Therapeutic Potential of Annexin A1 in Ischemia Reperfusion Injury

A systematic review and in silico analysis of studies investigating the ischaemic penumbra proteome in animal models of experimental stroke

Ischaemic stroke results in the formation of a cerebral infarction bordered by an ischaemic penumbra. Characterising the proteins within the ischaemic penumbra may identify neuro-protective targets and novel circulating markers to improve patient care. This review assessed data from studies using proteomic platforms to compare ischaemic penumbra tissues to controls following experimental stroke in animal models. Proteins reported to differ significantly between penumbra and control tissues were analysed in silico to identify protein-protein interactions and over-represented pathways. Sixteen studies using rat (n = 12), mouse (n = 2) or primate (n = 2) models were included. Heterogeneity in the design of the studies and definition of the penumbra were observed. Analyses showed high abundance of p53 in the penumbra within 24 hours of permanent ischaemic stroke and was implicated in driving apoptosis, cell cycle progression, and ATM- MAPK- and p53- signalling. Between 1 and 7 days after stroke there were changes in the abundance of proteins involved in the complement and coagulation pathways. Favourable recovery 1 month after stroke was associated with an increase in the abundance of proteins involved in wound healing. Poor recovery was associated with increases in prostaglandin signalling. Findings suggest that p53 may be a target for novel therapeutics for ischaemic stroke.

ANXA1sp attenuates sepsis-induced myocardial injury by promoting mitochondrial biosynthesis and inhibiting oxidative stress and autophagy via SIRT3 upregulation

Sepsis-induced myocardial injury is one of the most difficult complications of sepsis in intensive care units. Annexin A1 (ANXA1) short peptide (ANXA1sp) protects organs during the perioperative period. However, the protective effect of ANXA1sp against sepsis-induced myocardial injury remains unclear. We aimed to explore the protective effects and mechanisms of ANXA1sp against sepsis-induced myocardial injury both in vitro and in vivo. Cellular and animal models of myocardial injury in sepsis were established with lipopolysaccharide. The cardiac function of mice was assessed by high-frequency echocardiography. Elisa assay detected changes in inflammatory mediators and markers of myocardial injury. Western blotting detected autophagy and mitochondrial biosynthesis-related proteins. Autophagic flux changes were observed by confocal microscopy, and autophagosomes were evaluated by TEM. ATP, SOD, ROS, and MDA levels were also detected.ANXA1sp pretreatment enhanced the 7-day survival rate, improved cardiac function, and reduced TNF-α, IL-6, IL-1β, CK-MB, cTnI, and LDH levels. ANXA1sp significantly increased the expression of sirtuin-3 (SIRT3), mitochondrial biosynthesis-related proteins peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α), and mitochondrial transcription factor A (TFAM). ANXA1sp increased mitochondrial membrane potential (△Ψm), ATP, and SOD, and decreased ROS, autophagy flux, the production of autophagosomes per unit area, and MDA levels. The protective effect of ANXA1sp decreased significantly after SIRT3 silencing in vitro and in vivo, indicating that the key factor in ANXA1sp's protective role is the upregulation of SIRT3. In summary, ANXA1sp attenuated sepsis-induced myocardial injury by upregulating SIRT3 to promote mitochondrial biosynthesis and inhibit oxidative stress and autophagy.

An In Silico Analysis Reveals Sustained Upregulation of Neuroprotective Genes in the Post-Stroke Human Brain

Ischemic stroke is a cerebrovascular disease caused by an interruption of blood flow to the brain, thus determining a lack of oxygen and nutrient supply. The ischemic event leads to the activation of several molecular signaling pathways involved in inflammation and the production of reactive oxygen species, causing irreversible neuronal damage. Several studies have focused on the acute phase of ischemic stroke. It is not clear if this traumatic event can influence some of the molecular processes in the affected area even years after the clinical event. In our study, we performed an in silico analysis using freely available raw data with the purpose of evaluating the transcriptomic state of post-mortem brain tissue. The samples were taken from non-fatal ischemic stroke patients, meaning that they suffered an ischemic stroke and lived for a period of about 2 years after the event. These samples were compared with healthy controls. The aim was to evaluate possible recovery processes useful to mitigating neuronal damage and the detrimental consequences of stroke. Our results highlighted differentially expressed genes codifying for proteins along with long non-coding genes with anti-inflammatory and anti-oxidant functions. This suggests that even after an amount of time from the ischemic insult, different neuroprotective mechanisms are activated to ameliorate brain conditions and repair post-stroke neuronal injury.

Sex differences in the effects of high fat diet on underlying neuropathology in a mouse model of VCID

BACKGROUND

Damage to the cerebral vasculature can lead to vascular contributions to cognitive impairment and dementia (VCID). A reduction in blood flow to the brain leads to neuropathology, including neuroinflammation and white matter lesions that are a hallmark of VCID. Mid-life metabolic disease (obesity, prediabetes, or diabetes) is a risk factor for VCID which may be sex-dependent (female bias).

METHODS

We compared the effects of mid-life metabolic disease between males and females in a chronic cerebral hypoperfusion mouse model of VCID. C57BL/6J mice were fed a control or high fat (HF) diet starting at ~ 8.5 months of age. Three months after diet initiation, sham or unilateral carotid artery occlusion surgery (VCID model) was performed. Three months later, mice underwent behavior testing and brains were collected to assess pathology.

RESULTS

We have previously shown that in this VCID model, HF diet causes greater metabolic impairment and a wider array of cognitive deficits in females compared to males. Here, we report on sex differences in the underlying neuropathology, specifically white matter changes and neuroinflammation in several areas of the brain. White matter was negatively impacted by VCID in males and HF diet in females, with greater metabolic impairment correlating with less myelin markers in females only. High fat diet led to an increase in microglia activation in males but not in females. Further, HF diet led to a decrease in proinflammatory cytokines and pro-resolving mediator mRNA expression in females but not males.

CONCLUSIONS

The current study adds to our understanding of sex differences in underlying neuropathology of VCID in the presence of a common risk factor (obesity/prediabetes). This information is crucial for the development of effective, sex-specific therapeutic interventions for VCID.

Formyl peptide receptor 2 activation by mitochondrial formyl peptides stimulates the neutrophil proinflammatory response via the ERK pathway and exacerbates ischemia-reperfusion injury

BACKGROUND

Ischemia-reperfusion injury (IRI) is an inevitable process in renal transplantation that significantly increases the risk of delayed graft function, acute rejection, and even graft loss. Formyl peptide receptor 2 (FPR2) is an important receptor in multiple septic and aseptic injuries, but its functions in kidney IRI are still unclear. This study was designed to reveal the pathological role of FPR2 in kidney IRI and its functional mechanisms.

METHODS

To explore the mechanism of FPR2 in kidney IRI, the model rats were sacrificed after IRI surgery. Immunofluorescence, enzyme-linked immunosorbent assays, and western blotting were used to detect differences in the expression of FPR2 and its ligands between the IRI and control groups. WRW₄ (WRWWWW-NH2), a specific antagonist of FPR2, was administered to kidney IRI rats. Kidney function and pathological damage were detected to assess kidney injury and recovery. Flow cytometry was used to quantitatively compare neutrophil infiltration among the experimental groups. Mitochondrial formyl peptides (mtFPs) were synthesized and administered to primary rat neutrophils together with the specific FPR family antagonist WRW₄ to verify our hypothesis in vitro. Western blotting and cell function assays were used to examine the functions and signaling pathways that FPR2 mediates in neutrophils.

RESULTS

FPR2 was activated mainly by mtFPs during the acute phase of IRI, mediating neutrophil migration and reactive oxygen species production in the rat kidney through the ERK1/2 pathway. FPR2 blockade in the early phase protected rat kidneys from IRI.

CONCLUSIONS

mtFPs activated FPR2 during the acute phase of IRI and mediated rat kidney injury by activating the migration and reactive oxygen species generation of neutrophils through the ERK1/2 pathway.

