Caffeine and Selective Adenosine Receptor Antagonists as New Therapeutic Tools for the Motivational Symptoms of Depression

Common questions and misconceptions about caffeine supplementation: what does the scientific evidence really show?

Caffeine is a popular ergogenic aid that has a plethora of evidence highlighting its positive effects. A Google Scholar search using the keywords "caffeine" and "exercise" yields over 200,000 results, emphasizing the extensive research on this topic. However, despite the vast amount of available data, it is intriguing that uncertainties persist regarding the effectiveness and safety of caffeine. These include but are not limited to: 1. Does caffeine dehydrate you at rest? 2. Does caffeine dehydrate you during exercise? 3. Does caffeine promote the loss of body fat? 4. Does habitual caffeine consumption influence the performance response to acute caffeine supplementation? 5. Does caffeine affect upper vs. lower body performance/strength differently? 6. Is there a relationship between caffeine and depression? 7. Can too much caffeine kill you? 8. Are there sex differences regarding caffeine's effects? 9. Does caffeine work for everyone? 10. Does caffeine cause heart problems? 11. Does caffeine promote the loss of bone mineral? 12. Should pregnant women avoid caffeine? 13. Is caffeine addictive? 14. Does waiting 1.5-2.0 hours after waking to consume caffeine help you avoid the afternoon "crash?" To answer these questions, we performed an evidence-based scientific evaluation of the literature regarding caffeine supplementation.

Evaluation of the responsiveness pattern to caffeine through a smart data-driven ECG non-linear multi-band analysis

This study aimed to explore more efficient ways of administering caffeine to the body by investigating the impact of caffeine on the modulation of the nervous system's activity through the analysis of electrocardiographic signals (ECG). An ECG non-linear multi-band analysis using Discrete Wavelet Transform (DWT) was employed to extract various features from healthy individuals exposed to different caffeine consumption methods: expresso coffee (EC), decaffeinated coffee (ED), Caffeine Oral Films (OF_caffeine), and placebo OF (OF_placebo). Non-linear feature distributions representing every ECG minute time series have been selected by PCA with different variance percentages to serve as inputs for 23 machine learning models in a leave-one-out cross-validation process for analyzing the behavior differences between ED/EC and OF_placebo/OF_caffeine groups, respectively, over time. The study generated 50-point accuracy curves per model, representing the discrimination power between groups throughout the 50 min. The best model accuracies for ED/EC varied between 30 and 70 %, (using the decision tree classifier) and OF_placebo/OF_caffeine ranged from 62 to 84 % (using Fine Gaussian). Notably, caffeine delivery through OFs demonstrated effective capacity compared to its placebo counterpart, as evidenced by significant differences in accuracy curves between OF_placebo/OF_caffeine. Caffeine delivery via OFs also exhibited rapid dissolution efficiency and controlled release rate over time, distinguishing it from EC. The study supports the potential of caffeine delivery through Caffeine OFs as a superior technology compared to traditional methods by means of ECG analysis. It highlights the efficiency of OFs in controlling the release of caffeine and underscores their promise for future caffeine delivery systems.

Using caffeine as a chemical means to induce flow states

Flow is an intrinsically rewarding state characterised by positive affect and total task absorption. Because cognitive and physical performance are optimal in flow, chemical means to facilitate this state are appealing. Caffeine, a non-selective adenosine receptor antagonist, has been emphasized as a potential flow-inducer. Thus, we review the psychological and biological effects of caffeine that, conceptually, enhance flow. Caffeine may facilitate flow through various effects, including: i) upregulation of dopamine D1/D2 receptor affinity in reward-associated brain areas, leading to greater energetic arousal and 'wanting'; ii) protection of dopaminergic neurons; iii) increases in norepinephrine release and alertness, which offset sleep-deprivation and hypoarousal; iv) heightening of parasympathetic high frequency heart rate variability, resulting in improved cortical stress appraisal, v) modification of striatal endocannabinoid-CB1 receptor-signalling, leading to enhanced stress tolerance; and vi) changes in brain network activity in favour of executive function and flow. We also discuss the application of caffeine to treat attention deficit hyperactivity disorder and caveats. We hope to inspire studies assessing the use of caffeine to induce flow.

Does dietary intake of caffeine have an effect on transient global amnesia?

AIM

Amnesia is a cognitive disorder that may lead to memory loss. Caffeine is a psychoactive substance which have an effect on memory and cognitive functions. This study aimed to assess the association of transient global amnesia (TGA) with dietary intake of caffeine.

METHODS

This cross-sectional study was conducted on the Sabzevar Persian cohort data of 258 patients with TGA and 520 healthy individuals in Sabzevar, Iran. The Nutritional data were gathered in face-to-face interviews using a valid Food Frequency Questionnaire. Different models of logistic regression were used to determine the association between TGA and dietary caffeine intake after adjusting the confounders including age, sex, education, job, marital status, physical activity, BMI, and calorie intake.

RESULTS

There was no significant difference in terms of dietary calorie intake of (2279.5 ± 757.9 vs. 2365.5 ± 799.5, p = 0.19), protein (70.79 ± 25.27 vs. 72.94 ± 24.83, p = 0.31), fat (59.97 ± 23.79 vs. 60.13 ± 26.38, p = 0.93), carbohydrate (376 ± 134 vs. 393.1 ± 137.8, p = 0.14), and caffeine (196.4 ± 127.9 vs. 186.3 ± 128.5, p = 0.36) between the groups. No significant association was found between TGA and dietary intake of caffeine (OR: 0.99, 95% CI: 0.99-1.01, p = 0.36). The results did not change after adjusting the confounders.

CONCLUSIONS

No significant association was found between TGA and dietary intake of caffeine. Further prospective studies are required to confirm this finding.

Coffee consumption and risk of kidney function decline in a Dutch population-based cohort

BACKGROUND AND AIMS

Whether coffee consumption is associated with changes in estimated glomerular filtration rate (eGFR) is unknown. We investigated the relationship between coffee consumption and annual eGFR change in a large Dutch population-based study.

METHODS AND RESULTS

This study was performed in 78,346 participants without chronic kidney disease (CKD) in the population-based Lifelines Cohort Study. Coffee consumption was assessed at baseline using food frequency questionnaires. Outcomes were annual eGFR change and a composite kidney outcome (defined as eGFR <60 mL/min per 1.73 m2 or >20 % eGFR decline). Multivariable linear and logistic regression analyses were used to evaluate the associations of coffee consumption (categories and cups/day) with kidney outcomes. Overall, 90 % of the participants drank coffee daily and 36 % drank >2-4 cups/day. Unadjusted mean ± SD annual eGFR change ranged from -2.86 ± 2.96 (for non-coffee drinkers) to -2.35 ± 2.62 (for participants consuming >6 cups/day) mL/min per 1.73 m2. During 3.6 ± 0.9 years follow-up, 11.1 % of participants reached the composite kidney outcome. As compared to non-coffee drinkers, higher coffee consumption was associated with less annual eGFR decline in multivariable models (β [95 % CIs] ranged from 0.15 [0.07, 0.22] for >0-2 cups/day to 0.29 [0.20, 0.38] for >6 cups/day, P-trend <0.001). Consumption of one more cup of coffee per day was associated with a 3 % lower risk of the composite kidney outcome (OR [95%CI], 0.97 [0.96, 0.99]). The inverse association was more pronounced in a subgroup of individuals with diabetes.

CONCLUSION

Coffee consumption was inversely associated with annual eGFR change and CKD risk in a large Dutch population-based cohort.

Apathy and Motivation: Biological Basis and Drug Treatment

Apathy is a disabling syndrome associated with poor functional outcomes that is common across a broad range of neurological and psychiatric conditions. Currently, there are no established therapies specifically for the condition, and safe and effective treatments are urgently needed. Advances in the understanding of motivation and goal-directed behavior in humans and animals have shed light on the cognitive and neurobiological mechanisms contributing to apathy, providing an important foundation for the development of new treatments. Here, we review the cognitive components, neural circuitry, and pharmacology of apathy and motivation, highlighting converging evidence of shared transdiagnostic mechanisms. Though no pharmacological treatments have yet been licensed, we summarize trials of existing and novel compounds to date, identifying several promising candidates for clinical use and avenues of future drug development.

