Ac2-26 ameliorates lung ischemia-reperfusion injury via the eNOS pathway

Salidroside inhibits the ferroptosis to alleviate lung ischemia reperfusion injury via the JAK2/STAT3 signalling pathway

OBJECTIVE

The present study aims to investigate the protective potential of salidroside in both lung ischemia/reperfusion injury (LIRI) mice model and cell hypoxia/reoxygenation (H/R)model and the involvement of ferroptosis and JAK2/STAT3 pathway.

MATERIALS AND METHODS

After we established the IR-induced lung injury model in mice, we administered salidroside and the ferroptosis inhibitor, ferrostatin-1, then assessed the lung tissue injury, ferroptosis (levels of reactive oxygen species level, malondialdehyde and glutathione), and inflammation in lung tissues. The levels of ferroptosis-related proteins (glutathione peroxidase 4, fibroblast-specific protein 1, solute carrier family 1 member 5 and glutaminase 2) in the lung tissue were measured with Western blotting. Next, BEAS-2B cells were used to establish an H/R cell model and treated with salidroside or ferrostatin-1 before the cell viability and the levels of lactate dehydrogenase (LDH), inflammatory factor, ferroptosis-related proteins were measured. The activation of the JAK2/STAT3 signaling pathway was measured with Western blotting, then its role was confirmed with STAT3 knockdown.

RESULTS

Remarkably, salidroside was found to alleviate ferroptosis, inflammation, and lung injury in LIRI mice and the cell injury in H/R cell model. Severe ferroptosis were observed in LIRI mice models and H/R-induced BEAS-2B cells, which was alleviated by salidroside. Furthermore, salidroside could inhibit JAK2/STAT3 activation induced by LIRI. STAT3 knockdown could enhance the effect of salidroside treatment on H/R-induced cell damage and ferroptosis in vitro.

CONCLUSIONS

Salidroside inhibits ferroptosis to alleviate lung ischemia reperfusion injury via the JAK2/STAT3 signaling pathway.

Ac2-26 Reduced Lung Injury After Cardiopulmonary Bypass via the AKT1/GSK3β/eNOS Pathway

INTRODUCTION

Cardiopulmonary bypass (CPB) leads to severe inflammation and lung injury. Our previous study showed that Ac2-26 (an active n-terminal peptide of Annexin A1) can reduce acute lung injury. The aim of this study was to evaluate the effect of Ac2-26 on lung injury in CPB rats.

METHODS

Forty rats were randomly divided into the sham, CPB, Ac, Ac/serine/threonine kinase 1 (AKT1), and Ac/ glycogen synthase kinase (GSK)-3β groups. The rats in the sham group only received anesthesia, intubation, and cannulation. The rats in the other 4 groups received the standard CPB procedure. The rats in the CPB, Ac, Ac/AKT1, and Ac/GSK3β groups were immediately injected with saline, Ac2-26 (1 mg/kg), Ac2-26 combined with short hairpin RNA (AKT1), or Ac2-26 combined with a GSK3β inhibitor after CPB. At 12 h after the end of CPB, the PaO2/ fraction of inspired oxygen ratio, wet/dry weight ratio and protein content in the bronchoalveolar lavage fluid (BALF) were recorded. The numbers of macrophages and neutrophils in the BALF and blood were determined. Cytokine levels in the blood and BALF were investigated. Lung tissue histology and apoptosis were estimated. The expression of nuclear factor kappa- B, AKT1, GSK3β, endothelial nitric oxide synthase and apoptosis-related proteins was analyzed. The survival of all the rats was recorded.

RESULTS

Compared with the rats in the sham group, all the parameters examined worsened in the rats that received CPB. Compared with those in the CPB group, Ac2-26 significantly improved pulmonary capillary permeability, reduced cytokine levels, and decreased histological scores and apoptosis. The protective effect of Ac2-26 on lung injury was significantly reversed by AKT1 short hairpin RNA or a GSK3β inhibitor.

CONCLUSIONS

Ac2-26 significantly reduced lung injury and inflammation after CPB. The protective effect of Ac2-26 mainly depended on the AKT1/GSK3β/endothelial nitric oxide synthase pathway.

