Quercetin and curcumin effects in experimental pleural inflammation

The inflammatory mechanisms occur with the highest prevalence in pulmonary pathology in addition to oxidative stress and activation of intracellular signaling pathways. The oxidative stress represents the imbalance between pro-oxidants and antioxidants which can lead to the activation of the oxidative mechanisms with noxious potential to the body. Therefore, finding a therapy that would counteract the injurious effects of free radicals and inflammation is highly attractive. Quercetin is the most active flavonoid, with important anti-inflammatory and antioxidant effects, while curcumin has antioxidant effects that are similar to the standard antioxidants and exerts direct anti-inflammatory activity. The aim of this study is to evaluate the antioxidant effects of quercetin and curcumin on an experimental model, pleural inflammation induced by carrageenan. Eight groups of adult male rats were used: Ia and Ib - control groups, IIa and IIb - with carrageenan administration, IIIa and IIIb - received curcumin and carrageenan, IVa and IVb - quercetin and carrageenan administration. Blood and lung samples were taken at 4 hours (Ia, IIa, IIIa, IVa groups) and at 24 hours (Ib, IIb, IIIb, IVb groups) after carrageenan injection. At 4 and at 24 hours, curcumin and quercetin have shown protective systemic effects, decreasing significantly the oxidative stress (malondialdehyde level) and stimulating significantly the antioxidant protection (ceruloplasmin and glutathione levels) compared to the group that received only carrageenan. In the lungs, at 4 hours, the redox misbalance was significantly reduced only in animals that were treated with quercetin, modifications that were not observed at 24 hours. In serum, curcumin presented higher antioxidant effects, compared to quercetin. In lungs, quercetin administration showed superior beneficial effects, but only temporarily.