Adult alcohol drinking and emotional tone are mediated by neutral sphingomyelinase during development in males

Neutral sphingomyelinase controls acute and chronic alcohol effects on brain activity

Alcohol consumption is a widespread phenomenon throughout the world. However, how recreational alcohol use evolves into alcohol use disorder (AUD) remains poorly understood. The Smpd3 gene and its coded protein neutral sphingomyelinase (NSM) are associated with alcohol consumption in humans and alcohol-related behaviors in mice, suggesting a potential role in this transition. Using multiparametric magnetic resonance imaging, we characterized the role of NSM in acute and chronic effects of alcohol on brain anatomy and function in female mice. Chronic voluntary alcohol consumption (16 vol% for at least 6 days) affected brain anatomy in WT mice, reducing regional structure volume predominantly in cortical regions. Attenuated NSM activity prevented these anatomical changes. Functional MRI linked these anatomical adaptations to functional changes: Chronic alcohol consumption in mice significantly modulated resting state functional connectivity (RS FC) in response to an acute ethanol challenge (i.p. bolus of 2 g kg-1) in heterozygous NSM knockout (Fro), but not in WT mice. Acute ethanol administration in alcohol-naïve WT mice significantly decreased RS FC in cortical and brainstem regions, a key finding that was amplified in Fro mice. Regarding direct pharmacological effects, acute ethanol administration increased the regional cerebral blood volume (rCBV) in many brain areas. Here, chronic alcohol consumption otherwise attenuated the acute rCBV response in WT mice but enhanced it in Fro mice. Altogether, these findings suggest a differential role for NSM in acute and chronic functional brain responses to alcohol. Therefore, targeting NSM may be useful in the prevention or treatment of AUD.

Serotonin Signaling through Lipid Membranes

Serotonin (5-HT) is a vital modulatory neurotransmitter responsible for regulating most behaviors in the brain. An inefficient 5-HT synaptic function is often linked to various mental disorders. Primarily, membrane proteins controlling the expression and activity of 5-HT synthesis, storage, release, receptor activation, and inactivation are critical to 5-HT signaling in synaptic and extra-synaptic sites. Moreover, these signals represent information transmission across membranes. Although the lipid membrane environment is often viewed as fairly stable, emerging research suggests significant functional lipid-protein interactions with many synaptic 5-HT proteins. These protein-lipid interactions extend to almost all the primary lipid classes that form the plasma membrane. Collectively, these lipid classes and lipid-protein interactions affect 5-HT synaptic efficacy at the synapse. The highly dynamic lipid composition of synaptic membranes suggests that these lipids and their interactions with proteins may contribute to the plasticity of the 5-HT synapse. Therefore, this broader protein-lipid model of the 5-HT synapse necessitates a reconsideration of 5-HT's role in various associated mental disorders.

Sex-specific pleiotropic changes in emotional behavior and alcohol consumption in human α-synuclein A53T transgenic mice during early adulthood

Point mutations in the α-synuclein coding gene may lead to the development of Parkinson's disease (PD). PD is often accompanied by other psychiatric conditions, such as anxiety, depression, and drug use disorders, which typically emerge in adulthood. Some of these point mutations, such as SNCA and A30T, have been linked to behavioral effects that are not commonly associated with PD, especially regarding alcohol consumption patterns. In this study, we investigated whether the familial PD point mutation A53T is associated with changes in alcohol consumption behavior and emotional states at ages not yet characterized by α-synuclein accumulation. The affective and alcohol-drinking phenotypes remained unaltered in female PDGF-hA53T-synuclein-transgenic (A53T) mice during both early and late adulthood. Brain region-specific activation of ceramide-producing enzymes, acid sphingomyelinase (ASM), and neutral sphingomyelinase (NSM), known for their neuroprotective properties, was observed during early adulthood but not in late adulthood. In males, the A53T mutation was linked to a reduction in alcohol consumption in both early and late adulthood. However, male A53T mice displayed increased anxiety- and depression-like behaviors during both early and late adulthood. Enhanced ASM activity in the dorsal mesencephalon and ventral hippocampus may potentially contribute to these adverse behavioral effects of the mutation in males during late adulthood. In summary, the A53T gene mutation was associated with diverse changes in emotional states and alcohol consumption behavior long before the onset of PD, and these effects varied by sex. These alterations in behavior may be linked to changes in brain ceramide metabolism.

