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A case-control study was carried out, which included 107 cocaine and crack users and 115 controls who never used healthy cocaine and crack. The SNPs in the TNFA (-308G/A), IL-10 (-819C/T) and ENOS (-786T/C) genes were genotyped by real time PCR.
Our results suggest that genetic polymorphisms promote susceptibility or promote protection for clinical phenotypes of psychiatric comorbidities in cocaine and crack users and be considered as good prognostic markers.
Cocaine is used by an estimated 18.2 million people worldwide, about 0.4 percent of the global population aged between 15 and 64 years [1]. Disorders triggered by the use of cocaine and crack consist of a complex public health problem that involves consequences at the biological level and in social behavior [2, 3]. The chronic use of cocaine is often accompanied by several mental disorders, such as chronic depressive symptoms [4], suicide risk, post-traumatic stress disorder, antisocial personality disorder [5], and anxiety disorders [6].
From this perspective, several studies have demonstrated the role of single nucleotide polymorphisms (SNPs) in molecules of the immune system and oxidative stress that contribute to susceptibility to mental disorders [19-21]; however, there are no investigations involving drug users to understand the development of these disorders. In the present study, we hypothesize that IL-10 (-819C/T), TNFA (-30G/A8) and ENOS (-786T/C) polymorphisms can modulate the outcome of mental disorders in cocaine and crack users. The aim of this study was to investigate the role of genetic polymorphisms of cytokines and oxidative stress in the development of psychiatric comorbidities in cocaine and crack users.
The study was approved by the Ethics Committee of the Federal University of Alagoas, and all participants provided a free and informed consent term (protocol nº 2.408.885 and CAAE 67643417.3.0000.5013). For this research, we conducted a case-control study with a sample of 107 cocaine and crack users recruited from three therapeutic community groups in a state in Northeast Brazil. The control group (n=115) was composed of healthy volunteers who did not report an established clinical diagnosis of psychiatric comorbidities, were without positive diagnoses according to the MINI International Neuropsychiatric Interview (MINI version 5.0), were 18 years old, who reported that they had never used cocaine and crack, and agreed to participate in the research.
The inclusion criteria involved individuals over 18 years old who met the criteria for addiction, according to the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV), and reported crack/cocaine use. The exclusion criteria included a prior medical diagnosis of psychosis, mental retardation, or neurological or cognitive visible impairments that could compromise their ability to participate in the study. All participants provided informed consent. Regarding aspects of drug use, the following data were collected: age at which drug use was initiated, age at which cocaine/crack was used, and the first drug used.
The majority of participants were male (86.8%), with a mean age ranging from 18 to 54 years old (M=31.4, SD=8.5). Regarding drug use, the mean age in years for starting drug use was 14.3 years (SD=4.3) and for starting using cocaine/crack was 20.3 years (SD=7.2). The highest proportion of the participants was self-reported, mixed color (54%, n=60), and with incomplete elementary school (62,6%). Marijuana was the first drug used by the majority (32.7%) of the participants, followed by alcohol use (31.7%). Regarding the diagnoses tracked throughMINI, the most prevalent psychiatric disorder was the current major depressive episode among the participants, and 30.4% had a recurrent major depressive episode. 100 (75%) of the participants had a current alcohol addiction, while 63 (56.3%) have experienced current alcohol abuse and 50 (44.6%) had generalized anxiety disorder, and 52 (46.4%) antisocial personality disorder. Among the subjects included in the study, 55 (49.1%) had suicide risk (Table 1).
Regarding the SNP -308 of the TNFA gene, the analysis of the genotypic and allele frequencies showed that the G/G genotype was more prevalent in all the investigated groups. None of the groups showed the A/A genotype. Concerning the allelic distribution of the TNFA polymorphism -308, the G allele was the most frequent in all groups. After performing the binary logistic regression, we compared cocaine and crack users with and without the respective psychiatric comorbidities according to the instruments used. When assessing the distribution between the genotype and allele frequencies of the case and control group, no significant difference was found. We identified the G/A genotype in the codominant model (OR = 0.24; CI = 0.06 - 0.87; p = 0.03) and the A allele (OR = 0.30; CI = 0.09 - 0.93; p = 0.03) to be associated with reduced risk for dysthymic disorder in our population.
