Effect of the Covid-19 Pandemic on Neuroinflammatory Diseases

In December of 2019, SARS-CoV-2 surfaced and the global COVID-19 pandemic began. The pandemic has had far-reaching effects, socially, economically, and especially for healthcare, presenting challenges to patients with neuroinflammatory disorders. Apart from the well-known respiratory, pulmonary, and cardiovascular symptoms that COVID-19 is responsible for, studies continue to show its role in generating neuroinflammation and the different neurological effects that can arise. This review summarizes the relationship between the COVID-19 pandemic and neuroinflammatory diseases, with an emphasis on the effects on patients with neuroinflammatory disorders. Copyright © 2022, Biolife s.a.s.. All rights reserved.

Effect of the Covid-19 Pandemic on Neuroinflammatory Diseases

In December of 2019, SARS-CoV-2 surfaced and the global COVID-19 pandemic began. The pandemic has had far-reaching effects, socially, economically, and especially for healthcare, presenting challenges to patients with neuroinflammatory disorders. Apart from the well-known respiratory, pulmonary, and cardiovascular symptoms that COVID-19 is responsible for, studies continue to show its role in generating neuroinflammation and the different neurological effects that can arise. This review summarizes the relationship between the COVID-19 pandemic and neuroinflammatory diseases, with an emphasis on the effects on patients with neuroinflammatory disorders. Copyright © 2022, Biolife s.a.s.. All rights reserved.

Contribution of mast cells in SARS-CoV-2-induced inflammation

COVID-19, which first appeared in China, has so far caused an unexpected number of deaths, as our immune system has not been able to annihilate the SARS-CoV-2 virus. SARS-CoV-2 reacts to both innate and acquired immunity. In the first instance, when the virus enters our organism, it is attacked by innate immune cells, including macrophages and mast cells (MCs), which produce defensive cytokines such as IL-1, IL-6, IL-33 and TNF;but the overproduction of these cytokines is very harmful to the patient. Here, in this editorial, we report that the inflammatory cytokine network established in COVID-19, in the most serious cases, can lead to the death of the patient. Therefore, it is pertinent to think that by blocking the pro-inflammatory cytokines that cause the “cytokine storm”, a great therapeutical benefit can be achieved for COVID-19 disease.

Mast cells and virus

Mast cells (MCs) are hematopoietic cells that reside ubiquitously in all vascularized tissues. They are potential sources of a wide variety of biologically active secreted compounds, including diverse cytokines, chemokines and growth factors. In addition, they participate in innate and adaptive immune responses. MCs are the most important cells in immediate reactions and chronic IgE-associated allergic disorders and enhance the host resistance to certain biological agents, including viruses. Therefore, MCs influence many biological responses to viruses and other microbiological agents. Viruses activate MCs through TLR4 leading to the generation of several pro-inflammatory cytokines, including those of the IL-1 family. Here, we report how viruses can activate MCs producing severe inflammation and how these interesting cells can activate the immune system by carrying out a protective action for our organism.

