Blood pressure and heat shock protein expression in response to acute and chronic stress

The Role of Extracellular Heat Shock Proteins in Cardiovascular Diseases

In the early 1960s, heat shock proteins (HSPs) were first identified as vital intracellular proteinaceous components that help in stress physiology and reprogram the cellular responses to enable the organism's survival. By the early 1990s, HSPs were detected in extracellular spaces and found to activate gamma-delta T-lymphocytes. Subsequent investigations identified their association with varied disease conditions, including autoimmune disorders, diabetes, cancer, hepatic, pancreatic, and renal disorders, and cachexia. In cardiology, extracellular HSPs play a definite, but still unclear, role in atherosclerosis, acute coronary syndromes, and heart failure. The possibility of HSP-targeted novel molecular therapeutics has generated much interest and hope in recent years. In this review, we discuss the role of Extracellular Heat Shock Proteins (Ec-HSPs) in various disease states, with a particular focus on cardiovascular diseases.

Joint Effects of Antibody to Heat Shock Protein 60, Hypertension, and Diabetes on Risk of Coronary Heart Disease in Chinese

Background: Several studies have suggested an association between antibody to human heat shock protein 60 (anti-Hsp60) and coronary atherosclerosis, but the results have been inconsistent. The aim of this study was to investigate the association between anti-Hsp60 and coronary heart disease (CHD) and to determine whether anti-Hsp60, hypertension, and diabetes have joint effects on CHD risk.

Methods: We measured the concentrations of anti-Hsp60 in 1003 CHD patients and 1003 age- and sex-matched control subjects without CHD events.

Results: Concentrations of anti-Hsp60 were significantly higher in CHD patients than in controls. Increasing concentrations of anti-Hsp60 were significantly associated with higher risk of CHD (P for trend <0.0001) and with increasing severity of CHD as assessed by number of diseased vessels detected with angiography [odds ratio (OR) 3.67, 95% CI 1.56–8.64, P = 0.003] after multivariate adjustment for traditional CHD risk factors. There were strong joint effects of high concentrations of anti-Hsp60 and hypertension (OR 5.17, 95% CI 3.95–6.75, P < 0.0001) and diabetes (OR 6.49, 95% CI 4.52–9.33, P < 0.0001) on CHD risk; simultaneous occurrence of high anti-Hsp60 concentrations, hypertension, and diabetes conferred a dramatically higher risk of CHD (OR 20.99, 95% CI 12.50–35.24, P < 0.0001) in multivariate analyses.

Conclusions: Anti-Hsp60 is independently associated with CHD risk, and a combination of high anti-Hsp60, hypertension, and diabetes is particularly detrimental for CHD risk.

Exercise is the primary factor associated with Hsp70 induction in muscle of treadmill running rats

AIM

The cytoprotective, inducible stress protein, Hsp70, increases in muscles of rodents subjected to strenuous treadmill running. Most treadmill running protocols employ negative reinforcement to encourage animals to exercise. As these stimuli may themselves activate stress responses, the present investigation was conducted to determine their contribution to the exercise-induced expression of Hsp70.

METHODS

Twenty-one male Sprague-Dawley rats were randomly divided into three equal groups including an exercise group (EX), which ran on a treadmill at 30 m min(-1) for 60 min; a stimulation group (STIM), which was not allowed to run, but was stimulated with compressed air and mild electric shock concurrently with their exercising cohort; and a control group (CON), which was housed in the treadmill room during the exercise period. Animals were killed 24 h post-experiment and hearts (H), soleii (SOL) and white gastrocnemii (WG) were harvested and analysed for Hsp70 content (mean% +/- SEM of standard).

RESULTS

Significant increases in Hsp70 (as a % of standard) were noted in H and WG (H = 77.4 +/- 8.5; WG = 93.9 +/- 18.4) of EX but not in STIM (H = 32.5 +/- 4.6; WG = 32.0 +/- 3.4) or CON (H = 20.5 +/- 3.7; WG = 32.4 +/- 7.4). In SOL, Hsp70 expression in EX (126.7 +/- 6.2) was different from STIM (98.3 +/- 10.9) only. This occurred, despite the fact that all groups were exposed to a stressful environment and exhibited elevated (P < 0.001) temperatures (EX -41.2 +/- 0.1 degrees C > STIM -40.5 +/- 0.2 degrees C > CON -39.0 +/- 0.1 degrees C) indicative of a general stress response.

