Surgical intervention combined with weight-bearing walking training promotes recovery in patients with chronic spinal cord injury:a randomized controlled study

For patients with chronic spinal cord injury,the co nventional treatment is rehabilitation and treatment of spinal cord injury complications such as urinary tract infection,pressure sores,osteoporosis,and deep vein thrombosis.Surgery is rarely perfo rmed on spinal co rd injury in the chronic phase,and few treatments have been proven effective in chronic spinal cord injury patients.Development of effective therapies fo r chronic spinal co rd injury patients is needed.We conducted a randomized controlled clinical trial in patients with chronic complete thoracic spinal co rd injury to compare intensive rehabilitation(weight-bearing walking training)alone with surgical intervention plus intensive rehabilitation.This clinical trial was registered at ClinicalTrials.gov(NCT02663310).The goal of surgical intervention was spinal cord detethering,restoration of cerebrospinal fluid flow,and elimination of residual spinal cord compression.We found that surgical intervention plus weight-bearing walking training was associated with a higher incidence of American Spinal Injury Association Impairment Scale improvement,reduced spasticity,and more rapid bowel and bladder functional recovery than weight-bearing walking training alone.Overall,the surgical procedures and intensive rehabilitation were safe.American Spinal Injury Association Impairment Scale improvement was more common in T7-T11 injuries than in T2-T6 injuries.Surgery combined with rehabilitation appears to have a role in treatment of chronic spinal cord injury patients.

Dihydromyricetin ameliorates chronic liver injury by reducing pyroptosis

BACKGROUND Chronic liver injury(CLI) is now a worldwide disease. However, there is no effective treatment. Pyroptosis plays an essential role in CLI. Dihydromyricetin(DHM) resists oxidation and protects the liver. We hypothesize that the beneficial effect of DHM on CLI is related to its effect on the expression of pyroptosisrelated molecules. Therefore, we studied the influence of DHM on CLI and pyroptosis.AIM To study the role of pyroptosis in the pathogenesis of CLI and the therapeutic mechanism of DHM.METHODS Thirty-two mice were randomly divided into four groups: The control group was injected with olive oil, the carbon tetrachloride(CCl4) group was injected with CCl4, the vehicle group was injected with hydroxypropyl-β-cyclodextrin while injecting CCl4 and the DHM group was injected with DHM while injecting CCl4. After four weeks of treatment, liver tissues from the mice were stained with hematoxylin and eosin, and oil red O. Blood was collected from the angular vein for serological analysis. The severity of CLI was estimated. Some liver tissue was sampled for immunohistochemistry, Western blotting and quantitative reverse transcription PCR to observe the changes in pyroptosis-related molecules.RESULTS Serum total cholesterol, low density lipoprotein, aspartate aminotransferase(AST) and alanine aminotransferase(ALT) in the CCl4 group were higher than those in the control group, and serum total cholesterol, low density lipoprotein, AST and ALT in the DHM group were lower than those in the vehicle group. Hematoxylin and eosin and oil red O staining showed that there were more lipid droplets in the CCl4 group than in the control group, and there were fewer lipid droplets in the DHM group than in the vehicle group. Western blotting showed that the expression of the pyroptosis-related molecules caspase-1, NOD-, LRR-and pyrin domain-containing 3(NLRP3) and gasdermin D(GSDMD)-N in the CCl4 group was higher than that in the control group, while expression of these proteins in the DHM group was lower than that in the vehicle group. Quantitative reverse transcription PCR results showed that the expression of the pyroptosis-related genes caspase-1, NLRP3, GSDMD and interleukin-1β(IL-1β) in the CCl4 group was higher than that in the control group, while there was no significant change in NLRP3 and caspase-1 expression in the DHM group compared with that in the vehicle group, and the expression of GSDMD and IL-1β was decreased.CONCLUSION DHM improves CCl4-induced CLI and regulates the pyroptosis pathway in hepatocytes. DHM may be a potential therapeutic agent for CLI.

