Neurogenetics: insights into degenerative diseases and approaches to schizophrenia

The Pathophysiological Underpinnings of Gamma-Band Alterations in Psychiatric Disorders

Investigating the biophysiological substrates of psychiatric illnesses is of great interest to our understanding of disorders' etiology, the identification of reliable biomarkers, and potential new therapeutic avenues. Schizophrenia represents a consolidated model of γ alterations arising from the aberrant activity of parvalbumin-positive GABAergic interneurons, whose dysfunction is associated with perineuronal net impairment and neuroinflammation. This model of pathogenesis is supported by molecular, cellular, and functional evidence. Proof for alterations of γ oscillations and their underlying mechanisms has also been reported in bipolar disorder and represents an emerging topic for major depressive disorder. Although evidence from animal models needs to be further elucidated in humans, the pathophysiology of γ-band alteration represents a common denominator for different neuropsychiatric disorders. The purpose of this narrative review is to outline a framework of converging results in psychiatric conditions characterized by γ abnormality, from neurochemical dysfunction to alterations in brain rhythms.

Efecto del compuesto N-2,6-dicloro-aralquil-2-Aminoindano en la conducta estereotipada de ratas. Acción dopaminérgica selectiva central sobre los ganglios basales más que en las estructuras límbicas

Dopamine 1 is involved in neurodegenerative disorders affect-ing the central nervous system (CNS), such as Parkinson’s disease. Despite the absence of some available drugs capable of preventing, stopping or curing the progression of such diseases, there are numerous compounds designed, synthesized, and pharmacologically tested which give rise to pharmacophoric generalizations about the dopaminergic receptor required for the search of a drug able to improve or cure those pathologies. N-aralkyl-2-aminoindane de-rivatives have shown selective activity in the central dopaminergic system. Both the N-[(2,4-dichlorophenyl)-1-methyl-ethyl]-2-aminoindane hydrochloride 2and N-[(3,4-dichlorophenyl)-1-methyl-ethyl]-2-aminoindane hydrochloride 3 showed an agonistic activity mediated by central dopaminergic mechanisms. To contribute to the search of new drugs able to re-establish homeostasis in the dopaminergic transmission in Parkinson’s disease, the compound N-2,6-dichloro-aralkyl-2-aminoindane 4 was designed through medicinal chemistry strategies that contain pharmacophoric approximations of prodrugs. The phar-macological evaluation of compound 4 in the stereotyped behavior of male Sprague Dawley rats showed agonistic activity through the activation of central dopaminergic mechanisms and a higher selectivity in the responses of stereo-typed behavior characteristic of the basal ganglia over the typical responses from limbic structures.

Pharmacological screening of silibinin for antischizophrenic activity along with its acute toxicity evaluation in experimental animals

Silibinin (SIL), a flavolignan extracted from the medicinal plant "silybum marianum (milk thistle)", has traditionally been used to treat liver disease. This phytochemical has displayed neuroprotective properties, its activity against schizophrenia is not elucidated. The present study was designed to evaluate the antipsychotic potential of silibinin and probe its toxic potential. The acute oral toxicity study was assessed as per OECD 425 guidelines. Animals were divided into two groups of female rats (n = 6): one group served as the normal control and the other group received a 2,000 mg/kg dose of SIL. We also evaluated the antipsychotic potential of SIL. To this end, animals were divided into six groups (n = 10) of mice for both the preventive and curative protocols. Group I (CMC 1 mL/kg) served as the normal control and received CMC 1 mL/kg; group II was the diseased group treated with ketamine (10 mg/kg) i.p; group III was the standard group treated with clozapine 1 mg/kg; groups IV, V, and VI served as the treatment groups, receiving SIL 50, 100, and 200 mg/kg, respectively, orally for both protocols. Improvement in positive symptoms of the disease was evaluated by stereotypy and hyperlocomotion, while negative symptoms (behavioral despair) were determined by a forced swim test and a tail suspension test in the mice models. The results suggested that the LD₅₀ of SIL was greater than 2,000 mg/kg. Moreover, SIL prevented and reversed ketamine-induced increase in stereotypy (p < 0.001) and behavioral despair in the forced swim and tail suspension tests (p < 0.001). Taken together, the findings suggest that silibinin is a safe drug with low toxicity which demonstrates significant antipsychotic activity against the positive and negative symptoms of schizophrenia.

