Tissue-specific pattern of stress kinase activation in ischemic/reperfused heart and kidney

SP600125, a selective JNK inhibitor, protects ischemic renal injury via suppressing the extrinsic pathways of apoptosis

Accumulating evidence suggests that c-Jun N-terminal kinase (JNK) signaling pathway plays a critical role in renal ischemia/reperfusion injury. However, the downstream mechanism that accounts for the proapoptotic actions of JNK during renal ischemia/reperfusion has not been elucidated. We report that SP600125, a potent, cell-permeable, selective, and reversible inhibitor of c-Jun N-terminal kinase (JNK), potently decreased renal epithelial tubular cell apoptosis induced by renal ischemia/reperfusion via suppression of the extrinsic pathway. This corresponds to the decrease in JNK phosphorylation at 20 min and c-Jun phosphorylation (Ser63/73) at 3 h after renal ischemia. Additionally, SP600125 attenuated the increased expression of FasL induced by ischemia/reperfusion at 3 h. The administration of SP600125 prior to ischemia was also protective. Thus, our findings imply that SP600125 can inhibit the activation of the JNK-c-Jun-FasL pathway and protect renal tubular epithelial cells against ischemia/reperfusion-induced apoptosis. Taken together, these results indicate that targeting the JNK pathway provides a promising therapeutic approach for renal ischemia/reperfusion injury.

The role of basic leucine zipper protein-mediated transcription in physiological and pathological myocardial hypertrophy

Accumulating evidence suggests that nuclear transcription factors from the basic leucine zipper (bZIP) family play an important role in cardiac development and function. This class includes the CREB/ATF family of transcription factors, namely CREB, cAMP response element modulator (CREM), ATF, and the related AP-1 and C/EBP families. An effort has been made to elucidate the role of specific bZIP members in the heart. Unfortunately, little insight could be gained from knockout experiments, either due to embryonic lethal phenotypes or functional compensation by other bZIP family members. Surprisingly, cardiac overexpression of several inhibitory transcription factors from the bZIP family, such as a nonphosphorylatable form of CREB (CREB(ser133)), a nonfunctional isoform of CREM, or ATF3 resulted in massive atrial dilatation. In order to try and characterize this pathway we have expressed the potent bZIP inhibitory protein, Jun dimerization protein 2 (JDP2), specifically in the mouse heart in a temporally controlled manner. Expression of JDP2 resulted in massive biatrial dilatation; loss of connexin 40 (Cx40), connexin43 (Cx43), and myosin light chain 2 (MLC2a) expression; atrioventricular defects in conduction; and a lethal phenotype. All these effects were independent of any developmental events acquired during adulthood, and were totally reversible upon abolishing the bZIP inhibition. The results of this article suggest that bZIP inhibition is sufficient to cause atrial dilation, that this dilatation is acquired postnatally, and that it is reversible upon the relief of inhibition. Thus, bZIP repressors may serve as novel drug targets for the prevention of atrial dilatation a major risk of atrial fibrillation (AF).

Emodin suppresses interleukin-1beta induced mesangial cells proliferation and extracellular matrix production via inhibiting P38 MAPK

Previous findings indicate that emodin has anti-proliferation and anti-fibrosis effects on several cell lines. In this study, we investigated the effects of emodin on IL-1beta induced proliferation of mesangial cells (MCs) and on their production of extracellular matrix (ECM), and explored the possible mechanisms. To test the therapeutic effect of emodin on progressive renal disease, we administered emodin to rats in renal failure models induced by subtotal nephrectomy, the renal function was analyzed. Our results showed emodin significantly suppressed IL-1beta induced MC proliferation and arrested the cell-cycle progress in vitro. Fibronectin and collagen IV production by MC were significantly reduced after emodin treatment. P38 mRNA, protein levels of P-P38, P-MKK3/6 and P-MKK4 were quantified. We observed no alterations of P38 expression and P-MKK4 protein content; however, protein levels of P-P38 and P-MKK3/6 significantly decreased after emodin treatment. In the renal failure models, after administration of emodin for eight weeks, the rat renal lesions were significantly ameliorated, as evidenced by the decreased blood creatinine, urea, and the 24-hour urine protein. In conclusion, emodin suppresses IL-1beta induced MC proliferation and ECM production in vitro. We hypothesize that this is achieved by inactivating MKK3/6 and P38. Emodin ameliorates renal failure in subtotal nephrectomized rats, which suggests a potential role of emodin in the treatment of progressive renal diseases.

A peptide inhibitor of c-Jun NH2-terminal kinase reduces myocardial ischemia-reperfusion injury and infarct size in vivo

The c-Jun NH2-terminal kinase (JNK) pathway of the mitogen-activated protein kinase (MAPK) signaling cascade regulates cell function and survival after stress stimulation. Equally robust studies reported dichotomous results suggesting both protective and detrimental effects of JNK during myocardial ischemia-reperfusion (I/R). The lack of a highly specific JNK inhibitor contributed to this controversy. We recently developed a cell-penetrating, protease-resistant peptide inhibitor of JNK, d-JNKI-1. Here we report on the effects of d-JNKI-1 in myocardial I/R. d-JNKI-1 was tested in isolated-perfused adult rat hearts. Increased activation of JNK, p38-MAPK, and extracellular signal-regulated kinase-1/2 (ERK1/2), as assessed by kinase assays and Western blotting, occurred during I/R. d-JNKI-1 delivered before onset of ischemia prevented the increase in JNK activity while not affecting ERK1/2 and p38-MAPK activation. JNK inhibition reduced ischemic injury, as manifested by increased time to contracture ( P < 0.05) and decreased left ventricular end-diastolic pressure during ischemia ( P < 0.01), and enhanced posthypoxic recovery of systolic and diastolic function ( P < 0.01). d-JNKI-1 reduced mitochondrial cytochrome- c release, caspase-3 activation, and the number of apoptotic cells determined by terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling ( P < 0.05), indicating suppression of the mitochondrial machinery of apoptosis. d-JNKI-1 delivered at the time of reperfusion did not improve functional recovery but still prevented apoptosis. In vivo, d-JNKI-1 reduced infarct size after coronary artery occlusion and reperfusion by ∼50% ( P < 0.01). In conclusion, d-JNKI-1 is an important compound that can be used in preclinical models to investigate the role of JNK signaling in vivo. Inhibition of JNK during I/R is cardioprotective in anesthetized rats in vivo.

Effects of hypothalamic paraventricular nuclei on apoptosis and proliferation of gastric mucosal cells induced by ischemia/reperfusion in rats

AIM: To investigate the effects of electrical stimulation of hypothalamic paraventricular nuclei (PVN) on gastric mucosal cellular apoptosis and proliferation induced by gastric ischemia/reperfusion (I/R) injury.

METHODS: For different experimental purposes, stimulating electrode plantation or electrolytic destruction of the PVN was applied, then the animals’ GI/R injury model was established by clamping the celiac artery for 30 min and allowing reperfusing the artery for 30 min, 1 h, 3 h or 6 h respectively. Then histological, immunohistochemistry methods were used to assess the gastric mucosal damage index, the gastric mucosal cellular apoptosis and proliferation at different times.

RESULTS: The electrical stimulation of PVN significantly attenuated the GI/R injury at 30 min, 1 h and 3 h after reperfusion. The electrical stimulation of PVN decreased gastric mucosal apoptosis and increased gastric mucosal proliferation. The electrolytic destruction of the PVN could eliminate the protective effects of electrical stimulation of PVN on GI/R injury. These results indicated that the PVN participated in the regulation of GI/R injury as a specific area in the brain, exerting protective effects against the GI/R injury, and the protection was associated with the inhibition of cellular apoptosis and the promotion of gastric mucosal proliferation.

CONCLUSION: Stimulating PVN significantly inhibits the gastric mucosal cellular apoptosis and promots gastric mucosal cellular proliferation. This may explain the protective mechanisms of electrical stimulation of PVN against GI/R injury.

Mechanisms of cell death in oxidative stress

Reactive oxygen or nitrogen species (ROS/RNS) generated endogenously or in response to environmental stress have long been implicated in tissue injury in the context of a variety of disease states. ROS/RNS can cause cell death by nonphysiological (necrotic) or regulated pathways (apoptotic). The mechanisms by which ROS/RNS cause or regulate apoptosis typically include receptor activation, caspase activation, Bcl-2 family proteins, and mitochondrial dysfunction. Various protein kinase activities, including mitogen-activated protein kinases, protein kinases-B/C, inhibitor-of-I-kappaB kinases, and their corresponding phosphatases modulate the apoptotic program depending on cellular context. Recently, lipid-derived mediators have emerged as potential intermediates in the apoptosis pathway triggered by oxidants. Cell death mechanisms have been studied across a broad spectrum of models of oxidative stress, including H2O2, nitric oxide and derivatives, endotoxin-induced inflammation, photodynamic therapy, ultraviolet-A and ionizing radiations, and cigarette smoke. Additionally ROS generated in the lung and other organs as the result of high oxygen therapy or ischemia/reperfusion can stimulate cell death pathways associated with tissue damage. Cells have evolved numerous survival pathways to counter proapoptotic stimuli, which include activation of stress-related protein responses. Among these, the heme oxygenase-1/carbon monoxide system has emerged as a major intracellular antiapoptotic mechanism.

