Opium's capacity for addiction, physically and mentally, has been well-demonstrated. Drug abusers usually encounter a defective cycle that consists of positive and negative parts leading the individual to consume drugs repetitively. The incidence of opium consumption has been rising sustainably. This is considered a prevailing problem that imposes a tremendous financial and social burden on the healthcare system (1).
A significant number of studies have focused on the neurological aspects of opium addiction, and the effects of opium on the central nervous system have been clearly illustrated. Recently, much interest belonged in its influence on other organ systems, especially reproductive and cardiovascular systems, which have a connection with opium by three primary receptors (2-4).
Oxidative stress (OS) occurs when abnormal situations generate oxidants that exceed antioxidants, this can cause DNA damage and fragmentations (DF) (5). DF can result in a cascade of events by inducing protease activity and apoptosis, which account for some human disorders such as male infertility. Reactive oxygen species (ROS) produced by the integration of xanthine and xanthine oxidase generally participate in the normal process of capacitation of human spermatozoa (6). However, a high level of production and clearance of ROS are potent to trigger OS through a signaling loop. The process of impairment in sperm function is the leading cause of male infertility. It has been shown that chronic codeine exposure causes sperm DNA fragmentation and poor sperm quality primarily via oxidative stress rather than activation of caspase 3-dependent apoptosis (7, 8). Although some cases have well-known factors that play a pivotal role in male infertility, some patients cannot attribute their condition to any specific reason, these are denominated as idiopathic cases. The role of ROS in infertility has been proved, and it is thought that ROS production is the second primary reason for infertility, irrespective of congenital diseases (9) (Figure 1).
Figure 1. The sperm DNA fragmentation index (DFI) reflects the integrity of and the damage to the DNA, the genetic material of the sperm, thereby detecting potential sperm damage.
Based on recent studies, we wanted to review DF due to opiate consumption and display how it can play a role in male infertility. In this paper, we review the impact of Opium on DNA fragmentation and later, on infertility. A limited literature search was conducted by an information specialist on resources including PubMed, the Cochrane Library, and a focused Internet search. The search strategy was based on controlled vocabularies, such as the National Library of Medicine’s MeSH (Medical Subject Headings) and keywords. No filters were applied to limit the retrieval by study type. Where possible, recovery was limited to English, in documents published between January 1, 1985, and July 29, 2019. We aim to summarize the literature regarding the connection between Opium use and DNA fragmentation.
Despite the debatable history of opium use for medical purposes for the first time, most authors agree that the spread of Opium began in the early eighth century in India (10). Opium poppy (morphine, thebaine, codeine, papaverine, noscapine, Etc.) was used for narcotics and sedation purposes. Nowadays, Opium-derived substances, including morphine, codeine, and hydrocodone, are used as solid painkillers. In contrast, heroin, derived from Opium, can be harmful to an individual's health and can cause a high grade of addiction (11).
Apoptosis is characterized by a process that results in the breakdown of the cell's DNA into smaller fragments, almost similar to necrosis. DF occurrence depends on DNA fragmentation factors (DFF), containing 45-kDa and 40-kDa (12, 13).
During the apoptosis process, DFF45 is separated from DFF40 by caspase-3; then, DFF40 will be activated and will break DNA into smaller fragments that call DF (14). The disturbance of the apoptosis process can cause some disorders, including autoimmune diseases, cancer, etc.
Morphine is one of the subdivided opioids that have been widely used as an analgesic in patients with severe and chronic pain (15). The half-life of morphine is between 1.5 to 7 hours, and various types of its products can be used depending on some factors. The analgesic pathway of morphine which is similar to codeine has been illustrated. When morphine binds to its receptor (Mu (μ) opioid receptor), the signal will be received by some enzymes that regulate its effect (16). On the one hand, quite a few investigations showed that morphine can interrupt the immune system. Morphine not only influences lymphocyte counts, thymic weight, and splenic weight but also decreases the lymphocyte mitogenic process. These effects are attributed to either the direct impact of morphine on its lymphocyte receptor or the indirect effect of morphine on the nervous system receptor (17, 18). Sabita et al. demonstrated that low and high doses of morphine increase apoptosis of lymph node lymphocytes through different pathways (19). A low dose is associated with an increase in caspase‐3‐ and caspase‐8‐mediated apoptosis. Whereas the high dose of morphine has its effect by changes in NO level. Some other studies indicated that morphine (20 mg/kg, SC, for four days) was accompanied by an increase in corticosterone level, which initiated the apoptosis thymocytes cycles and DF (20).
