Ultramicronized Palmitoylethanolamide Inhibits NLRP3 Inflammasome Expression and Pro-Inflammatory Response Activated by SARS-CoV-2 Spike Protein in Cultured Murine Alveolar Macrophages

New insights in the mechanisms of opioid analgesia and tolerance: Ultramicronized palmitoylethanolamide down-modulates vascular endothelial growth factor-A in the nervous system

Growing evidence suggests that opioid analgesics modulate angiogenesis during pathophysiological processes. Vascular endothelial growth factor-A (VEGF-A) was recently proposed to be involved in pain development. To date, no anti-angiogenic drug is used for pain management. When administered in a bioavailable formulation, (i.e., ultramicronized) N-palmitoylethanolamine (PEA) delays the onset of morphine tolerance, improves morphine analgesic activity and reduces angiogenesis in in vivo models. This study aimed at investigating whether VEGF-A is involved in PEA-induced delay of morphine tolerance. The anti-VEGF-A monoclonal antibody bevacizumab was used as a reference drug. Preemptive and concomitant treatment with ultramicronized PEA delayed morphine tolerance and potentiated the analgesic effect of morphine, while counteracting morphine-induced increase of VEGF-A in the nervous system. Similar results were obtained when bevacizumab was administered together with morphine. Of note, bevacizumab showed an analgesic effect per se. In equianalgesic treatment regimens (obtained through increasing morphine doses and associating PEA), PEA resulted in lower expression of VEGF-A in dorsal root ganglia (DRG) and spinal cord compared to morphine alone. Similar results were observed for plasma levels of the soluble VEGF receptor 1 (sFLT-1). Moreover, in morphine-treated animals, two pain-related genes (i.e., Serpina3n and Eaat2) showed a more than 3-fold increase in their expression at spinal cord and DRG level, with the increase being significantly counteracted by PEA treatment. This study supports the hypothesis that the effects of PEA on morphine analgesia and tolerance may be mediated by the down-modulation of VEGF-A and sFLT-1 in the nervous system and plasma, respectively.

Spike Protein of SARS-CoV-2 Activates Cardiac Fibrogenesis through NLRP3 Inflammasomes and NF-κB Signaling

BACKGROUND

The spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is crucial to viral entry and can cause cardiac injuries. Toll-like receptor 4 (TLR4) and NOD-, LPR-, and pyrin-domain-containing 3 (NLRP3) inflammasome are critical immune system components implicated in cardiac fibrosis. The spike protein activates NLRP3 inflammasome through TLR4 or angiotensin-converting enzyme 2 (ACE2) receptors, damaging various organs. However, the role of spike protein in cardiac fibrosis in humans, as well as its interactions with NLRP3 inflammasomes and TLR4, remain poorly understood.

METHODS

We utilized scratch assays, Western blotting, and immunofluorescence to evaluate the migration, fibrosis signaling, mitochondrial calcium levels, reactive oxygen species (ROS) production, and cell morphology of cultured human cardiac fibroblasts (CFs) treated with spike (S1) protein for 24 h with or without an anti-ACE2 neutralizing antibody, a TLR4 blocker, or an NLRP3 inhibitor.

RESULTS

S1 protein enhanced CFs migration and the expressions of collagen 1, α-smooth muscle actin, transforming growth factor β1 (TGF-β1), phosphorylated SMAD2/3, interleukin 1β (IL-1β), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). S1 protein increased ROS production but did not affect mitochondrial calcium content and cell morphology. Treatment with an anti-ACE2 neutralizing antibody attenuated the effects of S1 protein on collagen 1 and TGF-β1 expressions. Moreover, NLRP3 (MCC950) and NF-kB inhibitors, but not the TLR4 inhibitor TAK-242, prevented the S1 protein-enhanced CFs migration and overexpression of collagen 1, TGF-β1, and IL-1β.

CONCLUSION

S1 protein activates human CFs by priming NLRP3 inflammasomes through NF-κB signaling in an ACE2-dependent manner.

