Retracted : Protective effects of Progranulin against focal cerebral ischemia‐reperfusion injury in rats by suppressing endoplasmic reticulum stress and NF‐κB activation in reactive astrocytes

Investigation of preconditioning and the protective effects of nicotinamide against cerebral ischemia-reperfusion injury in rats

This study investigated the antioxidant and neuroprotective effects of nicotinamide combined with ischemic preconditioning against cerebral ischemia reperfusion (CIR) injury. Thirty-five Wistar albino male rats were randomly divided into five groups: sham, preconditioned ischemia/reperfusion (IP+IR), ischemia/reperfusion (IR), preconditioned ischemia/reperfusion + nicotinamide (IP+IR+N), and ischemia/reperfusion + nicotinamide (IR+N). CIR was achieved with bilateral common carotid artery occlusion. IP+IR and IP+IR+N groups 30 min before ischemia; Three cycles of 10 sec ischemia/30 sec reperfusion followed by 20 min IR were applied. The IP+IR+N and IR+N groups received 500 mg/kg nicotinamide intraperitoneally. After 24 h of reperfusion, a neurological evaluation was performed and vertıcal pole test. Biochemically, malondialdehyde (MDA), glutathione (GSH) levels and catalase (CAT) activity were measured in blood and brain tissue samples. Rates of red neurons, sateliosis and spongiosis were determined histopathologically in the prefrontal cortex areas. After CIR, MDA levels increased significantly in serum and brain tissue in the IR group compared to the sham group, while GSH and CAT activity decreased in the brain tissue (p < 0.05). MDA levels in the tissues were found significantly decreased in the IR+N group compared to the IR group (p < 0.05). Administration of nicotinamide together with IP significantly decreased MDA levels in brain tissue and increased GSH and CAT activity (p < 0.05). Compared to the IR group, the morphological and neurological damage in the prefrontal cortex areas decreased in the IP+IR, IP+IR+N, and IR+N groups (p < 0.05). In addition, red neuron, sateliosis and spongiosis rates increased significantly in the IR group compared to the Sham, IP+IR+N, IR+N groups (p < 0.001 for all). In neurological evaluation, while the neurological score increased and the time on the vertical pole decreased significantly in the IR group, preconditioning, and nicotinamide groups reversed (p < 0.05). The study's results show that nicotinamide administration with ischemic preconditioning alleviates cerebral ischemia/reperfusion injury.

Linarin ameliorates ischemia-reperfusion injury by the inhibition of endoplasmic reticulum stress targeting AKR1B1

Due to various factors, there is still a lack of effective neuroprotective agents for ischemic stroke in clinical practice. Neuroinflammation and neuronal apoptosis mediated by endoplasmic reticulum stress are some of the important pathological mechanisms in ischemic stroke. Linarin has been reported to have anti-inflammation, antioxidant, and anti-apoptotic effects in myocardial ischemia, osteoarthritis, and kidney disease. Whether it exerts neuroprotective functions in ischemic stroke has not been investigated. The results showed that linarin could reduce the infarct volume in cerebral ischemia animal models, improve the neurological function scores and suppress the expression of inflammatory factors mediating the NF-κB. Meanwhile, it could protect the neurons from OGD/R-induced-apoptosis, which was related to the PERK-eIF2α pathway. Our results suggested linarin could inhibit neuronal inflammation and apoptosis induced by endoplasmic reticulum stress. Furthermore, the neuroprotective effect of linarin may be related to the inhibition of AKR1B1. Our study offers new insight into protecting against ischemia-reperfusion injury by linarin treatment in stroke.

Silencing of Long Noncoding RNA GAS5 Blocks Experimental Cerebral Ischemia-Reperfusion Injury by Restraining AQP4 Expression via the miR-1192/STAT5A Axis

