Onset Time of Spinal Anaesthesia in Pregnant Females in Knee-Chest Position: A Randomized Controlled Study

Objective

To assess the efficacy of knee-chest position in shortening the time of spinal induction in pregnant women undergoing elective cesarean section. We also assessed for any untoward adverse events that might limit their usefulness in real-life clinical scenarios.

Methods

Prospective, randomized controlled study was done in maternity operating room of tertiary care institution in 45 ASA II pregnant women undergoing elective cesarean section under spinal anaesthesia. Patients were randomly assigned to groups S (supine) and K (knee-chest position). After performing subarachnoid block (9 mg of 0.5% hyperbaric bupivacaine and 25 µg fentanyl) in the sitting position, women in group K were maintained in the knee-chest position for 60 seconds. Time to attain block height of T6 and maximum sensory blockade, intraoperative hemodynamics, Bromage score, intraoperative fluid, vasopressor requirement, and respiratory parameters were recorded. The newborn was evaluated using Apgar scores at 1 and 5 minutes.

Results:

Data of 45 patients were analyzed. Time to attain T6 block height (group K = 2.1 ± 0.65 minutes, 95% CI: 1.83-2.39; group S = 6.4 ± 0.77 minutes, 95% CI: 6.10-6.78) and time to achieve maximum sensory block height were significantly lower in group K (group K = 3.2 ± 1.35 minutes, 95% CI: 2.61-3.78; group S = 6.6 ± 0.89 min, CI: 6.19-6.98). The degree of motor block was higher in group K than that of group S at 2 minutes (P = .0002), 4 minutes (P < .0001), and 6 minutes (P < .0001), with no difference at 8 minutes. No statistically significant difference was observed in fluids and vasopressors requirement intraoperatively.

Conclusions

This study provides evidence that the onset of adequate surgical anaesthesia for the cesarean section can be hastened by placing the patient in the knee-chest position for a minute after performing the subarachnoid block in the sitting position.

Dysregulation of hypoxia-inducible factor-1α (Hif1α) expression in the Hmox1-deficient placenta

Introduction

Severe hypoxia exists in placentas during early pregnancy, with reoxygenation during mid-gestation. Hypoxia-inducible factor-1α (Hif1α), an oxygen sensor, initiates placental vascular development. We have shown that the placental vasculature in Hmox1-deficient (Hmox1^+/−, Het) pregnancies is impaired, with morphological defects similar to Hif1α-deficient placentas.

Materials and methods

Whole wild-type (WT) and Het mouse placentas were collected at E8.5 (1%–3% O₂) and E9.5–15.5 (8%–10% O₂). mRNA levels were determined using real-time RT-PCR or PCR arrays and protein levels using Western blot. Bone marrow-derived macrophages (BMDMs) from WT, Het, and Hmox1 knockout (KO) mice, representing different Hmox1 cellular levels, were generated to study the role of Hmox1 on Hif1α ′s response to hypoxia-reoxygenation and gestational age-specific placental lysates.

Results

Hif1α was expressed in WT and Het placentas throughout gestation, with protein levels peaking at E8.5 and mRNA levels significantly upregulated from E9.5–E13.5, but significantly lower in Het placentas. Genes associated with angiogenesis (Vegfa, Vegfr1, Mmp2, Cxcl12, Angpt1, Nos3), antioxidants (Sod1, Gpx1), and transcription factors (Ap2, Bach1, Nrf2) were significantly different in Het placentas. In response to in vitro hypoxia-reoxygenation and to WT or Het placental lysates, Hif1α transcription was lower in Het and Hmox1 KO BMDMs compared with WT BMDMs.

Discussion

These findings suggest that deficiencies in Hmox1 underlie the insufficient placental Hif1α response to hypoxia-reoxygenation during gestation and subsequently impair downstream placental vascular formation. Therefore, a dysregulation of Hif1α expression caused by any genetic defect or environmental influence in early pregnancy could be the root cause of pregnancy disorders.

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Expression of Hif1α in wild-type (WT) placentas is gestational age-dependent.

