Caffeine Protects Against Retinal Inflammation

Caffeine, one of the most consumed central nervous system (CNS) stimulants, is an antagonist of A1 and A2A adenosine receptors. In this study, we investigated the potential protective effects of this methylxanthine in the retinal tissue. We tested caffeine by using in vitro and in vivo paradigms of retinal inflammation. Human retinal pigment epithelial cells (ARPE-19) were exposed to lipopolysaccharide (LPS) with or without caffeine. This latter was able to reduce the inflammatory response in ARPE-19 cells exposed to LPS, attenuating the release of IL-1β, IL-6, and TNF-α and the nuclear translocation of p-NFκB. Additionally, caffeine treatment restored the integrity of the ARPE-19 monolayer assessed by transepithelial electrical resistance (TEER) and the sodium fluorescein permeability test. Finally, the ischemia reperfusion (I/R) injury model was used in C57BL/6J mice to induce retinal inflammation and investigate the effects of caffeine treatment. Mouse eyes were treated topically with caffeine, and a pattern electroretinogram (PERG) was used to assess the retinal ganglion cell (RGC) function; furthermore, we evaluated the levels of IL-6 and BDNF in the retina. Retinal BDNF dropped significantly (p < 0.05) in the I/R group compared to the control group (normal mice); on the contrary, caffeine treatment maintained physiological levels of BDNF in the retina of I/R eyes. Caffeine was also able to reduce IL-6 mRNA levels in the retina of I/R eyes. In conclusion, these findings suggest that caffeine is a good candidate to counteract inflammation in retinal diseases.

Efficacy of Caffeine Treatment for Wood Protection—Influence of Wood and Fungi Species

In the future, we can expect increased requirements to the health and ecological integrity of biocides used for the protection of wood against bio-attacks, and it is therefore necessary to search for and thoroughly test new active substances. Caffeine has been shown to have biocidal efficacy against wood-destroying fungi, moulds and insects. The aim of the research was to determine whether the effectiveness of caffeine, as a fungicide of natural origin, is affected by a different type of treated wood. Norway spruce mature wood (Picea abies), Scots pine sapwood (Pinus sylvestris), and European beech wood (Fagus sylvatica) were tested in this work. The samples were treated using long-term dipping technology or coating (according to EN 152:2012) and then tested against selected wood-destroying brown rot fungi according to the standard EN 839:2015, wood-staining fungi according to EN 152:2012, and against mould growth according to EN 15457:2015. The penetration of caffeine solution into wood depth was also evaluated using liquid extraction chromatography, as well as the effect of the treatment used on selected physical and mechanical properties of wood. The test results showed that the type of wood used and the specific type of wood-degrading agent had a significant effect on the effectiveness of caffeine protection. The most resistant wood was the treated spruce, whereas the most susceptible to deterioration was the treated white pine and beech wood. The results of the work showed that caffeine treatment is effective against wood-destroying fungi at a concentration of 2%, and at 1% in some of the tested cases. It can be used as an ecologically acceptable short-term protection alternative against wood-staining fungi in lumber warehouses and is also partially effective against moulds. It also does not have negative effects on changes in the physical and mechanical properties of the tested wood species.

Caffeine is a respiratory stimulant without effect on sleep in the short-term in late-preterm infants

Background Caffeine is widely used in preterm infants for apnea control. It has no effect on sleep in the only existing polysomnographic study including ten preterm infants Behavioral and polygraphic studies have conflicting results. Methods We studied 21 late-preterm infants at a median gestational age of 36 weeks. Polysomnography was performed twice, at baseline on day 1 and on the day after the onset of caffeine treatment (20 mg/kg loading and 5 mg/kg morning maintenance dose). Results Caffeine acted short term as a breathing stimulant with reduction of apneas, improved baseline SpO2 (p < 0.001), and decreased 95 percentile of end-tidal carbon dioxide level (p < 0.01). It also increased arousal frequency to SpO2 desaturations of more than 5% (p < 0.001). Caffeine did not affect sleep stage distribution, sleep efficiency, frequency of sleep stage transitions, appearance of REM periods, or the high number of spontaneous arousals. The median spontaneous arousal count was 18 per hour at baseline, and 16 per hour during caffeine treatment (p = 0.88). Conclusions In late-preterm infants, caffeine has a clear short-term respiratory stimulant effect, and it increases the arousal frequency to hypoxia. However, caffeine does not appear to act as a central nervous system stimulant, and it has no acute effect on sleep quality. Impact Effects of caffeine on sleep in preterm infants has previously been investigated with only one full polysomnographic study including ten preterm infants. The study showed no effect. The current study shows that caffeine acts short term as a respiratory stimulant and increases arousal frequency to hypoxia. Although a potent central nervous system (CNS) stimulant in adults, caffeine does not seem to have similar acute CNS effect in late-preterm infants. The onset of caffeine treatment has no short-term effect on sleep stage distribution, sleep efficiency, frequency of sleep stage transitions, appearance of REM periods, or the high number of spontaneous arousals.