The long noncoding RNA (lncRNA) GAS5 has been shown to affect disease development in stroke. This study aimed to elucidate the regulatory mechanism of the lncRNA GAS5 on STAT5A in cerebral ischemia/reperfusion (I/R) injury. First, GAS5 and STAT5A levels in the blood of patients with stroke were determined. Then, a middle cerebral artery occlusion and reperfusion rat model was established in which short hairpin RNAs targeting GAS5 or STAT5A were intracranially injected, followed by the assessment of neurological function, cerebral injury and water content, and inflammation. Primary rat astrocytes were induced with oxygen-glucose deprivation/reoxygenation (OGD/R), and cell proliferation, apoptosis, and inflammation were evaluated. Moreover, the interplay between GAS5, miR-1192, and STAT5A and the binding of STAT5A to the AQP4 promoter were identified. GAS5 and STAT5A were strongly expressed in stroke patients, and inhibition of GAS5 or STAT5A in model rats improved neurological function, reduced infarction and neuronal apoptosis, and diminished cerebral water content and astrocyte activation. Furthermore, GAS5 or STAT5A downregulation restored proliferation and restrained apoptosis and inflammation in OGD/R-induced astrocytes. Mechanistically, GAS5 targeted miR-1192, which negatively regulated STAT5A. Astrocytes showed perturbed proliferation and strengthened apoptosis and inflammation when miR-1192 was inhibited despite the silencing of GAS5, while these unfavorable effects were abolished by STAT5A silencing. STAT5A binds to the AQP4 promoter and regulates its expression. Silencing of GAS5 and overexpresion of AQP4 led to lower cell viability and higher apoptosis and inflammation than GAS5 silencing alone. Overall, GAS5 silencing inhibited AQP4 through the miR-1192/STAT5A axis, thus alleviating cerebral I/R injury.

miR-383-5p Regulated by the Transcription Factor CTCF Affects Neuronal Impairment in Cerebral Ischemia by Mediating Deacetylase HDAC9 Activity

Stroke, the leading cause of long-term disability worldwide, is caused by the blockage or hemorage of cerebral arteries. The resultant cerebral ischemia causes local neuronal death and brain injury. Histone deacetylase 9 (HDAC9) has been reported to be elevated in ischemic brain injury, but its mechanism in stroke is still enigmatic. The present study aimed to unveil the manner of regulation of HDAC9 expression and the effect of HDAC9 activation on neuronal function in cerebral ischemia. MicroRNAs (miRNAs) targeting HDAC9 were predicted utilizing bioinformatics analysis. We then constructed the oxygen glucose deprivation (OGD) cell model and the middle cerebral artery occlusion (MCAO) rat model, and elucidated the expression of CCCTC binding factor (CTCF)/miR-383-5p/HDAC9. Targeting between miR-383-5p and HDAC9 was verified by dual-luciferase reporter assay and RNAi. After conducting an overexpression/knockdown assay, we assessed neuronal impairment and brain injury. We found that CTCF inhibited miR-383-5p expression via its enrichment in the promoter region of miR-383-5p, whereas the miR-383-5p targeted and inhibited HDAC9 expression. In the OGD model and the MCAO model, we confirmed that elevation of HDAC9 regulated by the CTCF/miR-383-5p/HDAC9 pathway mediated apoptosis induced by endoplasmic reticulum stress, while reduction of HDAC9 alleviated apoptosis and the symptoms of cerebral infarction in MCAO rats. Thus, the CTCF/miR-383-5p/HDAC9 pathway may present a target for drug development against ischemic brain injury.

The Influence of Gut Dysbiosis in the Pathogenesis and Management of Ischemic Stroke

Recent research on the gut microbiome has revealed the influence of gut microbiota (GM) on ischemic stroke pathogenesis and treatment outcomes. Alterations in the diversity, abundance, and functions of the gut microbiome, termed gut dysbiosis, results in dysregulated gut–brain signaling, which induces intestinal barrier changes, endotoxemia, systemic inflammation, and infection, affecting post-stroke outcomes. Gut–brain interactions are bidirectional, and the signals from the gut to the brain are mediated by microbially derived metabolites, such as trimethylamine N-oxide (TMAO) and short-chain fatty acids (SCFAs); bacterial components, such as lipopolysaccharide (LPS); immune cells, such as T helper cells; and bacterial translocation via hormonal, immune, and neural pathways. Ischemic stroke affects gut microbial composition via neural and hypothalamic–pituitary–adrenal (HPA) pathways, which can contribute to post-stroke outcomes. Experimental and clinical studies have demonstrated that the restoration of the gut microbiome usually improves stroke treatment outcomes by regulating metabolic, immune, and inflammatory responses via the gut–brain axis (GBA). Therefore, restoring healthy microbial ecology in the gut may be a key therapeutic target for the effective management and treatment of ischemic stroke.