CONCLUSIONS

These data suggest that exercise per se, rather than environmental conditions or noxious stimuli, are responsible for the induction of Hsp70 in rat muscle during treadmill running.

Is preeclampsia associated with higher frequency of HSP70 gene polymorphisms?

AIM

To evaluate the possible association of three different HSP70 gene polymorphisms with preeclampsia.

STUDY DESIGN

HSPA1A G(190)C, HSPA1B A(1267)G and HSPA1L T(2437)C polymorphisms were analyzed from blood samples of 72 women with preeclampsia and of 70 healthy pregnant women as controls by PCR-RFLP method.

RESULTS

HSPA1B (1267)GG and HSPA1L (2437)CC genotypes occurred more frequently in preeclamptic patients compared to healthy controls (p<0.002 [RR: 4.38, 95% CI: 1.56-12.28]) and (p<0.03 [RR: 1.31, 95% CI: 1.03-1.67]), respectively. Significant difference was found in the distribution of HSPA1B A(1267)G genotype between the preeclamptic and control group (p<0.004 [RR: 0.67, 95% CI: 0.51-0.88]). Distribution of HSPA1A G(190)C was similar in the preeclamptic and control group. In controls, genotype distribution of HSPA1A G(190)C and HSPA1L T(2437)C was in Hardy-Weinberg equilibrium, while this criterion was not fulfilled for HSPA1B A(1267)G.

CONCLUSION

We concluded that HSPA1B (1267)GG and HSPA1L (2437)CC genotypes were more frequent among preeclamptic than control patients, suggesting that these genotypes may play a role in the susceptibility for preeclampsia.

Antibodies to human heat shock protein 60, hypertension and dyslipidemia. A study of joint effects on coronary risk

OBJECTIVE

High IgA-class (but not IgG-class) Anti-Heat-shock-protein 60 antibody level is a predictor of coronary risk in dyslipidemic middle-aged men. In this paper we studied the joint effects of high Anti-Hsp60-antibody level and the classical coronary risk factors.

METHODS

We used nested case-control design and logistic regression analyses. The cases consisted of 233 middle-aged men with myocardial infarction or coronary death during 8.5-year follow-up in Helsinki Heart Study, a coronary primary prevention study with gemfibrozil. The controls were subjects without coronary events, matched for drug treatment and the geographical area.

RESULTS

The relative coronary risks (Odds Ratios (ORs); 95% confidence interval) were 1.41 (0.96-2.05) for high IgA-class Anti-Hsp60 antibody level and 1.98 (1.35-2.90) for hypertension, defined as mean arterial pressure >114 mmHg. With simultaneous occurrence of high Anti-Hsp60 antibody level and hypertension, the ORs were 2.32 (1.26-4.27) for systolic and 2.99 (1.63-5.48) for diastolic hypertension. Similar patterns of joint effects were found between high Anti-Hsp60 antibody and lipoprotein cholesterol levels as well as antibodies against oxidized low-density lipoprotein.

CONCLUSIONS

Our results suggest that, while high IgA-class Anti-Hsp60 antibody level predicts coronary risk, the effect is modest without simultaneous occurrence of other classical risk factors.

Heat shock protein 70 is not increased in women with severe preeclampsia

OBJECTIVE

The purpose of this study is to determine if heat shock protein 70 (Hsp 70), a marker of cellular stress, is elevated in pregnancies complicated by severe preeclampsia.

METHODS

Maternal blood was collected from women with severe preeclampsia (n=47) matched for delivery gestational age to normotensive pregnant controls (n=51). Hsp 70 concentrations were measured by standard ELISA techniques. Data were analyzed with the Student's t-test and chi-square test.

MAIN OUTCOME MEASURES

The primary outcome measured was Hsp 70 concentrations. Our hypothesis prior to data collection was that HSP 70 would be increased in women with severe preeclampsia.

