International Journal of Molecular Sciences

This study evaluates and compares the protective effects of several type II taste receptor (T2R) agonists against LPS (lipopolysaccharide)-induced inflammatory damage in BEAS-2B cells, focusing on their action via an α-gustducin (encoded by GNAT3)-dependent signaling pathway that leads to NF-κB inhibition. To investigate gene expression, mRNA levels of target inflammatory cytokines and T2R subtypes were quantified by qRT-PCR. Cytotoxicity assessment of LPS and bitter agonists was conducted using the CCK-8 assay. The activation status of the NF-κB pathway was examined by Western blot analysis of total and phosphorylated forms of p65 and IκB. Finally, the specific and essential role of GNAT3 was definitively validated through siRNA-mediated gene knockdown. LPS treatment induced significant upregulation of IL-6 and IL-8 mRNA, along with increased phosphorylation of p65 and IκB in BEAS-2B cells. A direct, parallel comparison of the bitter taste agonists PTC (phenylthiourea), QN (quinine), CPD (carisoprodol), and LK (chloroquine) revealed their capacity to upregulate specific T2R subtypes, suppressing inflammatory mediator release and NF-κB activation. Critically, upon GNAT3 silencing, the inhibitory effects of all tested agonists on p-p65/p65 and p-IκB/IκB ratios were significantly attenuated, without altering total p65 or IκB abundance. This provides direct genetic evidence that GNAT3 is specifically required for mediating the anti-inflammatory effects elicited by these T2R agonists. Multiple bitter receptor agonists exert anti-inflammatory effects on airway epithelial cells in a GNAT3-dependent manner. Our study advances the field by systematically comparing agonist efficacy and establishing the indispensable role of GNAT3 within the anti-inflammatory signaling cascade triggered by T2R agonists, thereby revealing a refined mechanistic insight and potential therapeutic target for inflammatory lung diseases.

Infectious pathogens pose serious threats to public health, necessitating the development of more antimicrobials. In this study, oligohydroxybutyrates were obtained through the catalyzed polymerization of β-butyrolactone using N, N-dimethyl-4-aminopyridine (DMAP) and aluminum isopropoxide [Al(OiPr)₃] and applied as sustainable antimicrobial agents. The poly3-hydroxybutyrate (PHB) oligomers exhibited broad-spectrum antibacterial activities against both Gram-negative (E. coli) and Gram-positive (S. aureus) model bacteria. Additionally, PHB oligomers displayed robust (inhibiting rate: >95%) and rapid (action time: <20 min) antiviral activity against three notorious single-stranded RNA viruses, that is, influenza A virus (H1N1 and H3N2) and coronavirus (SARS-CoV-2). In particular, a comprehensive set of advanced experimental characterizations, including FT-IR, ¹H- and ¹³C-NMR, and H-ESI-MS/MS, was applied to analyze their chemical structures. The results confirmed the loss of terminal hydroxyl groups in the PHB intermediate and end products associated with theoretical calculations. These findings will also help provide deep insight into the major chain growth mechanism during the synthesis of PHB. The structural variations, which were treated as unwanted side reactions, were identified as a pivotal factor by deactivating the terminal hydroxy during chain growth. Their effective sterilization properties and degradability endowed the as-prepared PHB oligomers with a promising biomedical potential, including for use as disinfectants, sanitizers, and antiseptics.

Macrophages are key innate immune cells in the host defense against pathogens. Ionizing radiation can impair macrophage functions such as phagocytosis and activate them, potentially exacerbating tissue injury. Macrophage extracellular traps (METs) are formed upon stimulation of macrophages with PAMPs or DAMPs. We hypothesized that macrophages exposed to ionizing radiation can release extracellular traps. Peritoneal macrophages were collected from C57BL/6 mice and subjected to 5 Gy radiation. We performed assays to detect METs, including the immunofluorescence of citrullination of histone H3 and cell-free DNA measurement in cell culture medium as well as cell death. The exposure of ionizing radiation killed a significant number of mouse peritoneal macrophages through pyroptosis, which was mediated by Gasdermin D (GSDMD). The onset of pyroptosis eventually caused METs by suicidal METosis via pyroptosis and vital METosis occurring in the cells surviving after exposure to radiation. We found that exposure of peritoneal macrophages to 5 Gy radiation significantly increased METosis, as revealed by increased levels of citrullinated histone H3 and an increased surface area of extracellular DNA surrounding the cells. We discovered that peptidyl arginine deiminase (PAD) 2 and 4 are required for peritoneal macrophages to generate extracellular traps in response to radiation exposure. Our data demonstrate that the ionizing radiation induces METs via the activation of GSDMD, and we confirmed the requirement of PADs for METosis after exposure to the ionizing radiation. Targeting METs may direct a new therapeutic strategy for mitigating radiation-induced tissue injury.