Stress-mediated Injury Research Articles

Induction of REDD1 via AP-1 prevents oxidative stress-mediated injury in hepatocytes

Regulated in development and DNA damage responses 1 (REDD1) is an inducible gene in response to various stresses, which functions as a negative regulator of the mammalian target of rapamycin protein kinase in complex 1. In the present study, we identified the role of REDD1 under the oxidative stress-mediated hepatocyte injury and its regulatory mechanism. REDD1 protein was increased in H2O2 or tert-butylhydroperoxide (t-BHP)-treated hepatocytes· H2O2 also elevated REDD1 mRNA levels. This event was inhibited by antioxidants such as diphenyleneiodonium chloride, N-acetyl-L-cysteine, or butylated hydroxy anisole. Interestingly, we found that H2O2-mediated REDD1 induction was transcriptionally regulated by activator protein-1 (AP-1), and that overexpression of c-Jun increased REDD1 protein levels and REDD1 promoter-driven luciferase activity. Deletion of the putative AP-1 binding site in proximal region of the human REDD1 promoter significantly abolished REDD1 transactivation by c-Jun. A NF-E2-related factor 2 activator, tert-butylhydroquinone treatment also elevated REDD1 levels, but it was independent on NF-E2-related factor 2 activation. Furthermore, we observed that REDD1 overexpression attenuated H2O2 or t-BHP-derived reactive oxygen species formation as well as cytotoxicity. Conversely, siRNA against REDD1 aggravated t-BHP-induced reactive oxygen species generation and cell death. In addition, we showed that REDD1 was induced by in vitro or in vivo ischemia/reperfusion model. Our results demonstrate that REDD1 induction by oxidative stress is mainly transcriptionally regulated by AP-1, and protects oxidative stress-mediated hepatocyte injury. These findings suggest REDD1 as a novel molecule that reduced susceptibility to oxidant-induced liver injury.

Role of Mitochondrial Oxidative Stress in Sepsis.

Mitochondria are considered the power house of the cell and are an essential part of the cellular infrastructure, serving as the primary site for adenosine triphosphate production via oxidative phosphorylation. These organelles also release reactive oxygen species (ROS), which are normal byproducts of metabolism at physiological levels; however, overproduction of ROS under pathophysiological conditions is considered part of a disease process, as in sepsis. The inflammatory response inherent in sepsis initiates changes in normal mitochondrial functions that may result in organ damage. There is a complex system of interacting antioxidant defenses that normally function to combat oxidative stress and prevent damage to the mitochondria. It is widely accepted that oxidative stress-mediated injury plays an important role in the development of organ failure; however, conclusive evidence of any beneficial effect of systemic antioxidant supplementation in patients with sepsis and organ dysfunction is lacking. Nevertheless, it has been suggested that antioxidant therapy delivered specifically to the mitochondria may be useful.

Plasma exosomes induced by remote ischaemic preconditioning attenuate myocardial ischaemia/reperfusion injury by transferring miR-24

Remote ischaemic preconditioning (RIPC) is well known to protect the myocardium against ischaemia/reperfusion injury (IRI). Exosomes are small extracellular vesicles that have become the key mediators of intercellular communication. Various studies have confirmed that circulating exosomes mediate RIPC. However, the underlying mechanisms for RIPC-induced exosome-mediated cardioprotection remain elusive. In our study, we found that the expression level of miR-24 was higher in exosomes derived from the plasma of rats subjected to RIPC than in exosomes derived from the plasma of control rats in vivo. The rat plasma exosomes could be taken up by H9c2 cells. In addition, miR-24 was present in RIPC-induced exosomes and played a role in reducing oxidative stress-mediated injury and decreasing apoptosis by downregulating Bim expression in H2O2-treated H9c2 cells in vitro. In vivo, miR-24 in RIPC-induced exosomes reduced cardiomyocyte apoptosis, attenuated the infarct size and improved heart function. Furthermore, the apoptosis-reducing effect of miR-24 was counteracted by miR-24 antagomirs or inhibitors both in vitro and in vivo. Therefore, we provided evidence that RIPC-induced exosomes could reduce apoptosis by transferring miR-24 in a paracrine manner and that miR-24 in the exosomes plays a central role in mediating the protective effects of RIPC.

