Using caffeine and other adenosine receptor antagonists and agonists as therapeutic tools against neurodegenerative diseases: a review

Adora2A downregulation promotes caffeine neuroprotective effect against LPS-induced neuroinflammation in the hippocampus

Caffeine has been extensively studied in the context of CNS pathologies as many researchers have shown that consuming it reduces pro-inflammatory biomarkers, potentially delaying the progression of neurodegenerative pathologies. Several lines of evidence suggest that adenosine receptors, especially A1 and A2A receptors, are the main targets of its neuroprotective action. We found that caffeine pretreatment 15 min before LPS administration reduced the expression of Il1b in the hippocampus and striatum. The harmful modulation of caffeine-induced inflammatory response involved the downregulation of the expression of A2A receptors, especially in the hippocampus. Caffeine treatment alone promoted the downregulation of the adenosinergic receptor Adora2A; however, this promotion effect was reversed by LPS. Although administering caffeine increased the expression of the enzymes DNA methyltransferases 1 and 3A and decreased the expression of the demethylase enzyme Tet1, this effect was reversed by LPS in the hippocampus of mice that were administered Caffeine + LPS, relative to the basal condition; no significant differences were observed in the methylation status of the promoter regions of adenosine receptors. Finally, the bioinformatics analysis of the expanded network demonstrated the following results: the Adora2B gene connects the extended networks of the adenosine receptors Adora1 and Adora2A; the Mapk3 and Esr1 genes connect the extended Adora1 network; the Mapk4 and Arrb2 genes connect the extended Adora2A network with the extended network of the proinflammatory cytokine Il1β. These results indicated that the anti-inflammatory effects of acute caffeine administration in the hippocampus may be mediated by a complex network of interdependencies between the Adora2B and Adora2A genes.

Effect of Xanthohumol, a Bioactive Natural Compound from Hops, on Adenosine Pathway in Rat C6 Glioma and Human SH-SY5Y Neuroblastoma Cell Lines

Xanthohumol (Xn) is an antioxidant flavonoid mainly extracted from hops (Humulus lupulus), one of the main ingredients of beer. As with other bioactive compounds, their therapeutic potential against different diseases has been tested, one of which is Alzheimer's disease (AD). Adenosine is a neuromodulatory nucleoside that acts through four different G protein-coupled receptors: A1 and A3, which inhibit the adenylyl cyclases (AC) pathway, and A2A and A2B, which stimulate this activity, causing either a decrease or an increase, respectively, in the release of excitatory neurotransmitters such as glutamate. This adenosinergic pathway, which is altered in AD, could be involved in the excitotoxicity process. Therefore, the aim of this work is to describe the effect of Xn on the adenosinergic pathway using cell lines. For this purpose, two different cellular models, rat glioma C6 and human neuroblastoma SH-SY5Y, were exposed to a non-cytotoxic 10 µM Xn concentration. Adenosine A1 and A2A, receptor levels, and activities related to the adenosine pathway, such as adenylate cyclase, protein kinase A, and 5'-nucleotidase, were analyzed. The adenosine A1 receptor was significantly increased after Xn exposure, while no changes in A2A receptor membrane levels or AC activity were reported. Regarding 5'-nucleotidases, modulation of their activity by Xn was noted since CD73, the extracellular membrane attached to 5'-nucleotidase, was significantly decreased in the C6 cell line. In conclusion, here we describe a novel pathway in which the bioactive flavonoid Xn could have potentially beneficial effects on AD as it increases membrane A1 receptors while modulating enzymes related to the adenosine pathway in cell cultures.

Adenosine and Cortical Plasticity

Brain plasticity is the ability of the nervous system to change its structure and functioning in response to experiences. These changes occur mainly at synaptic connections, and this plasticity is named synaptic plasticity. During postnatal development, environmental influences trigger changes in synaptic plasticity that will play a crucial role in the formation and refinement of brain circuits and their functions in adulthood. One of the greatest challenges of present neuroscience is to try to explain how synaptic connections change and cortical maps are formed and modified to generate the most suitable adaptive behavior after different external stimuli. Adenosine is emerging as a key player in these plastic changes at different brain areas. Here, we review the current knowledge of the mechanisms responsible for the induction and duration of synaptic plasticity at different postnatal brain development stages in which adenosine, probably released by astrocytes, directly participates in the induction of long-term synaptic plasticity and in the control of the duration of plasticity windows at different cortical synapses. In addition, we comment on the role of the different adenosine receptors in brain diseases and on the potential therapeutic effects of acting via adenosine receptors.

An Assessment of Physical and N6-Cyclohexyladenosine-Induced Hypothermia in Rodent Distal Focal Ischemic Stroke

Therapeutic hypothermia (TH) mitigates damage in ischemic stroke models. However, safer and easier TH methods (e.g., pharmacological) are needed to circumvent physical cooling complications. This study evaluated systemic and pharmacologically induced TH using the adenosine A1 receptor agonist, N6-cyclohexyladenosine (CHA), with control groups in male Sprague-Dawley rats. CHA was administered intraperitoneally 10 minutes following a 2-hour intraluminal middle cerebral artery occlusion. We used a 1.5 mg/kg induction dose, followed by three 1.0 mg/kg doses every 6 hours for a total of 4 doses, causing 20-24 hours of hypothermia. Animals assigned to physical hypothermia and CHA-hypothermia had similar induction rates and nadir temperatures, but forced cooling lasted ∼6 hours longer compared with CHA-treated animals. The divergence is likely attributable to individual differences in CHA metabolism, which led to varied durations at nadir, whereas physical hypothermia was better regulated. Physical hypothermia significantly reduced infarction (primary endpoint) on day 7 (mean reduction of 36.8 mm3 or 39% reduction; p = 0.021 vs. normothermic animals; Cohen's d = 0.75), whereas CHA-induced hypothermia did not (p = 0.33). Similarly, physical cooling improved neurological function (physical hypothermia median = 0, physical normothermia median = 2; p = 0.008) and CHA-induced cooling did not (p > 0.99). Our findings demonstrate that forced cooling was neuroprotective compared with controls, but prolonged CHA-induced cooling was not neuroprotective.

Impairment of adenosine signaling disrupts early embryo development: unveiling the underlying mechanisms

Purinergic signaling has been implicated in many biological functions, including development. In this study, we investigate the functions of extracellular adenosine and adenosine receptors using a mouse embryonic stem cell (ESC) line and morula stages isolated from mouse embryos. Feeder-free mouse ESC was investigated in the absence and presence of the leukemia inhibitory factor (LIF), configuring undifferentiated cells and cells undergoing spontaneous differentiation. High alkaline phosphatase (ALPL) and low CD73 levels resulting in low adenosine (eADO) levels were characteristic for pluripotent cells in the presence of the LIF, while LIF deprivation resulted in augmented adenosine levels and reduced pluripotency marker expression, which indicated differentiation. Tracing ESC proliferation by BrdU labeling revealed that the inhibition of ALPL by levamisole resulted in a decrease in proliferation due to less eADO accumulation. Furthermore, caffeine and levamisole treatment, inhibiting adenosine receptor and eADO accumulation, respectively, reduced ESC migration, similar to that observed in the absence of the LIF. Pharmacological approaches of selective adenosine receptor subtype inhibition triggered specific adenosine receptor activities, thus triggering calcium or MAP kinase pathways leading to differentiation. In line with the in vitro data, mouse embryos at the morula stage were sensitive to treatments with A1 and A3 receptor antagonists, leading to the conclusion that A1 receptor and A3 receptor inhibition impairs proliferation and self-renewal and triggers inappropriate differentiation, respectively. The findings herein define the functions of eADO signaling in early development with implications for developmental disorders, in which adenosine receptors or ectonucleotidase dysfunctions are involved, and which could lead to malformations and miscarriages, due to exposure to caffeine.