Propofol rescued astrocytes from LPS-induced inflammatory response via blocking LncRNA-MEG3/NF-κB axis

OBJECTIVE

Evidences had demonstrated that propofol attenuated neuro-inflammation following brain ischemia. Moreover, LncRNA-MEG3 was identified as an independent prognostic marker for ischemic stroke patients, and was found to be correlated with cerebral ischemia in animal models. Therefore, the current study explored the role of propofol on lipopolysaccharide (LPS)-mediated inflammation in cultured astrocytes, along with the molecular mechanism involved in LncRNA-MEG3/NF-κB axis.

METHODS

The primary cultured astrocytes isolated from rats were used to establish an inflammatory model, which were treated with LPS. Propofol was administrated to the primary cultured astrocytes during LPS treatment. The effect of propofol on pro-inflammatory cytokines and the LncRNA-MEG3/NF-κB pathway were detected by ELISA, qRT-PCR and Western Blot assay, respectively. Then, dual-luciferase assay, chromatin immunoprecipitation and RNA immunoprecipitation were used to determine the interaction between LncRNA-MEG3 and NF-κB.

RESULTS

Our study found that propofol significantly reduced LncRNA-MEG3 expression, which was elevated in LPS-stimulated astrocytes. Moreover, both propofol and LncRNA-MEG3 knockdown remarkably alleviated LPS-induced cytotoxicity by suppressing expressions and release of pro-inflammatory cytokines. Loss of LncRNA-MEG3 notably suppressed the NF-κB activity and its phosphorylated activation. Additionally, it was also observed that LncRNA-MEG3 could bind nuclear p65/p50, and promote the binding of NF-κB to IL-6 and TNF-α promoters in the nucleus, subsequently stimulating the production of inflammatory cytokines in LPS-treated astrocytes. Furthermore, a specific inhibitor of NF-κB, PDTC rescued astrocytes from LPS exposure without affecting LncRNA-MEG3 expression.

CONCLUSION

These findings demonstrated that LncRNA-MEG3 acted as a positive regulator of NF-κB, mediated the neuroprotection of propofol in LPS-triggered astrocytes injury.

Longxuetongluo Capsule protects against cerebral ischemia/reperfusion injury through endoplasmic reticulum stress and MAPK-mediated mechanisms

Introduction

Longxuetongluo Capsule (LTC) is wildly applied to treat ischemic stroke in clinical practice in China. However, the pharmacological mechanism of LTC on ischemic stroke is still unstated.

Objective

Our research was designed to study the protective effect of LTC against cerebral ischemia–reperfusion (I/R) injury and reveal the underlying mechanism both in vivo and in vitro.

Methods

PC12 cells treated with glucose deprivation/reperfusion (OGD/R) were used to simulate in vitro ischemia/reperfusion (I/R) injury. The cell viability, apoptosis rate, and protein expressions of PC12 cells were evaluated. In vivo validation of the protective effect of LTC was carried out by middle cerebral artery occlusion (MCAO)/reperfusion treatment, and the underlying mechanism of its anti-apoptosis ability was further revealed by immunohistochemistry staining and Western blotting.

Results

In the current study, we observed that LTC effectively inhibited oxygen-glucose deprivation/reperfusion (OGD/R) induced apoptosis of PC12 cells through suppressing the cleavage of poly ADP-ribose polymerase (PARP), caspase-3, and caspase-9. Further investigation revealed that OGD/R insult remarkably triggered the endoplasmic reticulum stress responses (ER stress) to induce PC12 cell apoptosis. LTC treatment alleviated OGD/R induced ER stress by inhibiting the activation of protein kinase RNA (PKR)-like ER kinase (PERK)/eukaryotic translation initiation factor 2 (eIF2α) and inositol requiring enzyme 1 (IRE1)/tumor necrosis factor receptor-associated factor 2 (TRAF2) pathways. Additionally, LTC also restrained the OGD/R-induced PC12 cell apoptosis by reversing the activated mitogen-activated protein kinase (MAPK) through IRE1/TRAF2 pathway. Animal studies demonstrated LTC significantly restricted the infarct region induced by middle cerebral artery occlusion (MCAO)/reperfusion, the activation of ER stress and apoptosis of neuronal cells had also been suppressed by LTC in the penumbra region.

Conclusion

LTC protects the cerebral neuronal cell against ischemia/reperfusion injury through ER stress and MAPK-mediated mechanisms.