Relationship between sphingolipids-mediated neuroinflammation and alcohol use disorder

BACKGROUND

Alcohol use disorder is a chronic recurrent encephalopathy, and its pathogenesis has not been fully understood. Among possible explanations, neuroinflammation caused by the disorders of brain central immune signaling has been identified as one possible mechanism of alcohol use disorder. As the basic components of cells and important bioactive molecules, sphingolipids are essential in regulating many cellular activities. Recent studies have shown that sphingolipids-mediated neuroinflammation may be involved in the development of alcohol use disorder.

METHODS

PubMed databases were searched for literature on sphingolipids and alcohol use disorder (alcohol abuse, alcohol addiction, alcohol dependence, and alcohol misuse) including evidence of the relationship between sphingolipids-mediated neuroinflammation and alcohol use disorder (formation, withdrawal, treatment).

RESULTS

Disorders of sphingolipid metabolism, including the different types of sphingolipids and regulatory enzyme activity, have been found in patients with alcohol use disorder as well as animal models, which in turn cause neuro-inflammation in the central nervous system. Thus, these disorders may also be an important mechanism in the development of alcohol use disorder in patients. In addition, different sphingolipids may have different or even reverse effects on alcohol use disorder.

CONCLUSIONS

The sphingolipids-mediated neuroinflammation plays an important role in the development of alcohol use disorder. This review proposes a potential approach to prevent and treat alcohol use disorders by manipulating sphingolipid metabolism.

New ways to cope with depression-study protocol for a randomized controlled mixed methods trial of bouldering psychotherapy (BPT) and mental model therapy (MMT)

BACKGROUND

Due to the growing gap between the demand and supply of therapeutic services for people suffering from depression, with this study, we are investigating the effectiveness and factors of influence of new approaches in group treatments for depression. Two previous studies have already identified bouldering psychotherapy (BPT) as an effective option. It combines psychotherapeutic interventions with action- and body-oriented bouldering exercises. Mental model therapy (MMT) is a new cognitive-behavioral approach for treating depression. It focuses on identifying cognitive distortions, biases in decision making, and false assumptions and aims to correct and replace them with useful mental models. We aim to investigate the effectiveness of the interventions compared with a control group (CG) and to assess the factors of influence in a mixed methods approach.

METHODS

The study is being conducted as a randomized controlled intervention trial. Adult participants with unipolar depression are being randomized into three groups (BPT, MMT, or CG), and the first two groups are undergoing a 10-week treatment phase. CG follows their individual standard treatment as usual. A priori power analysis revealed that about 120 people should be included to capture a moderate effect. The primary outcome of the study is depression rated with the Montgomery and Asberg Depression Rating Scale (MADRS) before (t0), directly after (t1), and 12 months after the intervention phase (t2). Data are being collected via questionnaires, computer-assisted video interviews, and physical examinations. The primary hypotheses will be statistically analyzed by mixed model ANOVAs to compare the three groups over time. For secondary outcomes, further multivariate methods (e.g., mixed model ANOVAs and regression analyses) will be conducted. Qualitative data will be evaluated on the basis of the qualitative thematic analysis.

DISCUSSION

This study is investigating psychological and physical effects of BPT and MMT and its factors of influence on outpatients suffering from depression compared with a CG in a highly naturalistic design. The study could therefore provide insight into the modes of action of group therapy for depression and help to establish new short-term group treatments. Methodological limitations of the study might be the clinical heterogeneity of the sample and confounding effects due to simultaneous individual psychotherapy.

