Cerebral ischemia and the unfolded protein response

Melatonin: a promising neuroprotective agent for cerebral ischemia-reperfusion injury

Cerebral ischemia-reperfusion (CIR) injury is initiated by the generation of reactive oxygen species (ROS), which leads to the oxidation of cellular proteins, DNA, and lipids as an initial event. The reperfusion process impairs critical cascades that support cell survival, including mitochondrial biogenesis and antioxidant enzyme activity. Failure to activate prosurvival signals may result in increased neuronal cell death and exacerbation of CIR damage. Melatonin, a hormone produced naturally in the body, has high concentrations in both the cerebrospinal fluid and the brain. However, melatonin production declines significantly with age, which may contribute to the development of age-related neurological disorders due to reduced levels. By activating various signaling pathways, melatonin can affect multiple aspects of human health due to its diverse range of activities. Therefore, understanding the underlying intracellular and molecular mechanisms is crucial before investigating the neuroprotective effects of melatonin in cerebral ischemia-reperfusion injury.

The Role of NMDA Receptor Partial Antagonist, Carbamathione, as a Therapeutic Agent for Transient Global Ischemia

Carbamathione (Carb), an NMDA glutamate receptor partial antagonist, has potent neuroprotective functions against hypoxia- or ischemia-induced neuronal injury in cell- or animal-based stroke models. We used PC-12 cell cultures as a cell-based model and bilateral carotid artery occlusion (BCAO) for stroke. Whole-cell patch clamp recording in the mouse retinal ganglion cells was performed. Key proteins involved in apoptosis, endoplasmic reticulum (ER) stress, and heat shock proteins were analyzed using immunoblotting. Carb is effective in protecting PC12 cells against glutamate- or hypoxia-induced cell injury. Electrophysiological results show that Carb attenuates NMDA-mediated glutamate currents in the retinal ganglion cells, which results in activation of the AKT signaling pathway and increased expression of pro-cell survival biomarkers, e.g., Hsp 27, P-AKT, and Bcl2 and decreased expression of pro-cell death markers, e.g., Beclin 1, Bax, and Cleaved caspase 3, and ER stress markers, e.g., CHOP, IRE1, XBP1, ATF 4, and eIF2α. Using the BCAO animal stroke model, we found that Carb reduced the brain infarct volume and decreased levels of ER stress markers, GRP 78, CHOP, and at the behavioral level, e.g., a decrease in asymmetric turns and an increase in locomotor activity. These findings for Carb provide promising and rational strategies for stroke therapy.

Neuroprotective Effects of the Neural-Induced Adipose-Derived Stem Cell Secretome against Rotenone-Induced Mitochondrial and Endoplasmic Reticulum Dysfunction

Mesenchymal stem cells (MSCs) have therapeutic effects on neurodegenerative diseases (NDDs) known by their secreted molecules, referred to as the “secretome”. The mitochondrial complex I inhibitor, rotenone (ROT), reproduces α-synuclein (α-syn) aggregation seen in Parkinson’s disease (PD). In this present study, we examined the neuroprotective effects of the secretome from neural-induced human adipose tissue-derived stem cells (NI-ADSC-SM) during ROT toxicity in SH-SY5Y cells. Exposure to ROT significantly impaired the mitophagy by increased LRRK2, mitochondrial fission, and endoplasmic reticulum (ER) stress (ERS). ROT also increased the levels of calcium (Ca2+), VDAC, and GRP75, and decreased phosphorylated (p)-IP3R Ser1756/total (t)-IP3R1. However, NI-ADSC-SM treatment decreased Ca2+ levels along with LRRK2, insoluble ubiquitin, mitochondrial fission by halting p-DRP1 Ser616, ERS by reducing p-PERK Thr981, p-/t-IRE1α, p-SAPK, ATF4, and CHOP. In addition, NI-ADSC-SM restored the mitophagy, mitochondrial fusion, and tethering to the ER. These data suggest that NI-ADSC-SM decreases ROT-induced dysfunction in mitochondria and the ER, which subsequently stabilized tethering in mitochondria-associated membranes in SH-SY5Y cells.

Bone Marrow Culture-Derived Conditioned Medium Recovers Endothelial Function of Vascular Grafts following In Vitro Ischemia/Reperfusion Injury in Diabetic Rats

Ischemia/reperfusion injury (IRI) remains a challenge in coronary artery bypass grafting (CABG). Diabetic patients with coronary artery disease are more likely to require CABG and therefore run a high risk for cardiovascular complications. Conditioned medium (CM) from bone marrow-derived mesenchymal stem cells has been shown to have beneficial effects against IRI. We hypothesized that adding CM to physiological saline protects vascular grafts from IRI in diabetic rats. Bone-marrow derived cells were isolated from nondiabetic rat femurs/tibias, and CM was generated. As we previously reported, CM contains 23 factors involved in inflammation, oxidative stress, and apoptosis. DM was induced by streptozotocin administration. Eight weeks later, to measure vascular function, aortic rings were isolated and mounted in organ bath chambers (DM group) or stored in 4°C saline, supplemented either with a vehicle (DM-IR group) or CM (DM-IR+CM group). Although DM was associated with structural changes compared to controls, there were no functional alterations. However, compared to the DM group, in the DM-IR aortas, impaired maximum endothelium-dependent vasorelaxation in response to acetylcholine (DM 86.7 ± 0.1% vs. DM-IR 42.5 ± 2.5% vs. DM-IR+CM 61.9 ± 2.0%, p < 0.05) was improved, caspase-3, caspase-8, caspase-9, and caspase-12 immunoreactivity was decreased, and DNA strand breakage, detected by the TUNEL assay, was reduced by CM. We present the experimental finding that the preservation of vascular grafts with CM prevents endothelial dysfunction after IRI in diabetic rats. Targeting apoptosis by CM may contribute to its protective effect.

Spinal Stroke: Outcome Attenuation by Erythropoietin and Carbamylated Erythropoietin and Its Prediction by Sphingosine-1-Phosphate Serum Levels in Mice

Spinal strokes may be associated with tremendous spinal cord injury. Erythropoietin (EPO) improves the neurological outcome of animals after spinal cord ischemia (SCI) and its effects on ischemia-induced endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) are considered possible molecular mechanisms. Furthermore, sphingosin-1-phosphate (S1P) is suggested to correlate with SCI. In this study, the effect of recombinant human EPO (rhEPO) and carbamylated EPO (cEPO-Fc) on the outcome of mice after SCI and a prognostic value of S1P were investigated. SCI was induced in 12-month-old male mice by thoracic aortal cross-clamping after administration of rhEPO, cEPO-Fc, or a control. The locomotory behavior of mice was evaluated by the Basso mouse scale and S1P serum levels were measured by liquid chromatography-tandem mass spectrometry. The spinal cord was examined histologically and the expressions of key UPR proteins (ATF6, PERK, and IRE1a, caspase-12) were analyzed utilizing immunohistochemistry and real-time quantitative polymerase chain reaction. RhEPO and cEPO-Fc significantly improved outcomes after SCI. The expression of caspase-12 significantly increased in the control group within the first 24 h of reperfusion. Animals with better locomotory behavior had significantly higher serum levels of S1P. Our data indicate that rhEPO and cEPO-Fc have protective effects on the clinical outcome and neuronal tissue of mice after SCI and that the ER is involved in the molecular mechanisms. Moreover, serum S1P may predict the severity of impairment after SCI.

Potential Role of MANF, an ER Stress Responsive Neurotrophic Factor, in Protecting Against Alcohol Neurotoxicity

Alcohol exposure during pregnancy is harmful to the fetus and causes a wide range of long-lasting physiological and neurocognitive impairments, collectively referred to as fetal alcohol spectrum disorders (FASD). The neurobehavioral deficits observed in FASD result from structural and functional damages in the brain, with neurodegeneration being the most destructive consequence. Currently, there are no therapies for FASD. It is exigent to delineate the underlying mechanisms of alcohol neurotoxicity and develop an effective strategy of treatment. ER stress, caused by the accumulation of unfolded/misfolded proteins in the ER, is the hallmark of many neurodegenerative diseases, including alcohol-induced neurodegeneration. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a newly discovered endoplasmic reticulum (ER) stress responsive neurotrophic factor that regulates diverse neuronal functions. This review summarizes the recent findings revealing the effects of MANF on the CNS and its protective role against neurodegeneration. Particularly, we focus the role of MANF on alcohol-induced ER stress and neurodegeneration and discuss the therapeutic potential of MANF in treating alcohol neurotoxicity such as FASD.

Alteration of endoplasmic reticulum stress, inflammation and anti-oxidative status in cyclophosphamide-damaged liver of Nile tilapia (Oreochromis niloticus)

Cyclophosphamide (CTX) is a common immunosuppressant, and it can also results in liver injury in human and animals. In this study, the CTX-induced liver injury mechanism in tilapia (Oreochromis niloticus) was investigated by studying alteration of endoplasmic reticulum stress (ERS), inflammation and anti-oxidative status. Tilapia was intraperitoneally injected CTX at the doses of 10, 25, 50, 75 and 100 mg·kg^-1, and the blood and liver tissues were collected. The results showed that CTX administration had a significant cytotoxicity on hepatocytes, and increased the liver index. The extensive vacuolar degeneration, unclear cell outline and other histological lesions were also observed. CTX administration markedly decreased the antioxidant ability and enhanced lipid peroxidation in liver. Furthermore, qPCR data showed that CTX administration at 50-100 mg·kg^-1 up-regulated gene expressions of cyp1a, cyp2k1 and cyp3a, and inflammatory response-related genes including rel, relb, nfκb1, il-6, il-8, il-10 and tnf-α. CTX significantly promoted the mRNA levels of ERS-related genes (eif2α, crt, parp1, grp78, ire1, xbp1s and chop) in a dose dependent manner. Additionally, CTX injection at 75-100 mg·kg^-1 could down-regulate gene expressions of anti-oxidative status including nrf2, ucp2, ho-1, gpx3, gstα and cat. Overall results suggested CTX injection induced liver damage which was related to the cytotoxic effect on hepatocytes, decrease of antioxidant capacity, inflammatory response and ERS.

