Role of F-actin organization in p38 MAP kinase-mediated apoptosis and necrosis in neonatal rat cardiomyocytes subjected to simulated ischemia and reoxygenation

Unveiling the Therapeutic Potential of Herba Epimedii: Enhancing Bone Healing Through Cytoskeletal Regulation of RhoA/Rock1 Pathway

Herba Epimedii is widely used to promote bone healing, and their active ingredients are total flavonoids of Epimedium (TFE). Ras homolog gene family member A / Rho-associated protein kinase (RhoA/Rock), an important pathway regulating the cytoskeleton, has been proven to affect bone formation. However, whether TFE promotes bone healing via this pathway remains unclear. In this study, the therapeutic effects of TFE were estimated using micro-computed tomography and hematoxylin and eosin staining of pathological sections. F-actin in osteoblasts was stained to investigate the protective effects of TFE on the cytoskeleton. Its regulatory effects on the RhoA/Rock1 pathway were explored using RT-qPCR and Western blot analysis. Besides, flow cytometry, alkaline phosphatase and nodule calcification staining were performed to evaluate the effects on osteogenesis. The bone healing in rats was improved, the cytoskeletal damage in osteoblasts was reduced, the RhoA/Rock1 pathway was downregulated, and osteogenesis was enhanced after TFE treatment. Thus, TFE can promote bone formation at least partially by regulating the expression of key genes and proteins in the cytoskeleton. The findings of this study provided evidence for clinical applications and would contribute to a better understanding of Epimedium's mechanisms in treating bone defects.

Hydrogen sulfide promotes migration of trophoblast cells by a Rho GTPase mediated actin cytoskeleton reorganization

INTRODUCTION

Preeclampsia (PE) arises due to defective spiral artery remodelling which may be due to deficient migration of trophoblast cells. Migration of human endothelial cells has been shown to be promoted via Hydrogen sulphide(H2S)/Rho GTPase Rac1 axis. This novel role of H2S and its downstream processes have not yet been studied in the development and function of the placental trophoblast cells.

METHODS

Placental tissues were obtained post-delivery from consented preeclamptic and normotensive mothers (n = 60). The protein expression levels of cystathionine-gamma-lyase (CSE) and cystathionine-beta-synthase (CBS) along with its downstream migratory molecules were compared in both the arms. The pro-migratory role of H2S was investigated in a first trimester placental cell line.

RESULTS

H2S promoted the migration of trophoblast cells in a Rho GTPase dependent manner mediated by actin cytoskeleton reorganization. The reduced levels of H2S producing enzymes in the PE placentae along with decreased levels of Rho GTPases (Rac1 and Rho A) corroborate the results of PAG and AOAA treatment in down regulating the Rho GTPases in the in vitro grown placental cultures. Reduction of the migratory potential of trophoblastic cells caused due to hypoxia/reoxygenation was rescued by upregulating the H2S expression with the use of NaHS as a H2S donor.

DISCUSSION

Exogenous H2S increases the migratory potential of the placental cells in culture conditions and also post hypoxia/reoxygenation injury. H2S as a gaso-transmitter holds a great potential as a therapeutic agent. Its long-term effects need to be investigated using model systems (rat/mouse) of PE following it up with clinical regulatory trials.

Stabilization of F-Actin Cytoskeleton by Paclitaxel Improves the Blastocyst Developmental Competence through P38 MAPK Activity in Porcine Embryos

Changes in F-actin distribution and cortical F-actin morphology are important for blastocyst developmental competence during embryogenesis. However, the effect of paclitaxel as a microtubule stabilizer on embryonic development in pigs remains unclear. We investigated the role of F-actin cytoskeleton stabilization via P38 MAPK activation using paclitaxel to improve the developmental potential of blastocysts in pigs. In this study, F-actin enrichment and adducin expression based on blastomere fragment rate and cytokinesis defects were investigated in cleaved embryos after in vitro fertilization (IVF). Adducin and adhesive junction F-actin fluorescence intensity were significantly reduced with increasing blastomere fragment rate in porcine embryos. In addition, porcine embryos were cultured with 10 and 100 nM paclitaxel for two days after IVF. Adhesive junction F-actin stabilization and p-P38 MAPK activity in embryos exposed to 10 nM paclitaxel increased significantly with blastocyst development competence. However, increased F-actin aggregation, cytokinesis defects, and over-expression of p-P38 MAPK protein by 100 nM paclitaxel exposure disrupted blastocyst development in porcine embryos. In addition, exposure to 100 nM paclitaxel increased the misaligned α-tubulin of spindle assembly and adhesive junction F-actin aggregation at the blastocyst stage, which might be caused by p-P38 protein over-expression-derived apoptosis in porcine embryos.

Reperfusion Cardiac Injury: Receptors and the Signaling Mechanisms

It has been documented that Ca2+ overload and increased production of reactive oxygen species play a significant role in reperfusion injury (RI) of cardiomyocytes. Ischemia/reperfusion induces cell death as a result of necrosis, necroptosis, apoptosis, and possibly autophagy, pyroptosis and ferroptosis. It has also been demonstrated that the NLRP3 inflammasome is involved in RI of the heart. An increase in adrenergic system activity during the restoration of coronary perfusion negatively affected cardiac resistance to RI. Toll-like receptors are involved in RI of the heart. Angiotensin II and endothelin-1 aggravated ischemic/reperfusion injury of the heart. Activation of neutrophils, monocytes, CD4+ T-cells and platelets contributes to cardiac ischemia/reperfusion injury. Our review outlines the role of these factors in reperfusion cardiac injury.

Annexin A2-Mediated Internalization of Staphylococcus aureus into Bovine Mammary Epithelial Cells Requires Its Interaction with Clumping Factor B

BACKGROUND

Staphylococcus aureus is a leading cause of contagious mastitis in dairy cattle. Internalization of S. aureus by bovine mammary gland epithelial cells is thought to be responsible for persistent and chronic intramammary infection, but the underlying mechanisms are not fully understood.

METHODS

In the present study, we evaluated the role of Annexin A2 (AnxA2), a membrane-binding protein, in S. aureus invasion into bovine mammary epithelial cell line (MAC-T). In vitro binding assays were performed to co-immunoprecipitate the binding proteins of AnxA2 in the lysates of S. aureus.

