Role of Quercetin in Ameliorating the Histological Changes in a Rat Model of Acute Lung Injury: Histological and Immunohistochemical Study

Background: Acute lung injury (ALI) leads to disrupted endothelial and epithelial barriers due to associated acute inflammation. Oleic acid (OA)-induced lung injury is a model for induction of ALI in rats. Quercetin is a flavonoid with anti-inflammatory and antioxidant actions.Aim of the Work: This study was done to evaluate the role of quercetin in ameliorating the histological changes in a rat model of acute lung injury through using histological and immunohistochemical techniques.Materials and Methods: Forty-eight albino rats (200 - 250 grams; 8-9 weeks), were divided into three main groups. Group I (Control group), Group II (ALI-induced group): Eight rats received single injection of 50 μL OA dissolved in 1% BSA via rat tail vein, Group III: Sixteen rats received OA as group II, then divided into Subgroup IIIA& Subgroup IIIB: rats received 10 &50 mg/kg quercetin orally daily for 21 days respectively.Results: ALI-induced group showed thickened interalveolar septae, interstitial& perivascular inflammatory cellular infiltrations, congested blood vessels, disorganized alveoli with intra-alveolar and interstitial hemorrhage, bronchioles with separated epithelial lining, perinuclear vacuolation and their lumen contained exudate, and interstitial areas of homogenous acidophilia at H&E sections. Besides, significant increase in the mean area percentage of CD68 positive cells. Also, prominent ultrastructural changes of type I&II pneumocytes, and pulmonary blood capillaries. Quercetin treated groups showed dose-dependent improvement in the histological structure of the lung.Conclusion: Quercetin ameliorates ALI in rats in a dose dependent manner