<i>Spirulina platensis</i> Alleviates the Liver, Brain and Heart Oxidative Stress in Type 1 Diabetic Rats

Spirulina platensis (SPI) is a microalga with a high content of functional compounds, such as phenolics, phycocyanins and polysaccharides that has been shown to have antioxidant, anti-inflammatory, hypoglycemic, neuro-protective and immunomodulatory effects. The objectives of the present work were to study the possible effects of SPI treatment on the glycemic-lipid profile, oxidative stress, lipid peroxidation and cardiac performance in diabetic rats. Diabetes was induced by streptozotocin (STZ) in male Wistar rats. In diabetic animals SPI, at a dose of 50 mg/kg/day, reduced lipid peroxidation, nitrite levels and lipids in plasma and tissues. SPI exhibited an effective improvement on +dP/dT and −dP/dT in non-diabetic rats. This study showed that SPI significantly suppressed nitrite generation and lipoperoxidation in the hearts of diabetic animals, as well as an improvement in the cardiac function in control SPI-treated rats which is consistent with several studies that demonstrated the protective effect of antioxidants on oxidative stress-mediated injury caused by reactive oxygen species (ROS) produced in diabetic myocardial tissues.

Effects of Polyphenols on Oxidative Stress-Mediated Injury in Cardiomyocytes.

Cardiovascular diseases are the main cause of mortality and morbidity in the world. Hypertension, ischemia/reperfusion, diabetes and anti-cancer drugs contribute to heart failure through oxidative and nitrosative stresses which cause cardiomyocytes nuclear and mitochondrial DNA damage, denaturation of intracellular proteins, lipid peroxidation and inflammation. Oxidative or nitrosative stress-mediated injury lead to cardiomyocytes apoptosis or necrosis. The reactive oxygen (ROS) and nitrogen species (RNS) concentration is dependent on their production and on the expression and activity of anti-oxidant enzymes. Polyphenols are a large group of natural compounds ubiquitously expressed in plants, and epidemiological studies have shown associations between a diet rich in polyphenols and the prevention of various ROS-mediated human diseases. Polyphenols reduce cardiomyocytes damage, necrosis, apoptosis, infarct size and improve cardiac function by decreasing oxidative stress-induced production of ROS or RNS. These effects are achieved by the ability of polyphenols to modulate the expression and activity of anti-oxidant enzymes and several signaling pathways involved in cells survival. This report reviews current knowledge on the potential anti-oxidative effects of polyphenols to control the cardiotoxicity induced by ROS and RNS stress.

Involvement of a proapoptotic gene (BBC3) in islet injury mediated by cold preservation and rewarming.

Long-term pancreatic cold ischemia contributes to decreased islet number and viability after isolation and culture, leading to poor islet transplantation outcome in patients with type 1 diabetes. In this study, we examined mechanisms of pancreatic cold preservation and rewarming-induced injury by interrogating the proapoptotic gene BBC3/Bbc3, also known as Puma (p53 upregulated modulator of apoptosis), using three experimental models: 1) bioluminescence imaging of isolated luciferase-transgenic ("Firefly") Lewis rat islets, 2) cold preservation of en bloc-harvested pancreata from Bbc3-knockout (KO) mice, and 3) cold preservation and rewarming of human pancreata and isolated islets. Cold preservation-mediated islet injury occurred during rewarming in "Firefly" islets. Silencing Bbc3 by transfecting Bbc3 siRNA into islets in vitro prior to cold preservation improved postpreservation mitochondrial viability. Cold preservation resulted in decreased postisolation islet yield in both wild-type and Bbc3 KO pancreata. However, after culture, the islet viability was significantly higher in Bbc3-KO islets, suggesting that different mechanisms are involved in islet damage/loss during isolation and culture. Furthermore, Bbc3-KO islets from cold-preserved pancreata showed reduced HMGB1 (high-mobility group box 1 protein) expression and decreased levels of 4-hydroxynonenal (4-HNE) protein adducts, which was indicative of reduced oxidative stress. During human islet isolation, BBC3 protein was upregulated in digested tissue from cold-preserved pancreata. Hypoxia in cold preservation increased BBC3 mRNA and protein in isolated human islets after rewarming in culture and reduced islet viability. These results demonstrated the involvement of BBC3/Bbc3 in cold preservation/rewarming-mediated islet injury, possibly through modulating HMGB1- and oxidative stress-mediated injury to islets.

Grape seed proanthocyanidin extract protects the retina against early diabetic injury by activating the Nrf2 pathway.

