Oxidant preconditioning protects human proximal tubular cells against lethal oxidant injury via p38 MAPK and heme oxygenase-1

Andrographolide induced heme oxygenase-1 expression in MSC-like cells isolated from rat bone marrow exposed to environmental stress

BACKGROUND AND OBJECTIVES

Mesenchymal stem cells (MSC-like cells) are the most important stem cells that are used in transplantation clinically in various applications. The survival rate of MSC-like cells is strongly reduced due to adverse conditions in the microenvironment of transplantation, including environmental stress. Heme oxygenase-1 (HO-1) is a member of the heat shock protein, as well as a stress-induced enzyme, present throughout the body. The present study was conducted to investigate the effect of andrographolide, an active derivative from andrographolide paniculate, on HO-1 expression in mesenchymal stem cells derived from rat bone marrow.

MATERIALS AND METHODS

The rat bone marrow-derived mesenchymal stem cells (BMSC-like cells) were extracted and proliferated in several passages. The identity of MSC-like cells was confirmed by morphological observations and differential tests. The flow cytometry method was used to verify the MSC-specific markers. Isolated MSC-like cells were treated with different concentrations of andrographolide and then exposed to environmental stress. Cell viability was assessed using the MTT colorimetric assay. A real-time PCR technique was employed to evaluate the expression level of HO-1 in the treated MSC-like cells.

RESULTS

Isolated MSC-like cells demonstrated fibroblast-like morphology. These cells in different culture mediums differentiated into osteocytes and adipocytes and were identified using alizarin red and oil red staining, respectively. As well, MSC-like cells were verified by the detection of CD105 surface antigen and the absence of CD14 and CD45 antigens. The results of the MTT assay showed that the pre-treatment of MSC-like cells with andrographolide concentration independently increased the viability and resistance of these cells to environmental stress caused by hydrogen peroxide and serum deprivation (SD). Real-time PCR findings indicated a significant increase in HO-1 gene expression in the andrographolide-receiving groups (p < 0.01).

CONCLUSION

Our results suggest that andrographolide creates a promising strategy for enhancing the quality of cell therapy by increasing the resistance of MSC-like cells to environmental stress and inducing the expression of HO-1.

6-Shogaol protects against ischemic acute kidney injury by modulating NF-κB and heme oxygenase-1 pathways

Acute kidney injury (AKI) due to renal ischemia-reperfusion (I/R) is a major clinical problem without effective therapy. Ginger is one of the most widely consumed spices in the world, and 6-shogaol, a major ginger metabolite, has anti-inflammatory effects in neuronal and epithelial cells. Here, we demonstrate our novel findings that 6-shogaol treatment protected against renal I/R injury with decreased plasma creatinine, blood urea nitrogen, and kidney neutrophil gelatinase-associated lipocalin mRNA synthesis compared with vehicle-treated mice subjected to renal I/R. Additionally, 6-shogaol treatment reduced kidney inflammation (decreased proinflammatory cytokine and chemokine synthesis as well as neutrophil infiltration) and apoptosis (decreased TUNEL-positive renal tubular cells) compared with vehicle-treated mice subjected to renal I/R. In cultured human and mouse kidney proximal tubule cells, 6-shogaol significantly attenuated TNF-α-induced inflammatory cytokine and chemokine mRNA synthesis. Mechanistically, 6-shogaol significantly attenuated TNF-α-induced NF-κB activation in human renal proximal tubule cells by reducing IKKαβ/IκBα phosphorylation. Furthermore, 6-shogaol induced a cytoprotective chaperone heme oxygenase (HO)-1 via p38 MAPK activation in vitro and in vivo. Consistent with these findings, pretreatment with the HO-1 inhibitor zinc protoporphyrin IX completely prevented 6-shogaol-mediated protection against ischemic AKI in mice. Taken together, our study showed that 6-shogaol protects against ischemic AKI by attenuating NF-κB activation and inducing HO-1 expression. 6-Shogaol may provide a potential therapy for ischemic AKI during the perioperative period.

Peroxiredoxin 1 has an anti-apoptotic role via apoptosis signal-regulating kinase 1 and p38 activation in mouse models with oral precancerous lesions

