Juglans regia L. (Walnut) Leaf Extract Ameliorates Pulmonary Edema Against Airway Inflammation via Upregulation of Tight Junction Proteins and Heme Oxygenase-1 in the Lungs of Asthmatic Mice

Background: Juglans regia L. is renowned for its traditional use as a cure for respiratory diseases such as asthma and sinusitis. Objectives: This study was intended to assess the protective mechanism of the effects of hydroalcoholic extract of the leaf of Juglans regia L. against airway inflammation and pulmonary edema by measuring the expression levels of heme oxygenase-1 (HO-1), occludin, and Zonula occludens-1 (ZO-1) in the lung tissues. Methods: Ovalbumin (OVA) was used intraperitoneally to sensitize mice on Days 0 and 14 to induce allergic asthma by the intraperitoneal route. Animals were divided into 5 groups, consisting of normal control (NC), disease group (OVA, i.p), low-dose J. regia (LDJR) and high-dose J. regia (HDJR), methylprednisolone (MP), and reference control (RC) drug. On the 28th day, blood and bronchial alveolar lavage fluid (BALF) were collected for total leukocyte (TLC) and differential leukocyte (DLC) analysis. Hematoxylin and eosin (H&E) and periodic acid-Schiff (PAS) staining of the lungs were performed for the architectural changes caused by OVA-induced bronchial asthma. Tight junction proteins were assessed by measuring the expression levels of HO-1, occludin, and ZO-1 in the lung tissues by using real-time polymerase chain reaction. Results: Scores of inflammations, edema, and goblet cell hyperplasia were significantly increased (all p <= 0.05) in the DC group compared to the NC group, while treatment with LDJR and HDJR significantly reduced (all p <= 0.05) the scores of inflammations, edema, and goblet cell hyperplasia compared to the DC group. Real-time polymerase chain reaction data showed that expression levels of HO-1, occludin, and ZO-1 in lung tissues of the DC group were significantly reduced (all p <= 0.05), when the same was compared to the NC group, while treatment with LDJR and HDJR significantly increased (p <= 0.05) their expression level when compared to the DC group. Conclusion: Juglans regia L.'s hydroalcoholic extract possesses antiasthmatic activity by normalizing the TLC cells and DLC cells. Juglans regia L.'s hydroalcoholic extract resulted in the amelioration of pulmonary edema which is attributed to the upregulation of HO-1, occludin, and ZO-1 in the lung tissues of the Juglans regia L. treated groups when compared to the diseased control group. Administration of Juglans regia L.'s extract also reduces the scores of inflammation and vascular congestion by evaluation of the lungs' histopathology in the disease control group when compared to the NC group.