Ultramicronized Palmitoylethanolamide and Luteolin: Drug Candidates in Post-COVID-19 Critical Illness Neuropathy and Positioning-Related Peripheral Nerve Injury of the Upper Extremity

Coronavirus disease 2019 (COVID-19) is the most dramatic pandemic of the new millennium and patients with serious infection can stay in intensive care unit (ICU) for weeks in a clinical scenario of systemic inflammatory response syndrome, likely related to the subsequent development of critical illness polyneuropathy (CIP). It is in fact now accepted that COVID-19 ICU surviving patients can develop CIP; moreover, prone positioning-related stretch may favor the onset of positioning-related peripheral nerve injuries (PNI). Therefore, the urgent need to test drug candidates for the treatment of these debilitating sequelae is emerged even more. For the first time in medical literature, we have successfully treated after informed consent a 71-year-old Italian man suffering from post-COVID-19 CIP burdened with positioning-related PNI of the left upper extremity by means of ultramicronized palmitoylethanolamide 400 mg plus ultramicronized luteolin 40 mg (Glìalia), two tablets a day 12 hours apart for 6 months. In the wake of our pilot study, a larger clinical trial to definitively ascertain the advantages of this neuroprotective, neurotrophic, and anti-inflammatory therapy is advocated.

Intranasal administration of Escherichia coli Nissle expressing the spike protein of SARS-CoV-2 induces long-term immunization and prevents spike protein-mediated lung injury in mice

While current anti-Spike protein (SP) vaccines have been pivotal in managing the pandemic, their limitations in delivery, storage, and the inability to provide mucosal immunization (preventing infections) highlight the ongoing necessity for research and innovation. To tackle these constraints, our research group developed a bacterial-based vaccine using a non-pathogenic E. coli Nissle 1917 (EcN) strain genetically modified to express the SARS-CoV-2 spike protein on its surface (EcN-pAIDA1-SP). We intranasally delivered the EcN-pAIDA1-SP in two doses and checked specific IgG/IgA production as well as the key immune mediators involved in the process. Moreover, following the initial and booster vaccine doses, we exposed both immunized and non-immunized mice to intranasal delivery of SARS-CoV-2 SP to assess the effectiveness of EcN-pAIDA1-SP in protecting lung tissue from the inflammation damage. We observed detectable levels of anti-SARS-CoV-2 spike IgG in serum samples and IgA in bronchoalveolar lavage fluid two weeks after the initial treatment, with peak concentrations in the respective samples on the 35th day. Moreover, immunoglobulins displayed a progressively enhanced avidity index, suggesting a selective binding to the spike protein. Finally, the pre-immunized group displayed a decrease in proinflammatory markers (TLR4, NLRP3, ILs) following SP challenge, compared to the non-immunized groups, along with better preservation of tissue morphology. Our probiotic-based technology provides an effective immunobiotic tool to protect individuals against disease and control infection spread.

Function and inhibition of P38 MAP kinase signaling: Targeting multiple inflammation diseases

Inflammation is a natural host defense mechanism that protects the body from pathogenic microorganisms. A growing body of research suggests that inflammation is a key factor in triggering other diseases (lung injury, rheumatoid arthritis, etc.). However, there is no consensus on the complex mechanism of inflammatory response, which may include enzyme activation, mediator release, and tissue repair. In recent years, p38 MAPK, a member of the MAPKs family, has attracted much attention as a central target for the treatment of inflammatory diseases. However, many p38 MAPK inhibitors attempting to obtain marketing approval have failed at the clinical trial stage due to selectivity and/or toxicity issues. In this paper, we discuss the mechanism of p38 MAPK in regulating inflammatory response and its key role in major inflammatory diseases and summarize the synthetic or natural products targeting p38 MAPK to improve the inflammatory response in the last five years, which will provide ideas for the development of novel clinical anti-inflammatory drugs based on p38 MAPK inhibitors.

The Efficacy of Palmitoylethanolamide (Levagen+) on the Incidence and Symptoms of Upper Respiratory Tract Infection-A Double Blind, Randomised, Placebo-Controlled Trial

INTRODUCTION

Upper respiratory tract infections (URTIs) are caused by bacteria or viruses, with the most common causes being the common cold and influenza. The high occurrence of URTI means therapies that are effective with minimal side effects are in constant demand. Palmitoylethanolamide (PEA) is a signaling lipid previously shown to be effective in improving the incidence of URTIs. The aim of this study was to assess the effectiveness of PEA (Levagen+) on URTI incidence, duration, and severity.

