Myocardial ischaemia and the inflammatory response: release of heat shock protein 70 after myocardial infarction

Interaction of serum 70-kDa heat shock protein levels and HspA1B (+1267) gene polymorphism with disease severity in patients with chronic heart failure

BACKGROUND

Circulating heat shock protein 70 (Hsp70) is present in the circulation of healthy individuals and in patients with various disorders, including chronic heart failure (CHF). However, the source and routes of release of Hsp70 is only partially characterised in clinical samples.

AIMS

The purpose of this study was to study the clinical and biological correlates of Hsp70 in a CHF population and, for the first time, to investigate the association of HspA1B (also known as Hsp70-2) +1267 alleles with serum Hsp70 levels.

METHODS

A total of 167 patients (123 men, 44 women) with <45% left ventricular ejection fraction (LVEF) were enrolled; serum Hsp70 level was determined by enzyme-linked immunosorbent assay and HspA1B +1267 polymorphism by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

Increased Hsp70 levels were present in patients with severe CHF (NYHA III-IV) as compared to the group of NYHA I-II (p = 0.003). Hsp70 levels correlated with LVEF, NT-proBNP, serum bilirubin, aspartate aminotransferase, alanine aminotransferase, gammaGT (p < 0.05) concentrations in patients with severe CHF, although no correlation was observed between Hsp70 and CRP, TNF-alpha, or IL-6. HspA1B allele G was associated with higher Hsp70 levels (p = 0.001) in patients in NYHA IV class as compared to carriers of allele A.

CONCLUSIONS

Serum Hsp70 levels were associated with disease severity in heart failure patients. An interaction with the presence of HspA1B +1267 allele G was observed for Hsp70 concentrations. Hsp70 correlates with markers of heart function and hepatic injury, but not with signs of inflammation.

Heat shock proteins and toll-like receptors

Researchers have only just begun to elucidate the relationship between heat shock proteins (HSP) and Toll-like receptors (TLR). HSP were originally described as an intracellular molecular chaperone of naïve, aberrantly folded, or mutated proteins and primarily implicated as a cytoprotective protein when cells are exposed to stressful stimuli. However, recent studies have ascribed novel functions to the Hsp70 protein depending on its localization: Surface-bound Hsp70 specifically activate natural killer (NK) cells, while Hsp70 released into the extracellular milieu specifically bind to Toll-like receptors (TLR) 2 and 4 on antigen-presenting cells (APC) and exerts immunoregulatory effects, including upregulation of adhesion molecules, co-stimulatory molecule expression, and cytokine and chemokine release-a process known as the chaperokine activity of Hsp70. This chapter discusses the most recent advances in the understanding of heat shock protein (HSP) and TLR interactions in general and highlights recent findings that demonstrate Hsp70 is a ligand for TLR and its biological significance.

Elevated serum 70 kDa heat shock protein level reflects tissue damage and disease severity in the syndrome of hemolysis, elevated liver enzymes, and low platelet count

OBJECTIVE

We have recently demonstrated that serum 70 kDa heat shock protein (Hsp70) levels are increased in the syndrome of hemolysis, elevated liver enzymes, and low platelet count (HELLP syndrome). The aim of the present study was to investigate in an independent, larger cohort of patients whether serum Hsp70 levels are related to laboratory markers of HELLP syndrome.

STUDY DESIGN

The study population included 14 patients with HELLP syndrome. Serum Hsp70 levels were measured by enzyme-linked immunosorbent assay. The relationship between serum Hsp70 levels and laboratory markers of hemolysis, hepatocellular damage, renal insufficiency, inflammation or disseminated intravascular coagulation (DIC), as well as platelet count was investigated by calculating correlation coefficients, standardized regression coefficients and by principal component analysis.

RESULTS

Serum Hsp70 levels showed a very strong correlation to the markers of hemolysis (plasma free hemoglobin level, serum lactate dehydrogenase activity, and total bilirubin level) and of hepatocellular injury (serum aminotransferase activities), supported also by principal component analysis. Furthermore, circulating Hsp70 concentration reflected the severity of HELLP syndrome as expressed by the significant inverse correlation to the lowest platelet count. By contrast, there was no relationship between serum Hsp70 levels and markers of inflammation, coagulation, fibrinolysis or renal insufficiency.