Current therapeutic targets and multifaceted physiological impacts of caffeine

Caffeine, which shares consubstantial structural similarity with purine adenosine, has been demonstrated as a nonselective adenosine receptor antagonist for eliciting most of the biological functions at physiologically relevant dosages. Accumulating evidence supports caffeine's beneficial effects against different disorders, such as total cardiovascular diseases and type 2 diabetes. Conversely, paradoxical effects are also linked to caffeine ingestion in humans including hypertension-hypotension and tachycardia-bradycardia. These observations suggest the association of caffeine action with its ingested concentration and/or concurrent interaction with preferential molecular targets to direct explicit events in the human body. Thus, a coherent analysis of the functional targets of caffeine, relevant to normal physiology, and disease pathophysiology, is required to understand the pharmacology of caffeine. This review provides a broad overview of the experimentally validated targets of caffeine, particularly those of therapeutic interest, and the impacts of caffeine on organ-specific physiology and pathophysiology. Overall, the available empirical and epidemiological evidence supports the dose-dependent functional activities of caffeine and advocates for further studies to get insights into the caffeine-induced changes under specific conditions, such as asthma, DNA repair, and cancer, in view of its therapeutic applications.

Advances in Therapies to Treat Neonatal Hypoxic-Ischemic Encephalopathy

Neonatal hypoxic-ischemic encephalopathy (HIE) is a condition that results in brain damage in newborns due to insufficient blood and oxygen supply during or after birth. HIE is a major cause of neurological disability and mortality in newborns, with over one million neonatal deaths occurring annually worldwide. The severity of brain injury and the outcome of HIE depend on several factors, including the cause of oxygen deprivation, brain maturity, regional blood flow, and maternal health conditions. HIE is classified into mild, moderate, and severe categories based on the extent of brain damage and resulting neurological issues. The pathophysiology of HIE involves different phases, including the primary phase, latent phase, secondary phase, and tertiary phase. The primary and secondary phases are characterized by episodes of energy and cell metabolism failures, increased cytotoxicity and apoptosis, and activated microglia and inflammation in the brain. A tertiary phase occurs if the brain injury persists, characterized by reduced neural plasticity and neuronal loss. Understanding the cellular and molecular aspects of the different phases of HIE is crucial for developing new interventions and therapeutics. This review aims to discuss the pathophysiology of HIE, therapeutic hypothermia (TH), the only approved therapy for HIE, ongoing developments of adjuvants for TH, and potential future drugs for HIE.

Mechanisms of action of coffee bioactive compounds - a key to unveil the coffee paradox

The knowledge of the relationship between the chemical structure of food components with their mechanisms of action is crucial for the understanding of diet health benefits. This review relates the chemical variability present in coffee beverages with the mechanisms involved in key physiological events, supporting coffee as a polyvalent functional food. Coffee intake has been related with several health-promoting properties such as neuroprotective (caffeine, chlorogenic acids and melanoidins), anti-inflammatory (caffeine, chlorogenic acids, melanoidins, diterpenes), microbiota modulation (polysaccharides, melanoidins, chlorogenic acids), immunostimulatory (polysaccharides), antidiabetic (trigonelline, chlorogenic acids), antihypertensive (chlorogenic acids) and hypocholesterolemic (polysaccharides, chlorogenic acids, lipids). Nevertheless, caffeine and diterpenes are coffee components with ambivalent effects on health. Additionally, a large range of potentially harmful compounds, including acrylamide, hydroxymethylfurfural, furan, and advanced glycation end products, are formed during the roasting of coffee and are present in the beverages. However, coffee beverages are part of the daily human dietary healthy habits, configuring a coffee paradox.

Analysis of genetically determined gene expression suggests role of inflammatory processes in exfoliation syndrome

BACKGROUND

Exfoliation syndrome (XFS) is an age-related systemic disorder characterized by excessive production and progressive accumulation of abnormal extracellular material, with pathognomonic ocular manifestations. It is the most common cause of secondary glaucoma, resulting in widespread global blindness. The largest global meta-analysis of XFS in 123,457 multi-ethnic individuals from 24 countries identified seven loci with the strongest association signal in chr15q22-25 region near LOXL1. Expression analysis have so far correlated coding and a few non-coding variants in the region with LOXL1 expression levels, but functional effects of these variants is unclear. We hypothesize that analysis of the contribution of the genetically determined component of gene expression to XFS risk can provide a powerful method to elucidate potential roles of additional genes and clarify biology that underlie XFS.

RESULTS

Transcriptomic Wide Association Studies (TWAS) using PrediXcan models trained in 48 GTEx tissues leveraging on results from the multi-ethnic and European ancestry GWAS were performed. To eliminate the possibility of false-positive results due to Linkage Disequilibrium (LD) contamination, we i) performed PrediXcan analysis in reduced models removing variants in LD with LOXL1 missense variants associated with XFS, and variants in LOXL1 models in both multiethnic and European ancestry individuals, ii) conducted conditional analysis of the significant signals in European ancestry individuals, and iii) filtered signals based on correlated gene expression, LD and shared eQTLs, iv) conducted expression validation analysis in human iris tissues. We observed twenty-eight genes in chr15q22-25 region that showed statistically significant associations, which were whittled down to ten genes after statistical validations. In experimental analysis, mRNA transcript levels for ARID3B, CD276, LOXL1, NEO1, SCAMP2, and UBL7 were significantly decreased in iris tissues from XFS patients compared to control samples. TWAS genes for XFS were significantly enriched for genes associated with inflammatory conditions. We also observed a higher incidence of XFS comorbidity with inflammatory and connective tissue diseases.

CONCLUSION

Our results implicate a role for connective tissues and inflammation pathways in the etiology of XFS. Targeting the inflammatory pathway may be a potential therapeutic option to reduce progression in XFS.

Synergistic Effect of Rhodiola rosea and Caffeine Supplementation on the Improvement of Muscle Strength and Muscular Endurance: A Pilot Study for Rats, Resistance Exercise-Untrained and -Trained Volunteers

Multi-level studies have shown that Rhodiola rosea (RHO) and Caffeine (CAF) have the potential to be nutritional supplements to enhance physical performance in resistance exercise-untrained and -trained subjects. This study examined the synergistic effects of RHO (262.7 mg/kg for rats and 2.4 g for volunteers) and CAF (19.7 mg/kg for rats and 3 mg/kg for volunteers) supplementation on improving physical performance in rats, resistance exercise-untrained volunteers and resistance exercise-trained volunteers. Rats and volunteers were randomly grouped into placebo, CAF, RHO and CAF+RHO and administered accordingly with the nutrients during the training procedure, and pre- and post-measures were collected. We found that RHO+CAF was effective in improving forelimb grip strength (13.75%), erythropoietin (23.85%), dopamine (12.65%) and oxygen consumption rate (9.29%) in the rat model. Furthermore, the current results also indicated that the combination of RHO+CAF significantly increased the bench press one-repetition maximum (1RM) (16.59%), deep squat 1RM (15.75%), maximum voluntary isometric contraction (MVIC) (14.72%) and maximum repetitions of 60% 1RM bench press (22.15%) in resistance exercise-untrained volunteers. Additionally, despite the excellent base level of the resistance exercise-trained volunteers, their deep squat 1RM and MVIC increased substantially through the synergistic effect of RHO and CAF. In conclusion, combined supplementation of RHO+CAF is more beneficial in improving the resistance exercise performance for both resistance exercise-untrained and -trained volunteers. The present results provide practical evidence that the synergies of RHO and CAF could serve as potential supplementary for individuals, especially resistance exercise-trained subjects, to ameliorate their physical performances effectively and safely.