RESULTS

Compared with normotensive women, those with severe preeclampsia had similar maternal age, parity, delivery gestational age, maternal weight, and ethnicity. There was no difference in mean concentrations of Hsp 70 between women with severe preeclampsia and controls (35.4 +/- 96.7 vs. 30.1 +/- 11.5, p=0.80). Similar numbers of women with severe preeclampsia (n=28) and controls (n=30) had Hsp 70 concentrations below the 0.02 ng/dL level of detection (chi-square value=0.024, p=0.88).

CONCLUSION

Hsp 70 concentrations are not elevated in women with severe preeclampsia.

Stressful animal housing conditions and their potential effect on sympathetic neurotransmission in mice

Although the sympathetic nervous system (SNS) plays a major role in mediating the peripheral stress response, due consideration is not usually given to the effects of prolonged stress on the SNS. The present study examined changes in neurotransmission in the SNS after exposure of mice (BALB/c) to stressful housing conditions. Focal extracellular recording of excitatory junction currents (EJCs) was used as a relative measure of neurotransmitter release from different regions of large surface areas of the mouse vas deferens. Mice were either group housed (control), isolation housed (social deprivation), group housed in a room containing rats (rat odor stress), or isolation housed in a room containing rats (concurrent stress). Social deprivation and concurrent stressors induced an increase of 30 and 335% in EJC amplitude, respectively. The success rate of recording EJCs from sets of varicosities in the concurrent stressor group was greater compared with all other groups. The present study has shown that some common animal housing conditions act as stressors and induce significant changes in sympathetic neurotransmission.

The network and the remodeling theories of aging: historical background and new perspectives

Two general theories, i.e. "the network theory of aging" (1989) and "the remodeling theory of aging" (1995), as well as their implications, new developments, and perspectives are reviewed and discussed. Particular attention has been paid to illustrate: (i) how the network theory of aging fits with recent data on aging and longevity in unicellular organisms (yeast), multicellular organisms (worms), and mammals (mice and humans); (ii) the evolutionary and experimental basis of the remodeling theory of aging (immunological, genetic, and metabolic data in healthy centenarians, and studies on the evolution of the immune response, stress and inflammation) and its recent development (the concepts of "immunological space" and "inflamm-aging"); (iii) the profound relationship between these two theories and the data which suggest that aging and longevity are related, in a complex way, to the capability to cope with a variety of stressors.

The effects of exercise duration on adrenal HSP72/73 induction in rats

This study investigated the effects of varying durations of exercise training on heat shock proteins 72 and 73 (HSP72/73) induction in the rat adrenal gland. Female Sprague-Dawley rats (120 days old) were assigned to either a sedentary control group (C) or one of the three endurance exercise training groups. Trained animals ran on a treadmill at approximately 75% VO2max for 10 weeks (4-5 days week-1) at one of the three different exercise durations (30 min day-1=T30, 60 min day-1=T60, or 90 min day-1=T90). All durations of exercise training resulted in an increase in the HSP72 levels (P < 0.0001). The magnitude of the training-induced elevation in the HSP72 levels in the adrenal gland increased as a function of the training duration ( approximately 60-fold increase in T90; approximately 40-fold increase in T60; and approximately 15-fold increase in T30). Longer exercise durations (>60 min day-1), also resulted in small but significant increase in HSP73 level ( approximately 1.2-fold increase in both T60 and T90; P < 0.05). These results demonstrate that the physiological stress created by chronic treadmill running can induce both HSP72 and HSP73 in rat adrenal gland. Increased levels of adrenal HSP72/73 expression during rigorous exercise, may be one of the adaptive mechanisms of the adrenals to cope with an increased dose of stress.