Chronic caffeine treatment disrupts the circadian rhythm in Drosophila

The circadian clock governs the timing of sleep-wake cycles as well as of other behavioural, physiological and metabolic processes. While the endogenous circadian clock mediates the timing of sleep, homeostatic mechanisms modulate the amount and depth of sleep. Evidence from previous studies showed that caffeine intake promotes wakefulness, whereas adult-stage specific caffeine treatment not only suppresses sleep but also delays the phase of circadian rhythm in Drosophila. In humans, caffeine is consumed on a daily basis and hence it is important to understand the effect of prolonged caffeine intake on circadian and homeostatic regulation of sleep. In the present study we examined the differential effect of acute and chronic caffeine treatment on sleep ontogeny as well as on circadian and homeostatic regulation of sleep in Drosophila. The results of our study showed that acute caffeine treatment reduces day and night sleep in mature flies through the homeostatic pathway whereas it reduced only the day sleep in young flies. Chronic caffeine treatment did not exert any significant effect on sleep in young flies. On the other hand, it delayed the timing of sleep in mature flies and in addition flies under higher caffeine concentration reduced the morning and evening anticipatory activity under 12 hour: 12 hour light: dark cycles. These flies also exhibited either a longer free running period or arrhythmicity under constant darkness. The results of our study showed that acute caffeine treatment suppresses sleep through the homeostatic pathway whereas prolonged caffeine treatment disrupts the circadian rhythm in mature flies.

Effects of Different Onset Times of Early Caffeine Treatment on Mesenteric Tissue Oxygenation and Necrotizing Enterocolitis: A Prospective, Randomized Study

Objective Caffeine treatment is routinely used in premature infants to prevent development of apnea and bronchopulmonary dysplasia. Although a limited number of studies have reported that early caffeine treatment may cause development of necrotizing enterocolitis (NEC) by reducing mesenteric blood flow, this issue is still under discussion. The aim of this study is to investigate the possible effect of different onset times of early caffeine treatment on mesenteric tissue oxygen saturation and NEC development in premature infants. Study Design A total of 87 preterm infants with ≤1,250-g birth weight (BW) was included in this prospective study. The cases were randomized as group 1 (first 24 hours) and group 2 (72nd hour) caffeine treatment groups and monitored by near-infrared spectroscopy (NIRS) for 72 hours from the time of admission until cerebral, renal, and mesenteric tissue oxygen saturations (rSO2) were recorded. The cases were followed-up to the 40th week in terms of NEC and other neonatal morbidities. Results A total of 87 infants were included in the study, including 45 in group 1 and 42 in group 2. The groups were similar in terms of demographic characteristics. The incidence of NEC in group 1 (20%) was higher in comparison to group 2 (9%). The mesenteric rSO2 values in the first 72 hours of group 1 were lower than those of group 2. Low gestational week, BW, and late onset of enteral feeding were found to be other significant risk factors for NEC. Conclusion In this study, mesenteric tissue oxygenation was lower, and NEC was higher in group 1. Mesenteric rSO2 measurements may be useful in predicting the development of NEC in patients receiving early caffeine therapy. Key Points

Retinoic Acid Signaling Plays a Crucial Role in Excessive Caffeine Intake-Disturbed Apoptosis and Differentiation of Myogenic Progenitors