Targeting neuroinflammation to treat cerebral ischemia - The role of TIGAR/NADPH axis

Cerebral ischemia is a disease of ischemic necrosis of brain tissue caused by intracranial artery stenosis or occlusion and cerebral artery embolization. Neuroinflammation plays an important role in the pathophysiology of cerebral ischemia. Microglia, astrocytes, leukocytes and other cells that release a variety of inflammatory factors involved in neuroinflammation may play a damaging or protective role during the process of cerebral ischemia. TP53-induced glycolysis and apoptotic regulators (TIGAR) may facilitate the production of nicotinamide adenine dinucleotide phosphoric acid (NADPH) via the pentose phosphate pathway (PPP) to inhibit oxidative stress and neuroinflammation. TIGAR can also directly inhibit NF-κB to inhibit neuroinflammation. TIGAR thus protect against cerebral ischemic injury. Exogenous NADPH can inhibit neuroinflammation by inhibiting oxidative stress and regulating a variety of signals. However, since NADPH oxidase (NOX) may use NADPH as a substrate to generate reactive oxygen species (ROS) to mediate neuroinflammation, the combination of NADPH and NOX inhibitors may produce more powerful anti-neuroinflammatory effects. Here, we review the cells and regulatory signals involved in neuroinflammation during cerebral ischemia, and discuss the possible mechanisms of targeting neuroinflammation in the treatment of cerebral ischemia with TIGAR/NADPH axis, so as to provide new ideas for the prevention and treatment of cerebral ischemia.

17β-oestradiol alleviates endoplasmic reticulum stress injury induced by chronic cerebral hypoperfusion through the Haemoglobin/HIF 1α signalling pathway in ovariectomized rats

Endoplasmic reticulum stress (ERS) is known to be an essential target in protecting against ischaemic brain injury. In this study, using a vascular dementia (VaD) animal model induced by bilateral common carotid artery occlusion (BCCAO), we evaluated the effect and mechanism of 17β-oestradiol (E2) against VaD by inhibiting ERS at the early stage (14 d, 21 d, 28 d) and late stage (3 m) after BCCAO in the hippocampal CA1 region of ovariectomized rats. The results showed that the activation of the PERK-eIF2α-ATF4-CHOP axis, a typical ERS pathway, was significantly increased at the early and late stages after BCCAO. JNK (c-Jun N-terminal kinase)-cJun, a pro-death pathway, also displayed the same pattern as the ERS axis. E2 treatment profoundly suppressed the impairments caused by BCCAO. Further mechanistic studies revealed that cerebral blood flow (CBF) was sharply decreased at 14 d and returned to the normal level at 21 d after BCCAO. E2 could not change CBF, while it unexpectedly enhanced the ability to carry oxygen. This is evidenced by the fact that the protein expression of haemoglobin α/β (Hα/β), an oxygen carrier, robustly increased at BCCAO 21 d and 3 m after E2 treatment. The oxygen carrier increased strongly after 21 d and 3 m of BCCAO treated with E2. Moreover, E2 correspondingly enhanced the protein expression of hypoxia-inducible factor 1α (HIF 1α) in both the early and late stage after BCCAO in the hippocampal CA1 region. Finally, E2 administration markedly decreased the activities of caspase-8, caspase-3, and caspase-12 and increased the number of NeuN-positive cells. These findings suggest that E2 serves as a neuroprotectant to alleviate VaD by suppressing ERS injury involving the haemoglobin/HIF 1α signalling pathway.

Possible involvement of progranulin in the protective effect of elastase inhibitor on cerebral ischemic injuries of neuronal and glial cells

In a previous study, we demonstrated that neutrophil elastase is activated in the brain parenchyma after cerebral ischemia, which enzyme cleaves progranulin (PGRN), an anti-inflammatory factor. In that study, we also found that sivelestat, a selective neutrophil elastase inhibitor, attenuates ischemia-induced inflammatory responses. However, it was not clear whether this anti-inflammatory effect was due to the direct effect of sivelestat. In this study, we evaluated the effects of sivelestat or recombinant PGRN (rPGRN) on cell injuries in cultured neurons, astrocytes, and microglia under oxygen/glucose deprivation (OGD) conditions. We demonstrated that OGD-induced neuronal cell injury, astrocyte activation, and increased proinflammatory cytokines caused by microglial activation, were suppressed by rPGRN treatment, whereas sivelestat had no effect on any of these events. These results indicate that the anti-inflammatory responses after in vivo cerebral ischemia were not due to the direct action of sivelestat but due to the suppression of PGRN cleavage by inhibition of elastase activity. It was also suggested that the pleiotropic effect of rPGRN could be attributed to the differentiation of M1 microglia into anti-inflammatory type M2 microglia. Therefore, the inhibition of PGRN cleavage by sivelestat could contribute to the establishment of a new therapeutic approach for cerebral ischemia.

