Histamine receptors and COVID-19

Antihistamine and COVID-19 outcomes in outpatients

The World Health Organization declared the coronavirus disease 2019 (COVID-19) pandemic on March 11, 2020. Since then, researchers have been investigating the efficacy and side effects of its medication, up until now. From the viewpoint of Persian medicine, some medications such as antihistamines may cause retention of secretions and lead to exacerbation and spread of the disease in the body. There are studies with conflicting results regarding the effectiveness of antihistamines in COVID-19. Systematic reviews found a lack of data on beneficial effect of antihistamine-decongestant-analgesic combinations for the common cold and a limited short-term effect of antihistamines on severity of overall symptoms. This prospective cohort study was designed to investigate the relationship between the use of antihistamines and the severity of COVID-19 symptoms. Three hundred patients with a diagnosis of COVID-19 participated in the study in Shiraz, Iran from December 4, 2021 until January 24, 2022. The interviews were conducted via phone call by a single interviewer. Patients were followed weekly for 4 weeks. We collected information by using a data collection form, containing demographic information, underlying disease, COVID-19 symptoms, treatment methods, medications, and a list of antihistamines and herbs that might have been used. Generalized estimating equations were applied to assess the relationship between the severity of COVID-19 and the use of antihistamines, taking into account potential confounding factors such as time and herbal consumption. The difference in the severity of COVID-19 disease in antihistamine users compared to nonusers was not significant in 4 weeks despite the higher baseline severity in nonusers. The comparison of two groups of antihistamine users and nonusers showed that there was a significant difference (p = 0.001) regarding the use of herbal medicines.

A versatile attention-based neural network for chemical perturbation analysis and its potential to aid surgical treatment: an experimental study

Deep learning models have emerged as rapid, accurate, and effective approaches for clinical decisions. Through a combination of drug screening and deep learning models, drugs that may benefit patients before and after surgery can be discovered to reduce the risk of complications or speed recovery. However, most existing drug prediction methods have high data requirements and lack interpretability, which has a limited role in adjuvant surgical treatment. To address these limitations, the authors propose the attention-based convolution transpositional interfusion network (ACTIN) for flexible and efficient drug discovery. ACTIN leverages the graph convolution and the transformer mechanism, utilizing drug and transcriptome data to assess the impact of chemical pharmacophores containing certain elements on gene expression. Remarkably, just with only 393 training instances, only one-tenth of the other models, ACTIN achieves state-of-the-art performance, demonstrating its effectiveness even with limited data. By incorporating chemical element embedding disparity and attention mechanism-based parameter analysis, it identifies the possible pharmacophore containing certain elements that could interfere with specific cell lines, which is particularly valuable for screening useful pharmacophores for new drugs tailored to adjuvant surgical treatment. To validate its reliability, the authors conducted comprehensive examinations by utilizing transcriptome data from the lung tissue of fatal COVID-19 patients as additional input for ACTIN, the authors generated novel lead chemicals that align with clinical evidence. In summary, ACTIN offers insights into the perturbation biases of elements within pharmacophore on gene expression, which holds the potential for guiding the development of new drugs that benefit surgical treatment.

Mitigating the risks of post-acute sequelae of SARS-CoV-2 infection (PASC) with intranasal chlorpheniramine: perspectives from the ACCROS studies

BACKGROUND

The World Health Organization (WHO) declared the end of the COVID-19 (SARS-CoV-2) global public health emergency on May 5, 2023, but its long-term consequences have still been haunting the global population. Post-acute sequelae of COVID-19 (PASC) and long-term COVID-19 are serious concerns and present with various symptoms. Intranasal chlorpheniramine (iCPM) has been shown to decrease the viral burden of SARS-COV-2. iCPM uses decreased COVID-19 disease progression and severity in Accelerating COVID-19 Clinical Recovery in an Outpatient Setting (ACROSS)-I & III randomized control trials (RCT).

METHODS

This prospective survey study included 259 participants in ACROSS I and III RCTs. We compared the effect of iCPM versus placebo on the reduction of PASC symptoms. A PASC questionnaire containing 17 questions regarding the most common PASC symptoms was used in this study. T-test and Pearson chi-square statistics were performed according to continuous and categorical data using STATA 17.0 Basic Edition software.

FINDINGS

The iCPM cohort had a lower proportion of patients with fatigue or tiredness vs. placebo (0 Vs 17, 21, p < 0.001). iCPM cohort had a lower proportion of patients with difficulty concentrating or mental confusion (0 vs. 22, 27, p < 0.001). iCPM cohort had also a lower number of patients with difficulty in the ability to perform daily activities or work vs. placebo (1 Vs 38, 48, p < 0.001). A smaller number of patients in the iCPM cohort sought medical attention for PACS symptoms compared to placebo (0 vs. 48, 68, p < 0.001).