METHODS

Participants (n = 426) consumed either 300 mg of Levagen+ or a placebo (maltodextrin) twice daily for 12 weeks. Participants completed the Wisconsin Upper Respiratory Symptom Survey 24 questionnaire daily upon the commencement of symptoms until symptoms subsided.

RESULTS

The Levagen+ group reported fewer URTI episodes (39 vs. 64) compared to the placebo group. The Levagen+ group reported a significant reduction in the median severity score of URTI symptoms for scratchy throat (3 vs. 7) and cough (2 vs. 7) compared to the placebo group.

CONCLUSIONS

The results of this study show Levagen+ to be safe and effective in reducing the incidence and symptoms associated with URTIs.

Carbon dioxide and MAPK signalling: towards therapy for inflammation

Inflammation, although necessary to fight infections, becomes a threat when it exceeds the capability of the immune system to control it. In addition, inflammation is a cause and/or symptom of many different disorders, including metabolic, neurodegenerative, autoimmune and cardiovascular diseases. Comorbidities and advanced age are typical predictors of more severe cases of seasonal viral infection, with COVID-19 a clear example. The primary importance of mitogen-activated protein kinases (MAPKs) in the course of COVID-19 is evident in the mechanisms by which cells are infected with SARS-CoV-2; the cytokine storm that profoundly worsens a patient's condition; the pathogenesis of diseases, such as diabetes, obesity, and hypertension, that contribute to a worsened prognosis; and post-COVID-19 complications, such as brain fog and thrombosis. An increasing number of reports have revealed that MAPKs are regulated by carbon dioxide (CO2); hence, we reviewed the literature to identify associations between CO2 and MAPKs and possible therapeutic benefits resulting from the elevation of CO2 levels. CO2 regulates key processes leading to and resulting from inflammation, and the therapeutic effects of CO2 (or bicarbonate, HCO3-) have been documented in all of the abovementioned comorbidities and complications of COVID-19 in which MAPKs play roles. The overlapping MAPK and CO2 signalling pathways in the contexts of allergy, apoptosis and cell survival, pulmonary oedema (alveolar fluid resorption), and mechanical ventilation-induced responses in lungs and related to mitochondria are also discussed. Video Abstract.

Inflammasomes: a rising star on the horizon of COVID-19 pathophysiology

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a contagious respiratory virus that is the cause of the coronavirus disease 2019 (COVID-19) pandemic which has posed a serious threat to public health. COVID-19 is characterized by a wide spectrum of clinical manifestations, ranging from asymptomatic infection to mild cold-like symptoms, severe pneumonia or even death. Inflammasomes are supramolecular signaling platforms that assemble in response to danger or microbial signals. Upon activation, inflammasomes mediate innate immune defense by favoring the release of proinflammatory cytokines and triggering pyroptotic cell death. Nevertheless, abnormalities in inflammasome functioning can result in a variety of human diseases such as autoimmune disorders and cancer. A growing body of evidence has showed that SARS-CoV-2 infection can induce inflammasome assembly. Dysregulated inflammasome activation and consequent cytokine burst have been associated with COVID-19 severity, alluding to the implication of inflammasomes in COVID-19 pathophysiology. Accordingly, an improved understanding of inflammasome-mediated inflammatory cascades in COVID-19 is essential to uncover the immunological mechanisms of COVID-19 pathology and identify effective therapeutic approaches for this devastating disease. In this review, we summarize the most recent findings on the interplay between SARS-CoV-2 and inflammasomes and the contribution of activated inflammasomes to COVID-19 progression. We dissect the mechanisms involving the inflammasome machinery in COVID-19 immunopathogenesis. In addition, we provide an overview of inflammasome-targeted therapies or antagonists that have potential clinical utility in COVID-19 treatment.

