Attenuation of hyperoxia-induced lung injury in neonatal rats by 1α,25-Dihydroxyvitamin D3

Vitamin D3 improved hypoxia-induced lung injury by inhibiting the complement and coagulation cascade and autophagy pathway

BACKGROUND

Pulmonary metabolic dysfunction can cause lung tissue injury. There is still no ideal drug to protect against hypoxia-induced lung injury, therefore, the development of new drugs to prevent and treat hypoxia-induced lung injury is urgently needed. We aimed to explore the ameliorative effects and molecular mechanisms of vitamin D3 (VD3) on hypoxia-induced lung tissue injury.

METHODS

Sprague-Dawley (SD) rats were randomly divided into three groups: normoxia, hypoxia, and hypoxia + VD3. The rat model of hypoxia was established by placing the rats in a hypobaric chamber. The degree of lung injury was determined using hematoxylin and eosin (H&E) staining, lung water content, and lung permeability index. Transcriptome data were subjected to differential gene expression and pathway analyses. In vitro, type II alveolar epithelial cells were co-cultured with hepatocytes and then exposed to hypoxic conditions for 24 h. For VD3 treatment, the cells were treated with low and high concentrations of VD3.

RESULTS

Transcriptome and KEGG analyses revealed that VD3 affects the complement and coagulation cascade pathways in hypoxia-induced rats, and the genes enriched in this pathway were Fgb/Fga/LOC100910418. Hypoxia can cause increases in lung edema, inflammation, and lung permeability disruption, which are attenuated by VD3 treatment. VD3 weakened the complement and coagulation cascade in the lung and liver of hypoxia-induced rats, characterized by lower expression of fibrinogen alpha chain (Fga), fibrinogen beta chain (Fgb), protease-activated receptor 1 (PAR1), protease-activated receptor 3 (PAR3), protease-activated receptor 4 (PAR4), complement (C) 3, C3a, and C5. In addition, VD3 improved hypoxic-induced type II alveolar epithelial cell damage and inflammation by inhibiting the complement and coagulation cascades. Furthermore, VD3 inhibited hypoxia-induced autophagy in vivo and in vitro, which was abolished by the mitophagy inducer, carbonyl cyanide-m-chlorophenylhydrazone (CCCP).

CONCLUSION

VD3 alleviated hypoxia-induced pulmonary edema by inhibiting the complement and coagulation cascades and autophagy pathways.

Vitamin D Impacts on Skeletal Muscle Dysfunction in Patients with COPD Promoting Mitochondrial Health

Skeletal muscle dysfunction is frequently associated with chronic obstructive pulmonary disease (COPD), which is characterized by a permanent airflow limitation, with a worsening respiratory disorder during disease evolution. In COPD, the pathophysiological changes related to the chronic inflammatory state affect oxidant–antioxidant balance, which is one of the main mechanisms accompanying extra-pulmonary comorbidity such as muscle wasting. Muscle impairment is characterized by alterations on muscle fiber architecture, contractile protein integrity, and mitochondrial dysfunction. Exogenous and endogenous sources of reactive oxygen species (ROS) are present in COPD pathology. One of the endogenous sources of ROS is represented by mitochondria. Evidence demonstrated that vitamin D plays a crucial role for the maintenance of skeletal muscle health. Vitamin D deficiency affects oxidative stress and mitochondrial function influencing disease course through an effect on muscle function in COPD patients. This review will focus on vitamin-D-linked mechanisms that could modulate and ameliorate the damage response to free radicals in muscle fibers, evaluating vitamin D supplementation with enough potent effect to contrast mitochondrial impairment, but which avoids potential severe side effects.

