Specialized Pro-resolving Mediators Regulate Alveolar Fluid Clearance during Acute Respiratory Distress Syndrome

Extract of Nanhaia speciosa J. Compton & Schrire alleviates LPS-induced acute lung injury via the NF-κB/Nrf2/AQPs pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Nanhaia speciosas J. Compton & Schrire (the name Nanhaia speciosas J. Compton & Schrire has been accepted by the World Checklist of Vascular Plants https://www.worldfloraonline.org/taxon/wfo-0001444004) is a traditional Zhuang medicine that have been widely used for centuries. It has been used in the treatment of lung inflammation, tuberculosis, rheumatic pain, lumbar muscle strain, and various other ailments, such as chronic hepatitis, menoxenia, leukorrhea, and injuries. In addition, N. speciosa has also been used to treat acute lung injury (ALI).

AIM OF THE STUDY

The objective of this study was to conduct a comparative analysis of the effects of various constituents present in N. speciosas extract (NSE) on ALI and the related mechanisms while also elucidating the potential active monomeric components.

MATERIALS AND METHODS

NSE was extracted using an AB-8 macroporous resin column, and five fractions (Fr. 0%, 25%, 50%, 75% and 95%) were obtained. The anti-inflammatory and antioxidant capacities of the five fractions were evaluated in an A549 cell-based in vitro model, with the aim of evaluating their potential therapeutic effects. The anti-inflammatory and antioxidant capacities of NSE were assessed in a murine model of ALI induced by intratracheal injection of LPS. We utilized an in vitro model to analyse the critical molecular mechanisms through which NSE ameliorates ALI. The chemical composition of the optimal fraction was analysed and confirmed using UHPLC/MS.

RESULTS

Different fractions (especially Fr. 75%) significantly reduced inflammation and oxidative stress in A549 cells. Fr.75% abrogated LPS-induced pathological alterations and decreased the lung W/D ratio, total protein concentration in BALF, and the levels of the proinflammatory factors TNF-α, IL-6, and IL-1β. Moreover, Fr.75% reduced MPO and MDA concentrations and elevated SOD and GSH concentrations in pulmonary tissues. Additionally, it decreased the pulmonary tissue inflammation caused by LPS by downregulating the expression of p-NF-κB p65 and upregulating the expression of Nrf2, AQP1 and AQP5. Fr. 75% decreased p-NF-κB p65 protein levels; increased Keap1, Nrf2, HO-1, NQO1, AQP1 and AQP5 protein levels; and promoted the entry of Nrf2 into the nucleus. After UHPLC/MS analysis was conducted, the flavonoid Maackiain was determined to potentially play a pivotal role in this process.

CONCLUSION

Fr.75% alleviates ALI by regulating the NF-κB/Nrf2/AQPs signalling pathway. The flavonoid Maackiain may also play an important role in this process. Overall, N. speciosas may be a potential therapeutic agent for the prevention and treatment of ALI.

Lipoxin A 4 /FPR2 signaling mitigates ferroptosis of alveolar epithelial cells via NRF2-dependent pathway during lung ischemia-reperfusion injury

BACKGROUND

Post-lung transplantation (LTx) injury can involve sterile inflammation due to ischemia-reperfusion injury (IRI). We investigated the cell-specific role of ferroptosis (excessive iron-mediated cell death) in mediating lung IRI and determined if specialized pro-resolving mediators such as Lipoxin A4 (LxA 4 ) can protect against ferroptosis in lung IRI.

METHODS

Single-cell RNA sequencing of lung tissue from post-LTx patients was analyzed. Lung IRI was evaluated in C57BL/6 (WT), formyl peptide receptor 2 knockout ( Fpr2 -/- ) and nuclear factor erythroid 2-related factor 2 knockout ( Nrf2 -/- ) mice using a hilar-ligation model with or without LxA 4 administration. Furthermore, the protective efficacy of LxA 4 was evaluated employing a murine orthotopic LTx model and in vitro studies using alveolar type II epithelial (ATII) cells.