Mast cell virus infection and inflammatory cytokines

Mast cells (MCs) are hematopoietic cells developed from bone marrow progenitors in response to the ligand stem cell factor, a trans-membrane tyrosine kinase kit receptor. MCs are located virtually in all vascularized tissues and in proximity to neurons and play a decisive role in both innate and adaptive immune responses. Their activation is involved in oxidative stress correlated with infection and inflammation. Pro-inflammatory cytokines are secreted by MCs after physiologic and psychological stress due to virus infection, including SARS-CoV-2. MCs, along with macrophages and pulmonary alveolar epithelial cells, are the main targets attacked by the coronavirus. COVID-19 induced by SARS-CoV-2 causes inflammatory stress which activates MCs to secrete corticotrophin-releasing hormone (CRH), SP, IL-6, TNF, and IL-1. Toll-like receptor (TLR) virus activation in MCs leads to pro-inflammatory cytokine generation without degranulation, an effect that can be inhibited by IL-10, IL-4, IL-1Ra and IL-37. TLR has the ability to recognize extracellular PAMPs by causing the transcription of NLRP, pro-IL-1, and other pro-inflammatory cytokines. The multi-protein complex, comprising pro-caspase-1, activates caspase-1 which in turn activates pro-IL-1 that is transformed into highly inflammatory mature IL-1. In COVID-19, viral RNA is specifically recognized by TLR, followed by recruiting the signal transfer proteins MyD88, IRAK, IKK and TRAF6 which can activate the NF-κB, resulting in transcription of the pro-inflammatory cytokines IL-1 and TNF, responsible for the “cytokine storm” phenomenon. Meanwhile, a new variant of the coronavirus-19 called C.1.2. has been discovered in the United States in the past few days, the effects of which are unknown, and it is therefore of great concern. Researchers are now testing it on immune cells to see if they react and are comparing it to a delta variant. Thus, from the existing data in biomedical literature, we can conclude that the suppression of pro-inflammatory cytokines in viral infections (including COVID-19) mediated by MCs represents a promising therapy not only in this field of medicine, but also in autoimmune, allergic, and cardiovascular disorders, as well as tumor inflammation where MCs play a key role.

The British variant of the new coronavirus-19 (Sars-Cov-2) should not create a vaccine problem.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a highly contagious virus that infects humans and a number of animal species causing coronavirus disease-19 (COVID-19), a respiratory distress syndrome which has provoked a global pandemic and a serious health crisis in most countries across our planet. COVID-19 inflammation is mediated by IL-1, a disease that can cause symptoms such as fever, cough, lung inflammation, thrombosis, stroke, renal failure and headache, to name a few. Strategies that inhibit IL-1 are certainly helpful in COVID-19 and can represent one of the therapeutic options. However, until now, COVID-19 therapy has been scarce and, in many cases, ineffective, since there are no specific drugs other than the vaccine that can solve this serious health problem. Messenger RNA (mRNA) vaccines which are the newest approach, are already available and will certainly meet the many expectations that the population is waiting for. mRNA vaccines, coated with protected soft fatty lipids, use genetic mRNA (plus various inactive excipients) to make a piece of the coronavirus spike protein, which will instruct the immune system to produce specific antibodies. The soft fatty lipids allow the entry of mRNA into cells where it is absorbed into the cytoplasm and initiates the synthesis of the spike protein. In addition, vaccination also activates T cells that help the immune system respond to further exposure to the coronavirus. mRNA induces the synthesis of antigens of SARS-CoV-2 virus which stimulate the antibody response of the vaccinated person with the production of neutralizing antibodies. The new variant of the coronavirus-19 has been detected in the UK where, at the moment, the London government has imposed a lockdown with restrictions on international movements. The virus variant had already infected 1/4 of the total cases and in December 2020, it reached 2/3 of those infected in the UK. It has been noted that the spreading rate of the British variant could be greater than 70% of cases compared to the normal SARS-CoV-2 virus, with an R index growth of 0.4. Recent studies suggest that coronavirus-19 variation occurs at the level N501Y of the spike protein and involves 23 separate mutations on the spike, 17 of which are linked to the virus proteins, thus giving specific characteristics to the virus. In general, coronaviruses undergo many mutations that are often not decisive for their biological behavior and does not significantly alter the structure and the components of the virus. This phenomenon also occurs in SARS-CoV-2. It is highly probable that the variants recently described in the UK will not hinder vaccine-induced immunity. In fact, the variant will not break the vaccine although it may have some chance of making it a little less effective. Therefore, it is pertinent to think that the vaccine will work against the SARS-CoV-2 variant as well. In today's pandemic, the D614G mutation of the amino acid of corronavirus-19, which emerged in Europe in February 2020 is the most frequent form and causes high viral growth. The previously infrequent D614G mutation is now globally dominant. This variant, which is being tested by many international laboratories, is rapidly spreading across the countries and a series of vaccinated subjects are testing to see if their antibodies can neutralize the new variant of SARS-CoV-2. This variant has a very high viral growth and is less detectable with the RT-PCR technique in the laboratory. It has been reported that the British variant that increases viral load does not cause more severe effects in the respiratory tract and lung disease, therefore, it is certain that the variant is growing rapidly and must be kept under control; for this reason, laboratory data is expected impatiently. The study on the many variants that coronavirus-19 presents is very interesting and complete and clearer data on this topic will be ready in the near future. In addition, it is still unclear whether the different variants discovered in many countries, including Africa, share the same spike protein mutation and therefore, this is another study to elaborate on. In order to be certain and to not have unexpected surprises, we need to reduce the spread and the transmission speed of viral variants that could appear around the world, creating new pandemics. For this reason, the scientific community is on the alert since laboratory tests on serum antibodies from COVID-19 survivors have been reported to be less effective in attacking the variant. In light of the above, the scientific community must be on the alert as larger variants of the spike protein could escape vaccine-induced antibodies, which for now are of great help to the community and can save millions of lives. Deepening the study of spike protein mutations will help to better understand how to combat coronavirus-19 and its variants.

