1,3,7-trimethylxanthine (caffeine) may exacerbate acute inflammatory liver injury by weakening the physiological immunosuppressive mechanism

Moderate or greater daily coffee consumption is associated with lower incidence of metabolic syndrome in Taiwanese militaries: results from the CHIEF cohort study

Background

Daily moderate coffee intake was found with a lower risk of specific metabolic abnormalities, e.g., hypertension and hyperglycemia, while the association of coffee intake and incident metabolic syndrome (MetS) has not been clarified in prior studies, particularly in young adults.

Methods

A total of 2,890 military personnel, aged 18-39 years, free of MetS were followed for incident MetS from baseline (2014) until the end of 2020 in Taiwan. Daily coffee amount consumed was grouped to those ≥3 cups or 600 mL (moderate or more amount) and those without. Incidence of MetS was identified in annual health examinations. MetS was diagnosed on the basis of the guideline of the International Diabetes Federation. Multivariable Cox regression model with adjustments for sex, age, body mass index, physical activity and substance use status at baseline was performed to determine the association.

Results

At baseline, there were 145 subjects with daily coffee intake ≥3 cups or 600 mL (5.0%) in the overall cohort. During a mean follow-up of 6.0 years, 673 incident MetS (23.3%) were found. As compared to those consuming less coffee or none, those consuming daily coffee ≥3 cups had a lower risk of MetS [hazard ratio (HR): 0.69 (95% confidence interval: 0.48, 0.99)].

Conclusion

This study suggests that adhering to the guideline recommended moderate or greater daily coffee consumption for promoting health, may confer advantages in preventing the development of MetS among young adults.

The role of temperature on zebrafish ontogenic development and sensitivity to pharmaceuticals

This study assessed the effects of two emerging environmental pollutants caffeine (CAF) and metformin (METF) on juvenile zebrafish, raised at 22 °C or 27 ºC, after 96 h exposure. The temperature influenced the basal behaviour of unexposed juveniles, with higher swimming activity and a greater percentage of movements at the well edges observed in fish raised at 27 °C. A significant interaction between CAF and temperature was found for behavioural endpoints, but not for AChE activity, associated with neurotoxicity effects. CAF reduced swimming distance, increased erratic swimming, and inhibited AChE activity at 22 ºC, while at 27 ºC, CAF did not affect behaviour but increased AChE. METF exposure at 22 °C decreased swimming distance and increased erratic movements, but at 27 °C no effects were detected. Overall, temperature plays a more important role in the effects induced by CAF than METF.

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.

Hepatotoxicity due to herbal dietary supplements: Past, present and the future

Dietary supplements (DS) constitute a widely used group of products comprising vitamin, mineral, and botanical extract formulations. DS of botanical or herbal origins (HDS) comprise nearly 30% of all DS and are presented on the market either as single plant extracts or multi-extract-containing products. Despite generally safe toxicological profiles of most products currently present on the market, rising cases of liver injury caused by HDS - mostly by multi-ingredient and adulterated products - are of particular concern. Here we discuss the most prominent historical cases of HDS-induced hepatotoxicty - from Ephedra to Hydroxycut and OxyELITE Pro-NF, as well as products with suspected hepatotoxicity that are either currently on or are entering the market. We further provide discussion on overcoming the existing challenges with HDS-linked hepatotoxicity by introduction of advanced in silico, in vitro, in vivo, and microphysiological system approaches to address the matter of safety of those products before they reach the market.

Effects of caffeine on brain antioxidant status and mitochondrial respiration in acetaminophen-intoxicated mice

Hepatic encephalopathy is a pathophysiological complication of acute liver failure, which may be triggered by hepatotoxic drugs such as acetaminophen (APAP). Although APAP is safe in therapeutic concentration, APAP overdose may induce neurotoxicity, which is mainly associated with oxidative stress. Caffeine is a compound widely found in numerous natural beverages. However, the neuroprotective effect of caffeine remains unclear during APAP intoxication. The present study aimed to investigate the possible modulatory effects of caffeine on brain after APAP intoxication. Mice received intraperitoneal injections of APAP (250 mg/kg) and/or caffeine (20 mg/kg) and, 4 h after APAP administration, samples of brain and blood were collected for the biochemical analysis. APAP enhanced the transaminase activity levels in plasma, increased oxidative stress biomarkers (lipid peroxidation and reactive oxygen species), promoted an imbalance in endogenous antioxidant system in brain homogenate and increased the mortality. In contrast, APAP did not induce dysfunction of the mitochondrial bioenergetics. Co-treatment with caffeine modulated the biomarkers of oxidative stress as well as antioxidant system in brain. Besides, survival assays demonstrated that caffeine protective effects could be dose- and time-dependent. In addition, caffeine promoted an increase of mitochondrial bioenergetics response in brain by the enhancement of the oxidative phosphorylation, which could promote a better energy supply necessary for brain recovery. In conclusion, caffeine prevented APAP-induced biochemical alterations in brain and reduced lethality in APAP-intoxicated mice, these effects may relate to the preservation of the cellular antioxidant status, and these therapeutic properties could be useful in the treatment of hepatic encephalopathy induced by APAP intoxication.

Acute Liver Failure Caused by Use of Fat Burner: A Case Report

Acute liver failure is a rare condition consisting of abrupt and extensive hepatocyte injury, leading to significant liver dysfunction associated with a high mortality. Liver transplantation is the most effective treatment in severe cases. The most common cause of acute liver failure in Western countries is drug-induced liver injury caused by prescription drugs and herbal and dietary supplements. Thermogenics, or fat burners, are a category of dietary supplements that claim to increase the resting metabolic rate, leading to weight loss. There are previous reports of acute liver failure associated with specific thermogenic formulations. We report the case of a 36-year-old male patient who developed jaundice 7 days after he started taking a thermogenic dietary supplement (Thermo Gun), with progressive deterioration of hepatic function and development of hepatic encephalopathy 19 days after the beginning of the symptoms. He had a Model for End-Stage Liver Disease score of 38 and fulfilled 4 of the King's College Criteria for poor prognosis in patients with acute liver failure. He underwent liver transplantation, receiving a graft from a cadaveric donor, and is alive with good liver graft function 2 years after the transplant. No possible causes for acute liver injury were identified other than the use of the supplement, which contained N-acetyl-L-tyrosine; 1,3,7-trimenthylxanthine; white willow; and 1-hydroxypholedrine. We found no previous reports in the literature of acute liver failure associated with those particular substances. This manuscript is compliant with the Helsinki Congress and the Istanbul Declaration.

