Purinergic receptor ligands: the cytokine storm attenuators, potential therapeutic agents for the treatment of COVID-19

Retrospective Clinical Investigation into the Association Between Abnormal Blood Clotting, Oral Anticoagulant Therapy, and Medium-Term Mortality in a Cohort of COVID-19 Patients

Background/Objectives: People affected by COVID-19 are exposed to abnormal clotting and endothelial dysfunction, which may trigger thromboembolic events. This study aimed at retrospectively investigating whether oral anticoagulant therapy (OAT), encompassing either direct oral anticoagulants (DOACs), mainly apixaban, or the vitamin K antagonist (VKA) warfarin, could have impacted medium-term mortality in a cohort of SARS-CoV-2 patients. Methods: Among 1238 COVID-19 patients, hospitalized from 17 March 2020 to 15 June 2021, 247 survivors and 247 deceased within 90 days from hospitalization were matched 1:1 based on age, sex, and intensive care unit (ICU) admission within three days. Conditional logistic regression was used to estimate associations by means of odds ratio (OR) with a 95% confidence interval (CI). Results: A univariate regression analysis suggested that OAT, no differently from subcutaneous low-molecular-weight heparins (LMWHs) during hospitalization, has no significant impact (p value > 0.05) on medium-term mortality. A multivariate analysis, limited to baseline variables (i.e., comorbidities and pharmacotherapies at hospital admission) showing significant association (p < 0.05) to mortality in a univariate analysis, revealed that, compared to patients living at 90 days from hospitalization, deceased patients had cancer histories (OR 1.75, CI 1.06-2.90, p = 0.029) or suffered from asthma (OR 2.25, CI 1.13-4.47, p = 0.021). In contrast, heart failure (HF), atrial fibrillation (AF), arteriopathy, chronic obstructive pulmonary disease (COPD), and kidney failure (KF), which, in a univariate analysis, were found to be associated with the endpoint (p < 0.05), lost significance in a multivariate analysis. Therapy at admission with aldosterone antagonists also appeared to be associated with medium-term mortality (OR 2.49, CI 1.52-4.08, p < 0.001); whereas, vitamin D supplementation during hospitalization appeared to be beneficial. Although not conclusive, a search into the Eudravigilance database, combined with consulting a digital predictive platform (PLATO, polypharmacology platform prediction), suggested potential off-target activities, which might contribute to increasing the severity of SARS-CoV-2 infection. Conclusions: This retrospective clinical study furnished evidences of the impact of OAT, comorbidities and other pharmacological treatments on COVID-19 clinical course.

Current treatment of Psoriasis triggered by Cytokine Storm and future immunomodulation strategies

Psoriasis is a chronic condition caused by an inflammation mediated mainly by cytokines and T cells. In COVID-19, the same type of imbalance is common, generating the Cytokine Storm and promoting a worsening in the skin conditions of patients with autoimmune disorders, such as Psoriasis. In this context, one of the main mediators of immune responses presented by SARS-CoV-2 infected patients is the Purinergic System. This immunological resource is capable of stimulating the hyperinflammatory state presented by infected individuals, mainly by the activity of the P2X7 receptor, culminating in the Cytokine Storm and consequently in the Psoriasis crisis. Currently, different drugs are used for patients with Psoriasis, such as immunosuppressants and small molecules; however, the safety of these drugs in infected patients has not been analyzed yet. In this context, studies are being developed to evaluate the possible administration of these traditional drugs to COVID-19 patients with Psoriasis crisis. Along with that, researchers must evaluate the potential of administrating P2X7 antagonists to these patients as well, improving both the systemic and the dermatological prognostics of patients, by reducing the Cytokine Storm and its general effects, but also avoiding the provocation of Psoriasis crisis.

Cytokine storm in human monkeypox: A possible involvement of purinergic signaling

Some evidence has indicated that monkeypox can induce a cytokine storm. Purinergic signaling is a cell pathway related to the cytokine storm. However, the precise mechanisms that lead to cytokine storms in monkeypox infections and the possible involvement of purinergic signaling in the immune response to this virus remain unknown. In this review article, we aimed to highlight a body of scientific evidence that consolidates the role of the cytokine storm in monkeypox infection and proposes a new hypothesis regarding the roles of purinergic signaling in this immune-mediated mechanism. We further suggested some purinergic signaling modulators to mitigate the deleterious and aggravating effects of immune dysregulation in human monkeypox virus infection by inhibiting P2X3, P2X7, P2Y2, and P2Y12, reducing inflammation, and activating A1 and A2A receptors to promote an anti-inflammatory response.

Purinergic signaling: decoding its role in COVID-19 pathogenesis and promising treatment strategies

The pathogenesis of coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2), is complex and involves dysregulated immune responses, inflammation, and coagulopathy. Purinergic signaling, mediated by extracellular nucleotides and nucleosides, has emerged as a significant player in the pathogenesis of COVID-19. Extracellular adenosine triphosphate (ATP), released from damaged or infected cells, is a danger signal triggering immune responses. It activates immune cells, releasing pro-inflammatory cytokines, contributing to the cytokine storm observed in severe COVID-19 cases. ATP also promotes platelet activation and thrombus formation, contributing to the hypercoagulability seen in COVID-19 patients. On the other hand, adenosine, an immunosuppressive nucleoside, can impair anti-viral immune responses and promote tissue damage through its anti-inflammatory effects. Modulating purinergic receptors represents a promising therapeutic strategy for COVID-19. Understanding the role of purinergic signaling in COVID-19 pathogenesis and developing targeted therapeutic approaches can potentially improve patient outcomes. This review focuses on the part of purinergic signaling in COVID-19 pathogenesis and highlights potential therapeutic approaches targeting purinergic receptors.