IL-1 induces throboxane-A2 (TxA2) in COVID-19 causing inflammation and micro-thrombi: inhibitory effect of the IL-1 receptor antagonist (IL-1Ra)

IL-1 induces a significant number of metabolic and hematological changes. In experimental animals, IL-1 treatments cause hypotension due to rapid reduction of systemic blood pressure, reduced vascular resistance, increased heart rate and leukocyte aggregations. IL-1 causes endothelial dysfunction, the triggering factor of which may be of a different nature including pathogen infection. This dysfunction, which includes macrophage intervention and increased protein permeability, can be mediated by several factors including cytokines and arachidonic acid products. These effects are caused by the induction of IL-1 in various pathologies, including those caused by pathogenic viral infections, including SARSCoV-2 which provokes COVID-19. Activation of macrophages by coronavirus-19 leads to the release of pro-inflammatory cytokines, metalloproteinases and other proteolytic enzymes that can cause thrombi formation and severe respiratory dysfunction. Patients with COVID-19, seriously ill and hospitalized in intensive care, present systemic inflammation, intravascular coagulopathy with high risk of thrombotic complications, and venous thromboembolism, effects mostly mediated by IL-1. In these patients the lungs are the most critical target organ as it can present an increase in the degradation products of fibrin, fibrinogen and D-dimer, with organ lesions and respiratory failure. It is well known that IL-1 induces itself and another very important pro-inflammatory cytokine, TNF, which also participates in hemodynamic states, including shock syndrome in COVID-19. Both IL-1 and TNF cause pulmonary edema, thrombosis and bleeding. In addition to hypotension and resistance of systemic blood pressure, IL-1 causes leukopenia and thrombocytopenia. The formation of thrombi is the main complication of the circulatory system and functionality of the organ, and represents an important cause of morbidity and mortality. IL-1 causes platelet vascular thrombogenicity also on non-endothelial cells by stimulating the formation of thromboxane A2 which is released into the inflamed environment. IL-1 is the most important immune molecule in inducing fever, since it is involved in the metabolism of arachidonic acid which increases from vascular endothelial organs of the hypothalamus. The pathogenesis of thrombosis, vascular inflammation and angiogenesis involves the mediation of the activation of the prostanoid thromboxane A2 receptor. In 1988, in an interesting article we reported for the first time that IL-1 induces thromboxane B2 (TxB2) releases in activated neutrophils and macrophages. An increase in thromboxane can induce leukocyte aggregation and systemic inflammation, which would account for the dramatic thrombi formation and organ dysfunction. Hence, IL-1 stimulates endothelial cell-leukocyte adhesion, and TXB2 production. All these events are supported by the large increase in neutrophils that adhere to the lung and the decrease in lymphocytes. Therefore, eicosanoids such as TxA2 (detected as TxB2) have a powerful action on vascular inflammation and platelet aggregation, mediating the formation of thrombi. The thrombogenesis that occurs in COVID-19 includes platelet and cell aggregation with clotting abnormalities, and anti-clotting inhibitor agents are used in the prevention and therapy of thrombotic diseases. Prevention of or induction of TXA2 avoids thrombi formation induced by IL-1. However, in some serious vascular events where TxA2 increases significantly, it is difficult to inhibit, therefore, it would be much better to prevent its induction and generation by blocking its inductors including IL-1. The inhibition or lack of formation of IL-1 avoids all the above pathological events which can lead to death of the patient. The treatment of innate immune cells producing IL-1 with IL-1 receptor antagonist (IL-1Ra) can avoid hemodynamic changes, septic shock and organ inflammation by carrying out a new therapeutic efficacy on COVID-19 induced by SARS-CoV-2.

