The mechanisms of action of ivermectin against SARS-CoV-2-an extensive review

Considering the urgency of the ongoing COVID-19 pandemic, detection of new mutant strains and potential re-emergence of novel coronaviruses, repurposing of drugs such as ivermectin could be worthy of attention. This review article aims to discuss the probable mechanisms of action of ivermectin against SARS-CoV-2 by summarizing the available literature over the years. A schematic of the key cellular and biomolecular interactions between ivermectin, host cell, and SARS-CoV-2 in COVID-19 pathogenesis and prevention of complications has been proposed.Copyright © 2022 Japan Antibiotics Research Association. All rights reserved.

The antimicrobial and immunomodulatory effects of Ionophores for the treatment of human infection.

Ionophores are a diverse class of synthetic and naturally occurring ion transporter compounds which demonstrate both direct and in-direct antimicrobial properties against a broad panel of bacterial, fungal, viral and parasitic pathogens. In addition, ionophores can regulate the host-immune response during communicable and non-communicable disease states. Although the clinical use of ionophores such as Amphotericin B, Bedaquiline and Ivermectin highlight the utility of ionophores in modern medicine, for many other ionophore compounds issues surrounding toxicity, bioavailability or lack of in vivo efficacy studies have hindered clinical development. The antimicrobial and immunomodulating properties of a range of compounds with characteristics of ionophores remain largely unexplored. As such, ionophores remain a latent therapeutic avenue to address both the global burden of antimicrobial resistance, and the unmet clinical need for new antimicrobial therapies. This review will provide an overview of the broad-spectrum antimicrobial and immunomodulatory properties of ionophores, and their potential uses in clinical medicine for combatting infection.

Ionophore Antibiotics Inhibit Type II Feline Coronavirus Proliferation In Vitro.

Feline coronaviruses (FCoVs) infect cats worldwide and cause severe systemic diseases, such as feline infectious peritonitis (FIP). FIP has a high mortality rate, and drugs approved by the Food and Drug Administration have been ineffective for the treatment of FIP. Investigating host factors and the functions required for FCoV replication is necessary to develop effective drugs for the treatment of FIP. FCoV utilizes an endosomal trafficking system for cellular entry after binding between the viral spike (S) protein and its receptor. The cellular enzymes that cleave the S protein of FCoV to release the viral genome into the cytosol require an acidic pH optimized in the endosomes by regulating cellular ion concentrations. Ionophore antibiotics are compounds that form complexes with alkali ions to alter the endosomal pH conditions. This study shows that ionophore antibiotics, including valinomycin, salinomycin, and nigericin, inhibit FCoV proliferation in vitro in a dose-dependent manner. These results suggest that ionophore antibiotics should be investigated further as potential broad-spectrum anti-FCoV agents.

Inhibition of SARS-CoV-2 replication by zinc gluconate in combination with hinokitiol.

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic is currently the major challenge to global public health. Two proteases, papain-like protease (PLpro) and the 3-chymotrypsin-like protease (3CLpro or Mpro), are indispensable for SARS-CoV-2 replication, making them attractive targets for antiviral therapy development. Here we screened a panel of essential metal ions using a proteolytic assay and identified that zinc gluconate, a widely-used zinc supplement, strongly inhibited the proteolytic activities of the two proteases in vitro. Biochemical and crystallographic data reveal that zinc gluconate exhibited the inhibitory function via binding to the protease catalytic site residues. We further show that treatment of zinc gluconate in combination with a small molecule ionophore hinokitiol, could lead to elevated intracellular Zn2+ level and thereby significantly impaired the two protease activities in cellulo. Particularly, this approach could also be applied to rescue SARS-CoV-2 infected mammalian cells, indicative of potential application to combat coronavirus infections. Our studies provide the direct experimental evidence that elevated intracellular zinc concentration directly inhibits SARS-CoV-2 replication and suggest the potential benefits to use the zinc supplements for coronavirus disease 2019 (COVID-19) treatment.

Hydroxychloroquine Does Not Function as a Direct Zinc Ionophore.

Drug-mediated correction of abnormal biological zinc homeostasis could provide new routes to treating neurodegeneration, cancer, and viral infections. Designing therapeutics to facilitate zinc transport intracellularly is hampered by inadequate concentrations of endogenous zinc, which is often protein-bound in vivo. We found strong evidence that hydroxychloroquine, a drug used to treat malaria and employed as a potential treatment for COVID-19, does not bind and transport zinc across biological membranes through ionophoric mechanisms, contrary to recent claims. In vitro complexation studies and liposomal transport assays are correlated with cellular zinc assays in A549 lung epithelial cells to confirm the indirect mechanism of hydroxychloroquine-mediated elevation in intracellular zinc without ionophorism. Molecular simulations show hydroxychloroquine-triggered helix perturbation in zinc-finger protein without zinc chelation, a potential alternative non-ionophoric mechanism.