Peroxiredoxin 1 (Prx1) is important in the protection of cells from oxidative damage and the regulation of cell proliferation and apoptosis. Prx1 is overexpressed in oral precancerous lesions of oral leukoplakia (OLK) and oral cancer; however, the association between Prx1 expression and OLK pathogenesis remains unknown. The present study investigated the role of Prx1 and its molecular mechanisms in oxidative stress-induced apoptosis during the pathogenesis of OLK. Wild-type and Prx1 knockout mice were treated with 50 µg/ml 4-nitroquinoline-1-oxide (4NQO) or 4NQO + H₂O₂ for 16 weeks to establish mouse models with tongue precancerous lesions. Apoptotic cells were detected using terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. The expression of Prx1, apoptosis signal-regulating kinase 1 (ASK1), phosphor-ASK1, p38 and phosphor-p38 was analyzed using immunohistochemical staining, and their mRNA expression levels were evaluated by reverse transcription quantitative polymerase chain reaction. The present results demonstrated that 4NQO or 4NQO + H₂O₂ induced the development of tongue precancerous lesions in Prx1 knockout and wild-type mice. Prx1 was overexpressed in tongue precancerous lesions compared with normal tongue mucosa. There was a significant decrease in the degree of moderate or severe epithelial dysplasia, and mild epithelial dysplasia was clearly elevated, in Prx1 knockout mice treated with 4NQO + H₂O₂ compared with wild-type mice treated with 4NQO + H₂O₂. Prx1 suppressed apoptosis and upregulated phosphor-ASK1 and phosphor-p38 expression in tongue precancerous lesions. The present results suggest that Prx1 suppresses oxidative stress-induced apoptosis via the ASK1/p38 signalling pathway in mouse tongue precancerous lesions. In conclusion, Prx1 and H₂O₂ have a coordination role in promoting the progression of tongue precancerous mucosa lesions. The present findings provide novel insight into Prx1 function and the mechanisms of Prx1 in OLK pathogenesis.

A comparison of melatonin and α-lipoic acid in the induction of antioxidant defences in L6 rat skeletal muscle cells

Aging is characterized by a progressive deterioration in physiological functions and metabolic processes. The loss of cells during aging in vital tissues and organs is related to several factors including oxidative stress and inflammation. Skeletal muscle degeneration is common in elderly people; in fact, this tissue is particularly vulnerable to oxidative stress since it requires large amounts of oxygen, and thus, oxidative damage is abundant and accumulates with increasing age. Melatonin (N-acetyl-5-methoxytryptamine) is a highly efficient scavenger of reactive oxygen species and it also exhibits beneficial anti-inflammatory and anti-aging effects. This study investigated the susceptibility of rat L6 skeletal muscle cells to an induced oxidative stress following their exposure to hydrogen peroxide (50 μM) and evaluating the potential protective effects of pre-treatment with melatonin (10 nM) compared to the known beneficial effect of alpha-lipoic acid (300 μM). Hydrogen peroxide-induced obvious oxidative stress; it increased the expression of tumour necrosis factor-alpha and in turn promoted nuclear factor kappa-B and overrode the endogenous defence mechanisms. Conversely, pre-treatment of the hydrogen peroxide-exposed cells to melatonin or alpha-lipoic acid increased endogenous antioxidant enzymes, including superoxide dismutase-2 and heme oxygenase-1; moreover, they ameliorated significantly oxidative stress damage and partially reduced alterations in the muscle cells, which are typical of aging. In conclusion, melatonin was equally effective as alpha-lipoic acid; it exhibited marked antioxidant and anti-aging effects at the level of skeletal muscle in vitro even when it was given in a much lower dose than alpha-lipoic acid.

Hyperoxia-induced preconditioning against renal ischemic injury is mediated by reactive oxygen species but not related to heat shock proteins 70 and 32

OBJECTIVE

Pre-exposure of rats to normobaric hyperoxia (O2 ≥ 95%) may induce late preconditioning against renal ischemia-reperfusion (IR) injury. In this study we investigated probable mechanisms of IR injury such as the role of reactive oxygen species (ROS), renal antioxidant agents, and heat shock proteins (HSP) 32 and 70 during delayed hyperoxia-preconditioning (HO).

METHODS

Fifty-two rats were divided into 7 groups: (A) IR, (B) HO + IR, (C) mercaptopropionyl glycine (MPG) + HO + IR, (D) MPG + IR, (E) HO + sham, (F) MPG + sham, and (G) sham. Rats in the following study groups (group B, C and E) were kept in a normobaric hyperoxic environment for 4 h/day for 6 consecutive days, after which they were subjected to 40 minutes of ischemia; animals in the control group (group A, D, F, and G) were kept in a normoxic cage. At the end of the preconditioning period, 24 hours of reperfusion was performed. Renal function was assessed by measuring serum creatinine (Cr), blood urea nitrogen (BUN), and creatinine clearance (CLCr). Induction of the antioxidant system was evaluated by measuring renal catalase (CAT) and superoxide dismutase (SOD) activities and glutathione (GSH) and malondialdehyde (MDA) content. The role of ROS was investigated by use of MPG (a ROS scavenger). HSP32 & 70 mRNA and protein also were determined.

RESULTS

The hyperoxia-preconditioned IR group (B) had a lower plasma Cr and BUN and greater CLCr compared with the IR group (A) (P ≤ .016). Administration of MPG led to an increase in plasma Cr and BUN and a decrease in CLCr in group C compared with the hyperoxia-preconditioned group B (P ≤ .004). The hyperoxia-preconditioned IR group had a greater CAT activity and GSH level compared with the IR group A (P ≤ .007), whereas the administration of MPG did not change the GSH level but led to a decrease in CAT activity in group D compared with group B (P < .001). SOD activity did not change in hyperoxia-preconditioned ischemic rats compared with ischemic rats. Hyperoxia preconditioning and MPG administration in ischemic animals did not result in any considerable change in MDA level compared with the IR group A. Also, there were no clinically relevant differences in HSP32 & 70 mRNA and protein between all groups.

