Prevention of Oxygen-Induced Inflammatory Lung Injury by Caffeine in Neonatal Rats

Temporal Dynamics of Oxidative Stress and Inflammation in Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is the most common lung complication of prematurity. Despite extensive research, our understanding of its pathophysiology remains limited, as reflected by the stable prevalence of BPD. Prematurity is the primary risk factor for BPD, with oxidative stress (OS) and inflammation playing significant roles and being closely linked to premature birth. Understanding the interplay and temporal relationship between OS and inflammation is crucial for developing new treatments for BPD. Animal studies suggest that OS and inflammation can exacerbate each other. Clinical trials focusing solely on antioxidants or anti-inflammatory therapies have been unsuccessful. In contrast, vitamin A and caffeine, with antioxidant and anti-inflammatory properties, have shown some efficacy, reducing BPD by about 10%. However, more than one-third of very preterm infants still suffer from BPD. New therapeutic agents are needed. A novel tripeptide, N-acetyl-lysyltyrosylcysteine amide (KYC), is a reversible myeloperoxidase inhibitor and a systems pharmacology agent. It reduces BPD severity by inhibiting MPO, enhancing antioxidative proteins, and alleviating endoplasmic reticulum stress and cellular senescence in a hyperoxia rat model. KYC represents a promising new approach to BPD treatment.

Caffeine: The Story beyond Oxygen-Induced Lung and Brain Injury in Neonatal Animal Models-A Narrative Review

Caffeine is one of the most commonly used drugs in intensive care to stimulate the respiratory control mechanisms of very preterm infants. Respiratory instability, due to the degree of immaturity at birth, results in apnea of prematurity (AOP), hyperoxic, hypoxic, and intermittent hypoxic episodes. Oxidative stress cannot be avoided as a direct reaction and leads to neurological developmental deficits and even a higher prevalence of respiratory diseases in the further development of premature infants. Due to the proven antioxidant effect of caffeine in early use, largely protective effects on clinical outcomes can be observed. This is also impressively observed in experimental studies of caffeine application in oxidative stress-adapted rodent models of damage to the developing brain and lungs. However, caffeine shows undesirable effects outside these oxygen toxicity injury models. This review shows the effects of caffeine in hyperoxic, hypoxic/hypoxic-ischemic, and intermittent hypoxic rodent injury models, but also the negative effects on the rodent organism when caffeine is administered without exogenous oxidative stress. The narrative analysis of caffeine benefits in cerebral and pulmonary preterm infant models supports protective caffeine use but should be given critical consideration when considering caffeine treatment beyond the recommended corrected gestational age.

Strategies for cessation of caffeine administration in preterm infants

BACKGROUND

Apnea and intermittent hypoxemia (IH) are common developmental disorders in infants born earlier than 37 weeks' gestation. Caffeine administration has been shown to lower the incidence of these disorders in preterm infants. Cessation of caffeine treatment is based on different post-menstrual ages (PMA) and resolution of symptoms. There is uncertainty about the best timing for caffeine discontinuation.

OBJECTIVES

To evaluate the effects of early versus late discontinuation of caffeine administration in preterm infants.

SEARCH METHODS

We searched CENTRAL, PubMed, Embase, and three trial registries in August 2023; we applied no date limits. We checked the references of included studies and related systematic reviews.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) in preterm infants born earlier than 37 weeks' gestation, up to a PMA of 44 weeks and 0 days, who received caffeine for any indication for at least seven days. We compared three different strategies for caffeine cessation: 1. at different PMAs, 2. before or after five days without symptoms, and 3. at a predetermined PMA versus at the resolution of symptoms.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Primary outcomes were: restarting caffeine therapy, intubation within one week of treatment discontinuation, and the need for non-invasive respiratory support within one week of treatment discontinuation. Secondary outcomes were: number of episodes of apnea in the seven days after treatment discontinuation, number of infants with at least one episode of apnea in the seven days after treatment discontinuation, number of episodes of intermittent hypoxemia (IH) within seven days of treatment discontinuation, number of infants with at least one episode of IH in the seven days after of treatment discontinuation, all-cause mortality prior to hospital discharge, major neurodevelopmental disability, number of days of respiratory support after treatment discontinuation, duration of hospital stay, and cost of neonatal care. We used GRADE to assess the certainty of evidence for each outcome.