Oxygen Toxicity to the Immature Lung-Part I: Pathomechanistic Understanding and Preclinical Perspectives

In utero, the fetus and its lungs develop in a hypoxic environment, where HIF-1α and VEGFA signaling constitute major determinants of further development. Disruption of this homeostasis after preterm delivery and extrauterine exposure to high fractions of oxygen are among the key events leading to bronchopulmonary dysplasia (BPD). Reactive oxygen species (ROS) production constitutes the initial driver of pulmonary inflammation and cell death, altered gene expression, and vasoconstriction, leading to the distortion of further lung development. From preclinical studies mainly performed on rodents over the past two decades, the deleterious effects of oxygen toxicity and the injurious insults and downstream cascades arising from ROS production are well recognized. This article provides a concise overview of disease drivers and different therapeutic approaches that have been successfully tested within experimental models. Despite current studies, clinical researchers are still faced with an unmet clinical need, and many of these strategies have not proven to be equally effective in clinical trials. In light of this challenge, adapting experimental models to the complexity of the clinical situation and pursuing new directions constitute appropriate actions to overcome this dilemma. Our review intends to stimulate research activities towards the understanding of an important issue of immature lung injury.

Chitin-Derived AVR-48 Prevents Experimental Bronchopulmonary Dysplasia (BPD) and BPD-Associated Pulmonary Hypertension in Newborn Mice

Bronchopulmonary dysplasia (BPD) is the most common complication of prematurity and a key contributor to the large health care burden associated with prematurity, longer hospital stays, higher hospital costs, and frequent re-hospitalizations of affected patients through the first year of life and increased resource utilization throughout childhood. This disease is associated with abnormal pulmonary function that may lead to BPD-associated pulmonary hypertension (PH), a major contributor to neonatal mortality and morbidity. In the absence of any definitive treatment options, this life-threatening disease is associated with high resource utilization during and after neonatal intensive care unit (NICU) stay. The goal of this study was to test the safety and efficacy of a small molecule derivative of chitin, AVR-48, as prophylactic therapy for preventing experimental BPD in a mouse model. Two doses of AVR-48 were delivered either intranasally (0.11 mg/kg), intraperitoneally (10 mg/kg), or intravenously (IV) (10 mg/kg) to newborn mouse pups on postnatal day (P)2 and P4. The outcomes were assessed by measuring total inflammatory cells in the broncho-alveolar lavage fluid (BALF), chord length, septal thickness, and radial alveolar counts of the alveoli, Fulton’s Index (for PH), cell proliferation and cell death by immunostaining, and markers of inflammation by Western blotting and ELISA. The bioavailability and safety of the drug were assessed by pharmacokinetic and toxicity studies in both neonatal mice and rat pups (P3-P5). Following AVR-48 treatment, alveolar simplification was improved, as evident from chord length, septal thickness, and radial alveolar counts; total inflammatory cells were decreased in the BALF; Fulton’s Index was decreased and lung inflammation and cell death were decreased, while angiogenesis and cell proliferation were increased. AVR-48 was found to be safe and the no-observed-adverse-effect level (NOAEL) in rat pups was determined to be 100 mg/kg when delivered via IV dosing with a 20-fold safety margin. With no reported toxicity and with a shorter half-life, AVR-48 is able to reverse the worsening cardiopulmonary phenotype of experimental BPD and BPD-PH, compared to controls, thus positioning it as a future drug candidate.

Role of vitamin D-vitamin D receptor signaling on hyperoxia-induced bronchopulmonary dysplasia in neonatal rats

BACKGROUND

Vitamin D exerts therapeutic effects on bronchopulmonary dysplasia (BPD), but its underlying mechanisms remain unclear. The present study was designed to investigate the effects of vitamin D on hyperoxia-induced BPD and elucidate the underlying mechanisms.

METHODS

Neonatal rats were exposed to either room air (control) or 75% O₂ (hyperoxia) and intraperitoneally injected with vitamin D3. After 14 days, a histopathological examination was performed in the lungs of rats. Serum 25-hydroxyvitamin D (25OHD) was measured by liquid chromatography-tandom mass spectrometry (LC-MS)/MS. Interleukin 1 beta (IL-1β) and interferon gamma (IFN-γ) were measured by specific enzyme-linked immunosorbent assays. The messenger RNA and protein levels of vitamin D receptor (VDR), vascular endothelial growth factor (VEGF), VEGF receptor 2 (VEGFR2), and hypoxia-inducible factor 1α (HIF-1α) were determined by real-time quantitative reverse transcription polymerase chain reaction and immunoblot analysis, respectively.

