Many painful conditions occur more frequently in women, and estrogen is a predisposing factor. Estrogen may contribute to some pain syndromes by enhancing axon outgrowth by sensory dorsal root ganglion (DRG) neurons. The objective of the present study was to define mechanisms by which estrogen elicits axon sprouting. The estrogen receptor-alpha agonist propyl pyrazole triol induced neurite outgrowth from cultured neonatal DRG neurons, whereas the estrogen receptor-beta agonist diarylpropionitrile was ineffective. 17beta-Estradiol (E2) elicited sprouting from peripherin-positive unmyelinated neurons, but not larger NF200-positive myelinated neurons. Microarray analysis showed that E2 up-regulates angiotensin II (ANGII) receptor type 2 (AT2) mRNA in vitro, and studies in adult rats confirmed increased DRG mRNA and protein in vivo. AT2 plays a central role in E2-induced axon sprouting because AT2 blockade by PD123,319 eliminated estrogen-mediated sprouting in vitro. We assessed whether AT2 may be responding to locally synthesized ANGII. DRG from adult rats expressed mRNA for renin, angiotensinogen, and angiotensin converting enzyme (ACE), and protein products were present and occasionally colocalized within neurons and other DRG cells. We determined if locally synthesized ANGII plays a role in estrogen-mediated sprouting by blocking its formation using the ACE inhibitor enalapril. ACE inhibition prevented estrogen-induced neuritogenesis. These findings support the hypothesis that estrogen promotes DRG nociceptor axon sprouting by up-regulating the AT2 receptor, and that locally synthesized ANGII can induce axon formation. Therefore, estrogen may contribute to some pain syndromes by enhancing the pro-neuritogenic effects of AT2 activation by ANGII.

A preliminary characterization of protein adsorption and immunosorption kinetics carried out in polymer microchannels is reported. A photoablated poly(ethylene terephthalate) (PET) surface and a PET/polyethylene sealing laminate were used for the channel microfabrication. The surface state of the PET channel substrate and PET/polyethylene lamination were analyzed by using SEM and ATR-FTIR spectroscopy techniques. Protein adsorption and immunosorption studies were carried out using staphylococcal enterotoxin B (SEB) and polyclonal anti-SEB antibody (Ab) samples. Affinity purified polyclonal rabbit (Rb) anti-SEB Ab was radioiodinated and adsorbed in the microchannel. It was determined that the maximum amount of adsorbed antibody was about 13.0 pmol·cm-2 (about 2 μg·cm-2), which corresponds to 0.81 pmol per microchannel. The distribution of the adsorbed protein on the walls of the microchannel depended on the surface state of the polymer exposed to the solution. The amount of the radiolabeled antibody adsorbed on the photoablated PET was about 19.4 pmol·cm-2, whereas it was only 5.5 pmol·cm-2 on the PET/polyethylene lamination. About 30% of the anti-SEB Ab adsorbed on the microchannel surface was found to be biologically active. A study of the kinetics of the SEB−anti-SEB Ab immunochemical reaction was also carried out. It could be substantiated that the forward reaction is diffusion controlled and that the equilibrium for such a reaction could be achieved within about 1 min in the microchannels. This is in good agreement with the calculation of a diffusion-controlled reaction in such a microchannel, according to Fick's second law.