INTERPRETATION

The use of intranasal chlorpheniramine shows promise in preventing COVID-19 progression to the often-debilitating post-COVID-19 syndrome PASC. The association between iCPM use and a lower prevalence of PASC symptoms is strong. Further studies are needed to establish the role of ICPM in preventing PASC.

Opportunities and challenges in the therapeutic exploitation of histamine and histamine receptor pharmacology in inflammation-driven disorders

Inflammation-driven diseases encompass a wide array of pathological conditions characterised by immune system dysregulation leading to tissue damage and dysfunction. Among the myriad of mediators involved in the regulation of inflammation, histamine has emerged as a key modulatory player. Histamine elicits its actions through four rhodopsin-like G-protein-coupled receptors (GPCRs), named chronologically in order of discovery as histamine H1, H2, H3 and H4 receptors (H1-4R). The relatively low affinity H1R and H2R play pivotal roles in mediating allergic inflammation and gastric acid secretion, respectively, whereas the high affinity H3R and H4R are primarily linked to neurotransmission and immunomodulation, respectively. Importantly, however, besides the H4R, both H1R and H2R are also crucial in driving immune responses, the H2R tending to promote yet ill-defined and unexploited suppressive, protective and/or resolving processes. The modulatory action of histamine via its receptors on inflammatory cells is described in detail. The potential therapeutic value of the most recently discovered H4R in inflammatory disorders is illustrated via a selection of preclinical models. The clinical trials with antagonists of this receptor are discussed and possible reasons for their lack of success described.

Upregulation of key factors of viral entry of corona- and influenza viruses upon TLR3-signaling in cells from the respiratory tract and clinical treatment options by 1,8-Cineol

At the end of the 2019 coronavirus pandemic (COVID-19), highly contagious variants of coronaviruses had emerged. Together with influenza viruses, different variants of the coronavirus currently cause most colds and require appropriate drug treatment. We have investigated the expression of important factors for the replication of these viruses, namely transmembrane protease serine subtype 2 (TMPRSS2), neuropilin1 (NRP1), and angiotensin converting enzyme 2 (ACE2) or tumor necrosis factor-α (TNF-α) after toll like receptor-3 (TLR-3) stimulation using RT-qPCR and flow cytometry (FC) analysis. As model served primary fibroblasts derived from the lung and nasal cavity, as well as epidermal stem cells and fully matured respiratory epithelium. The stimulated cell cultures were treated with pharmaceuticals (Dexamethasone and Enzalutamide) and the outcome was compared with the phytomedicine 1,8-Cineol. The stimulation of TLR3 is sufficient to induce the expression of exactly those targets that were highly expressed in the corresponding culture type, specifically ACE2 and TMPRSS2 in respiratory epithelial stem cells and NRP1 in fibroblast cells. It seems this self-perpetuating cycle of infection-driven upregulation of key viral replication factors by the innate immune system represents an evolutionary advantage for viruses using these transcripts as viral replication factors. Likewise, to the standard pharmaceuticals with proven clinical efficiency, 1,8-Cineol was able to disrupt this self-perpetuating cycle. Considering the minor side effects and negligible pharmacological interactions with other drugs, it is conceivable that an adjuvant or combinatorial therapy with 1,8-Cineol for respiratory diseases caused by corona- or influenza viruses would be beneficial.

Increase in venous thromboembolism in SARS-CoV-2 infected lung tissue: proteome analysis of lung parenchyma, isolated endothelium, and thrombi

AIMS

COVID-19 pneumonia is characterized by an increased rate of deep venous thrombosis and pulmonary embolism. To better understand the pathophysiology behind thrombosis in COVID-19, we performed proteomics analysis on SARS-CoV-2 infected lung tissue.

METHODS

Liquid chromatography mass spectrometry was performed on SARS-CoV-2 infected postmortem lung tissue samples. Five protein profiling analyses were performed: whole slide lung parenchyma analysis, followed by analysis of isolated thrombi and endothelium, both stratified by disease (COVID-19 versus influenza) and thrombus morphology (embolism versus in situ). Influenza autopsy cases with pulmonary thrombi were used as controls.

RESULTS

Compared to influenza controls, both analyses of COVID-19 whole-tissue and isolated endothelium showed upregulation of proteins and pathways related to liver metabolism including urea cycle activation, with arginase being among the top upregulated proteins in COVID-19 lung tissue. Analysis of isolated COVID-19 thrombi showed significant downregulation of pathways related to platelet activation compared to influenza thrombi. Analysis of isolated thrombi based on histomorphology shows that in situ thrombi have significant upregulation of coronavirus pathogenesis proteins.

CONCLUSIONS

The decrease in platelet activation pathways in severe COVID-19 thrombi suggests a relative increase in venous thromboembolism, as thrombi from venous origin tend to contain fewer platelets than arterial thrombi. Based on histomorphology, in situ thrombi show upregulation of various proteins related to SARS-CoV-2 pathogenesis compared to thromboemboli, which may indicate increased in situ pulmonary thrombosis in COVID-19. Therefore, this study supports the increase of venous thromboembolism without undercutting the involvement of in situ thrombosis in severe COVID-19.