Inhibition of myocardial apoptosis by ischaemic and beta-adrenergic preconditioning is dependent on p38 MAPK

INTRODUCTION

Apoptosis occurring during ischaemia /reperfusion contributes independently to tissue damage, and involves activation of the stress-kinase, p38 MAPK during reperfusion. Ischaemic preconditioning (IPC) protects against ischaemia/reperfusion mediated necrosis and apoptosis. The role of p38 MAPK in the protective effect of preconditioning against apoptosis is unknown. Pharmacologic preconditioning with isoproterenol (beta-PC) also protects against necrosis, but it is not known whether it protects against apoptosis.

AIM

The aim of the study was to investigate whether the protective effect of IPC against apoptosis is related to activation of p38 MAPK and whether beta-PC also protects against apoptosis.

MATERIALS AND METHODS

Isolated perfused rat hearts were used to study the effect of ischaemia and reperfusion on apoptosis and infarct size. Ischaemic preconditioning was elicited by 3 x 5 min global ischaemia, and beta-PC by 5 min isoproterenol 10(-7) M. For infarct size hearts were subjected to regional ischaemia for 35 min followed by 120 min reperfusion. Infarct size was determined by the tetrazolium staining technique, and expressed as percentage of area at risk. For markers of apoptosis hearts were subjected to global ischaemia of 25 min plus 30 min reperfusion. Apoptosis was determined by Western blot using antibodies against caspase-3 and PARP. p38 MAPK activation was inhibited by SB203580 (1 microM) administration 10 min prior to commencing ischaemia, and bracketing the IPC and beta-PC preconditioning protocols. p38 MAPK was activated by administration of anisomycin (5 microM) 10 min prior to index ischaemia in one protocol, and 10 min during reperfusion in non-preconditioned as well as IPC and beta-PC hearts. Results were analysed using ANOVA and a Newman-Keuls post-hoc test.

RESULTS

In the apoptosis model using global ischaemia, IPC and beta-PC both resulted in a significant decrease in p38 MAPK activation at the end of reperfusion when compared to non-preconditioned hearts. This was accompanied by a significant decrease in apoptosis as measured with both caspase-3 activation and PARP cleavage. Inhibiting p38 MAPK by administration of SB203580 10 min prior to ischaemia resulted in a significant reduction in both markers of apoptosis. Bracketing the triggering phase of either IPC or beta-PC with SB203580 resulted in attenuated p38 MAPK activation during reperfusion and did not abolish the protective effect of IPC or beta-PC against apoptosis. Activating p38 MAPK with anisomycin prior to ischaemia resulted in a reduction of markers of apoptosis, whereas activation of p38 MAPK with anisomycin during reperfusion did not exacerbate apoptosis in any groups, exept for an increase in PARP cleavage in IPC hearts. In the model of regional ischaemia, IPC and beta-PC reduced infarct size significantly, and to the same extent as inhibition of p38 MAPK by administration of SB203580 10 min prior to ischaemia. Bracketing the triggering phase of either IPC or beta-PC did not abolish the reduction in infarct size. Activating p38 MAPK during reperfusion was accompanied by an increase in infarct size only in IPC hearts, but not in beta-PC hearts.

CONCLUSION

These results indicate that (1) Both IPC and beta-PC elicit protection against apoptosis and necrosis, (2) activation of p38 MAPK is not a trigger of preconditioning against apoptosis and necrosis and (3) activation of p38 MAPK during reperfusion increases necrosis only if ischaemia is used to precondition hearts, but not with pharmacologic preconditioning with isoproterenol.

Protein kinase C beta/early growth response-1 pathway: a key player in ischemia, atherosclerosis, and restenosis

Atherosclerosis, restenosis, and the consequences of ischemia are the major causes of morbidity and mortality worldwide. Elucidation of key contributing pathways in animal models of ischemia-reperfusion injury, atherosclerosis, and restenosis consequent to vascular injury may lead to great interest in determining if blocking these pathways could prevent vascular disease in human subjects. This review details the evidence that the protein kinase C (PKC) beta/early growth response-1 axis plays a central role in the response to both acute and chronic vascular stresses in animal models and also indicates the clinical implications of a specific inhibitor of PKCbeta, ruboxistaurin (LY333531).

Endotoxin and cisplatin synergistically stimulate TNF-alpha production by renal epithelial cells

Acute renal failure often occurs in the clinical setting of multiple renal insults. Tumor necrosis factor-alpha (TNF-alpha) has been implicated in the pathogenesis of cisplatin nephrotoxicity, ischemia-reperfusion injury, and endotoxin-induced acute renal failure. The current studies examined the interactions between cisplatin and endotoxin with particular emphasis on TNF-alpha production. Treatment of cultured murine proximal tubule cells (TKPTS cells) with cisplatin resulted in a modest production of TNF-alpha, while treatment with endotoxin did not result in any TNF-alpha production. However, the combination of cisplatin and endotoxin resulted in large amounts of TNF-alpha synthesis and secretion. The stimulation of TNF-alpha production was dependent on cisplatin-induced activation of p38 MAPK and was associated with phosphorylation of the translation initiation factor eIF4E and its upstream kinase Mnk1. Inhibition of p38 MAPK and, to a lesser extent, ERK, reduced cisplatin+endotoxin-stimulated TNF-alpha production and phosphorylation of Mnk1 and eIF4E. Synergy between cisplatin and endotoxin was also observed in certain tumor cell lines, but not in macrophages. In macrophages, in contrast to TKPTS cells, endotoxin alone activated p38 MAPK and stimulated TNF-alpha production with no added impact by cisplatin. The combination of cisplatin and endotoxin did not result in synergistic production of other cytokines, e.g., MCP-1 and MIP2, by TKPTS cells. In summary, these studies indicate that cisplatin sensitizes renal epithelial cells to endotoxin and dramatically increases the translation of TNF-alpha mRNA in a p38 MAPK-dependent manner. These interactions between cisplatin and endotoxin may be relevant to the pathogenesis of cisplatin nephrotoxicity in humans.

Controlling oxidative stress as a novel molecular approach to protecting the vascular wall in diabetes

PURPOSE OF REVIEW

In diabetes, oxidative stress plays a key role in the pathogenesis of vascular complications; therefore an antioxidant therapy would be of great interest in this disease.

RECENT FINDINGS

Hyperglycemia directly promotes an endothelial dysfunction--inducing process of overproduction of superoxide at the mitochondrial level. This is the first and key event able to activate all the pathways involved in the development of vascular complications of diabetes. It has recently been shown that statins, angiotensin-converting enzyme inhibitors, angiotensin II type 1 blockers, calcium channel blockers, and thiazolidinediones have a strong intracellular antioxidant activity.

SUMMARY

Classic antioxidants, such as vitamin E, failed to show beneficial effects on diabetic complications probably because their action is only "symptomatic". The preventive activity against hyperglycemia-induced oxidative stress shown by statins, angiotensin-converting enzyme inhibitors, angiotensin II type 1 blockers, calcium channel blockers, and thiazolidinediones justifies use of these compounds for preventing complications in patients with diabetes, in whom antioxidant defences have been shown to be defective.

Phosphoregulation of Signal Transduction Pathways in Ischemia and Reperfusion

Ischemia/reperfusion (I/R) injury triggered by pathogenic processes, such as organ transplant dysfunction, stroke, myocardial infarction, and shock, stimulate both immune and inflammatory pathways. Inflammatory cell activation and cytotoxic cytokine expression are associated with reperfusion injury. The activation of these inflammatory mediators initiates several interconnected downstream cascades regulated by phosphorylation and dephosphorylation reactions. These complex phosphorylation-dependent signal transduction pathways ultimately initiate nuclear transcription of inflammatory as well as anti-inflammatory genes to repair and assist in the recovery of damaged cells. Radical oxygen species (ROS) production, under ischemic conditions, initiates a cascade of events regulated by phosphorylation/dephosphorylation reactions and inflammatory gene expression. This is a review of the current understanding of the phosphoregulatory mechanisms that mediate the complex processes of signal transduction secondary to I/R injury. The rationale for inhibiting or activating signaling pathways as a promising molecular target for ameliorating reperfusion injury in I/R-related diseases, such as stroke, myocardial infarction, and storage for transplantation, is discussed on the basis of a new understanding of the mechanisms modulating phosphoregulatory pathways. In addition, we present part of our ongoing research in this field with phosphoregulatory signal transduction and its potential application.

Involvement of protein kinase B and mitogen-activated protein kinases in experimental normothermic liver ischaemia-reperfusion injury

BACKGROUND

This study evaluated the role of protein kinase B (PKB), phosphatidylinositol 3-kinase (PI3-K), Bcl-2-associated death protein (BAD) and mitogen-activated protein kinases (MAPKs) in normothermic ischaemia-reperfusion (IR)-induced apoptosis in rat liver.

METHODS

Rats were divided into two groups that received either phosphate-buffered saline (control) or the caspase inhibitor Z-Asp-2,6-dichorobenzoyloxymethylketone (Z-Asp-cmk), injected intravenously 2 min before the induction of 120 min of normothermic liver ischaemia. Liver apoptosis was assessed by the terminal deoxyribonucleotidyltransferase-mediated dUTP nick end labelling (TUNEL) method. PI3-K, PKB, BAD and MAPK activities were measured in ischaemic and non-ischaemic lobes at various times after reperfusion.