Annexin A1 (Ac2-26)-dependent Fpr2 receptor alleviates sepsis-induced acute kidney injury by inhibiting inflammation and apoptosis in vivo and in vitro

OBJECTIVES

Excessive inflammatory responses and apoptosis are critical pathologies that contribute to sepsis-induced acute kidney injury (SI-AKI). Annexin A1 (ANXA1), a member of the calcium-dependent phospholipid-binding protein family, protects against SI-AKI through its anti-inflammatory and antiapoptotic effects, but the underlying mechanisms are still largely unknown.

METHODS

In vivo, SI-AKI mouse models were established via caecal ligation and puncture (CLP) and were then treated with the Ac2-26 peptide of ANXA1 (ANXA1 (Ac2-26)), WRW4 (Fpr2 antagonist) or both. In vitro, HK-2 cells were induced by lipopolysaccharide (LPS) and then treated with ANXA1 (Ac2-26), Fpr2-siRNA or both.

RESULTS

In the present study, we found that the expression levels of ANXA1 were decreased, and the expression levels of TNF-α, IL-1β, IL-6, cleaved caspase-3, cleaved caspase-8 and Bax were significantly increased, accompanied by marked kidney tissue apoptosis in vivo. Moreover, we observed that ANXA1 (Ac2-26) significantly reduced the levels of TNF-α, IL-1β and IL-6 and cleaved caspase-3, cleaved caspase-8, FADD and Bax and inhibited apoptosis in kidney tissue and HK-2 cells, accompanied by pathological damage to kidney tissue. Seven-day survival, kidney function and cell viability were significantly improved in vivo and in vitro, respectively. Furthermore, the administration of ANXA1 (Ac2-26) inhibited the CLP- or LPS-induced phosphorylation of PI3K and AKT and downregulated the level of NF-κB in vivo and in vitro. Moreover, our data demonstrate that blocking the Fpr2 receptor by the administration of WRW4 or Fpr2-siRNA reversed the abovementioned regulatory role of ANXA1, accompanied by enhanced phosphorylation of PI3K and AKT and upregulation of the level of NF-κB in vivo and in vitro.

CONCLUSIONS

Taken together, this study provides evidence that the protective effect of ANXA1 (Ac2-26) on SI-AKI largely depends on the negative regulation of inflammation and apoptosis via the Fpr2 receptor.

Association between polymorphisms in miRNAs and ischemic stroke: A meta-analysis

BACKGROUND

Atherosclerosis remains a predominant cause of ischemic stroke (IS). Four miRNA polymorphisms associated with arteriosclerosis mechanism were meta-analyzed to explore whether they had predictive significance for IS.

METHODS

PubMed, Excerpta Medica database, Web of Science, Cochrane Library, Scopus, China National Knowledge Infrastructure, and China Wanfang Database were searched for relevant case-control studies published before September 2022. Two researchers independently reviewed the studies and extracted the data. Data synthesis was carried out on eligible studies. Meta-analysis, subgroup analysis, sensitivity analysis, and publication bias analysis were performed using Stata software 16.0.

RESULTS

Twenty-two studies were included, comprising 8879 cases and 12,091 controls. The results indicated that there were no significant associations between miR-146a C>G (rs2910164), miR-196a2 T>C (rs11614913) and IS risk in the overall analyses, but miR-149 T>C (rs2292832) and miR-499 A>G (rs3746444) increased IS risk under the allelic model, homozygote model and recessive model. The subgroup analyses based on Trial of Org 101072 in Acute Stroke Treatment classification indicated that rs2910164 increased small artery occlusion (SAO) risk under the allelic model, heterozygote model and dominant model; rs11614913 decreased the risk of SAO under the allelic model, homozygote model, heterozygote model and dominant model.

CONCLUSION

This Meta-analysis showed that all 4 single nucleotide polymorphisms were associated with the risk of IS or SAO, even though the overall and subgroup analyses were not entirely consistent.

Transcriptomic analysis identifies shared biological foundations between ischemic stroke and Alzheimer's disease

AIM

Alzheimer's disease (AD) and ischemic stroke (IS), two major neurological diseases, are suggested to be associated in clinical and pathophysiological levels. Previous studies have provided some insights into the possible genetic mechanisms behind the correlation between AD and IS, but this issue is still not clear. We implemented transcriptomic analysis to detect common hub genes and pathways to help promote the understanding of this issue.

MATERIALS AND METHODS

Four gene expression profiling datasets (GSE16561, GSE58294, GSE63060, and GSE63061) of peripheral whole blood, which contain 108 IS samples, 284 AD samples, and 285 matched controls, were employed to detect differentially expressed genes (DEGs) for AD and IS, which were further analyzed for shared biological pathways, candidate drugs, and transcription factors. Protein-protein interaction (PPI) network and drug-target interaction analysis were applied to identify hub genes and drug targets, respectively. Result verification was done with other independent datasets (GSE37587, GSE46480, and GSE140829). The difference in proportions of various immune cells in the peripheral blood of AD and IS patients were evaluated using CIBERSORT.

RESULTS

We identified 74 DEGs and 18 biological processes with statistical significance shared by AD and IS, 9 of which were immune-related pathways. Five hub genes scored high in the topological analysis of the PPI network, and we also found eight drug target genes and candidate drugs which were associated with AD and IS. As for immunological changes, an increase in the proportion of M0 macrophages was found in the peripheral circulation of both AD and IS patients, and SOD1 expression was significantly correlated with this change.

CONCLUSION

Collectively, the common DEGs and shared pathways found in this study suggest a potential shared etiology between AD and IS, behind which immune system, particularly the M0 macrophage elevation, might have important roles. While, the shared hub genes, potential therapeutic gene targets and drugs reported in this study provide promising treatment strategies for AD and IS.

Protective effects of annexin A1-derived peptide Ac2-26 on liver and kidney injuries induced by cisplatin in rats

AIMS

In this study we evaluated the effect of pharmacological treatment with annexin A1-derived peptide Ac_2-26 in an experimental model of toxicity induced by cisplatin.

MAIN METHODS

Male rats were divided into Sham (control), Cisplatin (received intraperitoneal injections of 10 mg/kg/day of cisplatin for 3 days) and Ac_2-26 (received intraperitoneal injections of 1 mg/kg/day of peptide, 15 min before cisplatin) groups.

KEY FINDINGS

After 6 h of the last dose of cisplatin, an acute inflammatory response was observed characterized by a marked increase in the number of neutrophils and GM-CSF, IL-1β, IL-6, IL-10 and TNF-α plasma levels. Treatment with Ac_2-26 produced higher levels of GM-CSF, corroborating the high numbers of neutrophils, and the anti-inflammatory cytokine IL-4. Ac_2-26 preserved the morphology of liver structures, preventing the damage caused by cisplatin, but did not reduce plasma levels of the hepatotoxicity biomarkers ARG1, GSTα and SDH. In the kidneys, the peptide maintained the markers of kidney damage CLU and KIM-1 at similar levels to the Sham group but did not avoid morphological changes caused by cisplatin. These effects of Ac_2-26 were associated with the reduction of Fpr1 and Fpr2 levels in the organs studied.

SIGNIFICANCE

Pharmacological treatment with peptide Ac_2-26 partially protects the liver and kidneys against the deleterious effects caused by cisplatin in this experimental model.

Therapeutic Peptides to Treat Myocardial Ischemia-Reperfusion Injury

Cardiovascular diseases (CVD) including acute myocardial infarction (AMI) rank first in worldwide mortality and according to the World Health Organization (WHO), they will stay at this rank until 2030. Prompt revascularization of the occluded artery to reperfuse the myocardium is the only recommended treatment (by angioplasty or thrombolysis) to decrease infarct size (IS). However, despite beneficial effects on ischemic lesions, reperfusion leads to ischemia-reperfusion (IR) injury related mainly to apoptosis. Improvement of revascularization techniques and patient care has decreased myocardial infarction (MI) mortality however heart failure (HF) morbidity is increasing, contributing to the cost-intense worldwide HF epidemic. Currently, there is no treatment for reperfusion injury despite promising results in animal models. There is now an obvious need to develop new cardioprotective strategies to decrease morbidity/mortality of CVD, which is increasing due to the aging of the population and the rising prevalence rates of diabetes and obesity. In this review, we will summarize the different therapeutic peptides developed or used focused on the treatment of myocardial IR injury (MIRI). Therapeutic peptides will be presented depending on their interacting mechanisms (apoptosis, necroptosis, and inflammation) reported as playing an important role in reperfusion injury following myocardial ischemia. The search and development of therapeutic peptides have become very active, with increasing numbers of candidates entering clinical trials. Their optimization and their potential application in the treatment of patients with AMI will be discussed.