Neurotherapeutic implications of sense and respond strategies generated by astrocytes and astrocytic tumours to combat pH mechanical stress

Aims

Astrocytes adapt to acute acid stress. Intriguingly, cancer cells with astrocytic differentiation thrive even better in an acidic microenvironment. How changes in extracellular pH (pHe) are sensed and measured by the cell surface assemblies that first intercept the acid stress, and how this information is relayed downstream for an appropriate survival response remains largely uncharacterized.

Methods

In vitro cell‐based studies were combined with an in vivo animal model to delineate the machinery involved in pH microenvironment sensing and generation of mechanoadaptive responses in normal and neoplastic astrocytes. The data was further validated on patient samples from acidosis driven ischaemia and astrocytic tumour tissues.

Results

We demonstrate that low pHe is perceived and interpreted by cells as mechanical stress. GM3 acts as a lipid‐based pH sensor, and in low pHe, its highly protonated state generates plasma membrane deformation stress which activates the IRE1‐sXBP1‐SREBP2‐ACSS2 response axis for cholesterol biosynthesis and surface trafficking. Enhanced surface cholesterol provides mechanical tenacity and prevents acid‐mediated membrane hydrolysis, which would otherwise result in cell leakage and death.

Conclusions

In summary, activating these lipids or the associated downstream machinery in acidosis‐related neurodegeneration may prevent disease progression, while specifically suppressing this key mechanical ‘sense‐respond’ axis should effectively target astrocytic tumour growth.

Mechanism of Endoplasmic Reticulum Stress in Cerebral Ischemia

Endoplasmic reticulum (ER) is the main organelle for protein synthesis, trafficking and maintaining intracellular Ca²⁺ homeostasis. The stress response of ER results from the disruption of ER homeostasis in neurological disorders. Among these disorders, cerebral ischemia is a prevalent reason of death and disability in the world. ER stress stemed from ischemic injury initiates unfolded protein response (UPR) regarded as a protection mechanism. Important, disruption of Ca²⁺ homeostasis resulted from cytosolic Ca²⁺ overload and depletion of Ca²⁺ in the lumen of the ER could be a trigger of ER stress and the misfolded protein synthesis. Brain cells including neurons, glial cells and endothelial cells are involved in the complex pathophysiology of ischemic stroke. This is generally important for protein underfolding, but even more for cytosolic Ca²⁺ overload. Mild ER stress promotes cells to break away from danger signals and enter the adaptive procedure with the activation of pro-survival mechanism to rescue ischemic injury, while chronic ER stress generally serves as a detrimental role on nerve cells via triggering diverse pro-apoptotic mechanism. What’s more, the determination of some proteins in UPR during cerebral ischemia to cell fate may have two diametrically opposed results which involves in a specialized set of inflammatory and apoptotic signaling pathways. A reasonable understanding and exploration of the underlying molecular mechanism related to ER stress and cerebral ischemia is a prerequisite for a major breakthrough in stroke treatment in the future. This review focuses on recent findings of the ER stress as well as the progress research of mechanism in ischemic stroke prognosis provide a new treatment idea for recovery of cerebral ischemia.

IRE1α RIDD activity induced under ER stress drives neuronal death by the degradation of 14-3-3 θ mRNA in cortical neurons during glucose deprivation

Altered protein homeostasis is associated with neurodegenerative diseases and acute brain injury induced under energy depletion conditions such as ischemia. The accumulation of damaged or unfolded proteins triggers the unfolded protein response (UPR), which can act as a homeostatic response or lead to cell death. However, the factors involved in turning and adaptive response into a cell death mechanism are still not well understood. Several mechanisms leading to brain injury induced by severe hypoglycemia have been described but the contribution of the UPR has been poorly studied. Cell responses triggered during both the hypoglycemia and the glucose reinfusion periods can contribute to neuronal death. Therefore, we have investigated the activation dynamics of the PERK and the IRE1α branches of the UPR and their contribution to neuronal death in a model of glucose deprivation (GD) and glucose reintroduction (GR) in cortical neurons. Results show a rapid activation of the PERK/p-eIF2α/ATF4 pathway leading to protein synthesis inhibition during GD, which contributes to neuronal adaptation, however, sustained blockade of protein synthesis during GR promotes neuronal death. On the other hand, IRE1α activation occurs early during GD due to its interaction with BAK/BAX, while ASK1 is recruited to IRE1α activation complex during GR promoting the nuclear translocation of JNK and the upregulation of Chop. Most importantly, results show that IRE1α RNase activity towards its splicing target Xbp1 mRNA occurs late after GR, precluding a homeostatic role. Instead, IRE1α activity during GR drives neuronal death by positively regulating ASK1/JNK activity through the degradation of 14-3-3 θ mRNA, a negative regulator of ASK and an adaptor protein highly expressed in brain, implicated in neuroprotection. Collectively, results describe a novel regulatory mechanism of cell death in neurons, triggered by the downregulation of 14-3-3 θ mRNA induced by the IRE1α branch of the UPR.

Conditioned Medium from Mesenchymal Stem Cells Alleviates Endothelial Dysfunction of Vascular Grafts Submitted to Ischemia/Reperfusion Injury in 15-Month-Old Rats

In patients undergoing coronary artery bypass grafting (CABG), ischemia/reperfusion injury (IRI) is the main contributor to organ dysfunction. Aging-induced vascular damage may be further aggravated during CABG. Favorable effects of conditioned medium (CM) from mesenchymal stem cells (MSCs) have been suggested against IRI. We hypothesized that adding CM to saline protects vascular grafts from IRI in rats. We found that CM contains 28 factors involved in apoptosis, inflammation, and oxidative stress. Thoracic aortic rings from 15-month-old rats were explanted and immediately mounted in organ bath chambers (aged group) or underwent 24 h of cold ischemic preservation in saline-supplemented either with vehicle (aged-IR group) or CM (aged-IR+CM group), prior to mounting. Three-month-old rats were used as referent young animals. Aging was associated with an increase in intima-to-media thickness, an increase in collagen content, higher caspase-12 mRNA levels, and immunoreactivity compared to young rats. Impaired endothelium-dependent vasorelaxation to acetylcholine in the aged-IR group compared to the aged-aorta was improved by CM (aged 61 ± 2% vs. aged-IR 38 ± 2% vs. aged-IR+CM 50 ± 3%, p < 0.05). In the aged-IR group, the already high mRNA levels of caspase-12 were decreased by CM. CM alleviates endothelial dysfunction following IRI in 15-month-old rats. The protective effect may be related to the inhibition of caspase-12 expression.

Traumatic Brain Injury: Ultrastructural Features in Neuronal Ferroptosis, Glial Cell Activation and Polarization, and Blood-Brain Barrier Breakdown

The secondary injury process after traumatic brain injury (TBI) results in motor dysfunction, cognitive and emotional impairment, and poor outcomes. These injury cascades include excitotoxic injury, mitochondrial dysfunction, oxidative stress, ion imbalance, inflammation, and increased vascular permeability. Electron microscopy is an irreplaceable tool to understand the complex pathogenesis of TBI as the secondary injury is usually accompanied by a series of pathologic changes at the ultra-micro level of the brain cells. These changes include the ultrastructural changes in different parts of the neurons (cell body, axon, and synapses), glial cells, and blood–brain barrier, etc. In view of the current difficulties in the treatment of TBI, identifying the changes in subcellular structures can help us better understand the complex pathologic cascade reactions after TBI and improve clinical diagnosis and treatment. The purpose of this review is to summarize and discuss the ultrastructural changes related to neurons (e.g., condensed mitochondrial membrane in ferroptosis), glial cells, and blood–brain barrier in the existing reports of TBI, to deepen the in-depth study of TBI pathomechanism, hoping to provide a future research direction of pathogenesis and treatment, with the ultimate aim of improving the prognosis of patients with TBI.

Orexin-A alleviates cerebral ischemia-reperfusion injury by inhibiting endoplasmic reticulum stress-mediated apoptosis

Orexin‑A (OXA) protects neurons against cerebral ischemia‑reperfusion injury (CIRI). Endoplasmic reticulum stress (ERS) induces apoptosis after CIRI by activating caspase‑12 and the CHOP pathway. The present study aimed to determine whether OXA mitigates CIRI by inhibiting ERS‑induced neuronal apoptosis. A model of CIRI was established, in which rats were subjected to middle cerebral artery occlusion with ischemic intervention for 2 h, followed by reperfusion for 24 h. Neurological deficit examination and 2,3,5‑triphenyltetrazolium chloride staining were performed to assess the level of CIRI and neuroprotection by OXA. Expression levels of ERS‑related proteins and cleaved caspase‑3 were measured via western blotting, while the rate of neuronal apoptosis in the cortex was determined using a TUNEL assay. OXA treatment decreased the infarct volume of rats after CIRI and attenuated neuron apoptosis. Furthermore, administration of OXA decreased the expression levels of GRP78, phosphorylated (p)‑PERK, p‑eukaryotic initiation factor‑2α, p‑inositol requiring enzyme 1α, p‑JNK, cleaved caspase‑12, CHOP and cleaved caspase‑3, all of which were induced by CIRI. Collectively, these findings suggested that OXA attenuated CIRI by inhibiting ERS‑mediated apoptosis, thus clarifying the mechanism underlying its neuroprotective effect and providing a novel therapeutic direction for the treatment of CIRI.