CONCLUSION

The present study demonstrates that repeated pre-exposure to hyperoxia can decrease subsequent renal IR damage in this rat model of renal ischemia. Free radical production after hyperoxia appears to play a pivotal role in the hyperoxia-induced renal protection independent of HSP level. Antioxidant enzyme activities and especially catalase seem to be implicated in this renal protective mechanism.

Protection of Tong-Sai-Mai Decoction against Apoptosis Induced by H2O2 in PC12 Cells: Mechanisms via Bcl-2-Mitochondria-ROS-INOS Pathway

Tong-Sai-Mai decoction (TSM) is a Chinese materia medica polyherbal formulation that has been applied in treating brain ischemia for hundreds of years. Because it could repress the oxidative stress in in vivo studies, now we focus on the in vitro studies to investigate the mechanism by targeting the oxidative stress dependent signaling. The relation between the neurogenesis and the reactive oxygen species (ROS) production remains largely unexamined. PC12 cells are excitable cell types widely used as in vitro model for neuronal cells. Most marker genes that are related to neurotoxicity, apoptosis, and cell cycles are expressed at high levels in these cells. The aim of the present study is to explore the cytoprotection of TSM against hydrogen peroxide- (H₂O₂-) induced apoptosis and the molecular mechanisms underlying PC12 cells. Our findings revealed that TSM cotreatment with H₂O₂ restores the expression of bcl-2, inducible nitric oxide synthase (INOS), and mitochondria membrane potential. Meanwhile, it reduces intracellular [Ca²⁺] concentration, lactate dehydrogenase (LDH) release, and the expression of caspase-3 and bax. The results of the present study suggested that the cytoprotective effects of the TSM might be mediated, at least in part, by the bcl-2-mitochondria-ROS-INOS pathway. Due to its nontoxic characteristics, TSM could be further developed to treat the neurodegenerative diseases which are closely associated with the oxidative stress.

ROS dependence of cyclooxygenase-2 induction in rats subjected to unilateral ureteral obstruction

Oxidative stress resulting from unilateral ureteral obstruction (UUO) may be aggravated by increased production of ROS. Previous studies have demonstrated increased cyclooxygenase (COX)-2 expression in renal medullary interstitial cells (RMICs) in response to UUO. We investigated, both in vivo and in vitro, the role of ROS in the induction of COX-2 in rats subjected to UUO and in RMICs exposed to oxidative and mechanical stress. Rats subjected to 3-day UUO were treated with two mechanistically distinct antioxidants, the NADPH oxidase inhibitor diphenyleneiodonium (DPI) and the complex I inhibitor rotenone (ROT), to interfere with ROS production. We found that UUO-mediated induction of COX-2 in the inner medulla was attenuated by both antioxidants. In addition, DPI and ROT reduced tubular damage and oxidative stress after UUO. Moreover, mechanical stretch induced COX-2 and oxidative stress in RMICs. Likewise, RMICs exposed to H2O2 as an inducer of oxidative stress showed increased COX-2 expression and activity, both of which were reduced by DPI and ROT. Similarly, ROS production, which was increased after exposure of RMICs to H2O2, was also reduced by DPI and ROT. Furthermore, oxidative stress-induced phosphorylation of ERK1/2 and p38 was blocked by both antioxidants, and inhibition of ERK1/2 and p38 attenuated the induction of COX-2 in RMICs. Notably, COX-2 inhibitors further exacerbated the oxidative stress level in H2O2-exposed RMICs. We conclude that oxidative stress as a consequence of UUO stimulates COX-2 expression through the activation of multiple MAPKs and that the induction of COX-2 may exert a cytoprotective function in RMICs.

Cytoprotection behind heme oxygenase-1 in renal diseases

Renal insults are considered a public health problem and are linked to increased rates of morbidity and mortality worldwide. The heme oxygenase (HO) system consists of evolutionary specialized machinery that degrades free heme and produces carbon monoxide, biliverdin and free iron. In this sense, the inducible isoform HO-1 seems to develop an important role and is widely studied. The reaction involved with the HO-1 molecule provides protection to injured tissue, directly by reducing the toxic heme molecule and indirectly by the release of its byproducts. The up regulation of HO-1 enzyme has largely been described as providing antioxidant, antiapoptotic, anti-inflammatory and immunomodulatory properties. Several works have explored the importance of HO-1 in renal diseases and they have provided consistent evidence that its overexpression has beneficial effects in such injuries. So, in this review we will focus on the role of HO-1 in kidney insults, exploring the protective effects of its up regulation and the enhanced deleterious effects of its inhibition or gene deletion.