Caffeine Exacerbates Postictal Hypoxia

A stroke-like event follows seizures which may be responsible for the postictal state and a contributing factor to the development of seizure-induced brain abnormalities and behavioral dysfunction associated with epilepsy. Caffeine is the world's most popular drug with ∼85% of people in the USA consuming it daily. Thus, persons with epilepsy are likely to have caffeine in their body and brain during seizures. This preclinical study investigated the effects of acute caffeine on local hippocampal tissue oxygenation pre and post seizure. We continuously measured local oxygen levels in the CA1 region of the hippocampus and utilized the electrical kindling model in rats. Rats were acutely administered either caffeine, or one of its metabolites, or agonists and antagonists at adenosine sub-receptor types or ryanodine receptors prior to the elicitation of seizures. Acute caffeine administration caused a significant drop in pre-seizure hippocampal pO₂. Following a seizure, caffeine, as well as two of its metabolites paraxanthine, and theophylline, increased the time below the severe hypoxic threshold (10 mmHg). Likewise, the specific A_2A receptor antagonist, SCH-58261, mimicked caffeine by causing a significant drop in pre-seizure pO₂ and the area and time below the severe hypoxic threshold. Moreover, the A_2A receptor agonist, CGS-21680 was able to prevent the effect of both caffeine and SCH-58261 adding further evidence that caffeine is likely acting through the A_2A receptor. Clinical tracking and investigations are needed to determine the effect of caffeine on postictal symptomology and blood flow in persons with epilepsy.

Caffeine Modulates Spontaneous Adenosine and Oxygen Changes during Ischemia and Reperfusion

Adenosine is an endogenous neuroprotectant that modulates vasodilation in the central nervous system. Oxygen changes occur when there is an increase in local cerebral blood flow and thus are a measure of vasodilation. Transient oxygen events following rapid adenosine events have been recently discovered, but the relationship between adenosine and blood flow change during ischemia/reperfusion (I/R) has not been characterized. Caffeine is a nonselective adenosine receptor antagonist that can modulate the effects of adenosine in the brain, but how it affects adenosine and oxygen levels during I/R is also unknown. In this study, extracellular changes in adenosine and oxygen were simultaneously monitored using fast-scan cyclic voltammetry during bilateral common carotid artery occlusion (BCCAO) and the effects of a specific A2A antagonist, SCH 442416, or general antagonist, caffeine, were studied. Measurements were made in the caudate-putamen for 1 h of normoxia, followed by 30 min of BCCAO and 30 min of reperfusion. The frequency and number of both adenosine and oxygen transient events significantly increased during I/R. The specific A2A antagonist, SCH 442416 (3 mg/kg, i.p.), eliminated the increase in adenosine and oxygen events caused by I/R. The general adenosine receptor antagonist, caffeine (100 mg/kg, i.p.), decreased the frequency of adenosine and oxygen transient events during I/R. These results demonstrate that, during BCCAO, there are more rapid release events of the neuromodulator adenosine and correlated local oxygen changes, and these rapid, local effects are dampened by caffeine and other A2A antagonists.

Effects of Caffeine Treatment on Hepatopulmonary Syndrome in Biliary Cirrhotic Rats

Hepatopulmonary syndrome (HPS) is a lethal complication of cirrhosis characterized by hypoxia and overt intrapulmonary shunting. In this study, we investigated the effect of caffeine in rats with common bile duct ligation (CBDL)-induced liver cirrhosis and HPS. CBDL rats were randomly allocated to receive caffeine or vehicle for 14 days. On the 28th day after CBDL, mortality rate, hemodynamics, liver, and renal biochemistry parameters and arterial blood gas analysis were evaluated. Lung and liver were dissected for the evaluation of inflammation, angiogenesis and protein expressions. In another series with parallel groups, the intrapulmonary shunting was determined. Caffeine significantly reduced portal pressure (caffeine vs. control: 10.0 ± 3.7 vs. 17.0 ± 8.1 mmHg, p < 0.05) in CBDL rats. The mortality rate, mean arterial pressure, biochemistry data and hypoxia were similar between caffeine-treated and control groups. Caffeine alleviated liver fibrosis and intrahepatic angiogenesis but intrapulmonary inflammation and angiogenesis were not ameliorated. The hepatic VEGF/Rho-A protein expressions were down-regulated but the pulmonary inflammation- and angiogenesis-related protein expressions were not significantly altered by caffeine. Caffeine did not reduce the intrapulmonary shunting, either. Caffeine has been shown to significantly improve liver fibrosis, intrahepatic angiogenesis and portal hypertension in cirrhotic rats, however, it does not ameliorate HPS.

Caffeine programs hepatic SIRT1-related cholesterol synthesis and hypercholesterolemia via A2AR/cAMP/PKA pathway in adult male offspring rats

