Repurposing drugs targeting the P2X7 receptor to limit hyperinflammation and disease during influenza virus infection

Changes in the Pannexin Channel in Ileum Myenteric Plexus and Intestinal Motility Following Ischemia and Reperfusion

BACKGROUND

Intestinal ischemia affects the functioning of the Enteric Nervous System (ENS). Pannexin-1 channel participates in cell communication and extracellular signaling. Probenecid (PB) is a pannexin-1 channel inhibitor, which can be a potential treatment for intestinal ischemia.

AIM

Study the effects of ileal ischemia and reperfusion (I/R) and PB treatment on myenteric neurons and in rats.

METHODS

Male Wistar rats were used for I/R induction, the ileal vessels were occluded for 45 min and reperfusion was performed after this time. The Sham groups underwent all surgical procedures without obstruction of the ileal vessels. Animals were euthanized 24 h or 14d post-I/R. The PB group received an injection of PB post-I/R. Ileal segments were collected for immunofluorescence analyses to identify neurons calretinin immunoreactive (-ir) and pannexin-1-ir. Neuronal density (cells/field), area (μm2), intestinal motility, and ultrastructural analyses were performed.

KEY RESULTS

The pannexin-1 channel was double-labeled with calretinin-ir neurons. Neuronal density reduced by 21% reduction in calretinin-ir neurons in the I/R 24 h group and recovered 26% in the PB 24 h group. In the 14d group, there was a 23% reduction in calretinin-ir neurons in the I/R 14d group and a recovery of 26% in the PB 14d group. The analysis of the contraction after electrical simulation was lower in the I/R 14 d group and recovered in the PB 14d.

CONCLUSIONS AND INFERENCES

Intestinal I/R affects myenteric neurons and causes morphological and functional changes. PB was able to attenuate the effects of I/R and could constitute a therapeutic tool for intestinal I/R.

NLRP3 deficiency abrogates silica-induced neutrophil infiltration, pulmonary damage and fibrosis

BACKGROUND

Silicosis is a progressive and often fatal occupational lung disease. The NLRP3 inflammasome is an innate immune sensor that is activated by silica. Accumulating evidence has implicated a role for NLRP3 in silicosis pathogenesis. In this study, we mechanistically elucidated the contribution of NLRP3 to silica-induced pulmonary disease.

METHODS

The in vivo role of NLRP3 was investigated following intranasal delivery of 2 mg of silica or diluent alone to wildtype, NLRP3 reporter, and NLRP3-deficient mice. Protein expression, inflammation, and histopathology were analyzed in the lung.

RESULTS

Intranasal administration of silica recapitulated the key pathological features of human silicosis, including nonresolving inflammation, the formation of silicotic nodules, and diffuse lung fibrosis. A reporter mouse placed under the native NLRP3 promoter revealed silica rapidly upregulated NLRP3 expression throughout the lung. NLRP3-deficient mice displayed marked early reductions in silica-induced IL-1β and IL-18 levels in the airways. Additionally, NLRP3 deficiency impaired the rapid infiltration of conventional Siglec-F- and fibrotic Siglec-F+ neutrophils, which correlated with reduced levels of neutrophil elastase. Deficiency in acute NLRP3-mediated inflammation correlated with significantly reduced pulmonary transforming growth factor beta and alpha smooth muscle actin expression, tissue damage, and fibrosis in the chronic phase of disease progression. Importantly, this included reduced silicotic nodule size and cellularity.

CONCLUSIONS

These findings highlight a major detrimental role for the NLRP3 inflammasome in driving silica-induced pulmonary neutrophil infiltration, TGFβ-mediated myofibroblast activation, tissue damage, and fibrosis.

Comprehensive insights into potential roles of purinergic P2 receptors on diseases: Signaling pathways involved and potential therapeutics

BACKGROUND

Purinergic P2 receptors, which can be divided into ionotropic P2X receptors and metabotropic P2Y receptors, mediate cellular signal transduction of purine or pyrimidine nucleoside triphosphates and diphosphate. Based on the wide expression of purinergic P2 receptors in tissues and organs, their significance in homeostatic maintenance, metabolism, nociceptive transmission, and other physiological processes is becoming increasingly evident, suggesting that targeting purinergic P2 receptors to regulate biological functions and signal transmission holds significant promise for disease treatment.

AIM OF REVIEW

This review highlights the detailed mechanisms by which purinergic P2 receptors engage in physiological and pathological progress, as well as providing prospective strategies for discovering clinical drug candidates.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The purinergic P2 receptors regulate complex signaling and molecular mechanisms in nervous system, digestive system, immune system and as a result, controlling physical health states and disease progression. There has been a significant rise in research and development focused on purinergic P2 receptors, contributing to an increased number of drug candidates in clinical trials. A few influential pioneers have laid the foundation for advancements in the evaluation, development, and of novel purinergic P2 receptors modulators, including agonists, antagonists, pharmaceutical compositions and combination strategies, despite the different scaffolds of these drug candidates. These advancements hold great potential for improving therapeutic outcomes by specifically targeting purinergic P2 receptors.

Purinergic signaling in the battlefield of viral infections

Purinergic signaling has been associated with immune defenses against pathogens such as bacteria, protozoa, fungi, and viruses, acting as a sentinel system that signals to the cells when a threat is present. This review focuses on the roles of purinergic signaling and its therapeutic potential for viral infections. In this context, the purinergic system may play potent antiviral roles by boosting interferon signaling. In other cases, though, it can contribute to a hyperinflammatory response and disease severity, resulting in poor outcomes, such as during flu and potentially COVID-19. Lastly, a third situation may occur since viruses are obligatory intracellular parasites that hijack the host cell machinery for their infection and replication. Viruses such as HIV-1 use the purinergic system to favor their infection and persistence within the host cell. Therefore, understanding the particular nuances of purinergic signaling in each viral infection may contribute to designing proper therapeutic strategies to treat viral diseases.

Does Adenosine Triphosphate via Purinergic Receptor Signalling Fuel Pulmonary Fibrosis?

BACKGROUND

Interstitial lung diseases (ILD) are poorly understood disorders characterised by diffuse damage to the lung parenchyma, with inflammation and fibrosis. Some manifest a progressive fibrotic phenotype with high fatality and limited treatment options, such as idiopathic pulmonary fibrosis.

SUMMARY

The degree to which inflammation plays a role in fibrosis progression is unknown. However, wound healing and fibrosis are intricate processes influenced by various inflammatory factors. Extracellular nucleosides and nucleotides, including adenosine triphosphate, activate pro-inflammatory responses to innate immunity and are widely implicated in tissue fibrosis across different organs. The pro-inflammatory effects of extracellular nucleotides occur via P1 and P2 purinergic receptors, expressed across the lung and immune system, and have been implicated in various pulmonary diseases including pulmonary fibrosis. This review amalgamates available data on the complex role of P1 and P2 purinergic receptor signalling in pulmonary fibrosis and discusses perspectives for novel treatments.

KEY MESSAGES

Purinergic signalling plays a complex and pivotal role in pulmonary fibrosis, warranting further study. The intricate interplay between P1 and P2 receptor pathways necessitates a comprehensive approach to understand their collective impact. While evidence from preclinical models is promising, human studies are essential for further understanding of pulmonary fibrosis. Advances in receptor-specific agonists and antagonists provide novel avenues for research and may ultimately lead to new therapies for patients.

BACKGROUND

Interstitial lung diseases (ILD) are poorly understood disorders characterised by diffuse damage to the lung parenchyma, with inflammation and fibrosis. Some manifest a progressive fibrotic phenotype with high fatality and limited treatment options, such as idiopathic pulmonary fibrosis.