RESULTS

Differential expression of ferroptosis-related genes was observed in post-LTx patient samples compared to healthy controls. A significant increase in the levels of oxidized lipids and reduction in the levels of intact lipids were observed in mice subjected to IRI compared to shams. Furthermore, pharmacological inhibition of ferroptosis with liproxstatin-1 mitigated lung IRI and lung dysfunction. Importantly, LxA 4 treatment attenuated pulmonary dysfunction, ferroptosis and inflammation in WT mice subjected to lung IRI, but not in Fpr2 -/- or Nrf2 -/- mice, after IRI. In the murine LTx model, LxA 4 treatment increased PaO 2 levels and attenuated lung IRI. Mechanistically, LxA 4 -mediated protection involves increase in NRF2 activation and glutathione concentration as well as decrease in MDA levels in ATII cells.

CONCLUSIONS

LxA 4 /FPR2 signaling on ATII cells mitigates ferroptosis via NRF2 activation and protects against lung IRI.

Signaling pathways and potential therapeutic targets in acute respiratory distress syndrome (ARDS)

Acute respiratory distress syndrome (ARDS) is a common condition associated with critically ill patients, characterized by bilateral chest radiographical opacities with refractory hypoxemia due to noncardiogenic pulmonary edema. Despite significant advances, the mortality of ARDS remains unacceptably high, and there are still no effective targeted pharmacotherapeutic agents. With the outbreak of coronavirus disease 19 worldwide, the mortality of ARDS has increased correspondingly. Comprehending the pathophysiology and the underlying molecular mechanisms of ARDS may thus be essential to developing effective therapeutic strategies and reducing mortality. To facilitate further understanding of its pathogenesis and exploring novel therapeutics, this review provides comprehensive information of ARDS from pathophysiology to molecular mechanisms and presents targeted therapeutics. We first describe the pathogenesis and pathophysiology of ARDS that involve dysregulated inflammation, alveolar-capillary barrier dysfunction, impaired alveolar fluid clearance and oxidative stress. Next, we summarize the molecular mechanisms and signaling pathways related to the above four aspects of ARDS pathophysiology, along with the latest research progress. Finally, we discuss the emerging therapeutic strategies that show exciting promise in ARDS, including several pharmacologic therapies, microRNA-based therapies and mesenchymal stromal cell therapies, highlighting the pathophysiological basis and the influences on signal transduction pathways for their use.

Possibility of averting cytokine storm in SARS-COV 2 patients using specialized pro-resolving lipid mediators

Fatal "cytokine storms (CS)" observed in critically ill COVID-19 patients are consequences of dysregulated host immune system and over-exuberant inflammatory response. Acute respiratory distress syndrome (ARDS), multi-system organ failure, and eventual death are distinctive symptoms, attributed to higher morbidity and mortality rates among these patients. Consequent efforts to save critical COVID-19 patients via the usage of several novel therapeutic options are put in force. Strategically, drugs being used in such patients are dexamethasone, remdesivir, hydroxychloroquine, etc. along with the approved vaccines. Moreover, it is certain that activation of the resolution process is important for the prevention of chronic diseases. Until recently Inflammation resolution was considered a passive process, rather it's an active biochemical process that can be achieved by the use of specialized pro-resolving mediators (SPMs). These endogenous mediators are an array of atypical lipid metabolites that include Resolvins, lipoxins, maresins, protectins, considered as immunoresolvents, but their role in COVID-19 is ambiguous. Recent evidence from studies such as the randomized clinical trial, in which omega 3 fatty acid was used as supplement to resolve inflammation in COVID-19, suggests that direct supplementation of SPMs or the use of synthetic SPM mimetics (which are still being explored) could enhance the process of resolution by regulating the aberrant inflammatory process and can be useful in pain relief and tissue remodeling. Here we discussed the biosynthesis of SPMs, & their mechanistic pathways contributing to inflammation resolution along with sequence of events leading to CS in COVID-19, with a focus on therapeutic potential of SPMs.

Potential role of lipoxin in the management of COVID-19: a narrative review

Severe acute respiratory syndrome coronavirus (SARS-CoV-2) infection leads to the development of coronavirus disease 2019 (COVID-19), which causes endothelial dysfunction (ED), oxidative stress (OS), and inflammatory disorders. These changes cause hypoxia and cytokine storm with the development of cardio-pulmonary complications. Bioactive lipids and other polyunsaturated fatty acids participate in a vital role in the SARS-CoV-2 infection process. One of these mediators is the anti-inflammatory compound, lipoxin (LX). LXs are produced from arachidonic acid (AA) by collaboration between 5-lipoxygenase (5-LO) and 12-15 LO during cell interactions. Thus, our goal was to review the probable role of LXs in COVID-19 regarding the effects of LXs on the inflammatory signaling pathways that are linked with COVID-19 pathogenesis and complications.

