Li-Min Zhang

Sevoflurane post-conditioning protects primary rat cortical neurons against oxygen-glucose deprivation/resuscitation via down-regulation in mitochondrial apoptosis axis of Bid, Bim, Puma-Bax and Bak mediated by Erk1/2.

Temporal post-conditioning helps provide neuroprotection against brain injury secondary to ischemia-reperfusion and is considered an effective intervention, but the exact mechanism of sevoflurane post-conditioning is unclear. The essential axis involves activator Bid, Bim, Puma (BH3s), Bax, and Bak; activates the mitochondrial death program; and might be involved in a cell death signal. Extracellular signal-related kinases 1/2 (Erk1/2) play a pivotal role in cell growth and proliferation. We hypothesized that sevoflurane post-conditioning might inhibit Bid, Bim, Puma, Bax, and Bak expression and is activated by phosphor-Erk1/2 to decrease neuronal death. To test this hypothesis, we exposed primary cortical neuron cultures to oxygen-glucose deprivation for 1h, along with resuscitation for 24h (OGD/R). MTT assays, propidium iodide uptake (PI), JC-1 fluorescence, and Western blot indicated the following: decreased cell viability (P<0.05); increased cell death (P<0.05); decreased mitochondrial membrane potential (P<0.05); and decreased Bid, Bim, Puma, Bax, and Bak expression with OGD/R exposure. Inhibition of Erk1/2 phosphorylation could attenuate sevoflurane post-conditioning that mediated an increase in neuronal viability and mitochondrial membrane potential, as well as a decrease in cell death and Bid, Bim, Puma, Bax, and Bak expression after OGD/R treatment. The results demonstrated that sevoflurane post-conditioning caused a marked decrease in cortical neuronal death secondary to OGD/R exposure through the downregulation of the mitochondrial apoptosis axis involving Bid, Bim, Puma, Bax, and Bak that was mediated by the phosphorylation/activation of Erk1/2.

Isoflurane post-conditioning protects primary cultures of cortical neurons against oxygen and glucose deprivation injury via upregulation of Slit2/Robo1

Different mechanisms have been suggested to contribute to isoflurane-mediated neuroprotection. Previous studies have suggested that the protein Slit can abrogate neuronal death in mixed neuronal-glial cultures exposed to oxygen-glucose deprivation (OGD) and reperfusion (OGD/R). We hypothesized that isoflurane increases the expression of Slit and its receptor Robo when cortical neurons are exposed to OGD/R. To test this hypothesis, we exposed primary cortical neurons to OGD for 90 min and reperfusion for 24h and investigated how isoflurane post-conditioning affected cell survival and expression of Slit2 and receptors Robo1 and Robo4. Cell survival increased after administration of isoflurane, as assessed by the lactate dehydrogenase assay, trypan blue analysis, and propidium iodide staining. Western blot analysis showed that cleaved caspase-3 was increased after OGD/R(P<0.01) but reduced by isoflurane post-conditioning. Real-time PCR and Western blot analysis showed that the expression levels of Slit2 and Robo1, but not Robo4, were increased after OGD/R (P<0.5) and increased even further by isoflurane post-conditioning (P<0.01). Our results suggest that isoflurane post-conditioning markedly attenuates apoptosis and necrosis of cortical neurons exposed to OGD/R possibly in part via elevation of Slit2 and Robo1 expression. These findings provide a novel explanation for the pleiotropic effects of isoflurane that could benefit the central nervous system.

Erythropoietin rescues primary rat cortical neurons from pyroptosis and apoptosis via Erk1/2-Nrf2/Bach1 signal pathway

The most commonly used inhalation anesthetics, sevoflurane, is reported to be a risk for development of learning disability. Erythropoietin (EPO) administration might be involved an effective therapy for sevoflurane neurotoxicity. EPO-EPO receptor-extracellular signal-related kinases 1/2 (Erk1/2) signal pathway plays a pivotal role in the neuroprotective effect. Nuclear factor erythroid 2-related factor (Nrf2)/BTB and CNC homology 1 (Bach1) ratio altering by Erk1/2 could ameliorate oxidative stress occurred in human macrophages. Primary cortical neuron cultures exposed to sevoflurane were assessed for cleaved caspase-1, cleaved caspase-3, Nrf2, Bach1, total Erk1/2, and phosphorylated Erk1/2 with the following: 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT); propidium iodide uptake (PI); lactate dehydrogenase (LDH); malondialdehyde (MDA); superoxide dismutase (SOD); Real-time PCR; and Western blot. We found that sevoflurane exposure increased cell pyroptosis, apoptosis, injury, and MDA (n=9, P<0.05), but decreased cell viability (n=9, P<0.05) and down-regulated SOD (n=9, P<0.05), while EPO partially rescued the neurotoxicity induced by sevoflurane (n=9, P<0.05), as well as increase the expression of Nrf2 mRNA and Nrf2/Bach1 ratio (n=9, P<0.05). Inhibition of Erk1/2 phosphorylation via PD98059 reversed the protective effect of EPO (n=9, P<0.05). Thus, protection of EPO markedly attenuated pyroptosis and apoptosis of neurons exposed to sevoflurane via Erk1/2-Nrf2/Bach1 signal pathway.