RESULTS

AnxA2 mediated the internalization but not adherence of S. aureus. Engagement of AnxA2 stimulated an integrin-linked protein kinase (ILK)/p38 MAPK cascade to induce S. aureus invasion. One of the AnxA2-precipitated proteins was identified as S. aureus clumping factor B (ClfB) through use of mass spectrometry. Direct binding of ClfB to AnxA2 was further confirmed by using a pull-down assay. Pre-incubation with recombinant ClfB protein enhanced S. aureus internalization, an effect that was specially blocked by anti-AnxA2 antibody.

CONCLUSION

Our results demonstrate that binding of ClfB to AnxA2 has a function in promoting S. aureus internalization. Targeting the interaction of ClfB and AnxA2 may confer protection against S. aureus mastitis.

P38 mitogen activated protein kinase inhibitor improves platelet in vitro parameters and in vivo survival in a SCID mouse model of transfusion for platelets stored at cold or temperature cycled conditions for 14 days

Platelets for transfusion are stored at room temperature (20-24°C) up to 7 days but decline in biochemical and morphological parameters during storage and can support bacterial proliferation. This decline is reduced with p38MAPK inhibitor, VX-702. Storage of platelets in the cold (4-6°C) can reduce bacterial proliferation but platelets get activated and have reduced circulation when transfused. Thermocycling (cold storage with brief periodic warm ups) reduces some of the effects of cold storage. We evaluated in vitro properties and in vivo circulation in SCID mouse model of human platelet transfusion of platelets stored in cold or thermocycled for 14 days with and without VX-702. Apheresis platelet units (N = 15) were each aliquoted into five storage bags and stored under different conditions: room temperature; cold temperature; thermocycled temperature; cold temperature with VX-702; thermocycled temperature with VX-702. Platelet in vitro parameters were evaluated at 1, 7 and 14 days. On day 14, platelets were infused into SCID mice to assess their retention in circulation by flow cytometry. VX-702 reduced negative platelet parameters associated with cold and thermocycled storage such as an increase in expression of activation markers CD62, CD63 and of phosphatidylserine (marker of apoptosis measured by Annexin binding) and lowered the rise in lactate (marker of increase in anaerobic metabolism). However, VX-702 did not inhibit agonist-induced platelet aggregation indicating that it does not interfere with platelet hemostatic function. In vivo, VX-702 improved initial recovery and area under the curve in circulation of human platelets infused into a mouse model that has been previously validated against a human platelet infusion clinical trial. In conclusion, inhibition of p38MAPK during 14-days platelet storage in cold or thermocycling conditions improved in vitro platelet parameters and platelet circulation in the mouse model indicating that VX-702 may improve cell physiology and clinical performance of human platelets stored in cold conditions.

The Role of Heat Shock Proteins in Regulating Receptor Signal Transduction

Heat shock proteins (Hsp) are a class of stress-inducible proteins that mainly act as molecular protein chaperones. This chaperone activity is diverse, including assisting in nascent protein folding and regulating client protein location and translocation within the cell. The main proteins within the Hsp family, particularly Hsp70 and Hsp90, also have a highly diverse and numerous set of protein clients, which when combined with the high expression levels of Hsp proteins (2%-6% of total protein content) establishes these molecules as "central regulators" of cell protein physiology. Among the client proteins, Hsps regulate numerous signal-transduction and receptor-regulatory kinases, and indeed directly regulate some receptors themselves. This also makes the Hsps, particularly Hsp90, central regulators of signal-transduction machinery, with important impacts on endogenous and drug ligand responses. Among these roles, Hsp90 in particular acts to maintain mature signaling kinases in a metastable conformation permissive for signaling activation. In this review, we will focus on the roles of the Hsps, with a special focus on Hsp90, in regulating receptor signaling and subsequent physiologic responses. We will also explore potential means to manipulate Hsp function to improve receptor-targeted therapies. Overall, Hsps are important regulators of receptor signaling that are receiving increasing interest and exploration, particularly as Hsp90 inhibitors progress toward clinical approval for the treatment of cancer. Understanding the complex interplay of Hsp regulation of receptor signaling may provide important avenues to improve patient treatment.

Crosstalk between mitogen-activated protein kinases and mitochondria in cardiac diseases: therapeutic perspectives

Cardiovascular diseases cause more mortality and morbidity worldwide than any other diseases. Although many intracellular signaling pathways influence cardiac physiology and pathology, the mitogen-activated protein kinase (MAPK) family has garnered significant attention because of its vast implications in signaling and crosstalk with other signaling networks. The extensively studied MAPKs ERK1/2, p38, JNK, and ERK5, demonstrate unique intracellular signaling mechanisms, responding to a myriad of mitogens and stressors and influencing the signaling of cardiac development, metabolism, performance, and pathogenesis. Definitive relationships between MAPK signaling and cardiac dysfunction remain elusive, despite 30 years of extensive clinical studies and basic research of various animal/cell models, severities of stress, and types of stimuli. Still, several studies have proven the importance of MAPK crosstalk with mitochondria, powerhouses of the cell that provide over 80% of ATP for normal cardiomyocyte function and play a crucial role in cell death. Although many questions remain unanswered, there exists enough evidence to consider the possibility of targeting MAPK-mitochondria interactions in the prevention and treatment of heart disease. The goal of this review is to integrate previous studies into a discussion of MAPKs and MAPK-mitochondria signaling in cardiac diseases, such as myocardial infarction (ischemia), hypertrophy and heart failure. A comprehensive understanding of relevant molecular mechanisms, as well as challenges for studies in this area, will facilitate the development of new pharmacological agents and genetic manipulations for therapy of cardiovascular diseases.

An inhibition of p38 mitogen activated protein kinase delays the platelet storage lesion

BACKGROUND AND OBJECTIVES

Platelets during storage undergo diverse alterations collectively known as the platelet storage lesion, including metabolic, morphological, functional and structural changes. Some changes correlate with activation of p38 mitogen activated protein kinase (p38 MAPK). Another MAPK, extracellular signal-related kinase (ERK), is involved in PLT activation. The aim of this study was to compare the properties of platelets stored in plasma in the presence or absence of p38 and ERK MAPK inhibitors.

MATERIALS AND METHODS

A single Trima apheresis platelet unit (n = 12) was aliquoted into five CLX storage bags. Two aliquots were continuously agitated with or without MAPK inhibitors. Two aliquots were subjected to 48 hours of interruption of agitation with or without MAPK inhibitors. One aliquot contained the same amount of solvent vehicle used to deliver the inhibitor. Platelets were stored at 20-24°C for 7 days and sampled on Days 1, 4, and 7 for 18 in vitro parameters.