H2O2 preconditioning modulates phase II enzymes through p38 MAPK and PI3K/Akt activation

Ischemic preconditioning is a complex cardioprotective phenomenon that involves adaptive changes in cells and molecules and occurs in a biphasic pattern: an early phase after 1-2 h and a late phase after 12-24 h. While it is widely accepted that reactive oxygen species are strongly involved in triggering ischemic preconditiong, it is not clear if they play a major role in the early or late phase of preconditioning and which are the mechanisms involved. The present study was designed to investigate the mechanisms behind H(2)O(2)-induced cardioprotection in rat neonatal cardiomyocytes. We focused on antioxidant and phase II enzymes and their modulation by protein kinase signaling pathways and nuclear-factor-E(2)-related factor-1 (Nrf1) and Nrf2. H(2)O(2) preconditioning was able to counteract oxidative stress more effectively in the late than in the early phase of adaptation. In particular, H(2)O(2) preconditioning counteracted oxidative stress-induced apoptosis by decreasing caspase-3 activity, increasing Bcl2 expression and selectively increasing the expression and activity of antioxidant and phase II enzymes through Nrf1 and Nrf2 translocation to the nucleus. The downregulation of Nrf1 and Nrf2 by small interfering RNA reduced the expression level of phase II enzymes. Specific inhibitors of phosphatidylinositol 3-kinase/Akt and p38 MAPK activation partially reduced the cardioprotection elicited by H(2)O(2) preconditioning and the induction and activity of phase II enzymes. These findings demonstrate, for the first time, a key role for Nrf1, and not only for Nrf2, in the induction of phase II enzymes triggered by H(2)O(2) preconditioning.

Isoflurane protects human kidney proximal tubule cells against necrosis via sphingosine kinase and sphingosine-1-phosphate generation

BACKGROUND/AIMS

We previously showed that the inhalational anesthetic isoflurane protects against renal ischemia reperfusion injury in part via sphingosine kinase (SK)-mediated synthesis of sphingosine-1-phosphate (S1P). In this study, we tested the hypothesis that isoflurane directly targets renal proximal tubule cells via SK activation, S1P synthesis and activation of S1P receptors to initiate cytoprotective signaling.

METHODS AND RESULTS

Isoflurane-mediated phosphorylation of extracellular signal-regulated kinase (ERK) and Akt and induction of HSP70 in human kidney proximal tubule (HK-2) cells were inhibited by dimethylsphingosine (DMS), an SK inhibitor, and VPC23019, an S1P(1/3) receptor selective antagonist, in HK-2 cells. A selective S1P(1) receptor agonist, SEW2781, mimicked isoflurane-induced phosphorylation of ERK and Akt and induction of HSP70. Moreover, isoflurane-mediated protection against H(2)O(2)-induced necrosis of HK-2 cells was significantly attenuated by an S1P(1/3) receptor antagonist, VPC23019, and by SK inhibitors DMS or 4-[[4- (4-chlorophenyl)-2-thiazolyl]amino]phenol. Finally, overexpression of the SK1 enzyme in HK-2 cells protected against H(2)O(2)-induced necrosis.

CONCLUSIONS

Collectively, our study demonstrates that S1P released via isoflurane-mediated SK1 stimulation produces direct anti-necrotic effects probably via S1P(1) receptor-mediated cytoprotective signaling (ERK/Akt phosphorylation and HSP70 induction) in HK-2 cells. Our findings may help to unravel the cellular signaling pathways of volatile anesthetic-mediated renal protection and lead to new therapeutic applications of volatile anesthetics during the perioperative period.

Differences in production of reactive oxygen species and mitochondrial uncoupling as events in the preconditioning signaling cascade between desflurane and sevoflurane

BACKGROUND

Signal transduction cascade of anesthetic-induced preconditioning has been extensively studied, yet many aspects of it remain unsolved. Here, we investigated the roles of reactive oxygen species (ROS) and mitochondrial uncoupling in cardiomyocyte preconditioning by two modern volatile anesthetics: desflurane and sevoflurane.

METHODS

Adult rat ventricular cardiomyocytes were isolated enzymatically. The preconditioning potency of desflurane and sevoflurane was assessed in cell survival experiments by evaluating myocyte protection from the oxidative stress-induced cell death. ROS production and flavoprotein fluorescence, an indicator of flavoprotein oxidation and mitochondrial uncoupling, were monitored in real time by confocal microscopy. The functional aspect of enhanced ROS generation by the anesthetics was assessed in cell survival and confocal experiments using the ROS scavenger Trolox.

RESULTS

Preconditioning of cardiomyocytes with desflurane or sevoflurane significantly decreased oxidative stress-induced cell death. That effect coincided with increased ROS production and increased flavoprotein oxidation detected during acute myocyte exposure to the anesthetics. Desflurane induced significantly greater ROS production and flavoprotein oxidation than sevoflurane. ROS scavenging with Trolox abrogated preconditioning potency of anesthetics and attenuated flavoprotein oxidation.

