The present study aimed to shed a light on the big picture of molecular changes in prenatal methamphetamine exposure during the first three years of life. Findings showed that three molecular pathways, including Primary immunodeficiency, Apoptosis, and Parkinson's disease are mostly affected by PME. Also, abnormalities in the bioenergetic, dopaminergic, and synaptic processes were detected at all time points. Based on expression profiling data a gene list of biomarkers was selected by machine learning to use as a potential model to diagnosis the PMEs.
Recently studies have focused on the effects of prenatal exposure to CNS stimulant drugs (19). Although there are several reports about the molecular, cognitive, and brain structure of methamphetamine use disorder, there is a great lack of information about PMEs. Few animal studies reported the PME effects on molecular pathways in the brain (20, 21, 22). In addition, some psychological studies evaluated the cognitive effects of PME in children at the age of six or seven or adolescence (23, 24).
Genome expression profiling on methamphetamine-treated animal model studies showed changes in critical genes for brain functions, including neuronal plasticity, mitochondrial energy metabolism, and immune response (25). METH treatment induction on mitochondrial energy metabolism and associated glutamate receptor alterations as a neurotoxic response in the brain (including the amygdala, prefrontal cortex, hippocampus, and striatum) of rats accompanied with a significant behavioral sensitization had reported (26, 27).
The present study may suggest that PME may induce chronic bioenergetic deregulations in children that, in turn, could increase the possibility of severe psychiatric disorders caused by mitochondrial dysfunction. Mitochondrial dysfunction especially in complex I of the respiratory chain are biomarkers for depressive mode (28,29) as well as psychosis and several cognitive dysfunctions in schizophrenia and bipolar disorder (30).
Neuron projection, which is the most affected cellular component during the follow up is any process extending from a neural cell, such as axons or dendrites, and is related to addiction tendency and stress problems, and changes in the brain circuitry (31, 32). Synaptic transmission and transmission of nerve impulses are two affected biological processes that are essential for normal cognitive functions such as learning and memory (33). Dysfunction in synaptic transmission and transmission of nerve impulses had been reported in several psychiatric disorders such as schizophrenia and autism (34, 35). Findings may explain the learning and cognitive problem (36, 37) and even anatomical changes in the brain of PMEs, such as reduced caudate and thalamus volume (38).
Probably the major and severe primary immunodeficiency is the most worrying effect of PME observed in the present study. METH treatment may cause an inflammatory response that plays a potential role in METH-induced neuronal injury and deregulation of cellular immune responses (39, 40). METH also could increase blood-brain barrier (BBB) permeability that may explain similarities between PMEs and methamphetamine use disorders (8), but taking together with primary immunodeficiency it could be considered as a risk factor for CNS infections (41). Immunodeficiency caused by methamphetamine can get escalated when accompanied by mitochondrial damage and increased levels of oxidative stress (42). By the way, primary immunodeficiency diseases (PIDs) are heterogeneous disorders, and many PIDs patients are diagnosed late. Due to poor prognosis, many cases suffer from complications by the burden of chronic infections, irretrievable end-organ damage, or even death before the definitive diagnosis (43, 44). Results revealed that PMEs are born at risk of lethal immunodeficiency disorders, but the bright side is that the targeted prognosis of PMEs may lead to timely diagnosis and appropriate treatment of those PMEs who may affect by PIDs.
Recent epidemiological cohort studies showed that methamphetamine use disorder increases the risk for developing Parkinson's disease (PD) and there are similar neurodegenerative processes in PDs and Meth use disorders that target the nigrostriatal system (45,46). Like addiction tendency, anxiety, and low-stress resilience, Parkinson's disease pathway also is mostly involved with dopaminergic and GABAergic pathways (47). Constant and severe deregulation of Parkinson-related genes in PMEs provide evidence that prenatal methamphetamine exposure can cause long-lasting disabilities or degeneration of dopaminergic cell bodies, and it may increase the risk of PD in PMEs as well as stress disorders and addictive behaviors. Also, these potential risks for PD can be detected in neonates.
The number of deregulations caused by methamphetamine, including reactive oxygen species activation and mitochondrial dysfunctions may lead to death receptor and ER pathways of apoptosis (48, 49). Methamphetamine-induced apoptosis pathways are mostly mitochondria-mediated (50), but also the footprints of the mTOR signaling pathway were detected (51). Several genes from both mitochondrial and mTOR were differentially expressed in PMEs. mTOR pathway is also associated with autistic-like behaviors and locomotor activity problems (52).
Based on our assessment to find predictive biomarkers for PME, we short-listed a gene list of seventeen genes. five genes of the biomarker list are involved in the dopamine pathway, dopamine receptors (D1, D2, and D3), brain-derived neurotrophic factor (BDNF), and MAOA. The similarity of expression pattern in PME and methamphetamine use disorder in adults may support the evidence that methamphetamine can pass through the blood-brain barrier of infants. MAOA down-regulation that observed almost constantly during all-time points may suggest that PME children could be at high risk for psychiatric disorders, also may explain the stress and violence problem of PMEs (4,5,53,54).
Genes related to the immune system that meet the criteria of biomarkers are all involved in neurodevelopmental disorders, especially ASD. Cytokines participate in normal neural development and function, and abnormal cytokine activity caused by meth neurotoxic effects may lead to several neurological dysfunctions. It may explain some of the similar symptoms of ASDs and PMEs, such as language impairments and lack of communication (4, 5,55).
Synaptogenesis dysfunctions are shared between PMEs and ASDs. Lack of function in SHANK2 may cause ASD-like behaviors such as reduced social interaction and social communication and repetitive behaviors (56, 57,58).
Transcription factors in the PMEs biomarker list, CREB1, DLG4, MECP2, EGR2, and FOXP2 are essential in memory formation, language function, and cognition. Findings may suggest that PMEs are vulnerable to affect by psychiatric disorders as well as syndromic and heterogeneous disabilities in executive functions such as memory abnormalities and language impairments (59, 60).
CYP2E1 is an essential protein for the cytochrome P450 mixed-unction oxidase system that is involved in the metabolism and degradation of drugs, toxic environmental chemicals, and carcinogens along with several basic metabolic reactions such as fatty acid oxidations, ethanol, and glucose metabolism (61). It seems that abnormal activity of the immune system in PMEs could cause constant effects on xenobiotic metabolism and several digestive pathways related to glucose and lipids. The expression level of interlukins (IL1B and IL8), CDK4, and TGFB1 were previously reported as modulators of humoral immunity via transcriptional programs and suppressed cellular energetics of both glycolysis and oxidative phosphorylation (62). Deregulation of these genes may lead to a number of autoimmune disorders.
These 17 DEGs may use as biomarkers to predict PME-associated disease in children. Constant up-regulation of dopamine receptors and down-regulation of dopamine degradation gene (MAOA) strongly suggest that PMEs could be high risk for psychotic disorders such as schizophrenia and bipolar disorder. Several transcription factors and synaptogenesis genes related to neurodevelopmental disorders could provide evidence that PME could be a risk factor for language impairments, ADHD, and Autistic like behaviors. It seems that the most PME associated potential diseases would be severe psychiatric disorders and autoimmune diseases.