Annexin-A1; the culprit or the solution?

Annexin‐A1 has a well‐defined anti‐inflammatory role in the innate immune system, but its function in adaptive immunity remains controversial. This glucocorticoid‐induced protein has been implicated in a range of inflammatory conditions and cancers, as well as being found to be overexpressed on the T cells of patients with autoimmune disease. Moreover, the formyl peptide family of receptors, through which annexin‐A1 primarily signals, has also been implicated in these diseases. In contrast, treatment with recombinant annexin‐A1 peptides resulted in suppression of inflammatory processes in murine models of inflammation. This review will focus on what is currently known about annexin‐A1 in health and disease and discuss the potential of this protein as a biomarker and therapeutic target.

Cardioprotective effects of alantolactone on isoproterenol-induced cardiac injury and cobalt chloride-induced cardiomyocyte injury

OBJECTIVES

Alantolactone (AL) is a compound extracted from the roots of Inula Racemosa that has shown beneficial effects in cardiovascular disease. However, the cardioprotective mechanism of AL against hypoxic/ischemic (H/I) injury is still unclear. This research aimed to determine AL's ability to protect the heart against isoproterenol (ISO)-induced MI injury in vivo and cobalt chloride (CoCl2) induced H/I injury in vitro.

METHODS

Electrocardiography (ECG), lactate dehydrogenase (LDH), creatine kinase (CK), and cardiac troponin I (cTnI) assays in addition to histological analysis of the myocardium were used to investigate the effects of AL in vivo. Influences of AL on L-type Ca2+ current (ICa-L) in isolated rat myocytes were observed by the patch-clamp technique. Furthermore, cell viability, apoptosis, oxidative stress injury, mitochondrial membrane potential, and intracellular Ca2+ concentration were examined in vitro.

RESULTS

The results indicated that AL treatment ameliorated the morphological and ECG changes associated with MI, and decreased levels of LDH, CK, and cTnI. Furthermore, pretreatment with AL elevated antioxidant enzyme activity and suppressed ROS production. AL prevented H/I-induced apoptosis, mitochondria damage, and calcium overload while reducing ICa-L in a concentration and time dependent fashion. The 50% inhibiting concentration (IC50) and maximal inhibitory effect (Emax) of AL were 17.29 μmol/L and 57.73 ± 1.05%, respectively.

CONCLUSION

AL attenuated MI-related injury by reducing oxidative stress, apoptosis, calcium overload, and mitochondria damage. These cardioprotective effects may be related to the direct inhibition of ICa-L.

Neutrophils and Platelets: Immune Soldiers Fighting Together in Stroke Pathophysiology

Neutrophils and platelets exhibit a diverse repertoire of functions in thromboinflammatory conditions such as stroke. Most cerebral ischemic events result from longstanding chronic inflammation secondary to underlying pathogenic conditions, e.g., hypertension, diabetes mellitus, obstructive sleep apnea, coronary artery disease, atrial fibrillation, morbid obesity, dyslipidemia, and sickle cell disease. Neutrophils can enable, as well as resolve, cerebrovascular inflammation via many effector functions including neutrophil extracellular traps, serine proteases and reactive oxygen species, and pro-resolving endogenous molecules such as Annexin A1. Like neutrophils, platelets also engage in pro- as well as anti-inflammatory roles in regulating cerebrovascular inflammation. These anucleated cells are at the core of stroke pathogenesis and can trigger an ischemic event via adherence to the hypoxic cerebral endothelial cells culminating in aggregation and clot formation. In this article, we review and highlight the evolving role of neutrophils and platelets in ischemic stroke and discuss ongoing preclinical and clinical strategies that may produce viable therapeutics for prevention and management of stroke.

Therapeutic Potential of Annexin A1 Modulation in Kidney and Cardiovascular Disorders

Renal and cardiovascular disorders are very prevalent and associated with significant morbidity and mortality. Among diverse pathogenic mechanisms, the dysregulation of immune and inflammatory responses plays an essential role in such disorders. Consequently, the discovery of Annexin A1, as a glucocorticoid-inducible anti-inflammatory protein, has fueled investigation of its role in renal and cardiovascular pathologies. Indeed, with respect to the kidney, its role has been examined in diverse renal pathologies, including acute kidney injury, diabetic nephropathy, immune-mediated nephropathy, drug-induced kidney injury, kidney stone formation, and renal cancer. Regarding the cardiovascular system, major areas of investigation include the role of Annexin A1 in vascular abnormalities, atherosclerosis, and myocardial infarction. Thus, this review briefly describes major structural and functional features of Annexin A1 followed by a review of its role in pathologies of the kidney and the cardiovascular system, as well as the therapeutic potential of its modulation for such disorders.

Acetylation of ANXA1 reduces caspase-3 activation by enhancing the phosphorylation of caspase-9 under OGD/R conditions

SIRT2, a Class III HDACs, aggravates cell damage and activates caspase-3 under oxygen-glucose deprivation/reoxygenation and glucose (OGD/R) conditions. In this paper, we demonstrated the adverse effects of SIRT2 on cells after OGD/R attacks, which were mediated by increased interactions between SIRT2 and ANXA1, and explicated the mechanisms by which acetylated ANXA1 affects the activation and cleavage of caspase-3. We found that the acetylation level of ANXA1 was decreased through the its increased interactions with SIRT2 after the OGD/R insult. The lysine 312 residue (K312) was selected as the target site in ANXA1 because it is associated with SIRT2, and its mimic (K312Q) and silent (K312R) mutants were then established through site mutagenesis. Under OGD/R conditions, the acetylation mimic of K312Q ANXA1 accumulated in the cytoplasm, decreasing the activity levels of caspase-3 and the upstream initiator caspase-9, compared with the levels of WT and K312R ANXA1. Furthermore, K312Q ANXA1 intervened in the interactions of caspase-3 to caspase-9 by increasing the phosphorylation levels of caspase-9 and inhibited its cleavage by downregulating PRKAR2B, a regulatory subunit of protein kinase A (PKA). In this process, K312Q ANXA1 was found to be directly associated with PRKAR2B, diminishing its restriction on the catalytic subunit of PKA. In conclusion, acetylated ANXA1 can promote the phosphorylation of caspase-9 to decrease the activation of caspase-3 by enhancing the expression of a kinase upstream of caspase-9 after the OGD/R stimulation.

The Role of Annexin A1 and Formyl Peptide Receptor 2/3 Signaling in Chronic Corticosterone-Induced Depression-Like behaviors and Impairment in Hippocampal-Dependent Memory

BACKGROUND

The activity of the Hypothalamic-Pituitary-Adrenal (HPA) axis is commonly dysregulated in stress-related psychiatric disorders. Annexin A1 (ANXA1), an endogenous ligand of Formyl Peptide Receptor (FPR) 2/3, is a member of the family of phospholipid- and calcium-binding proteins with a well-defined role in the delayed early inhibitory feedback of Glucocorticoids (GC) in the pituitary gland and implicated in the occurrence of behavioural disorders such as anxiety.

OBJECTIVE

The present study aimed to evaluate the potential role of ANXA1 and its main receptor, as a cellular mediator of behavioural disorders, in a model of Corticosterone (CORT)-induced depression and subsequently, the possible correlation between the depressive state and impairment of hippocampal memory.

METHODS

To induce the depression model, Wild-Type (WT), ANXA1 Knockout (KO), and FPR2/3 KO mice were exposed to oral administration of CORT for 28 days dissolved in drinking water. Following this, histological, biochemical and behavioural analyses were performed.