CONCLUSION

Preconditioning with desflurane or sevoflurane protects isolated rat cardiomyocytes from oxidative stress-induced cell death. Scavenging of ROS abolishes the preconditioning effect of both anesthetics and attenuates anesthetic-induced mitochondrial uncoupling, suggesting a crucial role for ROS in anesthetic-induced preconditioning and implying that ROS act upstream of mitochondrial uncoupling. Desflurane exhibits greater effect on stimulation of ROS production and mitochondrial uncoupling than sevoflurane.

Oxidative stress mediates a reduced expression of the activating receptor NKG2D in NK cells from end-stage renal disease patients

To characterize the immune defect of patients with end-stage renal disease (ESRD), we performed NK cell subset analysis in 66 patients with ESRD treated by hemodialysis (n = 59) or peritoneal dialysis (n = 7). Compared with healthy blood donors, patients undergoing chronic dialysis showed a profound decrease in NKG2D(+) cells within both the CD8(+) T cell (58% vs 67%, p = 0.03) and NK cell (39% vs 56%, p = 0.002) populations. CD56(dim) cells, which comprise the majority of NK cells in the periphery, were more affected in this regard than were CD56(bright) cells. Uremic serum could decrease NKG2D expression on NK cells from healthy donors. Among factors that could contribute to the decrease in NKG2D expression in ESRD patients, reactive oxygen species (ROS) play a major role. We found that catalase could reverse the effects of uremic serum on NKG2D expression (p < 0.001) and that ROS down-regulated NKG2D at the mRNA level and at the NK cell surface. Additionally, ESRD patients had both increased membrane-bound MHC class I-related chain A (MICA) on monocytes (p = 0.04) and increased soluble MICA (203 pg/ml vs 110 pg/ml; p < 0.001). Both ROS and uremic serum could significantly increase in vitro the expression of the NKG2D ligand MICA on the renal epithelial cell line HK-2. Taken together, these studies suggest for the first time that both low NKG2D expression and up-regulation of its ligand MICA are related to ROS production and may be involved in the immune deficiency of ESRD patients.

Involvement of ERK1/2 and p38 MAPK in up-regulation of 14-3-3 protein induced by hydrogen peroxide preconditioning in PC12 cells

OBJECTIVE

To investigate the protective effects of hydrogen peroxide preconditioning (HPP) on the pheochromocytoma (PC12) cells treated with 1-methyl-4-phenylpyridinium (MPP(+)) and to explore the potential mechanisms.

METHODS

The viability and apoptosis of PC12 cells were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and 4',6'-diamidino-2-phenylindole (DAPI) staining, respectively. The expressions of 14-3-3 protein and phosphorylated p38 mitogen-activated protein kinase (MAPK) were determined by Western blot. Enzyme-linked immunosorbent assay (ELISA) was used to measure the activity of extracellular signal-regulated protein kinase 1/2 (ERK1/2).

RESULTS

The cell viability decreased and the number of apoptotic cells increased dramatically in MPP(+) group compared with that in Control group. HPP induced a significant increase in cell viability and a marked decrease in population of apoptotic cells of the MPP(+)-treated PC12 cells, accompanied with up-regulation of 14-3-3 protein and increase of ERK1/2 and p38 MAPK activities. The 14-3-3 protein expression was positively correlated with the phosphorylation of ERK1/2. Furthermore, inhibition of the ERK1/2 with PD98059 abolished the 14-3-3 protein up-regulation in PC12 cells induced by HPP.

CONCLUSION

HPP protects PC12 cells against MPP(+) toxicity by up-regulating 14-3-3 protein expression through the ERK1/2 and p38 MAPK signaling pathways.

Morphine dependence protects rat kidney against ischaemia-reperfusion injury

Ischaemic preconditioning (IPC) protects the heart and kidneys against ischaemia-reperfusion (I/R) injury. It has been shown that opioid receptor activation can mimic cardiac IPC. In a kidney model of I/R, a single dose of morphine failed to mimic IPC. The aim of the present study was to determine the role of chronic morphine (dependence) in protection against renal I/R injury. Male Wistar rats were treated with increasing doses of morphine (20-30 mg/kg per day, s.c., for 5 days) to develop morphine dependence (MD). Three weeks before the I/R procedure, the right kidney was removed. Ischaemia-reperfusion injury was induced by clamping the left renal artery for 45 min, followed by 24 h reperfusion. Some MD rats were pretreated with naloxone (5 mg/kg, s.c.). Twenty-four hours later, creatinine and sodium concentrations were measured in serum and urine, then creatinine clearance (CCr) and the fractional excretion of sodium (FE(Na)) were calculated. Blood urea nitrogen (BUN) was measured only in serum samples. Kidneys were also assessed histologically for evidence of tissue injury. In the present study, MD decreased tissue injury (histological score), serum creatinine and BUN levels, increased CCr and decreased FE(Na) after I/R. Pretreatment with naloxone attenuated the protective effects of MD. Morphine dependence did not have any significant effect on urine volume. In conclusion, it seems that morphine dependence protects the kidney against I/R injury via opioid receptor-dependent pathways. Further studies are required to clearly determine the mechanisms involved.

