Intranasal co-administration of 1,8-cineole with influenza vaccine provide cross-protection against influenza virus infection

1,8-cineole (eucalyptol): A versatile phytochemical with therapeutic applications across multiple diseases

1,8-cineole (Eucalyptol), a naturally occurring compound derived from botanical sources such as eucalyptus, rosemary, and camphor laurel, has a long history of use in traditional medicine and exhibits an array of biological properties, including anti-inflammatory, antioxidant, antimicrobial, bronchodilatory, analgesic, and pro-apoptotic effects. Recent evidence has also indicated its potential role in managing conditions such as Alzheimer's disease, neuropathic pain, and cancer. This review spotlights the health advantages of 1,8-cineole, as demonstrated in clinical trials involving patients with respiratory disorders, including chronic obstructive pulmonary disease, asthma, bronchitis, and rhinosinusitis. In addition, we shed light on potential therapeutic applications of 1,8-cineole in various conditions, such as depression, epilepsy, peptic ulcer disease, diarrhea, cardiac-related heart diseases, and diabetes mellitus. A comprehensive understanding of 1,8-cineole's pharmacodynamics and safety aspects as well as developing effective formulations, might help to leverage its therapeutic value. This thorough review sets the stage for future research on diverse health benefits and potential uses of 1,8-cineole in tackling complex medical conditions.

Modes of Action of 1,8-Cineol in Infections and Inflammation

The monoterpene 1,8-Cineol is a natural plant-based therapeutic agent that is commonly applied to treat different inflammatory diseases due to its mucolytic, anti-microbial and anti-inflammatory properties. It has become increasingly clear in the recent years that 1,8-Cineol spreads almost everywhere in the human body after its oral administration, from the gut to the blood to the brain. Its anti-microbial potential and even its anti-viral effects have been observed to include numerous bacteria and fungi species. Many recent studies help to better understand the cellular and molecular immunological consequences of 1,8-Cineol treatment in inflammatory diseases and further provide information concerning the mechanistic modes of action in the regulation of distinct inflammatory biosynthetic pathways. This review aims to present a holistic and understandable overview of the different aspects of 1,8-Cineol in infections and inflammation.

Essential Oils and Their Compounds as Potential Anti-Influenza Agents

Essential oils (EOs) are chemical substances, mostly produced by aromatic plants in response to stress, that have a history of medicinal use for many diseases. In the last few decades, EOs have continued to gain more attention because of their proven therapeutic applications against the flu and other infectious diseases. Influenza (flu) is an infectious zoonotic disease that affects the lungs and their associated organs. It is a public health problem with a huge health burden, causing a seasonal outbreak every year. Occasionally, it comes as a disease pandemic with unprecedentedly high hospitalization and mortality. Currently, influenza is managed by vaccination and antiviral drugs such as Amantadine, Rimantadine, Oseltamivir, Peramivir, Zanamivir, and Baloxavir. However, the adverse side effects of these drugs, the rapid and unlimited variabilities of influenza viruses, and the emerging resistance of new virus strains to the currently used vaccines and drugs have necessitated the need to obtain more effective anti-influenza agents. In this review, essential oils are discussed in terms of their chemistry, ethnomedicinal values against flu-related illnesses, biological potential as anti-influenza agents, and mechanisms of action. In addition, the structure-activity relationships of lead anti-influenza EO compounds are also examined. This is all to identify leading agents that can be optimized as drug candidates for the management of influenza. Eucalyptol, germacrone, caryophyllene derivatives, eugenol, terpin-4-ol, bisabolene derivatives, and camphecene are among the promising EO compounds identified, based on their reported anti-influenza activities and plausible molecular actions, while nanotechnology may be a new strategy to achieve the efficient delivery of these therapeutically active EOs to the active virus site.

Antiviral Activities of Eucalyptus Essential Oils: Their Effectiveness as Therapeutic Targets against Human Viruses

Given the limited therapeutic management of infectious diseases caused by viruses, such as influenza and SARS-CoV-2, the medicinal use of essential oils obtained from Eucalyptus trees has emerged as an antiviral alternative, either as a complement to the treatment of symptoms caused by infection or to exert effects on possible pharmacological targets of viruses. This review gathers and discusses the main findings on the emerging role and effectiveness of Eucalyptus essential oil as an antiviral agent. Studies have shown that Eucalyptus essential oil and its major monoterpenes have enormous potential for preventing and treating infectious diseases caused by viruses. The main molecular mechanisms involved in the antiviral activity are direct inactivation, that is, by the direct binding of monoterpenes with free viruses, particularly with viral proteins involved in the entry and penetration of the host cell, thus avoiding viral infection. Furthermore, this review addresses the coadministration of essential oil and available vaccines to increase protection against different viruses, in addition to the use of essential oil as a complementary treatment of symptoms caused by viruses, where Eucalyptus essential oil exerts anti-inflammatory, mucolytic, and spasmolytic effects in the attenuation of inflammatory responses caused by viruses, in particular respiratory diseases.

