Flavonoids Activation of the Transcription Factor Nrf2 as a Hypothesis Approach for the Prevention and Modulation of SARS-CoV-2 Infection Severity

Antioxidants and COVID-19

Oxidative mechanisms are not only involved in chronic degenerative diseases but also in infectious diseases, among which viral respiratory diseases. Antioxidants have the capability to counteract the action of oxidants by scavenging reactive oxygen species (ROS) and by inhibiting oxidant generating enzymes. Overproduction of ROS and deprivation of antioxidant systems play a major role in COVID-19 occurrence, progression, and severity. Interconnected pathways account for the relationships between oxidative damage and inflammation resulting from an interplay between transcription factors having opposite effects. For instance, Nrf2 downregulates inflammation by inhibiting endogenous antioxidant enzymes such as NQO-1 and HO-1. On the other hand, NF-κB upregulates pro-inflammatory cytokines and chemokines, such as IL-1β, IL-6, IL-8, PGE-2, COX-2, TNF-α, MMP-3, and MMP-4. A central protective role against oxidants is played by reduced glutathione (GSH), which is depleted in SARS-CoV-2 infection. N-acetylcysteine (NAC), a precursor of GSH, is of particular interest as an anti-COVID-19 agent. GSH and NAC hamper binding of the S1 subunit of SARS-CoV-2 spike proteins to the angiotensin-converting enzyme 2 (ACE2) receptor. In addition, NAC and its derivatives possess a broad array of antioxidant and antiinflammatory mechanisms that could be exploited for COVID-19 prevention and adjuvant therapy. In particular, as demonstrated in a previous clinical trial evaluating influenza and influenza-like illnesses, the oral administration of NAC may be expected to decrease the risk of developing COVID-19. Furthermore, at the very high doses used worldwide as an antidote against paracetamol intoxication, intravenous NAC is likely to attenuate the pulmonary and systemic symptoms of COVID-19.

The Association of Respiratory Viruses with Oxidative Stress and Antioxidants. Implications for the COVID-19 Pandemic

The spread of a new strain of coronavirus, SARS-CoV-2, a pandemic, poses a serious health problem for all humanity. Compared with the previous outbreaks of coronavirus infection in 2002 and 2012, COVID-19 infection has high rates of lethality, contagiousness, and comorbidity. The effective methods of prevention and treatment are extremely limited. Oxidative stress is actively involved in the mechanisms of initiation and maintenance of violations of homeostatic reactions in respiratory viral infections. It is important to stop systemic inflammation aimed at "extinguishing" the cytokine "storm", caused by the production of reactive oxygen species. Antioxidant defense medications, such as vitamin C, N-acetylcysteine, melatonin, quercetin, glutathione, astaxanthin, polyphenols, fat-soluble vitamins, and polyunsaturated fatty acids have proven well in experimental and clinical studies of influenza, pneumonia, and other respiratory disorders. The use of medications with antioxidant activity could be justified and most probably would increase the effectiveness of the fight against new coronavirus.

Potential protective mechanisms of green tea polyphenol EGCG against COVID-19

Background

The world is in the midst of the COVID-19 pandemic. In this comprehensive review, we discuss the potential protective effects of (−)-epigallocatechin-3-gallate (EGCG), a major constituent of green tea, against COVID-19.

Scope and approach

Information from literature of clinical symptoms and molecular pathology of COVID-19 as well as relevant publications in which EGCG shows potential protective activities against COVID-19 is integrated and evaluated.

Key findings and conclusions

EGCG, via activating Nrf2, can suppress ACE2 (a cellular receptor for SARS-CoV-2) and TMPRSS2, which mediate cell entry of the virus. Through inhibition of SARS-CoV-2 main protease, EGCG may inhibit viral reproduction. EGCG via its broad antioxidant activity may protect against SARS-CoV-2 evoked mitochondrial ROS (which promote SARS-CoV-2 replication) and against ROS burst inflicted by neutrophil extracellular traps. By suppressing ER-resident GRP78 activity and expression, EGCG can potentially inhibit SARS-CoV-2 life cycle. EGCG also shows protective effects against 1) cytokine storm-associated acute lung injury/acute respiratory distress syndrome, 2) thrombosis via suppressing tissue factors and activating platelets, 3) sepsis by inactivating redox-sensitive HMGB1, and 4) lung fibrosis through augmenting Nrf2 and suppressing NF-κB. These activities remain to be further substantiated in animals and humans. The possible concerted actions of EGCG suggest the importance of further studies on the prevention and treatment of COVID-19 in humans. These results also call for epidemiological studies on potential preventive effects of green tea drinking on COVID-19.