The role of peroxisome proliferator-activated receptors in the modulation of hyperinflammation induced by SARS-CoV-2 infection: A perspective for COVID-19 therapy

Coronavirus disease 2019 (COVID-19) is a severe respiratory disease caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that affects the lower and upper respiratory tract in humans. SARS-CoV-2 infection is associated with the induction of a cascade of uncontrolled inflammatory responses in the host, ultimately leading to hyperinflammation or cytokine storm. Indeed, cytokine storm is a hallmark of SARS-CoV-2 immunopathogenesis, directly related to the severity of the disease and mortality in COVID-19 patients. Considering the lack of any definitive treatment for COVID-19, targeting key inflammatory factors to regulate the inflammatory response in COVID-19 patients could be a fundamental step to developing effective therapeutic strategies against SARS-CoV-2 infection. Currently, in addition to well-defined metabolic actions, especially lipid metabolism and glucose utilization, there is growing evidence of a central role of the ligand-dependent nuclear receptors and peroxisome proliferator-activated receptors (PPARs) including PPARα, PPARβ/δ, and PPARγ in the control of inflammatory signals in various human inflammatory diseases. This makes them attractive targets for developing therapeutic approaches to control/suppress the hyperinflammatory response in patients with severe COVID-19. In this review, we (1) investigate the anti-inflammatory mechanisms mediated by PPARs and their ligands during SARS-CoV-2 infection, and (2) on the basis of the recent literature, highlight the importance of PPAR subtypes for the development of promising therapeutic approaches against the cytokine storm in severe COVID-19 patients.

First Evidence of the Protective Effects of 2-Pentadecyl-2-Oxazoline (PEA-OXA) in In Vitro Models of Acute Lung Injury

Acute respiratory distress syndrome (ARDS) is a serious inflammatory lung disorder and a complication of SARS-CoV-2 infection. In patients with severe SARS-CoV-2 infection, the transition to ARDS is principally due to the occurrence of a cytokine storm and an exacerbated inflammatory response. The effectiveness of ultra-micronized palmitoylethanolamide (PEA-um) during the earliest stage of COVID-19 has already been suggested. In this study, we evaluated its protective effects as well as the effectiveness of its congener, 2-pentadecyl-2-oxazoline (PEA-OXA), using in vitro models of acute lung injury. In detail, human lung epithelial cells (A549) activated by polyinosinic-polycytidylic acid (poly-(I:C)) or Transforming Growth Factor-beta (TGF-β) were treated with PEA-OXA or PEA. The release of IL-6 and the appearance of Epithelial-Mesenchymal Transition (EMT) were measured by ELISA and immunofluorescence assays, respectively. A possible mechanism of action for PEA-OXA and PEA was also investigated. Our results showed that both PEA-OXA and PEA were able to counteract poly-(I:C)-induced IL-6 release, as well as to revert TGF-β-induced EMT. In addition, PEA was able to produce an "entourage" effect on the levels of the two endocannabinoids AEA and 2-AG, while PEA-OXA only increased PEA endogenous levels, in poly-(I:C)-stimulated A549 cells. These results evidence for the first time the superiority of PEA-OXA over PEA in exerting protective effects and point to PEA-OXA as a new promising candidate in the management of acute lung injury.

A comparative study of spike protein of SARS-CoV-2 and its variant Omicron (B.1.1.529) on some immune characteristics

The emergence of Omicron variant raises great concerns because of its rapid transmissibility and its numerous mutations in spike protein (S-protein). S-protein can act as a pathogen-associated molecular pattern and complement activator as well as antigen. We compared some immune characteristics of trimer S-proteins for wild type (WT-S) and B.1.1.529 Omicron (Omicron-S) to investigate whether the mutations have affected its pathogenicity and antigenic shift. The results indicated that WT-S and Omicron-S directly activated nuclear factor-κB (NF-κB) and induced the release of pro-inflammatory cytokines in macrophages, but the actions of Omicron-S were weaker. These inflammatory reactions could be abrogated by a Toll-like receptor 4 antagonist TAK-242. Two S-proteins failed to induce the production of antiviral molecular interferon-β. In contrast to pro-inflammatory effects, the ability of two S-proteins to activate complement was comparable. We also compared the binding ability of two S-proteins to a high-titer anti-WT-receptor-binding domain antibody. The data showed that WT-S strongly bound to this antibody, while Omicron-S was completely off-target. Collectively, the mutations of Omicron have a great impact on the pro-inflammatory ability and epitopes of S-protein, but little effect on its ability to activate complement. Addressing these issues can be helpful for more adequate understanding of the pathogenicity of Omicron and the vaccine breakthrough infection.

Palmitoylethanolamide Reduces Proinflammatory Markers in Unvaccinated Adults Recently Diagnosed with COVID-19: A Randomized Controlled Trial

BACKGROUND

Inflammation is at the core of many chronic conditions and exacerbates infectious conditions, including the severity of coronavirus disease 2019 (COVID-19) infections.

