Possible relationship between heat shock protein 70, cardiac hemodynamics, and survival in the early period after heart transplantation

Heat Shock Proteins: Potential Modulators and Candidate Biomarkers of Peripartum Cardiomyopathy

Peripartum cardiomyopathy (PPCM) is a potentially life-threatening condition in which heart failure and systolic dysfunction occur late in pregnancy or within months following delivery. To date, no reliable biomarkers or therapeutic interventions for the condition exist, thus necessitating an urgent need for identification of novel PPCM drug targets and candidate biomarkers. Leads for novel treatments and biomarkers are therefore being investigated worldwide. Pregnancy is generally accompanied by dramatic hemodynamic changes, including a reduced afterload and a 50% increase in cardiac output. These increased cardiac stresses during pregnancy potentially impair protein folding processes within the cardiac tissue. The accumulation of misfolded proteins results in increased toxicity and cardiac insults that trigger heart failure. Under stress conditions, molecular chaperones such as heat shock proteins (Hsps) play crucial roles in maintaining cellular proteostasis. Here, we critically assess the potential role of Hsps in PPCM. We further predict specific associations between the Hsp types Hsp70, Hsp90 and small Hsps with several proteins implicated in PPCM pathophysiology. Furthermore, we explore the possibility of select Hsps as novel candidate PPCM biomarkers and drug targets. A better understanding of how these Hsps modulate PPCM pathogenesis holds promise in improving treatment, prognosis and management of the condition, and possibly other forms of acute heart failure.

Damage-Associated Molecular Patterns in Myocardial Infarction and Heart Transplantation: The Road to Translational Success

In the setting of myocardial infarction (MI), ischemia reperfusion injury (IRI) occurs due to occlusion (ischemia) and subsequent re-establishment of blood flow (reperfusion) of a coronary artery. A similar phenomenon is observed in heart transplantation (HTx) when, after cold storage, the donor heart is connected to the recipient's circulation. Although reperfusion is essential for the survival of cardiomyocytes, it paradoxically leads to additional myocardial damage in experimental MI and HTx models. Damage (or danger)-associated molecular patterns (DAMPs) are endogenous molecules released after cellular damage or stress such as myocardial IRI. DAMPs activate pattern recognition receptors (PRRs), and set in motion a complex signaling cascade resulting in the release of cytokines and a profound inflammatory reaction. This inflammatory response is thought to function as a double-edged sword. Although it enables removal of cell debris and promotes wound healing, DAMP mediated signalling can also exacerbate the inflammatory state in a disproportional matter, thereby leading to additional tissue damage. Upon MI, this leads to expansion of the infarcted area and deterioration of cardiac function in preclinical models. Eventually this culminates in adverse myocardial remodeling; a process that leads to increased myocardial fibrosis, gradual further loss of cardiomyocytes, left ventricular dilation and heart failure. Upon HTx, DAMPs aggravate ischemic damage, which results in more pronounced reperfusion injury that impacts cardiac function and increases the occurrence of primary graft dysfunction and graft rejection via cytokine release, cardiac edema, enhanced myocardial/endothelial damage and allograft fibrosis. Therapies targeting DAMPs or PRRs have predominantly been investigated in experimental models and are potentially cardioprotective. To date, however, none of these interventions have reached the clinical arena. In this review we summarize the current evidence of involvement of DAMPs and PRRs in the inflammatory response after MI and HTx. Furthermore, we will discuss various current therapeutic approaches targeting this complex interplay and provide possible reasons why clinical translation still fails.

Macrophages in xenotransplantation

Xenotransplantation refers to organ transplantation across species. Immune rejection of xenografts is stronger and faster than that of allografts because of significant molecular differences between species. Recent studies have revealed the involvement of macrophages in xenograft and allograft rejections. Macrophages have been shown to play a critical role in inflammation, coagulation, and phagocytosis in xenograft rejection. This review presents a recent understanding of the role of macrophages in xenograft rejection and possible strategies to control macrophage-mediated xenograft rejection.

Heat Shock Proteins: Protection and Potential Biomarkers for Ischemic Injury of Cardiomyocytes After Surgery

The heat shock proteins are endogenous proteins with the ability to act as molecular chaperones. Methods that provide cell protection by way of some damage can positively influence the results of surgery. The present review summarizes current knowledge concerning the cardioprotective role of the heat shock proteins as occurs in heart damage, including relevant information about the stresses that regulate the expression of these proteins and their potential role as biomarkers of heart disease.