1,8-Cineole: a review of source, biological activities, and application

1,8-Cineole (also known as eucalyptol) is mostly extracted from the essential oils of plants, which showed extensively pharmacological properties including anti-inflammatory and antioxidant mainly via the regulation on NF-κB and Nrf2, and was used for the treatment of respiratory diseases and cardiovascular, etc. Although various administration routes have been used in the application of 1.8-cineole, few formulations have been developed to improve its stability and bioavailability. This review retrospects the researches on the source, biological activities, mechanisms, and application of 1,8-cineole since 2000, which provides a view for the further studies on the application and formulations of 1,8-cineole.

Intranasal vaccine from whole Leishmania donovani antigens provides protection and induces specific immune response against visceral leishmaniasis

Visceral leishmaniasis is a protozoan disease associated with high fatality rate in developing countries. Although the drug pipeline is constantly improving, available treatments are costly and live-threatening side effects are not uncommon. Moreover, an approved vaccine against human leishmaniasis does not exist yet. Using whole antigens from Leishmania donovani promastigotes (LdAg), we investigated the protective potential of a novel adjuvant-free vaccine strategy. Immunization of mice with LdAg via the intradermal or the intranasal route prior to infection decreases the parasitic burden in primary affected internal organs, including the liver, spleen, and bone marrow. Interestingly, the intranasal route is more efficient than the intradermal route, leading to better parasite clearance and remarkable induction of adaptive immune cells, notably the helper and cytotoxic T cells. In vitro restimulation experiments with Leishmania antigens led to significant IFN-γ secretion by splenocytes; therefore, exemplifying specificity of the adaptive immune response. To improve mucosal delivery and the immunogenic aspects of our vaccine strategy, we used polysaccharide-based nanoparticles (NP) that carry the antigens. The NP-LdAg formulation is remarkably taken up by dendritic cells and induces their maturation in vitro, as revealed by the increased expression of CD80, CD86 and MHC II. Intranasal immunization with NP-LdAg does not improve the parasite clearance in our experimental timeline; however, it does increase the percentage of effector and memory T helper cells in the spleen, suggesting a potential induction of long-term memory. Altogether, this study provides a simple and cost-effective vaccine strategy against visceral leishmaniasis based on LdAg administration via the intranasal route, which could be applicable to other parasitic diseases.

Visceral leishmaniasis is a neglected tropical disease caused by specific species of Leishmania parasites that affect internal organs including spleen, liver, and bone marrow. The infective stage called promastigote, is transmitted into the host skin via sandfly bites. Visceral leishmaniasis is usually associated with high mortality rate in poor and developing countries, lacking proper health assistance. Moreover, treatments are expensive while no approved vaccines exist to prevent infection and avoid disease outbreaks. This study suggests an affordable and adjuvant-free vaccine formulation made from the total lysate of promastigotes. Vaccine administration via the intranasal route, ensures a remarkable clearance of Leishmania parasites from the internal organs of infected experimental mice. In particular, intranasal route known to be not invasive, is efficient in inducing adequate immune response against the infective form of the parasite. Further studies are now required to improve this prophylactic vaccine and provide therefore the basis for a promising translational approach.

Screening of the essential oil effects on human H1N1 influenza virus infection: an in vitro study in MDCK cells

Nineteen essential oils (EOs) obtained from different plants have been evaluated for their potential in vitro anti-H1N1 influenza virus efficacy. Both multivariate analyses and bivariate correlation were performed to better understand how the composition influences the activity. The results evidenced that for the laboratory distilled EOs both rosemary hybrids (S. x lavandulaceus and S. x mendizabalii) showed a good antiviral activity with low cytotoxic effect. Concerning the commercial ones: Eucalyptus globulus and Juniperus communis EOs exhibited virtuous effects on influenza virus. These results were confirmed by the multivariate analyses and only eucalyptol showed a positive correlation with cell viability. On the contrary, o-cymene and terpinolene correlated to the inhibitory effect. Rosemary hybrids, E. globulus and J. communis could be considered as promising candidate to develop new alternative anti-H1N1 natural agent.

