Female sex and ipsilateral reoperation risk following mesh-based inguinal hernia repair: a cohort study including 131,626 repairs in adults from an integrated healthcare system over a 10-year period

PURPOSE

We sought to compare females and males for the risk of reoperation following different inguinal hernia repair approaches (open, laparoscopic, and robotic).

METHODS

We conducted a retrospective cohort study including all patients aged ≥ 18 who underwent first inguinal hernia repair with mesh within a US integrated healthcare system (2010-2020). Data were obtained from the system's integrated electronic health record. Multiple Cox proportional-hazards regression was used to evaluate the association between sex and risk for ipsilateral reoperation during follow-up. Analysis was stratified by surgical approach (open, laparoscopic, and robotic).

RESULTS

The study cohort was comprised of 110,805 patients who underwent 131,626 inguinal hernia repairs with mesh, 10,079 (7.7%) repairs were in females. After adjustment for confounders, females had a higher risk of reoperation than males following open groin hernia repair (hazard ratio [HR] = 1.98, 95% CI 1.74-2.25), but a lower reoperation risk following laparoscopic repair (HR = 0.70, 95% CI 0.51-0.97). The crude 5-year cumulative reoperation probability following robotic repair was 2.8% in males and no reoperations were observed for females. Of females who had a reoperation, 10.3% (39/378) were for a femoral hernia, while only 0.6% (18/3110) were for femoral hernias in males.

CONCLUSION

In a large multi-center cohort of mesh-based inguinal hernia repair patients, we found a higher risk for reoperation in females after an open repair approach compared to males. Lower risk was observed for females through a minimally invasive approach (laparoscopic or robotic) and may be due to the ability to identify an occult femoral hernia through these approaches.

Risk factors for reoperation following inguinal hernia repair: results from a cohort of patients from an integrated healthcare system

PURPOSE

Inguinal hernia repair is one of the most common operations performed globally. Identification of risk factors that contribute to hernia recurrence following an index inguinal hernia repair, especially those that are modifiable, is of paramount importance. Therefore, we sought to investigate risk factors for reoperation following index inguinal hernia repair.

METHODS

125,133 patients aged ≥ 18 years who underwent their first inguinal hernia repair with mesh within a large US integrated healthcare system were identified for a cohort study (2010-2020). Laparoscopic, robotic, and open procedures were included. The system's integrated electronic health record was used to obtain data on demographics, patient characteristics, surgical characteristics, and reoperations. The association of these characteristics with ipsilateral reoperation during follow-up was modeled using Cox proportional-hazards regression. Risk factors were selected into the final model by stepwise regression with Akaike Information Criteria, which quantifies the amount of information lost if a factor is left out of the model. Factors associated with reoperation with p < 0.05 were considered statistically significant.

RESULTS

The cumulative incidence of reoperation at 5-year follow-up was 2.4% (95% CI 2.3-2.5). Increasing age, female gender, increasing body mass index, White race, chronic pulmonary disease, diabetes, drug abuse, peripheral vascular disease, and bilateral procedures all associated with a higher risk for reoperation during follow-up.

CONCLUSION

This study identifies several risk factors associated with reoperation following inguinal hernia repair. These risk factors may serve as targets for optimization protocols prior to elective inguinal hernia repair, with the goal of reducing reoperation risk.

Mesh-based inguinal hernia repairs in an integrated healthcare system and surgeon and hospital volume: a cohort study of 110,808 patients from over a decade

PURPOSE

The aim of this study was to describe a cohort of patients who underwent inguinal hernia repair within a United States-based integrated healthcare system (IHS) and evaluate the risk for postoperative events by surgeon and hospital volume within each surgical approach, open, laparoscopic, and robotic.

METHODS

Patients aged ≥ 18 years who underwent their first inguinal hernia repair were identified for a cohort study (2010-2020). Average annual surgeon and hospital volume were broken into quartiles with the lowest volume quartile as the reference group. Multiple Cox regression evaluated risk for ipsilateral reoperation following repair by volume. All analyses were stratified by surgical approach (open, laparoscopic, and robotic).

RESULTS

110,808 patients underwent 131,629 inguinal hernia repairs during the study years; procedures were performed by 897 surgeons at 36 hospitals. Most repairs were open (65.4%), followed by laparoscopic (33.5%) and robotic (1.1%). Reoperation rates at 5 and 10 years of follow-up were 2.4% and 3.4%, respectively; rates were similar across surgical groups. In adjusted analysis, surgeons with higher laparoscopic volumes had a lower reoperation risk (27-46 average annual repairs: hazard ratio [HR] = 0.63, 95% confidence interval [CI] 0.53-0.74; ≥ 47 repairs: HR 0.53, 95% CI 0.44-0.64) compared to those in the lowest volume quartile (< 14 average annual repairs). No differences in reoperation rates were observed in reference to surgeon or hospital volume following open or robotic inguinal hernia repair.

CONCLUSION

High-volume surgeons may reduce reoperation risk following laparoscopic inguinal hernia repair. We hope to better identify additional risk factors for inguinal hernia repair complications and improve patient outcomes with future studies.

Hypoxic preconditioning enhances neural stem cell transplantation therapy after intracerebral hemorrhage in mice

Previous studies have shown that intraparenchymal transplantation of neural stem cells ameliorates neurological deficits in animals with intracerebral hemorrhage. However, hemoglobin in the host brain environment causes massive grafted cell death and reduces the effectiveness of this approach. Several studies have shown that preconditioning induced by sublethal hypoxia can markedly improve the tolerance of treated subjects to more severe insults. Therefore, we investigated whether hypoxic preconditioning enhances neural stem cell resilience to the hemorrhagic stroke environment and improves therapeutic effects in mice. To assess whether hypoxic preconditioning enhances neural stem cell survival when exposed to hemoglobin, neural stem cells were exposed to 5% hypoxia for 24 hours before exposure to hemoglobin. To study the effectiveness of hypoxic preconditioning on grafted-neural stem cell recovery, neural stem cells subjected to hypoxic preconditioning were grafted into the parenchyma 3 days after intracerebral hemorrhage. Hypoxic preconditioning significantly enhanced viability of the neural stem cells exposed to hemoglobin and increased grafted-cell survival in the intracerebral hemorrhage brain. Hypoxic preconditioning also increased neural stem cell secretion of vascular endothelial growth factor. Finally, transplanted neural stem cells with hypoxic preconditioning exhibited enhanced tissue-protective capability that accelerated behavioral recovery. Our results suggest that hypoxic preconditioning in neural stem cells improves efficacy of stem cell therapy for intracerebral hemorrhage.

Postconditioning mitigates cell death following oxygen and glucose deprivation in PC12 cells and forebrain reperfusion injury in rats

Postconditioning mitigates ischemia-induced cellular damage via a modified reperfusion procedure. Mitochondrial permeability transition (MPT) is an important pathophysiological change in reperfusion injury. This study explores the role of MPT modulation underlying hypoxic postconditioning (HPoC) in PC12 cells and studies the neuroprotective effects of ischemic postconditioning (IPoC) on rats. Oxygen-glucose deprivation (OGD) was performed for 10 hr on PC12 cells. HPoC was induced by three cycles of 10-min reoxygenation/10-min rehypoxia after OGD. The MPT inhibitor N-methyl-4-isoleucine cyclosporine (NIM811) and the MPT inducer carboxyatractyloside (CATR) were administered to selective groups before OGD. Cellular death was evaluated by flow cytometry and Western blot analysis. JC-1 fluorescence signal was used to estimate the mitochondrial membrane potential (△Ψm ). Transient global cerebral ischemia (tGCI) was induced via the two-vessel occlusion and hypotension method in male Sprague Dawley rats. IPoC was induced by three cycles of 10-sec reperfusion/10-sec reocclusion after index ischemia. HPoC and NIM811 administration attenuated cell death, cytochrome c release, and caspase-3 activity and maintained △Ψm of PC12 cells after OGD. The addition of CATR negated the protection conferred by HPoC. IPoC reduced neuronal degeneration and cytochrome c release and cleaved caspase-9 expression of hippocampal CA1 neurons in rats after tGCI. HPoC protected PC12 cells against OGD by modulating the MPT. IPoC attenuated degeneration of hippocampal neurons after cerebral ischemia.