Antioxidant and Anti-Glycation Potential of H2 Receptor Antagonists-In Vitro Studies and a Systematic Literature Review

Background: Histamine H2 receptor antagonists are a group of drugs that inhibit gastric juice secretion in gastrointestinal diseases. However, there is evidence to suggest that H2 blockers have a broader spectrum of activity. The antioxidant properties of H2 blockers have not been fully elucidated, and their anti-glycation potential has not been studied to date. Therefore, this is the first study to compare the antioxidant and antiglycation potentials of the most popular H2 antagonists (ranitidine, cimetidine, and famotidine) on protein glycoxidation in vitro. Methods: Bovine serum albumin (BSA) was glycated using sugars (glucose, fructose, galactose, and ribose) as well as aldehydes (glyoxal and methylglyoxal). Results: In the analyzed group of drugs, ranitidine was the only H2 blocker that significantly inhibited BSA glycation in all tested models. The contents of protein carbonyls, protein glycoxidation products (↓dityrosine, ↓N-formylkynurenine), and early (↓Amadori products) and late-stage (↓AGEs) protein glycation products decreased in samples of glycated BSA with the addition of ranitidine relative to BSA with the addition of the glycating agents. The anti-glycation potential of ranitidine was comparable to those of aminoguanidine and Trolox. In the molecular docking analysis, ranitidine was characterized by the lowest binding energy for BSA sites and could compete with protein amino groups for the addition of carbonyl groups. H2 blockers also scavenge free radicals. The strongest antioxidant properties are found in ranitidine, which additionally has the ability to bind transition metal ions. The systematic literature review also revealed that the anti-glycation effects of ranitidine could be attributed to its antioxidant properties. Conclusions: Ranitidine showed anti-glycation and antioxidant properties. Further research is needed, particularly in patients with diseases that promote protein glycation.

Expediting the drug discovery for ideal leads against SARS-CoV-2 via molecular docking of repurposed drugs

SARS-CoV-2, the novel coronavirus spreading worldwide urges the need to repurpose drugs that can quickly enter clinical trials to combat the on-going global pandemic. A cluster of proteins are encoded for by the viral genome, each assuming a critical role in pathogen endurance inside the host. To handle the adverse circumstances, robust virtual strategies such as repurposing are coming to the fore due to being economical, efficient and rapid. Five FDA approved repurposed drugs proposed to act as inhibitors by targeting SARS-CoV-2 were used for initial evaluation via molecular docking. Moreover, a comparative analysis of the selected SARS-CoV-2 proteins against five ligands (Clemizole hydrochloride, Exemestane, Nafamostat, Pregnenolone and Umifenovir) was designed. In this regard, non-structural proteins (nsp3, nsp5, nsp10, nsp12 and nsp15), structural proteins (Spike, Nucleocapsid protein) and accessory proteins (ORF 3a, ORF 7a and ORF 9 b) were selected. Here, we aim to expedite the search for a potential drug from the five FDA approved repurposing drugs already in use for treatment of multiple diseases. Based on docking analysis, Umifenovir and Pregnenolone are suggested to show potential inhibitory effects against most of the SARS-CoV-2 proteins. These drugs are noteworthy since they exhibit high binding towards target proteins and should be used as lead compounds towards in vitro and in vivo studies.Communicated by Ramaswamy H. Sarma.

Virtual screening and molecular dynamics simulations provide insight into repurposing drugs against SARS-CoV-2 variants Spike protein/ACE2 interface

After over two years of living with Covid-19 and hundreds of million cases worldwide there is still an unmet need to find proper treatments for the novel coronavirus, due also to the rapid mutation of its genome. In this context, a drug repositioning study has been performed, using in silico tools targeting Delta Spike protein/ACE2 interface. To this aim, it has been virtually screened a library composed by 4388 approved drugs through a deep learning-based QSAR model to identify protein-protein interactions modulators for molecular docking against Spike receptor binding domain (RBD). Binding energies of predicted complexes were calculated by Molecular Mechanics/Generalized Born Surface Area from docking and molecular dynamics simulations. Four out of the top twenty ranking compounds showed stable binding modes on Delta Spike RBD and were evaluated also for their effectiveness against Omicron. Among them an antihistaminic drug, fexofenadine, revealed very low binding energy, stable complex, and interesting interactions with Delta Spike RBD. Several antihistaminic drugs were found to exhibit direct antiviral activity against SARS-CoV-2 in vitro, and their mechanisms of action is still debated. This study not only highlights the potential of our computational methodology for a rapid screening of variant-specific drugs, but also represents a further tool for investigating properties and mechanisms of selected drugs.

An Overview of Antihistamines and their Properties used for Treatment of Different Diseases

BACKGROUND

By comparing the histamine impact to the instant response to an injected foreign protein in previously sensitized animals, one might hypothesize that histamine may be involved in this reaction. Through all four of the recognized types of histamine receptors, histamine is also essential for the control of immunological function and acute and chronic allergic inflammation.