Differential Expression of Alpha-Adrenoceptor Subtypes in Rat Dorsal Root Ganglion after Chronic Constriction Injury

Summary： mRNAs of alpha-adrenoceptor （α-AR） subtypes are found in neurons in dorsal root ganglion （DRG） and change after peripheral nerve injury. In this study, the distribution of α-AR subtype proteins was studied in L5 DRG of normal rats and rats with chronic constriction injury of sciatic nerve （CCI）. Using immunofluorescence technique, it was found that α1A-, α1B-, and α2A-AR proteins were expressed in large, medium, and small size neurons in normal DRG, and significantly increased in all size neurons 14 days after CCI. α1D- and α2C-AR was also expressed in all size neurons in normal DRG. However, α1D-AR was significantly increased and α2C-AR was decreased in small size neurons 14 days post CCI. α2B-AR neurons were not detectable in normal and CCI DRG. Co-expression of α1A- and α2A-AR in the same neuron was observed in normal DRG and increased post CCI. Collectively, these results indicated that there is distinct distribution of α-AR subtypes in DRG neurons, and the distribution and levels of expression of α-AR subtypes change differently after CCI. The up-regulation of α-AR subtypes in DRG neurons may play an important role in the process of generating and transmitting neuropathic pain.

Effect of Touch stimulus on the Expression of C-fos and TrkA in Spinal Cord Following Chronic Constriction Injury of the Sciatic Nerve in Rats

Summary: To study the mechanism of the innoxious touch-stimulus on the modulation of hyperalgesia and the expression of the C-fos and the nerve growth factor (NGF) receptor-TrkA in the spinal dorsal horn neurons following the chronic constriction injury (CCI) of the sciatic nerve in rats, 60 female Sprague-Dawley rats were randomly divided into sham-operation group and CCI group, with each group being further divided into 3 subgroups on the 7th,14th and 28th day after operation (n=10). The mechanical and the thermal withdrawal threshold were assessed following the touch stiumulation after the CCI, immunohistochemical methods were employed to observe the expression of the C-fos and TrkA in spinal dorsal horn. Our results showed that the hyperalgesia appeared on the 4th day and reached the maximal level on the 14th day after operation. The expression of the C-fos also increased significantly and reached its maximal level on the 14th day after the touch-stimulus. Meanwhile, the TrkA expression was elevated significantly in both groups, as compared with basic data, and the difference was statistically significant (P<0.05). It is concluded that the level of the C-fos expression changed with the paw withdrawal threshold variation and increased markedly following the innoxious touch-stimulus. The expression of the TrkA receptors also increased gradually following the development of the neuropathic pain. The results suggest that C-fos may play a crucial role in the development of the hyperalgesia in the earlier-time of the neuropathic pain, but TrkA receptors may be involved in the long-lasting adaptive changes of the central pathway in neuropathic pain.

Aloin attenuates chronic constriction injury-induced neuropathic pain in rats by inhibiting inflammatory cytokines and oxidative stress

Objective:To investigate the effect of aloin against chronic constriction injury(CCI)-induced neuropathic pain in rats.Methods:Rats were randomly divided into 7 groups:GroupⅠ(normal control),GroupⅡ(sham-operated),GroupⅢ(CCI control)and GroupⅣ,Ⅴ,Ⅵ,andⅦ,which underwent CCI surgery and then were administered with aloin(5 mg/kg,p.o.;25 mg/kg,p.o.;125 mg/kg,p.o.)and gabapentin(50 mg/kg,p.o.),respectively for 14 days.Peripheral neuropathy was induced by silk ligatures(4-0)loosely placed around the sciatic nerve.Nociceptive thresholds against mechanical stimuli(Von-Frey filaments)and thermal stimuli(12℃and 40℃)were measured at midplantar paw region ipsilateral to the compressed nerve on day-3,7,11,and 14.The concentration of cytokines including tumor necrosis factor-α(TNF-α),interleukin-6,and interleukin-1βwas estimated at day-7.At day 14,motor nerve conduction velocity was determined under urethane anesthesia(1.25 g/kg).Oxidative stress parameters(malondiadehyde,glutathione,catalase,and superoxide dismutase)were estimated in sciatic nerve homogenates at day 14.Representative nerve samples were processed for histological investigations.Results:Aloin significantly reduced CCI-induced mechanical and thermal allodynia.It also improved motor nerve conduction velocity and decreased oxidative stress in nerve tissues.In addition,it decreased pro-inflammatory cytokine levels and restored the histoarchitecture of compressed sciatic nerve.Conclusions:Aloin mitigates CCI-induced neuropathic pain in rats by inhibiting oxidative stress and pro-inflammatory cytokines in the afflicted sciatic nerve.

