C60 exposure augments cardiac ischemia/reperfusion injury and coronary artery contraction in Sprague Dawley rats.

The potential uses of engineered C60 fullerene (C60) have expanded in recent decades to include industrial and biomedical applications. Based on clinical findings associated with particulate matter exposure and our data with multi-walled carbon nanotubes, we hypothesized that ischemia/reperfusion (I/R) injury and pharmacological responses in isolated coronary arteries would depend upon the route of exposure and gender in rats instilled with C60. Male and female Sprague Dawley rats were used to test this hypothesis by surgical induction of cardiac I/R injury in situ 24 h after intratracheal (IT) or intravenous (IV) instillation of 28 µg of C60 formulated in polyvinylpyrrolidone (PVP) or PVP vehicle. Serum was collected for quantification of various cytokines. Coronary artery segments were isolated for assessment of vasoactive pharmacology via wire myography. Both IV and IT exposure to C60 resulted in expansion of myocardial infarction in male and female rats following I/R injury. Serum-collected post-I/R showed elevated concentrations of interleukin-6 and monocyte chemotactic protein-1 in male rats exposed to IV C60. Coronary arteries isolated from male rats exposed to IT C60 demonstrated augmented vasocontraction in response to endothelin-1 that was attenuated with Indomethacin. IV C60 exposure resulted in impaired acetylcholine relaxation in male rats and IT C60 exposure resulted in depressed vasorelaxation in response to sodium nitroprusside in female rats. Based on these data, we conclude that IT and IV exposure to C60 results in unique cardiovascular consequences that may favor heightened coronary resistance and myocardial susceptibility to I/R injury.

Expansion of cardiac ischemia/reperfusion injury after instillation of three forms of multi-walled carbon nanotubes.

BACKGROUND: The exceptional physical-chemical properties of carbon nanotubes have lead to their use in diverse commercial and biomedical applications. However, their utilization has raised concerns about human exposure that may predispose individuals to adverse health risks. The present study investigated the susceptibility to cardiac ischemic injury following a single exposure to various forms of multi-walled carbon nanotubes (MWCNTs). It was hypothesized that oropharyngeal aspiration of MWCNTs exacerbates myocardial ischemia and reperfusion injury (I/R injury). METHODS: Oropharyngeal aspiration was performed on male C57BL/6J mice with a single amount of MWCNT (0.01 - 100 µg) suspended in 100 µL of a surfactant saline (SS) solution. Three forms of MWCNTs were used in this study: unmodified, commercial grade (C-grade), and functionalized forms that were modified either by acid treatment (carboxylated, COOH) or nitrogenation (N-doped) and a SS vehicle. The pulmonary inflammation, serum cytokine profile and cardiac ischemic/reperfusion (I/R) injury were assessed at 1, 7 and 28 days post-aspiration. RESULTS: Pulmonary response to MWCNT oropharyngeal aspiration assessed by bronchoalveolar lavage fluid (BALF) revealed modest increases in protein and inflammatory cell recruitment. Lung histology showed modest tissue inflammation as compared to the SS group. Serum levels of eotaxin were significantly elevated in the carboxylated MWCNT aspirated mice 1 day post exposure. Oropharyngeal aspiration of all three forms of MWCNTs resulted in a time and/or dose-dependent exacerbation of myocardial infarction. The severity of myocardial injury varied with the form of MWCNTs used. The N-doped MWCNT produced the greatest expansion of the infarct at any time point and required a log concentration lower to establish a no effect level. The expansion of the I/R injury remained significantly elevated at 28 days following aspiration of the COOH and N-doped forms, but not the C-grade as compared to SS. CONCLUSION: Our results suggest that oropharyngeal aspiration of MWCNT promotes increased susceptibility of cardiac tissue to ischemia/reperfusion injury without a significant pulmonary inflammatory response. The cardiac injury effects were observed at low concentrations of MWCNTs and presence of MWCNTs may pose a significant risk to the cardiovascular system.

A carbon nanotube toxicity paradigm driven by mast cells and the IL-33/ST2 axis.

Concern about the use of nanomaterials has increased significantly in recent years due to potentially hazardous impacts on human health. Mast cells are critical for innate and adaptive immune responses, often modulating allergic and pathogenic conditions. Mast cells are well known to act in response to danger signals through a variety of receptors and pathways including IL-33 and the IL-1-like receptor ST2. Here, the involvement of mast cells and the IL-33/ST2 axis in pulmonary and cardiovascular responses to multi-walled carbon nanotube (MWCNT) exposure are examined. Toxicological effects of MWCNTs are observed only in mice with a sufficient population of mast cells and are not observed when mast cells are absent or incapable of responding to IL-33. Our findings establish for the first time that mast cells and the IL-33/ST2 axis orchestrates adverse pulmonary and cardiovascular responses to an engineered nanomaterial, giving insight into a previously unknown mechanism of toxicity. This novel mechanism of toxicity could be used for assessing the safety of engineered nanomaterials and provides a realistic therapeutic target for potential nanoparticle induced toxicities.