Zi-Xiang Cong

Amelioration of oxidative stress and protection against early brain injury by astaxanthin after experimental subarachnoid hemorrhage.

UNLABELLED OBJECT.: Aneurysmal subarachnoid hemorrhage (SAH) causes devastating rates of mortality and morbidity. Accumulating studies indicate that early brain injury (EBI) greatly contributes to poor outcomes after SAH and that oxidative stress plays an important role in the development of EBI following SAH. Astaxanthin (ATX), one of the most common carotenoids, has a powerful antioxidative property. However, the potential role of ATX in protecting against EBI after SAH remains obscure. The goal of this study was to assess whether ATX can attenuate SAH-induced brain edema, blood-brain barrier permeability, neural cell death, and neurological deficits, and to elucidate whether the mechanisms of ATX against EBI are related to its powerful antioxidant property. METHODS Two experimental SAH models were established, including a prechiasmatic cistern SAH model in rats and a one-hemorrhage SAH model in rabbits. Both intracerebroventricular injection and oral administration of ATX were evaluated in this experiment. Posttreatment assessments included neurological scores, body weight loss, brain edema, Evans blue extravasation, Western blot analysis, histopathological study, and biochemical estimation. RESULTS It was observed that an ATX intracerebroventricular injection 30 minutes post-SAH could significantly attenuate EBI (including brain edema, blood-brain barrier disruption, neural cell apoptosis, and neurological dysfunction) after SAH in rats. Meanwhile, delayed treatment with ATX 3 hours post-SAH by oral administration was also neuroprotective in both rats and rabbits. In addition, the authors found that ATX treatment could prevent oxidative damage and upregulate the endogenous antioxidant levels in the rat cerebral cortex following SAH. CONCLUSIONS These results suggest that ATX administration could alleviate EBI after SAH, potentially through its powerful antioxidant property. The authors conclude that ATX might be a promising therapeutic agent for EBI following SAH.

Knockdown of Nrf2 suppresses glioblastoma angiogenesis by inhibiting hypoxia‐induced activation of HIF‐1α

Concerns were increasingly raised that several types of cancers overexpressed the nuclear factor erythroid 2‐related factor 2 (Nrf2), which contributed strikingly to cancer biological capabilities and chemoresistance. However, the role of Nrf2 in the tumor vascular biology had yet to be mechanistically determined. Here, we investigated the involvement of Nrf2 in glioblastoma (GB) angiogenesis in hypoxia. First, we detected the overexpression of Nrf2 and correlated its protein level with microvessel density (MVD) in human GB tissues. Then, we established the stable RNAi‐mediated Nrf2‐knockdown cells and mimicked hypoxic condition in vitro. The knockdown of Nrf2 inhibited cell proliferation in vitro and suppressed tumor growth in mouse xenografts with a concomitant reduction in VEGF expression and MVD. Similar antiangiogenic effects were documented in endothelial tube formation assays. The downregulation of Nrf2 in glioma cells led to much lower accumulation of HIF‐1α protein and limited expression of VEGF and other HIF‐1α target genes in mimicking hypoxia. Mechanistic investigations suggested that HIF‐1α degradation during hypoxia could be attributed to reduced mitochondrial O2 consumption in Nrf2‐inhibited cells. It can be concluded that Nrf2, with its capacity for affecting the protein level of HIF‐1α expression, has good reasons to be considered as a critical transcription factor for controlling glioma angiogenesis.

FTY720 for cancer therapy (Review)

2-Amino-2-[2-(4-octylphenyl)]-1,3-propanediol hydrochloride (FTY720) is a potent immunosuppressant which has been approved by the Food and Drug Administration (FDA) as a new treatment for multiple sclerosis. As an immunosuppressant, it displays its anti-multiple sclerosis, immunosuppressive effects by activating sphingosine-1-phosphate receptors (S1PRs). In addition to the immunosuppressive effects, FTY720 also shows preclinical antitumor efficacy in several cancer models. In most cases, phosphorylation of FTY720 is not required for its cytotoxic effect, indicating the involvement of S1PR-independent mechanisms which are starkly different from the immunosuppressive property of FTY720. In the present study, we reviewed the rapidly advancing field of FTY720 in cancer therapy as well as some molecular targets of the unphosphorylated form of FTY720.