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Hif1α expression is reduced in Hmox1-deficient placentas.

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Expression of angiogenic genes is altered in Hmox1-deficient placentas.

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Hypoxia-reoxygenation induces a differential expression of Hif1α in cells.

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Adding placental lysates dysregulates expression of Hif1α in Hmox1-deficient cells.

Ultrasound-Guided Midpoint Transverse Process to Pleura Block in Breast Cancer Surgery: A Case Report

To avoid the safety issues related to thoracic paravertebral blocks, we performed midpoint transverse process to pleura blocks in 3 patients before general anesthesia for modified radical mastectomies. The midpoint transverse process to pleura blocks served as the major component of multimodal analgesia. With ultrasound guidance, 7 mL of a mixture of 0.75% ropivacaine and 2% lidocaine with epinephrine were deposited at T2, T4, and T6 levels. We noted decreased sensation to cold and pinprick from T2 to T8 dermatome level with sparing of axilla and infraclavicular areas. The maximum pain numeric rating scale score (0-10) was 4 out on movement and none had mean 24-hour numeric rating scale >3.

Absent or Excessive Corpus Luteum Number Is Associated With Altered Maternal Vascular Health in Early Pregnancy

Identifying modifiable factors that contribute to preeclampsia risk associated with assisted reproduction can improve maternal health. Vascular dysfunction predates clinical presentation of preeclampsia. Therefore, we examined if a nonphysiological hormonal milieu, a modifiable state, affects maternal vascular health in early pregnancy. Blood pressure, endothelial function, circulating endothelial progenitor cell numbers, lipid levels, and corpus luteum (CL) hormones were compared in a prospective cohort of women with infertility history based on number of CL: 0 CL (programmed frozen embryo transfer [FET], N=18); 1 CL (spontaneous conception [N=16] and natural cycle FET [N=12]); or >3 CL associated with in vitro fertilization [N=11]. Women with 0 or >3 CL lacked the drop in mean arterial blood pressure compared with those with 1 CL (both P=0.05). Reactive hyperemia index was impaired in women with 0 CL compared with 1 CL ( P=0.04) while baseline pulse wave amplitude was higher with > 3 CL compared with 1 CL ( P=0.01) or 0 CL ( P=0.01). Comparing only FET cycles, a lower reactive hyperemia index and a higher augmentation index is noted in FETs with suppressed CL compared with FETs in a natural cycle (both P=0.03). The number of angiogenic and nonangiogenic circulating endothelial progenitor cell numbers was lower in the absence of a CL in FETs ( P=0.01 and P=0.03). Vascular health in early pregnancy is altered in women with aberrant numbers of CL (0 or >3) and might represent insufficient cardiovascular adaptation contributing to an increased risk of preeclampsia.

Comparison of caudal epidural block with paravertebral block for renal surgeries in pediatric patients: A prospective randomised, blinded clinical trial

STUDY OBJECTIVE

This study was undertaken to compare the analgesic efficacy of ultrasound-guided single-shot caudal block with ultrasound-guided single-shot paravertebral block in children undergoing renal surgeries.

DESIGN

Randomised, interventional, blinded clinical trial.

SETTING

Operating rooms of All India Institute of Medical Sciences, New Delhi, India.

PATIENTS

50 children aged 2-10 years, of ASA status I/II, posted for elective renal surgeries.

INTERVENTIONS

The children were randomised into two groups (Group C-caudal block, Group P-paravertebral block). After induction of general anesthesia, single-shot caudal or paravertebral block was performed under ultrasound guidance, with 0.2% ropivacaine with 1:200000 adrenaline.

MEASUREMENTS

Time to first rescue analgesia, time to perform blocks, intraoperative and post-operative hemodynamics, post-operative FLACC scores, incidence of complications, parental satisfaction scores were recorded.

MAIN RESULTS

Children in Group P had significantly longer duration of analgesia (p < 0.0004) than Group C. Post-operative FLACC scores (p < 0.005) and analgesic requirements (p < 0.0004) were lower in Group P. The mean fentanyl requirement over 24 h in group P was 0.56 ± 0.82 μg/kg, compared to 1.8 ± 1.2 μg/kg in group C. Parents in Group P reported greater satisfaction (p < 0.02). No complications were seen in either of the groups.

