Confocal microscopic localization of constitutive and heat shock-induced proteins HSP70 and HSP27 in the rat heart

Heat Shock Protein 70 in Penile Neurovascular Regeneration Requires Cystathionine Gamma-Lyase

Purpose

Diabetes mellitus, one of the major causes of erectile dysfunction, leads to a poor response to phosphodiesterase-5 inhibitors. Heat shock protein 70 (Hsp70), a ubiquitous molecular chaperone, is known to play a role in cell survival and neuroprotection. Here, we aimed to assess whether and how Hsp70 improves erectile function in diabetic mice.

Materials and Methods

Eight-week-old male C57BL/6 mice and Hsp70-Tg mice were used in this study. We injected Hsp70 protein into the penis of streptozotocin (STZ)-induced diabetic mice. Detailed mechanisms were evaluated in WT or Hsp70-Tg mice under normal and diabetic conditions. Primary MCECs, and MPG and DRG tissues were cultivated under normal-glucose and high-glucose conditions.

Results

Using Hsp70-Tg mice or Hsp70 protein administration, we demonstrate that elevated levels of Hsp70 restores erectile function in diabetic mice. We found that cystathionine gamma-lyase (Cse) is a novel target of Hsp70 in this process, showing that Hsp70-Cse acts through the SDF1/HO-1/PI3K/Akt/eNOS/NF-κB p65 pathway to exert its neurovascular regeneration-promoting effects. Coimmunoprecipitation and pull-down assays using mouse cavernous endothelial cells treated with Hsp70 demonstrated physical interactions between Hsp70 and Cse with a dissociation constant of 1.8 nmol/L.

Conclusions

Our findings provide novel and solid evidence that Hsp70 acts through a Cse-dependent mechanism to mediate neurovascular regeneration and restoration of erectile function under diabetic conditions.

Role of 72-kDa Heat Shock Protein in Heat-stimulated Regeneration of Injured Muscle in Rat

The regeneration of injured muscles is facilitated by intermittent heat stress. The 72-kDa heat shock protein (HSP72), the level of which is increased by heat stress, is likely involved in this effect, but the precise mechanism remains unclear. This study was conducted to investigate the localization and role(s) of HSP72 in the regenerating muscles in heat-stressed rats using immunohistochemistry. Heat stress was applied by immersion of the rat lower body into hot water (42C, 30 min, every other day) following injection of bupivacaine into the soleus muscles. After 1 week, we found that HSP72 was expressed at high levels not only in the surviving myofibers but also in the blood vessels of the regenerating muscles in heated rats. In addition, leukocytes, possibly granulocytes, expressing cluster of differentiation 43 within the blood capillaries surrounding the regenerating myofibers also highly expressed HSP72. In contrast, marked expression of HSP72 was not observed in the intact or regenerating muscles without heat stress. These results suggest that heat-stress-induced HSP72 within the myofibers, blood vessels, and circulating leukocytes may play important roles in enhancing regeneration of injured muscles by heat stress. Our findings would be useful to investigate cell-specific role(s) of HSP72 during skeletal muscle regeneration.

Ten days of repeated local forearm heating does not affect cutaneous vascular function

The aim of the present study was to determine whether 10 days of repeated local heating could induce peripheral adaptations in the cutaneous vasculature and to investigate potential mechanisms of adaptation. We also assessed maximal forearm blood flow to determine whether repeated local heating affects maximal dilator capacity. Before and after 10 days of heat training consisting of 1-h exposures of the forearm to 42°C water or 32°C water (control) in the contralateral arm (randomized and counterbalanced), we assessed hyperemia to rapid local heating of the skin (n = 14 recreationally active young subjects). In addition, sequential doses of acetylcholine (ACh, 1 and 10 mM) were infused in a subset of subjects (n = 7) via microdialysis to study potential nonthermal microvascular adaptations following 10 days of repeated forearm heat training. Skin blood flow was assessed using laser-Doppler flowmetry, and cutaneous vascular conductance (CVC) was calculated as laser-Doppler red blood cell flux divided by mean arterial pressure. Maximal cutaneous vasodilation was achieved by heating the arm in a water-spray device for 45 min and assessed using venous occlusion plethysmography. Forearm vascular conductance (FVC) was calculated as forearm blood flow divided by mean arterial pressure. Repeated forearm heating did not increase plateau percent maximal CVC (CVC_max) responses to local heating (89 ± 3 vs. 89 ± 2% CVC_max, P = 0.19), 1 mM ACh (43 ± 9 vs. 53 ± 7% CVC_max, P = 0.76), or 10 mM ACh (61 ± 9 vs. 85 ± 7% CVC_max, P = 0.37, by 2-way repeated-measures ANOVA). There was a main effect of time at 10 mM ACh (P = 0.03). Maximal FVC remained unchanged (0.12 ± 0.02 vs. 0.14 ± 0.02 FVC, P = 0.30). No differences were observed in the control arm. Ten days of repeated forearm heating in recreationally active young adults did not improve the microvascular responsiveness to ACh or local heating.NEW & NOTEWORTHY We show for the first time that 10 days of repeated forearm heating is not sufficient to improve cutaneous vascular responsiveness in recreationally active young adults. In addition, this is the first study to investigate cutaneous cholinergic sensitivity and forearm blood flow following repeated local heat exposure. Our data add to the limited studies regarding repeated local heating of the cutaneous vasculature.

Tyrosol prevents ischemia/reperfusion-induced cardiac injury in H9c2 cells: involvement of ROS, Hsp70, JNK and ERK, and apoptosis

Ischemia-Reperfusion (I/R) injury causes ROS overproduction, creating oxidative stress, and can trigger myocyte death, resulting in heart failure. Tyrosol is an antioxidant abounded in diets and medicine. Our objective was to investigate the protective effect of tyrosol on I/R-caused mortality in H9c2 cardiomyocytes through its influence on ROS, Hsp70, ERK, JNK, Bcl-2, Bax and caspase-8. A simulated I/R model was used, myocytes loss was examined by MTT, and ROS levels were measured using DCFH-DA. Nuclear condensation and caspase-3 activity were assessed by DAPI staining and fluorometric assay. Phosphorylated ERK and JNK were determined by electrochemiluminescent ELISA, and Hsp70, Bcl-2, Bax and caspase-8 were examined by Western blotting. Results show that tyrosol salvaged myocyte loss, inhibited nuclear condensation and caspase-3 activity dose-dependently, indicating its protection against I/R-caused myocyte loss. Furthermore, tyrosol significantly inhibited ROS accumulation and activation of ERK and JNK, augmenting Hsp70 expression. Besides, tyrosol inhibited I/R-induced apoptosis, associated with retained anti-apoptotic Bcl-2 protein, and attenuated pro-apoptotic Bax protein, resulting in a preservation of Bcl-2/Bax ratio. Finally, tyrosol notably decreased cleaved caspase-8 levels. In conclusion, cytoprotection of tyrosol in I/R-caused myocyte mortality was involved with the mitigation of ROS, prohibition of the activation of ERK, JNK and caspase-8, and elevation of Hsp70 and Bcl-2/Bax ratio.