OBJECTIVES

This study aimed to examine the effects of a novel food supplement, palmitoylethanolamide (PEA), specifically Levagen+, as compared with a placebo on proinflammatory biomarkers in adults recently diagnosed with COVID-19 who were unvaccinated and nonhospitalized.

METHODS

This study was a double-blind randomized placebo-controlled trial conducted October 2020-March 2021 (clinicaltrials.gov: NCT04912921). Participants aged 19-53 y were unvaccinated and recently infected with COVID-19 as indicated by a positive test result per RT-PCR or antigen test, and they reported to the test site following diagnosis as allowed by the CDC's return-to-work policy. Participants were stratified by age, sex, and BMI and randomly assigned by coin toss to receive 600 mg Levagen+ twice daily (LEV) or placebo tablets twice daily (CON) for 4 wk. At baseline and week 4, participants completed health histories, 24-h dietary recalls, anthropometrics, and nonfasting blood sampling. The primary outcomes were the 4-wk change between groups for IL-6, C-reactive protein, ferritin, intercellular adhesion molecule 1, soluble P-selectin (sP-selectin), and neutrophil/lymphocyte ratio. Multiple linear regression models were utilized to assess treatment effects on outcomes, adjusting for covariates.

RESULTS

A total of 60 participants completed the study (LEV: n = 30; CON: n = 30). After 4 wk of supplementation, sP-selectin (β = -11.5; 95% CI: -19.8, -3.15; P = 0.0078), IL-1β (β = -22.9; 95% CI: -42.4, -3.40; P = 0.0222), and IL-2 (β = -1.73; 95% CI: -3.45, -0.065; P = 0.0492) concentrations were significantly reduced in the LEV group compared with the CON group.

CONCLUSIONS

Inflammatory mechanisms are crucial to optimal resolution of infectious conditions, yet unchecked secretion of inflammatory mediators can promote the dysregulated immune response implicated in COVID-19 complications. Overall, PEA supplementation produced anti-inflammatory effects in individuals recently diagnosed with COVID-19 who were nonhospitalized.

Blood gene expression predicts intensive care unit admission in hospitalised patients with COVID-19

Background

The COVID-19 pandemic has created pressure on healthcare systems worldwide. Tools that can stratify individuals according to prognosis could allow for more efficient allocation of healthcare resources and thus improved patient outcomes. It is currently unclear if blood gene expression signatures derived from patients at the point of admission to hospital could provide useful prognostic information.

Methods

Gene expression of whole blood obtained at the point of admission from a cohort of 78 patients hospitalised with COVID-19 during the first wave was measured by high resolution RNA sequencing. Gene signatures predictive of admission to Intensive Care Unit were identified and tested using machine learning and topological data analysis, TopMD.

Results

The best gene expression signature predictive of ICU admission was defined using topological data analysis with an accuracy: 0.72 and ROC AUC: 0.76. The gene signature was primarily based on differentially activated pathways controlling epidermal growth factor receptor (EGFR) presentation, Peroxisome proliferator-activated receptor alpha (PPAR-α) signalling and Transforming growth factor beta (TGF-β) signalling.

Conclusions

Gene expression signatures from blood taken at the point of admission to hospital predicted ICU admission of treatment naïve patients with COVID-19.

A randomized controlled trial assessing the safety and efficacy of palmitoylethanolamide for treating diabetic-related peripheral neuropathic pain

Background

Peripheral neuropathy is a common complication of diabetes. The management of the associated neuropathic pain remains difficult to treat.

Objective

This study explored the safety, tolerability and efficacy of a palmitoylethanolamide (PEA) formulation in treating diabetic-related peripheral neuropathic pain (PNP). Secondary outcomes included systemic inflammation, sleep and mood changes in patients diagnosed with type 1 and type 2 diabetes and PNP.

Design

This study was a single-centre, quadruple-blinded, placebo-controlled trial with 70 participants receiving 600 mg of PEA or placebo daily, for 8 weeks, with a 94% rate of study participation completion. Primary outcomes were neuropathic pain and specific pain types (the BPI-DPN and NPSI). The secondary outcomes were sleep quality (MOS sleep scale), mood (DASS-21), glucose metabolism and inflammation.