CONCLUSION

This study showed superior analgesia and parental satisfaction with single-shot paravertebral block in comparison to single-shot caudal block for renal surgeries in children. However, the block performance in children requires adequate expertise and practice.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Comorbidities among HIV-infected injection drug users in Chennai, India

BACKGROUND & OBJECTIVE

HIV-infected injection drugs users (IDUs) are known to have high rates of co-infections. A few reports exist on comorbidities among HIV-infected IDUs in India. We carried out a retrospective study to analyse data on comorbidities in India and treatment challenges faced when treating HIV-infected IDUs in India.

METHODS

A retrospective chart review of 118 HIV-infected IDUs who accessed care at the YRG Centre for Substance Abuse-Related Research, Chennai, between August 2005 and February 2006 was done. Demographic, laboratory and clinical information was extracted from medical records. Descriptive demographic and clinical characteristics and distributions of comorbidities across CD4 cell count strata were analysed.

RESULTS

All IDUs were male with a median age of 35.5 yr. The majority were married with average monthly income less than INR 3000 per month. The prevalence of hepatitis B and C infections were 11.9 and 94.1 per cent, respectively. Other common co-morbidities included oral candidiasis (43.2%), tuberculosis (33.9%), anaemia (22.9%), lower respiratory tract infections (16.1%), cellulitis (6.8%), herpes zoster (9.3%) and herpes simplex (9.3%). Among participants with CD4+ < 200 cells/microl, the prevalence of TB was 60 per cent.

INTERPRETATION & CONCLUSION

IDUs in Chennai were commonly co-infected with HBV, HCV and tuberculosis, complicating use of antiretroviral and anti-tuberculous therapy. The current regimens available for the management of HIV and TB in India may need to be re-assessed for IDUs given the potential for increased rates of hepatotoxicity.

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.

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.

A new approach for the investigation of reperfusion-related brain injury

Effective stroke therapies require recanalization of occluded cerebral blood vessels; however, early reperfusion can cause BBB (blood–brain barrier) injury, leading to cerebral oedema and/or devastating brain haemorrhage. These complications of early reperfusion, which result from excess production of ROS (reactive oxygen species), significantly limit the benefits of stroke therapies. Here, we summarize some of the findings that lead to the development of a novel animal model that facilitates identification of specific free radical-associated components of the reperfusion injury process and allows therapeutic interventions to be assessed. In this model, KO (knockout) mice containing 50% activity of the mitochondrial antioxidant manganese-SOD (superoxide dismutase) (SOD2-KO) undergo transient focal ischaemia followed by reperfusion. These animals have delayed (>24 h) BBB breakdown associated with activation of matrix metalloproteinase-9, inflammation and a high brain haemorrhage rate. These adverse consequences are absent from wild-type littermates, SOD2 overexpressors and minocycline-treated SOD2-KO animals. In addition, using microvessel isolations following in vivo ischaemia/reperfusion, we were able to show that the tight junction membrane protein, occludin, is an early and specific target in ROS-mediated microvascular injury. This new model is ideal for studying ischaemia/reperfusion-induced vascular injury and secondary brain damage and offers a unique opportunity to evaluate free radical-based neurovascular protective strategies.

Evaluating therapeutic targets for reperfusion-related brain hemorrhage

OBJECTIVE

Early reperfusion after an ischemic stroke can cause blood-brain barrier injury with subsequent cerebral edema and devastating brain hemorrhage. These complications of early reperfusion, which result from excess production of reactive oxygen species, significantly limit the benefits of stroke therapies. In this article, we use a novel animal model that facilitates identification of specific components of the reperfusion injury process, including vascular injury and secondary brain damage, and allows assessment of therapeutic interventions.