Progranulin promotes functional recovery and neurogenesis in the subventricular zone of adult mice after cerebral ischemia

Progranulin (PGRN), a secreted glycosylated protein, has been reported to attenuate ischemia-induced cerebral injury through anti-inflammation, attenuation of blood-brain barrier disruption and neuroprotection. However, the effect of PGRN on neurogenesis in the subventricular zone (SVZ) after cerebral ischemia remains unclear. In this study, adult C57BL/6 mice were subjected to permanent middle cerebral artery occlusion (pMCAO), and different doses of recombinant mouse PGRN (r-PGRN, 0.3 ng, 1 ng, 5 ng) were intracerebroventricularly administered 30 min after pMCAO. Results showed that 1 ng r-PGRN markedly reduced infarct volume and rescued functional deficits 24 h after pMCAO. Meanwhile, 1 ng r-PGRN increased SVZ cell proliferation, as shown by a high number of bromodeoxyuridine-positive (BrdU+) cells and Ki-67+ cells in the ischemic ipsilateral SVZ 7 d after pMCAO. Additionally, PGRN increased the percentage of BrdU+/Doublecortin (DCX)+ cells in the ipsilateral SVZ 14 d after pMCAO and increased the percentage of new neurons (BrdU+/NeuN+ cells) in the peri-infarct striatum 28 d after pMCAO, suggesting that PGRN promotes neuronal differentiation. PGRN also upregulated phosphorylation of ERK1/2 and Akt in the ipsilateral SVZ 3 d after pMCAO. Our data indicate that PGRN treatment promotes acute functional recovery; most importantly, it also stimulates neurogenesis in the SVZ, which could be beneficial for long-term recovery after cerebral ischemia. The increase in neurogenesis could be associated with activation of the MAPK/ERK and PI3K/Akt pathways. These results suggest a potential new strategy utilizing PGRN in ischemic stroke therapy.

Human progranulin-expressing mice as a novel tool for the development of progranulin-modulating therapeutics

The granulin protein (also known as, and hereafter referred to as, progranulin) is a secreted glycoprotein that contributes to overall brain health. Heterozygous loss-of-function mutations in the gene encoding the progranulin protein (Granulin Precursor, GRN) are a common cause of familial frontotemporal dementia (FTD). Gene therapy approaches that aim to increase progranulin expression from a single wild-type allele, an area of active investigation for the potential treatment of GRN-dependent FTD, will benefit from the availability of a mouse model that expresses a genomic copy of the human GRN gene. Here we report the development and characterization of a novel mouse model that expresses the entire human GRN gene in its native genomic context as a single copy inserted into a defined locus (Hprt) in the mouse genome. We show that human and mouse progranulin are expressed in a similar tissue-specific pattern, suggesting that the two genes are regulated by similar mechanisms. Human progranulin rescues a phenotype characteristic of progranulin-null mice, the exaggerated and early deposition of the aging pigment lipofuscin in the brain, indicating that the two proteins are functionally similar. Longitudinal behavioural and neuropathological analyses revealed no significant differences between wild-type and human progranulin-overexpressing mice up to 18 months of age, providing evidence that long-term increase of progranulin levels is well tolerated in mice. Finally, we demonstrate that human progranulin expression can be increased in the brain using an antisense oligonucleotide that inhibits a known GRN-regulating micro-RNA, demonstrating that the transgene is responsive to potential gene therapy drugs. Human progranulin-expressing mice represent a novel and valuable tool to expedite the development of progranulin-modulating therapeutics.

