نوع مقاله : مقاله پژوهشی
نویسندگان
1 دانشجوی دکتری فیزیولوژی ورزش، دانشکده علوم ورزشی، دانشگاه حکیم سبزواری، سبزوار، ایران.
2 استاد گروه فیزیولوژی ورزش، دانشکده علوم ورزشی، دانشگاه حکیم سبزواری، سبزوار، ایران.
3 دانشیار گروه مهندسی بافت و علوم سلولی کاربردی، مرکز تحقیقات سلولی و مولکولی، دانشکده پزشکی، دانشگاه علوم پزشکی قم، قم، ایران.
4 دانشیار گروه فیزیولوژی ورزش، دانشکده علوم ورزشی، دانشگاه حکیم سبزواری، سبزوار، ایران.
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Extended Abstract
Background and Aim: Methamphetamine abuse is associated with severe cardiovascular complications, including myocardial infarction, stroke, and increased risk of mortality. One of the fundamental mechanisms contributing to such pathological conditions is stress-induced cell death, which occurs primarily through necrosis and apoptosis. Apoptosis, or programmed cell death, is an active and regulated biological process that plays a crucial role in maintaining the balance between cell survival and death in various tissues, particularly in somatic tissues such as the brain, skeletal muscle, and myocardium.
Among the agents capable of inducing apoptotic cell death are opioids and psychostimulants, including methamphetamine. Methamphetamine exerts detrimental and potentially fatal effects on the cardiovascular system, such as hypertension, acute vasospasm, and accelerated atherosclerosis. Despite these known outcomes, the molecular mechanisms underlying methamphetamine-induced cardiovascular injury and associated pathological responses remain poorly understood.
Therefore, the present study aimed to investigate the effects of combined exercise training on the expression of Bax (Bcl-2-associated X protein) and vascular endothelial growth factor (VEGF) in the cardiac tissue of male rats following chronic methamphetamine administration.
Materials and Methods: This experimental-applied study was conducted on 30 male Wistar rats (8 weeks old; 200–210 g) to examine the effects of two factors on apoptosis-related markers in cardiac tissue. Animals were housed under standard laboratory conditions with free access to food and water, a 12:12-h light–dark cycle, and a controlled temperature of 23±2 °C. Rats were randomly assigned to groups based on body weight homogeneity.
Ten rats were allocated to the control group and received intraperitoneal injections of normal saline for 23 consecutive days. The remaining 20 rats received intraperitoneal injections of methamphetamine for 23 days. Methamphetamine administration followed a previously established protocol, with gradually increasing doses ranging from 2.5 to 10 mg/kg. After the addiction period, methamphetamine-treated rats were randomly divided into two groups (n=10 each): a sham (addicted) group and an addicted+combined training group.
The combined training protocol was performed for 6 weeks, 6 days per week, and consisted of alternating aerobic and resistance exercise sessions. Aerobic training was conducted on a motorized treadmill for laboratory animals at an intensity of 50–60% of maximal running speed. Resistance training was performed using a specialized ladder-climbing apparatus designed for rodents, with an intensity corresponding to 50–60% of one-repetition maximum (1RM). To determine training intensities, rats underwent a 24-hour familiarization period with the equipment, followed by an incremental treadmill exhaustion test to assess maximal aerobic capacity and a maximum strength test to establish baseline resistance loads.
At the end of the intervention period, cardiac tissue samples were collected. Bax protein expression was assessed using immunohistochemistry, a technique that enables the detection of specific cellular antigens through antigen–antibody binding. Vascular endothelial growth factor (VEGF) gene expression was evaluated using reverse transcription polymerase chain reaction (RT-PCR). Following cardiac tissue excision, total RNA was extracted, and VEGF expression levels were analyzed using a gene expression analysis system to determine the effects of methamphetamine exposure and combined exercise training. Data were analyzed using one-way ANOVA followed by Bonferroni post hoc test in SPSS version 26 at a significance level of p<0.01.
Findings: Immunohistochemical analysis revealed that intraperitoneal administration of methamphetamine significantly increased Bax protein expression in cardiac tissue in the sham (addicted) group compared with the control group. In contrast, Bax expression was markedly reduced in the combined training group relative to the sham group.
Analysis of VEGF gene expression demonstrated significant differences among groups (p<0.01). Methamphetamine administration in the sham group resulted in a significant decrease in VEGF expression compared with both the control and combined training groups. Conversely, the combined exercise group exhibited a significant increase in VEGF expression compared with the control (p<0.001) and the sham (p<0.0001) group (Figure 1).
Conclusion: Immunohistochemical findings demonstrated that Bax expression was significantly elevated in the sham (methamphetamine-dependent) group compared with both the control and combined training groups, whereas combined aerobic–resistance training markedly attenuated Bax expression. Apoptosis mediated by Bax occurs when cellular stress induces Bax translocation from the outer to the inner mitochondrial membrane, triggering cytochrome C release. This process promotes apoptosome formation through interaction with caspase-9 and apoptotic protease-activating factor-1 (Apaf-1), leading to downstream caspase activation and programmed cell death.
In contrast, VEGF expression was significantly reduced following methamphetamine administration, while combined training effectively restored and enhanced VEGF expression. Cardiomyocytes represent a major source of VEGF, a key cytokine involved in regulating vascular permeability, angiogenesis, and cell survival through anti-apoptotic mechanisms, including the upregulation of Bcl-2. The observed reduction in Bax expression following exercise training may therefore be attributed to increased Bcl-2 expression, as previously reported with regular exercise, and/or to improvements in antioxidant capacity. Indeed, moderate-intensity exercise has been shown to enhance total antioxidant status and suppress apoptotic signaling pathways in methamphetamine-dependent models.
Overall, the present findings indicate that chronic methamphetamine exposure impairs cardiomyocyte function by promoting apoptotic signaling. However, combined exercise training emerges as an effective, non-invasive intervention capable of mitigating methamphetamine-induced cardiac apoptosis. Despite these therapeutic benefits, primary prevention of exposure to toxic stimulants remains a critical priority for public health.
Compliance with ethical guideline: This study was conducted in compliance with all ethical principles of animal care and laboratory procedures, and was approved by the Ethics Committee of Qom University of Medical Sciences under the ethical code IR.MUQ.AEC.1400.007 at the Animal Care Center and the Cellular and Molecular Research Center of Qom University of Medical Sciences.
Funding: This article was produced without financial support.
Conflict of Interest: The authors declare that they have no conflict of interest in this study.
کلیدواژهها [English]
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