Guiqiu Li

Methicillin-resistant Staphylococcus aureus (MRSA) has become one of the most prevalent drug-resistant pathogens in many countries, posing a serious threat to global healthcare. Consequently, there is an urgent need to develop novel antibacterial agents. This study aimed to evaluate the antibacterial and antibiofilm activities of SX-682-an orally bioavailable allosteric inhibitor of CXCR1/2-against S. aureus and to elucidate its underlying mechanisms. Our findings demonstrate that SX-682 exhibits potent antibacterial activity against S. aureus, with minimum inhibitory concentration (MIC) values ranging from 8 to 16 µg/mL. Time-kill curves revealed a concentration-dependent bactericidal effect. Sub-inhibitory concentrations of SX-682 significantly inhibited the formation of S. aureus biofilms and effectively eradicated preformed mature biofilms. SX-682 enhances the membrane permeability of S. aureus and causes depolarization of the membrane potential, thereby damaging the integrity of the bacteria. By suppressing hemolytic activity and staphyloxanthin biosynthesis, SX-682 reduced the virulence of S. aureus. Additionally, proteomic analysis revealed that SX-682 treatment induced dysregulated expression of proteins in S. aureus, including SasG, FnbA, SdrC, SdrD, SaeR, SaeS, and SarX, which are associated with bacterial biofilm formation, bacterial virulence, and amino acid metabolism. Notably, in a murine model of MRSA-infected skin wounds, SX-682 significantly accelerated wound healing. Collectively, these findings highlight the considerable antibacterial and antibiofilm efficacy of SX-682 against S. aureus, supporting its potential as a promising therapeutic candidate for preventing and treating S. aureus infections.

The escalating prevalence of multidrug-resistant (MDR) gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and linezolid-resistant Enterococcus faecalis, highlights the critical demand for new antibacterial agents that target resistance pathways. BB-Cl-Amidine is originally considered as a peptidyl arginine deiminase inhibitor and till now, its potential antimicrobial activity has not been explored. This study sought to evaluate the antibacterial effectiveness and underlying mechanisms of BB-Cl-Amidine against MDR gram-positive pathogens. The results showed that BB-Cl-Amidine exhibited potent antibacterial activity with minimum inhibitory concentration (MIC) values ranging from 25 μM to 50 μM against MRSA, E. faecalis and various of Gram-positive bacteria clinical isolates. At sub-MIC concentrations, BB-Cl-Amidine significantly reduced biofilm formation in both S. aureus and E. faecalis. Moreover, the increased permeability and depolarizing membrane potential of S. aureus was found by BB-Cl-Amidine. The antibacterial activity of BB-Cl-Amidine can be neutralized by cardiolipin (CL) and phosphatidylglycerol (PG). Furthermore, BB-Cl-Amidine exposure resulted in the abnormal expression of functional proteins correlated with the cell membranes and phospholipid metabolas. In summary, the potential antibacterial and anti-biofilm activities of BB-Cl-Amidine are demonstrated via membrane disruption, offering a promising scaffold for combating MDR Gram-positive infections.

Background: Ketone β-hydroxybutyrate (BHB) has been reported to prevent tumor cell proliferation and improve drug resistance. However, the effectiveness of BHB in oxaliplatin (Oxa)-resistant colorectal cancer (CRC) and the underlying mechanism still require further proof. Methods: CRC-Oxa-resistant strains were established by increasing concentrations of CRC cells to Oxa. CRC-Oxa cell proliferation, apoptosis, invasion, migration, and epithelial-mesenchymal transition (EMT) were checked following BHB intervention in vitro. The subcutaneous and metastasis models were established to assess the effects of BHB on the growth and metastasis of CRC-Oxa in vivo. Eight Oxa responders and seven nonresponders with CRC were enrolled in the study. Then, the serum BHB level and H3K79me, H3K27ac, H3K14ac, and H3K9me levels in tissues were detected. DOT1L (H3K79me methyltransferase) gene knockdown or GNE-049 (H3K27ac inhibitor) use was applied to analyze further whether BHB reversed CRC-Oxa resistance via H3K79 demethylation and/or H3K27 deacetylation in vivo and in vitro. Results: Following BHB intervention based on Oxa, the proliferation, migration, invasion, and EMT of CRC-Oxa cells and the growth and metastasis of transplanted tumors in mice were suppressed. Clinical analysis revealed that the differential change in BHB level was associated with drug resistance and was decreased in drug-resistant patient serum. The H3K79me, H3K27ac, and H3K14ac expressions in CRC were negatively correlated with BHB. Furthermore, results indicated that H3K79me inhibition may lead to BHB target deletion, resulting in its inability to function. Conclusions: β-hydroxybutyrate resensitized CRC cells to Oxa by suppressing H3K79 methylation in vitro and in vivo.

Colorectal cancer (CRC) is characterized by a complex tumor inflammatory microenvironment, while angiogenesis and immunosuppression frequently occur concomitantly. However, the exact mechanism that controls angiogenesis and immunosuppression in CRC microenvironment remains unclear. Herein, we found that expression levels of lipid raft protein STOML2 were increased in CRC and were associated with advanced disease stage and poor survival outcomes. Intriguingly, we revealed that STOML2 is essential for CRC tumor inflammatory microenvironment, which induces angiogenesis and facilitates tumor immune escape simultaneously both in vitro and in vivo. Moreover, tumors with STOML2 overexpression showed effective response to anti-angiogenesis treatment and immunotherapy in vivo. Mechanistically, STOML2 regulates CRC proliferation, angiogenesis, and immune escape through activated NF-κB signaling pathway via binding to TRADD protein, resulting in upregulation of CCND1, VEGF, and PD-L1. Furthermore, treatment with NF-κB inhibitor dramatically reversed the ability of proliferation and angiogenesis. Clinically, we also observed a strong positive correlation between STOML2 expression and Ki67, CD31, VEGFC and PD-1 of CD8⁺T cell expression. Taken together, our results provided novel insights into the role of STOML2 in CRC inflammatory microenvironment, which may present a therapeutic opportunity for CRC.

