Pulmonary evaluation of whole-body inhalation exposure of polycarbonate (PC) filament 3D printer emissions in rats.

During fused filament fabrication (FFF) 3D printing with polycarbonate (PC) filament, a release of ultrafine particles (UFPs) and volatile organic compounds (VOCs) occurs. This study aimed to determine PC filament printing emission-induced toxicity in rats via whole-body inhalation exposure. Male Sprague Dawley rats were exposed to a single concentration (0.529 mg/m3, 40 nm mean diameter) of the 3D PC filament emissions in a time-course via whole body inhalation for 1, 4, 8, 15, and 30 days (4 hr/day, 4 days/week), and sacrificed 24 hr after the last exposure. Following exposures, rats were assessed for pulmonary and systemic responses. To determine pulmonary injury, total protein and lactate dehydrogenase (LDH) activity, surfactant proteins A and D, total as well as lavage fluid differential cells in bronchoalveolar lavage fluid (BALF) were examined, as well as histopathological analysis of lung and nasal passages was performed. To determine systemic injury, hematological differentials, and blood biomarkers of muscle, metabolic, renal, and hepatic functions were also measured. Results showed that inhalation exposure induced no marked pulmonary or systemic toxicity in rats. In conclusion, inhalation exposure of rats to a low concentration of PC filament emissions produced no significant pulmonary or systemic toxicity.

Nicotine and Microvascular Responses in Skeletal Muscle from Acute Exposure to Cigarettes and Vaping.

Despite claims of safety or harm reduction for electronic cigarettes (E-cig) use (also known as vaping), emerging evidence indicates that E-cigs are not likely safe, or necessarily safer than traditional cigarettes, when considering the user's risk of developing vascular dysfunction/disease. E-cigs are different from regular cigarettes in that E-cig devices are highly customizable, and users can change the e-liquid composition (such as the base solution, flavors, and nicotine level). Since the effects of E-cigs on the microvascular responses in skeletal muscle are poorly understood, we used intravital microscopy with an acute (one-time 10 puff) exposure paradigm to evaluate the individual components of e-liquid on vascular tone and endothelial function in the arterioles of the gluteus maximus muscle of anesthetized C57Bl/6 mice. Consistent with the molecular responses seen with endothelial cells, we found that the peripheral vasoconstriction response was similar between mice exposed to E-cig aerosol or cigarette smoke (i.e., 3R4F reference cigarette); this response was not nicotine dependent, and endothelial cell-mediated vasodilation was not altered within this acute exposure paradigm. We also report that, regardless of the base solution component [i.e., vegetable glycerin (VG)-only or propylene glycol (PG)-only], the vasoconstriction responses were the same in mice with inhalation exposure to 3R4F cigarette smoke or E-cig aerosol. Key findings from this work reveal that some component other than nicotine, in inhaled smoke or aerosol, is responsible for triggering peripheral vasoconstriction in skeletal muscle, and that regardless of one's preference for an E-cig base solution composition (i.e., ratio of VG-to-PG), the acute physiological response to blood vessels appears to be the same. The data suggest that vaping is not likely to be 'safer' than smoking towards blood vessels and can be expected to produce and/or result in the same adverse vascular health outcomes associated with smoking cigarettes.

Hazardous dusts from the fabrication of countertop: a review.

Artificial countertop materials, including solid surface composites (SSC) and engineered stone (ES) may pose significant pulmonary health risks for workers who manipulate them. These materials have rapidly become popular in the multibillion-dollar countertop industry, rivaling that of natural materials such as granite and marble due to their variety of desirable esthetic qualities and reduced costs. Both SSC and ES consist of a mineral substrate bound together in a polymer matrix. For SSC the mineral is about 70% aluminum trihydrate (ATH) while ES contains up to 95% crystalline silica by weight. Both materials emit airborne dusts when being manipulated with power tools during the fabrication process. Several deaths and dozens of cases of silicosis have been identified worldwide in workers who fabricate ES, while a single case of fatal pulmonary fibrosis has been associated with SCC dust exposure. This review examines the current state of knowledge for both SSC and ES regarding the composition, particle emission characteristics, workplace exposure data, particle constituent toxicity, and possible methods for reducing worker exposure.

Evaluation of Pulmonary Effects of 3-D Printer Emissions From Acrylonitrile Butadiene Styrene Using an Air-Liquid Interface Model of Primary Normal Human-Derived Bronchial Epithelial Cells.

