Induction of heat shock proteins prevents the arrhythmogenic substrate for atrial fibrillation

Role of heat shock protein 22 in the protective effect of geranylgeranylacetone in response to oxidized-LDL

Objective

The aim was to investigate the role and potential mechanism of geranylgeranylacetone (GGA) in the development of atherosclerosis, and to explore the role of heat shock protein 22 (HSP22) in mediating GGA effect.

Methods

Human coronary artery endothelial cell (HCAEC) was used for in vitro study. RNA interference was applied to suppress HSP22 in the cells. Cellular apoptosis and intracellular level of reactive oxygen species (ROS) were detected by flow cytometer, and proteins of HSP22, NF-κB, eNOS, and ICAM-1 were assessed by immunoblotting. HSP22^-/-//ApoE^-/-, and HSP22^+/+//ApoE^-/- mice were used to investigate the effect of GGA in the animal model of atherosclerosis. Atherosclerotic lesion of the mice aortas was evaluated by Oil Red O staining and H&E staining.

Results

GGA significantly inhibited HCAEC apoptosis in response to oxidized-LDL (ox-LDL), but stimulated HSP22 synthesis in the cells. Transfection of HSP22-siRNA in the cells resulted in complete blockage of the GGA effect on apoptosis. GGA also significantly inhibited ROS, NF-κB, and ICAM-1 in the cells transfected control siRNA, but not in the cells transfected with HSP22-siRNA. Atherosclerotic plaque in the aorta was significantly less in the wild type (WT) animals treated with GGA as stained either by Oil Red O or by H&E staining, but not in the HSP22-KO mice. GGA significantly inhibited expression of NF-κB and ICAM-1 in the WT mice, but not in the HSP22-KO mice.

Conclusion

GGA-induced HSP22, and inhibited ox-LDL-induced apoptosis as well as expression of NF-κB and ICAM-1 in the HCAECs. GGA also attenuated formation of atherosclerotic plaques in mice aorta. Suppression of HSP22 by siRNA resulted in blockage of the GGA inhibition on apoptosis or stimulation on NF-κB and ICAM-1. These findings suggested that GGA protects endothelial cells from injury in response to ox-LDL and block atherosclerotic development in mice aorta through induction of HSP22.

Angiotensin-(1-7) prevents atrial tachycardia induced-heat shock protein 27 expression

OBJECTIVE

We aimed to investigate the effects of angiotensin-(1-7) [Ang-(1-7)] on heat-shock protein 27 (HSP27) in a canine model of induced tachycardia.

METHODS

Eighteen dogs were randomized into three equal treatment groups: sham, pacing and pacing+Ang-(1-7) group. The dogs in the last two groups were subjected to 2weeks of rapid atrial pacing (500bpm). The effects of Ang-(1-7) on HSP27 were assessed by real-time polymerase chain reaction and western blot.

RESULTS

The expression levels of atrial HSP27 mRNA and protein were significantly (P<0.05) higher for the pacing group than the sham group and significantly (P<0.05) lower for the pacing+Ang-(1-7) group than the pacing group. There was no significant difference between the HSP27 expression levels in the right and left atria among all three groups.

CONCLUSIONS

Our findings suggest that the overexpression of HSP27 may possibly be occurring as an adaptive response that allows atrial tissues to cope with rapid atrial pacing, and an inhibiting effect of Ang-(1-7) on atrial remodeling may be one of the mechanisms responsible for the attenuation of HSP27 up-regulation induced by rapid pacing.

Pharmacologically dosed oral glutamine reduces myocardial injury in patients undergoing cardiac surgery: a randomized pilot feasibility trial

BACKGROUND AND OBJECTIVE

Glutamine (GLN) has been shown to protect against in vitro and in vivo myocardial injury. In humans, perioperative ischemia/reperfusion (I/R) injury during cardiac surgery is associated with higher morbidity and mortality. The objective of this safety and feasibility pilot trial was to determine if pharmacologically dosed, preoperative oral GLN attenuates myocardial injury in cardiac surgery patients.

METHODS

Patients undergoing elective cardiac surgery, requiring cardiopulmonary bypass, were enrolled in a randomized, double-blind pilot trial to receive 25 g twice of oral alanyl-glutamine (GLN; n = 7) or maltodextrin (CONT; n = 7) daily for 3 days preoperatively. Serum troponin (TROP I), creatine kinase (CK-MB), and myoglobin (MG) were measured at multiple perioperative time points. Clinical outcomes were also recorded and assessed.

RESULTS

GLN therapy significantly decreased TROP I levels at 24, 48, and 72 hours postoperatively (all P < .05) vs CONT. GLN also reduced CK-MB at 24 and 48 hours (P < .05, P < .001) vs CONT. MG was reduced at 24 hours vs control (P = .0397). GLN also significantly reduced pooled clinical complications vs CONT (P = .03).

CONCLUSION

This pilot study showed that pharmacologically dosed oral GLN therapy prior to cardiac surgery was safe, well tolerated, and feasible. GLN therapy reduced myocardial injury and clinical complications in this small randomized, blinded feasibility trial. These data indicate that a larger trial of preoperative GLN therapy in patients undergoing cardiac surgery is needed to confirm clinical benefit.