MicroRNA-670 aggravates cerebral ischemia/reperfusion injury via the Yap pathway

Apoptosis is an important programmed cell death process involved in ischemia/reperfusion injury. MicroRNAs are considered to play an important role in the molecular mechanism underlying the regulation of cerebral ischemia and reperfusion injury. However, whether miR-670 can regulate cell growth and death in cerebral ischemia/reperfusion and the underlying mechanism are poorly understood. In this study, we established mouse models of transient middle artery occlusion and Neuro 2a cell models of oxygen-glucose deprivation and reoxygenation to investigate the potential molecular mechanism by which miR-670 exhibits its effects during cerebral ischemia/reperfusion injury both in vitro and in vivo. Our results showed that after ischemia/reperfusion injury, miR-670 expression was obviously increased. After miR-670 expression was inhibited with an miR-670 antagomir, cerebral ischemia/reperfusion injury-induced neuronal death was obviously reduced. When miR-670 overexpression was induced by an miR-670 agomir, neuronal apoptosis was increased. In addition, we also found that miR-670 could promote Yap degradation via phosphorylation and worsen neuronal apoptosis and neurological deficits. Inhibition of miR-670 reduced neurological impairments after cerebral ischemia/reperfusion injury. These results suggest that microRNA-670 aggravates cerebral ischemia/reperfusion injury through the Yap pathway, which may be a potential target for treatment of cerebral ischemia/reperfusion injury. The present study was approved by the Institutional Animal Care and Use Committee of China Medical University on February 27, 2017 (IRB No. 2017PS035K).

Regulation of progranulin expression and location by sortilin in oxygen-glucose deprivation/reoxygenation injury

Progranulin is a secreted glycoprotein expressed in neurons and microglial cells that is involved in maintaining physiological functions. Many studies have found that progranulin may play a protective role against ischemic brain injury, but little is known about how the expression level and cellular localization status of progranulin is regulated after hypoxia-ischemia. Research has confirmed that sortilin, encoded by SORT1, can bind with progranulin and deliver a mature secretory isoform of progranulin to lysosomes, and progranulin is then cleaved. In the present study, we aimed to figure out whether sortilin could affect the expression and cellular localization of progranulin and regulate cell apoptosis during hypoxia-ischemia. In this study, oxygen-glucose deprivation/reoxygenation (OGD/R) in primary cortical neurons was used to mimic hypoxic-ischemic episodes. After OGD/R, the neuroprotective effects of progranulin against hypoxia-ischemia were examined, and primary cortical neurons were transduced with a SORT1 knockdown lentivirus to inhibit the expression of sortilin. The results showed that sortilin inhibition increased PGRN expression and alleviated cell injury induced by hypoxia-ischemia. Additionally, sortilin inhibition was associated with less PGRN localization in lysosomes. All of these findings suggest that sortilin can regulate the expression of PGRN, most likely by transporting it to lysosomes and affecting the cell injury in hypoxia-ischemia.

Dexmedetomidine pretreatment attenuates myocardial ischemia reperfusion induced acute kidney injury and endoplasmic reticulum stress in human and rat

BACKGROUND

Patients undergoing cardiopulmonary bypass (CPB) often develop acute kidney injury (AKI) caused by myocardial ischemia reperfusion (MI/R), and this renal injury can be resolved notably by dexmedetomidine. Endoplasmic reticulum (ER) stress was reported to get involved in organ injury including AKI.

OBJECTIVES

The current study aimed to address the correlation between MI/R induced AKI with ER stress and to assess the effects of dexmedetomidine pretreatment on AKI protection.

METHOD

Patients selected for heart valve replacement surgery were randomly assigned to NS group (pre-anesthesia with 0.9% NaCl) and DEX group (pre-anesthesia with dexmedetomidine). Rat MI/R model was induced by occluding coronary artery for 30 min followed by 48-hour reperfusion. Rats were randomized into Sham (0.9% NaCl), I/R (MI/R + 0.9% NaCl) and I/R + DEX (MI/R + dexmedetomidine). Organ function and ER stress condition were evaluated by blood chemistry, pathology, and molecular test.

RESULTS

Clinical data indicated dexmedetomidine pretreatment attenuated AKI and oxidative stress as well as postischemic myocardial injury in patients. Accordingly animal results suggested dexmedetomidine reduced cellular injury and improved postischemic myocardial and renal function. Dexmedetomidine also reduced myocardial and renal cells apoptosis and down-regulated ER stress.

CONCLUSIONS

These results suggested that dexmedetomidine pretreatment attenuates MI/R injury-induced AKI by relieving the ER stress.

Targeting the NF-κB pathway for therapy of ischemic stroke

Ischemic strokes occur when a major cerebral artery or its branches are occluded, resulting in activation of inflammatory processes that cause secondary tissue injury, breakdown of the blood–brain barrier, edema or hemorrhage. Treatments that inhibit inflammatory processes may thus be highly beneficial. A key regulator of the inflammatory process is the nuclear factor kappa B (NF-κB) pathway. In its active form, NF-κB regulates expression of proinflammatory and proapoptotic genes. The molecules that interact with NF-κB, and the subunits that compose NF-κB itself, represent therapeutic targets that can be modulated to decrease inflammation. This review focuses on our current understanding of the NF-κB pathway and the potential benefits of inhibiting NF-κB in ischemia-reperfusion injury of the brain.

