TY - JOUR
T1 - Intracellular C3 protects human airway epithelial cells from stress-associated cell death
AU - Kulkarni, Hrishikesh S.
AU - Elvington, Michelle L.
AU - Perng, Yi Chieh
AU - Liszewski, M. Kathryn
AU - Byers, Derek E.
AU - Farkouh, Christopher
AU - Yusen, Roger D.
AU - Lenschow, Deborah J.
AU - Brody, Steven L.
AU - Atkinson, John P.
N1 - Publisher Copyright:
Copyright © 2019 by the American Thoracic Society
PY - 2019/2
Y1 - 2019/2
N2 - The complement system provides host defense against pathogens and environmental stress. C3, the central component of complement, is present in the blood and increases in BAL fluid after injury. We recently discovered that C3 is taken up by certain cell types and cleaved intracellularly to C3a and C3b. C3a is required for CD4 1 T-cell survival. These observations made us question whether complement operates at environmental interfaces, particularly in the respiratory tract. We found that airway epithelial cells (AECs, represented by both primary human tracheobronchial cells and BEAS-2B [cell line]) cultured in C3-free media were unique from other cell types in that they contained large intracellular stores of de novo synthesized C3. A fraction of this protein reduced (“storage form”) but the remainder did not, consistent with it being pro-C3 (“precursor form”). These two forms of intracellular C3 were absent in CRISPR knockout-induced C3-deficient AECs and decreased with the use of C3 siRNA, indicating endogenous generation. Proinflammatory cytokine exposure increased both stored and secreted forms of C3. Furthermore, AECs took up C3 from exogenous sources, which mitigated stress-associated cell death (e.g., from oxidative stress or starvation). C3 stores were notably increased within AECs in lung tissues from individuals with different end-stage lung diseases. Thus, at-risk cells furnish C3 through biosynthesis and/or uptake to increase locally available C3 during inflammation, while intracellularly, these stores protect against certain inducers of cell death. These results establish the relevance of intracellular C3 to airway epithelial biology and suggest novel pathways for complement-mediated host protection in the airway.
AB - The complement system provides host defense against pathogens and environmental stress. C3, the central component of complement, is present in the blood and increases in BAL fluid after injury. We recently discovered that C3 is taken up by certain cell types and cleaved intracellularly to C3a and C3b. C3a is required for CD4 1 T-cell survival. These observations made us question whether complement operates at environmental interfaces, particularly in the respiratory tract. We found that airway epithelial cells (AECs, represented by both primary human tracheobronchial cells and BEAS-2B [cell line]) cultured in C3-free media were unique from other cell types in that they contained large intracellular stores of de novo synthesized C3. A fraction of this protein reduced (“storage form”) but the remainder did not, consistent with it being pro-C3 (“precursor form”). These two forms of intracellular C3 were absent in CRISPR knockout-induced C3-deficient AECs and decreased with the use of C3 siRNA, indicating endogenous generation. Proinflammatory cytokine exposure increased both stored and secreted forms of C3. Furthermore, AECs took up C3 from exogenous sources, which mitigated stress-associated cell death (e.g., from oxidative stress or starvation). C3 stores were notably increased within AECs in lung tissues from individuals with different end-stage lung diseases. Thus, at-risk cells furnish C3 through biosynthesis and/or uptake to increase locally available C3 during inflammation, while intracellularly, these stores protect against certain inducers of cell death. These results establish the relevance of intracellular C3 to airway epithelial biology and suggest novel pathways for complement-mediated host protection in the airway.
KW - Anaphylatoxins
KW - Chronic obstructive pulmonary disease
KW - Cystic fibrosis
KW - Interstitial lung disease
KW - Oxidants
UR - http://www.scopus.com/inward/record.url?scp=85060885112&partnerID=8YFLogxK
U2 - 10.1165/rcmb.2017-0405OC
DO - 10.1165/rcmb.2017-0405OC
M3 - Article
C2 - 30156437
AN - SCOPUS:85060885112
SN - 1044-1549
VL - 60
SP - 144
EP - 157
JO - American Journal of Respiratory Cell and Molecular Biology
JF - American Journal of Respiratory Cell and Molecular Biology
IS - 2
ER -