Remote Ischemic Preconditioning Enhances the Effect of Aerobic Exercise on Cardiac Endoplasmic Reticulum Stress in Rats with Myocardial Infarction Model

Document Type : Research Paper

Authors
atefeh ghorbanipor 1
Amin Farzaneh hesari 2
parvin farzanegi 3
abdolreza jafari 4
1 PhD Student, Department of Exercise Physiology, Sari Branch, Islamic Azad University, Sari, Iran
2 Associate Professor, Department of Exercise Physiology, Sari Branch, Islamic Azad University, Sari, Iran
3 Professor, Department of Exercise Physiology, Sari Branch, Islamic Azad University, Sari, Iran
4 Assistant Professor, Department of Exercise Physiology, Sari Branch, Islamic Azad University, Sari, Iran
10.22089/spj.2025.18049.2373
Abstract
Extended Abstract
Background and Purpose
Myocardial infarction (MI) remains a leading cause of morbidity and mortality worldwide. The endoplasmic reticulum (ER), a crucial cellular organelle, regulates calcium homeostasis, mediates protein folding, and synthesizes lipids. Disruptions caused by oxidative stress and ischemia adversely affect calcium equilibrium, resulting in accumulation of misfolded and unfolded proteins, thereby inducing ER stress. Increasing evidence implicates ER stress as a central pathogenic mechanism underlying various cardiovascular diseases. Notably, MI-induced excessive ER stress activates three primary signaling pathways leading to cardiomyocyte apoptosis. Aerobic exercise training has been demonstrated to enhance exercise capacity and cardiac function while preventing adverse remodeling of cardiac tissue, therefore serving as an effective adjunctive therapy in the prevention and treatment of cardiovascular disorders. Recent animal studies report that aerobic training mitigates oxidative stress, restores mitochondrial function, and corrects calcium handling abnormalities, positioning it as a promising modality to attenuate ER stress. Moreover, ischemic preconditioning (IPC) is an established cardioprotective strategy characterized by brief, sublethal episodes of local ischemia, which render tissues more resilient to subsequent ischemic insults. While IPC has consistently reduced infarct size in animal models, its combined effects with aerobic exercise training on ER stress regulation remain unclear. This study aimed to investigate the effects of aerobic training and IPC—applied singly or in combination—on myocardial PERK and ATF6 gene expression in a rat model of MI.
Materials and Methods
This experimental study employed a rigorous multi-group post-test design involving thirty-five male Wistar rats (8 weeks old; 225 ± 15 g). Animals were randomly allocated into seven groups: Control (C), MI, MI with one-leg ischemia (1IP), MI with two-leg ischemia (2IP), MI with aerobic training (T), MI with one-leg ischemia plus training (1IPT), and MI with two-leg ischemia plus training (2IPT).Myocardial infarction was experimentally induced by subcutaneous administration of isoproterenol (100 mg/kg) dissolved in normal saline for two consecutive days with a 24-hour interval. Confirmation of MI was obtained by measuring serum levels of cardiac troponin, creatine kinase, and lactate dehydrogenase extracted via blood samples from the medial canthus.Ischemic preconditioning was performed by applying a tourniquet to the upper hind limb(s), inducing ischemia for 5 minutes followed by 5 minutes reperfusion, repeated in 3 cycles. Complete occlusion was verified by absence of pulse, hypothermia, and cyanosis in the limb. Aerobic training commenced 20 minutes after the final IPC cycle.The aerobic exercise protocol spanned eight weeks with five sessions per week. Initial weeks involved treadmill running at 10 m/min for 15 minutes (weeks 1–2), escalating to 15 m/min for 20 minutes (weeks 3–4), 20 m/min for 25 minutes (weeks 5–6), and culminating at 25 m/min for 30 minutes (weeks 7–8), maintaining a constant 5% incline.Forty-eight hours post-training, rats were anesthetized and myocardial tissues harvested. Myocardial PERK and ATF6 mRNA expression levels were quantified using RT-PCR. Statistical analyses were performed via one-way ANOVA and Tukey post hoc tests with significance set at P < 0.05.