Inhibition of Inflammation and Regulation of AQPs/ENaCs/Na+-K+-ATPase Mediated Alveolar Fluid Transport by Total Flavonoids Extracted From Nervilia fordii in Lipopolysaccharide-induced Acute Lung Injury

Aims: The occurrence of vascular permeability pulmonary edema in acute lung injury (ALI) is related to the imbalance of alveolar fluid transport. Regulating the active transport of alveolar fluid by aquaporins (AQPs), epithelial sodium channels (ENaCs), and Na⁺-K⁺-ATPase can effectively reduce the edema fluid in the alveolar cavity and protect against ALI. We evaluated the therapeutic effects of total flavonoids, extracted from Nervilia fordii (TFENF), and investigated its potential mechanisms of alveolar fluid transport in a rat ALI model. Materials and methods: A model of lipopolysaccharide (LPS, 5 mg/kg)-induced ALI was established in Sprague-Dawley (SD) rats through the arteriae dorsalis penis. SD rats were divided into six groups, including the vehicle, LPS model, TFENF (6 mg/kg, 12 mg/kg, 24 mg/kg), and dexamethasone group (DEX group, 5 mg/kg). The wet-to-dry (W/D) lung weight ratio, oxygenation index, and histopathological observation were used to evaluate the therapeutic effect of TFENF. The mRNA expression of AQPs, ENaCs, and pro-inflammatory cytokines was determined using real-time polymerase chain reaction, whereas protein expression was determined using immunohistochemistry. The Na ⁺ -K ⁺ -ATPase activity was assessed using enzyme-linked immunosorbent assay. Results: LPS significantly stimulated the production of inflammatory mediators including tumor necrosis factor (TNF)-α and interleukin (IL)-1β, and disrupted the water transport balance in the alveolar cavity by inhibiting AQPs/ENaCs/Na ⁺ -K ⁺ -ATPase. Pretreatment with TFENF reduced the pathological damage and W/D ratio of the lungs and ameliorated the arterial blood oxygen partial pressure (PaO₂) and oxygenation index. TFENF further decreased the mRNA level of TNF-α and IL-1β; increased the expression of AQP-1, AQP-5, αENaC, and βENaC; and increased Na ⁺ -K ⁺ -ATPase activity. Moreover, the regulation of AQPs, βENaC, and Na ⁺ -K ⁺ -ATPase and the inhibition of TNF-α and IL-1β by TFENF were found to be dose dependent. Conclusion: TFENF protects against LPS-induced ALI, at least in part, through the suppression of inflammatory cytokines and regulation of the active transport capacity of AQPs/ENaCs/Na ⁺ -K ⁺ -ATPase. These findings suggest the therapeutic potential of TFENF as phytomedicine to treat inflammation and pulmonary edema in ALI.

Resolvin D1, therapeutic target in acute respiratory distress syndrome

Acute lung injury (ALI), or its more severe form, acute respiratory distress syndrome (ARDS), is a disease with high mortality and is a serious challenge facing the World Health Organization because there is no specific treatment. The excessive and prolonged immune response is the hallmark of this disorder, so modulating and regulating inflammation plays an important role in its prevention and treatment. Resolvin D1 (RvD1) as a specialized pro-resolving mediator has the potential to suppress the expression of inflammatory cytokines and to facilitate the production of antioxidant proteins by stimulating lipoxin A4 receptor/formyl peptide receptor 2 (ALX/FPR2). These changes limit the invasion of immune cells into the lung tissue, inhibit coagulation, and enhance cell protection against oxidative stress (OS). In particular, this biomolecule reduces the generation of reactive oxygen species (ROS) by blocking the activation of inflammatory transcription factors, especially nuclear factor-κB (NF-κB), and accelerating the synthesis of antioxidant compounds such as heme oxygenase 1 (HO-1) and superoxide dismutase (SOD). Therefore, the destruction and dysfunction of important cell components such as cytoplasmic membrane, mitochondria, Na+/k + adenosine triphosphatase (ATPase) and proteins involved in the phagocytic activity of scavenger macrophages are attenuated. Numerous studies on the effect of RvD1 over inflammation using animal models revealed that Rvs have both anti-inflammatory and pro-resolving capabilities and therefore, might have potential therapeutic value in treating ALI. Here, we review the current knowledge on the classification, biosynthesis, receptors, mechanisms of action, and role of Rvs in ALI/ARDS.

