Hailong Dong

Preconditioning with hyperbaric oxygen and hyperoxia induces tolerance against spinal cord ischemia in rabbits.

Background The aim of this study was to determine if the ischemic tolerance could be induced in the spinal cord by pretreatment with hyperbaric oxygen (HBO) and what components of HBO (hyperoxia, hyperbaricity, and combination of these two) were critical in the induction of tolerance against ischemic injury. Methods In experiment 1, 21 rabbits were randomly assigned to one of three groups (n = 7 each): animals in the control group received no HBO before spinal cord ischemia; animals in the HBO-1 and HBO-2 groups received HBO (2.5 atmosphere absolute [ATA], 100% O2) pretreatment 1 h/day for 3 and 5 days before ischemia, respectively. In experiment 2, 48 rabbits were randomly assigned to one of four groups (n = 12 each): the control group received no HBO (21% O2, 1 ATA, 1 h/day, 5 days) before spinal cord ischemia; the HB group received 1-h treatment in 21% O2 at 2.5 ATA each day for 5 days; the HO group received 1-h treatment in 100% oxygen at 1 ATA each day for 5 days; and the HBO group received HBO (2.5 ATA, 100% O2) treatment 1 h/day for 5 days. Twenty-four hours after the last treatment, spinal cord ischemia was induced by an infrarenal aorta clamping for 20 min. Forty-eight hours after reperfusion, hind-limb motor function and histopathology of the spinal cord were examined in a blinded fashion. Results In experiment 1, the neurologic outcome in the HBO-2 group was better than that of the control group (P = 0.004). The number of normal neurons in the anterior spinal cord in the HBO-2 group was more than that of the control group (P = 0.021). In experiment 2, the neurologic and histopathologic outcomes in the HBO group were better than that of the control group (P < 0.01). The histopathologic outcome in the HO group was better than that in the control group (P < 0.05). Conclusions Serial exposure to high oxygen tension induced ischemic tolerance in spinal cord of rabbits. Simple hyperbaricity (2.5 ATA, 21% O2) did not induce ischemic tolerance.

A feed-forward spinal cord glycinergic neural circuit gates mechanical allodynia

Neuropathic pain is characterized by mechanical allodynia induced by low-threshold myelinated Aβ-fiber activation. The original gate theory of pain proposes that inhibitory interneurons in the lamina II of the spinal dorsal horn (DH) act as gate control units for preventing the interaction between innocuous and nociceptive signals. However, our understanding of the neuronal circuits underlying pain signaling and modulation in the spinal DH is incomplete. Using a rat model, we have shown that the convergence of glycinergic inhibitory and excitatory Aβ-fiber inputs onto PKCγ+ neurons in the superficial DH forms a feed-forward inhibitory circuit that prevents Aβ input from activating the nociceptive pathway. This feed-forward inhibition was suppressed following peripheral nerve injury or glycine blockage, leading to inappropriate induction of action potential outputs in the nociceptive pathway by Aβ-fiber stimulation. Furthermore, spinal blockage of glycinergic synaptic transmission in vivo induced marked mechanical allodynia. Our findings identify a glycinergic feed-forward inhibitory circuit that functions as a gate control to separate the innocuous mechanoreceptive pathway and the nociceptive pathway in the spinal DH. Disruption of this glycinergic inhibitory circuit after peripheral nerve injury has the potential to elicit mechanical allodynia, a cardinal symptom of neuropathic pain.

Noninvasive limb remote ischemic preconditioning contributes neuroprotective effects via activation of adenosine A1 receptor and redox status after transient focal cerebral ischemia in rats