Coronavirus-19 (SARS-CoV-2) induces acute severe lung inflammation via IL-1 causing cytokine storm in COVID-19: a promising inhibitory strategy.

SARS-Cov-2 infection causes local and systemic inflammation mediated by pro-inflammatory cytokines and COX-2 eicosanoid products with metabolic dysfunction and tissue damage that can lead to patient death. These effects are primarily induced by IL-1 cytokines, which are involved in the elevation of hepatic acute phase proteins and fever. IL-1 has a broad spectrum of biological activities and participates in both innate and acquired immunity. In infections, IL-1 induces gene expression and synthesis of several cytokines/chemokines in both macrophages and mast cells (MCs). The activation of MCs triggers the secretion of mediators stored in the granules, and the de novo synthesis of pro-inflammatory cytokines. In microorganism infections, the release of IL-1 macrophage acts on adhesion molecules and endothelial cells leading to hypotension and septic shock syndrome. IL-1 activated by SARS-CoV-2 stimulates the secretion of TNF, IL-6 and other cytokines, a pro-inflammatory complex that can lead to cytokine storm and be deleterious in both lung and systemically. In SARS-CoV-2 septic shock, severe metabolic cellular abnormalities occur which can lead to death. Here, we report that SARS-CoV-2 induces IL-1 in macrophages and MCs causing the induction of gene expression and activation of other pro-inflammatory cytokines. Since IL-1 is toxic, its production from ubiquitous MCs and macrophages activated by SARS-CoV-2 can also provokes both gastrointestinal and brain disorders. Furthermore, in these immune cells, IL-1 also elevates nitric oxide, and the release of inflammatory arachidonic acid products such as prostaglndins and thromboxane A2. All together these effects can generate cytokine storm and be the primary cause of severe inflammation with respiratory distress and death. Although, IL-1 administered in low doses may be protective; when it is produced in high doses in infectious diseases can be detrimental, therefore, IL-1 blockade has been studied in many human diseases including sepsis, resulting that blocking it is absolutely necessary. This definitely nurtures hope for a new effective therapeutic treatment. Recently, two interesting anti-IL-1 cytokines have been widely described: IL-37 and IL-1Ra. IL-37, by blocking IL-1, has been observed to have anti-inflammatory action in rodents in vivo and in transfected cells. It has been reported that IL-37 is a very powerful protein which inhibits inflammation and its inhibition can be a valid therapeutic strategy. IL-37 is a natural suppressor of inflammation that is generated through a caspase-1 that cleaves pro-IL-37 into mature IL-37 which translocates to the nucleus and inhibits the transcription of pro-inflammatory genes; while IL-1Ra inhibits inflammation by binding IL-1 to its IL-1R (receptor). We firmly believe that blocking IL-1 with an anti-inflammatory cytokine such as IL-37 and/or IL-1Ra is an effective valid therapy in a wide spectrum of inflammatory disorders including SARS-CoV-2-induced COVID-19. Here, we propose for the first time that IL-37, by blocking IL-1, may have an important role in the therapy of COVID-19.

Mast cells activated by SARS-CoV-2 release histamine which increases IL-1 levels causing cytokine storm and inflammatory reaction in COVID-19.