CONCLUSION

Elevated serum 70 kDa heat shock protein level seems to reflect tissue damage (hemolysis and hepatocellular injury) and disease severity in patients with HELLP syndrome. However, further investigations are needed to determine the clinical relevance of these findings.

Plasma concentration of heat shock protein 27 and risk of cardiovascular disease: a prospective, nested case-control study

BACKGROUND

Heat shock protein 27 (HSP27) has been hypothesized to be a potential biomarker of atherothrombosis. However, no prospective studies have yet been performed to investigate the association between HSP27 plasma concentration and incident cardiovascular events among initially healthy individuals.

METHODS

We evaluated plasma concentrations of HSP27 at baseline among 255 initially healthy participants in the Women's Health Study who subsequently developed myocardial infarction, ischemic stroke, or cardiovascular death during a follow-up period of up to 5.9 years and among an equal number of women matched for age and smoking but who remained free of cardiovascular disease over the same time period.

RESULTS

Overall, HSP27 plasma concentrations were inversely associated with age (Spearman correlation coefficient r = -0.258, P <0.001), but not with other established cardiovascular risk factors. Conditional logistic regression analysis showed no significant association of baseline HSP27 plasma concentration with future cardiovascular disease; the odds ratio for upper vs lower tertile of HSP27 concentration at baseline was 0.99 (95% CI 0.62-1.57, P for trend = 0.99).

CONCLUSION

In this prospective study of initially healthy women, baseline HSP27 plasma concentration was not associated with incident cardiovascular events.

Mechanisms of HSP72 release

Currently two mechanisms are recognized by which heat shock proteins (HSP) are released from cells; a passive release mechanism, including necrotic cell death, severe blunt trauma, surgery and following infection with lytic viruses, and an active release mechanism which involves the non classical protein release pathway. HSPs are released both as free HSP and within exosomes. This review covers recent findings on the mechanism by which stress induces the release of HSP72 into the circulation and the biological significance of circulating HSP72 to host defense against disease.

Using lymphocyte and plasma Hsp70 as biomarkers for assessing coke oven exposure among steel workers

BACKGROUND

Hsp70, an early-response protein induced when organisms are confronted with simple or complicated environmental stresses, can act as either a cellular protector or a danger signal.

OBJECTIVES

The goal of this study was to evaluate levels of lymphocyte and/or plasma Hsp70 as biomarkers for assessing exposure response to complex coke oven emissions (COEs).

METHODS

We recruited 101 coke oven workers and determined levels of polycyclic aromatic hydrocarbon (PAH) exposure, urinary 1-hydroxypyrene (1-OHP), genotoxic damage by comet assay and micronuclei test, and other markers of damage, including plasma malondialdehyde (MDA) and lactate dehydrogenase (LDH). These were compared to levels of lymphocyte (intra-cellular) and plasma (extracellular) Hsp70 using Western blots and enzyme-linked immunosorbent assays (ELISA), respectively.

RESULTS

We observed a COEs-related dose-dependent increase in levels of DNA damage, micronuclei rate, MDA concentration, and LDH activity. Lymphocyte Hsp70 levels increased in the intermediate-exposure group (1.39 +/- 0.88) but decreased in the high-exposure group (1.10 +/- 0.55), compared with the low-exposure group. In contrast, plasma Hsp70 levels progressively increased as the dose of exposure increased. Negative correlations were seen between lymphocyte Hsp70 levels and olive tail moment and LDH activity in the intermediate- and high-exposure groups. However, we observed positive correlations between plasma Hsp70 levels and LDH activity in the low and intermediate groups.

CONCLUSIONS

In workers exposed to COEs, high lymphocyte Hsp70 levels may provide protection and high plasma Hsp70 levels may serve as a danger marker. Larger validation studies are needed to establish the utility of Hsp70 as a response marker.