Clinical and animal studies have indicated that hypercholesterolemia has intrauterine developmental origin. Our previous studies showed that prenatal caffeine exposure (PCE) increased the serum total cholesterol (TCH) levels in adult offspring rats. This study investigates the intrauterine programming mechanism of PCE male offspring rats susceptible to adult hypercholesterolemia. Pregnant Wistar rats were intragastrically administered caffeine (30, 60, and 120 mg/kg∙d) from gestational days (GD) 9 to 20. Male offspring were sacrificed under anesthesia at GD20 and postnatal week (PW) 12, and the serum and liver were collected. The effects of caffeine (0-100 μM, 24 h) on the expression of cholesterol synthesis related genes and their epigenetic mechanisms were confirmed in L02 cells. The results showed that PCE induced higher levels of serum TCH, LDL-C and higher ratios of TCH/HDL-C and LDL-C/HDL-C. Furthermore, the high levels of histone acetylation (via H3K14ac and H3K27ac) and the expression of genes (Srebf2, Hmgcr, Hmgcs1) were responsible for cholesterol synthesis. The results of PCE offspring in utero and the data in vitro exhibited similar changes, and accompanied by the reduced expression of adenosine A2A receptor (A2AR), cyclic adenosine monophosphate (cAMP), sirtuin1 and protein kinase A (PKA). These changes could be reversed by A2AR agonist (CGS-21680), cAMP agonist (forskolin) and sirtuin1 agonist (resveratrol). Therefore, our results confirmed that caffeine could enhance histone acetylation and expression levels of genes responsible for cholesterol synthesis via inhibiting the A2AR/cAMP/PKA pathway and down-regulating sirtuin1, which continued throughout adulthood and elevated hepatic cholesterol synthesis and hypercholesterolemia in the male offspring rats.

Caffeine attenuates brain injury but increases mortality induced by high-intensity blast wave exposure

Caffeine is a substance that is consumed worldwide, and it may exert neuroprotective effects against various cerebral insults, including neurotrauma, which is the most prevalent injury among military personnel. To investigate the effects of caffeine on high-intensity blast wave-induced severe blast injury in mice, three different paradigms of caffeine were applied to male C57BL/6 mice with severe whole body blast injury (WBBI). The results demonstrated that chronic caffeine treatment alleviated blast-induced traumatic brain injury (bTBI); however, both chronic and acute caffeine treatments exacerbated blast-induced lung injuries and, more importantly, increased both the cumulative and time-segmented mortalities postinjury. Interestingly, withdrawing caffeine intake preinjury resulted in favorable outcomes in mortality and lung injury, similar to the findings in water-treated mice, and had the trend to attenuate brain injury. These findings demonstrated that although drinking coffee or caffeine preparations attenuated blast-induced brain trauma, these beverages may place personnel in the battlefield at high risk of casualties, which will help us re-evaluate the therapeutic strategy of caffeine application, particularly in multiple-organ-trauma settings. Furthermore, these findings provided possible strategies for reducing the risk of casualties with caffeine consumption, which may help to change the coffee-drinking habits of military personnel.

Extracellular adenosine: a critical signal in liver fibrosis

Extracellular adenosine nucleoside is a potent, endogenous mediator that signals through specific G protein-coupled receptors, and exerts pleiotropic effects on liver physiology, in health and disease. Particularly, adenosinergic or adenosine-mediated signaling pathways impact the progression of hepatic fibrosis, a common feature of chronic liver diseases, through regulation of matrix deposition by liver myofibroblasts. This review examines the current lines of evidence on adenosinergic regulation of liver fibrosis and myofibroblasts, identifies unanswered research questions, and proposes important future areas of investigation.

Safety assessment of the dietary supplement OxyELITE™ Pro (New Formula) in inbred and outbred mouse strains

Herbal dietary supplements have gained wide acceptance as alternatives to conventional therapeutic agents despite concerns regarding their efficacy and safety. In 2013, a spate of severe liver injuries across the United States was linked to the dietary supplement OxyELITE Pro-New Formula (OEP-NF), a multi-ingredient product marketed for weight loss and exercise performance enhancement. The principal goal of this study was to assess the hepatotoxic potential of OEP-NF in outbred and inbred mouse models. In an acute toxicity study, significant mortality was observed after administering 10X and 3X mouse-equivalent doses (MED) of OEP-NF, respectively. Increases in liver/body weight ratio, ALT and AST were observed in female B6C3F₁ mice after gavaging 2X and 1.5X MED of OEP-NF. Similar findings were observed in a 90-day feeding study. These alterations were paralleled by altered expression of gene- and microRNA-signatures of hepatotoxicity, including Cd36, Nqo1, Aldoa, Txnrd1, Scd1 and Ccng1, as well as miR-192, miR-193a and miR-125b and were most pronounced in female B6C3F₁ mice. Body weight loss, observed at week 1, was followed by weight gain throughout the feeding studies. These findings bolster safety and efficacy concerns for OEP-NF, and argue strongly for implementation of pre-market toxicity studies within the dietary supplement industry.

The effect of caffeine on skeletal muscle anabolic signaling and hypertrophy

Caffeine is a widely consumed stimulant with the potential to enhance physical performance through multiple mechanisms. However, recent in vitro findings have suggested that caffeine may block skeletal muscle anabolic signaling through AMP-activated protein kinase (AMPK)-mediated inhibition of mechanistic target of rapamycin (mTOR) signaling pathway. This could negatively affect protein synthesis and the capacity for muscle growth. The primary purpose of this study was to assess the effect of caffeine on in vivo AMPK and mTOR pathway signaling, protein synthesis, and muscle growth. In cultured C2C12 muscle cells, physiological levels of caffeine failed to impact mTOR activation or myoblast proliferation or differentiation. We found that caffeine administration to mice did not significantly enhance the phosphorylation of AMPK or inhibit signaling proteins downstream of mTOR (p70S6k, S6, or 4EBP1) or protein synthesis after a bout of electrically stimulated contractions. Skeletal muscle-specific knockout of LKB1, the primary AMPK activator in skeletal muscle, on the other hand, eliminated AMPK activation by contractions and enhanced S6k, S6, and 4EBP1 activation before and after contractions. In rats, the addition of caffeine did not affect plantaris hypertrophy induced by the tenotomy of the gastrocnemius and soleus muscles. In conclusion, caffeine administration does not impair skeletal muscle load-induced mTOR signaling, protein synthesis, or muscle hypertrophy.