On the other hand, the bulk of indications showed that a low dose of morphine could hamper the destructive effects of oxidants on neural cells by inhibiting glycogen synthase kinase-3β and phosphatidylinositol 3-kinase, the latter being the target of rapamycin (21). Additionally, the antioxidant activity of morphine has been established based on different methods, including the thiocyanate method, which measures the total activity of morphine. According to Gulen’s study, as the concentration of morphine increases (from 25 to 75 micrograms per ml), in vitro, incremental antioxidant activity increases in parallel. Finally, they highlighted the importance of morphine in decreasing antioxidant activity with attention to concentration (14). Amini et al. showed that in a low dose of morphine (maximum 1 Pm), anti-inflammatory, anti-apoptotic, and neuroprotective effects could be expected (22). Hence, it is reasonable to use a low dose of morphine in patients with inflammatory disorders and neurological disorders. In contrast, morphine will have detrimental effects on a patient's health if it is administrated at high intensity. They also revealed that in an individual with an addiction to methamphetamine, which has become a global concern, applying morphine to routine treatment may help the patient to deal with the terrible effects of methamphetamine more conveniently.
Codeine and Codeinone
Codeine's capacity as a painkiller is similar to that of morphine. It also has the same adverse effects such as constipation, nausea, vomiting, itching, dry mouth, and addiction. The pain relief potential of codeine is less in comparison to morphine due to the lower potency of the Mu (μ) receptor, which is the same receptor between morphine and codeine (23, 24). Codeine has three main compounds: morphine, codeine 6-glucuronide, and codeinone; which are different in structure and potency. Codeinone production is based on oxidizing codeine; it exhibits the extreme cytotoxicity of morphine compounds against human promyelocytic leukemia cells.
There are no extended studies regarding the influence of codeine compounds on DF yet. It was outlined that codeinone's potential to induce apoptosis or necrosis, which is greatest among morphine compounds, can be used as an antitumor factor besides usual cancer treatment (25). In addition to apoptosis, codeinone can increase antinociceptive activity that resembles the antitumor activity of codeinone (18, 26). Masami et al. investigated the strength of morphine alkaloids in cytotoxicity activity. They demonstrated that the role in the antitumor activity of codeinone had been well understood in patients with oral tumors. The feasibility of inducing apoptosis results from the unsaturated ketones in codeinone structure that can be reduced by applying N-acetylcysteine.
Cocaine addiction is widely shared among Western societies, and the medical use of cocaine is restricted to topical anesthesia (27). It involves a broad spectrum of ages, and its exposure may be responsible for some congenital malformations and stillbirths. Regarding prenatal cocaine exposure; some studies have shown lower brain volume in children exposed intrauterine to cocaine, which is the leading cause of inappropriate behavior (28).
There is enough evidence of death in CNS tissue due to maternal exposure to cocaine. This was due to cell apoptosis through particular pathways (29, 30). However, the mechanisms have not been identified clearly. Genes encode apoptosis in brain cells and play a substantial role in the devastating cell death mechanism, according to Lidow et al.'s study. They clarified the interactions between cocaine and apoptosis genes that make fetal CNS cells vulnerable to apoptosis signals (31). One of the significant causes of death in cocaine abusers is cardiac abnormalities, ranging from arrhythmias to sudden cardiac death. Many efforts have been made to understand the reasons for death in individuals who use cocaine. Cocaine use leads to a rise in the blood level of catecholamine, which has been linked with a risk of cardiovascular events by a plethora of Reactive Oxygen Species (32). The other mechanism for cardiac cell death is calcium overload, which initiates the cascade of interactions based on Fleckenstein et al.'s study. In summary, both catecholamine release and rise in calcium blood level are the mainstays of severe cardiac events resulting from apoptosis and necrosis in addiction to cocaine (33, 34) (Table 1).