MAIN RESULTS

We included three RCTs (392 preterm infants). Discontinuation of caffeine at PMA less than 35 weeks' gestation versus PMA equal to or longer than 35 weeks' gestation This comparison included one single completed RCT with 98 premature infants with a gestational age between 25 + 0 and 32 + 0 weeks at birth. All infants had discontinued caffeine treatment for five days at randomization. The infants received either an oral loading dose of caffeine citrate (20 mg/kg) at randomization followed by oral maintenance dosage (6 mg/kg/day) until 40 weeks PMA, or usual care (controls), during which caffeine was stopped before 37 weeks PMA. Early cessation of caffeine administration in preterm infants at PMA less than 35 weeks' gestation may result in an increase in the number of IH episodes in the seven days after discontinuation of treatment, compared to prolonged caffeine treatment beyond 35 weeks' gestation (mean difference [MD] 4.80, 95% confidence interval [CI] 2.21 to 7.39; 1 RCT, 98 infants; low-certainty evidence). Early cessation may result in little to no difference in all-cause mortality prior to hospital discharge compared to late discontinuation after 35 weeks PMA (risk ratio [RR] not estimable; 98 infants; low-certainty evidence). No data were available for the following outcomes: restarting caffeine therapy, intubation within one week of treatment discontinuation, need for non-invasive respiratory support within one week of treatment discontinuation, number of episodes of apnea, number of infants with at least one episode of apnea in the seven days after discontinuation of treatment, or number of infants with at least one episode of IH in the seven days after discontinuation of treatment. Discontinuation based on PMA versus resolution of symptoms This comparison included two RCTs with a total of 294 preterm infants. Discontinuing caffeine at the resolution of symptoms compared to discontinuing treatment at a predetermined PMA may result in little to no difference in all-cause mortality prior to hospital discharge (RR 1.00, 95% CI 0.14 to 7.03; 2 studies, 294 participants; low-certainty evidence), or in the number of infants with at least one episode of apnea within the seven days after discontinuing treatment (RR 0.60, 95% CI 0.31 to 1.18; 2 studies; 294 infants; low-certainty evidence). Discontinuing caffeine based on the resolution of symptoms probably results in more infants with IH in the seven days after discontinuation of treatment (RR 0.38, 95% CI 0.20 to 0.75; 1 study; 174 participants; moderate-certainty evidence). No data were available for the following outcomes: restarting caffeine therapy, intubation within one week of treatment discontinuation, need for non-invasive respiratory support within one week of treatment discontinuation, or number of episodes of IH in the seven days after treatment discontinuation. Adverse effects In the Rhein 2014 study, five of the infants randomized to caffeine had the caffeine treatment discontinued at the discretion of the clinical team, because of tachycardia. The Pradhap 2023 study reported adverse events, including recurrence of apnea of prematurity (15% in the short and 13% in the regular course caffeine therapy group), varying severities of bronchopulmonary dysplasia, hyperglycemia, extrauterine growth restriction, retinopathy of prematurity requiring laser treatment, feeding intolerance, osteopenia, and tachycardia, with no significant differences between the groups. The Prakash 2021 study reported that adverse effects of caffeine therapy for apnea of prematurity included tachycardia, feeding intolerance, and potential neurodevelopmental impacts, though most were mild and transient. We identified three ongoing studies.

AUTHORS' CONCLUSIONS

There may be little or no difference in the incidence of all-cause mortality and apnea in infants who were randomized to later discontinuation of caffeine treatment. However, the number of infants with at least one episode of IH was probably reduced with later cessation. No data were found to evaluate the benefits and harms of later caffeine discontinuation for: restarting caffeine therapy, intubation within one week of treatment discontinuation, or need for non-invasive respiratory support within one week of treatment discontinuation. Further studies are needed to evaluate the short-term and long-term effects of different caffeine cessation strategies in premature infants.

Recent progress in neonatal hyperoxic lung injury

With the progress in neonatal intensive care, there has been an increase in the survival rates of premature infants. However, this has also led to an increased incidence of neonatal hyperoxia lung injury and bronchopulmonary dysplasia (BPD), whose pathogenesis is believed to be influenced by various prenatal and postnatal factors, although the exact mechanisms remain unclear. Recent studies suggest that multiple mechanisms might be involved in neonatal hyperoxic lung injury and BPD, with sex also possibly playing an important role, and numerous drugs have been proposed and shown promise for improving the treatment outcomes of hyperoxic lung injury. Therefore, this paper aims to analyze and summarize sex differences in neonatal hyperoxic lung injury, potential pathogenesis and treatment progress to provide new ideas for basic and clinical research in this field.

Bilirubin Exerts Protective Effects on Alveolar Type II Pneumocytes in an In Vitro Model of Oxidative Stress

Newborn infants face a rapid surge of oxygen and a more protracted rise of unconjugated bilirubin after birth. Bilirubin has a strong antioxidant capacity by scavenging free radicals, but it also exerts direct toxicity. This study investigates whether cultured rat alveolar epithelial cells type II (AEC II) react differently to bilirubin under different oxygen concentrations. The toxic threshold concentration of bilirubin was narrowed down by means of a cell viability test. Subsequent analyses of bilirubin effects under 5% oxygen and 80% oxygen compared to 21% oxygen, as well as pretreatment with bilirubin after 4 h and 24 h of incubation, were performed to determine the induction of apoptosis and the gene expression of associated transcripts of cell death, proliferation, and redox-sensitive transcription factors. Oxidative stress led to an increased rate of cell death and induced transcripts of redox-sensitive signaling pathways. At a non-cytotoxic concentration of 400 nm, bilirubin attenuated oxidative stress-induced responses and possibly mediated cellular antioxidant defense by influencing Nrf2/Hif1α- and NFκB-mediated signaling pathways. In conclusion, the study demonstrates that rat AEC II cells are protected from oxidative stress-induced impairment by low-dose bilirubin.

Association between coffee consumption and high C-reactive protein levels in Korean adults

The findings of studies investigating the relationship between coffee consumption and C-reactive protein (CRP) levels have been inconsistent, and few researchers considered the type of coffee. We examined the association between coffee consumption and high CRP levels, using data from the Korea National Health and Nutrition Examination Survey, 2016-2018, with 9337 adults aged 19-64 years. A 24-h diet recall was used to assess diet, including the amount and type of coffee consumed. We classified coffee into black coffee and coffee with sugar and/or cream (non-drinkers, or ≤ 1, 2-3, > 3 cups/d) and used multivariable logistic regression models with high CRP levels (≥ 2·2 mg/l). After the adjustment for potential confounders, 2-3 cups/d of coffee consumption were inversely associated with high CRP levels, compared with no consumption (OR = 0·83, 95 % CI 0·69, 0·99). By type of coffee, the inverse association was stronger in subjects consuming black coffee (OR = 0·61, 95 % CI 0·45, 0·84), while the inverse association was much weaker in those consuming coffee with sugar and/or cream (OR = 0·92, 95 % CI 0·74, 1·14). By sex, the inverse association of 2-3 cups of black coffee was found both in men (OR = 0·65, 95 % CI 0·41, 1·03) and women (OR = 0·55, 95 % CI 0·36, 0·83). More than three cups/d of heavy coffee consumption were not significantly associated with high CRP levels. Our findings indicate that moderate black coffee consumption of 2-3 cups/d is inversely associated with high CRP levels in Korean adults. Further prospective studies are warranted to provide definitive evidence.