Therapeutic Use and Chronic Abuse of CNS Stimulants and Anabolic Drugs

The available evidence suggests that affective disorders, such as depression and anxiety, increase risk for accelerated cognitive decline and late-life dementia in aging individuals. Behavioral neuropsychology studies also showed that cognitive decline is a central feature of aging impacting the quality of life. Motor deficits are common after traumatic brain injuries and stroke, affect subjective well-being, and are linked with reduced quality of life. Currently, restorative therapies that target the brain directly to restore cognitive and motor tasks in aging and disease are available. However, the very same drugs used for therapeutic purposes are employed by athletes as stimulants either to increase performance for fame and financial rewards or as recreational drugs. Unfortunately, most of these drugs have severe side effects and pose a serious threat to the health of athletes. The use of performance-enhancing drugs by children and teenagers has increased tremendously due to the decrease in the age of players in competitive sports and the availability of various stimulants in many forms and shapes. Thus, doping may cause serious health-threatening conditions including, infertility, subdural hematomas, liver and kidney dysfunction, peripheral edema, cardiac hypertrophy, myocardial ischemia, thrombosis, and cardiovascular disease. In this review, we focus on the impact of doping on psychopathological disorders, cognition, and depression. Occasionally, we also refer to chronic use of therapeutic drugs to increase physical performance and highlight the underlying mechanisms. We conclude that raising awareness on the health risks of doping in sport for all shall promote an increased awareness for healthy lifestyles across all generations.

Plasma Caffeine Levels and Risk of Alzheimer's Disease and Parkinson's Disease: Mendelian Randomization Study

We leveraged genetic variants associated with caffeine metabolism in the two-sample Mendelian randomization framework to investigate the effect of plasma caffeine levels on the risk of Alzheimer’s disease and Parkinson’s disease. Genetic association estimates for the outcomes were obtained from the International Genomics of Alzheimer’s Project, the International Parkinson’s Disease Genomics consortium, the FinnGen consortium, and the UK Biobank. Genetically predicted higher plasma caffeine levels were associated with a non-significant lower risk of Alzheimer’s disease (odds ratio 0.87; 95% confidence interval 0.76, 1.00; p = 0.056). A suggestive association was observed for genetically predicted higher plasma caffeine levels and lower risk of Parkinson’s disease in the FinnGen consortium. but not in the International Parkinson’s Disease Genomics consortium; no overall association was found (odds ratio 0.92; 95% confidence interval 0.77, 1.10; p = 0.347). This study found possible suggestive evidence of a protective role of caffeine in Alzheimer’s disease. The association between caffeine and Parkinson’s disease requires further study.

Aloe arborescens: In Vitro Screening of Genotoxicity, Effective Inhibition of Enzyme Characteristics for Disease Etiology, and Microbiological Activity

The present study assessed the genotoxicity, the possibility of inhibiting selected enzymes, and the microbial activity of lyophilisate from 3-year-old A. arborescens leaves obtained from controlled crops. The lyophilisate from 3-year-old A. arborescens leaves was standardized for aloin A and aloenin A content. Moreover, concentrations of polyphenolic compounds and phenolic acids were determined. The first stage of the research was to determine genotoxicity using the comet test, which confirmed the safety of A. arborescens. Assays of enzymatic inhibition were performed for hyaluronidase (IC50 = 713.24 ± 41.79 µg/mL), α-glucosidase (IC50 = 598.35 ± 12.58 µg/mL), acetylcholinesterase and butyrylcholinesterase (1.16 vs. 0.34 µM of eserine/g d.m., respectively). The next stage of the research was to determine the ability of the healing properties using the scratch test, which showed a positive response using the extract. Microbial activity was evaluated and obtained against Gram-negative and Gram-positive bacteria and yeasts. We concluded that A. arborescens leaf gel meets the important conditions for plant raw materials to obtain semi-solid forms of herbal medicinal products.

Higher Coffee Consumption Is Associated With Reduced Cerebral Gray Matter Volume: A Mendelian Randomization Study

Background

Recently published two-sample Mendelian randomization (MR) studies showed that genetically predicted coffee consumption may be associated with increased risk of Alzheimer’s disease and intracerebral hemorrhage but associated with a decreased risk of small vessel ischemic stroke. We aimed to investigate the effects of genetically predicted coffee consumption on magnetic resonance imaging (MRI) markers of cerebral small vessel disease and brain volume using the two-sample MR method.

Methods

Twelve single nucleotide polymorphisms (SNPs) in up to 375,833 individuals were used as genetic instruments for cups consumed per day of coffee. Another four SNPs from an independent sample were used to perform the replication analysis. Three SNPs in up to 45,821 individuals were used as genetic instruments for high coffee consumption vs. low/no coffee consumption.

Results

Mendelian randomization analysis showed that coffee consumption (cups/day) was inversely associated with gray matter volume (beta = −0.371, 95% CI = −0.596 to −0.147, p = 0.001). Replication analysis and multivariable analyses after adjusting for other risk factors confirmed the effect. High coffee consumption was also suggestively associated with decreased gray matter volume (beta = −0.061, 95% CI = −0.109 to −0.013, p = 0.013) compared with low/no coffee consumption. All analyses did not find an effect of coffee consumption on other outcomes including white matter hyperintensity volume, mean diffusivity, fractional anisotropy, brain microbleed, total brain volume, white matter volume, and hippocampus volume.

Conclusion

This two-sample MR study showed that genetically predicted higher coffee consumption is causally associated with reduced gray matter volume of the brain.

Optimization of 2-Amino-4,6-diarylpyrimidine-5-carbonitriles as Potent and Selective A1 Antagonists

We herein document a large collection of 108 2-amino-4,6-disubstituted-pyrimidine derivatives as potent, structurally simple, and highly selective A₁AR ligands. The most attractive ligands were confirmed as antagonists of the canonical cyclic adenosine monophosphate pathway, and some pharmacokinetic parameters were preliminarilly evaluated. The library, built through a reliable and efficient three-component reaction, comprehensively explored the chemical space allowing the identification of the most prominent features of the structure–activity and structure–selectivity relationships around this scaffold. These included the influence on the selectivity profile of the aromatic residues at positions R⁴ and R⁶ of the pyrimidine core but most importantly the prominent role to the unprecedented A₁AR selectivity profile exerted by the methyl group introduced at the exocyclic amino group. The structure–activity relationship trends on both A₁ and A_2AARs were conveniently interpreted with rigorous free energy perturbation simulations, which started from the receptor-driven docking model that guided the design of these series.

Adenosine A2A Receptor Occupancy by Caffeine After Coffee Intake in Parkinson's Disease

Background

Coffee intake can decrease the risk for Parkinson's disease (PD). Its beneficial effects are allegedly mediated by caffeine through adenosine A_2A receptor (A_2AR) antagonist action.

Objective

We aimed to calculate occupancy rates of striatal A_2ARs by caffeine after coffee intake in PD.

Methods

Five patients with PD underwent ¹¹C‐preladenant positron emission tomography scanning at baseline and after intake of coffee containing 129.5 mg (n = 3) or 259 mg (n = 2) of caffeine. Concurrently, serum caffeine levels were measured.

Results

The mean serum caffeine level (μg/mL) was 0.374 at baseline and increased to 4.48 and 8.92 by 129.5 and 259 mg of caffeine, respectively. The mean occupancy rates of striatal A_2ARs by 129.5 and 259 mg of caffeine were 54.2% and 65.1%, respectively.