RESULTS

The number of TUNEL-positive cells was significantly decreased after pretreatment with Z-Asp-cmk. In controls, PI3-K and PKB activities and BAD phosphorylation were inhibited in ischaemic liver lobes. The MAPKs (extracellular signal-regulated kinases, c-Jun N-terminal kinase and p38) showed different patterns of activation during IR. PKB activity was not modified by pretreatment with Z-Asp-cmk.

CONCLUSION

Induction of apoptosis during IR liver injury might be triggered by inactivation of the antiapoptotic PI3-K-PKB pathway and activation of the proapoptotic MAPKs.

Myocardial Preconditioning Against Ischemia-Induced Apoptosis and Necrosis in Man

BACKGROUND

Ischemic preconditioning (IPC) protects against apoptosis and necrosis but the contribution of the two forms of cell death and whether the beneficial effects are mediated by similar or different signal transduction pathways remains unclear. Here we have investigated the effect of IPC on the type of cell death in the human heart and whether the inhibition of apoptosis and necrosis by IPC requires the opening of mitoK(ATP) channels and the activation of PKC and p38MAPK.

MATERIALS AND METHODS AND RESULTS

Free-hand tissue sections (n = 6/group) obtained from the right atrium of patients at the time of coronary bypass surgery were subjected to 90-min simulated ischemia followed by 120-min reoxygenation (SI/R) with or without IPC (5 min SI/5 min R) prior to SI/R. IPC reduced apoptosis from 30.0 +/- 3.8 to 11.0 +/- 1.5% (P < 0.05) by TUNEL technique and necrosis from 11.6 +/- 2.4 to 4.2 +/- 1.7% (P < 0.05) by propidium iodide staining. When inhibitors of mitoKATP channels (1 mm 5-hydroxydecanoate), PKC (10 microm chelerythrine), and p38MAPK (10 microm SB203580) were added for 10 min before SI, the protection against necrosis was abolished. However, whereas 5-hydroxydecanoate and chelerythrine also abolished the protection of IPC against apoptosis, SB203580 did not. The activation of mitoKATP channels (100 microm diazoxide), PKC (1 microm PMA), and p38MAPK (1 nm anisomycin) were a mirror image of the findings with blockers.

CONCLUSIONS

IPC protects the human myocardium against both apoptosis and necrosis. The anti-necrotic effect is mediated by the opening of mitoKATP channels and activation of PKC and p38MAPK; however, the anti-apoptotic effect requires opening of the mitoKATP channels and PKC activation but is p38MAPK-independent.

Protease-activated receptor-1 protects rat astrocytes from apoptotic cell death via JNK-mediated release of the chemokine GRO/CINC-1

Thrombin at low doses is an endogenous mediator of protection in ischaemic and haemorrhagic models of stroke. However, the mechanism of thrombin-induced protection remains unclear. Recently accumulating evidence has shown that astrocytes play an important role in the brain after injury. We report that thrombin and thrombin receptor agonist peptide (TRag) up-regulated secretion of the chemokine growth-regulated oncogene/cytokine-induced neutrophil chemoattractant-1 (GRO/CINC-1) in primary rat astrocytes in a concentration-dependent manner. However, we found no increase of interleukin (IL)-6, IL-1beta and tumour necrosis factor-alpha secretion. Protease-activated receptor 1 (PAR-1)-induced GRO/CINC-1 release was mainly mediated by c-Jun N-terminal kinase (JNK) activation. Extracellular signal-regulated kinase 1/2 might be partially involved, but not p38 mitogen-activated protein kinase. Further studies demonstrated that PAR-1 activation, as well as application of recombinant GRO/CINC-1, protected astrocytes from C(2)-ceramide-induced cell death. Protection occurred with suppression of cytochrome c release from mitochondria. The inhibition of cytochrome c release was largely reduced by the antagonist of chemokine receptor CXCR2, SB-332235. Importantly, a specific JNK inhibitor significantly abolished the protective action of PAR-1. These results demonstrate for the first time that PAR-1 plays an important role in anti-apoptosis in the brain by regulating the release of chemokine GRO/CINC-1, which gives a feedback through its receptor CXCR2 to preserve astrocytes from toxic insults.

Inhibition of ceramide-redox signaling pathway blocks glomerular injury in hyperhomocysteinemic rats

Ceramide-activated NAD(P)H oxidase has been reported to participate in homocysteine (Hcys)-induced abnormal metabolism of the extracellular matrix (ECM) in rat glomerular mesangial cells. However, it remains unknown whether this ceramide-redox signaling pathway contributes to glomerular injury induced by hyperhomocysteinemia (hHcys) in vivo. The present study was designed to address this question, defining the role of ceramide and activated NAD(P)H oxidase in the development of hHcys-induced glomerular injury. Uninephrectomized Sprague-Dawley rats were fed a folate-free diet for 8 weeks to produce hHcys and the de novo ceramide synthesis inhibitor myriocin or the NAD(P)H oxidase inhibitor apocynin was administrated. Rats with folate-free diet significantly increased plasma Hcys levels, renal ceramide levels, and NAD(P)H oxidase activity accompanied by marked glomerular injury. Treatment of rats with myriocin significantly reduced ceramide levels and improved glomerular injury, as shown by decreased urinary albumin excretion and reduced glomerular damage index. ECM components changed towards to normal levels with decreased tissue inhibitor of metalloproteinase-1 and increased matrix metalloproteinase-1 activity. NAD(P)H oxidase activity and Rac GTPase activity were reduced by 69 and 66%, respectively. In rats treated with apocynin, similar beneficial effects in protecting glomeruli from hHcys-induced injury were observed. These results support the view that de novo ceramide production is involved in Hcys-induced NAD(P)H oxidase activity in the kidney of hHcys rats and indicate the important role of ceramide-mediated redox signaling in hHcys-induced glomerular injury in rats.

NFATc4 and ATF3 negatively regulate adiponectin gene expression in 3T3-L1 adipocytes

Expression of adiponectin decreases with obesity and insulin resistance. At present, the mechanisms responsible for negatively regulating adiponectin expression in adipocytes are poorly understood. In this investigation, we analyzed the effects of 5' serial deletion constructs on the murine adiponectin promoter. Here, we identified the repressor region located between -472 and -313 bp of the promoter. Removal of the putative nuclear factor of activated T-cells (NFATs) binding site increased the promoter activity, and overexpression of NFATc4 reduced the promoter activity. Treatment with the calcium ionophore A23187, an activator of NFAT, reduced mRNA as well as promoter activity. The binding of NFATc4 to the promoter was associated with increased recruitment of histone deacetylase 1 and reduced acetylation of histone H3 at the promoter site. In addition, binding of activating transcription factor 3 (ATF3) to the putative activator protein-1 site located adjacent to the NFAT binding site also repressed the promoter activity. Treatment with thapsigargin, an inducer of ATF3, reduced both mRNA and promoter activity. Importantly, the binding activities of NFATc4 and ATF3, increased significantly in white adipose tissues of ob/ob and db/db mice compared with controls. Taken together, this study demonstrates for the first time that NFATc4 and ATF3 function as negative regulators of adiponectin gene expression, which may play critical roles in downregulating adiponectin expression in obesity and type 2 diabetes.

Cardiac hypertrophy: a risk factor for QT-prolongation and cardiac sudden death

Cardiac hypertrophy was viewed as a compensatory response to hemodynamic stress. However, cumulative evidence obtained from studies using more advanced technologies in human patients and animal models suggests that cardiac hypertrophy is a maladaptive process of the heart in response to intrinsic and extrinsic stimuli. Although hypertrophy can normalize wall tension, it is a risk factor for QT-prolongation and cardiac sudden death. Studies using molecular biology techniques such as transgenic and knockout mice have revealed many important molecules that are involved in the development of heart hypertrophy and have demonstrated signaling pathways leading to the pathogenesis. With the same approach, the consequence of heart hypertrophy has been examined. The significance of hypertrophy in the development of overt heart failure has been demonstrated and several critical molecular pathways involved in the process were revealed. A comprehensive understanding of the threats of heart hypertrophy to patients has helped to develop novel treatment strategies. The recognition of hypertrophy as a major risk factor for QT-prolongation and cardiac sudden death is an important advance in cardiac medicine. Cellular and molecular mechanisms of this risk aspect are currently under extensively exploring. These studies would lead to more comprehensive approaches to prevention of potential life threatening arrhythmia and cardiac sudden death. The adaptation of new approaches such as functional genomics and proteomics will further advance our knowledge of heart hypertrophy.

Oxidative metabolism, apoptosis and perinatal brain injury

Perinatal hypoxic-ischaemic injury (HII) is a significant cause of neurodevelopmental impairment and disability. Studies employing 31P magnetic resonance spectroscopy to measure phosphorus metabolites in situ in the brains of newborn infants and animals have demonstrated that transient hypoxia-ischaemia leads to a delayed disruption in cerebral energy metabolism, the magnitude of which correlates with the subsequent neurodevelopmental impairment. Prominent among the biochemical features of HII is the loss of cellular ATP, resulting in increased intracellular Na+ and Ca2+, and decreased intracellular K+. These ionic imbalances, together with a breakdown in cellular defence systems following HII, can contribute to oxidative stress with a net increase in reactive oxygen species. Subsequent damage to lipids, proteins, and DNA and inactivation of key cellular enzymes leads ultimately to cell death. Although the precise mechanisms of neuronal loss are unclear, it is now clear both apoptosis and necrosis are the significant components of cell death following HII. A number of different factors influence whether a cell will undergo apoptosis or necrosis, including the stage of development, cell type, severity of mitochondrial injury and the availability of ATP for apoptotic execution. This review will focus on some pathological mechanisms of cell death in which there is a disruption to oxidative metabolism. The first sections will discuss the process of damage to oxidative metabolism, covering the data collected both from human infants and from animal models. Following sections will deal with the molecular mechanisms that may underlie cerebral energy failure and cell death in this form of brain injury, with a particular emphasis on the role of apoptosis and mitochondria.

