2-(4-(2-carboxyethyl)phenethylamino)-5--n-ethylcarboxamidoadenosine and Acute-Lung-Injury

The bone marrow-derived cell (BMDC)-associated inflammatory response plays a key role in the development of acute lung injury (ALI). Activation of adenosine A2A receptor (A2AR) is generally considered to be antiinflammatory, inhibiting BMDC activities to protect against ALI. However, in the present study, we found that in a mouse model of neurogenic ALI induced by severe traumatic brain injury (TBI), BMDC A2AR exerted a proinflammatory effect, aggravating lung damage. This is in contrast to the antiinflammatory effect observed in the mouse oleic acid-induced ALI model (a nonneurogenic ALI model.) Moreover, the A2AR agonist CGS21680 aggravated, whereas the antagonist ZM241385 attenuated, the severe TBI-induced lung inflammatory damage in mice. Further investigation of white blood cells isolated from patients or mouse TBI models and of cultured human or mouse neutrophils demonstrated that elevated plasma glutamate after severe TBI induced interaction between A2AR and the metabotropic glutamate receptor 5 (mGluR5) to increase phospholipase C-protein kinase C signaling, which mediated the proinflammatory effect of A2AR. These results are in striking contrast to the well-known antiinflammatory and protective role of A2AR in nonneurogenic ALI and indicate different therapeutic strategies should be used for nonneurogenic and neurogenic ALI treatment when targeting A2AR.

Topics: Acute Lung Injury; Adenosine; Adenosine A2 Receptor Agonists; Adult; Animals; Bone Marrow Cells; Brain Injuries; Disease Models, Animal; Female; Glutamic Acid; Humans; Male; Mice; Mice, Knockout; Middle Aged; Phenethylamines; Protein Kinase C; Receptor, Adenosine A2A; Receptor, Metabotropic Glutamate 5; Receptors, Metabotropic Glutamate; Signal Transduction; Triazines; Triazoles; Type C Phospholipases

Traumatic brain injury-induced acute lung injury (TBI-ALI) is a serious complication of traumatic brain injury (TBI). Our previous clinical study found that high levels of blood glutamate after TBI were closely related to the occurrence and severity of TBI-ALI, while it remains unknown whether a high concentration of blood glutamate directly causes or aggravates TBI-ALI. We found that inhibition of the adenosine A2A receptor (A2AR) after brain injury alleviated the TBI-ALI; however, it is unknown whether lowering blood glutamate levels in combination with inhibiting the A2AR would lead to better effects. Using mouse models of moderate and severe TBI, we found that intravenous administration of L-glutamate greatly increased the lung water content, lung-body index, level of inflammatory markers in bronchoalveolar lavage fluid and acute lung injury score and significantly decreased the PaO2/FiO2 ratio. Moreover, the incidence of TBI-ALI and the mortality rate were significantly increased, and the combined administration of A2AR activator and exogenous glutamate further exacerbated the above damaging effects. Conversely, lowering the blood glutamate level through peritoneal dialysis or intravenous administration of oxaloacetate notably improved the above parameters, and a further improvement was seen with concurrent A2AR genetic inactivation. These data suggest that A2AR activation aggravates the damaging effect of high blood glutamate concentrations on the lung and that combined treatment targeting both A2AR and blood glutamate may be an effective way to prevent and treat TBI-ALI.

Topics: Acute Lung Injury; Adenosine; Adenosine A2 Receptor Agonists; Animals; Brain Injuries, Traumatic; Bronchoalveolar Lavage Fluid; Glutamic Acid; Male; Mice; Mice, Knockout; Oxaloacetic Acid; Peritoneal Dialysis; Phenethylamines; Receptor, Adenosine A2A; Signal Transduction

