RESUMEN
Atp8b1 (ATPase, aminophospholipid transporter, class I, type 8B, member 1) is a cardiolipin transporter in the apical membrane of lung epithelial cells. While the role of Atp8b1 in pneumonia-induced acute lung injury (ALI) has been well studied, its potential role in oxidative stress-induced ALI is poorly understood. We herein show that Atp8b1G308V/G308V mice under hyperoxic conditions display exacerbated cell apoptosis at alveolar epithelium and aberrant proliferation of club cells at bronchiolar epithelium. This hyperoxia-induced ambivalent response in Atp8b1G308V/G308V lungs was followed by patchy distribution of non-uniform interstitial fibrosis at late recovery phase under normoxia. Since this club cell abnormality is commonly observed between Atp8b1G308V/G308V lungs under hyperoxic conditions and IPF lungs, we characterized this mouse fibrosis model focusing on club cells. Intriguingly, subcellular morphological analysis of IPF lungs, using transmission electron microscopy (TEM), revealed that metaplastic bronchiolar epithelial cells in fibrotic lesions and deformed type II alveolar epithelial cells (AECs) in alveoli with mild fibrosis, have common morphological features including cytoplasmic vacuolation and dysmorphic lamellar bodies. In conclusion, the combination of Atp8b1 mutation and hyperoxic insult serves as a novel platform to study unfocused role of club cells in IPF.
Asunto(s)
Adenosina Trifosfatasas/metabolismo , Oxígeno/toxicidad , Proteínas de Transferencia de Fosfolípidos/metabolismo , Fibrosis Pulmonar/etiología , Adenosina Trifosfatasas/genética , Animales , Muerte Celular , Proliferación Celular , Células Epiteliales/fisiología , Regulación de la Expresión Génica/efectos de los fármacos , Ratones , Mutación , Estrés Oxidativo , Proteínas de Transferencia de Fosfolípidos/genética , Alveolos Pulmonares/citología , Uteroglobina/genética , Uteroglobina/metabolismoRESUMEN
Increasing evidence shows that hyperoxia is a serious complication of oxygen therapy in acutely ill patients that causes excessive production of free radicals leading to hyperoxia-induced acute lung injury (HALI). Our previous studies have shown that P2X7 receptor activation is required for inflammasome activation during HALI. However, the role of P2X7 in HALI is unclear. The main aim of this study was to determine the effect of P2X7 receptor gene deletion on HALI. Wild-type (WT) and P2X7 knockout (P2X7 KO) mice were exposed to 100% O2 for 72 h. P2X7 KO mice treated with hyperoxia had enhanced survival in 100% O2 compared with the WT mice. Hyperoxia-induced recruitment of inflammatory cells and elevation of IL-1ß, TNF-α, monocyte chemoattractant protein-1, and IL-6 levels were attenuated in P2X7 KO mice. P2X7 deletion decreased lung edema and alveolar protein content, which are associated with enhanced alveolar fluid clearance. In addition, activation of the inflammasome was suppressed in P2X7-deficient alveolar macrophages and was associated with suppression of IL-1ß release. Furthermore, P2X7-deficient alveolar macrophage in type II alveolar epithelial cells (AECs) coculture model abolished protein permeability across mouse type II AEC monolayers. Deletion of P2X7 does not lead to a decrease in epithelial sodium channel expression in cocultures of alveolar macrophages and type II AECs. Taken together, these findings show that deletion of P2X7 is a protective factor and therapeutic target for the amelioration of hyperoxia-induced lung injury.
Asunto(s)
Lesión Pulmonar Aguda/genética , Hiperoxia/complicaciones , Inflamasomas/metabolismo , Receptores Purinérgicos P2X7/genética , Lesión Pulmonar Aguda/etiología , Lesión Pulmonar Aguda/inmunología , Células Epiteliales Alveolares/metabolismo , Animales , Caspasa 1/metabolismo , Células Cultivadas , Técnicas de Cocultivo , Femenino , Hiperoxia/genética , Hiperoxia/inmunología , Interleucina-1beta/biosíntesis , Peroxidación de Lípido , Masculino , Potenciales de la Membrana , Ratones Endogámicos C57BL , Ratones Noqueados , Infiltración Neutrófila , Factores Protectores , Receptores Purinérgicos P2X7/metabolismoRESUMEN
In this Perspective, we discuss some recent developments in the study of the mitochondrial scaffolding protein AKAP121 (also known as AKAP1, or AKAP149 as the human homolog), with an emphasis on its role in mitochondrial physiology. AKAP121 has been identified to function as a key regulatory molecule in several mitochondrial events including oxidative phosphorylation, the control of membrane potential, fission-induced apoptosis, maintenance of mitochondrial Ca(2+)homeostasis, and the phosphorylation of various mitochondrial respiratory chain substrate molecules. Furthermore, we discuss the role of hypoxia in prompting cellular stress and damage, which has been demonstrated to mediate the proteosomal degradation of AKAP121, leading to an increase in reactive oxgyen species production, mitochondrial dysfunction, and ultimately cell death.
Asunto(s)
Proteínas de Anclaje a la Quinasa A/fisiología , Apoptosis/fisiología , Potencial de la Membrana Mitocondrial/fisiología , Mitocondrias/fisiología , Modelos Biológicos , Estrés Oxidativo/fisiología , Animales , Humanos , Oxidación-Reducción , Complejo de la Endopetidasa Proteasomal/metabolismoRESUMEN
Prolonged exposure to oxidative stress causes Acute Lung Injury (ALI) and significantly impairs pulmonary function. Previously we have demonstrated that mitochondrial dysfunction is a key pathological factor in hyperoxic ALI. While it is known that hyperoxia induces the production of stable, but toxic 4-hydroxynonenal (4-HNE) molecule, it is unknown how the reactive aldehyde disrupts mitochondrial function. Our previous in vivo study indicated that exposure to hyperoxia significantly increases 4-HNE-Protein adducts, as well as levels of MDA in total lung homogenates. Based on the in vivo studies, we explored the effects of 4-HNE in human small airway epithelial cells (SAECs). Human SAECs treated with 25 µM of 4-HNE showed a significant decrease in cellular viability and increased caspase-3 activity. Moreover, 4-HNE treated SAECs showed impaired mitochondrial function and energy production indicated by reduced ATP levels, mitochondrial membrane potential, and aconitase activity. This was followed by a significant decrease in mitochondrial oxygen consumption and depletion of the reserve capacity. The direct effect of 4-HNE on the mitochondrial respiratory chain was confirmed using Rotenone. Furthermore, SAECs treated with 25 µM 4-HNE showed a time-dependent depletion of total Thioredoxin (Trx) proteins and Trx activity. Taken together, our results indicate that 4-HNE induces cellular and mitochondrial dysfunction in human SAECs, leading to an impaired endogenous antioxidant response.