Increased expression of c-fos and c-jun in the rat small intestinal epithelium after ischemia-reperfusion injury: a possible correlation with the proliferation or apoptosis of intestinal epithelial cells

BACKGROUND AND PURPOSE

An increased expression of immediate early genes, such as the c-fos and c-jun, is observed in some organs after ischemia-reperfusion (I/R) injury. These factors have been revealed to potentially induce apoptosis and proliferation of the postischemic cells. The purpose of this study is to analyze the relationship between the expression patterns of such immediate early genes and the cellular responses in the intestinal epithelial cells (IECs) after I/R stress.

METHODS

The rat small intestine was reperfused after 30 minutes ischemia. Semiquantitative reverse transcription-polymerase chain reaction was used to quantify c-fos and c-jun messenger RNAs. The proliferation and apoptosis of IECs were detected by immunohistochemistry and the in situ terminal deoxynucleotidyl transferase-mediated dUTP biotin nick-end labeling method, respectively.

RESULTS

The messenger RNA levels of the c-fos and c-jun showed characteristic patterns in the IECs after the I/R stress. The proliferation of the cells was initially observed after the I/R stress, followed by apoptosis of the cells.

CONCLUSIONS

The sequential expression patterns of these factors are possibly related to the proliferation and apoptosis of the IECs.

Extracellular pH changes activate the p38-MAPK signalling pathway in the amphibian heart

We investigated the activation of the p38-MAPK signalling pathway during extracellular pH changes in the isolated perfused amphibian heart. Extracellular alkalosis (pH 8.5 or 9.5) maximally activated p38-MAPK within 2 min (4.17- and 3.20-fold, respectively) and this effect was reversible since the kinase phosphorylation levels decreased upon reperfusing the heart with normal Tris–Tyrode's buffer. Extracellular acidosis also activated p38-MAPK moderately, but persistently (1.65-fold, at 1 min and 1.91-fold, at 60 min). The alkalosis-induced p38-MAPK activation depended upon the Na+/H+ exchanger (NHE) and Na+/K+-ATPase, because it was abolished when the NHE inhibitors amiloride and HOE642 and the Na+/K+-ATPase inhibitor, ouabain, were used. Our studies also showed that extracellular alkalosis (pH 8.5) induced MAPKAPK2 phosphorylation (2.59-fold, 2 min) and HSP27 phosphorylation (5.33-fold, 2 min) in a p38-MAPK-dependent manner, as it was inhibited with 1 μmol l–1 SB203580. Furthermore,immunohistochemical studies of the phosphorylated forms of p38-MAPK and HSP27 revealed that these proteins were localised in the perinuclear region and dispersedly in the cytoplasm of ventricular cells during alkalosis. Finally,alkalosis induced the increase of HSP70 protein levels (1.52-fold, 5 min), but independently of p38-MAPK activation. These data indicate that the p38-MAPK signalling pathway is activated by extracellular pH changes and in the case of alkalosis this activation may have a protective role.

Biologics in the treatment of transplant rejection and ischemia/reperfusion injury: new applications for TNFalpha inhibitors?

Tumor necrosis factor (TNF)-alpha inhibitors have proven efficacy in various autoimmune diseases such as Crohn disease, rheumatoid arthritis, psoriasis, and ankylosing spondylitis. Indeed, some TNFalpha inhibitors have already been approved for the management of the inflammatory manifestations associated with Crohn disease and rheumatoid arthritis. These agents are increasingly used for treatment of corticosteroid-resistant graft-versus-host disease after bone marrow transplantation, and case reports have documented their efficacy in treating corticosteroid- and muromonab-resistant rejection after intestinal transplantation. Thus, the potential role of TNFalpha inhibitors in transplantation of other vascularized solid organs is worthy of investigation. Experimental evidence indicates that TNFalpha plays a key role in mediating ischemia/reperfusion (IR) injury after liver, kidney, intestine, heart, lung, and pancreas transplantation. TNFalpha was also identified as a marker cytokine during organ rejection. Single-center studies evaluating the role of TNFalpha inhibitors in kidney transplantation have been initiated but the results are not yet available. TNFalpha is known to be a contributing factor in kidney allograft rejection, and may have value in predicting the onset of steroid-resistant acute rejection after liver transplantation. Experimental and preliminary clinical data have shown that circulating levels of TNFalpha are increased during cardiac graft rejection, and indicate that TNFalpha plays a role in the pathogenesis of acute cardiac allograft rejection. Anti-TNFalpha therapy was shown to prolong cardiac allograft survival when used alone or in combination with other drugs. TNFalpha genotype has been strongly associated with mortality in humans due to acute cell-mediated heart transplant rejection. In addition, there is evidence for a genetic predisposition toward acute rejection after kidney and simultaneous kidney-pancreas transplantation. TNFalpha inhibition has been used successfully as part of an induction therapy for pancreatic islet cell transplantation. Apart from IR injury and acute rejection after lung transplantation, TNFalpha was also found to be involved in the pathoimmunology of obliterative bronchiolitis. In conclusion, a substantial body of experimental evidence and preliminary clinical data suggest that TNFalpha inhibitors may play an important role in solid-organ transplantation, both in the amelioration of IR injury and in the treatment and prevention of acute rejection. Pharmacodynamic monitoring and pharmacogenetic screening may help to identify patients most likely to benefit from TNFalpha blockade. Randomized controlled trials in patients undergoing solid-organ transplantation are needed to further elucidate the clinical value of TNFalpha inhibition.

Ischemic and nephrotoxic acute renal failure are distinguished by their broad transcriptomic responses

Acute renal failure (ARF) has a high morbidity and mortality. In animal ARF models, effective treatments must be administered before or shortly after the insult, limiting their clinical potential. We used microarrays to identify early biomarkers that distinguish ischemic from nephrotoxic ARF or biomarkers that detect both injury types. We compared rat kidney transcriptomes at 2 and 8 h after ischemia/reperfusion and after mercuric chloride. Quality control and statistical analyses were necessary to normalize microarrays from different lots, eliminate outliers, and exclude unaltered genes. Principal component analysis revealed distinct ischemic and nephrotoxic trajectories and clear array groupings. Therefore, we used supervised analysis, t-tests, and fold changes to compile gene lists for each group, exclusive or nonexclusive, alone or in combination. There was little network connectivity, even in the largest group. Some microarray-identified genes were validated by TaqMan assay, ruling out artifacts. Western blotting confirmed that heme oxygenase-1 (HO-1) and activating transcription factor-3 (ATF3) proteins were upregulated; however, unexpectedly, their localization changed within the kidney. HO-1 staining shifted from cortical (early) to outer stripe of the outer medulla (late), primarily in detaching cells, after mercuric chloride but not ischemia/reperfusion. ATF3 staining was similar, but with additional early transient expression in the outer stripe after ischemia/reperfusion. We conclude that microarray-identified genes must be evaluated not only for protein levels but also for anatomical distribution among different zones, nephron segments, or cell types. Although protein detection reagents are limited, microarray data lay a rich foundation to explore biomarkers, therapeutics, and the pathophysiology of ARF.

Physiological and pathophysiological aspects of ceramide

Activation of cells by receptor- and nonreceptor-mediated stimuli not only requires a change in the activity of signaling proteins but also requires a reorganization of the topology of the signalosom in the cell. The cell membrane contains distinct domains, rafts that serve the spatial organization of signaling molecules in the cell. Many receptors or stress stimuli transform rafts by the generation of ceramide. These stimuli activate the acid sphingomyelinase and induce a translocation of this enzyme onto the extracellular leaflet of the cell membrane. Surface acid sphingomyelinase generates ceramide that serves to fuse small rafts and to form large ceramide-enriched membrane platforms. These platforms cluster receptor molecules, recruit intracellular signaling molecules to aggregated receptors, and seem to exclude inhibitory signaling factors. Thus ceramide-enriched membrane platforms do not seem to be part of a specific signaling pathway but may facilitate and amplify the specific signaling elicited by the cognate stimulus. This general function may enable these membrane domains to be critically involved in the induction of apoptosis by death receptors and stress stimuli, bacterial and viral infections of mammalian cells, and the regulation of cardiovascular functions.

Mitogen-activated protein kinases regulate platelet-activating factor-induced hyperpermeability

OBJECTIVE

The authors tested the hypothesis that p42/44- (ERK-1/2) and/or p38-mitogen-activated protein kinases (MAPK) are in vivo regulatory elements in the platelet-activating factor (PAF) activated signaling cascade that stimulates microvascular hyperpermeability.

METHODS

FITC-dextran 70 was used as the macromolecular tracer for microvascular permeability in the mouse mesenteric fat tissue. Interstitial integrated optical intensity (IOI) was used as an index of permeability.