Transforming growth factor-β-activated kinase 1 enhances H2O2-induced apoptosis independently of reactive oxygen species in cardiomyocytes

AIMS

Heat shock protein 70 (HSP70) protects against cardiac diseases such as ischemia/reperfusion injury and myocardial infarction. However, the underlying mechanisms have not yet been fully characterized.

METHODS

In this study, we investigated the effects of reactive oxygen species (ROS) and transforming growth factor-β-activated kinase 1 (TAK1) on HSP70-regulated cardiomyocyte protection. Cultured cardiomyocytes of neonatal rats were transfected with HSP70, TAK1 or both of them before exposure to H2O2, and the ROS generation, p38 mitogen-activated protein kinase (p38) activity and apoptosis were examined.

RESULTS

H2O2 significantly enhanced intracellular ROS generation and apoptosis as expected, and all these cellular events were greatly abolished by overexpression of HSP70. However, H2O2-induced increments in p38 phosphorylation and cardiac cell apoptosis were largely enhanced by TAK1 overexpression, whereas the similar transfection did not affect the ROS generation in the cardiomyocytes. Moreover, inhibition of H2O2-increased ROS generation, p38 phosphorylation, and cardiomyocytes apoptosis by overexpression of HSP70 tended to disappear when the cells were cotransfected with TAK1.

CONCLUSION

Our data suggest that HSP70 protects cardiomyocytes from apoptosis under oxidative stress through downregulation of intracellular ROS generation and inhibition of p38 phosphorylation. Although TAK1 itself has no effect on intracellular ROS accumulation, it may affect the inhibitory effects of HSP70 on ROS generation, p38 activity and cardiomyocyte injury.

Expression of heat shock proteins (hsp) 27 and 70 in various organ systems in cases of death due to fire

The expression of heat shock proteins (hsp) increases in case of variable types of endogenous and exogenous cellular stress, as for example thermal stress. Immunohistochemical staining with hsp antibodies can visualize these stress proteins. Fifty-three cases of death due to heat and a control group of 100 deaths without any antemortem thermic stress were examined regarding hsp27 and hsp70 expression in myocardial, pulmonary, and renal tissues. The results revealed a correlation between hsp expression, survival time, and cause of death. In cases of death due to fire, the expression of hsp is more extensive than in the control group, especially in pulmonary and renal tissues. The immunohistochemical investigation of an hsp expression can support the proof of vitality in cases of death related to fire.

Contribution of small heat shock proteins to muscle development and function

Investigations undertaken over the past years have led scientists to introduce the concept of protein quality control (PQC) systems, which are responsible for polypeptide processing. The PQC system monitors proteostasis and involves activity of different chaperones such as small heat shock proteins (sHSPs). These proteins act during normal conditions as housekeeping proteins regulating cellular processes, and during stress conditions. They also mediate the removal of toxic misfolded polypeptides and thereby prevent development of pathogenic states. It is postulated that sHSPs are involved in muscle development. They could act via modulation of myogenesis or by maintenance of the structural integrity of signaling complexes. Moreover, mutations in genes coding for sHSPs lead to pathological states affecting muscular tissue functioning. This review focuses on the question how sHSPs, still relatively poorly understood proteins, contribute to the development and function of three types of muscle tissue: skeletal, cardiac and smooth.

Regulation of heat shock proteins 27 and 70, p-Akt/p-eNOS and MAPKs by Naringin Dampens myocardial injury and dysfunction in vivo after ischemia/reperfusion

Naringin has antioxidant properties that could improve redox-sensitive myocardial ischemia reperfusion (IR) injury. This study was designed to investigate whether naringin restores the myocardial damage and dysfunction in vivo after IR and the mechanisms underlying its cardioprotective effects. Naringin (20–80 mg/kg/day, p.o.) or saline were administered to rats for 14 days and the myocardial IR injury was induced on 15^th day by occluding the left anterior descending coronary artery for 45 min and subsequent reperfusion for 60 min. Post-IR rats exhibited pronounced cardiac dysfunction as evidenced by significantly decreased mean arterial pressure, heart rate, +LVdP/dt_max (inotropic state), -LVdP/dt_max (lusitropic state) and increased left ventricular end diastolic pressure as compared to sham group, which was improved by naringin. Further, on histopathological and ultrastructural assessments myocardium and myocytes appeared more normal in structure and the infarct size was reduced significantly in naringin 40 and 80 mg/kg/day group. This amelioration of post-IR-associated cardiac injury by naringin was accompanied by increased nitric oxide (NO) bioavailability, decreased NO inactivation to nitrotyrosine, amplified protein expressions of Hsp27, Hsp70, β-catenin and increased p-eNOS/eNOS, p-Akt/Akt, and p-ERK/ERK ratio. In addition, IR-induced TNF-α/IKK-β/NF-κB upregulation and JNK phosphorylation were significantly attenuated by naringin. Moreover, western blotting and immunohistochemistry analysis of apoptotic signaling pathway further established naringin cardioprotective potential as it upregulated Bcl-2 expression and downregulated Bax and Caspase-3 expression with reduced TUNEL positivity. Naringin also normalized the cardiac injury markers (lactate dehydrogenase and creatine kinase-MB), endogenous antioxidant activities (superoxide dismutase, reduced glutathione and glutathione peroxidase) and lipid peroxidation levels. Thus, naringin restored IR injury by preserving myocardial structural integrity and regulating Hsp27, Hsp70, p-eNOS/p-Akt/p-ERK signaling and inflammatory response.