WTAP promotes myocardial ischemia/reperfusion injury by increasing endoplasmic reticulum stress via regulating m6A modification of ATF4 mRNA

Myocardial infarction (MI) is one of the leading causes of death. Wilms' tumor 1-associating protein (WTAP), one of the components of the m⁶A methyltransferase complex, has been shown to affect gene expression via regulating mRNA modification. Although WTAP has been implicated in various diseases, its role in MI is unclear. In this study, we found that hypoxia/reoxygenation (H/R) time-dependently increased WTAP expression, which in turn promoted endoplasmic reticulum (ER) stress and apoptosis, in human cardiomyocytes (AC16). H/R effects on ER stress and apoptosis were all blocked by silencing of WTAP, promoted by WTAP overexpression, and ameliorated by administration of ER stress inhibitor, 4-PBA. We then investigated the underlying molecular mechanism and found that WTAP affected m⁶A methylation of ATF4 mRNA to regulate its expression, and that the inhibitory effects of WTAP on ER stress and apoptosis were ATF4 dependent. Finally, WTAP’s effects on myocardial I/R injury were confirmed in vivo. WTAP promoted myocardial I/R injury through promoting ER stress and cell apoptosis by regulating m⁶A modification of ATF4 mRNA. These findings highlight the importance of WTAP in I/R injury and provide new insights into therapeutic strategies for MI.

Hepatocyte-derived MANF alleviates hepatic ischaemia-reperfusion injury via regulating endoplasmic reticulum stress-induced apoptosis in mice

BACKGROUND

Endoplasmic reticulum (ER) perturbations are novel subcellular effectors involved in the ischaemia-reperfusion injury. As an ER stress-inducible protein, mesencephalic astrocyte-derived neurotrophic factor (MANF) has been proven to be increased during ischaemic brain injury. However, the role of MANF in liver ischaemia reperfusion (I/R) injury has not yet been studied.

METHODS

To investigate the role of MANF in the process of liver ischaemia-reperfusion, Hepatocyte-specific MANF knockout (MANF^hep-/- ) mice and their wild-type (WT) littermates were used in our research. Mice partial (70%) warm hepatic I/R model was established by vascular occlusion. We detected the serum levels of MANF in both liver transplant patients and WT mice before and after liver I/R injury. Recombinant human MANF (rhMANF) was injected into the tail vein before 1 hour occlusion. AST, ALT and Suzuki score were used to evaluate the extent of I/R injury. OGD/R test was performed on primary hepatocytes to simulate IRI in vitro. RNA sequence and RT-PCR were used to detect the cellular signal pathway activation while MANF knockout.

RESULTS

We found that MANF expression and secretion are dramatically up-regulated during hepatic I/R. Hepatocyte-specific MANF knockout aggravates the I/R injury through the over-activated ER stress. The systemic administration of rhMANF before ischaemia has the potential to ameliorate I/R-triggered UPR and liver injury. Further study showed that MANF deficiency activated ATF4/CHOP and JNK/c-JUN/CHOP pathways, and rhMANF inhibited the activation of the two proapoptotic pathways caused by MANF deletion.

CONCLUSION

Collectively, our study unravels a previously unknown relationship among MANF, UPR and hepatic I/R injury.

N-Methyl-D-Aspartate Receptor Signaling-Protein Kinases Crosstalk in Cerebral Ischemia

Although stroke is very often the cause of death worldwide, the burden of ischemic and hemorrhagic stroke varies between regions and over time regarding differences in prognosis, prevalence of risk factors, and treatment strategies. Excitotoxicity, oxidative stress, dysfunction of the blood-brain barrier, neuroinflammation, and lysosomal membrane permeabilization, sequentially lead to the progressive death of neurons. In this process, protein kinases-related checkpoints tightly regulate N-methyl-D-aspartate (NMDA) receptor signaling pathways. One of the major hallmarks of cerebral ischemia is excitotoxicity, characterized by overactivation of glutamate receptors leading to intracellular Ca²⁺ overload and ultimately neuronal death. Thus, reduced expression of postsynaptic density-95 protein and increased protein S-nitrosylation in neurons is responsible for neuronal vulnerability in cerebral ischemia. In this chapter death-associated protein kinases, cyclin-dependent kinase 5, endoplasmic reticulum stress-induced protein kinases, hyperhomocysteinemia-related NMDA receptor overactivation, ephrin-B-dependent amplification of NMDA-evoked neuronal excitotoxicity and lysosomocentric hypothesis have been discussed.Consequently, ample evidences have demonstrated that enhancing extrasynaptic NMDA receptor activity triggers cell death after stroke. In this context, considering the dual roles of NMDA receptors in both promoting neuronal survival and mediating neuronal damage, selective augmentation of NR2A-containing NMDA receptor activation in the presence of NR2B antagonist may constitute a promising therapy for stroke.

Endoplasmic reticulum stress serves an important role in cardiac ischemia/reperfusion injury (Review)

Although acute myocardial infarction is one of the most common fatal diseases worldwide, the understanding of its underlying pathogenesis continues to develop. Myocardial ischemia/reperfusion (I/R) can restore myocardial oxygen and nutrient supply. However, a large number of studies have demonstrated that recovery of blood perfusion after acute ischemia causes reperfusion injury to the heart. With progress made in the understanding of the underlying mechanisms of myocardial I/R and oxidative stress, a novel area of research that merits greater study has been identified, that of I/R-induced endoplasmic reticulum (ER) stress (ERS). Cardiac I/R can alter the function of the ER, leading to the accumulation of unfolded/misfolded proteins. The resulting ERS then induces the activation of signal transduction pathways, which in turn contribute to the development of I/R injury. The mechanism of I/R injury, and the causal relationship between I/R and ERS are reviewed in the present article.

Zinc-dependent changes in oxidative and endoplasmic reticulum stress during cardiomyocyte hypoxia/reoxygenation

Myocardial zinc dyshomeostasis is associated with caspase-3 activation, ErbB2 degradation and apoptosis during hypoxia/reoxygenation. Zinc pyrithione replenishes intracellular zinc, suppresses caspase-3, augments ErbB2 levels and improves cell survival. We hypothesize that zinc is capable of modulating redox and endoplasmic reticulum (ER) stress in the setting of cardiomyocyte hypoxia-reoxygenation. Hypoxia/reoxygenation lowered intracellular zinc, increased ER as well as oxidative stress in H9c2 cells, both of which were effectively attenuated by zinc supplementation. Silencing of gp91phox attenuated oxidative and ER stress, decreased caspase-3 activation and improved cell survival. Mimicking the oxidative insult using 50 μM H2O2 increased the caspase-3 activity that correlated with decreased ErbB2 levels, concomitant with augmented ER stress. N-acetyl cysteine (NAC) administration completely suppressed ER stress as well as caspase-3 activity. Zinc depletion using TPEN also resulted in lowered ErbB2 and increased apoptosis, along with NOX2 mRNA upregulation, increased oxidative and ER stress. Repletion with zinc suppressed NOX2 mRNA, lowered oxidative as well as ER stress and decreased cell death. These results suggest that zinc dyshomeostasis, along with oxidative stress contribute to the unfolded protein response during myocardial H/R and that zinc replenishment corrects zinc homeostasis, alleviates associated stress and improves cardiomyocyte survival.

Rg1 in combination with mannitol protects neurons against glutamate-induced ER stress via the PERK-eIF2 α-ATF4 signaling pathway

AIMS

Ginseng and ginsenosides are known for their remarkable effects on the central nervous system. However, pharmacokinetic studies have suggested that the Ginsenoside Rg1 (Rg1) cannot be efficiently transported through the blood-brain barrier. To investigate the effects of Rg1 in combination with mannitol protects neurons against glutamate-induced ER stress via the PERK-eIF2 -ATF4 signaling pathway.

MAIN METHODS

Rg1, along with the BBB permeabilizer mannitol, exhibited a potent neuroprotective effect by significantly reducing the neurological scores and infarct volume in rats exposed to middle cerebral artery occlusion. We evaluated the effect of Rg1 on neuroprotection after MCAO, and also explored its potential mechanism of action.

KEY FINDINGS

Our results show that Rg1 reduced the number of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive neurons. This neuroprotection may be dependent, at least in part, on the preservation of the endoplasmic reticulum and mitochondrial function. Ischemia-induced brain injury is largely caused by the excessive release of glutamate, which results in excitotoxicity and cell death. Neurons were pretreated with Rg1 before inducing endoplasmic reticulum stress with glutamate. A reduction in the expression of Bax and a concomitant increase in Bcl2 expression prevented the induction of apoptosis. Furthermore, Rg1 downregulated the expression of endoplasmic reticulum stress genes.

SIGNIFICANCE

Our results indicate that Rg1 modulation of stress-responsive genes helps prevent glutamate-induced endoplasmic reticulum stress in neurons through the PERK-eIF2-α-ATF4 signaling pathway.

Trophic activities of endoplasmic reticulum proteins CDNF and MANF

Mesencephalic astrocyte-derived neurotrophic factor (MANF) and cerebral dopamine neurotrophic factor (CDNF) are endoplasmic reticulum (ER) luminal proteins that confer trophic activities in a wide range of tissues under diverse pathological conditions. Despite initially being classified as neurotrophic factors, neither protein structurally nor functionally resembles bona fide neurotrophic factors. Their highly homologous structures comprise a unique globular, saposin-like domain within the N-terminus joined by a flexible linker to a C-terminus containing a SAP-like domain, CXXC motif and an ER retention sequence. Neurotrophic factors exert effects by binding to cognate receptors in the plasma membrane; however, no cell surface receptors have been identified for MANF and CDNF. Both can act as unfolded protein response (UPR) genes that modulate the UPR and inflammatory processes. The trophic activity of MANF and CDNF extends beyond the central nervous system with MANF being crucial for the development of pancreatic β cells and both have trophic effects in a variety of diseases related to the liver, heart, skeletal tissue, kidney and peripheral nervous system. In this article, the unique features of MANF and CDNF, such as their structure and mechanisms of action related to ER stress and inflammation, will be reviewed. Recently identified interactions with lipids and membrane trafficking will also be described. Lastly, their function and therapeutic potential in different diseases including a recent clinical trial using CDNF to treat Parkinson's disease will be discussed. Collectively, this review will highlight MANF and CDNF as broad-acting trophic factors that regulate functions of the endoplasmic reticulum.