Skeletal muscle stiffness as measured by magnetic resonance elastography after chronic spinal cord injury:a cross-sectional pilot study

Skeletal muscle stiffness is altered after spinal cord injury(SCI).Assessing muscle stiffness is essential for rehabilitation and pharmaceutical interventions design after SCI.The study used magnetic resonance elastography to assess the changes in stiffness after chronic SCI compared to matched able-bodied controls and determine its association with muscle size,spasticity,and peak torque in persons with SCI.Previous studies examined the association between muscle stiffness and spasticity,however,we are unaware of other studies that examined the effects of muscle composition on stiffness after SCI.Ten participants(one female)with chronic SCI and eight(one female)matched able-bodied controls participated in this cross-sectional study.Magnetic resonance elastography was utilized to monitor stiffness derived from shear waves propagation.Modified Ashworth scale was used to evaluate spasticity scores in a blinded fashion.Peak isometric and isokinetic torques were measured using a biodex dynamometer.Stiffness values were non-significantly lower(12.5%;P=0.3)in the SCI group compared to able-bodied controls.Moreover,stiffness was positively related to vastus lateralis whole muscle cross-sectional area(CSA)(r2=0.64,P<0.005)and vastus lateralis absolute muscle CSA after accounting for intramuscular fat(r2=0.78,P<0.0007).Stiffness was also positively correlated to both isometric(r2=0.55-0.57,P<0.05)and isokinetic peak(r2=0.46-0.48,P<0.05)torques.Our results suggest that larger clinical trial is warranted to confirm the preliminary findings that muscle stiffness is altered after SCI compared to healthy controls.Stiffness appeared to be influenced by infiltration of intramuscular fat and modestly by the spasticity of the paralyzed muscles.The preliminary data indicated that the relationship between muscle stiffness and peak torque is not altered with changing the frequency of pulses or angular velocities.All study procedures were approved by the Institutional Review Board at the Hunter Holmes McGuire VA Medical Center,USA(IRB#:02314)on May 3,2017.

The triterpenoids-enriched extracts from Antrodia cinnamomea mycelia attenuate alcohol-induced chronic liver injury via suppression lipid accumulation in C57BL/6 mice

The major pathologic hallmark of the alcoholic liver disease(ALD)is the representation of chronic alcohol-induced hepatocyte lipid accumulation.This study aims to investigate the hepatoprotective role of triterpenoids-enriched extracts from Antrodia cinnamomea mycelia(ACT)in chronic alcohol-induced liver injury mice,establishing in C57BL/6 mice through gradient alcohol feeding for 24 weeks.In longterm alcohol consumption mice,the significantly lost body weight,increased organ indexes,hepatic alanine aminotransferase and aspartate aminotransferase levels were all remissed after 6-week ACT orally administration,showing its hepatoprotective property.ACT suppressed the triglyceride,total cholesterol and low-density lipoprotein levels,and enhanced high-density lipoprotein levels in serum or/and liver of chronic alcohol damaged mice.Combining with the pathological observations,ACT displayed an anti-steatosis effects to restrain the progress of ALD.Based on proteomic analysis and enzyme-linked immunosorbent assay,ACT had been confi rmed to regulate the levels of lipid biogeneration-related factors and depressed the over-accumulation of hepatic reactive oxygen species.According to further data,ACT prevented alcoholic liver injury may be associated with mediating lipid metabolism-related to PGC-1αand NF-κB signaling.In summary,ACT protected the body against chronic alcohol ingest induced liver injury through its regulation lipid on metabolism.

