Autophagic proteins regulate cigarette smoke induced apoptosis: protective role of heme oxygenase-1

HP Kim, X Wang, SJ Lee, MH Huang, Y Wan… - Autophagy, 2008 - Taylor & Francis
HP Kim, X Wang, SJ Lee, MH Huang, Y Wan, SW Ryter, AMK Choi
Autophagy, 2008Taylor & Francis
Cigarette smoke-induced cell death contributes to the pathogenesis of chronic obstructive
pulmonary disease, though the relative roles of apoptosis and autophagy remain unclear.
The inducible stress protein heme oxygenase-1 (HO-1) confers cytoprotection against
oxidative stress. We examined the relationships between these processes in human
bronchial epithelial cells (Beas-2b) exposed to cigarette smoke extract (CSE). CSE induced
morphological and biochemical markers of autophagy in Beas-2b cells. CSE induced …
Cigarette smoke-induced cell death contributes to the pathogenesis of chronic obstructive pulmonary disease, though the relative roles of apoptosis and autophagy remain unclear. The inducible stress protein heme oxygenase-1 (HO-1) confers cytoprotection against oxidative stress. We examined the relationships between these processes in human bronchial epithelial cells (Beas-2b) exposed to cigarette smoke extract (CSE). CSE induced morphological and biochemical markers of autophagy in Beas-2b cells. CSE induced autophagosome formation as evidenced by formation of GFP-LC3 puncta and electron microscopic analysis. Furthermore, CSE increased the processing of microtubule-associated protein-1 light chain-3 (LC3B-I) to LC3B-II, within 1 hr of exposure. Increased LC3B-II was associated with increased autophagy, since inhibitors of lysosomal proteases and of autophagosome-lysosome fusion further increased LC3B-II levels during CSE exposure. CSE concurrently induced extrinsic apoptosis in Beas-2b cells involving early activation of death-inducing-signaling-complex (DISC) formation and downstream activation of caspases (-8,-9,-3). The induction of extrinsic apoptosis by CSE was dependent in part on autophagic proteins. Reduction of beclin-1 levels with beclin 1 siRNA inhibited DISC formation and caspase-3/8 activation in response to CSE. LC3B siRNA also inhibited caspase-3/8 activation.
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