Balloon angioplasty induces heat shock protein 70 in human blood vessels

Balloon angioplasty produces a mechanically induced injury to the blood vessel wall. Heat shock protein 70 (HSP70) is a molecular chaperone whose expression can be induced by chemical or thermal stress. Thus, we hypothesized that the mechanical injury associated with balloon angioplasty would lead to increases in the expression of HSP70 in vascular smooth muscle. Segments of popliteal and trifurcation vessels from above-the-knee amputations were subject to transluminal balloon angioplasty, excised, and placed in organ cultures. Neighboring vessel that was not subjected to balloon angioplasty served as controls. Some vessels were treated with sodium arsenite (positive control, known to induce HSP70 expression). The vessels were homogenized and the proteins were separated by gel electrophoresis and transferred to Immobilon. Western blots with an antibody specific for the inducible form of HSP70 were analyzed by densitometry. Our results showed that HSP70 expression can be induced by the mechanical injury associated with balloon angioplasty in human atherosclerotic vessels.

Adrenocorticotrophin dose-response relationships in the rat: haemodynamic, metabolic and hormonal effects

OBJECTIVE

To determine adrenocorticotrophin dose-response relationships for increase of blood pressure and metabolic parameters of the Sprague-Dawley rat.

METHODS

We injected 120 male Sprague-Dawley rats twice daily subcutaneously for 10 days with 0.5, 1, 5, 50, 100, 200 or 500 microg/kg synthetic adrenocorticotrophin per day (all n = 10) or subjected them to sham injection (0.9% NaCl; n = 50). Systolic blood pressure, 24 h food intake, water intake, urine volume and body weight were measured. Data from a further 45 rats treated with 500 microg/kg per day adrenocorticotrophin in previous studies were included in the blood pressure analyses. After we had killed these rats, their organ weights (kidney, heart, adrenal) and plasma electrolyte, adrenocorticotrophin and serum corticosterone concentrations were measured.

RESULTS

On the final day of treatment systolic blood pressure of sham-injection control rats was 123 +/- 1 mmHg (n = 50). Compared with sham treatment, a low dose of adrenocorticotrophin (1 microg/kg per day) increased systolic blood pressure from 122 +/- 1 to 130 +/- 2 mmHg (P < 0.001) without any metabolic effects, whereas a high dose of adrenocorticotrophin (500 microg/kg per day) increased systolic blood pressure from 121 +/- 1 to 150 +/- 2 mmHg (P < 0.001, n = 55) with increases in intake of water and urine volume (P < 0.001, n = 10) and a decrease in body weight (P < 0.001, n = 10). Plasma adrenocorticotrophin and serum corticosterone concentrations for the sham-injection control group were 162 +/- 12 pg/ml (36 +/- 3 pmol/l) and 376 +/- 18 ng/ml (1038 +/- 50 nmol/l), respectively. Plasma adrenocorticotrophin concentration was elevated by injections of 100 (P < 0.05), 200 (P < 0.01) and 500 microg/kg adrenocorticotrophin per day (P = 0.001). Serum corticosterone concentration was not significantly different from that of sham-injection rats with 0.5-5 microg/kg adrenocorticotrophin per day but was increased by injection of 50-500 microg/kg adrenocorticotrophin per day (P < 0.001).

CONCLUSIONS

These results define 1 microg/kg adrenocorticotrophin per day, administered subcutaneously, as the threshold dose for causing a rise in blood pressure in the rat Thus administration of adrenocorticotrophin increases systolic blood pressure at doses that induce minimal adrenocorticotrophin metabolic effects. Administration of a low dose of adrenocorticotrophin to the rat is a suitable model for stress-induced hypertension.

Thrombin activates MAPKAP2 kinase in vascular smooth muscle

PURPOSE

Thrombin mediates hemostasis by promoting thrombus development and vasospasm, which reduces the size of the arterial injury. Thrombin stimulation of vascular smooth muscle is associated with activation of mitogen-associated protein kinase. The purpose of this investigation was to determine the subsequent cellular signaling events in thrombin-stimulated vascular smooth muscle contraction.

METHODS

Contractile responses of bovine carotid artery smooth muscle were determined in a muscle bath and compared with phosphorylation events with two-dimensional gel electrophoresis. The activity of a novel kinase, mitogen-activated protein kinase-activated protein-2 kinase (MAPKAP2 kinase), was determined by immunoprecipitation and a phosphotransferase assay. A small heat shock protein, HSP27, was identified with immunoblotting.