Sclareol exerts synergistic antidepressant effects with quercetin and caffeine, possibly suppressing GABAergic transmission in chicks

This study evaluated the effects of sclareol (SCL) with or without caffeine (CAF) and quercetin (QUR) using in-vivo and in-silico studies. For this, 5-day-old chicks weighing between 45 and 48 g were randomly divided into five groups and treated accordingly. The chicks were monitored to compare the occurrence, latency, and duration of sleep as well as the loss and gain of righting reflex in response to SCL-10 mg/kg, CAF-10 mg/kg, and QUR-50 mg/kg using a thiopental sodium (TS)-induced sleeping model. Data were analyzed by one-way ANOVA followed by t-Student-Newman-Keuls' as a posthoc test at 95% confidence intervals with multiple comparisons. An in-silico study was also performed to investigate the possible antidepressant mechanisms of the test and/or standard drugs with different subunits of GABAA receptors. In comparison to the SCL, CAF, and QUR individual groups, SCL+CAF+QUR significantly increased the latency while decreasing the length of sleep. The incidence of loss and gain of the righting reflex was also modulated in the combination group. SCL showed better interaction with GABAA (α2 and α5) subunits than QUR with α2, α3, and α5. All these compounds showed stronger interactions with the GABAA receptor subunits than the standard CAF. Taken together, SCL, CAF, and QUR reduced the TS-induced righting reflex and sleeping time in the combination group more than in the individual treatments. SCL may show its antidepressant effects, possibly through interactions with GABAA receptor subunits.

Higher caffeine consumption is associated with insufficient sleep time in Brazilian adults (CUME study)

We aimed to evaluate the association between caffeine intake and sleep time in Brazilian adults. This cross-sectional study was conducted with 6,356 participants from the Cohort of Universities of Minas Gerais (CUME Study). Data was collected through an online self-report questionnaire. Of the total, 31.9% of the participants had insufficient sleep. Women were found to sleep less than men (64.1 vs. 35.9%; p < 0.001), as well as being more likely to consume higher doses of caffeine (55.2%, p < 0.001). Coffee (35.7%), dark chocolate (25.2%), milk chocolate (15.2%), and diet soda (11.0%) were the foods that more contributed to caffeine intake. Individuals in the highest quartile of caffeine intake (87.0 - 572.0 mg/day) had a 19% higher prevalence of insufficient sleep compared with the lowest quartile (PR: 1.19; 95%CI: 1.08 - 1.31). Future studies are needed to investigate the genetic and hormonal factors involved in the interindividual response in this population.

Antidepressant-like Effects of Representative Types of Food and Their Possible Mechanisms

Depression is a mental disorder characterized by low mood, lack of motivation, negative cognitive outlook, and sleep problems. Suicide may occur in severe cases, although suicidal thoughts are not seen in all cases. Globally, an estimated 350 million individuals grapple with depression, as reported by the World Health Organization. At present, drug and psychological treatments are the main treatments, but they produce insufficient responses in many patients and fail to work at all in many others. Consequently, treating depression has long been an important topic in society. Given the escalating prevalence of depression, a comprehensive strategy for managing its symptoms and impacts has garnered significant attention. In this context, nutritional psychiatry emerges as a promising avenue. Extensive research has underscored the potential benefits of a well-rounded diet rich in fruits, vegetables, fish, and meat in alleviating depressive symptoms. However, the intricate mechanisms linking dietary interventions to brain function alterations remain largely unexplored. This review delves into the intricate relationship between dietary patterns and depression, while exploring the plausible mechanisms underlying the impact of dietary interventions on depression management. As we endeavor to unveil the pathways through which nutrition influences mental well-being, a holistic perspective that encompasses multidisciplinary strategies gains prominence, potentially reshaping how we approach and address depression.

How and why the adenosine A2A receptor became a target for Parkinson's disease therapy

Dopaminergic therapy for Parkinson's disease has revolutionised the treatment of the motor symptoms of the illness. However, it does not alleviate all components of the motor deficits and has only limited effects on non-motor symptoms. For this reason, alternative non-dopaminergic approaches to treatment have been sought and the adenosine A2A receptor provided a novel target for symptomatic therapy both within the basal ganglia and elsewhere in the brain. Despite an impressive preclinical profile that would indicate a clear role for adenosine A2A antagonists in the treatment of Parkinson's disease, the road to clinical use has been long and full of difficulties. Some aspects of the drugs preclinical profile have not translated into clinical effectiveness and not all the clinical studies undertaken have had a positive outcome. The reasons for this will be explored and suggestions made for the further development of this drug class in the treatment of Parkinson's disease. However, one adenosine A2A antagonist, namely istradefylline has been introduced successfully for the treatment of late-stage Parkinson's disease in two major areas of the world and has become a commercial success through offering the first non-dopaminergic approach to the treatment of unmet need to be introduced in several decades.

Dual A1 and A2A adenosine receptor antagonists, methoxy substituted 2-benzylidene-1-indanone, suppresses intestinal postprandial glucose and attenuates hyperglycaemia in fructose-streptozotocin diabetic rats

BACKGROUND/AIM

Recent research suggests that adenosine receptors (ARs) influence many of the metabolic abnormalities associated with diabetes. A non-xanthine benzylidene indanone derivative 2-(3,4-dihydroxybenzylidene)-4-methoxy-2,3-dihydro-1 H-inden-1-one (2-BI), has shown to exhibit higher affinity at A₁/A_2A ARs compared to caffeine. Due to its structural similarity to caffeine, and the established antidiabetic effects of caffeine, the current study was initiated to explore the possible antidiabetic effect of 2-BI.

METHODS

The study was designed to assess the antidiabetic effects of several A₁ and/or A_2A AR antagonists, via intestinal glucose absorption and glucose-lowering effects in fructose-streptozotocin (STZ) induced diabetic rats. Six-week-old male Sprague-Dawley rats were induced with diabetes via fructose and streptozotocin. Rats were treated for 4 weeks with AR antagonists, metformin and pioglitazone, respectively. Non-fasting blood glucose (NFBG) was determined weekly and the oral glucose tolerance test (OGTT) was conducted at the end of the intervention period.

RESULTS

Dual A₁/A_2A AR antagonists (caffeine and 2-BI) decreased glucose absorption in the intestinal membrane significantly (p < 0.01), while the selective A_2A AR antagonist (Istradefylline), showed the highest significant (p < 0.001) reduction in intestinal glucose absorption. The selective A₁ antagonist (DPCPX) had the least significant (p < 0.05) reduction in glucose absorption. Similarly, dual A₁/A_2A AR antagonists and selective A_2A AR antagonists significantly reduced non-fast blood glucose and improved glucose tolerance in diabetic rats from the first week of the treatment. Conversely, the selective A₁ AR antagonist did not reduce non-fast blood glucose significantly until the 4th week of treatment. 2-BI, caffeine and istradefylline compared well with standard antidiabetic treatments, metformin and pioglitazone, and in some cases performed even better.

CONCLUSION

2-BI exhibited good antidiabetic activity by reducing intestinal postprandial glucose absorption and improving glucose tolerance in a diabetic animal model. The dual antagonism of A₁/A_2A ARs presents a positive synergism that could provide a new possibility for the treatment of diabetes.