Increased apoptosis of peripheral blood mononuclear cells (PBMC) during general and epidural anaesthesia in dogs

The objective of the study was to investigate the hypothesis that perioperative lymphocytopenia was due to apoptosis of these cells induced by either halothane or epidural anaesthesia in dogs. The relationship between apoptosis induction and plasma concentrations of the stress hormone cortisol and the cytokines TNF-alpha and IL-10 was examined as well. The study was performed on 22 healthy mongrel dogs, equal numbers from both genders, weighing 18.3 +/- 2.9 kg, and aged between 3-5 years. Dogs were divided in three groups. Eight of the animals were anaesthetized with halothane, another eight received epidural anaesthesia using lidocaine, and six served as controls. Venous blood samples were obtained immediately before (0 minute) anaesthesia, during deep anaesthesia (120 minute), and on the next day (24 hour) in order to determine the following parameters: the total lymphocyte counts, the percentage of apoptotic peripheral blood mononuclear cells (PBMC) by flow cytometry, plasma concentrations of the cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10) by enzyme-linked immunosorbent assay (ELISA), and plasma cortisol levels by radioimmune assay. Both halothane and epidural anaesthesia in dogs induces apoptosis of PBMC with slight decrease in total lymphocyte counts. These immunomodulatory effects were transient and faded till the 24th hour. Concerning the mechanism of inducing lymphocyte apoptosis by general or epidural anaesthesia, it seemed that neither cortisol, nor the tested cytokines TNF-alpha and IL-10 were implicated in this process. Further investigations are necessary to confirm this assumption.

Heme oxygenase 1: does it have a role in renal cytoprotection?

Heme oxygenase (HO) was first identified as the rate-limiting enzyme in the degradative pathway of heme, but is now recognized to be involved in diverse biological processes. Different isoforms of HO exist; HO-1 (HMOX1) is ubiquitously present in mammalian tissue with low constitutive expression under physiological conditions, but is upregulated in response to a variety of potentially noxious stimuli. HO-1, an integral component of an important cytoprotective mechanism, mediates its action through removal of heme, the generation of heme breakdown reaction products (biliverdin, free iron, and carbon monoxide), and modulation of key cellular molecules. Data from experimental models in which HO-1 was induced or inhibited, together with observations in genetically modified animals, showed a beneficial effect of HO-1 in several pathways leading to kidney injury. The discovery of a functional guanosine thymine tandem repeat polymorphism in the promoter region of the human HO-1 gene has stimulated clinical investigations in a variety of diseases. However, despite theoretical and experimental support for an important pathophysiological role for HO-1, the relevance of this polymorphism in native kidney or renal transplant function is equivocal. This article reviews the molecular genetics of HO-1, its myriad cytoprotective effects allied to how these are mediated, and relates these findings to experimental and clinical evidence of HO-1 involvement in renal disease.

Role of the JAK-STAT pathway in protection of hydrogen peroxide preconditioning against apoptosis induced by oxidative stress in PC12 cells

The aim of this study was to investigate the role of JAK-STAT pathway in the cytoprotection afforded by preconditioning with H(2)O(2). It was shown that (1) Preconditioning with 100 micromol/L H(2)O(2) can markedly protect PC12 cells against apoptosis and cytotoxicity induced by 300 micromol/L H(2)O(2); (2) The expression and tyrosine phosphorylation of JAK2, not JAK1 were rapidly increased at 5 min after H(2)O(2) preconditioning; (3) The expression of STAT1 and STAT3 were significantly increased at 15 min after H(2)O(2) preconditioning, and the pTyr-STAT1 and pTyr-STAT3 were markedly increased at 60 min after H(2)O(2) preconditioning; (4) Pretreatment with the JAK inhibitor AG-490 (10 micromol/L) 20 min before H(2)O(2) preconditioning blocked not only the activation of JAK2, STAT1 and STAT3, but also the cytoprotection of H(2)O(2) preconditioning against apoptosis and cytotoxicity induced by oxidative stress. These findings suggested that preconditioning with H(2)O(2) activated the JAK-STAT pathway that played an important role in the cytoprotection induced by H(2)O(2) preconditioning.

