ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of spearmint oil on emphysema-like changes and the expression of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta(IL-1beta), matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-9) in lipopolysaccharide (LPS) treated rats.</p><p><b>METHOD</b>Emphysematous changes model was induced by intratracheal instillation of LPS once a week for up to 8 weeks in rats. Rats were divided into control, dexamethasone (0.3 mg x kg(-1)), and spearmint oil (10, 30,100 mg x kg(-1)) groups. Each group was treated with saline, dexamethasone, and spearmint of oil respectively for 4 weeks. Then total and different white blood cell counts in bronchoalveolar lavage fluid(BALF) were carried out. The pathologic changes of lung tissue such as alveolar structure, airway inflammation, and goblet cell metaplasia were observed by HE and AB-PAS staining. Expression of TNF-alpha, IL-1beta, TIMP-1 and MMP-9 were measured.</p><p><b>RESULT</b>Both spearmint and dexamethasone decreased the destruction of pulmonary alveolus. The total and different white blood cell counts in BALF including neutrophile and lymphocyte of spearmint oil 100 mg x kg(-1) and dexamethasone group were significantly reduced, and the goblet cell metaplasia was also inhibited. Dexamethasone had inhibitory effect on the expression of TNF-alpha, IL-1beta, TIMP-1 and MMP-9. Spearmint oil 30, 100 mg x kg(-1) significantly reduced TNF-alpha and IL-1beta respectively. Spearmint oil 10, 30 and 100 mg x kg(-1) had no effect on the expression of TIMP-1, but could decrease the expression of MMP-9 significantly in lung tissues.</p><p><b>CONCLUSION</b>Spearmint oil has protective effect on rats with emphysematous changes, since it improves alveolar destruction, pulmonary inflammation, and goblet cell metaplasia. The mechanism may include reducing TNF-alpha, IL-1beta content and inhibiting overexpression of matrix metalloproteinase-9 in lung tissues.</p>