Results
One-way ANOVA revealed significant differences in myocardial PERK gene expression among groups (F = 59.8, P = 0.001). MI induced a marked upregulation of PERK expression compared to controls (P = 0.0001). Tukey post hoc comparisons demonstrated significant downregulation of PERK in the 1IP (P = 0.032), 2IP (P = 0.004), T (P = 0.001), 1IPT (P = 0.0001), and 2IPT (P = 0.0001) groups relative to MI alone. Moreover, combined ischemia and training groups (1IPT and 2IPT) exhibited greater PERK reduction compared to single-modality groups: 1IP (P = 0.0001; P = 0.0001), 2IP (P = 0.0001; P = 0.005), and T (P = 0.045; P = 0.031). No significant difference was observed between 1IPT and 2IPT (P = 0.935).Regarding ATF6 expression, significant group differences were observed (F = 55.1, P = 0.0001). MI significantly elevated ATF6 compared to controls (P = 0.0001). The 1IP (P = 0.0001), 2IP (P = 0.0001), T (P = 0.003), 1IPT (P = 0.0001), and 2IPT (P = 0.0001) groups demonstrated significant reductions relative to MI. Notably, 1IPT reduced ATF6 expression more than 2IP (P = 0.0001), and 2IPT presented further reduction compared to both 1IP (P = 0.048) and 2IP (P = 0.0012). No difference was found between 1IPT and 2IPT (P = 0.989).
Conclusion
The induction of MI in Wistar rats is associated with elevated myocardial ER stress, as evidenced by increased expression of PERK and ATF6 genes. The present findings suggest that remote ischemic preconditioning enhances the protective effect of aerobic training in attenuating ER stress markers post-MI. This cardioprotection appears independent of the ischemic muscle mass involved (one leg vs. two legs). These data provide promising insights into combined interventions for mitigating cardiac ER stress and injury following MI. Further investigations are warranted to elucidate detailed mechanistic pathways underlying MI-induced ER stress.
Key Words: Ischemic Preconditioning, Aerobic Training, Endoplasmic Reticulum Stress, Cardiovascular Diseases
Article Message
Ischemic preconditioning of the limb—whether unilateral or bilateral—may augment the efficacy of aerobic exercise in modulating cardiac ER stress in the context of myocardial infarction. Remote ischemic preconditioning holds potential as an adjunctive therapeutic approach to improve cardiac function and health. Nonetheless, further studies are required to validate and extend these findings.
Ethical Considerations
This study was approved by the Research Ethics Committee of the Medical Sciences Faculty at Sari Islamic Azad University (Ethics Code: IR.IAU.SARI.REC.1403.299). All experimental procedures complied with institutional ethical guidelines.
Authors’ Contributions
Conceptualization: Amin Farzaneh Hesari
Data Collection: Atefeh Ghorbanipor
Data Analysis: Parvin Farzanegi, Abdolreza Jafari
Manuscript Writing: Atefeh Ghorbanipor, Parvin Farzanegi
Review and Editing: Amin Farzaneh Hesari
Responsible for Funding: Atefeh Ghorbanipor
Literature Review: Atefeh Ghorbanipor
Project Management: Amin Farzaneh Hesari
Conflict of Interest
The authors declare no conflict of interest.
Acknowledgments
AcknowledgmentsThis article is derived from the Professional Doctoral thesis in Exercise Physiology at Sari Islamic Azad University. The authors warmly thank all those who contributed to the successful completion of this research.
 
Keywords
Ischemic Preconditioning
Aerobic training
Endoplasmic Reticulum Stress
cardiovascular diseases

Main Subjects

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Sport Physiology
Volume 17, Issue 66
June 2025
Pages 49-34

  • Receive Date 11 May 2025
  • Revise Date 12 July 2025
  • Accept Date 10 August 2025