Bcl-2–related protein A1 is an endogenous and cytokine-stimulated mediator of cytoprotection in hyperoxic acute lung injury
Chuan Hua He, Aaron B. Waxman, Chun Geun Lee, Holger Link, Morgan E. Rabach, Bing Ma, Qingsheng Chen, Zhou Zhu, Mei Zhong, Keiko Nakayama, Keiichi I. Nakayama, Robert Homer, Jack A. Elias
Chuan Hua He, Aaron B. Waxman, Chun Geun Lee, Holger Link, Morgan E. Rabach, Bing Ma, Qingsheng Chen, Zhou Zhu, Mei Zhong, Keiko Nakayama, Keiichi I. Nakayama, Robert Homer, Jack A. Elias
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Article Pulmonology

Bcl-2–related protein A1 is an endogenous and cytokine-stimulated mediator of cytoprotection in hyperoxic acute lung injury

Abstract

Hyperoxic acute lung injury (HALI) is characterized by a cell death response with features of apoptosis and necrosis that is inhibited by IL-11 and other interventions. We hypothesized that Bfl-1/A1, an antiapoptotic Bcl-2 protein, is a critical regulator of HALI and a mediator of IL-11–induced cytoprotection. To test this, we characterized the expression of A1 and the oxygen susceptibility of WT and IL-11 Tg(+) mice with normal and null A1 loci. In WT mice, 100% O2 caused TUNEL+ cell death, induction and activation of intrinsic and mitochondrial-death pathways, and alveolar protein leak. Bcl-2 and Bcl-xl were also induced as an apparent protective response. A1 was induced in hyperoxia, and in A1-null mice, the toxic effects of hyperoxia were exaggerated, Bcl-2 and Bcl-xl were not induced, and premature death was seen. In contrast, IL-11 stimulated A1, diminished the toxic effects of hyperoxia, stimulated Bcl-2 and Bcl-xl, and enhanced murine survival in 100% O2. In A1-null mice, IL-11–induced protection, survival advantage, and Bcl-2 and Bcl-xl induction were significantly decreased. VEGF also conferred protection via an A1-dependent mechanism. In vitro hyperoxia also stimulated A1, and A1 overexpression inhibited oxidant-induced epithelial cell apoptosis and necrosis. A1 is an important regulator of oxidant-induced lung injury, apoptosis, necrosis, and Bcl-2 and Bcl-xl gene expression and a critical mediator of IL-11– and VEGF-induced cytoprotection.

Authors

Chuan Hua He, Aaron B. Waxman, Chun Geun Lee, Holger Link, Morgan E. Rabach, Bing Ma, Qingsheng Chen, Zhou Zhu, Mei Zhong, Keiko Nakayama, Keiichi I. Nakayama, Robert Homer, Jack A. Elias

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A1 regulation of hyperoxia-induced apoptosis and necrosis in vitro. MLE ...
A1 regulation of hyperoxia-induced apoptosis and necrosis in vitro. MLE cells were stably transfected with an expression construct alone (pcDNA3.1) (vector) or the same construct containing cDNA encoding A1a (A1a-pcDNA3.1) or A1d (A1d-pcDNA3.1). The cells were incubated under normal conditions (5% CO2 and air) or under hyperoxic conditions (95% O2 and 5% CO2). (A) Annexin V and propidium iodide (PI) staining are analyzed with FACS to compare the apoptosis and necrosis induced by 72 hours in 95% O2. (B) We compare the caspase activities in these cells before (0 hours) and at intervals after the start of 95% O2 exposure. The FACS diagrams are representative of a minimum of 4 similar evaluations. The values in B are the mean ± SEM of evaluations in a minimum of 5 mice. *P < 0.05; **P < 0.01.