Differential expression of EC-SOD, Mn-SOD and CuZn-SOD in rat lung exposed to crystalline silica

Effect of Different Molecular Weights of Polyacrylic Acid on Rat Lung Following Intratracheal Instillation

Background: We conducted intratracheal instillations of different molecular weights of polyacrylic acid (PAA) into rats in order to examine what kinds of physicochemical characteristics of acrylic acid-based polymer affect responses in the lung. Methods: F344 rats were intratracheally exposed to a high molecular weight (HMW) of 598 thousand g/mol or a low molecular weight (LMW) of 30.9 thousand g/mol PAA at low and high doses. Rats were sacrificed at 3 days, 1 week, 1 month, 3 months and 6 months post exposure. Results: HMW PAA caused persistent increases in neutrophil influx, cytokine-induced neutrophil chemoattractants (CINC) in the bronchoalveolar lavage fluid (BALF), and heme oxygenase-1 (HO-1) in the lung tissue from 3 days to 3 months and 6 months following instillation. On the other hand, LMW PAA caused only transient increases in neutrophil influx, CINC in BALF, and HO-1 in the lung tissue from 3 days to up to 1 week or 1 month following instillation. Histopathological findings of the lungs demonstrated that the extensive inflammation and fibrotic changes caused by the HMW PAA was greater than that in exposure to the LMW PAA during the observation period. Conclusion: HMW PAA induced persistence of lung disorder, suggesting that molecular weight is a physicochemical characteristic of PAA-induced lung disorder.

Inflammogenic effect of polyacrylic acid in rat lung following intratracheal instillation

Background

Some organic chemicals are known to cause allergic disorders such as bronchial asthma and hypersensitivity pneumonitis, and it has been considered that they do not cause irreversible pulmonary fibrosis. It has recently been reported, however, that cross-linked acrylic acid-based polymer, an organic chemical, might cause serious interstitial lung diseases, including pulmonary fibrosis. We investigated whether or not intratracheal instillation exposure to cross-linked polyacrylic acid (CL-PAA) can cause lung disorder in rats.

Methods

Male F344 rats were intratracheally instilled with dispersed CL-PAA at low (0.2 mg/rat) and high (1.0 mg/rat) doses, and were sacrificed at 3 days, 1 week, 1 month, 3 months and 6 months after exposure to examine inflammatory and fibrotic responses and related gene expressions in the lungs. Rat lungs exposed to crystalline silica, asbestos (chrysotile), and NiO and CeO2 nanoparticles were used as comparators.

Results

Persistent increases in total cell count, neutrophil count and neutrophil percentage, and in the concentration of the cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-2 and C-X-C motif chemokine 5 (CXCL5), which correlated with lung tissue gene expression, were observed in bronchoalveolar lavage fluid (BALF) from 3 days until at least 1 month following CL-PAA intratracheal instillation. Persistent increases in heme oxygenase-1 (HO-1) in the lung tissue were also observed from 3 days to 6 months after exposure. Histopathological findings of the lungs demonstrated that extensive inflammation at 3 days was greater than that in exposure to silica, NiO nanoparticles and CeO2 nanoparticles, and equal to or greater than that in asbestos (chrysotile) exposure, and the inflammation continued until 1 month. Fibrotic changes also progressed after 1 month postexposure.

Conclusion

Our results suggested that CL-PAA potentially causes strong neutrophil inflammation in the rat and human lung.

