Inhalation exposure to cigarette smoke induces endothelial nitric oxide synthase uncoupling and enhances vascular collagen deposition in streptozotocin-induced diabetic rats.

Smoking is an acknowledged risk factor for vascular disorders, and vascular complication is a main outcome of diabetes. Hence, we investigated the impact of cigarette smoke on blood vessels in diabetes, postulating that smoking might aggravate diabetic vascular impairment. Sprague-Dawley rats were divided into four groups: control, cigarette smoke-exposed, diabetic, and cigarette smoke-exposed diabetic groups. Streptozotocin-induced diabetic rats were exposed to cigarette smoke by inhalation at total particulate matter concentration of 200 µg/L for 4 h/day, 5 day/week for a total of 4 weeks. Diabetes caused structural change of aorta, but additional cigarette smoke exposure did not induce further alteration. Collagen, a marker for fibrosis, was increased in media of diabetic aorta, and this increase was augmented by cigarette smoke. Cigarette smoke induced endothelial nitric oxide synthase (eNOS) uncoupling in the diabetic group. Malondialdehyde was increased and glutathione was decreased in blood from diabetes, but these effects were not exaggerated by cigarette smoke. Cigarette smoke caused NADPH oxidase (NOX) 2 expression in diabetic aorta and enhanced diabetes-induced NOX4 expression in aorta. Taken together, cigarette smoke exposure can aggravate vascular fibrosis and induce eNOS uncoupling in diabetes under experimental condition, suggesting that smoking might exacerbate diabetic vascular impairments.

Derivation of occupational exposure limits for multi-walled carbon nanotubes and graphene using subchronic inhalation toxicity data and a multi-path particle dosimetry model.

In this study, we aimed to provide the recommended occupational exposure limits (OELs) for multi-walled carbon nanotubes (MWCNTs) and graphene nanomaterials based on data from a subchronic inhalation toxicity study using a lung dosimetry model. We used a no observed adverse effect level (NOAEL) of 0.98 mg m-3 and 3.02 mg m-3 in rats for MWCNTs and graphene, respectively. The NOAELs were obtained from a 13-week inhalation study in rats. The deposition fractions of MWCNTs and graphene in the respiratory tract of rats and humans were calculated by using the multi-path particle dosimetry model (MPPD model, v3.04). The deposition fraction in the alveolar region was 0.0527 and 0.0984 for MWCNTs and 0.0569 and 0.1043 for graphene in rats and human lungs, respectively. Then, the human equivalent exposure concentrations (HECs) of MWCNTs and graphene were calculated according to the method by the National Institute for Occupational Safety and Health (NIOSH). The HEC was estimated to be 0.17 mg m-3 for MWCNTs and to be 0.54 mg m-3 for graphene, which was relevant to the rat NOAEL of 0.98 mg m-3 and 3.02 mg m-3 for MWCNTs and graphene, respectively. Finally, we estimated the recommended OELs by applying uncertainty factors (UFs) to the HEC as follows: an UF of 3 for species differences (rats to humans), 2 for an experimental duration (subchronic to chronic), and 5 for inter-individual variations among workers. Thus, the OEL was estimated to be 6 µg m-3 for MWCNTs and 18 µg m-3 for graphene. These values could be useful in preventing the adverse health effects of nanoparticles in workers.

Cigarette smoke inhalation aggravates diabetic kidney injury in rats.

Diabetic kidney disease (DKD) is the leading cause of end-stage kidney disease. Epidemiological studies have demonstrated that cigarette smoke or nicotine is a risk factor for the progression of chronic kidney injury. The present study analyzed the kidney toxicity of cigarette smoke in experimental rats with DKD. Experimental diabetes was induced in 7-week-old Sprague-Dawley rats by a single intraperitoneal injection of streptozotocin (60 mg kg-1). Four weeks after the induction of diabetes, rats were exposed to cigarette smoke (200 µg L-1), 4 h daily, and 5 days per week for 4 weeks. Cigarette smoke did not affect the levels of plasma glucose, hemoglobin A1c, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol or non-esterified fatty acids in both control and diabetic rats under the experimental conditions. Cigarette smoke, however, significantly increased diabetes-induced glomerular hypertrophy and urinary kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) excretion, suggesting exacerbation of diabetic kidney injury. Cigarette smoke promoted macrophage infiltration and fibrosis in the diabetic kidney. As expected, cigarette smoke increased oxidative stress in both control and diabetic rats. These data demonstrated that four weeks of exposure to cigarette smoke aggravated the progression of DKD in rats.