Puerarin ameliorates oxidative stress in a rodent model of traumatic brain injury

BACKGROUND A wealth of evidence has suggested that oxidative stress is involved in the secondary brain injury after traumatic brain injury (TBI). Recently, numerous in vivo and in vitro studies were reported that puerarin could inhibit oxidative stress through the activation of phosphatidylinositol 3-kinase (PI3K)-Akt pathway. It is unknown, however, whether puerarin can provide neuroprotection and reduce oxidative stress after TBI. The present study investigated the effects of puerarin on the TBI-induced neurodegeneration, oxidative stress, and the possible role of PI3K-Akt pathway in the neuroprotection of puerarin, in a rat model of TBI. MATERIALS AND METHODS Rats were randomly distributed into various subgroups undergoing the sham surgery or TBI procedures. Puerarin (200 mg/kg) was given intraperitoneally at 10 min before injury and PI3K-Akt pathway inhibitor LY294002 was also administered intracerebroventricular in one subgroup. All rats were killed at 24 h after TBI for examination. RESULTS Our data indicated that puerarin could significantly reduce TBI-induced neuronal degeneration, accompanied by the partial restoration of the redox disturbance and enhanced expression of phospho-Akt in the pericontusional cortex after TBI. Moreover, PI3K-Akt pathway inhibitor LY294002 could partially abrogate the neuroprotection of puerarin in rats with TBI. CONCLUSIONS These results indicate that puerarin can ameliorate oxidative neurodegeneration after TBI, at least in part, through the activation of PI3K-Akt pathway.

Inhibition of transforming growth factor beta-activated kinase 1 confers neuroprotection after traumatic brain injury in rats

The transforming growth factor beta-activated kinase 1 (TAK1), a member of the Mitogen-activated protein kinase kinase kinase family, is characterized as a key regulator in inflammatory and apoptosis signaling pathways. The aim of the present study was to evaluate the role of the TAK1 pathway in experimental traumatic brain injury (TBI) in rats. Adult male Sprague-Dawley rats were subjected to TBI using a modified Feeneys weight-drop model. The time course showed that a significant increase of TAK1 and p-TAK1 expression in the cortex after TBI. Moreover, TBI induced TAK1 redistribution both in neurons and astrocytes of the lesion boundary zone. The effects of specific inhibition of the TAK1 pathway by 5Z-7-oxozeaenol (OZ, intracerebroventricular injection at 10min post-trauma) on histopathological and behavioral outcomes in rats were assessed at 24h post injury. The number of TUNEL-positive stained cells was diminished and neuronal survival and neurological function were improved with OZ treatment. Biochemically, the high dose of OZ significantly reduced the levels of TAK1 and p-TAK1, further decreased nuclear factor-κB and activator protein 1 activities and the release of inflammatory cytokines. In addition, we found that both 10min and 3h post-trauma OZ therapies could markedly improve neurological function and neuronal survival after long-term survival. These results revealed that the TAK1 pathway is activated after experimental TBI and the inhibitor OZ affords significant neuro- protection and amelioration of neurobehavioral deficits after experimental TBI, suggesting a potential rationale for manipulating this pathway in clinical practice.

Expression and cell distribution of metabotropic glutamate receptor 5 in the rat cortex following traumatic brain injury.

Traumatic brain injury (TBI)-released excessive glutamate resulted in the activation of glutamate receptors including the metabotropic glutamate receptor 5 (mGluR5). To investigate the expression and cell distribution of mGluR5 in the rat cortex following TBI, western blot and quantitative real-time PCR were used to study the protein and mRNA level of mGluR5 respectively while immunohistochemistry analysis and double immunofluorescence with neural cell marker were used to define the cell distribution of mGluR5. Furthermore, we examined the effects of post-TBI administration of (R,S)-2-chloro-5-hydroxyphenylglycine (CHPG), a selective mGluR5 agonist, on the neuronal degeneration in the cortex. In the present study, we found that the protein level of mGluR5 was up-regulated by traumatic brain injury, while TBI-induced mGluR5 mRNA expression displayed biphasic changes with up-regulation in the early time and down-regulation in the late time after TBI. And neuron, astrocyte and microglia in the cortex after TBI all expressed mGluR5. Moreover, CHPG treatment significantly reduced the number of degenerating neurons detected by Fluoro-Jade C staining. These findings demonstrate that expression of mGluR5 differentially changes both spatially and temporally after TBI and may be related to the neuroprotection after TBI. Therefore, understanding the expression and cell distribution of mGluR5 after TBI may give insight into pathophysiology after TBI and provide a new target for the therapy of TBI.

Alpha lipoic acid inhibits neural apoptosis via a mitochondrial pathway in rats following traumatic brain injury

Alpha lipoic acid (ALA) is a powerful antioxidant that has proven protective effects against brain damage following a traumatic brain injury (TBI) in rats. However, the molecular mechanisms underlying these effects are not well understood. This study investigated the effect of ALA on neural apoptosis and the potential mechanism of these effects in the weight-drop model of TBI in male Sprague-Dawley rats that were treated with ALA (20 or 100 mg/kg) or vehicle via intragastric administration 30 min after TBI. Brain samples were collected 48 h later for analysis. ALA treatment resulted in a downregulation of caspase-3 expression, reduced the number of positive cells in the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay and improved neuronal survival. Furthermore, the level of malondialdehyde and glutathione peroxidase activity were restored, while Bcl-2-associated X protein translocation to mitochondria and cytochrome c release into the cytosol were reduced by ALA treatment. These results demonstrate that ALA improves neurological outcome in rats by protecting neural cell against apoptosis via a mechanism that involves the mitochondria following TBI.