Nitric Oxide/Glucose Transporter Type 4 Pathway Mediates Cardioprotection against Ischemia/Reperfusion Injury under Hyperglycemic and Diabetic Conditions in Rats

INTRODUCTION

The comorbidities of ischemic heart disease (IHD) and diabetes mellitus (DM) compromise the protection of the diabetic heart from ischemia/reperfusion (I/R) injury. We hypothesized that manipulation of reperfusion injury salvage kinase (RISK) and survivor activating factor enhancement (SAFE) pathways might protect the diabetic heart, and intervention of these pathways could be a new avenue for potentially protecting the diabetic heart.

METHODS

All hearts were subjected to 30-min ischemia and 30-min reperfusion. During reperfusion, hearts were exposed to molecules proven to protect the heart from I/R injury. The hemodynamic data were collected using suitable software. The infarct size, troponin T levels, and protein levels in hearts were evaluated.

RESULTS

Both cyclosporine-A and nitric oxide donor (SNAP) infusion at reperfusion protected 4-week diabetic hearts from I/R injury. However, 6-week diabetic hearts were protected only by SNAP, but not cyclosporin-A. These treatments significantly (p < 0.05) improved cardiac hemodynamics and decreased infarct size.

CONCLUSIONS

The administration of SNAP to diabetic hearts protected both 4- and 6-week diabetic hearts; however, cyclosporine-A protected only the 4-week diabetic hearts. The eNOS/GLUT-4 pathway executed the SNAP-mediated cardioprotection.

Ac2-26 reduced the liver injury after cardiopulmonary bypass in rats via AKT1/GSK3β/eNOS pathway

OBJECTIVE

About 10% of patients after cardiopulmonary bypass (CPB) would undergo acute liver injury, which aggravated the mortality of patients. Ac2-26 has been demonstrated to ameliorate organic injury by inhibiting inflammation. The present study aims to evaluate the effect and mechanism of Ac2-26 on acute liver injury after CPB.

METHODS

A total of 32 SD rats were randomized into sham, CPB, Ac, and Ac/AKT1 groups. The rats only received anesthesia, and rats in other groups received CPB. The rats in Ac/AKT1 were pre-injected with the shRNA to interfere with the expression of AKT1. The rats in CPB were injected with saline, and rats in Ac and Ac/AKT1 groups were injected with Ac2-26. After 12 h of CPB, all the rats were sacrificed and the peripheral blood and liver samples were collected to analyze. The inflammatory factors in serum and liver were detected. The liver function was tested, and the pathological injury of liver tissue was evaluated.

RESULTS

Compared with the sham group, the inflammatory factors, liver function, and pathological injury were worsened after CPB. Compared with the CPB group, the Ac2-26 significantly decreased the pro-inflammatory factors and increased the anti-inflammatory factor, improved liver function, and ameliorated the pathological injury. All the therapeutic effects of Ac2-26 were notably attenuated by the shRNA of AKT1. The Ac2-26 increased the GSK3β and eNOS, and this promotion was inhibited by the shRNA.

CONCLUSION

The Ac2-26 significantly treated the liver injury, inhibited inflammation, and improved liver function. The effect of Ac2-26 on liver injury induced by CPB was partly associated with the promotion of AKT1/GSK3β/eNOS.

Ac2-26 activated the AKT1/GSK3β pathway to reduce cerebral neurons pyroptosis and improve cerebral function in rats after cardiopulmonary bypass

BACKGROUND

Cardiopulmonary bypass (CPB) results in brain injury, which is primarily caused by inflammation. Ac2-26 protects against ischemic or hemorrhage brain injury. The present study was to explore the effect and mechanism of Ac2-26 on brain injury in CPB rats.

METHODS

Forty-eight rats were randomized into sham, CPB, Ac, Ac/AKT1, Ac/GSK3βi and Ac/AKT1/GSK3βa groups. Rats in sham group only received anesthesia and in the other groups received standard CPB surgery. Rats in the sham and CPB groups received saline, and rats in the Ac, Ac/AKT1, Ac/GSK3βi and Ac/AKT1/GSK3βa groups received Ac2-26 immediately after CPB. Rats in the Ac/AKT1, Ac/GSK3βi and Ac/AKT1/GSK3βa groups were injected with shRNA, inhibitor and agonist of GSK3β respectively. The neurological function score, brain edema and histological score were evaluated. The neuronal survival and hippocampal pyroptosis were assessed. The cytokines, activity of NF-κB, S100 calcium-binding protein β(S100β) and neuron-specific enolase (NSE), and oxidative were tested. The NLRP3, cleaved-caspase-1 and cleaved-gadermin D (GSDMD) in the brain were also detected.