TRIAL REGISTRATION

ISRCTN, ISRCTN12347878. Registered 28 March 2022, https://www.isrctn.com/ISRCTN12347878 .

The beer component hordenine inhibits alcohol addiction-associated behaviours in mice

Alcohol consumption is a widespread behaviour that may eventually result in the development of alcohol use disorder (AUD). Alcohol, however, is rarely consumed in pure form but in fruit- or corn-derived preparations, like beer. These preparations add other compounds to the consumption, which may critically modify alcohol intake and AUD risk. We investigated the effects of hordenine, a barley-derived beer compound on alcohol use-related behaviours. We found that the dopamine D2 receptor agonist hordenine (50 mg/kg) limited ongoing alcohol consumption and prophylactically diminished relapse drinking after withdrawal in mice. Although not having reinforcing effects on its own, hordenine blocked the establishment of alcohol-induced conditioned place preference (CPP). However, it independently enhanced alcohol CPP retrieval. Hordenine had a dose-dependent inhibitory effect on locomotor activity. Chronic hordenine exposure enhanced monoamine tissue levels in many brain regions. Further characterization revealed monoaminergic binding sites of hordenine and found a strong binding on the serotonin and dopamine transporters, and dopamine D3 , and adrenergic α1A and α2A receptor activation but no effects on GABAA receptor or glycinergic signalling. These findings suggest that natural ingredients of beer, like hordenine, may work as an inhibitory and use-regulating factor by their modulation of monoaminergic signalling in the brain.

Self-management with alcohol over lifespan: psychological mechanisms, neurobiological underpinnings, and risk assessment

Self-management includes all behavioural measures and cognitive activities aimed at coping with challenges arising throughout the lifespan. While virtually all of these challenges can be met without pharmacological means, alcohol consumption has long been instrumentalized as a supporting tool to help coping with problems arising selectively at adolescence, adulthood, and ageing. Here, we present, to our knowledge, the first systematic review of alcohol instrumentalization throughout lifespan. We searched MEDLINE, Google Scholar, PsycINFO and CINAHL (from Jan, 1990, to Dec, 2022) and analysed consumption patterns, goals and potential neurobiological mechanisms. Evidence shows a regular non-addictive use of alcohol to self-manage developmental issues during adolescence, adulthood, and ageing. Alcohol is selectively used to overcome problems arising from dysfunctional personality traits, which manifest in adolescence. A large range of psychiatric disorders gives rise to alcohol use for the self-management of distinct symptoms starting mainly in adulthood. We identify those neuropharmacological effects of alcohol that selectively serve self-management under specific conditions. Finally, we discuss the adverse effects and associated risks that arise from the use of alcohol for self-management. Even well-controlled alcohol use adversely impacts health. Based on these findings, we suggest the implementation of an entirely new view. Health policy action may actively embrace both sides of the phenomenon through a personalized informed use that allows for harm-controlled self-management with alcohol.

Behavioural effects of APH199, a selective dopamine D4 receptor agonist, in animal models

RATIONALE

The dopamine D4 receptors (DRD4) play a key role in numerous brain functions and are involved in the pathogenesis of various psychiatric disorders. DRD4 ligands have been shown to moderate anxiety, reward and depression-like behaviours, and cognitive impairments. Despite a series of promising but ambiguous findings, the therapeutic advantages of DRD4 stimulation remain elusive.

OBJECTIVES

The investigation focused on the behavioural effects of the recently developed DRD4 agonist, APH199, to evaluate its impact on anxiety, anhedonia, behavioural despair, establishment and retrieval of alcohol reinforcement, and amphetamine (AMPH)-induced symptoms.

