Background Influenza is an acute viral respiratory illness that causes high morbidity and mortality globally. Therapeutic actions are limited to vaccines and a few anti-viral drugs. Polygala (P.) japonica herba is rich in Polygalasaponin F (PSF, C 53 H 86 O 23), used for acute bronchitis, pharyngitis, pneumonia, amygdalitis, and respiratory tract infections treatment in China. Hypercytokinemia is often correlated with severe pneumonia caused by several influenza viruses. PSF was reported to have anti-inflammatory effects and its mechanism is associated with the nuclear factor (NF)-κB signaling pathway. The action of PSF to alleviate pulmonary inflammation caused by influenza A virus (IAV) infection requires careful assessment. In the present study, we evaluated the effect and mechanism of PSF on mice with pneumonia caused by influenza H1N1 (A/ FM/1/47). Methods Mice were infected intranasally with fifteen 50% mouse lethal challenge doses (MLD 50) of influenza virus. BALB/c mice were treated with PSF or oseltamivir (oral administration) for 2 h post-infection and received concomitant treatment for 5 days after infection. On day 6 post-infection, 10 mice per group were killed to collect related samples, measure body weight and lung wet weight, and detect the viral load, cytokine, prostaglandins, pathological changes, and cell pathway protein expression in the lungs. In addition, the survival experiments were carried out to investigate the survival of mice. The expression profile of cell pathway proteins was detected and analyzed using a broad pathway antibody array and confirmed the findings from the array by western blotting. Results Polygalasaponin F and oseltamivir can protect against influenza viral infection in mice. PSF and oseltamivir significantly relieved the signs and symptoms, reduced body weight loss, and improved the survival rate of H1N1-infected mice. Moreover, PSF efficiently decreased the level of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-4, interferon (IFN)-γ, thromboxane A 2 (TXA 2), and prostaglandin E 2 (PGE 2) in lung tissues of mice infected with influenza virus (p < 0.05-0.01). Oseltamivir had a similar effect to lung cytokine of PSF, but did not decrease the levels of TXA 2 and PGE 2. There was a twofold or greater increase in four cell pathway protein, namely NF-κB p65 (2.68-fold), I-kappa-B-alpha (IκBα) (2.56-fold), and MAPK/ERK kinase 1 (MEK1) (7.15-fold) assessed in the array induced by influenza virus. Western blotting showed that the expression of these proteins was significantly decreased in lung after influenza virus challenge in PSF and oseltamivirtreated mice (p < 0.05-0.01). Conclusion Polygalasaponin F appears to be able to augment protection against IAV infection in mice via attenuation of pulmonary inflammatory responses. Its effect on IAV-induced pulmonary inflammation was associated with suppression of Raf/MEK/ERK and NF-κB expressions.

The recent emergence of the novel coronavirus (SARS-CoV-2) has resulted in a devastating pandemic with global concern. However, to date, there are no regimens to prevent and treat SARS-CoV-2 virus. There is an urgent need to identify novel leads with anti-viral properties that impede viral pathogenesis in the host system. Esculentoside A (EsA), a saponin isolated from the root of Phytolacca esculenta , is known to exhibit diverse pharmacological properties, especially anti-inflammatory activity. To our knowledge, SARS-CoV-2 uses angiotensin converting enzyme 2 (ACE2) to enter host cells. This is mediated through the proteins of SARS-CoV-2, especially the spike glycoprotein receptor binding domain. Thus, our primary goal is to prevent virus replication and binding to the host, which allows us to explore the efficiency of EsA on key surface drug target proteins using the computational biology paradigm approach. Here, the anti-coronavirus activity of EsA in vitro and its potential mode of inhibitory action on the S-protein of SARS-CoV-2 were investigated. We found that EsA inhibited the HCoV-OC43 coronavirus during the attachment and penetration stage. Molecular docking results showed that EsA had a strong binding affinity with the spike glycoprotein from SARS-CoV-2. The results of the molecular dynamics simulation revealed that EsA had higher stable binding with the spike protein. These results demonstrated that Esculentoside A can act as a spike protein blocker to inhibit SARS-CoV-2. Considering the poor bioavailability and low toxicity of EsA, it is suitable as novel lead for the inhibitor against binding interactions of SARS-CoV-2 of S-protein and ACE2.

Influenza is an acute viral respiratory disease that can also cause gastroenteritis-like symptoms, such as abdominal pain, nausea, vomiting, and diarrhea. Immune dysfunction of adipose tissue is involved in the occurrence and prognosis of influenza viral pneumonia. In this study, we analyzed intestinal and adipose immune responses in mice infected with influenza virus and found that the impairment of intestinal and adipose immunity to influenza virus infection could be reversed by treatment with puerarin, a medicinal compound isolated from Pueraria lobata (called "gegen" in Chinese). We found that the lungs, small intestines (duodenum, ileum, jejunum) and large intestines (colon and rectum) of infected mice showed obvious inflammatory lesions, with significantly increased levels of virus, inflammatory cytokines (interleukin [IL]-6, IL-17, and tumor necrosis factor-α), Toll-like receptors 3, 4, and 9, and integrin αvβ3 and α4, and a decreased level of secreted IgA compared to the normal control group (NC) (P < 0.05-0.001). Influenza virus infected mesenteric lymph nodes and adipose tissue, and adipokines (leptin, visfatin, "chemerin", and adiponectin) of lung and mesenteric adipose tissue were dysregulated. Puerarin treatment reversed the impairment of the intestinal and adipose immune responses in mice infected with influenza virus. Our findings suggest that influenza virus can infect adipose tissue and lead to intestinal adipose immune dysfunction in normal-weight mice and that the impairment of the intestinal and adipose immune response to influenza virus infection can be reversed by puerarin treatment.