MAPK pathway mediates EGR-1-HSP70-dependent cigarette smoke-induced chemokine production

Cigarette smoking, a major risk factor for chronic obstructive pulmonary disease, can cause airway inflammation, airway narrowing, and loss of elasticity, leading to chronic airflow limitation. In this report, we sought to define the signaling pathways activated by smoke and to identify molecules responsible for cigarette smoke-induced inflammation. We applied cigarette smoke water extract (CSE) to primary human lung fibroblasts and found that CSE significantly increased CXC chemokine IL-8 production. Meanwhile, 70-kDa heat shock protein (HSP70) was also induced by CSE in a dose- and time-dependent manner. CSE treatment stimulated HSP70 secretion by primary fibroblasts, which augmented IL-8 production. This was further confirmed by exogenously added recombinant HSP70. Using HSP70 small interfering RNA, we confirmed that CSE-induced chemokine production was dependent on heat shock protein expression. Further investigation showed that CSE could also stimulate early growth response-1 (EGR-1) in an ERK-dependent manner and that the expression of HSP70 was EGR-1 dependent. In view of these findings, we hypothesize that the MAPK-EGR-1-HSP70 pathway regulates the cigarette smoke-induced inflammatory process.

Heat shock treatment results in increased recruitment of labeled PMN following myocardial infarction

One of the proposed mechanisms for the myocardial protective effects of heat shock (HS) treatment has been a reduction in the inflammatory response. The objective of the present study was to evaluate the impact of HS treatment in an established model of polymorphonuclear cell (PMN) migration following myocardial infarction (MI). Isolated purified PMNs (10 x 10(6) cells) labeled with (51)Cr were injected into Lewis rats following a left thoracotomy and ligation of the left anterior descending coronary artery causing MI. Two experimental groups of animals were created: MI group (n = 11) and HS+MI group (n = 7). HS treatment consisted of an elevation in core temperature to 42 degrees C for 15 min 24 h prior to MI. An additional group of control animals underwent sham thoracotomy (n = 5). All animals were euthanized at 24 h after MI, and gamma counts were obtained to estimate PMN migration. Myocardial injury was confirmed in all experimental animals (histology and echocardiography). The serum troponin I and infarct size (triphenyltetrazolium chloride) were similar in both groups. Labeled PMN migration was significantly higher in HS+MI animals (14.3 x 10(4) +/- 3.7 x 10(4) PMN) compared with MI group (9.5 x 10(4) +/- 3.6 x 10(4); P = 0.01), suggesting increased PMN migration as a result of HS treatment. HS treatment did not affect PMN migration to positive skin control sites (LPS). ICAM-1 myocardial expression was not significantly increased in HS+MI compared with MI group. In summary, HS treatment results in increased PMN migration into myocardium following MI independent of ICAM-1. These findings suggest that the proposed cardioprotective effect of HS may not be entirely due to a downregulation of myocardial inflammation as previously proposed.

Stimulation of cysteinyl leukotriene production in mast cells by heat shock and acetylsalicylic acid

