Exposure to polychlorinated biphenyls enhances lipid peroxidation in human normal peritoneal and adhesion fibroblasts: a potential role for myeloperoxidase

Abstract

Nitric oxide, superoxide, and lipid peroxidation (LPO) produced under oxidative stress may contribute to the development of postoperative adhesions. The objective of this study was to determine the effects of polychlorinated biphenyls (PCBs) on LPO, superoxide dismutase, myeloperoxidase (MPO), and nitrite/nitrate in human normal peritoneal and adhesion fibroblasts. PCB treatment reduced inducible nitric oxide synthase (iNOS) expression as well as levels of nitrite/nitrate in both cell lines. Although there was no difference in iNOS expression between the two cell lines, adhesion fibroblasts manifested lower basal levels of MPO compared to normal peritoneal fibroblasts. There was a reduction in MPO expression and its activity in response to PCB treatment in normal peritoneal fibroblasts; however, this effect was minimal in adhesion fibroblasts. Moreover, adhesion fibroblasts manifested higher levels of LPO compared to normal peritoneal fibroblasts, whereas PCB treatment increased LPO levels in both cell types. We conclude that PCBs promote the development of the adhesion phenotype by generating an oxidative stress environment. This is evident by lower iNOS, MPO, and nitrite/nitrate and a simultaneous increase in LPO. Loss of MPO activity, possibly through a mechanism involving MPO heme depletion and free iron release, is yet another source of oxidative stress.

FIGURE 1

Real-time RT-PCR for iNOS, MPO, and SOD3. Expression of iNOS, MPO, and SOD3 mRNA levels in normal peritoneal and adhesion fibroblast treated with various PCBs. Results are representative of the mean of three independent experiments.

FIGURE 2

Nitric oxide levels in human normal peritoneal and adhesion fibroblasts (n=3). Griess assay was performed in 24 hrs culture media collected from human normal peritoneal and adhesion fibroblasts before and after various PCB treatments. *p<0.0002, **p=0.0003, ^#p=0.0116, ^##p<0.0001, and ^###p<0.0001 compared to adhesion fibroblasts, respectively. Results are representative of the mean of three independent experiments.

FIGURE 3

iNOS activity in human normal peritoneal and adhesion fibroblasts (n=3). ELISA was performed in cell lysates from human normal peritoneal and adhesion fibroblasts before and after PCBs treatment for 24hrs. *p=0.0102, **p=0.0119, ^#p=0.7418, ^##p<0.01, and ^###p<0.01 compared to adhesion fibroblasts before PCBs treatment, respectively. Results are representative of the mean of three independent experiments.

FIGURE 4

MPO activity in human normal peritoneal and adhesion fibroblasts (n=3). MPO activity was analyzed in cell lysates from human normal peritoneal and adhesion fibroblasts before and after various PCB treatments for 24 hours. *p=0.0017, **p=0.0004, ^#p=0.0007, ^##p=0.0003, and ^###p=0.0002 compared to adhesion fibroblasts before PCBs treatment, respectively. Results are representative of the mean of three independent experiments.

FIGURE 5

Lipid peroxidation levels in human normal peritoneal and adhesion fibroblasts (n=3). LPO was assessed in cell lysates from human normal peritoneal and adhesion fibroblasts before and after various PCB treatments for 24 hours. *p<0.0001, **p<0.0001, ^#p<0.0001, ^##p<0.0001, and ^###p<0.0001 compared to adhesion fibroblasts before PCBs treatment, respectively. Results are representative of the mean of three independent experiments.

Figure 6

A theoretical model has been created that shows the link between PCBs, MPO, SOD3, iNOS, and O₂^•− production.