The Analgesic Effect Of Indigo On Inflammatory Pain In Mice And Its Mechanism

Objectives This study was to investigate the anti-inflammatory and anti-nociceptive activities of indigo in mice and to explore the possible related mechanisms.Methods 1.The anti-inflammatory activities of indigo were assessed by using xylene-induced ear edema,carrageenan-induced paw edema and acetic acid-induced vascular permeability test in mice.2.The anti-nociceptive activities of indigo were assessed by using acetic acid-induced writhing,hot plate test and formalin test,as well as evaluation of spontaneous locomotor activity and motor performance.3.The protein expressions of IKK?,p-IKK?,I?B?,p-I?B?,p65 NF-?B,p-p65 NF-?B,COX-2 and i NOS in the spinal cord were assessed by western blot.4.The level of TNF-?,IL-1?,IL-6,PGE₂ were assessed by ELISA kits.Results 1.Compare to the vehicle group,?1?the xylene-induced ear edema of indigo?50,100,200 mg / kg?group had a significant reduced?P <0.05?.?2?the increase of capillary permeability in mice induced by acetic acid of indigo?100,200 mg / kg?group had a significant decreased?P <0.01?.?3?the carrageenan-induced paw edema of indigo?100,200 mg / kg?group had a significant reduced?P <0.05?2.Compare to the vehicle group,?1?the number of acetic acid-induced writhing of indigo?100,200 mg / kg?group had a significant reduced?P <0.01?.?2?indigo?50,100,200 mg / kg?group significantly reduced the time of the second phase of formalin-induced pain response?P <0.05?.?3?indigo?50,100,200 mg / kg?had no effect on the pain threshold of mice in hot plate test.?4?indigo?50,100,200 mg / kg?had no effect on the spontaneous locomotor activity and the coordination ability of the mice.3.Compared to the vehicle group,indigo significantly inhibited the protein expression levels of p-IKK??P<0.01?,p-I?B??P<0.01?,NF-?B?P<0.05?,p-NF-?B?P<0.05?,COX-2?P<0.05?and i NOS?P<0.01?.Meanwhile,the protein expression level of I?B? was dramatically upregulated by indigo?P<0.01?.4.Compared to the vehicle group,indigo significantly inhibited the levels of TNF-??P<0.01?,IL-1??P<0.01?,IL-6?P<0.01?,PGE₂?P<0.01?.Conclusion Indigo exerts significant anti-inflammatory and analgesic activities in mice by inhibiting IKK? phosphorylation,which leads to the reduction in the production of important pain mediators,such as PGE₂ and COX-2,via the IKK?/I?B/NF-?B pathway.