Punicalagin with anti-inflammatory activities affects Brd-4 mediated chromatin remodeling for attenuating inflammatory osteolysis

Inflammatory osteolysis is primarily characterized by an extensive macrophage-mediated inflammatory response coupled with osteoclast (OC) formation, triggered by bacterial byproducts and/or environmental stressors. Punicalagin (PUN), a hydrolyzable tannin derived from pomegranate extract, the suppression of pro-inflammatory cytokine production in macrophages. The therapeutic potential of PUN in mitigating inflammatory osteolysis remains inadequately elucidated. We evaluated the biocompatibility of PUN through CCK-8 assay and Calcein-AM/PI dual staining. The anti-osteoclastic and anti-inflammatory properties of PUN were assessed using TRAP staining, phalloidin staining and quantitative reverse transcription PCR (RT-qPCR). Transcriptome sequencing was used to explore the underlying molecular mechanisms. Intracellular reactive oxygen species (ROS) was detected by fluorescein prob. We established a lipopolysaccharide (LPS)-induced murine cranial osteolysis model to investigate the therapeutic efficacy of PUN in vivo. PUN demonstrated favourable biocompatibility and therapeutic potential in vitro, including potent anti-osteoclastic activity, ROS scavenging capacity, and epigenetic regulatory functions. PUN was found to inhibit bromodomain-containing protein 4 (Brd4)-mediated chromatin space remodeling, consequently upregulating the production of endogenous anti-inflammatory factors and antioxidant factors. In vivo experiments confirmed that PUN significantly attenuated LPS-induced cranial osteolysis in murine models. This study reveals a new therapeutic mechanism that PUN exerts anti-inflammatory effects and regulates epigenetic regulation by influencing Brd4-mediated chromatin remodeling. These findings showed the potential of PUN as a therapeutic drug for inflammatory diseases, especially inflammatory osteolysis. Notably, our work identifies a new strategy that synergistically combines osteoclast inhibition with epigenetic regulation, providing a promising direction for the therapies for bone-related inflammatory diseases.