Title : Active Compounds from Radix Rehmanniae Ameliorates CFA-Induced Inflammation by Attenuating Macrophage-Mediated Localized Response and Nitrative Damage
Objective: To investigate whether the active compounds from Radix Rehmanniae (PA) switch local immunological response in complete Freund’s adjuvant-induced (CFA-induced) inflammatory models to alleviate localized inflammatory response and nitrative damage.
Method: Twenty male C57BL/6N mice (~8 weeks) were randomly and equally divided into two groups by CFA-induced inflammatory model group and the PA treatment group. The inflammatory model was induced by the injection of CFA in the right hind paw. The treatment group was orally administrated with PA from day 0 to day 7. Mechanical allodynia and thermal hyperalgesia were measured by Von-Frey Test and Hargraves test. The immunohistochemical (IHC) and immunofluorescence (IF) method was applied to quantify the M1 and M2 macrophage phenotype biomarker and M1/M2 ratio in local subcutaneous tissue. The western blotting and qPCR were applied. The NF-kB inhibitor (JSH23 and Sau) and Mir-155-5p Mimics and inhibitors were employed.
Result: The behavioral assay results indicated that compared with the CFA-induced model group, the PA treatment group ameliorates the inflammatory pain was increased obviously. The IHC and IF staining quantified results indicated that compared with the PA treatment group, the M1/M2 ratio and M1 phenotype in the CFA-induced group were significantly reduced (P<0.05). The inflammatory related cytokines such as IL-10, IL-1b, TLR4, MyD88, TNFa and iNOS were reduced after PA treatment. In terms of the mechanism, bioinformatics analysis confirmed that PA could bind to the miR-155-5p inhibitor and promoter to transcriptionally activate miR-155-5p to the NF-kB pathway. Our results further investigated that MyD88 activation could diminish M1 macrophage polarization and promote M2 macrophage polarization via the MyD88/miR-155/NF-kB pathway. Furthermore, PA reduced the oxidative and nitrative stress in tissue-resident macrophages as well as triggered an immune reaction translated by activation of the nuclear factor-kappa-B (NF-κB) signaling pathway.
Conclusion: PA could result in improving analgesic effects. PA had a positive impact on the CFA-induced model, which may increase the polarization of M2 macrophages and release nitrative damage. And enhanced the localized expression of M2-related markers and might have an advantage in switching the M1/ M2 ratio to tissue protection and pain release.