Synergy of combined tPA-edaravone therapy in experimental thrombotic stroke

Edaravone, a potent antioxidant, may improve thrombolytic therapy because it benefits ischemic stroke patients on its own and mitigates adverse effects of tissue plasminogen activator (tPA) in preclinical models. However, whether the combined tPA-edaravone therapy is more effective in reducing infarct size than singular treatment is uncertain. Here we investigated this issue using a transient hypoxia-ischemia (tHI)-induced thrombotic stroke model, in which adult C57BL/6 mice were subjected to reversible ligation of the unilateral common carotid artery plus inhalation of 7.5% oxygen for 30 min. While unilateral occlusion of the common carotid artery suppressed cerebral blood flow transiently, the addition of hypoxia triggered reperfusion deficits, endogenous thrombosis, and attenuated tPA activity, leading up to infarction. We compared the outcomes of vehicle-controls, edaravone treatment, tPA treatment at 0.5, 1, or 4 h post-tHI, and combined tPA-edaravone therapies with mortality rate and infarct size as the primary end-points. The best treatment was further compared with vehicle-controls in behavioral, biochemical, and diffusion tensor imaging (DTI) analyses. We found that application of tPA at 0.5 or 1 h – but not at 4 h post-tHI – significantly decreased infarct size and showed synergistic (p<0.05) or additive benefits with the adjuvant edaravone treatment, respectively. The acute tPA-edaravone treatment conferred >50% reduction of mortality, ∼80% decline in infarct size, and strong white-matter protection. It also improved vascular reperfusion and decreased oxidative stress, inflammatory cytokines, and matrix metalloproteinase activities. In conclusion, edaravone synergizes with acute tPA treatment in experimental thrombotic stroke, suggesting that clinical application of the combined tPA-edaravone therapy merits investigation.

Manganese superoxide dismutase deficiency exacerbates ischemic brain damage under hyperglycemic conditions by altering autophagy

Both preischemic hyperglycemia and suppression of SOD2 activity aggravate ischemic brain damage. This study was undertaken to assess the effect of SOD2 mutation on ischemic brain damage and its relation to the factors involved in autophagy regulation in hyperglycemic wild-type (WT) and heterozygous SOD2 knockout (SOD2(-/+)) mice subjected to 30-min transient focal ischemia. The brain samples were analyzed at 5 and 24 h after recirculation for ischemic lesion volume, superoxide production, and oxidative DNA damage and protein levels of Beclin 1, damage-regulated autophagy modulator (DRAM), and microtubule-associated protein 1 light chain 3 (LC3). The results revealed a significant increase in infarct volume in hyperglycemic SOD2(-/+) mice, and this was accompanied with an early (5 h) significant rise in superoxide production and reduced SOD2 activity in SOD2(-/+) mice as compared to WT mice. The superoxide production is associated with oxidative DNA damage as indicated by colocalization of the dihydroethidium (DHE) signal with 8-OHdG fluorescence in SOD2(-/+) mice. In addition, while ischemia in WT hyperglycemics increased the levels of autophagy markers Beclin 1, DRAM, and LC3, ischemia in hyperglycemic, SOD2-deficient mice suppressed the levels of autophagy stimulators. These results suggest that SOD2 knockdown exacerbates ischemic brain damage under hyperglycemic conditions via increased oxidative stress and DNA oxidation. Such effect is associated with suppression of autophagy regulators.

Interleukin 6-preconditioned neural stem cells reduce ischaemic injury in stroke mice

Transplantation of neural stem cells provides a promising therapy for stroke. Its efficacy, however, might be limited because of massive grafted-cell death after transplantation, and its insufficient capability for tissue repair. Interleukin 6 is a pro-inflammatory cytokine involved in the pathogenesis of various neurological disorders. Paradoxically, interleukin 6 promotes a pro-survival signalling pathway through activation of signal transducer and activator of transcription 3. In this study, we investigated whether cellular reprogramming of neural stem cells with interleukin 6 facilitates the effectiveness of cell transplantation therapy in ischaemic stroke. Neural stem cells harvested from the subventricular zone of foetal mice were preconditioned with interleukin 6 in vitro and transplanted into mouse brains 6 h or 7 days after transient middle cerebral artery occlusion. Interleukin 6 preconditioning protected the grafted neural stem cells from ischaemic reperfusion injury through signal transducer and activator of transcription 3-mediated upregulation of manganese superoxide dismutase, a primary mitochondrial antioxidant enzyme. In addition, interleukin 6 preconditioning induced secretion of vascular endothelial growth factor from the neural stem cells through activation of signal transducer and activator of transcription 3, resulting in promotion of angiogenesis in the ischaemic brain. Furthermore, transplantation of interleukin 6-preconditioned neural stem cells significantly attenuated infarct size and improved neurological performance compared with non-preconditioned neural stem cells. This interleukin 6-induced amelioration of ischaemic insults was abolished by transfecting the neural stem cells with signal transducer and activator of transcription 3 small interfering RNA before transplantation. These results indicate that preconditioning with interleukin 6, which reprograms neural stem cells to tolerate oxidative stress after ischaemic reperfusion injury and to induce angiogenesis through activation of signal transducer and activator of transcription 3, is a simple and beneficial approach for enhancing the effectiveness of cell transplantation therapy in ischaemic stroke.

Abstract WP165: Prevention of JNK Phosphorylation and Activation of Dual Specificity Phosphatase as a Mechanism for Rosiglitazone in Neuroprotection after Transient Cerebral Ischemia

Rosiglitazone, a synthetic peroxisome proliferator-activated receptor-γ (PPAR γ) agonist, prevents cell death after cerebral ischemia in animal models, but the underlying mechanism has not been clarified. We examined how rosiglitazone protects neurons against ischemia. Mice treated with rosiglitazone were subjected to 60 minutes of focal ischemia followed by reperfusion. Rosiglitazone reduced infarct volume after ischemia and reperfusion. We found that this neuroprotective effect was reversed with a PPAR γ antagonist. Western blot analysis showed a significant increase in expression of phosphorylated stress-activated protein kinases (c-Jun N-terminal kinase [JNK] and p38) in ischemic brain tissue, especially in the cortex area after early reperfusion (3 hr). Rosiglitazone blocked this increase of phosphorylation which caused cell death signaling activation. Furthermore, we observed that rosiglitazone increased expression of the dual-specificity phosphatase 8 (DUSP8) protein and mRNA in ischemic brain tissue. DUSP8 is a mitogen-activated protein kinase phosphatase that can dephosphorylate JNK and p38. Another key finding of the present study was that knockdown of DUSP8 in primary cultured cortical neurons that were subjected to oxygen-glucose deprivation diminished rosiglitazone’s effect on downregulation of JNK phosphorylation. Thus, rosiglitazone’s neuroprotective effect after ischemia is mediated by blocking JNK phosphorylation induced by ischemia via DUSP8 upregulation.

Abstract WMP80: Enhancement Of Antioxidative Activity Facilitates Neural Stem Cell Transplantation Therapy For Hemorrhagic Stroke

Background: We focused on the effect of oxidative stress against grafted neural stem cells (NSCs) and hypothesized that conferring antioxidant properties to NSCs may overcome cell death in the hostile host environment and enhance neuroprotection after transplantation for hemorrhagic stroke.

Methods: NSCs were obtained from the striatum of copper/zinc-superoxide dismutase transgenic (Tg) mice and wild-type (Wt) mice. The NSCs were exposed to various forms of oxidative stress (hemoglobin, H2O2 and FeCl2). Cell viability and oxidative damage were assessed with WST-1, Live/Dead assay, and hydroethidine (HEt) staining. Intraparenchymal NSC transplantation was performed 3 days after autologous blood was injected into mouse striatum for NSC efficacy after transplantation. We performed 8-hydroxyguanosine (8-OHG) staining 4 hours after transplantation to assess oxidative damage in the grafted NSCs. Striatum size was measured to evaluate atrophy, and surviving neurons in the striatum were counted 35 days after hemorrhagic insult. Neurological evaluation was performed 1, 3, 7, 14, 21, 28, and 35 days after hemorrhagic insult.

Results: Cell viability of Tg NSCs was significantly increased compared with Wt NSCs. Both HEt and 8-OHG signals were suppressed in Tg NSCs. Tg NSC transplantation showed a significant reduction in striatum atrophy (86±3% vs 82±4%, n=7, p<0.05, striatum size/contralateral) and showed an increase in surviving neurons in the striatum (73±12% vs 57±12%, n=6, p<0.05, number of neurons/contralateral) compared with Wt NSC transplantation. In the Tg group, progressive improvement was observed 35 days after hemorrhagic insult compared with the Wt group (n=9, p<0.05).

Conclusion: Our results suggest that enhanced antioxidative activity in NSCs improves efficacy of stem cell therapy for the hemorrhagic stroke brain.

Abstract WP104: Chemical Preconditioning Enhances the Effectiveness of Stem Cell Therapy in Ischemic Stroke

Introduction: Transplantation of neural stem cells (NSCs) provides a promising therapy for stroke. Its efficacy, however, might be limited because of massive grafted-cell death following transplantation, as well as insufficient capability for tissue repair. Chemical preconditioning primes the cells to the ‘‘state of readiness’’ to withstand the rigors of lethal ischemia. In this study, we investigated whether cellular reprogramming of NSCs with minocycline or interleukin-6 (IL-6), both of which are known to possess cytoprotective properties, facilitates the effectiveness of stem cell therapy in ischemic stroke.

