Cytokine-regulatory activity and therapeutic efficacy of cinnamyl derivatives in endotoxin shock

Antiviral therapy for COVID-19: Derivation of optimal strategy based on past antiviral and favipiravir experiences

Favipiravir, a broad-spectrum RNA-dependent RNA polymerase inhibitor, inhibits the replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at significantly lower concentrations than the plasma trough levels achieved by the dosage adopted for influenza treatment and exhibits efficacy against coronavirus disease 2019 (COVID-19) pneumonia. Although high doses of favipiravir are required due to the molecule being a purine analog, its conversion into the active form in infected cells with active viral RNA synthesis enhances the antiviral specificity and selectivity as a chain terminator with lethal mutagenesis. Another characteristic feature is the lack of generation of favipiravir-resistant virus. COVID-19 pneumonia is caused by strong cell-mediated immunity against virus-infected cells, and the inflammatory response induced by adaptive immunity continues to peak for 3 to 5 days despite antiviral treatment. This has also been observed in herpes zoster (HZ) and cytomegalovirus (CMV) pneumonia. Inflammation due to an immune response may mask the effectiveness of favipiravir against COVID-19 pneumonia. Favipiravir significantly shortened the recovery time in patients with mild COVID-19 pneumonia by 3 days with the start of treatment by the 5th day of symptom onset. Since both CMV and COVID-19 pneumonia are caused by adaptive immunity and prevention of cytomegalovirus pneumonia is the standard treatment due to difficulties in treating refractory CMV pneumonia, COVID-19 pneumonia should be prevented with early treatment as well. In the present study, we have comprehensively reviewed the optimal antiviral therapy for COVID-19 based on clinical trials of favipiravir for the treatment of COVID-19 pneumonia and the concurrently established therapies for other viral infections, particularly HZ and CMV pneumonia. Optimally, antivirals should be administered immediately after COVID-19 diagnosis, similar to that after influenza diagnosis, to prevent COVID-19 pneumonia and complications resulting from microangiopathy.

Favipiravir, an anti-influenza drug against life-threatening RNA virus infections

Favipiravir has been developed as an anti-influenza drug and licensed as an anti-influenza drug in Japan. Additionally, favipiravir is being stockpiled for 2 million people as a countermeasure for novel influenza strains. This drug functions as a chain terminator at the site of incorporation of the viral RNA and reduces the viral load. Favipiravir cures all mice in a lethal influenza infection model, while oseltamivir fails to cure the animals. Thus, favipiravir contributes to curing animals with lethal infection. In addition to influenza, favipiravir has a broad spectrum of anti-RNA virus activities in vitro and efficacies in animal models with lethal RNA viruses and has been used for treatment of human infection with life-threatening Ebola virus, Lassa virus, rabies, and severe fever with thrombocytopenia syndrome. The best feature of favipiravir as an antiviral agent is the apparent lack of generation of favipiravir-resistant viruses. Favipiravir alone maintains its therapeutic efficacy from the first to the last patient in an influenza pandemic or an epidemic lethal RNA virus infection. Favipiravir is expected to be an important therapeutic agent for severe influenza, the next pandemic influenza strain, and other severe RNA virus infections for which standard treatments are not available.

Anti-Inflammatory Activity Comparison among Scropoliosides-Catalpol Derivatives with 6-O-Substituted Cinnamyl Moieties

We have previously shown that scropolioside B has higher anti-inflammatory activity than catalpol does after the inhibition of nuclear factor (NF)-κB activity and IL-1β expression, maturation, and secretion. Various scropoliosides were extracted, isolated, and purified from Scrophularia dentata Royle ex Benth. We then compared their anti-inflammatory activities against LPS-induced NF-κB activity, cytokines mRNA expression, IL-1β secretion, and cyclooxygenase-2 activity. The inhibitory effects of the scropoliosides varied depending on whether the 6-O-substituted cinnamyl moiety was linked to C′′ 2-OH, C′′3-OH, or C′′4-OH, and on the number of moieties linked, which is closely related to the enhancement of antiinflammatory activity. Among these compounds, scropolioside B had the strongest antiinflammatory effects.

Functional disorder of primary immunity responding to respiratory syncytial virus infection in offspring mice exposed to a flame retardant, decabrominated diphenyl ether, perinatally

Perinatal exposure to a representative flame retardant, decabrominated diphenyl ether (DBDE), was shown previously to increase viral titers in the lungs of respiratory syncytial virus (RSV)-infected offspring on day 5 post-infection, resulting in exacerbation of pneumonia. In this study, the significant increase of pulmonary viral titers was confirmed even on day 1 post-infection and the effect on the primary immune response to RSV infection were examined to assess a mode of DBDE action on developmental immunotoxicity. On day 1 after infection, the secretion of both TNF-alpha and IL-6 decreased significantly in the bronchoalveolar lavage fluid prepared from RSV-infected offspring exposed to DBDE perinatally, but IL-1beta increased. However, in ex vivo lipopolysaccharide stimulation test, the productivity of TNF-alpha in the bronchoalveolar lavage cells, which are mainly primary immune cells responding to RSV infection, prepared from offspring mice exposed to DBDE perinatally was not lower than that in the control. The primary immune cells retained normally the ability of cytokine production after the DBDE exposure. Gene expressions of innate pattern recognition receptors (Toll-like receptor 3 and 4, melanoma differentiation-associated gene-5, and retinoic acid-inducible gene I) in lung tissues were not affected by DBDE exposure. Because the levels of TNF-alpha, IL-6, and IL-1beta are known to be elevated in the lungs of RSV-infected mice, these irregular productions due to perinatal DBDE exposure indicate a disorder of the primary immune response to RSV infection. Thus, perinatal exposure to DBDE was suggested to cause a functional disorder of primary immunity responding to RSV infection.

Modulation of cytokine production by 7-hydroxycoumarin in vitro and its efficacy against influenza infection in mice

We previously demonstrated that 7-hydroxycoumarin (7HC) was effective in reducing proinflammatory cytokine production in lipopolysaccharide-exposed macrophage-like P388D1 cells and fever production by suppressing the increase in interleukin (IL)-1alpha production in an influenza virus-intranasal infection model in mice. In this study, we assessed the effects of modulation of cytokine production by 7HC on influenza virus infection in relation to its efficacy in influenza virus-infected mice. 7HC was confirmed to suppress proinflammatory cytokine levels in P388D1 cells due to influenza virus infection. In the murine infection model, oral administration of 7HC (30 mg/kg) was significantly effective in reducing the weight loss of infected mice and virus titers in the bronchoalveolar lavage fluid (BALF) of lungs and in prolonging survival times without toxicity. The rise of proinflammatory and Th1 cytokine (IL-12 and interferon-gamma) production in the BALF from infected mice was significantly suppressed by 7HC at two and four days post-infection, respectively. This suppression correlated with the reduction of virus titers and diminution of lung consolidation. Because 7HC did not exhibit direct anti-influenza virus activity in vitro, 7HC was suggested to suppress pneumonia in influenza virus-infected mice through suppression of the cytokine production induced by infection.