Translation Regulation by eIF2α Phosphorylation and mTORC1 Signaling Pathways in Non-Communicable Diseases (NCDs)

Non-communicable diseases (NCDs) are medical conditions that, by definition, are non-infectious and non-transmissible among people. Much of current NCDs are generally due to genetic, behavioral, and metabolic risk factors that often include excessive alcohol consumption, smoking, obesity, and untreated elevated blood pressure, and share many common signal transduction pathways. Alterations in cell and physiological signaling and transcriptional control pathways have been well studied in several human NCDs, but these same pathways also regulate expression and function of the protein synthetic machinery and mRNA translation which have been less well investigated. Alterations in expression of specific translation factors, and disruption of canonical mRNA translational regulation, both contribute to the pathology of many NCDs. The two most common pathological alterations that contribute to NCDs discussed in this review will be the regulation of eukaryotic initiation factor 2 (eIF2) by the integrated stress response (ISR) and the mammalian target of rapamycin complex 1 (mTORC1) pathways. Both pathways integrally connect mRNA translation activity to external and internal physiological stimuli. Here, we review the role of ISR control of eIF2 activity and mTORC1 control of cap-mediated mRNA translation in some common NCDs, including Alzheimer’s disease, Parkinson’s disease, stroke, diabetes mellitus, liver cirrhosis, chronic obstructive pulmonary disease (COPD), and cardiac diseases. Our goal is to provide insights that further the understanding as to the important role of translational regulation in the pathogenesis of these diseases.

Icariin protects neurons from endoplasmic reticulum stress-induced apoptosis after OGD/R injury via suppressing IRE1α-XBP1 signaling pathway

Icariin (ICA), a flavonol glycoside isolated from Epimedium, has been considered as a potential alternative therapy for ischemic stroke. However, the protective mechanisms of ICA on cerebral ischemia-reperfusion (I/R) are not fully illuminated yet. The effects of ICA on ER stress and inflammatory response which were involved in the pathological process of cerebral I/R were investigated in vitro. Microglia and neurons were subjected to OGD/R. ICA was administrated to microglia 1 h before OGD and maintained 2 h throughout OGD. At 24 h after reoxygenation, the protein expression of IL-1 β, IL-6, TNF-α in the supernatant of microglia was measured using ELISA assay; neuronal apoptosis was assessed by TUNEL staining; and cell viability was detected using CKK-8 assay; the expression of IRE1α, XBP1u, XBP1s, and cleaved caspase-3 in neurons was examined by western blotting and qRT-PCR; the expression of p-IRE1α in neurons was detected by western blotting. We found that OGD/R induced the expression of IL-1 β, IL-6, TNF-α in the supernatant of microglia; OGD/R and these proinflammatory cytokines promoted the mRNA as well as protein expression of XBP1u, XBP1s and cleaved caspase-3, increased the ratio of p-IRE1α/IRE1α, as well as apoptosis, and decreased cell viability in primary cortical neurons, while ICA reversed the levels of the above factors. IRE1 overexpression enhanced ER stress as well as apoptosis, and impaired the protective effects of ICA. These results suggested that ICA can inhibit apoptosis in neurons after OGD/R through IRE1/XBP1 signaling pathway beside its anti-inflammatory effect.

ER Stress and the UPR in Shaping Intestinal Tissue Homeostasis and Immunity

An imbalance in the correct protein folding milieu of the endoplasmic reticulum (ER) can cause ER stress, which leads to the activation of the unfolded protein response (UPR). The UPR constitutes a highly conserved and intricately regulated group of pathways that serve to restore ER homeostasis through adaptation or apoptosis. Numerous studies over the last decade have shown that the UPR plays a critical role in shaping immunity and inflammation, resulting in the recognition of the UPR as a key player in pathological processes including complex inflammatory, autoimmune and neoplastic diseases. The intestinal epithelium, with its many highly secretory cells, forms an important barrier and messenger between the luminal environment and the host immune system. It is not surprising, that numerous studies have associated ER stress and the UPR with intestinal diseases such as inflammatory bowel disease (IBD) and colorectal cancer (CRC). In this review, we discuss our current understanding of the roles of ER stress and the UPR in shaping immune responses and maintaining tissue homeostasis. Furthermore, the role played by the UPR in disease, with emphasis on IBD and CRC, is described here. As a key player in immunity and inflammation, the UPR has been increasingly recognized as an important pharmacological target in the development of therapeutic strategies for immune-mediated pathologies. We summarize available strategies targeting the UPR and their therapeutic implications. Understanding the balance between homeostasis and pathophysiology, as well as means of manipulating this balance, provides an important avenue for future research.

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.

Protective effects of HO-1 pathway on lung injury subsequent to limb ischemia reperfusion

Limb ischemia reperfusion (LIR) can activate endogenous cytoprotective mechanisms by generating specific proteins against reperfusion injury in remote organs. The present study investigated the roles of heme oxygenase-1 (HO-1) pathway and the molecular mechanisms underlying the regulation of this pathway on lung injury following LIR. LIR was induced by ischemia for 4 hours followed by reperfusion for 6 hours (LIR 6 hours) or 16 hours (LIR 16 hours) in male Sprague-Dawley rats. HO-1 inducer cobalt protoporphyrin (Copp) or HO-1 inhibitor zinc protoporphyrin (Znpp) was intravenously injected 24 hours before ischemia. The animals were randomly divided into nine groups, including normal control, LIR 6 hours, LIR 16 hours, Copp, Copp + LIR 6 hours, Copp + LIR 16 hours, and Znpp, Znpp+ LIR 6 hours, and Znpp + LIR 16 hours groups (each group included four samples). Lung injury was examined through histopathology. Quantitative real-time PCR, immunohistochemistry and Western blot were applied to detect the mRNA and protein levels of HO-1, Nrf2, and Bach1. Our study showed that LIR induced Nrf2 upregulation but Bach1 downregulation to promote HO-1 expression in lung tissues. Activation of HO-1 pathway by Copp potentially enhanced Nrf2 expression but inhibition of the pathway by Znpp promoted Bach1 expression. Inducer of HO-1 pathway, Copp injection improved the lung injury. Nevertheless, Znpp injection aggravated the lung injury following LIR. Our findings suggested that activated HO-1 pathway might exert protective effects on the lung injury following LIR.

Bestrophin-3 Expression in a Subpopulation of Astrocytes in the Neonatal Brain After Hypoxic-Ischemic Injury

Bestrophin-3, a potential candidate for a calcium-activated chloride channel, recently was suggested to have cell-protective functions. We studied the expression and alternative splicing of bestrophin-3 in neonatal mouse brain and after hypoxic-ischemic (HI) injury and in human neonatal brain samples. HI brain injury was induced in 9-day old mice by unilateral permanent common carotid artery occlusion in combination with exposure to 10% oxygen for 50 min. Endoplasmic reticulum stress was induced by thapsigargin treatment in primary culture of mouse brain astrocytes. We also investigated expression of bestrophin-3 protein in a sample of human neonatal brain tissue. Bestrophin-3 protein expression was detected with immunohistochemical methods and western blot; mRNA expression and splicing were analyzed by RT-PCR. HI induced a brain tissue infarct and a pronounced increase in the endoplasmic reticulum-associated marker CHOP. Three days after HI a population of astrocytes co-expressed bestrophin-3 and nestin in a penumbra-like area of the injured hemisphere. However, total levels of Bestrophin-3 protein in mouse cortex were reduced after injury. Mouse astrocytes in primary culture also expressed bestrophin-3 protein, the amount of which was reduced by endoplasmic reticulum stress. Bestrophin-3 protein was detected in astrocytes in the hippocampal region of the human neonatal brain which had patchy white matter gliosis and neuronal loss in the Sommer’s sector of the Ammon’s horn (CA1). Analysis of bestrophin-3 mRNA in mouse brain with and without injury showed the presence of two truncated spliced variants, but no full-length mRNA. Total amount of bestrophin-3 mRNA increased after HI, but showed only minor injury-related change. However, the splice variants of bestrophin-3 mRNA were differentially regulated after HI depending on the presence of tissue injury. Our results show that bestrophin-3 is expressed in neonatal mouse brain after injury and in the human neonatal brain with pathology. In mouse brain bestrophin-3 protein is upregulated in a specific astrocyte population after injury and is co-expressed with nestin. Splice variants of bestrophin-3 mRNA respond differently to HI, which might indicate their different roles in tissue injury.

Ferulic Acid Exerts Anti-apoptotic Effects against Ischemic Injury by Activating HSP70/Bcl-2- and HSP70/Autophagy-Mediated Signaling after Permanent Focal Cerebral Ischemia in Rats

This study assessed the anti-apoptotic effects of the administration of ferulic acid (FrA) in rats 30 min before middle cerebral artery occlusion (MCAo) followed by 3 d of ischemia and the involvement of 70 kDa heat shock protein (HSP70)-mediated signaling in the penumbral cortex. Our results demonstrated that FrA pretreatment at doses of 80 mg/kg (FrA-80 mg) and 100 mg/kg (FrA-100 mg) effectively ameliorated neurological functions and reduced the numbers of cytochrome c-, cleaved caspase-3-, and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive cells in the penumbral cortex 3 d after ischemia. Moreover, FrA-80 mg and FrA-100 mg pretreatment markedly upregulated cytosolic HSP70, Beclin-1, microtubule-associated protein 1 light chain 3 (LC3) A/B-II and autophagy-related protein 5 (Atg5) expression; cytosolic and mitochondrial X-linked inhibitor of apoptosis (XIAP) expression and the Bcl-2/Bax ratio. FrA pretreatment downregulated cytosolic cytochrome c, apoptosis-inducing factor (AIF), procathepsin B, and cathepsin B expression and mitochondrial and cytosolic second mitochondria-derived activator of caspase/direct inhibitor of apoptosis protein-binding protein with a low isoelectric point (Smac/DIABLO) expression in the penumbral cortex. Pretreatment with VER155008, a HSP70 family inhibitor, significantly inhibited the effects of FrA-100 mg on the expression of the aforementioned proteins expression in the penumbral cortex. FrA-80 mg and FrA-100 mg pretreatment exerts neuroprotective effects against caspase-dependent and -independent apoptosis through activating HSP70/Bcl-2- and HSP70/autophagy-induced signaling pathways. Furthermore, the HSP70/Bcl-2- and HSP70/autophagy-induced anti-apoptotic effects of FrA pretreatment can be attributed to the regulation of Bax/cytochrome c/Smac/DIABLO/XIAP/ caspase-3- (or Bax/AIF-) and Beclin-1/LC3A/B-II/Atg5-mediated signaling, respectively, in the penumbral cortex 3 d after permanent MCAo.