The involvement of Nrf2–ARE pathway in regulation of apoptosis in human glioblastoma cell U251

Abstract Objectives: NF-E2-related factor 2 (Nrf2)–antioxidant response element (ARE) pathway plays anti-apoptotic role in normal tissue and tumor. But the role of Nrf2 in apoptosis in glioma is still unknown. Here, we established this experiment to elucidate how Nrf2–ARE pathway participates in apoptosis in human glioblastoma cell U251. Methods: Two plasmids, pEGFP-Nrf2 and Si-Nrf2, were transfected to up- or downregulate the expression of Nrf2 in U251. After transfection, the apoptosis rate, expression of heme oxygenase-1 (HO-1), Bcl-2, Bax, caspases 3, 9 and activity of caspases 3, 9 were detected. Results: After increasing expression of Nrf2, the apoptosis rate was reduced accompanied with upregulated expression of HO-1, Bcl-2/Bax, decreased expression and activity of caspases 3, 9. After decreasing expression of Nrf2, the apoptosis rate was enhanced accompanied with downregulated expression of HO-1, Bcl-2/Bax, increased expression and activity of caspases 3, 9. Discussion: Our findings suggest that Nrf2 participates in the regulation of apoptosis in U251 through HO-1 and the ‘intrinsic’ apoptotic pathway.

Activation of metabotropic glutamate receptor 5 reduces the secondary brain injury after traumatic brain injury in rats

A wealth of evidence has shown that microglia-associated neuro-inflammation is involved in the secondary brain injury contributed to the poor outcome after traumatic brain injury (TBI). In vitro studies were reported that activation of metabotropic glutamate receptor 5 (mGluR5) could inhibit the microglia-associated inflammation in response to lipopolysaccharide and our previous study indicated that mGluR5 was expressed in activated microglia following TBI. However, there is little known about whether mGluR5 activation can provide neuro-protection and reduce microglia-associated neuro-inflammation in rats after TBI. The goal of the present study was to investigate the effects of mGluR5 activation with selective agonist CHPG, on cerebral edema, neuronal degeneration, microglia activation and the releasing of pro-inflammatory cytokines, in a rat model of TBI. Rats were randomly distributed into various subgroups undergoing the sham surgery or TBI procedures, and 250 nmol of CHPG or equal volume vehicle was given through intracerebroventricular injection at 30 min post-TBI. All rats were sacrificed at 24 h after TBI for the further measurements. Our data indicated that post-TBI treatment with CHPG could significantly reduce the secondary brain injury characterized by the cerebral edema and neuronal degeneration, lead to the inhibition of microglia activation and decrease the expression of pro-inflammatory cytokines in both mRNA transcription and protein synthesis. These results provide the substantial evidence that activation of mGluR5 reduces the secondary brain injury after TBI, in part, through modulating microglia-associated neuro-inflammation.

Differential Nrf2 expression between glioma stem cells and non‑stem‑like cells in glioblastoma

Glioblastoma multiforme (GBM), the most commonly occurring primary intracranial tumor, is associated with a negative outcome, regardless of the availability of multimodal therapies. However, the identification of glioma stem cells (GSCs), which are small groups of cells within the GBM, has resulted in novel avenues for research. GSCs are resistant to numerous types of environmental stress, such as irradiation, antitumor drugs and hypoxia. Nuclear factor erythroid 2-related factor 2 (Nrf2) has a significant role the cellular response to oxidative stress and previous studies have supported the significance of Nrf2 in GBM; however, the role of Nrf2 in GSCs remains unclear. In the present study, Nrf2 in CD133− GBM cells and CD133+ GSCs from GBM were compared. GSCs from GBM, which express the surface marker CD133, were separated by magnetic cell sorting and analyzed by immunofluorescence in 24-well clusters and cell counting using flow cytometry. The expression of Nrf2 was detected at the transcriptional and translational levels in CD133+ and CD133− cells, and the result indicated that GSCs were successfully isolated from the GBM. The percentage of tumor stem cells in total cells was between 0.49 and 0.91%. Nrf2 was overexpressed in CD133+ GSCs when compared with CD133− GBM cells, which indicated that the expression of Nrf2 in GSCs was closely correlated with malignant proliferation and differentiation of the GBM. Therefore, it was concluded that Nrf2 may be a potential biomarker and rational therapeutic target in GBM.