RESULTS

Compared to the sham group, all indicators were aggravated in rats that underwent CPB. Compared to the CPB group, Ac2-26 significantly improved neurological scores and brain edema and ameliorated pathological injury. Ac2-26 reduced the local and systemic inflammation, oxidative stress response and promoted neuronal survival. Ac2-26 reduced hippocampal pyroptosis and decreased pyroptotic proteins in brain tissue. The protection of Ac2-26 was notably lessened by shRNA and inhibitor of GSK3β. The agonist of GSK3β recovered the protection of Ac2-26 in presence of shRNA.

CONCLUSIONS

Ac2-26 significantly improved neurological function, reduced brain injury via regulating inflammation, oxidative stress response and pyroptosis after CPB. The protective effect of Ac2-26 primarily depended on AKT1/ GSK3β pathway.

Annexin A1 improves immune responses and control of tissue parasitism during Leishmania amazonensis infection in BALB/c mice

Leishmaniases, a group of diseases caused by the species of the protozoan parasite Leishmania, remains a significant public health concern worldwide. Host immune responses play a crucial role in the outcome of Leishmania infections, and several mediators that regulate inflammatory responses are potential targets for therapeutic approaches. Annexin A1 (AnxA1), an endogenous protein endowed with anti-inflammatory and pro-resolving properties, has emerged as a potential player. We have shown that during L. braziliensis infection, deficiency of AnxA1 exacerbates inflammatory responses but does not affect parasite burden. Here, we have investigated the role of AnxA1 in L. amazonensis infection, given the non-healing and progressive lesions characteristic of this infectious model. Infection of AnxA1 KO BALB/c mice resulted in increased lesion size and tissue damage associated with higher parasite burdens and enhanced inflammatory response. Notably, therapeutic application of the AnxA1 peptidomimetic Ac2-26 improves control of parasite replication and increases IL-10 production in vivo and in vitro, in both WT and AnxA1 KO mice. Conversely, administration of WRW4, an inhibitor of FPR2/3, resulted in larger lesions and decreased production of IL-10, suggesting that the effects of AnxA1 during L. amazonensis infection are associated with the engagement of these receptors. Our study illuminates the role of AnxA1 in L. amazonensis infection, demonstrating its impact on the susceptibility phenotype of BALB/c mice. Furthermore, our results indicate that targeting the AnxA1 pathway by using the Ac2-26 peptide could represent a promising alternative for new treatments for leishmaniasis.

Galectin-3 as TREM2 upstream factor contributes to lung ischemia-reperfusion injury by regulating macrophage polarization

Lung ischemia-reperfusion injury (LIRI) is a complex "aseptic" inflammatory response, macrophage play a pivotal role in the pathogenesis of LIRI. Galectin-3 (Gal3), a lectin implicated inflammation, has received limited attention in LIRI. Studies have reported Gal3 as a ligand for triggering receptor expressed on myeloid cell 2 (TREM2) in macrophages in Alzheimer's disease. Hence, we established LIRI C57BL/6 mice model and hypoxia/glucose deprivation and reoxygenation (OGD/R) model to investigate the relationship among Gal3, TREM2, and macrophage polarization. Our result demonstrated inhibition of Gal3 significantly reduced M1-type macrophage polarization while markedly increased M2-type in LIRI. In addition, we observed colocalization of Gal3 and TREM2 in macrophages, inhibition of Gal3 could recover the downregulation of TREM2 induced by LIRI while promoting TREM2 expression could attenuate lung injury in LIRI. In summary, our findings suggest Gal3 as an upstream factor of TREM2, play a crucial role in LIRI by regulating macrophage polarization.

