In vitro study methodologies to investigate genetic aspects and effects of drugs used in attention-deficit hyperactivity disorder

Methylphenidate Exposing During Neurodevelopment Alters Amino Acid Profile, Astrocyte Marker and Glutamatergic Excitotoxicity in the Rat Striatum

There is a public health concern about the use of methylphenidate (MPH) since the higher prescription for young individuals and non-clinical purposes is addressed to the limited understanding of its neurochemical and psychiatric consequences. This study aimed to evaluate the impact of early and chronic MPH treatment on the striatum focusing on amino acid profile, glutamatergic excitotoxicity, redox status, neuroinflammation and glial cell responses. Male Wistar rats were treated with MPH (2.0 mg/kg) or saline solution from the 15th to the 44th postnatal day. Biochemical and histological analyses were conducted after the last administration. MPH altered the amino acid profile in the striatum, increasing glutamate and ornithine levels, while decreasing the levels of serine, phenylalanine, and branched-chain amino acids (leucine, valine, and isoleucine). Glutamate uptake and Na+,K+-ATPase activity were decreased in the striatum of MPH-treated rats as well as increased ATP levels, as indicator of glutamatergic excitotoxicity. Moreover, MPH caused lipid peroxidation and nitrative stress, increased TNF alpha expression, and induced high levels of astrocytes, and led to a decrease in BDNF levels. In summary, our results suggest that chronic early-age treatment with MPH induces parallel activation of damage-associated pathways in the striatum and increases its vulnerability during the juvenile period. In addition, data presented here contribute to shedding light on the mechanisms underlying MPH-induced striatal damage and its potential implications for neurodevelopmental disorders.

Evidence That Methylphenidate Treatment Evokes Anxiety-Like Behavior Through Glucose Hypometabolism and Disruption of the Orbitofrontal Cortex Metabolic Networks

Methylphenidate (MPH) has been widely misused by children and adolescents who do not meet all diagnostic criteria for attention-deficit/hyperactivity disorder without a consensus about the consequences. Here, we evaluate the effect of MPH treatment on glucose metabolism and metabolic network in the rat brain, as well as on performance in behavioral tests. Wistar male rats received intraperitoneal injections of MPH (2.0 mg/kg) or an equivalent volume of 0.9% saline solution (controls), once a day, from the 15th to the 44th postnatal day. Fluorodeoxyglucose-18 was used to investigate cerebral metabolism, and a cross-correlation matrix was used to examine the brain metabolic network in MPH-treated rats using micro-positron emission tomography imaging. Performance in the light-dark transition box, eating-related depression, and sucrose preference tests was also evaluated. While MPH provoked glucose hypermetabolism in the auditory, parietal, retrosplenial, somatosensory, and visual cortices, hypometabolism was identified in the left orbitofrontal cortex. MPH-treated rats show a brain metabolic network more efficient and connected, but careful analyses reveal that the MPH interrupts the communication of the orbitofrontal cortex with other brain areas. Anxiety-like behavior was also observed in MPH-treated rats. This study shows that glucose metabolism evaluated by micro-positron emission tomography in the brain can be affected by MPH in different ways according to the region of the brain studied. It may be related, at least in part, to a rewiring in the brain the metabolic network and behavioral changes observed, representing an important step in exploring the mechanisms and consequences of MPH treatment.

