Yangdong He

Hemoglobin and iron handling in brain after subarachnoid hemorrhage and the effect of deferoxamine on early brain injury

The purpose of this study was to investigate hemoglobin and iron handling after subarachnoid hemorrhage (SAH), examine the relationship between iron and neuroglial cell changes, and determine whether deferoxamine (DFX) can reduce SAH-induced injury. The SAH was induced in Sprague-Dawley rats (n=110) using an endovascular perforation technique. Animals were treated with DFX (100 mg/kg) or vehicle 2 and 6 hours after SAH induction followed by every 12 hours for 3 days. Rats were killed at 6 hours, Days 1 and 3 to determine nonheme iron and examine iron-handling proteins using Western blot and immunohistochemistry. 8-Hydroxyl-2′-deoxyguanosine and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining were performed to assess oxidative DNA damage and neuronal cell death. After SAH, marked heme-oxygenase-1 (HO-1) upregulation at Day 3 (P<0.01) was accompanied by elevated nonheme iron (P<0.01), transferrin (Tf) (P<0.01), Tf receptor (P<0.05), and ferritin levels (P<0.01). Deferoxamine treatment reduced SAH-induced mortality (12% versus 29%, P<0.05), brain nonheme iron concentration, iron-handling protein expression, oxidative stress, and neuronal cell death at Day 3 (P<0.01) after SAH. These results suggest that iron overload in the acute phase of SAH causes oxidative injury leading to neuronal cell death. Deferoxamine effectively reduced oxidative stress and neuronal cell death, and may be a potential therapeutic agent for SAH.

Hyperbaric Oxygen-Induced Attenuation of Hemorrhagic Transformation After Experimental Focal Transient Cerebral Ischemia

Background and Purpose— An increased risk of hemorrhagic transformation is a major factor limiting the use of tissue plasminogen activator for stroke. Increased hemorrhagic transformation is also found in animals undergoing transient focal cerebral ischemia with hyperglycemia; this study examined whether hyperbaric oxygen (HBO) could reduce such hemorrhagic transformation in a rat model. Methods— Rats received an injection of 50% glucose (6 mL/kg intraperitoneally) and had a middle cerebral artery occlusion 10 minutes later. Rats were treated with HBO (3 ATA for 1 hour) 30 minutes after middle cerebral artery occlusion. Control rats received normobaric room air. Rats underwent reperfusion 2 hours after middle cerebral artery occlusion. Blood–brain barrier permeability (Evans blue), hemorrhagic transformation (hemoglobin content), brain edema, infarct volume, and mortality were measured. Results— HBO treatment reduced Evans blue leakage in the ipsilateral hemisphere (28.4±3.5 versus 71.8±13.1 &mgr;g/g in control group, P<0.01) 2 hours after reperfusion and hemorrhagic transformation (0.13±0.13 versus 0.31±0.28 mg hemoglobin in the control group, P<0.05) 22 hours later. Mortality was less in the HBO group (4% versus 27% in controls, P<0.05). Mean infarct volume and swelling in the caudate were also less in HBO-treated rats (P<0.05), but HBO failed to reduce brain water content in the ipsilateral hemisphere (P>0.05). Conclusions— Early intraischemic HBO treatment reduces the blood–brain barrier disruption, hemorrhagic transformation, and mortality after focal cerebral ischemia suggesting that HBO could be used to reduce hemorrhagic conversion in patients with stroke.

Myeloid-Specific Deletion of the Mineralocorticoid Receptor Reduces Infarct Volume and Alters Inflammation During Cerebral Ischemia

Background and Purpose— Mineralocorticoid receptor (MR) antagonists have protective effects in rodent models of ischemic stroke, but the cell type-specific actions of these drugs are unknown. In the present study, we examined the contribution of myeloid cell MR during focal cerebral ischemia using myeloid-specific MR knockout mice. Methods— Myeloid-specific MR knockout mice were subjected to transient (90 minutes) middle cerebral artery occlusion followed by 24 hours reperfusion (n=5 to 7 per group). Ischemic cerebral infarcts were identified by hematoxylin and eosin staining and quantified with image analysis software. Immunohistochemical localization of microglia and macrophages was performed using Iba1 staining, and the expression of inflammatory markers was measured after 24 hours of reperfusion by quantitative reverse transcription-polymerase chain reaction. Results— Myeloid-specific MR knockout resulted in a 65% reduction in infarct volume (P=0.005) after middle cerebral artery occlusion. This was accompanied by a significant reduction in activated microglia and macrophages in the ischemic core. Furthermore, myeloid-specific MR knockout suppressed classically activated M1 macrophage markers tumor necrosis factor-&agr;, interleukin-1&bgr;, monocyte chemoattractant protein-1, macrophage inflammatory protein-1&agr;, and interleukin-6 at the same time as partially preserving the induction of alternatively activated, M2, markers Arg1, and Ym1. Conclusions— These data demonstrate that myeloid MR activation exacerbates stroke and identify myeloid MR as a critical target for MR antagonists. Furthermore, these data indicate that MR activation has an important role in controlling immune cell function during the inflammatory response to stroke.

