Estradiol and dihydrotestosterone regulate endothelial cell barrier function after hypergravity-induced alterations in MAPK activity

Abstract

Postflight orthostatic intolerance (POI) was reported to be higher in female than male astronauts and may result from sex-dependent differences in endothelial cell (EC) barrier permeability. Here the effect of 17beta-estradiol (E(2)) and dihydrotestosterone (DHT) on the expression of the tight junction protein occludin, EC barrier function, and MAPK activation over time was 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 transendothelial electrical resistance, 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 phosphotyrosine occludin, decreased cytochrome-c oxidase 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 E(2) vs. DHT were observed. HUVEC showed delayed activation of MAPK with DHT, i.e., 4 h rather than 2 h for E(2), which correlated with decreased paracellular permeability and the observed sex differences in POI in astronauts. These data temporally separate E(2) and DHT effects in HUVEC and provide evidence for the possible protective roles of sex steroids on EC function after brief exposure to low hypergravity.

Effect of Hypergravity on Endothelial Cell Function and Gene Expression

“…Very different stimulation modalities have been used (continuous or discontinuous, g forces ranging from 2 to 2,000×g, treatments ranging from minutes to days). This could be the reason for contrasting results sometimes obtained by the authors on ECs (Spisni et al 2003;Versari et al 2007;Sumanasekera et al 2006Sumanasekera et al , 2007. Till now the studies have been conducted in HUVECs, where prolonged hypergravity exposure results in inhibited cell growth, enhanced migration and increased NO synthesis (Spisni et al 2003;Versari et al 2007).…”

“…Till now the studies have been conducted in HUVECs, where prolonged hypergravity exposure results in inhibited cell growth, enhanced migration and increased NO synthesis (Spisni et al 2003;Versari et al 2007). Others have documented a reduced barrier function and increased permeability after brief hypergravity profile (Sumanasekera et al 2006(Sumanasekera et al , 2007. This fact, together with the consideration that in physiological conditions endothelial cells bear different mechanical stimuli depending on the vascular district, suggested us the hypothesis that cell response to gravitational stress could be different in micro-and macrocirculation.…”

Prenatal Testosterone Induces Sex-Specific Dysfunction in Endothelium-Dependent Relaxation Pathways in Adult Male and Female Rats1

“…One could speculate that excess androgens in adult males and females may have differential effects on the endothelium, which may contribute to the differences in the endothelial pathways affected. Indeed, sexrelated differences with respect to both endothelial signaling molecule expression and endothelium-dependent vascular function have been documented [51][52][53][54]. The contribution of T, if any, to the differential and sex-specific vascular endothelial function in the prenatal T-exposed adults warrants future investigation.…”

Hypergravity induces ATP release and actin reorganization via tyrosine phosphorylation and RhoA activation in bovine endothelial cells

“…They also showed that hypogravity stimulated endothelial growth, enhanced nitric oxide production, and altered actin distribution [29]. Sumanasekera et al reported that brief hypergravity decreased the barrier function, which was attributed to the inhibition of MAPK phosphorylation, in HUVECs [26,27].…”