Effects of caffeine on behavioral and inflammatory changes elicited by copper in zebrafish larvae: Role of adenosine receptors

This study investigated the effects of caffeine in the behavioral and inflammatory alterations caused by copper in zebrafish larvae, attempting to correlate these changes with the modulation of adenosine receptors. To perform a survival curve, 7dpf larvae were exposed to 10μM CuSO₄, combined to different concentrations of caffeine (100μM, 500μM and 1mM) for up to 24h. The treatment with copper showed lower survival rates only when combined with 500μM and 1mM of caffeine. We selected 4 and 24h as treatment time-points. The behavior evaluation was done by analyzing the traveled distance, the number of entries in the center, and the length of permanence in the center and the periphery of the well. The exposure to 10μM CuSO₄ plus 500μM caffeine at 4 and 24h changed the behavioral parameters. To study the inflammatory effects of caffeine, we assessed the PGE₂ levels by using UHPLC-MS/MS, and TNF, COX-2, IL-6 and IL-10 gene expression by RT-qPCR. The expression of adenosine receptors was also evaluated with RT-qPCR. When combined to copper, caffeine altered inflammatory markers depending on the time of exposure. Adenosine receptors expression was significantly increased, especially after 4h exposure to copper and caffeine together or separately. Our results demonstrated that caffeine enhances the inflammation induced by copper by decreasing animal survival, altering inflammatory markers and promoting behavioral changes in zebrafish larvae. We also conclude that alterations in adenosine receptors are related to those effects.

Adenosine: an endogenous mediator in the pathogenesis of psoriasis

It is known that inflammatory and immune responses protect us from the invasion of micro-organisms and eliminate "wastes" from the injured sites, but they may also be responsible for significant tissue damage. Adenosine, as a purine nucleoside, which is produced in inflamed or injured sites, fulfills its role in limiting tissue damage. Although, it may have a pleiotropic effect, which signals it with a proinflammatory state in certain situations, it can be considered a potent anti-inflammatory mediator. The effects of adenosine, which acts through its receptors on T cell, on mast cell and macrophages, on endothelial cells, on neutrophils and dendritic cells, as they indicate TNF-alpha and cytokines, show that this mediator has a central role in the pathogenesis of psoriasis. The way it acts in psoriasis will be reviewed in this study.

Caffeine Improves Heart Rate Without Improving Sepsis Survival

INTRODUCTION

Caffeine is consumed on a daily basis for its nervous system stimulant properties and is a global adenosine receptor antagonist. Because adenosine receptors have been found to play a major role in regulating the immune response to a septic insult, we investigated if caffeine consumption prior to a septic insult would alter immunological and physiological responses, as well as survival.

METHODS

Two separate experimental designs were used, both using outbred female ICR mice. In the first experiment, mice were administered 20 mg/kg of caffeine (equal to 2-3 cups of coffee for a human) or normal saline intraperitoneally at the time of cecal ligation and puncture (CLP). Immunological parameters including cytokines and local cell recruitment were measured. In the second experiment, caffeine (10 mg/kg per hour) was delivered continuously for 24 h via a subcutaneous infusion pump placed the day prior to CLP, and hemodynamic parameters were examined. In both experiments, survival was followed for 5 days.

RESULTS

A single dose of caffeine at the initiation of sepsis did not alter survival. This single dose of caffeine did significantly increase in plasma levels of the chemokine KC 6 h after the onset of sepsis compared with septic mice given normal saline. There were no changes in interleukin 6 (IL-6) or IL-10 levels in the caffeine groups. Peritoneal lavages performed 24 h after CLP showed no difference in the levels of IL-6, tumor necrosis factor, KC, macrophage inflammatory protein 1, IL-10, or the IL-1 receptor antagonist between caffeine- and normal saline-treated mice. In addition, the lavages yielded similar numbers of cells (4.1 × 10 vehicle vs. 6.9 × 10 caffeine) and bacterial colony-forming units (CFUs, 4.1 million CFUs vehicle vs. 2.8 million CFUs caffeine). In the infusion group, caffeine also did not alter survival. However, caffeine infusion did increase the heart rate prior to CLP and prevented the decline in heart rate after CLP.

CONCLUSION

Caffeine increased the heart rate in mice but does not impact cytokine responses or survival during the acute phase of a polymicrobial sepsis challenge. These data indicate that patients consuming caffeine will not be at risk for increased sepsis mortality.

Caffeine protects against alcohol-induced liver fibrosis by dampening the cAMP/PKA/CREB pathway in rat hepatic stellate cells

Alcoholic liver fibrosis (ALF) is characterized by hyperplasia of extracellular matrix under long-term alcohol stimulation. Hepatic stellate cell (HSC) activation plays an important role in promoting hepatic fibrogenesis. Caffeine, as the main active component of coffee and tea, was widely consumed in daily life. It was always a thought that caffeine can reduce the probability of suffering from liver diseases. In this study, we attempt to validate the hypothesis that caffeine inhibits activation of HSCs which were isolated from rat ALF model. The rats were gavaged by ethanol to establish ALF model and then treated with different concentrations of caffeine or colchicine. Serum was collected to measure the contents of serum alanine aminotransferase (ALT), aspartate transaminase (AST), hyaluronic acid (HA), laminin (LN), N-terminal peptide of type III procollagen (PIIINP) and type IV collagen (CIV). Then liver tissues were obtained for hematoxylin-eosin staining and Sirius-red staining. Others were treated through liver perfusion to isolate primary rat HSCs. Interestingly, we found that caffeine significantly decreased ALT, AST, HA, LN, PIIINP and CIV levels and reversed liver fibrosis in rat ALF models. Results of immunohistochemistry, real-time PCR and western blot indicated that caffeine could reduce fibrosis and inhibit cAMP/PKA/CREB signal pathway in HSC. Caffeine has a preventive effect on ALF. The mechanism may be interpreted that caffeine inhibits the cAMP/PKA/CREB signal pathway through adenosine A2A receptors in HSC.