Heat stroke activates a stress-induced cytokine response in skeletal muscle

Heat stroke (HS) induces a rapid elevation in a number of circulating cytokines. This is often attributed to the stimulatory effects of endotoxin, released from damaged intestine, on immune cells. However, parenchymal cells also produce cytokines, and skeletal muscle, comprising a large proportion of body mass, is thought to participate. We tested the hypothesis that skeletal muscle exhibits a cytokine response to HS that parallels the systemic response in conscious mice heated to a core temperature of 42.4°C (TcMax). Diaphragm and hindlimb muscles showed a rapid rise in interleukin-6 (IL-6) and interleuin-10 (IL-10) mRNA and transient inhibition of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) throughout early recovery, a pattern that parallels changes in circulating cytokines. IL-6 protein was transiently elevated in both muscles at ∼32 min after reaching TcMax. Other responses observed included an upregulation of toll-like receptor-4 (TLR-4) and heat shock protein-72 (HSP-72) mRNA but no change in TLR-2 or HSP25 mRNA. Furthermore, c-jun and c-fos mRNA increased. Together, c-jun/c-fos form the activator protein-1 (AP-1) transcription factor, critical for stress-induced regulation of IL-6. Interestingly, a second “late-phase” (24 h) cytokine response, with increases in IL-6, IL-10, IL-1β, and TNF-α protein, were observed in hindlimb but not diaphragm muscle. These results demonstrate that skeletal muscle responds to HS with a distinct “stress-induced immune response,” characterized by an early upregulation of IL-6, IL-10, and TLR-4 and suppression of IL-1β and TNF-α mRNA, a pattern discrete from classic innate immune cytokine responses.

Alterations in the telomere length distribution and the subtelomeric methylation status in human vascular endothelial cells under elevated temperature in culture condition

Temperature-associated alteration in the telomere lengths of vascular endothelial cells has not been well investigated. Telomere length of human umbilical vein endothelial cells (HUVECs) cultured at a high temperature (42 °C) was analyzed. Here described are heat-associated phenotypical alterations of human vascular endothelial cell under prolonged heat stress in terms of telomere length, telomerase activity, and the expression of telomere associated proteins and heat shock proteins. The genomic DNA extracted from HUVECs cultured for 3 days under 42 °C was digested with methylation-sensitive and -insensitive isoschizomers and was subjected to genomic Southern blot probed with a telomere DNA fragment. Their telomere lengths and telomere length distributions were analyzed. Telomerase activity and the expressions of telomere-associated RNA, telomere-associated proteins (TERC, TERT, TRF1, and TRF2), and heat shock proteins (Hsp60, Hsp70, and Hsp90) were also analyzed. At 42 °C, cell growth was suppressed and the cell senescence rate was transiently elevated. A proportional decrease in the number of long telomeres was observed transiently at 42 °C. A trend of subtelomeric hypomethylation and lowered telomerase activity were observed at 42 °C after 3-day culture. The altered phenotypes on day 1 seemed reactive responses for cell protection to heat, and those on day 3 seemed exhausted reactions after 3-day culture. Maintained expression was observed in Hsps, TRF2, and TERC. These altered phenotypes might contribute to cell-survival under prolonged heat stress.

TAK1 activates AMPK-dependent cell death pathway in hydrogen peroxide-treated cardiomyocytes, inhibited by heat shock protein-70

The aim of this current study is to investigate the potential role of AMP-activated protein kinase (AMPK) in hydrogen peroxide (H2O2)-induced cardiomyocyte death, and focused on the signaling mechanisms of AMPK activation by H2O2. We observed a significant AMPK activation in H2O2-treated cardiomyocytes (both primary cells and H9c2 line). Inhibition of AMPK by its inhibitor or RNAi-reduced H2O2-induced cardiomyocyte death. We here proposed that transforming growth factor-β-activating kinase 1 (TAK1) might be the upstream kinase for AMPK activation by H2O2. H2O2-induced TAK1 activation, which recruited and activated AMPK. TAK1 inhibitor significantly suppressed H2O2-induced AMPK activation and following cardiomyocyte death, while over-expression of TAK1-facilitated AMPK activation and aggregated cardiomyocyte death. Importantly, heat shock protein-70 (HSP-70)-reduced H2O2-induced reactive oxygen species (ROS) accumulation, the TAK1/AMPK activation and cardiomyocyte death. In conclusion, we here suggest that TAK1 activates AMPK-dependent cell death pathway in H2O2-treated cardiomyocytes, and HSP-70 inhibits the signaling pathway by reducing ROS content.

Impact of exercise and metabolic disorders on heat shock proteins and vascular inflammation

Heat shock proteins (Hsp) play critical roles in the body's self-defense under a variety of stresses, including heat shock, oxidative stress, radiation, and wounds, through the regulation of folding and functions of relevant cellular proteins. Exercise increases the levels of Hsp through elevated temperature, hormones, calcium fluxes, reactive oxygen species (ROS), or mechanical deformation of tissues. Isotonic contractions and endurance- type activities tend to increase Hsp60 and Hsp70. Eccentric muscle contractions lead to phosphorylation and translocation of Hsp25/27. Exercise-induced transient increases of Hsp inhibit the generation of inflammatory mediators and vascular inflammation. Metabolic disorders (hyperglycemia and dyslipidemia) are associated with type 1 diabetes (an autoimmune disease), type 2 diabetes (the common type of diabetes usually associated with obesity), and atherosclerotic cardiovascular disease. Metabolic disorders activate HSF/Hsp pathway, which was associated with oxidative stress, increased generation of inflammatory mediators, vascular inflammation, and cell injury. Knock down of heat shock factor-1 (HSF1) reduced the activation of key inflammatory mediators in vascular cells. Accumulating lines of evidence suggest that the activation of HSF/Hsp induced by exercise or metabolic disorders may play a dual role in inflammation. The benefits of exercise on inflammation and metabolism depend on the type, intensity, and duration of physical activity.