RESULTS

An application of 10(-7) M PAF increased IOI from 23.1 +/- 3.6 to 70.8 +/- 7.4 (mean +/- SEM). Inhibition of ERK-1/2 with 3 microM and 30 microM AG126 reduced IOI to 32.3 +/- 2.5. Similarly, inhibition of p38-MAPK with 6 nM, 60 nM and 600 nM SB203580 lowered IOI to 29.1 +/- 2.4.

CONCLUSIONS

The results demonstrate that ERK-1/2 and p38MAPK participate in the signaling cascade that regulates PAF-induced microvascular hyperpermeability in vivo.

Interleukin-18 induces human cardiac endothelial cell death via a novel signaling pathway involving NF-κB-dependent PTEN activation

The tumor suppressor gene PTEN (phosphatase and tensin homologue deleted on chromosome 10) antagonizes the pro-survival signaling of Akt and promotes cell death. Previously, we demonstrated that IL-18 induced apoptosis in human cardiac microvascular endothelial cells (HCMEC). Here we have investigated the role of PTEN in this response. Our results demonstrate that IL-18 reduced phospho-Akt and bcl-2 levels, stimulated NF-kappaB activation, and induced PTEN-promoter-reporter activity, mRNA expression, and protein levels in HCMEC. IL-18-mediated PTEN transcription was enhanced by ectopic expression of wild type p65, but inhibited by dominant negative (dn) IkappaB-alpha, dnp65, and dnIKKbeta. Furthermore, overexpression of constitutively active Akt and wild type bcl-2 blocked IL-18-mediated cell death. While forced expression of PTEN potentiated, expression of catalytically inactive PTEN attenuated IL-18-mediated cell death. IL-18-induced activation of NF-kappaB and PTEN upregulation were mediated by p38MAPK. Together, these studies demonstrate a novel signal transduction pathway involving p38MAPK-NF-kappaB-PTEN in IL-18-mediated HCMEC death, and identify IL-18 as potential therapeutic target to inhibit or reduce myocardial inflammation and injury.

A Splice Variant of Stress Response Gene ATF3 Counteracts NF-κB-dependent Anti-apoptosis through Inhibiting Recruitment of CREB-binding Protein/p300 Coactivator

Activating transcription factor (ATF) 3 plays a role in determining cell fate and generates a variety of alternatively spliced isoforms in stress response. We have reported previously that splice variant ATF3deltaZip2, which lacks the leucine zipper region, is induced in response to various stress stimuli. However, its biological function has not been elucidated. By using cells treated with tumor necrosis factor-alpha and actinomycin D or cells overexpressing ATF3deltaZip2, we showed that ATF3deltaZip2 sensitizes cells to apoptotic cell death in response to tumor necrosis factor-alpha, at least in part through suppressing nuclear factor (NF)-kappaB-dependent transcription of anti-apoptotic genes such as cIAP2 and XIAP. ATF3deltaZip2 interacts with a p65 (RelA)-cofactor complex containing CBP/p300 and HDAC1 at NF-kappaB sites of the proximal promoter region of the cIAP2 gene in vivo and down-regulates the recruitment of CBP/p300. Our study revealed that ATF3deltaZip2 counteracts anti-apoptotic activity of NF-kappaB, at least in part, by displacing positive cofactor CBP/p300 and provides insight into the mechanism by which ATF3 regulates cell fate through alternative splicing in stress response.

Signaling Pathways Involved in the Cardioprotective Effects of Cannabinoids

The aim of the present article is to review the cardioprotective properties of cannabinoids, with an emphasis on the signaling pathways involved. Cannabinoids have been reported to protect against ischemia in rat isolated hearts, as well as in rats and mice in vivo. Although these effects have been observed mostly with a pre-treatment of a cannabinoid, we report that the selective CB(2)-receptor agonist JWH133 is able to reduce infarct size when administered either before ischemia, during the entire ischemic period, or just upon reperfusion. Little is known about the signaling pathways involved in these cardioprotective effects. Likely candidates include protein kinase C (PKC) and mitogen-activated protein kinases (MAPK) since they are activated during ischemia-reperfusion and contribute to the protective effect ischemic preconditioning. The use of pharmacological inhibitors suggests that PKC, p38 MAPK, and p42/p44 MAPK (ERK1/2) contribute to the protective effect of cannabinoids. In addition, perfusion with JWH133 in healthy hearts caused an increase in both p38 MAPK phosphorylation level and activity, whereas the CB(1)-receptor agonist ACEA was associated with an increase in the phosphorylation status of both ERK1 and ERK2 without any change in activity. During ischemia, both agonists doubled p38 MAPK activity, whereas ERK1/2 phosphorylation level and activity during reperfusion were enhanced only by the CB(1)-receptor agonist. Finally, although nitric oxide (NO) was shown to exert both pro and anti-apoptotic effects on cardiomyocytes, with an apparently controversial effect on myocardial survival, our data suggest that NO may contribute to the cardioprotective effect of some cannabinoids.

Isoflurane protects renal function against ischemia and reperfusion through inhibition of protein kinases, JNK and ERK

Isoflurane has a pharmacological preconditioning effect against ischemia in the heart and brain, but whether this also occurs in the kidney is unclear. In this study, we investigated pharmacological preconditioning by isoflurane in the rat kidney. In the isoflurane preconditioning group (1.5% isoflurane for 20 min before renal ischemia) serum creatinine (1.2 +/- 0.7 and 1.1 +/- 0.2 mg/dL) and blood urea nitrogen (99 +/- 29 and 187 +/- 31 mg/dL) were significantly smaller at 24 and 48 h after reperfusion than in the nonpreconditioning group (creatinine; 2.4 +/- 1.2 and 2.9 +/- 0.9 mg/dL, urea; 62 +/- 19 and 79 +/- 20 mg/dL). We also investigated the intracellular signal transduction involved in isoflurane preconditioning in the kidney. The activities of the stress protein kinases, JNK and ERK but not p38, were significantly less in the kidneys of the preconditioning group than in those of the nonpreconditioning group (P < 0.05). We conclude that isoflurane has a preconditioning effect against renal ischemia/reperfusion injury when administered before ischemia. Inhibition of the protein kinases, JNK and ERK, might be involved in the mechanisms of isoflurane preconditioning.

p38 Mitogen Activated Protein Kinase Mediates Both Death Signaling and Functional Depression in the Heart

BACKGROUND

Understanding the myocardial inflammatory response to ischemia is an important part of achieving the elusive clinical goal of long-enduring myocardial protection. p38 mitogen-activated protein kinase (MAPK) has been implicated in oxidant stress-induced myocardial tumor necrosis factor production. However, it is unknown whether p38 MAPK mediates the following important events in both myocardial apoptosis and functional depression: mitogen-activated protein kinase-activated protein kinase 2, caspase-1, caspase-3, and caspase-11 activation, and tumor necrosis factor, interleukin-1beta and interleukin-6 production.

METHODS

Isolated rat hearts were perfused and subjected to an ischemia-reperfusion insult, with and without preischemic infusion of 20 microM SB203580 (p38 MAPK inhibitor). Myocardial functional measurements were continuously recorded throughout the experiments. Myocardial tissue was then assessed for products of p38 MAPK activation, expression of tumor necrosis factor, interleukin-1beta and interleukin-6, and activation of caspase-1, caspase-3 and caspase-11.

RESULTS

Postischemic recovery of left ventricular developed pressure, +dP/dt and -dP/dt was significantly increased by p38 MAPK inhibition (MKI) (left ventricular developed pressure: 48.4 +/- 3.87 MKI versus 32.7 +/- 4.32 mm Hg; +dP/dt: 1392.0 +/- 141.7 MKI versus 896.7 +/- 128.5 mm Hg/s; -dP/dt: -889.9 +/- 97.63 MKI versus -548.9 +/- 71.29 mmHg/s). p38 MAPK inhibition also significantly reduced ischemia-reperfusion-induced elevation of left ventricular end-diastolic pressure (82.76 +/- 4.59 MKI vs 69.95 +/- 3.55 mm Hg). p38 MKI decreased myocardial tumor necrosis factor, interleukin-1beta and interleukin-6 protein levels, and reduced active myocardial caspase-1, caspase-3 and caspase-11.

CONCLUSIONS

The p38 MAPK pathway indeed mediates the following important events in myocardial apoptosis and functional depression: mitogen-activated protein kinase-activated protein kinase 2, caspase-1, caspase-3 and caspase-11 activation, and tumor necrosis factor, interleukin-1beta, interleukin-6 production after myocardial ischemia. Single site (p38 MAPK) inhibition of these events may have important therapeutic implications in myocardial protection.

Aprotinin improves kidney function and decreases tubular cell apoptosis and proapoptotic signaling after renal ischemia-reperfusion

OBJECTIVE

The purpose of the study was to determine the effects of aprotinin on (1) renal function, (2) apoptosis and apoptotic signaling, and (3) the inflammatory response of the kidney after ischemia-reperfusion injury.

METHODS

Male rats underwent a sham procedure or left renal ischemia for 1 hour. Rats were divided into three groups and received no reperfusion, reperfusion for 1 hour, or reperfusion for 24 hours. The animals undergoing ischemia received saline solution alone or aprotinin (60,000 kIU/kg). At the end of the experiment, a sample for serum creatinine was taken and the left kidney was harvested. The kidney was analyzed for expression of tumor necrosis factor alpha, interleukin 1beta, and interleukin 6 (enzyme-linked immunosorbent assay and reverse transcriptase-polymerase chain reaction) and activation of p38 mitogen-activated protein kinase, caspase 3, and caspase 8 (Western blot). The kidney was assessed for apoptosis with enzyme-linked immunosorbent assay and by terminal deoxynucleotidyl transferase biotin-deoxyuridine triphosphate nick-end labeling staining of tissue slides.