Minocycline-Induced Attenuation of Iron Overload and Brain Injury After Experimental Intracerebral Hemorrhage

Background and Purpose— Brain iron overload plays a detrimental role in brain injury after intracerebral hemorrhage (ICH). A recent study found that minocycline acts as an iron chelator and reduces iron-induced neuronal death in vitro. The present study investigated if minocycline reduces iron overload after ICH and iron-induced brain injury in vivo. Methods— This study was divided into 4 parts: (1) rats with different sizes of ICH were euthanized 3 days later for serum total iron and brain edema determination; (2) rats had an ICH treated with minocycline or vehicle. Serum iron, brain iron, and brain iron handling proteins were measured; (3) rats had an intracaudate injection of saline, iron, iron+minocycline, or iron+macrophage/microglia inhibitory factor and were used for brain edema and neuronal death measurements; and (4) rats had an intracaudate injection of iron and were treated with minocycline. The brains were used for edema measurement. Results— After ICH, serum total iron and brain nonheme iron increased and these changes were reduced by minocycline treatment. Minocycline also reduced ICH-induced upregulation of brain iron handling proteins and neuronal death. Intracaudate injection of iron caused brain edema, blood–brain barrier leakage, and brain cell death, all of which were significantly reduced by coinjection with minocycline. Conclusions— The current study found that minocycline reduces iron overload after ICH and iron-induced brain injury. It is also well known minocycline is an inhibitor of microglial activation. Minocycline may be very useful for patients with ICH because both iron accumulation and microglia activation contribute to brain damage after ICH.

The Role of Complement C3 in Intracerebral Hemorrhage-Induced Brain Injury

Activation of the complement cascade contributes to brain injury after intracerebral hemorrhage (ICH). However, a recent study found that complement C5 deficient mice had enhanced ICH-induced brain injury. The present study, therefore, investigated the role of complement C3 (which is upstream from C5) in ICH. Male complement C3 deficient and sufficient mice had an intracerebral infusion of 30-μL autologous whole blood. The mice were killed and the brains were sampled for edema, Western blotting, immunohistochemistry and histologic analysis. Behavioral tests including forelimb use asymmetry test and corner turn were also performed before and after ICH. Compared to complement C3 sufficient mice, C3 deficient mice had less brain edema, lower hemeoxygenase-1 levels, less microglia activation and neutrophil infiltration around the clot after ICH. In addition, the C3-deficient mice had less ICH-induced forelimb use asymmetry deficits compared with C3-sufficient mice. These results suggest complement activation may affect heme metabolism and the inflammatory response after ICH suggesting that complement C3 is an important factor causing ICH-induced brain injury.

Activated autophagy pathway in experimental subarachnoid hemorrhage.

Recent results have suggested a role for autophagy in acute brain injury but an involvement in subarachnoid hemorrhage (SAH) has not been investigated. Although, autophagy is a regulated process essential for cellular homeostasis, it may represent an additional type of cell death mechanism. This study employed a modified endovascular perforation rat model under guidance by intracranial pressure monitoring to investigate whether autophagy pathway is involved in the early brain injury following SAH. Sham-operated control rats underwent an identical procedure without vessel perforation. Electron microscopy was performed to examine the ultrastructural changes in neural cells after SAH. Additionally, microtubule-associated protein light chain-3 (LC3), cathepsin-D and beclin-1 were investigated by Western blot analysis and immunohistochemistry. Electron microscopically, there was a marked increase in autophagosomes and autolysosomes in neurons at Day 1 following SAH. Although LC3 could be detected in sham-operated control rats, the conversion of LC3-I to LC3-II was significantly increased at Day 1 (P<0.01) and Day 3 (P<0.05). The time-course of beclin-1 expression paralleled the LC3 conversion. Cathepsin-D expression was also elevated at Day 1 (P<0.01). Immunohistochemical study with antibodies against cathepsin-D and beclin-1 showed numerous positive stained cells after SAH, especially in deep layers of the fronto-basal cortex. Double immunolabeling revealed beclin-1 expression predominantly in neurons. This present study showed that the autophagy pathway is activated in neurons in the acute phase after SAH.