Examination of Surfactant Protein D as a Biomarker for Evaluating Pulmonary Toxicity of Nanomaterials in Rat

This work studies the relationship between lung inflammation caused by nanomaterials and surfactant protein D (SP-D) kinetics and investigates whether SP-D can be a biomarker of the pulmonary toxicity of nanomaterials. Nanomaterials of nickel oxide and cerium dioxide were classified as having high toxicity, nanomaterials of two types of titanium dioxides and zinc oxide were classified as having low toxicity, and rat biological samples obtained from 3 days to 6 months after intratracheal instillation of those nanomaterials and micron-particles of crystalline silica were used. There were different tendencies of increase between the high- and low-toxicity materials in the concentration of SP-D in bronchoalveolar-lavage fluid (BALF) and serum and in the expression of the SP-D gene in the lung tissue. An analysis of the receiver operating characteristics for the toxicity of the nanomaterials by SP-D in BALF and serum showed a high accuracy of discrimination from 1 week to 3 or 6 months after exposure. These data suggest that the differences in the expression of SP-D in BALF and serum depended on the level of lung inflammation caused by the nanomaterials and that SP-D can be biomarkers for evaluating the pulmonary toxicity of nanomaterials.

Nutrigenetics of antioxidant enzymes and micronutrient needs in the context of viral infections

Sustaining adequate nutritional needs of a population is a challenging task in normal times and a priority in times of crisis. There is no 'one-size-fits-all' solution that addresses nutrition. In relevance to the COVID-19 (coronavirus disease 2019) pandemic crisis, viral infections in general and RNA viruses in particular are known to induce and promote oxidative stress, consequently increasing the body's demand for micronutrients, especially those related to antioxidant enzymic systems, thus draining the body of micronutrients, and so hindering the human body's ability to cope optimally with oxidative stress. Common polymorphisms in major antioxidant enzymes, with world population minor allele frequencies ranging from 0·5 to 50 %, are related to altered enzymic function, with substantial potential effects on the body's ability to cope with viral infection-induced oxidative stress. In this review we highlight common SNP of the major antioxidant enzymes relevant to nutritional components in the context of viral infections, namely: superoxide dismutases, glutathione peroxidases and catalase. We delineate functional polymorphisms in several human antioxidant enzymes that require, especially during a viral crisis, adequate and potentially additional nutritional support to cope with the pathological consequences of disease. Thus, in face of the COVID-19 pandemic, nutrition should be tightly monitored and possibly supplemented, with special attention to those carrying common polymorphisms in antioxidant enzymes.

Predictive Biomarkers for the Ranking of Pulmonary Toxicity of Nanomaterials

We analyzed the mRNA expression of chemokines in rat lungs following intratracheal instillation of nanomaterials in order to find useful predictive markers of the pulmonary toxicity of nanomaterials. Nickel oxide (NiO) and cerium dioxide (CeO₂) as nanomaterials with high pulmonary toxicity, and titanium dioxide (TiO₂) and zinc oxide (ZnO) as nanomaterials with low pulmonary toxicity, were administered into rat lungs (0.8 or 4 mg/kg BW). C-X-C motif chemokine 5 (CXCL5), C-C motif chemokine 2 (CCL2), C-C motif chemokine 7 (CCL7), C-X-C motif chemokine 10 (CXCL10), and C-X-C motif chemokine 11 (CXCL11) were selected using cDNA microarray analysis at one month after instillation of NiO in the high dose group. The mRNA expression of these five genes were evaluated while using real-time quantitative polymerase chain reaction (RT-qPCR) from three days to six months after intratracheal instillation. The receiver operating characteristic (ROC) results showed a considerable relationship between the pulmonary toxicity ranking of nanomaterials and the expression of CXCL5, CCL2, and CCL7 at one week and one month. The expression levels of these three genes also moderately or strongly correlated with inflammation in the lung tissues. Three chemokine genes can be useful as predictive biomarkers for the ranking of the pulmonary toxicity of nanomaterials.

Metalloproteins and apolipoprotein C: candidate plasma biomarkers of T2DM screened by comparative proteomics and lipidomics in ZDF rats

Background

Early diagnosis of type 2 diabetes mellitus (T2DM) is still difficult. Screening of plasma biomarkers has great significance of optimizing diagnosis and predicting the complications of T2DM.