The role of annexin A1 peptide in regulating PI3K/Akt signaling pathway to reduce lung injury after cardiopulmonary bypass in rats

INTRODUCTION

Cardiopulmonary bypass (CPB) -induced lung ischemia-reperfusion (I/R) injury remains a large challenge in cardiac surgery; up to date, no effective treatment has been found. Annexin A1 (AnxA1) has an anti-inflammatory effect, and it has been proven to have a protective effect on CPB-induced lung injury. However, the specific mechanism of AnxA1 in CPB-induced lung injury is not well studied. Therefore, we established a CPB-induced lung injury model to explore the relevant mechanism of AnxA1 and try to find an effective treatment for lung protection.

METHODS

Male rats were randomized into five groups (n = 6, each): sham (S group), I/R exposure (I/R group), I/R + dimethyl sulfoxide (D group), I/R + Ac2-26 (AnxA1 peptide) (A group), and I/R + LY294002 (a PI3K specific inhibitor) (AL group). Arterial blood gas analysis and calculation of the oxygenation index, and respiratory index were performed. The morphological changes in lung tissues were observed under light and electron microscopes. TNF-α and IL-6 and total protein in lung bronchoalveolar lavage fluid were detected via enzyme-linked immunosorbent assay. The expressions of PI3K, Akt, and NF-κB (p65) as well as p-PI3K, p-Akt, p-NF-κB (p65), and AnxA1 were detected via western blotting.

RESULTS

Compared with the I/R group, the A group showed the following: lower lung pathological damage score; decreased expression of IL-6 and total protein in the bronchoalveolar lavage fluid, and TNF-α in the lung; increased lung oxygenation index; and improved lung function. These imply the protective role of Ac2-26, and show that LY294002 inhibited the ameliorative preconditioning effect of Ac2-26.

CONCLUSION

This finding suggested that the AnxA1 peptide Ac2-26 decreased the inflammation reaction and CPB-induced lung injury in rats, the lung protective effects of AnxA1may be correlated with the activation of PI3K/Akt signaling pathway.

Inhibition of DNA methylation attenuates lung ischemia-reperfusion injury after lung transplantation

OBJECTIVE

DNA methylation plays an important role in inflammation and oxidative stress. This study aimed to investigate the effect of inhibiting DNA methylation on lung ischemia-reperfusion injury (LIRI).

METHODS

We adopted a completely random design for our study. Thirty-two rats were randomized into the sham, LIRI, azathioprine (AZA), and pluripotin (SC1) groups. The rats in the LIRI, AZA, and SC1 groups received left lung transplantation and intravenous injection of saline, AZA, and SC1, respectively. After 24 hours of reperfusion, histological injury, the arterial oxygen partial pressure to fractional inspired oxygen ratio, the wet/dry weight ratio, protein and cytokine concentrations in lung tissue, and DNA methylation in lung tissue were evaluated. The pulmonary endothelium that underwent hypoxemia and reoxygenation was treated with AZA or SC1. Endothelial apoptosis, chemokines, reactive oxygen species, nuclear factor-κB, and apoptotic proteins in the endothelium were studied.

RESULTS

Inhibition of DNA methylation by AZA attenuated lung injury, inflammation, and the oxidative stress response, but SC1 aggravated LIRI injury. AZA significantly improved endothelial function, suppressed apoptosis and necrosis, reduced chemokines, and inhibited nuclear factor-κB.

CONCLUSIONS

Inhibition of DNA methylation ameliorates LIRI and apoptosis and improves pulmonary function via the regulation of inflammation and oxidative stress.

Ac2-26 attenuates hepatic ischemia-reperfusion injury in mice via regulating IL-22/IL-22R1/STAT3 signaling