METHODS

Knock-out (KO) mice containing 50% manganese-superoxide dismutase activity (SOD2-KO) and transgenic mice overexpressing SOD2 undergo transient focal ischemia and reperfusion followed by assessment of infarct, edema, hemorrhage rates, metalloproteinase activation, and microvascular injury.

RESULTS

SOD2-KO mice demonstrate delayed (>24h) blood-brain barrier breakdown associated with activation of matrix metalloproteinases, inflammation, and high brain hemorrhage rates. These adverse consequences are absent in wild-type littermates and minocycline-treated SOD2-KO animals. Increased hemorrhage rates also are absent in SOD2 overexpressors, which have reduced vascular endothelial cell death. Finally, we show that the tight junction membrane protein, occludin, is an early and specific target in oxidative stress-induced microvascular injury.

INTERPRETATION

This model is ideal for studying ischemia/reperfusion-induced vascular injury and secondary brain hemorrhage and offers a unique opportunity to evaluate antioxidant-based neurovascular protective strategies as potential adjunct treatments to currently approved stroke therapies such as thrombolysis and endovascular clot retrieval.

Mild hypoxia promotes survival and proliferation of SOD2-deficient astrocytes via c-Myc activation

Mouse astrocytes deficient in the mitochondrial form of manganese superoxide dismutase (SOD2) do not survive in culture under atmospheric air with 20% oxygen (O2), which is a common condition for cell cultures. Seeding the cells and maintaining them under mild hypoxic conditions (5% O2) circumvents this problem and allows the cells to grow and become confluent. Previous studies from our laboratory showed that this adaptation of the cells was not attributable to compensation by other enzymes of the antioxidant defense system. We hypothesized that transcriptional activity and upregulation of genes other than those with an antioxidant function are involved. Our present study shows that c-Myc was significantly induced and that it inhibited p21 and induced proteins such as cyclin-dependent kinases, cyclin D, and cyclin E, which are involved in the cell cycle process, along with phosphorylation of the retinoblastoma protein and Cdc2 (cell division cycle 2). These mechanisms contribute to cell proliferation. Small interfering RNA of c-Myc, however, blocked proliferation of SOD2 homozygous (SOD2-/-) astrocytes under mild hypoxia consisting of 5% O2, whereas it did not affect the growth of wild-type astrocytes. Our results indicate that c-Myc plays a critical role in hypoxia-induced proliferation and survival of SOD2-/- astrocytes by overcoming injury caused by oxidative stress.

Epo protects SOD2-deficient mouse astrocytes from damage by oxidative stress

Erythropoietin (Epo) expression, which regulates erythropoiesis, has been shown in rat and mouse brain after hypoxia. A previous study from our laboratory showed that astrocytes from manganese-superoxide dismutase (SOD2) homozygous knockout (SOD2(-/-)) mice can survive under 5% O(2), but not under normal aerobic conditions. However, the mechanism involved is not clear. Our preliminary study using reverse transcriptase-polymerase chain reaction showed increased Epo mRNA expression in astrocytes cultured with 5% hypoxia compared with astrocytes under normal conditions. After administration of anti-sense Epo, protection decreased with time. Dose-dependent administration of Epo to SOD2(-/-) mouse astrocytes improved their survivability under normal conditions. Survivability of heterozygous SOD2(-/+) mutant and wild-type mouse astrocyte cultures was the same under normal conditions but, after administration of 2 mM of paraquat, a reactive oxygen species generator, survivability of the SOD2(-/+) astrocytes decreased remarkably compared with the wild-type cells. Epo administration 24 h before exposure to paraquat significantly improved the survivability of the SOD2(-/+) astrocytes. Western blot studies suggest that Jak-Stat signal transduction pathways are involved in this process. Our study demonstrates an important role for Epo in the protection of astrocytes from reactive oxygen species. We suggest that Epo can compensate in part for the antioxidant properties of mitochondrial SOD2 deficiency.