Caffeine and rolipram affect Smad signalling and TGF-β1 stimulated CTGF and transgelin expression in lung epithelial cells

Caffeine administration is an important part of the therapeutic treatment of bronchopulmonary dysplasia (BPD) in preterm infants. However, caffeine mediated effects on airway remodelling are still undefined. The TGF-β/Smad signalling pathway is one of the key pathways involved in airway remodelling. Connective tissue growth factor (CTGF), a downstream mediator of TGF-β, and transgelin, a binding and stabilising protein of the cytoskeleton, are both regulated by TGF-β1 and play an important role in airway remodelling. Both have also been implicated in the pathogenesis of BPD. The aim of the present study was to clarify whether caffeine, an unspecific phosphodiesterase (PDE) inhibitor, and rolipram, a prototypical PDE-4 selective inhibitor, were both able to affect TGF-β1-induced Smad signalling and CTGF/transgelin expression in lung epithelial cells. Furthermore, the effect of transgelin knock-down on Smad signalling was studied. The pharmacological effect of caffeine and rolipram on Smad signalling was investigated by means of a luciferase assay via transfection of a TGF-β1-inducible reporter plasmid in A549 cells. The regulation of CTGF and transgelin expression by caffeine and rolipram were studied by promoter analysis, real-time PCR and Western blot. Endogenous transgelin expression was down-regulated by lentiviral transduction mediating transgelin-specific shRNA expression. The addition of caffeine and rolipram inhibited TGF-β1 induced reporter gene activity in a concentration-related manner. They also antagonized the TGF-β1 induced up-regulation of CTGF and transgelin on the promoter-, the mRNA-, and the protein-level. Functional analysis showed that transgelin silencing reduced TGF-β1 induced Smad-signalling and CTGF induction in lung epithelial cells. The present study highlights possible new molecular mechanisms of caffeine and rolipram including an inhibition of Smad signalling and of TGF-β1 regulated genes involved in airway remodelling. An understanding of these mechanisms might help to explain the protective effects of caffeine in prevention of BPD and suggests rolipram to be a potent replacement for caffeine.

Caffeine induces alveolar apoptosis in the hyperoxia-exposed developing mouse lung

BACKGROUND

Caffeine is a nonspecific adenosine receptor antagonist used in premature neonates to treat apnea of prematurity. While its use may reduce the incidence of bronchopulmonary dysplasia (BPD), the precise mechanisms remain unknown. Evidence of increased adenosine levels are noted in chronic lung diseases including tracheal aspirates of infants with BPD. Utilizing a well-characterized newborn mouse model of alveolar hypoplasia, we hypothesized that hyperoxia-induced alveolar inflammation and hypoplasia is associated with alterations in the adenosine signaling pathway.

METHODS

Newborn murine pups were exposed to a 14-d period of hyperoxia and daily caffeine administration followed by a 14-d recovery period in room air. Lungs were collected at both time points for bronchoalveolar lavage (BAL) analysis as well as histopathology and mRNA and protein expression.

RESULTS

Caffeine treatment increased inflammation and worsened alveolar hypoplasia in hyperoxia-exposed newborn mice. These changes were associated with decreased alveolar type II (ATII) cell numbers, increased cell apoptosis, and decreased expression of A2A receptors. Following discontinuation of caffeine and hyperoxia, lung histology returned to baseline levels comparable to hyperoxia exposure alone.

CONCLUSION

Results of this study suggest a potentially adverse role of caffeine on alveolar development in a murine model of hyperoxia-induced alveolar hypoplasia.

Extracellular adenosine controls NKT-cell-dependent hepatitis induction

Extracellular adenosine regulates inflammatory responses via the A2A adenosine receptor (A2AR). A2AR deficiency results in much exaggerated acute hepatitis, indicating nonredundancy of adenosine-A2AR pathway in inhibiting immune activation. To identify a critical target of immunoregulatory effect of extracellular adenosine, we focused on NKT cells, which play an indispensable role in hepatitis. An A2AR agonist abolished NKT-cell-dependent induction of acute hepatitis by concanavalin A (Con A) or α-galactosylceramide in mice, corresponding to downregulation of activation markers and cytokines in NKT cells and of NK-cell co-activation. These results show that A2AR signaling can downregulate NKT-cell activation and suppress NKT-cell-triggered inflammatory responses. Next, we hypothesized that NKT cells might be under physiological control of the adenosine-A2AR pathway. Indeed, both Con A and α-galactosylceramide induced more severe hepatitis in A2AR-deficient mice than in WT controls. Transfer of A2AR-deficient NKT cells into A2AR-expressing recipients resulted in exaggeration of Con A-induced liver damage, suggesting that NKT-cell activation is controlled by endogenous adenosine via A2AR, and this physiological regulatory mechanism of NKT cells is critical in the control of tissue-damaging inflammation. The current study suggests the possibility to manipulate NKT-cell activity in inflammatory disorders through intervention to the adenosine-A2AR pathway.

Caffeine protects neuronal cells against injury caused by hyperoxia in the immature brain

Caffeine administered to preterm infants has been shown to reduce rates of cerebral palsy and cognitive delay, compared to placebo. We investigated the neuroprotective potential of caffeine for the developing brain in a neonatal rat model featuring transient systemic hyperoxia. Using 6-day-old rat pups, we found that after 24 and 48h of 80% oxygen exposure, apoptotic (TUNEL(+)) cell numbers increased in the cortex, hippocampus, and central gray matter, but not in the hippocampus or dentate gyrus. In the dentate gyrus, high oxygen exposure led to a decrease in the number of proliferating (Ki67(+)) cells and the number of Ki67(+) cells double staining for nestin (immature neurons), doublecortin (progenitors), and NeuN (mature neurons). Absolute numbers of nestin(+), doublecortin(+), and NeuN(+) cells also decreased after hyperoxia. This was mirrored in a decline of transcription factors expressed in immature neurons (Pax6, Sox2), progenitors (Tbr2), and mature neurons (Prox1, Tbr1). Administration of a single dose of caffeine (10mg/kg) before high oxygen exposure almost completely prevented these effects. Our findings suggest that caffeine exerts protection for neonatal neurons exposed to high oxygen, possibly via its antioxidant capacity.