Results

There was a significant reduction (P ≤ 0.001) in BPI-DPN total pain and pain interference, NPSI total score and sub-scores, except for evoked pain (P = 0.09) in the PEA group compared with the placebo group. The MOS sleep problem index and sub-scores significantly improved (P ≤ 0.001). DASS-21 depression scores significantly reduced (P = 0.03), but not anxiety or stress scores. Interleukin-6 and elevated C-reactive protein levels significantly reduced in the PEA group (P = 0.05), with no differences in fibrinogen between groups (P = 0.78) at treatment completion. There were no changes in safety pathology parameters, and the treatment was well tolerated.

Conclusions

The study demonstrated that the PEA formulation reduced diabetic peripheral neuropathic pain and inflammation along with improving mood and sleep. Further studies on the mechanistic effectiveness of PEA as an adjunct medicine and as a monotherapy pain analgesic are warranted.

Clinical Trial Registration

Registry name: Australian New Zealand Clinical Trials Registry (ANZCTR), Registration number: ACTRN12620001302943, Registration link: https://anzctr.org.au/Trial/Registration/TrialReview.aspx?id=380826, Actual study start date: 20 November 2020.

N-Palmitoyl-D-Glucosamine Inhibits TLR-4/NLRP3 and Improves DNBS-Induced Colon Inflammation through a PPAR-α-Dependent Mechanism

Similar to canine inflammatory enteropathy, inflammatory bowel disease (IBD) is a chronic idiopathic condition characterized by remission periods and recurrent flares in which diarrhea, visceral pain, rectal bleeding/bloody stools, and weight loss are the main clinical symptoms. Intestinal barrier function alterations often persist in the remission phase of the disease without ongoing inflammatory processes. However, current therapies include mainly anti-inflammatory compounds that fail to promote functional symptoms-free disease remission, urging new drug discoveries to handle patients during this step of the disease. ALIAmides (ALIA, autacoid local injury antagonism) are bioactive fatty acid amides that recently gained attention because of their involvement in the control of inflammatory response, prompting the use of these molecules as plausible therapeutic strategies in the treatment of several chronic inflammatory conditions. N-palmitoyl-D-glucosamine (PGA), an under-researched ALIAmide, resulted in being safe and effective in preclinical models of inflammation and pain, suggesting its potential engagement in the treatment of IBD. In our study, we demonstrated that micronized PGA significantly and dose-dependently reduces colitis severity, improves intestinal mucosa integrity by increasing the tight junction proteins expression, and downregulates the TLR-4/NLRP3/iNOS pathway via PPAR-α receptors signaling in DNBS-treated mice. The possibility of clinically exploiting micronized PGA as support for the treatment and prevention of inflammation-related changes in IBD patients would represent an innovative, effective, and safe strategy.

Therapeutic Targeting of Innate Immune Receptors Against SARS-CoV-2 Infection

The innate immune system is the first line of host's defense against invading pathogens. Multiple cellular sensors that detect viral components can induce innate antiviral immune responses. As a result, interferons and pro-inflammatory cytokines are produced which help in the elimination of invading viruses. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) belongs to Coronaviridae family, and has a single-stranded, positive-sense RNA genome. It can infect multiple hosts; in humans, it is responsible for the novel coronavirus disease 2019 (COVID-19). Successful, timely, and appropriate detection of SARS-CoV-2 can be very important for the early generation of the immune response. Several drugs that target the innate immune receptors as well as other signaling molecules generated during the innate immune response are currently being investigated in clinical trials. In this review, we summarized the current knowledge of the mechanisms underlying host sensing and innate immune responses against SARS-CoV-2 infection, as well as the role of innate immune receptors in terms of their therapeutic potential against SARS-CoV-2. Moreover, we discussed the drugs undergoing clinical trials and the FDA approved drugs against SARS-CoV-2. This review will help in understanding the interactions between SARS-CoV-2 and innate immune receptors and thus will point towards new dimensions for the development of new therapeutics, which can be beneficial in the current pandemic.

