Abstract
Ethnopharmacological relevance
The flowers of Hylocereus undatus (Haw.) Britton & Rose (HUF), commonly known as "Jianhua" or "Bawanghua", represent a well-known medicinal-edible plant in South China. In folk practice, HUF is traditionally applied to ameliorate respiratory disorders, including cough, sore throat and other influenza-like symptoms. Cumulative pharmacological evidence has demonstrated that HUF extracts possess anti-inflammatory and immunomodulatory activities. Nevertheless, its protective effects against influenza infection remain largely unclarified, with the underlying molecular mechanisms yet to be elucidated.Aim of the study
This study sought to explore the prophylactic effects of HUF aqueous extract against influenza infection in mice, and to probe into its possible molecular mechanisms.Materials and methods
The chemical constituents of HUF aqueous extract were characterized using UPLC-MS. HUF were intragastrically administered to mice prior to viral challenge to evaluate its prophylactic effects. Clinical symptom scores were recorded by daily observation, and lung pathological alterations were assessed via hematoxylin-eosin (H&E) staining. Pulmonary viral load was quantified by plaque forming assay, and inflammatory cytokine mRNA levels were determined using RT-qPCR. To uncover the underlying mechanism, comparative transcriptomic profiling was conducted on mouse lung tissues. Key molecules within the TLR4/MyD88/NF-κB signaling pathway were further validated via Western blot and RT-qPCR. In addition, a specific TLR4 inhibitor (TAK-242) was applied to confirm the regulatory role of TLR4. Finally, the potential of HUF combined with oseltamivir was evaluated.Results
UPLC-MS analysis demonstrated that the HUF aqueous extract contained flavonoid glycosides, organic acids, nucleosides, and coumarin derivatives. In the H1N1-infected murine model, oral HUF treatment conferred dose-dependent protective outcomes. Compared with the untreated model group, high-dose HUF intervention effectively decreased morbidity severity of infected mice by approximately 50% and significantly alleviated influenza-induced body weight loss, while markedly ameliorating inflammatory pulmonary histopathological lesions. Further detection verified that HUF treatment suppressed viral proliferation and pulmonary inflammation, with pulmonary viral loads reduced by 24.0%-56.0% from low to high dosage, accompanied by a gradual, dose-related downregulation of viral NP protein expression and pro-inflammatory TNF-α and IL-6 mRNA levels. Mechanistically, HUF restrained the excessive phosphorylation and activation of the TLR4/MyD88/NF-κB inflammatory cascade in virus-infected lung tissues. Pharmacological blockade of TLR4 with the specific inhibitor TAK-242 failed to augment HUF's prophylactic effects, indicating that TLR4 participates in HUF-mediated protection against influenza infection. Furthermore, combined treatment with HUF and oseltamivir produced better outcomes than oseltamivir monotherapy, as evidenced by reduced pulmonary viral loads and alleviated pulmonary inflammation.Conclusion
This study provides the first in vivo evidence for the prophylactic effects of HUF against influenza A virus infection. Its protective action may be linked to modulation of the TLR4/MyD88/NF-κB signaling axis. Collectively, our work elucidates the host-targeted antiviral properties of HUF, affording experimental support for its development as a novel adjunct for influenza intervention.