Killer proteases and little strokes--how the things that do not kill you make you stronger

The phenomenon of ischemic preconditioning was initially observed over 20 years ago. The basic tenant is that if stimuli are applied at a subtoxic level, cells upregulate endogenous protective mechanisms to block injury induced by subsequent stress. Since this discovery, many conserved signaling mechanisms that contribute to activation of this potent protective program have been identified in the brain. A clinical correlate of this basic research finding can be found in patients with a history of transient ischemic attack (TIA), who have a decreased morbidity after stroke. In spite of multidisciplinary efforts to design safer, more effective stroke therapies, we have thus far failed to translate our understanding of endogenous protective pathways to treatments for neurodegeneration. This review is designed to provide clinicians and basic scientists with an overview of stress biology after TIA and preconditioning, discuss new therapeutic strategies to target the protein dysfunction that follows ischemic injury, and propose enhanced biochemical profiling to identify individuals at risk of stroke after TIA. We pay particular attention to the unanticipated consequences of overly aggressive intervention after TIA in which we have found that traditional cytotoxic agents such as free radicals and apoptosis associated proteases is essential for neuroprotection and communication in the stressed brain. These data emphasize the importance of understanding the complex interplay between chaperones, apoptotic proteases including caspases, and the proteolytic degradation machinery in adaptation to neurological injury.

Docosahexaenoic acid enhances the antioxidant response of human fibroblasts by upregulating γ-glutamyl-cysteinyl ligase and glutathione reductase

The chemopreventive effects of dietaryn-3 PUFA in various pathologies has so far remained controversial, and we were interested in studying their potential influence on cell redox status. DHA (22:6n-3), a typical highly unsaturatedn-3 PUFA, was used at 30µmol/l in a model of human fibroblast cell culture. A dose–response effect, roughly linear, was checked for DHA between 0 and 60µmol/l, and was accompanied by a large increase in intracellular GSH content. A time course study of this effect shows that, after a short fall, as soon as 4h after the beginning of the experiment, the large increase in the GSH content was associated with elevated catalytic activities of γ-glutamyl-cysteinyl ligase, glutathione reductase and glutathioneS-transferase. This coordinated response is characteristic of an antioxidant response and was confirmed by the induction of expression of mRNA for γ-glutamyl-cysteinyl ligase, glutathione reductase and haem-oxygenase. This large increase in the GSH content contributes to decreasing the reactive oxygen species level, as assessed by the decreased accumulation of dichlorofluorescein inside cells. To our knowledge, this is the first report on a specific and potent effect of DHA for decreasing the oxidative stress of human fibroblasts.

Ischemic preconditioning provides both acute and delayed protection against renal ischemia and reperfusion injury in mice

Acute as well as delayed ischemic preconditioning (IPC) provides protection against cardiac and neuronal ischemia reperfusion (IR) injury. This study determined whether delayed preconditioning occurs in the kidney and further elucidated the mechanisms of renal IPC in mice. Mice were subjected to IPC (four cycles of 5 min of ischemia and reperfusion) and then to 30 min of renal ischemia either 15 min (acute IPC) or 24 h (delayed IPC) later. Both acute and delayed renal IPC provided powerful protection against renal IR injury. Inhibition of Akt but not extracellular signal-regulated kinase phosphorylation prevented the protection that was afforded by acute IPC. Neither extracellular signal-regulated kinase nor Akt inhibition prevented protection that was afforded by delayed renal IPC. Pretreatment with an antioxidant, N-(2-mercaptopropionyl)-glycine, to scavenge free radicals prevented the protection that was provided by acute but not delayed renal IPC. Inhibition of protein kinase C or pertussis toxin-sensitive G-proteins attenuated protection from both acute and delayed renal IPC. Delayed renal IPC increased inducible nitric oxide synthase (iNOS) as well as heat-shock protein 27 synthesis, and the renal protective effects of delayed preconditioning were attenuated by a selective inhibitor of iNOS (l-N(6)[1-iminoethyl]lysine). Moreover, delayed IPC was not observed in iNOS knockout mice. Both acute and delayed IPC were independent of A(1) adenosine receptors (AR) as a selective A(1)AR antagonist failed to block preconditioning and acute and delayed preconditioning occurred in mice that lacked A(1)AR. Therefore, this study demonstrated that acute or delayed IPC provides renal protection against IR injury in mice but involves distinct signaling pathways.

Limb ischemic preconditioning induces brain ischemic tolerance via p38 MAPK

It has been reported that limb ischemic preconditioning (LIP) could induce brain ischemic tolerance. In the present study, we investigated the role of p38 MAPK in the induction of brain ischemic tolerance by observing expression of phosphorylated p38 (p-p38) MAPK in the hippocampus after LIP and the effect of p38 MAPK inhibitor SB 203580 on the protection of LIP against delayed neuronal death (DND) in the CA1 hippocampus induced normally by brain ischemic insult. The results of Flow cytometry and Western blotting showed that expression of p-p38 MAPK initially increased at 6 h after LIP compared with sham group in the CA1 hippocampus. The increases reached peak at 12 h and lasted to 24 h after LIP. Expression of p-p38 MAPK was also increased in the CA3/dentate gyrus (DG) regions after LIP, but the beginning and peaking times were 1 and 3 days after LIP, which were relatively later than those in the CA1. Histological evaluation showed that LIP protected the CA1 hippocampal pyramidal neurons against DND induced by global brain ischemic insult for 8 min, suggesting the occurrence of brain ischemic tolerance. Pretreatment with SB 203580 at 30 min before LIP effectively blocked the ischemic tolerance induced by LIP. Together, it could be concluded that activation of p38 MAPK played an important role in the brain ischemic tolerance induced by LIP, and that components of the p38 MAPK cascade might be targets to modify neuronal survival in ischemic tolerance.