Infertility has become one of the significant concerns of society, with the prevalence of 60-80 million couples which is steadily rising (35). The definition of infertility has been described as not gaining achievement in pregnancy after at least one year of consecutive unprotected intercourse, which is related to both male and female factors. Infertility can be categorized into primary and secondary infertility based on the history of successful conception. It can be divided into three groups considering causes: male factors, female factors, and a combination of them (36).
Causes of male infertility
Concerning male infertility, viable spermatogenesis necessitates appropriate communication between endocrine, paracrine, and autocrine systems that can be disturbed by various factors that lead to infertility (37). A few acquired and congenital situations, such as testicular torsion, orchitis, well-known cytotoxic drugs, and Klinefelter syndrome, may interrupt spermatogenesis, mainly causing azoospermia. At the same time, most infertility factors that are recognized as idiopathic factors have not been elucidated clearly. Although many factors have been identified underpinning infertility, a widespread study discussing infertility factors does not exist. Oddly enough, male fertility has decreased recently, and clear reasons for male infertility remain uncertain (38). It is believed that environmental factors may be the prominent cause of the increasing incidence of male infertility.
Causes of female infertility
Female infertility encompasses a variety of causes, from anatomical problems, which are the most important causes of infertility, to unknown causes (39). The age of women at the time of attempting pregnancy has risen during the last 20 years, and this is one of the reasons for the growing incidence of infertility among women. As age increases, the ovary becomes less effective, the chance of chromosomal abnormalities increases, and the number of intercourses decreases remarkably. In women with ovarian failure, further the anatomical and pathological causes, numerous endocrine disorders possibly impair the physiological function of the ovary (40). The role of pelvic adhesions in female infertility due to free radicals should not be neglected (41). It is hypothesized that ROS production is dependent on the air of the operative room following surgery, and ROS worsens the situation by progressing pelvic adhesions.
Infertility and DNA fragmentation
Damaging the DNA of sperm can emerge with six mechanisms, which can interfere with either the process of sperm maturing or during sperm transport. DF happens throughout spermatogenesis and moves toward seminiferous tubules and epididymis. Besides, DF is induced by endogenous endonucleases, radiotherapy, chemotherapy, and environmental factors (42). First, Aitken et al. in 1987 stated the role of OS in male infertility by ROS with interrupting sperm plasma membrane integrity (43, 44). After that, Iwasaki et al. showed that with an increase in ROS, an inevitable decrease in the motility and intensity of sperm would happen (44, 45). There are reports that ROS is the critical factor in 25-40% of males with idiopathic infertility regardless of varicocele existence. ROS can be originated from white blood cells, primarily polymorphonuclear leukocytes. Consequently, the high level of white blood cells is accompanied by a high level of ROS through simple pathways. Therefore, it can be expected that situations causing leukocytopenia, can reduce fertility odds by enhancing the level of ROS (46).
Infertility and illicit drugs
Despite the role of illicit substances in emerging oxidative stress (OS), the susceptibility of human spermatozoa to OS is inconsistent with the idea that supports the responsibility of opium in the morphology and motility of sperm abnormalities (47). From the many clinical and experimental studies on illicit substances' effect on male production, only some of them describe that base on DNA damage. In contrast, the rest of the studies described that on account of hormonal changes, vasoconstriction of testicular blood, decrease in the diameter of seminiferous tubules, and amount of total germ cells (48, 49).
