Glycyrrhizin, an active component of licorice roots, reduces morbidity and mortality of mice infected with lethal doses of influenza virus

Abstract

The antiviral effect of glycyrrhizin (GR), an active component of licorice roots, was investigated in mice infected with influenza virus A2 (H2N2). When mice that had been exposed to 10 50% lethal doses of the virus were treated intraperitoneally with 10 mg of GR per kg of body weight 1 day before infection and 1 and 4 days postinfection, all of the mice survived over the 21-day experimental period. At the end of this period, the mean survival time (in days) for control mice treated with saline was 10.5 days, and there were no survivors. The grade of pulmonary consolidations and the virus titers in the lung tissues of infected mice treated with GR were significantly lower than those in the lung tissues of infected mice treated with saline. GR did not show any effects on the viability or replication of influenza virus A2 in vitro. When splenic T cells from GR-treated mice were adoptively transferred to mice exposed to influenza virus, 100% of the recipients survived, compared to 0% survival for recipient mice inoculated with naive T cells or splenic B cells and macrophages from GR-treated mice. In addition, the antiviral activities of GR on influenza virus infection in mice were not demonstrated when it was administered to infected mice in combination with anti-gamma interferon (anti-IFN-gamma) monoclonal antibody. These results suggest that GR may protect mice exposed to a lethal amount of influenza virus through the stimulation of IFN-gamma production by T cells, because T cells have been shown to be producer cells of IFN-gamma stimulated with the compound.

Influenza (“Bird Flu”), inflammation and anti-inflammatory/analgesic drugs

“…An explanation of the beneficial effects of aspirin on the immune functions in the elderly is that this drug may ameliorate the inhibitory effects of prostaglandin E 2 (PGE 2 ) on lymphocyte and macrophage functions. ated by administration of γ-IFN, further confirming a T-cell mediated phenomena being affected by glycyrrhizin (Utsunomiya et al, 1997).…”

“…Glycyrrhizin, which is present in liquorice roots and used in a number of traditional cough remedies, reduced the severity of infection in mice infected with influenza A H2N2 and reduced the lethality of the infection (Utsunomiya et al, 1997). This natural product did not affect virus replication in vitro but the protection appeared to be mediated by effects of this agent on T-cells.…”

Glycyrrhizin enhances interleukin-10 production by liver dendritic cells in mice with hepatitis

“…18,19 In addition, GL has anti-viral capacity against herpes simplex virus, cytomegalovirus, and influenza virus. [20][21][22] However, Ito et al 23 reported that GL treatment did not influence the HCV viral load. Several reports also indicate that GL has immune-modulatory capacity.…”

Glycyrrhizin inhibits highly pathogenic H5N1 influenza A virus-induced pro-inflammatory cytokine and chemokine expression in human macrophages

“…Mice were prevented from lethal H2N2 infection by glycyrrhizin although no influence on virus replication was detected. The mechanism was suggested to be induction of interferon-c in T cells by glycyrrhizin [48]. In a recent report, glycyrrhizin reduced H3N2 titres in lungderived cells [28].…”