RESULTS

Inhibition of p38 MAPK by VX-702 leads to better maintenance of all platelet in vitro storage parameters including platelet mitochondrial function. Accelerated by interruption of agitation, the platelet storage lesion of units stored with VX-702 was diminished to that of platelets stored with continuous agitation. Inhibition of ERK MAPK did not ameliorate decrements in any in vitro platelet properties.

CONCLUSION

Signaling through p38 MAPK, but not ERK, is associated with platelet deterioration during storage.

Dual modes of antitumor action of an amphiphilic peptide A(9)K

Following our recent report of attractive antibacterial properties of a designed amphiphilic peptide, A(9)K, we have investigated its antitumor activities by examining the modes of its action against different mammalian cell types. The peptide strongly inhibited the growth of cancerous HeLa cells and human promyelocytic leukemia HL60 cells whilst remaining benign to the host cells, including Cos 7 cells, mouse fibroblast NIH3T3 cells and human red blood cells. Images from SEM and fluorescence microscopy showed that A(9)K penetrated HeLa cell membranes and disrupted membrane structures, a feature broadly similar to that observed from its bactericidal actions. Further interactions of A(9)K with inner cellular membranes caused mitochondrial dysfunction associated with the F-actin reorganization and the decreased transcription of bcl-2 and c-myc genes, resulting in HeLa cell apoptosis in a mitochondria-induced apoptosis pathway. Thus A(9)K has high selectivity against cancerous cells and kills them by dual modes of action: membrane disruption and cell apoptosis. In addition, the peptide does not induce non-specific immunological effects and is not degraded by proteases. These features are crucial for developing their applications in future research.

Role of p38 inhibition in cardiac ischemia/reperfusion injury

The p38 mitogen-activated protein kinases (p38s) are Ser/Thr kinases that are activated as a result of cellular stresses and various pathological conditions, including myocardial ischemia/reperfusion. p38 activation has been shown to accentuate myocardial injury and impair cardiac function. Inhibition of p38 activation and its activity has been proposed to be cardioprotective by slowing the rate of myocardial damage and improving cardiac function. The growing body of evidence on the use of p38 inhibitors as therapeutic means for responding to heart problems is controversial, since both beneficial as well as a lack of protective effects on the heart have been reported. In this review, the outcomes from studies investigating the effect of p38 inhibitors on the heart in a wide range of study models, including in vitro, ex vivo, and in vivo models, are discussed. The correlations of experimental models with practical clinical usefulness, as well as the need for future studies regarding the use of p38 inhibitors, are also addressed.

Distortion of axonal cytoskeleton: an early sign of glaucomatous damage

PURPOSE

Glaucoma damages the retinal nerve fiber layer (RNFL). The purpose of this study was to investigate the distribution of major cytoskeleton components, F-actin, microtubules (MTs), and neurofilaments (NFs), in the RNFL during the development of glaucoma. methods: Intraocular hypertension was induced in a rat model by laser photocoagulation of the trabecular meshwork. Retinas were obtained after 2 to 3.5 weeks of treatment. Multiple fluorescent stains were used to identify F-actin, MTs, NFs, and nuclei simultaneously in the same tissue. Distribution of these components in a whole-mounted retina was examined by confocal microscopy. Fluorescent stain was quantitatively described.

RESULTS

In normal RNFL F-actin, MTs, and NFs were intensely stained. Along the bundles, F-actin and MTs were strongly colocalized, but alternating strands of F-actin and NFs were apparent. Normal RNFL lacked nuclei. In glaucomatous retinas, irregular staining of F-actin, MTs, and NFs was found within the bundles. A strong network of F-actin appeared on the RNFL surface and between the bundles. In severely damaged retinal regions total loss of F-actin and MTs was found, whereas residual strands of NFs were evident. Before the decrease in RNFL thickness, irregularity of F-actin stain and density of nuclei in the RNFL significantly increased.

CONCLUSIONS

The results suggest that F-actin, MTs, and NFs are rich and approximately uniformly distributed in the normal RNFL. Glaucoma causes alteration of the cytoskeleton in the RNFL. F-actin is the most sensitive component in its response to stress on the retina. An increase in the number of nuclei in the RNFL may be an early sign of glaucomatous damage.

Rottlerin Inhibits Lonicera japonica-Induced Photokilling in Human Lung Cancer Cells through Cytoskeleton-Related Signaling Cascade

This study demonstrated that many apoptotic signaling pathways, such as Rho family, PKC family, MAP kinase family, and mitochondria-mediated apoptotic pathway, were triggered by Lonicera japonica extracts and irradiation in CH27 cells. Rottlerin, a PKCδ -selective inhibitor, reversed the photoactivated Lonicera japonica extract-induced decrease in PKCδ protein expression and change in cell morphology in this study. In addition, rottlerin inhibited the photoactivated Lonicera japonica-induced decrease in protein expression of Ras, ERK, p38, PKCα, and PKCε, which are the kinases of prosurvival signaling pathway. We also demonstrated that pretreatment with rottlerin prevented actin microfilaments and microtubules from damage during the photoactivated Lonicera japonica-induced CH27 cell death. Furthermore, the promotion of the cytoskeleton-related signaling cascade following rottlerin by upregulation of cytoskeleton-related mediators (p38, HSP27, FAK, paxillin, and tubulin) and molecules of downstream of F-actin (mitochondria-mediated apoptosis pathway) reduces CH27 cell death, indicating that cytoskeleton is the potential target in the photoactivated Lonicera japonicaextract-induced photokilling of CH27 cells.

Photodynamic activity of aloe-emodin induces resensitization of lung cancer cells to anoikis

Aloe-emodin was found to be a photosensitizer and possess anti-tumor activity. However, the detailed mechanism underlying the biological effects of aloe-emodin remains unknown. In this study, we explored the mechanisms of photocytotoxicity induced by aloe-emodin in lung cancer H460 cells. According to the results of the photoactivated aloe-emodin-induced disruption of cytoskeleton, we verify that aloe-emodin with irradiation induces anoikis of H460 cells. Photosensitized aloe-emodin-induced anoikis is associated with the protein expression of α-actinin and mitogen-activated protein (MAP) kinase members. In this study, a rapid opening of the mitochondrial permeability transition pore and the change in apoptosis-related protein expression were involved in photoactivated aloe-emodin-induced cell death. We also demonstrated that anoikis induced by aloe-emodin with irradiation is mediated through the intrinsic and extrinsic death pathways in a caspase-dependent manner in H460 cells.