The present study aimed to investigate whether grape seed proanthocyanidin extract (GSPE) has a protective effect on diabetic retinal function. A total of 30 Wistar rats were randomly divided into three equal groups, including the control, diabetic and GSPE-treated diabetic groups. Retinal tissue was harvested and subsequently stained with hematoxylin and eosin. Superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and methane dicarboxylic aldehyde (MDA) levels were evaluated using respective assay kits; whereas nuclear erythroid 2-related factor 2 (Nrf2) and heme oxygenase (HO)-1 expression levels were assessed by immunohistochemical and western blot analysis. Cell apoptosis in the retina was determined using the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling method. The results showed that the structure of the retina was damaged in diabetic rats, as compared with the control rats. Notably, the structure of the retina improved in the GSPE-treated diabetic group, as compared with the diabetic group. SOD and GSH-Px activities were significantly increased in the retina of rats in the GSPE-treated diabetic group, as compared with the diabetic group (P=0.011 and P=0.001, respectively). Furthermore, a significant reduction in MDA was detected (P=0.013) and the expression levels of Nrf2 and HO-1 in the bladders of rats in the GSPE-treated diabetic group were significantly increased, as compared with the diabetic group (P=0.038 and P=0.043, respectively). Apoptosis of retinal cells was significantly increased in the diabetic group, as compared with the control group (P<0.001); a significant reduction was also detected in the GSPE-treated diabetic group, as compared with the diabetic group (P=0.014). These results demonstrate that GSPE administration may protect the retina against hyperglycemic damage, possibly by ameliorating oxidative stress-mediated injury via the activation of the Nrf2 pathway.

Hypothermic Preconditioning Reverses Tau Ontogenesis in Human Cortical Neurons and is Mimicked by Protein Phosphatase 2A Inhibition

Hypothermia is potently neuroprotective, but the molecular basis of this effect remains obscure. Changes in neuronal tau protein are of interest, since tau becomes hyperphosphorylated in injury-resistant, hypothermic brains. Noting inter-species differences in tau isoforms, we have used functional cortical neurons differentiated from human pluripotent stem cells (hCNs) to interrogate tau modulation during hypothermic preconditioning at clinically-relevant temperatures. Key tau developmental transitions (phosphorylation status and splicing shift) are recapitulated during hCN differentiation and subsequently reversed by mild (32°C) to moderate (28°C) cooling — conditions which reduce oxidative and excitotoxic stress-mediated injury in hCNs. Blocking a major tau kinase decreases hCN tau phosphorylation and abrogates hypothermic neuroprotection, whilst inhibition of protein phosphatase 2A mimics cooling-induced tau hyperphosphorylation and protects normothermic hCNs from oxidative stress. These findings indicate a possible role for phospho-tau in hypothermic preconditioning, and suggest that cooling drives human tau towards an earlier ontogenic phenotype whilst increasing neuronal resilience to common neurotoxic insults. This work provides a critical step forward in understanding how we might exploit the neuroprotective benefits of cooling without cooling patients.

Polarized Human Embryonic Stem Cell-Derived Retinal Pigment Epithelial Cell Monolayers Have Higher Resistance to Oxidative Stress-Induced Cell Death Than Nonpolarized Cultures

Oxidative stress-mediated injury to the retinal pigment epithelium (RPE) is a major factor involved in the pathogenesis of age-related macular degeneration (AMD), the leading cause of blindness in the elderly. Human embryonic stem cell (hESC)-derived RPE cells are currently being evaluated for their potential for cell therapy in AMD patients through subretinal injection of cells in suspension and subretinal placement as a polarized monolayer. To gain an understanding of how transplanted RPE cells will respond to the highly oxidatively stressed environment of an AMD patient eye, we compared the survival of polarized and nonpolarized RPE cultures following oxidative stress treatment. Polarized, nonpolarized/confluent, nonpolarized/subconfluent hESC-RPE cells were treated with H2O2. Terminal deoxynucleotidyl transferase dUTP nick end labeling stains revealed the highest amount of cell death in subconfluent hESC-RPE cells and little cell death in polarized hESC-RPE cells with H2O2 treatment. There were higher levels of proapoptotic factors (phosphorylated p38, phosphorylated c-Jun NH2-terminal kinase, Bax, and cleaved caspase 3 fragments) in treated nonpolarized RPE-particularly subconfluent cells-relative to polarized cells. On the other hand, polarized RPE cells had constitutively higher levels of cell survival and antiapoptotic signaling factors such as p-Akt and Bcl-2, as well as antioxidants superoxide dismutase 1 and catalase relative to nonpolarized cells, that possibly contributed to polarized cells' higher tolerance to oxidative stress compared with nonpolarized RPE cells. Subconfluent cells were particularly sensitive to oxidative stress-induced apoptosis. These results suggest that implantation of polarized hESC-RPE monolayers for treating AMD patients with geographic atrophy should have better survival than injections of hESC-RPE cells in suspension.

