Neuroprotection Of Ketone Metabolism On Inhibiting Inflammatory Response By Regulating Macrophage Polarization After Acute Cervical Spinal Cord Contusive Injury

Part I:Neuroprotection of ketone metabolism via alleviating inflammation after acute spinal cord injuryObjective:To explore the macrophage polarization and inflammation regulation under ketone metabolism after acute spinal cord injury(SCI),and evaluate its neuroprotection mechanism.Methods:Sixty-four adult male Sprague-Dawley rats were randomly divided into sham group,standard diet group(SD),ketone diet group(KD)and 1,3-butanediol group(BD).The sham group underwent unilateral laminectomy at C5 while the rest groups underwent hemi-contusion on C5 spinal cord.The impactor(1.5mm in diameter)pointed 22.5 ° and 1.4mm laterally to posterior mid-line,and contused the spinal cord with speed of 100mm/s and displacement of 1.5mm.Rats in KD group were fed with ketogenic food and the rest with standard food.Additionally,1,3-butanediol was added daily to BD group via gavage(1ml/100g).On the 7th day post injury,spinal cord of 8 rats from each group were harvested to detect the protein expression of inducible nitric oxide synthase(iNOS),arginase-1 and inflammatory factors,and gene expression of inflammatory factors.Blood kotone detection and behavioral evaluation were conducted on the rest rats at every other week for 12 weeks.Spinal cord were harvested at 12th week to compare the spare gray&white matter and the axon&myelin sheaths at the epicenter between groups.Results:The blood ketone level of KD and BD groups significantly increased.The gene and protein expression of TNF-α and IL-1β increased after SCI,and the expression of these indicators were inhibited in KD and BD groups.The protein expression of iNOS,marker of M1 macrophage,were inhibited in KD and BD groups,while the expression of arginase 1,marker of M2 macrophage,were boosted in these groups.The rearing test indicated that the usage of ipsilateral forelimb was higher in KD than SD after injury.There was no significant difference between groups in other behavioral evaluation.The injury groups demonstrated obvious lesion area at the epicenter,without statistical difference between groups.However,the spare gray matter area was greater in KD than in SD and BD.Conclusion:The ketone metabolism has a protective effect on neural function after SCI by promoting the M2 macrophage polarization and inhibiting inflammation.Part II:The comparison of vertical and oblique hemi-contusion on cervical spinal cord in rats.Objective:To investigate the histological,behavioral,electrophysiological and MRI characterizations between vertical hemi-contusion and oblique hemi-contusion of C5 spinal cord injury in rats.Methods:Twenty-four adult male Sprague-Dawley rats were randomly divided into sham,vertical and oblique groups.In vertical group,the impactor contused the left side of C5 spinal cord vertically with speed of 500mm/s and displacement of 2.0mm.In oblique group,the impactor pointed 22.5° and 1.4mm laterally to posterior midline,and contused the spinal cord with speed of 600mm/s and displacement of 2.2mm.The sham group underwent unilateral laminectomy at C5.Behavioral evaluation were conducted at pre-injury and at every other week post injury.The somatosensory evoked potentials(SEPs)and motor evoked potentials(MEPs)were conducted for electrophysiological evaluation at pre-injury and at the 1st,2nd,4th and 8th week post injury.The lesion areas were scanned and analyzed in vivo by MRI at 12th week post injury.The proportion of spare gray&white matter at the epicenter were analyzed after infusion and harvest.Results:The usage of ipsilateral forelimb of three behavioral tests decreased in vertical and oblique group after SCI.The motor function loss of large joints and skilled reaching were more severe in vertical group than in oblique group.The MEP amplitude decreased in both vertical and oblique groups,however,the oblique group presented slightly higher amplitude than vertical group.The SEP latency was significantly prolonged in vertical group,and interestingly,the SEP latency of oblique was similar as sham groups and both remained at baseline.There was extensive lesion area in unilateral side of spinal cord in vertical group,while the oblique group presented smaller lesion area.The vertical group demonstrated less spare gray matter at ventral,dorsal and lateral regions,and less spare white matter at dorsal region than in oblique group.Conclusion:The vertical contusion demonstrated more severe loss in motor function of large joints and skilled reaching than oblique contusion.There was extensive lesion in unilateral spinal cord in vertical contusion,while the loss of white matter at dorsal region was lighter in oblique contusion.Additionally,the contusion had less effect on SEPs latency in oblique group than vertical group.