Tissue-specific upregulation of HSP72 in mice following short-term administration of alcohol

Oxidative stress and cellular injury have been implicated in induction of HSP72 by alcohol. We investigated the association between HSP72 induction and oxidative stress in mouse tissues following short-term administration of high doses of alcohol and caffeine alone or in combination. Adult male C57BL/6J mice were gavaged with vehicle, alcohol (∼1.7 g/kg/day), caffeine (∼44 mg/kg/day), or alcohol plus caffeine once daily for ten consecutive days. Upon completion of the treatments, tissues were collected for structural and biochemical analyses. Alcohol alone caused mild to moderate lesions in heart, liver, and gastrocnemius muscle. Similar structural changes were observed following administration of alcohol and caffeine combined. Alcohol administration also led to decreased glutathione levels in all three tissues and reduced plasma superoxide dismutase capacity. In contrast, alcohol and caffeine in combination reduced glutathione levels only in liver and gastrocnemius muscle and had no effect on plasma superoxide dismutase. Significant elevations in HSP72 protein and mRNA and in HSF1 protein levels were noted only in liver by alcohol alone or in combination with caffeine. No significant changes in morphology and HSP72 were detected in any tissues tested following administration of caffeine alone. These results suggest that a redox mechanism is involved in the structural impairment caused by short-term high-dose alcohol. Oxidative tissue injury by alcohol may not be associated with tissue HSP72 induction. Induction of HSP72 in liver by alcohol is mediated at both the transcriptional and translational levels.

Adora2b adenosine receptor signaling protects during acute kidney injury via inhibition of neutrophil-dependent TNF-α release

Renal ischemia is among the leading causes of acute kidney injury (AKI). Previous studies have shown that extracellular adenosine is a prominent tissue-protective cue elicited during ischemia, including signaling events through the adenosine receptor 2b (Adora2b). To investigate the functional role of Adora2b signaling in cytokine-mediated inflammatory pathways, we screened wild-type and Adora2b-deficient mice undergoing renal ischemia for expression of a range of inflammatory cytokines. These studies demonstrated a selective and robust increase of TNF-α levels in Adora2b-deficient mice following renal ischemia and reperfusion. Based on these findings, we next sought to understand the contribution of TNF-α on ischemic AKI through a combination of loss- and gain-of-function studies. Loss of TNF-α, through either Ab blockade or study of Tnf-α-deficient animals, resulted in significantly attenuated tissue injury and improved kidney function following renal ischemia. Conversely, transgenic mice with overexpression of TNF-α had significantly pronounced susceptibility to AKI. Furthermore, neutrophil depletion or reconstitution of Adora2b(-/-) mice with Tnf-α-deficient neutrophils rescued their phenotype. In total, these data demonstrate a critical role of adenosine signaling in constraining neutrophil-dependent production of TNF-α and implicate therapies targeting TNF-α in the treatment of ischemic AKI.

Pilot study on which foods should be avoided by patients with psoriasis

FUNDAMENT: Psoriasis is a chronic inflammatory systemic disease mediated by immune factors. We will explore the foods that act on these factors contributing to psoriasis. As a systemic disease, which shares the same pathophysiological substrate with other comorbidities, diet also leads to worsening of comorbidities.

OBJECTIVE

To indicate a group of foods that can act as a factor of manifestation and/or aggravation of psoriasis and, at the same time, enable strategies for individuals to introduce these foods to their diet.

METHODS

43 patients with various forms of psoriasis (excluding pustular and erythrodermic psoriasis) were selected and answered a questionnaire about their eating habits in the first visit, with special attention to the consumption of black coffee, black tea, chocolate, yerba mate, pepper, smoked foods, beef and flavor enhancer (monosodium glutamate). Next, the patient was instructed to suspend alcoholic drinks and tobacco.

RESULTS

Beef is the most consumed food by patients followed by MSG (monosodium glutamate), which exists in processed foods, yerba matte, black coffee, chocolate, smoked foods, pepper and black tea. 88.37% noticed reduced scaling and erythema, milder outbreaks during the year and improved quality of life; 11.63% (5 patients) did not notice any effects on the skin.

CONCLUSION

We found poor dietary intake in patients with psoriasis. In addition to receiving proper scientific advice, patients need to be educated regarding their eating habits for a better quality of life and as an adjuvant to the drug therapy.

The development and immunosuppressive functions of CD4(+) CD25(+) FoxP3(+) regulatory T cells are under influence of the adenosine-A2A adenosine receptor pathway

The A2A adenosine receptor (A2AR)-mediated immunosuppression is firmly implicated in the life-saving down-regulation of collateral tissue damage during the anti-pathogen immune response and in highly undesirable protection of cancerous tissues during anti-tumor immune response. Therefore, depending on specific clinical situation there is a need to either weaken or strengthen the intensity of A2AR signal. While the A2AR-mediated immunosuppression was shown to be T cell autonomous in studies of effector T cells, it was not clear how A2AR stimulation affects regulatory T cells (Treg). Here we show in parallel assays that while A2AR stimulation on T cells directly inhibits their activation, there is also indirect and longer-lasting T cell inhibitory effect through modulation of Treg. A2AR stimulation expanded CD4⁺ CD25^hi FoxP3⁺ cells, which also express CD39, CD73, and CTLA-4. Treg cultured with A2AR agonist showed increased expression of CTLA-4 and stronger immunosuppressive activity. There was a significant increase of Treg cell number after A2AR stimulation. The CD4⁺ FoxP3⁺ population contained those induced from CD4⁺ CD25⁻ cells, but CD4⁺ FoxP3⁺ cells predominantly derived from CD4⁺ CD25⁺ natural Treg. Thus, A2AR stimulation numerically and functionally enhanced Treg-mediated immunosuppressive mechanism. These data suggest that the A2AR-mediated stimulation of lymphocytes using A2AR agonists should be considered in protocols for ex vivo expansion of Treg before the transfer to patients in different medical applications.