Danger signals in regulating the immune response to solid organ transplantation

Endogenous danger signals, or damage-associated molecular patterns (DAMPs), are generated in response to cell stress and activate innate immunity to provide a pivotal mechanism by which an organism can respond to damaged self. Accumulating experimental and clinical data have established the importance of DAMPs, which signal through innate pattern recognition receptors (PRRs) or DAMP-specific receptors, in regulating the alloresponse to solid organ transplantation (SOT). Moreover, DAMPs may incite distinct downstream cellular responses that could specifically contribute to the development of allograft fibrosis and chronic graft dysfunction. A growing understanding of the role of DAMPs in directing the immune response to transplantation has suggested novel avenues for the treatment or prevention of allograft rejection that complement contemporary immunosuppression and could lead to improved outcomes for solid organ recipients.

Overexpression of inducible 70-kDa heat shock protein in mouse improves structural and functional recovery of skeletal muscles from atrophy

Heat shock proteins play a key regulatory role in cellular defense. To investigate the role of the inducible 70-kDa heat shock protein (HSP70) in skeletal muscle atrophy and subsequent recovery, soleus (SOL) and extensor digitorum longus (EDL) muscles from overexpressing HSP70 transgenic mice were immobilized for 7 days and subsequently released from immobilization and evaluated after 7 days. Histological analysis showed that there was a decrease in cross-sectional area of type II myofiber from EDL and types I and II myofiber from SOL muscles at 7-day immobilization in both wild-type and HSP70 mice. At 7-day recovery, EDL and SOL myofibers from HSP70 mice, but not from wild-type mice, recovered their size. Muscle tetanic contraction decreased only in SOL muscles from wild-type mice at both 7-day immobilization and 7-day recovery; however, it was unaltered in the respective groups from HSP70 mice. Although no effect in a fatigue protocol was observed among groups, we noticed a better contractile performance of EDL muscles from overexpressing HSP70 groups as compared to their matched wild-type groups. The number of NCAM positive-satellite cells reduced after immobilization and recovery in both EDL and SOL muscles from wild-type mice, but it was unchanged in the muscles from HSP70 mice. These results suggest that HSP70 improves structural and functional recovery of skeletal muscle after disuse atrophy, and this effect might be associated with preservation of satellite cell amount.

Radicicol improves regeneration of skeletal muscle previously damaged by crotoxin in mice

This work investigates the influence of heat shock proteins (HSPs) on necrosis and subsequent skeletal muscle regeneration induced by crotoxin (CTX), the major component of Crotalus durissus terrificus venom. Mice were treated with radicicol, a HSP inductor, followed by an intramuscular injection of CTX into the gastrocnemius muscle. Treated groups were sacrificed 1, 10 and 21 days after CTX injection. Muscle histological sections were stained with toluidine blue and assayed for acid phosphatase or immunostained with either neuronal cell adhesion molecule (NCAM) or neonatal myosin heavy chain (MHCn). Muscle samples were also submitted to Western blotting analysis. The results show that CTX alone and CTX combined with radicicol induced a similar degree of myofiber necrosis. CTX-injured muscles treated with radicicol had increased cross-sectional areas at 10 and 21 days post-lesion compared with untreated CTX-injured muscles. Additionally, radicicol significantly increased the number of NCAM-positive satellite cells in the gastrocnemius at one day post-CTX injury. CTX-injured muscles treated with radicicol contained more MHCn-positive regenerating myofibers compared with untreated CTX-injured muscles. These results suggest that HSPs contribute to the regeneration of myofibers damaged by CTX. Additionally, further studies should investigate the potential therapeutic effects of radicicol in skeletal muscles affected by Crotalus venom.

Overexpression of inducible 70-kDa heat shock protein in mouse attenuates skeletal muscle damage induced by cryolesioning

Heat shock protein expression is elevated upon exposure to a variety of stresses and limits the extent of stress-induced damage. To investigate the putative role of inducible 70-kDa heat shock protein (HSP70) in skeletal muscle damage and regeneration, soleus and tibialis anterior (TA) muscles from HSP70-overexpressing transgenic mice were subjected to cryolesioning and analyzed after 1, 10, and 21 days. Histological analysis showed that the muscles from both HSP70 and wild-type mice treated with radicicol (a HSP inducer) had decreased necrosis after cryolesioning compared with controls. The decrease in muscle fiber cross-sectional area in both soleus and TA muscles in 10 days postlesioning was attenuated in HSP70 mice compared with wild-type mice. Glutathione peroxidase activity was increased 1 day after cryolesioning in both HSP70 and control mice and remained elevated for up to 21 days. Immunodetection of neuronal cell adhesion molecule (a satellite cell marker) and developmental/neonatal MHC were significantly lower in cryolesioned HSP70-overexpressing mice than in cryolesioned controls. These results suggest that HSP70 protects skeletal muscle against injury and radicicol might be useful as a skeletal muscle protective agent.