EGFR inhibitor-driven endoplasmic reticulum stress-mediated injury on intestinal epithelial cells

AimsThe aim of this study is to understand the underlying mechanisms regulating the adverse effect of diarrhea caused by epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs). Main methodsWe comparatively examined the effects of two EGFR-TKIs, gefitinib and icotinib, on intestinal epithelial cells (IEC-6). Cell proliferation was measured using MTT analysis. Expression of multiple cytokines was assayed by real-time PCR. Cell cycle and apoptosis of IEC were evaluated using flow cytometry. Protein levels were determined by Western blot. Key findingsThese two EGFR-TKIs exerted cytotoxicity to inhibit proliferation and induce apoptosis in IEC-6 cells. These effects are due to the ability of these EGFR-TKIs to cause cell cycle arrest at G0/G1 by regulating the expression of cyclin D1 and p27. In addition, gefitinib and icotinib significantly suppressed the levels of cell adhesion molecules while increasing the expression of the proinflammatory cytokines interleukin (IL)-6 and IL-25. Finally, these EGFR-TKIs triggered an endoplasmic reticulum (ER) stress response, characterized by the activation of the RNA dependent protein kinase-like ER kinase (PERK) pathway and the transcriptional induction of XBP-1 signaling, resulting in ER-mediated cell death. Moreover, gefitinib exerted more cytotoxicity than icotinib on IEC-6 cells. SignificanceBecause diarrhea is a common adverse event occurring in patients receiving small-molecular EGFR-TKI chemotherapy, the results of this study are clinically significant. The finding that icotinib exerts less cytotoxic activity than gefitinib on IEC-6 cells indicates its usefulness as a less toxic treatment option for non-small-cell lung cancer.

Cyclooxygenase-2, prostaglandin E2, and prostanoid receptor EP2 in fluid flow shear stress-mediated injury in the solitary kidney.

Hyperfiltration subjects podocytes to increased tensile stress and fluid flow shear stress (FFSS). We showed a 1.5- to 2.0-fold increase in FFSS in uninephrectomized animals and altered podocyte actin cytoskeleton and increased synthesis of prostaglandin E2 (PGE2) following in vitro application of FFSS. We hypothesized that increased FFSS mediates cellular changes through specific receptors of PGE2. Presently, we studied the effect of FFSS on cultured podocytes and decapsulated isolated glomeruli in vitro, and on solitary kidney in uninephrectomized sv129 mice. In cultured podocytes, FFSS resulted in increased gene and protein expression of cyclooxygenase (COX)-2 but not COX-1, prostanoid receptor EP2 but not EP4, and increased synthesis and secretion of PGE2, which were effectively blocked by indomethacin. Next, we developed a special flow chamber for applying FFSS to isolated glomeruli to determine its effect on an intact glomerular filtration barrier by measuring change in albumin permeability (Palb) in vitro. FFSS caused an increase in Palb that was blocked by indomethacin (P < 0.001). Finally, we show that unilateral nephrectomy in sv129 mice resulted in glomerular hypertrophy (P = 0.006), increased glomerular expression of COX-2 (P < 0.001) and EP2 (P = 0.039), and increased urinary albumin excretion (P = 0.001). Activation of the COX-2-PGE2-EP2 axis appears to be a specific response to FFSS in podocytes and provides a mechanistic basis for alteration in podocyte structure and the glomerular filtration barrier, leading to albuminuria in hyperfiltration-mediated kidney injury. The COX-2-PGE2-EP2 axis is a potential target for developing specific interventions to ameliorate the effects of hyperfiltration-mediated kidney injury in the progression of chronic kidney disease.

