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1.
Mol Med ; 28(1): 57, 2022 05 16.
Article in English | MEDLINE | ID: covidwho-1846786

ABSTRACT

BACKGROUND: Severe COVID-19 is characterized by pro-inflammatory cytokine release syndrome (cytokine storm) which causes high morbidity and mortality. Recent observational and clinical studies suggest famotidine, a histamine 2 receptor (H2R) antagonist widely used to treat gastroesophageal reflux disease, attenuates the clinical course of COVID-19. Because evidence is lacking for a direct antiviral activity of famotidine, a proposed mechanism of action is blocking the effects of histamine released by mast cells. Here we hypothesized that famotidine activates the inflammatory reflex, a brain-integrated vagus nerve mechanism which inhibits inflammation via alpha 7 nicotinic acetylcholine receptor (α7nAChR) signal transduction, to prevent cytokine storm. METHODS: The potential anti-inflammatory effects of famotidine and other H2R antagonists were assessed in mice exposed to lipopolysaccharide (LPS)-induced cytokine storm. As the inflammatory reflex is integrated and can be stimulated in the brain, and H2R antagonists penetrate the blood brain barrier poorly, famotidine was administered by intracerebroventricular (ICV) or intraperitoneal (IP) routes. RESULTS: Famotidine administered IP significantly reduced serum and splenic LPS-stimulated tumor necrosis factor (TNF) and IL-6 concentrations, significantly improving survival. The effects of ICV famotidine were significantly more potent as compared to the peripheral route. Mice lacking mast cells by genetic deletion also responded to famotidine, indicating the anti-inflammatory effects are not mast cell-dependent. Either bilateral sub-diaphragmatic vagotomy or genetic knock-out of α7nAChR abolished the anti-inflammatory effects of famotidine, indicating the inflammatory reflex as famotidine's mechanism of action. While the structurally similar H2R antagonist tiotidine displayed equivalent anti-inflammatory activity, the H2R antagonists cimetidine or ranitidine were ineffective even at very high dosages. CONCLUSIONS: These observations reveal a previously unidentified vagus nerve-dependent anti-inflammatory effect of famotidine in the setting of cytokine storm which is not replicated by high dosages of other H2R antagonists in clinical use. Because famotidine is more potent when administered intrathecally, these findings are also consistent with a primarily central nervous system mechanism of action.


Subject(s)
COVID-19 , Famotidine , Animals , Anti-Inflammatory Agents , Cytokine Release Syndrome , Famotidine/pharmacology , Histamine , Histamine H2 Antagonists , Lipopolysaccharides , Mice , Reflex , Vagus Nerve , alpha7 Nicotinic Acetylcholine Receptor
2.
Mol Cell Biochem ; 477(3): 711-726, 2022 Mar.
Article in English | MEDLINE | ID: covidwho-1616202

ABSTRACT

The novel coronavirus pandemic has emerged as one of the significant medical-health challenges of the current century. The World Health Organization has named this new virus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Since the first detection of SARS-CoV-2 in November 2019 in Wuhan, China, physicians, researchers, and others have made it their top priority to find drugs and cures that can effectively treat patients and reduce mortality rates. The symptoms of Coronavirus Disease 2019 (COVID-19) include fever, dry cough, body aches, and anosmia. Various therapeutic compounds have been investigated and applied to mitigate the symptoms in COVID-19 patients and cure the disease. Degenerative virus analyses of the infection incidence and COVID-19 have demonstrated that SARS-CoV-2 penetrates the pulmonary alveoli's endothelial cells through Angiotensin-Converting Enzyme 2 (ACE2) receptors on the membrane, stimulates various signaling pathways and causes excessive secretion of cytokines. The continuous triggering of the innate and acquired immune system, as well as the overproduction of pro-inflammatory factors, cause a severe condition in the COVID-19 patients, which is called "cytokine storm". It can lead to acute respiratory distress syndrome (ARDS) in critical patients. Severe and critical COVID-19 cases demand oxygen therapy and mechanical ventilator support. Various drugs, including immunomodulatory and immunosuppressive agents (e.g., monoclonal antibodies (mAbs) and interleukin antagonists) have been utilized in clinical trials. However, the studies and clinical trials have documented diverging findings, which seem to be due to the differences in these drugs' possible mechanisms of action. These drugs' mechanism of action generally includes suppressing or modulating the immune system, preventing the development of cytokine storm via various signaling pathways, and enhancing the blood vessels' diameter in the lungs. In this review article, multiple medications from different drug families are discussed, and their possible mechanisms of action are also described.