Methods

We used a special diet, Purina #5008, to induce diabetes in Zucker leptin receptor gene-deficient rats (fa/fa) to establish Zucker diabetic fatty (ZDF) rats, simulating the early stage of T2DM. The differentially expressed proteins (DEP) and lipids (DEL), as potential biomarkers, were screened to compare the plasma expression levels in ZDF rats and their basic diet-fed wild-type controls (fa/+) by Tandem Mass Tags (TMT) and liquid chromatography-tandem mass spectrometry.

Results

These two groups had different plasma proteins and lipids profiles consisting of 84 DEPs and, 179 DELs identified in the positive ion mode and 178 DELs in the negative ion mode, respectively. Enrichment analysis of these different indicators showed that oxidative stress, insulin resistance and metabolic disorders of glycan and lipid played an important role in generating the difference. Some markers can be used as candidate biomarkers in prediction and treatments of T2DM, such as ceruloplasmin, apolipoprotein C-I, apolipoprotein C-II and apolipoprotein C-IV.

Conclusion

These plasma differences help to optimize the diagnosis and predict the complications of T2DM, although this remains to be verified in the crowd. Trace elements related-metalloproteins, such as ceruloplasmin, and lipid metabolism and transport-related apolipoprotein C are expected to be candidate biomarkers of T2DM and should be given more attention.

Assessment of Cytokine-Induced Neutrophil Chemoattractants as Biomarkers for Prediction of Pulmonary Toxicity of Nanomaterials

This work determines whether cytokine-induced neutrophil chemoattractants (CINC)-1, CINC-2 and CINC-3 can be markers for predicting high or low pulmonary toxicity of nanomaterials (NMs). We classified NMs of nickel oxide (NiO) and cerium dioxide (CeO₂) into high toxicity and NMs of two types of titanium dioxides (TiO₂ (P90 and rutile)) and zinc oxide (ZnO) into low toxicity, and we analyzed previous data of CINCs in bronchoalveolar lavage fluid (BALF) of rats from three days to six months after intratracheal instillation (0.2 and 1.0 mg) and inhalation exposure (0.32–10.4 mg/m³) of materials (NiO, CeO₂, TiO₂ (P90 and rutile), ZnO NMs and micron-particles of crystalline silica (SiO₂)). The concentration of CINC-1 and CINC-2 in BALF had different increase tendency between high and low pulmonary toxicity of NMs and correlated with the other inflammatory markers in BALF. However, CINC-3 increased only slightly in a dose-dependent manner compared with CINC-1 and CINC-2. Analysis of receiver operating characteristics for the toxicity of NMs by CINC-1 and CINC-2 showed the most accuracy of discrimination of the toxicity at one week or one month after exposure and CINC-1 and CINC-2 in BALF following intratracheal instillation of SiO₂ as a high toxicity could accurately predict the toxicity at more than one month after exposure. These data suggest that CINC-1 and CINC-2 may be useful biomarkers for the prediction of pulmonary toxicity of NMs relatively early in both intratracheal instillation and inhalation exposure.

Role of SOD3 in silica-related lung fibrosis and pulmonary vascular remodeling

BACKGROUND

Work-place exposure to silica dust may lead to progressive lung inflammation culminating in the development of silicosis, an irreversible condition that can be complicated by onset of pulmonary hypertension (PH). The molecular mechanisms leading to the development of PH and lung fibrosis in response to silica are not well understood. Oxidant/antioxidant imbalance in the lung may promote fibroproliferation and vascular smooth muscle proliferation, ultimately leading to the development of PH. Herein, we analyze the development of PH and lung fibrosis in mice deficient in extracellular superoxide dismutase (SOD3), an enzyme with anti-oxidant activity.

METHODS

PH and silicosis were induced in wild-type and Sod3-/- mice through intratracheal injection of crystalline silica at dose 0.4 g/kg. Pulmonary hypertension and lung fibrosis were characterized by changes in right ventricular systolic pressure (RVSP) and collagen deposition 28 days following silica injections. Vascular remodeling was analyzed using immunohistochemistry and morphometric analysis. The expression of genes were analyzed using qRT-PCR and Western blot.

