Extended Abstract

Introduction
Methamphetamine, a highly addictive substance, poses severe social and psychological risks. Acting as a central nervous system stimulant, it mimics the sympathetic nervous system and influences the central nervous system by imitating two catecholamine neurotransmitters: Dopamine and norepinephrine. Methamphetamine abuse causes significant health problems in vital organs, particularly within the cardiovascular system, with 68% of cases exhibiting common histopathological features, such as myocardial hypertrophy, atherosclerosis, and necrosis. Methamphetamine may increase cardiovascular diseases through catecholamine toxicity or direct effects on cardiac and vascular tissues. Studies have shown that short-term and long-term exposures to methamphetamine induce cellular damage and hypertrophy in isolated cultured cardiomyocytes, suggesting a role in direct, catecholamine-independent cardiac toxicity. Although the complete biochemical mechanism and chronic methamphetamine abuse remain unclear, reports indicate that methamphetamine is involved in the release of dopamine into the synaptic cleft, decreasing dopamine receptor levels, and increasing dependence on the substance. Dopamine receptors are distributed in the atrial and ventricular walls. By signaling through dopamine receptors, dopamine increases myocardial contractility and cardiac output without changing heart rate. Conversely, repeated methamphetamine use reduces dopamine synthesis and its receptors. Poly (adenosin diphosphat [ADP]-ribose polymerase (PARP) is an enzyme involved in responding to DNA damage and genetic problems. Excessive activation of PARP1 due to DNA strand breaks can lead to a decrease in nicotinamide adenine dinucleotide (NAD+) and prevent optimal adenosine triphosphate (ATP) synthesis. This can result in the depletion of these important intracellular energy stores and impaired cellular function, ultimately leading to cell death. Given that methamphetamine users experience heart failure, PARP could be considered a protein involved in the mechanism of cardiovascular disorders in these patients. Exercise is currently considered a crucial non-pharmacological strategy for the treatment and prevention of cardiovascular diseases. Evidence suggests that exercise can act as an accelerator in promoting neurocognitive development and can compensate for the decreased production of catecholamines (dopamine, serotonin, and norepinephrine) caused by drug abuse. Exercise reduces damage to dopaminergic and serotonergic monoaminergic terminals and increases their levels in the blood. Berberine, a supplement derived from barberry, has various effects, including antidepressant, anti-inflammatory, analgesic, anticancer, antimicrobial, antioxidant, antihypertensive, glucose-lowering, lipid-lowering, regulated blood cholesterol, improved cardiovascular function, and improved liver function. Although cardiovascular complications are shown to be the second leading cause of death in methamphetamine users, the exact molecular mechanisms of this substance on the cardiovascular system remain unknown. However, chronic methamphetamine use induces inflammation and oxidative stress status, which play a crucial role in the cardiovascular system. Additionally, the dopamine system plays a significant role in the behavioral changes caused by methamphetamine; however, the expression levels of various dopamine receptors, particularly in the hearts of methamphetamine-addicted animal models, are unclear. Furthermore, one of the side effects of methamphetamine use is DNA damage and the production of free radicals, with PARP being one of the markers of this damage and playing an important role in inflammation, apoptosis, and necrosis. Excessive PARP activity plays a crucial role in cardiovascular disease. Berberine, as an antagonist of the D1 and D2 dopamine receptor family with anti-inflammatory and antioxidant effects, as well as physical activity, which improves cardiac function and oxidative and inflammatory status, may be beneficial through changes in gene expression. Therefore, this study aimed to determine the effects of four weeks of aerobic exercise and berberine supplementation on the expression of dopamine 5 receptor and PARP genes in the heart tissue of methamphetamine exposed rats.
Methods
This experimental study was conducted on 30 female Wistar rats weighing 160±10 g. Animals were housed in a quarantine room for one week with an ambient temperature of 22°C, with 50% humidity and a 12-hour light-dark cycle. Rats were then randomly allocated into five groups of six: Control, methamphetamine, methamphetamine + aerobic exercise, methamphetamine + berberine, and methamphetamine + aerobic exercise + berberine.
Methamphetamine was induced by intraperitoneal injection at a dose of 10 mg/kg of body weight per day for 5 days. Forty-eight hours after methamphetamine induction, all groups (except the control group) received berberine supplementation, aerobic exercise, or both for four weeks during the methamphetamine withdrawal period based on the intervention type. The control and methamphetamine groups were housed in their cages during the four-week withdrawal period and received no intervention. The berberine dose was 100 mg/kg in drinking water for the four-week withdrawal period. The aerobic exercise protocol was performed in the form of strength exercise on a rodent treadmill (Danesh Salar Iranian). The aerobic exercise mainly involved a treadmill running program for 4 weeks, 6 days per week (a total of 24 sessions) at a constant speed of 25 m/min for 30 minutes per day. Training sessions were conducted between 9 AM and 12 PM.
After completing the 4-week training and receiving the protocol, rats were anesthetized, and heart tissue samples were separated. The expression levels of dopamine 5 and PARP genes were quantified using real-time polymerase chain reaction (PCR), following the manufacturer’s instructions for the GENEALL (South Korea) kit. The glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene was used as an internal control.
Results
No significant difference was found in PARP gene expression between the amphetamine group (0.02±0.65) and the control group (1.02±0.24). Similarly, there was no significant difference in dopamine 5 receptor gene expression between the amphetamine group (5.74±4.94) and the control group (4.76±2.63).
Furthermore, no significant differences were observed in the expression of both PARP and dopamine 5 receptor genes among the groups. Gene expression of PARP and dopamine 5 receptor following exercise were 1.01±0.55 and 4.30±1.96, respectively. For berberine supplementation, the values were 0.61±0.25 and 2.97±1.45, respectively. Moreover, for the combined intervention, the values were 0.67±0.30 and 3.43±1.87, respectively.
Conclusion
Based on the results of this study, methamphetamine consumption did not induce significant changes in cardiac PARP gene expression compared to the control group. Moreover, four-week interventions during the methamphetamine withdrawal period, including aerobic exercise, berberine supplementation consumption, and a combination of both, did not result in significant changes in PARP gene expression compared to the methamphetamine group.
Ethical Statement
This study was approved by the Research Ethics Committees of Islamic Azad University, Shahrood Branch (IR.IAU.SHAHROOD.REC.1402.016).
Funding
This article has been extracted from the master’s thesis of Ms. Zahra Aghajani, a graduate student in the Department of Physiology and Sports Nutrition at the Faculty of Humanities, Islamic Azad University, Shahrood Branch.
Conflicts of Interest
No conflict of interest.
Acknowledgment
We would like to thank all those who assisted us in conducting this study.

Key message: A short-term (5-day) induction of methamphetamine did not result in significant changes in the expression of dopamine 5 receptor and PARP genes in the hearts of female rats. Consequently, therapeutic interventions, such as aerobic exercise, berberine supplementation, and their combination during the withdrawal period did not alter the expression of these genes.