A quantum chemical approach representing a new perspective concerning agonist and antagonist drugs in the context of schizophrenia and Parkinson's disease

Assessment of electroencephalography modification by antipsychotic drugs in patients with schizophrenia spectrum disorders using frontier orbital theory: A preliminary study

AIM

Schizophrenia is characterized by an abnormality in electroencephalography (EEG), which can be affected by antipsychotic drugs. Recently, the mechanism underlying these EEG alterations in schizophrenia patients was reframed from the perspective of redox abnormalities. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) can be calculated using a computational method and may be useful for evaluating the antioxidant/prooxidant effect of antipsychotic drugs. Thus, we examined the association between the effects of antipsychotic monotherapy on quantitative EEG and HOMO/LUMO energy.

METHODS

We used medical report data including EEG results of psychiatric patients admitted to Hokkaido University Hospital. We extracted the EEG records of patients diagnosed with a schizophrenia spectrum disorder undergoing antipsychotic monotherapy during the natural course of treatment (n = 37). We evaluated the HOMO/LUMO energy of all antipsychotic drugs using computational methods. Multiple regression analyses were used to examine the relationship between the HOMO/LUMO energy of all antipsychotic drugs and spectral band power in all patients. Statistical significance was set at p < 6.25 × 10^-4 adjusted with Bonferroni correction.

RESULTS

We showed that the HOMO energy of all antipsychotic drugs had weak positive correlations with delta- and gamma-band power (e.g., standardized β = 0.617 for delta in the F3 channel, p = 6.6 × 10^-5 ; standardized β = 0.563 for gamma in the O1 channel, p = 5.0 × 10^-4 ).

CONCLUSION

Although there may be unexpected bias and confounding factors, our findings suggest that the effect of antipsychotic drugs on EEG may be related to their antioxidant actions.

Electron Donor-Acceptor Properties of Different Muscarinic Ligands: On the Road to Control Schizophrenia

Schizophrenia is a severe neuropsychiatric disorder that deteriorates perception, affection, and cognitive mental functions. The current treatments are mainly focused on the dopamine system, but the so-named dopamine hypothesis of schizophrenia fails to explain all the symptoms. Previous studies have shown that there is a reciprocal relationship between muscarinic acetylcholine receptors and dopamine receptor function. Some muscarinic ligands show antidopaminergic activity, and therefore, they should have some antipsychotic efficacy. In this work, conceptual density functional theory is employed to analyze the properties of acetylcholine's agonists, partial agonists, or antagonists. The aim is to establish a classification of the antipsychotic-like or pro-psychotic activities of these molecules based on the electron-donor and electron-acceptor properties. Most of the agonists and antagonists are better electron donors and worse electron acceptors than partial agonists. We found that acetylcholine antagonists that clinically promote psychotic symptoms are good electron-donor molecules, and acetylcholine agonists that clinically relieve symptoms of psychosis are good electron donors. These results represent a further advance on the road to understanding the charge-transfer properties of drugs used as possible treatments for schizophrenia.

Main interactions of dopamine and risperidone with the dopamine D2 receptor

Psychosis is one of the psychiatric disorders that is controlled by dopaminergic drugs such as antipsychotics that have affinity for the dopamine D2 receptor (DRD2). In this investigation we perform quantum chemical calculations of two molecules [dopamine and risperidone] within a large cavity of DRD2 that represents the binding site of the receptor. Dopamine is an endogenous neurotransmitter and risperidone is a second-generation antipsychotic. Non-covalent interactions of dopamine and risperidone with DRD2 are analyzed using the Quantum Theory of Atoms in Molecules (QTAIM) and the Non-Covalent Interaction index (NCI). The QTAIM results show that these molecules strongly interact with the receptor. There are 22 non-covalent interactions for dopamine and 54 for risperidone. The electron density evaluated at each critical binding point is small in both systems but it is higher for dopamine than for risperidone, indicating that the interactions of DRD2 with the first are stronger than with the second molecule. However, the binding energy is higher for risperidone (-72.6 kcal mol-1) than for dopamine (-22.8 kcal mol-1). Thus, the strength of the binding energy is due to the number of contacts rather than the strength of the interactions themselves. This could be related to the ability of risperidone to block DRD2 and may explain the efficacy of this drug for controlling the symptoms of schizophrenia, but likewise its secondary effects.

