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Updated: Jul 28, 2026
Imaging of Estrogen Receptor-α in Rat Pial Arterioles using a Digital Immunofluorescent Microscope
Published on: November 29, 2011
Effects of estrogen on nitric oxide synthase expression in rat aorta allograft and smooth muscle cells
1Department of Surgery, Georgetown University Medical Center, Washington, DC 20007, USA.
Background:
We find that chronic estradiol treatment inhibits the development of transplant arteriosclerosis (TA). The mechanism of this inhibition remains unclear. The objective of this study is to investigate in a non-cyclosporin-requiring TA model whether estradiol-17beta treatment modulates the expression of both endothelial nitric oxide synthase (ecNOS) and inducible nitric oxide synthase (iNOS) in the early phase following transplantation.
Methods:
Orthotopic abdominal aorta allograft transplantation was performed in male rats using Brown-Norway rats as donors and Lewis rats as recipients. The recipients (n = 50) were treated with estradiol 20 microg/kg/day or placebo by osmotic minipump from 2 days prior to surgery until sacrifice on post-operative days 1, 3, 7, 14, and 21. The allografts were harvested and cross-sections of the vascular tissues were used for immunohistochemical staining of ecNOS and iNOS. The effects of estradiol on cytokine-induced (tumor necrosis factor-alpha and interleukin-1 beta iNOS protein and messenger RNA (mRNA) expression were also evaluated on rat aorta smooth muscle cells by Western blotting and RT-PCR in vitro, respectively.
Results:
The expression of ecNOS and iNOS was graded semiquantitatively from 0 to +3. Estrogen elevates ecNOS expression in the intima in the early phase following transplantation, 0.85 +/- 0.14 (day 7) and 1.08 +/- 0.11 (day 14) vs 1.53 +/- 0.25 (day 7) and 1.60 +/- 0.17 (day 14) for placebo and estradiol treated groups respectively, p < 0.01. Estrogen suppresses iNOS expression in neointima (0.67 +/- 0.17 vs 0.24 +/- 0.04, p < 0.01, day 14), media (1.03 +/- 0.15 vs 0.4 +/- 0.09, p < 0.01, day 7), and adventitia (1.55 +/- 0.12 vs 1.02 +/- 0.10, p < 0.05, day 14) in the same phase. Estradiol treatment inhibits cytokine-induced iNOS mRNA expression in cultured smooth muscle cells.
Conclusions:
Chronic estrogen treatment modulates both ecNOS and iNOS expression in the early phase following transplantation. This is associated with the estrogen-protective effects on TA.
Insights
Estradiol treatment inhibits transplant arteriosclerosis by increasing endothelial nitric oxide synthase (ecNOS) and decreasing inducible nitric oxide synthase (iNOS) expression in the early stages post-transplantation.
Area of Science:
- Vascular Biology
- Immunology
- Endocrinology
Background:
- Chronic estradiol treatment demonstrates inhibitory effects on transplant arteriosclerosis (TA).
- The precise mechanisms underlying estradiol's protective role in TA remain incompletely understood.
- This study investigates estradiol-17beta's impact on nitric oxide synthase expression in a rat TA model.
Purpose of the Study:
- To determine if estradiol-17beta modulates endothelial nitric oxide synthase (ecNOS) and inducible nitric oxide synthase (iNOS) expression.
- To examine these modulations in the early phase following allograft transplantation.
- To elucidate the cellular mechanisms of estradiol's anti-TA effects.
Main Methods:
- Orthotopic abdominal aorta allografts were performed in Lewis rats from Brown-Norway donors.
- Recipients received daily estradiol or placebo treatment via osmotic minipump.
- Immunohistochemistry, Western blotting, and RT-PCR were used to assess ecNOS and iNOS expression in graft tissues and cultured smooth muscle cells.
Main Results:
- Estradiol significantly elevated ecNOS expression in the intima during the early post-transplant period.
- Estradiol suppressed iNOS expression in the neointima, media, and adventitia.
- In vitro studies confirmed that estradiol inhibits cytokine-induced iNOS mRNA expression in smooth muscle cells.
Conclusions:
- Chronic estrogen administration modulates both ecNOS and iNOS expression post-transplantation.
- These molecular changes are linked to the observed protective effects of estrogen against transplant arteriosclerosis.
- The findings highlight a potential therapeutic role for estrogen in managing TA.