Appropriate use of essential oils and their components in the management of upper respiratory tract symptoms in patients with COVID-19

Introduction

The involvement of the upper respiratory tract is common in COVID-19, and the majority of patients are treated at home with a mild-to-moderate form of the disease. Many approaches based on essential oils have been proposed for the symptomatic treatment of COVID-19. This work aims to outline the potential and safe evidence-based uses of essential oils and their major components for the clinical management of mild respiratory symptoms caused by uncomplicated coronavirus infections, including SARS-CoV-2. Due to their wide use, a focus on the constituents eucalyptol and menthol has been provided.

Methods

An overview of the scientific literature with a critical discussion of retrieved evidence and clinical recommendations.

Results

In general, eucalyptol and essential oils or blends whose content is rich in it, may be used as an integrative remedy for the symptomatic improvement of patients with mild and uncomplicated infections caused by coronaviruses. Menthol is not recommended in patients with COVID-19, due to a potential reduction of the self-perception of dyspnea, which can lead infected patients to underestimate the actual disease severity and to delay medical attention.

Discussion

Based on available evidence, symptomatic remedies for COVID-19, such as essential oils and their isolated compounds, can be useful, but are not an alternative to standard medical therapy and do not exempt patients from following precautionary measures issued by health authorities. Clinical recommendations on the appropriate use of essential oils for the management of upper airway symptoms of COVID-19 are provided. Further studies on the topic are advised.

Potential anti-influenza effective plants used in Turkish folk medicine: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Due to the outbreaks such as SARS, bird flu and swine flu, which we frequently encounter in our century, we need fast solutions with no side effects today more than ever. Due to having vast ethnomedical experience and the richest flora (34% endemic) of Europe and the Middle East, Turkey has a high potential for research on this topic. Plants that locals have been using for centuries for the prevention and treatment of influenza can offer effective alternatives to combat this problem. In this context, 224 herbal taxa belonging to 45 families were identified among the selected 81 studies conducted in the seven regions of Turkey. However, only 35 (15.6%) of them were found to be subjected to worldwide in vitro and in vivo research conducted on anti-influenza activity. Quercetin and chlorogenic acid, the effectiveness of which has been proven many times in this context, have been recorded as the most common (7.1%) active ingredients among the other 56 active substances identified.

AIM OF THE STUDY

This study has been carried out to reveal the inventory of plant species that have been used in flu treatment for centuries in Turkish folk medicine, which could be used in the treatment of flu or flu-like pandemics, such as COVID 19, that humanity has been suffering with, and also compare them with experimental studies in the literature.

MATERIALS AND METHODS

The investigation was conducted in two stages on the subject above by using electronic databases, such as Web of Science, Scopus, ScienceDirect, ProQuest, Medline, Cochrane Library, EBSCO, HighWire Press, PubMed and Google Scholar. The results of both scans are presented in separate tables, together with their regional comparative analysis.

RESULTS

Data obtained on taxa are presented in a table, including anti-influenza mechanism of actions and the active substances. Rosa canina (58.7%) and Mentha x piperita (22.2%) were identified as the most common plants used in Turkey. Also, Sambucus nigra (11.6%), Olea europaea (9.3%), Eucalyptus spp., Melissa officinalis, and Origanum vulgare (7.0%) emerged as the most investigated taxa.

CONCLUSION

This is the first nationwide ethnomedical screening work conducted on flu treatment with plants in Turkey. Thirty-nine plants have been confirmed in the recent experimental anti-influenza research, which strongly shows that these plants are a rich pharmacological source. Also, with 189 (84.4%) taxa, detections that have not been investigated yet, they are an essential resource for both national and international pharmacological researchers in terms of new natural medicine searches. Considering that the production of antimalarial drugs and their successful use against COVID-19 has begun, this correlation was actually a positive and remarkable piece of data, since there are 15 plants, including Centaurea drabifolia subsp. Phlocosa (an endemic taxon), that were found to be used in the treatment of both flu and malaria.