The role of adenosine A2A receptors in Alzheimer's disease and tauopathies

Adenosine signals through four distinct G protein-coupled receptors that are located at various synapses, cell types and brain areas. Through them, adenosine regulates neuromodulation, neuronal signaling, learning and cognition as well as the sleep-wake cycle, all strongly impacted in neurogenerative disorders, among which Alzheimer's Disease (AD). AD is a complex form of cognitive deficits characterized by two pathological hallmarks: extracellular deposits of aggregated β-amyloid peptides and intraneuronal fibrillar aggregates of hyper- and abnormally phosphorylated Tau proteins. Both lesions contribute to the early dysfunction and loss of synapses which are strongly associated to the development of cognitive decline in AD patients. The present review focuses on the pathophysiological impact of the A_2ARs dysregulation observed in cognitive area from AD patients. We are reviewing not only evidence of the cellular changes in A_2AR levels in pathological conditions but also describe what is currently known about their consequences in term of synaptic plasticity, neuro-glial miscommunication and memory abilities. We finally summarize the proof-of-concept studies that support A_2AR as credible targets and the clinical interest to repurpose adenosine drugs for the treatment of AD and related disorders. This article is part of the Special Issue on "Purinergic Signaling: 50 years".

Clinical and pharmacological correlates of caffeine consumption in subjects with schizophrenia - Data from the FACE-SZ cohort

Caffeine is the most consumed psychoactive substance worldwide. Previous studies suggested higher caffeine consumption in subjects with schizophrenia spectrum disorders (SSD) as well as associations with symptoms, medication and medication side-effects. In a large and well-characterized sample of SSD subjects we explored the association between caffeine consumption and clinical (psychosis related, severity, general health) as well as pharmacological (antipsychotic treatment, sedation potential) variables. Eight hundred four subjects with data on their caffeine (coffee and tea) consumption successively recruited were included in this study. After controlling for potential confounders (demographic variables, smoking) only the negative dimension of psychosis was associated with the amount of caffeine ingested. Less severe negative symptoms were associated with higher caffeine consumption. The effect size of this association was small (partial correlation coefficient = -0.12) but significant.

Coffee and caffeine intake and depression in postpartum women: A cross-sectional study from the National Health and Nutrition Examination Survey 2007-2018

This cross-sectional study examines the association between coffee and caffeine consumption and depressive symptoms in postpartum women. In total, 821 postpartum women who met the study's inclusion criteria were interviewed. Data were extracted from the 2007-2018 National Health and Nutrition Examination Survey. Coffee consumption and 11 confounding variables were considered and analyzed as baseline data. Weighted logistic regression models were constructed by adjusting the variables, and the odds ratios of total coffee, caffeinated coffee, and decaffeinated coffee were assessed for their impact on depression status. In addition, subgroup analyses were conducted according to race, breastfeeding status, and postpartum period. The results show that generic coffee and caffeinated coffee intake have a potentially protective effect in postpartum women. Drinking more than three cups of caffeinated coffee may lower the risk of postpartum depression, particularly in the 1-2 year postpartum period and in non-breastfeeding women. The association between decaffeinated coffee consumption and postpartum depression remains unclear.

Rotenone induced olfactory deficit in Parkinson's disease rat model: The protective role of adenosine A2A receptors antagonist

BACKGROUND

Parkinson's disease is both a motor and non-motor disorder. Despite the non-motor being an intrinsic feature of PD, it has been poorly researched and understood in clinical practices; olfactory deficit is one of the first established non motor symptom and nearly all ∼90 % of sporadic PD cases are associated with olfactory dysfunction and there is inconsistency in various pharmacological approaches. Hence this study aimed to evaluate the impact of caffeine at the A2A receptors of the olfactory bulb of a rotenone rat model of Parkinson's disease.

MATERIALS AND METHODS

About 50 male Adult Wistar Rats were used for this study. The rats were randomly divided into five groups of 10 rats each as follows: Group A (vehicle; ethanol), Group B (rotenone 3 mg/kg, i.p), Group C (caffeine 30 mg/kg, i.p + rotenone 3 mg/kg, i.p), Group D (rotenone 3 mg/kg, i.p + caffeine 30 mg/kg, i.p), Group E (caffeine 30 mg/kg, i.p). The animals were subjected to neurobehavioral assay and sacrificed, and brains were excised, weighed, and processed histologically; appropriate sections were taken and processed. The photomicrographs, Morphometric and Statistical analysis was done using Omax led digital Microscope, Image J Software and Graph Pad Prism 7, respectively.

RESULTS

The results showed a significant decrease in body weight (P < 0.05), relative brain weight, mitral/tufted cells count, and high latency in food-seeking test in Rotenone treated groups. Histopathological presentations include degenerated concentric layers of Olfactory bulb, neuronal degeneration, distorted appearance, degenerated neuropile and vacuolation, all of which were abrogated/reversed following caffeine treatment.

CONCLUSION

In conclusion, this study was able to establish the neuroprotective and therapeutic candidature of caffeine acting via the A2A receptor to ameliorate or reverse the various pathological insults caused by rotenone administration.

Combined Exposure to Chronic Sleep Deprivation and Caffeine Potentiates Behavioural Deficits by Altering Neurochemical Profile and Synaptophysin Expression in Long-Evans Rats

Using the Unpredictable Chronic Sleep Deprivation (UCSD) paradigm we developed, the combined effects of chronic sleep deprivation and high caffeine intake on prefrontal cortical synaptophysin expression, neurochemical profiles, and behavioural outcomes in Long-Evans rats were evaluated. The combination of chronic sleep deprivation and high-dose caffeine treatment produced varying degrees of behavioural impairments, depletion of antioxidants, serotonin, and an upregulation of acetylcholinesterase (AChE) activity in the prefrontal cortex. An immunohistochemical assessment revealed a reduction in synaptophysin protein expression in the prefrontal cortex following exposure to high-dose caffeine and chronic sleep deprivation. Overall, our findings support the advocacy for adequate sleep for optimal mental performance as a high intake of caffeine to attenuate the effects of sleep deprivation that may alter the neurochemical profile and synaptic plasticity in the prefrontal cortex, significantly increasing the risk of neuropsychiatric/degenerative disorders.

Yap1-mediated Flr1 expression reveals crosstalk between oxidative stress signaling and caffeine resistance in Saccharomyces cerevisiae

Caffeine, a methylxanthine derivative, affects various physiological conditions such as cell growth, proliferation, and energy metabolism. A genome-wide screening for genes required for caffeine resistance in Schizosaccharomyces pombe revealed several candidates, including Pap1 and downstream target genes involved in caffeine efflux. We found that Yap1, a budding yeast AP-1 homolog required for oxidative stress response, has a caffeine tolerance function. Although the Yap1 mutant is not sensitive to caffeine, overexpression of Yap1 renders cells resistant to high concentrations of caffeine. Caffeine sensitivity of mutants lacking two multidrug transporters, Pdr5 or Snq2, is completely recovered by Yap1 overexpression. Among Yap1-dependent target genes, FLR1, a fluconazole-resistant gene, is necessary but not sufficient for caffeine tolerance. Low concentrations of hydrogen peroxide induce Yap1 activation, which restores cell viability against caffeine toxicity. Intriguingly, oxidative stress-mediated cellular adaptation to caffeine toxicity requires Yap1, but not Flr1. Moreover, caffeine is involved in reduction of intracellular reactive oxygen species (ROS), as well as mutation rate and Rad52 foci formation. Altogether, we identified novel reciprocal crosstalk between ROS signaling and caffeine resistance.

Natural product-based pharmacological studies for neurological disorders

Central nervous system (CNS) disorders and diseases are expected to rise sharply in the coming years, partly because of the world's aging population. Medicines for the treatment of the CNS have not been successfully made. Inadequate knowledge about the brain, pharmacokinetic and dynamic errors in preclinical studies, challenges with clinical trial design, complexity and variety of human brain illnesses, and variations in species are some potential scenarios. Neurodegenerative diseases (NDDs) are multifaceted and lack identifiable etiological components, and the drugs developed to treat them did not meet the requirements of those who anticipated treatments. Therefore, there is a great demand for safe and effective natural therapeutic adjuvants. For the treatment of NDDs and other memory-related problems, many herbal and natural items have been used in the Ayurvedic medical system. Anxiety, depression, Parkinson's, and Alzheimer's diseases (AD), as well as a plethora of other neuropsychiatric disorders, may benefit from the use of plant and food-derived chemicals that have antidepressant or antiepileptic properties. We have summarized the present level of knowledge about natural products based on topological evidence, bioinformatics analysis, and translational research in this review. We have also highlighted some clinical research or investigation that will help us select natural products for the treatment of neurological conditions. In the present review, we have explored the potential efficacy of phytoconstituents against neurological diseases. Various evidence-based studies and extensive recent investigations have been included, which will help pharmacologists reduce the progression of neuronal disease.