SARS-CoV-2 and Pre-existing Vascular Diseases: Guilt by Association?

Severe Acute Respiratory Syndrome coronavirus-2 has rapidly spread and emerged as a pandemic. Although evidence on its pathophysiology is growing, there are still issues that should be taken into consideration, including its effects on pre-existing peripheral vascular disease. The aim of this review is to describe the thrombotic and endothelial dysfunctions caused by SARS-CoV-2, assess if cardiovascular comorbidities render an individual susceptible to the infection and determine the course of pre-existing vascular diseases in infected individuals. A search through MEDLINE, PubMed and EMBASE was conducted and more than 260 articles were identified and 97 of them were reviewed; the rest were excluded because they were not related to the aim of this study. Hypertension, cardiovascular disease, diabetes mellitus and cerebrovascular diseases comprised 24.30% ± 16.23%, 13.29% ± 12.88%, 14.82% ± 7.57% and 10.82% ± 11.64% of the cohorts reviewed, respectively. Arterial and venous thrombotic complications rocketed up to 31% in severely infected individuals in some studies. We suggest that hypertension, cardiovascular diseases, diabetes and cerebrovascular diseases may render an individual susceptible to severe COVID-19 infection. Pre-existing vascular diseases are expected to deteriorate with SARS-CoV-2 infection as a consequence of its increased thrombotic burden and the development of endothelial dysfunction. COVID-19 has emerged only a few months ago and it is premature to predict the long-term effects to the vascular system. Its disturbances of the coagulation mechanisms and effects on vascular endothelium will likely provoke a surge of vascular complications in the coming months.

Nanotechnology-Based Drug Delivery to Improve the Therapeutic Benefits of NRF2 Modulators in Cancer Therapy

The disadvantages of conventional anticancer drugs, such as their low bioavailability, poor targeting efficacy, and serious side effects, have led to the discovery of new therapeutic agents and potential drug delivery systems. In particular, the introduction of nano-sized drug delivery systems (NDDSs) has opened new horizons for effective cancer treatment. These are considered potential systems that provide deep tissue penetration and specific drug targeting. On the other hand, nuclear factor erythroid 2-related factor 2 (NRF2)-based anticancer treatment approaches have attracted tremendous attention and produced encouraging results. However, the lack of effective formulation strategies is one of the factors that hinder the clinical application of NRF2 modulators. In this review, we initially focus on the critical role of NRF2 in cancer cells and NRF2-based anticancer treatment. Subsequently, we review the preparation and characterization of NDDSs encapsulating NRF2 modulators and discuss their potential for cancer therapy.

6,7,4'-Trihydroxyflavanone Mitigates Methamphetamine-Induced Neurotoxicity in SH-SY5y Cells via Nrf2/heme Oxyganase-1 and PI3K/Akt/mTOR Signaling Pathways

Methamphetamine (METH) is a synthetic psychostimulant drug that has detrimental effects on the health of its users. Although it has been investigated as a cause of neurodegenerative disease due to its neurotoxicity, whether small molecules derived from natural products attenuate these side effects remains elusive. 6,7,4'-trihydroxyflavanone (THF) is a flavanone family that possesses various pharmacological activities, including anti-rheumatic, anti-ischemic, anti-inflammatory, anti-osteoclastogenic, and protective effects against METH-induced deactivation of T cells. However, little is known about whether THF protects neuronal cells from METH-induced neurotoxicity. Here, we investigated the protective effects of THF on neurotoxicity induced by METH exposure by enhancing the Nrf2/HO-1 and PI3K/Akt/mTOR signaling pathways in SH-SY5y cells. Treatment with THF did not lead to cytotoxicity, but attenuated METH-induced neurotoxicity by modulating the expression of apoptosis-related proteins, METH-induced oxidative stress, and PI3K/Akt/mTOR phosphorylation in METH-exposed SH-SY5y cells. Moreover, we found THF induced Nrf2 nuclear translocation and HO-1 expression. An inhibitor assay confirmed that the induction of HO-1 by THF attenuates METH-induced neurotoxicity. Therefore, we suggest that THF preserves neuronal cells from METH-induced neurotoxicity by upregulating HO-1 expression through the Nrf2 and PI3K/Akt/mTOR signaling pathways. Thus, THF has therapeutic potential for use in the treatment of METH-addicts suffering from neurodegenerative diseases.