Methods: NSCs harvested from the subventricular zone of fetal mice were preconditioned with minocycline (10 μM) or IL-6 (20 ng/ml) for 24 hours in vitro . For an in vitro study, the NSCs were subjected to oxygen-glucose deprivation and reoxygenation (n=4). For an in vivo study, the NSCs were transplanted into mouse brains 6 hours or 7 days after transient middle cerebral artery occlusion (n=8). Histological and behavioral tests were examined from days 0 to 28 after stroke.

Results: Minocycline preconditioning up-regulated the expression of Nrf2 (2.7-fold), as well as Nrf2-regulated antioxidant genes (HO-1: 4.0-fold/NQO1: 20-fold), and induced the NSCs to release paracrine factors, including BDNF, NGF, GDNF, and VEGF. IL-6 preconditioning activated STAT3-mediated up-regulation of SOD2 (2.3-fold), a primary mitochondrial antioxidant enzyme, and induced VEGF secretion (2.2-fold). Transplantation of minocycline- or IL-6-preconditioned NSCs significantly reduced grafted cell death, attenuated infarct size, and improved neurological performance compared with non-preconditioned NSCs. This minocycline- or IL-6-induced amelioration of ischemic insults was abolished by transfecting the NSCs with Nrf2- or STAT3-small interfering RNA before transplantation.

Conclusions: Chemical preconditioning, which reprograms NSCs to tolerate oxidative stress after ischemic reperfusion injury and to induce trophic effects, is a simple and beneficial approach for enhancing the effectiveness of cell transplantation therapy in ischemic stroke.

Complement component 3 inhibition by an antioxidant is neuroprotective after cerebral ischemia and reperfusion in mice

Oxidative stress after stroke is associated with the inflammatory system activation in the brain. The complement cascade, especially the degradation products of complement component 3, is a key inflammatory mediator of cerebral ischemia. We have shown that pro-inflammatory complement component 3 is increased by oxidative stress after ischemic stroke in mice using DNA array. In this study, we investigated whether up-regulation of complement component 3 is directly related to oxidative stress after transient focal cerebral ischemia in mice and oxygen-glucose deprivation in brain cells. Persistent up-regulation of complement component 3 expression was reduced in copper/zinc-superoxide dismutase transgenic mice, and manganese-superoxide dismutase knock-out mice showed highly increased complement component 3 levels after transient focal cerebral ischemia. Antioxidant N-tert-butyl-α-phenylnitrone treatment suppressed complement component 3 expression after transient focal cerebral ischemia. Accumulation of complement component 3 in neurons and microglia was decreased by N-tert-butyl-α-phenylnitrone, which reduced infarct volume and impaired neurological deficiency after cerebral ischemia and reperfusion in mice. Small interfering RNA specific for complement component 3 transfection showed a significant increase in brain cells viability after oxygen-glucose deprivation. Our study suggests that the neuroprotective effect of antioxidants through complement component 3 suppression is a new strategy for potential therapeutic approaches in stroke.

The CEPHEUS Pan-Asian survey: high low-density lipoprotein cholesterol goal attainment rate among hypercholesterolaemic patients undergoing lipid-lowering treatment in a Hong Kong regional centre

OBJECTIVES. To evaluate attainment of low-density lipoprotein cholesterol goals among hypercholesterolaemic patients undergoing lipid-lowering drug treatment in Hong Kong and to identify potential determinants of treatment outcomes. DESIGN. Cross-sectional observational study. SETTING. A single site in Hong Kong, as part of the CEPHEUS Pan-Asian survey. PATIENTS. Subjects with hypercholesterolaemia aged 18 years or above, who had been on lipid-lowering drug treatment for at least 3 months with no dose adjustment for at least 6 weeks. RESULTS. A total of 561 such patients (mean age, 65.3; standard deviation, 9.7 years) were evaluated. Most had major cardiovascular risk factors; 534 (95.2%) of 561 patients had coronary heart disease and 534 (95.4%) of 560 patients had low-density lipoprotein cholesterol goals set at lower than 70 mg/dL. In all, 465 (82.9%) patients attained their respective low-density lipoprotein cholesterol goals. Among 75 patients who had coronary heart disease or equivalent risk, and multiple risk factors with a 10-year coronary heart disease risk of over 20%, 62 (82.7%) attained their respective low-density lipoprotein cholesterol goals. Significant predictors of low-density lipoprotein cholesterol goal attainment included the patient's baseline lipid profile (total cholesterol and low-density lipoprotein cholesterol levels), blood pressure, and drugs (statin/non-statin) used for treatment. CONCLUSIONS. Hypercholesterolaemic patients undergoing lipid-lowering drug treatment in the present Hong Kong study were able to achieve a very high attainment rate for the low-density lipoprotein cholesterol goal, despite the fact that most of them had major cardiovascular risk factors.

Crush, culotte, T and protrusion: which 2-stent technique for treatment of true bifurcation lesions? - insights from in vitro experiments and micro-computed tomography

BACKGROUND

Percutaneous coronary intervention of complex true bifurcation lesions often fails to ensure continuous stent coverage and strut apposition in both the side branch and main vessel. Struts left unopposed floating in the lumen disturb blood flow and are increasingly recognized as increasing the risk of stent thrombosis.

METHODS AND RESULTS

In this study, we compared the results of different bifurcation treatment strategies: Crush (n=5); Culotte (n=3); T-/T with Protrusion (TAP) (n=4) using drug-eluting stents deployed in-vitro in representative coronary bifurcation models. After final kissing balloon post-dilatation, the rate of malapposition within the bifurcation quantified from micro-computed tomography scanning was on average 41.5 ± 8.2% with the Crush technique, reduced to respectively 31.4 ± 5.2% with Culotte and 36.7 ± 8.0% with T-/TAP approach. Overlaying layers of struts in the Crush and Culotte techniques lead to a significantly higher rate of strut malapposition in the proximal vessel than with the T-/TAP technique (Crush: 39.1 ± 10.7%, Culotte: 26.1 ± 7.7%, TAP: 4.2 ± 7.2%, P<0.01). Maximal wall-malapposed strut distance was also found on average to be higher with the Crush (1.36 ± 0.4mm) and Culotte techniques (1.32 ± 0.1mm) than with T-/TAP (1.08 ± 0.1mm, P=0.04).

CONCLUSIONS

In this model, the Crush technique resulted in a higher risk of malapposition than either the Culotte or T-/TAP technique.

Involvement of mitogen-activated protein kinase pathways in expression of the water channel protein aquaporin-4 after ischemia in rat cortical astrocytes

Brain edema after ischemic brain injury is a key determinant of morbidity and mortality. Aquaporin-4 (AQP4) plays an important role in water transport in the central nervous system and is highly expressed in brain astrocytes. However, the AQP4 regulatory mechanisms are poorly understood. In this study, we investigated whether mitogen-activated protein kinases (MAPKs), which are involved in changes in osmolality, might mediate AQP4 expression in models of rat cortical astrocytes after ischemia. Increased levels of AQP4 in primary cultured astrocytes subjected to oxygen-glucose deprivation (OGD) and 2 h of reoxygenation were observed, after which they immediately decreased at 0 h of reoxygenation. Astrocytes exposed to OGD injury had significantly increased phosphorylation of three kinds of MAPKs. Treatment with SB203580, a selective p38 MAPK inhibitor, or SP600125, a selective c-Jun N-terminal kinase inhibitor, significantly attenuated the return of AQP4 to its normal level, and SB203580, but not SP600125, significantly decreased cell death. In an in vivo study, AQP4 expression was upregulated 1-3 days after reperfusion, which was consistent with the time course of p38 phosphorylation and activation, and decreased by the p38 inhibition after transient middle cerebral artery occlusion (MCAO). These results suggest that p38 MAPK may regulate AQP4 expression in cortical astrocytes after ischemic injury.

Neural stem cells genetically modified to overexpress cu/zn-superoxide dismutase enhance amelioration of ischemic stroke in mice

BACKGROUND AND PURPOSE

The harsh host brain microenvironment caused by production of reactive oxygen species after ischemic reperfusion injury offers a significant challenge to survival of transplanted neural stem cells (NSCs) after ischemic stroke. Copper/zinc-superoxide dismutase (SOD1) is a specific antioxidant enzyme that counteracts superoxide anions. We have investigated whether genetic manipulation to overexpress SOD1 enhances survival of grafted stem cells and accelerates amelioration of ischemic stroke.

METHODS

NSCs genetically modified to overexpress or downexpress SOD1 were administered intracerebrally 2 days after transient middle cerebral artery occlusion. Histological and behavioral tests were examined from Days 0 to 28 after stroke.