Our results describe for the first time a quantitative association of IL-10 (-819C/T), TNFA (-308G/A) and ENOS (-786T/C) SNPs of candidate genes markers in cocaine/crack users with mental disorders in a Brazilian sample. These polymorphisms may affect the response to antidepressant therapy of major depressive disorder in the Polish population [26], high levels of anxiety in women after breast cancer surgery in the American population [27], methamphetamine-induced psychosis in the Japanese population [28], and schizophrenia in Germany population [29].
Cytokines have pro and anti-inflammatory properties and consist of a large group of small proteins that play a significant role in cell signaling and regulate a variety of processes in organisms, including proliferation and differentiation of many cells, mediation in defense response, and regulation of hematopoiesis [30]. In this context, the use of cocaine and crack has been shown to trigger immunomodulatory effects; the TNF alpha cytokine has been associated with the activation of the serotonergic system in patients with depression, suggesting a close relationship between cytokines and serotonergic systems. Few studies have linked the increased IL-10 serum levels [31] and decreased TNF alpha levels [18] with the development of psychiatric changes in drug users in the Brazilian and Spanish populations, respectively.
IL-10 is an anti-inflammatory cytokine activated by monocytes and lymphocytes and plays several immune functions, including a restraint biosynthesis of proinflammatory cytokines and suppression of cellular immunity in the central nervous system, favoring neural and glial cells [32]. In our population of cocaine and crack users, we identified T allele with a risk association for the development of the psychotic syndrome and alcohol abuse and C allele with a protective role for panic disorder. Elevated serum levels of IL-10 have been linked to susceptibility to schizophrenia in the Italian and Chinese population [33, 34]; however, decreased levels were found in patients with aggressive and psychotic behavior [35] and were found to be associated with decreased anti-inflammatory response in schizophrenia, especially in patients with severe symptoms in Chinese population [34]. Regarding panic disorder, there was a discrepancy in the serum levels of this cytokine in the Brazilian population [36], and IL-10 polymorphisms were not associated with panic disorder in an Estonian population [37]; however, elevated serum levels of IL-10 have been found in the American population [38].
The effects of cocaine seem to be more prominent in the frontal cortical regions of the brain, including the prefrontal cortex [47], where cerebral blood flow is most affected [48, 49]. A previous study showed that the chronic administration of cocaine in mice induced cerebral ischemia [50]. Oxidative stress induces a decrease in nitric oxide levels, which leads to a disruption in muscle function due to the microvascular dysfunction in mental disorders, including depression [51, 52]. In our study, we did not identify a relationship between the ENOS (-786T/C) polymorphism and the development of mental disorders and suicide risk in cocaine and crack users; however, the power value of 11% for ENOS (-786T/C) polymorphism indicates that our sample size was inadequate and insufficient to detect a true association.
The genetic background and miscegenation of the Brazilian population may clarify the different outcomes presented in this paper. Further, studies including a larger sample size genomewide association are needed to enhance the prediction of these results and better understand the interaction between genes and outcome of clinical mental disorders in cocaine/crack users.
In conclusion, our results demonstrate the polymorphisms in IL-10 (-819C/T) and TNFA (-308G/A) genes to be associated with the clinical phenotypes of mental disorders in cocaine/crack users. These results indicate that genetic polymorphisms of molecules involved in the synergic immune system might play an important role in the outcome of mental disorders in cocaine/crack users, and may be considered as prognostic biomarkers before stratification to improve addiction treatment. Furthermore, this study presents a significant step forward in determining the contribution of genetic factors in previously observed inter-individual variability with respect to mental disorders and addiction to cocaine/crack. 2ff7e9595c
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