Electrophysiological correlation and prognostic impact of heat shock protein 27 in atrial fibrillation

BACKGROUND

Heat shock protein (HSP) 27 is related to the pathogenesis of AF. However, the clinical relationship between HSP27 and AF is unclear. The present study was conducted to determine the clinical relationship between HSP27 and atrial fibrillation (AF).

METHODS AND RESULTS

A case-control study was conducted (AF, n=114; control, n=100). Serum HSP27 (HSP27S) levels were measured by ELISA, and its correlations with electrophysiological characteristics and catheter ablation outcomes were investigated. The patients with AF had a larger left atrial diameter (LAD), waist circumference, and body mass index, and a lower baseline HSP27S level, than controls. After logistic multivariate analysis, low baseline HSP27S was independently associated with AF. In patients with AF, those with paroxysmal AF (PAF) had higher baseline HSP27S levels compared with those without PAF. In patients with PAF, lower baseline HSP27S was associated with larger LAD, whereas baseline HSP27S was not correlated with LAD in controls. In PAF, low baseline HSP27S (≤3.85 ng/mL) was associated with low atrial voltage and nonpulmonary vein ectopies. In non-PAF, the mean fractionated interval had a good correlation with baseline HSP27S. After catheter ablation, a high baseline HSP27S level could predict sinus rhythm maintenance in the patients with PAF. Baseline HSP27S was also correlated with interleukin 10 and tumor necrosis factor-α levels. Analysis of buffy coat mRNA levels showed the same correlations.

CONCLUSIONS

The HSP27S levels were correlated with LAD, left atrial voltage, and fractionated intervals, and predicted AF recurrence after catheter ablation. The mechanisms could be related to inflammation.

Heat shock proteins in stabilization of spontaneously restored sinus rhythm in permanent atrial fibrillation patients after mitral valve surgery

A spontaneously restored sinus rhythm in permanent atrial fibrillation patients has been often observed after mitral valve (MV) surgery, but persisting duration in sinus rhythm varies from patient to patient. Heat shock proteins (Hsps) may be involved in pathogenesis of atrial fibrillation. We hypothesized that stabilization of restored sinus rhythm is associated with expression of Hsps in the atria. To test this hypothesis, clinical data, biopsies of right atrial appendage, and blood samples were collected from 135 atrial fibrillation patients who spontaneously restored sinus rhythm after conventional isolated MV replacement. Comparison was made between patients who had recurrence of atrial fibrillation within 7 days (AF) vs. patients with persisted sinus rhythm for more than 7 days (SR). Results showed that SR patients had higher activity of heat shock transcription factor 1 (HSF1) as well as upregulated expressions of heat shock cognate 70, Hsp70, and Hsp27 in the tissues. The activation of HSF1-Hsps pathway was associated with less-aggressive pathogenesis as reflected by lower rates of myolysis, apoptosis, interstitial fibrosis, and inflammation in SR patients. However, Hsp60 was lower in both tissue and plasma in SR patients, and was positively correlated with apoptosis, interstitial fibrosis, and inflammation. These findings suggest that the Hsps play important roles in stabilization of restored sinus rhythm after MV surgery by inhibiting AF-related atrial remodeling and arrhythmogenic substrates in atrial fibrillation patients. Low circulating Hsp60 levels preoperatively might predict a stable spontaneously restored sinus rhythm postoperatively.

Development of a novel proteomic approach for mitochondrial proteomics from cardiac tissue from patients with atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia affecting approximately 2.2 million Americans. Because several studies have suggested that changes in mitochondrial function and morphology may contribute to AF, we developed a novel proteomic workflow focused on the identification of differentially expressed mitochondrial proteins in AF patients. Right human atrial tissue was collected from 20 patients, 10 with and 10 without AF, and the tissue was subjected to hydrostatic pressure cycling-based lysis followed by label-free mass spectrometric (MS) analysis of mitochondrial enriched isolates. Approximately 5% of the 700 proteins identified by MS analysis were differentially expressed between the AF and non-AF samples. We chose four differentially abundant proteins for further verification using reverse phase protein microarray analysis based on their known importance in energy production and regulatory association with atrial ion channels: four and a half LIM, destrin, heat shock protein 2, and chaperonin-containing TCP1. These initial study results provide evidence that a workflow to identify AF-related proteins that combines a powerful upfront tissue cell lysis with high resolution MS for discovery and protein array technology for verification may be an effective strategy for discovering candidate markers in highly fibrous tissue samples.

New pharmacological targets and treatments for atrial fibrillation

Atrial fibrillation (AF) is an arrhythmia of growing clinical concern that is increasing in prevalence and is associated with significant morbidity and mortality. Pharmacological agents remain the first-line therapy for the AF patient, and the potential advantages of sinus rhythm maintenance motivate continued efforts to identify novel pharmacological means to restore and maintain sinus rhythm. Traditional antiarrhythmic agents only moderately suppress AF and present problematic concerns of proarrhythmia and extracardiac toxicity. Current investigational or recently approved strategies for improving efficacy and safety of anti-AF agents include (i) specific or predominant blockade of atrial ion channels; (ii) "upstream therapies" affecting non-ion channel targets that influence electrical and structural remodeling, inflammation and oxidative stress; (iii) amiodarone derivatives with an improved safety profile; (iv) intracellular calcium handling; and (v) therapies aiming at alleviating conduction disturbances (gap junction coupling enhancers). This review provides a succinct overview of some of these strategies.