Proteomic analysis reveals ATP-dependent steps and chaperones involvement in luteolin-induced lung cancer CH27 cell apoptosis

The present study applied 2D electrophoresis to analyze the proteins involved in luteolin (50 microM)-induced CH27 cell apoptosis. We found 7 proteins to be markedly changed. According to the data of analysis of these protein spots, we hypothesized that ATP synthetic pathway and heat shock proteins were involved in luteolin-induced CH27 cell apoptosis. In this study, luteolin induced a significant change in intracellular ATP levels and mitochondrial activity of CH27 cells. Further experiments demonstrated that pretreatment with forskolin blocked the luteolin-induced cell death. P38 and heat shock protein 27 may be important participants in the luteolin-induced changes in organization of actin microfilaments in this study. In addition, endoplasmic reticulum stress is also important in the luteolin-induced CH27 cell apoptosis. Our findings suggested that the function of mitochondria and endoplasmic reticulum is the integral factor in luteolin-induced CH27 cell apoptosis.

Proteomic profiling of medial degeneration in human ascending aorta

OBJECTIVE

The objective of this study was the construction of a reference map for aortic medial degeneration by a proteomic approach.

DESIGN AND METHODS

A proteomic profiling of the media of human ascending aorta was performed by two-dimensional electrophoresis and MALDI-TOF mass spectrometry.

RESULTS

A reliable protocol for two-dimensional electrophoresis analysis of human aortic media proteins was developed allowing the selection and identification of 52 spots. Protein identifications revealed that the predominant vascular smooth muscle cell proteins isolated from grade 1 aortic medial degeneration (MD) included proteins involved in muscle contraction, protein folding, cytoskeletal structure and metabolic processes, and those with antioxidant or transport functions. The most populated functional classes were those related to muscle contraction and cytoskeletal proteins, including actin, calmodulin, calponin, myosin light chain, tropomyosin, vimentin, profilin and transgelin.

CONCLUSIONS

The obtained aortic MD proteomic profile provides a relevant background for future studies aimed to find further specific molecular changes potentially related to the aortic MD process.

Heat shock protein 27 phosphorylation: kinases, phosphatases, functions and pathology

The small heat shock protein Hsp27 or its murine homologue Hsp25 acts as an ATP-independent chaperone in protein folding, but is also implicated in architecture of the cytoskeleton, cell migration, metabolism, cell survival, growth/differentiation, mRNA stabilization, and tumor progression. A variety of stimuli induce phosphorylation of serine residues 15, 78, and 82 in Hsp27 and serines 15 and 86 in Hsp25. This post-translational modification affects some of the cellular functions of Hsp25/27. As a consequence of the functional importance of Hsp25/27 phosphorylation, aberrant Hsp27 phosphorylation has been linked to several clinical conditions. This review focuses on the different Hsp25/27 kinases and phosphatases that regulate the phosphorylation pattern of Hsp25/27, and discusses the recent findings of the biological implications of these phosphorylation events in physiological and pathological processes. Novel therapeutic strategies aimed at restoring anomalous Hsp27 phosphorylation in human diseases will be presented.

Kinetics of the translocation and phosphorylation of alphaB-crystallin in mouse heart mitochondria during ex vivo ischemia

alphaB-crystallin (alphaBC) is a small heat shock protein expressed at high levels in the myocardium where it protects from ischemia-reperfusion damage. Ischemia-reperfusion activates p38 MAP kinase, leading to the phosphorylation of alphaBC on serine 59 (P-alphaBC-S59), enhancing its ability to protect myocardial cells from damage. In the heart, ischemia-reperfusion also causes the translocation of alphaBC from the cytosol to other cellular locations, one of which was recently shown to be mitochondria. However, it is not known whether alphaBC translocates to mitochondria during ischemia-reperfusion, nor is it known whether alphaBC phosphorylation takes place before or after translocation. In the present study, analyses of mitochondrial fractions isolated from mouse hearts subjected to various times of ex vivo ischemia-reperfusion showed that alphaBC translocation to mitochondria was maximal after 20 min of ischemia and then declined steadily during reperfusion. Phosphorylation of mitochondrial alphaBC was maximal after 30 min of ischemia, suggesting that at least in part it occurred after alphaBC association with mitochondria. Consistent with this was the finding that translocation of activated p38 to mitochondria was maximal after only 10 min of ischemia. The overexpression of alphaBC-AAE, which mimics alphaBC phosphorylated on serine 59, has been shown to stabilize mitochondrial membrane potential and to inhibit apoptosis. In the present study, infection of neonatal rat cardiac myocytes with adenovirus-encoded alphaBC-AAE decreased peroxide-induced mitochondrial cytochrome c release. These results suggest that during ischemia alphaBC translocates to mitochondria, where it is phosphorylated and contributes to modulating mitochondrial damage upon reperfusion.

Hyperosmotic stress induces Rho/Rho kinase/LIM kinase-mediated cofilin phosphorylation in tubular cells: key role in the osmotically triggered F-actin response

Hyperosmotic stress induces cytoskeleton reorganization and a net increase in cellular F-actin, but the underlying mechanisms are incompletely understood. Whereas de novo F-actin polymerization likely contributes to the actin response, the role of F-actin severing is unknown. To address this problem, we investigated whether hyperosmolarity regulates cofilin, a key actin-severing protein, the activity of which is inhibited by phosphorylation. Since the small GTPases Rho and Rac are sensitive to cell volume changes and can regulate cofilin phosphorylation, we also asked whether they might link osmostress to cofilin. Here we show that hyperosmolarity induced rapid, sustained, and reversible phosphorylation of cofilin in kidney tubular (LLC-PK1 and Madin-Darby canine kidney) cells. Hyperosmolarity-provoked cofilin phosphorylation was mediated by the Rho/Rho kinase (ROCK)/LIM kinase (LIMK) but not the Rac/PAK/LIMK pathway, because 1) dominant negative (DN) Rho and DN-ROCK but not DN-Rac and DN-PAK inhibited cofilin phosphorylation; 2) constitutively active (CA) Rho and CA-ROCK but not CA-Rac and CA-PAK induced cofilin phosphorylation; 3) hyperosmolarity induced LIMK-2 phosphorylation, and 4) inhibition of ROCK by Y-27632 suppressed the hypertonicity-triggered LIMK-2 and cofilin phosphorylation.We thenexamined whether cofilin and its phosphorylation play a role in the hypertonicity-triggered F-actin changes. Downregulation of cofilin by small interfering RNA increased the resting F-actin level and eliminated any further rise upon hypertonic treatment. Inhibition of cofilin phosphorylation by Y-27632 prevented the hyperosmolarity-provoked F-actin increase. Taken together, cofilin is necessary for maintaining the osmotic responsiveness of the cytoskeleton in tubular cells, and the Rho/ROCK/LIMK-mediated cofilin phosphorylation is a key mechanism in the hyperosmotic stress-induced F-actin increase.