Progranulin Decreases Susceptibility to Streptococcus pneumoniae in Influenza and Protects against Lethal Coinfection

Streptococcus pneumoniae coinfection is a major cause of mortality in influenza pandemics. Growing evidence shows that uncontrolled immune response results in severe tissue damage and thereby promotes death in coinfection. Progranulin (PGRN) is widely expressed in immune and epithelial cells and exerts anti-inflammatory role in many diseases. We found that PGRN levels were significantly elevated in clinical influenza/S. pneumoniae-coinfected patients. C57BL/6 wild-type (WT) and PGRN-deficient (PGRN^-/-) mice were infected with influenza virus PR8 and then superchallenged with S. pneumoniae serotype 19F. Coinfected PGRN^-/- mice showed increased mortality and weight loss compared with WT mice. PGRN deficiency led to increased bacterial loads in lungs without altering influenza virus replication, suggesting a role of PGRN in decreasing postinfluenza susceptibility to S. pneumoniae coinfection. Administration of recombinant PGRN improved survival of WT and PGRN^-/- mice in lethal coinfection. Additionally, loss of PGRN resulted in aggravated lung damage along with massive proinflammatory cytokine production and immune cell infiltration during coinfection. Endoplasmic reticulum stress (ERS) during influenza, and coinfection was strongly induced in PGRN^-/- mice that subsequently activated apoptosis signaling pathways. Treatment of recombinant PGRN or inhibition of ERS by 4-phenylbutyrate decreased apoptosis and bacterial loads in lungs of coinfected mice. These results suggest that PGRN decreases postinfluenza susceptibility to S. pneumoniae coinfection via suppressing ERS-mediated apoptosis. Impaired bacterial clearance and increased lung inflammation are associated with the lethal outcome of coinfected PGRN^-/- mice. Our study provides therapeutic implication of PGRN to reduce morbidity and mortality in influenza/S. pneumoniae coinfection.

Effects of resveratrol postconditioning on cerebral ischemia in mice: role of the sirtuin-1 pathway

Evidence has demonstrated that resveratrol preconditioning exhibits neuroprotection against cerebral ischemia-reperfusion (IR) injury. The current investigation aimed to explore whether pharmacological postconditioning, by administering resveratrol, after a sustained ischemia and prior to prolonged reperfusion abrogates cerebral IR injury. Cerebral IR-induced injury mice model was employed in this study to evaluate the neuroprotective effects of pharmacological postconditioning with resveratrol (30 mg/kg; i.p.) administered 5 min before reperfusion. We administered sirtinol, a SIRT1/2 selective inhibitor (10 mg/kg; i.p.) 10 min before ischemia (17 min) and reperfusion (24 h), to elucidate whether the neuroprotection with resveratrol postconditioning depends on SIRT1 activation. Various biochemical and behavioural parameters and histopathological changes were assessed to examine the effect of pharmacological postconditioning. Infarct size is estimated using TTC staining. It was established that resveratrol postconditioning abrogated the deleterious effects of IR injury expressed with regard to biochemical parameters of oxidative stress (TBARS, SOD, GSH), acetylcholinesterase activity, behavioural parameters (memory, motor coordination), infarct size, and histopathological changes. Sirtinol significantly reversed the effect of resveratrol postconditioning. We conclude that induced neuroprotective benefits of resveratrol postconditioning may be the consequence of SIRT1 activation and resveratrol can be considered, for further studies, as potential agent inducing pharmacological postconditioning in clinical situations.