Oxidative Stress and Respiratory System: Pharmacological and Clinical Reappraisal of N-Acetylcysteine

The large surface area for gas exchange makes the respiratory system particularly susceptible to oxidative stress-mediated injury. Both endogenous and exogenous pro-oxidants (e.g. cigarette smoke) trigger activation of leukocytes and host defenses. These mechanisms interact in a “multilevel cycle” responsible for the control of the oxidant/antioxidant homeostasis. Several studies have demonstrated the presence of increased oxidative stress and decreased antioxidants (e.g. reduced glutathione [GSH]) in subjects with chronic obstructive pulmonary disease (COPD), but the contribution of oxidative stress to the pathophysiology of COPD is generally only minimally discussed. The aim of this review was to provide a comprehensive overview of the role of oxidative stress in the pathogenesis of respiratory diseases, particularly COPD, and to examine the available clinical and experimental evidence on the use of the antioxidant N-acetylcysteine (NAC), a precursor of GSH, as an adjunct to standard therapy for the treatment of COPD. The proposed concept of “multilevel cycle” helps understand the relationship between respiratory diseases and oxidative stress, thus clarifying the rationale for using NAC in COPD. Until recently, antioxidant drugs such as NAC have been regarded only as mucolytic agents. Nevertheless, several clinical trials indicate that NAC may reduce the rate of COPD exacerbations and improve small airways function. The most plausible explanation for the beneficial effects observed in patients with COPD treated with NAC lies in the mucolytic and antioxidant effects of this drug. Modulation of bronchial inflammation by NAC may further account for these favorable clinical results.

Erlotinib promotes endoplasmic reticulum stress-mediated injury in the intestinal epithelium

Erlotinib, a popular drug for treating non-small cell lung cancer (NSCLC), causes diarrhea in approximately 55% of patients receiving this drug. In the present study, we found that erlotinib induced barrier dysfunction in rat small intestine epithelial cells (IEC-6) by increasing epithelial permeability and down-regulating E-cadherin. The mRNA levels of various pro-inflammatory cytokines (Il-6, Il-25 and Il-17f) were increased after erlotinib treatment in IEC-6 cells. Erlotinib concentration- and time-dependently induced apoptosis and endoplasmic reticulum (ER) stress in both IEC-6 and human colon epithelial cells (CCD 841 CoN). Intestinal epithelial injury was also observed in male C57BL/6J mice administrated with erlotinib. Knockdown of C/EBP homologous protein (CHOP) with small interference RNA partially reversed erlotinib-induced apoptosis, production of IL-6 and down-regulation of E-cadherin in cultured intestinal epithelial cells. In conclusion, erlotinib caused ER stress-mediated injury in the intestinal epithelium, contributing to its side effects of diarrhea in patients.

Heme Oxygenase-1 Mediates Oxidative Stress and Apoptosis in Coxsackievirus B3-Induced Myocarditis

Background: Heme oxygenase-1 (HO-1), which is suggested to play a role in defending the organism against oxidative stress-mediated injuries, can be induced by diverse factors including viruses and iron. As coxsackievirus B3 (CVB3)-infected SWR/J mice susceptible for chronic myocarditis were found to have a significant iron incorporation and HO-1 upregulation in the myocardium, we aimed to investigate the molecular interplay between HO-1 expression and iron homeostasis in the outcome of viral myocarditis. Methods and Results: In susceptible SWR/J mice, but not in resistant C57BL/6 mice, we observed at later stages of CVB3 myocarditis significant iron deposits in macrophages and also in cardiomyocytes, which were spatially associated with oxidative stress, upregulation of HO-1 and caspase-3 activation. HO-1, which is also expressed in cultivated RAW 264.7 macrophages upon incubation with iron and/or CVB3, could be downregulated by inhibition of NO/iNOS using L-NAME. Moreover, specific inhibition of HO-1 by tin mesoporphyrin revealed a suppression of superoxide production in iron and/or CVB3-treated macrophages. The molecular relationship of HO-1 and caspase-3 activation was proven by downregulation with HO-1 siRNA in iron- and/or CVB3-treated cultivated cells. Importantly, iron was found to increase viral replication in vitro. Conclusion: These results indicate that HO-1 induces a paracrine signalling in macrophages via reactive oxygen species production, mediating apoptosis of heart muscle cells at later stages of myocarditis. Notably, in genetically susceptible mice iron potentiates the detrimental effects of CVB3 by the NO/HO-1 pathway, thus increasing cardiac pathogenicity.

RAAV/ABAD-DP-6His attenuates oxidative stress-induced injury of PC12 cells.