The prospects of regenerative medicine combined with rehabilitative approaches for chronic spinal cord injury animal models

Regenerative medicine has opened a window for functional recovery in acute-to-subacute phase spinal cord injury（SCI）.By contrast,there are still only a few studies have focused on the treatment of the chronically injured spinal cord,in which cell-based regenerative medicine seems less effective.Since the majority of SCI patients are in the chronic phase,representing a major challenge for the clinical application of cellbased regenerative medicine.Although combined therapies for the treatment of chronic SCI have attracted attention of researchers and its potential importance is also widely recognized,there had been very few studies involving rehabilitative treatments to date.In a recent study,we have demonstrated for the first time that treadmill training combined with cell transplantation significantly promotes functional recovery even in chronic SCI,not only in additive but also in synergistic manner.Even though we have succeeded to outline the profiles of recovery secondary to the combination therapy,the mechanism underlying the effects remain unsolved.In this review article,we summarize the present progress and consider the prospect of the cell-based regenerative medicine particularly combined with rehabilitative approaches for chronic SCI animal models.

Future directions for using estrogen receptor agonists in the treatment of acute and chronic spinal cord injury

All synthetic and natural estrogen receptor agonists, in- cluding the most potent physiological molecule estrogen or estradiol （E2）, work typically via activation of nuclear estrogen receptor alpha （ERα） and estrogen receptor beta （ERβ）. Both ERα and ERβ modulate the expression of a variety of genes in the cells. Neurons and glial cells express ERa and ERβ. Many studies so far from our and other laboratories have firmly established the mode of actions that ERα and ERβ agonists are very promising anti-inflammatory and neuroprotective agents in the treatment of neurodegenera- rive diseases and injuries including spinal cord injury （SCI） （Chakrabarti et al., 2014a）.

Mori fructus aqueous extracts attenuates liver injury by inhibiting ferroptosis via the Nrf2 pathway

Background Liver fibrosis and hepatocellular carcinogenesis secondary to liver fibrosis are serious liver diseases with no effective treatments.Mori fructus aqueous extracts(MFAEs)have served as successful treatments for many types of liver injury including fibrosis although the molecular mechanisms are unknown at present.Purpose To investigate the effect of MFAEs in alleviating acute and chronic liver injury and tried to decipher the underlying mechanism.Methods and results Mice were divided into 5 groups(n ps:contro=8)for acute(groups:control,0.3%CCl_(4),bifendate(BD),100 and 200 mg/kg MFAEs,7 d)and chronic(groul,10%CCl_(4),BD,100 and 200 mg/kg MFAEs,4 weeks)liver injury study.Each mouse was injected intraperitoneally with 10μL/g corn oil containing CCl_(4)expect the control group.HepG2 cells were used in vitro study.Eighteen communal components were identified by UPLC-LTQOrbitrap-MS.We utilized a mouse model for acute and chronic liver injury using CCl_(4)and MFAEs administration effectively blocked fibrosis and significantly inhibited inflammation in the liver.MFAEs activated the nuclear factor erythroid derived 2 like 2/heme oxygenase 1(Nrf2/HO-1)pathway and promoted the synthesis of the antioxidants glutathione(GSH),superoxidedismutase(SOD)and glutathione peroxidase(GSH-Px)that resulted in reduced levels of CCl_(4)-induced oxidative stress molecules including reactive oxygen species.These extracts administered to mice also inhibited ferroptosis in the liver by regulating the expression of Acyl-CoA synthetase long chain family member 4(ACSL4),solute carrier family 7 member 11(SLC7A11)and glutathione peroxidase 4(GPX4),thus reducing the occurrence of liver fibrosis.Both in vivo and in vitro tests indicated that the mechanism of MFAEs protection against liver fibrosis was linked to activation of Nrf2 signaling.These effects were blocked in vitro by the addition of a specific Nrf2 inhibitor.Conclusion MFAEs inhibited oxidative stress,ferroptosis and inflammation of the liver by activating Nrf2 signal pathway and provided a significant protective effect against CCl_(4)-induced liver fibrosis.

Animal model of repetitive mild traumatic brain injury for human traumatic axonal injury and chronic traumatic encephalopathy

Chronic traumatic encephalopathy（CTE）is a chronic neurodegenerative disease featured with tauopathy.CTE is tightly related with repetitive mild traumatic brain injury（m TBI）,which is interchangeably known as concussion（Mc Kee et al.,2009,2013）.This disease is differentiated by neuropathological features from other neurological diseases that involve tau protein aggregation and tangle formation abnormalities like Alzheimer＇s disease （AD）, frontotemporal dementia, and Parkinson- ism linked to chromosome 17 （FTDP-17）.