RESULTS

Overexpression of SOD1 suppressed production of superoxide anions after ischemic reperfusion injury and reduced NSC death after transplantation. In contrast, downexpression of SOD1 promoted superoxide generation and increased oxidative stress-mediated NSC death. Transplantation of SOD1-overexpressing NSCs enhanced angiogenesis in the ischemic border zone through upregulation of vascular endothelial growth factor. Moreover, grafted SOD1-overexpressing NSCs reduced infarct size and improved behavioral performance compared with NSCs that were not genetically modified.

CONCLUSIONS

Our findings reveal a strong involvement of SOD1 expression in NSC survival after ischemic reperfusion injury. We propose that conferring antioxidant properties on NSCs by genetic manipulation of SOD1 is a potential approach for enhancing the effectiveness of cell transplantation therapy in ischemic stroke.

Release of mitochondrial apoptogenic factors and cell death are mediated by CK2 and NADPH oxidase

Activation of the NADPH oxidase subunit, NOX2, and increased oxidative stress are associated with neuronal death after cerebral ischemia and reperfusion. Inhibition of NOX2 by casein kinase 2 (CK2) leads to neuronal survival, but the mechanism is unknown. In this study, we show that in copper/zinc-superoxide dismutase transgenic (SOD1 Tg) mice, degradation of CK2α and CK2α' and dephosphorylation of CK2β against oxidative stress were markedly reduced compared with wild-type (WT) mice that underwent middle cerebral artery occlusion. Inhibition of CK2 pharmacologically or by ischemic reperfusion facilitated accumulation of poly(ADP-ribose) polymers, the translocation of apoptosis-inducing factor (AIF), and cytochrome c release from mitochondria after ischemic injury. The eventual enhancement of CK2 inhibition under ischemic injury strongly increased 8-hydroxy-2'-deoxyguanosine and phosphorylation of H2A.X. Furthermore, CK2 inhibition by tetrabromocinnamic acid (TBCA) in SOD1 Tg and gp91 knockout (KO) mice after ischemia reperfusion induced less release of AIF and cytochrome c than in TBCA-treated WT mice. Inhibition of CK2 in gp91 KO mice subjected to ischemia reperfusion did not increase brain infarction compared with TBCA-treated WT mice. These results strongly suggest that NOX2 activation releases reactive oxygen species after CK2 inhibition, triggering release of apoptogenic factors from mitochondria and inducing DNA damage after ischemic brain injury.

Induction of thioredoxin-interacting protein is mediated by oxidative stress, calcium, and glucose after brain injury in mice

Oxidative stress and glucose affect the expression of various genes that contribute to both reactive oxygen species generation and antioxidant systems. However, systemic alteration of oxidative stress-related gene expression in normal brains and in brains with a high-glucose status after ischemic-reperfusion has not been explored. Using a polymerase chain reaction array system, we demonstrate that thioredoxin-interacting protein (Txnip) is induced by both oxidative stress and glucose. We found that Txnip mRNA is induced by ischemic-reperfusion injury and that Txnip is located in the cytoplasm of neurons. Moreover, in vitro oxygen-glucose deprivation (OGD) and subsequent reoxygenation without glucose and in vivo administration of 3-nitropropionic acid also promoted an increase in Txnip in a time-dependent manner, indicating that oxidative stress without glucose can induce Txnip expression in the brain. However, calcium channel blockers inhibit induction of Txnip after OGD and reoxygenation. Using the polymerase chain reaction array with ischemic and hyperglycemic-ischemic samples, we confirmed that enhanced expression of Txnip was observed in hyperglycemic-ischemic brains after middle cerebral artery occlusion. Finally, transfection of Txnip small interfering RNA into primary neurons reduced lactate dehydrogenase release after OGD and reoxygenation. This is the first report showing that Txnip expression is induced in neurons after oxidative or glucose stress under either ischemic or hyperglycemic-ischemic conditions, and that Txnip is proapoptotic under these conditions.

Abstract 3162: Enhancement Of Antioxidative Activity Facilitates Cell Transplantation Therapy For Stroke

Background: Recent studies show that neural stem cells (NSCs) transplanted in the brain provide a potential therapy not only for ischemic stroke, but also for hemorrhagic stroke. However, the low survival rate of grafted NSCs in the brain might preclude a therapeutic effect. We focused on the effect of oxidative stress against grafted cells and hypothesized that conferring antioxidant properties to the NSCs before transplantation into the host tissue may overcome cell death in the hostile host environment and enhance neuroprotection after transplantation.

Methods: NSCs were obtained from the striatum of copper/zinc-superoxide dismutase (SOD1) transgenic mice, manganese-superoxide dismutase (SOD2) transgenic mice and wild-type mice. The NSCs were exposed to several kinds of oxidative stress (oxygen-glucose deprivation and reoxygenation, hemoglobin, H2O2, NO), and preconditioning was performed before exposure to oxidative stress. Preconditioning with IL-6 induced SOD2 up-regulation via Janus activating kinase-signal transducer activator of transcription 3 in NSCs and preconditioning with minocycline up-regulated Nrf-2, which is a crucial component of the endogenous antioxidant system. Cell viability was assessed with LDH assay, WST-1 assay and TUNEL staining. To examine survival of the grafted cells in the ischemic region in vivo, they were transplanted into the cortical ischemic penumbra 6 hours after ischemia, and TUNEL staining was performed 2 days after transplantation. Neurological evaluation was performed before and 1, 7, 14, 21 and 28 days after transplantation.

Results: Death of transgenic (SOD1 and SOD2) NSCs and preconditioned (PC) NSCs was significantly decreased compared with wild-type non-PC NSCs after exposure to oxidative stress. Furthermore, these NSCs showed that hydroethidine signals, which represent superoxide production, were suppressed under oxidative conditions. Preconditioning reduced the number of TUNEL-positive grafted cells in the ischemic brain 2 days after transplantation compared with non-PC NSCs (IL-6 by 40%, n=4, p<0.005; minocycline by 76%, n=4, p<0.001). Minocycline PC NSCs also showed a significant reduction in infarct volume (by 15%, n=7, p<0.05, cortex lesion size/contralateral) and showed functional recovery from 1 through 28 days after transplantation compared with the non-transplanted control group (n=7).

Conclusion: Our results suggest that enhanced antioxidative activity in NSCs before transplantation provides improved survival of NSCs in the stroke brain. The increased survival of these NSCs may provide therapeutic potential for neuroprotection in stroke patients.

Provisional and Complex Techniques for Bifurcation Treatment – Trading Apposition for Scaffolding?

Provisional T-stenting with stenting of the main branch and optional side branch (SB) stenting in the case of significant SB occlusion with thrombolysis in myocardial infarction (TIMI) flow <3 is the strategy chosen nowadays by most interventionalists for treating simple bifurcation lesions. Percutaneous coronary intervention (PCI) of complex true bifurcation lesions remains, however, the subject of debate: treatment of complex bifurcation lesions requires more time than treatment of simple bifurcations and can lead to significantly higher rates of restenosis, target lesion revascularisation and myocardial infarction. Current bifurcation techniques often fail to ensure continuous stent coverage of the SB ostium and of the two bifurcation branches without a simultaneous increase in the rate of malapposed struts. Stent struts left unapposed in the lumen disturb blood flow and are increasingly recognised as increasing the risk of stent thrombosis and focal in-stent restenosis, limiting the success of stent procedures in these lesions. New technology and dedicated designs may, in the near future, overcome such limitations of conventional two-stent bifurcation strategies.

Neuroprotection by interleukin-6 is mediated by signal transducer and activator of transcription 3 and antioxidative signaling in ischemic stroke

BACKGROUND AND PURPOSE

Interleukin-6 (IL-6) has been shown to have a neuroprotective effect in brain ischemic injury. However, its molecular mechanisms are still poorly understood. In this study, we investigated the neuroprotective role of the IL-6 receptor (IL-6R) by IL-6 in the reactive oxygen species defense system after transient focal cerebral ischemia (tFCI).

METHODS

IL-6 was injected in mice before and after middle cerebral artery occlusion. Coimmunoprecipitation assays were performed for analysis of an IL-6R association after tFCI. Primary mouse cerebral cortical neurons were transfected with small interfering RNA probes targeted to IL-6Rα or gp130 and were used for chromatin-immunoprecipitation assay, luciferase promoter assay, and cell viability assay. Reduction in infarct volumes by IL-6 was measured after tFCI.

RESULTS

IL-6R was disrupted through a disassembly between IL-6Rα and gp130 associated by protein oxidation after reperfusion after tFCI. This suppressed phosphorylation of signal transducer and activator of transcription 3 (STAT3) and finally induced neuronal cell death through a decrease in manganese-superoxide dismutase. However, IL-6 injections prevented disruption of IL-6R against reperfusion after tFCI, consequently restoring activity of STAT3 through recovery of the binding of STAT3 to gp130. Moreover, IL-6 injections restored the transcriptional activity of the manganese-superoxide dismutase promoter through recovery of the recruitment of STAT3 to the manganese-superoxide dismutase promoter and reduced infarct volume after tFCI.