Conclusions

A sufficient A_2AR occupancy can be obtained by drinking a cup of coffee, which is equivalent to approximately 100 mg of caffeine. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

The mechanism of microglia-mediated immune inflammation in ischemic stroke and the role of natural botanical components in regulating microglia: A review

Ischemic stroke (IS) is one of the most fatal diseases. Neuroimmunity, inflammation, and oxidative stress play important roles in various complex mechanisms of IS. In particular, the early proinflammatory response resulting from the overactivation of resident microglia and the infiltration of circulating monocytes and macrophages in the brain after cerebral ischemia leads to secondary brain injury. Microglia are innate immune cells in the brain that constantly monitor the brain microenvironment under normal conditions. Once ischemia occurs, microglia are activated to produce dual effects of neurotoxicity and neuroprotection, and the balance of the two effects determines the fate of damaged neurons. The activation of microglia is defined as the classical activation (M1 type) or alternative activation (M2 type). M1 type microglia secrete pro-inflammatory cytokines and neurotoxic mediators to exacerbate neuronal damage, while M2 type microglia promote a repairing anti-inflammatory response. Fine regulation of M1/M2 microglial activation to minimize damage and maximize protection has important therapeutic value. This review focuses on the interaction between M1/M2 microglia and other immune cells involved in the regulation of IS phenotypic characteristics, and the mechanism of natural plant components regulating microglia after IS, providing novel candidate drugs for regulating microglial balance and IS drug development.

Caenorhabditis elegans provides an efficient drug screening platform for GNAO1-related disorders and highlights the potential role of caffeine in controlling dyskinesia

Dominant GNAO1 mutations cause an emerging group of childhood-onset neurological disorders characterized by developmental delay, intellectual disability, movement disorders, drug-resistant seizures and neurological deterioration. GNAO1 encodes the α-subunit of an inhibitory GTP/GDP-binding protein regulating ion channel activity and neurotransmitter release. The pathogenic mechanisms underlying GNAO1-related disorders remain largely elusive and there are no effective therapies. Here, we assessed the functional impact of two disease-causing variants associated with distinct clinical features, c.139A > G (p.S47G) and c.662C > A (p.A221D), using Caenorhabditis elegans as a model organism. The c.139A > G change was introduced into the orthologous position of the C. elegans gene via CRISPR/Cas9, whereas a knock-in strain carrying the p.A221D variant was already available. Like null mutants, homozygous knock-in animals showed increased egg laying and were hypersensitive to aldicarb, an inhibitor of acetylcholinesterase, suggesting excessive neurotransmitter release by different classes of motor neurons. Automated analysis of C. elegans locomotion indicated that goa-1 mutants move faster than control animals, with more frequent body bends and a higher reversal rate and display uncoordinated locomotion. Phenotypic profiling of heterozygous animals revealed a strong hypomorphic effect of both variants, with a partial dominant-negative activity for the p.A221D allele. Finally, caffeine was shown to rescue aberrant motor function in C. elegans harboring the goa-1 variants; this effect is mainly exerted through adenosine receptor antagonism. Overall, our findings establish a suitable platform for drug discovery, which may assist in accelerating the development of new therapies for this devastating condition, and highlight the potential role of caffeine in controlling GNAO1-related dyskinesia.

Memory enhancement with stimulants: Differential neural effects of methylphenidate, modafinil, and caffeine. A pilot study

Human memory is susceptible to manipulation in many respects. While consolidation is well known to be prone to disruption, there is also growing evidence for the enhancement of memory function. Beside cognitive strategies and mnemonic training, the use of stimulants may improve memory processing in healthy adults. In this single-dose, double-blind, within-subject, randomized, placebo-controlled pilot study, 20 mg methylphenidate (N = 13) or 200 mg modafinil (N = 12) or 200 mg caffeine (N = 14) were administrated to in total 39 healthy participants while performing a declarative memory task. Each participant received only one substance and functional magnetic resonance imaging (fMRI) was used to assess drug-dependent memory effects of the substance for encoding and recognition compared to task-related activation under placebo. While methylphenidate showed some behavioral effect regarding memory recall performance, on the neural level, methylphenidate-dependent deactivations were found in fronto-parietal and temporal regions during recognition of previously learned words. No BOLD alterations were seen during encoding. Caffeine led to deactivations in the precentral gyrus during encoding whereas modafinil did not show any BOLD signal alterations at all. These results should be interpreted with caution since this a pilot study with several limitations, most importantly the small number of participants per group. However, our main finding of task-related deactivations may point to a drug-dependent increase of efficiency in physiological response to memory processing.

Response to Hypoxia in Cognitive Decline

Inflammaging, the increase of proinflammatory processes with increasing age, has multiple mechanisms from increasing numbers of senescent cells secreting cytokines to changes in metabolic processes. Alterations of oxygen metabolism with aging, especially decreased levels of O₂ with age resulting from endocrine and cardiovascular dysfunction as well as desensitization of cellular response to hypoxia, may exacerbate inflammaging, which in turn creates further oxygen metabolic dysfunction. During aging, decline in levels of erythrocyte 2,3-bisphosphoglycerate (2,3-BPG), BPG mutase, and adenosine A2B receptor, a key adenosine signaling receptor that can augment 2,3-BPG expression, may fail to protect sensitive brain tissue from subtly reduced O₂ levels, in turn resulting in increased numbers of activated microglia and secretion of proinflammatory cytokines, ultimately promoting inflammaging and senescence of endothelial cells. Interventions to restore O₂ levels directly or via increasing 2,3-BPG may help promote cognitive health in old age, but significant work to quantify the degree of reduced O₂ during aging in mammals, and especially humans, needs to be pursued.

Anti-inflammatory Therapy by Cholinergic and Purinergic Modulation in Multiple Sclerosis Associated with SARS-CoV-2 Infection

The virus "acute respiratory syndrome coronavirus 2" (SARS-CoV-2) is the etiologic agent of coronavirus disease 2019 (COVID-19), initially responsible for an outbreak of pneumonia in Wuhan, China, which, due to the high level of contagion and dissemination, has become a pandemic. The clinical picture varies from mild to critical cases; however, all of these signs already show neurological problems, from sensory loss to neurological diseases. Thus, patients with multiple sclerosis (MS) infected with the new coronavirus are more likely to develop severe conditions; in addition to worsening the disease, this is due to the high level of pro-inflammatory cytokines, which is closely associated with increased mortality both in COVID-19 and MS. This increase is uncontrolled and exaggerated, characterizing the cytokine storm, so a possible therapy for this neuronal inflammation is the modulation of the cholinergic anti-inflammatory pathway, since acetylcholine (ACh) acts to reduce pro-inflammatory cytokines and acts directly on the brain for being released by cholinergic neurons, as well as acting on other cells such as immune and blood cells. In addition, due to tissue damage, there is an exacerbated release of adenosine triphosphate (ATP), potentiating the inflammatory process and activating purinergic receptors which act directly on neuroinflammation and positively modulate the inflammatory cycle. Associated with this, in neurological pathologies, there is greater expression of P2X7 in the cells of the microglia, which positively activates the immune inflammatory response. Thus, the administration of blockers of this receptor can act in conjunction with the action of ACh in the anticholinergic inflammatory pathway. Finally, there will be a reduction in the cytokine storm and triggered hyperinflammation, as well as the level of mortality in patients with multiple sclerosis infected with SARS-CoV-2 and the development of possible neurological damage.

High coffee consumption, brain volume and risk of dementia and stroke

BACKGROUND

Coffee is a highly popular beverage worldwide, containing caffeine which is a central nervous system stimulant.

OBJECTIVES

We examined whether habitual coffee consumption is associated with differences in brain volumes or the odds of dementia or stroke.