Palmitoylethanolamide (PEA) Inhibits SARS-CoV-2 Entry by Interacting with S Protein and ACE-2 Receptor

Lipids play a crucial role in the entry and egress of viruses, regardless of whether they are naked or enveloped. Recent evidence shows that lipid involvement in viral infection goes much further. During replication, many viruses rearrange internal lipid membranes to create niches where they replicate and assemble. Because of the close connection between lipids and inflammation, the derangement of lipid metabolism also results in the production of inflammatory stimuli. Due to its pivotal function in the viral life cycle, lipid metabolism has become an area of intense research to understand how viruses seize lipids and to design antiviral drugs targeting lipid pathways. Palmitoylethanolamide (PEA) is a lipid-derived peroxisome proliferator-activated receptor-α (PPAR-α) agonist that also counteracts SARS-CoV-2 entry and its replication. Our work highlights for the first time the antiviral potency of PEA against SARS-CoV-2, exerting its activity by two different mechanisms. First, its binding to the SARS-CoV-2 S protein causes a drop in viral infection of ~70%. We show that this activity is specific for SARS-CoV-2, as it does not prevent infection by VSV or HSV-2, other enveloped viruses that use different glycoproteins and entry receptors to mediate their entry. Second, we show that in infected Huh-7 cells, treatment with PEA dismantles lipid droplets, preventing the usage of these vesicular bodies by SARS-CoV-2 as a source of energy and protection against innate cellular defenses. This is not surprising since PEA activates PPAR-α, a transcription factor that, once activated, generates a cascade of events that leads to the disruption of fatty acid droplets, thereby bringing about lipid droplet degradation through β-oxidation. In conclusion, the present work demonstrates a novel mechanism of action for PEA as a direct and indirect antiviral agent against SARS-CoV-2. This evidence reinforces the notion that treatment with this compound might significantly impact the course of COVID-19. Indeed, considering that the protective effects of PEA in COVID-19 are the current objectives of two clinical trials (NCT04619706 and NCT04568876) and given the relative lack of toxicity of PEA in humans, further preclinical and clinical tests will be needed to fully consider PEA as a promising adjuvant therapy in the current COVID-19 pandemic or against emerging RNA viruses that share the same route of replication as coronaviruses.

PPAR Ligands Induce Antiviral Effects Targeting Perturbed Lipid Metabolism during SARS-CoV-2, HCV, and HCMV Infection

Simple Summary

The current coronavirus disease 2019 pandemic turned the attention of researchers to developing novel strategies to counteract virus infections. Despite several antiviral drugs being commercially available, there is an urgent need to identify novel molecules efficacious against viral infections that act through different mechanisms of action. In this context, our attention is focused on novel compounds acting on nuclear receptors, whose activity could be beneficial in viral infections, including coronavirus, hepatitis C virus, and cytomegalovirus.

Abstract

The manipulation of host metabolisms by viral infections has been demonstrated by several studies, with a marked influence on the synthesis and utilization of glucose, nucleotides, fatty acids, and amino acids. The ability of virus to perturb the metabolic status of the infected organism is directly linked to the outcome of the viral infection. A great deal of research in recent years has been focusing on these metabolic aspects, pointing at modifications induced by virus, and suggesting novel strategies to counteract the perturbed host metabolism. In this review, our attention is turned on PPARs, nuclear receptors controlling multiple metabolic actions, and on the effects played by PPAR ligands during viral infections. The role of PPAR agonists and antagonists during SARS-CoV-2, HCV, and HCMV infections will be analyzed.

Jacareubin inhibits TLR4-induced lung inflammatory response caused by the RBD domain of SARS-CoV-2 Spike protein

BACKGROUND

COVID-19, the disease caused by SARS-CoV-2 virus infection, has been a major public health problem worldwide in the last 2 years. SARS-CoV-2-dependent activation of innate immune receptors contributes to the strong local and systemic inflammatory reaction associated with rapid disease evolution. The receptor-binding domain (RBD) of Spike (S) viral protein (S-RBD) is essential for virus infection and its interacting molecules in target cells are still under identification. On the other hand, the search for accessible natural molecules with potential therapeutic use has been intense and remains an active field of investigation.

METHODS

C57BL6/J (control) and Toll-like receptor (TLR) 4-deficient (Lps del) mice were nebulized with recombinant S-RBD. Tumor Necrosis Factor-alpha (TNF-α) and Interleukin (IL)-6 production in bronchoalveolar lavages (BALs) was determined by enzyme-linked immunosorbent assay (ELISA). Lung-infiltrating cells recovered in BALs were quantified by hematoxylin-eosin (H&E) stain. In selected groups of animals, the natural compound Jacareubin or dexamethasone were intraperitoneally (ip) administered 2 hours before nebulization.