Astrocytes and major depression: The purinergic avenue

Major depressive disorder (MDD) is one of the most prevalent psychiatric illnesses worldwide which impairs the social functioning of the afflicted patients. Astrocytes promote homeostasis of the CNS and provide defense against various types of harmful influences. Increasing evidence suggests that the number, morphology and function of astrocytes are deteriorated in the depressed brain and the malfunction of the astrocytic purinergic system appears to participate in the pathophysiology of MDD. Adenosine 5'-triphosphate (ATP) released from astrocytes modulates depressive-like behavior in animal models and probably also clinical depression in patients. Astrocytes possess purinergic receptors, such as adenosine A_2A receptors (Rs), and P2X7, P2Y₁, and P2Y₁₁Rs, which mediate neuroinflammation, neuro(glio)transmission, and synaptic plasticity in depression-relevant areas of the brain (e.g. medial prefrontal cortex, hippocampus, amygdala nuclei). By contrast, astrocytic A₁Rs are neuroprotective and immunosuppressive. In the present review, we shall discuss the release of purines from astrocytes, and the expression/function of astrocytic purinergic receptors. Subsequently, we shall review in more detail novel evidence indicating that the dysregulation of astrocytic purinergic signaling actively contributes to the pathophysiology of depression and shall discuss possible therapeutic options based on knowledge recently acquired in this field.

Rapid Eye Movement Sleep Deprivation Enhances Adenosine Receptor Activation and the CREB1/YAP1/c-Myc Axis to Alleviate Depressive-like Behaviors in Rats

As neuromodulators, adenosine and its receptors are mediators of sleep-wake regulation. A putative correlation between CREB1 and depression has been predicted in our bioinformatics analyses, and its expression was also predicted to be upregulated in response to sleep deprivation. Therefore, this study aims to elaborate the A1 and A2A adenosine receptors and CREB1-associated mechanism underlying the antidepressant effect of rapid eye movement sleep deprivation (REMSD) in rats with chronic unpredictable mild stress (CUMS)-induced depressive-like behaviors. The modeled rats were injected with adenosine A1 receptor antagonist DPCPX or adenosine A2A receptor antagonist ZM241385 to assess the role of adenosine receptors in depression. In addition, ectopic expression and depletion experiments of CREB1 and YAP1 were also conducted in vivo and in vitro. It was found that REMSD alleviated depressive-like behaviors in CUMS rats, as shown by increased spontaneous activity, sucrose consumption and percentage, and shortened escape latency and immobility duration. Meanwhile, A1 or A2A adenosine receptor antagonists negated the antidepressant effect of REMSD. REMSD enhanced adenosine receptor activation and promoted the phosphorylation of CREB1, thus increasing the expression of CREB1. In addition, the overexpression of CREB1 activated the YAP1/c-Myc axis and consequently alleviated depressive-like behaviors. Collectively, our results provide new mechanistic insights for an understanding of the antidepressant effect of REMSD, which is associated with the activation of adenosine receptors and the CREB1/YAP1/c-Myc axis.

Biological Role of Nutrients, Food and Dietary Patterns in the Prevention and Clinical Management of Major Depressive Disorder

Major Depressive Disorder (MDD) is a growing disabling condition affecting around 280 million people worldwide. This complex entity is the result of the interplay between biological, psychological, and sociocultural factors, and compelling evidence suggests that MDD can be considered a disease that occurs as a consequence of an evolutionary mismatch and unhealthy lifestyle habits. In this context, diet is one of the core pillars of health, influencing multiple biological processes in the brain and the entire body. It seems that there is a bidirectional relationship between MDD and malnutrition, and depressed individuals often lack certain critical nutrients along with an aberrant dietary pattern. Thus, dietary interventions are one of the most promising tools to explore in the field of MDD, as there are a specific group of nutrients (i.e., omega 3, vitamins, polyphenols, and caffeine), foods (fish, nuts, seeds fruits, vegetables, coffee/tea, and fermented products) or dietary supplements (such as S-adenosylmethionine, acetyl carnitine, creatine, amino acids, etc.), which are being currently studied. Likewise, the entire nutritional context and the dietary pattern seem to be another potential area of study, and some strategies such as the Mediterranean diet have demonstrated some relevant benefits in patients with MDD; although, further efforts are still needed. In the present work, we will explore the state-of-the-art diet in the prevention and clinical support of MDD, focusing on the biological properties of its main nutrients, foods, and dietary patterns and their possible implications for these patients.

Untargeted Metabolomics Reveals the Potential Antidepressant Activity of a Novel Adenosine Receptor Antagonist

Depression is the most common mental illness, affecting approximately 4.4% of the global population. Despite many available treatments, some patients exhibit treatment-resistant depression. Thus, the need to develop new and alternative treatments cannot be overstated. Adenosine receptor antagonists have emerged as a promising new class of antidepressants. The current study investigates a novel dual A₁/A_2A adenosine receptor antagonist, namely 2-(3,4-dihydroxybenzylidene)-4-methoxy-2,3-dihydro-1H-inden-1-one (1a), for antidepressant capabilities by determining its metabolic profiles and comparing them to those of two reference compounds (imipramine and KW-6002). The metabolic profiles were obtained by treating male Sprague-Dawley rats with 1a and the reference compounds and subjecting them to the forced swim test. Serum and brain material was consequently collected from the animals following euthanasia, after which the metabolites were extracted and analyzed through untargeted metabolomics using both ¹H-NMR and GC-TOFMS. The current study provides insight into compound 1a's metabolic profile. The metabolic profile of 1a was similar to those of the reference compounds. They potentially exhibit their antidepressive capabilities via downstream effects on amino acid and lipid metabolism.

Effects of Postnatal Caffeine Exposure on Absence Epilepsy and Comorbid Depression: Results of a Study in WAG/Rij Rats

The present study aims to investigate effect of early caffeine exposure on epileptogenesis and occurrence of absence seizures and comorbid depression in adulthood. For this purpose, Wistar Albino Glaxo from Rijswijk (WAG/Rij) rats were enrolled in a control and two experimental groups on the 7th day after the delivery. The rats in experimental groups received either 10 or 20 mg/kg caffeine subcutaneously while animals in control group had subcutaneous injections of 0.9% saline. The injections started at postnatal day 7 (PND7) and were continued each day for 5 days. At 6–7 months of age, electroencephalogram (EEG) recordings and behavioral recordings in the forced swimming test, sucrose consumption/preference test and locomotor activity test were carried out. At 6 months of age, 10 mg/kg and 20 mg/kg caffeine-treated WAG/Rij rats showed increased immobility latency and active swimming duration in forced swimming test when compared with the untreated controls. In addition, 20 mg/kg caffeine treatment decreased immobility time. In sucrose preference/consumption tests, WAG/Rij rats in 10 mg/kg caffeine group demonstrated higher sucrose consumption and preference compared to untreated controls. The rats treated with 20 mg/kg caffeine showed higher sucrose preference compared to control rats. The exploratory activity of rats in the 10 mg/kg caffeine-treated group was found to be higher than in the 20 mg/kg caffeine-treated and control groups in the locomotor activity test. At 7 months of age, caffeine-treated animals showed a decreased spike-wave discharge (SWD) number compared to the control animals. These results indicate that postnatal caffeine treatment may decrease the number of seizure and depression-like behaviors in WAG/Rij rats in later life. Caffeine blockade of adenosine receptors during the early developmental period may have beneficial effects in reducing seizure frequency and depression-like behaviors in WAG/Rij rat model.