Myocardial accumulation and localization of the inducible 70-kDa heat shock protein, Hsp70, following exercise

Exercise increases the 70-kDa heat shock protein (Hsp70) in the myocardium, and this exercise-induced increase is associated with significantly improved cardiac recovery following insult. However, while heat shock has been shown to elevate Hsp70 primarily in the cardiac vasculature of the myocardium, the localization following exercise is unknown. Male Sprague-Dawley rats performed continuous treadmill running at 30 m/min for 60 min (2% incline) on either 1 or 5 consecutive days. At 30 min and 24 h following exercise, hearts were extirpated, and the left ventricle was isolated, OCT-cork mounted, and sectioned for immunofluorescent analysis. Whereas immunofluorescent analysis revealed little to no Hsp70 in control hearts and 30 min postexercise, the accumulation of Hsp70 24 h after a single exercise bout or 5 days of training was predominantly located in large blood vessels and, in particular, colocalized with a marker of smooth muscle. Furthermore, higher core temperatures attained during exercise led to more abundant accumulation in smaller vessels and the endothelium. It is concluded that the accumulation of myocardial Hsp70 following acute exercise predominantly occurs in a cell type-specific manner, such that changes in the cardiac vasculature account for much of the increase. This accumulation appears first in the smooth muscle of larger vessels and then increases in smaller vessels and the endothelium, as core temperature attained during exercise increases. This finding supports the observations after heat shock and further suggests that the vasculature is a primary target in exercise-induced cardioprotection.

hsp70 mRNA temporal localization in rat skeletal myofibers and blood vessels post-exercise

Rapid transcription of the survival transcript, inducible heat shock protein 70 (hsp70), is critical for mounting cytoprotection against severe cellular stress, like elevated temperature. Previous investigations have demonstrated that exercise-induced expression of Hsp70 protein occurs in a fiber-specific pattern; however, the activation pattern of hsp70 mRNA expression remains unclear in skeletal muscle. Consequentially, the temporal localization of hsp70 mRNA was characterized via in situ hybridization (ISH) experiments examining fast-muscle, white vastus: 1, 3, 10, and 24 h after a single bout of intense treadmill running (1 h, 30 m/min, 6% grade) in rats. The role that the physiologic temperature stress associated with exercise (raising core body temperature to 40.0°C for 15 min (HS-40.0°C)) might play in inducing hsp70 mRNA expression was also explored. In skeletal muscle myofibers (SkM), hsp70 mRNA ISH signal was observed to be concentrated in a punctate manner that was associated with nuclei post-exercise. HS-40°C treatment produced minimal detectable hsp70 mRNA ISH signal in SkM. In large intermyofibrillar blood vessels (BV), peak hsp70 mRNA signal, distributed throughout the vessel wall, was observed 1 h post-exercise. In BV, no differences in hsp70 mRNA signal were observed between HS-40°C and EX-1 h. Results indicate that the majority of hsp70 mRNA is retained in a perinuclear localization in SkM post-exercise. They further suggest a muscle-type specific time course for peak hsp70 mRNA expression. This investigation suggests that the physiologic rise in core temperature associated with exercise per se is not the key stimulus responsible for inducing hsp70 mRNA transcription in SkM.

Large potentials of small heat shock proteins

Modern classification of the family of human small heat shock proteins (the so-called HSPB) is presented, and the structure and properties of three members of this family are analyzed in detail. Ubiquitously expressed HSPB1 (HSP27) is involved in the control of protein folding and, when mutated, plays a significant role in the development of certain neurodegenerative disorders. HSPB1 directly or indirectly participates in the regulation of apoptosis, protects the cell against oxidative stress, and is involved in the regulation of the cytoskeleton. HSPB6 (HSP20) also possesses chaperone-like activity, is involved in regulation of smooth muscle contraction, has pronounced cardioprotective activity, and seems to participate in insulin-dependent regulation of muscle metabolism. HSPB8 (HSP22) prevents accumulation of aggregated proteins in the cell and participates in the regulation of proteolysis of unfolded proteins. HSPB8 also seems to be directly or indirectly involved in regulation of apoptosis and carcinogenesis, contributes to cardiac cell hypertrophy and survival and, when mutated, might be involved in development of neurodegenerative diseases. All small heat shock proteins play important "housekeeping" roles and regulate many vital processes; therefore, they are considered as attractive therapeutic targets.

Heat-shock proteins in cardiovascular disease

Heat-shock proteins (HSPs) belong to a group of highly conserved families of proteins expressed by all cells and organisms and their expression may be constitutive or inducible. They are generally considered as protective molecules against different types of stress and have numerous intracellular functions. Secretion or release of HSPs has also been described, and potential roles for extracellular HSPs reported. HSP expression is modulated by different stimuli involved in all steps of atherogenesis including oxidative stress, proteolytic aggression, or inflammation. Also, antibodies to HSPs may be used to monitor the response to different types of stress able to induce changes in HSP levels. In the present review, we will focus on the potential implication of HSPs in atherogenesis and discuss the limitations to the use of HSPs and anti-HSPs as biomarkers of atherothrombosis. HSPs could also be considered as potential therapeutic targets to reinforce vascular defenses and delay or avoid clinical complications associated with atherothrombosis.

Estrogen, aging and the cardiovascular system

Estrogen is a powerful hormone with pleiotropic effects. Estrogens have potent antioxidant effects and are able to reduce inflammation, induce vasorelaxation and alter gene expression in both the vasculature and the heart. Estrogen treatment of cultured cardiac myocytes and endothelial cells rapidly activates NFkappaB, induces heat-shock protein (HSP)-72, a potent intracellular protective protein, and protects cells from simulated ischemia. In in vivo models, estrogens protect against ischemia and trauma/hemorrhage. Estrogens may decrease the expression of soluble epoxide hydrolase, which has deleterious effects on the cardiovascular system through metabolism of epoxyeicosatrienoic acids. Natural (endogenous) estrogens in premenopausal women appear to protect against cardiovascular disease and yet controlled clinical trials have not indicated a benefit from estrogen replacement postmenopause. Much remains to be understood in regards to the many properties of this powerful hormone and how changes in this hormone interact with aging-associated changes. The unexpected negative results of trials of estrogen replacement postmenopause probably arise from our lack of understanding of the many effects of this hormone.