Post-Concussion Syndrome after a Mild Traumatic Brain Injury: A Minefield for Clinical Practice

In this clinical practice review, the controversies and difficulties managing post concussion symptoms following mild traumatic brain injury are discussed. Based on considerable clinical experience in a designated Concussion Clinic, the authors (a neuropsychologist, a psychiatrist, and a neurologist) review relevant literature and issues for clinical practice, particularly with respect to understanding risk factors for and vulnerability to, development of chronic post-concussion symptoms. We contend it is not just the kind of head that matters but also the kind of complications, the kind of outcomes and the kind of management that can influence injury recovery. Given these complexities, a bio-psychosocial conceptualization of chronic post-concussion syndrome is appropriate. Though understanding is still elusive, management should not be biased by physiogenic or psychogenic aetiological theories for management needs to address patient reported outcomes regardless of underpinning aetiology.

Microencapsulation improves inhibitory effects of transplanted olfactory ensheathing cells on pain after sciatic nerve injury

Olfactory bulb tissue transplantation inhibits P2X2/3 receptor-mediated neuropathic pain. However, the olfactory bulb has a complex cellular composition, and the mechanism underlying the action of purified transplanted olfactory ensheathing cells（OECs） remains unclear. In the present study, we microencapsulated OECs in alginic acid, and transplanted free and microencapsulated OECs into the region surrounding the injured sciatic nerve in rat models of chronic constriction injury. We assessed mechanical nociception in the rat models 7 and 14 days after surgery by measuring paw withdrawal threshold, and examined P2X2/3 receptor expression in L4–5 dorsal root ganglia using immunohistochemistry. Rats that received free and microencapsulated OEC transplants showed greater withdrawal thresholds than untreated model rats, and weaker P2X2/3 receptor immunoreactivity in dorsal root ganglia. At 14 days, paw withdrawal threshold was much higher in the microencapsulated OEC-treated animals. Our results confirm that microencapsulated OEC transplantation suppresses P2X2/3 receptor expression in L4–5 dorsal root ganglia in rat models of neuropathic pain and reduces allodynia, and also suggest that transplantation of microencapsulated OECs is more effective than transplantation of free OECs for the treatment of neuropathic pain.

Altered leukocyte gene expression after traumatic spinal cord injury:clinical implications

In addition to changes in motor and sensory function, individuals with spinal cord injury （SCI） experience immunological changes. These changes are clinically significant, as infections are the leading cause of death for this population. Along with increased infections, inflammation is commonly observed in persons with SCI, where it may promote many common medical consequences. These include elevated risk of cardio- vascular disease, impaired wound healing, diabetes and neuropathic pain. It has also been proposed that chronic inflammation dampens neurological recovery. In order to identify therapeutic strategies to im- prove immune function, we need a greater understanding of the molecular changes that occur in immune cells after SCI. The purpose of this mini-review is to discuss two recent studies that used functional genom- ics to investigate gene expression in circulating leukocytes isolated from persons with SCI. In the future, the molecular pathways that are altered after SCI may be targeted to improve immunological function, as well as overall health and functional recovery, after SCI.

Effect of Pulsed Radiofrequency on Rat Sciatic Nerve Chronic Constriction Injury： A Preliminary Study

Background：Pulsed radiofrequency （PRF） application to the dorsal root ganglia can reduce neuropathic pain （NP） in animal models,but the effect of PRF on damaged peripheral nerves has not been examined.We investigated the effect of PRF to the rat sciatic nerve （SN） on pain-related behavior and SN ultrastructure following chronic constriction injury （CCI）.Methods：The analgesic effect was measured by hindpaw mechanical withdrawal threshold （MWT） and thermal withdrawal latency （TWL）.Twenty rats with NP induced by ligating the common SN were then randomly divided into a PRF treatment group and a sham group.The contralateral SN served as a control.The MWT and TWL were determined again 2,4,6,8,10,12,and 14 days after the PRF or sham treatment.On day 14,ipsilateral and contralateral common SNs were excised and examined by electron microscopy.Results：Ipsilateral MWT was significantly reduced and TWL significantly shorter compared to the contralateral side 14 days after CCI （both P =0.000）.In the PRF group,MWT was significantly higher and TWL significantly longer 14 days after the PRF treatment compared to before PRF treatment （both P =0.000）,while no such difference was observed in the sham group （P ＞ 0.05）.Electron microscopy revealed extensive demyelination and collagen fiber formation in the ipsilateral SN of sham-treated rats but sparse demyelination and some nerve fiber regrowth in the PRF treatment group.Conclusions：Hyperalgesia is relieved,and ultrastructural damage ameliorated after direct PRF treatment to the SN in the CCI rat model of NP.