CONCLUSIONS

This study demonstrates that IL-6 has a neuroprotective effect against cerebral ischemic injury through IL-6R-mediated STAT3 activation and manganese-superoxide dismutase expression.

SOD1 overexpression improves features of the oligodendrocyte precursor response in vitro

Spinal cord injury (SCI) produces a significant loss of oligodendrocytes (OL) and demyelination. The oligodendrocyte precursor cells (OPCs) response includes a group of cellular changes in OPCs that are directed to replenish OL loss from the injury. However, this adaptive response is hampered and OPCs eventually die or fail to differentiate to mature and functional OL. In this study, we wanted to evaluate if overexpression of human superoxide dismutase 1 (hSOD1) in OPCs from the SOD1 transgenic rat could improve some of the features of the OPC response in vitro. We found that hSOD1 overexpression increases the proliferation of OPCs and accelerates their differentiation to mature OL in vitro. Furthermore, hSOD1 overexpression reduces oxidative stress-mediated death in OPCs. These results suggest hSOD1 as a therapeutic target to increase OPC response success and potentially, OL replacement and remyelination after SCI.

Oxidative stress in ischemic brain damage: mechanisms of cell death and potential molecular targets for neuroprotection

Significant amounts of oxygen free radicals (oxidants) are generated during cerebral ischemia/reperfusion, and oxidative stress plays an important role in brain damage after stroke. In addition to oxidizing macromolecules, leading to cell injury, oxidants are also involved in cell death/survival signal pathways and cause mitochondrial dysfunction. Experimental data from laboratory animals that either overexpress (transgenic) or are deficient in (knock-out) antioxidant proteins, mainly superoxide dismutase, have provided strong evidence of the role of oxidative stress in ischemic brain damage. In addition to mitochondria, recent reports demonstrate that NADPH oxidase (NOX), an important pro-oxidant enzyme, is also involved in the generation of oxidants in the brain after stroke. Inhibition of NOX is neuroprotective against cerebral ischemia. We propose that superoxide dismutase and NOX activity in the brain is a major determinant for ischemic damage/repair and that these major anti- and pro-oxidant enzymes are potential endogenous molecular targets for stroke therapy.

Consistent injury to medium spiny neurons and white matter in the mouse striatum after prolonged transient global cerebral ischemia

A reproducible transient global cerebral ischemia (tGCI) mouse model has not been fully established. Although striatal neurons and white matter are recognized to be vulnerable to ischemia, their injury after tGCI in mice has not been elucidated. The purpose of this study was to evaluate injuries to striatal neurons and white matter after tGCI in C57BL/6 mice, and to develop a reproducible tGCI model. Male C57BL/6 mice were subjected to tGCI by bilateral common carotid artery occlusion (BCCAO). Mice whose cortical cerebral blood flow after BCCAO decreased to less than 13% of the pre-ischemic value were used. Histological analysis showed that at 3 days after 22 min of BCCAO, striatal neurons were injured more consistently than those in other brain regions. Quantitative analysis of cytochrome c release into the cytosol and DNA fragmentation in the striatum showed consistent injury to the striatum. Immunohistochemistry and Western blot analysis revealed that DARPP-32-positive medium spiny neurons, the majority of striatal neurons, were the most vulnerable among the striatal neuronal subpopulations. The striatum (especially medium spiny neurons) was susceptible to oxidative stress after tGCI, which is probably one of the mechanisms of vulnerability. SMI-32 immunostaining showed that white matter in the striatum was also consistently injured 3 days after 22 min of BCCAO. We thus suggest that this is a tGCI model using C57BL/6 mice that consistently produces neuronal and white matter injury in the striatum by a simple technique. This model can be highly applicable for elucidating molecular mechanisms in the brain after global ischemia.

NADPH oxidase mediates striatal neuronal injury after transient global cerebral ischemia

Medium spiny neurons (MSNs) constitute most of the striatal neurons and are known to be vulnerable to ischemia; however, the mechanisms of the vulnerability remain unclear. Activated forms of nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase (NOX), which require interaction between cytosolic and membrane-bound subunits, are among the major sources of superoxide in the central nervous system. Although increasing evidence suggests that NOX has important roles in neurodegenerative diseases, its roles in MSN injury after transient global cerebral ischemia (tGCI) have not been elucidated. To clarify this issue, C57BL/6 mice were subjected to tGCI by bilateral common carotid artery occlusion for 22 minutes. Western blot analysis revealed upregulation of NOX subunits and recruitment of cytosolic subunits to the cell membrane at early (3 to 6 hours) and late (72 hours) phases after tGCI. Taken together with immunofluorescent studies, this activation arose in MSNs and endothelial cells at the early phase, and in reactive microglia at the late phase. Pharmacological and genetic inhibition of NOX attenuated oxidative injury, microglial activation, and MSN death after tGCI. These findings suggest that NOX has pivotal roles in MSN injury after tGCI and could be a therapeutic target for brain ischemia.

NADPH oxidase is involved in post-ischemic brain inflammation

Nicotinamide adenine dinucleotide phosphate oxidase (NOX) is widely expressed in brain tissue including neurons, glia, and endothelia in neurovascular units. It is a major source of oxidants in the post-ischemic brain and significantly contributes to ischemic brain damage. Inflammation occurs after brain ischemia and is known to be associated with post-ischemic oxidative stress. Post-ischemic inflammation also causes progressive brain injury. In this study we investigated the role of NOX2 in post-ischemic cerebral inflammation using a transient middle cerebral artery occlusion model in mice. We demonstrate that mice with NOX2 subunit gp91(phox) knockout (gp91 KO) showed 35-44% less brain infarction at 1 and 3 days of reperfusion compared with wild-type (WT) mice. Minocycline further reduced brain damage in the gp91 KO mice at 3 days of reperfusion. The gp91 KO mice exhibited less severe post-ischemic inflammation in the brain, as evidenced by reduced microglial activation and decreased upregulation of inflammation mediators, including interleukin-1β (IL-1β), tumor necrosis factor-α, inducible nitric oxide synthases, CC-chemokine ligand 2, and CC-chemokine ligand 3. Finally, we demonstrated that an intraventricular injection of IL-1β enhanced ischemia- and reperfusion-mediated brain damage in the WT mice (double the infarction volume), whereas, it failed to aggravate brain infarction in the gp91 KO mice. Taken together, these results demonstrate the involvement of NOX2 in post-ischemic neuroinflammation and that NOX2 inhibition provides neuroprotection against inflammatory cytokine-mediated brain damage.

Hemoglobin-induced oxidative stress contributes to matrix metalloproteinase activation and blood-brain barrier dysfunction in vivo

Hemoglobin (Hb) released from extravasated erythrocytes is implicated in brain edema after intracerebral hemorrhage (ICH). Hemoglobin is a major component of blood and a potent mediator of oxidative stress after ICH. Oxidative stress and matrix metalloproteinases (MMPs) are associated with blood-brain barrier (BBB) dysfunction. This study was designed to elucidate whether Hb-induced oxidative stress contributes to MMP-9 activation and BBB dysfunction in vivo. An intracerebral injection of Hb into rat striata induced increased hydroethidine (HEt) signals in parallel with MMP-9 levels. In situ gelatinolytic activity colocalized with oxidized HEt signals in vessel walls, accompanied by immunoglobulin G leakage and a decrease in immunoactivity of endothelial barrier antigen, a marker of endothelial integrity. Administration of a nonselective MMP inhibitor prevented MMP-9 levels and albumin leakage in injured striata. Moreover, reduction in oxidative stress by copper/zinc-superoxide dismutase (SOD1) overexpression reduced oxidative stress, MMP-9 levels, albumin leakage, and subsequent apoptosis compared with wild-type littermates. We speculate that Hb-induced oxidative stress may contribute to early BBB dysfunction and subsequent apoptosis, partly through MMP activation, and that SOD1 overexpression may reduce Hb-induced oxidative stress, BBB dysfunction, and apoptotic cell death.

Oxidative stress increases phosphorylation of IkappaB kinase-alpha by enhancing NF-kappaB-inducing kinase after transient focal cerebral ischemia

The IkappaB kinase (IKK) complex is a central component in the classic activation of the nuclear factor-kappaB (NF-kappaB) pathway. It has been reported to function in physiologic responses, including cell death and inflammation. We have shown that IKK is regulated by oxidative status after transient focal cerebral ischemia (tFCI) in mice. However, the mechanism by which oxidative stress influences IKKs after tFCI is largely unknown. Nuclear accumulation and phosphorylation of IKKalpha (pIKKalpha) were observed 1 h after 30 mins of tFCI in mice. In copper/zinc-superoxide dismutase knockout mice, levels of NF-kappaB-inducing kinase (NIK) (an upstream kinase of IKKalpha), pIKKalpha, and phosphorylation of histone H3 (pH3) on Ser10 were increased after tFCI and were higher than in wild-type mice. Immunohistochemistry showed nuclear accumulation and pIKKalpha in mouse brain endothelial cells after tFCI. Nuclear factor-kappaB-inducing kinase was increased, and it enhanced pH3 by inducing pIKKalpha after oxygen-glucose deprivation (OGD) in mouse brain endothelial cells. Both NIK and pH3 interactions with IKKalpha were confirmed by coimmunoprecipitation. Treatment with IKKalpha small interfering RNA significantly reduced cell death after OGD. These results suggest that augmentation of NIK, IKKalpha, and pH3 in response to oxidative stress is involved in cell death after cerebral ischemia (or stroke).

