Effects of HMGB1 gene silencing on respiratory syncytial virus-induced inflammatory response

Abstract

Abstract Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infections among infants and young children worldwide. High mobility group box 1 protein (HMGB1) is a redox-sensitive multifunctional protein that serves as both DNA regulatory protein and an extracellular cytokine signaling molecule that mediates the activation of innate and adaptive immune responses to infection, injury and inflammation. The goal of this study is to investigate the effect of HMGB1 gene silencing using short interfering RNA (siRNA) in RSV-induced airway inflammation. Studies were conducted in airway epithelial cells, human lung carcinoma cell line (A549) and normal small alveolar epithelial (SAE) cells. Cells were transfected with siRNA followed by infection with RSV, and NFκB, Nrf2, HDAC1 and catalase expression were determined. HMGB1-siRNA achieved a reduction of ~60–70% in nuclear HMGB1 expression in the airway epithelial cells. The Knockdown of nuclear HMGB1 was found to worsen inflammation in RSV-infected lung epithelial cells, highlighting a role for intracellular HMGB1 in cellular protection. We also found that HMGB1 gene silencing resulted in decreased HMGB1 release with significant downregulation of Nrf2, catalase and HDAC1 and increased NFκB and MAPK expression. These results indicated that downregulation of nuclear HMGB1 by siRNA might not only decrease its proinflammatory extracellular role by reducing its release but also serve to maintain its beneficial intracellular role, thus protecting against RSV -induced airway inflammation. Understanding the role of HMGB1 and associated cellular signaling in RSV-induced lung inflammation may pave the way for the development of novel therapeutic interventions.