Immunoglobulin (Ig) E-dependent activation of mast cells is central to the allergic response. The engagement of IgE-occupied receptors initiates a series of molecular events that causes the release of preformed, and de novo synthesis of, allergic mediators. Cysteinyl leukotrienes are able to contract airway smooth muscle and increase mucus secretion and vascular permeability and recruit eosinophils. Mast cells have also recently been recognized as active participants in innate immune responses. Heat stress can modulate innate immunity by inducing stress proteins such as heat-shock proteins (HSPs). We previously demonstrated that treatment of mast cells with heat shock or acetylsalicylic acid results in an increase of TNF-alpha and IL-6 release. This effect was paralleled by expression of HSP70. In the current study, we further investigated the effects of heat shock and acetylsalicylic acid on the activation of mast cells and the release of cysteinyl leukotrienes. In mouse mast cells, derived from a culture of bone marrow cells, responsiveness to heat shock, acetylsalicylic acid and exogenous or endogenous HSP70 was monitored by measuring leukotriene C4 release. We show that after heat shock treatment and exposure to acetylsalicylic acid leukotriene production was increased. Moreover, exogenous rHSP70 also induced leukotriene production. Because it has been reported that leukotriene production in mast cells may be mediated by Toll like receptor (TLR) activation, and HSP70 also activates TLRs signaling, we further explored these issues by using mast cells that are not able to produce HSP70, i.e. heat shock factor-1 (HSF-1) knockout cells. We found that in HSF-1 knockout bone marrow derived mast cells, heat shock and acetylsalicylic acid failed to induce release of leukotrienes. Moreover, in wild type cells the surface expression of TLR4 was attenuated, whereas the intracellular expression was up-regulated. We conclude that heat shock and acetylsalicylic acid induce the production and release of heat shock proteins from mast cells, which in turn stimulate leukotriene synthesis through activation of TLR4.

Proteomics of ischemia and reperfusion injuries in rabbit myocardium with and without intervention by an oxygen-free radical scavenger

A brief period of ischemia followed by timely reperfusion may lead to prolonged, yet reversible, contractile dysfunction (myocardial stunning). Damage to the myocardium occurs not only during ischemia, but also during reperfusion, where a massive release of oxygen-free radicals (OFR) occurs. We have previously utilized 2-DE and MS to define 57 protein spot changes during brief ischemia/reperfusion (15 min ischemia, 60 min reperfusion; 15I/60R) injury in a rabbit model (White, M. Y., Cordwell, S. J., McCarron, H. C. K., Prasan, A. M. et al., Proteomics 2005, 5, 1395-1410) and shown that the majority of these occur because of physical and/or chemical PTMs. In this study, we subjected rabbit myocardium to 15I/60R in the presence of the OFR scavenger N-(2-mercaptopropionyl) glycine (MPG). Thirty-seven of 57 protein spots altered during 15I/60R remained at control levels in the presence of MPG (15I/60R + MPG). Changes to contractile proteins, including myosin light chain 2 (MLC-2) and troponin C (TnC), were prevented by the addition of MPG. To further investigate the individual effects of ischemia and reperfusion, we generated 2-DE gels from rabbit myocardium subjected to brief ischemia alone (15I/0R), and observed alterations of 33 protein spots, including 18/20 seen in both 15I/60R-treated and 15I/60R + MPG-treated tissue. The tissue was also subjected to ischemia in the presence of MPG (15I/0R + MPG), and 21 spot changes, representing 14 protein variants, remained altered despite the presence of the OFR scavenger. These ischemia-specific proteins comprised those involved in energy metabolism (lactate dehydrogenase and ATP synthase alpha), redox regulation (NADH ubiquinone oxidoreductase 51 kDa and GST Mu), and stress response (Hsp27 and 70, and deamidated alpha B-crystallin). We conclude that contractile dysfunction associated with myocardial stunning is predominantly caused by OFR damage at the onset of reperfusion, but that OFR-independent damage also occurs during ischemia. These ischemia-specific protein modifications may be indicative of early myocardial injury.

Neuregulin 1-Beta cytoprotective role in AML 12 mouse hepatocytes exposed to pentachlorophenol