Hsp27 associates with the titin filament system in heat-shocked zebrafish cardiomyocytes

Injury to muscle tissue plays a central role in various cardiovascular pathologies. Overexpression of the small heat shock protein Hsp27 protects muscle cells against thermal, oxidative and ischemic stress. However, underlying mechanisms of this protection have not been resolved. A distinctive feature of muscle cells is the stress-induced association of Hsp27 with the sarcomere. The association of Hsp27 with the cytoskeleton, in both muscle and non-muscle cells, is thought to represent interaction with Z-line components or filamentous actin. Here, we examined the association of Hsp27 with myofibrils in adult zebrafish myocardium subjected to hyperthermia and mechanical stretching. Consistent with previously published results, Hsp27 in resting length myofibrils localized to narrowly defined regions, or bands, which colocalized with Z-line markers. However, analysis of stretched myofibrils revealed that the association of Hsp27 with myofibrils was independent of desmin, alpha-actinin, myosin, and filamentous actin. Instead, Hsp27 maintained a consistent relationship with a marker for the titin A/I border over various sarcomeric lengths. Finally, extraction of actin filaments revealed that Hsp27 binds to a component of the remaining sarcomere. Together, these novel data support a mechanism of Hsp27 function where interactions with the titin filament system protect myofibrils from stress-induced degradation.

Cellular distribution of Hsp70 expression in rat skeletal muscles. Effects of moderate exercise training and chronic hypoxia

Rat hindlimb muscles constitutively express the inducible heat shock protein 72 (Hsp70), apparently in proportion to the slow myosin content. Since it remains controversial whether chronic Hsp70 expression reflects the overimposed stress, we investigated Hsp70 cellular distribution in fast muscles of the posterior rat hindlimb after (1) mild exercise training (up to 30 m/min treadmill run for 1 h/day), which induces a remodeling in fast fiber composition, or (2) prolonged exposure to normobaric hypoxia (10%O(2)), which does not affect fiber-type composition. Both conditions increased significantly protein Hsp70 levels in the skeletal muscle. Immunohistochemistry showed the labeling for Hsp70 in subsets of both slow/type 1 and fast/type 2A myofibers of control, sedentary, and normoxic rats. Endurance training increased about threefold the percentage of Hsp70-positive myofibers (P < 0.001), and changed the distribution of Hsp70 immunoreactivity, which involved a larger subset of both type 2A and intermediate type 2A/2X myofibers (P < 0.001) and vascular smooth muscle cells. Hypoxia induced Hsp70 immunoreactivity in smooth muscle cells of veins and did not increase the percentage of Hsp70-positive myofibers; however, sustained exposure to hypoxia affected the distribution of Hsp70 immunoreactivity, which appeared detectable in a very small subset of type 2A fibers, whereas it concentrated in type 1 myofibers (P < 0.05) together with the labeling for heme-oxygenase isoform 1, a marker of oxidative stress. Therefore, the chronic induction of Hsp70 expression in rat skeletal muscles is not obligatory related to the slow fiber phenotype but reveals the occurrence of a stress response.

Variation in basal heat shock protein 70 is correlated to core temperature in human subjects

Heat shock proteins are highly conserved proteins and play an important chaperone role in aiding the folding of nascent proteins within cells. The heat shock protein response to various stressors, both in vitro and in vivo, is well characterised. However, basal levels of heat shock protein 70 (Hsp70) have not previously been investigated. Monocyte-expressed Hsp70 was determined every 4 h, over a 24 h time period, in 17 healthy male subjects (177 +/- 6.4 cm, 75.7 +/- 10.9 kg, 19.8 +/- 4.3 years) within a temperature and activity controlled environment. Core temperature was measured at 5-min intervals during the 24 h period. Hsp70 showed significant diurnal variation (F = 7.4; p < 0.001), demonstrating peaks at 0900 and 2100 hours, and a nadir at 05.00. Core temperature followed a similar temporal trend (range = 35.96-38.10 degrees C) and was significantly correlated with Hsp70 expression (r(s) = 0.44; p < 0.001). These findings suggest a high responsiveness of Hsp70 expression in monocytes to slight variations in core temperature.

Molecular imaging-assisted optimization of hsp70 expression during laser-induced thermal preconditioning for wound repair enhancement

Patients at risk for impaired healing may benefit from prophylactic measures aimed at improving wound repair. Several photonic devices claim to enhance repair by thermal and photochemical mechanisms. We hypothesized that laser-induced thermal preconditioning would enhance surgical wound healing that was correlated with hsp70 expression. Using a pulsed diode laser (lambda=1.85 microm, tau(p)=2 ms, 50 Hz, H=7.64 mJ cm(-2)), the skin of transgenic mice that contain an hsp70 promoter-driven luciferase was preconditioned 12 hours before surgical incisions were made. Laser protocols were optimized in vitro and in vivo using temperature, blood flow, and hsp70-mediated bioluminescence measurements as benchmarks. Biomechanical properties and histological parameters of wound healing were evaluated for up to 14 days. Bioluminescent imaging studies indicated that an optimized laser protocol increased hsp70 expression by 10-fold. Under these conditions, laser-preconditioned incisions were two times stronger than control wounds. Our data suggest that this molecular imaging approach provides a quantitative method for optimization of tissue preconditioning and that mild laser-induced heat shock may be a useful therapeutic intervention prior to surgery.

Insulin-induced myocardial protection in isolated ischemic rat hearts requires p38 MAPK phosphorylation of Hsp27

Six hours after insulin treatment, hearts express heat shock protein 70 (Hsp70) and have improved contractile function after ischemia-reperfusion injury. In this study we examined hearts 1 h after insulin treatment for contractile function and for expression of Hsp70 and Hsp27. Adult, male Sprague-Dawley rats were assigned to groups: 1) sham, 2) control, 3) insulin injected (200 μU/g body wt), 4) heat shock treated (core body temperature, 42°C for 15 min), and 5) heat shock and insulin treated. At 1 h after these treatments, hearts were isolated, equilibrated to Langendorff perfusion for 30 min, and then subjected for 30 min no-flow global ischemia (37°C) followed by 2 h of reperfusion. Insulin-treated hearts had significantly increased contractile function compared with control hearts. At 1 h after insulin treatment, a minimal change in Hsp70 and Hsp27 content were detected. By 3 h after insulin treatment, a significant increase in Hsp70, but not Hsp27, was detected by Western blot analysis. By immunofluorescence, minimal Hsp70 was detected in insulin-treated hearts, whereas Hsp27 was detected in all hearts, indicative of its constitutive expression. Phosphospecific isoforms of Hsp27 were detected in insulin-, heat shock-, and heat shock and insulin-treated hearts. After ischemia and reperfusion, the insulin-treated hearts had significantly elevated levels of phosphorylated Hsp27. Inhibition of p38 MAPK with SB-203580 blocked the insulin-induced phosphorylation of Hsp27 and the improved functional recovery. In conclusion, insulin induces an apparent rapid phosphorylation of Hsp27 that is associated with improved functional recovery after ischemia-reperfusion injury.