RESULTS

FPR2/3 KO and ANXA1 KO mice showed improvement in anxiety and depression-like behaviour compared with WT mice after CORT administration. In addition, FPR2/3 KO and ANXA1 KO mice showed a reduction in histological alterations and neuronal death in hippocampal sections. Moreover, CORT+ FPR2/3 KO and ANXA1 KO, exhibited a higher expression of Brain-Derived Neurotrophic Factor (BDNF), phospho-ERK, cAMP response element-binding protein (pCREB) and a decrease in Serotonin Transporter Expression (SERT) compared to WT(CORT+) mice.

CONCLUSION

In conclusion, the absence of the ANXA1 protein, even more than the absence of its main receptor (FPR 2/3), was fundamental to the inhibitory action of GC on the HPA axis; it also maintained the hippocampal homeostasis by preventing neuronal damage associated with depression.

Detecting retinal cell stress and apoptosis with DARC: Progression from lab to clinic

DARC (Detection of Apoptosing Retinal Cells) is a retinal imaging technology that has been developed within the last 2 decades from basic laboratory science to Phase 2 clinical trials. It uses ANX776 (fluorescently labelled Annexin A5) to identify stressed and apoptotic cells in the living eye. During its development, DARC has undergone biochemistry optimisation, scale-up and GMP manufacture and extensive preclinical evaluation. Initially tested in preclinical glaucoma and optic neuropathy models, it has also been investigated in Alzheimer, Parkinson's and Diabetic models, and used to assess efficacy of therapies. Progression to clinical trials has not been speedy. Intravenous ANX776 has to date been found to be safe and well-tolerated in 129 patients, including 16 from Phase 1 and 113 from Phase 2. Results on glaucoma and AMD patients have been recently published, and suggest DARC with an AI-aided algorithm can be used to predict disease activity. New analyses of DARC in GA prediction are reported here. Although further studies are needed to validate these findings, it appears there is potential of the technology to be used as a biomarker. Much larger clinical studies will be needed before it can be considered as a diagnostic, although the relatively non-invasive nature of the nasal as opposed to intravenous administration would widen its acceptability in the future as a screening tool. This review describes DARC development and its progression into Phase 2 clinical trials from lab-based research. It discusses hypotheses, potential challenges, and regulatory hurdles in translating technology.

Inhibition of SENP6 restrains cerebral ischemia-reperfusion injury by regulating Annexin-A1 nuclear translocation-associated neuronal apoptosis

Rationale: Annexin-A1 (ANXA1) has previously been proposed to play a crucial role in neuronal apoptosis during ischemic stroke injury. Our recent study demonstrated that ANXA1 was modified by SUMOylation, and that this modification was greatly weakened after cerebral ischemia, but its effect on neuronal death and the underlying mechanism have not been fully elucidated. Methods: Mice subjected to middle cerebral artery occlusion were established as the animal model and primary cultured neurons treated with oxygen-glucose deprivation and reperfusion was established as the cell model of ischemic stroke. The Ni²⁺-NTA agarose affinity pull-down assay was carried out to determine the SUMOylation level of ANXA1. Co-immunoprecipitation assays was utilized to explore the protein interaction. Immunoblot analysis, quantitative real-time PCR, Luciferase reporter assay were performed to identify the regulatory mechanism. LDH release and TUNEL staining was performed to investigate the neuronal cytotoxicity and apoptosis, respectively. Results: In this study, we identified the deSUMOylating enzyme sentrin/SUMO-specific protease 6 (SENP6) as a negative regulator of ANXA1 SUMOylation. Notably, we found that SENP6-mediated deSUMOylation of ANXA1 induced its nuclear translocation and triggered neuronal apoptosis during cerebral ischemic injury. A mechanistic study demonstrated that SENP6-mediated deSUMOylation of ANXA1 promoted TRPM7- and PKC-dependent phosphorylation of ANXA1. Furthermore, blocking the deSUMOylation of ANXA1 mediated by SENP6 inhibited the transcriptional activity of p53, decreased Bid expression, suppressed caspase-3 pathway activation and reduced the apoptosis of primary neurons subjected to oxygen-glucose deprivation and reperfusion. More importantly, SENP6 inhibition by overexpression of a SENP6 catalytic mutant in neurons resulted in significant improvement in neurological function in the mouse model of ischemic stroke. Conclusions: Taken together, the results of this study identified a previously unidentified function of SENP6 in neuronal apoptosis and strongly indicated that SENP6 inhibition may provide therapeutic benefits for cerebral ischemia.

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.

Annexin Animal Models-From Fundamental Principles to Translational Research

Routine manipulation of the mouse genome has become a landmark in biomedical research. Traits that are only associated with advanced developmental stages can now be investigated within a living organism, and the in vivo analysis of corresponding phenotypes and functions advances the translation into the clinical setting. The annexins, a family of closely related calcium (Ca²⁺)- and lipid-binding proteins, are found at various intra- and extracellular locations, and interact with a broad range of membrane lipids and proteins. Their impacts on cellular functions has been extensively assessed in vitro, yet annexin-deficient mouse models generally develop normally and do not display obvious phenotypes. Only in recent years, studies examining genetically modified annexin mouse models which were exposed to stress conditions mimicking human disease often revealed striking phenotypes. This review is the first comprehensive overview of annexin-related research using animal models and their exciting future use for relevant issues in biology and experimental medicine.

The impact of thrombo-inflammation on the cerebral microcirculation

The intertwined processes of thrombosis and inflammation (termed "thrombo-inflammation") are significant drivers of cerebrovascular diseases, and as such, they represent prime targets for drug discovery programs focusing on treatment and management of cerebrovascular diseases. Most cerebrovascular events result from chronic systemic microcirculatory dysfunction due to underlying conditions, for example, hypertension, diabetes mellitus, coronary artery disease, dyslipidemia, and sickle cell disease. Immune cells especially neutrophils play a critical role in the onset and maintenance of neuroinflammatory responses in the microcirculation. Neutrophils have the ability to drive both inflammatory and anti-inflammatory/pro-resolution effects depending on the underlying vascular state (physiological vs. pathological). In this article, we highlight the pathophysiological role of neutrophils in stroke and discuss ongoing pharmacotherapeutic strategies that are focused on identifying potential therapeutic targets for enhancing neuroprotection, mitigating inflammatory pathways, and enabling resolution.

Targeting the AnxA1/Fpr2/ALX pathway regulates neutrophil function, promoting thromboinflammation resolution in sickle cell disease

Neutrophils play a crucial role in the intertwined processes of thrombosis and inflammation. An altered neutrophil phenotype may contribute to inadequate resolution, which is known to be a major pathophysiological contributor of thromboinflammatory conditions such as sickle cell disease (SCD). The endogenous protein annexin A1 (AnxA1) facilitates inflammation resolution via formyl peptide receptors (FPRs). We sought to comprehensively elucidate the functional significance of targeting the neutrophil-dependent AnxA1/FPR2/ALX pathway in SCD. Administration of AnxA1 mimetic peptide AnxA1Ac2-26 ameliorated cerebral thrombotic responses in Sickle transgenic mice via regulation of the FPR2/ALX (a fundamental receptor involved in resolution) pathway. We found direct evidence that neutrophils with SCD phenotype play a key role in contributing to thromboinflammation. In addition, AnxA1Ac2-26 regulated activated SCD neutrophils through protein kinase B (Akt) and extracellular signal-regulated kinases (ERK1/2) to enable resolution. We present compelling conceptual evidence that targeting the AnxA1/FPR2/ALX pathway may provide new therapeutic possibilities against thromboinflammatory conditions such as SCD.