Neuroprotective effects of erythropoietin against sevoflurane-induced neuronal apoptosis in primary rat cortical neurons involving the EPOR-Erk1/2-Nrf2/Bach1 signal pathway

OBJECTIVE Erythropoietin (EPO)-induced activation of the EPO receptor (EPOR) against sevoflurane-induced neuronal apoptosis is an effective intervention, but the underlying mechanism is poorly understood. Previous studies have shown that alteration of the nuclear factor erythroid 2-related factor (Nrf2)/BTB-to-CNC homology 1 (Bach1) ratio by extracellular signal-related kinases (Erk) 1/2 ameliorates the oxidative stress which occurs in human macrophages. In this study, we determined whether or not EPO attenuates sevoflurane-induced neuronal apoptosis via the EPOR-Erk1/2-Nrf2/Bach1 signal pathway. METHODS Primary rat cortical neurons were exposed to 4% sevoflurane for 6h. Neuronal viability, injury, apoptosis, and oxidative stress were assessed using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), lactate dehydrogenase (LDH), propidium iodide uptake (PI), malondialdehyde (MDA), and superoxide dismutase (SOD) assays. A real-time PCR assay was used to measure EPOR expression. Western blotting was used to assess Nrf2, Bach1, and heme oxygenase-1 (HO-1) expression. RESULTS Sevoflurane exposure increased cell apoptosis, injury, and MDA (P<0.05), but decreased cell viability and the Nrf2:Bach1 ratio (P<0.05), and down-regulated superoxide dismutase (SOD; P<0.05), while EPO partially rescued the neurotoxicity induced by sevoflurane (P<0.05). Inhibition of EPOR via EPO-specific monoclonal antibody or Erk1/2 phosphorylation via PD98059 reversed the protective effect of EPO (P<0.05). CONCLUSION The neuroprotective effects of EPO against sevoflurane-induced neuronal apoptosis in primary rat cortical neurons involves the EPOR-Erk1/2-Nrf2/Bach1 signal pathway.

Sevoflurane pre-conditioning increases phosphorylation of Erk1/2 and HO-1 expression via inhibition of mPTP in primary rat cortical neurons exposed to OGD/R

BACKGROUND As an indispensable clinical inhalation anesthetic, sevoflurane is widely used for peri-operative sedation. The neuroprotective effect of sevoflurane pre-conditioning against cerebral ischemia/reperfusion has been gradually realized, but the underlying mechanism during the early reperfusion period has not been established. METHOD Primary cultured cortical neurons were treated with 2% sevoflurane pre-conditioning for 30min, exposed to oxygen-glucose deprivation for 90min, and followed by 60min of reperfusion (OGD/R). Additionally, neuronal cells were treated with an inhibitor of extracellular signal-related kinases 1 and 2 (Erk1/2) phosphorylation (PD98059), a mPTP opener (atractyloside), or a mPTP opening inhibitor (cyclosporine A) before sevoflurane pre-conditioning. RESULT Sevoflurane pre-conditioning decreased neuronal apoptosis (assessed by TUNEL), oxidative stress (assessed by malondialdehyde [MDA], superoxide dismutase [SOD], and heme oxygenase [HO]-1), and opening of mitochondrial permeability transition pores [mPTPs] (assessed by calcein-cobalt), but increased neuronal viability (assessed by MTT) and mitochondrial membrane potential (assessed by JC-1) after OGD/R exposure compared with OGD/R treatment alone. Pre-treatment with the mPTP opener and inhibitor of Erk1/2 phosphorylation abolished the protective effect induced by sevoflurane pre-conditioning. Pre-treatment with the mPTP opener attenuated the phosphorylation of Erk1/2 in mitochondria of neuronal cultures exposed to OGD/R induced by sevoflurane pre-conditioning. The mPTP opening inhibitor, like sevoflurane pre-conditioning, increased phosphorylation of Erk1/2 after OGD/R exposure, while PD98059 failed to reverse inhibition of mPTP opening in cultures exposed to OGD/R induced by sevoflurane pre-conditioning. CONCLUSION The neuroprotective mechanism of sevoflurane pre-conditioning might be associated with increased Erk1/2 phosphorylation in mitochondria via inhibition of mPTP opening in the early reperfusion period.