PURPOSESnTo investigate whether activation of adenosine A1 receptor (A1R) through limb remote ischemic preconditioning (RIPC) by a noninvasive tourniquet contribute neuroprotective effects against rat focal cerebral ischemic injury induced by transient middle cerebral artery occlusion (MCAO).nnnMETHODSnOne hundred twenty-eight Sprague-Dawley (SD) rats were randomly assigned into eight groups (n=16 each): MCAO, Control, 8-cyclopentyl-1,3-dipropulxanthine (DPCPX, Adenosine A1 receptor antagonist), RIPC, DPCPX+RIPC, Vehicle+RIPC, 2-chloro-N(6)-cyclopentyladenosine (CCPA, Adenosine A1 receptor agonist) and CCPA+DPCPX groups. All animals underwent right middle cerebral artery occlusion (MCAO) for 2 h. Limb RIPC consisted of three cycles of 5-minute ischemia followed by 5-minute reperfusion in right hind-limb by tourniquet application. Neurological deficit scores were evaluated 24 h after reperfusion, and then the infarct volume was assessed with diffusion weighted imaging (DWI) and 2, 3, 5-triphenyltetrazolium chloride (TTC) staining. Inflammation was assessed by serum tumor necrosis factor α (TNF(α)) and NO; oxidative stress was estimated by malondialdehyde (MDA) and 4-hydroxyalkenals (4-HAD), superoxide dismutase (SOD) activity and GSH.nnnRESULTSnAnimals in the RIPC, Vehicle+RIPC and CCPA groups developed lower neurological deficit scores and smaller brain infarct volumes than the Control group (P<0.01). Animals in the DPCPX, DPCPX+RIPC and CCPA+DPCPX groups developed higher neurological deficit scores and larger brain infarct volumes than the RIPC, Vehicle+RIPC and CCPA groups (P<0.01). DPCPX abolished the protective effects of RIPC and CCPA. RIPC or CCPA induced a significant increase in brain MnSOD (manganese SOD) activity and NO generation, and this activity was abolished by DPCPX pretreatment. RIPC or CCPA induced a significant reduction (P<0.05) in the GSH and MDA+4HDA concentration and an accumulation in the GSSG concentration in both compartments (serum and tissue) as compared with the MCAO group.nnnCONCLUSIONSnThe present study demonstrates that limb RIPC induced by noninvasive tourniquet reduces cerebral ischemic injury in rats, and the effect of neuroprotection may depend on the activation of adenosine A1 receptors. CCPA pretreatment can induce delayed ischemic tolerance against cerebral ischemia/reperfusion injury. These protective effects are associated with a reduction in oxidative stress, inflammation and endogenous antioxidant preservation.

Effects of remote ischemic preconditioning on biochemical markers and neurologic outcomes in patients undergoing elective cervical decompression surgery: a prospective randomized controlled trial.

Background Remote ischemic preconditioning (RIPC) may protect the spinal cord from ischemic injury. This randomized clinical trial was designed to assess whether a large clinical trial testing the effect of RIPC on neurologic outcome in patients undergoing spine surgery is warranted. This trial was registered with ClinicalTrials.gov, number NCT00778323. Methods Forty adult cervical spondylotic myelopathy patients undergoing elective decompression surgery were randomly assigned to either the RIPC group (n=20) or the control group (n=20). Limb RIPC consisted of three 5-minutes cycles of upper right limb ischemia with intervening 5-minute periods of reperfusion. Neuron-specific enolase and S-100B levels were measured in serum at set time points. Median nerve somatosensory-evoked potentials (SEPs) were also recorded. Neurologic recovery rate was evaluated using a Japanese Orthopaedic Association scale. Results RIPC significantly reduced serum S-100B release at 6 hours and 1 day after surgery, and reduced neuron-specific enolase release at 6 hours, and then at 1, 3, and 5 days after surgery. No differences were observed in SEP measurements or the incidence of SEP changes during surgery between the control and RIPC groups. Recovery rate at 7 days, and at 1 and 3 months after surgery was higher in the RIPC group than in the control group (P<0.05). Conclusions Our results for markers of neuronal ischemic injury and rate of recovery suggest that a clinical trial with sufficient statistical power to detect an effect of RIPC on the incidence of neurologic complications (paresis, palsy, etc) due to spinal cord ischemia-reperfusion injury after spine surgery.

Protective Effect of Delayed Remote Limb Ischemic Postconditioning: Role of Mitochondrial KATP Channels in a Rat Model of Focal Cerebral Ischemic Reperfusion Injury

Delayed remote ischemic postconditioning (DRIPost) has been shown to protect the rat brain from ischemic injury. However, extremely short therapeutic time windows hinder its translational use and the mechanism of action remains elusive. Because opening of the mitochondria KATP channel is crucial for cell apoptosis, we hypothesized that the neuroprotective effect of DRIPost may be associated with KATP channels. In the present study, the neuroprotective effects of DRIPost were investigated using adult male Sprague-Dawley rats. Rats were exposed to 90 minutes of middle cerebral artery occlusion followed by 72 hours of reperfusion. Delayed remote ischemic postconditioning was performed with three cycles of bilateral femoral artery occlusion/reperfusion for 5 minutes at 3 or 6 hours after reperfusion. Neurologic deficit scores and infarct volumes were assessed, and cellular apoptosis was monitored by terminal deoxynucleotidyl transferase nick-end labeling. Our results showed that DRIPost applied at 6 hours after reperfusion exerted neuroprotective effects. The KATP opener, diazoxide, protected rat brains from ischemic injury, while the KATP blocker, 5-hydroxydecanote, reversed the neuroprotective effects of DRIPost. These findings indicate that DRIPost reduces focal cerebral ischemic injury and that the neuroprotective effects of DRIPost may be achieved through opening of KATP channels.