Acute respiratory distress syndrome (ARDS) causes significant morbidity and mortality. Exacerbating factors increasing the risk of ARDS remain unknown. Supplemental oxygen is often necessary in both mild and severe lung disease. The potential effects of supplemental oxygen may include augmentation of lung inflammation by inhibiting anti-inflammatory pathways in alveolar macrophages. We sought to determine oxygen-derived effects on the anti-inflammatory A2A adenosinergic (ADORA2A) receptor in macrophages, and the role of the ADORA2A receptor in lung injury. Wild-type (WT) and ADORA2A(-/-) mice received intratracheal lipopolysaccharide (IT LPS), followed 12 hours later by continuous exposure to 21% oxygen (control mice) or 60% oxygen for 1 to 3 days. We measured the phenotypic endpoints of lung injury and the alveolar macrophage inflammatory state. We tested an ADORA2A-specific agonist, CGS-21680 hydrochloride, in LPS plus oxygen-exposed WT and ADORA2A(-/-) mice. We determined the specific effects of myeloid ADORA2A, using chimera experiments. Compared with WT mice, ADORA2A(-/-) mice exposed to IT LPS and 60% oxygen demonstrated significantly more histologic lung injury, alveolar neutrophils, and protein. Macrophages from ADORA2A(-/-) mice exposed to LPS plus oxygen expressed higher concentrations of proinflammatory cytokines and cosignaling molecules. CGS-21680 prevented the oxygen-induced augmentation of lung injury after LPS only in WT mice. Chimera experiments demonstrated that the transfer of WT but not ADORA2A(-/-) bone marrow cells into irradiated ADORA2A(-/-) mice reduced lung injury after LPS plus oxygen, demonstrating myeloid ADORA2A protection. ADORA2A is protective against lung injury after LPS and oxygen. Oxygen after LPS increases macrophage activation to augment lung injury by inhibiting the ADORA2A pathway.

Topics: Acute Lung Injury; Adenosine; Adenosine A2 Receptor Agonists; Animals; Bronchoalveolar Lavage Fluid; Cells, Cultured; Chemokines; Gene Knockout Techniques; Inflammation Mediators; Lipopolysaccharides; Lung; Macrophages, Alveolar; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Oxygen; Oxygen Inhalation Therapy; Phenethylamines; Receptor, Adenosine A2A

The amiloride-sensitive epithelial sodium channel α-subunit (α-ENaC) is an important factor for alveolar fluid clearance during acute lung injury. The relationship between adenosine receptor A(2a) (A(2a)AR) expressed in alveolar epithelial cells and α-ENaC is poorly understood. We targeted the A(2a)AR in this study to investigate its role in the expression of α-ENaC and in acute lung injury.. A549 cells were incubated with different concentrations of A(2a)AR agonist CGS-21680 and with 100 µmol/L CGS-21680 for various times. Rats were treated with lipopolysaccharide (LPS) after CGS-21680 was injected. Animals were sacrificed and tissue was harvested for evaluation of lung injury by analysis of the lung wet-to-dry weight ratio, lung permeability and myeloperoxidase activity. RT-PCR and Western blotting were used to determine the mRNA and protein expression levels of α-ENaC in A549 cells and alveolar type II epithelial cells.. Both mRNA and protein levels of α-ENaC were markedly higher from 4 hours to 24 hours after exposure to 100 µmol/L CGS-21680. There were significant changes from 0.1 µmol/L to 100 µmol/L CGS-21680, with a positive correlation between increased concentrations of CGS-21680 and expression of α-ENaC. Treatment with CGS-21680 during LPS induced lung injury protected the lung and promoted α-ENaC expression in the alveolar epithelial cells.. Activation of A(2a)AR has a protective effect during the lung injury, which may be beneficial to the prognosis of acute lung injury.

Topics: Acute Lung Injury; Adenosine; Animals; Blotting, Western; Cell Line; Epithelial Sodium Channels; Humans; Male; Phenethylamines; Pulmonary Alveoli; Purinergic P1 Receptor Agonists; Rats; Receptors, Purinergic P1; Reverse Transcriptase Polymerase Chain Reaction