RESULTS

C57BL6 mice exposed to silica showed attenuated expression of Sod3 in the lung suggesting a protective role for Sod3. Consistent with this, Sod3-/- mice developed more severe fibrotic inflammatory nodules with increased collagen deposition. Furthermore, the expression of genes involved in tissue remodeling (Timp1), fibrotic lesion formation (Fsp1) and inflammatory response (Mcp1) were significantly elevated in Sod3-/- mice compared to Sod3+/+ mice treated with silica. Infiltration of neutrophils and activated macrophages into affected lung was significantly higher in Sod3 deficient mice. In addition, silica produced more profound effects on elevation of RVSP in Sod3-/- compared to wild-type littermate. Increase in RVSP was concomitant with hypertrophy of pulmonary arteries located in silicotic nodules of both mouse strains, however, vascular remodeling in unaffected areas of lung was detected only in Sod3-/- mice.

CONCLUSIONS

Our data suggest that Sod3 and extracellular oxidative stress may play an important role in the development of pneumoconiosis and pulmonary vascular remodeling following exposure to environmental and occupational silica.

Usefulness of myeloperoxidase as a biomarker for the ranking of pulmonary toxicity of nanomaterials

BACKGROUND

In order to examine whether myeloperoxidase (MPO) can be a useful marker for evaluating the pulmonary toxicity of nanomaterials, we analyzed MPO protein in bronchoalveolar lavage fluid (BALF) samples obtained from previous examinations of a rat model. In those examinations we performed intratracheal instillation exposures (dose: 0.2-1.0 mg) and inhalation exposures (exposure concentration: 0.32-10.4 mg/m3) using 9 and 4 nanomaterials with different toxicities, respectively. Based on those previous studies, we set Nickel oxide nanoparticles (NiO), cerium dioxide nanoparticles (CeO2), multi wall carbon nanotubes with short or long length (MWCNT (S) and MWCNT (L)), and single wall carbon nanotube (SWCNT) as chemicals with high toxicity; and titanium dioxide nanoparticles (TiO2 (P90) and TiO2 (Rutile)), zinc oxide nanoparticles (ZnO), and toner with external additives including nanoparticles as chemicals with low toxicity. We measured the concentration of MPO in BALF samples from rats from 3 days to 6 months following a single intratracheal instillation, and from 3 days to 3 months after the end of inhalation exposure.

RESULTS

Intratracheal instillation of high toxicity NiO, CeO2, MWCNT (S), MWCNT (L), and SWCNT persistently increased the concentration of MPO, and inhalation of NiO and CeO2 increased the MPO in BALF. By contrast, intratracheal instillation of low toxicity TiO2 (P90), TiO2 (Rutile), ZnO, and toner increased the concentration of MPO in BALF only transiently, and inhalation of TiO2 (Rutile) and ZnO induced almost no increase of the MPO. The concentration of MPO correlated with the number of total cells and neutrophils, the concentration of chemokines for neutrophils (cytokine-induced neutrophil chemoattractant (CINC)-1 and heme oxygenase (HO)-1), and the activity of released lactate dehydrogenase (LDH) in BALF. The results from the receiver operating characteristics (ROC) for the toxicity of chemicals by the concentration of MPO proteins in the intratracheal instillation and inhalation exposures showed that the largest areas under the curves (AUC) s in both examinations occurred at 1 month after exposure.

CONCLUSION

These data suggest that MPO can be a useful biomarker for the ranking of the pulmonary toxicity of nanomaterials, especially at 1 month after exposure, in both intratracheal instillation and inhalation exposure.