Background: The contributive role of the microbiome in tumor progression has been reported in multiple studies, such as the Fusobacterium nucleatum (F. nucleatum) in breast cancer (BC). This study aimed to explore the role of F. nucleatum-derived small extracellular vesicles (Fn-EVs) in BC and preliminarily uncover the mechanism. Methods: Ten normal and 20 cancerous breast tissues were harvested to investigate the gDNA expression of F. nucleatum and its relation with the clinical characteristics of BC patients. After isolating Fn-EVs by ultracentrifugation from F. nucleatum (ATCC 25,586), both MDA-MB-231 and MCF-7 cells were treated with PBS, Fn, or Fn-EVs, followed by being subjected to CCK-8, Edu staining, wound healing, and Transwell assays to detect their cell viability, proliferation, migration, and invasion. TLR4 expression in BC cells with diverse treatments was assessed by western blot. In vivo experiments were performed to verify its role in tumor growth and liver metastasis. Results: The F. nucleatum gDNA levels of breast tissues in BC patients were significantly higher than those in normal subjects, and positively associated with tumor size and metastasis. Fn-EVs administration significantly enhanced the cell viability, proliferation, migration, and invasion of BC cells, while knocking down TLR4 in BC cells could block these effects. Furthermore, in vivo study verified the contributive role of Fn-EVs in tumor growth and metastasis of BC, which might rely on its regulation of TLR4. Conclusions: Collectively, our results suggest that F. nucleatum plays an important role in BC tumor growth and metastasis by regulating TLR4 through Fn-EVs. Thus, a better understanding of this process may aid in the development of novel therapeutic agents.

Although the potent antibacterial ability of radezolid against Staphylococcus aureus has been widely reported worldwide, its antibacterial and anti-biofilm activity against the S. aureus clinical isolates from China remains elusive. In this study, the minimum inhibitory concentration (MIC) of radezolid was determined in S. aureus clinical isolates from China using the agar dilution method, and the relationship between radezolid susceptibility and ST distribution was also investigated. The anti-biofilm activity of radezolid against S. aureus was determined by a crystal violet assay and compared with that of linezolid and contezolid. The quantitative proteomics of S. aureus treated with radezolid was analyzed, and the genetic mutations in radezolid-induced resistant S. aureus were determined by whole-genome sequencing. The dynamic changes in transcriptional expression levels of several biofilm-related genes were analyzed by quantitative RT-PCR. Our data showed that radezolid MIC ranged from ≤0.125 to 0.5 mg/L, which was almost 1/4 × MIC of linezolid against S. aureus, indicating the greater antibacterial activity of radezolid than linezolid. The S. aureus clinical isolates with radezolid MICs of 0.5 mg/L were most widely distributed in ST239 of MRSA and ST7 of MSSA. Moreover, the more robust anti-biofilm activity of radezolid with subinhibitory concentrations (1/8 × MIC and 1/16 × MIC) was demonstrated against S. aureus when compared with that of contezolid and linezolid. Genetic mutations were found in glmS, 23S rRNA, and DUF1542 domain-containing protein in radezolid-induced resistant S. aureus selected by in vitro induction of drug exposure. Quantitative proteomic analysis of S. aureus indicated that the global expression of some biofilm-related and virulence-related proteins was downregulated. Quantitative RT-PCR further confirmed that the expressions of some downregulated biofilm-related proteins, including sdrD, carA, sraP, hlgC, sasG, spa, sspP, fnbA, and oatA, were decreased after 12 h and 24 h of exposure to radezolid. Conclusively, radezolid shows robust antibacterial and anti-biofilm activity against S. aureus clinical isolates from China when compared with contezolid and linezolid.

Mortality rates for patients with Staphylococcus aureus (S. aureus) infections have improved only modestly in recent decades and S. aureus infections remain a major clinical challenge This study investigated the in vitro antimicrobial activity of erevacycline (erava) against clinical S. aureus isolates from China, as well as the heteroresistance frequency of erava and sequence types (STs) represented in the sample. A sample of 328 non-duplicate clinical S. aureus isolates, including 138 methecillin-resistant (MRSA) and 190 methecillin-sensitive (MSSA) isolates, were collected retrospectively in China. Erava exhibited excellent in vitro activity (MIC50 ≤ 0.25 mg/L) against MRSA and MSSA, including isolates harboring Tet specific resistance genes. The frequency of erava heteroresistance in MSSA with erava MICs = 0.5 mg/L was 13.79% (4/29); no MRSA with erava MICs ≤0.5 mg/L exhibited heteroresistance. Heteroresistance- derived clones had no 30S ribosome subunit mutations, but their erava MICs (range, 1–4 mg/L) were suppressed dramatically in the presence of efflux protein inhibitors. Conclusively, erava exhibited excellent in vitro activity against S. aureus, however hints of erava heteroresistance risk and MIC creep were detected, particularly among MSSA with MICs of 0.5 mg/L.