Deficiency of CD73/ecto-5'-nucleotidase in mice enhances acute graft-versus-host disease

Extracellular ATP and adenosine have immunoregulatory roles during inflammation. Elevated extracellular ATP is known to exacerbate GVHD, and the pharmacologic activation of the adenosine A2A receptor is protective. However, the role of endogenous adenosine is unknown. We used gene-targeted mice and a pharmacologic inhibitor to test the role of adenosine generated by CD73/ecto-5'-nucleotidase in GVHD. In allogeneic transplants, both donor and recipient CD73 were protective, with recipient CD73 playing the dominant role. CD73 deficiency led to enhanced T-cell expansion and IFN-γ and IL-6 production, and the migratory capacity of Cd73-/- T cells in vitro was increased. However, the number of regulatory T cells and expression of costimulatory molecules on antigen-presenting cells were unchanged. A2A receptor deficiency led to increased numbers of allogeneic T cells, suggesting that signaling through the A2A receptor via CD73-generated adenosine is a significant part of the mechanism by which CD73 limits the severity of GVHD. Pharmacologic blockade of CD73 also enhanced graft-versus-tumor activity. These data have clinical implications, as both the severity of GVHD and the strength of an alloimmune antitumor response could be manipulated by enhancing or blocking CD73 activity or adenosine receptor signaling depending on the clinical indication.

Advances of molecular clinical pharmacology in gastroenterology and hepatology

During developmental age, differences in pharmacodynamic reactions to several drugs may reflect polymorphisms of genes encoding drug-transporting proteins, receptors, drug targets, and gene products, whose disturbed activity sometimes plays an important role in certain diseases. Administration of drugs with a narrow therapeutic index may quite easily be associated with changes in pharmacokinetics and development of adverse drug reactions, which occasionally may cause fatalities. In such cases, polypragmasy and resulting drug interactions may enhance effects of changes in drug-metabolizing enzymes' activities. Phenotyping and genotyping of patients slowly are finding their place in some therapeutic regimens used in clinical gastroenterology and hepatology. At present, some assays to measure, for example, thiopurine S-methyltransferase activity are already commercially available. Polymorphisms of CYP450 enzymes, interleukins, and altered gene expression play an important role in some patients' various gastrointestinal tract and liver diseases. Herbal drugs also affect proinflammatory and antiinflammatory cytokine and nitric oxide balance in the body. Therapeutic use of recombined proteins, such as infliximab, natalizumab, onercept, humanized antibody to integrin α-4 β-7, or IFN-β in some large-bowel diseases increased therapeutic efficacy. IFN-α used in the patients with chronic hepatitis C improved cellular immunity in these subjects and exerted antiviral activity. Practical application of progress in pharmacogenetics, pharmacokinetics, pharmacodynamics, and use of bioproducts in novel therapeutic regimens has opened therapeutic frontiers and increased clinical safety.

International Union of Basic and Clinical Pharmacology. LXXXI. Nomenclature and classification of adenosine receptors--an update

In the 10 years since our previous International Union of Basic and Clinical Pharmacology report on the nomenclature and classification of adenosine receptors, no developments have led to major changes in the recommendations. However, there have been so many other developments that an update is needed. The fact that the structure of one of the adenosine receptors has recently been solved has already led to new ways of in silico screening of ligands. The evidence that adenosine receptors can form homo- and heteromultimers has accumulated, but the functional significance of such complexes remains unclear. The availability of mice with genetic modification of all the adenosine receptors has led to a clarification of the functional roles of adenosine, and to excellent means to study the specificity of drugs. There are also interesting associations between disease and structural variants in one or more of the adenosine receptors. Several new selective agonists and antagonists have become available. They provide improved possibilities for receptor classification. There are also developments hinting at the usefulness of allosteric modulators. Many drugs targeting adenosine receptors are in clinical trials, but the established therapeutic use is still very limited.

Chronic or high dose acute caffeine treatment protects mice against oleic acid-induced acute lung injury via an adenosine A2A receptor-independent mechanism

The antagonism or genetic deletion of adenosine A(2A) receptors has been shown to exacerbate tissue damage in acute lung injury. Caffeine, a widely consumed behavioral drug, acts as a non-selective antagonist of A(2A) receptor and also has additional pharmacological effects. Thus, the protective vs. deleterious effects of caffeine in acute lung injury should be evaluated. In a murine oleic acid-induced model of acute lung injury, we found that chronic caffeine treatment by drinking water (0.1g/l or 0.25g/l for 2 weeks before acute lung injury) or acute caffeine treatment at high dose (i.p. 50mg/kg, injection, 30min before acute lung injury) significantly attenuated the lung edema, hemorrhage, neutrophil recruitment as well as the inflammatory cytokine tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1) expressions in both of the wild type (WT) and A(2A) receptor knockout (KO) mice. This profile was accompanied by increased cAMP levels and up-regulation of A2B receptor mRNAs in the lungs. In contrast, acute caffeine treatment at low dose (i.p. 5mg/kg or 15mg/kg, injection, 30min before acute lung injury) enhanced the inflammation and lung damage in WT mice with decreasing cAMP but not in A(2A) receptor KO mice. These results indicate that caffeine either enhances lung damage by antagonizing A(2A) receptor or exerts protection against lung damage via A(2A) receptor-independent mechanisms, depending on the timing of exposure (chronic vs. acute) and dose of administration (low vs. high). These findings provide new insight of caffeine in acute lung injury and highlight the potential benefit and strategy of caffeine intake or administration for preventing acute lung injury.

Circulating adenosine increases during human experimental endotoxemia but blockade of its receptor does not influence the immune response and subsequent organ injury

Introduction

Preclinical studies have shown that the endogenous nucleoside adenosine prevents excessive tissue injury during systemic inflammation. We aimed to study whether endogenous adenosine also limits tissue injury in a human in vivo model of systemic inflammation. In addition, we studied whether subjects with the common 34C > T nonsense variant (rs17602729) of adenosine monophosphate deaminase (AMPD1), which predicts increased adenosine formation, have less inflammation-induced injury.

Methods

In a randomized double-blinded design, healthy male volunteers received 2 ng/kg E. Coli LPS intravenously with (n = 10) or without (n = 10) pretreatment with the adenosine receptor antagonist caffeine (4 mg/kg body weight). In addition, lipopolysaccharide (LPS) was administered to 10 subjects heterozygous for the AMPD1 34C > T variant.