Could psychedelic drugs have a role in the treatment of schizophrenia? Rationale and strategy for safe implementation

Schizophrenia is a widespread psychiatric disorder that affects 0.5-1.0% of the world's population and induces significant, long-term disability that exacts high personal and societal cost. Negative symptoms, which respond poorly to available antipsychotic drugs, are the primary cause of this disability. Association of negative symptoms with cortical atrophy and cell loss is widely reported. Psychedelic drugs are undergoing a significant renaissance in psychiatric disorders with efficacy reported in several conditions including depression, in individuals facing terminal cancer, posttraumatic stress disorder, and addiction. There is considerable evidence from preclinical studies and some support from human studies that psychedelics enhance neuroplasticity. In this Perspective, we consider the possibility that psychedelic drugs could have a role in treating cortical atrophy and cell loss in schizophrenia, and ameliorating the negative symptoms associated with these pathological manifestations. The foremost concern in treating schizophrenia patients with psychedelic drugs is induction or exacerbation of psychosis. We consider several strategies that could be implemented to mitigate the danger of psychotogenic effects and allow treatment of schizophrenia patients with psychedelics to be implemented. These include use of non-hallucinogenic derivatives, which are currently the focus of intense study, implementation of sub-psychedelic or microdosing, harnessing of entourage effects in extracts of psychedelic mushrooms, and blocking 5-HT2A receptor-mediated hallucinogenic effects. Preclinical studies that employ appropriate animal models are a prerequisite and clinical studies will need to be carefully designed on the basis of preclinical and translational data. Careful research in this area could significantly impact the treatment of one of the most severe and socially debilitating psychiatric disorders and open an exciting new frontier in psychopharmacology.

Alternative Therapy of Psychosis: Potential Phytochemicals and Drug Targets in the Management of Schizophrenia

Schizophrenia is a chronic mental and behavioral disorder characterized by clusters of symptoms including hallucinations, delusions, disorganized thoughts and social withdrawal. It is mainly contributed by defects in dopamine, glutamate, cholinergic and serotonergic pathways, genetic and environmental factors, prenatal infections, oxidative stress, immune system activation and inflammation. Management of schizophrenia is usually carried out with typical and atypical antipsychotics, but it yields modest benefits with a diversity of side effects. Therefore, the current study was designed to determine the phytochemicals as new drug candidates for treatment and management of schizophrenia. These phytochemicals alter and affect neurotransmission, cell signaling pathways, endocannabinoid receptors, neuro-inflammation, activation of immune system and status of oxidative stress. Phytochemicals exhibiting anti-schizophrenic activity are mostly flavonoids, polyphenols, alkaloids, terpenoids, terpenes, polypropanoids, lactones and glycosides. However, well-designed clinical trials are consequently required to investigate potential protective effect and therapeutic benefits of these phytochemicals against schizophrenia.

Investigating the Structure of Neurotoxic Protein Aggregates Inside Cells

Neurodegenerative diseases affect the lives of millions of people across the world, being particularly prevalent in the aging population. Despite huge research efforts, conclusive insights into the disease mechanisms are still lacking. Therefore, therapeutic strategies are limited to symptomatic treatments. A common histopathological hallmark of many neurodegenerative diseases is the presence of large pathognomonic protein aggregates, but their role in the disease pathology is unclear and subject to controversy. Here, we discuss imaging methods allowing investigation of these structures within their cellular environment: conventional electron microscopy (EM), super-resolution light microscopy (SR-LM), and cryo-electron tomography (cryo-ET). Multidisciplinary approaches are key for understanding neurodegenerative diseases and may contribute to the development of effective treatments. For simplicity, we focus on huntingtin aggregates, characteristic of Huntington's disease.

