Mucous cell metaplasia in the airways of rats exposed to machining fluids

Targeted deletion of nrf2 impairs lung development and oxidant injury in neonatal mice

AIMS

Nrf2 is an essential transcription factor for protection against oxidant disorders. However, its role in organ development and neonatal disease has received little attention. Therapeutically administered oxygen has been considered to contribute to bronchopulmonary dysplasia (BPD) in prematurity. The current study was performed to determine Nrf2-mediated molecular events during saccular-to-alveolar lung maturation, and the role of Nrf2 in the pathogenesis of hyperoxic lung injury using newborn Nrf2-deficient (Nrf2(-/-)) and wild-type (Nrf2(+/+)) mice.

RESULTS

Pulmonary basal expression of cell cycle, redox balance, and lipid/carbohydrate metabolism genes was lower while lymphocyte immunity genes were more highly expressed in Nrf2(-/-) neonates than in Nrf2(+/+) neonates. Hyperoxia-induced phenotypes, including mortality, arrest of saccular-to-alveolar transition, and lung edema, and inflammation accompanying DNA damage and tissue oxidation were significantly more severe in Nrf2(-/-) neonates than in Nrf2(+/+) neonates. During lung injury pathogenesis, Nrf2 orchestrated expression of lung genes involved in organ injury and morphology, cellular growth/proliferation, vasculature development, immune response, and cell-cell interaction. Bioinformatic identification of Nrf2 binding motifs and augmented hyperoxia-induced inflammation in genetically deficient neonates supported Gpx2 and Marco as Nrf2 effectors.

INNOVATION

This investigation used lung transcriptomics and gene targeted mice to identify novel molecular events during saccular-to-alveolar stage transition and to elucidate Nrf2 downstream mechanisms in protection from hyperoxia-induced injury in neonate mouse lungs.

CONCLUSION

Nrf2 deficiency augmented lung injury and arrest of alveolarization caused by hyperoxia during the newborn period. Results suggest a therapeutic potential of specific Nrf2 activators for oxidative stress-associated neonatal disorders including BPD.

Respiratory Toxicology of Mineral Oils in Laboratory Animals

Early subchronic and chronic inhalation toxicology studies on various petroleum mineral oils and formulated lubricants supported the ACGIH TLV of 5 mg/m(3) for mineral oil mist. Additional subchronic studies with aerosolized mineral base oils and lubricants during the last 15 years demonstrated that exposures to aerosols of mineral base oils (often >100 mg/m(3)) resulted mainly in concentration-related accumulation in the lung of alveolar macrophages laden with oil droplets. Inflammatory cells were observed with higher aerosol concentrations, consistent with the clinical literature from highly exposed workers. These pulmonary changes appeared to be a nonspecific response to the presence of deposited aerosol. Studies on sensory irritation during exposures of lab animals to mineral oils indicate possible effects only with very high aerosol concentrations. Coupled with changes in refining to remove carcinogenic polynuclear aromatic hydrocarbons from mineral oils several decades ago, this information indicates that current aerosols of mineral oils have a profile of low toxicity from acute to long-term exposures. Available information suggests that additives in some formulated products and/or maintenance of mineral-based metalworking fluids may play a much more significant role in potential health effects.

Antiviral activity of Nrf2 in a murine model of respiratory syncytial virus disease

RATIONALE

Respiratory syncytial virus (RSV) is the most frequent cause of significant lower respiratory illness in infants and young children, but its pathogenesis is not fully understood. The transcription factor Nrf2 protects lungs from oxidative injury and inflammation via antioxidant response element (ARE)-mediated gene induction.

OBJECTIVES

The current study was designed to determine the role of Nrf2-mediated cytoprotective mechanisms in murine airway RSV disease.

METHODS

Nrf2-deficient (Nrf2(-/-)) and wild-type (Nrf2(+/+)) mice were intranasally instilled with RSV or vehicle. In a separate study, Nrf2(+/+) and Nrf2(-/-) mice were treated orally with sulforaphane (an Nrf2-ARE inducer) or phosphate-buffered saline before RSV infection.

MEASUREMENTS AND MAIN RESULTS

RSV-induced bronchopulmonary inflammation, epithelial injury, and mucus cell metaplasia as well as nasal epithelial injury were significantly greater in Nrf2(-/-) mice than in Nrf2(+/+) mice. Compared with Nrf2(+/+) mice, significantly attenuated viral clearance and IFN-gamma, body weight loss, heightened protein/lipid oxidation, and AP-1/NF-kappaB activity along with suppressed antioxidant induction was found in Nrf2(-/-) mice in response to RSV. Sulforaphane pretreatment significantly limited lung RSV replication and virus-induced inflammation in Nrf2(+/+) but not in Nrf2(-/-) mice.

CONCLUSIONS

The results of this study support an association of oxidant stress with RSV pathogenesis and a key role for the Nrf2-ARE pathway in host defense against RSV.

Metalworking fluid--the toxicity of a complex mixture

Various chemicals are used in the manufacture of cooling and lubricating fluids and fall into the classes of straight, soluble, semisynthetic, and synthetic metalworking fluids. The diversity of chemicals and in-use contaminants makes the risk assessment of metalworking fluids quite difficult. Toxicologists have used a number of methods to evaluate the component(s) responsible for the adverse pulmonary effects of metal working fluid aerosols encountered in the workplace. Although investigators have studied the adverse effects of metalworking fluid chemicals alone and in combination, the majority of evidence strongly suggests that the microbial changes that occur in fluid composition, during use and storage in the workplace, are responsible for the pulmonary effects reported for workers exposed to metalworking fluid aerosols. This review discusses the methodologies used to examine the toxicity of the complex nature of modern metalworking fluids and the findings that point toward bacterial endotoxin as a major contributor to their adverse effects.