2-Methoxyestradiol Protects Against Lung Ischemia/Reperfusion Injury by Upregulating Annexin A1 Protein Expression

Background: 2-Methoxyestradiol (2ME), a natural 17-β estradiol metabolite, is a potent anti-inflammatory agent, but its effect on ischemia/reperfusion (IR)-induced acute lung inflammation remains unknown. Annexin A1 (AnxA1), a glucocorticoid-regulated protein, is effective at inhibiting neutrophil transendothelial migration by binding the formyl peptide receptors (FPRs). We aimed to investigate whether 2ME upregulates the expression of AnxA1 and protects against IR-induced lung damage. Methods: IR-mediated acute lung inflammation was induced by ischemia for 40 min followed by reperfusion for 60 min in an isolated, perfused rat lung model. The rat lungs were randomly treated with vehicle or 2ME, and the functional relevance of AnxA1 was determined using an anti-AnxA1 antibody or BOC2 (a pan-receptor antagonist of the FPR). In vitro, human primary alveolar epithelial cells (HPAECs) and rat neutrophils were pretreated with 2ME and an AnxA1 siRNA or anti-AnxA1 antibody and subjected to hypoxia-reoxygenation (HR). Results: 2ME significantly decreased all lung edema parameters, neutrophil infiltration, oxidative stress, proinflammatory cytokine production, lung cell apoptosis, tight junction protein disruption, and lung tissue injury in the IR-induced acute lung inflammation model. 2ME also increased the expression of the AnxA1 mRNA and protein and suppressed the activation of nuclear factor-κB (NF-κB). In vitro, 2ME attenuated HR-triggered NF-κB activation and interleukin-8 production in HPAECs, decreased transendothelial migration, tumor necrosis factor-α production, and increased apoptosis in neutrophils exposed to HR. These protective effects of 2ME were significantly abrogated by BOC2, the anti-AnxA1 antibody, or AnxA1 siRNA. Conclusions: 2ME ameliorates IR-induced acute lung inflammation by increasing AnxA1 expression. Based on these results, 2ME may be a promising agent for attenuating IR-induced lung injury.

Regulation of Inflammation and Oxidative Stress by Formyl Peptide Receptors in Cardiovascular Disease Progression

G protein-coupled receptors (GPCRs) are the most important regulators of cardiac function and are commonly targeted for medical therapeutics. Formyl-Peptide Receptors (FPRs) are members of the GPCR superfamily and play an emerging role in cardiovascular pathologies. FPRs can modulate oxidative stress through nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent reactive oxygen species (ROS) production whose dysregulation has been observed in different cardiovascular diseases. Therefore, many studies are focused on identifying molecular mechanisms of the regulation of ROS production. FPR1, FPR2 and FPR3 belong to the FPRs family and their stimulation triggers phosphorylation of intracellular signaling molecules and nonsignaling proteins that are required for NADPH oxidase activation. Some FPR agonists trigger inflammatory processes, while other ligands activate proresolving or anti-inflammatory pathways, depending on the nature of the ligands. In general, bacterial and mitochondrial formylated peptides activate a proinflammatory cell response through FPR1, while Annexin A1 and Lipoxin A4 are anti-inflammatory FPR2 ligands. FPR2 can also trigger a proinflammatory pathway and the switch between FPR2-mediated pro- and anti-inflammatory cell responses depends on conformational changes of the receptor upon ligand binding. Here we describe the detrimental or beneficial effects of the main FPR agonists and their potential role as new therapeutic and diagnostic targets in the progression of cardiovascular diseases.

Annexin A1 alleviates kidney injury by promoting the resolution of inflammation in diabetic nephropathy

Since failed resolution of inflammation is a major contributor to the progression of diabetic nephropathy, identifying endogenously generated molecules that promote the physiological resolution of inflammation may be a promising therapeutic approach for this disease. Annexin A1 (ANXA1), as an endogenous mediator, plays an important role in resolving inflammation. Whether ANXA1 could affect established diabetic nephropathy through modulating inflammatory states remains largely unknown. In the current study, we found that in patients with diabetic nephropathy, the levels of ANXA1 were upregulated in kidneys, and correlated with kidney function as well as kidney outcomes. Therefore, the role of endogenous ANXA1 in mouse models of diabetic nephropathy was further evaluated. ANXA1 deficiency exacerbated kidney injuries, exhibiting more severe albuminuria, mesangial matrix expansion, tubulointerstitial lesions, kidney inflammation and fibrosis in high fat diet/streptozotocin-induced-diabetic mice. Consistently, ANXA1 overexpression ameliorated kidney injuries in mice with diabetic nephropathy. Additionally, we found Ac2-26 (an ANXA1 mimetic peptide) had therapeutic potential for alleviating kidney injuries in db/db mice and diabetic Anxa1 knockout mice. Mechanistic studies demonstrated that intracellular ANXA1 bound to the transcription factor NF-κB p65 subunit, inhibiting its activation thereby modulating the inflammatory state. Thus, our data indicate that ANXA1 may be a promising therapeutic approach to treating and reversing diabetic nephropathy.

Decreased serum Annexin A1 levels in Kawasaki disease with coronary artery aneurysm

BACKGROUND

Kawasaki disease (KD) is an acute and systemic vasculitis whose etiology remains unclear. The most crucial complication is the formation of coronary artery aneurysm (CAA). Annexin A1 (ANXA1) is an endogenous anti-inflammatory agent and pro-resolving mediator involved in inflammation-related diseases. This study sought to investigate the serum ANXA1 levels in KD patients and further explore the relationship between ANXA1 and CAA, as well as additional clinical parameters.

METHODS

Serum samples were collected from 95 KD patients and 39 healthy controls (HCs). KD patients were further divided into two groups: KD with CAAs (KD-CAAs) and KD non-CAAs (KD-NCAAs). Serum levels of ANXA1 and interleukin-6 (IL-6) were determined using enzyme-linked immunosorbent assays.

RESULTS

Serum ANXA1 levels in the KD group were significantly lower than in the HC group. In particular, serum ANXA1 levels were substantially lower in the KD-CAA groups. Moreover, serum ANXA1 levels were positively correlated with N%, C-reactive protein (CRP), and IL-6 but negatively correlated with L% in the KD group. Positive correlations between serum ANXA1 levels and erythrocyte sedimentation rate (ESR), IL-6, and D-dimer (DD) were observed in the KD-CAA group.

CONCLUSIONS

ANXA1 may be involved in the development of KD, and downregulation of ANXA1 may lead to the hypercoagulability seen in KD.

IMPACT

For the first time, it was demonstrated that serum ANXA1 levels were significantly decreased in Kawasaki disease with coronary artery aneurysms. ANXA1 might be involved in the acute phase of Kawasaki disease. Low serum concentrations of ANXA1 might lead to the hypercoagulability stage in Kawasaki disease. ANXA1 might be a potential therapeutic target for patients with Kawasaki disease.

Annexin-A1 SUMOylation regulates microglial polarization after cerebral ischemia by modulating IKKα stability via selective autophagy

Annexin-A1 (ANXA1) has recently been proposed to play a role in microglial activation after brain ischemia, but the underlying mechanism remains poorly understood. Here, we demonstrated that ANXA1 is modified by SUMOylation, and SUMOylated ANXA1 could promote the beneficial phenotype polarization of microglia. Mechanistically, SUMOylated ANXA1 suppressed nuclear factor κB activation and the production of proinflammatory mediators. Further study revealed that SUMOylated ANXA1 targeted the IκB kinase (IKK) complex and selectively enhanced IKKα degradation. Simultaneously, we detected that SUMOylated ANXA1 facilitated the interaction between IKKα and NBR1 to promote IKKα degradation through selective autophagy. Further work revealed that the overexpression of SUMOylated ANXA1 in microglia/macrophages resulted in marked improvement in neurological function in a mouse model of cerebral ischemia. Collectively, our study demonstrates a previously unidentified mechanism whereby SUMOylated ANXA1 regulates microglial polarization and strongly indicates that up-regulation of ANXA1 SUMOylation in microglia may provide therapeutic benefits for cerebral ischemia.