Hepatic ischemia-reperfusion injury (HIRI) is one of the major sources of mortality and morbidity associated with hepatic surgery. Ac2-26, a short peptide of Annexin A1 protein, has been proved to have a protective effect against IRI. However, whether it exerts a protective effect on HIRI has not been reported. The HIRI mice model and the oxidative damage model of H₂O₂-induced AML12 cells were established to investigate whether Ac2-26 could alleviate HIRI by regulating the activation of IL-22/IL-22R1/STAT3 signaling. The protective effect of Ac2-26 was measured by various biochemical parameters related to liver function, apoptosis, inflammatory reaction, mitochondrial function and the expressions of IL-22, IL-22R1, p-STAT3^Tyr705. We discovered that Ac2-26 reduced the Suzuki score and cell death rate, and increased the cell viability after HIRI. Moreover, we unraveled that Ac2-26 significantly decreased the number of apoptotic hepatocytes, and the expressions of cleaved-caspase-3 and Bax/Bcl-2 ratio. Furthermore, HIRI increased the contents of malondialdehyde (MDA), NADP⁺/NADPH ratio and reactive oxygen species (ROS), whereas Ac2-26 decreased them significantly. Additionally, Ac2-26 remarkably alleviated mitochondria dysfunction, which was represented by an increase in the adenosine triphosphate (ATP) content and mitochondrial membrane potential, a decrease in mitochondrial DNA (mtDNA) damage. Finally, we revealed that Ac2-26 pretreatment could significantly inhibit the activation of IL-22/IL22R1/STAT3 signaling. In conclusion, this work demonstrated that Ac2-26 ameliorated HIRI by reducing oxidative stress and inhibiting the mitochondrial apoptosis pathway, which might be closely related to the inhibition of the IL-22/IL22R1/STAT3 signaling pathway.

Lipoxin A4 attenuates the lung ischaemia reperfusion injury in rats after lung transplantation

BACKGROUND

Lung ischaemia reperfusion injury (LIRI) is the major cause of primary lung dysfunction after lung transplantation. Lipoxin A4 inhibits the oxidative stress and inflammation. This study aimed to evaluate the potential protective effect of lipoxin A4 on LIRI in rats.

METHODS

SD (Sprague-Dawley) rats were randomised into the sham, LIRI and LA4 groups. Rats in the sham group received anaesthesia, thoracotomy and intravenous injection of saline, while those in the LIRI or LA4 group received left lung transplantation and intravenous injection of saline or lipoxin A4, respectively. After 24 h of reperfusion, the PaO₂/FiO₂ (Partial pressure of O2 to fraction inspiratory O2), wet/dry weight ratios and protein levels in lungs were measured to assess the alveolar capillary permeability. The oxidative stress response and inflammation were examined. The histological and apoptosis analyses of lung tissues were performed via HE staining (Haematoxylin-eosin staining) and TUNEL assay, respectively. The effects of lipoxin A4 on the endothelial viability and tube formation of hypoxaemia and reoxygenation-challenged rat pulmonary microvascular endothelium cells were determined.

RESULTS

Lipoxin A4 significantly ameliorated the alveolar capillary permeability, reduced the oxidative stress and inflammation in transplanted lungs. The histological injury and apoptosis of lung tissues were also alleviated by lipoxin A4. In vitro lipoxin A4 treatment promoted the endothelial tube formation and improved the endothelial viability.

CONCLUSION

Lipoxin A4 protects LIRI after lung transplantation in rats, and its therapeutic effect is associated with the properties of anti-inflammation, anti-oxidation, and endothelium protection.Key messages:Lung transplantation is a treatment approach for the patients with lung disease.LIRI is the major cause of postoperative primary lung dysfunction.Lipoxins A4 exhibits strong anti-inflammatory properties.

Ac2-26 mitigated acute respiratory distress syndrome rats via formyl peptide receptor pathway

BACKGROUND

Acute respiratory distress syndrome (ARDS) is characterized by severe local and systemic inflammation. Ac2-26, an Annexin A1 Peptide, can reduce the lung injury induced by reperfusion via the inhibition of inflammation. The present study aims to evaluate the effect and mechanism of Ac2-26 in ARDS.

METHODS

Thirty-two rats were anaesthetized and randomized into four groups: sham (S), ARDS (A), ARDS/Ac2-26 (AA), and ARDS/Ac2-26/BOC-2 (AAB) groups. Rats in the S group received saline for intratracheal instillation, while rats in the other three groups received endotoxin for intratracheal instillation, in order to prepare the ARDS and inject the saline, Ac2-26, and Ac2-26 combined with BOC-2. After 24 h, the PaO2/FiO2 ratio was calculated. The lung tissue wet-to-dry weight ratio and the protein level in bronchoalveolar lavage fluid (BALF) were tested. Then, the cytokines in BALF and serum, and the inflammatory cells in BALF were investigated. Afterwards, the oxidative stress response and histological injury was evaluated. Subsequently, the epithelium was cultured and analyzed to estimate the effect of Ac2-26 on apoptosis.