SUMMARY

The degree to which inflammation plays a role in fibrosis progression is unknown. However, wound healing and fibrosis are intricate processes influenced by various inflammatory factors. Extracellular nucleosides and nucleotides, including adenosine triphosphate, activate pro-inflammatory responses to innate immunity and are widely implicated in tissue fibrosis across different organs. The pro-inflammatory effects of extracellular nucleotides occur via P1 and P2 purinergic receptors, expressed across the lung and immune system, and have been implicated in various pulmonary diseases including pulmonary fibrosis. This review amalgamates available data on the complex role of P1 and P2 purinergic receptor signalling in pulmonary fibrosis and discusses perspectives for novel treatments.

KEY MESSAGES

Purinergic signalling plays a complex and pivotal role in pulmonary fibrosis, warranting further study. The intricate interplay between P1 and P2 receptor pathways necessitates a comprehensive approach to understand their collective impact. While evidence from preclinical models is promising, human studies are essential for further understanding of pulmonary fibrosis. Advances in receptor-specific agonists and antagonists provide novel avenues for research and may ultimately lead to new therapies for patients.

Harnessing Endogenous Peptide Compounds as Potential Therapeutics for Severe Influenza

BACKGROUND

Excessive pulmonary inflammation and damage are characteristic features of severe influenza virus infections. LAT8881 is a synthetic 16-amino acid cyclic peptide form of a naturally occurring C-terminal fragment of human growth hormone with therapeutic efficacy against influenza. Shorter linear peptides are typically easier to manufacture and formulate for delivery than larger cyclic peptides. A 6-amino acid linear peptide fragment of LAT8881, LAT9997, was investigated as a potential influenza therapy.

METHODS

LAT9997 was evaluated for its potential to limit disease in a preclinical mouse model of severe influenza infection.

RESULTS

Intranasal treatment of mice with either LAT8881 or LAT9997 from day 1 following influenza infection significantly improved survival outcomes. Initiating LAT9997 treatment at the onset of severe disease also significantly improved disease severity. Greater disease resistance in LAT9997-treated mice correlated with reduced lung immunopathology, damage markers, vascular leak, and epithelial cell death. Treatment reduced viral loads, cytokines, and neutrophil infiltration in the airways yet maintained protective alveolar macrophages in a dose-dependent manner. Sequential trimming of N- and C-terminal amino acids from LAT9997 revealed a structure-activity relationship.

CONCLUSIONS

These findings provide preclinical evidence that therapeutic LAT9997 treatment limits viral burden and characteristic features of severe influenza, including hyperinflammation and lung damage.

SUMMARY

Excessive pulmonary inflammation and damage are characteristic features of severe influenza virus infections. LAT9997 is a linear peptide fragment derived from human growth hormone. This study provides preclinical evidence that therapeutic LAT9997 treatment limits viral burden, hyperinflammation, and lung damage.

Probenecid Inhibits Human Metapneumovirus (HMPV) Replication In Vitro and in BALB/c Mice

Human metapneumovirus (HMPV) is an important cause of acute respiratory tract infection and causes significant morbidity and mortality. There is no specific antiviral drug to treat HMPV or vaccine to prevent HMPV. This study determined if probenecid, a host-targeting antiviral drug, had prophylactic (pre-virus) or therapeutic (post-virus) efficacy to inhibit HMPV replication in LLC-MK2 cells in vitro and in the lungs of BALB/c mice. This study showed that ≥0.5 μM probenecid significantly inhibited HMPV replication in vitro, and 2-200 mg/kg probenecid prophylaxis or treatment reduced HMPV replication in BALB/c mice.

Genetic Polymorphisms of P2RX7 but Not of ADORA2A Are Associated with the Severity of SARS-CoV-2 Infection

SARS-CoV-2 infection ranges from mild to severe presentations, according to the intensity of the aberrant inflammatory response. Purinergic receptors dually control the inflammatory response: while adenosine A2A receptors (A2ARs) are anti-inflammatory, ATP P2X7 receptors (P2X7Rs) exert pro-inflammatory effects. The aim of this study was to assess if there were differences in allelic and genotypic frequencies of a loss-of-function SNP of ADORA2A (rs2298383) and a gain-of-function single nucleotide polymorphism (SNP) of P2RX7 (rs208294) in the severity of SARS-CoV-2-associated infection. Fifty-five individuals were enrolled and categorized according to the severity of the infection. Endpoint genotyping was performed in blood cells to screen for both SNPs. The TT genotype (vs. CT + CC) and the T allele (vs. C allele) of P2RX7 SNP were found to be associated with more severe forms of COVID-19, whereas the association between ADORA2A SNP and the severity of infection was not significantly different. The T allele of P2RX7 SNP was more frequent in people with more than one comorbidity and with cardiovascular conditions and was associated with colorectal cancer. Our findings suggest a more prominent role of P2X7R rather than of A2AR polymorphisms in SARS-CoV-2 infection, although larger population-based studies should be performed to validate our conclusions.

Drug repurposing: A multi targetted approach to treat cardiac disease from existing classical drugs to modern drug discovery

Cardiovascular diseases (CVDs) are characterized by abnormalities in the heart, blood vessels, and blood flow. CVDs comprise a diverse set of health issues. There are several types of CVDs like stroke, endothelial dysfunction, thrombosis, atherosclerosis, plaque instability and heart failure. Identification of a new drug for heart disease takes longer duration and its safety efficacy test takes even longer duration of research and approval. This chapter explores drug repurposing, nano-therapy, and plant-based treatments for managing CVDs from existing drugs which saves time and safety issues with testing new drugs. Existing drugs like statins, ACE inhibitor, warfarin, beta blockers, aspirin and metformin have been found to be useful in treating cardiac disease. For better drug delivery, nano therapy is opening new avenues for cardiac research by targeting interleukin (IL), TNF and other proteins by proteome interactome analysis. Nanoparticles enable precise delivery to atherosclerotic plaques, inflammation areas, and damaged cardiac tissues. Advancements in nano therapeutic agents, such as drug-eluting stents and drug-loaded nanoparticles are transforming CVDs management. Plant-based treatments, containing phytochemicals from Botanical sources, have potential cardiovascular benefits. These phytochemicals can mitigate risk factors associated with CVDs. The integration of these strategies opens new avenues for personalized, effective, and minimally invasive cardiovascular care. Altogether, traditional drugs, phytochemicals along with nanoparticles can revolutionize the future cardiac health care by identifying their signaling pathway, mechanism and interactome analysis.

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.

Toward targeted treatments for silicosis

PURPOSE OF REVIEW

There has been a rapid increase in silicosis cases, particularly related to artificial stone. The key to management is avoidance of silica exposure. Despite this, many develop progressive disease and there are no routinely recommended treatments. This review provides a summary of the literature pertaining to pharmacological therapies for silicosis and examines the plausibility of success of such treatments given the disease pathogenesis.

RECENT FINDINGS

In-vitro and in-vivo models demonstrate potential efficacy for drugs, which target inflammasomes, cytokines, effector cells, fibrosis, autophagy, and oxidation.

SUMMARY

There is some evidence for potential therapeutic targets in silicosis but limited translation into human studies. Treatment of silicosis likely requires a multimodal approach, and there is considerable cross-talk between pathways; agents that modulate both inflammation, fibrosis, autophagy, and ROS production are likely to be most efficacious.