Reperfusion and neurovascular dysfunction in stroke: from basic mechanisms to potential strategies for neuroprotection

Effective stroke therapies require recanalization of occluded cerebral blood vessels. However, reperfusion can cause neurovascular injury, leading to cerebral edema, brain hemorrhage, and neuronal death by apoptosis/necrosis. These complications, which result from excess production of reactive oxygen species in mitochondria, significantly limit the benefits of stroke therapies. We have developed a focal stroke model using mice deficient in mitochondrial manganese-superoxide dismutase (SOD2-/+) to investigate neurovascular endothelial damage that occurs during reperfusion. Following focal stroke and reperfusion, SOD2-/+ mice had delayed blood-brain barrier breakdown, associated with activation of matrix metalloproteinase and high brain hemorrhage rates, whereas a decrease in apoptosis and hemorrhage was observed in SOD2 overexpressors. Thus, induction and activation of SOD2 is a novel strategy for neurovascular protection after ischemia/reperfusion. Our recent study identified the signal transducer and activator of transcription 3 (STAT3) as a transcription factor of the mouse SOD2 gene. During reperfusion, activation of STAT3 and its recruitment into the SOD2 gene were blocked, resulting in increased oxidative stress and neuronal apoptosis. In contrast, pharmacological activation of STAT3 induced SOD2 expression, which limits ischemic neuronal death. Our studies point to antioxidant-based neurovascular protective strategies as potential treatments to expand the therapeutic window of currently approved therapies.

Mitochondrial and apoptotic neuronal death signaling pathways in cerebral ischemia

Mitochondria play important roles as the powerhouse of the cell. After cerebral ischemia, mitochondria overproduce reactive oxygen species (ROS), which have been thoroughly studied with the use of superoxide dismutase transgenic or knockout animals. ROS directly damage lipids, proteins, and nucleic acids in the cell. Moreover, ROS activate various molecular signaling pathways. Apoptosis-related signals return to mitochondria, then mitochondria induce cell death through the release of pro-apoptotic proteins such as cytochrome c or apoptosis-inducing factor. Although the mechanisms of cell death after cerebral ischemia remain unclear, mitochondria obviously play a role by activating signaling pathways through ROS production and by regulating mitochondria-dependent apoptosis pathways.

Inhibition of NADPH oxidase is neuroprotective after ischemia-reperfusion

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) is well known as a major source for superoxide radical generation in leukocytes. Superoxide radicals play a significant role in brain ischemia-reperfusion (I/R) injury. Recent data have also shown expression of NOX in the brain. However, the manner by which NOX is involved in pathologic processes after cerebral ischemia remains unknown. Therefore, we subjected mice deficient in the NOX subunit, gp91(phox) (gp91(phox)-/-), those treated with the NOX inhibitor, apocynin, and wild-type (WT) mice to 75 mins of focal ischemia followed by reperfusion. At 24 h of reperfusion, the gp91(phox)-/- and apocynin-treated mice showed 50% less brain infarction and 70% less cleaved spectrin compared with WT mice. The levels of 4-hydroxy-2-nonenal, malondialdehyde, and 8-hydroxy-2'-deoxyguanosine increased significantly after I/R, indicating oxidative brain injury. NADPH oxidase inhibition reduced biomarker generation. Furthermore, NOX was involved in postischemic inflammation in the brains, as less intercellular adhesion molecule-1 upregulation and less neutrophil infiltration were found in the NOX-inhibited mice after I/R. Moreover, gp91(phox) expression increased after ischemia, and was further aggravated by genetic copper/zinc-superoxide dismutase (SOD1) ablation, but ameliorated in SOD1-overexpressing mice. This study suggests that NOX plays a role in oxidative stress and inflammation, thus contributing to ischemic brain injury.

NADPH oxidase is the primary source of superoxide induced by NMDA receptor activation

Neuronal NMDA receptor (NMDAR) activation leads to the formation of superoxide, which normally acts in cell signaling. With extensive NMDAR activation, the resulting superoxide production leads to neuronal death. It is widely held that NMDA-induced superoxide production originates from the mitochondria, but definitive evidence for this is lacking. We evaluated the role of the cytoplasmic enzyme NADPH oxidase in NMDA-induced superoxide production. Neurons in culture and in mouse hippocampus responded to NMDA with a rapid increase in superoxide production, followed by neuronal death. These events were blocked by the NADPH oxidase inhibitor apocynin and in neurons lacking the p47(phox) subunit, which is required for NADPH oxidase assembly. Superoxide production was also blocked by inhibiting the hexose monophosphate shunt, which regenerates the NADPH substrate, and by inhibiting protein kinase C zeta, which activates the NADPH oxidase complex. These findings identify NADPH oxidase as the primary source of NMDA-induced superoxide production.

Faster recovery of cerebral perfusion in SOD1-overexpressed rats after cardiac arrest and resuscitation

BACKGROUND AND PURPOSE

Protracted hypoperfusion is one of the hallmarks of secondary cerebral derangement after cardiac arrest and resuscitation (CAR), and reactive oxygen species have been implicated in reperfusion abnormalities.

METHODS

Using transgenic (Tg) rats overexpressing copper zinc superoxide dismutase (SOD1), we investigated the role of this intrinsic antioxidant in the restoration of cerebral blood flow (CBF) after CAR. Nine Tg and 11 wild-type (WT) rats were subjected to a nominal 15-minute cardiac arrest, and CBF was measured using the noninvasive arterial spin labeling MRI method before and during cardiac arrest, and 0 to 2 hours and 1 to 5 days after resuscitation.

RESULTS

The SOD1-Tg rats showed rapid normalization of CBF 1 day after the insult, whereas CBF in WT animals remained abnormal for at least 5 days, showing a progressive increase in CBF from hypo- to hyperperfusion on postresuscitation days 1 to 5. The long-term outcome, as measured by survival time, change in body weight, and mapping of apparent diffusion coefficient (ADC) for ion/water homeostasis, was significantly better in the SOD1-Tg rats.

CONCLUSIONS

Our results support the notion that reactive oxygen species are at least partially responsible for microvascular reperfusion disorders.

Oxidative stress and mitochondrial dysfunction as determinants of ischemic neuronal death and survival

Mitochondria are the powerhouse of the cell. Their primary physiological function is to generate adenosine triphosphate through oxidative phosphorylation via the electron transport chain. Reactive oxygen species generated from mitochondria have been implicated in acute brain injuries such as stroke and neurodegeneration. Recent studies have shown that mitochondrially-formed oxidants are mediators of molecular signaling, which is implicated in the mitochondria-dependent apoptotic pathway that involves pro- and antiapoptotic protein binding, the release of cytochrome c, and transcription-independent p53 signaling, leading to neuronal death. Oxidative stress and the redox state of ischemic neurons are also implicated in the signaling pathway that involves phosphatidylinositol 3-kinase/Akt and downstream signaling, which lead to neuronal survival. Genetically modified mice or rats that over-express or are deficient in superoxide dismutase have provided strong evidence in support of the role of mitochondrial dysfunction and oxidative stress as determinants of neuronal death/survival after stroke and neurodegeneration.

VEGF Stimulates the ERK 1/2 signaling pathway and apoptosis in cerebral endothelial cells after ischemic conditions

BACKGROUND AND PURPOSE

Cerebral endothelial cells that line microvessels play an important role in maintaining blood flow homeostasis within the brain-forming part of the blood-brain barrier. These cells are injured by hypoxia-induced reperfusion, leading to blood-brain barrier breakdown and exacerbation of ischemic injury. We investigated the roles of vascular endothelial growth factor (VEGF) and the downstream extracellular signal-regulated kinase (ERK) protein after oxygen-glucose deprivation (OGD) in primary endothelial cells.

METHODS

Primary mouse endothelial cells were isolated and subjected to OGD. Western analysis of VEGF and ERK 1/2 protein levels was performed. Cells were transfected with VEGF small interference RNA. A terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling (TUNEL) assay and DNA fragmentation assay were used on mouse endothelial cells that overexpress copper/zinc-superoxide dismutase (SOD1).

