Baicalin from Scutellaria baicalensis blocks respiratory syncytial virus (RSV) infection and reduces inflammatory cell infiltration and lung injury in mice.

Hengfei Shi,Erguang Li,Ren Xiang Tan,Wei Zhang,Baojie Lv,Ke Ren,Ying Zhao

doi:10.1038/srep35851

Abstract

The roots of Scutellaria baicalensis has been used as a remedy for inflammatory and infective diseases for thousands of years. We evaluated the antiviral activity against respiratory syncytial virus (RSV) infection, the leading cause of childhood infection and hospitalization. By fractionation and chromatographic analysis, we determined that baicalin was responsible for the antiviral activity of S. baicalensis against RSV infection. The concentration for 50% inhibition (IC50) of RSV infection was determined at 19.9 ± 1.8 μM, while the 50% cytotoxic concentration (CC50) was measured at 370 ± 10 μM. We then used a mouse model of RSV infection to further demonstrate baicalin antiviral effect. RSV infection caused significant lung injury and proinflammatory response, including CD4 and CD8 T lymphocyte infiltration. Baicalin treatment resulted in reduction of T lymphocyte infiltration and gene expression of proinflammatory factors, while the treatment moderately reduced RSV titers recovered from the lung tissues. T lymphocyte infiltration and cytotoxic T lymphocyte modulated tissue damage has been identified critical factors of RSV disease. The study therefore demonstrates that baicalin subjugates RSV disease through antiviral and anti-inflammatory effect.

Highlights

The human respiratory syncytial virus (RSV) infection is a leading cause of acute respiratory tract infections in early childhood[1]
To determine the antiviral effect, we performed a quick assay against RSV infection in cell cultures using an aqueous extract from the roots of S. baicalensis (SBE)
Baicalin which was isolated as a major component and 3 other compounds were identified by spectroscopic methods and by comparison with literature reports

Summary

Introduction

The human respiratory syncytial virus (RSV) infection is a leading cause of acute respiratory tract infections in early childhood[1]. The infection causes flu-like symptoms and is frequently associated with bronchiolitis and pneumonia. It was estimated by the World Health Organization that RSV is responsible for over 33 million new episodes of acute lower respiratory infection in children younger than 5 years[2]. RSV infection is the leading cause of hospitalization of young children with respiratory infections[3,4,5] It has become a significant burden in the elderly among the industrialized countries[3,4,6]. We determined the relative content of flavonoids in an extract from S. baicalensis and found that baicalin represents the antiviral effect of the radices. We report the antiviral effect of baicalin against RSV infection

Methods

Results

Conclusion