METHODS

We conducted prospective analyses of habitual coffee consumption on 398,646 UK Biobank participants (age 37-73 years), including 17,702 participants with MRI information. We examined the associations with brain volume using covariate adjusted linear regression, and with odds of dementia (4,333 incident cases) and stroke (6,181 incident cases) using logistic regression.

RESULTS

There were inverse linear associations between habitual coffee consumption and total brain (fully adjusted β per cup -1.42, 95% CI -1.89, -0.94), grey matter (β -0.91, 95% CI -1.20, -0.62), white matter (β -0.51, 95% CI -0.83, -0.19) and hippocampal volumes (β -0.01, 95% CI -0.02, -0.003), but no evidence to support an association with white matter hyperintensity (WMH) volume (β -0.01, 95% CI -0.07, 0.05). The association between coffee consumption and dementia was non-linear (P_{non-linearity}= 0.0001), with evidence for higher odds for non-coffee and decaffeinated coffee drinkers and those drinking >6 cups/day, compared to light coffee drinkers. After full covariate adjustment, consumption of >6 cups/day was associated with 53% higher odds of dementia compared to consumption of 1-2 cups/day (fully adjusted OR 1.53, 95% CI 1.28, 1.83), with less evidence for an association with stroke (OR 1.17, 95% CI 1.00, 1.37, p= 0.055).

CONCLUSION

High coffee consumption was associated with smaller total brain volumes and increased odds of dementia.

Erythrocyte adenosine A2B receptor prevents cognitive and auditory dysfunction by promoting hypoxic and metabolic reprogramming

Hypoxia drives aging and promotes age-related cognition and hearing functional decline. Despite the role of erythrocytes in oxygen (O2) transport, their role in the onset of aging and age-related cognitive decline and hearing loss (HL) remains undetermined. Recent studies revealed that signaling through the erythrocyte adenosine A2B receptor (ADORA2B) promotes O2 release to counteract hypoxia at high altitude. However, nothing is known about a role for erythrocyte ADORA2B in age-related functional decline. Here, we report that loss of murine erythrocyte-specific ADORA2B (eAdora2b-/-) accelerates early onset of age-related impairments in spatial learning, memory, and hearing ability. eAdora2b-/- mice display the early aging-like cellular and molecular features including the proliferation and activation of microglia and macrophages, elevation of pro-inflammatory cytokines, and attenuation of hypoxia-induced glycolytic gene expression to counteract hypoxia in the hippocampus (HIP), cortex, or cochlea. Hypoxia sufficiently accelerates early onset of cognitive and cochlear functional decline and inflammatory response in eAdora2b-/- mice. Mechanistically, erythrocyte ADORA2B-mediated activation of AMP-activated protein kinase (AMPK) and bisphosphoglycerate mutase (BPGM) promotes hypoxic and metabolic reprogramming to enhance production of 2,3-bisphosphoglycerate (2,3-BPG), an erythrocyte-specific metabolite triggering O2 delivery. Significantly, this finding led us to further discover that murine erythroblast ADORA2B and BPGM mRNA levels and erythrocyte BPGM activity are reduced during normal aging. Overall, we determined that erythrocyte ADORA2B-BPGM axis is a key component for anti-aging and anti-age-related functional decline.

Urinary biomarkers indicative of recovery from spinal cord injury: A pilot study

Current assessments of recovery following spinal cord injury (SCI) focus on clinical outcome measures. These assessments bear an inherent risk of bias, emphasizing the need for more reliable prognostic biomarkers to measure SCI severity. This study evaluated fluid biomarkers as an objective tool to aid with prognosticating outcomes following SCI. Using a 1H nuclear magnetic resonance (NMR)-based quantitative metabolomics approach of urine samples, the objectives were to determine (a) if alterations in metabolic profiles reflect the extent of recovery of individual SCI patients, (b) whether changes in urine metabolites correlate to patient outcomes, and (c) whether biological pathway analysis reflects mechanisms of neural damage and repair. An inception cohort exploratory pilot study collected morning urine samples from male SCI patients (n=6) following injury and again at 6-months post-injury. A 700 MHz Bruker Avance III HD NMR spectrometer was used to acquire the metabolic signatures of urine samples, which were used to derive metabolic pathways. Multivariate statistical analyses were used to identify changes in metabolic signatures, which were correlated to clinical outcomes in the Spinal Cord Independence Measure (SCIM). Among SCI-induced metabolic changes, biomarkers which significantly correlated to patient SCIM scores included caffeine (R = -0.76, p < 0.01), 3-hydroxymandelic acid (R= -0.85, p < 0.001), L-valine (R = 0.90, p < 0.001; R = -0.64, p < 0.05), and N-methylhydantoin (R = -0.90, p < 0.001). The most affected pathway was purine metabolism. These findings indicate that urinary metabolites reflect SCI lesion severity and recovery and provide potentially prognostic biomarkers of SCI outcome in precision medicine approaches.

Multi-target Natural and Nature-Inspired Compounds against Neurodegeneration: A Focus on Dual Cholinesterase and Phosphodiesterase Inhibitors

Alzheimer’s disease is a memory-related neurodegenerative condition leading to cognitive impairment. Cholinergic deficit, together with other underlying mechanisms, leads the to onset and progression of the disease. Consequently, acetylcholinesterase inhibitors are used for the symptomatic treatment of dementia, even if limited efficacy is observed. More recently, some specific phosphodiesterase isoforms emerged as promising, alternative targets for developing inhibitors to contrast neurodegeneration. Phosphodiesterase isoforms 4, 5 and 9 were found to be expressed in brain regions that are relevant for cognition. Given the complex nature of Alzheimer’s disease and the combination of involved biochemical mechanisms, the development of polypharmacological agents acting on more than one pathway is desirable. This review provides an overview of recent reports focused on natural and Nature-inspired small molecules, or plant extracts, acting as dual cholinesterase and phosphodiesterase inhibitors. In the context of the multi-target directed ligand approach, such molecules would pave the way for the development of novel agents against neurodegeneration. More precisely, according to the literature data, xanthines, other alkaloids, flavonoids, coumarins and polyphenolic acids represent promising scaffolds for future optimization.

Acute visceral pain relief mediated by A3AR agonists in rats: involvement of N-type voltage-gated calcium channels

ABSTRACT

Pharmacological tools for chronic visceral pain management are still limited and inadequate. A3 adenosine receptor (A3AR) agonists are effective in different models of persistent pain. Recently, their activity has been related to the block of N-type voltage-gated Ca2+ channels (Cav2.2) in dorsal root ganglia (DRG) neurons. The present work aimed to evaluate the efficacy of A3AR agonists in reducing postinflammatory visceral hypersensitivity in both male and female rats. Colitis was induced by the intracolonic instillation of 2,4-dinitrobenzenesulfonic acid (DNBS; 30 mg in 0.25 mL 50% EtOH). Visceral hypersensitivity was assessed by measuring the visceromotor response and the abdominal withdrawal reflex to colorectal distension. The effects of A3AR agonists (MRS5980 and Cl-IB-MECA) were evaluated over time after DNBS injection and compared to that of the selective Cav2.2 blocker PD173212, and the clinically used drug linaclotide. A3AR agonists significantly reduced DNBS-evoked visceral pain both in the postinflammatory (14 and 21 days after DNBS injection) and persistence (28 and 35 days after DNBS) phases. Efficacy was comparable to effects induced by linaclotide. PD173212 fully reduced abdominal hypersensitivity to control values, highlighting the role of Cav2.2. The effects of MRS5980 and Cl-IB-MECA were completely abolished by the selective A3AR antagonist MRS1523. Furthermore, patch-clamp recordings showed that A3AR agonists inhibited Cav2.2 in dorsal root ganglia neurons isolated from either control or DNBS-treated rats. The effect on Ca2+ current was PD173212-sensitive and prevented by MRS1523. A3AR agonists are effective in relieving visceral hypersensitivity induced by DNBS, suggesting a potential therapeutic role against abdominal pain.