Exposure to cigarette smoke via respiratory system may induce abnormal alterations of reproductive organs in female diabetic rats.

Cigarette smoke (CS) has harmful effects on human fertility, reproduction, and development as well as on patients suffering from metabolic diseases such as diabetes than on healthy individuals. This study was conducted to investigate the relationship between CS exposure and histological alterations of reproductive organs in female diabetic rats. We evaluated the histology of uteruses and ovaries obtained from female rats exposed to smoke from standard cigarettes for 4 weeks (28 hours a week). After CS exposure, tissue slides were made from uterine and ovarian samples and examined after hematoxylin and eosin staining. Immunohistochemistry was used for detection of matrix metallopeptidase 9 (MMP9), C-X-C chemokine receptor type 4 (CXCR4), and estrogen receptor (ER)α in the uterus and ovary. MMP9 is an inflammatory biomarker that increases during progression to endometriosis. As a chemokine receptor, CXCR4 is involved in development of the inner wall of the uterus and cell adhesion. In the uterus, the occurrence of MMP9, CXCR4, and ERα and the number of endometrial glands were increased by CS exposure, while in the ovary, occurrence of MMP9, CXCR4, ERα, proliferating cell nuclear antigen and the number of corpus lutea or cyst follicles were increased by CS exposure. Collectively, this study indicates that CS induced abnormal development of the uterus and ovary under induced diabetes, leading to adverse effects on normal function of reproductive organs in female rats. HIGHLIGHTS: Cigarette smoke (CS) exposure adversely affected reproductive organs of diabetic female rats. In the uterus, expression of matrix metallopeptidase 9 (MMP9), C-X-C chemokine receptor type 4 (CXCR4), estrogen receptor (ER)α, and the number of endometrial glands were increased by CS exposure, In the ovary, the expression of MMP9, CXCR4, ERα, and proliferating cell nuclear antigen and the number of corpus lutea or cyst follicles were increased by CS exposure. Exposure to CS via the respiratory system exerted a harmful impact on the uterus and ovary in female rats with diabetes.

Cigarette smoke impaired maturation of ovarian follicles and normal growth of uterus inner wall of female wild-type and hypertensive rats.

Cigarette smoke (CS) is well known to be very harmful to human body functions such as fertility, reproduction, and development. CS is considered to more affect patients with hypertension (HT). To estimate the effect of CS associated with female rat's fertility, we examined the histopathological characteristics of the uterus and ovary which were obtained from the female rats exposed to smoke of the standard cigarette (3R4F) for 4 weeks (10h a week) according to the OECD guidelines. The female wild-type Wistar Kyoto (WK) rats (WTR) and spontaneously hypertensive WK rats (SHR) were used to compare the effect of CS on healthy and hypertensive rats. After CS exposure, we manufactured tissue slides from uterine and ovarian samples and evaluated the maturation of follicles of ovary and cell proliferation in the uterus by H&E staining and immunohistochemistry (IHC). In IHC analysis on ovarian tissues, the expression of proliferating cell nuclear antigen (PCNA) and the number of follicles were decreased by CS exposure. On the contrary, PCNA expression and cell proliferation in the uterine inner layers were increased by CS exposure. The protein expression of C/EBP homologous protein (CHOP), an endoplasmic reticulum (ER)-stress marker, and BAX, a pro-apoptotic protein, was decreased by CS exposure. This phenomenon was more exacerbated in SHR rats than in WTR rats. Taken together, acute exposure to CS induced the decreased maturation of ovarian follicles and abnormal over-growth of uterine inner wall, leading to a harmful effect on female rat's normal function. In addition, this harmful effect of CS may be displayed more seriously in rats with HT.

Subchronic inhalation toxicity of silver nanoparticles.

