Antiviral effects of modified Dingchuan decoction against respiratory syncytial virus infection in vitro and in an immunosuppressive mouse model

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Abstract

Ethnopharmacological relevance

Modified Dingchuan decoction (MDD) is used in traditional Chinese medicine for the treatment of cough, chronic bronchitis, asthma and viral pneumonia.

Aim of the study

To investigate antiviral potentials of MDD in respiratory syncytial virus (RSV) infected mice.

Materials and methods

MDD and each component were evaluated for antiviral efficacy against RSV in vitro in cell culture. Mice were were treated with cyclophosphamide and infected with RSV. Then, treatments with MDD at doses of 1.75 g/kg, 3.5 g/kg and 7.0 g/kg, respectively, were oral administrated daily for 5 days after challenge. The levels of Eotaxin, IL-4 and IFN-γ in serum and lung tissue were detected by ELISA, viral loads in lung tissues were detected by RFQ-PCR while expressions of NF-κB and TLR4 mRNA were also detected by RFQ-PCR.

Results

A selective index of >36.8 (2.5 times greater than that observed for ribavirin) was determined in the in vitro studies for this herbal medicine. MDD exhibited significant antiviral and anti-inflammatory effects on decreasing levels of Eotaxin, IL-4 and IFN-γ in serum and lung tissue, inhibiting pneumonia, decreasing lung viral loads and reversaling RSV-induced inflammation through down-regulation of TLR4 and NF-κB mRNA expression in the lung tissue of RSV-infected mice.

Conclusions

MDD could exhibit antiviral and anti-inflammatory effects on RSV-infected mice as a suppressor of Eotaxin, IL-4 and IFN-γ. These effects appeared to be mediated by inhibitions of TLR4 and NF-κB activation. Therefore, MDD could provide an effective therapeutic approach for RSV and its subsequent viral bronchitis.

Introduction

Respiratory syncytial virus (RSV) is a major cause of pneumonia and bronchiolitis in infants, young children and even in the elderly. The global annual infection figure for RVS is estimated to be 64 million. In the USA, RSV directly causes 18 000–75 000 hospitalisations and up to 1900 deaths annually, and contributes to another 17 000 deaths (Paes, 2003, Krilov et al., 2010). However, the ineffectiveness of vaccine is one of the major barriers for RSV prevention (Graham, 2011) and only a relatively nonspecific antiviral agent, ribavirin, which is reported to be obvious myelocytotoxic, is used for treatment (Narayana et al., 2002, Maggon and Barik, 2004). Thus, the development of novel anti-RSV drugs is still warranted.

Traditional herbal medicines have been used as remedies against infectious diseases for thousands of years due to their significant anti-inflammatory, antimicrobial and antiviral activities with no or few adverse effects (Ma et al., 2002, Ojwang et al., 2005, Sharma et al., 2009). Especially, therapeutic effects of the mixed formulas of Chinese herbal medicines are based on the synergic action of its mass constituents (Glatthaar-Saalmüller et al., 2011, Wang et al., 2011, Chang et al., 2012).

Dingchuan decoction, which is described in a famous traditional Chinese medicine (TCM) monograph Shesheng Zhongmiaofang in Ming Dynasty of China, has been used for approximately 500 years for treatment of cough, asthma and viral pneumonia. According to clinical experience, a modified Dingchuan decoction (MDD) was developed to ameliorate the complicated pathologic state of bronchiolitis in the acute phases, which is prepared with Salviae miltiorrhizae Radix, Scutellariae Radix, Farfarae Flos and Ephedrae Herba. Recently, MDD is widely used in east China as an herbal recipe for its efficiency in treating cough, asthma, pneumonia and bronchiolitis, but its actual mechanisms in the therapeutic process remains unclear. Therefore, this study is to investigate protective potentials of MDD on the levels of inflammatory cytokines, viral loads and expressions of NF-κB and TLR4 in lung tissues of RSV-infected mice.

Section snippets

Virus, cell and reagents

Human RSV (A strain) was donated by Professor Yiyu Lu from Zhejiang Center for Disease Control and Prevention, China. The virus was propagated in Hep-2 Cells for the preparation of a large stock of the virus. Hep-2 Cells were grown in DMEM (Sigma Co.) containing Eagle's balanced salt solution supplemented with 10% FBS, 100 U/mL of penicillin, 25 µg/mL of gentamicin, and 2 mM of l-glutamine (growth medium). RSV-infected cells were maintained in DMEM supplemented with 1% FBS (maintenance medium).

Results and discussion

This study demonstrated that MDD was effective in the protection of RSV infection. Aqueous extracts from 4 herbs and their mixture were studied to detect antiviral activity against RSV. As shown in Table 2, the 5 tested samples exhibited anti-RSV activity to different extents. MDD showed obvious antiviral activity with IC50 value 27.2 μg/mL, which was among those of 4 herbal extracts. It indicated that the therapeutic effect of the herbal medicine MDD was based on the synergic action of its mass

Acknowledgments

This work was a project supported by Scientific Research Fund of Zhejiang Provincial Education Department (NO. Y201017708). We thank Professor Yi-yu Lu for technical help in the animal experiment.

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