The R213G polymorphism in SOD3 protects against allergic airway inflammation

Oxidative stress is important in the pathogenesis of allergic asthma. Extracellular superoxide dismutase (EC-SOD; SOD3) is the major antioxidant in lungs, but its role in allergic asthma is unknown. Here we report that asthmatics have increased SOD3 transcript levels in sputum and that a single nucleotide polymorphism (SNP) in SOD3 (R213G; rs1799895) changes lung distribution of EC-SOD, and decreases likelihood of asthma-related symptoms. Knockin mice analogous to the human R213G SNP had lower airway hyperresponsiveness, inflammation, and mucus hypersecretion with decreased interleukin-33 (IL-33) in bronchoalveolar lavage fluid and reduced type II innate lymphoid cells (ILC2s) in lungs. SOD mimetic (Mn (III) tetrakis (N-ethylpyridinium-2-yl) porphyrin) attenuated Alternaria-induced expression of IL-33 and IL-8 release in BEAS-2B cells. These results suggest that R213G SNP potentially benefits its carriers by resulting in high EC-SOD in airway-lining fluid, which ameliorates allergic airway inflammation by dampening the innate immune response, including IL-33/ST2-mediated changes in ILC2s.

Pulmonary toxicity of well-dispersed cerium oxide nanoparticles following intratracheal instillation and inhalation

We performed inhalation and intratracheal instillation studies of cerium dioxide (CeO₂) nanoparticles in order to investigate their pulmonary toxicity, and observed pulmonary inflammation not only in the acute and but also in the chronic phases. In the intratracheal instillation study, F344 rats were exposed to 0.2 mg or 1 mg of CeO₂ nanoparticles. Cell analysis and chemokines in bronchoalveolar lavage fluid (BALF) were analyzed from 3 days to 6 months following the instillation. In the inhalation study, rats were exposed to the maximum concentration of inhaled CeO₂ nanoparticles (2, 10 mg/m³, respectively) for 4 weeks (6 h/day, 5 days/week). The same endpoints as in the intratracheal instillation study were examined from 3 days to 3 months after the end of the exposure. The intratracheal instillation of CeO₂ nanoparticles caused a persistent increase in the total and neutrophil number in BALF and in the concentration of cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-2, chemokine for neutrophil, and heme oxygenase-1 (HO-1), an oxidative stress marker, in BALF during the observation time. The inhalation of CeO₂ nanoparticles also induced a persistent influx of neutrophils and expression of CINC-1, CINC-2, and HO-1 in BALF. Pathological features revealed that inflammatory cells, including macrophages and neutrophils, invaded the alveolar space in both studies. Taken together, the CeO₂ nanoparticles induced not only acute but also chronic inflammation in the lung, suggesting that CeO₂ nanoparticles have a pulmonary toxicity that can lead to irreversible lesions.

NADPH oxidase mediated maneb- and paraquat-induced oxidative stress in rat polymorphs: Crosstalk with mitochondrial dysfunction

Oxidative stress is a key factor in Parkinson's disease (PD) pathogenesis. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and impaired mitochondrion regulate oxidative stress-mediated maneb (MB)- and paraquat (PQ)-induced Parkinsonism. However, their contribution in the MB- and PQ-induced toxicity in polymorphonuclear leukocytes (PMNs) is still elusive. The study investigated the role of NADPH oxidase and mitochondria in MB- and/or PQ-induced oxidative stress in the PMNs and the crossing point between the two. Animals were treated with MB and/or PQ for 1-3 weeks along with respective controls. In a few sets of experiments, rats were treated with/without NADPH oxidase inhibitor, apocynin, an hour prior to MB and/or PQ treatment. PMNs of MB and/or PQ treated animals were also treated with/without carbonyl cyanide 3-chlorophenylhydrazone (CCCP) to assess the role of the mitochondria in superoxide and total free radical productions. MB and/or PQ were found to increase the level of total reactive oxygen species (ROS), superoxide radicals, catalytic activity and expression of NADPH oxidase and superoxide dismutase (SOD1/2) and mitochondrial ROS content in a time dependent manner. Conversely, catalase activity and mitochondrial membrane potential were attenuated. Apocynin alleviated MB- and/or PQ-induced changes in total ROS, superoxide radicals, expression/catalytic activity of NADPH oxidase and SOD1/2 along with the mitochondrial ROS and membrane potential. CCCP also inhibited ROS and superoxide levels in the PMNs of MB and/or PQ-treated animals. The results demonstrate the involvement of NADPH oxidase and mitochondrial dysfunction in MB and PQ-induced oxidative stress in PMNs and a plausible crosstalk between them.