Neuroprotective and Neurological/Cognitive Enhancement Effects of Curcumin after Brain Ischemia Injury with Alzheimer's Disease Phenotype

In recent years, ongoing interest in ischemic brain injury research has provided data showing that ischemic episodes are involved in the development of Alzheimer's disease-like neuropathology. Brain ischemia is the second naturally occurring neuropathology, such as Alzheimer's disease, which causes the death of neurons in the CA1 region of the hippocampus. In addition, brain ischemia was considered the most effective predictor of the development of full-blown dementia of Alzheimer's disease phenotype with a debilitating effect on the patient. Recent knowledge on the activation of Alzheimer's disease-related genes and proteins-e.g., amyloid protein precursor and tau protein-as well as brain ischemia and Alzheimer's disease neuropathology indicate that similar processes contribute to neuronal death and disintegration of brain tissue in both disorders. Although brain ischemia is one of the main causes of death in the world, there is no effective therapy to improve the structural and functional outcomes of this disorder. In this review, we consider the promising role of the protective action of curcumin after ischemic brain injury. Studies of the pharmacological properties of curcumin after brain ischemia have shown that curcumin has several therapeutic properties that include anti-excitotoxic, anti-oxidant, anti-apoptotic, anti-hyperhomocysteinemia and anti-inflammatory effects, mitochondrial protection, as well as increasing neuronal lifespan and promoting neurogenesis. In addition, curcumin also exerts anti-amyloidogenic effects and affects the brain's tau protein. These results suggest that curcumin may be able to serve as a potential preventive and therapeutic agent in neurodegenerative brain disorders.

Neuroprotective Functions Through Inhibition of ER Stress by Taurine or Taurine Combination Treatments in a Rat Stroke Model

Taurine, as a free amino acid, is found at high levels in many tissues including brain, heart and skeletal muscle and is known to demonstrate neuroprotective effects in a range of disease conditions including stroke and neurodegenerative disease. Using in vitro culture systems we have demonstrated that taurine can elicit protection against endoplasmic reticulum stress (ER stress) from glutamate excitotoxicity or from excessive reactive oxygen species in PC12 cells or rat neuronal cultures. In our current investigation we hypothesized that taurine treatment after stroke in the rat middle cerebral artery occlusion (MCAO) model would render protection against ER stress processes as reflected in decreased levels of expression of ER stress pathway components. We demonstrated that taurine elicited high level protection and inhibited both ATF-6 and IRE-1 ER stress pathway components. As ischemic stroke has a complex pathology it is likely that certain combination treatment approaches targeting multiple disease mechanisms may have excellent potential for efficacy. We have previously employed the partial NMDA antagonist DETC-MeSO to render protection against in vivo ischemic stroke using a rat cerebral ischemia model. Here we tested administration of subcutaneous administration of 0.56 mg/kg DETC-MeSO or 40 mg/kg of taurine separately or as combined treatment after a 120 min cerebral ischemia in the rat MCAO model. Neither drug alone demonstrated protection at the low doses employed. Remarkably however the combination of low dose DETC-MeSO plus low dose taurine conferred a diminished infarct size and an enhanced Neuroscore (reflecting decreased neurological deficit). Analysis of ER stress markers pPERK, peIF-2-alpha and cleaved ATF-6 all showed decreased expression demonstrating that all 3 ER stress pathways were inhibited concurrent with a synergistic protective effect by the post-stroke administration of this DETC-MeSO-taurine combination treatment.

Protective Effects of Curcumin Against Ischemia-Reperfusion Injury in the Nervous System

Ischemia-reperfusion injury (I/R injury) is a common feature of ischemic stroke which occurs when blood supply is restored after a period of ischemia. Although stroke is an important cause of death in the world, effective therapeutic strategies aiming at improving neurological outcomes in this disease are lacking. Various studies have suggested the involvement of different mechanisms in the pathogenesis of I/R injury in the nervous system. These mechanisms include oxidative stress, platelet adhesion and aggregation, leukocyte infiltration, complement activation, blood-brain barrier (BBB) disruption, and mitochondria-mediated mechanisms. Curcumin, an active ingredient of turmeric, can affect all these pathways and exert neuroprotective activity culminating in the amelioration of I/R injury in the nervous system. In this review, we discuss the protective effects of curcumin against I/R injury in the nervous system and highlight the studies that have linked biological functions of curcumin and I/R injury improvement.

Melatonin protects brain against ischemia/reperfusion injury by attenuating endoplasmic reticulum stress

Endoplasmic reticulum (ER) stress plays a vital role in mediating ischemic reperfusion damage in brain. In this study, we evaluated whether melatonin inhibits ER stress in cultured neurons exposed to oxygen and glucose deprivation (OGD) and in rats subjected to transient focal cerebral ischemia. Sprague-Dawley rats were treated with melatonin (5 mg/kg) or control at reperfusion onset after transient occlusion of the right middle cerebral artery (MCA) for 90 min. Brain infarction and hemorrhage within infarcts were measured. The expression of ER stress proteins of phosphorylation of PRKR-like endoplasmic reticulum kinase (p-PERK), phosphorylation of eukaryotic translation initiation factor 2α (p-eIF2α), activating transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP) were detected by western blotting and immunohistochemistry analysis. The terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) method, cleaved caspase-3 and cytochrome c were used to investigate cell apoptosis in OGD-induced cultured neurons. Our results demonstrated that animals treated with melatonin had significantly reduced infarction volumes and individual cortical lesion sizes as well as increased numbers of surviving neurons. Melatonin can significantly modulate protein levels by decreasing both p-PERK and p-eIF2α in the ischemic core and penumbra. Moreover, the expressions of ATF4 and CHOP were restrained in the ischemic core and penumbra, respectively. Furthermore, pretreatment with melatonin at 10–100 µM effectively reduced the levels of p-PERK and p-eIF2α in cultured neurons after OGD injury. Melatonin treatment also effectively decreased neuron apoptosis resulting from OGD-induced neuron injury. These results indicate that melatonin effectively attenuated post-ischemic ER stress after ischemic stroke.

CCAAT/enhancer binding protein homologous protein knockdown alleviates hypoxia-induced myocardial injury in rat cardiomyocytes exposed to high glucose

Diabetic patients are more sensitive to ischemic injury than non-diabetics. Endoplasmic reticulum (ER) stress has been reported to be closely associated with the pathophysiology of ischemic injury in diabetes. The aim of the present study was to investigate the mechanisms involved in the progression of diabetes complicated by myocardial infarction (MI) and further verify the role of CCAAT/enhancer binding protein (C/EBP)-homologous protein (CHOP) using an in vitro model of diabetes/MI. The rats were exposed to 65 mg/kg streptozotocin (STZ) and left anterior descending (LAD) coronary artery ligation. ST-segment elevation, heart rate, left ventricular systolic pressure (LVSP) and LV end-diastolic pressure (LVEDP) were measured. Serum creatinine kinase-MB (CK-MB) and cardiac troponin T (cTnT) levels were examined by ELISA. Infarct size and apoptosis were measured by triphenyltetrazolium chloride staining and terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling assay. Pathological changes were evaluated by hematoxylin and eosin staining. H9c2 cells were used to establish an in vitro model of diabetes complicated by MI. Following CHOP knockdown, cell viability, cell cycle distribution and apoptosis were examined by Cell Counting Kit-8 assay, flow cytometry and Hoechst staining. Glucose-regulated protein 78 (GRP78), CHOP, B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), endoplasmic reticulum oxidoreductase 1 (Ero1)-α, Ero1β and protein disulfide isomerase (PDI) levels in both myocardial tissues and H9c2 cells were determined by western blotting. In the present study, diabetes complicated by MI promoted ST-segment elevation and myocardial apoptosis, increased infarct size, induced pathological changes and elevated LVEDP, CK-MB, cTnT, GRP78, CHOP, Bax, Ero1α, Ero1β and PDI; however, it decreased heart rate, LVSP and Bcl-2. Additionally, high glucose combined with hypoxic treatment reduced cell viability, induced cell cycle arrest at G1 phase, promoted cell apoptosis, and activated the GRP78/CHOP and Ero1/PDI signaling pathways, which were reversed by CHOP knockdown. Thus, CHOP may be an effective therapeutic target for the treatment of diabetes complicated by MI.

Protective effect of Danhong Injection combined with Naoxintong Capsule on cerebral ischemia-reperfusion injury in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Danhong Injection (DHI) and Naoxintong Capsule (NXT) are renowned traditional Chinese medicine in China. The drug combination of DHI and NXT is frequently applied for the treatment of cardiovascular and cerebrovascular diseases in clinic. However, there had been no pharmacological experiment studies of interaction between DHI and NXT. Due to the drug interactions, exploring their interaction profile is of great importance.