Mental health dished up-the use of iPSC models in neuropsychiatric research

Genetic and molecular mechanisms that play a causal role in mental illnesses are challenging to elucidate, particularly as there is a lack of relevant in vitro and in vivo models. However, the advent of induced pluripotent stem cell (iPSC) technology has provided researchers with a novel toolbox. We conducted a systematic review using the PRISMA statement. A PubMed and Web of Science online search was performed (studies published between 2006–2020) using the following search strategy: hiPSC OR iPSC OR iPS OR stem cells AND schizophrenia disorder OR personality disorder OR antisocial personality disorder OR psychopathy OR bipolar disorder OR major depressive disorder OR obsessive compulsive disorder OR anxiety disorder OR substance use disorder OR alcohol use disorder OR nicotine use disorder OR opioid use disorder OR eating disorder OR anorexia nervosa OR attention-deficit/hyperactivity disorder OR gaming disorder. Using the above search criteria, a total of 3515 studies were found. After screening, a final total of 56 studies were deemed eligible for inclusion in our study. Using iPSC technology, psychiatric disease can be studied in the context of a patient’s own unique genetic background. This has allowed great strides to be made into uncovering the etiology of psychiatric disease, as well as providing a unique paradigm for drug testing. However, there is a lack of data for certain psychiatric disorders and several limitations to present iPSC-based studies, leading us to discuss how this field may progress in the next years to increase its utility in the battle to understand psychiatric disease.

Methylphenidate alters Akt-mTOR signaling in rat pheochromocytoma cells

The exponential increase in methylphenidate (MPH) prescriptions in recent years has worried researchers about its misuse among individuals who do not meet the full diagnostic criteria for attention-deficit/hyperactivity disorder (ADHD) such as young children and students in search of cognitive improvement or for recreational reasons. The action of MPH is based mainly on inhibition of dopamine transporter, but the complete cellular effects are still unknown. Based upon prior studies, we attempted to determine whether the treatment with MPH (1μM) influences protein kinase B-mammalian target of rapamycin complex 1 signaling pathways (Akt-mTOR), including translation repressor protein (4E-BP1) and mitogen activated protein kinase (S6K), in rat pheochromocytoma cells (PC12), a well characterized cellular model, in a long or short term. MPH effects on the Akt substrates [cAMP response element-binding protein (CREB), forkhead box protein O1 (FoxO1), and glycogen synthase kinase 3 beta (GSK-3β)] were also evaluated. Whereas short term MPH treatment decreased the pAkt/Akt, pmTOR/mTOR and pS6K/S6K ratios, as well as pFoxO1 immunocontent in PC12 cells, long term treatment increased pAkt/Akt, pmTOR/mTOR and pGSK-3β/GSK-3β ratio. Phosphorylation levels of 4E-BP1 were decreased at 15 and 30 min and increased at 1 and 6 h by MPH. pCREB/CREB ratio was decreased. This study shows that the Akt-mTOR pathway, as well as other important Akt substrates which have been described as important regulators of protein synthesis, as well as being implicated in cellular survival, synaptic plasticity and memory consolidation, was affected by MPH in PC12 cells, representing an important step in exploring the MPH effects.

Challenges in understanding psychiatric disorders and developing therapeutics: a role for zebrafish

The treatment of psychiatric disorders presents three major challenges to the research and clinical community: defining a genotype associated with a disorder, characterizing the molecular pathology of each disorder and developing new therapies. This Review addresses how cellular and animal systems can help to meet these challenges, with an emphasis on the role of the zebrafish. Genetic changes account for a large proportion of psychiatric disorders and, as gene variants that predispose to psychiatric disease are beginning to be identified in patients, these are tractable for study in cellular and animal systems. Defining cellular and molecular criteria associated with each disorder will help to uncover causal physiological changes in patients and will lead to more objective diagnostic criteria. These criteria should also define co-morbid pathologies within the nervous system or in other organ systems. The definition of genotypes and of any associated pathophysiology is integral to the development of new therapies. Cell culture-based approaches can address these challenges by identifying cellular pathology and by high-throughput screening of gene variants and potential therapeutics. Whole-animal systems can define the broadest function of disorder-associated gene variants and the organismal impact of candidate medications. Given its evolutionary conservation with humans and its experimental tractability, the zebrafish offers several advantages to psychiatric disorder research. These include assays ranging from molecular to behavioural, and capability for chemical screening. There is optimism that the multiple approaches discussed here will link together effectively to provide new diagnostics and treatments for psychiatric patients.

Summary: In this review, we discuss strengths and limitations of prevalent laboratory models that are used for understanding psychiatric disorders and developing therapeutics, with emphasis on the zebrafish.