Submitted on August 4, 2006
Accepted on March 8, 2007
Estradiol and dihydrotestosterone regulate endothelial cell barrier function following hypergravity-induced alterations in MAPK activity
Wasana K Sumanasekera1, Gamini U Sumanasekera2, Kathleen A Mattingly1, Susan M Dougherty1, Robert S Keynton3, and Carolyn M. Klinge4*
1 Biochemistry & Molecular Biology, University of Louisville, Louisville, Kentucky, United States
2 Physics, University of Louisville, Louisville, Kentucky, United States
3 Bioengineering, University of Louisville, Louisville, Kentucky, United States
4 Biochemistry & Molecular Biology, University of Louisville, Louisville, Kentucky, United States; Louisville, Kentucky, United States
* To whom correspondence should be addressed. E-mail: carolyn.klinge{at}louisville.edu.
Post-flight orthostatic intolerance (POI) was reported to be higher in female than male astronauts and may result from gender-dependent differences in endothelial cell (EC) barrier permeability. Here, the effect of estradiol (E2) and dihydrotestosterone (DHT) on the expression of the tight junction protein occludin, EC barrier function, and MAPK activation over time were tested after subjecting human umbilical vein EC (HUVEC) to brief hypergravity identical to that experienced by astronauts during liftoff (LO) into space. After LO hypergravity, HUVEC showed a time-dependent decrease in occludin correlating with an increase in paracellular permeability and a decrease in trans-endothelial electrical resistance (TEER), indicating a decrease in EC barrier function. LO hypergravity inhibited MAPK activation which remained suppressed 4 h after LO. Inhibition of MAPK activation correlated with decreased phospho-tyrosine occludin, decreased cytochrome c oxidase (COX) activity, and increased paracellular permeability, suggesting a mechanism by which LO hypergravity decreased EC barrier function. Time-dependent differences in MAPK activation, decreased occludin, and EC barrier function between HUVEC treated with E2 versus DHT were observed. HUVEC showed delayed activation of MAPK with DHT, i.e., 4 h, rather than 2 h for E2, which correlated with decreased paracellular permeability and the observed gender differences in POI in astronauts. These data temporally separate E2 and DHT effects in HUVECs and provide evidence for the possible protective roles of sex steroids on EC function following brief exposure to low hypergravity.