Role of specialized pro-resolving lipid mediators in pulmonary inflammation diseases: mechanisms and development

Inflammation is an essential mechanism of various diseases. The development and resolution of inflammation are complex immune-modulation processes which induce the involvement of various types of immune cells. Specialized pro-resolving lipid mediators (SPMs) have been demonstrated to be signaling molecules in inflammation. SPMs are involved in the pathophysiology of different diseases, especially respiratory diseases, including asthma, pneumonia, and chronic obstructive pulmonary disease. All of these diseases are related to the inflammatory response and its persistence. Therefore, a deeper understanding of the mechanisms and development of inflammation in respiratory disease, and the roles of the SPM family in the resolution process, might be useful in the quest for novel therapies and preventive measures for pulmonary diseases.

Role of DAMPs in respiratory virus-induced acute respiratory distress syndrome-with a preliminary reference to SARS-CoV-2 pneumonia

When surveying the current literature on COVID-19, the "cytokine storm" is considered to be pathogenetically involved in its severe outcomes such as acute respiratory distress syndrome, systemic inflammatory response syndrome, and eventually multiple organ failure. In this review, the similar role of DAMPs is addressed, that is, of those molecules, which operate upstream of the inflammatory pathway by activating those cells, which ultimately release the cytokines. Given the still limited reports on their role in COVID-19, the emerging topic is extended to respiratory viral infections with focus on influenza. At first, a brief introduction is given on the function of various classes of activating DAMPs and counterbalancing suppressing DAMPs (SAMPs) in initiating controlled inflammation-promoting and inflammation-resolving defense responses upon infectious and sterile insults. It is stressed that the excessive emission of DAMPs upon severe injury uncovers their fateful property in triggering dysregulated life-threatening hyperinflammatory responses. Such a scenario may happen when the viral load is too high, for example, in the respiratory tract, "forcing" many virus-infected host cells to decide to commit "suicidal" regulated cell death (e.g., necroptosis, pyroptosis) associated with release of large amounts of DAMPs: an important topic of this review. Ironically, although the aim of this "suicidal" cell death is to save and restore organismal homeostasis, the intrinsic release of excessive amounts of DAMPs leads to those dysregulated hyperinflammatory responses-as typically involved in the pathogenesis of acute respiratory distress syndrome and systemic inflammatory response syndrome in respiratory viral infections. Consequently, as briefly outlined in this review, these molecules can be considered valuable diagnostic and prognostic biomarkers to monitor and evaluate the course of the viral disorder, in particular, to grasp the eventual transition precociously from a controlled defense response as observed in mild/moderate cases to a dysregulated life-threatening hyperinflammatory response as seen, for example, in severe/fatal COVID-19. Moreover, the pathogenetic involvement of these molecules qualifies them as relevant future therapeutic targets to prevent severe/ fatal outcomes. Finally, a theory is presented proposing that the superimposition of coronavirus-induced DAMPs with non-virus-induced DAMPs from other origins such as air pollution or high age may contribute to severe and fatal courses of coronavirus pneumonia.

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

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

Can N-3 polyunsaturated fatty acids be considered a potential adjuvant therapy for COVID-19-associated cardiovascular complications?

Coronavirus disease 2019 (COVID-19), caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), has currently led to a global pandemic with millions of confirmed and increasing cases around the world. The novel SARS-CoV-2 not only affects the lungs causing severe acute respiratory dysfunction but also leads to significant dysfunction in multiple organs and physiological systems including the cardiovascular system. A plethora of studies have shown the viral infection triggers an exaggerated immune response, hypercoagulation and oxidative stress, which contribute significantly to poor cardiovascular outcomes observed in COVID-19 patients. To date, there are no approved vaccines or therapies for COVID-19. Accordingly, cardiovascular protective and supportive therapies are urgent and necessary to the overall prognosis of COVID-19 patients. Accumulating literature has demonstrated the beneficial effects of n-3 polyunsaturated fatty acids (n-3 PUFA) toward the cardiovascular system, which include ameliorating uncontrolled inflammatory reactions, reduced oxidative stress and mitigating coagulopathy. Moreover, it has been demonstrated the n-3 PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are precursors to a group of potent bioactive lipid mediators, generated endogenously, which mediate many of the beneficial effects attributed to their parent compounds. Considering the favorable safety profile for n-3 PUFAs and their metabolites, it is reasonable to consider n-3 PUFAs as potential adjuvant therapies for the clinical management of COVID-19 patients. In this article, we provide an overview of the pathogenesis of cardiovascular complications secondary to COVID-19 and focus on the mechanisms that may contribute to the likely benefits of n-3 PUFAs and their metabolites.