L-Carnitine augments probenecid anti-inflammatory effect in monoiodoacetate-induced knee osteoarthritis in rats: involvement of miRNA-373/P2X7/NLRP3/NF-κB milieu

Osteoarthritis (OA) is a degenerative joint disease, whereas the underlying molecular trails involved in its pathogenesis are not fully elucidated. Hence, the current study aimed to investigate the role of miRNA-373/P2X7/NLRP3/NF-κB trajectory in its pathogenesis as well as the possible anti-inflammatory effects of probenecid and l-carnitine in ameliorating osteoarthritis via modulating this pathway. In the current study, male Sprague Dawley rats were used and monoiodoacetate (MIA)-induced knee osteoarthritis model was adopted. Probenecid and/or L-carnitine treatments for 14 days succeeded in reducing OA knee size and reestablishing motor coordination and joint mobility assessed by rotarod testing. Moreover, different treatments suppressed the elevated serum levels of IL-1β, IL-18, IL-6, and TNF-α via tackling the miRNA-373/P2X7/NLRP3/NF-κB, witnessed as reductions in protein expressions of P2X7, NLRP3, cleaved caspase-1 and NF-κB. These were accompanied by increases in procaspase-1 and IκB protein expression and in miRNA-373 gene expression OA knee to various extents. In addition, different regimens reversed the abnormalities observed in the H and E as well as Safranin O-Fast green OA knees stained sections. Probenecid or l-carnitine solely showed comparable results on the aforementioned parameters, whereas the combination therapy had the most prominent effect on ameliorating the aforementioned parameters. In conclusion, l-carnitine augmented the probenecid's anti-inflammatory effect to attenuate MIA-induced osteoarthritis in rats by provoking the miRNA-373 level and inhibiting the P2X7/NLRP3/NF-κB milieu, leading to the suppression of serum inflammatory cytokines: IL-1β, IL-18, IL-6, and TNF-α. These findings suggest the possibility of using probenecid and l-carnitine as a useful therapeutic option for treatment of osteoarthritis.

Probenecid Inhibits Influenza A(H5N1) and A(H7N9) Viruses In Vitro and in Mice

Avian influenza (AI) viruses cause infection in birds and humans. Several H5N1 and H7N9 variants are highly pathogenic avian influenza (HPAI) viruses. H5N1 is a highly infectious bird virus infecting primarily poultry, but unlike other AIs, H5N1 also infects mammals and transmits to humans with a case fatality rate above 40%. Similarly, H7N9 can infect humans, with a case fatality rate of over 40%. Since 1996, there have been several HPAI outbreaks affecting humans, emphasizing the need for safe and effective antivirals. We show that probenecid potently inhibits H5N1 and H7N9 replication in prophylactically or therapeutically treated A549 cells and normal human broncho-epithelial (NHBE) cells, and H5N1 replication in VeroE6 cells and mice.

Regulation and functions of the NLRP3 inflammasome in RNA virus infection

Virus infection is one of the greatest threats to human life and health. In response to viral infection, the host's innate immune system triggers an antiviral immune response mostly mediated by inflammatory processes. Among the many pathways involved, the nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome has received wide attention in the context of viral infection. The NLRP3 inflammasome is an intracellular sensor composed of three components, including the innate immune receptor NLRP3, adaptor apoptosis-associated speck-like protein containing CARD (ASC), and the cysteine protease caspase-1. After being assembled, the NLRP3 inflammasome can trigger caspase-1 to induce gasdermin D (GSDMD)-dependent pyroptosis, promoting the maturation and secretion of proinflammatory cytokines such as interleukin-1 (IL-1β) and interleukin-18 (IL-18). Recent studies have revealed that a variety of viruses activate or inhibit the NLRP3 inflammasome via viral particles, proteins, and nucleic acids. In this review, we present a variety of regulatory mechanisms and functions of the NLRP3 inflammasome upon RNA viral infection and demonstrate multiple therapeutic strategies that target the NLRP3 inflammasome for anti-inflammatory effects in viral infection.

Antiviral Activity of Probenecid and Oseltamivir on Influenza Virus Replication

Influenza can cause respiratory infections, leading to significant morbidity and mortality in humans. While current influenza vaccines offer varying levels of protection, there remains a pressing need for effective antiviral drugs to supplement vaccine efforts. Currently, the FDA-approved antiviral drugs for influenza include oseltamivir, zanamivir, peramivir, and baloxavir marboxil. These antivirals primarily target the virus, making them vulnerable to drug resistance. In this study, we evaluated the efficacy of the neuraminidase inhibitor, oseltamivir, against probenecid, which targets the host cells and is less likely to engender resistance. Our results show that probenecid has superior antiviral efficacy compared to oseltamivir in both in vitro replication assays and in vivo mouse models of influenza infection.

Aggregated Hendra virus C-protein activates the NLRP3 inflammasome to induce inflammation

BACKGROUND

Hendra virus is an emerging virus with a geographically broad host reservoir. In humans, Hendra virus causes excessive inflammatory disease of the lung and nervous system. Our current understanding as to how Hendra virus or what factors induce inflammation is limited and as such, there are currently no therapeutic options available for patients who contract Hendra virus. Recent studies have identified viral aggregating proteins as drivers of inflammation in influenza A virus and SARS-CoV-2 virus. In this study, we sought to identify potential aggregating Hendra virus proteins as proof-of-concept that inflammasome activation may induce inflammation and contribute to disease pathology.

RESULTS

Here, we have identified that a peptide analogue of Hendra virus C protein (termed HeVc) forms aggregates and activates the NLRP3 inflammasome through phagocytic uptake into cells in vitro. Treatment of cells with the specific NLRP3 inhibitor MCC950 ameliorated IL-1β secretion responses in vitro. Critically, in vivo intranasal inoculation of mice with aggregated HeVc peptide induced pulmonary inflammation, suggesting HeVc may drive immunopathology during infection. Importantly, mice treated with MCC950 demonstrated reduced IL-1β secretion into the bronchoalveolar space, highlighting the role of NLRP3 in host HeV infections and a potential therapeutic strategy to reduce disease pathology.

CONCLUSION

Taken together, these results identify Hendra virus C protein as a possible contributor to immunopathology during Hendra virus infections. Importantly, these studies highlight a potential role for NLRP3 in driving disease-associated inflammation, critically identifying a possible therapeutic strategy to alleviate disease-associated inflammation of infected patients through targeting of the NLRP3 inflammasome.

Gasdermin D promotes hyperinflammation and immunopathology during severe influenza A virus infection

Excessive inflammation and tissue damage during severe influenza A virus (IAV) infection can lead to the development of fatal pulmonary disease. Pyroptosis is a lytic and pro-inflammatory form of cell death executed by the pore-forming protein gasdermin D (GSDMD). In this study, we investigated a potential role for GSDMD in promoting the development of severe IAV disease. IAV infection resulted in cleavage of GSDMD in vivo and in vitro in lung epithelial cells. Mice genetically deficient in GSDMD (Gsdmd-/-) developed less severe IAV disease than wildtype mice and displayed improved survival outcomes. GSDMD deficiency significantly reduced neutrophil infiltration into the airways as well as the levels of pro-inflammatory cytokines TNF, IL-6, MCP-1, and IL-1α and neutrophil-attracting chemokines CXCL1 and CXCL2. In contrast, IL-1β and IL-18 responses were not largely impacted by GSDMD deficiency. In addition, Gsdmd-/- mice displayed significantly improved influenza disease resistance with reduced viral burden and less severe pulmonary pathology, including decreased epithelial damage and cell death. These findings indicate a major role for GSDMD in promoting damaging inflammation and the development of severe IAV disease.

