cGMP-dependent ADP depolymerization of actin mediates estrogen increase in cervical epithelial permeability

Estrogen increasessecretion of cervical mucus in women, and the effect depends onfragmentation of the cytoskeleton. The objective of the present studywas to understand the molecular mechanism of estrogen action. Treatmentof human cervical epithelial cells with 17-estradiol, sodiumnitroprusside (SNP), or 8-bromoguanosine 3',5'-cyclic monophosphate(8-Br-cGMP) increased cellular monomeric G-actin and decreasedpolymerized F-actin. The effects of estradiol were blocked bytamoxifen, by the guanylate cyclase inhibitor LY-83583, and by thecGMP-dependent protein kinase inhibitor KT-5823. The effects of SNPwere blocked by LY-83583 and KT-5823, while the effects of 8-Br-cGMPwere blocked only by KT-5823. Treatment with phalloidin decreasedparacellular permeability and G-actin. Treatment with 17-estradiol,SNP, or 8-Br-cGMP attenuated SNP-induced phosphorylation of[³²P]adenylate NAD in vitro: tamoxifen blocked the effectof estrogen; LY-83583 blocked the effect of SNP but not that of8-Br-cGMP, while KT-5823 blocked effects of both SNP and 8-Br-cGMP.These results indicate that estrogen, nitric oxide (NO), and cGMPstimulate actin depolymerization. A possible mechanism is NO-induced,cGMP-dependent protein kinase augmentation of ADP-ribosylation ofmonomeric actin.