This study investigated the inhalation toxicity of the emissions from 3-D printing with acrylonitrile butadiene styrene (ABS) filament using an air-liquid interface (ALI) in vitro model. Primary normal human-derived bronchial epithelial cells (NHBEs) were exposed to ABS filament emissions in an ALI for 4 hours. The mean and mode diameters of ABS emitted particles in the medium were 175 ± 24 and 153 ± 15 nm, respectively. The average particle deposition per surface area of the epithelium was 2.29 × 107 ± 1.47 × 107 particle/cm2, equivalent to an estimated average particle mass of 0.144 ± 0.042 µg/cm2. Results showed exposure of NHBEs to ABS emissions did not significantly affect epithelium integrity, ciliation, mucus production, nor induce cytotoxicity. At 24 hours after the exposure, significant increases in the pro-inflammatory markers IL-12p70, IL-13, IL-15, IFN-γ, TNF-α, IL-17A, VEGF, MCP-1, and MIP-1α were noted in the basolateral cell culture medium of ABS-exposed cells compared to non-exposed chamber control cells. Results obtained from this study correspond with those from our previous in vivo studies, indicating that the increase in inflammatory mediators occur without associated membrane damage. The combination of the exposure chamber and the ALI-based model is promising for assessing 3-D printer emission-induced toxicity.

In vitro toxicity assessment of respirable solid surface composite sawing particles.

Solid surface composites (SSCs) are a class of popular construction materials composed of aluminum trihydrate and acrylic polymers. Previous investigations have demonstrated that sawing SSC releases substantial airborne dusts, with a number-based geometric mean diameter of 1.05 µm. We reported that in mice, aspiration exposure to airborne SSC dusts induced symptoms of pulmonary inflammation at 24-h postexposure: neutrophilic influx, alveolitis, and increased lactate dehydrogenase (LDH) and pro-inflammatory cytokine levels in lavage fluid. The particles appeared to be poorly cleared, with 81% remaining at 14-day postexposure. The objective of this study was to determine the toxicity specifically of respirable particles on a model of human alveolar macrophages (THP-1). The relative toxicities of subfractions (0.07, 0.66, 1.58, 5.0, and 13.42 µm diameter) of the airborne particles were also determined. THP-1 macrophages were exposed for 24 h to respirable particles from sawing SSC (0, 12.5, 25, 50, or 100 µg/ml) or size-specific fractions (100 µg/ml). Exposure to respirable SSC particles induced THP-1 macrophage toxicity in a dose-dependent manner. Viability was decreased by 15% and 19% after exposure to 50 and 100 µg/ml SSC, respectively, which correlated with increased cell culture supernatant LDH activity by 40% and 70% when compared to control. Reactive oxygen species (ROS) production and inflammatory cytokines were increased in a dose-dependent manner. A size-dependent cytotoxic effect was observed in the cells exposed to subfractions of SSC particles. SSC particles of 0.07, 0.66, and 1.58 µm diameter killed 36%, 17%, and 22% of cells, respectively. These results indicate a potential for cytotoxicity of respirable SSC particles and a relationship between particle size and toxicity, with the smallest fractions appearing to exhibit the greatest toxicity.

Mouse pulmonary response to dust from sawing Corian®, a solid-surface composite material.

Corian®, a solid-surface composite (SSC), is composed of alumina trihydrate and acrylic polymer. The aim of the present study was to examine the pulmonary toxicity attributed to exposure to SSC sawing dust. Male mice were exposed to either phosphate buffer saline (PBS, control), 62.5, 125, 250, 500, or 1000 µg of SSC dust, or 1000 µg silica (positive control) via oropharyngeal aspiration. Body weights were measured for the duration of the study. Bronchoalveolar lavage fluid (BALF) and tissues were collected for analysis at 1 and 14 days post-exposure. Enhanced-darkfield and histopathologic analysis was performed to assess particle distribution and inflammatory responses. BALF cells and inflammatory cytokines were measured. The geometric mean diameter of SSC sawing dust following suspension in PBS was 1.25 µm. BALF analysis indicated that lactate dehydrogenase (LDH) activity, inflammatory cells, and pro-inflammatory cytokines were significantly elevated in the 500 and 1000 µg SSC exposure groups at days 1 and 14, suggesting that exposure to these concentrations of SSC induced inflammatory responses, in some cases to a greater degree than the silica positive control. Histopathology indicated the presence of acute alveolitis at all doses at day 1, which was largely resolved by day 14. Alveolar particle deposition and granulomatous mass formation were observed in all exposure groups at day 14. The SSC particles were poorly cleared, with 81% remaining at the end of the observation period. These findings demonstrate that SSC sawing dust exposure induces pulmonary inflammation and damage that warrants further investigation. Abbreviations: ANOVA: Analysis of Variance; ATH: Alumina Trihydrate; BALF: Bronchoalveolar Lavage Fluid; Dpg: Geometric Mean Diameter; FE-SEM: Field Emission Scanning Electron Microscopy; IACUC: Institutional Animal Care and Use Committee; IFN-γ: Interferon Gamma; IL-1 Β: Interleukin-1 Beta; IL-10: Interleukin-10; IL-12: Interleukin-12; IL-2: Interleukin-2; IL-4: Interleukin-4; IL-5: Interleukin-5; IL-6: Interleukin-6; KC/GRO: Neutrophil-Activating Protein 3; MMAD: Mass Median Aerodynamic Diameter; PBS: Phosphate-Buffered Saline; PEL: Permissible Exposure Limit; PM: Polymorphonuclear Leukocytes; PNOR: Particles Not Otherwise Regulated; SEM/EDX: Scanning Electron Microscope/Energy-Dispersive X-Ray; SSA: Specific Surface Area; SSC: Solid Surface Composite; TNFα: Tumor Necrosis Factor-Alpha; VOC: Volatile Organic Compounds; σg: Geometric Standard Deviation.