Li et al. exposed male rats to cocaine daily for almost three months, and they saw the highest rate of apoptosis of seminiferous tubules on day 30 which persisted until day 90 (50). They showed the insults of cocaine by inducing apoptosis. According to Yamamoto’s study, the apoptosis effect of methamphetamine started from a 5mg/kg dosage in rats and tubules. Apoptosis was dependent on dosage and a higher dosage showed a higher rate of apoptosis (51). Barneys et al. performed a study on rats treated with three different dosages of 3, 4. Methylenedioxymethamphetamine or ecstasy (0.5mg/kg, 5mg/kg, 10mg/kg). They showed that sperm concentration and motility were notably decreased at 5mg/kg and 10mg/kg, mainly due to the increasing rate of DNA damage. The study's other finding was interstitial adenoma in the case group, which can occur regardless of sperm concentration and motility. The effect of opium on infertility based on DF is limited. Although opium affects fertility through intrinsic and extrinsic pathways by inducing apoptosis, an increase in apoptotic molecules may be in normal cell death (Table 1). Tramadol administration is associated with decreases in sexual hormonal levels and disruption of the pathology of seminiferous tubules similar to apoptotic cells in rats. Most studies have addressed the link between opium addiction and male infertility, and there is scarce evidence concerning opium addiction and female infertility. Asadikaram et al. studied the effect of opium addiction on both rats with diabetes and rats with no diabetes. The study found that the rate of apoptosis in the ovary of female rats increases in rats who are addicted to opium and if they have diabetes (52).
Table 1. A brief review of studies related to opium and fertility
Ghasemi-Esmailabad S (52)
Morphine can decrease sperm chromatin condensation and increases the rate of sperm apoptosis
Genistein administration could increase the quality of spermatozoa and prevent morphine-induced adverse effects on sperm parameters.
In cases of unexplained infertility in men, opium consumption should be considered as a possible factor.
Subirán N (55)
The presence of the opioid system in sperm cells also represents a novel opportunity for reproductive management, for either enhancing the probability of fertilization or reducing it through the development of novel targeted contraceptives
Estomba H (56)
The role of the opioid receptors in spermatogenesis could help to develop new strategies to employ the opioid system as a biochemical tool for the diagnosis and treatment of male infertility
Takzare N (57)
The population of spermatogenesis cycle cells at spermatogonia, spermatocyte, spermatid, and spermatozoa stages were significantly decreased in those rats that received opioids in comparison to the control group
Upregulation of estrogen signaling associated with enhanced testicular HER2 and Ki67 expression during the recovery period is seemingly beneficial in protecting against codeine-related testicular injury and infertility.
Some antioxidants have shown promising results to prevent the destructive effect of ROS on cell DNA. Lipid peroxidation, the leading cause of DNA damage, could be suppressed by glutathione peroxidase. Hence the motility of sperm can be saved, according to Juan et al.,'s study, which agrees with Lewis et al.,'s analysis. It showed the efficiency of antioxidants in reducing the DF of sperm. However, no differences were observed in sperm parameters in the treatment group (53-56). Following Eskenazi et al.,'s study, vitamins C and E as antioxidants have a beneficial effect on sperm count and motility in healthy, non-smoking males (57). DF and inflammatory processes that happen in individuals with oral consumption of codeine can modulate the level of testicular enzymes and, apart from that, cause changes in the morphology of testis cells. Given an overview by Lombardo et al., the outcomes of using antioxidants in men with infertility often were unmet, they need more relevant studies to support this idea. In addition, they indicated that antioxidants are perhaps concomitant with some complications and suggested pros and cons before administering antioxidants to patients. Collectively, antioxidants should be considered one of the treatment choices in men with idiopathic infertility.
The rate of fertility decreases in individuals who administrate illicit substances and many studies illuminated that in addition to the hormonal modulation levels and pathological changes, DNA fragmentation should be considered as a response mechanism. Thus, antioxidants can be used in patients with infertility for unknown reasons. The outcomes of antioxidants in animal studies were satisfactory; however, against all the odds, the results in human clinical studies were not as good as in experimental studies. We suggest perfuming more clinical studies regarding the relationship between illicit substances and infertility, and more extensive studies are warranted to establish the reverse relationship between them. Soon, the medication of opioids will be limited to some occasions regarding the infertility problem of patients. The limitation was the limited geographic diversity of published articles.
All authors contributed equally.
Special thanks to the Urology Research Center (URC), Tehran University of Medical Sciences, Tehran, Iran.
Conflict of interest
The author declares that there are no conflicts of interest.
Data will be provided on request.
DFF DNA fragmentation factors
OS Oxidative stress
ROS Reactive oxygen species