Oral Probenecid for Nonhospitalized Adults with Symptomatic Mild-to-Moderate COVID-19

Probenecid is an orally bioavailable, uricosuric agent that was first approved in 1951 for the treatment of gout, but was later found to have potent, broad-spectrum antiviral activity against several respiratory viruses including SARS-CoV-2. We conducted a phase 2 randomized, placebo-controlled, single-blind, dose-range finding study in non-hospitalized patients with symptomatic, mild-to-moderate COVID-19. Patients were randomly assigned in a 1:1:1 ratio to receive either 500 mg of probenecid, 1000 mg of probenecid, or a matching placebo every 12 h for five days. The patients' COVID-19 viral load hospitalization, or death from any cause through day 28, as well as safety, were evaluated. COVID-19-related symptoms were assessed at baseline, and on days 3, 5, 10, 15, and 28. The primary endpoints of the study were time to first negative SARS-CoV-2 viral test (or viral clearance) and the proportion of patients that were symptom-free at day 5. A total of 75 patients were randomized, with 25 patients in each group. All of the patients completed the study as planned with no hospitalizations or deaths being reported. The median time to viral clearance was significantly shorter for the probenecid 1000 mg group than for placebo (7 days vs. 11 days, respectively; p < 0.0001), and for the probenecid 500 mg group versus placebo (9 days vs. 11 days, respectively; p < 0.0001). In addition, the median time to viral clearance was significantly shorter for the probenecid 1000 mg group than for the probenecid 500 mg group (7 days vs. 9 days, respectively; p < 0.0001). All patients reported at least one COVID-19-related symptom on days 3 and 5; however, on day 10, a significantly greater proportion of patients receiving probenecid 1000 mg reported the complete resolution of symptoms versus placebo (68% vs. 20%, respectively; p = 0.0006), as well as for those receiving probenecid 500 mg versus placebo (56% vs. 20%, respectively, p = 0.0087). The incidence of adverse events during treatment was similar across all groups for any adverse event, and was 12%. All events were mild with no serious adverse events reported and no discontinuations due to an adverse event. The treatment of patients with symptomatic, mild-to-moderate COVID-19 with probenecid resulted in a significant, dose-dependent decrease in the time to viral clearance and a significantly higher proportion of patients reporting complete symptom resolution by day 10. (Supported by TrippBio; ClinicalTrials.gov number, NCT05442983 and Clinical Trials Registry India number CTRI/2022/07/043726).

Targeting Inflammasome Activation in Viral Infection: A Therapeutic Solution?

Inflammasome activation is exclusively involved in sensing activation of innate immunity and inflammatory response during viral infection. Accumulating evidence suggests that the manipulation of inflammasome assembly or its interaction with viral proteins are critical factors in viral pathogenesis. Results from pilot clinical trials show encouraging results of NLRP3 inflammasome suppression in reducing mortality and morbidity in SARS-CoV-2-infected patients. In this article, we summarize the up-to-date understanding of inflammasomes, including NLRP3, AIM2, NLRP1, NLRP6, and NLRC4 in various viral infections, with particular focus on RNA viruses such as SARS-CoV-2, HIV, IAV, and Zika virus and DNA viruses such as herpes simplex virus 1. We also discuss the current achievement of the mechanisms involved in viral infection-induced inflammatory response, host defense, and possible therapeutic solutions.

A novel dual NLRP1 and NLRP3 inflammasome inhibitor for the treatment of inflammatory diseases

Objectives

Inflammasomes induce maturation of the inflammatory cytokines IL-1β and IL-18, whose activity is associated with the pathophysiology of a wide range of infectious and inflammatory diseases. As validated therapeutic targets for the treatment of acute and chronic inflammatory diseases, there has been intense interest in developing small-molecule inhibitors to target inflammasome activity and reduce disease-associated inflammatory burden.

Methods

We examined the therapeutic potential of a novel small-molecule inhibitor, and associated derivatives, termed ADS032 to target and reduce inflammasome-mediated inflammation in vivo. In vitro, we characterised ADS032 function, target engagement and specificity.

Results

We describe ADS032 as the first dual NLRP1 and NLRP3 inhibitor. ADS032 is a rapid, reversible and stable inflammasome inhibitor that directly binds both NLRP1 and NLRP3, reducing secretion and maturation of IL-1β in human-derived macrophages and bronchial epithelial cells in response to the activation of NLPR1 and NLRP3. ADS032 also reduced NLRP3-induced ASC speck formation, indicative of targeting inflammasome formation. In vivo, ADS032 reduced IL-1β and TNF-α levels in the serum of mice challenged i.p. with LPS and reduced pulmonary inflammation in an acute model of lung silicosis. Critically, ADS032 protected mice from lethal influenza A virus challenge, displayed increased survival and reduced pulmonary inflammation.

Conclusion

ADS032 is the first described dual inflammasome inhibitor and a potential therapeutic to treat both NLRP1- and NLRP3-associated inflammatory diseases and also constitutes a novel tool that allows examination of the role of NLRP1 in human disease.

Pinellia ternata (Thunb.) Breit. Attenuates the allergic airway inflammation of cold asthma via inhibiting the activation of TLR4-medicated NF-kB and NLRP3 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Pinellia ternata (Thunb.) Breit. (PT) has been demonstrated to be effective against the allergic airway inflammation (AAI) in clinical practices, especially in cold asthma (CA). Until now, the active ingredients, protective effect, and possible mechanism of PT against CA remain unknown.

AIM OF THE STUDY

The aim of this investigation was to examine the therapeutic impact and elucidate the underlying mechanism of PT on the AAI of CA.

METHODS

The compositions of PT water extract were determined via the UPLC-Q-TOF-MS/MS. The ovalbumin (OVA) and cold-water baths were used to induce CA in female mice. Morphological characteristic observations, expectorant effect, bronchial hyperreactivity (BHR), excessive mucus secretion, and inflammatory factors were used to uncover the treatment effect of PT water extract. In addition, the mucin 5AC (MUC5AC) mRNA and protein levels and the aquaporin 5 (AQP5) mRNA and protein levels were detected via qRT-PCR, immunohistochemistry (IHC), and western blotting. Moreover, the protein expressions associated with the TLR4, NF-κB, and NLRP3 signaling pathway were monitored by western blot analysis.

RESULTS

Thirty-eight compounds were identified from PT water extract. PT showed significant therapeutic effects on mice with cold asthma in terms of expectorant activity, histopathological changes, airway inflammation, mucus secretion, and hyperreactivity. PT exhibited good anti-inflammatory effects in vitro and in vivo. The expression levels of MUC5AC mRNA and protein decreased significantly, while AQP5 expression levels increased significantly in the lung tissues of mice after administration with PT as compared to mice induced by CA. Furthermore, the protein expressions of TLR4, p-iκB, p-p65, IL-1β, IL-18, NLRP3, cleaved caspase-1, and ASC were markedly reduced following PT treatment.

CONCLUSIONS

PT attenuated the AAI of CA by modulating Th1- and Th2-type cytokines. PT could inhibit the TLR4-medicated NF-kB signaling pathway and activate the NLRP3 inflammasome to reduce CA. This study provides an alternative therapeutic agent of the AAI of CA after administration with PT.

Tissue- and temporal-specific roles of extracellular ATP on T cell metabolism and function

The activation and function of T cells is fundamental for the control of infectious diseases and cancer, and conversely can mediate several autoimmune diseases. Among the signaling pathways leading to T cell activation and function, the sensing of extracellular adenosine triphosphate (eATP) has been recently appreciated as an important component. Through a plethora of purinergic receptors, most prominently P2RX7, eATP sensing can induce a wide variety of processes in T cells, such as proliferation, subset differentiation, survival, or cell death. The downstream roles of eATP sensing can vary according to (a) the T cell subset, (b) the tissue where T cells are, and (c) the time after antigen exposure. In this mini-review, we revisit the recent findings on how eATP signaling pathways regulate T-cell immune responses and posit important unanswered questions on this field.

Naturally derived cytokine peptides limit virus replication and severe disease during influenza A virus infection

Objectives

Novel host‐targeted therapeutics could treat severe influenza A virus (IAV) infections, with reduced risk of drug resistance. LAT8881 is a synthetic form of the naturally occurring C‐terminal fragment of human growth hormone. Acting independently of the growth hormone receptor, it can reduce inflammation‐induced damage and promote tissue repair in an animal model of osteoarthritis. LAT8881 has been assessed in clinical trials for the treatment of obesity and neuropathy and has an excellent safety profile. We investigated the potential for LAT8881, its metabolite LAT9991F and LAT7771 derived from prolactin, a growth hormone structural homologue, to treat severe IAV infection.

Methods

LAT8881, LAT9991F and LAT7771 were evaluated for their effects on cell viability and IAV replication in vitro, as well as their potential to limit disease in a preclinical mouse model of severe IAV infection.