Effects of heat stress on filamentous actin and prestin of outer hair cells in mice

When the ear is exposed to traumatic loud noise, outer hair cells (OHCs) are damaged and thus permanent hearing loss occurs. Recently, prior conditioning with heat stress has been reported to protect OHCs from traumatic noise exposure by increasing the stiffness of the OHC soma and has also been reported to enhance distortion product otoacoustic emissions [DPOAEs; Murakoshi, M., Yoshida, N., Kitsunai, Y., Iida, K., Kumano, S., Suzuki, T., Kobayashi, T., Wada, H., 2006. Effects of heat stress on Young's modulus of outer hair cells in mice. Brain Res. 1107, 121-130]. In the present study, to further investigate the heat stress-induced protective mechanism of hearing and such stress-induced DPOAE enhancement mechanism, the amount of filamentous actin (F-actin), which is concerned with cell stiffness, and the amount of prestin, which is concerned with the generation of DPOAEs, were examined in OHCs, with and without heat stress. Heat stress was found to increase the amount of F-actin 6-24 h after heat stress. The greatest increase in the amount of F-actin was observed at the cuticular plate where F-actin anchors the roots of the stereocilia to the cell body. Based on this result, the part of the stereocilia most reinforced and protected by heat stress was concluded to be the roots of the stereocilia. In contrast with F-actin, heat stress did not affect the amount of prestin.

H2O2 activation of HSP25/27 protects desmin from calpain proteolysis in rat ventricular myocytes

Ischemia-reperfusion-induced Ca2+ overload results in activation of calpain-1 in the heart. Calpain-dependent proteolysis contributes to myocardial dysfunction and cell death. Previously, preischemic treatment with low doses of H2O2 was shown to improve postischemic function and reduce myocardial infarct size. Our aim was to determine the mechanism by which H2O2 protects the heart. We hypothesized that H2O2 causes the activation of p38 MAPK which initiates translocation of heat shock protein 25/27 (HSP25/27) to the myofilament Z disk. We further hypothesized that HSP25/27 shields structural proteins, particularly desmin, from calpain-induced proteolysis. To address this hypothesis, we first determined that an ischemia-reperfusion-induced decrease in desmin content could be blocked by H2O2 pretreatment of hearts from rats. We next determined that ventricular myocytes that underwent Ca2+ overload also demonstrated a calpain-dependent disruption of desmin that could be reduced by H2O2/p38 MAPK activation. Furthermore, myocytes acutely treated with H2O2 exhibited a decrease in cleavage of desmin upon exposure to exogenous calpain-1 compared with myocytes not pretreated with H2O2. The H2O2-induced attenuation of desmin degradation by calpain-1 was blocked by inhibition of p38 MAPK. In a final series of experiments, we demonstrated that cardiac myofilaments exposed to recombinant phosphorylated HSP27, but not nonphosphorylated HSP27, had a significant reduction in the calpain-induced degradation of desmin compared with non-HSP27-treated myofilaments. These findings are consistent with the hypothesis that H2O2-induced activation of p38 MAPK and subsequent HSP25/27 translocation attenuates desmin degradation brought about by calpain-1 activation in ischemia-reperfused hearts.

Exercise training improves myocardial tolerance to ischemia in male but not in female rats

Acute exercise increases myocardial tolerance to ischemia-reperfusion (I-R) injury in male but not in female rat hearts, possibly due to a decreased heat shock protein 70 (Hsp70) response in the female hearts. This study examined whether repetitive exercise training would increase Hsp70 and myocardial tolerance to I-R injury in female rat hearts. Adaptations in myocardial manganese superoxide dismutase (MnSOD) and endothelial nitric oxide synthase (eNOS) were also assessed. Ten-week old male (M) and female (F) Sprague-Dawley rats ( n = 40 total) exercise-trained for 14 wk; the last 8 wk consisted of running 1 h at 30 m/min (2% incline), 5 days/wk. Following training, left ventricle mechanical function (LVMF) was monitored for 30 min of reperfusion following 30 min of global ischemia (Langendorff procedure). Myocardial Hsp70 content was not different in M and F control groups, while increases were observed in both trained groups (M greater than F; P < 0.05). Although MnSOD content did not differ between groups, endothelial nitric oxide synthase (eNOS) levels were decreased in F, with no change in M, following training ( P < 0.05). Hearts from control F demonstrated a greater recuperation of all indices of LVMF following I-R compared with control M hearts ( P < 0.05). Hearts of trained M exhibited improved recovery of LVMF (left ventricular diastolic pressure, left ventrcular end-diastolic pressure, +dP/d t, −dP/d t) during reperfusion compared with control M hearts ( P < 0.05). In contrast, hearts of trained F did not show any change in recovery from I-R. Hence, exercise training is more beneficial to M than F in improving myocardial function following I-R injury.

IDENTIFICATION OF DIFFERENTIALLY EXPRESSED GENES AFTER HEAT SHOCK IN ISOLATED RAT AORTA

1. In a previous study, we demonstrated that heat shock augments vascular contractility through the stress response. 2. The current study was designed to identify differentially expressed genes after heat shock by using a novel annealing control primer (ACP) system, which was developed recently to identify authentic genes. 3. Rat aortic rings were mounted in organ baths, exposed to 42 degrees C for 45 min and harvested 4 h after the end of heat shock. Total RNA were used for amplification by the reverse transcriptase-polymerase chain reaction (RT-PCR) with ACP system. Differentially amplified PCR products were sequenced, searched against the GenBank and confirmed by RT-PCR. 4. Genes for connective tissue growth factor, stress-inducible protein 1 and heat shock protein 25 were upregulated, whereas a gene for interferon regulatory factor 1 was downregulated. Immunohistochemistry revealed upregulation of the phosphorylated form of Hsp25 in aortic rings after heat shock. 5. These results suggest that phosphorylated Hsp25 plays a pivotal role in the augmentation of vascular contraction after heat shock.

