N-acetylcysteine alleviates pulmonary alveolar proteinosis induced by indium-tin oxide nanoparticles in male rats: involvement of the NF-κB signaling pathway

Lipid-Laden Macrophages in Pulmonary Diseases

Pulmonary surfactants play a crucial role in managing lung lipid metabolism, and dysregulation of this process is evident in various lung diseases. Alternations in lipid metabolism lead to pulmonary surfactant damage, resulting in hyperlipidemia in response to lung injury. Lung macrophages are responsible for recycling damaged lipid droplets to maintain lipid homeostasis. The inflammatory response triggered by external stimuli such as cigarette smoke, bleomycin, and bacteria can interfere with this process, resulting in the formation of lipid-laden macrophages (LLMs), also known as foamy macrophages. Recent studies have highlighted the potential significance of LLM formation in a range of pulmonary diseases. Furthermore, growing evidence suggests that LLMs are present in patients suffering from various pulmonary conditions. In this review, we summarize the essential metabolic and signaling pathways driving the LLM formation in chronic obstructive pulmonary disease, pulmonary fibrosis, tuberculosis, and acute lung injury.

Role of macrophage bioenergetics in N-acetylcysteine-mediated mitigation of lung injury and oxidative stress induced by nitrogen mustard

Nitrogen mustard (NM) is a toxic vesicant that causes acute injury to the respiratory tract. This is accompanied by an accumulation of activated macrophages in the lung and oxidative stress which have been implicated in tissue injury. In these studies, we analyzed the effects of N-acetylcysteine (NAC), an inhibitor of oxidative stress and inflammation on NM-induced lung injury, macrophage activation and bioenergetics. Treatment of rats with NAC (150 mg/kg, i.p., daily) beginning 30 min after administration of NM (0.125 mg/kg, i.t.) reduced histopathologic alterations in the lung including alveolar interstitial thickening, blood vessel hemorrhage, fibrin deposition, alveolar inflammation, and bronchiolization of alveolar walls within 3 d of exposure; damage to the alveolar-epithelial barrier, measured by bronchoalveolar lavage fluid protein and cells, was also reduced by NAC, along with oxidative stress as measured by heme oxygenase (HO)-1 and Ym-1 expression in the lung. Treatment of rats with NAC attenuated the accumulation of macrophages in the lung expressing proinflammatory genes including Ptgs2, Nos2, Il-6 and Il-12; macrophages expressing inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2 and tumor necrosis factor (TNF)α protein were also reduced in histologic sections. Conversely, NAC had no effect on macrophages expressing the anti-inflammatory proteins arginase-1 or mannose receptor, or on NM-induced increases in matrix metalloproteinase (MMP)-9 or proliferating cell nuclear antigen (PCNA), markers of tissue repair. Following NM exposure, lung macrophage basal and maximal glycolytic activity increased, while basal respiration decreased indicating greater reliance on glycolysis to generate ATP. NAC increased both glycolysis and oxidative phosphorylation. Additionally, in macrophages from both control and NM treated animals, NAC treatment resulted in increased S-nitrosylation of ATP synthase, protecting the enzyme from oxidative damage. Taken together, these data suggest that alterations in NM-induced macrophage activation and bioenergetics contribute to the efficacy of NAC in mitigating lung injury.

Pathological Comparison of Rat Pulmonary Models Induced by Silica Nanoparticles and Indium-Tin Oxide Nanoparticles

Purpose

The objective of this study was to evaluate and compare the histopathological implications of silica nanoparticles (Nano-SiO₂) and indium-tin oxide nanoparticles (Nano-ITO), in vivo.

Methods

Male Sprague-Dawley rats were exposed to Nano-SiO₂ (50 mg/kg) and Nano-ITO (6 mg/kg) by a single intratracheal instillation, respectively. Broncho-alveolar lavage fluid (BALF) and lung tissue were obtained at 7, 14, 28, and 56 days post exposure for analysis of BALF inflammatory factors, total protein, and for lung tissue pathology. Histopathological and ultrastructural change in lungs were investigated by hematoxylin and eosin, Masson’s trichrome, sirius red staining, periodic acid Schiff stain, and transmission electron microscopy. The expression of SP-A, collagen type I and III in lung tissue was determined by immunohistochemistry and ELISA.

Results

The rats in both models exhibited obvious collagen fibrosis and the severity of the lung injury increased with time after exposure to respective dosage increased. Several parameters of pulmonary inflammation and fibrosis significantly increased in both groups, which was reflected by increased LDH activity, total proteins, TNF-α, and IL-6 levels in BALF, and confirmed by histopathological examination. The results also showed that the two models exhibited different features. Exposure to Nano-ITO caused persistent chronic lung inflammation, illustrated by the infiltration of a large amount of enlarged and foamy macrophages and neutrophils into the lung parenchyma. In Nano-SiO₂ exposed rat lung tissue, granulomatous inflammation was most prominent followed by progressive and massive fibrotic nodules. Compared with the Nano-SiO₂ rats, Nano-ITO exposed rats exhibited significantly severe pulmonary alveolar proteinosis (PAP) pathological changes, lower fibrosis, and higher levels of inflammatory biomarkers. However, Nano-SiO₂ exposed rats had greater fibrosis pathological changes and more severe granulomas than Nano-ITO exposed rats.

Conclusion

This study suggests that the Nano-SiO₂-induced model has greater value in research into granulomas and fibrosis, while the Nano-ITO-induced model has greater repeatability in area of PAP.