Targeting AnxA1/Formyl Peptide Receptor 2 Pathway Affords Protection against Pathological Thrombo-Inflammation

Stroke is a leading cause of death and disability globally and is associated with a number of co-morbidities including sepsis and sickle cell disease (SCD). Despite thrombo-inflammation underlying these co-morbidities, its pathogenesis remains complicated and drug discovery programs aimed at reducing and resolving the detrimental effects remain a major therapeutic challenge. The objective of this study was to assess whether the anti-inflammatory pro-resolving protein Annexin A1 (AnxA1) was able to reduce inflammation-induced thrombosis and suppress platelet activation and thrombus formation in the cerebral microvasculature. Using two distinct models of pathological thrombo-inflammation (lipopolysaccharide (LPS) and sickle transgenic mice (STM)), thrombosis was induced in the murine brain using photoactivation (light/dye) coupled with intravital microscopy. The heightened inflammation-induced microvascular thrombosis present in these two distinct thrombo-inflammatory models was inhibited significantly by the administration of AnxA1 mimetic peptide AnxA1_Ac2-26 (an effect more pronounced in the SCD model vs. the endotoxin model) and mediated by the key resolution receptor, Fpr2/ALX. Furthermore, AnxA1_Ac2-26 treatment was able to hamper platelet aggregation by reducing platelet stimulation and aggregation (by moderating α_IIbβ₃ and P-selectin). These findings suggest that targeting the AnxA1/Fpr2/ALX pathway represents an attractive novel treatment strategy for resolving thrombo-inflammation, counteracting e.g., stroke in high-risk patient cohorts.

Insights into the Activation Mechanism of the ALX/FPR2 Receptor

The formyl peptide receptor 2 (ALX/FPR2), a G-protein-coupled receptor (GPCR), plays an important role in host defense and inflammation. This receptor can be driven as pro- or anti-inflammatory depending on its agonist, such as N-formyl-Met-Leu-Phe-Lys (fMLFK) and resolvin D1 (RvD1) or its aspirin-triggered 17 (R)-epimer, AT-RvD1, respectively. However, the activation mechanism of ALX/FPR2 by pro- and anti-inflammatory agonists remains unclear. In this work, on the basis of molecular dynamics simulations, we evaluated a model of the ALX/FPR2 receptor activation process using two agonists, fMLFK and AT-RvD1, with opposite effects. The simulations by both fMLFK and AT-RvD1 induced the ALX/FPR2 activation through a set of receptor-core residues, in particular, R205, Q258, and W254. In addition, the activation was dependent on the disruption of electrostatic interactions in the cytoplasmic region of the receptor. We also found that in the AT-RvD1 simulations, the position of the H8 helix was similar to that of the same helix in other class-A GPCRs coupled to arrestin. Thus our results shed light on the mechanism of activation of the ALX/FPR2 receptor by pro-inflammatory and pro-resolution agonists.

The Contribution of Formyl Peptide Receptor Dysfunction to the Course of Neuroinflammation: A Potential Role in the Brain Pathology

Chronic inflammatory processes within the central nervous system (CNS) are in part responsible for the development of neurodegenerative and psychiatric diseases. These processes are associated with, among other things, the increased and disturbed activation of microglia and the elevated production of proinflammatory factors. Recent studies indicated that the disruption of the process of resolution of inflammation (RoI) may be the cause of CNS disorders. It is shown that the RoI is regulated by endogenous molecules called specialized pro-resolving mediators (SPMs), which interact with specific membrane receptors. Some SPMs activate formyl peptide receptors (FPRs), which belong to the family of seven-transmembrane G protein-coupled receptors. These receptors take part not only in the proinflammatory response but also in the resolution of the inflammation process. Therefore, the activation of FPRs might have complex consequences.

This review discusses the potential role of FPRs, and in particular the role of FPR2 subtype, in the brain under physiological and pathological conditions and their involvement in processes underlying neurodegenerative and psychiatric disorders as well as ischemia, the pathogenesis of which involves the dysfunction of inflammatory processes.

Prokineticin 2 relieves hypoxia/reoxygenation-induced injury through activation of Akt/mTOR pathway in H9c2 cardiomyocytes

Prokineticin 2 (PK2) was reported to be decreased in the hearts of end-state heart failure patients. Our study aimed to explore the effects of PK2 on hypoxia/reoxygenation (H/R) injury and the underlying mechanism. H9c2 cardiomyocytes were treated with 5 nM PK2 in the presence or absence of 5 mM dual phosphatidylinositol 3-kinase (PI3K)/the mammalian target of rapamycin (mTOR) inhibitor (BEZ235) for 24 h and then subjected to H/R treatment. Cell viability and lactate dehydrogenase (LDH) release were evaluated by CCK-8 and LDH release assays, respectively. Apoptosis was determined by flow cytometry analysis. Oxidative stress was assessed by measuring superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities and malondialdehyde (MDA) content. Results showed that H/R treatment decreased PK2 expression and inactivated the Akt/mTOR pathway in H9c2 cardiomyocytes. PK2 treatment activated the Akt/mTOR pathway in H/R-exposed H9c2 cardiomyocytes. H/R stimulation suppressed cell viability, increased LDH release, induced apoptosis and oxidative stress in H9c2 cardiomyocytes, while these effects were neutralised by treatment with PK2. However, the inhibitory effects of PK2 on H/R-induced injury in H9c2 cardiomyocytes were abolished by the addition of BEZ235. In conclusion, PK2 relieved H/R-induced injury in H9c2 cardiomyocytes by activation of the Akt/mTOR pathway.

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.

Use of DAMPs and SAMPs as Therapeutic Targets or Therapeutics: A Note of Caution

This opinion article discusses the increasing attention paid to the role of activating damage-associated molecular patterns (DAMPs) in initiation of inflammatory diseases and suppressing/inhibiting DAMPs (SAMPs) in resolution of inflammatory diseases and, consequently, to the future roles of these novel biomarkers as therapeutic targets and therapeutics. Since controlled production of DAMPs and SAMPs is needed to achieve full homeostatic restoration and repair from tissue injury, only their pathological, not their homeostatic, concentrations should be therapeutically tackled. Therefore, distinct caveats are proposed regarding choosing DAMPs and SAMPs for therapeutic purposes. For example, we discuss the need to a priori identify and define a context-dependent “homeostatic DAMP:SAMP ratio” in each case and a “homeostatic window” of DAMP and SAMP concentrations to guarantee a safe treatment modality to patients. Finally, a few clinical examples of how DAMPs and SAMPs might be used as therapeutic targets or therapeutics in the future are discussed, including inhibition of DAMPs in hyperinflammatory processes (e.g., systemic inflammatory response syndrome, as currently observed in Covid-19), administration of SAMPs in chronic inflammatory diseases, inhibition of SAMPs in hyperresolving processes (e.g., compensatory anti-inflammatory response syndrome), and administration/induction of DAMPs in vaccination procedures and anti-cancer therapy.

Phosphorylation Sites in Protein Kinases and Phosphatases Regulated by Formyl Peptide Receptor 2 Signaling

FPR1, FPR2, and FPR3 are members of Formyl Peptides Receptors (FPRs) family belonging to the GPCR superfamily. FPR2 is a low affinity receptor for formyl peptides and it is considered the most promiscuous member of this family. Intracellular signaling cascades triggered by FPRs include the activation of different protein kinases and phosphatase, as well as tyrosine kinase receptors transactivation. Protein kinases and phosphatases act coordinately and any impairment of their activation or regulation represents one of the most common causes of several human diseases. Several phospho-sites has been identified in protein kinases and phosphatases, whose role may be to expand the repertoire of molecular mechanisms of regulation or may be necessary for fine-tuning of switch properties. We previously performed a phospho-proteomic analysis in FPR2-stimulated cells that revealed, among other things, not yet identified phospho-sites on six protein kinases and one protein phosphatase. Herein, we discuss on the selective phosphorylation of Serine/Threonine-protein kinase N2, Serine/Threonine-protein kinase PRP4 homolog, Serine/Threonine-protein kinase MARK2, Serine/Threonine-protein kinase PAK4, Serine/Threonine-protein kinase 10, Dual specificity mitogen-activated protein kinase kinase 2, and Protein phosphatase 1 regulatory subunit 14A, triggered by FPR2 stimulation. We also describe the putative FPR2-dependent signaling cascades upstream to these specific phospho-sites.

L-Carnitine Reduces Myocardial Oxidative Stress and Alleviates Myocardial Ischemia-Reperfusion Injury by Activating Nuclear Transcription-Related Factor 2 (Nrf2)/Heme Oxygenase-1 (HO-1) Signaling Pathway

Background

Myocardial ischemia-reperfusion injury (IRI) is an important injury mechanism of myocardial infarction. The purpose of this study was to explore the effects of L-carnitine (LC) on myocardial IRI and its mechanism.

