Anti-inflammatory Effect Of Total Flavones Of Bidens Bipinnata L (TFB) And The Possible Mechanisms

Total flavones of Bidens bipinnata L（TFB） is the ethanol extracts obtained fromBidens bipinnata L., which is a medicinal plant of Compositae tubular flower subfamilyBidens L.. Results of our previous studies confirmed that TFB was the effectivecomponent of Bidens bipinnata, with obvious therapeutic effects on inflammationassociated diseases including acute chemical liver injury and hepatic fibrosis induced byCCL₄,immune hepatic fibrosis induced by pig serum, and hepatic fibrosis induced byschistosomiasis. The aim of the present study is to investigate the anti-inflammatoryeffect of TFB using acute and chronic inflammation models and to explore its possiblemechanism.OBJECTIVETo investigate the anti-inflammatory effect of TFB using acute and chronicinflammation models and to explore its possible mechanism.METHODS1. The acute inflammatory mice model was induced by smearing dimethylbenzene tomice ear. The degree of ear edema was measured, and the serum concentrations oftumor necrosis factor-α （TNF-α）, Interleukin-1（IL-1）, IL-6and IL-8were detectedusing enzyme linked immunosorbent assay （ELISA）. 2. Freund’s complete adjuvant （FCA） was injected intradermally to establish AA ratmodel. To investigate the effect of TFB on the FCA-induced acute primaryinflammation, the swelling degrees of the injection paw were measured0,6,12,18,24hafter FCA injected, and the serum contents of tumor necrosis factor-α （TNF-α）,interleukin-1（IL-1）, IL-2, IL-6and IL-8were detected using enzyme linkedimmunosorbent assay （ELISA）. The histopathological changes of rats joint wereobserved using hematoxylin-eosin （HE） staining, and the protein expression of ASIC1ain cartilage tissue of AA rats was detected using immunohistochemistry.To explore the effect of TFB on the FCA-induced chronic secondary inflammation,the swelling degree of contralateral non-inflamed paws were measured, and thepolyarthritis index （PI） were evaluated. Serum concentrations of TNF-α, IL-1, IL-2,IL-6and IL-8in the secondary stage of AA rats were detected by ELISA, Thehistopathological changes of rats joint were observed using HE staining, and the proteinexpression of OPG, RANKL and ASIC1a in cartilage tissue of AA rats was detectedusing immunohistochemistry.RESULTS1. Compared with those of the normal mices, the ear edema degree and serumconcentrations of TNF-α, IL-1, IL-6, IL-8in the model mice were obviouslyincreased（P<0.05）. Administration of TFB（100,200mg·kg-1） ig lasted three days couldsuppress the ear edema induce by dimethylbenzene and decrease serum TNF-α, IL-1,IL-6, IL-8contents（P<0.05）.2The paws of the inflammatory side in AA rats began swellen6h after intradermalinjection with FCA, and the swelling degree reached the peak at18h then began towane. Administration of TFB（67,133mg·kg-1） ig for three days could significantlyreduce the primary foot swelling degree of AA rats; compared with those of the normalgroup, serum contents of TNF-α, IL-1, IL-6and IL-8in AA model rats were significantly increased whereas IL-2content decreased obviously, TFB （67,133mg·kg-1）ig could significantly reduce serum TNF-α, IL-1, IL-6and IL-8content and elevate theserum IL-2level. The histopathological changes in the knee joint of AA rats includingthe increasing number of inflammatory cells and inflammatory infiltration could beameliorated by TFB. The expression of ASIC1a protein in the cartilage tissue of AA ratsduring primary inflammation phase was upregulated, which could be downregulated bytreatment with TFB（67,133mg·kg-1）.Compared with the normal group, the contralateral non-inflamed paws of AA ratswere swellen d12, d16, d20, d24, d28after intradermal injection of FCA, and thepolyarthritis index increased significantly, indicating the FCA-induced secondaryinflammation of AA rats. Consistent with these results, the serum concentrations ofTNF-α, IL-1, IL-6and IL-8were elevated in AA group. Treatment with TFB （67,133mg·kg-1） could increase the body weight gain, weaken AA rats secondary palm swellingand PI in d12, d16, d20, d24, d28, reduce serum TNF-α, IL-1, IL-6and IL-8contents,and increase IL-2content. Histopathology results showed that TFB can improve thesymptoms of inflammation of rats and alleviate cartilage damage in a certain extent.Moreover, treatment of TFB could increase the expression of OPG protein remarkablywith a significant inhibitory effect on the expression of RANKL and ASIC1a in thecartilage tissue of AA rats.CONCLUSIONTFB has anti-inflammatory effect in the actue inflammation model induced bydimethylbenzene and chronicity immune inflammation induced by FCA. Themechanism of TFB on actue inflammation might be associated with its activity ofinhibitting the release of inflammatory mediators, while its mechanism on chronicimmune inflammation might be related to its ability in downregulating ASIC1a,keeping the balance of cytokine network, and regulating the activity of RANKL/OPG channel, which eventually alleviate the cartilage destruction.