general, C, N, and P concentrations increased, whereas seed C:N:P ratios decreased with elevation. These results inform our understanding of the altitudinal patterns of seed stoichiometry and how to model ecosystem nutrient cycling.

Genome Sequencing of Amomum tsao-ko Provides Novel Insight Into Its Volatile Component Biosynthesis

As an important economic and medicinal crop, Amomum tsao-ko is rich in volatile oils and widely used in food additives, essential oils, and traditional Chinese medicine. However, the lack of the genome remains a limiting factor for understanding its medicinal properties at the molecular level. Here, based on 288.72 Gb of PacBio long reads and 105.45 Gb of Illumina paired-end short reads, we assembled a draft genome for A. tsao-ko (2.70 Gb in size, contig N50 of 2.45 Mb). Approximately 90.07% of the predicted genes were annotated in public databases. Based on comparative genomic analysis, genes involved in secondary metabolite biosynthesis, flavonoid metabolism, and terpenoid biosynthesis showed significant expansion. Notably, the DXS, GGPPS, and CYP450 genes, which participate in rate-limiting steps for terpenoid backbone biosynthesis and modification, may form the genetic basis for essential oil formation in A. tsao-ko. The assembled A. tsao-ko draft genome provides a valuable genetic resource for understanding the unique features of this plant and for further evolutionary and agronomic studies of Zingiberaceae species.