Didecyldimethylammonium chloride (DDAC), a representative dialkyl-quaternary ammonium compound (QAC), could contaminate working atmospheres when used in disinfectant operation and adversely affect human health. Furthermore, the development of bacteria resistant to DDAC might become public health concern. We postulated that DDAC instillation in the lungs alters pulmonary antioxidant and antimicrobial responses and increases susceptibility to systemic administration of a bacterial component lipopolysaccharide (LPS). Mice were intratracheally instilled with DDAC and sacrificed 1, 3, or 7 days after treatment. Pulmonary cytotoxicity in recovered bronchoalveolar lavage was evident on Days 1 and 7, and inflammatory cell influx and interleukin-6 expression peaked on Day 7, in association with altered antioxidant and antimicrobial responses, as demonstrated by measuring heme oxygenase-1, glutathione peroxidase 2, lactoferrin, and mouse β-defensin-2 and -3 mRNA in the lung samples. The impaired defense system tended to enhance the inflammatory reaction caused by a systemic administration of LPS; the effect was in association with increased expression of toll-like receptor-4 mRNA. The results suggest that DDAC alters pulmonary defense system, which may contribute to susceptibility to an exogenous infectious agent.
Chronic lung injury resulting from a variety of different causes is frequently associated with the develop ment of pulmonary fibrosis in humans. Although the etiology of pulmonary fibrosis is generally unknown, several sources of evidence support the hypothesis that a number of environmental and occupational agents play an etiologic role in the pathogenesis of this disease. The agents discussed in this review include beryllium, nylon flock, textile printing aerosols, polyvinyl chloride and didecyldimethylammonium chloride. The authors also describe a variety of animal models, including genetically modified mice, in order to investigate the molecular mechanism of pulmonary fibrosis, focusing on chemokine receptors, regulatory T cells and transforming growth factor-β and bone morphogenetic protein signaling. Overall, we propose the concept of toxicological pulmonary fibrosis as a lung disease induced in response to environmental cues.
Dimethylarsinic acid (DMA V ), the major excreted metabolite of inorganic arsenic, is carcinogenic to the rat urinary bladder. Oxidative stress has been proposed as one possible mechanism of DMA V -induced carcinogenesis. The authors determined whether the antioxidant N-acetylcysteine (NAC) modifies DMA V -induced urinary bladder injury in rats. The treatment solutions-DMA V at 10 mg/kg, NAC at 90 or 1.6 mg/kg (high or low dose, respectively), and their combination-were intravesically instilled into female F344 rats over two hours under pentobarbital anesthesia. The treatment was conducted twice with an interval of three days. All animals were euthanized one day after the second treatment. NAC (low dose) alone did not induce histopathological changes or increase 5-bromo-2 0 -deoxyuridine (BrdU) labeling index in urothelial cells. Both DMA V and NAC (high dose) induced a weak neutrophil infiltration and an increase in the BrdU labeling index; these pathological changes were enhanced by the combined treatment of DMA V and NAC (high or low dose). Increased oxidative stress and urothelial cell hyperplasia with evidence of activated p44/42 MAPK (ERK1/2) and cyclin D1 were found in the DMA V and NAC (high dose) cotreated group. These results suggest that cotreatment with NAC enhanced DMA V -induced urinary bladder injury and that the effects may be mediated by excess oxidative stress and ERK signaling.
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