Results

In vitro LAT8881 treatment enhanced cell viability, particularly in the presence of cytotoxic stress, which was countered by siRNA inhibition of host lanthionine synthetase C‐like proteins. Daily intranasal treatment of mice with LAT8881 or LAT9991F, but not LAT7771, from day 1 postinfection significantly improved influenza disease resistance, which was associated with reduced infectious viral loads, reduced pro‐inflammatory cytokines and increased abundance of protective alveolar macrophages. LAT8881 treatment in combination with the antiviral oseltamivir phosphate led to more pronounced reduction in markers of disease severity than treatment with either compound alone.

Conclusion

These studies provide the first evidence identifying LAT8881 and LAT9991F as novel host‐protective therapies that improve survival, limit viral replication, reduce local inflammation and curtail tissue damage during severe IAV infection. Evaluation of LAT8881 and LAT9991F in other infectious and inflammatory conditions of the airways is warranted.

Drug repurposing for cardiovascular diseases: New targets and indications for probenecid

The available pharmacological options in the management of cardiovascular diseases such as ischaemic heart disease and subsequent heart failure are effective in slowing the progression of this condition. However, the long-term prognosis is still poor, raising the demand for new therapeutic strategies. Drug repurposing is a time- and cost-effective drug development strategy that offers approved and abandoned drugs a new chance for new indications. Recently, drugs used for the management of gout-related inflammation such as canakinumab or colchicine have been considered for drug repurposing in cardiovascular indications. The old uricosuric drug, probenecid, has been identified as a novel therapeutic option in the management of specific cardiac diseases as well. Probenecid can modulate myocardial contractility and vascular tone and exerts anti-inflammatory properties. The mechanisms behind these beneficial effects might be related inhibition of inflammasomes, and to modulation purinergic-pannexin-1 signalling and TRPV2 channels, which are recently identified molecular targets of probenecid. In this review, we provide an overview on repurposing probenecid for ischaemic heart disease and subsequent heart failure by summarizing the related experimental and clinical data and propose its potential repurposing to treat cardiovascular diseases.

Enhanced activity of NLRP3 inflammasome and its proinflammatory effect in influenza A viral pneumonia

Aim: The aim of this study was to investigate the activity of NLRP3 inflammasome and its effect on inducing severe pneumonia 1 week after influenza A virus (IAV) infection. Materials & methods: The expression levels of NLRP3, caspase-1 and IL-1β were assessed in murine macrophages stimulated with IAV. And the severity of viral pneumonia in mice was explored. Results & conclusion: The data showed that although the expression of NLRP3 diverged, activity of NLRP3 inflammasome was enhanced 1 week after IAV infection, and more severe viral pneumonia was associated with IL-1β in serum. It infers that enhanced activity of NLRP3 inflammasome induces augmented expression of IL-1β and severe pneumonia in a NLRP3-independent way, 1 week after IAV infection.

Emerging roles of the P2X7 receptor in cancer pain

Cancer pain is the most prevalent symptom experienced by cancer patients. It substantially impacts a patient’s long-term physical and emotional health, making it a pressing issue that must be addressed. Purinergic receptor P2X7 (P2X7R) is a widely distributed and potent non-selective ATP-gated ion channel that regulates tumor proliferation, chronic pain, and the formation of inflammatory lesions in the central nervous system. P2X7R plays an essential role in cancer pain and complications related to cancer pain including depression and opioid tolerance. This review focuses on the structure and distribution of P2X7R, its role in diverse tissues in cancer pain, and the application of P2X7R antagonists in the treatment of cancer pain to propose new ideas for cancer pain management.

Probenecid induces the recovery of renal ischemia/reperfusion injury via the blockade of Pannexin 1/P2X7 receptor axis

Renal ischemia/reperfusion injury (RI/RI) is one of the main driving causes of acute kidney injury. However, effective treatment to limit injury and promote recovery and/or survival is still unavailable. Probenecid (PBN), a drug indicated for refractory gout, exhibits protective activities against several preclinical diseases including cerebral and myocardial I/RI via Pannexin 1 (Panx1) and P2X7 receptors' (P2X7R) inhibition. However, its protective role against RI/RI has not been previously addressed. Accordingly, we subjected rats to bilateral RI/RI with/or without PBN treatment. Twenty-four hours post-reperfusion, PBN showed mild tubular injury and reduced serum nephrotoxicity indices, gene and protein expression levels of Panx 1 and P2X7R, and ATP and pro-inflammatory cytokines' levels. The nucleotide-binding domain-like receptor protein 3 (NLRP3) inflammasome signaling was also downregulated, as demonstrated by reduced gene and protein expression of NLRP3 and caspase-1, along with suppressed IL-1β maturation. Furthermore, PBN enhanced Tregs activity as indicated by elevated FoxP3 gene expression, IL-10, and TGF-β renal levels. On day 5 post-reperfusion, PBN noticeably enhanced renal recovery, as demonstrated by intact tubular epithelium and restored nephrotoxicity indices, Panx 1 and P2X7R gene and protein expression levels, ATP and pro-inflammatory cytokine levels, and NLRP3 inflammasome signaling. Besides, renal Tregs activity was also significantly increased. Our study elaborates for the first time the effectiveness of PBN in recovering post-ischemic renal injury through synergistic inhibition in Panx1/P2X7R axis leading to inactivation of NLRP3 inflammasome signaling and activation of Tregs in ischemic renal tissues. Therefore, PBN can be considered a promising drug for RI/RI treatment.

NLRP3 Inflammasome as a Therapeutic Target for Atherosclerosis: A Focus on Potassium Outflow

Atherosclerosis is a risk factor for various cardiovascular diseases, and is linked to high rates of morbidity and mortality across the globe. Although numerous complex processes are involved in the development and progression of atherosclerosis, the exact mechanisms behind its pathogenesis remain unclear. Inflammation and endothelial cell damage exert a lasting effect on atherosclerosis, causing lipid and fibrous tissue accumulation in the intima of the artery to form plaques, and subsequently promoting atherosclerosis. Nod-like receptor protein 3 (NLRP3) inflammatory corpuscle is thought to be the link between lipid metabolism and inflammation. Long Potassium outflow is a vital activator of NLRP3, with a simultaneous effect as a start-up and adjustment. The majority of existing drugs for atherosclerosis targeting the NLRP3 signaling pathway target IL-1, whereas drugs targeting the critical link of potassium efflux are relatively new. This review discusses the NLRP3 inflammatory corpuscle as a critical regulator of the immunological inflammatory pathway in atherosclerosis. Moreover, current knowledge on NLRP3 inflammatory corpuscle start and activation pathways were integrated, emphasizing potassium-involved outflow-related proteins. We highlight potential treatment approaches for NLRP3 inflammatory corpuscle pathways, specifically targeting potassium outflow channels of targeted drugs. Collectively, these insights indicate that targeting the NLRP3 inflammatory corpuscle is a vital anti-inflammatory therapy for treating atherosclerosis.

BzATP Activates Satellite Glial Cells and Increases the Excitability of Dorsal Root Ganglia Neurons In Vivo

The purinergic system plays an important role in pain transmission. Recent studies have suggested that activation of P2-purinergic receptors (P2Rs) may be involved in neuron-satellite glial cell (SGC) interactions in the dorsal root ganglia (DRG), but the details remain unclear. In DRG, P2X7R is selectively expressed in SGCs, which closely surround neurons, and is highly sensitive to 3’-O-(4-Benzoyl) benzoyl-ATP (BzATP). Using calcium imaging in intact mice to survey a large number of DRG neurons and SGCs, we examined how intra-ganglionic purinergic signaling initiated by BzATP affects neuronal activities in vivo. We developed GFAP-GCaMP6s and Pirt-GCaMP6s mice to express the genetically encoded calcium indicator GGCaM6s in SGCs and DRG neurons, respectively. The application of BzATP to the ganglion induced concentration-dependent activation of SGCs in GFAP-GCaMP6s mice. In Pirt-GCaMP6s mice, BzATP initially activated more large-size neurons than small-size ones. Both glial and neuronal responses to BzATP were blocked by A438079, a P2X7R-selective antagonist. Moreover, blockers to pannexin1 channels (probenecid) and P2X3R (A317491) also reduced the actions of BzATP, suggesting that P2X7R stimulation may induce the opening of pannexin1 channels, leading to paracrine ATP release, which could further excite neurons by acting on P2X3Rs. Importantly, BzATP increased the responses of small-size DRG neurons and wide-dynamic range spinal neurons to subsequent peripheral stimuli. Our findings suggest that intra-ganglionic purinergic signaling initiated by P2X7R activation could trigger SGC-neuron interaction in vivo and increase DRG neuron excitability.