Results

The increase in adenosine levels tended to be more pronounced in the subjects heterozygous for the AMPD1 34C > T variant (71 ± 22%, P=0.04), compared to placebo- (59 ± 29%, P=0.012) and caffeine-treated (53 ± 47%, P=0.29) subjects, but this difference between groups did not reach statistical significance. Also the LPS-induced increase in circulating cytokines was similar in the LPS-placebo, LPS-caffeine and LPS-AMPD1-groups. Endotoxemia resulted in an increase in circulating plasma markers of endothelial activation [intercellular adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM)], and in subclinical renal injury, measured by increased urinary excretion of tubular injury markers. The LPS-induced increase of these markers did not differ between the three groups.

Conclusions

Human experimental endotoxemia induces an increase in circulating cytokine levels and subclinical endothelial and renal injury. Although the plasma adenosine concentration is elevated during systemic inflammation, co-administration of caffeine or the presence of the 34C > T variant of AMPD1 does not affect the observed subclinical organ damage, suggesting that adenosine does not affect the inflammatory response and subclinical endothelial and renal injury during human experimental endotoxemia.

Trial Registration

ClinicalTrials (NCT): NCT00513110.

Methylxanthines, inflammation, and cancer: fundamental mechanisms

Methylxanthines are an integral part of everyday food and drink consumption even though the majority of humans do not identify them by their chemical name. The breakthrough in understanding the action(s) of methylxanthines was in large part due to the understanding that methylxanthines can function as antagonists of adenosine receptors. This represented an example of scientific search and was instructive in view of both new therapeutic options and alarming realizations. It was the subsequent demonstration of the in vivo critical role of A2A adenosine receptors in controlling excessive collateral inflammatory damage that attracted the attention of immunologists to the A2A-adenosine-receptor-antagonizing methylxanthines. We summarize here data showing that caffeine is capable of preventing the inhibition of antitumor T cells in a hypoxic tumor microenvironment. On the other hand, caffeine may exacerbate liver damage by weakening the tissue-protecting A2A adenosine receptor signaling during episodes of acute liver inflammation. However, methylxanthines may also prevent the excessive hepatic connective tissue deposition that is associated with the progression of chronic hepatitis to cirrhosis, which is one of the common causes of mortality.

Methylxanthines and inflammatory cells

Both caffeine and theophylline have a variety of roles in regulating inflammatory responses. At pharmacologically relevant concentrations most of the effects of these commonly used methylxanthines are attributable to adenosine receptor blockade and histone deacetylase activation. In addition, at higher concentrations methylxanthines can suppress inflammation by inhibiting phosphodiesterases, thereby elevating intracellular cyclic adenosine monophosphate levels. In summary, methylxanthines regulate inflammation by multiple mechanisms.

Correlation between serum caffeine levels and changes in cytokine profile in a cohort of preterm infants

OBJECTIVE

To determine changes in cytokine levels associated with caffeine treatment in a cohort of preterm infants.

STUDY DESIGN

For this observational prospective study, we collected clinical data from 26 preterm infants (≤ 30 weeks gestational age). In addition to caffeine levels, cytokine profiles in peripheral blood (PB) and tracheal aspirates (TA) were determined with enzyme-linked immunosorbent assay at birth, before and after (at 24 hours and 1 week) initiation of caffeine. Non-parametric statistics were applied.

RESULTS

Included infants were 26.9 ± 1.7 weeks gestational age and weighed 985 ± 202 g. At birth, all cytokine concentrations were significantly greater in TA than PB. Serum caffeine levels were 11.1 μg/mL (interquartile range, 1.85) at approximately 24 hours post-load and 16.4 (8.7) μg/mL at 1 week on treatment. At approximately 24 hours post-load, interleukin (IL)-10 levels decreased by 47.5% (P = .01) in PB and 38.5% (P = .03) in TA, whereas other cytokine levels remained unchanged. At 1 week, caffeine levels were correlated (U-shaped) with changes in proinflammatory tumor necrosis factor-α (R(2) = 0.65; P = .0008), interleukin (IL)-1β (R(2) = 0.73; P = .0007), and IL-6 (R(2) = 0.59; P = .003), whereas inversely correlated (linear) with the anti-inflammatory IL-10 (R(2) = 0.64; P = .0008). Altogether, caffeine, at serum levels ≥ 20 μg/mL, was associated with a proinflammatory profile after 1 week of treatment.

CONCLUSIONS

Caffeine treatment for apnea of prematurity correlates with changes in cytokine profile. Caffeine levels ≥ 20 μg/mL are associated with a proinflammatory profile in our cohort of preterm infants.

A2A adenosine receptor may allow expansion of T cells lacking effector functions in extracellular adenosine-rich microenvironments

Immunosuppressive signaling via the A2A adenosine receptor (A2AR) provokes a mechanism that protects inflamed tissues from excessive damage by immune cells. This mechanism is desirable not only for preventing uncontrolled tissue destruction by overactive immune responses, but also for protecting tumor tissues from antitumor immune responses. In aforementioned circumstances, T cell priming may occur in an environment containing high concentrations of extracellular adenosine. To examine qualitative changes in T cells activated in the presence of adenosine, we asked whether different functional responses of T cells are equally susceptible to A2AR agonists. In this study, we demonstrate that A2AR signaling during T cell activation strongly inhibited development of cytotoxicity and cytokine-producing activity in T cells, whereas the inhibition of T cell proliferation was only marginal. Both CD8(+) and CD4(+) T cells proliferated well in the presence of A2AR agonists, but their IFN-gamma-producing activities were susceptible to inhibition by cAMP-elevating A2AR. Importantly, the impaired effector functions were maintained in T cells even after removal of the A2AR agonist, reflecting T cell memory of the immunoregulatory effect of adenosine. Thus, although the adenosine-rich environment may allow for the expansion of T cells, the functional activation of T cells may be critically impaired. This physiological mechanism could explain the inefficiency of antitumor T cells in the tumor microenvironment.