Hypoxia increases transepithelial electrical conductance and reduces occludin at the plasma membrane in alveolar epithelial cells via PKC-ζ and PP2A pathway.
During pulmonary edema, the alveolar space is exposed to a hypoxic environment. The integrity of the alveolar epithelial barrier is required for the reabsorption of alveolar fluid. Tight junctions (TJ) maintain the integrity of this barrier. We set out to determine whether hypoxia creates a dysfunctional alveolar epithelial barrier, evidenced by an increase in transepithelial electrical conductance (G(t)), due to a decrease in the abundance of TJ proteins at the plasma membrane. Alveolar epithelial cells (AEC) exposed to mild hypoxia (Po(2) = 50 mmHg) for 30 and 60 min decreased occludin abundance at the plasma membrane and significantly increased G(t). Other cell adhesion molecules such as E-cadherin and claudins were not affected by hypoxia. AEC exposed to hypoxia increased superoxide, but not hydrogen peroxide (H(2)O(2)). Overexpression of superoxide dismutase 1 (SOD1) but not SOD2 prevented the hypoxia-induced G(t) increase and occludin reduction in AEC. Also, overexpression of catalase had a similar effect as SOD1, despite not detecting any increase in H(2)O(2) during hypoxia. Blocking PKC-ζ and protein phosphatase 2A (PP2A) prevented the hypoxia-induced occludin reduction at the plasma membrane and increase in G(t). In summary, we show that superoxide, PKC-ζ, and PP2A are involved in the hypoxia-induced increase in G(t) and occludin reduction at the plasma membrane in AEC.
University of Iowa, Internal Medicine Department, Division of Pulmonary, Critical Care and Occupation Medicine, Iowa City, Iowa 52242, USA.
Juan Carlos
JC
Caraballo
Cecilia
C
Yshii
Maria L
ML
Butti
Whitney
W
Westphal
Jennifer A
JA
Borcherding
Chantal
C
Allamargot
Alejandro P
AP
Comellas
D056809:Alveolar Epithelial Cells / Q000166:cytology* / Q000201:enzymology*; D000818:Animals; D002374:Catalase / Q000378:metabolism; D015687:Cell Hypoxia; D002462:Cell Membrane / Q000378:metabolism*; D004553:Electric Conductivity; D006863:Hydrogen-Ion Concentration; D007811:Lanthanum / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D062793:Occludin; D010313:Partial Pressure; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D013482:Superoxide Dismutase / Q000378:metabolism; D000072105:Superoxide Dismutase-1; D013481:Superoxides / Q000378:metabolism; D000099221:Protein Kinase C zeta
D002374:Catalase; D007811:Lanthanum; D008565:Membrane Proteins; D062793:Occludin; D011493:Protein Kinase C; D054648:Protein Phosphatase 2; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D013481:Superoxides; D000099221:Protein Kinase C zeta; C568987:Ocln protein, rat; C000606292:Sod1 protein, rat
Proc Natl Acad Sci U S A. 1998 Sep 29;95(20):11715-20
9751731
Am J Physiol Lung Cell Mol Physiol. 2006 Sep;291(3):L301-6
16698856
Proc Natl Acad Sci U S A. 2009 Mar 3;106(9):3591-6
19208806
J Biol Chem. 1993 Jan 25;268(3):1982-6
8420972
J Cell Biol. 2002 Sep 2;158(5):967-78
12196510
Biochimie. 2007 Sep;89(9):1107-12
17400358
Circ Res. 2006 May 26;98(10):1314-22
16614303
Hum Gene Ther. 1998 Jun 10;9(9):1381-6
9650622
Antioxid Redox Signal. 2009 Nov;11(11):2673-83
19580395
Cardiovasc Res. 2008 Oct 1;80(1):47-54
18599478
Am J Physiol Lung Cell Mol Physiol. 2009 Mar;296(3):L267-74
19118091
Am J Respir Crit Care Med. 2001 May;163(6):1376-83
11371404
Am J Physiol. 1997 Jul;273(1 Pt 1):L246-55
9252562
Nat Med. 1998 Jun;4(6):698-704
9623979
Am J Physiol. 1996 Jul;271(1 Pt 1):L70-8
8760134
Physiol Genomics. 2003 Feb 06;12(3):209-19
12464684
Am J Respir Cell Mol Biol. 2006 Jul;35(1):127-32
16498080
Adv Exp Med Biol. 2007;618:159-68
18269195
J Cell Sci. 2002 Sep 15;115(Pt 18):3565-73
12186943
Am J Respir Cell Mol Biol. 2008 Jul;39(1):113-23
18314537
J Cell Sci. 2000 Sep;113 ( Pt 18):3187-96
10954417
J Clin Invest. 2000 Sep;106(5):621-6
10974012
Am J Physiol Lung Cell Mol Physiol. 2000 Dec;279(6):L1110-9
11076801
J Virol. 1998 Dec;72(12):9637-44
9811697
Am J Respir Cell Mol Biol. 2003 Jul;29(1):62-70
12600828
Antioxid Redox Signal. 2009 Oct;11(10):2453-65
19358684
Neuroscience. 2007 Jul 13;147(3):664-73
17560040
Am J Respir Cell Mol Biol. 2006 Nov;35(5):519-27
16741163
Am Rev Respir Dis. 1986 Jul;134(1):141-5
3637065
Eur Respir J. 2008 May;31(5):1107-13
18448505
J Clin Invest. 2003 Apr;111(7):1057-64
12671055
J Immunol Methods. 1984 Jun 8;71(1):61-7
6725961
Cell Cycle. 2004 May;3(5):606-10
15034297
Biol Pharm Bull. 2005 Jun;28(6):1083-6
15930750
Physiol Rev. 2002 Jul;82(3):569-600
12087129
J Clin Invest. 2005 Oct;115(10):2702-15
16184195
Free Radic Biol Med. 1999 Sep;27(5-6):572-9
10490277
J Biol Chem. 2007 Apr 13;282(15):11487-98
17298946
Biochem J. 2009 Jun 12;421(1):59-70
19356149
Prog Biophys Mol Biol. 2003 Jan;81(1):1-44
12475568