Nutraceuticals in the Prevention of Viral Infections, including COVID-19, among the Pediatric Population: A Review of the Literature

In recent years, there has been a growth in scientific interest in nutraceuticals, which are those nutrients in foods that have beneficial effects on health. Nutraceuticals can be extracted, used for food supplements, or added to foods. There has long been interest in the antiviral properties of nutraceuticals, which are especially topical in the context of the ongoing COVID-19 pandemic. Therefore, the purpose of this review is to evaluate the main nutraceuticals to which antiviral roles have been attributed (either by direct action on viruses or by modulating the immune system), with a focus on the pediatric population. Furthermore, the possible applications of these substances against SARS-CoV-2 will be considered.

Specialized proresolving mediators in infection and lung injury

Specialized proresolving mediators (SPMs) are endogenous lipid metabolites of long-chain polyunsaturated fatty acids that are involved in promoting the resolution of inflammation. Many disease conditions characterized by excessive inflammation have impaired or altered SPM biosynthesis, which may lead to chronic, unresolved inflammation. Exogenous administration of SPMs in infectious conditions has been shown to be effective at improving infection clearance and survival in preclinical models. SPMs have also shown tremendous promise in the context of inflammatory lung conditions, such as acute respiratory distress syndrome and chronic obstructive pulmonary disease, mostly in preclinical settings. To date, SPMs have not been studied in the context of the novel Coronavirus, severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2), however their preclinical efficacy in combatting infections and improving acute respiratory distress suggest they may be a valuable resource in the fight against Coronavirus disease-19 (COVID-19). Overall, while the research on SPMs is still evolving, they may offer a novel therapeutic option for inflammatory conditions.

Natural product derived phytochemicals in managing acute lung injury by multiple mechanisms

Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS) as common life-threatening lung diseases with high mortality rates are mostly associated with acute and severe inflammation in lungs. With increasing in-depth studies of ALI/ARDS, significant breakthroughs have been made, however, there are still no effective pharmacological therapies for treatment of ALI/ARDS. Especially, the novel coronavirus pneumonia (COVID-19) is ravaging the globe, and causes severe respiratory distress syndrome. Therefore, developing new drugs for therapy of ALI/ARDS is in great demand, which might also be helpful for treatment of COVID-19. Natural compounds have always inspired drug development, and numerous natural products have shown potential therapeutic effects on ALI/ARDS. Therefore, this review focuses on the potential therapeutic effects of natural compounds on ALI and the underlying mechanisms. Overall, the review discusses 159 compounds and summarizes more than 400 references to present the protective effects of natural compounds against ALI and the underlying mechanism.

Bone marrow mesenchymal stem cells derived miRNA-130b enhances epithelial sodium channel by targeting PTEN

Aims

Acute lung injury (ALI) is a clinical syndrome with high morbidity and mortality, and severe pulmonary edema is one of the characteristics. Epithelial sodium channel (ENaC) located on the apical side of alveolar type 2 epithelial (AT2) cells is the primary rate limiting segment in alveolar fluid clearance. Many preclinical studies have revealed that mesenchymal stem cells (MSCs) based therapy has great therapeutic potential for ALI, while the role of ENaC in this process is rarely known.

Methods

We studied the effects of bone marrow-derived MSCs (BMSCs) on the protein/mRNA expression and activity of ENaC in primary mouse AT2 and human H441 cells by co-culture with them, respectively. Moreover, the changes of miRNA-130b in AT2 cells were detected by qRT-PCR, and we studied the involvement of phosphatase and tensin homolog deleted on chromosome ten (PTEN) and the downstream PI3K/AKT pathway in the miRNA-130b regulation of ENaC.