Therapeutic potential of P2X7 purinergic receptor modulation in the main organs affected by the COVID-19 cytokine storm

Defined by the World Health Organization as a global public health pandemic, coronavirus 2019 (COVID-19) has a global impact and the death of thousands of people. The "severe acute respiratory syndrome coronavirus 2" virus (SARS-CoV-2) is the etiologic agent of this disease, which uses the angiotensin-converting enzyme receptor 2 (ACE2) to infect the body, so any organ that expresses the gene ACE2 is a possible target for the new coronavirus. In addition, in severe cases of COVID-19, a cytokine storm occurs, which triggers widespread systemic inflammation due to the uncontrolled release of proinflammatory cytokines. In this perspective, the modulation of purinergic receptors are highlighted in the literature as a possible therapy, considering its application in other viral infections and systemic inflammation. Therefore, the objective of this review is to gather information on the modulation of the P2X7 receptor in the main organs directly affected by the virus and by the cytokine storm: heart, brain, lung, liver and kidneys. Thus, demonstrating possible therapies for reducing inflammation, as well as reducing the level of morbidity and mortality of COVID-19.

Another One Fights the Dust - Targeting the NLRP3 Inflammasome for the Treatment of Silicosis

Silicosis is a multifaceted lung disease, characterised by persistent inflammation and structural remodelling. Despite its poor prognosis, there are no treatments currently available for patients with silicosis. Recent pre-clinical findings in models of lung fibrosis have suggested a major role for the nucleotide binding domain and leucine-rich repeat pyrin domain containing 3 (NLRP3) inflammasome in silica-driven inflammation and fibrosis. This review outlines the beneficial effects of targeting the NLRP3 inflammasome in in vitro cell experiments and in in vivo animal models, whereby inflammation and fibrosis are abrogated following NLRP3 inflammasome inhibition. While preclinical evidence is promising, studies which explore NLRP3 inflammasomes in the clinical setting are warranted. In particular, there is still a need to identify biomarkers which may be helpful for the early detection of silicosis and to fully elucidate mechanisms underlying these beneficial effects to further develop or repurpose existing anti-NLRP3 drugs as novel treatments that limit disease progression.

Repurposing Probenecid to Inhibit SARS-CoV-2, Influenza Virus, and Respiratory Syncytial Virus (RSV) Replication

Viral replication and transmissibility are the principal causes of endemic and pandemic disease threats. There remains a need for broad-spectrum antiviral agents. The most common respiratory viruses are endemic agents such as coronaviruses, respiratory syncytial viruses, and influenza viruses. Although vaccines are available for SARS-CoV-2 and some influenza viruses, there is a paucity of effective antiviral drugs, while for RSV there is no vaccine available, and therapeutic treatments are very limited. We have previously shown that probenecid is safe and effective in limiting influenza A virus replication and SARS-CoV-2 replication, along with strong evidence showing inhibition of RSV replication in vitro and in vivo. This review article will describe the antiviral activity profile of probenecid against these three viruses.

Effect of 2D and 3D Culture Microenvironments on Mesenchymal Stem Cell-Derived Extracellular Vesicles Potencies

Therapeutic benefits of mesenchymal stem cells (MSCs) are now widely believed to come from their paracrine signalling, i.e. secreted factors such as cytokines, chemokines, and extracellular vesicles (EVs). Cell-free therapy using EVs is an active and emerging field in regenerative medicine. Typical 2D cultures on tissue culture plastic is far removed from the physiological environment of MSCs. The application of 3D cell culture allows MSCs to adapt to their cellular environment which, in turn, influences their paracrine signalling activity. In this study we evaluated the impact of 3D MSCs culture on EVs secretion, cargo proteome composition, and functional assessment in immunomodulatory, anti-inflammatory and anti-fibrotic properties.

MSC-EVs from 2D and 3D cultures expressed classical EV markers CD81, CD63, and CD9 with particle diameter of &lt;100 nm. There were distinct changes in immunomodulatory potencies where 3D cultures exhibited reduced indoleamine 2,3-dioxygenase (IDO) activity and significantly reduced macrophage phagocytosis. Administration of 2D and 3D EVs following double dose bleomycin challenge in aged mice showed a marked increase of bodyweight loss in 3D group throughout days 7–28. Histopathological observations of lung tissues in 3D group showed increased collagen deposition, myofibroblast differentiation and leukocytes infiltrations. Assessment of lung mechanics showed 3D group did not improve lung function and instead exhibited increased resistance and tissue damping. Proteome profiling of MSC-EV composition revealed molecular enrichment of EV markers (compared to parental cells) and differential proteome between EVs from 2D and 3D culture condition associated with immune-based and fibrosis/extracellular matrix/membrane organization associated function.

This study provides insight into distinct variation in EV protein composition dependent on the cellular microenvironment of the parental cells, which could have implications in their therapeutic effect and potency. Overall, this work suggests that EVs produced from 3D MSC cultures did not enhance typical MSC-EV properties expected from 2D cultures (immunomodulation, anti-fibrotic, anti-inflammatory). The outcome highlights critical differences between MSC-EVs obtained from different culture microenvironments, which should be considered when scaling up MSC culture for clinical manufacturing.

EROS is a selective chaperone regulating the phagocyte NADPH oxidase and purinergic signalling

EROS (essential for reactive oxygen species) protein is indispensable for expression of gp91phox, the catalytic core of the phagocyte NADPH oxidase. EROS deficiency in humans is a novel cause of the severe immunodeficiency, chronic granulomatous disease, but its mechanism of action was unknown until now. We elucidate the role of EROS, showing it acts at the earliest stages of gp91phox maturation. It binds the immature 58 kDa gp91phox directly, preventing gp91phox degradation and allowing glycosylation via the oligosaccharyltransferase machinery and the incorporation of the heme prosthetic groups essential for catalysis. EROS also regulates the purine receptors P2X7 and P2X1 through direct interactions, and P2X7 is almost absent in EROS-deficient mouse and human primary cells. Accordingly, lack of murine EROS results in markedly abnormal P2X7 signalling, inflammasome activation, and T cell responses. The loss of both ROS and P2X7 signalling leads to resistance to influenza infection in mice. Our work identifies EROS as a highly selective chaperone for key proteins in innate and adaptive immunity and a rheostat for immunity to infection. It has profound implications for our understanding of immune physiology, ROS dysregulation, and possibly gene therapy.

Disulfiram attenuates MCMV-Induced pneumonia by inhibition of NF-κB/NLRP3 signaling pathway in immunocompromised mice

Cytomegalovirus (CMV) pneumonia in immunocompromised individuals is associated with damaging hyperinflammation and leads to high morbidity and mortality. It is urgently needed to develop new strategies to treat CMV-induced pneumonia. As disulfiram (DSF) reportedly inhibits inflammatory responses in different disease models, its therapeutic effects in CMV-induced pneumonia are proposed. In this study, we demonstrated that DSF effectively attenuated pulmonary injury and improved survival in murine CMV (MCMV) pneumonia model. DSF treatment inhibited lung inflammatory responses, e.g. reducing pro-inflammatory cytokines, upregulating anti-inflammatory cytokine, and lowering the accumulation of leukocytes in the lung. Similar to the in vivo results, DSF attenuated inflammatory responses and modulated NF-κB/NLRP3 inflammasome activation in MCMV-infected BMDMs. Furthermore, DSF reduced pulmonary fibrosis and viral loads in MCMV pneumonia mice and BMDMs. The mechanism of anti-inflammatory effects of DSF may due to its regulating NF-κB signaling and NLRP3 inflammasome activation. Collectively, our results suggest that DSF-mediated anti-hyperinflammatory effects have potentials for therapy of human CMV pneumonia.