Therapeutic Potential of EGCG, a Green Tea Polyphenol, for Treatment of Coronavirus Diseases

Epigallocatechin gallate (EGCG) is a major catechin found in green tea, and there is mounting evidence that EGCG is potentially useful for the treatment of coronavirus diseases, including coronavirus disease 2019 (COVID-19). Coronaviruses encode polyproteins that are cleaved by 3CL protease (the main protease) for maturation. Therefore, 3CL protease is regarded as the main target of antivirals against coronaviruses. EGCG is a major constituent of brewed green tea, and several studies have reported that EGCG inhibits the enzymatic activity of the coronavirus 3CL protease. Moreover, EGCG has been reported to regulate other potential targets, such as RNA-dependent RNA polymerase and the viral spike protein. Finally, recent studies have demonstrated that EGCG treatment interferes with the replication of coronavirus. In addition, the bioavailability of EGCG and future research prospects are discussed.

Flavonoids against the SARS-CoV-2 induced inflammatory storm

The disease severity of COVID-19, especially in the elderly and patients with co-morbidities, is characterized by hypercytokinemia, an exaggerated immune response associated with an uncontrolled and excessive release of proinflammatory cytokine mediators (cytokine storm). Flavonoids, important secondary metabolites of plants, have long been studied as therapeutic interventions in inflammatory diseases due to their cytokine-modulatory effects. In this review, we discuss the potential role of flavonoids in the modulation of signaling pathways that are crucial for COVID-19 disease, particularly those related to inflammation and immunity. The immunomodulatory ability of flavonoids, carried out by the regulation of inflammatory mediators, the inhibition of endothelial activation, NLRP3 inflammasome, toll-like receptors (TLRs) or bromodomain containing protein 4 (BRD4), and the activation of the nuclear factor erythroid-derived 2-related factor 2 (Nrf2), might be beneficial in regulating the cytokine storm during SARS-CoV-2 infection. Moreover, the ability of flavonoids to inhibit dipeptidyl peptidase 4 (DPP4), neutralize 3-chymotrypsin-like protease (3CL^pro) or to affect gut microbiota to maintain immune response, and the dual action of angiotensin-converting enzyme 2 (ACE-2) may potentially also be applied to the exaggerated inflammatory responses induced by SARS-CoV-2. Based on the previously proven effects of flavonoids in other diseases or on the basis of newly published studies associated with COVID-19 (bioinformatics, molecular docking), it is reasonable to assume positive effects of flavonoids on inflammatory changes associated with COVID-19. This review highlights the current state of knowledge of the utility of flavonoids in the management of COVID-19 and also points to the multiple biological effects of flavonoids on signaling pathways associated with the inflammation processes that are deregulated in the pathology induced by SARS-CoV-2. The identification of agents, including naturally occurring substances such as flavonoids, represents great approach potentially utilizable in the management of COVID-19. Although not clinically investigated yet, the applicability of flavonoids against COVID-19 could be a promising strategy due to a broad spectrum of their biological activities.

