Effects of 4-nonylphenol and/or diisononylphthalate on THP-1 cells: impact of endocrine disruptors on human immune system parameters.

The aim of the present work is to investigate the link between two endocrine disruptor compounds (EDCs), which are chemicals that interfere with the hormone system in human and wildlife, and the human immune response through a study of their effects on the THP-1 human cell line which was used as a model for macrophages. We used two EDCs, diisononylphthalate (DiP) and 4-n-nonylphenol (NP) alone or in combination in order to evaluate the effects of these compounds on several parameters of the immune response - cytokine secretion, phagocytosis and the putative implication of the estrogen receptors - by studying the level of MAPK activation. NP and DiP strongly reduced phagocytosis and modify cytokine secretions. Indeed, differentiated THP-1 cell exposures (i) to 5 and 10 microM of combination of NP and DiP induced an IL-8 level in the medium respectively of 28.9 and 45 percent higher than the level obtained for the control (untreated cells), (ii) to combination of NP and DiP at 10 microM induced an increase of IL-1ß level in comparison to the control level, (iii) to combination of NP and DiP induced an increase of TNF-α level whatever the concentration of EDCs tested (between 0 and 10 microM). Lastly, differentiated THP-1 cell exposure to NP, DiP alone or in combination (2 microM for each condition) induced a decrease of ERK1/2 phosphorylation in comparison to ERK1/2 phosphorylation level of the control. Moreover, differentiated THP-1 cell treatments by ICI-182780 (an estrogen receptor antagonist) supressed the EDC effects on ERK1/2 phosphorylation level which indicates an estrogen receptor-dependent pathway. These results suggest that EDCs have the ability to alter the human immune function, maybe by interfering with endocrine balance.

Oxidative stress induction by nanoparticles in THP-1 cells with 4-HNE production: stress biomarker or oxidative stress signalling molecule?

The aim of this study was to investigate whether carbon black (CB) nanoparticles might induce toxicity to monocytic cells in vitro via an oxidative stress mechanism involving formation of the lipid peroxidation product 4-hydroxynonenal (4-HNE) and the subsequent role of 4-HNE in inducing further cytotoxic effects. ROS production in cells by CB nanoparticles was shown by the oxidation of DCFH after a short time exposure. These particles induced the formation of 4-HNE-protein adducts and significant modification of glutathione content corresponding to an increase of oxidized glutathione form (GSSG) and a decrease of total glutathione (GSX) content. These results attest to an oxidative stress induced by the carbon black nanoparticles, although no induction of HO-1 protein expression was detected. Concerning the effects of a direct exposure to 4-HNE, our results showed that 4-HNE is not cytotoxic for concentrations lower than 12.5 microM. By contrast, it provokes a very high cytotoxicity for concentrations above 25 microM. An induction of HO-1 expression was observed from concentrations above 5 microM of 4-HNE. Finally, glutathione content decreased significantly from 5 microM of 4-HNE but no modification was observed under this concentration. The discrepancy between effects of carbon black nanoparticles and 4-HNE on the intracellular markers of oxidative stress suggests that 4-HNE is not directly implied in the signalling of oxidative toxicity of nanoparticles but is an effective biomarker of oxidative effects of nanoparticles.

Effect of polycyclic aromatic hydrocarbons and carbon black particles on pro-inflammatory cytokine secretion: impact of PAH coating onto particles.

It has been suggested that the organic fraction of particulate matter in air pollution has a major role in the toxicity of this pollutant, notably via its effects on inflammation. The major organic compounds adsorbed onto these particles are polycyclic aromatic hydrocarbons (PAH), among which benzo[a]pyrene (B[a]P), benzo[b]fluoranthene (B[b]F), and pyrene (Pyr) are quantitatively the most important. Generally, cells or organisms are exposed to organic extracts of the particles rather than the native particles in order to study the effects of these PAH. In this study, B[a]P, B[b]F, and Pyr were tested alone and/or adsorbed onto carbon black (CB) particles differing in size in order to evaluate their impact on cytokine production (with or without LPS stimulation) by THP-1 macrophage-like cells. PAH induced significant secretion of IL-1beta, IL-8, and IL-12 after 24 or 48 hr of treatment, an effect reinforced by LPS stimulation; no effect on IL-10 secretion was noted. Fine CB particles (260 nm diameter) induced secretion of each cytokine. In general, coating the CB with PAH did not modify the effect of the CB alone; the exception was that LPS-induced IL-1beta secretion was reduced. In contrast, ultrafine CB (14 nm diameter: ufCB) caused a decrease in cytokine secretion; this effect was modified by PAH coating. For example, PAH coating on ufCB amplified the inhibitory effect of ufCB against IL-1beta secretion but did not modify IL-8 formation. Moreover, PAH coating on ufCB tended to minimize the effect of LPS stimulation; this included (i) inhibition of the decrease in IL-12 secretion induced by uncoated ufCB and (ii) stimulation of IL-10 production. It was concluded that adsorption of PAH onto these particles could decrease their bioavailability and so their abilities to affect cell cytokine production. The results also showed that when PAH were adsorbed onto the fine particles, any observed increases in cytokine secretion consistently appeared to be due to the particles themselves. In contrast, while ufCB alone almost uniformly led to decreases in cytokine formation by the cells, the added presence of the test PAHs led to variable effects - depending on whether stimulation with LPS took place or not. Thus, while some PAHs likely to be associated with PM are clearly immunomodulants, their ultimate effects in situ will likely depend on the properties of the particles themselves, in particular, their size.