Neuregulins are a family of growth factor domain proteins that are structurally related to the epidermal growth factor. Accumulating evidence has shown that neuregulins have cyto- and neuroprotective properties in various cell types. In particular, the neuregulin-1 Beta (NRG1-Beta) isoform is well documented for its antiinflammatory properties in rat brain after acute stroke episodes. Pentachlorophenol (PCP) is an organochlorine compound that has been widely used as a biocide in several industrial, agricultural, and domestic applications. Previous investigations from our laboratory have demonstrated that PCP exerts both cytotoxic and mitogenic effects in human liver carcinoma (HepG2) cells, primary catfish hepatocytes and AML 12 mouse hepatocytes. We have also shown that in HepG2 cells, PCP has the ability to induce stress genes that may play a role in the molecular events leading to toxicity and tumorigenesis. In the present study, we hypothesize that NRG1-Beta will exert its cytoprotective effects in PCP-treated AML 12 mouse hepatocytes by its ability to suppress the toxic effects of PCP. To test this hypothesis, we performed the MTT-cell respiration assay to assess cell viability, and Western-blot analysis to assess stress-related proteins as a consequence of PCP exposure. Data obtained from 48 h-viability studies demonstrated a biphasic response; showing a dose-dependent increase in cell viability within the range of 0 to 3.87 microg/mL, and a gradual decrease within the concentration range of 7.75 to 31.0 microg/mL in concomitant treatments of NRG1-Beta+PCP and PCP. Cell viability percentages indicated that NRG1-Beta+PCPtreated cells were not significantly impaired, while PCP-treated cells were appreciably affected; suggesting that NRG1-Beta has the ability to suppress the toxic effects of PCP. Western Blot analysis demonstrated the potential of PCP to induce oxidative stress and inflammatory response (c-fos), growth arrest and DNA damage (GADD153), proteotoxic effects (HSP70), cell cycle arrest as consequence of DNA damage (p53), mitogenic response (cyclin- D1), and apoptosis (caspase-3). NRG1-Beta exposure attenuated stress-related protein expression in PCP-treated AML 12 mouse hepatocytes. Here we provide clear evidence that NRG1-Beta exerts cytoprotective effects in AML 12 mouse hepatocytes exposed to PCP.

Heat shock response and acute lung injury

All cells respond to stress through the activation of primitive, evolutionarily conserved genetic programs that maintain homeostasis and assure cell survival. Stress adaptation, which is known in the literature by a myriad of terms, including tolerance, desensitization, conditioning, and reprogramming, is a common paradigm found throughout nature, in which a primary exposure of a cell or organism to a stressful stimulus (e.g., heat) results in an adaptive response by which a second exposure to the same stimulus produces a minimal response. More interesting is the phenomenon of cross-tolerance, by which a primary exposure to a stressful stimulus results in an adaptive response whereby the cell or organism is resistant to a subsequent stress that is different from the initial stress (i.e., exposure to heat stress leading to resistance to oxidant stress). The heat shock response is one of the more commonly described examples of stress adaptation and is characterized by the rapid expression of a unique group of proteins collectively known as heat shock proteins (also commonly referred to as stress proteins). The expression of heat shock proteins is well described in both whole lungs and in specific lung cells from a variety of species and in response to a variety of stressors. More importantly, in vitro data, as well as data from various animal models of acute lung injury, demonstrate that heat shock proteins, especially Hsp27, Hsp32, Hsp60, and Hsp70 have an important cytoprotective role during lung inflammation and injury.

Circulating heat shock proteins and inflammatory markers in patients with idiopathic left ventricular dysfunction: their relationships with myocardial and microvascular impairment

Little information is available on peripheral levels of Hsp72, Hsp60, and anti-Hsp60 antibodies in patients with left ventricular (LV) dysfunction due to non-atherosclerotic cardiac disease. In this study, serum Hsp72, Hsp60 and anti-Hsp60 antibodies, IL-6, and C-reactive protein (CRP) were measured in 44 healthy controls and in 82 patients with angiographically normal coronary arteries (LV ejection fraction [EF] > or = 50%, n=22; -35% to <50%, n=32; <35%, n=28). Patients with more severe disease (more depressed myocardial blood flow at rest and during dipyridamole, indicative of coronary microvascular impairment) showed more elevated circulating Hsp60 and auto-antibodies, Hsp72, and CRP levels. IL-6 was increased progressively as a function of severity of LV dysfunction. Anti-Hsp60 antibodies, Hsp72, and IL-6 were significantly correlated with brain natriuretic peptide (BNP) levels and LV end-diastolic dimensions (LVEDD) values. IL-6 tended to be related with Hsp72 in particular in patients with more severe disease (r = 0.45, P = 0.021). Hsp60 and Hsp72 activation and inflammatory markers were correlated with the extent of cardiac and microvascular dysfunction in patients with angiographycally normal coronary arteries. These results suggest a pathogenic role of infective-metabolic insult and inflammatory reaction in the development of vascular and myocardial damage in patients with heart failure even in the absence of overt coronary artery disease.