METHODS

Recent evidence points to anti-IgE antibodies and specific antibodies to cytokines like IL-4 or IL-5 that are associated with allergic inflammation as probable causes of Allergic Rhinitis. The therapeutic advantage of antihistamines is a decrease in allergy symptoms and any other allergy-related symptoms. We research the many diseases and dose forms in which antihistamines are used. Pediatric age groups have never been thoroughly studied for firstgeneration antihistamines. Oral antihistamines are suggested as the first line of therapy for people with mild to severe intermittent Allergic Rhinitis symptoms.

RESULTS

Currently, approximately 100 different antihistamine-containing medicines and around 20 different H1-receptor antagonists are available for therapeutic use. Antihistamines of the second generation are more efficient and secure than those of the first generation. We conducted a research on the sedative and non-sedative effects of antihistamines used to treat various diseases.

CONCLUSION

The present investigation highlights the use of antihistamines in various diseases at different ages, their sedative and non-sedative effect, and their utility in treating insomnia based on their safety and current use among the patient population, as well as our observation.

Correlation between Medications Used during COVID Infection and Post-conditions after the Acute Phase of Infection: A Cross-sectional Study

Background:

During the COVID-19 pandemic, off-label medication prescribing and utilizing herbal products and multiple vitamins in the treatment, prevention, and symptom management of COVID-19 was an urgently needed practice to halt the SARS-CoV-2 infection crisis and progression.

Objectives:

This study aimed to determine the correlation between medications used during the pandemic and SARS-CoV-2 infection post-recovery symptoms.

Methods:

A cross-sectional questionnaire-based study was conducted on recovered COVID-19 patients. There were 20 multiple-choice questions, including patient demographics, treatment, and post-recovery symptoms. Chi-square and Fisher’s exact tests were used to investigate significant relationships. In addition, Binary logistic regression was performed to determine confounders. Data were analyzed using SPSS version 22.

Results:

Medications and supplements varied in their therapeutic effects on SARS-CoV-2 post-recovery symptoms. Patients who took vitamin D and calcium experienced increased symptom frequency, and patients taking ACE inhibitors experienced more headaches and coughs. Furthermore, patients receiving azithromycin were asymptomatic after recovery. Patients who took H2 antagonists reported persistent headaches and muscle pain.

Conclusion:

Patients infected with SARS-CoV-2 have responded differently to medications, multivitamins, and herbal supplements. Patients reported resolution of some symptoms and persistence of others post-recovery. Therefore, expert opinion should be considered in COVID-19 management until randomized controlled trials answer many questions and determine medications' safety and efficacy in prevention, treatment strategies, and symptoms of SARS-CoV-2 infection post-recovery.

A Scoping Review of the Use of Pioglitazone in the Treatment of Temporo-Mandibular Joint Arthritis

Thiazolidinediones (TZDs) are a group of diabetes medications currently being investigated for anti-arthritis effectiveness, one of which is pioglitazone. The purpose of this scoping review is to evaluate the potential use of pioglitazone in the treatment of temporomandibular joint (TMJ) arthritis. The criteria of eligibility were studies with the diagnosis of arthritis and pioglitazone treatment with a change in any inflammation index as an outcome. Of the 1169 records initially identified following the selection process, two animal studies and four clinical studies were included in the review. Improvements from the baseline were observed in each treatment group for each inflammation indicator. The results of the animal studies on the temporomandibular joints and on patients with rheumatoid and psoriatic arthritis indicate that the drug in question may have potential to treat arthritis, including within the temporomandibular joint.

The role of berberine in Covid-19: potential adjunct therapy

Coronavirus disease 2019 (Covid-19) is a global diastrophic disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Covid-19 leads to inflammatory, immunological, and oxidative changes, by which SARS-CoV-2 leads to endothelial dysfunction (ED), acute lung injury (ALI), acute respiratory distress syndrome (ARDS), and multi-organ failure (MOF). Despite evidence illustrating that some drugs and vaccines effectively manage and prevent Covid-19, complementary herbal medicines are urgently needed to control this pandemic disease. One of the most used herbal medicines is berberine (BBR), which has anti-inflammatory, antioxidant, antiviral, and immune-regulatory effects; thus, BBR may be a prospective candidate against SARS-CoV-2 infection. This review found that BBR has anti-SARS-CoV-2 effects with mitigation of associated inflammatory changes. BBR also reduces the risk of ALI/ARDS in Covid-19 patients by inhibiting the release of pro-inflammatory cytokines and inflammatory signaling pathways. In conclusion, BBR has potent anti-inflammatory, antioxidant, and antiviral effects. Therefore, it can be utilized as a possible anti-SARS-CoV-2 agent. BBR inhibits the proliferation of SARS-CoV-2 and attenuates the associated inflammatory disorders linked by the activation of inflammatory signaling pathways. Indeed, BBR can alleviate ALI/ARDS in patients with severe Covid-19. In this sense, clinical trials and prospective studies are suggested to illustrate the potential role of BBR in treating Covid-19.