Pulmonary toxicity of well-dispersed titanium dioxide nanoparticles following intratracheal instillation

In order to investigate the pulmonary toxicity of titanium dioxide (TiO₂) nanoparticles, we performed an intratracheal instillation study with rats of well-dispersed TiO₂ nanoparticles and examined the pulmonary inflammation and histopathological changes in the lung. Wistar Hannover rats were intratracheally administered 0.2 mg (0.66 mg/kg) and 1.0 mg (3.3 mg/kg) of well-dispersed TiO₂ nanoparticles (P90; diameter of agglomerates: 25 nm), then the pulmonary inflammation responses were examined from 3 days to 6 months after the instillation, and the pathological features were examined up to 24 months. Transient inflammation and the upregulation of chemokines in the broncho-alveolar lavage fluid were observed for 1 month. No respiratory tumors or severe fibrosis were observed during the recovery time. These data suggest that transient inflammation induced by TiO₂ may not lead to chronic, irreversible legions in the lung, and that TiO₂ nanoparticles may not have a high potential for lung disorder.

Pulmonary toxicity of well-dispersed titanium dioxide nanoparticles following intratracheal instillation

In order to investigate the pulmonary toxicity of titanium dioxide (TiO₂) nanoparticles, we performed an intratracheal instillation study with rats of well-dispersed TiO₂ nanoparticles and examined the pulmonary inflammation and histopathological changes in the lung. Wistar Hannover rats were intratracheally administered 0.2 mg (0.66 mg/kg) and 1.0 mg (3.3 mg/kg) of well-dispersed TiO₂ nanoparticles (P90; diameter of agglomerates: 25 nm), then the pulmonary inflammation responses were examined from 3 days to 6 months after the instillation, and the pathological features were examined up to 24 months. Transient inflammation and the upregulation of chemokines in the broncho-alveolar lavage fluid were observed for 1 month. No respiratory tumors or severe fibrosis were observed during the recovery time. These data suggest that transient inflammation induced by TiO₂ may not lead to chronic, irreversible legions in the lung, and that TiO₂ nanoparticles may not have a high potential for lung disorder.

Expression of cytokine-induced neutrophil chemoattractant in rat lungs following an intratracheal instillation of micron-sized nickel oxide nanoparticle agglomerates

OBJECTIVE

In our previous study, we reported that the micron-sized nickel oxide nanoparticle agglomerates induced neutrophil infiltration and the gene expression of the cytokine-induced neutrophil chemoattractant (CINC)-2αβ in a rat lung. In this study, we examined the expression of the CINCs family in the lung using the same rat model exposed to micron-sized nickel oxide nanoparticle agglomerates.

METHODS

The count median diameter of nickel oxide nanoparticle agglomerates suspended in saline was 1.34 μm (primary diameter: 8.41 nm). Male Wistar rats received an intratracheal instillation of 1 mg (3.3 mg/kg) of nickel oxide nanoparticles and were dissected at 3 days, 1 week, 1 month, 3 months, and 6 months after the instillation. The negative control group received an instillation of saline. The concentration of CINC-1 in the lung and the bronchoalveolar lavage fluid (BALF), CINC-2αβ in the BALF, and CINC-3 in the lung and the BALF was examined.

RESULTS

The concentration of CINC-1 was elevated at 3 days, 3 months, and 6 months in the lung tissue and from 3 days to 6 months in the BALF. The concentration of CINC-2αβ was elevated from 3 days to 3 months in the BALF. The concentration of CINC-3 was also elevated at 3 days, 1 week, 3 months, and 6 months in the lung tissue. Infiltration of neutrophil and alveolar macrophage was observed mainly in the alveoli during the observed time period.

CONCLUSION

These results suggest that CINC-1 to -3 were totally involved in the lung injury caused by micron-sized nickel oxide nanoparticle agglomerates.