RESULTS

Aprotinin significantly decreased the rise in serum creatinine and apoptosis caused by ischemia-reperfusion. Aprotinin significantly reduced interleukin 1 and 6 messenger RNA production and showed a trend toward reducing tumor necrosis factor messenger RNA production after ischemia. Aprotinin also significantly reduced caspase 8 activation and showed a trend toward decreasing p38 mitogen-activated protein kinase activation after 1 hour of reperfusion.

CONCLUSION

These results suggest that aprotinin provides protection from renal ischemia-reperfusion injury. They also suggest that aprotinin may do so by affecting apoptotic signaling and inflammatory cytokine production. Aprotinin is a potential therapeutic measure in clinical situations where renal ischemia-reperfusion injury can be anticipated, provided adequate heparinization is possible.

Poly(ADP-ribose) polymerase-mediated cell injury in acute renal failure

Acute Renal Failure (ARF) is the most costly kidney disease in hospitalized patients and remains as a serious problem in clinical medicine. The mortality rate among ARF patients remains around 50% and no pharmaceutical agents are currently available to improve its clinical outcome. Although several successful therapeutic approaches have been developed in animal models of the disease, translation of the results to clinical ARF remains elusive. Understanding the cellular and molecular mechanisms of vascular and tubular dysfunction in ARF is important for developing acceptable therapeutic interventions. Following an ischemic episode, cells of the affected nephron undergo necrotic and/or apoptotic cell death. Necrotic cell death is widely considered to be a futile process that cannot be modulated by pharmacological means as opposed to apoptosis. However, recent reports from various laboratories including ours indicate that inhibition or absence of poly(ADP)-ribose polymerase (PARP), one of the molecules involved in cell death, provides remarkable protection in disease models such as stroke, myocardial infarction and renal ischemia which are characterized predominantly by necrotic type of cell death. Overactivation of PARP in conditions such as ischemic renal injury leads to cellular depletion of its substrate NAD+ and consequently ATP. The severely compromised cellular energetic state induces acute cell injury and diminishes renal functions. PARP activation also enhances the expression of proinflammatory agents and adhesion molecules in ischemic kidneys. Pharmacological inhibition and gene ablation of PARP-1 decreased energy depletion, inflammatory response and improved renal functions in the setting renal ischemia/reperfusion injury. The biochemical pathways and the cellular and molecular mechanisms mediated by PARP-1 activation in eliciting the energy depletion and inflammatory responses in ischemic kidney are not fully elucidated. Dissecting the molecular mechanisms by which PARP activation contributes to oxidant-induced cell death will provide new strategies to interfere in those pathways to modulate cell death in renal ischemia. The current review evaluates the experimental evidences in animal and cell culture models implicating PARP as a pathophysiological modulator of acute renal failure with particular emphasis on ischemic renal injury.

Activation of mitogen-activated protein kinases during human lung transplantation

BACKGROUND

Ischemia-reperfusion is one of the unavoidable steps in lung transplantation; it is associated with acute inflammatory responses and cell death. The intracellular signal transduction mechanisms of these events are largely unknown. We hypothesize that activation of mitogen-activated protein kinases (MAPKs) is one of the important signaling events during human lung transplantation.

METHODS

Lung tissue biopsies were performed on 15 patients undergoing transplantation: after cold ischemic preservation; after warm ischemia (implantation); and after 1- or 2-hour reperfusion. The phosphorylation status of MAPK isoforms (ERK, p38-MAPK and JNK) was examined by Western blotting.

RESULTS

Phosphorylation of ERK was dramatically increased during the first 2 hours of reperfusion. Phosphorylation of JNK also significantly increased at lower levels. In contrast, phosphorylation of p38 showed no significant changes.

CONCLUSIONS

We speculate that the rapid and sustained activation of ERK and JNK during the early reperfusion period may contribute to acute inflammatory responses and cell death of lung grafts.

Wounding activates p38 map kinase and activation transcription factor 3 in leading keratinocytes

Quiescent epidermis anchors to laminin 5 in the basement membrane via integrin alpha6beta4. Wounding elevates expression of laminin 5, generating leading keratinocytes (LKs) that migrate via beta1 integrins. Laminin 5 was evaluated as a regulator of cell signaling, and mRNA and protein expression in LKs. An in vitro wound model was developed based on suspension and re-adhesion of quiescent human keratinocytes (HKs). DNA microarrays identified multiple mRNAs elevated 1.5 hours after suspension and re-adhesion including activation transcription factor 3 (ATF3). In vitro and in vivo, levels of ATF3 protein elevate in nuclei of LKs, but not in nuclei of the following cells, 2 hours after suspension or wounding but decline by 12-18 hours post injury. Significantly, null defects in laminin 5 or integrin beta4 that inhibit anchorage chronically elevate ATF3 in vivo. This suggests that adhesion to laminin 5, but not other ligands, suppresses activation. On suspension, ATF3 and other transcripts in the microarrays are elevated by phosphorylated p38 mitogen-activated protein kinase (P-p38), a stress kinase that regulates mRNA and cell motility. Inhibition of P-p38 with SB203580 prevents phosphorylation of ATF2, a transcription factor for ATF3 in LKs. Re-adhesion to laminin 5 via alpha6beta4 dephosphorylates P-p38 and suppresses ATF3 protein relative to cells in suspension. Thus, wounding of quiescent HKs disrupts laminin 5 adhesion to activate p38, generating mRNA transcripts that define LKs. Adhesion to deposits of laminin 5 via alpha6beta4 suppresses P-p38 and activation mRNAs including ATF3. Defects in laminin 5 and alpha6beta4 sustain P-p38 with probable pathological effects on transcription and migration.

Peroxisome proliferator-activated receptors gamma ligands and ischemia and reperfusion injury

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors that are related to retinoid, steroid and thyroid hormone receptors. The PPAR subfamily comprises of three members, PPAR-alpha, PPAR-beta and PPAR-gamma. PPAR-gamma has recently been implicated as a regulator of cellular proliferation and inflammatory responses. There is good evidence that ligands of PPAR-gamma, including certain thiazolinediones, reduce tissue injury associated with ischemia and reperfusion. The potential utility of PPAR-gamma ligands in ischemia and reperfusion will be discussed in this review.

Mechanical ventilation and acute renal failure

OBJECTIVE

To review the current literature on possible mechanisms by which mechanical ventilation may initiate or aggravate acute renal failure.

DATA SOURCE

A Medline database and references from identified articles were used to perform a literature search relating to mechanical ventilation and acute renal failure.

DATA SYNTHESIS

Acute renal failure may be initiated or aggravated by mechanical ventilation through three different mechanisms. First, strategies such as permissive hypercapnia or permissive hypoxemia may compromise renal blood flow. Second, through effects on cardiac output, mechanical ventilation affects systemic and renal hemodynamics. Third, mechanical ventilation may cause biotrauma-a pulmonary inflammatory reaction that may generate systemic release of inflammatory mediators. The harmful effects of mechanical ventilation may become more significant when a comorbidity is present. In these situations, it is more difficult to maintain normal gas exchange, and moderate arterial hypoxemia and hypercapnia are often accepted. Renal blood flow is compromised due to a decreased cardiac output as a consequence of high intrathoracic pressures. Furthermore, the effects of biotrauma are not limited to the lungs but may lead to a systemic inflammatory reaction.

CONCLUSIONS

The development of acute renal failure during mechanical ventilation likely represents a multifactorial process that may become more important in the presence of comorbidities. Development of optimal interventional strategies requires an understanding of physiologic principles and greater insight into the precise molecular and cellular mechanisms that may also play a role.

Stress response gene ATF3 is a target of c-myc in serum-induced cell proliferation

The c-myc proto-oncogene encodes a transcription factor that promotes cell cycle progression and cell proliferation, and its deficiency results in severely retarded proliferation rates. The ATF3 stress response gene encodes a transcription factor that plays a role in determining cell fate under stress conditions. Its biological significance in the control of cell proliferation and its crosstalk regulation, however, are not well understood. Here, we report that the serum response of the ATF3 gene expression depends on c-myc gene and that the c-Myc complex at ATF/CREB site of the gene promoter plays a role in mediating the serum response. Intriguingly, ectopic expression of ATF3 promotes proliferation of c-myc-deficient cells, mostly by alleviating the impeded G1-phase progression observed in these cells, whereas ATF3 knockdown significantly suppresses proliferation of wild-type cells. Our study demonstrates that ATF3 is downstream of the c-Myc signaling pathway and plays a role in mediating the cell proliferation function of c-Myc. Our results provide a novel insight into the functional link of the stress response gene ATF3 and the proto-oncogene c-myc.