Glucocorticoids and COVID-19

Coronavirus Disease 19 (COVID-19) is associated with high morbidity and mortality rates globally, representing the greatest health and economic challenge today. Several drugs are currently approved for the treatment of COVID-19. Among these, glucocorticoids (GCs) have received particular attention due to their anti-inflammatory and immunosuppressive effects. In fact, GC are widely used in current clinical practice to treat inflammatory, allergic and autoimmune diseases. Major mechanisms of GC action include inhibition of innate and adaptive immune activity. In particular, an important role is played by the inhibition of pro-inflammatory cytokines and chemokines, and the induction of proteins with anti-inflammatory activity. Overall, as indicated by various national and international regulatory agencies, GCs are recommended for the treatment of COVID-19 in patients requiring oxygen therapy, with or without mechanical ventilation. Regarding the use of GCs for the COVID-19 treatment of non-hospitalized patients at an early stage of the disease, many controversial studies have been reported and regulatory agencies have not recommended their use. The decision to start GC therapy should be based not only on the severity of COVID-19 disease, but also on careful considerations of the benefit/risk profile in individual patients, including monitoring of adverse events. In this review we summarize the effects of GCs on the major cellular and molecular components of the inflammatory/immune system, the benefits and the adverse common reactions in the treatment of inflammatory/autoimmune diseases, as well as in the management of COVID-19.

Mast Cell Activation Syndrome in COVID-19 and Female Reproductive Function: Theoretical Background vs. Accumulating Clinical Evidence

Coronavirus disease 2019 (COVID-19), a pandemic disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, can affect almost all systems and organs of the human body, including those responsible for reproductive function in women. The multisystem inflammatory response in COVID-19 shows many analogies with mast cell activation syndrome (MCAS), and MCAS may be an important component in the course of COVID-19. Of note, the female sex hormones estradiol (E2) and progesterone (P4) significantly influence mast cell (MC) behavior. This review presents the importance of MCs and the mediators from their granules in the female reproductive system, including pregnancy, and discusses the mechanism of potential disorders related to MCAS. Then, the available data on COVID-19 in the context of hormonal disorders, the course of endometriosis, female fertility, and the course of pregnancy were compiled to verify intuitively predicted threats. Surprisingly, although COVID-19 hyperinflammation and post-COVID-19 illness may be rooted in MCAS, the available clinical data do not provide grounds for treating this mechanism as significantly increasing the risk of abnormal female reproductive function, including pregnancy. Further studies in the context of post COVID-19 condition (long COVID), where inflammation and a procoagulative state resemble many aspects of MCAS, are needed.

Organ-specific or personalized treatment for COVID-19: rationale, evidence, and potential candidates

Although extrapulmonary manifestations of coronavirus disease 2019 (COVID-19) are increasingly reported, no effective therapeutic strategy for these multisystemic complications is available due to a poor understanding of the pathophysiology of COVID-19 multiorgan involvement. In this study, differentially expressed genes (DEGs) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected extrapulmonary organs including human pluripotent stem cells (hPSCs)-derived liver organoids and choroid plexus organoids besides transformed lung alveolar (A549) cells were analyzed. First, pathway enrichment analysis was done to compare the underlying biological pathways enriched upon SARS-CoV-2 infection in different organs. Then, these lists of DEGs were used in a connectivity map (CMap)-based drug repurposing experiment. Also, protein-protein interaction (PPI) network analysis was done to compare the associated hub genes. The results revealed different biological pathways and genes responsible for SARS-CoV-2 multisystemic pathogenesis based on the organ involved that highlighted the need for considering organ-specific treatments or even personalized therapy. Besides, some FDA-approved drugs were proposed as the potential therapeutic candidates for each infected cell line.

Histamine research advancements in the second year of the COVID-19 pandemic: report of the European Histamine Research Society (EHRS)

In the light of cancellation of the 50th Annual Meeting of the European Histamine Research Society (EHRS) due to continuing challenges and restrictions imposed by the coronavirus disease 2019 (COVID-19) outbreak, the EHRS Council decided to organize a series of online events spread in 2021 to allow dissemination of histamine research progress and advancement among the Society members and beyond. This report summarizes the outcomes of the EHRS Council initiative that comprised the organization of four webinars, each focusing on a highly relevant histamine research scientific area. These included insights into novel therapeutic targets related to the histaminergic system in the eye, histamine intolerance, and the role of histamine and the histaminergic system in the regulation of the nervous system, as well as an update on studies leading to the development of novel methods for histamine detection. The outcome of this series of virtual events conformed that histamine research continued to develop despite the pandemic, and we witnessed stimulating advancements in 2021. Importantly, the EHRS Council brought histaminologists together in this unprecedented time.

