The neuroepithelial body (NEB) is a highly dynamic structure that responds to chronic airway injury through hyperplasia of associated pulmonary neuroendocrine (PNE) cells. Although NEB dysplasia is correlated with preneoplastic conditions and PNE cells are thought to serve as a precursor for development of small cell lung carcinoma, mechanisms regulating expansion of the PNE cell population are not well understood. Based on studies performed in animal models, it has been suggested that NEB-associated progenitor cells that are phenotypically distinct from PNE cells contribute to PNE cell hyperplasia. We have previously used a Clara cell-specific toxicant, naphthalene, to induce airway injury in mice and have demonstrated that naphthalene-resistant Clara cells, characterized by their expression of Clara cell secretory protein (CCSP), and PNE cells contribute to airway repair and associated hyperplasia of NEBs. This study was conducted to define the contribution of NEB-associated CCSP-expressing progenitor cells to PNE cell hyperplasia after Clara cell ablation. Transgenic (CCtk) mice were generated in which herpes simplex virus thymidine kinase was expressed within all CCSP-expressing cells of the conducting airway epithelium through the use of transcriptional regulatory elements from the mouse CCSP promoter. Chronic administration of ganciclovir (GCV) to CCtk transgenic mice resulted in selective ablation of CCSP-expressing cells within conducting airways. Proliferation and hyperplasia of PNE cells occurred in the absence of detectable proliferation among any other residual airway epithelial cell populations. These results demonstrate that PNE cells function as a self-renewing progenitor population and that NEB-associated Clara cells are not necessary for PNE cell hyperplasia.

Particulates such as silica crystal (silica) and aluminum salts (alum) activate the inflammasome and induce the secretion of proinflammatory cytokines in macrophages. These particulates also induce the production of immunoglobulin E via a T helper 2 (Th2) cell-associated mechanism. However, the mechanism involved in the induction of type 2 immunity has not been elucidated. Here, we showed that silica and alum induced lipopolysaccharide-primed macrophages to produce the lipid mediator prostaglandin E₂ (PGE₂) and interleukin-1β (IL-1β). Macrophages deficient in the inflammasome components caspase 1, NALP3, and ASC revealed that PGE₂ production was independent of the NALP3 inflammasome. PGE₂ expression was markedly reduced in PGE synthase-deficient (Ptges⁻/⁻) macrophages, and Ptges⁻/⁻ mice displayed reduced antigen-specific serum IgE concentrations after immunization with alum or silica. Our results indicate that silica and alum regulate the production of PGE₂ and that the induction of PGE₂ by particulates controls the immune response in vivo.

Objective: We reviewed studies on pulmonary, reproductive, and developmental toxicity caused by carbon nanotubes (CNTs). In paricular, we analyzed how CNT exposure affects the several processes of pulmonary toxicity, including inflammation, injury, fibrosis, and pulmonary tumors. Methods: In pulmonary toxicity, there are various processes, including inflammation, injury, fibrosis, respiratory tumor in the lungs, and biopersistence of CNTs and genotoxicity as tumor-related factors, to develop the respiratory tumor. We evaluated the evidence for the carcinogenicity of CNTs in each process. In the fields of reproductive and developmental toxicity, studies of CNTs have been conducted mainly with mice. We summarized the findings of reproductive and developmental toxicity studies of CNTs. Results: In animal studies, exposure to CNTs induced sustained inflammation, fibrosis, lung cancer following long-term inhalation, and gene damage in the lung. CNTs also showed high biopersistence in animal studies. Fetal malformations after intravenous and intraperitoneal injections and intratracheal instillation, fetal loss after intravenous injection, behavioral changes in offsprings after intraperitoneal injection, and a delay in the delivery of the first litter after intratracheal instillation were reported in mice-administered multi-walled carbon nanotubes (MWCNTs). Single-walled carbon nanotubes (SWCNTs) appeared to be embryolethal and teratogenic in mice when given by intravenous injection; moreover, the tubes induced death and growth retardation in chicken embryos. Conclusion: CNTs are considered to have carcinogenicity and can cause lung tumors. However, the carcinogenicity of CNTs may attenuate if the fiber length is shorter. The available data provide initial information on the potential reproductive and developmental toxicity of CNTs.

Particulate pollution is thought to function as an adjuvant that can induce allergic responses. However, the exact cell types and immunological factors that initiate the lung-specific immune responses are unclear. We found that upon intratracheal instillation, particulates such as aluminum salts and silica killed alveolar macrophages (AMs), which then released interleukin-1α (IL-1α) and caused inducible bronchus-associated lymphoid tissue (iBALT) formation in the lung. IL-1α release continued for up to 2 weeks after particulate exposure, and type-2 allergic immune responses were induced by the inhalation of antigen during IL-1α release and iBALT formation, even long after particulate instillation. Recombinant IL-1α was sufficient to induce iBALTs, which coincided with subsequent immunoglobulin E responses, and IL-1-receptor-deficient mice failed to induce iBALT formation. Therefore, the AM-IL-1α-iBALT axis might be a therapeutic target for particulate-induced allergic inflammation.