Effects of cerebral ischemia on neuronal hemoglobin

This study examined whether neuronal hemoglobin (Hb) is present in rats. It then examined whether cerebral ischemia or ischemic preconditioning (IPC) affects neuronal Hb levels in vivo and in vitro. In vivo, male Sprague-Dawley rats were subjected to either 15 mins of transient middle cerebral artery occlusion (MCAO) with 24 h of reperfusion, an IPC stimulus, or 24 h of permanent MCAO (pMCAO), or IPC followed 3 days later by 24 h of pMCAO. In vitro, primary cultured neurons were exposed to 2 h of oxygen—glucose deprivation (OGD) with 22 h of reoxygenation. Results showed that Hb is widely expressed in rat cerebral neurons but not astrocytes. Hemoglobin expression was significantly upregulated in the ipsilateral caudate and the cortical core of the middle cerebral artery territory after IPC. Hemoglobin levels also increased more in the penumbral cortex and the contralateral hemisphere 24 h after pMCAO, but expressions in the ipsilateral caudate and the cortical core area were decreased. Ischemic preconditioning modified pMCAO-induced brain Hb changes. Neuronal Hb levels in vitro were increased by 2 h of OGD and 22 h of reoxygenation. These results indicate that Hb is synthesized in neurons and can be upregulated by ischemia.

Thrombin-induced autophagy: a potential role in intracerebral hemorrhage

Autophagy occurs in the brain after intracerebral hemorrhage (ICH) and thrombin contributes to ICH-induced brain injury and cell death. In this study, we investigated whether thrombin may activate autophagy (in vivo and in cultured astrocytes) and its potential role in ICH. Autophagy was examined using electron microscopy, conversion of light chain 3(LC3) from the LC3-I form to LC3-II, cathepsin D Western blotting and monodansylcadaverine (MDC) staining to detect autophagic vacuoles. 3-Methyladenine (3-MA) was used as an autophagy inhibitor. In vivo, we found that intracaudate injection of thrombin increased conversion of LC3-I to LC3-II, cathepsin D levels, and formation of autophagic vacuoles in the ipsilateral basal ganglia. ICH-induced upregulation of LC3-I to LC3-II conversion and cathepsin D levels was reduced by a thrombin inhibitor, hirudin. In cultured astrocytes, thrombin enhanced the conversion of LC3-I to LC3-II and increased MDC-labeled autophagic vacuoles. 3-MA inhibited thrombin-induced autophagic vacuole formation and exacerbated thrombin-induced cell death. These results indicate that thrombin activates autophagy in the brain and that thrombin has a role in ICH-induced autophagy.

Deferoxamine reduces brain swelling in a rat model of hippocampal intracerebral hemorrhage

In this study, we examine the effects of deferoxamine on hemoglobin-induced brain swelling in a newly developed hippocampal model of intracerebral hemorrhage (ICH). There were 2 parts to the experiments in this study. In the first part, male Sprague-Dawley rats received a 10-microL infusion of either packed red blood cells (RBC), lysed RBC, hemoglobin, ferrous iron, or saline, into the hippocampus. In the second part, rats received a 10-microL infusion of hemoglobin and then were treated with either deferoxamine (100 mg/kg, intraperitoneally, given immediately after hemoglobin injection, then every 12h for 24h) or vehicle. Rats were then killed to obtain hippocampus size and DNA damage measurements. We found that lysed RBC induced marked brain swelling in the hippocampus. Compared to saline, hemoglobin or iron injection caused swelling. Systemic use of deferoxamine reduced hemoglobin-induced brain swelling (6.14 +/- 0.45 vs. 7.11 +/- 0.58 mm2 in the vehicle group, p < 0.05). In addition, deferoxamine reduced hemoglobin-induced DNA damage. These results indicate that iron has a key role in hemoglobin-induced brain swelling. Deferoxamine may be a useful treatment for ICH patients.

Hyperbaric oxygen for experimental intracerebral hemorrhage

Acute brain edema formation contributes to brain injury after intracerebral hemorrhage (ICH). It has been reported that hyperbaric oxygen (HBO) is neuroprotective in cerebral ischemia, subarachnoid hemorrhage, and brain trauma. In this study, we investigated the effects of HBO on brain edema following ICH in rats. Male Sprague-Dawley rats received intracerebral infusion of autologous whole blood, thrombin, or ferrous iron. HBO (100% O2, 3.0 ATA for 1 h) was initiated 1 h after intracerebral injection. Control rats were exposed to air at room pressure. Brains were sampled at 24 or 72 h for water content, ion measurement, and Western blot analysis. We found that 1 session of HBO reduced perihematomal brain edema (p < 0.05) 24 h after ICH. HBO also reduced heat shock protein-32 (HSP-32) levels (p < 0.05) in ipsilateral basal ganglia 24h after ICH. However, HBO failed to attenuate thrombin-induced brain edema and exaggerated ferrous iron-induced brain edema (p < 0.05). Three sessions of HBO also failed to reduce brain edema 72h after ICH. In summary, HBO reduced early perihematomal brain edema and HSP-32 levels in brain. HBO-related brain protection does not occur through reduction in thrombin toxicity because HBO failed to attenuate thrombin-induced brain edema. Our results also indicate that HBO treatment after hematoma lysis for ICH may be harmful, since HBO amplifies iron-induced brain edema.