Human Identical Sequences, hyaluronan, and hymecromone ─ the new mechanism and management of COVID-19

COVID-19 caused by SARS-CoV-2 has created formidable damage to public health and market economy. Currently, SARS-CoV-2 variants has exacerbated the transmission from person-to-person. Even after a great deal of investigation on COVID-19, SARS-CoV-2 is still rampaging globally, emphasizing the urgent need to reformulate effective prevention and treatment strategies. Here, we review the latest research progress of COVID-19 and provide distinct perspectives on the mechanism and management of COVID-19. Specially, we highlight the significance of Human Identical Sequences (HIS), hyaluronan, and hymecromone ("Three-H") for the understanding and intervention of COVID-19. Firstly, HIS activate inflammation-related genes to influence COVID-19 progress through NamiRNA-Enhancer network. Accumulation of hyaluronan induced by HIS-mediated HAS2 upregulation is a substantial basis for clinical manifestations of COVID-19, especially in lymphocytopenia and pulmonary ground-glass opacity. Secondly, detection of plasma hyaluronan can be effective for evaluating the progression and severity of COVID-19. Thirdly, spike glycoprotein of SARS-CoV-2 may bind to hyaluronan and further serve as an allergen to stimulate allergic reaction, causing sudden adverse effects after vaccination or the aggravation of COVID-19. Finally, antisense oligonucleotides of HIS or inhibitors of hyaluronan synthesis (hymecromone) or antiallergic agents could be promising therapeutic agents for COVID-19. Collectively, Three-H could hold the key to understand the pathogenic mechanism and create effective therapeutic strategies for COVID-19.

Immunouniverse of SARS-CoV-2

SARS-CoV-2 virus has become a global health problem that has caused millions of deaths worldwide. The infection can present with multiple clinical features ranging from asymptomatic or mildly symptomatic patients to patients with severe or critical illness that can even lead to death. Although the immune system plays an important role in pathogen control, SARS-CoV-2 can drive dysregulation of this response and trigger severe immunopathology. Exploring the mechanisms of the immune response involved in host defense against SARS-CoV-2 allows us to understand its immunopathogenesis and possibly detect features that can be used as potential therapies to eliminate the virus. The main objective of this review on SARS-CoV-2 is to highlight the interaction between the virus and the immune response. We explore the function and action of the immune system, the expression of molecules at the site of infection that cause hyperinflammation and hypercoagulation disorders, the factors leading to the development of pneumonia and subsequent severe acute respiratory distress syndrome which is the leading cause of death in patients with COVID-19.

Functional and Nutraceutical Compounds of Tomatoes as Affected by Agronomic Practices, Postharvest Management, and Processing Methods: A Mini Review

Tomatoes and their by-products are indisputable sources of substances with antioxidants properties. Several factors limit the production and influence the nutritional and antioxidant quality of tomato fruit. However, consumers can benefit from the effects of environmental factors, such as water and hydric stress, UV radiation, agronomic practices, among others, which lead to changes in the content of secondary metabolites in tomatoes. Molecules as phenolic compounds, carotenoids, and biogenic amines are often formed in response to environmental adversities. In this way, the consumption of tomato fruits or their by-products with higher levels of antioxidants may be important adjuvants in the prevention or reduction of diseases. In this mini-review, we will present how pre- and postharvest conditions may influence the content of some bioactive compounds in tomatoes. Furthermore, we will present how some heat processing methods may change the antioxidant content, as well as, the functional and nutritional properties of the final product.

Histamine Potentiates SARS-CoV-2 Spike Protein Entry Into Endothelial Cells

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which causes coronavirus disease (COVID-19) is one of the most serious global health crises in recent history. COVID-19 patient symptoms range from life-threatening to mild and asymptomatic, which presents unique problems in identifying, quarantining, and treating the affected individuals. The emergence of unusual symptoms among survivors, now referred to as “Long COVID”, is concerning, especially since much about the condition and the treatment of it is still relatively unknown. Evidence so far also suggests that some of these symptoms can be attributed to vascular inflammation. Although famotidine, the commonly used histamine H2 receptor (H2R) blocker, was shown to have no antiviral activity, recent reports indicate that it could prevent adverse outcomes in COVID-19 patients. Histamine is a classic proinflammatory mediator, the levels of which increase along with other cytokines during COVID-19 infection. Histamine activates H2R signaling, while famotidine specifically blocks H2R activation. Investigating the effects of recombinant SARS-CoV-2 spike protein S1 Receptor-Binding Domain (Spike) on ACE2 expression in cultured human coronary artery endothelial cells, we found that the presence of histamine potentiated spike-mediated ACE2 internalization into endothelial cells. This effect was blocked by famotidine, protein kinase A inhibition, or by H2 receptor protein knockdown. Together, these results indicate that histamine and histamine receptor signaling is likely essential for spike protein to induce ACE2 internalization in endothelial cells and cause endothelial dysfunction and that this effect can be blocked by the H2R blocker, famotidine.