Caffeine and Its Neuroprotective Role in Ischemic Events: A Mechanism Dependent on Adenosine Receptors

Ischemia is characterized by a transient, insufficient, or permanent interruption of blood flow to a tissue, which leads to an inadequate glucose and oxygen supply. The nervous tissue is highly active, and it closely depends on glucose and oxygen to satisfy its metabolic demand. Therefore, ischemic conditions promote cell death and lead to a secondary wave of cell damage that progressively spreads to the neighborhood areas, called penumbra. Brain ischemia is one of the main causes of deaths and summed with retinal ischemia comprises one of the principal reasons of disability. Although several studies have been performed to investigate the mechanisms of damage to find protective/preventive interventions, an effective treatment does not exist yet. Adenosine is a well-described neuromodulator in the central nervous system (CNS), and acts through four subtypes of G-protein-coupled receptors. Adenosine receptors, especially A₁ and A_2A receptors, are the main targets of caffeine in daily consumption doses. Accordingly, caffeine has been greatly studied in the context of CNS pathologies. In fact, adenosine system, as well as caffeine, is involved in neuroprotection effects in different pathological situations. Therefore, the present review focuses on the role of adenosine/caffeine in CNS, brain and retina, ischemic events.

Transcriptional profiling reveals the transcription factor networks regulating the survival of striatal neurons

The striatum is structurally highly diverse, and its organ functionality critically depends on normal embryonic development. Although several studies have been conducted on the gene functional changes that occur during striatal development, a system-wide analysis of the underlying molecular changes is lacking. Here, we present a comprehensive transcriptome profile that allows us to explore the trajectory of striatal development and identify the correlation between the striatal development and Huntington's disease (HD). Furthermore, we applied an integrative transcriptomic profiling approach based on machine learning to systematically map a global landscape of 277 transcription factor (TF) networks. Most of these TF networks are linked to biological processes, and some unannotated genes provide information about the corresponding mechanisms. For example, we found that the Meis2 and Six3 were crucial for the survival of striatal neurons, which were verified using conditional knockout (CKO) mice. Finally, we used RNA-Seq to speculate their downstream targets.

Adenosine Receptor and Its Downstream Targets, Mod(mdg4) and Hsp70, Work as a Signaling Pathway Modulating Cytotoxic Damage in Drosophila

Adenosine (Ado) is an important signaling molecule involved in stress responses. Studies in mammalian models have shown that Ado regulates signaling mechanisms involved in “danger-sensing” and tissue-protection. Yet, little is known about the role of Ado signaling in Drosophila. In the present study, we observed lower extracellular Ado concentration and suppressed expression of Ado transporters in flies expressing mutant huntingtin protein (mHTT). We altered Ado signaling using genetic tools and found that the overexpression of Ado metabolic enzymes, as well as the suppression of Ado receptor (AdoR) and transporters (ENTs), were able to minimize mHTT-induced mortality. We also identified the downstream targets of the AdoR pathway, the modifier of mdg4 (Mod(mdg4)) and heat-shock protein 70 (Hsp70), which modulated the formation of mHTT aggregates. Finally, we showed that a decrease in Ado signaling affects other Drosophila stress reactions, including paraquat and heat-shock treatments. Our study provides important insights into how Ado regulates stress responses in Drosophila.

A Case-Control Study of the Effects of Chimarrão (Ilex paraguariensis) and Coffee on Parkinson's Disease

Introduction: Coffee has been inversely associated with Parkinson's disease (PD) in many studies, and caffeine is the leading candidate to mediate this effect. Mate (Ilex paraguariensis, IP), a caffeinated beverage rich in antioxidants consumed in South America, was also inversely associated with PD in one study from Argentina. Other varieties of IP infusion, such as chimarrão, were never studied in PD. Chimarrão is a common caffeinated beverage consumed in Brazil made with the leaves and stems of IP.

Methods: A case–control study was conducted to evaluate the relationship between chimarrão ingestion and PD in southern Brazil. All subjects answered a questionnaire about the frequency of chimarrão and coffee intake. A multiple regression analysis adjusted for age and sex was performed to assess the association between PD and chimarrão consumption.

Results: We included 200 PD patients and 200 healthy controls. High consumption of chimarrão was inversely associated with PD (OR = 0.44, 95% CI = 0.24–0.81, P = 0.008). High consumption of coffee was also inversely associated with PD, as expected. Chimarrão remained associated when adjusted for coffee consumption, smoking history, and age (OR 0.46, 95% CI = 0.25–0.86, P = 0.014). These two exposures showed an additive effect.

Conclusion:Chimarrão consumption was inversely associated with PD, even after adjusting for coffee intake, suggesting a possible protective role. IP's effect can be mediated by caffeine and through its antioxidant components. Chimarrão has a lower concentration of caffeine compared with coffee and has numerous substances with antioxidative effects that may be important to PD protection. Further studies are needed to test this hypothesis.

Effects of Caffeine on Brown Adipose Tissue Thermogenesis and Metabolic Homeostasis: A Review

The impact of brown adipose tissue (BAT) metabolism on understanding energy balance in humans is a relatively new and exciting field of research. The pathogenesis of obesity can be largely explained by an imbalance between caloric intake and energy expenditure, but the underlying mechanisms are far more complex. Traditional non-selective sympathetic activators have been used to artificially elevate energy utilization, or suppress appetite, however undesirable side effects are apparent with the use of these pharmacological interventions. Understanding the role of BAT, in relation to human energy homeostasis has the potential to dramatically offset the energy imbalance associated with obesity. This review discusses paradoxical effects of caffeine on peripheral adenosine receptors and the possible role of adenosine in increasing metabolism is highlighted, with consideration to the potential of central rather than peripheral mechanisms for caffeine mediated BAT thermogenesis and energy expenditure. Research on the complex physiology of adipose tissue, the embryonic lineage and function of the different types of adipocytes is summarized. In addition, the effect of BAT on overall human metabolism and the extent of the associated increase in energy expenditure are discussed. The controversy surrounding the primary β-adrenoceptor involved in human BAT activation is examined, and suggestions as to the lack of translational findings from animal to human physiology and human in vitro to in vivo models are provided. This review compares and distinguishes human and rodent BAT effects, thus developing an understanding of human BAT thermogenesis to aid lifestyle interventions targeting obesity and metabolic syndrome. The focus of this review is on the effect of BAT thermogenesis on overall metabolism, and the potential therapeutic effects of caffeine in increasing metabolism via its effects on BAT.

Supplementing pregnant Merino ewes with caffeine to improve neonatal lamb thermoregulation and viability

Percentages of lamb mortalities prior to weaning are a significant and persistent problem for the Australian sheep industry. Maternal caffeine supplementation reduced stillbirths and improved viability in piglets; however, the efficacy of caffeine in enhancing viability and lamb survival is equivocal. The aim of this study was to determine the optimal concentration and duration of maternal caffeine supplementation to improve lamb viability; time to stand and suck with consumption of colostrum occurring, as well as survival to weaning. Multiparous Merino ewes were supplemented with either 0 (CTL), 10 (C10) or 20 mg/kg (C20) body weight (BW) caffeine in feed after day 120 of gestation (dG), or 20 mg/kg BW (LC20) caffeine from dG 142 until parturition. Ewes were housed indoors in individual lambing pens from dG 130 to 72 -h post-partum (pp). Values for pp ewe and lamb variables were analysed using a generalised linear mixed model in IBM SPSS version 25. While ewes within the CTL, C10 and LC20 groups consumed more caffeine compared to C20 ewes (P =  0.001), lambs of C20 ewes had greater rectal temperatures at 20 -h pp (P =  0.021), greater 4 -h serum IgG concentrations (P =  0.041), a longer latency to first sucking bout (P =  0.030), and a greater number of sucking attempts (P =  0.044) compared to lambs from CTL, C10 and LC20 ewes. These results indicate that caffeine supplementation during late-gestation stimulates neonatal lambs as a result of increased sucking (4 -h serum IgG) and increased temperatures within the first 24 -h.

