Silymarin Reduces OVA-induced Allergic Airway Inflammation

Abstract

RationaleInexpensive, readily available drugs are needed for prevention and treatment of asthma. Oxidative stress, or an imbalance of reactive oxygen species (ROS) and antioxidants, occurs in asthma with infiltration of inflammatory cells, such as eosinophils, into the airways resulting in inflammation and tissue damage. Silymarin, a flavonoid complex from Silybum marianum (milk thistle plant), reduces ROS by increasing antioxidant enzymes, such as catalase, in human hepatotoxicity and cancer. However, the effect of silymarin on allergic airway inflammation and asthma is unknown. We hypothesized silymarin decreases ovalbumin (OVA)-induced airway inflammation in BALB/c mice by increasing catalase levels.MethodsBALB/c female mice were sensitized to OVA conjugated with aluminum hydroxide on day -14. Two weeks later, mice were challenged with 1% OVA aerosol daily on days 0 to 3. One hour prior to each OVA challenge mice were orally given silymarin (50-200mg/kg body weight) or vehicle (0.4% methylcellulose). On day 4, blood, bronchoalveolar lavage (BAL) fluid and lungs were harvested. Serum IgE levels and IL-13, a Th2 cytokine upregulated with allergic airway inflammation, were determined by ELISA. Infiltration of inflammatory cells was examined in BAL fluid. Catalase mRNA expression was examined by real-time PCR.ResultsSilymarin significantly decreased lymphocytes and eosinophils in the BAL fluid (n=11-12, p<0.05) and decreased BAL fluid levels of IL-13. IgE serum levels were not altered with silymarin (p=0.013). Silymarin increased mRNA expression levels of catalase (n=11-12, p<0.05).ConclusionsSilymarin attenuated OVA-induced allergic airway inflammation, but had no effect on IgE levels. Therefore, silymarin may be a potential therapeutic for asthma. RationaleInexpensive, readily available drugs are needed for prevention and treatment of asthma. Oxidative stress, or an imbalance of reactive oxygen species (ROS) and antioxidants, occurs in asthma with infiltration of inflammatory cells, such as eosinophils, into the airways resulting in inflammation and tissue damage. Silymarin, a flavonoid complex from Silybum marianum (milk thistle plant), reduces ROS by increasing antioxidant enzymes, such as catalase, in human hepatotoxicity and cancer. However, the effect of silymarin on allergic airway inflammation and asthma is unknown. We hypothesized silymarin decreases ovalbumin (OVA)-induced airway inflammation in BALB/c mice by increasing catalase levels. Inexpensive, readily available drugs are needed for prevention and treatment of asthma. Oxidative stress, or an imbalance of reactive oxygen species (ROS) and antioxidants, occurs in asthma with infiltration of inflammatory cells, such as eosinophils, into the airways resulting in inflammation and tissue damage. Silymarin, a flavonoid complex from Silybum marianum (milk thistle plant), reduces ROS by increasing antioxidant enzymes, such as catalase, in human hepatotoxicity and cancer. However, the effect of silymarin on allergic airway inflammation and asthma is unknown. We hypothesized silymarin decreases ovalbumin (OVA)-induced airway inflammation in BALB/c mice by increasing catalase levels. MethodsBALB/c female mice were sensitized to OVA conjugated with aluminum hydroxide on day -14. Two weeks later, mice were challenged with 1% OVA aerosol daily on days 0 to 3. One hour prior to each OVA challenge mice were orally given silymarin (50-200mg/kg body weight) or vehicle (0.4% methylcellulose). On day 4, blood, bronchoalveolar lavage (BAL) fluid and lungs were harvested. Serum IgE levels and IL-13, a Th2 cytokine upregulated with allergic airway inflammation, were determined by ELISA. Infiltration of inflammatory cells was examined in BAL fluid. Catalase mRNA expression was examined by real-time PCR. BALB/c female mice were sensitized to OVA conjugated with aluminum hydroxide on day -14. Two weeks later, mice were challenged with 1% OVA aerosol daily on days 0 to 3. One hour prior to each OVA challenge mice were orally given silymarin (50-200mg/kg body weight) or vehicle (0.4% methylcellulose). On day 4, blood, bronchoalveolar lavage (BAL) fluid and lungs were harvested. Serum IgE levels and IL-13, a Th2 cytokine upregulated with allergic airway inflammation, were determined by ELISA. Infiltration of inflammatory cells was examined in BAL fluid. Catalase mRNA expression was examined by real-time PCR. ResultsSilymarin significantly decreased lymphocytes and eosinophils in the BAL fluid (n=11-12, p<0.05) and decreased BAL fluid levels of IL-13. IgE serum levels were not altered with silymarin (p=0.013). Silymarin increased mRNA expression levels of catalase (n=11-12, p<0.05). Silymarin significantly decreased lymphocytes and eosinophils in the BAL fluid (n=11-12, p<0.05) and decreased BAL fluid levels of IL-13. IgE serum levels were not altered with silymarin (p=0.013). Silymarin increased mRNA expression levels of catalase (n=11-12, p<0.05). ConclusionsSilymarin attenuated OVA-induced allergic airway inflammation, but had no effect on IgE levels. Therefore, silymarin may be a potential therapeutic for asthma. Silymarin attenuated OVA-induced allergic airway inflammation, but had no effect on IgE levels. Therefore, silymarin may be a potential therapeutic for asthma.