Cilostazol ameliorates ischemia/reperfusion-induced tight junction disruption in brain endothelial cells by inhibiting endoplasmic reticulum stress

Endoplasmic reticulum (ER) stress is essential for brain ischemia/reperfusion (I/R) injury. However, whether it contributes to I/R-induced blood-brain barrier (BBB) injury remains unclear. cilostazol exerts protective effects toward I/R-induced BBB injury, with unclear mechanisms. This study explored the potential role of ER stress in I/R-induced endothelial cell damage and determined whether the therapeutic potential of cilostazol, with respect to I/R-induced endothelial cell damage, is related to inhibition of ER stress. We found that exposing brain endothelial cells (bEnd.3) to oxygen-glucose deprivation/reoxygenation (OGD/R) significantly activated ER stress and diminished the barrier function of cell monolayers; treatment with the ER stress inhibitor 4-phenylbutyric acid (4-PBA) or cilostazol prevented OGD/R-induced ER stress and preserved barrier function. Furthermore, OGD/R induced the expression and secretion of matrix metalloproteinase-9 and nuclear translocation of phosphorylated NF-κB. These changes were partially reversed by 4-PBA or cilostazol treatment. In vivo, 4-PBA or cilostazol significantly attenuated I/R-induced ER stress and ameliorated Evans blue leakage and tight junction loss. These results demonstrate that I/R-induced ER stress participates in BBB disruption. Targeting ER stress could be a useful strategy to protect the BBB from ischemic stroke, and cilostazol is a promising therapeutic agent for this process.-Nan, D., Jin, H., Deng, J., Yu, W., Liu, R., Sun, W., Huang, Y. Cilostazol ameliorates ischemia/reperfusion-induced tight junction disruption in brain endothelial cells by inhibiting endoplasmic reticulum stress.

Phenothiazines Enhance the Hypothermic Preservation of Liver Grafts: A Pilot in Vitro Study

In vitro liver conservation is an issue of ongoing critical importance in graft transplantation. In this study, we investigated the possibility of augmenting the standard pre-transplant liver conservation protocol (University of Wisconsin (UW) cold solution) with the phenothiazines chlorpromazine and promethazine. Livers from male Sprague-Dawley rats were preserved either in UW solution alone, or in UW solution plus either 2.4, 3.6, or 4.8 mg chlorpromazine and promethazine (C+P, 1:1). The extent of liver injury following preservation was determined by alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, the ratio of AST/ALT, morphological changes as assessed by hematoxylin-eosin staining, apoptotic cell death as determined by ELISA, and by expression of the apoptotic regulatory proteins BAX and Bcl-2. Levels of glucose (GLU) and lactate dehydrogenase (LDH) in the preservation liquid were determined at 3, 12, and 24 h after incubation to assess glucose metabolism. Oxidative stress was assessed by levels of superoxide dismutase (SOD), reactive oxygen species (ROS), and malondialdehyde (MDA), and inflammatory cytokine expression was evaluated with Western blotting. C+P augmentation induced significant reductions in ALT and AST activities; the AST/ALT ratio; as well as in cellular swelling, vacuolar degeneration, apoptosis, and BAX expression. These changes were associated with lowered levels of GLU and LDH; decreased expression of SOD, MDA, ROS, TNF-α, and IL-1β; and increased expression of Bcl-2. We conclude that C+P augments hypothermic preservation of liver tissue by protecting hepatocytes from ischemia-induced oxidative stress and metabolic dysfunction. This result provides a basis for improvement of the current preservation strategy, and thus for the development of a more effective graft conservation method.

Xingnaojing Injection Protects against Cerebral Ischemia Reperfusion Injury via PI3K/Akt-Mediated eNOS Phosphorylation

Xingnaojing (XNJ) injection, derived from traditional Chinese medicine formulation, has a protective effect against stroke, but the underlying mechanism is unclear, which severely limited its clinical application. This research aims to elucidate the role and mechanism of XNJ in reducing cerebral ischemic reperfusion (I/R) injury. Rats received 2 h cerebral ischemia followed by reperfusion of 24 h and were intraperitoneally given 5, 10, or 15 ml/kg XNJ 24 h before ischemia and at the onset of reperfusion, respectively. TTC staining, HE staining, and neurological score were implied to evaluate the effectiveness of XNJ. The protein expressions of PI3K/Akt and eNOS signaling were measured. Experiments were further performed in human brain microvascular endothelial cells (HBMECs) to investigate the protective mechanisms of XNJ. HBMECs were subjected to 3 h oxygen and glucose deprivation following 24 h of reoxygenation (OGD) to mimic cerebral I/R in vitro. PI3K inhibitor LY294002 was added with or without the preconditioning of XNJ. Multiple methods including western blot, immunofluorescence, DAPI staining, JC-1, and flow cytometry were carried out to evaluate the effect of XNJ on HBMECs. XNJ could improve rat cerebral ischemic injury and OGD induced HBMECs apoptosis. In vivo and in vitro researches indicated that the mechanism might be relevant to the activation of PI3K/Akt/eNOS signaling.