Insulin induces myocardial protection and Hsp70 localization to plasma membranes in rat hearts

Insulin induces the expression of the 70-kDa heat shock protein (Hsp70) in rat hearts. In this study, we examined insulin- and heat shock-treated hearts for improved contractile recovery after 30 min of ischemia, activation of the heat shock transcription factor, and localization of the Hsp70 in relation to dystrophin and α-tubulin. Adult male Sprague-Dawley rats were assigned to groups: 1) control, 2) sham control, 3) insulin injected (200 μU/g body wt), 4) heat shock treated (core body temperature 42°C for 15 min), and 5) heat shock and insulin treated. Six hours later, hearts were isolated for Langendorff perfusion to determine cardiac function, or myocardial tissues were collected and prepared for either electrophoretic mobility shift assay, Western blot analysis, or immunofluorescence microscopy. Insulin treatment with 6 h of recovery enhances postischemic myocardial recovery of contractile function and increases Hsp70 expression through activation of the heat shock transcription factor. Insulin-treated hearts had elevated levels of Hsp70, particularly in the membrane fraction. In contrast, heat-shocked hearts had elevated levels of Hsp70 in the cytosol, membrane, and pellet fractions. After insulin treatment, Hsp70 was mostly colocalized to the plasma membrane with dystrophin. In contrast, after heat shock, Hsp70 was localized mostly between cardiomyocytes in apparent vascular or perivascular elements. The localization of Hsp70 is dependent on the inducing stimuli of either heat shock or insulin treatment. The cell membrane versus vascular localization of Hsp70 suggests the interesting possibility of functionally distinct roles for Hsp70 in the heart, whether induced by insulin or heat shock treatment.

HEAT SHOCK-INDUCED AUGMENTATION OF VASCULAR CONTRACTILITY IS INDEPENDENT OF RHO-KINASE

In a previous study, we demonstrated that heat shock augments the contractility of vascular smooth muscle through the stress response. 2. In the present study, we investigated whether Rho-kinases play a role in heat shock-induced augmentation of vascular contractility in rat isolated aorta. 3. Rat aortic strips were mounted in organ baths, exposed to 42 C for 45 min and subjected to contractile or relaxant agents 5 h later. 4. The level of expression of Rho-kinases in heat shock-exposed tissues was no different to that of control tissues, whereas heat shock induced heat shock protein (Hsp) 72 at 3 and 5 h. Heat shock resulted in an increase in vascular contractility in response to phenylephrine 5 h later. 5. The Rho-kinase inhibitors Y27632 (30 nmol/L-10 mmol/L) or HA 1077 (10 nmol/L-10 mmol/L) relaxed 1.0 mmol/L phenylephrine-precontracted vascular strips in a concentration-dependent manner; these effects were attenuated in heat shock-exposed strips. Pretreatment with Y27632 resulted in greater inhibition of the maximum contraction in control strips compared with those in heat shock-exposed strips. 6. The results of the present study suggest that Rho-kinases are unlikely to be involved in heat shock-induced augmentation of vascular contractility.

Correlation of HSP70 expression and cell viability following thermal stimulation of bovine aortic endothelial cells

Thermal preconditioning protocols for cardiac cells were identified which produce elevated HSP70 levels while maintaining high cell viability. Bovine aortic endothelial cells were heated with a water bath at temperatures ranging from 44 to 50 degrees C for periods of 1-30 min. Thermal stimulation protocols were determined which induce HSP70 expression levels ranging from 2.3 to 3.6 times the control while maintaining cell viabilities greater than 90%. An Arrhenius injury model fit to the cell damage data yielded values of A = 1.4 X 10(66) s(-1) and Ea = 4.1 X 10(5) J/mol. Knowledge of the injury parameters and HSP70 kinetics will enhance dosimetry guideline development for thermal stimulation of heat shock proteins expression in cardiac tissue.

Cloning, characterization, and heat stress-induced redistribution of a protein homologous to human hsp27 in the zebrafish Danio rerio

Hsp27 is a small heat shock protein (shsp) regulating stress tolerance and increasingly thought to play roles in tissue homeostasis and differentiation. The zebrafish Danio rerio is an important model for the study of developmental processes, but little is known regarding shsps in this animal. Here, we report the sequence, expression, regulation, and function of a zebrafish protein (zfHsp27) homologous to human Hsp27. zfHsp27 contains three conserved phosphorylatable serines and a cysteine important for regulation of apoptosis, but it lacks much of a C-terminal tail domain and shows low homology in two putative actin interacting domains that are features of mammalian Hsp27. zfHsp27 mRNA is most abundant in adult skeletal muscle and heart and is upregulated during early embryogenesis. zfHsp27 expressed in mammalian fibroblasts was phosphorylated in response to heat stress and anisomycin, and this phosphorylation was prevented by treatment with SB202190, an inhibitor of p38 MAPK. Expression of zfHsp27 and human Hsp27 in mammalian fibroblasts promoted a similar degree of tolerance to heat stress. zfHsp27 fusion proteins entered the nucleus and associated with the cytoskeleton of heat stressed cells in vitro and in zebrafish embryos. These results reveal conservation in regulation and function of mammalian and teleost Hsp27 proteins and define zebrafish as a new model for the study of Hsp27 function.

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

OBJECTIVES

To test the hypothesis that heat shock protein (Hsp) 70 may be released into the circulation after acute myocardial infarction (AMI) by exploring the kinetics of Hsp70 release and the relations between Hsp70 and markers of inflammation and myocardial damage in AMI.

DESIGN

Blood samples from 24 patients were prospectively collected through to the first day after AMI. Hsp70, interleukin (IL) 6, IL-8, and IL-10 in serum were measured by enzyme linked immunosorbent assay (ELISA).

RESULTS

Median Hsp70 concentrations in AMI patients measured at arrival, six hours thereafter, and the following morning were 686, 868, and 607 pg/ml, respectively. These concentrations were all significantly different from those of the control patients with angina with a median serum Hsp70 concentration of 306 pg/ml. Peak Hsp70 correlated with creatine kinase (CK) MB (r = 0.62, p < 0.01) and cardiac troponin T (r = 0.58, p < 0.01). Furthermore, serum Hsp70 correlated with IL-6 and IL-8 at six hours (r = 0.60, p < 0.01 and r = 0.59, p < 0.01, respectively).

CONCLUSIONS

In this study, Hsp70 was rapidly released into the circulation after AMI. Circulating Hsp70 is suggested as a marker of myocardial damage. In addition, Hsp70 may have a role in the inflammatory response after AMI.