HSP-72 expression in pre-transplant donor kidney biopsies and post-transplant outcome

In experimental transplant models, upregulation of renal heat shock proteins (HSP) represents a new therapeutic tool to improve allograft survival. In this clinical study, we hypothesized that HSP-72 expression in pretransplant donor kidney biopsies predicts posttransplant outcome. Expression of HSP-72 in pretransplant biopsies was assessed by immunohistochemistry and in situ hybridization in 82 consecutive renal transplantations and clinical data were collected prospectively during the first six months posttransplant. Renal tubular expression of HSP-72 was low and not influenced by donor-, graft-, or procedure-related risk factors. Neither strength nor pattern of pretransplant HSP-72 staining discriminated allografts with complicated (40%) posttransplant courses from those without complications (60%). The low HSP-72 expression in pretransplant donor kidney biopsies failed to predict delayed graft function or acute rejection. These findings suggest that constitutive HSP-72 gene expression at the time of engraftment does not play a role in graft protection.

Heat shock protein 72 and apoptosis indicate cardiac decompensation during early multiple organ failure in sheep

OBJECTIVE

Inducible heat shock protein 72 (HSP 72) preserves myocardial function and prevents apoptosis. We investigated the expression and localization of HSP 72 and apoptosis in our previously described new model of multiple organ failure.

DESIGN

Eighteen adult-instrumented sheep and three healthy controls were randomly assigned to one of three groups: (a) norfenefrine-masked hypovolemia plus endotoxemia (NMH+ENDO); (b) norfenefrine-masked hypovolemia without endotoxemia (NMH); (c) recurrent endotoxemia during normovolemia (ENDO); and (d) normovolemia without endotoxemia (CONTROLS).

MEASUREMENTS AND RESULTS

Hearts were analyzed by light microscopy, Western blots, immunohistochemistry, and TUNEL staining. HSP 72 expression was approximately threefold increased in NMH+ENDO compared with the other groups ( p<0.05) and was localized mainly in left ventricular cardiomyocytes. HSP 72 was elevated in animals with norfenefrine-refractory shock compared to survivors ( p=0.015). TUNEL-positive cells in the left ventricle were significantly elevated in the NMH+ENDO group ( p=0.05) and correlated with HSP 72 expression (r=0.51, p=0.018). HSP 72 correlated positively with heart rate (r=0.76, p<0.0001), the prefinal hourly dose of norfenefrine (r=0.88, p<0.0001), and negatively with left ventricular stroke work index (r=-0.52, p=0.028). Double staining revealed TUNEL-positive cells with and without HSP 72 expression. Micronecroses were only detectable in NMH and NMH+ENDO without intergroup difference or correlations with hemodynamics.

CONCLUSION

HSP 72 overexpression and apoptosis, but not necrosis, indicate cardiovascular decompensation and poor outcome during early multiple organ failure.

Different skeletal muscle HSP70 responses to high-intensity strength training and low-intensity endurance training

Heat shock protein, e.g. HSP70, can be induced in human skeletal muscle undergoing exercise training, and plays important role in adaptation to stress. This study was designed to investigate the effects of high-intensity strength training and low-intensity endurance training on the HSP70 response to exercise, bearing in mind whether HSP70 is induced in the well-trained muscle during low-intensity endurance training. Six well-trained rowers (male, aged 18 years) underwent a training program which consisted of 3 weeks high-intensity training (HIT) and 3 weeks low-intensity endurance training (ET), followed by 1 week of recovery each (R1 and R2, respectively). HSP70 (2.5 microg total protein loaded) was determined by Western blot with reference to a series of known amount of standard HSP70. HSP70 mRNA was analyzed by RT-PCR, and the relative percentage change was referred to the baseline level (before training). HSP70 increased significantly at the end of HIT (from 51 to 73 ng), decreased at the end of R1(66 ng), and remained unchanged throughout ET and R2. HSP70 mRNA increased significantly after HIT (257%) and decreased gradually afterwards (194%, 166%, and 119% for R1, ET, and R2, respectively). It can be concluded that: (1) HSP70 was induced by high-intensity training, but not by endurance training at low intensity, and (2) there was a discrepancy in terms of HSP70 regulation between the protein and mRNA levels, suggesting that posttranscriptional regulation may play a role in HSP70 expression in human skeletal muscle in response to exercise.

Increased beta-myosin heavy chain in acute cellular rejection following human heart transplantation

BACKGROUND

Increased expression of smooth muscle and nonmuscle myosin heavy chains has been previously reported in animal models of cardiac allograft rejection. However, altered expression of beta-myosin heavy chain in human cardiac rejection has not been determined.