Pannexin-1 channel opening is critical for COVID-19 pathogenesis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapidly rampaged worldwide, causing a pandemic of coronavirus disease (COVID -19), but the biology of SARS-CoV-2 remains under investigation. We demonstrate that both SARS-CoV-2 spike protein and human coronavirus 229E (hCoV-229E) or its purified S protein, one of the main viruses responsible for the common cold, induce the transient opening of Pannexin-1 (Panx-1) channels in human lung epithelial cells. However, the Panx-1 channel opening induced by SARS-CoV-2 is greater and more prolonged than hCoV-229E/S protein, resulting in an enhanced ATP, PGE₂, and IL-1β release. Analysis of lung lavages and tissues indicate that Panx-1 mRNA expression is associated with increased ATP, PGE₂, and IL-1β levels. Panx-1 channel opening induced by SARS-CoV-2 spike protein is angiotensin-converting enzyme 2 (ACE-2), endocytosis, and furin dependent. Overall, we demonstrated that Panx-1 channel is a critical contributor to SARS-CoV-2 infection and should be considered as an alternative therapy.

Targeting purinergic receptors to suppress the cytokine storm induced by SARS-CoV-2 infection in pulmonary tissue

The etiological agent of coronavirus disease (COVID-19) is the new member of the Coronaviridae family, a severe acute respiratory syndrome coronavirus 2 virus (SARS-CoV-2), responsible for the pandemic that is plaguing the world. The single-stranded RNA virus is capable of infecting the respiratory tract, by binding the spike (S) protein on its viral surface to receptors for the angiotensin II-converting enzyme (ACE2), highly expressed in the pulmonary tissue, enabling the interaction of the virus with alveolar epithelial cells promoting endocytosis and replication of viral material. The infection triggers the activation of the immune system, increased purinergic signaling, and the release of cytokines as a defense mechanism, but the response can become exaggerated and prompt the so-called “cytokine storm”, developing cases such as severe acute respiratory syndrome (SARS). This is characterized by fever, cough, and difficulty breathing, which can progress to pneumonia, failure of different organs and death. Thus, the present review aims to compile and correlate the mechanisms involved between the immune and purinergic systems with COVID-19, since the modulation of purinergic receptors, such as A2A, A2B, and P2X7 expressed by immune cells, seems to be effective as a promising therapy, to reduce the severity of the disease, as well as aid in the treatment of acute lung diseases and other cases of generalized inflammation.

Probenecid inhibits SARS-CoV-2 replication in vivo and in vitro

Effective vaccines are slowing the COVID-19 pandemic, but SARS-CoV-2 will likely remain an issue in the future making it important to have therapeutics to treat patients. There are few options for treating patients with COVID-19. We show probenecid potently blocks SARS-CoV-2 replication in mammalian cells and virus replication in a hamster model. Furthermore, we demonstrate that plasma concentrations up to 50-fold higher than the protein binding adjusted IC₉₀ value are achievable for 24 h following a single oral dose. These data support the potential clinical utility of probenecid to control SARS-CoV-2 infection in humans.

Too young to die? How aging affects cellular innate immune responses to influenza virus and disease severity

Influenza is a respiratory viral infection that causes significant morbidity and mortality worldwide. The innate immune cell response elicited during influenza A virus (IAV) infection forms the critical first line of defense, which typically is impaired as we age. As such, elderly individuals more commonly succumb to influenza-associated complications, which is reflected in most aged animal models of IAV infection. Here, we review the important roles of several major innate immune cell populations in influenza pathogenesis, some of which being deleterious to the host, and the current knowledge of how age-associated numerical, phenotypic and functional cell changes impact disease development. Further investigation into age-related modulation of innate immune cell responses, using appropriate animal models, will help reveal how immunity to IAV may be compromised by aging and inform the development of novel therapies, tailored for use in this vulnerable group.

Interleukin-1β exacerbates disease and is a potential therapeutic target to reduce pulmonary inflammation during severe influenza A virus infection

Hyperinflammatory responses including the production of NLRP3-dependent interleukin (IL)-1β is a characteristic feature of severe and fatal influenza A virus (IAV) infections. The NLRP3 inflammasome has been shown to play a temporal role during severe IAV immune responses, with early protective and later detrimental responses. However, the specific contribution of IL-1β in modulating IAV disease in vivo is currently not well defined. Here, we identified that activation of NLRP3-dependent IL-1β responses occurs rapidly following HKx31 H3N2 infection, prior to the onset of severe IAV disease. Mature IL-1β was detectable in vivo in both hemopoietic and nonhemopoietic cells. Significantly, therapeutic inhibition of IL-1β in the airways with intranasal anti-IL-1β antibody treatment from day 3 postinfection, corresponding to the onset of clinical signs of disease, significantly prolonged survival and reduced inflammation in the airways. Importantly, early targeting of IL-1β from day 1 postinfection also improved survival. Together, these studies specifically define a role for IL-1β in contributing to the development of hyperinflammation and disease and indicate that targeting IL-1β is a potential therapeutic strategy for severe IAV infections.

Evaluation of Adjunctive Photobiomodulation (PBMT) for COVID-19 Pneumonia via Clinical Status and Pulmonary Severity Indices in a Preliminary Trial

PURPOSE

Evidence-based and effective treatments for COVID-19 are limited, and a new wave of infections and deaths calls for novel, easily implemented treatment strategies. Photobiomodulation therapy (PBMT) is a well-known adjunctive treatment for pain management, wound healing, lymphedema, and cellulitis. PBMT uses light to start a cascade of photochemical reactions that lead to local and systemic anti-inflammatory effects at multiple levels and that stimulate healing. Numerous empirical studies of PBMT for patients with pulmonary disease such as pneumonia, COPD and asthma suggest that PBMT is a safe and effective adjunctive treatment. Recent systematic reviews suggest that PBMT may be applied to target lung tissue in COVID-19 patients. In this preliminary study, we evaluated the effect of adjunctive PBMT on COVID-19 pneumonia and patient clinical status.

PATIENTS AND METHODS

We present a small-scale clinical trial with 10 patients randomized to standard medical care or standard medical care plus adjunctive PBMT. The PBMT group received four daily sessions of near-infrared light treatment targeting the lung tissue via a Multiwave Locked System (MLS) laser. Patient outcomes were measured via blood work, chest x-rays, pulse oximetry and validated scoring tools for pneumonia.

RESULTS

PBMT patients showed improvement on pulmonary indices such as SMART-COP, BCRSS, RALE, and CAP (Community-Acquired Pneumonia questionnaire). PBMT-treated patients showed rapid recovery, did not require ICU admission or mechanical ventilation, and reported no long-term sequelae at 5 months after treatment. In the control group, 60% of patients were admitted to the ICU for mechanical ventilation. The control group had an overall mortality of 40%. At a 5-month follow-up, 40% of the control group experienced long-term sequelae.

CONCLUSION

PBMT is a safe and effective potential treatment for COVID-19 pneumonia and improves clinical status in COVID-19 pneumonia.