Caffeine: A potential strategy to improve survival of neonatal pigs and sheep

Caffeine is commonly used to treat pre-and postnatal injuries, including apnoea in premature infants, as well as neurological impairment caused by hypoxia or asphyxiation often associated with difficult birthing. As an adenosine antagonist, caffeine is metabolised rapidly and transported into many tissues. Caffeine stimulates the brain respiratory centre, improving respiratory function in immature infants or neonates, provides neuroprotection to the fetal brain, and initiates non-shivering thermoregulation increasing metabolic rates. Recently, potential benefits of caffeine for animal production have been investigated. This has particularly occurred in pig production, where large litters are associated with relatively long parturition durations, and piglets born near the end of the parturition period have an increased risk of mortality due to asphyxia-related birthing injury. Similarly, in sheep, dystocia or prolonged parturition is a significant problem, where neonatal injury, dystocia and death in utero contributes to approximately 46 % of lamb mortalities. Within these two livestock production systems, large prevalence's of neonatal mortality is a persistent issue contributing to lost revenue, as well as being a significant animal welfare concern. Pre-partum maternal caffeine supplementation is a promising strategy to reduce neonatal mortality; however, there needs to be refinement of appropriate quantities administered, duration and administration pathway to provide producers with an efficient and cost-effective method to reduce mortality rates and increase production output. The information in this review details effects, benefits and important considerations regarding caffeine use in animal production, and identifies areas of limited knowledge where further research is needed.

Caffeine Effect on Cognitive Function during a Stroop Task: fNIRS Study

Acting as a brain stimulant, coffee resulted in heightening alertness, keeping arousal, improving executive speed, maintaining vigilance, and promoting memory, which are associated with attention, mood, and cognitive function. Functional near-infrared spectroscopy (fNIRS) is a noninvasive optical method to monitor brain activity by measuring the absorption of the near-infrared light through the intact skull. This study is aimed at acquiring brain activation during executing task performance. The aim is to explore the effect of coffee on cognitive function by the fNIRS neuroimaging method, particularly on the prefrontal cortex regions. The behavioral experimental results on 31 healthy subjects with a Stroop task indicate that coffee can easily and effectively modulate the execute task performance by feedback information of the response time and accuracy rate. The findings of fNIRS showed that apparent hemodynamic changes were detected in the bilateral VLPFC regions and the brain activation regions varied with different coffee conditions.

Caffeine reverses the unconsciousness produced by light anesthesia in the continued presence of isoflurane in rats

Currently no drugs are employed clinically to reverse the unconsciousness induced by general anesthetics. Our previous studies showed that caffeine, when given near the end of an anesthesia session, accelerated emergence from isoflurane anesthesia, likely caused by caffeine’s ability to elevate intracellular cAMP levels and to block adenosine receptors. These earlier studies showed that caffeine did not rouse either rats or humans from deep anesthesia (≥ 1 minimum alveolar concentration, MAC). In this current crossover study, we examined whether caffeine reversed the unconsciousness produced by light anesthesia (< 1 MAC) in the continued presence of isoflurane. The primary endpoint of this study was to measure isoflurane levels at the time of recovery of righting reflex, which was a proxy for consciousness. Rats were deeply anesthetized with 2% isoflurane (~1.5 MAC) for 20 minutes. Subsequently, isoflurane was reduced to 1.2% for 10 minutes, then by 0.2% every 10 min; animals were monitored until the recovery of righting reflex occurred, in the continued presence of isoflurane. Respiration rate, heart rate and electroencephalogram (EEG) were monitored. Our results show that caffeine-treated rats recovered their righting reflex at a significantly higher inspired isoflurane concentration, corresponding to light anesthesia, than the same rats treated with saline (control). Respiration rate and heart rate increased initially after caffeine injection but were then unchanged for the rest of the anesthesia session. Deep anesthesia is correlated with burst suppression in EEG recordings. Our data showed that caffeine transiently reduced the burst suppression time produced by deep anesthesia, suggesting that caffeine altered neuronal circuit function but not to a point where it caused arousal. In contrast, under light anesthesia, caffeine shifted the EEG power to high frequency beta and gamma bands. These data suggest that caffeine may represent a clinically viable drug to reverse the unconsciousness produced by light anesthesia.

Spinal Cord Injury: Pathophysiology, Multimolecular Interactions, and Underlying Recovery Mechanisms

Spinal cord injury (SCI) is a destructive neurological and pathological state that causes major motor, sensory and autonomic dysfunctions. Its pathophysiology comprises acute and chronic phases and incorporates a cascade of destructive events such as ischemia, oxidative stress, inflammatory events, apoptotic pathways and locomotor dysfunctions. Many therapeutic strategies have been proposed to overcome neurodegenerative events and reduce secondary neuronal damage. Efforts have also been devoted in developing neuroprotective and neuro-regenerative therapies that promote neuronal recovery and outcome. Although varying degrees of success have been achieved, curative accomplishment is still elusive probably due to the complex healing and protective mechanisms involved. Thus, current understanding in this area must be assessed to formulate appropriate treatment modalities to improve SCI recovery. This review aims to promote the understanding of SCI pathophysiology, interrelated or interlinked multimolecular interactions and various methods of neuronal recovery i.e., neuroprotective, immunomodulatory and neuro-regenerative pathways and relevant approaches.

8-Benzylaminoxanthine scaffold variations for selective ligands acting on adenosine A2A receptors. Design, synthesis and biological evaluation

A library of 34 novel compounds based on a xanthine scaffold was explored in biological studies for interaction with adenosine receptors (ARs). Structural modifications of the xanthine core were introduced in the 8-position (benzylamino and benzyloxy substitution) as well as at N1, N3, and N7 (small alkyl residues), thereby improving affinity and selectivity for the A_2A AR. The compounds were characterized by radioligand binding assays, and our study resulted in the development of the potent A_2A AR ligands including 8-((6-chloro-2-fluoro-3-methoxybenzyl)amino)-1-ethyl-3,7-dimethyl-3,7-dihydro-1H-purine-2,6-dione (12d; K_i human A_2AAR: 68.5 nM) and 8-((2-chlorobenzyl)amino)-1-ethyl-3,7-dimethyl-3,7-dihydro-1H-purine-2,6-dione (12h; K_i human A_2AAR: 71.1 nM). Moreover, dual A₁/A_2AAR ligands were identified in the group of 1,3-diethyl-7-methylxanthine derivatives. Compound 14b displayed K_i values of 52.2 nM for the A₁AR and 167 nM for the A_2AAR. Selected A_2AAR ligands were further evaluated as inactive for inhibition of monoamine oxidase A, B and isoforms of phosphodiesterase-4B1, -10A, which represent classical targets for xanthine derivatives. Therefore, the developed 8-benzylaminoxanthine scaffold seems to be highly selective for AR activity and relevant for potent and selective A_2A ligands. Compound 12d with high selectivity for ARs, especially for the A_2AAR subtype, evaluated in animal models of inflammation has shown anti-inflammatory activity. Investigated compounds were found to display high selectivity and may therefore be of high interest for further development as drugs for treating cancer or neurodegenerative diseases.

