Effect of Callicarpa nudiflora on wound healing and PI3K/AKT/mTOR pathway by regulating M2 macrophage polarization in rats with diabetic foot ulcer

Objective To analyze the effect of Callicarpa nudiflora on wound healing and phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway by regulating M2 macrophage polarization in rats with diabetic foot ulcer.

Methods A total of 40 rats were selected, with 10 rats in control group (topical application of saline), and the remaining 30 were used to establish rat model of diabetic foot ulcer. Ultimately, 27 rats were successfully modeled and divided into model group (topical application of saline), Callicarpa nudiflora group (topical application of Callicarpa nudiflora), and Callicarpa nudiflora combined with inhibitor group (topical application of Callicarpa nudiflora combined with CD206 inhibitor, a marker protein of M2 macrophages), with 9 rats in each group. The wound healing rate, levels of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF), relative expression levels of inducible nitric oxide synthase (iNOS), CD16/32, CD206, PI3K, AKT and mTOR as well as mRNA expression levels of PI3K, AKT and mTOR were compared among groups.

Results On the 3rd, 7th and 14th days after intervention, compared with the control group, the wound healing rate, VEGF, bFGF, relative expression level of CD206, relative expression of PI3K, AKT and mTOR at mRNA and protein levels were significantly decreased while the relative expression levels of iNOS and CD16/32 were significantly increased in all other groups (P < 0.05); compared with the model group, the Callicarpa nudiflora group and the Callicarpa nudiflora combined with inhibitor group showed significant increased wound healing rate, VEGF, bFGF, relative expression level of CD206, and relative expression of PI3K, AKT and mTOR at mRNA and protein levels, and significant decreased relative expression levels of iNOS and CD16/32 (P < 0.05); compared with the Callicarpa nudiflora group, the Callicarpa nudiflora combined with inhibitor group showed significant decreased wound healing rate, VEGF, bFGF, relative expression level of CD206, and relative expression of PI3K, AKT and mTOR at mRNA and protein levels, and significant increased relative expression levels of iNOS and CD16/32 (P < 0.05).

Conclusion Callicarpa nudiflora can promote M2 macrophage polarization, increase wound healing rate and levels of VEGF and bFGF in rats with diabetic foot ulcer, and activate the PI3K/AKT/mTOR signaling pathway.