RESULTS

Compared to the S group, all indexes worsened in the A, AA, and AAB groups. Furthermore, compared to the S group, Ac2-26 significantly improved the lung injury and alveolar-capillary permeability, and inhibited the oxidative stress response. In addition, Ac2-26 reduced the local and systemic inflammation through the regulation of pro- and anti-inflammatory cytokines, and the decrease in inflammatory cells in BALF. Moreover, Ac2-26 inhibited the epithelium apoptosis induced by LPS through the modulation of apoptosis-regulated proteins. The protective effect of Ac2-26 on ARDS was partially reversed by the FPR inhibitor, BOC-2.

CONCLUSION

Ac2-26 reduced the lung injury induced by LPS, promoted alveolar-capillary permeability, ameliorated the local and systemic inflammation, and inhibited the oxidative stress response and apoptosis. The protection of Ac2-26 on ARDS was mainly dependent on the FPR pathway.

Annexin A1 protects against cerebral ischemia-reperfusion injury by modulating microglia/macrophage polarization via FPR2/ALX-dependent AMPK-mTOR pathway

Background

Cerebral ischemia–reperfusion (I/R) injury is a major cause of early complications and unfavorable outcomes after endovascular thrombectomy (EVT) therapy in patients with acute ischemic stroke (AIS). Recent studies indicate that modulating microglia/macrophage polarization and subsequent inflammatory response may be a potential adjunct therapy to recanalization. Annexin A1 (ANXA1) exerts potent anti-inflammatory and pro-resolving properties in models of cerebral I/R injury. However, whether ANXA1 modulates post-I/R-induced microglia/macrophage polarization has not yet been fully elucidated.

Methods

We retrospectively collected blood samples from AIS patients who underwent successful recanalization by EVT and analyzed ANXA1 levels longitudinally before and after EVT and correlation between ANXA1 levels and 3-month clinical outcomes. We also established a C57BL/6J mouse model of transient middle cerebral artery occlusion/reperfusion (tMCAO/R) and an in vitro model of oxygen–glucose deprivation and reoxygenation (OGD/R) in BV2 microglia and HT22 neurons to explore the role of Ac2-26, a pharmacophore N-terminal peptide of ANXA1, in regulating the I/R-induced microglia/macrophage activation and polarization.

Results

The baseline levels of ANXA1 pre-EVT were significantly lower in 23 AIS patients, as compared with those of healthy controls. They were significantly increased to the levels found in controls 2–3 days post-EVT. The increased post-EVT levels of ANXA1 were positively correlated with 3-month clinical outcomes. In the mouse model, we then found that Ac2-26 administered at the start of reperfusion shifted microglia/macrophage polarization toward anti-inflammatory M2-phenotype in ischemic penumbra, thus alleviating blood–brain barrier leakage and neuronal apoptosis and improving outcomes at 3 days post-tMCAO/R. The protection was abrogated when mice received Ac2-26 together with WRW4, which is a specific antagonist of formyl peptide receptor type 2/lipoxin A4 receptor (FPR2/ALX). Furthermore, the interaction between Ac2-26 and FPR2/ALX receptor activated the 5’ adenosine monophosphate-activated protein kinase (AMPK) and inhibited the downstream mammalian target of rapamycin (mTOR). These in vivo findings were validated through in vitro experiments.

Conclusions

Ac2-26 modulates microglial/macrophage polarization and alleviates subsequent cerebral inflammation by regulating the FPR2/ALX-dependent AMPK-mTOR pathway. It may be investigated as an adjunct strategy for clinical prevention and treatment of cerebral I/R injury after recanalization. Plasma ANXA1 may be a potential biomarker for outcomes of AIS patients receiving EVT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02174-3.

Netrin-1 reduces lung ischemia-reperfusion injury by increasing the proportion of regulatory T cells

Objective

Inflammation is the primary mechanism of lung ischemia-reperfusion injury (LIRI) and neurologic factors can regulate inflammatory immune responses. Netrin-1 is an axonal guidance molecule, but whether Netrin-1 plays a role in LIRI remains unclear.