Targeting Neurological Manifestations of Coronaviruses by Candidate Phytochemicals: A Mechanistic Approach

The novel coronavirus 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has made a wide range of manifestations. In this regard, growing evidence is focusing on COVID-19 neurological associations; however, there is a lack of established pathophysiological mechanisms and related treatments. Accordingly, a comprehensive review was conducted, using electronic databases, including PubMed, Scopus, Web of Science, and Cochrane, along with the author's expertize in COVID-19 associated neuronal signaling pathways. Besides, potential phytochemicals have been provided against neurological signs of COVID-19. Considering a high homology among SARS-CoV, Middle East Respiratory Syndrome and SARS-CoV-2, revealing their precise pathophysiological mechanisms seems to pave the road for the treatment of COVID-19 neural manifestations. There is a complex pathophysiological mechanism behind central manifestations of COVID-19, including pain, hypo/anosmia, delirium, impaired consciousness, pyramidal signs, and ischemic stroke. Among those dysregulated neuronal mechanisms, neuroinflammation, angiotensin-converting enzyme 2 (ACE2)/spike proteins, RNA-dependent RNA polymerase and protease are of special attention. So, employing multi-target therapeutic agents with considerable safety and efficacy seems to show a bright future in fighting COVID-19 neurological manifestations. Nowadays, natural secondary metabolites are highlighted as potential multi-target phytochemicals in combating several complications of COVID-19. In this review, central pathophysiological mechanisms and therapeutic targets of SARS-CoV-2 has been provided. Besides, in terms of pharmacological mechanisms, phytochemicals have been introduced as potential multi-target agents in combating COVID-19 central nervous system complications.

Insights to SARS-CoV-2 life cycle, pathophysiology, and rationalized treatments that target COVID-19 clinical complications

BACKGROUND

Gaining further insights into SARS-CoV-2 routes of infection and the underlying pathobiology of COVID-19 will support the design of rational treatments targeting the life cycle of the virus and/or the adverse effects (e.g., multi-organ collapse) that are triggered by COVID-19-mediated adult respiratory distress syndrome (ARDS) and/or other pathologies.

MAIN BODY

COVID-19 is a two-phase disease being marked by (phase 1) increased virus transmission and infection rates due to the wide expression of the main infection-related ACE2, TMPRSS2 and CTSB/L human genes in tissues of the respiratory and gastrointestinal tract, as well as by (phase 2) host- and probably sex- and/or age-specific uncontrolled inflammatory immune responses which drive hyper-cytokinemia, aggressive inflammation and (due to broad organotropism of SARS-CoV-2) collateral tissue damage and systemic failure likely because of imbalanced ACE/ANGII/AT1R and ACE2/ANG(1-7)/MASR axes signaling.

CONCLUSION

Here we discuss SARS-CoV-2 life cycle and a number of approaches aiming to suppress viral infection rates or propagation; increase virus antigen presentation in order to activate a robust and durable adaptive immune response from the host, and/or mitigate the ARDS-related "cytokine storm" and collateral tissue damage that triggers the severe life-threatening complications of COVID-19.

Anti-Viral Potential and Modulation of Nrf2 by Curcumin: Pharmacological Implications

Nuclear factor erythroid 2-related factor 2 (Nrf2) is an essential transcription factor that maintains the cell's redox balance state and reduces inflammation in different adverse stresses. Under the oxidative stress, Nrf2 is separated from Kelch-like ECH-associated protein 1 (Keap1), which is a key sensor of oxidative stress, translocated to the nucleus, interacts with the antioxidant response element (ARE) in the target gene, and then activates the transcriptional pathway to ameliorate the cellular redox condition. Curcumin is a yellow polyphenolic curcuminoid from Curcuma longa (turmeric) that has revealed a broad spectrum of bioactivities, including antioxidant, anti-inflammatory, anti-tumor, and anti-viral activities. Curcumin significantly increases the nuclear expression levels and promotes the biological effects of Nrf2 via the interaction with Cys151 in Keap1, which makes it a marvelous therapeutic candidate against a broad range of oxidative stress-related diseases, including type 2 diabetes (T2D), neurodegenerative diseases (NDs), cardiovascular diseases (CVDs), cancers, viral infections, and more recently SARS-CoV-2. Currently, the multifactorial property of the diseases and lack of adequate medical treatment, especially in viral diseases, result in developing new strategies to finding potential drugs. Curcumin potentially opens up new views as possible Nrf2 activator. However, its low bioavailability that is due to low solubility and low stability in the physiological conditions is a significant challenge in the field of its efficient and effective utilization in medicinal purposes. In this review, we summarized recent studies on the potential effect of curcumin to activate Nrf2 as the design of potential drugs for a viral infection like SARS-Cov2 and acute and chronic inflammation diseases in order to improve the cells' protection.

