Background The anti-inflammatory properties of the cannabinoid 2 receptor (CB2R) in injury and inflammatory diseases have been widely substantiated. Specifically, the anti-inflammatory effect of CB2R may be achieved by regulating macrophage polarisation. Several research findings suggested that the activation of CB2R could attenuate inflammation by reducing pro-inflammatory M1 macrophage polarisation and promoting anti-inflammatory M2 polarisation. However, considering CB2R inhibits fibrosis and M2 promotes fibrosis, that the activation of CB2R may lead to an increase in M2 macrophages seems contradictory. Therefore, we hypothesised that the activation of CB2R to attenuate inflammation is not achieved by up-regulating M2 macrophages. Methods We established an incised wound model using mouse skin and used this to evaluate the effect of CB2R agonists (JWH133 or GP1a) and an antagonist (AM630) on wound healing. At various post-injury intervals, we used western blot analysis, immunofluorescence staining, enzyme-linked immunosorbent assay and quantitative reverse transcription polymerase chain reaction assays to determine CB2R protein expression, M1/M2 macrophage infiltration, and the protein and gene expression of M1/M2-associated markers and cytokines in skin lesions. Results Activation of CB2R significantly reduced M1 macrophage infiltration and slightly increased M2 macrophage infiltration. Similarly, gene expression and protein levels of M1-associated markers and cytokines (interleukin [IL]-6, IL-12, CD86 and inducible nitric oxide synthase) were significantly down-regulated after CB2R agonist administration; in contrast, markers and cytokines were increased in the CB2R antagonist-treated group. Conversely, the administration of agonists slightly increased gene expression and protein levels of M2-associated markers and cytokines (IL-4, IL-10, CD206 and arginase-1 [Arg-1]); however, a statistical significance at most time points post-injury was not noted. Conclusion In summary, our findings suggested that during incised skin wound healing in mice, increased levels of CB2R may affect inflammation by regulating M1 rather than M2 macrophage subtype polarisation. These results offer a novel understanding of the molecular mechanisms involved in the inhibition of inflammation by CBR2 that may lead to new treatments for cutaneous inflammation.

中文翻译：

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大麻素 2 受体通过抑制 M1 巨噬细胞而不是激活 M2 巨噬细胞来减轻皮肤伤口愈合过程中的炎症。

背景 大麻素 2 受体 (CB2R) 在损伤和炎症性疾病中的抗炎特性已被广泛证实。具体而言，CB2R 的抗炎作用可以通过调节巨噬细胞极化来实现。一些研究结果表明，CB2R 的激活可以通过减少促炎 M1 巨噬细胞极化和促进抗炎 M2 极化来减轻炎症。然而，考虑到CB2R抑制纤维化而M2促进纤维化，CB2R的激活可能导致M2巨噬细胞的增加似乎是矛盾的。因此，我们假设激活 CB2R 以减轻炎症不是通过上调 M2 巨噬细胞来实现的。方法 我们使用小鼠皮肤建立切开伤口模型，并用它来评估 CB2R 激动剂（JWH133 或 GP1a）和拮抗剂（AM630）对伤口愈合的影响。在不同的损伤后间隔，我们使用蛋白质印迹分析、免疫荧光染色、酶联免疫吸附测定和定量逆转录聚合酶链反应测定来确定 CB2R 蛋白表达、M1/M2 巨噬细胞浸润以及 M1/ 的蛋白质和基因表达。皮肤病变中的 M2 相关标志物和细胞因子。结果 CB2R的激活显着降低了M1巨噬细胞浸润，略微增加了M2巨噬细胞浸润。同样，M1 相关标志物和细胞因子（白介素 [IL]-6、IL-12、CD86 和诱导型一氧化氮合酶）在 CB2R 激动剂给药后显着下调；相反，标志物和细胞因子在 CB2R 拮抗剂治疗组中增加。相反，激动剂的施用略微增加了 M2 相关标志物和细胞因子（IL-4、IL-10、CD206 和 arginase-1 [Arg-1]）的基因表达和蛋白质水平；然而，在受伤后的大多数时间点没有发现统计学意义。结论 总之，我们的研究结果表明，在小鼠皮肤切口愈合过程中，CB2R 水平升高可能通过调节 M1 而非 M2 巨噬细胞亚型极化来影响炎症。这些结果提供了对 CBR2 抑制炎症所涉及的分子机制的新认识，这可能导致皮肤炎症的新疗法。