The subchronic inhalation toxicity of silver nanoparticles was studied in Sprague-Dawley rats. Eight-week-old rats, weighing approximately 253.2 g (males) and 162.6 g (females), were divided into four groups (10 rats in each group): fresh-air control, low dose (0.6 x 10(6) particle/cm(3), 49 microg/m(3)), middle dose (1.4 x 10(6) particle/cm(3), 133 microg/m(3)), and high dose (3.0 x 10(6) particle/cm(3), 515 microg/m(3)). The animals were exposed to silver nanoparticles (average diameter 18-19 nm) for 6 h/day, 5 days/week, for 13 weeks in a whole-body inhalation chamber. In addition to mortality and clinical observations, body weight, food consumption, and pulmonary function tests were recorded weekly. At the end of the study, the rats were subjected to a full necropsy, blood samples were collected for hematology and clinical chemistry tests, and the organ weights were measured. Bile-duct hyperplasia in the liver increased dose dependently in both the male and female rats. Histopathological examinations indicated dose-dependent increases in lesions related to silver nanoparticle exposure, including mixed inflammatory cell infiltrate, chronic alveolar inflammation, and small granulomatous lesions. Target organs for silver nanoparticles were considered to be the lungs and liver in the male and female rats. No observable adverse effect level of 100 microg/m(3) is suggested from the experiments.

Lung function changes in Sprague-Dawley rats after prolonged inhalation exposure to silver nanoparticles.

The antimicrobial activity of silver nanoparticles has resulted in their widespread use in many consumer products. However, despite the continuing increase in the population exposed to silver nanoparticles, the effects of prolonged exposure to silver nanoparticles have not been thoroughly determined. Accordingly, this study attempted to investigate the inflammatory responses and pulmonary function changes in rats during 90 days of inhalation exposure to silver nanoparticles. The rats were exposed to silver nanoparticles (18 nm diameter) at concentrations of 0.7 x 10(6) particles/cm(3) (low dose), 1.4 x 10(6) particles /cm(3) (middle dose), and 2.9 x 10(6) particles /cm(3) (high dose) for 6 h/day in an inhalation chamber for 90 days. The lung function was measured every week after the daily exposure, and the animals sacrificed after the 90-day exposure period. Cellular differential counts and inflammatory measurements, such as albumin, lactate dehydrogenase (LDH), and total protein, were also monitored in the acellular bronchoalveolar lavage (BAL) fluid of the rats exposed to the silver nanoparticles for 90 days. Among the lung function test measurements, the tidal volume and minute volume showed a statistically significant decrease during the 90 days of silver nanoparticle exposure. Although no statistically significant differences were found in the cellular differential counts, the inflammation measurements increased in the high-dose female rats. Meanwhile, histopathological examinations indicated dose-dependent increases in lesions related to silver nanoparticle exposure, such as infiltrate mixed cell and chronic alveolar inflammation, including thickened alveolar walls and small granulomatous lesions. Therefore, when taken together, the decreases in the tidal volume and minute volume and other inflammatory responses after prolonged exposure to silver nanoparticles would seem to indicate that nanosized particle inhalation exposure can induce lung function changes, along with inflammation, at much lower mass dose concentrations when compared to submicrometer particles.

Comparison of high MRI T1 signals with manganese concentration in brains of cynomolgus monkeys after 8 months of stainless steel welding-fume exposure.

Several pharmacokinetic studies on inhalation exposure to manganese (Mn) have already demonstrated that Mn readily accumulates in the olfactory and brain regions. However, a shortening of the magnetic resonance imaging (MRI) T1 relaxation time or high T1 signal intensity in specific sites of the brain, including the globus pallidus and subcortical frontal white matter, as indicative of tissue manganese accumulation has not yet been clearly established for certain durations of known doses of welding-fume exposure in experimental animals. Accordingly, to investigate the movement of manganese after welding-fume exposure, six cynomolgus monkeys were acclimated and assigned to three dose groups: unexposed, low dose (31 mg/m(3) total suspended particulate [TSP], 0.9 mg/m(3) of Mn), and high dose (62 mg/m(3) TSP, 1.95 mg/m(3) of Mn) of total suspended particulate. The primates were exposed to manual metal arc stainless steel (MMA-SS) welding fumes for 2 h per day in an inhalation chamber system equipped with an automatic fume generator. Magnetic resonance imaging (MRI) studies were conducted before the initiation of exposure and thereafter every month. The tissue Mn concentrations were then measured after a plateau was reached regarding the shortening of the MRI T1 relaxation time. A dose-dependent increase in the Mn concentration was found in the lungs, while noticeable increases in the Mn concentrations were found in certain tissues, such as the liver, kidneys, and testes. Slight increases in the Mn concentrations were found in the caudate, putamen, frontal lobe, and substantia nigra, while a dose-dependent noticeable increase was only found in the globus pallidus. Therefore, the present results indicated that a shortening of the MRI T1 relaxation time corresponded well with the Mn concentration in the globus pallidus after prolonged welding-fume exposure.

