Endothelial cell leptin receptors, leptin and interleukin-8 in the pathogenesis of preeclampsia: An in-vitro study

Abstract

Objective: Increased leptin hormone and leptin receptor may enhance the generation of proinflammatory cytokines by endothelial cells and lead to endothelial dysfunction. This study assessed the umbilical cord endothelial leptin receptor levels in preeclampsia and investigated the effect of leptin on endothelial interleukin-8 (IL-8) production.

Materials and methods: The association between IL-8 levels with leptin stimulation was investigated in leptin-treated human endothelial cells. Endothelial cell leptin receptor levels were evaluated using immunohistochemistry staining, and endothelial IL-8 protein expression by Western blot analysis. Data are presented as mean ± standard error of the mean (SEM). Statistical significance was analyzed using Student's t-test or Mann-Whitney U test and one-way analysis of variance.

Results: Leptin receptor immunoreactivity increased significantly in umbilical cord venous and arterial endothelial cells in normal pregnancy (n=12) compared with preeclampsia (n=7) endothelial cells. The corresponding preeclampsia versus control histologic scores (mean ± SEM) were 67.9±8.8 vs. 127.6±23.1, (p=0.011) for the leptin receptor and 55.4±8,0 vs. 93.7±17.1 (p=0.035), respectively, for the vein endothelial cells. Leptin treatment significantly increased IL-8 protein levels (control vs. 100 and 1000 ng/mL, p=0.003).

Conclusion: The findings of increased umbilical cord endothelial leptin receptor levels in preeclampsia and increased endothelial IL-8 expression with exposure to higher leptin concentrations may indicate the contribution of leptin to endothelial dysfunction and increased neutrophil-endothelial interaction, which are significant pathophysiologic features of preeclampsia.

Keywords: Preeclampsia; endothelial cell; interleukin-8; leptin; leptin receptor; umbilical cord.

Figure 1. Leptin receptor immunoreactivity in umbilical cord arterial and venous sections from gestational age-matched preeclamptic and normal pregnancies. Representative micrographs of immunohistochemical staining for leptin receptor in preeclampsia (n=7) (A, B, C, D) and normal pregnancy (n=12) (E, F, G, H). Graphs represent the histologic score analysis of leptin receptor immunostaining in umbilical cord vein (I) and umbilical cord artery (J) endothelial cells expressed as mean ± standard error of the mean *p=0.035; endothelial cells of the umbilical vein, preeclampsia vs. normal pregnancy **p=0.011; endothelial cells of the umbilical artery, preeclampsia vs. normal pregnancy PE: Preeclampsia

Figure 2. Leptin stimulates interleukin-8 expression in endothelial cells. Representative immunoblotting in human endometrial endothelial cells (n=2) and human umbilical vein endothelial cells (n=1) cultures treated with leptin for 24 hours. Western blot analysis demonstrating the effect of leptin on interleukin-8 levels in human endometrial endothelial cells and human umbilical vein endothelial cells. Confluent human endometrial endothelial cells and human umbilical vein endothelial cells cultures were treated with vehicle (control), 0.1 1, 10, 100 and l000 ng/mL leptin, respectively, for 24 hours, to evaluate the effect of leptin. Immunoblot bands for interleukin-8 were quantified using Image J. Bars represent mean ± standard error of the mean (n=3) *p<0.05; both for 100 and 1000 ng/mL leptin vs. control. Data are representative of three independent experiments IL: Interleukin