Molsidomine decreases hyperoxia-induced lung injury in neonatal rats

BACKGROUND

The study's objective is to evaluate if Molsidomine (MOL), an anti-oxidant, anti-inflammatory, and anti-apoptotic drug, is effective in treating hyperoxic lung injury (HLI).

METHODS

The study consisted of four groups of neonatal rats characterized as the Control, Control+MOL, HLI, HLI + MOL groups. Near the end of the study, the lung tissue of the rats were evaluated with respect to apoptosis, histopathological damage, anti-oxidant and oxidant capacity as well as degree of inflammation.

RESULTS

Compared to the HLI group, malondialdehyde and total oxidant status levels in lung tissue were notably reduced in the HLI + MOL group. Furthermore, mean superoxide dismutase, glutathione peroxidase, and glutathione activities/levels in lung tissue were significantly higher in the HLI + MOL group as compared to the HLI group. Tumor necrosis factor-α and interleukin-1β elevations associated with hyperoxia were significantly reduced following MOL treatment. Median histopathological damage and mean alveolar macrophage numbers were found to be higher in the HLI and HLI + MOL groups when compared to the Control and Control+MOL groups. Both values were increased in the HLI group when compared to the HLI + MOL group.

CONCLUSIONS

Our research is the first to demonstrate that bronchopulmonary dysplasia may be prevented through the protective characteristics of MOL, an anti-inflammatory, anti-oxidant, and anti-apoptotic drug.

IMPACT

Molsidomine prophylaxis significantly decreased the level of oxidative stress markers. Molsidomine administration restored the activities of antioxidant enzymes. Molsidomine prophylaxis significantly reduced the levels of inflammatory cytokines. Molsidomine may provide a new and promising therapy for BPD in the future. Molsidomine prophylaxis decreased lung damage and macrophage infiltration in the tissue.

Meconium aspiration syndrome: a comprehensive review

Meconium aspiration syndrome (MAS) is a complex respiratory disease that continues to be associated with significant morbidities and mortality. The pathophysiological mechanisms of MAS include airway obstruction, local and systemic inflammation, surfactant inactivation and persistent pulmonary hypertension of the newborn (PPHN). Supplemental oxygen and non-invasive respiratory support are the main therapies for many patients. The management of the patients requiring invasive mechanical ventilation could be challenging because of the combination of atelectasis and air trapping. While studies have explored various ventilatory modalities, evidence to date does not clearly support any singular modality as superior. Patient's pathophysiology, symptom severity, and clinician/unit expertise should guide the respiratory management. Early identification and concomitant management of PPHN is critically important as it contributes significantly to mortality and morbidities.

Overview of Caffeine Effects on Human Health and Emerging Delivery Strategies

Caffeine is a naturally occurring alkaloid found in various plants. It acts as a stimulant, antioxidant, anti-inflammatory, and even an aid in pain management, and is found in several over-the-counter medications. This naturally derived bioactive compound is the best-known ingredient in coffee and other beverages, such as tea, soft drinks, and energy drinks, and is widely consumed worldwide. Therefore, it is extremely important to research the effects of this substance on the human body. With this in mind, caffeine and its derivatives have been extensively studied to evaluate its ability to prevent diseases and exert anti-aging and neuroprotective effects. This review is intended to provide an overview of caffeine's effects on cancer and cardiovascular, immunological, inflammatory, and neurological diseases, among others. The heavily researched area of caffeine in sports will also be discussed. Finally, recent advances in the development of novel nanocarrier-based formulations, to enhance the bioavailability of caffeine and its beneficial effects will be discussed.

Cardiorespiratory and Neuroprotective Effects of Caffeine in Neonate Animal Models

Caffeine is widely used to improve neonatal health in animals with low vitality. Due to its pharmacokinetics and pharmacodynamics, caffeine stimulates the cardiorespiratory system by antagonism of adenosine receptors and alteration in Ca+2 ion channel activity. Moreover, the availability of intracellular Ca+2 also has positive inotropic effects by increasing heart contractibility and by having a possible positive effect on neonate vitality. Nonetheless, since neonatal enzymatic and tissular systems are immature at birth, there is a controversy about whether caffeine is an effective therapy for newborns. This review aims to analyze the basic concepts of caffeine in neonatal animal models (rat and mouse pups, goat kids, lambs, and piglets), and it will discuss the neuroprotective effect and its physiological actions in reducing apnea in newborns.

Single-cell transcriptomes reveal heterogeneity of chlorine-induced mice acute lung injury and the inhibitory effect of pentoxifylline on ferroptosis

To investigate the effect of pentoxifylline (PTX) on Chlorine (Cl₂)-induced acute lung injury (ALI) by single-cell RNA sequencing (scRNA-seq). Female BALB/c mice were exposed to Cl₂ at 400 ppm for 15 min. H&E staining was used to observe the degree of lung injury. scRNA-seq was conducted to analysis of normal and Cl₂-exposed mice lung tissues. Immunofluorescence was used to observe genes of interest. Thirty-two mice were randomly divided into four groups: Control, Cl₂, Cl₂+Fer-1, Cl₂+PTX. TEM, WB and ELISA were used to detect ferroptosis-related indicators. The 5, 8, 10, 12, 16, 20 clusters were epithelial cells and 4, 15, 18, 19, 21 clusters were endothelial cells. Pseudo-time analysis revealed the differentiation trajectory of epithelial cells and key regulatory genes (Gclc, Bpifa1, Dnah5 and Dnah9) during the process of injury. Cell-cell communication analysis identified several important receptor-ligand complexes (Nrp1-Vegfa, Nrp2-Vegfa, Flt1-Vegfa and Flt4-Vegfa). Ferroptosis were found up-regulated in epithelial and endothelial cells by GSVA analysis. Highly expressed genes to which closely related ferroptosis were found by SCENIC analysis. PTX could significantly decrease the levels of MDA and abnormal high expression of solute carrier family 7 member 11 (SLC7A11, the key transporter of cystine) as well as increase the expression of GSH/GSSG and glutathione peroxidase 4 (GPX4) (p < 0.05). This study revealed novel molecular features of Cl₂-induced ALI. PTX may be a potential specific drug by inhibiting the process of ferroptosis in epithelial and endothelial cells.