Results

Our results demonstrated that BMSCs could increase ENaC protein expression and function, as well as the expression level of miRNA-130b. The dual luciferase target gene assay verified that PTEN was one of the target genes of miR-130b, which showed adverse effects on the protein expression of α/γ-ENaC and PTEN in AT2 cells. Upregulating miR-130b and/or knocking down PTEN resulted in the increase of α/γ-ENaC protein level, and the protein expression of p-AKT/AKT was enhanced by miR-130b. Both α and γ-ENaC protein expressions were increased after AT2 cells were transfected with siPTEN, which could be reversed by the co-administration of PI3K/AKT inhibitor LY294002.

Conclusion

In summary, miRNA-130b in BMSCs can enhance ENaC at least partially by targeting PTEN and activating PI3K/AKT pathway, which may provide a promising new direction for therapeutic strategy in ALI.

The Role of Micronutrients in Support of the Immune Response against Viral Infections

Viral infections are a leading cause of morbidity and mortality worldwide, and the importance of public health practices including handwashing and vaccinations in reducing their spread is well established. Furthermore, it is well known that proper nutrition can help support optimal immune function, reducing the impact of infections. Several vitamins and trace elements play an important role in supporting the cells of the immune system, thus increasing the resistance to infections. Other nutrients, such as omega-3 fatty acids, help sustain optimal function of the immune system. The main aim of this manuscript is to discuss of the potential role of micronutrients supplementation in supporting immunity, particularly against respiratory virus infections. Literature analysis showed that in vitro and observational studies, and clinical trials, highlight the important role of vitamins A, C, and D, omega-3 fatty acids, and zinc in modulating the immune response. Supplementation with vitamins, omega 3 fatty acids and zinc appears to be a safe and low-cost way to support optimal function of the immune system, with the potential to reduce the risk and consequences of infection, including viral respiratory infections. Supplementation should be in addition to a healthy diet and fall within recommended upper safety limits set by scientific expert bodies. Therefore, implementing an optimal nutrition, with micronutrients and omega-3 fatty acids supplementation, might be a cost-effective, underestimated strategy to help reduce the burden of infectious diseases worldwide, including coronavirus disease 2019 (COVID-19).

Aquaporins in lung health and disease: Emerging roles, regulation, and clinical implications

Aquaporins (AQPs) aka water channels are a family of conserved transmembrane proteins (~30 kDa monomers) expressed in various organ systems. Of the 13 AQPs (AQP0 through AQP12) in the human body, four (AQPs 1, 3, 4, and 5) are expressed in the respiratory system. These channels are conventionally known for mediating transcellular fluid movements. Certain AQPs (aquaglyceroporins) have the capability to transport glycerol and potentially other solutes. There is an emerging body of literature unveiling the non-conventional roles of AQPs such as in cell proliferation and migration, gas permeation, signal potentiation, etc. Initial gene knock-out studies established a physiological role for lung AQPs, particularly AQP5, in maintaining homeostasis, by mediating fluid secretion from submucosal glands onto the airway surface liquid (ASL) lining. Subsequent studies have highlighted the functional significance of AQPs, particularly AQP1 and AQP5 in lung pathophysiology and diseases, including but not limited to chronic and acute lung injury, chronic obstructive pulmonary disease (COPD), other inflammatory lung conditions, and lung cancer. AQP1 has been suggested as a potential prognostic marker for malignant mesothelioma. Recent efforts are directed toward exploiting AQPs as targets for diagnosis, prevention, intervention, and/or treatment of various lung conditions. Emerging information on regulatory pathways and directed mechanistic research are posited to unravel novel strategies for these clinical implications. Future considerations should focus on development of AQP inhibitors, blockers, and modulators for therapeutic needs, and better understanding the role of lung-specific AQPs in inter-individual susceptibility to chronic lung diseases such as COPD and cancer.