MATERIAL AND METHODS

In this study, focal cerebral I/R injury in adult male Sprague-Dawley rats were induced by transient middle cerebral artery occlusion (tMCAO) for 1h followed by reperfusion. Rats were divided into 5 groups: sham group, ischemia reperfusion untreated group (IRU), DHI group (DHI 10mL/kg/d), NXT group (NXT 0.5g/kg/d), DHI plus NXT group (DHI-NXT, DHI 10mL/kg/d plus NXT 0.5g/kg/d). All drug-treated groups were respectively successive administrated for 7 days after ischemia/ reperfusion (I/R) injury. The effects on rat neurological function were estimated by neurological defect scores. Brain infarct volumes were determined based on 2, 3, 5-triphenyltetrazolium chloride (TTC) staining. Pathological changes in brain tissues were observed using hematoxylin and eosin (H&E) staining and transmission electron microscope (TEM). Levels of nitric oxide (NO), granulocyte colony-stimulating factor (G-CSF) and granulocyte macrophage colony-stimulating factor (GM-CSF) in serum were determined with enzyme-linked immunosorbent assay (ELISA). Immunohisto-chemistry and Western blot were used to detect the expressions of basic fibroblast growth factor (bFGF), von Willebrand factor-microvessel vascular density (vWF-MVD), vascular endothelial cell growth factor (VEGF), transforming growth factor-β1 (TGF-β1), angiogenin-1 (Ang-1), angiogenin-2 (Ang-2) and platelet derived growth factor (PDGF) at day 7 after ischemia/reperfusion (I/R) injury.

RESULTS

Compared with IRU group and mono-therapy group (DHI group or NXT group), Danhong Injection combined with Naoxintong Capsule (DHI-NXT) group significantly ameliorated neurological deficits scores, infarct volume and pathological change, significantly decreased the overexpression of NO and the level of Ang-1, significantly increased the expressions of VEGF, Ang-2, G-CSF, GM-CSF, bFGF, PDGF, vWF, TGF-β1.

CONCLUSION

The protective benefits on rat brain against I/R injury were clearly produced when DHI and NXT were used in combination, which provided rational guidance for clinical combined application of DHI and NXT, and this protection maybe associated with the up-regulation expressions of the related chemokines and growth factors of angiogenesis.

Acute Limb Ischemia-Much More Than Just a Lack of Oxygen

Acute ischemia of an extremity occurs in several stages, a lack of oxygen being the primary contributor of the event. Although underlying patho-mechanisms are similar, it is important to determine whether it is an acute or chronic event. Healthy tissue does not contain enlarged collaterals, which are formed in chronically malperfused tissue and can maintain a minimum supply despite occlusion. The underlying processes for enhanced collateral blood flow are sprouting vessels from pre-existing vessels (via angiogenesis) and a lumen extension of arterioles (via arteriogenesis). While disturbed flow patterns with associated local low shear stress upregulate angiogenesis promoting genes, elevated shear stress may trigger arteriogenesis due to increased blood volume. In case of an acute ischemia, especially during the reperfusion phase, fluid transfer occurs into the tissue while the vascular bed is simultaneously reduced and no longer reacts to vaso-relaxing factors such as nitric oxide. This process results in an exacerbative cycle, in which increased peripheral resistance leads to an additional lack of oxygen. This whole process is accompanied by an inundation of inflammatory cells, which amplify the inflammatory response by cytokine release. However, an extremity is an individual-specific composition of different tissues, so these processes may vary dramatically between patients. The image is more uniform when broken down to the single cell stage. Because each cell is dependent on energy produced from aerobic respiration, an event of acute hypoxia can be a life-threatening situation. Aerobic processes responsible for yielding adenosine triphosphate (ATP), such as the electron transport chain and oxidative phosphorylation in the mitochondria, suffer first, thus disrupting the integrity of cellular respiration. One consequence of this is irreparable damage of the cell membrane due to an imbalance of electrolytes. The eventual increase in net fluid influx associated with a decrease in intracellular pH is considered an end-stage event. Due to the lack of ATP, individual cell organelles can no longer sustain their activity, thus initiating the cascade pathways of apoptosis via the release of cytokines such as the BCL2 associated X protein (BAX). As ischemia may lead to direct necrosis, inflammatory processes are further aggravated. In the case of reperfusion, the flow of nascent oxygen will cause additional damage to the cell, further initiating apoptosis in additional surrounding cells. In particular, free oxygen radicals are formed, causing severe damage to cell membranes and desoxyribonucleic acid (DNA). However, the increased tissue stress caused by this process may be transient, as radical scavengers may attenuate the damage. Taking the above into final consideration, it is clearly elucidated that acute ischemia and subsequent reperfusion is a process that leads to acute tissue damage combined with end-organ loss of function, a condition that is difficult to counteract.

Hydrogen-Rich Saline Ameliorates Hepatic Ischemia-Reperfusion Injury Through Regulation of Endoplasmic Reticulum Stress and Apoptosis

OBJECTIVE

To evaluate the effect of hydrogen-rich saline (HS) on hepatic ischemia-reperfusion (I/R) injury.

METHODS

Forty rats were randomly allocated into five groups: one sham group (control group), one group treated with 20 min of ischemia and normal saline (NS; I/R1 + NS group), one group treated with 20 min of ischemia and HS (I/R1 + HS group), one group treated with 60 min of ischemia and NS (I/R2 + NS group), and one group treated with 60 min of ischemia and HS (I/R2 + HS group). After reperfusion for 6 h, hepatic function, oxidative stress, pathological changes, and apoptosis of hepatic cells were evaluated. Furthermore, the expression levels of endoplasmic reticulum (ER) stress-associated proteins were identified.

RESULTS

Serum ALT and AST levels and tissue MDA content in the I/R + HS groups were significantly lower than those in the I/R + NS groups. Pathological changes were also significantly ameliorated in the HS groups compared with those in the NS groups. Moreover, HS appeared to significantly attenuate hepatic I/R-induced ER stress responses, as indicated by the decreased expression of C/EBP homologous protein, protein-kinase-RNA-like ER kinase, and inositol-requiring protein-1α, as well as the increased expression of GRP78 proteins. Finally, the levels of apoptotic markers such as caspase-3 and TUNEL-positive cells were significantly lower in the HS groups than in the NS control groups, whereas the level of Bcl2 protein increased in the HS groups.

CONCLUSION

The protective effect of HS can be attributed to ER stress and apoptosis inhibition.

Chrysophanol inhibits endoplasmic reticulum stress in cerebral ischemia and reperfusion mice

Endoplasmic reticulum (ER) stress plays a critical role in mediating ischemia/reperfusion (I/R) damage in the brain. Our previous study showed that Chrysophanol (CHR) alleviated cerebral ischemic injury in mice and nuclear factor-κB (NF-κB) involved in its neuroprotective effect, but the precise mechanism remains not fully understood. The present study investigated the effect of CHR treatment on I/R-induced ER stress. Mice were subjected to middle cerebral artery occlusion (MCAO) for 45min and received either vehicle or CHR (0.1mg/kg) for 14 days after reperfusion. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) was used to detect apoptotic cells in penumbral tissue. The expression of ER stress-related factors including glucose-regulated protein 78 (GRP78), phosphorylated eukaryotic initiation factor 2α (p-eIF2α), CCAAT-enhancer-binding protein homologous protein (CHOP), and caspase-12 as well as inhibitory κB-α (IκB-α), the inhibitor of NF-κB, was assessed. Our results demonstrated that CHR treatment reduced MCAO-induced upregulation of GRP78, p-eIF2α, CHOP, and caspase-12 in the ischemic brain. Moreover, the TUNEL-positive neuronal cells, which were colocalized with CHOP and caspase-12, decreased in response to CHR treatment, indicating that CHR protects against I/R injury by inhibiting ER stress-associated neuronal apoptosis. In addition, CHR reversed the decrease in IκB-α level induced by MCAO, which was attributed at least in part to the attenuation of translational inhibition induced by eIF2α phosphorylation, indicating that CHR exerts anti-inflammatory effects following I/R by inhibiting ER stress response. These results suggest that attenuation of ER stress may be involved in the mechanisms of neuroprotective effects of CHR.

Bisoprolol protects myocardium cells against ischemia/reperfusion injury by attenuating unfolded protein response in rats

Bisoprolol (B) exerts potential cardioprotective effects against myocardial ischemia/reperfusion (I/R) injury. Unfolded protein response (UPR) attenuates I/R injury induced apoptosis by reducing oxidative damage and inflammation response. The current study investigated whether the protective effects of bisoprolol resulted from modulating UPR and anti-inflammatory during myocardial I/R condition and elucidated its potential mechanisms. Sprague-Dawley rats were treated with B in the absence or presence of the injected UPR activator dithiothreitol (DTT) and then subjected to myocardial I/R surgery. In vitro, cultured H9C2 cells were pretreated with B or DTT and then subjected to simulate ischemia reperfusion (SIR) operation. Bisoprolol conferred cardioprotective effects by improving postischemic cardiac function, decreasing infarct size, reducing apoptotic index, diminishing serum creatine kinase and lactate dehydrogenase levels, suppressing TNF-α and IL-6 secretion, inhibiting UPR signal pathways and downregulating caspase-12 and caspase-3 expressions. Consistently, B conferred similar antioxidative and anti-inflammatory effects against SIR injury in cultured H9C2 cardiomyocytes. Pretreatment with DTT or C/EBP homologous protein (CHOP) overexpression mediated by lentivirus administration both abolished these effects. In summary, our results demonstrate that Bisoprolol protects myocardium cells against ischemia/reperfusion injury partly by attenuating unfolded protein response.

Curcumin inhibits endoplasmic reticulum stress induced by cerebral ischemia-reperfusion injury in rats

The aim of the present study was to observe the dynamic changes of the growth arrest and DNA damage-inducible 153 (GADD153) gene and caspase-12 in the brain tissue of rats with cerebral ischemia-reperfusion injury (CIRI) and the impact of curcumin pretreatment. A total of 60 rats were randomly divided into the normal group (N), the sham operation group (S), the dimethyl sulfoxide control group (D) and the curcumin treatment group (C). For group D and C, 12 (T1), 24 (T2) and 72 h (T3) of reperfusion were performed after 2 h ischemia. The expression levels of GADD153 and caspase-12 in the brain tissue were detected and compared among the groups by immunohistochemistry, immunofluorescence double staining and western blotting. The expression levels of GADD153 and caspase-12 were increased at T1compared with groups N and S, and the expression of caspase-12 peaked at T2 in group D, while GADD153 was increased until T3 in group D. Compared with group D, the expression levels of GADD153 and caspase-12 in group C at T2 and T3 were significantly decreased (P<0.05). Endoplasmic reticulum stress is involved in the pathological process of CIRI. Curcumin may decrease the expression levels of the above two factors, thus exhibiting protective effects against CIRI in rats.