Subject(s)
Antiviral Agents/immunology , COVID-19/drug therapy , Immunomodulating Agents/pharmacology , Antibodies, Monoclonal, Humanized/immunology , Antibodies, Monoclonal, Humanized/pharmacology , Antiviral Agents/pharmacology , Azetidines/immunology , Azetidines/pharmacology , COVID-19/etiology , Dexamethasone/immunology , Dexamethasone/pharmacology , Famotidine/immunology , Famotidine/pharmacology , Humans , Hydroxymethylglutaryl-CoA Reductase Inhibitors/immunology , Hydroxymethylglutaryl-CoA Reductase Inhibitors/pharmacology , Infliximab/immunology , Infliximab/pharmacology , Interleukin 1 Receptor Antagonist Protein/immunology , Interleukin 1 Receptor Antagonist Protein/pharmacology , Melatonin/immunology , Melatonin/pharmacology , Purines/immunology , Purines/pharmacology , Pyrazoles/immunology , Pyrazoles/pharmacology , Sulfonamides/immunology , Sulfonamides/pharmacology
4.
J Biol Chem ; 297(2): 100925, 2021 08.
Article in English | MEDLINE | ID: covidwho-1336599

ABSTRACT

Apart from prevention using vaccinations, the management options for COVID-19 remain limited. In retrospective cohort studies, use of famotidine, a specific oral H2 receptor antagonist (antihistamine), has been associated with reduced risk of intubation and death in patients hospitalized with COVID-19. In a case series, nonhospitalized patients with COVID-19 experienced rapid symptom resolution after taking famotidine, but the molecular basis of these observations remains elusive. Here we show using biochemical, cellular, and functional assays that famotidine has no effect on viral replication or viral protease activity. However, famotidine can affect histamine-induced signaling processes in infected Caco2 cells. Specifically, famotidine treatment inhibits histamine-induced expression of Toll-like receptor 3 (TLR3) in SARS-CoV-2 infected cells and can reduce TLR3-dependent signaling processes that culminate in activation of IRF3 and the NF-κB pathway, subsequently controlling antiviral and inflammatory responses. SARS-CoV-2-infected cells treated with famotidine demonstrate reduced expression levels of the inflammatory mediators CCL-2 and IL6, drivers of the cytokine release syndrome that precipitates poor outcome for patients with COVID-19. Given that pharmacokinetic studies indicate that famotidine can reach concentrations in blood that suffice to antagonize histamine H2 receptors expressed in mast cells, neutrophils, and eosinophils, these observations explain how famotidine may contribute to the reduced histamine-induced inflammation and cytokine release, thereby improving the outcome for patients with COVID-19.


Subject(s)
Famotidine/pharmacology , Histamine Antagonists/pharmacology , SARS-CoV-2/drug effects , Toll-Like Receptor 3/metabolism , A549 Cells , Binding Sites , Caco-2 Cells , Chemokine CCL2/metabolism , Coronavirus 3C Proteases/metabolism , HeLa Cells , Humans , Interferon Regulatory Factor-3/metabolism , Interleukin-6/metabolism , Molecular Docking Simulation , NF-kappa B/metabolism , Protein Binding , SARS-CoV-2/physiology , Signal Transduction , Toll-Like Receptor 3/chemistry , Virus Replication
5.
Drug Res (Stuttg) ; 71(6): 295-301, 2021 Jul.
Article in English | MEDLINE | ID: covidwho-1146573

