Studies On The Effects And Mechanisms Of Ephrin-B3 On Pain In Mice

Objective: Eph receptor tyrosine kinases and their membrane-bound ligands, ephrins, have critical roles in the developing and moderating of pain. To date, the mechanisms for the ephrin-B3 effects on analgesia in mice remains unclear. This paper is designed to measure the effects and mechanisms of ephrin-B3 in mice. These finding provide evidence for new targets of analgesic and anti-tumor drugs. Methods: The changes of pain thresholds were measured using hot plate and other pain test in the wild and Efnb3 mutant mice. Tamoxifen was given to induce Cre in different time points to rescue the expression of ephrin-B3. The inflammation cytokines and lymphocyte count were detected by ELISA essay and routine blood tests from mice treated with injection of formalin, respectively. In addition, the effect of ephrin-B3 on T lymphocytes was determined by the lymphocyte proliferation test. The signal pathways of ephrin-B3 was determination by western blot. The changes of the myelin sheath were detected under transmission electron microscopy. The tumor-bearing mice model was established to investigate the effect of ephrin-B3 in cancer.Results: The pain thresholds of ephrin-B3 mutant mice were significantly longer than that of wild mice in the radiant heat test and Von Frey test during the 7th to 10 th week. After given tamoxifen, the two groups in the two tests have no significantly difference in the 8th week. In the formalin test, the licking time of mice was decreased in ephrin-B3 mutant mice group, compared with wild mice group. The numbers of WBC, lymphocyte count in mutant mice were lower than that of wild mice. After given formalin, the WBC of wild mice did not change and the lymphocytes decreased obviously, while the WBC of mutant mice was obviously increased and the lymphocytes did not change. In the lymphocyte proliferation test, the proliferation of T cells in mutant mice was significantly lower than that of the wild group. Under transmission electron microscopy, ephrin-B3 mutant mice had demylinating compare with wild mice. There was significant difference of PLP expression between ephrin-B3 mutant group and wild mice group during 4th week. After injection of tamoxifen, the PLP content was obviously increased during 8 th week. The tumor weight of ephrin-B3 knockout mice was significantly lower than that of wild mice. The number of WBC, lymphocyte count, and mononuclear phagocyte in mutant mice were lower than that of wild mice by routine blood tests. The necrosis of tumor tissue and the chromatin marginalization of the nucleus in knockout mice were more severe. The expression level of Bax/Bcl-2 was significantly increased in ephrin-B3 knockout mice.Conclusion: Knockout efnb3 gene could increase the pain threshold, inhibition of inflammatory pain by inhibition of T cell immune response and inhibit H22 tumor growth through apoptosis in mice.