Caffeine dosing regimens in preterm infants with or at risk for apnea of prematurity

BACKGROUND

Very preterm infants often require respiratory support and are therefore exposed to an increased risk of bronchopulmonary dysplasia (chronic lung disease) and later neurodevelopmental disability. Caffeine is widely used to prevent and treat apnea (temporal cessation of breathing) associated with prematurity and facilitate extubation. Though widely recognized dosage regimes have been used for decades, higher doses have been suggested to further improve neonatal outcomes. However, observational studies suggest that higher doses may be associated with harm.

OBJECTIVES

To determine the effects of higher versus standard doses of caffeine on mortality and major neurodevelopmental disability in preterm infants with (or at risk of) apnea, or peri-extubation.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, CINAHL, the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP), and clinicaltrials.gov in May 2022. The reference lists of relevant articles were also checked to identify additional studies.

SELECTION CRITERIA

We included randomized (RCTs), quasi-RCTs and cluster-RCTs, comparing high-dose to standard-dose strategies in preterm infants. High-dose strategies were defined as a high-loading dose (more than 20 mg of caffeine citrate/kg) or a high-maintenance dose (more than 10 mg of caffeine citrate/kg/day). Standard-dose strategies were defined as a standard-loading dose (20 mg or less of caffeine citrate/kg) or a standard-maintenance dose (10 mg or less of caffeine citrate/kg/day). We specified three additional comparisons according to the indication for commencing caffeine: 1) prevention trials, i.e. preterm infants born at less than 34 weeks' gestation, who are at risk for apnea; 2) treatment trials, i.e. preterm infants born at less than 37 weeks' gestation, with signs of apnea; 3) extubation trials: preterm infants born at less than 34 weeks' gestation, prior to planned extubation.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. We evaluated treatment effects using a fixed-effect model with risk ratio (RR) for categorical data and mean, standard deviation (SD), and mean difference (MD) for continuous data.  MAIN RESULTS: We included seven trials enrolling 894 very preterm infants (reported in Comparison 1, i.e. any indication). Two studies included infants for apnea prevention (Comparison 2), four studies for apnea treatment (Comparison 3) and two for extubation management (Comparison 4); in one study, indication for caffeine administration was both apnea treatment and extubation management (reported in Comparison 1, Comparison 3 and Comparison 4). In the high-dose groups, loading and maintenance caffeine doses ranged from 30 mg/kg to 80 mg/kg, and 12 mg/kg to 30 mg/kg, respectively; in the standard-dose groups, loading and maintenance caffeine doses ranged from 6 mg/kg to 25 mg/kg, and 3 mg/kg to 10 mg/kg, respectively. Two studies had three study groups: infants were randomized in three different doses (two of them matched our definition of high dose and one matched our definition of standard dose); high-dose caffeine and standard-dose caffeine were compared to theophylline administration (the latter is included in a separate review). Six of the seven included studies compared high-loading and high-maintenance dose to standard-loading and standard-maintenance dose, whereas in one study standard-loading dose and high-maintenance dose was compared to standard-loading dose and standard-maintenance dose. High-dose caffeine strategies (administration for any indication) may have little or no effect on mortality prior to hospital discharge (risk ratio (RR) 0.86, 95% confidence of interval (CI) 0.53 to 1.38; risk difference (RD) -0.01, 95% CI -0.05 to 0.03; I² for RR and RD = 0%; 5 studies, 723 participants; low-certainty evidence). Only one study enrolling 74 infants reported major neurodevelopmental disability in children aged three to five years (RR 0.79, 95% CI 0.51 to 1.24; RD -0.15, 95% CI -0.42 to 0.13; 46 participants; very low-certainty evidence). No studies reported the outcome mortality or major neurodevelopmental disability in children aged 18 to 24 months and 3 to 5 years. Five studies reported bronchopulmonary dysplasia at 36 weeks' postmenstrual age (RR 0.75, 95% CI 0.60 to 0.94; RD -0.08, 95% CI -0.15 to -0.02; number needed to benefit (NNTB) = 13; I² for RR and RD = 0%; 723 participants; moderate-certainty evidence). High-dose caffeine strategies may have little or no effect on side effects (RR 1.66, 95% CI 0.86 to 3.23; RD 0.03, 95% CI -0.01 to 0.07; I² for RR and RD = 0%; 5 studies, 593 participants; low-certainty evidence). The evidence is very uncertain for duration of hospital stay (data reported in three studies could not be pooled in meta-analysis because outcomes were expressed as medians and interquartile ranges) and seizures (RR 1.42, 95% CI 0.79 to 2.53; RD 0.14, 95% CI -0.09 to 0.36; 1 study, 74 participants; very low-certainty evidence). We identified three ongoing trials conducted in China, Egypt, and New Zealand.

AUTHORS' CONCLUSIONS

High-dose caffeine strategies in preterm infants may have little or no effect on reducing mortality prior to hospital discharge or side effects. We are very uncertain whether high-dose caffeine strategies improves major neurodevelopmental disability, duration of hospital stay or seizures. No studies reported the outcome mortality or major neurodevelopmental disability in children aged 18 to 24 months and 3 to 5 years. High-dose caffeine strategies probably reduce the rate of bronchopulmonary dysplasia. Recently completed and future trials should report long-term neurodevelopmental outcome of children exposed to different caffeine dosing strategies in the neonatal period. Data from extremely preterm infants are needed, as this population is exposed to the highest risk for mortality and morbidity. However, caution is required when administering high doses in the first hours of life, when the risk for intracranial bleeding is highest. Observational studies might provide useful information regarding potential harms of the highest doses.