RESULTS

VEGF protein expression was induced and its receptor, Flk-1, was stimulated by OGD. Phosphorylation of ERK 1/2 protein levels was upregulated. Inhibition of phosphorylated ERK (pERK) expression by U0126 reduced endothelial cell death by OGD. Transfection of small interfering RNA for VEGF also inhibited an increase in pERK, suggesting that VEGF acts via ERK. The TUNEL and DNA fragmentation assays showed a significant decrease in TUNEL-positivity in the SOD1-overexpressing endothelial cells compared with wild-type cells after OGD.

CONCLUSIONS

Our data suggest that OGD induces VEGF signaling via its receptor, Flk-1, and activates ERK via oxidative-stress-dependent mechanisms. Our study shows that in cerebral endothelial cells the ERK 1/2 signaling pathway plays a significant role in cell injury after OGD.

Potential role of PUMA in delayed death of hippocampal CA1 neurons after transient global cerebral ischemia

BACKGROUND AND PURPOSE

p53-upregulated modulator of apoptosis (PUMA), a BH3-only member of the Bcl-2 protein family, is required for p53-dependent and -independent forms of apoptosis. PUMA localizes to mitochondria and interacts with antiapoptotic Bcl-2 and Bcl-X(L) or proapoptotic Bax in response to death stimuli. Although studies have shown that PUMA is associated with pathomechanisms of cerebral ischemia, clearly defined roles for PUMA in ischemic neuronal death remain unclear. The purpose of this study was to determine potential roles for PUMA in cerebral ischemia.

METHODS

Five minutes of transient global cerebral ischemia (tGCI) were induced by bilateral common carotid artery occlusion combined with hypotension.

RESULTS

PUMA was upregulated in vulnerable hippocampal CA1 neurons after tGCI as shown by immunohistochemistry. In Western blot and coimmunoprecipitation analyses, PUMA localized to mitochondria and was bound to Bcl-X(L) and Bax in the hippocampal CA1 subregion after tGCI. PUMA upregulation was inhibited by pifithrin-alpha, a specific inhibitor of p53, suggesting that PUMA is partly controlled by the p53 transcriptional pathway after tGCI. Furthermore, reduction in oxidative stress by overexpression of copper/zinc superoxide dismutase, which is known to be protective of vulnerable ischemic hippocampal neurons, inhibited PUMA upregulation and subsequent hippocampal CA1 neuronal death after tGCI.

CONCLUSIONS

These results imply a potential role for PUMA in delayed CA1 neuronal death after tGCI and that it could be a molecular target for therapy.

The role of Akt signaling in oxidative stress mediates NF-kappaB activation in mild transient focal cerebral ischemia

Reactive oxygen species, derived from hypoxia and reoxygenation during transient focal cerebral ischemia (tFCI), are associated with the signaling pathway that leads to neuronal survival or death, depending on the severity and duration of the ischemic insult. The Akt survival signaling pathway is regulated by oxidative stress and is implicated in activation of nuclear factor-kappaB (NF-kappaB). Mild cerebral ischemia in mice was used to induce increased levels of Akt phosphorylation in the cortex and striatum. To clarify the role of Akt activation by NF-kappaB after tFCI, we injected the specific Akt inhibitor IV that inhibits Akt phosphorylation/activation. Inhibition of Akt phosphorylation induced decreases in sequential NF-kappaB signaling after 30 mins of tFCI at 1 h. Furthermore, the downstream survival signals of the Akt pathway were also decreased. Akt inhibitor IV increased ischemic infarct volume and apoptotic-related DNA fragmentation. Superoxide production in the ischemic brains of mice pretreated with the Akt inhibitor was higher than in vehicle-treated mice. In addition, those pretreated mice showed a reduction of approximately 33% in copper/zinc-superoxide dismutase expression. We propose that Akt signaling exerts its neuroprotective role by NF-kappaB activation in oxidative cerebral ischemia in mice.

Induction of mmp-9 expression and endothelial injury by oxidative stress after spinal cord injury

Matrix metalloproteinase-9 (MMP-9) activation plays an important role in blood-brain barrier (BBB) dysfunction after central nervous system injury. Oxidative stress is also implicated in the pathogenesis after cerebral ischemia and spinal cord injury (SCI), but the relationship between MMP-9 activation and oxidative stress after SCI has not yet been clarified. We examined MMP-9 expression after SCI using copper/zinc-superoxide dismutase (SOD1) transgenic (Tg) rats. Our results show that MMP-9 activity significantly increased after SCI in both SOD1 Tg rats and their wild-type (Wt) littermates, although the increase was less in the SOD1 Tg rats. This pattern of MMP-9 expression was further confirmed by immunostaining and Western blot analysis. In situ zymography showed that gelatinolytic activity increased after SCI in the Wt rats, while the increase was less in the Tg rats. Evans blue extravasation increased in both the Wt and Tg rats, but was less in the SOD1 Tg rats. Inhibitor studies showed that, with an intrathecal injection of SB-3CT (a selective MMP-2/MMP-9 inhibitor), the MMP activity, Evans blue extravasation, and apoptotic cell death decreased after SCI. We conclude that increased oxidative stress after SCI leads to MMP-9 upregulation, BBB disruption, and apoptosis, and that overexpression of SOD1 in Tg rats decreases oxidative stress and further attenuates MMP-9 mediated BBB disruption.

Deleterious role of superoxide dismutase in the mitochondrial intermembrane space

This work demonstrates how increased activity of copper-zinc superoxide dismutase (SOD1) paradoxically boosts production of toxic reactive oxygen species (ROS) in the intermembrane space (IMS) of mitochondria. Even though SOD1 is a cytosolic enzyme, a fraction of it is found in the IMS, where it is thought to provide protection against oxidative damage. We found that SOD1 controls cytochrome c-catalyzed peroxidation in vitro when superoxide is available. The presence of SOD1 significantly increased the rate of ROS production in mitoplasts, which are devoid of outer membrane and IMS. In response to inhibition of respiration with antimycin A, isolated mouse wild-type mitochondria increased ROS production, but the mitochondria from mice lacking SOD1 (SOD1(-/-)) did not. Also, lymphocytes isolated from SOD1(-/-) mice produced significantly less ROS than did wild-type cells and were more resistant to apoptosis induced by inhibition of respiration. Moreover, an increased amount of the toxic mutant G93A SOD1 in the IMS increased ROS production. The mitochondrial dysfunction and cell damage paradoxically induced by SOD1-mediated ROS production may be implicated in chronic degenerative diseases.

Increased expression of a proline-rich Akt substrate (PRAS40) in human copper/zinc-superoxide dismutase transgenic rats protects motor neurons from death after spinal cord injury

The serine-threonine kinase, Akt, plays an important role in the cell survival signaling pathway. A proline-rich Akt substrate, PRAS40, has been characterized, and an increase in phospho-PRAS40 (pPRAS40) is neuroprotective after transient focal cerebral ischemia. However, the involvement of PRAS40 in the cell death/survival pathway after spinal cord injury (SCI) is unclear. Liposome-mediated PRAS40 transfection was performed to study whether overexpression of pPRAS40 is neuroprotective. We further examined the expression of pPRAS40 after SCI by immunohistochemistry and Western blot using copper/zinc-superoxide dismutase (SOD1) transgenic (Tg) rats and wild-type (Wt) littermates. We then examined the relationship between PRAS40 and Akt by injection of LY294002, a phosphatidylinositol 3-kinase (PI3K) pathway inhibitor, or Akt inhibitor IV, a compound that inhibits Akt activation after SCI. Our data demonstrated that increased pPRAS40 resulted in survival of more motor neurons compared with control complementary DNA transfection. Phosphorylated PRAS40 increased in the Wt rats after SCI, whereas there was a greater and prolonged increase in the SOD1 Tg rats. Coimmunoprecipitation showed that binding of pPRAS40 with 14-3-3 increased 1 day after SCI in the Wt rats, whereas there was a significant increase in the Tg rats. The inhibitor studies showed that phospho-Akt and pPRAS40 were decreased after injection of LY294002 or Akt inhibitor IV. We conclude that an increase in pPRAS40 by transfection after SCI results in survival of motor neurons, and overexpression of SOD1 in the Tg rats results in an increase in endogenous pPRAS40 and a decrease in motor neuron death through the PI3K/Akt pathway.