Hepatocyte-Specific Ablation or Whole-Body Inhibition of Xanthine Oxidoreductase in Mice Corrects Obesity-Induced Systemic Hyperuricemia Without Improving Metabolic Abnormalities.

Systemic hyperuricemia (HyUA) in obesity/type 2 diabetes facilitated by elevated activity of xanthine oxidoreductase (XOR), which is the sole source of uric acid (UA) in mammals, has been proposed to contribute to the pathogenesis of insulin resistance/dyslipidemia in obesity. Here, the effects of hepatocyte-specific ablation of Xdh, the gene encoding XOR (HXO), and whole-body pharmacologic inhibition of XOR (febuxostat) on obesity-induced insulin resistance/dyslipidemia were assessed. Deletion of hepatocyte Xdh substantially lowered liver and plasma UA concentration. When exposed to an obesogenic diet, HXO and control floxed (FLX) mice became equally obese, but systemic HyUA was absent in HXO mice. Despite this, obese HXO mice became as insulin resistant and dyslipidemic as obese FLX mice. Similarly, febuxostat dramatically lowered plasma and tissue UA and XOR activity in obese wild-type mice without altering obesity-associated insulin resistance/dyslipidemia. These data demonstrate that hepatocyte XOR activity is a critical determinant of systemic UA homeostasis, that deletion of hepatocyte Xdh is sufficient to prevent systemic HyUA of obesity, and that neither prevention nor correction of HyUA improves insulin resistance/dyslipidemia in obesity. Thus, systemic HyUA, although clearly a biomarker of the metabolic abnormalities of obesity, does not appear to be causative.

Toxicological assessment of dust from sanding micronized copper-treated lumber in vivo.

Micronized copper azole (MCA) is a lumber treatment improve longevity. In this study, the in vivo response to PM2.5 sanding dust generated from MCA-treated lumber was compared to that of untreated yellow pine (UYP) or soluble copper azole-treated (CA-C) lumber to determine if the MCA was more bioactive than CA-C. Mice were exposed to doses (28, 140, or 280 µg/mouse) of UYP, MCA, or CA-C sanding dust using oropharyngeal aspiration. Bronchoalveolar lavage fluid (BALF) lactate dehydrogenase activity was increased at 1 day post-exposure to 280 µg/mouse of MCA and CA-C compared to UYP. BALF polymorphonuclear cells were increased by MCA and CA-C. There were increases in BALF cytokines in MCA and CA-C-exposed groups at 1 day post-exposure. Lung histopathology indicated inflammation with infiltration of neutrophils and macrophages. Pulmonary responses were more severe in MCA and CA-C-exposed groups at 1 day post-exposure. MCA caused more severe inflammatory responses than CA-C at 1 day post-exposure. These findings suggest that the MCA and CA-C sanding dusts are more bioactive than the UYP sanding dust, and, moreover, the MCA sanding dust is more bioactive in comparison to the CA-C sanding dust. No chronic toxic effects were observed among all observed sanding dusts.

Chronic exposure to electronic cigarettes results in impaired cardiovascular function in mice.