Tissue distribution of manganese in iron-sufficient or iron-deficient rats after stainless steel welding-fume exposure.

Welders can be exposed to high levels of manganese through welding fumes. Although it has already been suggested that excessive manganese exposure causes neurotoxicity, called manganism, the pathway of manganese transport to the brain with welding-fume exposure remains unclear. Iron is an essential metal that maintains a homeostasis in the body. The divalent metal transporter 1 (DMT1) transports iron and other divalent metals, such as manganese, and the depletion of iron is known to upregulate DMT1 expression. Accordingly, this study investigated the tissue distribution of manganese in iron-sufficient and iron-deficient rats after welding-fume exposure. The feeding of an iron-deficient diet for 4 wk produced a depletion of body iron, such as decreased iron levels in the serum and tissues, and upregulated the DMT1 expression in the rat duodenum. The iron-sufficient and iron-deficient rats were then exposed to welding fumes generated from manual metal arc stainless steel at a concentration of 63.5 +/- 2.3 mg/m3 for 2 h per day over a 30-day period. Animals were sacrificed on days 1, 15, and 30. The level of body iron in the iron-deficient rats was restored to the control level after the welding-fume exposure. However, the tissue distributions of manganese after the welding-fume exposure showed similar patterns in both the iron-sufficient and iron-deficient groups. The concentration of manganese increased in the lungs and liver on days 15 and 30, and increased in the olfactory bulb on day 30. Slight and heterogeneous increases of manganese were observed in different brain regions. Consequently, these findings suggest that the presence of Fe in the inhaled welding fumes may not have a significant effect on the uptake of Mn into the brain. Thus, the condition of iron deficiency did not seem to have any apparent effect on the transport of Mn into the brain after the inhalation of welding fumes.

Changes in blood manganese concentration and MRI t1 relaxation time during 180 days of stainless steel welding-fume exposure in cynomolgus monkeys.

Welders are at risk of being exposed to high concentrations of welding fumes and developing pneumoconiosis or other welding-fume exposure-related diseases. Among such diseases, manganism resulting from welding-fume exposure remains a controversial issue, as although the movement of manganese into specific brain regions has been established, the similar movement of manganese presented with other metals, such as welding fumes, has not been clearly demonstrated as being similar to that of manganese alone. Meanwhile, the competition between Mn and iron for iron transporters, such as transferrin and DMT-1, to the brain has also been implicated in the welding-fume exposure. Thus, the increased signal intensities in the basal ganglia, including the globus pallidus and subcortical frontal white matter, based on T1-weighted magnetic resonances in welders, require further examination as regards the correspondence with an increased manganese concentration. Accordingly, to investigate the movement of manganese after welding-fume exposure, 6 cynomolgus monkeys were acclimated for 1 mo and assigned to 3 dose groups: unexposed, low dose of (total suspended particulate [TSP] 31 mg/m3, 0.9 mg/m3 of Mn), and high dose of total suspended particulate (62 mg/m3 TSP, 1.95 mg/m3 of Mn). The primates were exposed to manual metal-arc stainless steel (MMA-SS) welding fumes for 2 h/day in an inhalation chamber system equipped with an automatic fume generator for 6 mo. Magnetic resonance imaging (MRI) studies of the basal ganglia were conducted before the initiation of exposure and thereafter every month. During the exposure, the blood chemistry was monitored every 2 wk and the concentrations of metal components in the blood were measured every 2 wk and compared with ambient manganese concentrations. The manganese concentrations in the blood did not show any significant increase until after 2 mo of exposure, and then reached a plateau after 90 days of exposure, showing that an exposure period of at least 60 days was required to build up the blood Mn concentration. Furthermore, as the blood Mn concentration continued to build, a continued decrease in the MRI T1 relaxation time in the basal ganglia was also detected. These data suggested that prolonged inhalation of welding fumes induces a high MRI T1 signal intensity with an elevation of the blood manganese level. The presence of a certain amount of iron or other metals, such as Cr and Ni, in the inhaled welding fumes via inhalation was not found to have a significant effect on the uptake of Mn into the brain or the induction of a high MRI T1 signal intensity.