METHODS

Male C57BL/6 J mice and Sprague-Dawley rats were examined in five independent experiments. We assessed APH199 (0.1-5 mg/kg, i.p.) effects on a broad range of behavioural parameters in the open field (OF) test, conditioned place preference test (CPP), elevated plus maze (EPM), light-dark box (LDB), novelty suppressed feeding (NSF), forced swim test (FST), sucrose preference test (SPT), AMPH-induced hyperlocomotion test (AIH), and prepulse inhibition (PPI) of the acoustic startle response in AMPH-sensitized rats.

RESULTS

APH199 caused mild and sporadic anxiolytic and antidepressant effects in EPM and FST, but no remarkable impact on behaviour in other tests in mice. However, we found a significant increase in AMPH-induced hyperactivity, suggesting an exaggeration of the psychotic-like responses in the AMPH-sensitized rats.

CONCLUSIONS

Our data challenged the hypothesis of the therapeutic benefits of DRD4 agonists, pointing out a possible aggravation of psychosis. We suggest a need for further preclinical studies to ensure the safety of antipsychotics with DRD4 stimulating properties.

Characterization of a Neutral Sphingomyelinase Activity in Human Serum and Plasma

Alterations of sphingolipids and their metabolizing enzymes play a role in various diseases. However, peripheral biomarkers for such changes are limited. Particularly, in the increasingly reported involvement of neutral sphingomyelinase (NSM) with four described isoforms in tissues or cells, a peripheral marker is lacking. We here describe the detection of an NSM activity in human serum and plasma samples which hydrolyses fluorescently labeled sphingomyelin to ceramide in a time- and volume-dependent manner. Reaction rates were linear up to 10 days, and serum volumes above 2 vol-% were inhibitory. Biochemical properties were different from acid sphingomyelinase (ASM) with respect to detergent specificity (sodium deoxycholate), pH profile (pH 7-9), and cation dependence: Serum NSM activity was inhibited by EDTA ≥ 1 µM and restored in EDTA-anticoagulated plasma with the addition of ≥ 100 µM Co²⁺. It was independent of Mg²⁺, the typical cofactor of cellular NSM species, and even inhibited by [Mg²⁺] ≥ 20 mM. Serum NSM activity was not correlated with ASM activity and was independent of sex and age in 24 healthy adults. Since human peripheral NSM activity is very low and activities in rodents are even lower or undetectable, future research should aim to increase the reaction rate and determine the source of this enzymatic activity. The established activity could serve as a future biomarker or therapeutic target in diseases affected by sphingolipid derangements.

Allosteric Inhibition of Neutral Sphingomyelinase 2 (nSMase2) by DPTIP: From Antiflaviviral Activity to Deciphering Its Binding Site through In Silico Studies and Experimental Validation

Flavivirus comprises globally emerging and re-emerging pathogens such as Zika virus (ZIKV), Dengue virus (DENV), and West Nile virus (WNV), among others. Although some vaccines are available, there is an unmet medical need as no effective antiviral treatment has been approved for flaviviral infections. The development of host-directed antivirals (HDAs) targeting host factors that are essential for viral replication cycle offers the opportunity for the development of broad-spectrum antivirals. In the case of flaviviruses, recent studies have revealed that neutral sphingomyelinase 2, (nSMase2), involved in lipid metabolism, plays a key role in WNV and ZIKV infection. As a proof of concept, we have determined the antiviral activity of the non-competitive nSMase2 inhibitor DPTIP against WNV and ZIKV virus. DPTIP showed potent antiviral activity with EC₅₀ values of 0.26 µM and 1.56 µM for WNV and ZIKV, respectively. In order to unravel the allosteric binding site of DPTIP in nSMase2 and the details of the interaction, computational studies have been carried out. These studies have revealed that DPTIP could block the DK switch in nSMase2. Moreover, the analysis of the residues contributing to the binding identified His463 as a crucial residue. Interestingly, the inhibitory activity of DPTIP on the H463A mutant protein supported our hypothesis. Thus, an allosteric cavity in nSMase2 has been identified that can be exploited for the development of new inhibitors with anti-flaviviral activity.