N-acetylcysteine attenuates cigaret smoke-induced pulmonary exacerbation in a mouse model of emphysema

The effects of chronic smoking on lung tissue and the role of alpha lipoic acid

We investigated the effects of alpha lipoic acid (ALA) on blood and lung tissue exposed chronically to cigarette smoke (CS). Female Sprague-Dawley rats were divided into three groups. Group 1 was the control group (CON): fresh air was supplied twice daily and 0.1 ml physiological saline was given orally for 8 weeks. Group 2 was exposed to CS: 12 cigarettes were smoked daily at two sessions for 1 h and 0.1 ml saline was given orally for 8 weeks. Group 3 (CS + ALA) was exposed to 12 cigarettes daily in two sessions for 1 h and 100 mg/kg/day ALA was given orally for 8 weeks. DNA damage was assessed using comet analysis; oxidative damage was assessed using ischemia-modified albumin (IMA) from blood; and total oxidant status (TOS), total antioxidant status (TAS) and oxidative stress index (OSI) were measured in blood and lung tissue. Histopathological and immunohistochemical evaluation of hypoxia-inducible factor (HIF)-1α, and -2α, caspase-3, vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF₂) were conducted using lung tissue. The oxidative markers, TOS, OSI and IMA, and the comet analysis score were increased and the TAS level was decreased in the blood of the CS group compared to the CON group. IMA levels in blood, and TOS and OSI levels in the lung were decreased significantly in the CS + ALA group compared to the CS group. We observed increased septal wall thickness, marked and diffuse inflammatory reaction, emphysema, and necrotic cell debris in bronchial and bronchiolar lumens in the CS group. HIF-1α, HIF-2α, caspase-3 and FGF₂ expressions were increased, while VEGF expression decreased in the lung tissues of the CS group compared to the CON group. ALA slightly ameliorated the damage caused by chronic exposure to CS in the lungs, but further investigation is needed to determine its possible protective effects at different dosages.

Effects of particulate matter from straw burning on lung fibrosis in mice

OBJECTIVE

To investigate the impacts of particulate matter 2.5 (PM2.5) from straw burning on the acute exacerbation of lung fibrosis in mice and the preventive effects of N-acetylcysteine (NAC).

METHODS

The composition, particle size, and 30-min concentration change in an exposure system of the PM2.5 from straw-burning were determined. Forty C57BL male mice were equally randomized to two groups: bleomycin (BLM)-induced lung fibrosis with an exposure to air (BLM+air) and BLM+PM2.5 groups. On day 7 after receiving intratracheal injection of BLM, mice were exposed to air or PM2.5 in an exposure system for 30min twice daily and then sacrificed after one-week or four-week exposure (10 mice/group). Mouse survival, lung histopathology, macrophage accumulation in the lung, and pro-inflammatory cytokine levels in alveolar lavage fluid (ALF) were determined.

RESULTS

PM2.5 from straw burning were mainly composed of organic matter (74.1%); 10.92% of the inorganic matter of the PM2.5 were chloride ion; 4.64% were potassium ion; other components were sulfate, nitrate, and nitrite. Particle size was 10nm-2μm. Histopathology revealed a greater extent of inflammatory cell infiltration in the lung, widened alveolar septum, and lung fibrosis in the BLM+PM2.5 group than in the BLM+air group and a greater extent of those adverse effects after four-week than after one-week exposure to PM2.5. The BLM+PM2.5 group also showed macrophages containing particular matter and increased pulmonary collagen deposition as the exposure to PM2.5 increased. Interleukin (IL)-6 and TNF-α levels in ALF were significantly higher in the BLM+PM2.5 group than in the BLM+air group (P<0.05) and significantly higher after four-week exposure than after one-week exposure to PM2.5 (P<0.05). TGF-β levels in ALF after four-week exposure were significantly higher in the BLM+PM2.5 group than in the BLM+air group (P<0.05). The levels of IL-6, TNF-α, and TGF-β in peripheral serum were not significantly different in the BLM+PM2.5 and BLM+air groups. Lung hydroxyproline contents increased as the exposure to PM2.5 increased and were significantly higher after four-week than after one-week exposure (P=0.019). Exposure to PM2.5 did not affect the survival of normal mice (100%) but reduced the survival of mice with BLM-induced IPF (30%), whereas NAC extended the survival (70%, vs. BLM+PM2.5, P=0.032).

CONCLUSION

Exposure of mice with BLM-induced IPF to PM2.5 from straw burning exacerbated lung inflammation and fibrosis and increased mortality; NAC increased the mouse survival, indicating protective effects.