Our previous studies have revealed that amyloid β (Aβ)-binding alcohol dehydrogenase (ABAD) decoy peptide antagonizes Aβ42-induced neurotoxicity. However, whether it improves oxidative stress injury remains unclear. In this study, a recombinant adenovirus constitutively secreting and expressing Aβ-ABAD decoy peptide (rAAV/ABAD-DP-6His) was successfully constructed. Our results showed that rAAV/ABAD-DP-6His increased superoxide dismutase activity in hydrogen peroxide-induced oxidative stress-mediated injury of PC12 cells. Moreover, rAAV/ABAD-DP-6His decreased malondialdehyde content, intracellular Ca2+ concentration, and the level of reactive oxygen species. rAAV/ABAD-DP-6His maintained the stability of the mitochondrial membrane potential. In addition, the ATP level remained constant, and apoptosis was reduced. Overall, the results indicate that rAAV/ABAD-DP-6His generates the fusion peptide, Aβ-ABAD decoy peptide, which effectively protects PC12 cells from oxidative stress injury induced by hydrogen peroxide, thus exerting neuroprotective effects.

Putting the Rit in cellular resistance

Cells mobilize diverse signaling pathways to protect against stress-mediated injury. Ras family GTPases play critical roles in this process, controlling the activation and integration of multiple regulatory cascades. p38 mitogen-activated protein kinase (MAPK) signaling serves as a critical fulcrum in this process, regulating networks that stimulate cellular apoptosis but also promote cell survival. However, this functional dichotomy is incompletely understood, particularly regulation of p38-dependent survival. Here, we discuss our recent evidence that the Rit GTPase associates with and is required for stress-mediated activation of a scaffolded p38-MK2-HSP27-Akt pro-survival signaling cascade. Drosophila lacking D-Ric, a Rit homologue, are susceptible to a variety of environmental stresses, while embryonic fibroblasts derived from Rit knockout mice display blunted stress-dependent signaling and decreased viability. Conversely, expression of constitutively active Rit triggers p38-Akt-dependent cell survival. Together, our studies establish Rit as the central regulator of an evolutionarily conserved, p38-dependent signaling cascade that functions as a critical survival mechanism in response to stress.

P67 Slow release H2S donors protect human microvascular endothelial cells from oxidative stress induced cell death: Markedly increased potency by mitochondria-targeting

Introduction Microvascular endothelial dysfunction (MED) is observed in diabetic and hypertensive patients, due at least in part to increased vascular oxidative stress and mitochondrial dysfunction. Lower levels of H 2 S were observed in diabetic subjects compared to age and BMI-matched controls and H 2 S levels negatively correlated with MED in vivo. This suggests that reduced vascular synthesis of H 2 S contributes to MED and that increasing H 2 S bioavailability may protect the vasculature from oxidative stress-induced injury. Methods Human microvascular endothelial cells (HMEC) were exposed to slow release H 2 S donors (SRHD; 100 μM) GYY4137, AP67, AP72 and two mitochondria-targeted H 2 S donors AP39 and AP123 (0.1 μM), before and after the induction of oxidative stress using SIN-1 (100 μM), H 2 O 2 (100 μM) and 4-HNE (10 μM). Cell viability (alamarBlue), intracellular oxidant generation (ROS; DHE, H 2 DCFDA, mitosoxRed) and mitochondrial membrane potential (MMP; TMRM) were determined. Western blotting and fluorescence assays were used for Akt, Erk1/2, caspases 3, 7 and 9 expression and activity. Phosphatidylserine externalisation and plasma membrane integrity were assessed by flow cytometry. Oxidative stress significantly reduced cell viability, MMP and increased ROS generation (ANOVA, p p p Conclusion These data suggest SHRD can inhibit and/or reverse oxidative stress-mediated cellular injury and highlight strategies which increase vascular H 2 S bioavailability, and in particular target mitochondria, represent a new therapeutic opportunity to limit MED.

