Antimicrobial peptides (AMPs) represent a promising antibiotic alternative to overcome drug-resistant bacteria by inserting into the membrane of bacteria, resulting in cell lysis. However, therapeutic applications of AMPs have been hindered by their ability to lyse eukaryotic cells. GF-17 is a truncated peptide of LL-37, which has perfect amphipathicity and a higher hydrophobicity, resulting in higher haemolytic activity. However, there is no significant difference in the cytotoxicity against human lung epithelial cells between the GF-17 and LL-37 groups, indicating that there are significant differences in the sensitivity of different human cells to GF-17. In this study, LL-37 and GF-17 were administered to mouse lungs via intranasal inoculation. Blood routine examination results showed that LL-37 did not affect the red blood cells, platelet, white blood cells and neutrophil counts, but GF-17 decreased the white blood cells and neutrophil counts with the increasing concentration of peptides. GF-17-treated mice suffer a body weight loss of about 2.3 g on average in 24 h, indicating that GF-17 is highly toxic to mice. The total cell counts in the bronchoalveolar lavage fluid from GF-17-treated mice were 4.66-fold that in the untreated group, suggesting that GF-17 treatment leads to inflammation in the lungs of mice. Similarly, the histological results showed the infiltration of neutrophils in the lungs of GF-17-treated mice. The results suggest that the administration of GF-17 in the lungs of mice does not affect the red blood cells and platelet counts in the blood but promotes neutrophil infiltration in the lungs, leading to an inflammatory response. Therefore, we established a mouse acute lung injury model to preliminarily evaluate the in vivo toxicity of AMPs. For AMPs with a clinical application value, systematic research is still needed to evaluate their acute and long-term toxicity.

SAAP-148, a derivative of LL-37, exhibits a well-defined amphipathic structure and enhanced antimicrobial activity; however, it also displays significant cytotoxicity towards human cells. In this study, we employed Lys-scan to produce a series of amphiphilic SAAP-148 analogs derived from the SAAP-148 sequence to investigate the impact of the distribution of positively charged residues on the biological viability of the antimicrobial peptides (AMPs). The physical properties and biological activity of the designed peptides were subsequently compared. The substitution of lysine resulted in an increase in the overall charge of SAAP-148 and a decrease in its overall hydrophobicity and hyd. moment, except for SAAP-10 where an analogue substitution occurred at the 18th residue. The replacement of lysine led to a reduction in hemolytic activity compared to SAAP-148, with slightly higher haemolysis rates observed in SAAP-11 and SAAP-13. The cytotoxicity of peptides towards human normal lung epithelial cells (BEAS-2B) was closely linked to their haemolytic activity, indicating that substituting lysine may mitigate the cytotoxic effects of SAAP-148. Additionally, the arrangement of positively charged residues in the peptides significantly influenced its antimicrobial activity. Our findings suggest that the positioning of a positively charged residue has a significant impact on the biophysical properties of the peptide. Additionally, the substitution of lysine at different positions demonstrates an influence on the anti-lipopolysaccharide (anti-LPS) activity of SAAP-148. These discoveries provide valuable insights for the design and optimization of antimicrobial peptides, which will be advantageous for the future development of antimicrobial agents.

Numerous disposable plastic masks had been produced and used for preventing the worldwide COVID-19 pandemic effectively. Discarded masks are a potential source of microplastic pollution in marine ecosystems. The effect of discarded masks on offshore microorganisms is still unclear. Herein, we profiled the interaction between the microplastics released by discarded masks and marine microbes. The effects of mask quantity, time, and environment on the microplastic-related communities were determined. We characterized the bacterial communities of each group using 16S rRNA gene sequencing and metagenomic sequencing and correlated the community diversity to the physicochemical properties of seawater. We found that the diversity and richness of microflora on the surface of microplastics with different quantity and time varied significantly. Proteobacteria are the main bacteria on microplastics, and the KEGG metabolic pathway prediction shows that amino acid metabolism and carbohydrate metabolism were abundant. In addition, there was a correlation between bacterial communities and Antibiotic Resistance Ontology (ARO). We used scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) techniques to evaluate the plastic polymer characteristics of disposable medical masks. Our research shows that disposable medical masks immersed in seawater can alter the microbial community. This study provides the most recent data and insights into the contamination of discarded masks in the marine environment.

Tea polysaccharide (TPS) is a naturally occurring polysaccharide that has garnered increasing attention due to its remarkable biological activity and significant potential for application. This study focused on examining the alterations in gut microbiota composition and the physiological health of mice subjected to TPS exposure. In this study, a control group (CTRL), a high-dose TPS group (TPH), and a low-dose TPS group (TPL) were established to investigate the effects of TPS on the physiological condition of the intestinal microbiota, liver, intestines, and blood in mice. The findings indicated that TPS significantly increased the relative abundance of beneficial probiotics, including Bacteroidota and Muribaculum, while concurrently diminishing the relative abundance of detrimental intestinal bacteria such as Prevotella_copri and Desulfovibrionia. Additionally, with respect to health indicators, TPS was found to effectively lower the glutamate-glutamate ratio (AST/ALT) and creatine kinase (CK). Serum amylase (AMY) and glucose (Glu) levels were elevated in TPH mice, suggesting improved glucose metabolism. Beta-diversity analysis showed distinct clustering of microbial communities in TPL group, though alpha diversity remained unchanged across groups. Histopathological analysis confirmed no adverse effects on liver or intestinal integrity. Correlation heatmaps highlighted significant associations between gut microbiota (e.g., Bacteroides_H) and metabolic markers (e.g., CO₂, AMY). These findings underscore TPS’s role in reshaping gut microbiota, enhancing metabolic health, and mitigating inflammation.

Perfluorooctane sulfonic acid (PFOS) is a persistent organic pollutant that has attracted much attention due to its wide environmental distribution and potential toxicity. Intestinal microbiota is an important regulator of host health, and its composition and metabolic function are easily interfered with by environmental pollutants. In this study, the effects of PFOS exposure on gut microbiota, lipid metabolism, and host health were investigated in mice. The results showed that PFOS exposure did not significantly change α diversity, but significantly affected the β diversity and community structure of intestinal microflora in mice. At the taxonomic level, the ratio of Firmicutes to Bacteroidetes decreased, and the changes in the abundance of specific bacteria were closely related to liver diseases and lipid metabolism disorders. PFOS exposure also interfered with the gut–liver axis mechanism, increased blood lipids and liver function related indicators in mice, and induced intestinal and liver histological lesions. This study revealed the toxic mechanism of PFOS mediated by intestinal microbiota, providing a new research perspective for health problems caused by environmental pollutants and theoretical support for the formulation of relevant public health policies.