Eicosapentaenoic acid increases endothelial function and Heme oxygenase-1 in pulmonary inflammation

INTRODUCTION: Endothelial cell (EC) dysfunction results in reduced nitric oxide (NO) bioavailability leading to inflammation and increased susceptibility to infectious agents. Heme oxygenase-1 (HO-1) produces potent antioxidant and anti-inflammatory products including carbon monoxide. SARS-CoV-2 and influenza affect ECs in multiple vascular beds, including pulmonary tissue. The omega-3 fatty acid eicosapentaenoic acid (EPA) and its metabolites preserve EC function in a manner that may contribute to reduced incident cardiovascular events (REDUCE-IT). Currently, EPA is being tested in patients with or at risk for COVID-19. This study tested the effects of EPA on NO and peroxynitrite (ONOO-) release under conditions of inflammation using lipopolysaccharide (LPS) and the cytokine IL-6. We also measured expression of HO-1 after cell challenge with IL-6. METHODS: Human lung microvascular endothelial cells (HMVEC-L) were pretreated with vehicle or EPA (40 μM) in 2% FBS for 2 h, then challenged with either IL-6 (12 ng/ml) or LPS (200 ng/ml) for 24 h. Cells (including untreated controls) were stimulated with calcium ionophore to measure maximum production of NO and peroxynitrite (ONOO-) using tandem porphyrinic nanosensors. Proteomic analysis was performed using LC/MS to assess relative expression levels. Only significant (p< 0.05) changes in protein expression between treatment groups >1-fold were analyzed. RESULTS: HMVEC-L challenged with LPS and IL-6 showed a pronounced loss of NO release by 22% (p< 0.01) and 18% (p< 0.01), respectively, concomitant with an increase in ONOO- by 28% (p< 0.01) and 26% (p< 0.01), respectively. As a result, the [NO]/[ONOO-] ratio, a marker of eNOS coupling efficiency, decreased by 39% (p< 0.001) and 35% (p< 0.001) with LPS and IL-6, respectively. However, EPA increased this ratio by 39% (p< 0.01) in both LPS and IL-6 treated cells. EPA also caused a 5.7-fold (p = 4.4 × 10-38) increase in expression of HO-1 with IL-6. CONCLUSIONS: These findings indicate that EPA improves NO bioavailability and reduces nitroxidative stress in pulmonary ECs during inflammation with LPS or IL-6. These studies indicate a protective effect of EPA on pulmonary ECs that may reduce inflammatory activation during sepsis, influenza, or advanced COVID-19 that may mediate many aspects of multiorgan system failure.

Salicylanilides Reduce SARS-CoV-2 Replication and Suppress Induction of Inflammatory Cytokines in a Rodent Model.

SARS-CoV-2 virus has recently given rise to the current COVID-19 pandemic where infected individuals can range from being asymptomatic, yet highly contagious, to dying from acute respiratory distress syndrome. Although the world has mobilized to create antiviral vaccines and therapeutics to combat the scourge, their long-term efficacy remains in question especially with the emergence of new variants. In this work, we exploit a class of compounds that has previously shown success against various viruses. A salicylanilide library was first screened in a SARS-CoV-2 activity assay in Vero cells. The most efficacious derivative was further evaluated in a prophylactic mouse model of SARS-CoV-2 infection unveiling a salicylanilide that can reduce viral loads, modulate key cytokines, and mitigate severe weight loss involved in COVID-19 infections. The combination of anti-SARS-CoV-2 activity, cytokine inhibitory activity, and a previously established favorable pharmacokinetic profile for the lead salicylanilide renders salicylanilides in general as promising therapeutics for COVID-19.

Direct Potentiometric Study of Cationic and Nonionic Surfactants in Disinfectants and Personal Care Products by New Surfactant Sensor Based on 1,3-Dihexadecyl-1H-benzo[d]imidazol-3-ium.

A novel, simple, low-cost, and user-friendly potentiometric surfactant sensor based on the new 1,3-dihexadecyl-1H-benzo[d]imidazol-3-ium-tetraphenylborate (DHBI-TPB) ion-pair for the detection of cationic surfactants in personal care products and disinfectants is presented here. The new cationic surfactant DHBI-Br was successfully synthesized and characterized by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectrometry, liquid chromatography-mass spectrometry (LC-MS) and elemental analysis and was further employed for DHBI-TPB ion-pair preparation. The sensor gave excellent response characteristics for CTAB, CPC and Hyamine with a Nernstian slope (57.1 to 59.1 mV/decade) whereas the lowest limit of detection (LOD) value was measured for CTAB (0.3 × 10-6 M). The sensor exhibited a fast dynamic response to dodecyl sulfate (DDS) and TPB. High sensor performances stayed intact regardless of the employment of inorganic and organic cations and in a broad pH range (2-11). Titration of cationic and etoxylated (EO)-nonionic surfactant (NSs) (in Ba2+) mixtures with TPB revealed the first inflexion point for a cationic surfactant and the second for an EO-nonionic surfactant. The increased concentration of EO-nonionic surfactants and the number of EO groups had a negative influence on titration curves and signal change. The sensor was successfully applied for the quantification of technical-grade cationic surfactants and in 12 personal care products and disinfectants. The results showed good agreement with the measurements obtained by a commercial surfactant sensor and by a two-phase titration. A good recovery for the standard addition method (98-102%) was observed.