Dendritic cells and autoimmune heart failure

Dilated cardiomyopathy is the most common cause of heart failure in young patients and often results from autoimmunity triggered by viral or bacterial infections. Dendritic cells are professional antigen-presenting cells residing in lymphatic tissue and in the heart. They are involved in both, host defense and maintenance of peripheral tolerance. Animal models suggest an important role for dendritic cells in the induction of autoimmune myocarditis. Activated and self-antigen loaded dendritic cells, for example, induce myocarditis and heart failure in susceptible mice. It appears that the combined presence of tissue damage and innate activation exceeding a certain threshold prompts dendritic cells to prime and amplify potentially autoreactive T cells targeting the heart. The concept of dendritic cell induced myocarditis helps us to understand disease pathogenesis and offers a nice approach to develop novel therapeutic strategies against a devastating heart disease.

Initiation of the Immune Response by Extracellular Hsp72: Chaperokine Activity of Hsp72

Heat shock proteins exert their beneficial effects via basically two modes of action depending on their relative location within the host. Intracellular heat shock proteins found within cells serve a cytoprotective role by chaperoning naïve, misfolded and/or denatured proteins in response to stressful stimuli by a process known as the stress response. However, stressful stimuli also induce the release of intracellular heat shock proteins into the extracellular milieu and circulation. The extracellular heat shock protein proteins serve a cytostimulatory role by initiating immune responses designed to fend off microbial infection and destroy neoplastic transformed cells. This review will briefly cover recent advances into elucidating the mechanism(s) by which stress induces the release of heat shock proteins into the circulation, how it initiates immune responses and suggest the possible biological significance of circulating Hsp to the host.

Elevated circulating levels of heat shock protein 70 are related to systemic inflammatory reaction through monocyte Toll signal in patients with heart failure after acute myocardial infarction

BACKGROUND

Recent studies have shown that heat shock protein (HSP) 70 may serve as a "damage signal" to the immune system and could be the endogenous ligand for Toll-like receptor (TLR) 4 mediating synthesis of inflammatory cytokines.

AIMS

To explore the relationship between circulating HSP70 levels and activation of monocyte TLR4 and myocardial damage after AMI.

METHODS AND RESULTS

This study examined circulating HSP70 and monocyte TLR4 levels in 52 patients with AMI and 20 controls, and analyzed ex vivo inflammatory cytokine productions using HSP70-stimulated monocytes. Circulating HSP70 levels were higher in AMI patients on day 1 after onset than in controls and remained elevated in AMI patients 14 days after onset. HSP70 levels were positively correlated with monocyte TLR4, plasma interleukin-6 and tumor necrosis factor-alpha levels in AMI patients. HSP70 levels 14 days after onset were higher in AMI patients with heart failure (n=15) than in those without heart failure. In our in vitro study, HSP70-stimulated monocytes resulted in dose-dependent TLR4 expression and release of inflammatory cytokines. TLR4 antibody inhibited inflammatory cytokines release.

CONCLUSIONS

Elevated circulating levels of HSP70 may be involved in TLR4 signal-mediated immune response and the progression of heart failure after AMI.

Acetylsalicylic acid-induced release of HSP70 from mast cells results in cell activation through TLR pathway

OBJECTIVE

Mast cells are considered major players in IgE-mediated allergic responses, but have also recently been recognized as active participants in innate as well as specific immune responses. Heat stress can modulate innate immunity by inducing stress proteins such as heat shock proteins (HSPs). It has been reported that HSPs are capable of inducing the production of pro-inflammatory cytokines by the monocyte-macrophage system. In the current study, we explored whether the stress response induces HSPs and affects the signaling pathways of mast cells.

