Gene expression profile in monocyte during in vitro mineral fiber degradation

N-acetylcysteine prevents cytotoxic effects induced by man-made mineral fibers in a human bronchial epithelial cell line

Man-made mineral fibres (MMMFs) such as glass wool (GW), rock wool (RW) and refractory ceramic fibres (RCFs) are widely used as substitutes of asbestos. The present study aimed to investigate the cytotoxic effects on human bronchial epithelial cells (BEAS-2B) exposed to GW1, RW1 and RCF2, considering their properties similar to that of asbestos. We assessed cell viability; cell morphological changes; apoptotic rate; DNA damage; reactive oxygen species (ROS) generation; activities of caspase-3, caspase-8 and caspase-9; and expression levels of FasL, phosphorylated p38, and total p38 MAPK proteins. N-acetyl-l-cysteine (NAC) was used as an ROS scavenger. We observed that MMMFs, especially RCF2, evidently changed cellular morphology, promoted DNA damage, and induced apoptosis. In addition, the cytotoxicities of MMMFs were dependent on ROS generation, and NAC could decrease their toxicity. Furthermore, our results showed that apoptosis induced by MMMFs was mediated by the mitochondrial apoptotic pathway and Fas death receptor pathway. Moreover, the p38 MAPK signalling pathway was also involved in the cytotoxicities of MMMFs. NAC exerts a protective effect against apoptosis and DNA damage induced by GW1, RW1 and RCF2. This study provides important implications for understanding the potential toxic effects of GW1, RW1 and RCF2 exposure; it also indicates that NAC may prevent respiratory diseases induced by exposure to MMMFs.

Impact of gold nanoparticle coating on redox homeostasis

Gold nanoparticles (AuNP) hold great potential for biomedical applications. This study was aimed at examination of the effect of AuNP coating on the redox status of their environment. Two kinds of AuNP were tested, similar by shape and size, but with different surface coatings: either stabilized with citrate or functionalized with dihydrolipoic acid (Au@DHLA NP). Interestingly, whereas citrate-stabilized AuNP interact in vitro with reduced glutathione (GSH) and S-nitrosoglutathione, Au@DHLA NP do not interfere with both biomolecules. Albumin exhibits higher affinity toward citrate-stabilized AuNP than Au@DHLA NP, increasing their hydrodynamic diameter (8.0- and 1.3-fold, respectively). Furthermore, the AuNP coating affects also their internalization by macrophages (which was two fold higher for citrate-stabilized AuNP), following an exposure to a subtoxic NP concentration (10 nM, 80% viability). Citrate-stabilized AuNP were found to decrease the intracellular GSH level (ca. 20%), with no increase in reactive oxygen species production. Furthermore, these AuNP did not induce apoptosis (as shown by caspase-3 activity and nfkb2 transcription factor), and also did not activate gene expression related to oxidative stress (ncf1) and inflammatory response (tnfα). The present data highlight that the functionalization of AuNP with DHLA decreases their reactivity with biomolecules and cells, resulting in a promising medical platform.

Drug delivery by polymeric nanoparticles induces autophagy in macrophages

Drug delivery nanosystems are currently used in human therapy. In preliminary studies we have observed that Eudragit RS nanoparticles, prepared by nanoprecipitation or double emulsion techniques, are cytotoxic for NR8383 rat macrophages. In this study, we expand our previous analysis and suggest that unloaded Eudragit RS nanoparticles prepared by nanoprecipitation (NP/ERS) may induce important morphological and biochemical cellular modifications leading to cellular death. In NR8383 rat macrophages cell line exposed to doses varying from 15 to 100 μg/mL, NP/ERS nanoparticles are internalized inside the cells, reach the mitochondria and alter the structure of these organelles. In addition, the exposure to nanoparticles induces cellular autophagy as demonstrated by electron microscopy analysis, microchip array, qRT-PCR and Western blot assays. Although toxicity of nanoparticles has already been evidenced, it is the first time that results show clearly that the toxicity of polymeric nanovectors may be related to an activation of autophagy.

Macrophage culture as a suitable paradigm for evaluation of synthetic vitreous fibers

The ultimate goal of toxicologic investigation of synthetic vitreous fibers (SVFs) is to provide essential input for the assessment of human risk to their exposure. Toxicity of mineral fibers is usually evaluated by testing biopersistence in rodent model. However, a cellular model would be much appreciated in order to reduce, refine, and replace animal models. Pulmonary disorders triggered by inhalation of occupational or environmental mineral particulates can be the endpoints of a chronic inflammatory process in which alveolar macrophages (AMs) play a crucial role. Depending on the type of SVF involved, phagocytosis of fiber leads to activation of macrophages, resulting in release of fiber components and potent mediators, such as reactive oxygen or nitrogen species and cytokines. As a matter of fact, macrophages should be the cells of choice since SVF toxicity is the consequence of fibers and alveolar macrophages interaction. Today, monocytes and macrophages culture are firmly established as a paradigm in toxicology when several endpoints are assayed in macrophages: (1) fiber durability, (2) fiber surface changes, (3) oxidative stress and genotoxicity in macrophage, and (4) macrophage cell viability and apoptosis. This article is a review of up-to-date knowledge of in vitro studies involving macrophages, and assesses endpoints of macrophage toxicity with an emphasis on (1) dissolution, (2) scanning electron microscopy analysis, (3) cytotoxicity, and (4) gene expression.