Anti-Inflammatory Effect of Caffeine on Muscle under Lipopolysaccharide-Induced Inflammation

Evidence has shown that caffeine administration reduces pro-inflammatory biomarkers, delaying fatigue and improving endurance performance. This study examined the effects of caffeine administration on the expression of inflammatory-, adenosine receptor- (the targets of caffeine), epigenetic-, and oxidative metabolism-linked genes in the vastus lateralis muscle of mice submitted to lipopolysaccharide (LPS)-induced inflammation. We showed that caffeine pre-treatment before LPS administration reduced the expression of Il1b, Il6, and Tnfa, and increased Il10 and Il13. The negative modulation of the inflammatory response induced by caffeine involved the reduction of inflammasome components, Asc and Casp1, promoting an anti-inflammatory scenario. Caffeine treatment per se promoted the upregulation of adenosinergic receptors, Adora1 and Adora2A, an effect that was counterbalanced by LPS. Moreover, there was observed a marked Adora2A promoter hypermethylation, which could represent a compensatory response towards the increased Adora2A expression. Though caffeine administration did not alter DNA methylation patterns, the expression of DNA demethylating enzymes, Tet1 and Tet2, was increased in mice receiving Caffeine+LPS, when compared with the basal condition. Finally, caffeine administration attenuated the LPS-induced catabolic state, by rescuing basal levels of Ampk expression. Altogether, the anti-inflammatory effects of caffeine in the muscle can be mediated by modifications on the epigenetic landscape.

Protective Effects of Early Caffeine Administration in Hyperoxia-Induced Neurotoxicity in the Juvenile Rat

High-risk preterm infants are affected by a higher incidence of cognitive developmental deficits due to the unavoidable risk factor of oxygen toxicity. Caffeine is known to have a protective effect in preventing bronchopulmonary dysplasia associated with improved neurologic outcomes, although very early initiation of therapy is controversial. In this study, we used newborn rats in an oxygen injury model to test the hypothesis that near-birth caffeine administration modulates neuronal maturation and differentiation in the hippocampus of the developing brain. For this purpose, newborn Wistar rats were exposed to 21% or 80% oxygen on the day of birth for 3 or 5 days and treated with vehicle or caffeine (10 mg/kg/48 h). Postnatal exposure to 80% oxygen resulted in a drastic reduction of associated neuronal mediators for radial glia, mitotic/postmitotic neurons, and impaired cell-cycle regulation, predominantly persistent even after recovery to room air until postnatal day 15. Systemic caffeine administration significantly counteracted the effects of oxygen insult on neuronal maturation in the hippocampus. Interestingly, under normoxia, caffeine inhibited the transcription of neuronal mediators of maturing and mature neurons. The early administration of caffeine modulated hyperoxia-induced decreased neurogenesis in the hippocampus and showed neuroprotective properties in the neonatal rat oxygen toxicity model.

Bone mesenchymal stem cell-derived exosomes prevent hyperoxia-induced apoptosis of primary type II alveolar epithelial cells in vitro

Background

The presence of alveolar epithelial type II cells (AECIIs) is one of the most important causes of bronchopulmonary dysplasia (BPD). Exosomes from bone mesenchymal stem cells (BMSCs) can reduce hyperoxia-induced damage and provide better results in terms of alveolar and pulmonary vascularization parameters than BMSCs. Currently, intervention studies using BMSC-derived exosomes on the signaling pathways regulating proliferation and apoptosis of alveolar epithelial cells under the condition of BPD have not been reported. This study investigated the effects of rat BMSC-derived exosomes on the proliferation and apoptosis of hyperoxia-induced primary AECIIs in vitro.

Methods

The isolated AECIIs were grouped as follows: normal control (21% oxygen), hyperoxia (85% oxygen), hyperoxia+exosome (20 µg/mL), hyperoxia+exosome+LY294002 (PI3K/Akt inhibitor, 20 µM), and hyperoxia+exosome+rapamycin (mTOR inhibitor, 5 nM). We used the PI3K/Akt inhibitor LY294002 and the mTOR inhibitor rapamycin to determine the roles of the PI3K/Akt and mTOR signaling pathways. The effects of BMSC-derived exosomes on AECII proliferation and apoptosis were assessed, respectively.

Results

Decreased levels of the antiapoptotic protein Bcl-2, the cell proliferation protein Ki67, p-PI3K, p-Akt, and p-mTOR, as well as increased levels of AECII apoptosis and the proapoptotic protein Bax in the hyperoxia group were observed. Notably, Sprague Dawley rat BMSC-derived exosomes could reverse the effect of hyperoxia on AECII proliferation. However, the application of LY294002 and rapamycin inhibited the protective effects of BMSC-derived exosomes.

Conclusion

Our findings revealed that BMSC-derived exosomes could regulate the expression of apoptosis-related proteins likely via the PI3K/Akt/mTOR signaling pathway, thereby preventing hyperoxia-induced AECII apoptosis.

Caffeine and bronchopulmonary dysplasia: Clinical benefits and the mechanisms involved

Bronchopulmonary dysplasia (BPD) is a chronic respiratory disease that occurs during the neonatal period and is commonly associated with prematurity. This condition results in a severe economic burden on society and the families involved. Caffeine is used not only for the treatment of apnea in prematurity, but also for the prevention of BPD. There are multiple clinical benefits of caffeine treatment, including improved extubation success, a reduced duration of mechanical ventilation, improved lung function, and a reduction of patent ductus arteriosus requiring treatment. These clinical benefits of caffeine for the treatment of BPD are supported by both clinical trials and evidence from animal models. However, the mechanism by which caffeine protects against BPD remains unclear. Here, we review the clinical value of caffeine in the prevention of BPD and its potential mechanisms of action, including anti-inflammatory, antioxidant, antifibrotic, and antiapoptotic properties, the regulation of angiogenesis, and diuretic effects. Our aim is to provide a new theoretical basis for the clinical treatment of BPD.