Up and down-regulation of mRNA in the cytotoxicity and genotoxicity of Plumbagin in HepG2/C3A

Studies that evaluated the mechanisms of action of Plumbagin (PLB) and its toxicity may contribute to future therapeutic applications of this compound. We investigate biomarker important in the mechanisms of action correlate the expression of mRNA with the cytotoxic and genotoxic effects of PLB on HepG2/C3A. In the analysis of cytotoxicity, PLB decreased cell viability and membrane integrity at concentrations ≥ 15μM. Xenobiotic-metabolizing system showed strong mRNA induction of CYP1A1, CYP1A2, and CYP3A4, suggesting extensive metabolization. PLB induced apoptosis and an increase in the mRNA expression of genes BBC3, CASP3, and CASP8. At a concentration of 15μM, there was a reduction in the expression of PARP1 mRNA and an increase in the expression of BECN1 mRNA, suggesting that PLB may also induce cell death by autophagy. PLB induced an arrest at the G2/M phase due to DNA damage, as observed in the comet assay. This damage is associated with the increased mRNA expression of genes p21, GADD45A, and H2AFX and with changes in the expression of proteins H2AX, p21, p53, Chk1, and Chk2. These results allow a better understanding of the cellular action of PLB and of its toxicity, thereby contributing to the development of PLB-based drugs, with markers of mRNA expression possibly playing a role as indicators for monitoring toxicity in human cells.

The role of amyloidogenic protein oligomerization in neurodegenerative disease

A common pathological hallmark in many neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Huntington's disease, is the formation of fibrillar protein aggregates referred to as amyloids. The amyloidogenic aggregates were long thought to be toxic, but mounting evidence supports the notion that a variety of amyloid aggregate intermediates to fibril formation, termed oligomers, may in fact be the primary culprit leading to neuronal dysfunction and cell death. While amyloid formation is a complex, heterogeneous process, aggregates formed by diverse, diseases-related proteins share many conformational similarities, suggesting common toxic mechanisms among these diseases. Ideally, similar therapeutic strategies may be applicable. This review focuses on the potential role of amyloidogenic oligomers in neurodegenerative disease, highlighting some promising therapeutic strategies.

In vivo and in vitro genotoxicity studies of aqueous extract of Xanthium spinosum

The use of plants as a source of palliative or cure for pathological conditions is quite common worldwide. Xanthium spinosum (Asteraceae), popularly known in Brazil as 'espinho de carneiro', is an annual weed from South America, which has been used by empiric medicine to treat neoplasias. Owing to the extensive use of the above-mentioned plant and to the lack of reports about the real effects of its infusion, current study evaluated the genotoxic potential of its aqueous extract at concentrations 0.02 g L-1, 0.1 g L-1 and 0.2 g L-1 by fish micronucleus test and by comet human leukocytes assay. The micronucleus test featured at least 50 cells with micronuclei to every 2,000 cells scored, as a mutagenic parameter. The comet assay was used as a parameter for assessing the level of cell damage and the damage index. Since no significant changes in strain cells exposed to the aqueous extract in the comet and micronucleus assays were reported, it seems that no genotoxicity evidence is extant at the concentrations and in the assays performed.

Neurobiology of schizophrenia

With its hallucinations, delusions, thought disorder, and cognitive deficits, schizophrenia affects the most basic human processes of perception, emotion, and judgment. Evidence increasingly suggests that schizophrenia is a subtle disorder of brain development and plasticity. Genetic studies are beginning to identify proteins of candidate genetic risk factors for schizophrenia, including dysbindin, neuregulin 1, DAOA, COMT, and DISC1, and neurobiological studies of the normal and variant forms of these genes are now well justified. We suggest that DISC1 may offer especially valuable insights. Mechanistic studies of the properties of these candidate genes and their protein products should clarify the molecular, cellular, and systems-level pathogenesis of schizophrenia. This can help redefine the schizophrenia phenotype and shed light on the relationship between schizophrenia and other major psychiatric disorders. Understanding these basic pathologic processes may yield novel targets for the development of more effective treatments.

What is the role of protein aggregation in neurodegeneration?

Neurodegenerative diseases typically involve deposits of inclusion bodies that contain abnormal aggregated proteins. Therefore, it has been suggested that protein aggregation is pathogenic. However, several lines of evidence indicate that inclusion bodies are not the main cause of toxicity, and probably represent a cellular protective response. Aggregation is a complex multi-step process of protein conformational change and accretion. The early species in this process might be most toxic, perhaps through the exposure of buried moieties such as main chain NH and CO groups that could serve as hydrogen bond donors or acceptors in abnormal interactions with other cellular proteins. This model implies that the pathogenesis of diverse neurodegenerative diseases arises by common mechanisms, and might yield common therapeutic targets.