Role of p38 Mitogen-Activated Protein Kinase Activation in Podocyte Injury and Proteinuria in Experimental Nephrotic Syndrome

Podocytes play an important role in maintaining normal glomerular function and structure, and podocyte injury leads to proteinuria and glomerulosclerosis. The family of mitogen-activated protein kinases (MAPK; extracellular signal-regulated kinase [ERK], c-Jun N-terminal kinase, and p38) may be implicated in the progression of various glomerulopathies, but the role of MAPK in podocyte injury remains elusive. This study examined phosphorylation of p38 MAPK in clinical glomerulopathies with podocyte injury, as well as in rat puromycin aminonucleoside (PAN) nephropathy and mouse adriamycin (ADR) nephropathy. The effect of treatment with FR167653, an inhibitor of p38 MAPK, was also investigated in rodent models. In human podocyte injury diseases, the increased phosphorylation of p38 MAPK was observed at podocytes. In PAN and ADR nephropathy, the phosphorylation of p38 MAPK and ERK was marked but transient, preceding overt proteinuria. Pretreatment with FR167653 (day -2 to day 14, subcutaneously) to PAN or ADR nephropathy completely inhibited p38 MAPK activation and attenuated ERK phosphorylation, with complete suppression of proteinuria. Electron microscopy and immunohistochemistry for nephrin and connexin43 revealed that podocyte injury was markedly ameliorated by FR167653. Furthermore, early treatment with FR167653 effectively prevented glomerulosclerosis and renal dysfunction in the chronic phase of ADR nephropathy. In cultured podocytes, PAN or oxidative stress induced the phosphorylation of p38 MAPK along with actin reorganization, and FR167653 inhibited such changes. These findings indicate that the activation of MAPK is necessary for podocyte injury, suggesting that p38 MAPK and, possibly, ERK should become a potential target for therapeutic intervention in proteinuric glomerulopathies.

The role of Akt and mitogen-activated protein kinase systems in the protective effect of poly(ADP-ribose) polymerase inhibition in Langendorff perfused and in isoproterenol-damaged rat hearts

Blocking poly(ADP-ribosyl)ation of nuclear proteins protects the heart from ischemia-reperfusion injury. In addition, activation of Akt and mitogen-activated protein kinase (MAPK) cascades also plays a pivotal role in the survival of cardiomyocytes during ischemia-reperfusion; however, the potential interplay between these pathways is yet to be elucidated. We therefore tested the hypothesis whether poly(ADP-ribose) polymerase (PARP) inhibition can modulate Akt and MAPK signaling of ischemic-reperfused rat hearts. A novel PARP inhibitor, L-2286 [2-[(2-piperidin-1-yletil)thio]quinazolin-4(3H)-one] was administered during ischemia-reperfusion in Langendorff perfused rat hearts and in isoproterenol-induced myocardial infarction. Thereafter, the cardiac energy metabolism, oxidative damage, and the phosphorylation state of Akt and MAPK cascades were monitored. L-2286 exerted significant protective effect against ischemia-reperfusion-induced myocardial injury in both experimental models. More importantly, L-2286 facilitated the ischemia-reperfusion-induced activation of Akt, extracellular signal-regulated kinase, and p38-MAPK in both isolated hearts and in vivo cardiac injury. By contrast, isoproterenol-induced rapid c-Jun N-termainal kinase activation was repressed by L-2286. Here, we provide evidence for the first time that PARP inhibition beneficially modulates the cardiac Akt and MAPK signaling in ex vivo and in vivo ischemia-reperfusion models. We therefore propose that this novel mechanism may contribute to the cardioprotective properties of PARP inhibitors.

Homocysteine activates NADH/NADPH oxidase through ceramide-stimulated Rac GTPase activity in rat mesangial cells

BACKGROUND

We recently demonstrated that homocysteine (Hcys) increases superoxide (O2-) production via NADH/NADPH oxidase in renal mesangial cells. This O2- production contributes to increased expression of tissue inhibitor of metalloproteinase (TIMP-1) and consequent deposition of collagen in response to Hcys. However, the mechanism by which Hcys activates NADH/NADPH oxidase remains unknown. Given that ceramide is an intracellular activator of this oxidase in several cell types, the present study tests the hypothesis that Hcys activates NADH/NADPH oxidase through a ceramide-mediated signaling pathway in rat mesangial (MG) cells, resulting in O2- production.

METHODS

Rat MG cells were incubated with L-homocysteine (L-Hcys) to determine the mechanism by which Hcys activates NADH/NADPH oxidase. Thin layer chromatography (TLC), Western blot analysis, Rac GTPase activity pull down assay, and NADH/NADPH oxidase activity measurements were performed.

RESULTS

TLC analysis demonstrated that L-Hcys increased de novo production of ceramide in MG cells. L-Hcys and increased ceramide did not alter the amount of NADH/NADPH oxidase subunit p47phox and p67phox in both membrane and cytosolic fractions from MG cells. However, L-Hcys or ceramide markedly increased the level of GTP-bound Rac, which was accompanied by enhanced activity of NADH/NADPH oxidase. These Hcys or ceramide-induced actions were substantially blocked by a Rac GTPase inhibitor, GDPbetaS, and a de novo ceramide synthesis inhibitor, fumonisin B1 (FB1).

CONCLUSION

These results indicate that Hcys activates NADH/NADPH oxidase by stimulating de novo ceramide synthesis, and subsequently enhancing Rac GTPase activity in rat MG cells. This ceramide-Rac GTPase signaling pathway may mediate Hcys-induced oxidative stress in these glomerular cells.

Phosphorylation-dependent degradation of p300 by doxorubicin-activated p38 mitogen-activated protein kinase in cardiac cells

p300 and CBP are general transcriptional coactivators implicated in different cellular processes, including regulation of the cell cycle, differentiation, tumorigenesis, and apoptosis. Posttranslational modifications such as phosphorylation are predicted to select a specific function of p300/CBP in these processes; however, the identification of the kinases that regulate p300/CBP activity in response to individual stimuli and the physiological significance of p300 phosphorylation have not been elucidated. Here we demonstrate that the cardiotoxic anticancer agent doxorubicin (adriamycin) induces the phosphorylation of p300 in primary neonatal cardiomyocytes. Hyperphosphorylation precedes the degradation of p300 and parallels apoptosis in response to doxorubicin. Doxorubicin-activated p38 kinases alpha and beta associate with p300 and are implicated in the phosphorylation-mediated degradation of p300, as pharmacological blockade of p38 prevents p300 degradation. p38 phosphorylates p300 in vitro at both the N and C termini of the protein, and enforced activation of p38 by the constitutively active form of its upstream kinase (MKK6EE) triggers p300 degradation. These data support the conclusion that p38 mitogen-activated protein kinase regulates p300 protein stability and function in cardiomyocytes undergoing apoptosis in response to doxorubicin.

Preconditioning with 1,25-Dihydroxyvitamin D3 Protects against Subsequent Ischemia-Reperfusion Injury in the Rat Kidney

BACKGROUND/AIM

Induction of heat shock protein 70 (HSP70) is important in the tolerance of subsequent ischemia-reperfusion (I/R) injury. The aim of this study was to evaluate the effect of HSP70 induction by 1,25-dihydroxyvitamin D3 (VD3) on subsequent I/R injury in rats.

METHODS

HSP70 was induced in Sprague-Dawley rats by VD3 treatment for 7 days, and the effect of VD3 pretreatment on subsequent I/R injury was evaluated in terms of renal function, tubular necrosis score, tumor necrosis factor alpha mRNA expression, mitogen-activated protein kinase expression, and proliferating cell nuclear antigen expression.

RESULTS

VD3 treatment increased HSP70 expression which was localized to renal tubular cells in the outer medulla. Pretreatment with VD3 before I/R injury resulted in (1) decreased blood urea nitrogen and serum creatinine levels; (2) decreased tubular cell necrosis; (3) increased tubular cell proliferation as determined by proliferating cell nuclear antigen expression; (4) decreased tumor necrosis factor alpha mRNA expression, and (5) increased extracellular signal regulated protein kinase and decreased c-Jun N-terminal kinase expression.

CONCLUSION

Our study demonstrates that VD3 is a nontoxic inducer of HSP70 and exerts a protective effect against subsequent I/R injury.

The p38 MAP kinase pathway and its biological function

p38 is a mitogen-activated protein (MAP) kinase with structural and functional characteristics that distinguish it from JNK and ERK MAP kinases. p38 activity is upregulated when cells are exposed to a variety of stimuli including bacterial pathogens, proinflammatory cytokines, certain growth factors, and other forms of environmental stress. By regulating downstream substrates that include protein kinases and transcription factors, p38 participates in transmission, amplification, and diversification of the extracellular signal, initiating several different cellular responses. Studies have revealed that activation of p38 pathway is related to many pathological changes that occur in the course of inflammatory/immunologic and cardiovascular diseases.