Proponents for electronic cigarettes (E-cigs) claim that they are a safe alternative to tobacco-based cigarettes; however, little is known about the long-term effects of exposure to E-cig vapor on vascular function. The purpose of this study was to determine the cardiovascular consequences of chronic E-cig exposure. Female mice (C57BL/6 background strain) were randomly assigned to chronic daily exposure to E-cig vapor, standard (3R4F reference) cigarette smoke, or filtered air ( n = 15/group). Respective whole body exposures consisted of four 1-h-exposure time blocks, separated by 30-min intervals of fresh air breaks, resulting in intermittent daily exposure for a total of 4 h/day, 5 days/wk for 8 mo. Noninvasive ultrasonography was used to assess cardiac function and aortic arterial stiffness (AS), measured as pulse wave velocity, at three times points (before, during, and after chronic exposure). Upon completion of the 8-mo exposure, ex vivo wire tension myography and force transduction were used to measure changes in thoracic aortic tension in response to vasoactive-inducing compounds. AS increased 2.5- and 2.8-fold in E-cig- and 3R4F-exposed mice, respectively, compared with air-exposed control mice ( P < 0.05). The maximal aortic relaxation to methacholine was 24% and 33% lower in E-cig- and 3R4F-exposed mice, respectively, than in controls ( P < 0.05). No differences were noted in sodium nitroprusside dilation between the groups. 3R4F exposure altered cardiac function by reducing fractional shortening and ejection fraction after 8 mo ( P < 0.05). A similar, although not statistically significant, tendency was also observed with E-cig exposure ( P < 0.10). Histological and respiratory function data support emphysema-associated changes in 3R4F-exposed, but not E-cig-exposed, mice. Chronic exposure to E-cig vapor accelerates AS, significantly impairs aortic endothelial function, and may lead to impaired cardiac function. The clinical implication from this study is that chronic use of E-cigs, even at relatively low exposure levels, induces cardiovascular dysfunction. NEW & NOTEWORTHY Electronic cigarettes (E-cigs) are marketed as safe, but there has been insufficient long-term exposure to humans to justify these claims. This is the first study to report the long-term in vivo vascular consequences of 8 mo of exposure to E-cig vapor in mice (equivalent to ~25 yr of exposure in humans). We report that E-cig exposure increases arterial stiffness and impairs normal vascular reactivity responses, similar to other risk factors, including cigarette smoking, which contribute to the development of cardiovascular disease.

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

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 via 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.

The effects of six weeks of supplementation with multi-ingredient performance supplements and resistance training on anabolic hormones, body composition, strength, and power in resistance-trained men.

BACKGROUND: Resistance training (RT) enhances muscle protein synthesis and hypertrophy while increasing strength and power. Some multi-ingredient performance supplements (MIPS) have been shown to augment the physiological improvements associated with RT. The purpose of this study was to investigate the impact of specific pre- and post-workout MIPS on anabolic hormones, body composition, muscle strength, and power in resistance-trained men participating in a periodized RT program. METHODS: Twenty-four ( mean ± SE; 24.0 ± 0.9 years; 180.5 ± 5.8 cm; 83.7 ± 0.5 kg) resistance-trained men completed 6 wks of periodized RT (3x/wk). Participants were assigned to one of two groups based upon maximal voluntary contraction of the quadriceps (Biodex) to lean mass (LM) ratio. Group 1 (n = 13; MIPS) consumed one serving of NO-Shotgun® (whey protein, casein protein, branched-chain amino acids, creatine, beta alanine, and caffeine) before each workout and one serving of NO-Synthesize® (whey protein, casein protein, branched-chain amino acids, creatine, and beta alanine; Vital Pharmaceuticals, Inc., Davie, FL) immediately after each workout and on non-RT days. Group 2 (n = 11; Placebo; PLA) consumed a flavor-matched isocaloric maltodextrin placebo. Serum insulin-like growth factor 1, human growth hormone, testosterone, body composition (DXA), circumferences, 1-repetition maximal strength (1RM) of the upper (chest press) and lower body (leg press), and anaerobic power (Wingate test) were assessed before and after the intervention. Statistical analysis included a 2 × 2 (group x time) ANOVA with repeated measures. Tukey LSD post hoc tests were used to examine pairwise differences. Significance was set at p < 0.05. RESULTS: There was a main time effect (p = 0.035) for testosterone to increase, but no differences between groups were observed. There were no differences in the other blood hormones. Group x time interactions were observed for LM (MIPS: PRE, 62.9 ± 2.1 to POST, 65.7 ± 2.0 vs. PLA: PRE, 63.5 ± 2.3 to POST, 64.8 ± 2.5 kg; p = 0.017). Only a main effect of time was noted for circumference measures. Both groups increased upper and lower body 1RM strength to a similar degree. MIPS significantly increased peak anaerobic power (PRE, 932.7 ± 172.5 W vs. POST, 1119.2 ± 183.8 W, p = 0.002) while PLA remained unchanged (PRE, 974.4 ± 44.1 W vs. POST, 1033.7 ± 48.6 W, p = 0.166). CONCLUSION: Consumption of MIPS during the course of a periodized RT program facilitated training-induced improvement in LM in trained males, whereas the consumption of PLA did not. MIPS improved measures of anaerobic power while PLA did not.