A novel protein kinase A-independent, beta-arrestin-1-dependent signaling pathway for p38 mitogen-activated protein kinase activation by beta2-adrenergic receptors

A growing body of evidence has demonstrated that p38 mitogen-activated protein kinase (MAPK) has a crucial role in various physiological and pathological processes mediated by beta(2)-adrenergic receptors (beta(2)-ARs). However, the detailed mechanism of beta(2)-ARs-induced p38 MAPK activation has not yet been fully defined. The present study demonstrates a novel kinetic model of p38 MAPK activation induced by beta(2)-ARs in human embryonic kidney 293A cells. The beta(2)-AR agonist isoproterenol induced a time-dependent biphasic phosphorylation of p38 MAPK: the early phase peaked at 10 min, and was followed by a delayed phase that appeared at 90 min and was sustained for 6 h. Interestingly, inhibition of the cAMP/protein kinase A (PKA) pathway failed to affect the early phosphorylation but abolished the delayed activation. By contrast, silencing of beta-arrestin-1 expression by small interfering RNA inhibited the early phase activation of p38 MAPK. Furthermore, the NADPH oxidase complex is a downstream target of beta-arrestin-1, as evidenced by the fact that isoproterenol-induced Rac1 activation was also suppressed by beta-arrestin-1 knockdown. In addition, early phase activation of p38 MAPK was prevented by inactivation of Rac1 and NADPH oxidase by pharmacological inhibitors, overexpression of a dominant negative mutant of Rac1, and p47(phox) knockdown by RNA interference. Of note, we demonstrated that only early activation of p38 MAPK is involved in isoproterenol-induced F-actin rearrangement. Collectively, these data suggest that the classic cAMP/PKA pathway is responsible for the delayed activation, whereas a beta-arrestin-1/Rac1/NADPH oxidase-dependent signaling is a heretofore unrecognized mechanism for beta(2)-AR-mediated early activation of p38 MAPK.

The action of nitric oxide to enhance cell survival in chick cardiomyocytes is mediated through a cGMP and ERK1/2 pathway while p38 mitogen-activated protein kinase-dependent pathways do not alter cell death

The objective of this study was to determine whether the dual action of nitric oxide (NO) on cardiomyocyte cell viability is mediated through p38 mitogen-activated protein kinase (MAPK)-induced cell death and extracellular signal-regulated kinase (ERK1/2)-mediated cell survival pathways, and whether either of these is mediated through a cGMP-protein kinase G (PKG) pathway. Cell viability of embryonic chick cardiomyocytes was assessed by the MTT assay, which is based on the ability of viable cells to reduce 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide. The NO donor sodium nitroprusside (SNP) produced a significant (P < 0.01) concentration-dependent reduction in cell viability or increase in cell death. Sodium nitroprusside induced ERK1/2 phosphorylation, and the mitogen-activated protein kinase (MEK1/2) inhibitor PD 98059 significantly increased cell death. In contrast, SB202190, a relatively selective inhibitor of p38 MAPK, did not affect SNP-induced cell death. The cardioprotective effect of NO was prbably mediated in part via cGMP because 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, a selective inhibitor of NO-sensitive guanylyl cyclase, produced a significant enhancement of SNP-induced cell death. In contrast, the PKG inhibitor KT5823 did not affect cell viability. In summary, these data suggest that NO, via stimulation of soluble guanylyl cyclase, activates MEK1/2 whose product, ERK1/2, protects against cell death. In contrast, SNP-induced p38 MAPK activation does not modulate NO-induced cardiomyocyte cell death. Not all cGMP targets affect NO-induced cell death, since the PKG pathway does not enhance or suppress NO-induced cardiomyocyte cell death. Enhancement of the ERK1/2 responses to NO may permit the beneficial effects of NO to predominate.

Myocardial ischemia/reperfusion causes VDAC phosphorylation which is reduced by cardioprotection with a p38 MAP kinase inhibitor

Myocardial ischemia (MI) and reperfusion (R) results in activation of the p38 MAP kinase pathway. This pathway phosphorylates transcription factors and cytoplasmic proteins leading to expression of adhesion molecules and cytokines, increased neutrophil activation, and finally, myocardial necrosis and apoptosis. We studied the effects of a p38 MAP kinase inhibitor, PD169316, on cardioprotection, protein expression, and tyrosine phosphorylation, in a rabbit model of 1 h of (MI) and 3 h of (R). PD169316 administered just before (R) significantly reduced myocardial neutrophil accumulation, necrosis area (28.4 +/- 7.9% vs. 56.4 +/- 7.9% necrosis/AAR), and CK release compared to a vehicle treated group (p<0.05). We found several proteins altered in expression following MI + R alone or with p38 inhibition including myofilament proteins, energetics proteins, heat shock proteins, and the mitochondrial porin VDAC-1. p38 MAPK inhibition significantly reduced the phosphorylation of VDAC-1 which is a known mitochondrial regulator of cell survival. Thus, p38 MAP kinase inhibition with PD169316 is cardioprotective, reduces neutrophil activation, and controls protein expression and phosphorylation in MI and reperfusion.