Material/Methods

The IRI model was made by ligating the left anterior descending coronary artery. Then, we injected LC intraperitoneally into the rats of the experimental group to assess the effect of LC on IRI rats by use of serum markers, Western blot, and qRT-PCR. H9c2 cells were cultured and then treated with hypoxia-reoxygenation. The effect of LC on oxidative stress, apoptosis, and nuclear transcription-related factor 2/heme oxygenase-1 (Nrf2/HO-1) signaling pathway of H9c2 cells were detected by Western blot, RT-PCR, and flow cytometry.

Results

LC significantly reduced malondialdehyde (MDA), creatine kinase (CK), and lactate dehydrogenase (LDH) levels in rat myocardial tissue and increased superoxide dismutase (SOD) expression. LC also increased the expression of SOD1/2 and Bcl-2 in rat myocardial tissue and H9c2 cells and decreased the expression of caspase3/8 and Bax. In addition, LC increased the expression of Nrf2/HO-1 signaling pathway-related molecules in H9c2 cells and increased the activity of the Nrf2/HO-1 signaling pathway. Moreover, inhibition of the Nrf2/HO-1 signaling pathway attenuated the protective effect of LC on H9c2 cells.

Conclusions

LC can activate the Nrf2/HO-1 signaling pathway and reduce oxidative stress and apoptosis in cardiomyocytes, thereby reducing myocardial IRI.

Enhancing the Bystander and Abscopal Effects to Improve Radiotherapy Outcomes

In this paper, we summarize published articles and experiences related to the attempt to improve radiotherapy outcomes and, thus, to personalize the radiation treatment according to the individual characteristics of each patient. The evolution of ideas and the study of successively published data have led us to envisage new biophysical models for the interpretation of tumor and healthy normal tissue response to radiation. In the development of the model, we have shown that when mesenchymal stem cells (MSCs) and radiotherapy are administered simultaneously in experimental radiotherapy on xenotumors implanted in a murine model, the results of the treatment show the existence of a synergic mechanism that is able to enhance the local and systemic actions of the radiation both on the treated tumor and on its possible metastasis. We are convinced that, due to the physical hallmarks that characterize the neoplastic tissues, the physical-chemical tropism of MSCs, and the widespread functions of macromolecules, proteins, and exosomes released from activated MSCs, the combination of radiotherapy plus MSCs used intratumorally has the effect of counteracting the pro-tumorigenic and pro-metastatic signals that contribute to the growth, spread, and resistance of the tumor cells. Therefore, we have concluded that MSCs are appropriate for therapeutic use in a clinical trial for rectal cancer combined with radiotherapy, which we are going to start in the near future.

Ischemia-Reperfusion Injury in Sickle Cell Disease: From Basics to Therapeutics

Sickle cell disease (SCD) is one of the most common hereditary hemoglobinopathies worldwide, affecting almost 400,000 newborns globally each year. It is characterized by chronic hemolytic anemia and endothelial dysfunction, resulting in a constant state of disruption of the vascular system and leading to recurrent episodes of ischemia-reperfusion injury (I/RI) to multiple organ systems. I/RI is a fundamental vascular pathobiological paradigm and contributes to morbidity and mortality in a wide range of conditions, including myocardial infarction, stroke, acute kidney injury, and transplantation. I/RI is characterized by an initial restriction of blood supply to an organ, which can lead to ischemia, followed by the subsequent restoration of perfusion and concomitant reoxygenation. Recent advances in the pathophysiology of SCD have led to an understanding that many of the consequences of this disease can be explained by mechanisms associated with I/RI. The following review focuses on the evolving pathobiology of SCD, how various complications of SCD can be attributed to I/RI, and the role of timely therapeutic intervention(s) based on targeting mediators or pathways that influence I/R insult.

Proteomic Analysis of Rat Cerebral Cortex in the Subacute to Long-Term Phases of Focal Cerebral Ischemia-Reperfusion Injury

Stroke is a leading cause of mortality and disability, and ischemic stroke accounts for more than 80% of the disease occurrence. Timely reperfusion is essential in the treatment of ischemic stroke, but it is known to cause ischemia-reperfusion (I/R) injury and the relevant studies have mostly focused on the acute phase. Here we reported on a global proteomic analysis to investigate the development of cerebral I/R injury in the subacute and long-term phases. A rat model was used, with 2 h-middle cerebral artery occlusion (MCAO) followed with 1, 7, and 14 days of reperfusion. The proteins of cerebral cortex were analyzed by SDS-PAGE, whole-gel slicing, and quantitative LC-MS/MS. Totally 5621 proteins were identified, among which 568, 755, and 492 proteins were detected to have significant dys-regulation in the model groups with 1, 7, and 14 days of reperfusion, respectively, when compared with the corresponding sham groups (n = 4, fold change ≥1.5 or ≤0.67 and p ≤ 0.05). Bioinformatic analysis on the functions and reperfusion time-dependent dys-regulation profiles of the proteins exhibited changes of structures and biological processes in cytoskeleton, synaptic plasticity, energy metabolism, inflammation, and lysosome from subacute to long-term phases of cerebral I/R injury. Disruption of cytoskeleton and synaptic structures, impairment of energy metabolism processes, and acute inflammation responses were the most significant features in the subacute phase. With the elongation of reperfusion time to the long-term phase, a tendency of recovery was detected on cytoskeleton, while inflammation pathways different from the subacute phase were activated. Also, lysosomal structures and functions might be restored. This is the first work reporting the proteome changes that occurred at different time points from the subacute to long-term phases of cerebral I/R injury and we expect it would provide useful information to improve the understanding of the mechanisms involved in the development of cerebral I/R injury and suggest candidates for treatment.

Annexin A1 Bioactive Peptide Promotes Resolution of Neuroinflammation in a Rat Model of Exsanguinating Cardiac Arrest Treated by Emergency Preservation and Resuscitation

Neuroinflammation initiated by damage-associated molecular patterns, including high mobility group box 1 protein (HMGB1), has been implicated in adverse neurological outcomes following lethal hemorrhagic shock and polytrauma. Emergency preservation and resuscitation (EPR) is a novel method of resuscitation for victims of exsanguinating cardiac arrest, shown in preclinical studies to improve survival with acceptable neurological recovery. Sirtuin 3 (SIRT3), the primary mitochondrial deacetylase, has emerged as a key regulator of metabolic and energy stress response pathways in the brain and a pharmacological target to induce a neuronal pro-survival phenotype. This study aims to examine whether systemic administration of an Annexin-A1 bioactive peptide (ANXA1sp) could resolve neuroinflammation and induce sirtuin-3 regulated cytoprotective pathways in a novel rat model of exsanguinating cardiac arrest and EPR. Adult male rats underwent hemorrhagic shock and ventricular fibrillation, induction of profound hypothermia, followed by resuscitation and rewarming using cardiopulmonary bypass (EPR). Animals randomly received ANXA1sp (3 mg/kg, in divided doses) or vehicle. Neuroinflammation (HMGB1, TNFα, IL-6, and IL-10 levels), cerebral cell death (TUNEL, caspase-3, pro and antiapoptotic protein levels), and neurologic scores were assessed to evaluate the inflammation resolving effects of ANXA1sp following EPR. Furthermore, western blot analysis and immunohistochemistry were used to interrogate the mechanisms involved. Compared to vehicle controls, ANXA1sp effectively reduced expression of cerebral HMGB1, IL-6, and TNFα and increased IL-10 expression, which were associated with improved neurological scores. ANXA1sp reversed EPR-induced increases in expression of proapoptotic protein Bax and reduction in antiapoptotic protein Bcl-2, with a corresponding decrease in cerebral levels of cleaved caspase-3. Furthermore, ANXA1sp induced autophagic flux (increased LC3II and reduced p62 expression) in the brain. Mechanistically, these findings were accompanied by upregulation of the mitochondrial protein deacetylase Sirtuin-3, and its downstream targets FOXO3a and MnSOD in ANXA1sp-treated animals. Our data provide new evidence that engaging pro-resolving pharmacological strategies such as Annexin-A1 biomimetic peptides can effectively attenuate neuroinflammation and enhance the neuroprotective effects of EPR after exsanguinating cardiac arrest.

