PPARγ affects nitric oxide in human umbilical vein endothelial cells exposed to Porphyromonas gingivalis

Human Coronary Artery Endothelial Cell Response to Porphyromonas gingivalis W83 in a Collagen Three-Dimensional Culture Model

P. gingivalis has been reported to be an endothelial cell inflammatory response inducer that can lead to endothelial dysfunction processes related to atherosclerosis; however, these studies have been carried out in vitro in cell culture models on two-dimensional (2D) plastic surfaces that do not simulate the natural environment where pathology develops. This work aimed to evaluate the pro-inflammatory response of human coronary artery endothelial cells (HCAECs) to P. gingivalis in a 3D cell culture model compared with a 2D cell culture. HCAECs were cultured for 7 days on type I collagen matrices in both cultures and were stimulated at an MOI of 1 or 100 with live P. gingivalis W83 for 24 h. The expression of the genes COX-2, eNOS, and vWF and the levels of the pro-inflammatory cytokines thromboxane A2 (TXA-2) and prostaglandin I2 (PGI2) were evaluated. P. gingivalis W83 in the 2D cell culture increased IL-8 levels at MOI 100 and decreased MCP-1 levels at both MOI 100 and MOI 1. In contrast, the 3D cell culture induced an increased gene expression of COX-2 at both MOIs and reduced MCP-1 levels at MOI 100, whereas the gene expression of eNOS, vWF, and IL-8 and the levels of TXA2 and PGI2 showed no significant changes. These data suggest that in the collagen 3D culture model, P. gingivalis W83 induces a weak endothelial inflammatory response.

The roles of PPARs in human diseases

Peroxisome proliferator-activated receptors (PPARs), as members of nuclear hormone receptor superfamily, can be activated by binding natural or synthetic ligands. The use of related ligands has revealed many potential roles for PPARs in the pathogenesis of some human metabolic disorders and inflammatory-related disease. Based on the previous studies, this review primarily concluded the current progress of knowledge regarding the specific biological activity of PPARs in cancers, atherosclerosis, and type 2 diabetes mellitus, providing a foundation for the potential therapeutic use of PPAR ligands in human diseases.

Emodin, A Chinese Herbal Medicine, Inhibits Reoxygenation-Induced Injury in Cultured Human Aortic Endothelial Cells by Regulating the Peroxisome Proliferator-Activated Receptor-γ (PPAR-γ) and Endothelial Nitric Oxide Synthase (eNOS) Signaling Pathway

Background

Ischemia-reperfusion injury is associated with vascular dysfunction. The aim of this study was to investigate the role of emodin, a Chinese herbal medicine, in hypoxia-reoxygenation injury in cultured human aortic endothelial cells (HAECs) and its effects on the expression of the peroxisome proliferator-activated receptor-γ (PPAR-γ) and endothelial nitric oxide synthase (eNOS) signaling pathway.

Material/Methods

An in vitro hypoxia-reoxygenation model used cultured human aortic endothelial cells (HAECs). A colorimetric method evaluated the activity of peroxisome proliferator-activated receptor-γ (PPAR-γ). Phosphorylation of PPAR-γ and endothelial nitric oxide synthase (eNOS) were measured by Western blotting. Expression of inflammatory cytokines, tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-8 were evaluated by enzyme-linked immunosorbent assay (ELISA) and Western blotting. Nitric oxide (NO) production was detected by diaminofluorescein-FM diacetate (DAF-FM DA) fluorescence. Immunoprecipitation was used to evaluate the molecular coupling of heat shock protein (HSP)90 and eNOS.

Results

Hypoxia-reoxygenation injury of HAECs reduced the activity and phosphorylation of PPAR-γ, and eNOS, NO production, and HSP90/eNOS molecular coupling in a time-dependent manner. Hypoxia-reoxygenation increased the levels of inflammatory cytokines TNF-α, IL-6, and IL-8 in a time-dependent manner. Emodin treatment recovered PPAR-γ activity and phosphorylation, eNOS phosphorylation, and HSP90/eNOS coupling in HAECS in a concentration-dependent manner, which was reversed by the PPAR-γ inhibitor GW9662, and the eNOS inhibitor, L-NAME. The recovery of HSP90/eNOS coupling by emodin was impaired by GW9662 treatment.

Conclusions

An in vitro hypoxia-reoxygenation (ischemia-reperfusion injury) model of induction of endothelial cell inflammatory mediators showed that emodin recovered the PPAR-γ and eNOS pathway activity.