Antiviral activity of puerarin as potent inhibitor of influenza virus neuraminidase

Puerarin is a major isofiavone compound isolated from the root of Pueraria lobata. It was reported that puerarin had antioxidant, antiinflammatory, antitumor, cholesterol lowering, liver protective, and neuroprotective properties. However, few studies have explored the antiviral effect of puerarin and its target mechanism related to influenza virus. Here, the antiinfluenza activity of puerarin in vitro and in vivo and its mode of action on the potential inhibition of neuraminidase (NA) were investigated. Puerarin displayed an inhibitory effect on A/FM/1/1947(H1N1) (EC₅₀ = 52.06 μM). An indirect immunofluorescence assay indicated that puerarin blocked the nuclear export of viral NP. The inhibition of NA activity confirmed that puerarin can block the release of newly formed virus particles from infected cells. Puerarin (100 and 200 mg/kg/d) exhibited effective antiviral activity in mice, conferring 50% and 70% protection from death against H1N1, reducing virus titers, and effectively alleviating inflammation in the lungs. The molecular docking results showed that puerarin had a strong binding affinity with NA from H1N1. The results of the molecular dynamics simulation revealed that puerarin had higher stable binding at the 150-loop region of the NA protein. These results demonstrated that puerarin acts as a NA blocker to inhibit influenza A virus both in cellular and animal models. Thus, puerarin has potential utility for the treatment of the influenza virus infection.

Eucalyptol alleviates inflammation and pain responses in a mouse model of gout arthritis

BACKGROUND AND PURPOSE

Gout arthritis, which is provoked by monosodium urate (MSU) crystal accumulation in the joint and periarticular tissues, induces severe pain and affects quality of life of the patients. Eucalyptol (1,8-cineol), the principal component in the essential oils of eucalyptus leaves, is known to possess anti-inflammatory and analgesic properties. We aimed to examine the therapeutic effects of eucalyptol on gout arthritis and related mechanisms.

EXPERIMENTAL APPROACH

A mouse model of gout arthritis was established via MSU injection into the ankle joint. Ankle oedema, mechanical allodynia, neutrophil infiltration, oxidative stress, NLRP3 inflammasome, and TRPV1 expression were examined.

KEY RESULTS

Eucalyptol attenuated MSU-induced mechanical allodynia and ankle oedema in dose-dependently, with effectiveness similar to indomethacin. Eucalyptol reduced inflammatory cell infiltrations in ankle tissues. Eucalyptol inhibited NLRP3 inflammasome activation and pro-inflammatory cytokine production induced by MSU in ankle tissues in vivo. Eucalyptol reduced oxidative stress induced by MSU in RAW264.7 cells in vitro as well as in ankle tissues in vivo, indicated by an increase in activities of antioxidant enzymes and reduction of ROS. Eucalyptol attenuated MSU-induced up-regulation of TRPV1 expression in ankle tissues and dorsal root ganglion neurons innervating the ankle. The in vivo effects of eucalyptol on ankle oedema, mechanical allodynia, NLRP3 inflammasome, IL-1β, and TRPV1 expression were mimicked by treating MSU-injected mice with antioxidants.

CONCLUSION AND IMPLICATIONS

Eucalyptol alleviates MSU-induced pain and inflammation via mechanisms possibly involving anti-oxidative effect. Eucalyptol and other antioxidants may represent promising therapeutic options for gout arthritis.

Polygalasaponin F treats mice with pneumonia induced by influenza virus

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, C₅₃H₈₆O₂₃), 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 (MLD₅₀) 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 A₂ (TXA₂), and prostaglandin E₂ (PGE₂) 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 TXA₂ and PGE₂. 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 oseltamivir-treated 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.

Intranasal immunization with Mycobacterium tuberculosis Rv3615c induces sustained adaptive CD4+ T-cell and antibody responses in the respiratory tract

Sustained adaptive immunity to pathogens provides effective protection against infections, and effector cells located at the site of infection ensure rapid response to the challenge. Both are essential for the success of vaccine development. To explore new vaccination approach against Mycobacterium tuberculosis (M.tb) infection, we have shown that Rv3615c, identified as ESX-1 substrate protein C of M.tb but not expressed in BCG, induced a dominant Th1-type response of CD4⁺ T cells from patients with tuberculosis pleurisy, which suggests a potential candidate for vaccine development. But subcutaneous immunization with Rv3615c induced modest T-cell responses systemically, and showed suboptimal protection against virulent M.tb challenge at the site of infection. Here, we use a mouse model to demonstrate that intranasal immunization with Rv3615c induces sustained capability of adaptive CD4⁺ T- and B-cell responses in lung parenchyma and airway. Rv3615c contains a dominant epitope of mouse CD4⁺ T cells, Rv3615c_41-50 , and elicits CD4⁺ T-cell response with an effector-memory phenotype and multi-Th1-type cytokine coexpressions. Since T cells resident at mucosal tissue are potent at control of infection at early stage, our data show that intranasal immunization with Rv3615c promotes a sustained regional immunity to M.tb, and suggests a potency in control of M.tb infection. Our study warranties a further investigation of Rv3615c as a candidate for development of effective vaccination against M.tb infection.