Long-Term Right Ventricular Adaptation to Postnatal Hyperoxia: Too Much of a Good Thing?

Inhibition of CX3C receptor 1-mediated autophagy in macrophages alleviates pulmonary fibrosis in hyperoxic lung injury

AIMS

To investigate the role of CX3CR1 in hyperoxic lung injury induced pulmonary fibrosis.

MATERIALS AND METHODS

Hyperoxic lung injured mice were used as the disease model. Pulmonary fibrosis was determined by H&E and Masson's staining. Autophagy was investigated by western blot, immunofluorescence staining, and transmission electron microscopy.

KEY FINDINGS

We observed that increased CX3CR1 expression corresponded with increased pulmonary fibrosis. Additionally, silencing of CX3CR1 significantly alleviated the fibrosis when compared to the control. We observed that exposure of mouse to hyperoxic environment increased macrophage levels along with an increased CD11b expression in the lung tissues. Subsequently, we also observed an increased expression of LC3-II and decreased p62 expression in hyperoxic mice models, suggesting the potential role of hyperoxia induced autophagy. CD11b and LC3/CX3CR1 were expressed and co-localized in a manner indicating CX3CR1 indeed does regulate macrophage autophagy in the hyperoxic lung injury model. We observed a decrease in hyperoxia-associated fibrosis, along with a decrease in autophagy when we used 3-MA (autophagy inhibitor) in our hyperoxic lung injury model. To elucidate the pathway through which CX3CR1 regulated autophagy, we further analyzed the Akt1 pathway. Our experimental results indicated that the Akt1 inhibitor (A-674563) did significantly decrease macrophage autophagy and fibrosis in hyperoxic mice models.

SIGNIFICANCE

Thus, our data indicates a novel role of CX3CR1 in regulation of macrophage autophagy and promotion of pulmonary fibrosis in hyperoxic lung injured mice.

Pulmonary Hypertension Associated with Bronchopulmonary Dysplasia: A Review

Early pulmonary vascular disease (PVD) and established pulmonary hypertension (PH) are common associations of bronchopulmonary dysplasia (BPD). Diagnosis of PH is often made by echocardiography because of technical and logistic difficulties with the neonatal population. Optimization of respiratory support is the focus of treatment, however, medical therapies are being used with increased frequency. The prognosis for PH associated with BPD (PH-BPD) is tied to the child's respiratory status. PH is associated with increased risk of death in this population, so active screening and treatment is recommended to minimize morbidity and mortality. In this review, we discuss the pathophysiology of PH in infants with BPD, evaluate the current understanding of screening, diagnosis, and follow-up evaluation; describe comorbid conditions; and provide a framework for targeted physiology-based management strategies.