The Problem of Malnutrition Associated with Major Depressive Disorder from a Sex-Gender Perspective

Major depressive disorder (MDD) is an incapacitating condition characterized by loss of interest, anhedonia and low mood, which affects almost 4% of people worldwide. With rising prevalence, it is considered a public health issue that affects economic productivity and heavily increases health costs alone or as a comorbidity for other pandemic non-communicable diseases (such as obesity, cardiovascular disease, diabetes, inflammatory bowel diseases, etc.). What is even more noteworthy is the double number of women suffering from MDD compared to men. In fact, this sex-related ratio has been contemplated since men and women have different sexual hormone oscillations, where women meet significant changes depending on the age range and moment of life (menstruation, premenstruation, pregnancy, postpartum, menopause…), which seem to be associated with susceptibility to depressive symptoms. For instance, a decreased estrogen level promotes decreased activation of serotonin transporters. Nevertheless, sexual hormones are not the only triggers that alter neurotransmission of monoamines and other neuropeptides. Actually, different dietary habits and/or nutritional requirements for specific moments of life severely affect MDD pathophysiology in women. In this context, the present review aims to descriptively collect information regarding the role of malnutrition in MDD onset and course, focusing on female patient and especially macro- and micronutrient deficiencies (amino acids, ω3 polyunsaturated fatty acids (ω3 PUFAs), folate, vitamin B12, vitamin D, minerals…), besides providing evidence for future nutritional intervention programs with a sex-gender perspective that hopefully improves mental health and quality of life in women.

Imperatorin Influences Depressive-like Behaviors: A Preclinical Study on Behavioral and Neurochemical Sex Differences

Imperatorin, a naturally derived furanocoumarin, exerts promising neuropharmacological properties. Therefore, it might be applicable in the treatment of brain diseases such as depression. In the present project, we aimed to investigate the sex-dependent effects of imperatorin (1, 5, and 10 mg/kg) on behavior and neurochemistry associated with antidepressant effects. The depressive-like behaviors of male and female Swiss mice were investigated in a forced swim test (FST). Subsequently, High-Performance Liquid Chromatography (HPLC) was used to evaluate the level of serotonin, its metabolite, 5-HIAA, and noradrenaline, in mouse brains. The study revealed that only males responded to imperatorin (1 and 5 mg/kg) treatment and caused an antidepressant effect, such as with respect to depressive-like behaviors, lowering immobility time and increasing immobility latency. The HPLC analysis demonstrated that serotonin levels in the prefrontal cortex of females decreased with the middle dose of imperatorin (5 mg/kg), while in the male prefrontal cortex, the lower dose (1 mg/kg) boosted serotonin levels. There were no evident changes observed with respect to noradrenaline and serotonin metabolite levels in the male hippocampus. To conclude, we propose that imperatorin has antidepressant potential, seemingly only in males, influencing brain serotonin level, but the direct mechanism of action requires further investigation.

Selection of Aptamers for Sensing Caffeine and Discrimination of Its Three Single Demethylated Analogues

With the growing consumption of caffeine-containing beverages, detection of caffeine has become an important biomedical, bioanalytical, and environmental topic. We herein isolated four high-quality aptamers for caffeine with dissociation constants ranging from 2.2 to 14.6 μM as characterized using isothermal titration calorimetry. Different binding patterns were obtained for the three single demethylated analogues: theobromine, theophylline, and paraxanthine, highlighting the effect of the molecular symmetry of the arrangement of the three methyl groups in caffeine. A structure-switching fluorescent sensor was designed showing a detection limit of 1.2 μM caffeine, which reflected the labeled caffeine concentration within 6.1% difference for eight commercial beverages. In 20% human serum, a detection limit of 4.0 μM caffeine was achieved. With the four aptamer sensors forming an array, caffeine and the three analogues were well separated from nine other closely related molecules.

Habitual caffeine consumption moderates the antidepressant effect of dorsomedial intermittent theta-burst transcranial magnetic stimulation

BACKGROUND

Potentiating current antidepressant treatment is much needed. Based on animal studies, caffeine may augment the effects of currently available antidepressants.

OBJECTIVE

Here, we tested whether habitual caffeine consumption moderates the antidepressant effects of repetitive transcranial magnetic stimulation (rTMS) using intermittent theta-burst stimulation (iTBS).

METHODS

Forty patients with current depressive episodes were randomized to active iTBS (n = 19) or sham treatment (n = 21; shielded side of the coil and weak transcutaneous electrical stimulation) delivered two times per day for 10-15 weekdays. Neuronavigated stimulation was applied to the dorsomedial prefrontal cortex. Symptom improvement was measured using change in self-reported Montgomery-Åsberg Depression Rating Scale (MADRS) scores. Pretreatment habitual caffeine consumption was quantified using self-reports of number of cups of coffee and energy drinks consumed the 2 days before the treatment starts.

RESULTS

Habitual caffeine consumption was associated with symptom improvement following active iTBS (r = 0.51, 95% confidence interval (CI): 0.08-0.78, p = 0.025) but not following sham treatment (r = -0.02, 95% CI: -0.45 to 0.42, p = 0.938). A multiple regression analysis corroborated the findings by showing a significant caffeine consumption × treatment group interaction (β = 0.62, p = 0.043), but no main effects of treatment group (β = 0.22, p = 0.140) or caffeine consumption (β = -0.01, p = 0.948). No group differences in pretreatment symptom scores or caffeine consumption were detected (p values > 0.86).

CONCLUSION

Habitual caffeine consumption moderated the antidepressant effect of dorsomedial iTBS, consistent with caffeine improving antidepressant pharmacological treatments in animals. Caffeine is an antagonist of adenosine receptors and may enhance antidepressant effects through downstream dopaminergic targets.

24-Epibrassinolide modulates the neurodevelopmental outcomes of high caffeine exposure in zebrafish (Danio rerio) embryos

Previous embryonic fish data have shown caffeine to induce potential teratogenic and long-term neurodevelopmental outcomes through oxidative stress-mediated apoptosis. In this context, antioxidants may have the potential to counteract the caffeine-induced effects. Therefore, the present study aimed to investigate the potential protective role of 24-epibrassinolide (24-EPI), a natural brassinosteroid with proven antioxidant properties, against caffeine-induced teratogenic effects during early zebrafish development. Embryos (~2 h post-fertilization - hpf) were exposed to 0.5 mM caffeine, co-exposed to 24-EPI (0.01, 0.1 and 1 μM) and to 24-EPI alone (1 μM) for 96 h. During exposure, lethal and sublethal developmental parameters were evaluated. At the end of the exposure, biochemical evaluations were made, and 24 h after, different behavioural paradigms were assessed. An increased number of animals showing oedema and malformations were observed after caffeine exposure, while these were reduced after co-exposure to 24-EPI concentration, namely the tail curvature. The results showed oxidative stress and related parameters similar among treatments. Yet, caffeine exposure resulted in locomotor deficits (decreased speed and distance) and disrupted anxiety-like and avoidance responses. The co-exposure to caffeine and to the highest 24-EPI concentrations resulted in less pronounced behavioural deficits. Overall, there was an absence of effects in the embryo/larvae exposed solely to 24-EPI, while caffeine caused developmental and neurotoxic effects. Although further studies are needed, the results showed promising protective effects of the highest 24-EPI concentration tested against the toxicity induced by caffeine in zebrafish.

The relationship of caffeinated beverages with depressive symptoms and decision-making

BACKGROUND: Caffeine can affect depressive symptoms and decision-making. OBJECTIVE: This study aims to examine the relationship between caffeinated beverages consumption with depressive symptoms and decision-making styles. METHODS: This cross-sectional study was conducted with 432 adults working in office environment. The questionnaire consisting of individuals’ socio-demographic attributes, the frequency and the amount of caffeinated beverages consumption, the “Epidemiological Research Center-Depression (CES-D) Scale” and the “Decision-Making Styles Scale” were used. The frequency and amount of caffeinated beverages were determined using the food frequency questionnaire (FFQ). The participants were asked to choose which cup/mug they prefer to drink their caffeinated beverages and what amount they consume that beverage at a time. All the data were collected using online platforms. RESULTS: In the study, 76.7%of the participants were female and the mean age was 31.5±8.0 years. The average daily total caffeine intake of the participants was 425.8±461.4 mg and the total CES-D scale score was 17.7±11.2 points. It was found that as the amount of caffeine consumed increased, intuitive decision-making decreased and depressive symptoms increased (p <  0.05). In linear regression analysis, total caffeine consumption was found to be a significant predictor for the intuitive decision-making score (B: –0.151; p:0.002). When caffeine consumption is controlled, intuitive and rational decision making decreases with increasing depressive symptoms while addiction and avoidance decision making increased (p <  0.05). CONCLUSIONS: As a result, the amount of caffeine consumed daily was related to intuitive decision-making but did not effect depression. It has been observed that depressive symptoms affect decision-making styles in different ways. To our knowledge, our study is the first to examine the effects of caffeine consumption on depression and decision-making styles. Accordingly, future studies may focus on the link between caffeine consumption, depression, and decision-making styles in larger populations and the mechanisms that influence this relationship.