New information of dopaminergic agents based on quantum chemistry calculations

Dopamine is an important neurotransmitter that plays a key role in a wide range of both locomotive and cognitive functions in humans. Disturbances on the dopaminergic system cause, among others, psychosis, Parkinson's disease and Huntington's disease. Antipsychotics are drugs that interact primarily with the dopamine receptors and are thus important for the control of psychosis and related disorders. These drugs function as agonists or antagonists and are classified as such in the literature. However, there is still much to learn about the underlying mechanism of action of these drugs. The goal of this investigation is to analyze the intrinsic chemical reactivity, more specifically, the electron donor-acceptor capacity of 217 molecules used as dopaminergic substances, particularly focusing on drugs used to treat psychosis. We analyzed 86 molecules categorized as agonists and 131 molecules classified as antagonists, applying Density Functional Theory calculations. Results show that most of the agonists are electron donors, as is dopamine, whereas most of the antagonists are electron acceptors. Therefore, a new characterization based on the electron transfer capacity is proposed in this study. This new classification can guide the clinical decision-making process based on the physiopathological knowledge of the dopaminergic diseases.

The effect of neuroleptic drugs on DPPC/sphingomyelin/cholesterol membranes

The hydrophobic nature of neuroleptic drugs renders that these molecules interact not only with protein receptors, but also with the lipids constituting the membrane bilayer. We present a systematic study of the effect of seven neuroleptic drugs on a biomembrane model composed of DPPC, sphingomyelin, and cholesterol. Differential scanning calorimetry (DSC) measurements were used to monitor the gel-fluid phase transition of the lipid bilayer at three pH values and also as a function of drug concentration. The implementation of a new methodology to mix lipids homogeneously allowed us to assemble bilayers completely free of organic solvents. The seven neuroleptics were: trifluoperazine, haloperidol decanoate, clozapine, quetiapine, olanzapine, aripiprazole, and amisulpride. The DSC results show that the insertion of the drug into the bilayer produces a fluidization and a disordering of the bilayer. The bilayer perturbation is qualitatively the same for all the studied drugs, but quantitatively different. The driving force for the neuroleptic drug to place itself in the lipid bilayer is entropic in nature, signaling to the importance of the size and geometry of the drugs. The drug protonated species produce stronger effects than their non-protonated forms. At high concentrations two of the neuroleptics revert the fluidization effect and another completely abolishes the gel-fluid transition. The DSC data and the associated discussion contribute to the understanding of the interactions between neuroleptic drugs and lipid membranes.

Dopamine antagonists for the treatment of drug addiction: PF-4363467 and related compounds

Drug addiction refers to an out-of-control and compulsive use of substances, which can reach epidemic magnitudes. It is a health concern throughout the world and has major economic impact. Dopamine receptor agonists and antagonists have been cited as molecular targets for the treatment of drug addiction. In this report, the main idea is to analyze the new D3R/D2R ligands that are proposed for the treatment of drug abuse, in terms of their electron donor/acceptor properties. Substances catalogued as agonists represent good electron donors, whereas antagonists represent good electron acceptors. HOMO and LUMO eigenvalues indicate that more energy is necessary to remove an electron from the antagonists, and likewise more energy is gained when antagonists accept an electron. The combination of two molecules (PF-592379 and PNU-177864) produces a new compound (PF-4363467) with properties that are intermediate. Irrespective of the characteristics of the receptor, the classification of ligands is important, in order to further understanding of the reaction mechanism of these compounds. This may help in the design of new molecules for the treatment of drug addiction.