The Conflicting Role of Caffeine Supplementation on Hyperoxia-Induced Injury on the Cerebellar Granular Cell Neurogenesis of Newborn Rats

Preterm birth disrupts cerebellar development, which may be mediated by systemic oxidative stress that damages neuronal developmental stages. Impaired cerebellar neurogenesis affects several downstream targets important for cognition, emotion, and speech. In this study, we demonstrate that oxidative stress induced with high oxygen (80%) for three or five postnatal days (P3/P5) could significantly damage neurogenesis and proliferative capacity of granular cell precursor and Purkinje cells in rat pups. Reversal of cellular neuronal damage after recovery to room air (P15) was augmented by treatment with caffeine. However, downstream transcripts important for migration and differentiation of postmitotic granular cells were irreversibly reduced by hyperoxia, without rescue by caffeine. Protective effects of caffeine in the cerebellum were limited to neuronal survival but failed to restore important transcript signatures.

Pharmacotherapy in Bronchopulmonary Dysplasia: What Is the Evidence?

Bronchopulmonary Dysplasia (BPD) is a multifactorial disease affecting over 35% of extremely preterm infants born each year. Despite the advances made in understanding the pathogenesis of this disease over the last five decades, BPD remains one of the major causes of morbidity and mortality in this population, and the incidence of the disease increases with decreasing gestational age. As inflammation is one of the key drivers in the pathogenesis, it has been targeted by majority of pharmacological and non-pharmacological methods to prevent BPD. Most extremely premature infants receive a myriad of medications during their stay in the neonatal intensive care unit in an effort to prevent or manage BPD, with corticosteroids, caffeine, and diuretics being the most commonly used medications. However, there is no consensus regarding their use and benefits in this population. This review summarizes the available literature regarding these medications and aims to provide neonatologists and neonatal providers with evidence-based recommendations.

Perinatal Hyperoxia and Developmental Consequences on the Lung-Brain Axis

Approximately 11.1% of all newborns worldwide are born preterm. Improved neonatal intensive care significantly increased survival rates over the last decades but failed to reduce the risk for the development of chronic lung disease (i.e., bronchopulmonary dysplasia (BPD)) and impaired neurodevelopment (i.e., encephalopathy of prematurity (EoP)), two major long-term sequelae of prematurity. Premature infants are exposed to relative hyperoxia, when compared to physiological in-utero conditions and, if needed to additional therapeutic oxygen supplementation. Both are associated with an increased risk for impaired organ development. Since the detrimental effects of hyperoxia on the immature retina are known for many years, lung and brain have come into focus in the last decade. Hyperoxia-induced excessive production of reactive oxygen species leading to oxidative stress and inflammation contribute to pulmonary growth restriction and abnormal neurodevelopment, including myelination deficits. Despite a large body of studies, which unraveled important pathophysiological mechanisms for both organs at risk, the majority focused exclusively either on lung or on brain injury. However, considering that preterm infants suffering from BPD are at higher risk for poor neurodevelopmental outcome, an interaction between both organs seems plausible. This review summarizes recent findings regarding mechanisms of hyperoxia-induced neonatal lung and brain injury. We will discuss common pathophysiological pathways, which potentially link both injured organ systems. Furthermore, promises and needs of currently suggested therapies, including pharmacological and regenerative cell-based treatments for BPD and EoP, will be emphasized. Limited therapeutic approaches highlight the urgent need for a better understanding of the mechanisms underlying detrimental effects of hyperoxia on the lung-brain axis in order to pave the way for the development of novel multimodal therapies, ideally targeting both severe preterm birth-associated complications.

Adaptation of the Oxygen Sensing System during Lung Development

During gestation, the most drastic change in oxygen supply occurs with the onset of ventilation after birth. As the too early exposure of premature infants to high arterial oxygen pressure leads to characteristic diseases, we studied the adaptation of the oxygen sensing system and its targets, the hypoxia-inducible factor- (HIF-) regulated genes (HRGs) in the developing lung. We draw a detailed picture of the oxygen sensing system by integrating information from qPCR, immunoblotting, in situ hybridization, and single-cell RNA sequencing data in ex vivo and in vivo models. HIF1α protein was completely destabilized with the onset of pulmonary ventilation, but did not coincide with expression changes in bona fide HRGs. We observed a modified composition of the HIF-PHD system from intrauterine to neonatal phases: Phd3 was significantly decreased, while Hif2a showed a strong increase and the Hif3a isoform Ipas exclusively peaked at P0. Colocalization studies point to the Hif1a-Phd1 axis as the main regulator of the HIF-PHD system in mouse lung development, complemented by the Hif3a-Phd3 axis during gestation. Hif3a isoform expression showed a stepwise adaptation during the periods of saccular and alveolar differentiation. With a strong hypoxic stimulus, lung ex vivo organ cultures displayed a functioning HIF system at every developmental stage. Approaches with systemic hypoxia or roxadustat treatment revealed only a limited in vivo response of HRGs. Understanding the interplay of the oxygen sensing system components during the transition from saccular to alveolar phases of lung development might help to counteract prematurity-associated diseases like bronchopulmonary dysplasia.