Reactive Nitrogen Species Reactivities with Nitrones: Theoretical and Experimental Studies

Reactive nitrogen species (RNS) such as nitrogen dioxide ((•)NO(2)), peroxynitrite (ONOO(-)), and nitrosoperoxycarbonate (ONOOCO(2)(-)) are among the most damaging species present in biological systems due to their ability to cause modification of key biomolecular systems through oxidation, nitrosylation, and nitration. Nitrone spin traps are known to react with free radicals and nonradicals via electrophilic and nucleophilic addition reactions and have been employed as reagents to detect radicals using electron paramagnetic resonance (EPR) spectroscopy and as pharmacological agents against oxidative stress-mediated injury. This study examines the reactivity of cyclic nitrones such as 5,5-dimethylpyrroline N-oxide (DMPO) with (•)NO(2), ONOO(-), ONOOCO(2)(-), SNAP, and SIN-1 using EPR. The thermochemistries of nitrone reactivity with RNS and isotropic hfsc's of the addition products were also calculated at the PCM(water)/B3LYP/6-31+G**//B3LYP/6-31G* level of theory with and without explicit water molecules to rationalize the nature of the observed EPR spectra. Spin trapping of other RNS such as azide ((•)N(3)), nitrogen trioxide ((•)NO(3)), amino ((•)NH(2)) radicals and nitroxyl (HNO) were also theoretically and experimentally investigated by EPR spin trapping and mass spectrometry. This study also shows that other spin traps such as 5-carbamoyl-5-methyl-pyrroline N-oxide, 5-ethoxycarbonyl-5-methyl-pyrroline N-oxide, and 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide can react with radical and nonradical RNS, thus making spin traps suitable probes as well as antioxidants against RNS-mediated oxidative damage.

Extracellular heat shock protein 72 protects schwann cells from hydrogen peroxide‐induced apoptosis

The cytoprotective role of extracellular heat shock protein (Hsp) 72 has been demonstrated in various cell types, including neuronal cells; however, few studies have investigated the actual role of Hsp72 in the survival of Schwann cells (SCs). In the present study, we investigated the effect of exogenous Hsp72 on Schwann cell apoptotic cell death induced by H₂O₂. We determined that extracellular exposure to Hsp72 reduced cell death in rat SCs in a dose-dependent manner, with the protection resulting from downregulation of apoptosis induced by H₂O₂ (as shown by TUNEL and annexin V flow cytometry analyses). Moreover, we observed that Hsp72 suppressed caspase-3 and -9 activation induced by H₂O₂. This was accompanied by upregulation of the antiapoptotic protein Bcl-2. These findings indicate that extracellular Hsp72 can afford neuroprotection to peripheral nerves via its ability to inhibit Schwann cell apoptosis and diminish oxidative stress-mediated injuries.

The design and delivery of a thermally responsive peptide to inhibit S100B-mediated neurodegeneration

S100B, a glial-secreted protein, is believed to play a major role in neurodegeneration in Alzheimer's disease, Down syndrome, traumatic brain injury, and spinocerebellar ataxia type 1 (SCA1). SCA1 is a trinucleotide repeat disorder in which the expanded polyglutamine mutation in the protein ataxin-1 primarily targets Purkinje cells of the cerebellum. Currently, the exact mechanism of S100B-mediated Purkinje cell damage in SCA1 is not clear. However, here we show that S100B may act via the activation of the receptor for advanced glycation end product (RAGE) signaling pathway, resulting in oxidative stress-mediated injury to mutant ataxin-1-expressing neurons. To combat S100B-mediated neurodegeneration, we have designed a selective thermally responsive S100B inhibitory peptide, Synb1-ELP-TRTK. Our therapeutic polypeptide was developed using three key elements: (1) the elastin-like polypeptide (ELP), a thermally responsive polypeptide, (2) the TRTK12 peptide, a known S100B inhibitory peptide, and (3) a cell-penetrating peptide, Synb1, to enhance intracellular delivery. Binding studies revealed that our peptide, Synb1-ELP-TRTK, interacts with its molecular target S100B and maintains a high S100B binding affinity as comparable with the TRTK12 peptide alone. In addition, in vitro studies revealed that Synb1-ELP-TRTK treatment reduces S100B uptake in SHSY5Y cells. Furthermore, the Synb1-ELP-TRTK peptide decreased S100B-induced oxidative damage to mutant ataxin-1-expressing neurons. To test the delivery capabilities of ELP-based therapeutic peptides to the cerebellum, we treated mice with fluorescently labeled Synb1-ELP and observed that thermal targeting enhanced peptide delivery to the cerebellum. Here, we have laid the framework for thermal-based therapeutic targeting to regions of the brain, particularly the cerebellum. Overall, our data suggest that thermal targeting of ELP-based therapeutic peptides to the cerebellum is a novel treatment strategy for cerebellar neurodegenerative disorders.