Molecular basis of heme oxygenase-1 induction: implications for chemoprevention and chemoprotection

Heme oxygenase (HO)-1, involved in the heme degradation process, is an important antioxidant enzyme. The induction of HO-1 gene expression, in response to diverse oxidative stimuli, represents a critical event in adaptive cellular response. Experimental models of various diseases, including acute inflammation, atherosclerosis, degenerative diseases, and carcinogenesis, have demonstrated that the induction of HO-1 can prevent or mitigate the symptoms associated with these ailments. Recent progress in our understanding of cellular signaling networks as critical modulators of gene transcription sheds light on the molecular basis of HO-1 gene expression. A panel of redox-sensitive transcription factors such as activator protein-1, nuclear factor- kappaB, and nuclear factor E2-related factor-2, and some of the upstream kinases have been identified as regulators of HO-1 gene induction. The scope of this review is limited to focus on molecular mechanisms underlying HO-1 expression and the significance of targeted induction of HO-1 as a strategy to achieve chemoprevention and chemoprotection.

PrP(106-126) activates neuronal intracellular kinases and Egr1 synthesis through activation of NADPH-oxidase independently of PrPc

Prion diseases are characterised by severe neural lesions linked to the presence of an abnormal protease-resistant isoform of cellular prion protein (PrPc). The peptide PrP(106-126) is widely used as a model of neurotoxicity in prion diseases. Here, we examine in detail the intracellular signalling cascades induced by PrP(106-126) in cortical neurons and the participation of PrPc. We show that PrP(106-126) induces the activation of subsets of intracellular kinases (e.g., ERK1/2), early growth response 1 synthesis and induces caspase-3 activity, all of which are mediated by nicotinamide adenine dinucleotide phosphate hydrogen-oxidase activity and oxidative stress. However, cells lacking PrPc are similarly affected after peptide exposure, and this questions the involvement of PrPc in these effects.

Caveolins in the repair phase of acute renal failure after oxidative stress

Ischaemia-reperfusion and toxic injury are leading causes of acute renal failure (ARF). Both of these injury initiators use secondary mediators of damage in oxygen-derived free radicals. Several recent publications about ischaemia-reperfusion and toxin-induced ARF have indicated that plasma membrane structures called caveolae, and their proteins, the caveolins, are potential participants in protecting or repairing renal tissues. Caveolae and caveolins have previously been ascribed many functions, a number of which may mediate cell death or survival of injured renal cells. This review proposes possible pathophysiological mechanisms by which altered caveolin-1 expression and localization may affect renal cell survival following oxidative stress.

Preconditioning of skeletal muscle against contraction-induced damage: the role of adaptations to oxidants in mice

Adaptations of skeletal muscle following exercise are accompanied by changes in gene expression, which can result in protection against subsequent potentially damaging exercise. One cellular signal activating these adaptations may be an increased production of reactive oxygen and nitrogen species (ROS). The aim of this study was to examine the effect of a short period of non-damaging contractions on the subsequent susceptibility of muscle to contraction-induced damage and to examine the changes in gene expression that occur following the initial contraction protocol. Comparisons with changes in gene expression in cultured myotubes following treatment with a non-damaging concentration of hydrogen peroxide (H(2)O(2)) were used to identify redox-sensitive genes whose expression may be modified by the increased ROS production during contractions. Hindlimb muscles of mice were subjected to a preconditioning, non-damaging isometric contraction protocol in vivo. After 4 or 12 h, extensor digitorum longus (EDL) and soleus muscles were removed and subjected to a (normally) damaging contraction protocol in vitro. Muscles were also analysed for changes in gene expression induced by the preconditioning protocol using cDNA expression techniques. In a parallel study, C(2)C(12) myotubes were treated with a non-damaging concentration (100 microM) of H(2)O(2) and, at 4 and 12 h following treatment, myotubes were treated with a damaging concentration of H(2)O(2) (2 mM). Myotubes were analysed for changes in gene expression at 4 h following treatment with 100 microM H(2)O(2) alone. Data demonstrate that a prior period of non-damaging contractile activity resulted in significant protection of EDL and soleus muscles against a normally damaging contraction protocol 4 h later. This protection was associated with significant changes in gene expression. Prior treatment of myotubes with a non-damaging concentration of H(2)O(2) also resulted in significant protection against a damaging treatment, 4 and 12 h later. Comparison of changes in gene expression in both studies identified haem oxygenase-1 as the sole gene showing increased expression during adaptation in both instances suggesting that activation of this gene results from the increased ROS production during contractile activity and that it may play a role in protection of muscle cells against subsequent exposure to damaging activity.