Rationale for the Use of Radiation-Activated Mesenchymal Stromal/Stem Cells in Acute Respiratory Distress Syndrome

We have previously shown that the combination of radiotherapy with human umbilical-cord-derived mesenchymal stromal/stem cells (MSCs) cell therapy significantly reduces the size of the xenotumors in mice, both in the directly irradiated tumor and in the distant nonirradiated tumor or its metastasis. We have also shown that exosomes secreted from MSCs preirradiated with 2 Gy are quantitatively, functionally and qualitatively different from the exosomes secreted from nonirradiated mesenchymal cells, and also that proteins, exosomes and microvesicles secreted by MSCs suffer a significant change when the cells are activated or nonactivated, with the amount of protein present in the exosomes of the preirradiated cells being 1.5 times greater compared to those from nonirradiated cells. This finding correlates with a dramatic increase in the antitumor activity of the radiotherapy when is combined with MSCs or with preirradiated mesenchymal stromal/stem cells (MSCs*). After the proteomic analysis of the load of the exosomes released from both irradiated and nonirradiated cells, we conclude that annexin A1 is the most important and significant difference between the exosomes released by the cells in either status. Knowing the role of annexin A1 in the control of hypoxia and inflammation that is characteristic of acute respiratory-distress syndrome (ARDS), we designed a hypothetical therapeutic strategy, based on the transplantation of mesenchymal stromal/stem cells stimulated with radiation, to alleviate the symptoms of patients who, due to pneumonia caused by SARS-CoV-2, require to be admitted to an intensive care unit for patients with life-threatening conditions. With this hypothesis, we seek to improve the patients' respiratory capacity and increase the expectations of their cure.

Potential benefits and risks of omega-3 fatty acids supplementation to patients with COVID-19

Studies have shown that infection, excessive coagulation, cytokine storm, leukopenia, lymphopenia, hypoxemia and oxidative stress have also been observed in critically ill Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) patients in addition to the onset symptoms. There are still no approved drugs or vaccines. Dietary supplements could possibly improve the patient's recovery. Omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), present an anti-inflammatory effect that could ameliorate some patients need for intensive care unit (ICU) admission. EPA and DHA replace arachidonic acid (ARA) in the phospholipid membranes. When oxidized by enzymes, EPA and DHA contribute to the synthesis of less inflammatory eicosanoids and specialized pro-resolving lipid mediators (SPMs), such as resolvins, maresins and protectins. This reduces inflammation. In contrast, some studies have reported that EPA and DHA can make cell membranes more susceptible to non-enzymatic oxidation mediated by reactive oxygen species, leading to the formation of potentially toxic oxidation products and increasing the oxidative stress. Although the inflammatory resolution improved by EPA and DHA could contribute to the recovery of patients infected with SARS-CoV-2, Omega-3 fatty acids supplementation cannot be recommended before randomized and controlled trials are carried out.

COVID-19 and pneumonia: a role for the uPA/uPAR system

Here, we highlight recent findings on the urokinase plasminogen activator (uPA)/uPA receptor (uPAR) system that suggest its potential role as a main orchestrator of fatal progression to pulmonary, kidney, and heart failure in patients with coronavirus. Patients with prolonged background inflammation can present aberrant inflammatory reactions, well recognized as the main factors that can result in death and probably sustained by a dysregulated uPA/uPAR system. SuPAR, the soluble form of uPAR, represents a biomarker of disease progression, and its levels correlate well with comorbidities associated with the death of patients with coronavirus. New drugs that regulate the uPA/uPAR system could help treat the severe complications of highly pathogenic human coronaviruses (hCoVs), including pandemic coronavirus 2019 (COVID-19).

Optimal Nutritional Status for a Well-Functioning Immune System Is an Important Factor to Protect against Viral Infections

Public health practices including handwashing and vaccinations help reduce the spread and impact of infections. Nevertheless, the global burden of infection is high, and additional measures are necessary. Acute respiratory tract infections, for example, were responsible for approximately 2.38 million deaths worldwide in 2016. The role nutrition plays in supporting the immune system is well-established. A wealth of mechanistic and clinical data show that vitamins, including vitamins A, B6, B12, C, D, E, and folate; trace elements, including zinc, iron, selenium, magnesium, and copper; and the omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid play important and complementary roles in supporting the immune system. Inadequate intake and status of these nutrients are widespread, leading to a decrease in resistance to infections and as a consequence an increase in disease burden. Against this background the following conclusions are made: (1) supplementation with the above micronutrients and omega-3 fatty acids is a safe, effective, and low-cost strategy to help support optimal immune function; (2) supplementation above the Recommended Dietary Allowance (RDA), but within recommended upper safety limits, for specific nutrients such as vitamins C and D is warranted; and (3) public health officials are encouraged to include nutritional strategies in their recommendations to improve public health.