Nrf2-interacting nutrients and COVID-19: time for research to develop adaptation strategies

There are large between- and within-country variations in COVID-19 death rates. Some very low death rate settings such as Eastern Asia, Central Europe, the Balkans and Africa have a common feature of eating large quantities of fermented foods whose intake is associated with the activation of the Nrf2 (Nuclear factor (erythroid-derived 2)-like 2) anti-oxidant transcription factor. There are many Nrf2-interacting nutrients (berberine, curcumin, epigallocatechin gallate, genistein, quercetin, resveratrol, sulforaphane) that all act similarly to reduce insulin resistance, endothelial damage, lung injury and cytokine storm. They also act on the same mechanisms (mTOR: Mammalian target of rapamycin, PPARγ:Peroxisome proliferator-activated receptor, NFκB: Nuclear factor kappa B, ERK: Extracellular signal-regulated kinases and eIF2α:Elongation initiation factor 2α). They may as a result be important in mitigating the severity of COVID-19, acting through the endoplasmic reticulum stress or ACE-Angiotensin-II-AT₁R axis (AT₁R) pathway. Many Nrf2-interacting nutrients are also interacting with TRPA1 and/or TRPV1. Interestingly, geographical areas with very low COVID-19 mortality are those with the lowest prevalence of obesity (Sub-Saharan Africa and Asia). It is tempting to propose that Nrf2-interacting foods and nutrients can re-balance insulin resistance and have a significant effect on COVID-19 severity. It is therefore possible that the intake of these foods may restore an optimal natural balance for the Nrf2 pathway and may be of interest in the mitigation of COVID-19 severity.

Food-derived antioxidants and COVID-19

SARS-CoV-2 (previously 2019-nCoV), the pathogenic agent of COVID-19 disease, started to expand from Wuhan, China, on December 2019 and in 2 months, it spread worldwide giving origin to a pandemic. COVID-19 has a stronger transmission capacity by inhalation of infectious aerosols and after an incubation time of 3-14 days, it may be responsible for diseases ranging from the asymptomatic to fatal consequences. COVID-19 has emerged as a multifaceted, multisystem, multi-organ disorder, which produces its pathogenic effects through a quite ubiquitous target at the level of multiple organs and in which oxidative stress and inflammatory process play relevant roles. Thus, besides the development of a pharmacological therapy, in the field of alternative and coadjutant therapeutic, the use of dietary supplements or nutraceuticals for the prevention or treatment of SARS-CoV-2 infection may be a useful strategy. Herein, we specifically comment on some literature evidences, which link the food-derived antioxidants and metal-chelating agents with treatment and prevention of oxidative stress and inflammation that play a key role in the progression of COVID-19. PRACTICAL APPLICATIONS: Oxidative stress and inflammation are key factors increasing COVID-19 severity especially in the presence of chronic diseases associated with the antioxidant system fragility. These evidences support the recommendation of antioxidants supplementation as useful strategies against COVID-19. In light with these observations, herein, a comment which describes the major antioxidants and metal-chelating agents from food sources that might be useful for the treatment and prevention of oxidative stress and inflammation during COVID-19.

Flavonoid Profiles of Two New Approved Romanian Ocimum Hybrids

Basil (Ocimum spp.) is a traditional herbal medicine abundant in antioxidants such as phenolic compounds. As part of a diet, this herb is proved to have some roles in decreasing the risk of cancer, and in the treatment of inflammation and neurodegenerative diseases. This study aims to explore the total phenolic and flavonoid content of two new basil hybrids growing in Romania, namely "Aromat de Buzau" (AB) and "Macedon" (MB). The antioxidant capacity of those two species was also analyzed by DPPH and cyclic voltammetry. Six different flavonoids, such as catechin (+), rutin, hyperoside, naringin, naringenin, and genistein, were separated, identified, and quantified by HPLC-DAD chromatography, for the first time, from romanian basil hybrids. The main flavonoid of the extracts was found to be naringin which is present in the highest amount (26.18 mg/kg) in "Aromat de Buzau" (O. basilicum) methanolic extract. These results suggest that dietary intake of these new hybrids can be a source of antioxidant compounds.