Neuroprotective effect of orexin-A is mediated by an increase of hypoxia-inducible factor-1 activity in rat.

Background:Recent studies suggest that the novel neuropeptide orexin-A may play an essential role during neuronal damage. However, the function of orexin-A during brain ischemia remains unclear. Recently, hypoxia-inducible factor-1&agr; (HIF-1&agr;) was shown to be activated by orexin-A. The aim of the current study is to test the hypothesis that administration of exogenous orexin-A can attenuate ischemia-reperfusion injury through the facilitation of HIF-1&agr; expression. Methods:Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion for 120 min. Rats were treated with different doses of orexin-A or vehicle before the ischemia and at the onset of reperfusion. To investigate the action of HIF-1&agr; in the neuroprotective effects of orexin-A, the HIF-1&agr; inhibitor YC-1 was used alone or combined with orexin-A. Neurologic deficit scores and infarct volume were assessed. Brains were harvested for immunohistochemical staining and western blot analysis. Results:Orexin-A significantly ameliorated neurologic deficit scores and reduced infarct volume after cerebral ischemia reperfusion. Administration of 30 &mgr;g/kg orexin-A showed optimal neuroprotective effects. This effect was still present 7 days after reperfusion. Furthermore, orexin-A decreased the number of apoptotic cells and significantly enhanced HIF-1&agr; expression after cerebral ischemia reperfusion. Moreover, the facilitation of HIF-1&agr; expression was accompanied with inhibition of von Hippel-Lindau expression. Administration of HIF-1&agr; inhibitor suppressed the increase of HIF-1&agr; and reversed the neuroprotective effects of orexin-A. Conclusions:Orexin-A has a neuroprotective effect against cerebral ischemia-reperfusion injury. These effects may be mediated through the HIF-1&agr; pathway.

Limb remote ischemic preconditioning protects the spinal cord from ischemia-reperfusion injury: a newly identified nonneuronal but reactive oxygen species-dependent pathway.

Background:It remains to be established whether spinal cord ischemic tolerance can be induced by limb remote ischemic preconditioning (RIPC), and the mechanisms underlying the neuroprotective effects of RIPC on the spinal cord need to be clarified. Methods:Spinal cord ischemia was studied in New Zealand White rabbits. In experiment 1, all rabbits were subjected to 20-min spinal cord ischemia by aortic occlusion. Thirty minutes before ischemia, rabbits were subjected to sham intervention or RIPC achieved by bilateral femoral artery occlusion (10 min ischemia/10 min reperfusion, two cycles). Dimethylthiourea (500 mg/kg, intravenously), a hydroxyl radical scavenger, or vehicle was given 1 h before RIPC. Antioxidant enzyme activity was measured along with spinal cord histology and neurologic function. In experiment 2, rabbits were subjected to spinal cord ischemia, with or without RIPC. In addition, rabbits were pretreated with various doses of hexamethonium. Results:RIPC improved neurologic function and reduced histologic damage. This was associated with increased endogenous antioxidant activity. Dimethylthiourea inhibited the protective effects of RIPC. In contrast, there was no effect of hexamethonium on the protective effect of RIPC. Conclusions:An initial oxidative stress acts as a trigger to upregulate antioxidant enzyme activity, rather than the neural pathway, and plays an important role in the formation of the tolerance against spinal cord ischemia by limb RIPC.

Transcutaneous electric acupoint stimulation reduces intra-operative remifentanil consumption and alleviates postoperative side-effects in patients undergoing sinusotomy: a prospective, randomized, placebo-controlled trial

BACKGROUNDnAlthough opioids are widely used as analgesics in general anaesthesia, they have unpleasant side-effects and can delay postoperative recovery. Acupuncture and related techniques are effective for acute and chronic pain, and reduces some side-effects. We assessed the effect of transcutaneous electric acupoint stimulation (TEAS) on intra-operative remifentanil consumption and the incidences of anaesthesia-related side-effects.nnnMETHODSnSixty patients undergoing sinusotomy were randomly assigned to TEAS or control group. TEAS consisted of 30 min of stimulation (6-9 mA, 2/10 Hz) on the Hegu (LI4), Neiguan (PC6), and Zusanli (ST36) before anaesthesia. The patients in the control group had the electrodes applied, but received no stimulation. Bispectral index was used to monitor the depth of anaesthesia. Perioperative haemodynamics were recorded, and peripheral blood samples were collected to measure the levels of mediators of surgical stress. The primary end point was intraoperative remifentanil consumption and the secondary endpoints were recovery quality and anaesthesia-related side-effects.nnnRESULTSnPatients in the TEAS group required 39% less remifentanil during surgery than controls [0.0907 (SD 0.026) μg kg(-1) min(-1) vs 0.051 (0.018) μg kg(-1) min(-1)]. There were no differences in intra-operative haemodynamics or surgical stress between groups. However, the time to extubation and recall in the control group was 16.8 (6.8) min and 23.0 (5.0) min, respectively, significantly longer than that in the TEAS group (P<0.01). TEAS also decreased the incidence of dizziness and pruritus within the first 24 h after surgery (P<0.01).nnnCONCLUSIONnThe use of TEAS significantly reduced intra-operative remifentanil consumption and alleviated postoperative side-effects in patients undergoing sinusotomy.nnnCLINICAL TRIAL REGISTRATIONnThe trial was registered at clinicaltrials.gov (NCT01700855).

