Anti‑inflammatory Properties of Bixa Orellana Leaves Extract are Associated with Suppression of Bradykinin‑induced Endothelial Hyperpermeability

Background: Previous study showed that an aqueous extract of Bixa orellana L. (Family of Bixaceae) leaf (AEBO) is capable of inhibiting bradykinin (BK)‑induced inflammation in animal models. Objective: This study further investigates the effect of AEBO on BK‑induce inflammation in vitro model. Materials and Methods: The endothelial barrier protective effect of AEBO was examined via an in vitro endothelial permeability assay. Human umbilical vein endothelial cell (HUVEC) was first pretreated with AEBO with a concentration range from 0.1, 0.2, and 0.4 mg/mL and then induced with BK. Fluorescein isothiocyanate‑conjugated‑dextran was used as an indicator of permeability flux. To elucidate its mechanism of action, the phospholipase C (PLC) – nitric oxide (NO) – cyclic guanosine monophosphate (cGMP) signaling pathway and protein kinase C (PKC) activity were evaluated. Results: Pretreatment of AEBO significantly (P < 0.05) suppressed BK‑induced HUVEC hyperpermeability and 0.4 mg/mL possessed the maximal inhibitory effect (87%, 70%, and 57% inhibition rate at 5, 15, and 30 min time point, respectively). Moreover, AEBO has presented remarkable IC50 = 0.24 mg/mL for anti‑PLC activity, 0.36 mg/mL for anti‑NO production, and 0.19 mg/mL for anti‑cGMP production. For PKC inhibition, the IC50 (0.42 mg/mL) was slightly higher compared to others. Conclusion: This study provided supportive evidence for the previous study where AEBO exhibited anti‑inflammatory activity against BK in vivo. The anti‑inflammatory activity of AEBO may partly be associated with the reduction of endothelial hyperpermeability via the suppression of PLC‑NO‑cGMP signaling and PKC activity.