Whether or not the process of somitogenesis and myogenesis is affected by excessive caffeine intake still remains ambiguous. In this study, we first showed that caffeine treatment results in chest wall deformities and simultaneously reduced mRNA expressions of genes involved in myogenesis in the developing chicken embryos. We then used embryo cultures to assess in further detail how caffeine exposure affects the earliest steps of myogenesis, and we demonstrated that the caffeine treatment suppressed somitogenesis of chicken embryos by interfering with the expressions of crucial genes modulating apoptosis, proliferation, and differentiation of myogenic progenitors in differentiating somites. These phenotypes were abrogated by a retinoic acid (RA) antagonist in embryo cultures, even at low caffeine doses in C2C12 cells, implying that excess RA levels are responsible for these phenotypes in cells and possibly in vivo. These findings highlight that excessive caffeine exposure is negatively involved in regulating the development of myogenic progenitors through interfering with RA signaling. The RA somitogenesis/myogenesis pathway might be directly impacted by caffeine signaling rather than reflecting an indirect effect of the toxicity of excess caffeine dosage.

Sex Affects Human Premature Neonates’ Blood Metabolome According to Gestational Age, Parenteral Nutrition, and Caffeine Treatment

Prematurity is the leading cause of neonatal deaths and high economic costs; it depends on numerous biological and social factors, and is highly prevalent in males. Several factors can affect the metabolome of premature infants. Accordingly, the aim of the present study was to analyze the role played by gestational age (GA), parenteral nutrition (PN), and caffeine treatment in sex-related differences of blood metabolome of premature neonates through a MS/MS-based targeted metabolomic approach for the detection of amino acids and acylcarnitines in dried blood spots. GA affected the blood metabolome of premature neonates: male and female very premature infants (VPI) diverged in amino acids but not in acylcarnitines, whereas the opposite was observed in moderate or late preterm infants (MLPI). Moreover, an important reduction of metabolites was observed in female VPI fed with PN, suggesting that PN might not satisfy an infant’s nutritional needs. Caffeine showed the highest significant impact on metabolite levels of male MLPI. This study proves the presence of a sex-dependent metabolome in premature infants, which is affected by GA and pharmacological treatment (e.g., caffeine). Furthermore, it describes an integrated relationship among several features of physiology and health.

High Time Resolution Analysis of Voltage-Dependent and Voltage-Independent Calcium Sparks in Frog Skeletal Muscle Fibers

In amphibian skeletal muscle calcium (Ca2+) sparks occur both as voltage-dependent and voltage-independent ligand-activated release events. However, whether their properties and their origin show similarities are still in debate. Elevated K+, constant Cl– content solutions were used to initiate small depolarizations of the resting membrane potential to activate dihydropyridine receptors (DHPR) and caffeine to open ryanodine receptors (RyR) on intact fibers. The properties of Ca2+ sparks observed under control conditions were compared to those measured on depolarized cells and those after caffeine treatment. Calcium sparks were recorded on intact frog skeletal muscle fibers using high time resolution confocal microscopy (x-y scan: 30 Hz). Sparks were elicited by 1 mmol/l caffeine or subthreshold depolarization to different membrane potentials. Both treatments increased the frequency of sparks and altered their morphology. Images were analyzed by custom-made computer programs. Both the amplitude (in ΔF/F0; 0.259 ± 0.001 vs. 0.164 ± 0.001; n = 24942 and 43326, respectively; mean ± SE, p &lt; 0.001) and the full width at half maximum (FWHM, in μm; parallel with fiber axis: 2.34 ± 0.01 vs. 1.92 ± 0.01, p &lt; 0.001; perpendicular to fiber axis: 2.08 ± 0.01 vs. 1.68 ± 0.01, p &lt; 0.001) of sparks was significantly greater after caffeine treatment than on depolarized cells. 9.8% of the sparks detected on depolarized fibers and about one third of the caffeine activated sparks (29.7%) overlapped with another one on the previous frame on x-y scans. Centre of overlapping sparks travelled significantly longer distances between consecutive frames after caffeine treatment then after depolarization (in μm; 1.66 ± 0.01 vs. 0.95 ± 0.01, p &lt; 0.001). Our results suggest that the two types of ryanodine receptors, the junctional RyRs controlled by DHPRs and the parajunctional RyRs are activated independently, using alternate ways, with the possibility of cooperation between neighboring release channels.