SARS-CoV-2 virus is an infectious agent commonly found in certain mammalian animal species and today also in humans. SARS-CoV-2, can cause a pandemic infection with severe acute lung injury respiratory distress syndrome in patients with COVID-19, that can lead to patient death across all ages. The pathology associated with pandemic infection is linked to an over-response of immune cells, including virus-activated macrophages and mast cells (MCs). The local inflammatory response in the lung that occurs after exposure to SARS-CoV-2 is due to a complex network of activated inflammatory innate immune cells and structural lung cells such as bronchial epithelial cells, endothelial cells and fibroblasts. Bronchial epithelial cells and fibroblasts activated by SARS-CoV-2 can result in the up-regulation of pro-inflammatory cytokines and induction of MC differentiation. In addition, endothelial cells which control leukocyte traffic through the expression of adhesion molecules are also able to amplify leukocyte activation by generating interleukin (IL)-1, IL-6 and CXC chemokines. In this pathologic environment, the activation of mast cells (MCs) causes the release of histamine, proteases, cytokines, chemokines and arachidonic acid compounds, such as prostaglandin D2 and leukotrienes, all of which are involved in the inflammatory network. Histamine is stored endogenously within the secretory granules of MCs and is released into the vessels after cell stimulation. Histamine is involved in the expression of chemokine IL-8 and cytokine IL-6, an effect that can be inhibited by histamine receptor antagonists. IL-1 is a pleiotropic cytokine that is mainly active in inflammation and immunity. Alveolar macrophages activated by SARS-CoV-2 through the TLR produce IL-1 which stimulates MCs to produce IL-6. IL-1 in combination with IL-6 leads to excessive inflammation which can be lethal. In an interesting study published several years ago (by E. Vannier et al., 1993), it was found that histamine as well as IL-1 are implicated in the pathogenesis of pulmonary inflammatory reaction, after micorganism immune cell activation. IL-1 in combination with histamine can cause a strong increase of IL-1 levels and, consequently, a higher degree of inflammation. However, it has been reported that histamine alone has no effect on IL-1 production. Furthermore, histamine enhances IL-1-induced IL-6 gene expression and protein synthesis via H2 receptors in peripheral monocytes. Therefore, since MCs are large producers of histamine in inflammatory reactions, this vasoactive amine, by increasing the production of IL-1, can amplify the inflammatory process in the lung infected with SARS-CoV-2. Here, we have proposed for the first time an emerging role for histamine released by MCs which in combination with IL-1 can cause an increase in lung inflammation induced by the viral infection SARS-CoV-2.

Induction of pro-inflammatory cytokines (IL-1 and IL-6) and lung inflammation by COVID-19: anti-inflammatory strategies

COVID-19 (coronavirus disease-19) involves humans as well as animals and may cause serious damage to the respiratory tract including the lung. This pathogenic virus has been identified in swabs performed on the throat and nose of patients who suffer from or are suspected of the disease. When COVID-19 infect the upper and lower respiratory tract it can cause mild or highly acute respiratory syndrome with consequent release of pro-inflammatory cytokines, including interleukin (IL)-1b and IL-6. The binding of COVID-19 to the Toll Like Receptor (TLR) causes the release of pro-IL-1b which is cleaved by caspase-1, followed by inflammasome activation and production of active mature IL-1b which is a mediator of lung inflammation, fever and fibrosis. Suppression of pro-inflammatory IL-1 family members and IL-6 have been shown to have a therapeutic effect in many inflammatory diseases, including viral infections. Cytokine IL-37 has the ability to suppress innate and acquired immune response and also has the capacity to inhibit inflammation by acting on IL-18Ra receptor. IL-37 performs its immunosuppressive activity by acting on mTOR and increasing the adenosine monophosphate (AMP) kinase. This cytokine inhibits class II histocompatibility complex (MHC) molecules and inflammation in inflammatory diseases by suppressing MyD88 and subsequently IL-1β, IL-6, TNF and CCL2. The suppression of IL-1b by IL-37 in inflammatory state induced by COVID-19 can have a new therapeutic effect previously unknown. Another inhibitory cytokine is IL-38, the newest cytokine of the IL-1 family members, produced by several immune cells including B cells and macrophages. IL-38 is also a suppressor cytokine which inhibits IL-1b and other pro-inflammatory IL-family members. IL-38 is a potential therapeutic cytokine which inhibits inflammation in viral infections including that caused by COVID-19, providing a new relevant strategy.