Oxidative stress and neuronal death/survival signaling in cerebral ischemia

It has been demonstrated by numerous studies that apoptotic cell death pathways are implicated in ischemic cerebral injury in ischemia models in vivo. Experimental ischemia and reperfusion models, such as transient focal/global ischemia in rodents, have been thoroughly studied and the numerous reports suggest the involvement of cell survival/death signaling pathways in the pathogenesis of apoptotic cell death in ischemic lesions. In these models, reoxygenation during reperfusion provides oxygen as a substrate for numerous enzymatic oxidation reactions and for mitochondrial oxidative phosphorylation to produce adenosine triphosphate. Oxygen radicals, the products of these biochemical and physiological reactions, are known to damage cellular lipids, proteins, and nucleic acids and to initiate cell signaling pathways after cerebral ischemia. Genetic manipulation of intrinsic antioxidants and factors in the signaling pathways has provided substantial understanding of the mechanisms involved in cell death/survival signaling pathways and the role of oxygen radicals in ischemic cerebral injury. Future studies of these pathways could provide novel therapeutic strategies in clinical stroke.

Neuroprotection by hypoxic preconditioning involves oxidative stress-mediated expression of hypoxia-inducible factor and erythropoietin

BACKGROUND AND PURPOSE

Hypoxic preconditioning is an endogenous protection against subsequent lethal hypoxia, but the mechanism involved is not understood. Hypoxia is followed by reactive oxygen species (ROS) production and induces hypoxia-inducible factor (HIF) and its downstream factor erythropoietin (Epo), which is associated with neuroprotection. We hypothesized that these endogenous processes may contribute to hypoxic preconditioning.

METHODS

We used a mouse neuronal culture model, with 2 hours of hypoxia as preconditioning followed by 15 hours of hypoxic insult, and examined the expression of HIF-1alpha, Epo, and their downstream proteins by Western blotting. Copper/zinc-superoxide dismutase (SOD1) transgenic (Tg) mice were used to detect the effect of ROS. Cell survival and apoptosis were detected by mitogen-activated protein 2 quantification, apoptotic-related DNA fragmentation, and caspase-3 fragmentation. Antisense Epo was used to block endogenously produced Epo.

RESULTS

Hypoxic preconditioning was protective in wild-type (Wt) neurons but not in neurons obtained from SOD1 Tg mice. In Wt neurons, HIF-1alpha and Epo expression showed a greater increase after hypoxia compared with Tg neurons and reached a higher level with preconditioned hypoxia, followed by pJak2, pStat5, and nuclear factor kappaB (NF-kappaB) expression. Antisense Epo decreased these downstream proteins and the neuroprotection of hypoxic preconditioning.

CONCLUSIONS

Hypoxic preconditioning induces ROS, which may downregulate the threshold for production of HIF-1alpha and Epo expression during subsequent lethal hypoxia, thus exerting neuroprotection through the Jak2-Stat5 and NF-kappaB pathways.

Overexpression of human copper/zinc-superoxide dismutase in transgenic animals attenuates the reduction of apurinic/apyrimidinic endonuclease expression in neurons afterin vitroischemia and after transient global cerebral ischemia

Oxidative stress after ischemia/reperfusion has been shown to induce DNA damage and subsequent DNA repair activity. Apurinic/apyrimidinic endonuclease (APE) is a multifunctional protein in the DNA base excision repair pathway which repairs apurinic/apyrimidinic sites in DNA. We investigated the involvement of oxidative stress and expression of APE in neurons after oxygen-glucose deprivation and after global cerebral ischemia. Our results suggest that overexpression of human copper/zinc-superoxide dismutase reduced oxidative stress with a subsequent decrease in APE expression. Production of oxygen free radicals and inhibition of the base excision repair pathway may play pivotal roles in the cell death pathway after ischemia.