Neuromotor activity inhibition in zebrafish early-life stages after exposure to environmental relevant concentrations of caffeine

Caffeine (CAF), a neuroactive compound, has been found in surface waters at concentrations ranging from few nanograms up to micrograms and may induce adverse effects in aquatic vertebrates. Thus, the aim of this study was to evaluate the potential of CAF in affecting fish early-life stages in a wide concentration range, including occurring levels in surface waters. Specimens of zebrafish in early-life stages were exposed to CAF for 168 h and survival, developmental alterations, locomotor activity and acetylcholinesterase activity were evaluated. CAF induced mortality in embryos unable to hatch or in larvae after hatching (LC₅₀ - 168 h = 283.2 mg/L). Tail deformities were observed in organisms exposed to concentrations ≥ 40 mg/L, while edemas were found at concentrations of 100 mg/L. CAF also decreased the total swimming time and distance moved of exposed organisms (LOEC = 0.0006 mg/L). Locomotor inhibition may be associated with an acetylcholinesterase inhibition observed at concentration ≥ 0.0088 mg/L. Therefore, the hazard of CAF for fish populations deserves further attention since unexpected effects on neuro-behavioral parameters occurs at concentrations often detected in natural aquatic ecosystems.

Exploring the Role of Nutraceuticals in Major Depressive Disorder (MDD): Rationale, State of the Art and Future Prospects

Major depressive disorder (MDD) is a complex and common disorder, with many factors involved in its onset and development. The clinical management of this condition is frequently based on the use of some pharmacological antidepressant agents, together with psychotherapy and other alternatives in most severe cases. However, an important percentage of depressed patients fail to respond to the use of conventional therapies. This has created the urgency of finding novel approaches to help in the clinical management of those individuals. Nutraceuticals are natural compounds contained in food with proven benefits either in health promotion or disease prevention and therapy. A growing interest and economical sources are being placed in the development and understanding of multiple nutraceutical products. Here, we summarize some of the most relevant nutraceutical agents evaluated in preclinical and clinical models of depression. In addition, we will also explore less frequent but interest nutraceutical products which are starting to be tested, also evaluating future roads to cover in order to maximize the benefits of nutraceuticals in MDD.

Design and Synthesis of Novel Thiazolo[5,4-d]pyrimidine Derivatives with High Affinity for Both the Adenosine A1 and A2A Receptors, and Efficacy in Animal Models of Depression

New compounds with a 7-amino-2-arylmethyl-thiazolo[5,4-d]pyrimidine structure were synthesized and evaluated in vitro for their affinity and/or potency at the human (h) A₁, hA_2A, hA_2B, and hA₃ adenosine receptors (ARs). Several compounds (5, 8–10, 13, 18, 19) were characterized by nanomolar and subnanomolar binding affinities for the hA₁ and the hA_2A AR, respectively. Results of molecular docking studies supported the in vitro results. The 2-(2-fluorobenzyl)-5-(furan-2yl)-thiazolo[5,4-d]pyrimidin-7-amine derivative 18 (hA₁ K_i = 1.9 nM; hA_2A K_i = 0.06 nM) was evaluated for its antidepressant-like activity in in vivo studies, the forced swimming test (FST), the tail suspension test (TST), and the sucrose preference test (SPT) in mice, showing an effect comparable to that of the reference amitriptyline.

The impact of caffeine consumption on clinical symptoms in patients with bipolar disorder: A systematic review

OBJECTIVES

In healthy populations, caffeine appears to have beneficial effects on health; however, patients with bipolar disorder (BD) are routinely advised to limit caffeine use in psychoeducation programmes. We aimed to examine all literature reporting whether caffeine intake/withdrawal impacts the natural course of BD, in terms of clinical outcomes.

METHODS

PubMed, Embase and PsycINFO were searched (up to 17/07/2020) and all studies reporting data on individuals with BD comparing a measure of caffeine use with illness severity (symptoms of mania, depression, psychosis, anxiety, sleep or suicidality) were included.

RESULTS

Of the 1678 records reviewed, 17 studies met inclusion criteria (10 case reports, 1 retrospective cohort study, 5 cross-sectional studies, 1 interventional study). Most case reports described people with BD switching to manic, hypomanic or mixed states after consuming caffeine in variable amounts and/or whose serum lithium concentrations increased after reducing caffeine consumption. The interventional study found that caffeine may suppress lithium concentrations, while the retrospective cohort study reported that participants who drank coffee had more suicidality than non-drinkers.

CONCLUSIONS

The literature examining clinical effects of caffeine in patients with BD is not conclusive. Acute increases in caffeine consumption may precede the occurrence of manic symptoms in patients with BD, potentially through a direct stimulant effect, affecting sleep patterns and/or the metabolism of lithium or other medications, although increases in caffeine intake could also be a consequence of an ongoing manic relapse or a prodromal sign. Further research is needed to determine whether caffeine use impacts the long-term prognosis of BD.

Caffeine Intake and Mental Health in College Students

Background The effect of caffeine on the human body, both short-term and long-term, has been studied in great depth, particularly its association with psychiatric disorders. This study aims to investigate whether there is a correlation between caffeine intake and anxiety and depression among college students. Methodology A survey was administered to college students at Florida State University. Data regarding participant characteristics and caffeine intake were collected. Generalized Anxiety Disorder-7 and Patient Health Questionnaire-9 scores were used to assess symptoms of anxiety and depression, respectively. Results A total of 114 participants were included in the survey, consisting mainly of women (94 [82.5%]) and junior-level students (37 [32.5%]). The main source of caffeine was coffee (64.0%), and the main reasons for caffeine intake were pleasure (43.9%) and to study outside of class (29.8%); however, no association was found between sex or grade point average and number of cups of caffeine consumed. Upper levels of education (super senior or fifth-year students), depressive symptoms (poor appetite, overeating, sleep disorders, depressed mood), and anxiety were statistically associated with greater caffeine intake (P < 0.05). Conclusions As caffeine is commonly consumed and our study showed that its intake was associated with depressive symptoms and higher levels of anxiety in college students, further studies are needed to determine a possible causality, so that measures may be taken to educate these students about alternative methods for increasing energy and alertness.

Caffeine protects against stress-induced murine depression through activation of PPARγC1α-mediated restoration of the kynurenine pathway in the skeletal muscle

Exercise prevents depression through peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α)-mediated activation of a particular branch of the kynurenine pathway. From kynurenine (KYN), two independent metabolic pathways produce neurofunctionally different metabolites, mainly in somatic organs: neurotoxic intermediate metabolites via main pathway and neuroprotective end product, kynurenic acid (KYNA) via the branch. Elevated levels of KYN have been found in patients with depression. Herein, we investigated whether and how caffeine prevents depression, focusing on the kynurenine pathway. Mice exposed to chronic mild stress (CMS) exhibited depressive-like behaviours with an increase and decrease in plasma levels of pro-neurotoxic KYN and neuroprotective KYNA, respectively. However, caffeine rescued CMS-exposed mice from depressive-like behaviours and restored the plasma levels of KYN and KYNA. Concomitantly, caffeine induced a key enzyme converting KYN into KYNA, namely kynurenine aminotransferase-1 (KAT1), in murine skeletal muscle. Upon caffeine stimulation murine myotubes exhibited KAT1 induction and its upstream PGC-1α sustainment. Furthermore, a proteasome inhibitor, but not translational inhibitor, impeded caffeine sustainment of PGC-1α, suggesting that caffeine induced KAT1 by inhibiting proteasomal degradation of PGC-1α. Thus, caffeine protection against CMS-induced depression may be associated with sustainment of PGC-1α levels and the resultant KAT1 induction in skeletal muscle, and thereby consumption of pro-neurotoxic KYN.