New Inhibitory Effects of Cilnidipine on Microglial P2X7 Receptors and IL-1β Release: An Involvement in its Alleviating Effect on Neuropathic Pain

P2X7 receptors (P2X7Rs) belong to a family of ATP-gated non-selective cation channels. Microglia represent a major cell type expressing P2X7Rs. The activation of microglial P2X7Rs causes the release of pro-inflammatory cytokines such as interleukin-1β (IL-1β). This response has been implicated in neuroinflammatory states in the central nervous system and in various diseases, including neuropathic pain. Thus, P2X7R may represent a potential therapeutic target. In the present study, we screened a chemical library of clinically approved drugs (1979 compounds) by high-throughput screening and showed that the Ca2+ channel blocker cilnidipine has an inhibitory effect on rodent and human P2X7R. In primary cultured rat microglial cells, cilnidipine inhibited P2X7R-mediated Ca2+ responses and IL-1β release. Moreover, in a rat model of neuropathic pain, the intrathecal administration of cilnidipine produced a reversal of nerve injury-induced mechanical hypersensitivity, a cardinal symptom of neuropathic pain. These results point to a new inhibitory effect of cilnidipine on microglial P2X7R-mediated inflammatory responses and neuropathic pain, proposing its therapeutic potential.

P2RX7 at the Host-Pathogen Interface of Infectious Diseases

The P2X7 receptor (P2RX7) is an important molecule that functions as a danger sensor, detecting extracellular nucleotides from injured cells and thus signaling an inflammatory program to nearby cells. It is expressed in immune cells and plays important roles in pathogen surveillance and cell-mediated responses to infectious organisms. There is an abundance of literature on the role of P2RX7 in inflammatory diseases and the role of these receptors in host-pathogen interactions. Here, we describe the current knowledge of the role of P2RX7 in the host response to a variety of pathogens, including viruses, bacteria, fungi, protozoa, and helminths. We describe in vitro and in vivo evidence for the critical role these receptors play in mediating and modulating immune responses. Our observations indicate a role for P2X7 signaling in sensing damage-associated molecular patterns released by nearby infected cells to facilitate immunopathology or protection. In this review, we describe how P2RX7 signaling can play critical roles in numerous cells types in response to a diverse array of pathogens in mediating pathogenesis and immunity to infectious agents.

The potential involvement of P2X7 receptor in COVID-19 pathogenesis: A new therapeutic target?

Coronavirus disease 2019 (COVID-19) pathogenesis remains under investigation. Growing evidence indicates the establishment of a hyperinflammatory response, characterized by sustained production of cytokines, such as IL-1β. The release and maturation of this cytokine are dependent on the activation of a catalytic multiprotein complex, known as "inflammasome". The most investigated is the NLRP3 inflammasome, which can be activated by various stimuli, such as the recognition of extracellular ATP by the P2X7 receptor. Based on the recent literature, we present evidence that supports the idea that the P2X7R/NLRP3 axis may be involved in the immune dysregulation caused by the SARS-CoV-2 infection.

Low level laser therapy as a modality to attenuate cytokine storm at multiple levels, enhance recovery, and reduce the use of ventilators in COVID-19

The global pandemic COVID-19 is a contagious disease and its mortality rates ranging from 1% to 5% are likely due to acute respiratory distress syndrome (ARDS), and cytokine storm. A significant proportion of patients who require intubation succumb to the disease, despite the availability of ventilators and the best treatment practices. Researchers worldwide are in search of anti-inflammatory medicines in the hope of finding a cure for COVID-19. Low-level laser therapy (LLLT) has strong, anti-inflammatory effects confirmed by meta-analyses, and it may be therapeutic to ARDS. LLLT has been used for pain management, wound healing, and other health conditions by physicians, physiotherapists, and nurses worldwide for decades. In addition, it has been used in veterinary medicine for respiratory tract disease such as pneumonia. Laser light with low-power intensity is applied to the surface of the skin to produce local and systemic effects. Based on the clinical experience, peer-reviewed studies, and solid laboratory data in experimental animal models, LLLT attenuates cytokine storm at multiple levels and reduces the major inflammatory metabolites. LLLT is a safe, effective, low-cost modality without any side-effects that may be combined with conventional treatment of ARDS. We summarize the effects of LLLT on pulmonary inflammation and we provide a protocol for augmenting medical treatment in COVID-19 patients. LLLT combined with conventional medical therapy has the potential to prevent the progression of COVID-19, minimize the length of time needed on a ventilator, enhance the healing process, and shorten recovery time.

P2 Purinergic Signaling in the Distal Lung in Health and Disease

The distal lung provides an intricate structure for gas exchange in mammalian lungs. Efficient gas exchange depends on the functional integrity of lung alveoli. The cells in the alveolar tissue serve various functions to maintain alveolar structure, integrity and homeostasis. Alveolar epithelial cells secrete pulmonary surfactant, regulate the alveolar surface liquid (ASL) volume and, together with resident and infiltrating immune cells, provide a powerful host-defense system against a multitude of particles, microbes and toxicants. It is well established that all of these cells express purinergic P2 receptors and that purinergic signaling plays important roles in maintaining alveolar homeostasis. Therefore, it is not surprising that purinergic signaling also contributes to development and progression of severe pathological conditions like pulmonary inflammation, acute lung injury/acute respiratory distress syndrome (ALI/ARDS) and pulmonary fibrosis. Within this review we focus on the role of P2 purinergic signaling in the distal lung in health and disease. We recapitulate the expression of P2 receptors within the cells in the alveoli, the possible sources of ATP (adenosine triphosphate) within alveoli and the contribution of purinergic signaling to regulation of surfactant secretion, ASL volume and composition, as well as immune homeostasis. Finally, we summarize current knowledge of the role for P2 signaling in infectious pneumonia, ALI/ARDS and idiopathic pulmonary fibrosis (IPF).

Critical Role for the NLRP3 Inflammasome in Mediating IL-1β Production in Shigella sonnei-Infected Macrophages

Shigella is one of the leading bacterial causes of diarrhea worldwide, affecting more than 165 million people annually. Among the serotypes of Shigella, Shigella sonnei is physiologically unique and endemic in human immunodeficiency virus-infected men who have sex with men. The NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome, a protein complex composed of NLRP3, apoptosis-associated speck-like protein, and caspase-1, recognizes, and responds to pathogen infection and diverse sterile host-derived or environmental danger signals to induce IL-1β and IL-18 production. Although the Shigella flexneri-mediated activation of the NLRP3 inflammasome has been reported, the effect of S. sonnei on NLRP3 inflammasome activation remains unclear. We found that S. sonnei induced IL-1β production through NLRP3-dependent pathways in lipopolysaccharide-primed macrophages. A mechanistic study revealed that S. sonnei induced IL-1β production through P₂X₇ receptor-mediated potassium efflux, reactive oxygen species generation, lysosomal acidification, and mitochondrial damage. In addition, the phagocytosis of viable S. sonnei was important for IL-1β production. Furthermore, we demonstrated that NLRP3 negatively regulated phagocytosis and the bactericidal activity of macrophages against S. sonnei. These findings provide mechanistic insight into the activation of the NLRP3 inflammasome by S. sonnei in macrophages.

Disulfiram suppresses NLRP3 inflammasome activation to treat peritoneal and gouty inflammation

The NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome plays a vital role in mediating the innate immune system. Its aberrant activation contributes to the progression of several devastating diseases such as acute peritonitis, acute liver injury, sepsis, gout, and others. However, the medications targeting NLRP3 inflammasome are not available in the clinic. Reusing marketed drugs, which have been already proved to possess good pharmacokinetic profiles and safety, is a strategy to develop new NLRP3 inflammasome inhibitors for clinical trials. In this study, we identified disulfiram (DSF), an old marketed drug as a treatment for alcoholism, could effectively inhibit NLRP3 inflammasome activation and suppress pyroptotic cell death. DSF prevented lysosomal cathepsin B releasing into the cytoplasm, which in turn inactivated the NLRP3 inflammasome. DSF also reduced mitochondrial-independent ROS production. More importantly, treatment with DSF showed remarkable therapeutic effects on the LPS-induced peritoneal inflammation and MSU-induced gouty inflammation. This study provides a potential pharmacological approach to treating NLRP3-driven diseases and a tool to study NLRP3 biology.