Excessive nNOS/NO/AMPK signaling activation mediated by the blockage of the CBS/H2S system contributes to oxygen‑glucose deprivation‑induced endoplasmic reticulum stress in PC12 cells

Hypoxic‑ischemia stress causes severe brain injury, leading to death and disability worldwide. Although it has been reported that endoplasmic reticulum (ER) stress is an essential step in the progression of hypoxia or ischemia‑induced brain injury, the underlying molecular mechanisms are and have not yet been fully elucidated. Accumulating evidence has indicated that both nitric oxide (NO) and hydrogen sulfide (H2S) play an important role in the development of cerebral ischemic injury. In the present study, we aimed to investigate the effect of the association between NO signaling and the cystathionine β‑synthase (CBS)/H2S system on ER stress in a cell model of cerebral hypoxia‑ischemia injury. We found that oxygen‑glucose deprivation (OGD) markedly increased the NO level and neuronal NO synthase (nNOS) activity. 3‑Bromo‑7‑nitroindazole (3‑Br‑7‑NI), a relatively selective nNOS inhibitor, abolished the OGD‑induced inhibition of cell viability and the increased expression of ER stress‑related proteins, including glucose‑regulated protein 78 (GRP78), C/EBP homologous protein (CHOP) and cleaved caspase‑12 in PC12 cells, indicating the contribution of excessive nNOS/NO signaling to OGD‑induced ER stress. Furthermore, we found that OGD increased the phosphorylated AMP‑activated protein kinase (p‑AMPK)/AMPK ratio, and the AMPK activator, 5‑aminoimidazole‑4‑carboxamide‑1‑β‑D‑ribofuranoside (AICAR), attenuated the effects on OGD‑induced ER stress, suggesting that OGD‑induced NO overproduction results in AMPK activation in PC12 cells. We also found that OGD induced the downregulation of the CBS/H2S system, as indicated by the decreased H2S level in the culture supernatant and CBS activity in PC12 cells. In addition, we found that treatment with NaHS (a H2S donor) or S‑adenosyl‑L‑methionine (SAM, a CBS agonist) mitigated OGD‑induced ER stress, as well as the NO level, nNOS activity and AMPK phosphorylation in PC12 cells. On the whole, these results suggest that the inhibition of the CBS/H2S system, which facilitated excessive nNOS/NO/AMPK activation, contributes to OGD‑induced ER stress.

Aberrant plasticity of peripheral sensory axons in a painful neuropathy

Neuronal cells express considerable plasticity responding to environmental cues, in part, through subcellular mRNA regulation. Here we report on the extensive changes in distribution of mRNAs in the cell body and axon compartments of peripheral sensory neurons and the 3' untranslated region (3'UTR) landscapes after unilateral sciatic nerve entrapment (SNE) injury in rats. Neuronal cells dissociated from SNE-injured and contralateral L4 and L5 dorsal root ganglia were cultured in a compartmentalized system. Axonal and cell body RNA samples were separately subjected to high throughput RNA sequencing (RNA-Seq). The injured axons exhibited enrichment of mRNAs related to protein synthesis and nerve regeneration. Lengthening of 3'UTRs was more prevalent in the injured axons, including the newly discovered alternative cleavage and polyadenylation of NaV1.8 mRNA. Alternative polyadenylation was largely independent from the relative abundance of axonal mRNAs; but they were highly clustered in functional pathways related to RNA granule formation in the injured axons. These RNA-Seq data analyses indicate that peripheral nerve injury may result in highly selective mRNA enrichment in the affected axons with 3'UTR alterations potentially contributing to the mechanism of neuropathic pain.

Unfolded protein response plays a critical role in heart damage after myocardial ischemia/reperfusion in rats

The unfolded protein response (UPR) plays a critical role in cell death mediated by ischemia/reperfusion (I/R) injury. However, little is known about the exact mechanism of UPR signaling pathways after myocardial I/R injury in rats. An attempt was therefore made to assess whether the myocardial I/R induced UPR, and which branch of UPR (ATF6, IRE1 and PERK) signal pathway was activated. Sprague-Dawley rats were pretreated with UPR stimulator dithiothreitol (DTT) and UPR inhibitor 4-phenylbutyrate (4PBA) and then subjected to myocardial I/R surgery. Compared with sham-operated group, the expression of GRP78, ATF6, CHOP and sXBP1 in the I/R injured group is significantly increased at transcript and protein levels, which indicated that all the three signal pathways of UPR were activated in the myocardial I/R injury. Compared with the I/R injured group, treatment with 4PBA effectively decreased myocardium infarct size, reduced myocardial apoptosis, down-regulated caspase-12 expression, diminished serum creatine kinase and lactate dehydrogenase levels. In contrast, these effects were reversed in DTT treated group. In summary, these results demonstrated that myocardial I/R injury activates UPR and inhibiting cell UPR possesses a cardioprotective effect through the suppression of ER stress-induced apoptosis. Therefore, inhibition of UPR might be used as a therapeutic target during myocardial I/R injury.

Embryonic lethal abnormal vision proteins and adenine and uridine-rich element mRNAs after global cerebral ischemia and reperfusion in the rat

Prolonged translation arrest correlates with delayed neuronal death of hippocampal CA1 neurons following global cerebral ischemia and reperfusion. Many previous studies investigated ribosome molecular biology, but mRNA regulatory mechanisms after brain ischemia have been less studied. Here we investigated the embryonic lethal abnormal vision/Hu isoforms HuR, HuB, HuC, and HuD, as well as expression of mRNAs containing adenine and rich uridine elements following global ischemia in rat brain. Proteomics of embryonic lethal abnormal vision immunoprecipitations or polysomes isolated from rat hippocampal CA1 and CA3 from controls or following 10 min ischemia plus 8 h of reperfusion showed distinct sets of mRNA-binding proteins, suggesting differential mRNA regulation in each condition. Notably, HuB, HuC, and HuD were undetectable in NIC CA1. At 8 h reperfusion, polysome-associated mRNAs contained 46.1% of ischemia-upregulated mRNAs containing adenine and rich uridine elements in CA3, but only 18.7% in CA1. Since mRNAs containing adenine and rich uridine elements regulation are important to several cellular stress responses, our results suggest CA1 is disadvantaged compared to CA3 in coping with ischemic stress, and this is expected to be an important contributing factor to CA1 selective vulnerability. (Data are available via ProteomeXchange identifier PXD004078 and GEO Series accession number GSE82146).

Activation of the ATF6 branch of the unfolded protein response in neurons improves stroke outcome

Impaired function of the endoplasmic reticulum (ER stress) is a hallmark of many human diseases including stroke. To restore ER function in stressed cells, the unfolded protein response (UPR) is induced, which activates 3 ER stress sensor proteins including activating transcription factor 6 (ATF6). ATF6 is then cleaved by proteases to form the short-form ATF6 (sATF6), a transcription factor. To determine the extent to which activation of the ATF6 UPR branch defines the fate and function of neurons after stroke, we generated a conditional and tamoxifen-inducible sATF6 knock-in mouse. To express sATF6 in forebrain neurons, we crossed our sATF6 knock-in mouse line with Emx1-Cre mice to generate ATF6-KI mice. After the ATF6 branch was activated in ATF6-KI mice with tamoxifen, mice were subjected to transient middle cerebral artery occlusion. Forced activation of the ATF6 UPR branch reduced infarct volume and improved functional outcome at 24 h after stroke. Increased autophagic activity at early reperfusion time after stroke may contribute to the ATF6-mediated neuroprotection. We concluded that the ATF6 UPR branch is crucial to ischemic stroke outcome. Therefore, boosting UPR pro-survival pathways may be a promising therapeutic strategy for stroke.

Valproate Attenuates Endoplasmic Reticulum Stress-Induced Apoptosis in SH-SY5Y Cells via the AKT/GSK3β Signaling Pathway

Endoplasmic reticulum (ER) stress-induced apoptosis plays an important role in a range of neurological disorders, such as neurodegenerative diseases, spinal cord injury, and diabetic neuropathy. Valproate (VPA), a typical antiepileptic drug, is commonly used in the treatment of bipolar disorder and epilepsy. Recently, VPA has been reported to exert neurotrophic effects and promote neurite outgrowth, but its molecular mechanism is still unclear. In the present study, we investigated whether VPA inhibited ER stress and promoted neuroprotection and neuronal restoration in SH-SY5Y cells and in primary rat cortical neurons, respectively, upon exposure to thapsigargin (TG). In SH-SY5Y cells, cell viability was detected by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, and the expression of ER stress-related apoptotic proteins such as glucose‑regulated protein (GRP78), C/EBP homologous protein (CHOP), and cleaved caspase-12/-3 were analyzed with Western blot analyses and immunofluorescence assays. To explore the pathway involved in VPA-induced cell proliferation, we also examined p-AKT, GSK3β, p-JNK and MMP-9. Moreover, to detect the effect of VPA in primary cortical neurons, immunofluorescence staining of β-III tubulin and Anti-NeuN was analyzed in primary cultured neurons exposed to TG. Our results demonstrated that VPA administration improved cell viability in cells exposed to TG. In addition, VPA increased the levels of GRP78 and p-AKT and decreased the levels of ATF6, XBP-1, GSK3β, p-JNK and MMP-9. Furthermore, the levels of the ER stress-induced apoptosis response proteins CHOP, cleaved caspase-12 and cleaved caspase-3 were inhibited by VPA treatment. Meanwhile, VPA administration also increased the ratio of Bcl-2/Bax. Moreover, VPA can maintain neurite outgrowth of primary cortical neurons. Collectively, the neurotrophic effect of VPA is related to the inhibition of ER stress-induced apoptosis in SH-SY5Y cells and the maintenance of neuronal growth. Collectively, our results suggested a new approach for the therapeutic function of VPA in neurological disorders and neuroprotection.