Neuroprotective role of a proline-rich Akt substrate in apoptotic neuronal cell death after stroke: relationships with nerve growth factor

The Akt signaling pathway contributes to regulation of apoptosis after a variety of cell death stimuli. A novel proline-rich Akt substrate (PRAS) was recently detected and found to be involved in apoptosis. In our study, Akt activation was modulated by growth factors, and treatment with nerve growth factor (NGF) reduced apoptotic cell death after ischemic injury. However, the role of the PRAS pathway in apoptotic neuronal cell death after ischemia remains unknown. Phosphorylated PRAS (pPRAS) and the binding of pPRAS/phosphorylated Akt (pPRAS/pAkt) to 14-3-3 (pPRAS/14-3-3) were detected, and their expression transiently decreased in mouse brains after transient focal cerebral ischemia (tFCI). Liposome-mediated pPRAS cDNA transfection induced overexpression of pPRAS, promoted pPRAS/14-3-3, and inhibited apoptotic neuronal cell death after tFCI. The expression of pPRAS, pPRAS/pAkt, and pPRAS/14-3-3 increased in NGF-treated mice but decreased with inhibition of phosphatidylinositol-3 kinase and the NGF receptor after tFCI. These results suggest that PRAS phosphorylation and its interaction with pAkt and 14-3-3 might play an important role in neuroprotection mediated by NGF in apoptotic neuronal cell death after tFCI.

Neuronal death/survival signaling pathways in cerebral ischemia

Cumulative evidence suggests that apoptosis plays a pivotal role in cell death in vitro after hypoxia. Apoptotic cell death pathways have also been implicated in ischemic cerebral injury in in vivo ischemia models. Experimental ischemia and reperfusion models, such as transient focal/global ischemia in rodents, have been thoroughly studied and the numerous reports suggest the involvement of cell survival/death signaling pathways in the pathogenesis of apoptotic cell death in ischemic lesions. In these models, reoxygenation during reperfusion provides a substrate for numerous enzymatic oxidation reactions. Oxygen radicals damage cellular lipids, proteins and nucleic acids, and initiate cell signaling pathways after cerebral ischemia. Genetic manipulation of intrinsic antioxidants and factors in the signaling pathways has provided substantial understanding of the mechanisms involved in cell death/survival signaling pathways and the role of oxygen radicals in ischemic cerebral injury. Future studies of these pathways may provide novel therapeutic strategies in clinical stroke.

Role of superoxide in poly(ADP-ribose) polymerase upregulation after transient cerebral ischemia

Oxidative stress plays a pivotal role in ischemic-reperfusion cell injury. Oxygen-derived free radicals trigger DNA strand damage, which is responsible for the activation of poly(ADP-ribose) polymerase (PARP). Recent studies have shown that peroxynitrite is the primary mediator of DNA damage and, hence, PARP activation after ischemia. PARP activation depletes NAD and ATP pools, ultimately resulting in necrotic cell death by loss of energy stores. Our study shows that PARP is upregulated as early as 15 min after 1 h of transient focal cerebral ischemia and remains for 8 h. We also examined the role of superoxide in PARP induction using copper/zinc-superoxide dismutase transgenic mice. Immunohistochemical and Western blotting data showed that there was no increased induction in PARP expression in these mice, suggesting that one of the mechanisms by which ischemic injury is attenuated in these mice might be by the inhibition of PARP induction. Furthermore, double staining of ischemic tissue with a PARP antibody and terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling (TUNEL) indicated that most cells that are positive for TUNEL do not stain for the PARP antibody, confirming recent reports that PARP activation is involved in necrotic cell death rather than apoptosis during ischemic-reperfusion injury.

Rapidly progressive fatal cutaneous T cell lymphoma with a trauma-related presentation

A case of rapidly progressive cutaneous T cell lymphoma with a trauma-related presentation in a 73-year-old man is reported. Clinically, the patient presented with an ulcerated cutaneous mass at the site of trauma-related hematoma of the leg. The histopathology was that of tumor phase cutaneous T cell lymphoma with involvement of the skin and subcutis. The diagnostic challenge of this clinical presentation and the rapidly progressive course are highlighted.

