Pachymic Acid Accelerated Diabetic Ulcer Healing by Enhancing Macrophage Efferocytosis via the MEK/ERK/TGFβ1 Signaling Axis.
TL;DR
The mechanism of PA was elucidated, providing a theoretical foundation for its clinical translation as a novel drug to promote DW healing and enhancing macrophage efferocytosis and alleviating local oxidative stress.
Abstract
Objective
Diabetic ulcers (DUs) are severe and prevalent complications of type 2 diabetes, characterized by impaired macrophage efferocytosis and sustained chronic inflammation within the wound microenvironment. Pachymic acid (PA) is a natural triterpenoid with potent anti-inflammatory and immunomodulatory properties. This research is aimed at exploring whether PA facilitates healing of DUs by activating the MEK/ERK/TGFβ1 signaling axis to restore macrophage efferocytosis.
Methods
In vitro, cell viability was evaluated using CCK-8 assay. An inflammatory macrophage model was established via LPS/IFN-γ induction to assess the impact of PA on reactive oxygen species (ROS) and proinflammatory mediator levels. Macrophages were cocultured with apoptotic cells to evaluate efferocytosis. Transcriptome sequencing, bioinformatics analyses, and RT-qPCR validation were conducted on PA-treated macrophages to explore the core regulatory networks, whereas western blot was utilized to verify the underlying proefferocytotic mechanisms. In vivo, a diabetic wound (DW) mouse model was established and treated with PA. Western blot, immunofluorescence, and histological staining were performed to evaluate macrophage polarization, the activation of the MEK/ERK/TGFβ1 pathway, angiogenesis, and the expression levels of efferocytosis-related proteins.
Results
In vitro experiments demonstrated that PA exhibited minimal cytotoxicity, significantly reduced ROS levels, and suppressed the secretion of proinflammatory mediators in macrophages while enhancing their ability to engulf apoptotic cells. Transcriptomic profiling, RT-qPCR validation, and protein-protein interaction network analyses revealed that PA's regulatory targets were enriched in efferocytosis and the MEK/ERK pathway. In the DW mouse model, PA treatment alleviated inflammatory cell infiltration, promoted collagen deposition and angiogenesis, improved the SPOT skin wound score, and accelerated wound closure. Both in vitro and in vivo analyses confirmed that PA upregulated the expression of P-MEK1/2, P-ERK1/2, and TGFβ1, and key efferocytosis receptors, which drove the phenotypic transition of wound macrophages from a proinflammatory state to an anti-inflammatory and restorative state.
Conclusion
PA upregulated the expression of vital efferocytosis receptors by activating the MEK/ERK/TGFβ1 signaling axis, enhancing macrophage efferocytosis, and alleviating local oxidative stress. This study elucidated the mechanism of PA in treating DUs, providing a theoretical foundation for its clinical translation as a novel drug to promote DW healing.