Erythropoietin Rescues Primary Rat Cortical Neurons by Altering the Nrf2:Bach1 Ratio: Roles of Extracellular Signal-Regulated Kinase 1/2

While inhalation anesthetics are indispensable, and generally considered safe and effective, there is growing concern about the selective neurotoxicity of these agents, especially sevoflurane. Erythropoetin (EPO)-induced protection against sevoflurane-induced neuronal death is an effective intervention, but the underlying mechanism is poorly understood. Extracellular signal-related kinases (Erk) 1/2 plays a pivotal role in cell growth and proliferation. Alteration of the nuclear factor erythroid 2-related factor (Nrf2)/BTB-to-CNC homology 1 (Bach1) ratio by Erk1/2 ameliorates the oxidative stress which occurs in human macrophages. Primary cortical neuron cultures exposed to sevoflurane were assessed for Nrf2, Bach1, total Erk1/2, and phosphorylated Erk1/2 with the following: 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide; propidium iodide uptake; lactate dehydrogenase; malondialdehyde (MDA); superoxide dismutase (SOD); and Western blot. Sevoflurane exposure increased cell death, injury, and MDA (n = 9, P < 0.05), but decreased cell viability and the Nrf2:Bach1 ratio (n = 9, P < 0.05) and down-regulated SOD (n = 9, P < 0.05), while EPO partially rescued the neurotoxicity induced by sevoflurane (n = 9, P < 0.05). Inhibition of Erk1/2 phosphorylation via PD98059 reversed the protective effect of EPO (n = 9, P < 0.05). Thus, protection of EPO markedly attenuated death of neurons exposed to sevoflurane by altering the Nrf2:Bach1 ratio mediated by phosphorylation and activation of Erk1/2.

Increased Transfusion of Fresh Frozen Plasma is Associated with Mortality or Worse Functional Outcomes After Severe Traumatic Brain Injury: A Retrospective Study

BACKGROUND The fresh frozen plasma (FFP) transfusion threshold and timing for traumatic brain injury (TBI)-associated coagulopathy are controversial. Thus, a multicenter retrospective study was conducted to determine whether or not FFP transfusion is associated with poor outcomes after severe TBI. METHODS Data from decompressive craniotomy after blunt force trauma that took place between December 2013 and June 2016 were collected in a multicenter chart. The primary outcomes were mortality and survival, as well as worse outcomes (defined as a Glasgow Outcome Scale [GOS] score ≤3) and better outcomes (GOS score ≥4). Secondary outcomes included 90-day survival rates in all patients with or without FFP transfusion, as well as length of hospital stay in patients with a better prognosis (GOS score ≥4). Univariate analysis, bivariate logistic regression, Spearman rank correlation, and Kaplan-Meier analysis were performed to account for the association between perioperative FFP transfusion and different outcomes. RESULTS Bivariate logistic analysis showed that mortality and worse outcomes were correlated with FFP transfusion and Glasgow Coma Scale score (P < 0.05). Kaplan-Meier analysis suggested that mortality was statistically higher in the FFP transfusion groups compared with the no FFP transfusion groups, regardless of the severity of TBI (P < 0.05). The overall complications, acute respiratory distress syndrome, and pneumonia rate were significantly higher for patients receiving FFP transfusion (P < 0.05). CONCLUSIONS Increased perioperative FFP infusion was independently associated with mortality or worse outcomes across a spectrum of surgical risk profiles.

Increased Perioperative Crystalloid Transfusion Is Associated with Better Outcomes After Spontaneous Hypertensive Putamen Hemorrhage: A Retrospective Study

BACKGROUND The appropriate amount of transfused fluids, and which types of fluids should be transfused during the peri-operative period, is a matter of controversy among neurosurgeons. Thus, a retrospective study was conducted to assess whether crystalloid transfusion is associated with better outcomes after spontaneous hypertensive putamen hemorrhage (HPH). METHODS Data from acute spontaneous HPH surgeries performed between December 2013 and June 2016 were collected in a multi-center chart. The primary outcome was prognosis, with better outcome defined as a Glasgow outcome score (GOS) of 4 or greater. The secondary outcome was survival, with survival defined as a GOS score of 2 or greater. Univariate analysis and bivariate logistic regression were performed to account for the association between perioperative HPH and different outcomes. We also used Spearman rank correlation and linear regression to determine the correlation between length of stay (LOS) and the univariate analysis significant factors in patients with a GOS score of 4 or greater. RESULTS Bivariate logistic regression showed a marked correlation between better outcome and age (odds ratio [OR], 0.927; 95% confidence interval [CI], 0.851-0.995), Glasgow Coma Scale (GCS; OR, 1.162; 95% CI, 1.049-1.356), and crystalloid transfusion (OR, 1.083; 95% CI, 1.005-1.142). In addition, bivariate logistic regression also revealed a significant correlation between survival and GCS score (OR, 1.097; 95% CI, 1.056-1.199). In patients with a GOS of 4 or greater, Spearman rank correlation and linear regression suggested that a higher GCS score was more likely to prolong the LOS. CONCLUSION Increased perioperative crystalloid transfusion was independently associated with better outcome across a spectrum of surgical risk profiles after spontaneous HPH.