Ischemic preconditioning: from molecular mechanisms to therapeutic opportunities

Ischemia/reperfusion (I/R) injury is a major contributory factor to cardiac dysfunction and infarct size that determines patient prognosis after acute myocardial infarction. Considerable interest exists in harnessing the heart's endogenous capacity to resist I/R injury, known as ischemic preconditioning (IPC). The IPC research has contributed to uncovering the pathophysiology of I/R injury on a molecular and cellular basis and to invent potential therapeutic means to combat such damage. However, the translation of basic research findings learned from IPC into clinical practice has often been inadequate because the majority of basic research findings have stemmed from young and healthy animals. Few if any successful implementations of IPC have occurred in the diseased hearts that are the primary target of viable therapies activating cardioprotective mechanisms to limit cardiac dysfunction and infarct size. Therefore, the first purpose of this review is to facilitate understanding of pathophysiology of I/R injury and the mechanisms of cardioprotection afforded by IPC in the normal heart. Then I focus on the problems and opportunities for successful bench-to-bedside translation of IPC in the diseased hearts.

Oxidative stress and adenosine A1 receptor activation differentially modulate subcellular cardiomyocyte MAPKs

The mechanism by which distinct stimuli activate the same mitogen-activated protein kinases (MAPKs) is unclear. We examined compartmentalized MAPK signaling and altered redox state as possible mechanisms. Adult rat cardiomyocytes were exposed to the adenosine A1 receptor agonist 2-chloro- N6-cyclopentyladenosine (CCPA; 500 nM) or H2O2 (100 μM) for 15 min. Nuclear/myofilament, cytosolic, Triton-soluble membrane, and Triton-insoluble membrane fractions were generated. CCPA and H2O2 activated p38 MAPK and p44/p42 ERKs in cytosolic fractions. In Triton-soluble membrane fractions, H2O2 activated p38 MAPK and p42 ERK, whereas CCPA had no effect on MAPK activation in this fraction. The greatest difference between H2O2 and CCPA was in the Triton-insoluble membrane fraction, where H2O2 increased p38 and p42 activation and CCPA reduced MAPK activation. CCPA also increased protein phosphatase 2A activity in the Triton-insoluble membrane fraction, suggesting that the activation of this phosphatase may mediate CCPA effects in this fraction. The Triton-insoluble membrane fraction was enriched in the caveolae marker caveolin-3, and >85% of p38 MAPK and p42 ERK was bound to this scaffolding protein in these membranes, suggesting that caveolae may play a role in the divergence of MAPK signals from different stimuli. The antioxidant N-2-mercaptopropionyl glycine (300 μM) reduced H2O2-mediated MAPK activation but failed to attenuate CCPA-induced MAPK activation. H2O2 but not CCPA increased reactive oxygen species (ROS). Thus the adenosine A1 receptor and oxidative stress differentially modulate subcellular MAPKs, with the main site of divergence being the Triton-insoluble membrane fraction. However, the adenosine A1 receptor-mediated MAPK activation does not involve ROS formation.

Amplification of PVT1 contributes to the pathophysiology of ovarian and breast cancer

PURPOSE

This study was designed to elucidate the role of amplification at 8q24 in the pathophysiology of ovarian and breast cancer because increased copy number at this locus is one of the most frequent genomic abnormalities in these cancers.

EXPERIMENTAL DESIGN

To accomplish this, we assessed the association of amplification at 8q24 with outcome in ovarian cancers using fluorescence in situ hybridization to tissue microarrays and measured responses of ovarian and breast cancer cell lines to specific small interfering RNAs against the oncogene MYC and a putative noncoding RNA, PVT1, both of which map to 8q24.

RESULTS

Amplification of 8q24 was associated with significantly reduced survival duration. In addition, small interfering RNA-mediated reduction in either PVT1 or MYC expression inhibited proliferation in breast and ovarian cancer cell lines in which they were both amplified and overexpressed but not in lines in which they were not amplified/overexpressed. Inhibition of PVT1 expression also induced a strong apoptotic response in cell lines in which it was overexpressed but not in lines in which it was not amplified/overexpressed. Inhibition of MYC, on the other hand, did not induce an apoptotic response in cell lines in which MYC was amplified and overexpressed.

CONCLUSIONS

These results suggest that MYC and PVT1 contribute independently to ovarian and breast pathogenesis when overexpressed because of genomic abnormalities. They also suggest that PVT1-mediated inhibition of apoptosis may explain why amplification of 8q24 is associated with reduced survival duration in patients treated with agents that act through apoptotic mechanisms.

Role of p38 mitogen-activated protein kinase pathway on heart failure in the infant rat after burn injury

We examined the hypothesis that post-burn activation of the p38 mitogen-activated protein kinase (MAPK) pathway is one aspect of the signalling cascade culminating in post-burn secretion of tumour necrosis factor (TNF)-alpha which contributes to post-burn myocardial apoptosis. Studies were designed to determine the time course of the induction of p38MAPK, TNF-alpha and myocardial apoptosis after burn injury. Our quantitative bacterial culture data demonstrated that viable bacteria reached the heart, and Western blotting data identified the increase in the phosphorylation of p38MAPK at an early time after burn. The peak incidence of myocardial apoptosis was also seen at an early time after burn. The expression of TNF-alpha mRNA, infiltrated neutrophils and serum creatine phosphokinase myocardial band data peaked at a late time after burn. FR167653, a specific inhibitor of p38MAPK, prevented the induction of myocardial apoptosis, TNF-alpha expression and myocardial injury after burn. Presumably, the bacterial LPS-induced activation of p38MAPK pathway occurring at an early time after burn induced the subsequent myocardial apoptosis. The p38MAPK-induced activation of pro-inflammatory cytokine appeared to promote the degenerative myocardial injury at a late time after burn. Our present data provided evidence for the hypothesis that the p38MAPK pathway controls both myocardial apoptosis and the pro-inflammatory mediator.

Potential of p38-MAPK inhibitors in the treatment of ischaemic heart disease

Chronic heart failure is debilitating, often fatal, expensive to treat and common. In most patients it is a late consequence of myocardial infarction (MI). The intracellular signals following infarction that lead to diminished contractility, apoptosis, fibrosis and ultimately heart failure are not fully understood but probably involve p38-mitogen activated protein kinases (p38), a family of serine/threonine kinases which, when activated, cause cardiomyocyte contractile dysfunction and death. Pharmacological inhibitors of p38 suppress inflammation and are undergoing clinical trials in rheumatoid arthritis, Chrohn's disease, psoriasis and surgery-induced tissue injury. In this review, we discuss the mechanisms, circumstances and consequences of p38 activation in the heart. The purpose is to evaluate p38 inhibition as a potential therapy for ischaemic heart disease.