Protective Effects of 18β-Glycyrrhetinic Acid on Neonatal Rats with Hyperoxia Exposure

Bronchopulmonary dysplasia (BPD) is a common devastating pulmonary complication in preterm infants. Supplemental oxygen is a lifesaving therapeutic measure used for premature infants with pulmonary insufficiency. However, oxygen toxicity is a significant trigger for BPD. Oxidative stress disrupts lung development, accompanied by increased pro-inflammatory cytokines and chemokines expression and immune cells infiltration in lung tissue. Licorice, a typical traditional herbal medicine, is commonly used in the medicine and food industries. 18β-Glycyrrhetinic acid (18β-GA), a primary active ingredient of licorice, has powerful anti-oxidative and anti-inflammatory effects. This study aimed to determine whether 18β-GA has a protective effect on neonatal rats with hyperoxia exposure. Newborn Sprague-Dawley rats were kept in either 21% (normoxia) or 80% O₂ (hyperoxia) continuously from postnatal day (PN) 1 to 14. 18β-GA was injected intragastrically at 50 or 100 mg/kg body weight once a day from PN 1 to 14. We examined the body weight and alveolar development and measured ROS level and the markers of pulmonary inflammation. Mature-IL-1β and NF-κB pathway proteins, and the NLRP3 inflammasome, were assessed; concurrently, caspase-1 activity was measured. Our results indicated that hyperoxia resulted in alveolar simplification and decreased bodyweight of neonatal rats. Hyperoxia increased ROS level and pulmonary inflammation and activated NF-κB and the NLRP3 inflammasome. 18β-GA treatment inhibited the activation of NF-κB and the NLRP3 inflammasome, decreased ROS level and pulmonary inflammation, improved alveolar development, and increased the bodyweight of neonatal rats with hyperoxia exposure. Our study demonstrates that 18β-GA has a protective effect on neonatal rats with hyperoxia exposure.

Molecular Mechanism of Caffeine in Preventing Bronchopulmonary Dysplasia in Premature Infants

Bronchopulmonary dysplasia (BPD) is a chronic respiratory complication commonly seen in premature infants. Following continuous advances in neonatal intensive care diagnosis and treatment technology, an increasing number of premature babies are being treated successfully. Despite these remarkable improvements, there has been no significant decline in the incidence of BPD; in fact, its incidence has increased as more extremely preterm infants survive. Therefore, in view of the impact of BPD on the physical and mental health of children and the increased familial and social burden on these children, early prevention of BPD is emphasized. In recent decades, the clinical application of caffeine in treating primary apnea in premature infants was shown not only to stimulate the respiratory center but also to confer obvious protection to the nervous and respiratory systems. Numerous clinical cross-sectional and longitudinal studies have shown that caffeine plays a significant role in the prevention and treatment of BPD, but there is a lack of overall understanding of its potential molecular mechanisms. In this review, we summarize the possible molecular mechanisms of caffeine in the prevention or treatment of BPD, aiming to better guide its clinical application.

Hyperoxia Induced Bronchopulmonary Dysplasia-Like Inflammation via miR34a-TNIP2-IL-1β Pathway

Lung injury induced by oxygen is a key contributor to the pathogenesis of preterm infant bronchopulmonary dysplasia (BPD). To date, there are comprehensive therapeutic strategy for this disease, but the underlying mechanism is still in progress. By using lentivirus, we constructed microRNA34a (miR34a)-overexpressing or knockdown A549 cell lines, and exposure to hyperoxia to mimic oxygen induce lung injury. In this study, we investigated 4 proinflammatory cytokines, interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), angiopoietin-1 (Ang-1), and Cyclooxygenase-2 (COX-2) in the secreted sputum of infants who received mechanical ventilation, and found that IL-1β was substantially elevated in the first week after oxygen therapy and with no significant decrease until the fourth week, while TNF-α, Ang-1, and COX-2 were increased in the first week but decreased quickly in the following weeks. In addition, in vitro assay revealed that hyperoxia significantly increased the expression of miR-34a, which positively regulated the proinflammatory cytokine IL-1β in a time- and concentration-dependent manner in A549 cells. Overexpressing or knockdown miR34 would exacerbate or inhibit production of IL-1β and its upstream NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome signaling pathway. Mechanically, it's found that TNFAIP3 interacting protein 2 (TNIP2), an inhibitor of nuclear factor κB (NF-κB), is a direct target of miR34a, negatively regulated activation of NLRP3 inflammasome and the production of IL-1β. Overexpressing TNIP2 ameliorated hyperoxia-induced production of IL-1β and cell apoptosis. Our findings suggest that TNIP2 may be a potential clinical marker in the diagnosis of BPD.

GABAB Receptor-Mediated Impairment of Intermediate Progenitor Maturation During Postnatal Hippocampal Neurogenesis of Newborn Rats

The neurotransmitter GABA and its receptors assume essential functions during fetal and postnatal brain development. The last trimester of a human pregnancy and early postnatal life involves a vulnerable period of brain development. In the second half of gestation, there is a developmental shift from depolarizing to hyperpolarizing in the GABAergic system, which might be disturbed by preterm birth. Alterations of the postnatal GABA shift are associated with several neurodevelopmental disorders. In this in vivo study, we investigated neurogenesis in the dentate gyrus (DG) in response to daily administration of pharmacological GABA_A (DMCM) and GABA_B (CGP 35348) receptor inhibitors to newborn rats. Six-day-old Wistar rats (P6) were daily injected (i.p.) to postnatal day 11 (P11) with DMCM, CGP 35348, or vehicle to determine the effects of both antagonists on postnatal neurogenesis. Due to GABA_B receptor blockade by CGP 35348, immunohistochemistry revealed a decrease in the number of NeuroD1 positive intermediate progenitor cells and a reduction of proliferative Nestin-positive neuronal stem cells at the DG. The impairment of hippocampal neurogenesis at this stage of differentiation is in line with a significantly decreased RNA expression of the transcription factors Pax6, Ascl1, and NeuroD1. Interestingly, the number of NeuN-positive postmitotic neurons was not affected by GABA_B receptor blockade, although strictly associated transcription factors for postmitotic neurons, Tbr1, Prox1, and NeuroD2, displayed reduced expression levels, suggesting impairment by GABA_B receptor antagonization at this stage of neurogenesis. Antagonization of GABA_B receptors decreased the expression of neurotrophins (BDNF, NT-3, and NGF). In contrast to the GABA_B receptor blockade, the GABA_A receptor antagonization revealed no significant changes in cell counts, but an increased transcriptional expression of Tbr1 and Tbr2. We conclude that GABAergic signaling via the metabotropic GABA_B receptor is crucial for hippocampal neurogenesis at the time of rapid brain growth and of the postnatal GABA shift. Differentiation and proliferation of intermediate progenitor cells are dependent on GABA. These insights become more pertinent in preterm infants whose developing brains are prematurely exposed to spostnatal stress and predisposed to poor neurodevelopmental disorders, possibly as sequelae of early disruption in GABAergic signaling.

