Quantitative proteomic and phosphoproteomic analyses of the hippocampus reveal the involvement of NMDAR1 signaling in repetitive mild traumatic brain injury

The cumulative damage caused by repetitive mild traumatic brain injury can cause long-term neurodegeneration leading to cognitive impairment.This cognitive impairment is thought to result specifically from damage to the hippocampus.In this study,we detected cognitive impairment in mice 6 weeks after repetitive mild traumatic brain injury using the novel object recognition test and the Morris water maze test.Immunofluorescence staining showed that p-tau expression was increased in the hippocampus after repetitive mild traumatic brain injury.Golgi staining showed a significant decrease in the total density of neuronal dendritic spines in the hippocampus,as well as in the density of mature dendritic spines.To investigate the specific molecular mechanisms underlying cognitive impairment due to hippocampal damage,we performed proteomic and phosphoproteomic analyses of the hippocampus with and without repetitive mild traumatic brain injury.The differentially expressed proteins were mainly enriched in inflammation,immunity,and coagulation,suggesting that non-neuronal cells are involved in the pathological changes that occur in the hippocampus in the chronic stage after repetitive mild traumatic brain injury.In contrast,differentially expressed phosphorylated proteins were mainly enriched in pathways related to neuronal function and structure,which is more consistent with neurodegeneration.We identified N-methyl-D-aspartate receptor 1 as a hub molecule involved in the response to repetitive mild traumatic brain injury,and western blotting showed that,while N-methyl-D-aspartate receptor 1 expression was not altered in the hippocampus after repetitive mild traumatic brain injury,its phosphorylation level was significantly increased,which is consistent with the omics results.Administration of GRP78608,an N-methyl-D-aspartate receptor 1 antagonist,to the hippocampus markedly improved repetitive mild traumatic brain injury-induced cognitive impairment.In conclusion,our findings suggest that N-methyl-D-aspartate receptor 1 signaling in the hippocampus is involved in cognitive impairment in the chronic stage after repetitive mild traumatic brain injury and may be a potential target for intervention and treatment.

Peripheral BDNF Regulates Somatosensory–Sympathetic Coupling in Brachial Plexus Avulsion-Induced Neuropathic Pain

Brachial plexus avulsion(BPA)is a combined injury involving the central and peripheral nervous systems.Patients with BPA often experience severe neuropathic pain(NP)in the affected limb.NP is insensitive to the existing treatments,which makes it a challenge to researchers and clinicians.Accumulated evidence shows that a BPA-induced pain state is often accompanied by sympathetic nervous dysfunction,which suggests that the excitation state of the sympathetic nervous system is correlated with the existence of NP.However,the mechanism of how somatosensory neural crosstalk with the sympathetic nerve at the peripheral level remains unclear.In this study,through using a novel BPA C7 root avulsion mouse model,we found that the expression of BDNF and its receptor TrκB in the DRGs of the BPA mice increased,and the markers of sympathetic nervous system activity includingα1 andα2 adrenergic receptors(α1-AR andα2-AR)also increased after BPA.The phenomenon of superexcitation of the sympathetic nervous system,including hypothermia and edema of the affected extremity,was also observed in BPA mice by using CatWalk gait analysis,an infrared thermometer,and an edema evaluation.Genetic knockdown of BDNF in DRGs not only reversed the mechanical allodynia but also alleviated the hypothermia and edema of the affected extremity in BPA mice.Further,intraperitoneal injection of adrenergic receptor inhibitors decreased neuronal excitability in patch clamp recording and reversed the mechanical allodynia of BPA mice.In another branch experiment,we also found the elevated expression of BDNF,TrκB,TH,α1-AR,andα2-AR in DRG tissues from BPA patients compared with normal human DRGs through western blot and immunohistochemistry.Our results revealed that peripheral BDNF is a key molecule in the regulation of somatosensory-sympathetic coupling in BPA-induced NP.This study also opens a novel analgesic target(BDNF)in the treatment of this pain with fewer complications,which has great potential for clinical transformation.