Analysis of bronchoalveolar lavage fluid adhering to lung surfactant. Experiment on intratracheal instillation of nickel oxide with different diameters

Nickel oxide with two different particle sizes, micron size (NiO) and submicron size (nNiOm), as well as crystalline silica as a positive control and titanium dioxide as a negative control, were intratracheally instilled in rats and the phospholipid concentration and the protein concentration and surface tension of bronchoalveolar lavage fluid (BALF), which are used in surfactant assessment, were measured to see if they could be effective biomarkers in toxicity assessment. The results showed that the NiO instilled group showed no significant difference compared to the control group throughout the observation period. In contrast, a significant difference was found in the nNiOm instilled group compared to the control group throughout the observation period. Moreover, a significant difference was found in the crystalline silica instilled group for each measurement compared to the control group while for the titanium dioxide group, almost no significant difference was found. These results indicate that submicronsized particles of nickel oxide with smaller median diameters potentially have a stronger biological effect than micron size particles. They also indicate that screening can be done by measuring the phospholipid concentration and the protein concentration and surface tension of BALF.

Expression of inflammation-related cytokines following intratracheal instillation of nickel oxide nanoparticles

The objective of this study was to examine what kinds of cytokines are related to lung disorder by well-dispersed nanoparticles. The mass median diameter of nickel oxide in distilled water was 26 nm. Rats intratracheally received 0.2 mg of nickel oxide suspended in distilled water, and were sacrificed from three days to six months. The concentrations of 21 cytokines including inflammation, fibrosis and allergy-related ones were measured in the lung. Infiltration of alveolar macrophages was observed persistently in the nickel oxide-exposed group. Expression of macrophage inflammatory protein-1alpha showed a continued increase in lung tissue and broncho-alveolar lavage fluid (BALF) while interleukin-1alpha (IL-1alpha), IL-1beta in lung tissue and monocyte chemotactic protein-1 in BALF showed transient increases. Taken together, it was suggested that nano-agglomerates of nickel oxide nanoparticles have a persistent inflammatory effect, and the transient increase in cytokine expression and persistent increases in CC chemokine were involved in the persistent pulmonary inflammation.

Inflammogenic effect of well-characterized fullerenes in inhalation and intratracheal instillation studies

Background

We used fullerenes, whose dispersion at the nano-level was stabilized by grinding in nitrogen gas in an agitation mill, to conduct an intratracheal instillation study and an inhalation exposure study. Fullerenes were individually dispersed in distilled water including 0.1% Tween 80, and the diameter of the fullerenes was 33 nm. These suspensions were directly injected as a solution in the intratracheal instillation study. The reference material was nickel oxide in distilled water. Wistar male rats intratracheally received a dose of 0.1 mg, 0.2 mg, or 1 mg of fullerenes and were sacrificed after 3 days, 1 week, 1 month, 3 months, and 6 months. In the inhalation study, Wistar rats were exposed to fullerene agglomerates (diameter: 96 ± 5 nm; 0.12 ± 0.03 mg/m³; 6 hours/days for 5 days/week) for 4 weeks and were sacrificed at 3 days, 1 month, and 3 months after the end of exposure. The inflammatory responses and gene expression of cytokine-induced neutrophil chemoattractants (CINCs) were examined in rat lungs in both studies.

Results

In the intratracheal instillation study, both the 0.1 mg and 0.2 mg fullerene groups did not show a significant increase of the total cell and neutrophil count in BALF or in the expression of CINC-1,-2αβ and-3 in the lung, while the high-dose, 1 mg group only showed a transient significant increase of neutrophils and expression of CINC-1,-2αβ and -3. In the inhalation study, there were no increases of total cell and neutrophil count in BALF, CINC-1,-2αβ and-3 in the fullerene group.

Conclusion

These data in intratracheal instillation and inhalation studies suggested that well-dispersed fullerenes do not have strong potential of neutrophil inflammation.