Possible Beneficial Actions of Caffeine in SARS-CoV-2

The COVID-19 pandemic has established an unparalleled necessity to rapidly find effective treatments for the illness; unfortunately, no specific treatment has been found yet. As this is a new emerging chaotic situation, already existing drugs have been suggested to ameliorate the infection of SARS-CoV-2. The consumption of caffeine has been suggested primarily because it improves exercise performance, reduces fatigue, and increases wakefulness and awareness. Caffeine has been proven to be an effective anti-inflammatory and immunomodulator. In airway smooth muscle, it has bronchodilator effects mainly due to its activity as a phosphodiesterase inhibitor and adenosine receptor antagonist. In addition, a recent published document has suggested the potential antiviral activity of this drug using in silico molecular dynamics and molecular docking; in this regard, caffeine might block the viral entrance into host cells by inhibiting the formation of a receptor-binding domain and the angiotensin-converting enzyme complex and, additionally, might reduce viral replication by the inhibition of the activity of 3-chymotrypsin-like proteases. Here, we discuss how caffeine through certain mechanisms of action could be beneficial in SARS-CoV-2. Nevertheless, further studies are required for validation through in vitro and in vivo models.

The relationship between intermittent hypoxemia events and neural outcomes in neonates

This brief review examines 1) patterns of intermittent hypoxemia in extremely preterm infants during early postnatal life, 2) the relationship between neonatal intermittent hypoxemia exposure and outcomes in both human and animal models, 3) potential mechanistic pathways, and 4) future alterations in clinical care that may reduce morbidity. Intermittent hypoxemia events are pervasive in extremely preterm infants (<28 weeks gestation at birth) during early postnatal life. An increased frequency of intermittent hypoxemia events has been associated with a range of poor neural outcomes including language and cognitive delays, motor impairment, retinopathy of prematurity, impaired control of breathing, and intraventricular hemorrhage. Neonatal rodent models have shown that exposure to short repetitive cycles of hypoxia induce a pathophysiological cascade. However, not all patterns of intermittent hypoxia are deleterious and some may even improve neurodevelopmental outcomes. Therapeutic interventions include supplemental oxygen, pressure support and pharmacologic drugs but prolonged hyperoxia and pressure exposure have been associated with cardiopulmonary morbidity. Therefore, it becomes imperative to distinguish high risk from neutral and/or even beneficial patterns of intermittent hypoxemia during early postnatal life. Identification of such patterns could improve clinical care with targeted interventions for high-risk patterns and minimal or no exposure to treatment modalities for low-risk patterns.

When to start and stop caffeine and why respiratory status matters

Caffeine as tested in the CAP trial is safe and effective for preterm infants with birthweights less than 1250 g. Evidence for its use beyond the indications and timing used in this trial is of low quality and conflicting. Some studies suggest that earlier use of caffeine increases the risk of mortality while others suggest it has important benefits. It appears that infants with apnea of prematurity and those receiving assisted ventilation are the most likely to benefit from caffeine. Based on currently available evidence, routine early prescription of caffeine does not appear to be indicated. Infants continue to have potentially damaging episodes of hypoxia secondary to apnea beyond 34 weeks' postmenstrual age. It is unclear whether prolonged use of caffeine improves outcomes in these infants. Randomized trials to resolve these uncertainties are required. They need to be large, at least the size of the CAP trial, and include neurodevelopmental outcomes.

Precision Medicine in Neonates: Future Perspectives for the Lung

Bronchopulmonary dysplasia (BPD) is the most common complication of pre-term birth with long lasting sequelae. Since its first description more than 50 years ago, many large randomized controlled trials have been conducted, aiming to improve evidence-based knowledge on the optimal strategies to prevent and treat BPD. However, most of these intervention studies have been performed on a population level without regard for the variation in clinical and biological diversity (e.g., gestational age, ethnicity, gender, or disease progression) between patients that is driven by the complex interaction of genetic pre-disposition and environmental exposures. Nevertheless, clinicians provide daily care such as lung protective interventions on an individual basis every day despite the fact that research supporting individualized or precision medicine for monitoring or treating pre-term lungs is immature. This narrative review summarizes four potential developments in pulmonary research that might facilitate the process of individualizing lung protective interventions to prevent development of BPD. Electrical impedance tomography and electromyography of the diaphragm are bedside monitoring tools to assess regional changes in lung volume and ventilation and spontaneous breathing effort, respectively. These non-invasive tools allow a more individualized optimization of invasive and non-invasive respiratory support. Investigation of the genomic variation in caffeine metabolism in pre-term infants can be used to optimize and individualize caffeine dosing regimens. Finally, volatile organic compound analysis in exhaled breath might accurately predict BPD at an early stage of the disease, enabling clinicians to initiate preventive strategies for BPD on an individual basis. Before these suggested diagnostic or monitoring tools can be implemented in daily practice and improve individualized patient care, future research should address and overcome their technical difficulties, perform extensive external validation and show their additional value in preventing BPD.