Copper-zinc superoxide dismutase prevents the early decrease of apurinic/apyrimidinic endonuclease and subsequent DNA fragmentation after transient focal cerebral ischemia in mice

BACKGROUND AND PURPOSE

DNA damage and its repair mechanism are thought to be involved in ischemia/reperfusion injury in the brain. We have previously shown that apurinic/apyrimidinic endonuclease (APE/Ref-1), a multifunctional protein in the DNA base excision repair pathway, rapidly decreased after transient focal cerebral ischemia (FCI) before the peak of DNA fragmentation. To further investigate the role of reactive oxygen species in APE/Ref-1 expression in vivo, we examined the expression of APE/Ref-1 and DNA damage after FCI in wild-type and transgenic mice overexpressing copper-zinc superoxide dismutase.

METHODS

Transgenic mice overexpressing copper-zinc superoxide dismutase and wild-type littermates were subjected to 60 minutes of transient FCI by intraluminal blockade of the middle cerebral artery. APE/Ref-1 protein expression was analyzed by immunohistochemistry and Western blot analysis. DNA damage was evaluated by gel electrophoresis and terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end-labeling (TUNEL).

RESULTS

A similar level of APE/Ref-1 was detected in the control brains from both groups. APE/Ref-1 was significantly reduced 1 hour after transient FCI in both groups, whereas the transgenic mice had less reduction than that seen in wild-type mice 1 and 4 hours after FCI. DNA laddering was detected 24 hours after FCI and was decreased in transgenic mice. Double staining with APE/Ref-1 and TUNEL showed that the neurons that lost APE/Ref-1 immunoreactivity became TUNEL positive.

CONCLUSIONS

These results suggest that reactive oxygen species contribute to the early decrease of APE/Ref-1 and thereby exacerbate DNA fragmentation after transient FCI in mice.

Ten kilobases of 5'-flanking region confers proper regulation of the mouse alcohol dehydrogenase-1 (Adh-1) gene in kidney and adrenal of transgenic mice

The expression profile of the mouse Adh-1 gene, which encodes class I alcohol dehydrogenase enzyme (ADH), is complex and includes tissue specificity and differential hormone responsiveness. Whereas kidney Adh-1 transcription rate is stimulated six- to sevenfold by testosterone treatment, adrenal gland ADH-1 mRNA is reduced to less than 5% of control level within 18 h following hormone administration. Androgen receptor is required for both responses since neither occurs in Tfm mutant mice lacking receptor. Hormonal and tissue-specific aspects of Adh-1 regulation were studied in transgenic mice harboring either of two constructs containing either -2.5 kb or -10 kb of 5'-flanking sequence attached to an Adh-1 minigene. The minigene transcript was expressed in kidney and adrenal tissues, but not liver, in five independent lines harboring a transgene with -2.5 kb of 5'-flanking sequence. Androgen treatment repressed the level of the minigene transcript in adrenal gland, but did not cause induction in kidney. In four lines of transgenic mice carrying the construct with -10 kb of 5'-flanking sequence, the minigene transcript was both repressed in adrenal and induced in kidney by testosterone. These lines have no detectable transgene expression in liver tissue. The -10 kb region in the mouse Adh-1 gene contains necessary controlling regions for proper tissue expression and hormonal regulation in kidney and adrenal; however, this region does not contain all essential elements necessary for expression in liver.

Methylmalonyl-CoA mutase induction by cerebral ischemia and neurotoxicity of the mitochondrial toxin methylmalonic acid

Differential screening of gerbil brain hippocampal cDNA libraries was used to search for genes expressed in ischemic, but not normal, brain. The methylmalonyl-CoA mutase (MCM) cDNA was highly expressed after ischemia and showed a 95% similarity to mouse and 91% similarity to the human MCM cDNAs. Transient global ischemia induced a fourfold increase in MCM mRNA on Northern blots from both hippocampus and whole forebrain. MCM protein exhibited a similar induction on Western blots of gerbil cerebral cortex 8 and 24 hr after ischemia. Treatment of primary brain astrocytes with either the branched-chain amino acid (BCAA) isoleucine or the BCAA metabolite, propionate, induced MCM mRNA fourfold. Increased concentrations of BCAAs and odd-chain fatty acids, both of which are metabolized to propionate, may contribute to inducing the MCM gene during ischemia. Methylmalonic acid, which is formed from the MCM substrate methylmalonyl-CoA and which inhibits succinate dehydrogenase (SDH), produced dose-related cell death when injected into the basal ganglia of adult rat brain. This neurotoxicity is similar to that of structurally related mitochondrial SDH inhibitors, malonate and 3-nitropropionic acid. Methylmalonic acid may contribute to neuronal injury in human conditions in which it accumulates, including MCM mutations and B12 deficiency. This study shows that methylmalonyl-CoA mutase is induced by several stresses, including ischemia, and would serve to decrease the accumulation of an endogenous cellular mitochondrial inhibitor and neurotoxin, methylmalonic acid.