Hypoglycemic neuronal death is triggered by glucose reperfusion and activation of neuronal NADPH oxidase

Hypoglycemic coma and brain injury are potential complications of insulin therapy. Certain neurons in the hippocampus and cerebral cortex are uniquely vulnerable to hypoglycemic cell death, and oxidative stress is a key event in this cell death process. Here we show that hypoglycemia-induced oxidative stress and neuronal death are attributable primarily to the activation of neuronal NADPH oxidase during glucose reperfusion. Superoxide production and neuronal death were blocked by the NADPH oxidase inhibitor apocynin in both cell culture and in vivo models of insulin-induced hypoglycemia. Superoxide production and neuronal death were also blocked in studies using mice or cultured neurons deficient in the p47(phox) subunit of NADPH oxidase. Chelation of zinc with calcium disodium EDTA blocked both the assembly of the neuronal NADPH oxidase complex and superoxide production. Inhibition of the hexose monophosphate shunt, which utilizes glucose to regenerate NADPH, also prevented superoxide formation and neuronal death, suggesting a mechanism linking glucose reperfusion to superoxide formation. Moreover, the degree of superoxide production and neuronal death increased with increasing glucose concentrations during the reperfusion period. These results suggest that high blood glucose concentrations following hypoglycemic coma can initiate neuronal death by a mechanism involving extracellular zinc release and activation of neuronal NADPH oxidase.

Reduction in oxidative stress by superoxide dismutase overexpression attenuates acute brain injury after subarachnoid hemorrhage via activation of Akt/glycogen synthase kinase-3beta survival signaling

Recent studies have revealed that oxidative stress has detrimental effects in several models of neurodegenerative diseases, including subarachnoid hemorrhage (SAH). However, how oxidative stress affects acute brain injury after SAH remains unknown. We have previously reported that overexpression of copper/zinc-superoxide dismutase (SOD1) reduces oxidative stress and subsequent neuronal injury after cerebral ischemia. In this study, we investigated the relationship between oxidative stress and acute brain injury after SAH using SOD1 transgenic (Tg) rats. SAH was produced by endovascular perforation in wild-type (Wt) and SOD1 Tg rats. Apoptotic cell death at 24 h, detected by a cell death assay, was significantly decreased in the cerebral cortex of the SOD1 Tg rats compared with the Wt rats. The mortality rate at 24 h was also significantly decreased in the SOD1 Tg rats. A hydroethidine study demonstrated that superoxide anion production after SAH was reduced in the cerebral cortex of the SOD1 Tg rats. Moreover, phosphorylation of Akt and glycogen synthase kinase-3beta (GSK3beta), which are survival signals in apoptotic cell death, was more enhanced in the cerebral cortex of the SOD1 Tg rats after SAH using Western blot analysis and immunohistochemistry. We conclude that reduction in oxidative stress by SOD1 overexpression may attenuate acute brain injury after SAH via activation of Akt/GSK3beta survival signaling.

Reduced oxidative stress promotes NF-kappaB-mediated neuroprotective gene expression after transient focal cerebral ischemia: lymphocytotrophic cytokines and antiapoptotic factors

Nuclear factor-kappa B (NF-kappaB) is activated by oxidative stress such as that induced by transient focal cerebral ischemia (tFCI). Whether NF-kappaB has a role in cell survival or death in stroke is a matter of debate. We proposed that the status of oxidative stress may determine its role in cell death or survival after focal ischemia. To characterize the coordinated expression of genes in NF-kappaB signaling after mild cerebral ischemia, we investigated the temporal profile of a NF-kappaB-pathway-focused DNA array after 30 mins of tFCI in wild-type (WT) mice and human copper/zinc-superoxide dismutase transgenic (SOD1 Tg) mice that had a significantly reduced level of superoxide. Differentially expressed genes among 96 NF-kappaB-related genes were further confirmed and compared in the WT and SOD1 Tg mice using quantitative polymerase chain reaction, Western blotting, and immunohistochemistry. Persistent upregulation of NF-kappaB seen at 7 days in the WT mice was decreased in the SOD1 Tg mice. Lymphocytotrophic cytokine genes such as interleukin-2, interleukin-12, and interferon-alpha1 were increased in the SOD1 Tg mice compared with the WT mice after tFCI. In addition, antiapoptosis factors bcl-2 and tumor necrosis factor receptor-associated factor 1 rapidly increased in the SOD1 Tg mice compared with the WT mice. This study indicates that reduced oxidative stress by SOD1 overexpression increased NF-kappaB-related rapid defenses, such as immune response and antiapoptosis factors, and prevented brain damage after tFCI-induced oxidative stress.

Bad as a converging signaling molecule between survival PI3-K/Akt and death JNK in neurons after transient focal cerebral ischemia in rats

Bad, a proapoptotic Bcl-2 family protein, plays a critical role in determining cell death/survival. The phosphatidylinositol 3-kinase (PI3-K)/Akt pathway and the c-Jun N-terminal kinase (JNK) pathway are thought to be involved in regulation of Bad. Therefore, the present study was performed to clarify the role of Bad as a common target of the PI3-K/Akt and JNK pathways after transient focal cerebral ischemia (tFCI) in rats. We found that Akt activity increased at 3 h and then decreased, whereas JNK activity increased 7 to 24 h in the peripheral area after tFCI. Administration of LY294002, a PI3-K-specific inhibitor, exacerbated DNA fragmentation, whereas administration of SP600125, a JNK-specific inhibitor, attenuated it. Inhibited by LY294002, phospho-Bad (Ser136) expression increased in the peripheral area 3 h after tFCI, with suppression of Akt activity. Furthermore, phospho-Bad (Ser136) and phospho-Akt (Ser473) were colocalized. Decreases in phospho-Bad (Ser136) and Bad/14-3-3 dimerization and increases in Bcl-X(L)/Bad or Bcl-2/Bad dimerization observed 7 to 24 h after tFCI, were prevented by SP600125 administration, with inhibition of JNK activity. The present study indicates that signal predominance varies from PI3-K/Akt-mediated survival signaling to JNK-mediated death signaling with the development of neuronal damage in the peripheral area after tFCI. This study also suggests that PI3-K/Akt has a role in Bad inactivation, whereas the JNK pathway is involved in Bad activation. We conclude that Bad may be an integrated checkpoint of PI3-K/Akt-mediated survival signaling and JNK-mediated death signaling and that it contributes to cell fate in the peripheral area after cerebral ischemia.

Mitochondrial translocation of p53 underlies the selective death of hippocampal CA1 neurons after global cerebral ischaemia

p53, a tumour suppressor, is involved in DNA repair and cell death processes and mediates apoptosis in response to death stimuli by transcriptional activation of pro-apoptotic genes and by transcription-independent mechanisms. In the latter process, p53 induces permeabilization of the outer mitochondrial membrane by forming an inhibitory complex with a protective Bcl-2 family protein, resulting in cytochrome c release in several cell line systems. However, it is unclear how the mitochondrial p53 pathway mediates neuronal apoptosis after cerebral ischaemia. We examined interaction between the mitochondrial p53 pathway and vulnerable hippocampal CA1 neurons using a tGCI (transient global cerebral ischaemia) rat model. We showed mitochondrial translocation of p53 and its binding to Bcl-X(L). Mitochondrial p53 translocation, interaction between p53 and Bcl-X(L), and cytochrome c release from mitochondria and subsequent CA1 neuronal death were prevented by pifithrin-alpha, a p53-specific inhibitor. These results suggest that the mitochondrial p53 pathway plays a role in delayed CA1 neuronal death after tGCI.

Influence of hyperglycemia on oxidative stress and matrix metalloproteinase-9 activation after focal cerebral ischemia/reperfusion in rats: relation to blood-brain barrier dysfunction

BACKGROUND AND PURPOSE

Hyperglycemia is linked to a worse outcome after ischemic stroke. Among the manifestations of brain damage caused by ischemia are blood-brain barrier (BBB) disruption and edema formation. Oxidative stress and matrix metalloproteinase-9 (MMP-9) activation are implicated in BBB dysfunction after ischemia/reperfusion injury. Our present study was designed to clarify the relation among hyperglycemia, oxidative stress, and MMP-9 activation associated with BBB dysfunction after transient focal cerebral ischemia (tFCI).

METHODS

We used a model of 60 minutes of middle cerebral artery occlusion on the following animals: normoglycemic wild-type rats, wild-type rats with hyperglycemia induced by streptozotocin, and human copper/zinc superoxide dismutase (SOD1) transgenic rats with streptozotocin-induced hyperglycemia. We evaluated edema volume, Evans blue leakage, and oxidative stress, such as the carbonyl groups and oxidized hydroethidine (HEt), SOD activity, and gelatinolytic activity, including MMP-9.

RESULTS

Hyperglycemia significantly increased edema volume and Evans blue leakage. Moreover, it enhanced the levels of the carbonyl groups, the oxidized HEt signals, and MMP-9 activity after tFCI without alteration in SOD activity. Gelatinolytic activity and oxidized HEt signals had a clear spatial relation in the hyperglycemic rats. SOD1 overexpression reduced the hyperglycemia-enhanced Evans blue leakage and MMP-9 activation after tFCI.

CONCLUSIONS

Hyperglycemia increases oxidative stress and MMP-9 activity, exacerbating BBB dysfunction after ischemia/reperfusion injury. Superoxide overproduction may be a causal link among hyperglycemia, MMP-9 activation, and BBB dysfunction.