The Effect And Mechanism Of Flufenamic Acid On Repair Of Spinal Cord Injury

Spinal cord injury(SCI)disrupts neurons and axons,leading to sensory and motor impairment and even paralysis.Acute spinal cord injury(SCI)induces secondary hemorrhage.All types of secondary injury,which can include ischemia/hypoxia,oxidative stress,free radical injury,lipid peroxidation,immune inflammatory reactions,and excitotoxicity,are considered responsible for progressive secondary hemorrhage.The up-regulation of transient receptor potential melastatin 4(Trpm4)after injury plays a crucial role in secondary hemorrhage,which is the most destructive mechanism in secondary injuries in the central nervous system.SCI also induces initial blood-spinal cord barrier(BSCB)disruption.The matrix metalloprotease(MMP)-mediated disruption of the BSCB leads to an inflammatory response,neurotoxin production and neuronal cell apoptosis,which inhibits the functional recovery in SCI.Thus,preventing secondary hemorrhage and BSCB disruption should be an important goal of therapeutic interventions in SCI.Flufenamic acid(FFA)has been known to exert anti-inflammatory and analgesic effects for more than 50 years.Recently,many in vitro cell culture experiments have confirmed that the Trpm4 channel is very sensitive and specific to FFA and that its expression is highly reduced by FFA.Based on previous research,we hypothesized that FFA might be a potential therapeutic agent in SCI,which might promote the functional recovery by reducing the secondary hemorrhage.In this study,we first applied FFA to treat SCI.Firstly,we assessed the effect of FFA as a therapy for SCI,and then explored the mechanism underlying the role of FFA as a treatment for SCI.Based on the previous discussion,the main contents and results were shown as follows:(1)Establish the contusion injury model:We used the NYU impactor to induce a weight-drop contusion injury at T10 of the spinal cord,and then assessed the contusion injury model.The results in this study confirmed that the injury model for SCI was stable and reliable.(2)Assess the effect of FFA as a therapy for SCI: FFA was injected intraperitoneally 1 h after SCI and then continuously once per day for one week.And then the motor function and morphological changes of the cords were observed and assessed.The results in this study demonstrated that the behavioral outcome was improved after the treatment of FFA.And also,we shown that FFA treatment was associated with smaller lesions,less reactive gliosis,decreased cavity formation and lesion area,better myelin preservation,promoted axonal preservation and it protected neurons and motor neurons.All these results indicated that FFA improved functional recovery after SCI.(3)Assess the morphological changes of the muscle after the treatment of FFA:In order to further explore how did the FFA interfere the downstream peripheral muscle,this paper studied the morphological changes of the tibialis anterior and gastrocnemius muscles,the changes of motor neurons which dominating the corresponding muscles and the motor endplate in anterior and gastrocnemius after the treatment with FFA.The results in this research demonstrated that the FFA protected the dominated motor neurons of the tibialis anterior and gastrocnemius,and reduced the atrophy degree of the corresponding muscles.Thus,the study in this paper furtherly confirmed that FFA improve the functional recovery after SCI.(4)Explore the potential mechanism underlying the role of FFA as a treatment for SCI: In this study,we observed the extent of secondary hemorrhage and the permeability of the BSCB.And also,we examined the Trpm4 expression,the activation and expression of MMP-9 and MMP-2,the extent of angiogenesis and the inflammatory immune response.Our results demonstrated that treatment with FFA inhibited Trpm4 expression,secondary hemorrhage,and capillary fragmentation and promoted angiogenesis.In addition,FFA significantly inhibited the expression and activation of MMP-2 and MMP-9 and significantly attenuated BSCB disruption at 1 d and 3 d after injury.Furthermore,we found that FFA decreased the hemorrhage-and BSCB disruption-induced activation of microglia/macrophages.In summary,the results of this study confirmed that the treatment of FFA repaired the injuried axons and improved the functional outcome.And also,the research of this study indicated that the neuroprotective effect of FFA is mediated in part by the following four mechanisms:(1)the blocking the Trpm4 channel reduces capillary fragmentation and subsequent secondary hemorrhage;(2)the inhibition of MMP-9 and MMP-2 expression and activation blocks BSCB disruption;(3)the inhibition of the expression of Trpm4 promotes angiogenesis;(4)the reduction of inflammatory immune response triggered by secondary hemorrhage and BSCB disruption.Thus,the results of this study suggest that FFA may represent a potential therapeutic agent for promoting functional recovery,and it will be applied for clinical treatment in future.