RESULTS

Treatment with vitamin D3 increased serum 25OHD and upregulated VDR in lung tissues with or without hyperoxia. In addition, treatment with vitamin D3 attenuated alveolar simplification, increased VEGF and VEGFR2, and protected alveolar simplification induced by hyperoxia. Furthermore, treatment with vitamin D3 resulted in a decrease of IL-1β and IFN-γ and an increase of HIF-1α in lung tissues under hyperoxia conditions.

CONCLUSION

Vitamin D exerts protective effects on hyperoxia-induced BPD in neonatal rats by regulating vitamin D-VDR signaling pathways.

Maternal Vitamin D Deficiency Causes Sustained Impairment of Lung Structure and Function and Increases Susceptibility to Hyperoxia-induced Lung Injury in Infant Rats

Vitamin D deficiency (VDD) during pregnancy is associated with increased respiratory morbidities and risk for chronic lung disease after preterm birth. However, the direct effects of maternal VDD on perinatal lung structure and function and whether maternal VDD increases the susceptibility of lung injury due to hyperoxia are uncertain. In the present study, we sought to determine whether maternal VDD is sufficient to impair lung structure and function and whether VDD increases the impact of hyperoxia on the developing rat lung. Four-week-old rats were fed VDD chow and housed in a room shielded from ultraviolet A/B light to achieve 25-hydroxyvitamin D concentrations <10 ng/ml at mating and throughout lactation. Lung structure was assessed at 2 weeks for radial alveolar count, mean linear intercept, pulmonary vessel density, and lung function (lung compliance and resistance). The effects of hyperoxia for 2 weeks after birth were assessed after exposure to fraction of inspired oxygen of 0.95. At 2 weeks, VDD offspring had decreased alveolar and vascular growth and abnormal airway reactivity and lung function. Impaired lung structure and function in VDD offspring were similar to those observed in control rats exposed to postnatal hyperoxia alone. Maternal VDD causes sustained abnormalities of distal lung growth, increases in airway hyperreactivity, and abnormal lung mechanics during infancy. These changes in VDD pups were as severe as those measured after exposure to postnatal hyperoxia alone. We speculate that antenatal disruption of vitamin D signaling increases the risk for late-childhood respiratory disease.

Hyperoxia causes miR199a-5p-mediated injury in the developing lung

BACKGROUND

Hyperoxia-induced acute lung injury (HALI) is characterized by increased permeability and infiltration of inflammatory cells, impairment of alveolar development, and compromised lung function. Recent evidence has determined that microRNAs (miRs) are implicated in hyperoxia-induced lung injury, including bronchopulmonary dysplasia (BPD). However, the expression profile and functional role of miR199a-5p in developing lungs have not been reported.

METHODS

The present study was undertaken to explore the role of miR199a-5p in developing mice lungs and human neonates. We exposed neonatal mice for 7 days, mouse lung epithelial cells (MLE12), mouse lung endothelial cells (MLECs), and macrophages (RAW246.7), to hyperoxia at different time points.

RESULTS

Our results demonstrated enhanced miR199a-5p expression in hyperoxia-exposed mice lungs and cells, as well as in tracheal aspirates of infants developing BPD, with significant reduction in the expression of its target, caveolin-1. Next, we observed that miR199a-5p-mimic worsens HALI as evidenced by increased inflammatory cells, cytokines, and lung vascular markers. Conversely, miR199a-5p-inhibitor treatment attenuated HALI.

CONCLUSION

Thus, our findings suggest that miR199a-5p is a potential target for attenuating HALI pathophysiology in the developing lung. Moreover, miR199a-5p-inhibitor could be part of a novel therapeutic strategy for improving BPD in preterm neonates.

Maternal inflammation exacerbates neonatal hyperoxia-induced kidney injury in rat offspring

BACKGROUND

Preclinical studies have demonstrated that maternal inflammation or neonatal hyperoxia adversely affects kidney maturation. This study explored whether prenatal lipopolysaccharide (LPS) exposure can augment neonatal hyperoxia-induced kidney injury.

METHODS

Pregnant Sprague-Dawley rats received intraperitoneal injections of LPS (0.5 mg/kg) in normal saline (NS) or NS on 20 and 21 days of gestation. The pups were reared in room air (RA) or 2 weeks of 85% O₂, creating the four study groups, NS + RA, NS + O₂, LPS + RA, and LPS + O₂. Kidneys were taken for oxidase stress and histological analyses.