METHODS

Two-dimensional (2D)-gel electrophoresis of endomyocardial biopsies taken from patients with (Grade 3A, n = 6) and without (Grade 0, n = 6) acute rejection were analyzed. Increased expression of two protein spots (MW approximately 12 kDa) were identified in the presence of acute rejection and were further characterized by mass spectrometry analysis. In patients who had acute rejection, protein expression was subsequently analyzed by immunoblotting on biopsies preceding, during, and following treatment of rejection.

RESULTS

Mass spectrometric analysis of the protein spots detected 6 and 22 tryptic peptides, respectively. Protein sequence database search analysis identified the first protein as beta-myosin heavy chain and the second spot consisted of proteins of unidentified nature that may represent novel proteins. Immunoblotting analysis showed 1.4 x fold increase (p < 0.01) of protein expression of beta-myosin heavy chain expression in the presence of acute rejection.

CONCLUSIONS

To our knowledge, this is the first 2D-gel study to describe increased expression of beta-myosin heavy chain and other proteins of unidentified nature in association with human cardiac allograft rejection.

Increased level of HSP27 but not of HSP72 in human heart allografts in relation to acute rejection

BACKGROUND

Increased expression of heat shock proteins (HSPs) was assumed during cardiac allograft rejection. To find evidence for this in man, we quantified HSP27 and HSP72 in cardiac allograft biopsies.

METHODS

In parallel to histological assessment of rejection, HSP27 was quantified by Western blotting in a total of 43 biopsies sampled from 3 patients. HSP72 was analyzed in parallel in 30 of the 43 cases. For comparison, HSPs were analyzed in myocardium.

RESULTS

HSP27 was significantly higher in rejecting cardiac allografts than in non-rejecting allografts and non-failing myocardium (1.52 +/- 0.25 vs. 0.83 +/- 0.11 vs. 0.50 +/- 0.05 microg/mg protein). Similarity for HSP72 (6.27 +/- 1.54 vs. 4.06 +/- 1.03 vs. 6.27 +/- 0.76 microg/mg protein) was not found.

CONCLUSION

For the first time in humans with cardiac allograft rejection, increased expression of HSP27, which could be important for cardiac self-protection, was demonstrated. For the lack of increased HSP72 expression, the influence of the cyclosporine A treatment was discussed.

Metallothionein: localization in human transplant endomyocardium, relation to cytokines and allograft function

BACKGROUND

The aim of this study was to investigate the role of metallothionein in cardiac transplants in relation to cytokines and allograft function. Recent studies have revealed an association of allograft dysfunction with elevated proinflammatory cytokines independent of cellular rejection. In animal experiments, cytokines induced overexpression of metallothionein, a low-molecular-weight protein implicated in cellular stress response.

METHODS

In 105 consecutive biopsies from 15 patients during the first 3 months after heart transplantation, metallothionein expression was investigated immunohistochemically. Its relation to serum interleukin-6, tumor necrosis factor-alpha, interleukin-2 (IL-2), soluble interleukin-2 receptor rejection, and echocardiographic parameters was determined. Forty-three biopsies of 12 patients with idiopathic ventricular tachycardia served as controls.

RESULTS

Metallothionein expression was demonstrated in small vessels, cardiomyocytes, fibrocytes, and interstitial round cells. A positive relation between interleukin-6 levels and the number of metallothionein-positive small vessels (p < 0.028) was observed. Patients with lower serum IL-2 levels showed significantly higher numbers of metallothionein-positive small vessels (p < 0.043). Grafts with prolonged ischemic time (>150 minutes) showed a significantly higher myocardial metallothionein score (p < 0.021). Metallothionein expression was associated with lower fractional shortening, larger left ventricular end-systolic diameter, and lower mean arterial pressure but not with acute cellular rejection.

CONCLUSIONS

Metallothionein expression is associated with elevated interleukin-6 and decreased interleukin-2 serum levels and left ventricular allograft dysfunction in the absence of rejection.

Heat shock proteins as cellular lifeguards

Cells have developed complex ways to respond to various stresses. Interestingly, stresses such as heat, ischaemia and radiation can induce different cellular responses depending on their strength. While a mild stress induces a protective heat shock response, a more potent stress stimulus induces apoptosis and an even stronger one leads to necrosis. The heat shock or stress response, ie the synthesis of heat shock proteins (Hsps, stress proteins) in response to a mild stress, allows cells to adapt to gradual changes in their environment and to survive in otherwise lethal conditions. The ability of Hsps to protect cultured cells from both apoptosis and necrosis has been well demonstrated. Novel data suggest an important protective role for them also in vivo as they can protect heart and brain against ischaemia and lungs and liver against sepsis. Moreover, they can render tumours resistant to anticancer therapy. These and other cytoprotective effects of Hsps make them tempting targets for therapeutic interventions in several diseases.