Regulation of pentraxin-3 by antioxidants

Abstract

Background: Pentraxin-3 (PTX3) may be a useful biomarker in sepsis, but its regulatory mechanisms are still unclear. Oxidative stress is well defined in patients with sepsis and has a role in regulation of inflammatory pathways which may include PTX3. We undertook an in vitro study of the effect of antioxidants on regulation of PTX3 in endothelial cells combined with a prospective observational pilot study of PTX3 in relation to markers of antioxidant capacity and oxidative stress in patients with sepsis.

Methods: Human endothelial cells were cultured with lipopolysaccharide 2 microg ml(-1), peptidoglycan G 20 microg ml(-1), tumour necrosis factor (TNF) alpha 10 ng ml(-1), interleukin-1 (IL-1) beta 20 ng ml(-1), or killed Candida albicans yeast cells plus either N-acetylcysteine (NAC) 25 mM, trolox 100 mM, or idebenone 1 microM. Plasma samples were obtained from 15 patients with sepsis and 11 healthy volunteers.

Results: PTX3 levels in plasma were higher in patients with sepsis than in healthy people [26 (1-202) ng ml(-1) compared with 6 (1-12) ng ml(-1), P=0.01]. Antioxidant capacity was lower in patients with sepsis than healthy controls [0.99 (0.1-1.7) mM compared with 2.2 (1.3-3.3) mM, P=0.01]. In patients with sepsis, lipid hydroperoxide levels were 3.32 (0.3-10.6) nM and undetectable in controls. We found no relationship between PTX3 and antioxidant capacity or lipid hydroperoxides. Cell expression of PTX3 increased with all inflammatory stimulants but was highest in cells treated with TNFalpha plus IL-1beta. PTX3 concentrations were lower in cells co-treated with antioxidants (all P<0.05), associated with lower nuclear factor kappaB expression for NAC and trolox (P<0.05).

Conclusions: PTX3 expression is down-regulated in vitro by antioxidants. Plasma levels of PTX3 are elevated in sepsis but seem to be unrelated to markers of oxidant stress or antioxidant capacity.

Fig 1

(a) Plasma PTX3 concentrations in 15 patients with sepsis and 11 healthy subjects. Squares are females, circles are males. (b) Data sets compared using Mann–Whitney U-test. Plasma PTX3 concentrations according to APACHE II score quartile in 15 patients with sepsis.

Fig 2

Plasma total antioxidant capacity in 15 patients with sepsis and 11 healthy subjects. Data sets compared using Mann–Whitney U-test.

Fig 3

The effect of different inflammatory stimuli on PTX3 expression by human endothelial cells in vitro. Note the different scales on the two graphs. Data are from four replicate experiments conducted in triplicate. LPS, lipopolysaccharide (2 µg ml⁻¹); PepG, peptidoglycan G (20 µg ml⁻¹); TNFα, tumour necrosis factor α (10 ng ml⁻¹); IL-1β, interleukin-1β (20 ng ml⁻¹); C. albicans, heat-killed Candida albicans cells (MOI=3).

Fig 4

The effect of antioxidants on PTX3 and NFκB expression in human endothelial cells treated with TNFα and IL-1β. Data are from four replicate experiments conducted in triplicate and were analysed by the Kruskal–Wallis with Mann–Whitney U post hoc testing. *Significantly lower than cells without antioxidant (P<0.001).