RESULTS

The rats exposed to maternal LPS or neonatal hyperoxia exhibited significantly higher kidney injury score, lower glomerular number, higher toll-like receptor 4 (TLR4), myeloperoxidase (MPO), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) expressions, and higher MPO activity compared with the rats exposed to maternal NS and neonatal RA. The rats exposed to both maternal LPS and neonatal hyperoxia exhibited significantly lower glomerular number, higher kidney injury score, TLR4, MPO, and 8-OHdG expressions compared with the rats exposed to maternal LPS or neonatal hyperoxia.

CONCLUSION

Maternal inflammation exacerbates neonatal hyperoxia-induced kidney injury and the underlying mechanism may be related to activation of TLR4 and increased oxidative stress.

Vitamin D and IL-10 Deficiency in Preterm Neonates With Bronchopulmonary Dysplasia

Introduction: Vitamin D deficiency and inflammation are involved with bronchopulmonary dysplasia (BPD) in preterm neonates; however, the clinical evidence still remains scarce. We hypothesized that vitamin D and inflammatory cytokines may be risk factors for BPD in infants. Methods: Preterm infants born between 28 and 31 weeks' gestation were recruited between January 2016 and 2017. Blood samples were all collected at corresponding time points. Vitamin D was measured using an automatic biochemical analyzer, and inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-10) were measured using ELISA. Results: The baseline characteristics for preterm infants without BPD (non-BPD control, n = 20) or with BPD (n = 19) were similar. In the blood samples collected 24-h post birth, vitamin D was significantly reduced in the BPD neonates (non-BPD vs. BPD, 28.96 ± 3.404 vs. 17.99 ± 2.233 nmol/l, p = 0.0134). Inflammatory cytokines TNF-α, IL-1β, and IL-6 were comparable in both groups. The anti-inflammatory cytokine IL-10, however, was significantly decreased in 24-h blood samples from BPD preterm infants (non-BPD vs. BPD, 44.61 ± 10.48 vs. 11.64 ± 2.351 pg/ml, p = 0.0054). In the BPD infants with mild or moderate disease, vitamin D deficiency was quite similar. IL-10 deficiency, however, was more aggravated in the BPD infants with moderate disease. No changes in Vitamin D or cytokines (TNF-α, IL-1β, IL-6, and IL-10) were observed for blood samples collected 2 or 4 weeks after birth. Conclusion: In our pilot study, Vitamin D and IL-10 levels at 24-h of life were risk factors for the development of BPD in very preterm infants.

Oxidative stress diseases unique to the perinatal period: A window into the developing innate immune response

The innate immune system has evolved to play an integral role in the normally developing lung and brain. However, in response to oxidative stress, innate immunity, mediated by specific cellular and molecular programs and signaling, contributes to pathology in these same organ systems. Despite opposing drivers of oxidative stress, namely hyperoxia in neonatal lung injury and hypoxia/ischemia in neonatal brain injury, similar pathways-including toll-like receptors, NFκB and MAPK cascades-have been implicated in tissue damage. In this review, we consider recent insights into the innate immune response to oxidative stress in both neonatal and adult models to better understand hyperoxic lung injury and hypoxic-ischemic brain injury across development and aging. These insights support the development of targeted immunotherapeutic strategies to address the challenge of harnessing the innate immune system in oxidative stress diseases of the neonate.

Mechanisms of Action of Vitamin D as Supplemental Therapy for Pneumocystis Pneumonia

