To investigate the protective effects of β-carotene in rats against the development of chronic bronchitis induced by cigarette smoking Methods Forty-two Male Wistar rats were randomly divided into three study groups: ① control (n=15), animals underwent no treatment; ② cigarette smoking (n=15), animals developed chronic bronchitis through long-term cigarette smoking twice a day for 75 d; ③ β-carotene plus cigarette smoking animals (n=12) were given 1 ml or 15 mg/kg β-carotene orally every day just before cigarette smoking The levels of IL-6, IL-8, NO, superoxide dismutase (SOD) and lipoperoxide (LPO) in serum, bronchoalveolar lavage fluid (BALF) and lung tissue were measured and the pathological changes to lung tissue were analyzed using light microscopy Results Long-term cigarette smoking caused an obvious increase in the amount of IL-6, IL-8 and LPO and a sharp decrease in the levels of NO and SOD in smoking animals compared to controls β-carotene intake reversed all the changes induced by smoking and alleviated the pathological changes caused by chronic bronchitis Conclusions Quantitative oral intake of β-carotene had protective effects against chronic bronchitis induced by long-term cigarette smoking, which was associated with the increased production of NO, the clearance of some oxidative free radicals (OFR) and the alleviation of chronic inflammation To investigate the protective effects of β-carotene in rats against the development of chronic bronchitis induced by cigarette smoking Forty-two Male Wistar rats were randomly divided into three study groups: ① control (n = 15), animals underwent no treatment; ② cigarette smoking (n = 15), animals developed chronic bronchitis through long-term cigarette smoking twice a day for 75 days; ③β-carotene plus cigarette smoking animals (n = 12) were given 1 ml or 15 mg / kg β-carotene orally every day just before cigarette smoking The levels of IL-6, IL-8, NO, superoxide dismutase (SOD) and lipoperoxide (LPO) in serum, bronchoalveolar lavage fluid (BALF) and lung tissue were measured and the pathological changes to lung tissue were analyzed using light microscopy Results Long-term cigarette smoking caused an obvious increase in the amount of IL-6, IL-8 and LPO and a sharp decrease in the levels of NO and SOD in smoking animals compared to controls β-carotene intake revers ed all the changes induced by smoking and alleviated the pathological changes caused by chronic bronchitis Conclusions Quantitative oral intake of β-carotene had protective effects against chronic bronchitis induced by long-term cigarette smoking, which was associated with the increased production of NO, the clearance of some oxidative free radicals (OFR) and the alleviation of chronic inflammation