Impact of Caffeine on Ethanol-Induced Stimulation and Sensitization: Changes in ERK and DARPP-32 Phosphorylation in Nucleus Accumbens

BACKGROUND

Caffeine is frequently consumed with ethanol to reduce the impairing effects induced by ethanol, including psychomotor slowing or incoordination. Both drugs modulate dopamine (DA)-related markers in accumbens (Acb), and Acb DA is involved in voluntary locomotion and locomotor sensitization. The present study determined whether caffeine can affect locomotion induced by acute and repeated ethanol administration in adult male CD-1 mice.

METHODS

Acute administration of caffeine (7.5 to 30.0 mg/kg) was evaluated for its effects on acute ethanol-induced (1.5 to 3.5 g/kg) changes in open-field horizontal locomotion, supported rearing, and rearing not supported by the wall. DA receptor-dependent phosphorylation markers were assessed: extracellular signal-regulated kinase (pERK), and dopamine-and cAMP-regulated phosphoprotein Mr32kDa phosphorylated at threonine 75 site (pDARPP-32-Thr75) in Acb core and shell. Acutely administered caffeine was also evaluated in ethanol-sensitized (1.5 g/kg) mice.

RESULTS

Acute ethanol decreased both types of rearing. Caffeine increased supported rearing but did not block ethanol -induced decreases in rearing. Both substances increased horizontal locomotion in a biphasic manner, and caffeine potentiated ethanol-induced locomotion. Although ethanol administered repeatedly induced sensitization of locomotion and unsupported rearing, acute administration of caffeine to ethanol-sensitized mice in an ethanol-free state resulted in blunted stimulant effects compared with those seen in ethanol-naïve mice. Ethanol increased pERK immunoreactivity in both subregions of the Acb, but coadministration with caffeine blunted this increase. There were no effects on pDARPP-32(Thr75) immunoreactivity.

CONCLUSIONS

The present results demonstrated that, after the first administration, caffeine potentiated the stimulating actions of ethanol, but did not counteract its suppressant or ataxic effects. Moreover, our results show that caffeine has less activating effects in ethanol-sensitized animals.

Pleiotropic Effects of Caffeine Leading to Chromosome Instability and Cytotoxicity in Eukaryotic Microorganisms

Caffeine, a methylxanthine analog of purine bases, is a compound that is largely consumed in beverages and medications for psychoactive and diuretic effects and plays many beneficial roles in neuronal stimulation and enhancement of anti-tumor immune responses by blocking adenosine receptors in higher organisms. In single-cell eukaryotes, however, caffeine somehow impairs cellular fitness by compromising cell wall integrity, inhibiting target of rapamycin (TOR) signaling and growth, and overriding cell cycle arrest caused by DNA damage. Among its multiple inhibitory targets, caffeine specifically interacts with phosphatidylinositol 3-kinase (PI3K)-related kinases causing radiosensitization and cytotoxicity via specialized intermediate molecules. Caffeine potentiates the lethality of cells in conjunction with several other stressors such as oxidants, irradiation, and various toxic compounds through largely unknown mechanisms. In this review, recent findings on caffeine effects and cellular detoxification schemes are highlighted and discussed with an emphasis on the inhibitory interactions between caffeine and its multiple targets in eukaryotic microorganisms such as budding and fission yeasts.

Purinergic transmission in depressive disorders

Purinergic signaling involves the actions of purine nucleotides and nucleosides (such as adenosine) at P1 (adenosine), P2X, and P2Y receptors. Here, we present recent data contributing to a comprehensive overview of the association between purinergic signaling and depression. We start with background information on adenosine production and metabolism, followed by a detailed characterization of P1 and P2 receptors, with an emphasis on their expression and function in the brain as well as on their ligands. We provide data suggestive of altered metabolism of adenosine in depressed patients, which might be regarded as a disease biomarker. We then turn to considerable amount of preclinical/behavioral data obtained with the aid of the forced swim test, tail suspension test, learned helplessness model, or unpredictable chronic mild stress model and genetic activation/inactivation of P1 or P2 receptors as well as nonselective or selective ligands of P1 or P2 receptors. We also aimed to discuss the reason underlying discrepancies observed in such studies.

Adenosine at the Interphase of Hypoxia and Inflammation in Lung Injury

Hypoxia and inflammation often coincide in pathogenic conditions such as acute respiratory distress syndrome (ARDS) and chronic lung diseases, which are significant contributors to morbidity and mortality for the general population. For example, the recent global outbreak of Coronavirus disease 2019 (COVID-19) has placed viral infection-induced ARDS under the spotlight. Moreover, chronic lung disease ranks the third leading cause of death in the United States. Hypoxia signaling plays a diverse role in both acute and chronic lung inflammation, which could partially be explained by the divergent function of downstream target pathways such as adenosine signaling. Particularly, hypoxia signaling activates adenosine signaling to inhibit the inflammatory response in ARDS, while in chronic lung diseases, it promotes inflammation and tissue injury. In this review, we discuss the role of adenosine at the interphase of hypoxia and inflammation in ARDS and chronic lung diseases, as well as the current strategy for therapeutic targeting of the adenosine signaling pathway.

Caffeine Consumption and Behavioral Symptoms in Nursing Home Residents: A Cross-Sectional Analysis

OBJECTIVE

Although behavioral changes are common in nursing home residents with dementia and caffeine is known to influence behavior in healthy adults, the effects of caffeine on the behavior of persons with dementia has received little attention. In this study we assessed the relationship of caffeine and behavioral symptoms in older persons with dementia.

DESIGN

A multicenter sub-cohort study embedded in the Elderly Care Physicians (ECP) training program.

SETTING

Dutch nursing homes associated with the ECP training program.

PARTICIPANTS

A total of 206 individuals with both diabetes and dementia resident in Dutch nursing homes.

MEASUREMENTS

Trainee ECPs collected data on caffeine consumption, cognition and behavioral symptoms using the NPI-NH, MDS-DRS and AES-C. Data on factors known to influence behavior in persons with dementia (e.g. marital status, kidney function, urinary tract infection and medication) were also collected.

RESULTS

Of the 206 participants, 70% showed behavioral symptoms. An increase in caffeine consumption was associated with a decrease in the presence of behavioral symptoms in the NPI-NH cluster affect and NPI-NH item agitation. Caffeine consumption groups also differed on the presence of disinhibition and depression. In addition, the severity of dementia influenced agitation, anxiety and the clusters affect and psychomotor.

CONCLUSION

In a large group of older persons with dementia resident in nursing homes, a low daily consumption of caffeine was associated with greater behavioral symptoms.