Methods

A mouse model of LIRI was established. Immunohistochemistry was used to detect expression of Netrin-1 and to enumerate macrophages and T cells in lung tissue. The proportion of regulatory T cells (Tregs) was assessed by flow cytometry. Levels of apoptosis were assessed by terminal deoxynucleotidyl transferase dUTP nick end staining.

Results

Numbers of macrophages and T cells in the lung tissues of mice with LIRI were elevated, while expression of netrin-1 was significantly decreased. Flow cytometry showed that the proportion of Tregs in mice with LIRI was significantly decreased. The proportion of Tregs among lymphocytes was positively correlated with netrin-1 expression. In vitro experiments showed that netrin-1 promoted an increase in Treg proportion through the A2b receptor. Animal experiments showed that netrin-1 could inhibit apoptosis and reduce T cell and macrophage infiltration by increasing the proportion of Tregs, ultimately reducing LIRI. Treg depletion using an anti-CD25 monoclonal antibody blocked the effects of netrin-1.

Conclusion

Netrin-1 reduced LIRI by increasing the proportion of Tregs.

Ac2-26 mimetic peptide of annexin A1 to treat severe COVID-19: A hypothesis

The Coronavirus Diseases-2019 (COVID-19) pandemic leads many researchers around the world to study the SARS-CoV-s2 infection and pathology to find a treatment for it. This generates a massive production of papers including pre-clinical, clinical and revisions but till now no specific treatment were identified. Meanwhile, like other coronavirus infections, COVID-19 leads to the cytokine storm syndrome resulting in hyperinflammation, exacerbated immune response and multiple organ dysfunctions indicating that drugs that modulate this response, as glucocorticoids could be a treatment option. However glucocorticoids have several side effects or usage limitations. In this sense a drug with anti-inflammatory effects and capable to reduce inflammation but with less after-effects could be a powerful tool to combat COVID-19. Thus the Ac2-26 Mimetic Peptide of Annexin A1 emerges as a possible therapy. The peptide has many anti-inflammatory effects described including the reduction of interleukin (IL)-6, one of the main mediators of cytokine storm syndrome. Therefore the hypothesis to use the Ac2-26 peptide to treat severe COVID-19 will be highlighted in this paper.

Ac2-26 Alleviates Brain Injury after Cardiac Arrest and Cardiopulmonary Resuscitation in Rats via the eNOS Pathway

Background

Brain injury is the leading cause of death following cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). Ac2-26 and endothelial nitric oxide synthase (eNOS) have been shown to reduce neuroinflammation. This study is aimed at determining the mechanism by which Ac2-26 protects against inflammation during brain injury following CA and CPR.

Methods

Sixty-four rats were randomized into sham, saline, Ac2-26, and Ac2-26+L-NIO (endothelial nitric oxide synthase (eNOS) inhibitor) groups. Rats received Ac2-26, Ac2-26+L-NIO, or saline after CPR. Neurologic function was assessed at baseline, 24, and 72 hours after CPR. At 72 hours after resuscitation, serum and brain tissues were collected.

Results

Blood-brain barrier (BBB) permeability increased, and the number of surviving neurons and neurological function decreased in the saline group compared to the sham group. Anti-inflammatory and proinflammatory factors, neuron-specific enolase (NSE) levels, and the expression of eNOS, phosphorylated (p)-eNOS, inducible nitric oxide synthase (iNOS), and oxidative stress-related factors in the three CA groups significantly increased (P < 0.05). BBB permeability decreased, and the number of surviving neurons and neurological function increased in the Ac2-26 group compared to the saline group (P < 0.05). Ac2-26 increased anti-inflammatory and reduced proinflammatory markers, raised NSE levels, increased the expression of eNOS and p-eNOS, and reduced the expression of iNOS and oxidative stress-related factors compared to the saline group (P < 0.05). The effect of Ac2-26 on brain injury was reversed by L-NIO (P < 0.05).

Conclusions

Ac2-26 reduced brain injury after CPR by inhibiting oxidative stress and neuroinflammation and protecting the BBB. The therapeutic effect of Ac2-26 on brain injury was largely dependent on the eNOS pathway.