p38 MAP kinase inhibition ameliorates cisplatin nephrotoxicity in mice

Cisplatin is an important chemotherapeutic agent but can cause acute renal injury. Part of this acute renal injury is mediated through tumor necrosis factor-alpha (TNF-alpha). The pathway through which cisplatin mediates the production of TNF-alpha and injury is not known. Cisplatin activates p38 MAPK and induces apoptosis in cancer cells. p38 MAPK activation leads to increased production of TNF-alpha in ischemic injury and in macrophages. However, little is known concerning the role of p38 MAPK in cisplatin-induced renal injury. Therefore, we examined the effect of cisplatin on p38 MAPK activity and the role of p38 MAPK in mediating cisplatin-induced TNF-alpha production and renal injury. In vitro, cisplatin caused a dose-dependent activation of p38 MAPK in proximal tubule cells. Inhibition of p38 MAPK activation led to inhibition of TNF-alpha production. In vivo, mice treated with a single dose of cisplatin (20 mg/kg body wt) developed severe renal dysfunction at 72 h [blood urea nitrogen (BUN): 154 +/- 34 mg/dl, creatinine: 1.4 +/- 0.4 mg/dl], which was accompanied by an increase in kidney p38 MAPK activity and an increase in infiltrating leukocytes. However, animals treated with the p38 MAPK inhibitor SKF-86002 along with cisplatin showed less renal dysfunction (BUN: 55 +/- 14 mg/dl, creatinine: 0.3 +/- 0.02 mg/dl, P < 0.05), less severe histological damage, and fewer leukocytes compared with cisplatin+vehicle-treated animals. Serum levels of TNF-alpha, sTNFRI, and sTNFRII also increased significantly in cisplatin-treated mice compared with SKF-86002-treated mice (P < 0.05). Kidney mRNA levels of TNF-alpha were significantly increased in cisplatin-treated mice compared with either SKF-86002- or saline-treated animals. The hydroxyl radical scavenger DMTU (100 mg.kg body wt(-1).day(-1)) prevented the activation of p38 MAPK by cisplatin both in vitro and in vivo. DMTU also completely prevented cisplatin-induced renal injury (BUN: 140 +/- 27 vs. 22 +/- 2 mg/dl, P < 0.005) and the increase in serum TNF-alpha (33 +/- 7 vs. 4 +/- 2 pg/ml, P < 0.005) and kidney TNF-alpha mRNA in vivo. We conclude that hydroxyl radicals, either directly or indirectly, activate p38 MAPK and that p38 MAPK plays an important role in mediating cisplatin-induced acute renal injury and inflammation, perhaps through production of TNF-alpha.

The role of MAP kinases in rapid gene induction after lesioning of the rat sciatic nerve

Lesion of the sciatic nerve caused a rapid activation of p38MAP kinase in the injured nerve adjacent to the site of transection. This activation was detectable 3 min after lesioning, increased during the next 15 min and remained high for several hours. Erk1/2 activation was also observed as early as 15 min after lesioning. Activation of these MAP kinases was seen in both the external sheaths and the endoneurium. The separation of the external sheaths from the endoneurium accelerated the p38MAP kinase activation. To evaluate whether the injury-activated MAP kinase cascades are implicated in the rapid gene induction observed after nerve lesion, experiments were performed with an ex vivo model. Segments of sciatic nerves were incubated in oxygenated Krebs-Ringer buffer. MAP kinases were activated at 15 min and remained active after 6 h. Induction of mRNA was also observed for nerve growth factor (NGF), interleukin 6 (IL-6), leukaemia inhibitory factor (LIF) and deiodinases of type 2 (D2) and type 3 (D3). Thus, the ex vivo model mimics events occurring in the animal after nerve section. Finally, nerve segments were incubated in the presence of specific inhibitors of Erk1/2 activation (U0126) and of p38MAP kinase activity (SB203580). U0126 inhibited D3, LIF and to a lesser extent NGF mRNA induction, but did not affect significantly the induction of D2 and IL-6 mRNAs. SB203580 inhibited the expression of the genes for D3 and LIF. We conclude that MAP kinase cascades, activated by nerve transection, are involved in the rapid gene induction in the nerve.

Activation of ERK or inhibition of JNK ameliorates H(2)O(2) cytotoxicity in mouse renal proximal tubule cells

BACKGROUND

Our previous studies suggest that the balance between the activation of extracellular signal-regulated kinase (ERK) and the c-Jun N-terminal/stress-activated protein kinase (JNK) might determine cell fate following oxidant injury in vivo.

METHODS

The mouse proximal tubule cell line (TKPTS) was used to study hydrogen peroxide (H(2)O(2))-induced death and survival. The role of ERK and JNK in this process was studied by using adenoviruses that contain either a constitutively active mitogen-activated protein kinase kinase 1 (MEK1) or a dominant-negative JNK. Acridine orange plus ethidium bromide staining was applied to distinguish between viable, apoptotic, and necrotic cells following H(2)O(2) treatment. We analyzed cell cycle events by fluorescence-activated cell sorter (FACS) analysis and the phosphorylation status of ERK and JNK by Western blotting.

RESULTS

TKPTS cells survived a moderate level of oxidative stress (0.5 mM/L H(2)O(2)) via temporary growth arrest, while high dose of H(2)O(2) (1 mM/L) caused extensive necrosis. Survival was associated with activation of both ERK and JNK, while death was associated with JNK activation only. Prior adenovirus-mediated up-regulation of ERK or inhibition of JNK function increased the survival (8- or 7-fold, respectively) of TKPTS cells after 1 mmol/L H(2)O(2) treatment. Interestingly, ERK activation and, thus, survival was associated with growth arrest not proliferation.

CONCLUSION

We demonstrate that oxidant injury-induced necrosis could be ameliorated by either up-regulation of endogenous ERK or by inhibition of JNK-related pathways. These results directly demonstrate that the intracellular balance between prosurvival and prodeath mitogen-activated protein kinases (MAPKs) determine proximal tubule cell survival from oxidant injury and reveal possible mediators of survival.

Mechanisms of apoptosis in the heart

Apoptosis is a complex and highly regulated form of cell death, and believed to contribute to the continuous decline of ventricular function in heart failure. Apoptotic cell death is observed in a variety of cardiovascular diseases, including myocardial infarction, ischemia-reperfusion injury, end-stage heart failure, arrhythmias, and adriamycin cardiomyopathy. There are several pathways leading to programmed cell death. Apoptosis can be initiated by extracellular or intracellular stimuli, leading to the activation of caspases and subsequent cell death. A better understanding of the process of apoptosis in the heart is clearly important as it may lead to the identification of novel therapies for cardiovascular disease. This review is focused on the basic cellular mechanisms of apoptosis, as well as our current understanding of this process in the heart.

Oxalate inhibits renal proximal tubule cell proliferation via oxidative stress, p38 MAPK/JNK, and cPLA2 signaling pathways

Exposure of renal proximal tubule cells to oxalate may play an important role in cell proliferation, but the signaling pathways involved in this effect have not been elucidated. Thus the present study was performed to examine the effect of oxalate on 3H-labeled thymidine incorporation and its related signal pathway in primary cultured rabbit renal proximal tubule cells (PTCs). The effects of oxalate on [3H]thymidine incorporation, lactate dehydrogenase (LDH) release, Trypan blue exclusion, H2O2 release, activation of mitogen-activated protein kinases (MAPKs), and 3H-labeled arachidonic acid (AA) release were examined in primary cultured renal PTCs. Oxalate inhibited [3H]thymidine incorporation in a time- and dose-dependent manner. However, its analogs did not affect [3H]thymidine incorporation. Oxalate (1 mM) significantly increased H2O2 release, which was blocked by N-acetyl-l-cysteine (NAC) and catalase (antioxidants). Oxalate significantly increased p38 MAPK and stress-activated protein kinase (SAPK)/c-Jun NH2-terminal kinase (JNK) activity, not p44/42 MAPK. Oxalate stimulated [3H]AA release and translocation of cytosolic phospholipase A2 (cPLA2) from the cytosolic fraction to the membrane fraction. Indeed, oxalate significantly increased prostaglandin E2 (PGE2) production compared with control. Oxalate-induced inhibition of [3H]thymidine incorporation and increase of [3H]AA release were prevented by antioxidants (NAC), a p38 MAPK inhibitor (SB-203580), a SAPK/JNK inhibitor (SP-600125), or PLA2 inhibitors [mepacrine and arachidonyl trifluoromethyl ketone (AACOCF3)], but not by a p44/42 MAPK inhibitor (PD-98059). These findings suggest that oxalate inhibits renal PTC proliferation via oxidative stress, p38 MAPK/JNK, and cPLA2 signaling pathways.

TNFalpha-induced ATF3 expression is bidirectionally regulated by the JNK and ERK pathways in vascular endothelial cells

ATF3 (Activating transcription factor 3), a member of the CREB/ATF family, can be induced by stress and growth factors in mammalian cells, and is thought to play an important role in the cardiovascular system. However, little is currently known about how the induction of ATF3 is regulated, except that the JNK pathway is involved. Here, we investigated the differential roles of the MAPK pathways involved in TNFalpha (tumour necrosis factor alpha)-induced ATF3 expression in vascular endothelial cells. In human umbilical vein endothelial cells, the expression of constitutively active MKK7 (MAPK kinase 7) increased the number of ATF3-positive cells, and dominant negative MKK7 suppressed the TNFalpha-induced expression of ATF3, indicating a requirement for the JNK pathway. In contrast, the expression of constitutively active or dominant negative MEK1/2 (MAPK/ERK kinase 1/2) suppressed or enhanced TNFalpha-mediated induction of ATF3, respectively. In support of this, the MEK1/2 specific inhibitor U0126 enhanced the expression of ATF3 induced by TNFalpha. Furthermore, the ERK pathway inhibits the TNFalpha-mediated induction of ATF3 mRNA, but not its stability, suggesting the involvement of ERK activity in the transcriptional regulation of the ATF3 gene. Our results suggest that TNFalpha-induced ATF3 gene expression is bidirectionally regulated by the JNK and ERK pathways in vascular endothelial cells.