Famotidine activates the vagus nerve inflammatory reflex to attenuate cytokine storm

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 was 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 α and interleukin-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.

Antihistamines for Postacute Sequelae of SARS-CoV-2 Infection

Postacute sequelae of SARS-CoV2 (PASC) infection is an emerging global health crisis, variably affecting millions worldwide. PASC has no established treatment. We describe 2 cases of PASC in response to opportune administration of over-the-counter antihistamines, with significant improvement in symptoms and ability to perform activities of daily living. Future studies are warranted to understand the potential role of histamine in the pathogenesis of PASC and explore the clinical benefits of antihistamines in the treatment of PASC.

Kinases as Potential Therapeutic Targets for Anti-coronaviral Therapy

The global coronavirus disease-19 (COVID-19) has affected more than 140 million and killed more than 3 million people worldwide as of April 20, 2021. The novel human severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been identified as an etiological agent for COVID-19. Several kinases have been proposed as possible mediators of multiple viral infections, including life-threatening coronaviruses like SARS-CoV-1, Middle East syndrome coronavirus (MERS-CoV), and SARS-CoV-2. Viral infections hijack abundant cell signaling pathways, resulting in drastic phosphorylation rewiring in the host and viral proteins. Some kinases play a significant role throughout the viral infection cycle (entry, replication, assembly, and egress), and several of them are involved in the virus-induced hyperinflammatory response that leads to cytokine storm, acute respiratory distress syndrome (ARDS), organ injury, and death. Here, we highlight kinases that are associated with coronavirus infections and their inhibitors with antiviral and potentially anti-inflammatory, cytokine-suppressive, or antifibrotic activity.

Therapeutic Status of Famotidine in COVID-19 Patients: A Review

The novel coronavirus, SARS-coV-2, which emerged in Wuhan in November 2019, has increasingly spread worldwide. More than 272 million cases of infection have been identified. COVID-19 has affected 223 countries and territories across the world. The principal target of the SARS-CoV-2 infection is the lower respiratory tract. Series of moderate to non-specific severe clinical signs and symptoms appear two to fourteen days after exposure to SARS-CoV-2 in patients with COVID-19 disease, including cough, breath deficiency, and at least two of these symptoms: headache, fever, chills, repeated rigor, myalgia, oropharyngitis, anosmia, and ageusia. No therapeutic agents have been validated to have substantial efficacy in the clinical care of COVID-19 patients in large-scale trials, despite worsening infected rates of COVID-19. Early clinical evidence from many sources suggests that treatment with famotidine may decrease COVID-19-related morbidity and mortality. The mechanism by which famotidine could improve the outcomes of COVID-19 is currently unknown. A more recent postulated mechanism is that the effect of famotidine is mediated by histamine-2 receptor antagonism or inverse agonism, inferring that the SARS-CoV-2, resulting in COVID-19 infection, at least partially leads to the abnormal release of histamine and perhaps dysfunction of mast cells.

Races of small molecule clinical trials for the treatment of COVID-19: An up-to-date comprehensive review

The coronavirus disease‐19 (COVID‐19) pandemic has become a global threat since its first outbreak at the end of 2019. Several review articles have been published recently, focusing on the aspects of target biology, drug repurposing, and mechanisms of action (MOAs) for potential treatment. This review gathers all small molecules currently in active clinical trials, categorizes them into six sub‐classes, and summarizes their clinical progress. The aim is to provide the researchers from both pharmaceutical industries and academic institutes with the handful information and dataset to accelerate their research programs in searching effective small molecule therapy for treatment of COVID‐19.

Efficacy and Safety of Non-brain Penetrating H1-Antihistamines for the Treatment of Allergic Diseases

H₁ receptor antagonists, known as H₁-antihistamines (AHs), inactivate the histamine H₁-receptor thereby preventing histamine causing the primary symptoms of allergic diseases, such as atopic dermatitis, pollinosis, food allergies, and urticaria. AHs, which are classified into first-generation (fgAHs) and second-generation (sgAHs) antihistamines, are the first line of treatment for allergic diseases. Although fgAHs are effective, they cause adverse reactions such as potent sedating effects, including drowsiness, lassitude, and cognitive impairment; anticholinergic effects, including thirst and tachycardia. Consequently, the use of fgAHs is not recommended for allergic diseases. Today, sgAHs, which are minimally sedating and, therefore, may be used at more effective doses, are the first-line treatment for alleviating the symptoms of allergic diseases. Pharmacologically, the use of sedating fgAHs is limited to antiemetics, anti-motion sickness drugs, and antivertigo drugs. The use of histamine H₁-receptor occupancy (H₁RO) based on positron emission tomography (PET) has been developed for the evaluation of brain penetrability. Based on the results of the H₁RO-PET studies, non-brain-penetrating AHs (nbpAHs) have recently been reclassified among sgAHs. The nbpAHs are rapidly acting and exhibit minimal adverse reactions and, thus, are considered first-line drugs for allergic diseases. In this review, we will introduce recent topics on the pharmacodynamics and pharmacokinetics of AHs and make recommendations for the use of nbpAHs as first-line treatment options for allergic diseases.