Astrocyte survival and HSP70 heat shock protein induction following heat shock and acidosis

Although severe acidosis is an important mediator of brain infarction, recent evidence suggests that mild acidosis may protect ischemic cells. The HSP70 heat shock protein is induced by acidosis in cultured cells and in ischemic brain and protects cells against many types of injury. Therefore, this study determined whether induction of heat shock proteins protects cultured astrocytes against acidosis. Brief exposure of cultured cortical astrocytes to acid (pH 5.2 for 40 min) or heat shock (45 degrees C for 40 min) markedly induced hsp70 mRNA and HSP70 protein. HSP70 protein was detected with the C92 monoclonal antibody (Welch and Suhan: J Cell Biol 103:2035, 1986), which has been shown to recognize the protein product of the full-length rat hsp70 cDNA (Longo et al: J Neurosci Res 36:325, 1993). Heat shock of the cultured cortical astrocytes completely protected the astrocytes from an otherwise lethal heat exposure 24 h later (45 degrees C for 4 h). In contrast, heat pretreatment sensitized the astrocytes to injury from acidosis 24 h later. Acid pretreatment, which markedly induced the HSP70 protein without producing astrocytic cell death, similarly sensitized the cells to injury from acidosis 24 h later (60% survival following pH 5.2 for 3 h versus 90% survival in controls; P < 0.0001). Surprisingly, heat shock pretreatment protected astrocytes against exposure to acid 48 h later (P < 0.05, 1.5-3 h), whereas acid pretreatment had no effect on astrocyte survival 48 h later. Since heat shock did not protect against acidosis at 24 h when HSP70 induction was maximal but did protect at 48 h when HSP70 was markedly diminished, the protective effect of heat shock at 48 h may be related to stress proteins present at 48 h. It is concluded that induction of HSP70 and other heat shock proteins by heat shock protects astrocytes against subsequent lethal heat shock. However, heat shock and acid treatment increase the vulnerability of astrocytes to acidosis 24 h later in spite of the induction of HSP70 heat shock proteins. The finding that heat shock protected astrocytes against acidosis 2 days later may suggest that delayed induction of stress proteins partially protects the astrocytes against damage produced by high concentrations of hydrogen ions.

cDNA cloning and expression of stress-inducible rat hsp70 in normal and injured rat brain

A reverse transcriptase-polymerase chain reaction (RT-PCR) product obtained from ischemic rat brain RNA was used to screen a rat ischemic forebrain cDNA library for a cDNA clone containing the entire open reading frame for the inducible hsp70. The coding sequence for the rat hsp70 cDNA demonstrated significant similarities with the human hsp70 of Hunt and Morimoto (Proc Natl Acad Sci 82:6455-6459, 1985) and the mouse hsp70 of Hunt and Calderwood (Gene 87:199-204, 1990). The rat inducible hsp70 and constitutive hsc73 sequences are distinct. There was a low level of hsp70 mRNA expression in normal rat brain as in found in other tissues. hsp70 mRNA was markedly induced in rat brain 8 hours following global ischemia and kainic acid-induced seizures. Northern blots showed a approximately 2.9kb hsp70 mRNA band from control, kainic acid, and ischemic brains. RT-PCR confirmed the presence of hsp70 mRNA in normal rat brain. Since there are at least five human and six mouse inducible hsp70 genes known, many other rat hsp70 genes probably exist that could function in different cells or organelles or be induced under different circumstances.