ABSTRACT

BACKGROUND: COVID-19 caused by SARS-CoV-2 was declared as a global pandemic by the WHO. Famotidine is a histamine-2 (H2) receptor antagonist which blocks the H2 receptors in the parietal cells, decreasing gastric acid secretion. Our review aims to study all the available scientific evidence on famotidine research outcomes systematically to introspect its clinical efficacy and probable mechanisms and clinical efficacy against SARS-CoV-2. METHODOLOGY: An electronic search of PubMed, Scopus and Google Scholar was performed using MeSH terms "SARS CoV-2" OR "COVID-19" AND"FAMOTIDINE". Relevant informationwas extracted from studies reporting the efficacy of famotidine in COVID-19. RESULTS: We found a total of 32 studies, out of which only 14 were relevant and were included in our review.Molecular computational studies showed that famotidine selectively acts on viral replication proteases papain-like protease (PLpro) and 3-chymotrypsin-like protease (3CLpro). Additionally, it acts via inverse-agonism on the H2 receptors present in neutrophils and eosinophils which leads to inhibition of cytokine release. Clinical study findings have pointed toward significant improvements in COVID-19 patient-reported symptoms in non-hospitalized patients and reduction in intubation or death in critically ill patients associated with the usage of famotidine. However,in one of the studies,famotidine has failed to show any significant benefit in reducing mortality due to COVID-19. CONCLUSION: Famotidine has the potential to answer the ongoing global challenge owing to its selective action on viral replication. Additionally, clinical findings in COVID-19 patients support its efficacy to reduce clinical symptoms of COVID-19.We suggest that further optimally powered randomized clinical trials should be carried out to come up with definitive conclusions.


Subject(s)
COVID-19/drug therapy , Drug Repositioning , Famotidine/therapeutic use , Histamine H2 Antagonists/therapeutic use , COVID-19/immunology , COVID-19/mortality , COVID-19/virology , Cytokines/metabolism , Drug Evaluation, Preclinical , Famotidine/pharmacology , Histamine H2 Antagonists/pharmacology , Humans , Molecular Docking Simulation , Observational Studies as Topic , Pandemics/prevention & control , Patient Reported Outcome Measures , Randomized Controlled Trials as Topic , Receptors, Histamine H2/metabolism , SARS-CoV-2/drug effects , SARS-CoV-2/immunology , Signal Transduction/drug effects , Signal Transduction/immunology , Treatment Outcome , Virus Replication/drug effects
6.
Sci Rep ; 11(1): 5433, 2021 03 08.
Article in English | MEDLINE | ID: covidwho-1123148

ABSTRACT

The lack of coronavirus-specific antiviral drugs has instigated multiple drug repurposing studies to redirect previously approved medicines for the treatment of SARS-CoV-2, the coronavirus behind the ongoing COVID-19 pandemic. A recent, large-scale, retrospective clinical study showed that famotidine, when administered at a high dose to hospitalized COVID-19 patients, reduced the rates of intubation and mortality. A separate, patient-reported study associated famotidine use with improvements in mild to moderate symptoms such as cough and shortness of breath. While a prospective, multi-center clinical study is ongoing, two parallel in silico studies have proposed one of the two SARS-CoV-2 proteases, 3CLpro or PLpro, as potential molecular targets of famotidine activity; however, this remains to be experimentally validated. In this report, we systematically analyzed the effect of famotidine on viral proteases and virus replication. Leveraging a series of biophysical and enzymatic assays, we show that famotidine neither binds with nor inhibits the functions of 3CLpro and PLpro. Similarly, no direct antiviral activity of famotidine was observed at concentrations of up to 200 µM, when tested against SARS-CoV-2 in two different cell lines, including a human cell line originating from lungs, a primary target of COVID-19. These results rule out famotidine as a direct-acting inhibitor of SARS-CoV-2 replication and warrant further investigation of its molecular mechanism of action in the context of COVID-19.


Subject(s)
Famotidine/pharmacology , Peptide Hydrolases/metabolism , SARS-CoV-2/enzymology , Virus Replication/drug effects , A549 Cells , Animals , COVID-19/virology , Chlorocebus aethiops , Humans , SARS-CoV-2/drug effects , Vero Cells
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