Chemical Probes for Histamine Receptor Subtypes

Ligands with different properties and different selectivity are highly needed for in vitro and in vivo studies on the (patho)physiological influence of the chemical mediator histamine and its receptor subtypes. A selection of well-described ligands for the different receptor subtypes and different studies is shown with a particular focus on affinity and selectivity. In addition, compounds with radioactive or fluorescence elements will be presented with their beneficial use for other species or different investigations.

The Complex Interplay between Immunonutrition, Mast Cells, and Histamine Signaling in COVID-19

There is an ongoing need for new therapeutic modalities against SARS-CoV-2 infection. Mast cell histamine has been implicated in the pathophysiology of COVID-19 as a regulator of proinflammatory, fibrotic, and thrombogenic processes. Consequently, mast cell histamine and its receptors represent promising pharmacological targets. At the same time, nutritional modulation of immune system function has been proposed and is being investigated for the prevention of COVID-19 or as an adjunctive strategy combined with conventional therapy. Several studies indicate that several immunonutrients can regulate mast cell activity to reduce the de novo synthesis and/or release of histamine and other mediators that are considered to mediate, at least in part, the complex pathophysiology present in COVID-19. This review summarizes the effects on mast cell histamine of common immunonutrients that have been investigated for use in COVID-19.

A Birds-Eye (Re)View of Acid-Suppression Drugs, COVID-19, and the Highly Variable Literature

This Perspective examines a recent surge of information regarding the potential benefits of acid-suppression drugs in the context of COVID-19, with a particular eye on the great variability (and, thus, confusion) that has arisen across the reported findings, at least as regards the popular antacid famotidine. The degree of inconsistency and discordance reflects contradictory conclusions from independent, clinical-based studies that took roughly similar approaches, in terms of both experimental design (retrospective, observational, cohort-based, etc.) and statistical analysis workflows (propensity-score matching and stratification into sub-cohorts, etc.). The contradictions and potential confusion have ramifications for clinicians faced with choosing therapeutically optimal courses of intervention: e.g., do any potential benefits of famotidine suggest its use in a particular COVID-19 case? (If so, what administration route, dosage regimen, duration, etc. are likely optimal?) As succinctly put this March in Freedberg et al. (2021), "…several retrospective studies show relationships between famotidine and outcomes in COVID-19 and several do not." Beyond the pressing issue of possible therapeutic indications, the conflicting data and conclusions related to famotidine must be resolved before its inclusion/integration in ontological and knowledge graph (KG)-based frameworks, which in turn are useful for drug discovery and repurposing. As a broader methodological issue, note that reconciling inconsistencies would bolster the validity of meta-analyses which draw upon the relevant data-sources. And, perhaps most broadly, developing a system for treating inconsistencies would stand to improve the qualities of both 1) real world evidence-based studies (retrospective), on the one hand, and 2) placebo-controlled, randomized multi-center clinical trials (prospective), on the other hand. In other words, a systematic approach to reconciling the two types of studies would inherently improve the quality and utility of each type of study individually.

Could Histamine H1 Receptor Antagonists Be Used for Treating COVID-19?

COVID-19 has rapidly become a pandemic worldwide, causing extensive and long-term health issues. There is an urgent need to identify therapies that limit SARS-CoV-2 infection and improve the outcome of COVID-19 patients. Unbalanced lung inflammation is a common feature in severe COVID-19 patients; therefore, reducing lung inflammation can undoubtedly benefit the clinical manifestations. Histamine H1 receptor (H1 receptor) antagonists are widely prescribed medications to treat allergic diseases, while recently it has emerged that they show significant promise as anti-SARS-CoV-2 agents. Here, we briefly summarize the novel use of H1 receptor antagonists in combating SARS-CoV-2 infection. We also describe the potential antiviral mechanisms of H1 receptor antagonists on SARS-CoV-2. Finally, the opportunities and challenges of the use of H1 receptor antagonists in managing COVID-19 are discussed.

The Relationship between COVID-19 and Innate Immunity in Children: A Review

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus responsible for the pandemic viral pneumonia that was first identified in Wuhan, China, in December 2019, and has since rapidly spread around the world. The number of COVID-19 cases recorded in pediatric age is around 1% of the total. The immunological mechanisms that lead to a lower susceptibility or severity of pediatric patients are not entirely clear. At the same time, the immune dysregulation found in those children who developed the multisystem inflammatory syndrome (MIC-S) is not yet fully understood. The aim of this review is to analyze the possible influence of children's innate immune systems, considering the risk of contracting the virus, spreading it, and developing symptomatic disease or complications related to infection.