Up-regulation of ANXA1 suppresses polymorphonuclear neutrophil infiltration and myeloperoxidase activity by activating STAT3 signaling pathway in rat models of myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury (MIRI) is recognized as a major cause of morbidity and mortality which is commonly associated with coronary artery disease. In recent studies, annexin A1 gene (ANXA1) has been discovered to be involved in the treatment for MIRI. In this study, the primary focus was on the molecular mechanism of ANXA1 in polymorphonuclear neutrophil (PMN) infiltration and myeloperoxidase (MPO) activity in rats with MIRI. Initially, microarray analysis was carried out in order to identify differentially expressed genes. Moreover, a rat model of MIRI was established for evaluating the expression of ANXA1, signal transducer and activator of transcription 3 (STAT3) and vascular endothelial growth factor (VEGF) in myocardial tissues. Following this, the ANXA1 vector, siRNA-ANXA1, and Stattic (inhibitor of STAT3 signaling pathway) were utilized for analyzing the regulatory role of ANXA1 in physiological indexes, hemodynamic parameters, inflammatory factors, myocardial infarct size, MPO activity, PMN infiltration, and apoptosis of PMNs. Furthermore, the relationship between ANXA1 and STAT3 signaling pathway was analyzed. Initially, a reduction in the expression of ANXA1, STAT3 and VEGF in myocardial tissues of MIRI rats was found. To elaborate, overexpressed ANXA1 inhibited levels of inflammatory factors, the activation of PMN infiltration, reduced the degree of PMN infiltration, and decreased the apoptosis of PMNs. More importantly, down-regulated ANXA1 inhibited the activation of STAT3 signaling pathway, which thereby suppressed VEGF expression. With this all taken into account, the present study presents that up-regulated ANXA1 inhibits PMN infiltration and MPO activity by activation of STAT3 signaling pathway in rats with MIRI.

Advancements of Annexin A1 in inflammation and tumorigenesis

Annexin A1 is a Ca²⁺-dependent phospholipid binding protein involved in a variety of pathophysiological processes. Accumulated evidence has indicated that Annexin A1 has important functions in cell proliferation, apoptosis, differentiation, metastasis, and inflammatory response. Moreover, the abnormal expression of Annexin A1 is closely related to the occurrence and development of tumors. In this review article, we focus on the structure and function of Annexin A1 protein, especially the recent evidence of Annexin A1 in the pathophysiological role of inflammatory and cancer. This summary will be very important for further investigation of the pathophysiological role of Annexin A1 and for the development of novel therapeutics of inflammatory and cancer based on targeting Annexin A1 protein.

Annexin-A1: Therapeutic Potential in Microvascular Disease

Annexin-A1 (ANXA1) was first discovered in the early 1980's as a protein, which mediates (some of the) anti-inflammatory effects of glucocorticoids. Subsequently, the role of ANXA1 in inflammation has been extensively studied. The biology of ANXA1 is complex and it has many different roles in both health and disease. Its effects as a potent endogenous anti-inflammatory mediator are well-described in both acute and chronic inflammation and its role in activating the pro-resolution phase receptor, FPR2, has been described and is now being exploited for therapeutic benefit. In the present mini review, we will endeavor to give an overview of ANXA1 biology in relation to inflammation and functions that mediate pro-resolution that are independent of glucocorticoid induction. We will focus on the role of ANXA1 in diseases with a large inflammatory component focusing on diabetes and microvascular disease. Finally, we will explore the possibility of exploiting ANXA1 as a novel therapeutic target in diabetes and the treatment of microvascular disease.

Cardioprotective Actions of the Annexin-A1 N-Terminal Peptide, Ac2-26, Against Myocardial Infarction

The anti-inflammatory, pro-resolving annexin-A1 protein acts as an endogenous brake against exaggerated cardiac necrosis, inflammation, and fibrosis following myocardial infarction (MI) in vivo. Little is known, however, regarding the cardioprotective actions of the N-terminal-derived peptide of annexin A1, Ac_2-26, particularly beyond its anti-necrotic actions in the first few hours after an ischemic insult. In this study, we tested the hypothesis that exogenous Ac_2-26 limits cardiac injury in vitro and in vivo. Firstly, we demonstrated that Ac_2-26 limits cardiomyocyte death both in vitro and in mice subjected to ischemia-reperfusion (I-R) injury in vivo (Ac_2-26, 1 mg/kg, i.v. just prior to post-ischemic reperfusion). Further, Ac_2-26 (1 mg/kg i.v.) reduced cardiac inflammation (after 48 h reperfusion), as well as both cardiac fibrosis and apoptosis (after 7-days reperfusion). Lastly, we investigated whether Ac_2-26 preserved cardiac function after MI. Ac_2-26 (1 mg/kg/day s.c., osmotic pump) delayed early cardiac dysfunction 1 week post MI, but elicited no further improvement 4 weeks after MI. Taken together, our data demonstrate the first evidence that Ac_2-26 not only preserves cardiomyocyte survival in vitro, but also offers cardioprotection beyond the first few hours after an ischemic insult in vivo. Annexin-A1 mimetics thus represent a potential new therapy to improve cardiac outcomes after MI.

Matrix metalloproteinase-12 as an endogenous resolution promoting factor following myocardial infarction

Following myocardial infarction (MI), timely resolution of inflammation promotes wound healing and scar formation while limiting excessive tissue damage. Resolution promoting factors (RPFs) are agents that blunt leukocyte trafficking and inflammation, promote necrotic and apoptotic cell clearance, and stimulate scar formation. Previously identified RPFs include mediators derived from lipids (resolvins, lipoxins, protectins, and maresins), proteins (glucocorticoids, annexin A1, galectin 1, and melanocortins), or gases (CO, H₂S, and NO). Matrix metalloproteinase-12 (MMP-12; macrophage elastase) has shown promising RPF qualities in a variety of disease states. We review here the evidence that MMP-12 may serve as a novel RPF with potential therapeutic efficacy in the setting of MI.

Silencing of Annexin A1 suppressed the apoptosis and inflammatory response of preeclampsia rat trophoblasts

Preeclampsia (PE) is a disorder that is characterized by pregnancy-induced hypertension. It has been reported that Annexin A1 (ANXA1) is highly expressed in the plasma of women diagnosed with PE. Therefore, the present study aimed to examine the effect of ANXA1 on PE rats. The PE animal model was constructed in rats using Nω-nitro-L-arginine methyl ester (L-NAME), and the blood pressure and urine protein levels of rats were detected. The pathological features of placental tissue, and the levels of inflammatory factors and ANXA1 were respectively measured by hematoxylin-eosin staining, enzyme-linked immunosorbent assay and immunohistochemical assay. The activity of trophoblasts obtained from PE placental tissue was measured using immunofluorescence staining, while cell apoptosis was assessed using flow cytometry. The levels of associated factors were determined by reverse transcription-quantitative polymerase chain reaction and western blot analysis. The results identified that systolic blood pressure, diastolic blood pressure, mean arterial pressure and urine protein levels were enhanced, and that the contents of ANXA1, tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-6 and IL-8 were increased in the L-NAME group. Transfection with small interfering RNA (siRNA)-ANXA1 markedly decreased the apoptosis and inflammatory response of trophoblasts. In addition, siRNA-ANXA1 upregulated the levels of B-cell lymphoma-2 (Bcl-2) and pro-caspase-3, and downregulated the levels of Bcl-2-associated X protein, cleaved-caspase-3, TNF-α, IL-1β, IL-6 and IL-8. Furthermore, siRNA-ANXA1 repressed the phosphorylation of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3); however, siRNA-ANXA1 did not alter the levels of JAK2 and STAT3. Therefore, silencing of ANXA1 suppressed the apoptosis and inflammatory response of PE rat trophoblasts, and downregulated JAK2/STAK3 pathway.