Activation of canonical notch signaling pathway is involved in the ischemic tolerance induced by sevoflurane preconditioning in mice.

Background:A wealth of evidence has demonstrated that sevoflurane preconditioning induces brain ischemic tolerance, but the mechanism remains poorly understood. This study was designed to investigate the role of canonical Notch signaling in the neuroprotection induced by sevoflurane preconditioning in a mouse model. Methods:C57BL/6 mice were pretreated with 1-h sevoflurane exposure at a dose of 2.5% for 5 consecutive days. Twenty-four hours after the last exposure, all mice were subjected to focal cerebral ischemia by right middle cerebral artery occlusion for 60 min. Neurobehavioral scores, brain infarct volumes, and cellular apoptosis were determined at 72 h after reperfusion (n = 10 per group). The activation of Notch signaling was evaluated (n = 5 per group), and its role in ischemic tolerance was assessed by intraperitoneal administration of &ggr;-secretase inhibitor DAPT (100 mg/kg, n = 10 per group) and conditional Notch-RBP-J knockout technique (n = 8 per group). Results:Sevoflurane preconditioning reduced brain infarct volumes (42.5%), improved neurologic outcomes (P < 0.01 vs. control), and attenuated neuronal cell apoptosis (cells positive for terminal deoxynucleotidyl transferase-mediated 2′-deoxyuridine 5′-triphosphate nick-end labeling reduced to 21.2%). The expression of Notch1 intracellular domain (1.35 folds) and the transcriptions of Hes1 (1.95 times) and Hes5 (1.48 times) were up-regulated. DAPT augmented the brain infarcts (1.64-fold) and decreased neurologic scores (P = 0.43 vs. sevoflurane) in sevoflurane-preconditioned mice. Brain infarct volumes, neurobehavioral scores, and apoptotic cell numbers showed no significance between Notch knockout mice with sevoflurane preconditioning and wild-type mice without preconditioning. Conclusions:Sevoflurane preconditioning-induced protective effects against transient cerebral ischemic injuries are mediated by the activation of canonical Notch signaling pathway in mice.

Preconditioning With Repeated Hyperbaric Oxygen Induces Myocardial and Cerebral Protection in Patients Undergoing Coronary Artery Bypass Graft Surgery: A Prospective, Randomized, Controlled Clinical Trial

OBJECTIVESnTo evaluate the cerebral and myocardial protective effects of hyperbaric oxygen preconditioning in both on-pump and off-pump coronary artery bypass graft surgery.nnnDESIGNnA prospective, randomized, single-blinded study including patients scheduled for elective on-pump or off-pump surgery between December 2007 and February 2009.nnnSETTINGnA tertiary care university teaching hospital.nnnPARTICIPANTSnForty-nine elective on-pump or off-pump coronary artery bypass graft surgery patients.nnnINTERVENTIONSnPatients were randomized to either the control (15 patients with on-pump procedure and 10 patients with off-pump procedure, respectively) or hyperbaric oxygen (HBO; 14 patients with on-pump procedure and 10 patients with off-pump procedure, respectively) groups. Patients in the HBO groups underwent preconditioning for 5 days before surgery.nnnMEASUREMENTS AND MAIN RESULTSnOn-pump coronary artery bypass graft surgery patients preconditioned with HBO had significant decreases in S100B protein, neuron-specific enolase, and troponin I perioperative serum levels compared with the on-pump control group. Postsurgically, patients in the on-pump HBO group had a reduced length of stay in the intensive care unit and a decreased use of inotropic drugs. Serum catalase activity 24 hours postoperatively was significantly increased compared with the on-pump control group. In the off-pump groups, there was no difference in any of the same parameters.nnnCONCLUSIONSnPreconditioning with HBO resulted in both cerebral and cardiac protective effects as determined by biochemical markers of neuronal and myocardial injury and clinical outcomes in patients undergoing on-pump coronary artery bypass graft surgery. No protective effects were noted in off-pump coronary artery bypass graft surgery.