Thrombospondin-1 mediates multi-walled carbon nanotube induced impairment of arteriolar dilation

<p>Pulmonary exposure to multi-walled carbon nanotubes (MWCNT) has been shown to disrupt endothelium-dependent arteriolar dilation in the peripheral microcirculation. The molecular mechanisms behind these arteriolar disruptions have yet to be fully elucidated. The secreted matricellular matrix protein thrombospondin-1 (TSP-1) is capable of moderating arteriolar vasodilation by inhibiting soluble guanylate cyclase activity. We hypothesized that TSP-1 may be a link between nanomaterial exposure and observed peripheral microvascular dysfunction. To test this hypothesis, wild-type C57B6J (WT) and TSP-1 knockout (KO) mice were exposed <i>via</i> lung aspiration to 50 μg MWCNT or a Sham dispersion medium control. Following exposure (24 h), arteriolar characteristics and reactivity were measured in the gluteus maximus muscle using intravital microscopy (IVM) coupled with microiontophoretic delivery of acetylcholine (ACh) or sodium nitroprusside (SNP). In WT mice exposed to MWCNT, skeletal muscle TSP-1 protein increased > fivefold compared to Sham exposed, and exhibited a 39% and 47% decrease in endothelium-dependent and -independent vasodilation, respectively. In contrast, TSP-1 protein was not increased following MWCNT exposure in KO mice and exhibited no loss in dilatory capacity. Microvascular leukocyte–endothelium interactions were measured by assessing leukocyte adhesion and rolling activity in third order venules. The WT + MWCNT group demonstrated 223% higher leukocyte rolling compared to the WT + Sham controls. TSP-1 KO animals exposed to MWCNT showed no differences from the WT + Sham control. These data provide evidence that TSP-1 is likely a central mediator of the systemic microvascular dysfunction that follows pulmonary MWCNT exposure.</p

Multi-walled carbon nanotubes induce arachidonate 5-lipoxygenase expression and enhance the polarization and function of M1 macrophages <i>in vitro</i>

Fibrogenic carbon nanotubes (CNTs) induce the polarization of M1 and M2 macrophages in mouse lungs. Polarization of the macrophages regulates the production of proinflammatory and pro-resolving lipid mediators (LMs) to mediate acute inflammation and its resolution in a time-dependent manner. Here we examined the molecular mechanism by which multi-walled CNTs (MWCNTs, Mitsui-7) induce M1 polarization in vitro. Treatment of murine macrophages (J774A.1) with Mitsui-7 MWCNTs increased the expression of Alox5 mRNA and protein in a concentration- and time-dependent manner. The MWCNTs induced the expression of CD68 and that induction persisted for up to 3 days post-exposure. The expression and activity of inducible nitric oxide synthase, an intracellular marker of M1, were increased by MWCNTs. Consistent with M1 polarization, the MWCNTs induced the production and secretion of proinflammatory cytokines tumor necrosis factor-α and interleukin-1β, and proinflammatory LMs leukotriene B4 (LTB4) and prostaglandin E2 (PGE2). The cell-free media from MWCNT-polarized macrophages induced the migration of neutrophilic cells (differentiated from HL-60), which was blocked by Acebilustat, a specific leukotriene A4 hydrolase inhibitor, or LY239111, an LTB4 receptor antagonist, but not NS-398, a cyclooxygenase 2 inhibitor, revealing LTB4 as a major mediator of neutrophil chemotaxis from MWCNT-polarized macrophages. Knockdown of Alox5 using specific small hairpin-RNA suppressed MWCNT-induced M1 polarization, LTB4 secretion, and migration of neutrophils. Taken together, these findings demonstrate the polarization of M1 macrophages by Mitsui-7 MWCNTs in vitro and that induction of Alox5 is an important mechanism by which the MWCNTs promote proinflammatory responses by boosting M1 polarization and production of proinflammatory LMs.</p

The Sources of Inflammatory Mediators in the Lung after Silica Exposure-6

<p><b>Copyright information:</b></p><p>Taken from "The Sources of Inflammatory Mediators in the Lung after Silica Exposure"</p><p>Environmental Health Perspectives 2004;112(17):1679-1685.</p><p>Published online 16 Aug 2004</p><p>PMCID:PMC1253659.</p><p>This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original DOI.</p

A New Stochastic Kriging Method for Modeling Multi-Source Exposure–Response Data in Toxicology Studies

One of the most fundamental steps in risk assessment is to quantify the exposure–response relationship for the material/chemical of interest. This work develops a new statistical method, referred to as SKQ (stochastic kriging with qualitative factors), to synergistically model exposure–response data, which often arise from multiple sources (e.g., laboratories, animal providers, and shapes of nanomaterials) in toxicology studies. Compared to the existing methods, SKQ has several distinct features. First, SKQ integrates data across multiple sources and allows for the derivation of more accurate information from limited data. Second, SKQ is highly flexible and able to model practically any continuous response surfaces (e.g., dose–time–response surface). Third, SKQ is able to accommodate variance heterogeneity across experimental conditions and to provide valid statistical inference (i.e., quantify uncertainties of the model estimates). Through empirical studies, we have demonstrated SKQ’s ability to efficiently model exposure–response surfaces by pooling information across multiple data sources. SKQ fits into the mosaic of efficient decision-making methods for assessing the risk of a tremendously large variety of nanomaterials and helps to alleviate safety concerns regarding the enormous amount of new nanomaterials

The Sources of Inflammatory Mediators in the Lung after Silica Exposure-1

<p><b>Copyright information:</b></p><p>Taken from "The Sources of Inflammatory Mediators in the Lung after Silica Exposure"</p><p>Environmental Health Perspectives 2004;112(17):1679-1685.</p><p>Published online 16 Aug 2004</p><p>PMCID:PMC1253659.</p><p>This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original DOI.</p

Characterization of WC-Co NP via A) TEM (scale bar = 500 nm) and B) SEM (scale bar = 1 μm).

<p>Characterization of WC-Co NP via A) TEM (scale bar = 500 nm) and B) SEM (scale bar = 1 μm).</p

Summary of the characteristics of WC-Co NP, including size and elemental composition.

<p>Summary of the characteristics of WC-Co NP, including size and elemental composition.</p

Inflammatory cells quantified in BAL fluid samples following 24-hr exposure to WC-Co and CeO₂ NPs: A) alveolar macrophages (AM) and B) polymorphonuclear leukocytes (PMN), represented as the total number of AM/PMN per 10⁶ isolated BAL cells per rat.

<p>Values presented as mean ± SD. (†P < 0.01 compared to the vehicle control and WC-Co NP exposed groups)</p

Inflammatory cytokine concentrations in A) BAL fluid and B) blood plasma.

<p>(†P < 0.05 compared to the vehicle control and WC-Co NP exposed groups)</p

Histology of isolated BAL fluid cells from a representative A) control (vehicle only) rat and B) 500 μg WC-Co NP exposed rat.

<p>Scale bars = 20 μm. (black arrow = alveolar macrophage, AM; arrow head = erythrocyte; dotted arrow = polymorphonuclear leukocyte, PMN; wide arrow = AM with WC-Co NPs)</p