Ionophore antibiotic X-206 is a potent inhibitor of SARS-CoV-2 infection in vitro.

Pandemic spread of emerging human pathogenic viruses, such as the current SARS-CoV-2, poses both an immediate and future challenge to human health and society. Currently, effective treatment of infection with SARS-CoV-2 is limited and broad spectrum antiviral therapies to meet other emerging pandemics are absent leaving the World population largely unprotected. Here, we have identified distinct members of the family of polyether ionophore antibiotics with potent ability to inhibit SARS-CoV-2 replication and cytopathogenicity in cells. Several compounds from this class displayed more than 100-fold selectivity between viral-induced cytopathogenicity and inhibition of cell viability, however the compound X-206 displayed >500-fold selectivity and was furthermore able to inhibit viral replication even at sub-nM levels. The antiviral mechanism of the polyether ionophores is currently not understood in detail. We demonstrate, e.g. through unbiased bioactivity profiling, that their effects on the host cells differ from those of cationic amphiphiles such as hydroxychloroquine. Collectively, our data suggest that polyether ionophore antibiotics should be subject to further investigations as potential broad-spectrum antiviral agents.

A possible application of hinokitiol as a natural zinc ionophore and anti-infective agent for the prevention and treatment of COVID-19 and viral infections.

Zinc and the combination with zinc ionophore have been reported in basic research and several clinical investigations as a potentially viable and economical preventive and therapeutic options for COVID-19 treatment. Zinc is a vital microelement that actively supports respiratory epithelium barrier integrity, innate and adaptive immune functions, and inflammatory regulations. Moreover, zinc may also prevent viral entry, suppress viral replication, and mitigate the damages due to oxidative stress and hyperinflammatory reaction in patients with respiratory infections. Hinokitiol (ß-thujaplicin) is a natural monoterpenoid and is considered as a safe zinc ionophore to help zinc transport into cells. It has been widely used in skin and oral care, and therapeutic products for its potent antiviral, antimicrobial, antifungal, anti-inflammatory, and anticancer applications. The ongoing COVID-19 pandemic and the significant morbidity and mortality exist in the high-risk group of patients associated with other respiratory infections such as influenza, respiratory syncytial virus, and dengue fever. There is an urgent need for the development of inexpensive, safe, and effective therapeutics to prevent and treat these viral infections. Considering that hydroxychloroquine (HCQ), the most studied zinc ionophore drug for COVID-19, is linked to potentially serious side effects, we propose the implementation of hinokitiol as a zinc ionophore and anti-infective agent for the prevention and treatment of COVID-19 and other viral infections.

Zinc sulfate in combination with a zinc ionophore may improve outcomes in hospitalized COVID-19 patients.

Introduction. COVID-19 has rapidly emerged as a pandemic infection that has caused significant mortality and economic losses. Potential therapies and prophylaxis against COVID-19 are urgently needed to combat this novel infection. As a result of in vitro evidence suggesting zinc sulphate may be efficacious against COVID-19, our hospitals began using zinc sulphate as add-on therapy to hydroxychloroquine and azithromycin.Aim. To compare outcomes among hospitalized COVID-19 patients ordered to receive hydroxychloroquine and azithromycin plus zinc sulphate versus hydroxychloroquine and azithromycin alone.Methodology. This was a retrospective observational study. Data was collected from medical records for all patients with admission dates ranging from 2 March 2020 through to 11 April 2020. Initial clinical characteristics on presentation, medications given during the hospitalization, and hospital outcomes were recorded. The study included patients admitted to any of four acute care NYU Langone Health Hospitals in New York City. Patients included were admitted to the hospital with at least one positive COVID-19 test and had completed their hospitalization. Patients were excluded from the study if they were never admitted to the hospital or if there was an order for other investigational therapies for COVID-19.Results. Patients taking zinc sulphate in addition to hydroxychloroquine and azithromycin (n=411) and patients taking hydroxychloroquine and azithromycin alone (n=521) did not differ in age, race, sex, tobacco use or relevant comorbidities. The addition of zinc sulphate did not impact the length of hospitalization, duration of ventilation or intensive care unit (ICU) duration. In univariate analyses, zinc sulphate increased the frequency of patients being discharged home, and decreased the need for ventilation, admission to the ICU and mortality or transfer to hospice for patients who were never admitted to the ICU. After adjusting for the time at which zinc sulphate was added to our protocol, an increased frequency of being discharged home (OR 1.53, 95 % CI 1.12-2.09) and reduction in mortality or transfer to hospice among patients who did not require ICU level of care remained significant (OR 0.449, 95 % CI 0.271-0.744).Conclusion. This study provides the first in vivo evidence that zinc sulphate may play a role in therapeutic management for COVID-19.

Ivermectin, antiviral properties and COVID-19: a possible new mechanism of action.

Ivermectin is an antiparasitic drug that has shown also an effective pharmacological activity towards various infective agents, including viruses. This paper proposes an alternative mechanism of action for this drug that makes it capable of having an antiviral action, also against the novel coronavirus, in addition to the processes already reported in literature.