The combination of trimethoprim and sulfamethoxazole (TMP-SMX) is the most effective regimen for therapy of Pneumocystis pneumonia (PCP). As many patients with PCP are allergic or do not respond to it, efforts have been devoted to develop alternative therapies for PCP. We have found that the combination of vitamin D₃ (VitD3) (300 IU/kg/day) and primaquine (PMQ) (5 mg/kg/day) was as effective as TMP-SMX for therapy of PCP. In this study, we investigated the mechanisms by which vitamin D enhances the efficacy of PMQ. C57BL/6 mice were immunosuppressed by CD4⁺ cell depletion, infected with Pneumocystismurina for 8 weeks, and then treated for 9 days with the combination of VitD3 and PMQ (VitD3-PMQ) or with TMP-SMX or PMQ to serve as controls. The results showed that vitamin D supplementation increased the number of CD11c⁺ cells, suppressed the production of proinflammatory cytokines (tumor necrosis factor alpha [TNF-α], gamma interferon [IFN-γ], and interleukin-6 [IL-6]) and inducible nitric oxide synthase (iNOS), and enhanced the expression of genes related to antioxidation (glutathione reductase and glutamate-cysteine ligase modifier subunit), antimicrobial peptides (cathelicidin), and autophagy (ATG5 and beclin-1). These results suggest that the main action of vitamin D is enhancing the ability of the host to defend against Pneumocystis infection.

Vitamin D attenuates hyperoxia-induced lung injury through downregulation of Toll-like receptor 4

With considerable morbidity and mortality, bron-chopulmonary dysplasia (BPD) is a focus of attention in neonatology. Hyperoxia-induced lung injury has long been used as a model of BPD. Among all the signaling pathways involved, Toll-like receptor 4 (TLR4) has been demonstrated to play an important role, and is known to be regulated by vitamin D. This study aimed at elucidating the effect of vitamin D on hyperoxia-induced lung injury and the role of TLR4 in the process. Vitamin D was administered to hyperoxia-treated neonatal rats to investigate changes in the morphology of lungs and expression of pro-inflammatory cytokines, apoptotic proteins and TLR4. Vitamin D attenuated hyperoxia-induced lung injury by protecting the integrity of the lung structure, decreasing extracellular matrix deposition and inhibiting inflammation. The upregulation of TLR4 by hyperoxia was ameliorated by vitamin D and apoptosis was reduced. Vitamin D administration antagonized the activation of TLR4 and therefore alleviated inflammation, reduced apoptosis and preserved lung structure.

Protective effect of vitamin D against hyperoxia-induced lung injury in newborn rats

INTRODUCTION

Preterm infants have risks of developing vitamin D deficiency. Thus we aimed to investigate the effect of vitamin D on hyperoxia-induced lung injury in newborn rats.

METHODS

Full term rat pups were included in the study 12-24 hr after delivery. The pups were randomly divided into eight groups as follows: normoxia control group (NC), normoxia plus vitamin D group (ND1, 1 ng/gr/day vitamin D), normoxia plus vitamin D group (ND2, 3 ng/gr/day vitamin D), normoxia plus vitamin D group (ND3, 5 ng/gr/day vitamin D), hyperoxia control group (HC), hyperoxia plus vitamin D group (HD1, 1 ng/gr/day vitamin D), hyperoxia plus Vitamin D group (HD2, 3 ng/gr/day vitamin D), hyperoxia plus vitamin D group (HD3, 5 ng/gr/day vitamin D). The histopathological effects of vitamin D were assessed by alveolar surface area (with mean linear intercept (MLI) method), apoptosis index and proliferating cell nuclear antigen (PCNA) index.

RESULTS

MLI values were significantly lower among three groups (HD1: 83.93 ± 1.95 μm, HD2: 81.76 ± 1.68 μm, and HD3: 82.33 ± 1.87 μm) when compared with HC group (92.98 ± 2.09 μm) (P = 0.001, P = 0.0004, P = 0.002, respectively). Apoptotic cell index were significantly lower among three treatment groups (HD1: 1.455 ± 0.153, HD2: 0.575 ± 0.079, and HD3: 0.700 ± 0.105) when compared with HC group (2.500 ± 0.263) (P = 0.001, P = 0.001, P = 0.001, respectively). Although PCNA positive cell index did not change in HD1 group (0.132 ± 0.008) (P > 0.05), there were significant increases in HD2 (0.277  ± 0.026) and HD3 (0.266 ± 0.018) group when compared with HC group (0.142 ± 0.010) (HD2 P = 0.001, HD3 P = 0.001).

CONCLUSION

Vitamin D seems to protect hyperoxia-induced lung injury in newborn rats. Pediatr Pulmonol. 2017;52:69-76. © 2016 Wiley Periodicals, Inc.