Pro-resolving lipid mediators in sepsis and critical illness

PURPOSE OF REVIEW

Sepsis is a life-threatening condition caused by a dysregulated host response to infection that remains a huge clinical challenge. Recent evidence indicates that bioactive lipid mediators derived from polyunsaturated fatty acids termed specialized pro-resolving mediators (SPMs) are promising new candidates for treating critical illness.

RECENT FINDINGS

We highlight herein the protective actions of SPMs in experimental sepsis, cardiac dysfunction, and also lung and cerebral injury, and discuss their mechanisms of action. We also emphasize that failed resolution responses and dysregulated SPM pathways may provide an explanation for the ongoing chronic inflammation in many diseases including chronic heart failure.

SUMMARY

Importantly, monitoring plasma SPM profiles can predict patient outcomes in sepsis indicating their utility as new early biomarkers that may help stratify patients upon ICU admission.

The Role of Maresins in Inflammatory Pain: Function of Macrophages in Wound Regeneration

Although acute inflammatory responses are host-protective and generally self-limited, unresolved and delayed resolution of acute inflammation can lead to further tissue damage and chronic inflammation. The mechanism of pain induction under inflammatory conditions has been studied extensively; however, the mechanism of pain resolution is not fully understood. The resolution of inflammation is a biosynthetically active process, involving specialized pro-resolving mediators (SPMs). In particular, maresins (MaRs) are synthesized from docosahexaenoic acid (DHA) by macrophages and have anti-inflammatory and pro-resolving capacities as well as tissue regenerating and pain-relieving properties. A new class of macrophage-derived molecules—MaR conjugates in tissue regeneration (MCTRs)—has been reported to regulate phagocytosis and the repair and regeneration of damaged tissue. Macrophages not only participate in the biosynthesis of SPMs, but also play an important role in phagocytosis. They exhibit different phenotypes categorized as proinflammatory M1-like phenotypes and anti-inflammatory M2 phenotypes that mediate both harmful and protective functions, respectively. However, the signaling mechanisms underlying macrophage functions and phenotypic changes have not yet been fully established. Recent studies report that MaRs help resolve inflammatory pain by enhancing macrophage phagocytosis and shifting cytokine release to the anti-inflammatory M2 phenotypes. Consequently, this review elucidated the characteristics of MaRs and macrophages, focusing on the potent action of MaRs to enhance the M2 macrophage phenotype profiles that possess the ability to alleviate inflammatory pain.

Lipoxin A4 ameliorates alveolar fluid clearance disturbance in lipopolysaccharide-induced lung injury via aquaporin 5 and MAPK signaling pathway

Background

A characteristic of acute lung injury (ALI) is the inflammatory damage of alveolar fluid transport. Lipoxins are endogenous lipids involving in the resolution of inflammation. It is found that lipoxin A4 (LXA4) has the distinct properties to improve the anti-edema and pro-resolution function in inflammation. Since aquaporins (AQPs) have essential roles in the integrity of barrier function during fluid transport, especially AQP5 in the maintaining of the epithelium permeability, the current study is aimed to evaluate the potential role of LXA4 in regulating alveolar fluid clearance (AFC) during fluid transport and the corresponding change of AQP5 in the lung.

Methods

ALI was induced by the lipopolysaccharide (LPS) intraperitoneal injection, and LXA4 treatment was given 8 hours after LPS administration. We investigated changes in the capacity of AFC, pro-inflammatory cytokine concentrations in bronchoalveolar lavage fluid (BALF) and the severity of ALI. Then AQP5 expression in lung tissue and potential regulatory pathways in LPS-induced ALI was explored.

Results

LXA4 treatment was found to inhibit AFC capacity, inflammatory cytokine release, partially, alleviate ALI severity, and restored AQP5 expression partially. Additionally, we found that LXA4 played a protective role by the inhibition of the phosphorylation of p38 and JNK.

Conclusions

In summary, our results suggest that LXA4 plays a protective role in lipopolysaccharide-induced ALI by restoring AFC capacity and upregulating AQP5 expression and inhibiting the phosphorylation of p38 and JNK. These findings suggest potential new mechanism of LXA4 as anti-inflammation therapy for the impairment of alveolar fluid transport in ALI.