RESULTS

A rapid lung production of TNF-α and IL-6 and cell infiltration was induced by S-RBD nebulization in control but not in Lps del mice. Pre-treatment with Jacareubin or dexamethasone prevented S-RBD-induced TNF-α and IL-6 secretion in BALs from control animals.

CONCLUSIONS

S-RBD domain promotes lung TNF-α and IL-6 production in a TLR4-dependent fashion in C57BL6/J mice. Xanthone Jacareubin possesses potential anti-COVID-19 properties that, together with the previously tested anti-inflammatory activity, safety, and tolerance, make it a valuable drug to be further investigated for the treatment of cytokine production caused by SARS-CoV-2 infection.

Hepatoprotective role of peroxisome proliferator-activated receptor-α in non-cancerous hepatic tissues following transcatheter arterial embolization

Transcatheter arterial embolization (TAE) is a widely used technique in treating hepatic carcinoma but may cause liver injury in some cases. This study investigated the hepatoprotective effect of the preprocessed peroxisome proliferator-activated receptor-α (PPAR-α) agonist-WY-14643 following TAE. A total of 60 rabbit liver cancer models were developed and divided into a combined treatment (WY-14643 and TAE), TAE, and control groups. After TAE, we examined the histopathological picture and liver functions. Further, the expression of antioxidant enzymes, tumor necrosis factor-α (TNF-α), nuclear factor of κ-light chain of enhancer-activated B cells (NF-κB), PPAR-α, and B-cell lymphoma-2 (Bcl-2) was analyzed. Liver function tests, pathology score, and apoptosis index significantly worsened in the TAE group but were normalized in the combined treatment group. In addition, ELISA results showed that antioxidant enzyme activity significantly increased, while the malondialdehyde content and level of inflammatory cytokines were significantly reduced in the combined treatment group. Furthermore, compared to the TAE group, the expressions of PPAR-α, antioxidant enzymes superoxide dismutase1 (SOD1) and SOD2, and Bcl-2 were significantly elevated, while NF-κB was significantly reduced in the combined treatment group. On the other hand, the expression of NF-κB in tumor tissues was significantly reduced by pretreatment with WY-14643. Therefore, PPAR-α can ameliorate liver injury by exerting its anti-oxidative, anti-inflammatory, and anti-apoptotic functions.

Cannabidiol inhibits SARS-Cov-2 spike (S) protein-induced cytotoxicity and inflammation through a PPARγ-dependent TLR4/NLRP3/Caspase-1 signaling suppression in Caco-2 cell line

Given the abundancy of angiotensin converting enzyme 2 (ACE‐2) receptors density, beyond the lung, the intestine is considered as an alternative site of infection and replication for severe acute respiratory syndrome by coronavirus type 2 (SARS‐CoV‐2). Cannabidiol (CBD) has recently been proposed in the management of coronavirus disease 2019 (COVID‐19) respiratory symptoms because of its anti‐inflammatory and immunomodulatory activity exerted in the lung. In this study, we demonstrated the in vitro PPAR‐γ‐dependent efficacy of CBD (10⁻⁹‐10⁻⁷ M) in preventing epithelial damage and hyperinflammatory response triggered by SARS‐CoV‐2 spike protein (SP) in a Caco‐2 cells. Immunoblot analysis revealed that CBD was able to reduce all the analyzed proinflammatory markers triggered by SP incubation, such as tool‐like receptor 4 (TLR‐4), ACE‐2, family members of Ras homologues A‐GTPase (RhoA‐GTPase), inflammasome complex (NLRP3), and Caspase‐1. CBD caused a parallel inhibition of interleukin 1 beta (IL‐1β), IL‐6, tumor necrosis factor alpha (TNF‐α), and IL‐18 by enzyme‐linked immunosorbent assay (ELISA) assay. By immunofluorescence analysis, we observed increased expression of tight‐junction proteins and restoration of transepithelial electrical resistance (TEER) following CBD treatment, as well as the rescue of fluorescein isothiocyanate (FITC)–dextran permeability induced by SP. Our data indicate, in conclusion, that CBD is a powerful inhibitor of SP protein enterotoxicity in vitro.