Role of p38 mitogen-activated protein kinase on cardiac dysfunction after hemorrhagic shock in rats

Cardiac dysfunction is a well-known complication of hemorrhagic shock as a consequence of local inflammatory response. Several studies have indicated that p38 mitogen-activated protein kinase (MAPK) is a key mediator in organ dysfunction that is associated with the inflammatory state through the activation of proinflammatory cytokines such as TNF-alpha and IL-1beta. Whether the same applies to cardiac dysfunction after hemorrhagic shock has not been clearly determined. Therefore, in this study, the role of p38 MAPK on cardiac dysfunction after hemorrhagic shock was studied up to 5 h after a hemorrhage using FR167653, a specific inhibitor of p38 MAPK phosphorylation. The p38 MAPK phosphorylation, the cardiac mRNA expressions of TNF-alpha and IL-1beta, and intracardiac serum concentrations of each cytokine and creatine phosphokinase-MB isozyme increased after a hemorrhage. Activated neutrophil accumulation in the heart, histological inflammation-related injuries, and frequent ventricular arrhythmia were observed in the late phase after hemorrhagic shock. FR167653 inhibited these hemorrhagic changes except the induction of the primary hypotensive state. These results demonstrate that p38 MAPK phosphorylation in hemorrhagic shock plays an important role in the cardiac expression of the proinflammatory cytokines and in the development of cardiac dysfunction relative to the inflammatory responses.

Interactive effects of surface topography and pulsatile electrical field stimulation on orientation and elongation of fibroblasts and cardiomyocytes

In contractile tissues such as myocardium, functional properties are directly related to the cellular orientation and elongation. Thus, tissue engineering of functional cardiac patches critically depends on our understanding of the interaction between multiple guidance cues such as topographical, adhesive or electrical. The main objective of this study was to determine the interactive effects of contact guidance and electrical field stimulation on elongation and orientation of fibroblasts and cardiomyocytes, major cell populations of the myocardium. Polyvinyl surfaces were abraded using lapping paper with grain size 1-80 microm, resulting in V-shaped abrasions with the average abrasion peak-to-peak width in the range from 3 to 13 microm, and the average depth in the range from 140 to 700 nm (AFM). The surfaces with abrasions 13 microm wide and 700 nm deep, exhibited the strongest effect on neonatal rat cardiomyocyte elongation and orientation as well as statistically significant effect on orientation of fibroblasts, thus they were utilized for electrical field stimulation. Electrical field stimulation was performed using a regime of relevance for heart tissue in vivo as well as for cardiac tissue engineering. Stimulation (square pulses, 1 ms duration, 1 Hz, 2.3 or 4.6 V/cm) was initiated 24 h after cell seeding and maintained for additional 72 h. The cover slips were positioned between the carbon rod electrodes such that the abrasions were either parallel or perpendicular to the field lines. Non-abraded surfaces were utilized as controls. Field stimulation did not affect cell viability. The presence of a well-developed contractile apparatus in neonatal rat cardiomyocytes (staining for cardiac Troponin I and actin filaments) was identified in the groups cultivated on abraded surfaces in the presence of field stimulation. Overall we observed that (i) fibroblast and cardiomyocyte elongation on non-abraded surfaces was significantly enhanced by electrical field stimulation, (ii) electrical field stimulation promoted orientation of fibroblasts in the direction perpendicular to the field lines when the abrasions were also placed perpendicular to the field lines and (iii) topographical cues were a significantly stronger determinant of cardiomyocyte orientation than the electrical field stimulation. The orientation and elongation response of cardiomyocytes was completely abolished by inhibition of actin polymerization (Cytochalasin D) and only partially by inhibition of phosphatidyl-inositol 3 kinase (PI3K) pathway (LY294002).

Multiple mechanisms underlying the anticancer action of nanocrystalline fullerene

Using the rat glioma cell line C6 and the human glioma cell line U251, we demonstrate the multiple mechanisms underlying the in vitro anticancer effects of the C(60) fullerene water suspension (nano-C(60) or nC(60)) produced by solvent exchange method. Nano-C(60) in a dose-dependent manner reduced the tumor cell numbers after 24 h of incubation. The observed antiglioma action of nC(60) at high concentration (1 microg/ml) was due to a reactive oxygen species-mediated necrotic cell damage that was partly dependent on oxidative stress-induced activation of extracellular signal-regulated kinase (ERK). On the other hand, low-dose nC(60) (0.25 microg/ml) did not induce either necrotic or apoptotic cell death, but caused oxidative stress/ERK-independent cell cycle block in G(2)/M phase and subsequent inhibition of tumor cell proliferation. Treatment with either high-dose or low-dose nC(60) caused the appearance of acidified intracytoplasmic vesicles indicative of autophagy, but only the antiglioma effect of low-dose nC(60) was significantly attenuated by inhibiting autophagy with bafilomycin A1. Importantly, primary rat astrocytes were less sensitive than their transformed counterparts to a cytostatic action of low-dose nC(60). These data provide grounds for further development of nC(60) as an anticancer agent.

Roles of Na+/H+ exchange in regulation of p38 mitogen-activated protein kinase activity and cell death after chemical anoxia in NIH3T3 fibroblasts

Activation of Na(+)/H(+) exchange (NHE) plays a major role in cell death following ischemia/hypoxia in many cell types, yet counteracts apoptotic cell death after other stimuli. To address the role of NHE activity in regulation of cell death/survival, we examined the causal relationship between NHE, p38 mitogen-activated protein kinase (MAPK), ERK1/2, p53, and Akt activity, and cell death, after chemical anoxia in NIH3T3 fibroblasts. The NHE1 inhibitor 5'-(N-ethyl-N-isopropyl) amiloride (EIPA) (5 muM), as well as removal of extracellular Na(+) [replaced by N-methyl-D: -glucamine (NMDG(+))], prevented recovery of intracellular pH (pH(i)) during chemical anoxia (10 mM NaN(3) +/- 10 mM glucose), indicating that activation of NHE was the dominating mechanism of pH(i) regulation under these conditions. NHE activation by chemical anoxia was unaffected by inhibitors of p38 MAPK (SB203580) and extracellular signal-regulated kinase (ERK) (PD98059). In contrast, chemical anoxia activated p38 MAPK in an NHE-dependent manner, while ERK1/2 activity was unaffected. Anoxia-induced cell death was caspase-3-independent, mildly attenuated by EIPA, potently exacerbated by SB203580, and unaffected by PD98059. Ser(15) phosphorylation of p53 was increased by anoxia in an NHE- and p38 MAPK-independent manner, while Akt activity was unaffected. It is suggested that after chemical anoxia in NIH3T3 fibroblasts, NHE activity is required for activation of p38 MAPK, which in turn protects the cells against anoxia-induced death. In spite of this, NHE inhibition slightly attenuates anoxia-induced cell death, likely due to the involvement of NHE in other anoxia-induced death pathways.