RESULTS

Thrombin induces contraction of vascular smooth muscle and is associated with increased activity of MAPKAP2 kinase and increased phosphorylation of HSP27. Multiple isoforms of HSP27 are the predominant phosphoproteins in vascular smooth muscle, and peptide mapping suggests that the isoforms of HSP27 are structurally related and phosphorylated within similar peptide sequences.

CONCLUSIONS

Activation of the MAPKAP2 kinase pathway and phosphorylation of HSP27 are associated with thrombin-induced contraction of vascular smooth muscle.

Hypertension: genes and environment

Hypertension can be classified as either Mendelian hypertension or essential hypertension, on the basis of the mode of inheritance. The Mendelian forms of hypertension develop as a result of a single gene defect, and as such are inherited in a simple Mendelian manner. In contrast, essential hypertension occurs as a consequence of a complex interplay of a number of genetic alterations and environmental factors, and therefore does not follow a clear pattern of inheritance, but exhibits familial aggregation of cases. In this review, we discuss recent advances in understanding the pathogenesis of both types of hypertension. We review the causal gene defects identified in several monogenic forms of hypertension, and we discuss their possible relevance to the development of essential hypertension. We describe the current approaches to identifying the genetic determinants of human essential hypertension and rat genetic models of hypertension, and summarise the results obtained to date using these methods. Finally, we discuss the significance of environmental factors, such as stress and diet, in the pathogenesis of hypertension, and we describe their interactions with specific hypertension susceptibility genes.

Psychological stress induces heat shock protein 70 expression in rat aorta

Psychological stress without any physical stimuli caused a rapid and marked increase in the level of heat shock protein (HSP) 70 mRNA in rat aorta, but had little effect on the other tested tissues. The maximum increase in HSP70 mRNA level in the aorta was observed at 0.5-1 hr after the stress, and then it declined. Moreover, this stress also increased the level of HSP70 protein in the aorta, but had little effect on the other tested tissues. These results indicate that exposure of rats to mild psychological stress results in the induction of HSP70, especially in the blood vessels.

The role of heat shock proteins in protection and pathophysiology of the arterial wall

The arterial wall is an integrated functional component of the circulatory system that is continually remodelling in response to various stressors, including localized injury, toxins, smoking and hypercholesterolaemia. These stimuli directly or indirectly cause changes in blood pressure and damage to the vessel wall, and eventually induce arterial stiffness and obstruction. To maintain the homeostasis of the vessel wall, the vascular cells produce a high level of stress proteins, also known as heat shock proteins, which protect against damage during haemodynamic stress. However, an immune reaction to heat shock proteins might contribute to the development of atherosclerosis. We hypothesize that the induction of heat shock proteins is beneficial in the arterial wall's response to stress but is harmful in certain other circumstances.

Activation of heat shock protein (hsp)70 and proto-oncogene expression by alpha1 adrenergic agonist in rat aorta with age

Induction of heat shock proteins (hsp) most likely is a homeostatic mechanism in response to metabolic and environmental insults. We have investigated signal transduction mechanisms involved in alpha1, adrenergic receptor stimulation of hsp7O gene expression in isolated aortas with age. We found that alpha1 adrenergic agonists directly induced hsp70 mRNA in rat aorta in vitro; the alpha1, selective antagonist prazosin blocked this effect whereas chloroethylclonidine, an antagonist which has some selectivity for alpha1B receptors, was ineffective. This response was insensitive to pertussis toxin and was partially blocked by the protein kinase C inhibitor H7. Removal of extracellular calcium attenuated induction of hsp70 mRNA but not the induction of c-fos or c-myc. The induction of hsp70 mRNA by either norepinephrine or by phorbol dibutyrate was blunted in aortas from old (24-27 mo) rats whereas c-fos responses were not diminished in the older vessels. The hsp70 response to elevated temperature (42 degrees C) was not changed with age. Activation of hsp70 expression most likely involves a pertussis toxin insensitive G protein which activates protein kinase C, and requires extracellular calcium. With age, hsp70 gene expression induced by stimulation of alpha1 adrenergic receptors is markedly attenuated, which could modify responses to stress or vascular injury with aging.