Radial shock wave therapy in the treatment of chronic constriction injury model in rats： a preliminary study

Background Pain physicians pay close attention to neuropathic pain （NP）,since there is currently no ideal treatment.Radial shock wave therapy （RSWT） is a noninvasive treatment to chronic pain of soft tissue disorders.So far,there is no information on the use of RSWT for the treatment of NP.Therefore we observe the effects of RSWT on a NP model induced by chronic constriction injury （CCI） in rats.Methods Four different energy densities （1.0,1.5,2.0 and 2.5 bar） RSWT administered as a single session or repeated sessions in rats with NP induced by CCI of the sciatic nerve.The analgesic effect was assessed by measuring mechanical withdrawal threshold （MWT） and thermal withdrawal latency （TWL）.The safety was assessed through calculating sciatic functional index （SFI）.Results MWT and TWL increased after a single session of RSWT from day 1 to day 5 but retumed to baseline levels by day 10.Following repeated sessions of RSWT,both the MWT and TWL were significantly higher than NP group （P ＜ 0.01）for at least 4 weeks.In addition,no significant changes of SFI were observed in any groups after repeated sessions of RSWT and no increased pain or other side effects in any animals.Conclusions A single session of RSWT is rapidly effective in the treatment of CCI,but the efficacy maintained in a short period.However,repeated sessions of RSWT have prolonged efficacy.

Transforming growth factor beta 1, a cytokine with regenerative functions

We review the biology and role of transforming growth factor beta 1 （TGF-β1） in peripheral nerve injury and regeneration, as it relates to injuries to large nerve trunks （i.e., sciatic nerve, brachial plexus）, which often leads to suboptimal functional recovery. Experimental studies have suggested that the reason for the lack of functional recovery resides in the lack of sufficient mature axons reaching their targets, which is a result of the loss of the growth-supportive environment provided by the Schwann cells in the distal stump of injured nerves. Using an established chronic nerve injury and delayed repair animal model that accu- rately mimics chronic nerve injuries in humans, we summarize our key findings as well as others to better understand the pathophysiology of poor functional recovery. We demonstrated that 6 month TGF-β1 treat- ment for chronic nerve injury significantly improved Schwann cell capacity to support axonal regeneration. When combined with forskolin, the effect was additive, as evidenced by a near doubling of regenerated axons proximal to the repair site. We showed that in vivo application of TGF-β1 and forskolin directly onto chronically injured nerves reactivated chronically denervated Schwann cells, induced their proliferation, and upregulated the expression of regeneration-associated proteins. The effect of TGF-β1 and forskolin on old nerve injuries is quite impressive and the treatment regiment appears to mediate a growth-supportive milieu in the injured peripheral nerves. In summary, TGF-β1 and forskolin treatment reactivates chronical- ly denervated Schwann cells and could potentially be used to extend and prolong the regenerative responses to promote axonal regeneration.

Molecular mechanisms underlying the effects of acupuncture on neuropathic pain

Acupuncture has been used to treat neuropathic pain for a long time, but its mechanisms of action remain unknown. In this study, we observed the effects of electroacupuncture and manual acu- puncture on neuropathic pain and on ephrin-B/EphB signaling in rats models of chronic constriction injury-induced neuropathic pain. The results showed that manual acupuncture and electroacu- puncture significantly reduced mechanical hypersensitivity following chronic constriction injury, es- pecially electroacupuncture treatment. Real-time PCR results revealed that ephrin-B1/B3 and EphB1/B2 mRNA expression levels were significantly increased in the spinal dorsal horns of chronic constriction injury rats. Electroacupuncture and manual acupuncture suppressed the high expres- sion of ephrin-B1 mRNA, and elevated EphB3/B4 mRNA expression. Electroacupuncture signifi- cantly enhanced the mRNA expression of ephrin-B3 and EphB3/B6 in the dorsal horns of neuro- pathic pain rats. Western blot results revealed that electroacupuncture in particular, and manual acupuncture, significantly up-regulated ephrin-B3 protein levels in rat spinal dorsal horns. The re- sults of this study suggest that acupuncture could activate ephrin-B/EphB signaling in neuropathic pain rats and improve neurological function.