Expression of Glucose-Regulated Protein 78 and miR-199a in Rat Brain After Fatal Ligature Strangulation

The roles of endoplasmic reticulum (ER) stress and microRNA in the brain tissue after fatal mechanical asphyxia have not been clearly elucidated. We examined the expression of glucose-regulated protein 78 (GRP78), the key regulator of unfolded protein response, and miR-199a in the brain tissues of rats subjected to fatal ligature strangulation to understand the roles of ER stress and microRNA in ligature strangulation. The expressions of GRP78 and miR-199a in rat cortex, hippocampi, and midbrain were measured by immunohistochemistry and Western blot analysis in a rat model of ligature strangulation. Furthermore, the levels of miR-199a-3p and miR-199a-5p were detected by real-time fluorescent quantitative polymerase chain reaction. Glucose-regulated protein 78 was highly expressed in the cortex and midbrain in the ligature strangulation group (P < 0.01) when compared with the control group. The expression of GRP78 in the hippocampi showed no significant difference between the 2 groups. miR-199a-3p in the cortex and midbrain was significantly down-regulated in the ligature strangulation group (P < 0.01). However, miR-199a-5p in each brain region showed no significant difference between the 2 groups. In conclusion, ER stress was involved in the physiological and pathological processes of ligature strangulation. Furthermore, upstream miR-199a may play an important regulatory role in mechanical asphyxia.

Tunicamycin impairs olfactory learning and synaptic plasticity in the olfactory bulb

Tunicamycin (TM) induces endoplasmic reticulum (ER) stress and inhibits N-glycosylation in cells. ER stress is associated with neuronal death in neurodegenerative disorders, such as Parkinson's disease and Alzheimer's disease, and most patients complain of the impairment of olfactory recognition. Here we examined the effects of TM on aversive olfactory learning and the underlying synaptic plasticity in the main olfactory bulb (MOB). Behavioral experiments demonstrated that the intrabulbar infusion of TM disabled aversive olfactory learning without affecting short-term memory. Histological analyses revealed that TM infusion upregulated C/EBP homologous protein (CHOP), a marker of ER stress, in the mitral and granule cell layers of MOB. Electrophysiological data indicated that TM inhibited tetanus-induced long-term potentiation (LTP) at the dendrodendritic excitatory synapse from mitral to granule cells. A low dose of TM (250nM) abolished the late phase of LTP, and a high dose (1μM) inhibited the early and late phases of LTP. Further, high-dose, but not low-dose, TM reduced the paired-pulse facilitation ratio, suggesting that the inhibitory effects of TM on LTP are partially mediated through the presynaptic machinery. Thus, our results support the hypothesis that TM-induced ER stress impairs olfactory learning by inhibiting synaptic plasticity via presynaptic and postsynaptic mechanisms in MOB.

Promotion of the Unfolding Protein Response in Orexin/Dynorphin Neurons in Sudden Infant Death Syndrome (SIDS): Elevated pPERK and ATF4 Expression

We previously demonstrated that sudden infant death syndrome (SIDS) infants have decreased orexin immunoreactivity within the hypothalamus and pons compared to non-SIDS infants. In this study, we examined multiple mechanisms that may promote loss of orexin expression including programmed cell death, impaired maturation/structural stability, neuroinflammation and impaired unfolding protein response (UPR). Immunofluorescent and immunohistochemical staining for a number of markers was performed in the tuberal hypothalamus and pons of infants (1-10 months) who died from SIDS (n = 27) compared to age- and sex-matched non-SIDS infants (n = 19). The markers included orexin A (OxA), dynorphin (Dyn), cleaved caspase 3 (CC3), cleaved caspase 9 (CC9), glial fibrillary acid protein (GFAP), tubulin beta chain 3 (TUBB3), myelin basic protein (MBP), interleukin 1β (IL-1β), terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL), c-fos and the UPR activation markers: phosphorylated protein kinase RNA-like endoplasmic reticulum kinase (pPERK), and activating transcription factor 4 (ATF4). It was hypothesised that pPERK and ATF4 would be upregulated in Ox neurons in SIDS compared to non-SIDS. Within the hypothalamus, OxA and Dyn co-localised with a 20 % decrease in expression in SIDS infants (P = 0.001). pPERK and ATF4 expression in OxA neurons were increased by 35 % (P = 0.001) and 15 % (P = 0.001) respectively, with linear relationships between the decreased OxA/Dyn expression and the percentages of co-localised pPERK/OxA and ATF4/OxA evident (P = 0.01, P = 0.01). No differences in co-localisation with CC9, CC3, TUNEL or c-fos, nor expression of MBP, TUBB3, IL-1β and GFAP, were observed in the hypothalamus. In the pons, there were 40 % and 20 % increases in pPERK expression in the locus coeruleus (P = 0.001) and dorsal raphe (P = 0.022) respectively; ATF4 expression was not changed. The findings that decreased orexin levels in SIDS infants may be associated with an accumulation of pPERK suggest decreased orexin translation. As pPERK may inhibit multiple neuronal groups in the pons in SIDS infants, it could also indicate that a common pathway promotes loss of protein expression and impaired functionality of multiple brainstem neuronal groups.

Adaptive preconditioning in neurological diseases - therapeutic insights from proteostatic perturbations

In neurological disorders, both acute and chronic neural stress can disrupt cellular proteostasis, resulting in the generation of pathological protein. However in most cases, neurons adapt to these proteostatic perturbations by activating a range of cellular protective and repair responses, thus maintaining cell function. These interconnected adaptive mechanisms comprise a 'proteostasis network' and include the unfolded protein response, the ubiquitin proteasome system and autophagy. Interestingly, several recent studies have shown that these adaptive responses can be stimulated by preconditioning treatments, which confer resistance to a subsequent toxic challenge - the phenomenon known as hormesis. In this review we discuss the impact of adaptive stress responses stimulated in diverse human neuropathologies including Parkinson׳s disease, Wolfram syndrome, brain ischemia, and brain cancer. Further, we examine how these responses and the molecular pathways they recruit might be exploited for therapeutic gain. This article is part of a Special Issue entitled SI:ER stress.

Urinary congophilia in women with hypertensive disorders of pregnancy and preexisting proteinuria or hypertension

BACKGROUND

Congophilia indicates the presence of amyloid protein, which is an aggregate of misfolded proteins, that is implicated in the pathophysiologic condition of preeclampsia. Recently, urinary congophilia has been proposed as a test for the diagnosis and prediction of preeclampsia.

OBJECTIVES

The purpose of this study was to determine whether urine congophilia is present in a cohort of women with preeclampsia and in pregnant and nonpregnant women with renal disease.

STUDY DESIGN

With the use of a preeclampsia, chronic hypertension, renal disease, and systemic lupus erythematosus cohort, we analyzed urine samples from healthy pregnant control subjects (n = 31) and pregnant women with preeclampsia (n = 23), gestational hypertension (n = 10), chronic hypertension (n = 14), chronic kidney disease; n = 28), chronic kidney disease with superimposed preeclampsia (n = 5), and chronic hypertension and superimposed preeclampsia (n = 12). Samples from nonpregnant control subjects (n = 10) and nonpregnant women with either systemic lupus erythematosus with (n = 25) and without (n = 14) lupus nephritis were analyzed. For each sample, protein concentration was standardized before it was mixed with Congo Red, spotted to nitrocellulose membrane, and rinsed with methanol. The optical density of the residual Congo Red stain was determined; Congo red stain retention was calculated, and groups were compared with the use of the Mann-Whitney test or Kruskal-Wallis analysis of Variance test, as appropriate.

RESULTS

Congophilia was increased in urine from women with preeclampsia (median Congo red stain retention, 47%; interquartile range, 22-68%) compared with healthy pregnant control subjects (Congo red stain retention: 16%; interquartile range, 13-21%; P = .002), women with gestational hypertension (Congo red stain retention, 20%; interquartile range, 13-27%; P = .008), or women with chronic hypertension (Congo red stain retention, 17%; interquartile range, 12-28%; P = .01). There were no differences in Congo red retention between pregnant women with chronic hypertension and normal pregnant control subjects (Congo red stain retention, 17% [interquartile range, 12-28%] vs 16% [interquartile range, 13-21%], respectively; P = .72). Congophilia was present in pregnant women with chronic kidney disease (Congo red stain retention, 32%; interquartile range, 14-57%), being similar to values found in women with preeclampsia (P = .22) and for women with chronic kidney disease and superimposed preeclampsia (Congo red stain retention, 57%; [interquartile range, 29-71%; P = .18). Nonpregnant women with lupus nephritis had higher congophilia levels compared with nonpregnant female control subjects (Congo red stain retention, 38% [interquartile range, 17-73%] vs 9% [7-11%], respectively; P < .001) and nonpregnant women with systemic lupus erythematosus without nephritis (Congo red stain retention, 38% [interquartile range, 17-73%] vs 13% [interquartile range, 11-17%], respectively; P = .001). A significant positive correlation was observed between congophilia and protein:creatinine ratio (Spearman rank correlations, 0.702; 95% confidence interval, 0.618-0.770; P < .001).

CONCLUSION

This study confirms that women with preeclampsia and chronic kidney disease without preeclampsia have elevated urine congophilia levels compared with healthy pregnant women. Nonpregnant women with lupus nephritis also have elevated urine congophilia levels compared with healthy control subjects. An elevated Congo Red stain retention may not be able to differentiate between these conditions; further research is required to explore the use of congophilia in clinical practice.