The Anti-Inflammatory and Pain-Relieving Effects of AR170, an Adenosine A3 Receptor Agonist, in a Rat Model of Colitis

The pharmacological activation of A₃ receptors has shown potential usefulness in the management of bowel inflammation. However, the role of these receptors in the control of visceral hypersensitivity in the presence of intestinal inflammation has not been investigated. The effects of AR170, a potent and selective A₃ receptor agonist, and dexamethasone (DEX) were tested in rats with 2,4-dinitrobenzene sulfonic acid (DNBS)-induced colitis to assess their tissue inflammatory parameters. The animals received AR170, DEX, or a vehicle intraperitoneally for 6 days, starting 1 day before the induction of colitis. Visceral pain was assessed by recording the abdominal responses to colorectal distension in animals with colitis. Colitis was associated with a decrease in body weight and an increase in spleen weight. The macroscopic damage score and tissue tumor necrosis factor (TNF), interleukin 1β (IL-1β), and myeloperoxidase (MPO) levels were also enhanced. AR170, but not DEX, improved body weight. Both drugs counteracted the increase in spleen weight, ameliorated macroscopic colonic damage, and decreased TNF, IL-1β, and MPO tissue levels. The enhanced visceromotor response (VMR) in rats with colitis was decreased via AR170 administration. In rats with colitis, AR170 counteracted colonic inflammatory cell infiltration and decreased pro-inflammatory cytokine levels, thereby relieving visceral hypersensitivity.

Adenosine Receptors in Modulation of Central Nervous System Disorders

The ubiquitous signaling nucleoside molecule, adenosine is found in different cells of the human body to provide its numerous pharmacological role. The associated actions of endogenous adenosine are largely dependent on conformational change of the widely expressed heterodimeric G-protein-coupled A1, A2A, A2B, and A3 adenosine receptors (ARs). These receptors are well conserved on the surface of specific cells, where potent neuromodulatory properties of this bioactive molecule reflected by its easy passage through the rigid blood-brainbarrier, to simultaneously act on the central nervous system (CNS). The minimal concentration of adenosine in body fluids (30-300 nM) is adequate to exert its neuromodulatory action in the CNS, whereas the modulatory effect of adenosine on ARs is the consequence of several neurodegenerative diseases. Modulatory action concerning the activation of such receptors in the CNS could be facilitated towards neuroprotective action against such CNS disorders. Our aim herein is to discuss briefly pathophysiological roles of adenosine on ARs in the modulation of different CNS disorders, which could be focused towards the identification of potential drug targets in recovering accompanying CNS disorders. Researches with active components with AR modulatory action have been extended and already reached to the bedside of the patients through clinical research in the improvement of CNS disorders. Therefore, this review consist of recent findings in literatures concerning the impact of ARs on diverse CNS disease pathways with the possible relevance to neurodegeneration.

Medicinal Chemistry and Therapeutic Potential of Agonists, Antagonists and Allosteric Modulators of A1 Adenosine Receptor: Current Status and Perspectives

Adenosine is a purine nucleoside, responsible for the regulation of a wide range of physiological and pathophysiological conditions by binding with four G-protein-coupled receptors (GPCRs), namely A1, A2A, A2B and A3 adenosine receptors (ARs). In particular, A1 AR is ubiquitously present, mediating a variety of physiological processes throughout the body, thus represents a promising drug target for the management of various pathological conditions. Agonists of A1 AR are found to be useful for the treatment of atrial arrhythmia, angina, type-2 diabetes, glaucoma, neuropathic pain, epilepsy, depression and Huntington's disease, whereas antagonists are being investigated for the treatment of diuresis, congestive heart failure, asthma, COPD, anxiety and dementia. However, treatment with full A1 AR agonists has been associated with numerous challenges like cardiovascular side effects, off-target activation as well as desensitization of A1 AR leading to tachyphylaxis. In this regard, partial agonists of A1 AR have been found to be beneficial in enhancing insulin sensitivity and subsequently reducing blood glucose level, while avoiding severe CVS side effects and tachyphylaxis. Allosteric enhancer of A1 AR is found to be potent for the treatment of neuropathic pain, culminating the side effects related to off-target tissue activation of A1 AR. This review provides an overview of the medicinal chemistry and therapeutic potential of various agonists/partial agonists, antagonists and allosteric modulators of A1 AR, with a particular emphasis on their current status and future perspectives in clinical settings.

Neferine and lianzixin extracts have protective effects on undifferentiated caffeine-damaged PC12 cells

BACKGROUND

The embryos of Nelumbo nucifera Gaertn seeds, lianzixin, are used in China as food and traditional herbal medicine. Principal therapeutic indications are insomnia, anxiety and pyrexia. Caffeine is a psychostimulant and excessive use predisposes to cell damage and neurotoxicity. We aimed to investigate the potential protect effect of Neferine and lianzixin extracts on undifferentiated caffeine-damaged phaeochromocytoma cells (PC12 cells).

METHODS

A cell damage model based on undifferentiated PC12 was established with caffeine. Effect of Lianzixin extracts (total alkaloids, alcohol extract and water extract) and neferine on caffeine-damaged PC12 cells was evaluated. Cell viability was assessed using the methyl thiazolyl tetrazolium (MTT) assay, cellular morphology by inverted microscope, the nucleus by Hoechst 33342 staining and cleaved poly ADP-ribose polymerase (PARP) expression by western blot analysis.

RESULTS

Lianzixin extracts (total alkaloids, alcohol extract and water extract) and neferine improved the viability of PC12 cells damaged by caffeine. The morphology of PC12 cells pretreated with neferine, or alcohol or water extract of lianzixin aggregated and attached better than caffeine-damaged cells, but cells pretreated with total alkaloids of lianzixin showed abnormal morphology. Compared with caffeine-damaged cells, cells pretreated with neferine, or alcohol or water extract of lianzixin showed a notable increase in nucleus staining and an obvious decrease in cleaved PARP expression.

CONCLUSIONS

Lianzixin extracts and neferine have protective effects against caffeine-induced damage in PC12 cells, which laid a foundation for finding a new medicine value of Lianzixin.

5-Caffeoylquinic Acid Ameliorates Cognitive Decline and Reduces Aβ Deposition by Modulating Aβ Clearance Pathways in APP/PS2 Transgenic Mice

The accumulation of amyloid β (Aβ) in the brain is a major pathological feature of Alzheimer's disease (AD). In our previous study, we demonstrated that coffee polyphenols (CPP) prevent cognitive dysfunction and Aβ deposition in the brain of an APP/PS2 transgenic mouse AD model. The underlying mechanisms, however, remain to be elucidated. Here, we investigated the effects of the chronic administration of 5-caffeoylquinic acid (5-CQA), the most abundant component of CPP, on cognitive dysfunction in APP/PS2 mice to identify the role of CPP in Aβ elimination. Relative to the untreated controls, the mice fed a 5-CQA-supplemented diet showed significant improvements in their cognitive function assessed by Y-maze and novel object recognition tests. Histochemical analysis revealed that 5-CQA substantially reduced Aβ plaque formation and neuronal loss in the hippocampi. Moreover, 5-CQA upregulated the gene encoding low-density lipoprotein receptor-related protein 1, an Aβ efflux receptor, and normalized the perivascular localization of aquaporin 4, which facilitates Aβ clearance along the paravascular pathway. These results suggest that 5-CQA reduces Aβ deposition in the brain by modulating the Aβ clearance pathways and ameliorating cognitive decline and neuronal loss in APP/PS2 mice. Thus, 5-CQA may be effective in preventing cognitive dysfunction in AD.