Proteomic profiling and identification of cofilin responding to oxidative stress in vascular smooth muscle

We used 2-DE and MALDI-TOF/TOF to identify proteins of vascular smooth muscle cells whose expression was or was not altered by exposure to 500 microM H2O2 for 30 min. We detected more than 800 proteins on silver-stained gels of whole protein extracts from rat aortic smooth muscle strips. Of these proteins, 135 clearly unaffected and 19 having levels altered by exposure to H2O2 were identified. Protein characterization revealed that the most prominent vascular smooth muscle proteins were those with antioxidant, cytoskeletal structure, or muscle contraction. In addition, cofilin, an isoform of the actin depolymerizing factor family, shifted to its basic site on the 2-DE gel as a result of H2O2 treatment. In Western blot analysis of proteins from A7r5 aortic smooth muscle cells, the phosphorylation, but not the expression, of cofilin was decreased by H2O2 in a dose-dependent manner. The H2O2-induced dephosphorylation of cofilin and apoptosis was inhibited by Na3VO4, an inhibitor of protein tyrosine phosphatase (PTP). These results suggest that cofilin is one of the proteins regulated by H2O2 treatment in vascular smooth muscle, and has an important role in the induction of vascular apoptosis through PTP-dependent mechanisms.

Heat shock protects cardiac cells from doxorubicin-induced toxicity by activating p38 MAPK and phosphorylation of small heat shock protein 27

Doxorubicin (DOX) and its derivatives are used as chemotherapeutic drugs to treat cancer patients. However, production of DOX-mediated reactive oxygen species (ROS) by prolonged use of these drugs has been found to cause dilative cardiomyopathy and congestive heart failure. Thus various preventive modalities have been developed to avoid this side effect. We have found that the DOX-mediated oxidant-induced toxicity in cardiac cells could be minimized by hyperthermia-induced small heat shock protein 27 (HSP27); that is, this protein acts as an endogenous antioxidant against DOX-derived oxidants such as H(2)O(2). Heat shock-induced HSP27 was found to act as an antiapoptotic protein (reducing ROS and Bax-to-Bcl2 ratio) against DOX, and its phosphorylated isoforms stabilized F-actin remodeling in DOX-treated cardiac cells and, hence, attenuated the toxicity. Protein kinase assays and proteomic analyses suggested that higher expression of HSP27 and its phosphorylation are responsible for the protection in heat-shocked cells. Two-dimensional gel electrophoresis showed six isoforms (nonphosphorylated and phosphorylated) of HSP27. Matrix-assisted laser desorption/ionization time of flight analyses showed alpha- and beta-isoforms of HSP27, which are phosphorylated by various protein kinases. Ser(15) and Ser(85) phosphorylation of HSP27 by MAPK-assisted protein kinase 2 was found to be the key mechanism in reduction of apoptosis and facilitation of F-actin remodeling. The present study illustrates that hyperthermia protects cells from DOX-induced death through induction and phosphorylation of HSP27 and its antiapoptotic and actin-remodeling activities.

Osmotic stress and the cytoskeleton: the R(h)ole of Rho GTPases

Hyperosmotic stress initiates a variety of compensatory and adaptive responses, which either serve to restore near-normal volume or remodel and reinforce the cell structure to withstand the physical challenge. The latter response is brought about by the reorganization of the cytoskeleton; however, the underlying mechanisms are not well understood. Recent research has provided major breakthroughs in our knowledge about the link between message and structure, i.e. between signalling and cytoskeletal remodelling, predominantly in the context of cell migration. The major components of this progress are the in-depth characterization of Rho family small GTPases, master regulators of the cytoskeleton, and the discovery of the actin-related protein 2/3 complex, a signalling-sensitive structural element of the actin polymerization machinery. The primary aim of this review is to find the place of these novel and crucial players in osmotically induced (volume-dependent) remodelling of the cytoskeleton. We aim to address three questions: (1) What are the major structural changes in the cytoskeleton under hyperosmotic conditions? (2) Are the Rho family small GTPases (Rho, Rac and Cdc42) regulated by osmotic stress, and if so, by what mechanisms? (3) Are Rho GTPases involved, as mediators, in major adaptive responses, including cytoskeleton rearrangement, changes in ion transport and genetic reprogramming? Our answers will show how fragmentary our current knowledge is in these areas. Therefore, this overview has been written with the hardly disguised intention that it might foster further research in this field by highlighting some intriguing questions.

Role of Mechanical Stress in the Form of Cardiomyocyte Death During the Early Phase of Reperfusion

BACKGROUND

The hypothesis that mechanical stress during reperfusion produces myocyte oncosis and inhibits apoptosis was tested in the present study.

METHODS AND RESULTS

Isolated and perfused rat hearts were subjected to 30 min ischemia followed by 150 min reperfusion. In the control-reperfusion heart, the form of myocyte death was a mixture of apoptosis only, oncosis only, and both apoptosis and oncosis. Apoptotic myocytes contained mitochondria that maintained membrane potential (Deltapsim), whereas oncotic myocytes contained only Deltapsim-collapsed mitochondria. Treatment with the contractile blocker 2,3-butanedione monoxime (BDM) during reperfusion increased caspase-3 activity and produced predominantly apoptosis. However, withdrawal of BDM provoked oncosis in terminal deoxynucleotide nick-end labeling (TUNEL)-positive myocytes. Myocardial stretch by inflating an intraventricular balloon at the time of reperfusion with BDM increased only oncotic myocytes, whereas the same mechanical stress 120 min after reperfusion increased oncotic myocytes positive for TUNEL. Increased mechanical stress at the time of reperfusion by treatment with isoproterenol or hyposmotic buffer inhibited caspase-3 activity and increased only oncotic myocytes. Co-treatment with the caspase-3 inhibitor, Ac-DEVD-CHO, and BDM during reperfusion inhibited myocyte apoptosis and oncosis but did not inhibit oncosis after withdrawal of BDM.

CONCLUSIONS

These results suggest that mechanical stress is a critical determinant of the form of myocyte death during the early phase of reperfusion.