A new human somatic stem cell from placental cord blood with intrinsic pluripotent differentiation potential

Here a new, intrinsically pluripotent, CD45-negative population from human cord blood, termed unrestricted somatic stem cells (USSCs) is described. This rare population grows adherently and can be expanded to 10¹⁵ cells without losing pluripotency. In vitro USSCs showed homogeneous differentiation into osteoblasts, chondroblasts, adipocytes, and hematopoietic and neural cells including astrocytes and neurons that express neurofilament, sodium channel protein, and various neurotransmitter phenotypes. Stereotactic implantation of USSCs into intact adult rat brain revealed that human Tau-positive cells persisted for up to 3 mo and showed migratory activity and a typical neuron-like morphology. In vivo differentiation of USSCs along mesodermal and endodermal pathways was demonstrated in animal models. Bony reconstitution was observed after transplantation of USSC-loaded calcium phosphate cylinders in nude rat femurs. Chondrogenesis occurred after transplanting cell-loaded gelfoam sponges into nude mice. Transplantation of USSCs in a noninjury model, the preimmune fetal sheep, resulted in up to 5% human hematopoietic engraftment. More than 20% albumin-producing human parenchymal hepatic cells with absence of cell fusion and substantial numbers of human cardiomyocytes in both atria and ventricles of the sheep heart were detected many months after USSC transplantation. No tumor formation was observed in any of these animals.

Acute p38 MAPK activation decreases force development in ventricular myocytes

Evidence suggests that p38 mitogen-activated protein kinase (MAPK) activation influences cardiac function on an acute basis. The characterization and mechanisms by which this occurs were investigated in the present study. Adult rat ventricular myocytes treated with 1 mM arsenite for 30 min had a 16-fold increase in p38 MAPK phosphorylation that was attenuated by SB-203580 (a p38 MAPK inhibitor). Extracellular signal-regulated protein kinase (ERK) and c-Jun NH2-terminal kinase (JNK) were also minimally activated, but this activation was not sensitive to SB-203580. In addition, arsenite caused a p38 MAPK-independent translocation/activation of protein phosphatase 2a (PP2a) and decrease in phosphorylation of myosin light chain 2 (LC2). Arsenite-p38 MAPK activation led to translocation of heat shock protein 27 but not alpha B-crystallin to the myofilaments. Using isolated cardiomyocytes, we determined that arsenite reduces isometric tension without a change in Ca2+ sensitivity of tension via p38 MAPK and lowers myofibrillar actomyosin Mg2+-ATPase activity in a p38 MAPK-independent manner. Thus arsenite induces a p38 MAPK-independent change in PP2a and LC2 that may account for the arsenite-dependent decrease in ATPase and a p38 MAPK-dependent modification of the myofilaments that decreases myocardial force development.

HSP70.1 and -70.3 are required for late-phase protection induced by ischemic preconditioning of mouse hearts

We investigated the role of inducible heat shock proteins 70.1 and 70.3 (HSP70.1 and HSP70.3, respectively) in myocardial ischemic preconditioning (IP) in mice. Wild-type (WT) mice and HSP70.1- and HSP70.3-null [HSP70.1/3(-/-)] mice were subjected to IP and examined 24 h later during the late phase of protection. IP significantly increased steady-state levels of HSP70.1 and HSP70.3 mRNA and expression of inducible HSP70 protein in WT myocardium. To assess protection against tissue injury, mice were subjected to 30 min of regional ischemia and 3 h of reperfusion. In WT mice, IP reduced infarct size by 43% compared with sham IP-treated mice. In contrast, IP did not reduce infarct size in HSP70.1/3(-/-) mice. Absence of inducible HSP70.1 and HSP70.3 had no effect, however, on classical or early-phase protection produced by IP, which significantly reduced infarct size in HSP70.1/3(-/-) mice. We conclude that inducible HSP70.1 and HSP70.3 are required for late-phase protection against infarction following IP in mice.

Heat-induced increases in endothelial NO synthase expression and activity and endothelial NO release

Endothelial nitric oxide (NO) synthase (eNOS) is regulated by heat shock protein 90 (HSP90), a heat-inducible protein; however, the effect of heat shock on eNOS expression and eNO release is unknown. Bovine aortic endothelial cells were incubated for 1 h at 37 degrees C, 42 degrees C, or 45 degrees C and cell lysates were evaluated with the use of Western blotting. We observed a 2.1 +/- 0.1-fold increase in eNOS protein content, but no change in HSP90 content, HSP70 content, or HSP90/eNOS association, 24 h after heat shock at 42 degrees C. We also observed a 7.7 +/- 1.5-fold increase in HSP70 protein content, but did not observe a change in eNOS or HSP90 24 h after heat shock at 45 degrees C. eNOS activity and maximal bradykinin-stimulated NO release was significantly increased 24 h after heat shock at 42 degrees C. Heat shock in rats (core temperature: 42 degrees C, 15 min) resulted in a significant increase in aortic eNOS, HSP90, and HSP70 protein content. The aorta from heat-shocked rats exhibited a decreased maximal contractile response to phenylephrine, which was abolished by preincubation with NG-nitro-l-arginine. We conclude that prior heat shock is a physical stimulus of increased eNOS expression and is associated with an increase in eNOS activity, agonist-stimulated NO release, and a decreased vasoconstrictor response.

Proteins Involved in Salvage of the Myocardium

In the Western world, cardiac ischemic disease is still the most common cause of death despite significant improvements of therapeutic drugs and interventions. The fact that the heart possesses an intrinsic protection mechanism has been systematically overlooked before the 1980s. It has been clearly shown that the activation of this mechanism can reduce the infarct size after an ischemic insult. Prerequisite is the induction of the synthesis of such cardio-protective proteins as heat shock proteins (HSPs) and anti-oxidative enzymes. HSPs are involved in the maintenance of cell homeostasis by guiding the synthesis, folding and degradation of proteins. Besides, the various family members cover a broad spectrum of anti-oxidative, anti-apoptotic and anti-inflammatory activities. Although the major inducible HSP72 has received most attention, other HSPs are able to confer cardioprotection as well. In addition, it seems that there is a concerted action between the various cardio-protective proteins. One drawback is that the beneficial effects of HSPs seem to be less effective in the compromised than in the normal heart. Although clinical studies have shown that there is a therapeutic potential for HSPs in the compromised heart, major efforts are needed to fully understand the role of HSPs in these hearts and to find a safe and convenient way to activate these protective proteins.