Guanosine-Mediated Anxiolytic-Like Effect: Interplay with Adenosine A1 and A2A Receptors

Acute or chronic administration of guanosine (GUO) induces anxiolytic-like effects, for which the adenosine (ADO) system involvement has been postulated yet without a direct experimental evidence. Thus, we aimed to investigate whether adenosine receptors (ARs) are involved in the GUO-mediated anxiolytic-like effect, evaluated by three anxiety-related paradigms in rats. First, we confirmed that acute treatment with GUO exerts an anxiolytic-like effect. Subsequently, we investigated the effects of pretreatment with ADO or A₁R (CPA, CCPA) or A_2AR (CGS21680) agonists 10 min prior to GUO on a GUO-induced anxiolytic-like effect. All the combined treatments blocked the GUO anxiolytic-like effect, whereas when administered alone, each compound was ineffective as compared to the control group. Interestingly, the pretreatment with nonselective antagonist caffeine or selective A₁R (DPCPX) or A_2AR (ZM241385) antagonists did not modify the GUO-induced anxiolytic-like effect. Finally, binding assay performed in hippocampal membranes showed that [³H]GUO binding became saturable at 100–300 nM, suggesting the existence of a putative GUO binding site. In competition experiments, ADO showed a potency order similar to GUO in displacing [³H]GUO binding, whereas AR selective agonists, CPA and CGS21680, partially displaced [³H]GUO binding, but the sum of the two effects was able to displace [³H]GUO binding to the same extent of ADO alone. Overall, our results strengthen previous data supporting GUO-mediated anxiolytic-like effects, add new evidence that these effects are blocked by A₁R and A_2AR agonists and pave, although they do not elucidate the mechanism of GUO and ADO receptor interaction, for a better characterization of GUO binding sites in ARs.

Of adenosine and the blues: The adenosinergic system in the pathophysiology and treatment of major depressive disorder

Major depressive disorder (MDD) is the foremost cause of global disability, being responsible for enormous personal, societal, and economical costs. Importantly, existing pharmacological treatments for MDD are partially or totally ineffective in a large segment of patients. As such, the search for novel antidepressant drug targets, anchored on a clear understanding of the etiological and pathophysiological mechanisms underpinning MDD, becomes of the utmost importance. The adenosinergic system, a highly conserved neuromodulatory system, appears as a promising novel target, given both its regulatory actions over many MDD-affected systems and processes. With this goal in mind, we herein review the evidence concerning the role of adenosine as a potential player in pathophysiology and treatment of MDD, combining data from both human and animal studies. Altogether, evidence supports the assertions that the adenosinergic system is altered in both MDD patients and animal models, and that drugs targeting this system have considerable potential as putative antidepressants. Furthermore, evidence also suggests that modifications in adenosine signaling may have a key role in the effects of several pharmacological and non-pharmacological antidepressant treatments with demonstrated efficacy, such as electroconvulsive shock, sleep deprivation, and deep brain stimulation. Lastly, it becomes clear from the available literature that there is yet much to study regarding the role of the adenosinergic system in the pathophysiology and treatment of MDD, and we suggest several avenues of research that are likely to prove fruitful.

Comprehensive Investigation of Metabolic Changes Occurring in the Rat Brain Hippocampus after Fluoxetine Administration Using Two Complementary In Vivo Techniques: Solid Phase Microextraction and Microdialysis

Fluoxetine is among the most prescribed antidepressant drugs worldwide. Nevertheless, limited information is known about its definitive mechanism. Although in vivo examinations performed directly in related brain structures can provide more realistic, and therefore more insightful, knowledge regarding the mechanisms and efficacy of this drug, only a few techniques are applicable for in vivo monitoring of metabolic alterations in the brain following an inducement. Among them, solid phase microextraction (SPME) and microdialysis (MD) have emerged as ideal in vivo tools for extraction of information from biosystems. In this investigation, we scrutinized the capabilities of SPME and MD to detect ongoing changes in the brain following acute fluoxetine administration. Sequential in vivo samples were collected simultaneously from male rats' hippocampi using SPME and MD before drug administration in order to establish a baseline; then samples were collected again following fluoxetine administration for an investigation of small molecule alterations. Our results indicate that MD provides more comprehensive information for polar compounds, while SPME provides superior information with respect to lipids and other medium level polar molecules. Interestingly, in the lipidomic investigation, all dysregulated features were found to be membrane lipids and associated compounds. Moreover, in the metabolomic investigations, dysregulation of hippocampal metabolite levels associated with fatty acid transportation and purine metabolisms were among the most notable findings. Overall, our evaluation of the obtained data corroborates that, when used in tandem, SPME and MD are capable of providing comprehensive information regarding the effect of fluoxetine in targeted brain structures and further elucidating this drug's mechanisms of action in the brain.

The non-selective adenosine antagonist theophylline reverses the effects of dopamine antagonism on tremor, motor activity and effort-based decision-making

Considerable evidence indicates that adenosine and dopamine systems interact in the regulation of basal ganglia function. Nonselective adenosine antagonists such as the methylxanthine caffeine as well as selective adenosine A_2A antagonists have been shown to produce antiparkinsonian and antidepressant effects in animal models. The present studies were conducted to assess if another methylxantine, theophylline, can reverse motor and motivational impairments induced by dopamine antagonism in rats. RESULTS: Theophylline (3.75-30.0 mg/kg, IP) reversed tremulous jaw movements (TJMs), catalepsy, and locomotor suppression induced by the dopamine D2 antagonist pimozide. It also reversed TJMs induced by the muscarinic receptor agonist pilocarpine, which is a well-known tremorogenic agent. Parallel studies assessed the ability of theophylline (5.0-20.0 mg/kg, IP) to reverse the changes in effort-related choice behavior induced by the dopamine D1 antagonist ecopipam (0.2 mg/kg, IP) and the D2 antagonist haloperidol (0.1 mg/kg, IP). Rats were tested on two different operant choice tasks which assess the tendency to work for a preferred reinforcer by lever pressing (for palatable pellets or a high 5% sucrose solution) vs. approaching and consuming a less preferred reinforcer (freely available lab chow or a less concentrated 0.3% sucrose solution). Theophylline restored food and sucrose-reinforced lever pressing in animals treated with the D2 antagonist. However, it was unable to reverse the effects of the D1 antagonist. Overall, the effects of theophylline resembled those previously reported for adenosine A_2A antagonists, and suggest that theophylline could be clinically useful for the treatment of motor and motivational symptoms in humans.

Some Reasons Why Preclinical Studies of Psychiatric Disorders Fail to Translate: What Can Be Rescued from the Misunderstanding and Misuse of Animal 'Models'?

The repeated failure of animal models to yield findings that translate into humans is a serious threat to the credibility of preclinical biomedical research. The use of animals in research that lacks translational validity is unacceptable in any ethical environment, and so this problem needs urgent attention. To reproduce any human illness in animals is a serious challenge, but this is especially the case for psychiatric disorders. Yet, many authors do not hesitate to describe their findings as a 'model' of such a disorder. More cautious scientists describe the behavioural phenotype as 'disorder-like', without specifying the way(s) in which the abnormal behaviour could be regarded as being analogous to any of the diagnostic features of the disorder in question. By way of discussing these problems, this article focuses on common, but flawed, assumptions that pervade preclinical research of depression and antidepressants. Particular attention is given to the difference between putative 'models' of this illness and predictive screens for candidate drug treatments, which is evidently widely misunderstood. However, the problems highlighted in this article are generic and afflict research of all psychiatric disorders. This dire situation will be resolved only when funders and journal editors take action to ensure that researchers interpret their findings in a less ambitious, but more realistic, evidence-based way that would parallel changes in research of the cause(s), diagnosis and treatment of psychiatric problems in humans.

Antidepressant Effect of Shaded White Leaf Tea Containing High Levels of Caffeine and Amino Acids

The young leaves of green tea become lighter in color than usual when protected from sunlight by a shading net for about two weeks while growing. These leaves are called "shaded white leaf tea" or SWLT. In the eluate of SWLT, the amount of amino acids (361 mg/L) was significantly higher than that in regular tea (53.5 mg/L). Since theanine and arginine, the first and second most abundant amino acids in SWLT, have significant antistress effects, we examined the antistress effect of SWLT on humans. SWLT or placebo green tea (3 g) was eluted with room-temperature water (500 mL). Participants consumed the tea for one week prior to pharmacy practice and continued for 10 days in the practice period. The state-trait anxiety inventory, an anxiety questionnaire, tended to be scored lower in the SWLT group than the placebo, but other stress markers showed no differences. The effect of the difference in SWLT components examined with mice showed that aspartic acid and asparagine, which are abundant in SWLT, counteracted the antistress effects of theanine and arginine. Large amounts of caffeine also interfered with SWLT's antistress effect. Thus, SWLT, which is high in caffeine and amino acids, suppressed depressant behavior in mice.