Low-Frequency Electroacupuncture Alleviates Chronic Constrictive Injury-Induced Mechanical Allodynia by Inhibiting NR2B Upregulation in Ipsilateral Spinal Dorsal Horn in Rats

Objective: To study the effects of electroacupuncture(EA) in chronic constrictive injury(CCI) rat model and the expression of N-methyl-D-aspartate receptor type 2B(NR2B) in ipsilateral spinal dorsal horn in rats to explore the analgesic mechanisms of EA. Methods: According to the random number table, totally 180 rats were evenly divided into a sham group, a CCI group, and an EA group. CCI model was conducted with four4–0 chromic gut ligatures loosely ligated around the left sciatic nerve 1 cm above the trifurcation. Rats in the EA group received 2 Hz EA therapy bilaterally at acupoints of Zusanli(ST 36) and Sanyinjiao(SP 6) once daily(30 min/d) for 30 days after surgery. Paw withdrawal thresholds(PWTs) were measured on 0(baseline), 1, 3, 7, 15,30 days after surgery. Rats were sacri?ced on 0, 1, 3, 7, 15 and 30 days after surgery, and the L4–5 segments of spinal cord were removed to detect the expression of NR2B by immunohistochemistry and quantitative polymerase chain reaction. Results: PWTs in the CCI group were signi?cantly lower than the sham group at Day1–30 after surgery, and reached its lowest at Day 1(P<0.01). After EA treatment, the PWTs recovered rapidly and were signi?cantly higher than those in the CCI group on 3, 7, 15 and 30 days after surgery(P<0.01). The numbers of NR2B-immunoreactive cells of the CCI group signi?cantly increased after CCI surgery compared with the sham group(P<0.01). Compared with the CCI group, stimulation of EA markedly decreased the numbers of NR2B-immunoreactive cells at Day 3, 7, 15 and 30(P<0.05). In the sham group, NR2B mRNA was expressed at a low level. It increased after CCI surgery, which increased rapidly at Day 7(P<0.01) and reached its peak value at Day 15(P<0.01). After EA stimulation, relative quantity of NR2B mRNA expression was less than that in the CCI group at Day 15 and 30(P<0.05). Conclusions: Low frequency of EA had antinociceptive effect in CCI rat model. The analgesic effects of EA might be through the inhibition of NR2B.

Estrogen affects neuropathic pain through upregulating N-methyl-D-aspartate acid receptor 1 expression in the dorsal root ganglion of rats

Estrogen affects the generation and transmission of neuropathic pain,but the specific regulatory mechanism is still unclear.Activation of the N-methyl-D-aspartate acid receptor 1（NMDAR1） plays an important role in the production and maintenance of hyperalgesia and allodynia.The present study was conducted to determine whether a relationship exists between estrogen and NMDAR1 in peripheral nerve pain.A chronic sciatic nerve constriction injury model of chronic neuropathic pain was established in rats.These rats were then subcutaneously injected with 17β-estradiol,the NMDAR1 antagonist D（-）-2-amino-5-phosphonopentanoic acid（AP-5）,or both once daily for 15 days.Compared with injured drug na？ve rats,rats with chronic sciatic nerve injury that were administered estradiol showed a lower paw withdrawal mechanical threshold and a shorter paw withdrawal thermal latency,indicating increased sensitivity to mechanical and thermal pain.Estrogen administration was also associated with increased expression of NMDAR1 immunoreactivity（as assessed by immunohistochemistry） and protein（as determined by western blot assay） in spinal dorsal root ganglia.This 17β-estradiol-induced increase in NMDAR1 expression was blocked by co-administration with AP-5,whereas AP-5 alone did not affect NMDAR1 expression.These results suggest that 17β-estradiol administration significantly reduced mechanical and thermal pain thresholds in rats with chronic constriction of the sciatic nerve,and that the mechanism for this increased sensitivity may be related to the upregulation of NMDAR1 expression in dorsal root ganglia.