ABSTRACT-Effectsof KB-5492, a new anti-ulcer agent, on various experimental gastric mucosal lesions and mucosal defensive factors in rats were compared with those of teprenone and cimetidine. KB-5492 administered orally at 12.5 200 mg/kg inhibited water-immersion stress and indomethacin-induced gastric mucosal lesions in a dose-dependent manner with ED50 values of 46 and 27 mg/kg, respectively, indicat ing that KB-5492 was more potent than teprenone but less potent than cimetidine. KB-5492, administered orally at 12.5 -100 mg/kg, also inhibited ethanol-induced gas tric mucosal lesions in a dose-dependent manner with an ED50 of 23 mg/kg, so KB 5492 was 3 times more potent than teprenone, whereas cimetidine produced no ob vious inhibition. In addition, KB-5492, administered orally at 25 and 50 mg/kg twice daily for 10 consecutive days, significantly accelerated the healing of acetic acid-in duced gastric ulcers more potently than teprenone and cimetidine. KB-5492 at anti ulcer doses significantly increased gastric mucosal blood flow in normal anesthetized rats and inhibited the reduction of gastric mucosal hexosamine content induced by aspirin, but did not affect gastric acid secretion in pylorus-ligated rats. These results indicate that KB-5492 has potent and broad anti-ulcer properties, which are probably exerted by its enhancement of gastric mucosal defensive factors through increasing gastric mucosal blood flow and/or retaining gastric mucus, and not by its inhibition of gastric acid secretion.It is generally accepted that peptic ulcers are caused by a disruption in the balance of aggressive factors (gastric acid and pepsin) and mucosal defensive factors (blood flow, mucus, HC03 secretion, etc.) (1). Anti-ulcer agents have therefore been used either for suppres sing aggressive factors or for enhancing mucosal defensive factors. However, in recent years, it has been considered that different anti-ulcer agents should be used for gastric and duodenal ulcers, because of the patho physiological differences between the two ulcer types. That is, as gastric acid secretion is generally greater in duodenal ulcer patients than in normal subjects (2-4), agents such as H2-receptor antagonists or proton pump in hibitors, which strongly inhibit gastric acid secretion, show prominent effects on duodenal ulcers. In contrast, since gastric acid secretion is usually normal or below normal in gastric ulcer patients, gastric ulcers are presumed to be caused by weaknesses in gastric mucosal re sistance (4, 5). Therefore, agents which en hance mucosal defensive factors would be ex pected to show desirable effects against gastric ulcers. Although various agents in this catego ry have already been developed so far, they have not been particularly effective, so anti secretory agents are used preferably, even in the treatment of gastric ulcers.Seeking a novel agent which would enhance mucosal defensive factors more potently than existing agents, we developed 4-methoxy phenyl 4-(3,4,5-trimethoxybenzyl)-1-piperazine acetate monofumarate m...

In order to examine whether intratracheal instillation studies can be useful for determining the harmful effect of nanoparticles, we performed inhalation and intratracheal instillation studies using samples of the same nanoparticles. Nickel oxide nanoparticles (NiO) and titanium dioxide nanoparticles (TiO2) were used as chemicals with high and low toxicities, respectively. In the intratracheal instillation study, rats were exposed to 0.2 or 1 mg of NiO or TiO2. Cell analysis and chemokines in bronchoalveolar lavage fluid (BALF) were analyzed from 3 days to 6 months following the single intratracheal instillation. In the inhalation study, rats were exposed to inhaled NiO or TiO2 (1.65, 1.84 mg/m(3), respectively) for 4 weeks. The same endpoints were examined from 3 days to 3 months after the end of exposure. Inhalation of NiO induced an increase in the number of neutrophils in BALF and concentrations of cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-2 and heme oxygenase (HO)-1. Intratracheal instillation of NiO induced persistent inflammation and upregulation of these cytokines was observed in the rats. However, inhalation of TiO2 did not induce pulmonary inflammation, and intratracheal instillation of TiO2 transiently induced an increase in the number of neutrophils in BALF and the concentrations of CINC-1, CINC-2 and HO-1. Taken together, a difference in pulmonary inflammation was observed between the high and low toxicity nanomaterials in the intratracheal instillation studies, as in the inhalation studies, suggesting that intratracheal instillation studies may be useful for ranking the harmful effects of nanoparticles.

Multi-walled carbon nanotubes (MWCNTs), dispersed in suspensions consisting mainly of individual tubes, were used for intratracheal instillation and inhalation studies. Rats intratracheally received a dose of 0.2 mg, or 1 mg of MWCNTs and were sacrificed from 3 days to 6 months. MWCNTs induced a pulmonary inflammation, as evidenced by a transient neutrophil response in the low-dose groups, and presence of small granulomatous lesion and persistent neutrophil infiltration in the high-dose groups. In the inhalation study, rats were exposed to 0.37 mg/m(3) aerosols of well-dispersed MWCNTs (>70% of MWCNTs were individual fibers) for 4 weeks, and were sacrificed at 3 days, 1 month, and 3 months after the end of exposure. The inhalation exposures delivered less amounts of MWCNTs into the lungs, and therefore less pulmonary inflammation responses was observed, as compared to intratracheal instillation. The results of our study show that well-dispersed MWCNT can produce pulmonary lesions, including inflammation.

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.