Effects of Purinergic Receptor Deletion or Pharmacologic Modulation on Pulmonary Inflammation in Mice

COVID-19 disease is associated with progressive accumulation of SARS-CoV-2-specific mRNA, which is recognized by innate immune receptors, such as TLR3. This in turn leads to dysregulated production of multiple cytokines, including IL-6, IFN-γ, CXCL1, and TNF-α. Excessive production of these cytokines leads to acute lung injury (ALI), which consequently compromises alveolar exchange of O2 and CO2. It is therefore of considerable interest to develop novel therapies that reduce pulmonary inflammation and stem production of pro-inflammatory cytokines, potentially for COVID-19 patients that are at high risk of developing severe disease. Purinergic signaling has a central role in fine-tuning the innate immune system, with P2 (nucleotide) receptor antagonists and adenosine receptor agonists having anti-inflammatory effects. Accordingly, we focused here on the potential role of purinergic receptors in driving neutrophilic inflammation and cytokine production in a mouse model of pulmonary inflammation. To mimic the effects of SARS-CoV-2-specific RNA accumulation in mice, we administered progressively increasing daily doses of a viral mimetic, polyinosinic:polycytidylic acid [poly(I:C)] into the airways of mice over the course of 1 week. Some mice also received increasing daily doses of ovalbumin to mimic virus-encoded protein accumulation. Animals receiving both poly(I:C) and ovalbumin displayed particularly high cytokine levels and neutrophilia, suggestive of both innate and antigen-specific, adaptive immune responses. The extent of these responses was diminished by genetic deletion (P2Y14R, P2X7R) or pharmacologic modulation (P2Y14R antagonists, A3AR agonists) of purinergic receptors. These results suggest that pharmacologic modulation of select purinergic receptors might be therapeutically useful in treating COVID-19 and other pulmonary infections.

Alterations in CD39/CD73 axis of T cells associated with COVID-19 severity

Purinergic signaling modulates immune function and is involved in the immunopathogenesis of several viral infections. This study aimed to investigate alterations in purinergic pathways in coronavirus disease 2019 (COVID‐19) patients. Mild and severe COVID‐19 patients had lower extracellular adenosine triphosphate and adenosine levels, and higher cytokines than healthy controls. Mild COVID‐19 patients presented lower frequencies of CD4⁺CD25⁺CD39⁺ (activated/memory regulatory T cell [mTreg]) and increased frequencies of high‐differentiated (CD27⁻CD28⁻) CD8⁺ T cells compared with healthy controls. Severe COVID‐19 patients also showed higher frequencies of CD4⁺CD39⁺, CD4⁺CD25⁻CD39⁺ (memory T effector cell), and high‐differentiated CD8⁺ T cells (CD27⁻CD28⁻), and diminished frequencies of CD4⁺CD73⁺, CD4⁺CD25⁺CD39⁺ mTreg cell, CD8⁺CD73⁺, and low‐differentiated CD8⁺ T cells (CD27⁺CD28⁺) in the blood in relation to mild COVID‐19 patients and controls. Moreover, severe COVID‐19 patients presented higher expression of PD‐1 on low‐differentiated CD8⁺ T cells. Both severe and mild COVID‐19 patients presented higher frequencies of CD4⁺Annexin‐V⁺ and CD8⁺Annexin‐V⁺ T cells, indicating increased T‐cell apoptosis. Plasma samples collected from severe COVID‐19 patients were able to decrease the expression of CD73 on CD4⁺ and CD8⁺ T cells of a healthy donor. Interestingly, the in vitro incubation of peripheral blood mononuclear cell from severe COVID‐19 patients with adenosine reduced the nuclear factor‐κB activation in T cells and monocytes. Together, these data add new knowledge to the COVID‐19 immunopathology through purinergic regulation.

The Potential of Purinergic Signaling to Thwart Viruses Including SARS-CoV-2

A long-shared evolutionary history is congruent with the multiple roles played by purinergic signaling in viral infection, replication and host responses that can assist or hinder viral functions. An overview of the involvement of purinergic signaling among a range of viruses is compared and contrasted with what is currently understood for SARS-CoV-2. In particular, we focus on the inflammatory and antiviral responses of infected cells mediated by purinergic receptor activation. Although there is considerable variation in a patient's response to SARS-CoV-2 infection, a principle immediate concern in Coronavirus disease (COVID-19) is the possibility of an aberrant inflammatory activation causing diffuse lung oedema and respiratory failure. We discuss the most promising potential interventions modulating purinergic signaling that may attenuate the more serious repercussions of SARS-CoV-2 infection and aspects of their implementation.