METHODS

In mouse mast cells, derived from a culture of bone marrow cells of male BALB/cBy and null HSF-1(-/-) mice, responsiveness to exogenous and endogenous HSP70 was monitored by measuring cytokine release.

RESULTS

Using BMMC, we show that treatment with heat shock or acetylsalicylic acid results in a selective induction of HSPs, and leads to release of HSP70 into the extracellular environment. The release of HSP70 from mast cells may be of functional importance. We found that after induction of HSP70, the production of TNF-alpha and IL-6 was increased. In a number of experiments, we demonstrated that exogenous/secreted HSP70 is most likely responsible for the activation of mast cells to produce cytokines. Extracellular HSP70 induced production of TNF-alpha and IL-6 through the activation of the TLR4 receptor pathway, which was evidenced by an abrogation of the response in mast cells cultured from TLR4(null) or HSF-1(-/-) mice.

CONCLUSION

Our experiments suggest that stress conditions can induce pro-inflammatory cytokine production by mast cells through an autocrine or paracrine stimulation of TLR receptors after a heat shock response. The recognition that heat shock proteins induce mast cell activation suggests an involvement of these cells in the immunological processes induced by heat shock response.

Comparative plasma proteome analysis of lymphoma-bearing SJL mice

In SJL mice, growth of RcsX lymphoma cells induces an inflammatory response by stimulating V(beta)16+ T cells. During inflammation, various serum protein levels can increase (e.g., acute phase reactants) or decrease (e.g., albumin), and most of these altered proteins are thus potential biomarkers. Although blood plasma is a valuable and promising sample for biomarker discovery for diseases or for novel drug targets, its proteome is complex. To address this, we have focused on a comprehensive comparison of the plasma proteomes from normal and RcsX-tumor-bearing SJL mice using the 1D-Gel-LC-MS/MS method after removing albumin and immunoglobulins. This analysis resulted in the identification of a total of 1079 nonredundant mouse plasma proteins; more than 480 in normal and 790 in RcsX-tumor-bearing SJL mouse plasma. Of these, only 191 proteins were found in common. The molecular weights ranged from 2 to 876 kDa, covering the pI values between 4.22 and 12.09, and included proteins with predicted transmembrane domains. By comparing the plasma proteomic profile of normal and RcsX-tumor-bearing SJL mice, we found significant changes in the levels of many proteins in RcsX-tumor-bearing mouse plasma. Most of the up-regulated proteins were identified as acute-phase proteins (APPs). Also, several unique proteins i.e., haptoglobin, proteosome subunits, fetuin-B, 14-3-3 zeta, MAGE-B4 antigen, etc, were found only in the tumor-bearing mouse plasma; either secreted, shed by membrane vesicles, or externalized due to cell death. These results affirm the effectiveness of this approach for protein identification from small samples, and for comparative proteomics in potential animal models of human disorders.

Ischemic preconditioning of free muscle flaps: An experimental study

The aim of this study was to apply the hypothesis of ischemic preconditioning (IP) on free skeletal muscle (rat thigh flap). Five groups of Sprague-Dawley rats (n = 6) were used. In group A (control group), standard free autologous flap transfers were performed. Flaps in groups B and C underwent 4 and 6 h, respectively, of ischemia before transfer. In groups D and E, muscle flaps were preconditioned (3 x 10 min ischemia interrupted by 10 min of reperfusion, clip applied on the dissected artery of the flap) and subjected to 4 and 6 h, respectively, of ischemia before transfer. After 48 h of reperfusion, the muscle flaps were evaluated macroscopically as well as by histological and immunohystochemical staining. In group A, the viability was 100%, whereas in groups D and E the viability was 83.3% and 100%, respectively. Groups B and C had undergone macroscopically parceled to total necrosis, further confirmed by histological findings (fragmentation and disappearance of muscle striations, combined with tissue necrosis and intravascular thrombosis). The beneficial effect of IP demonstrated in the heart, liver, and small bowel extends to skeletal muscle, which can be used in free-flap transfers, if the transfer includes a long period of predictable ischemia.