Nuclear translocation of annexin 1 following oxygen-glucose deprivation-reperfusion induces apoptosis by regulating Bid expression via p53 binding

Annexin A1: The dawn of ischemic stroke (Review)

Ischemic stroke is a prevalent clinical condition that poses a significant global challenge. Developing innovative strategies to address this issue is crucial. Annexin A1 (ANXA1), a key member of the annexin superfamily, performs various functions, such as inhibiting inflammatory factor release, promoting phagocytosis, and blocking leukocyte migration. Evidence indicates that ANXA1 plays a pivotal role in the pathogenesis of ischemic stroke. The present article reviews involvement of ANXA1 in anti‑atherosclerosis, inflammatory processes, blood‑brain barrier protection, platelet aggregation and anti‑apoptotic mechanisms. The potential applications of ANXA1 in treating ischemic stroke are also explored.

MRPL41, as a target for acupuncture, promotes neuron apoptosis in models of ischemic stroke via activating p53 pathway

Neuronal death is the key cause of ischemic stroke. Acupuncture (Acu) is a recognized method for the treatment and amelioration of cerebral ischemia. However, the molecular mechanism of Acu for treating ischemic stroke has not yet been detailedly elucidated. Based our microarray analysis results, mitochondrial ribosomal protein L41 (MRPL41), which is related to apoptosis, was identified as the target of Acu. MRPL41 expression was increased in middle cerebral artery occlusion/reperfusion (MCAO/R) model and reduced after Acu treatment. Following, MCAO/R model and oxygen and glucose deprivation/reoxygenation (OGD/R) model were established to explore the effect of MRPL41. Knockdown of MRPL41 increased cell viability and ani-apoptotic protein (Bcl-2) expression, and reduced apoptosis intensity and pro-apoptotic protein (Bax and Cleaved caspase-3) of OGD/R neurons. In vivo, MRPL41 silencing decreased neurological severity score, shrank infarct area, reduced encephaledema and neuron apoptosis. In addition, reduction of MRPL41 caused loss of p53. Our data uncover that Acu targets MRPL41, following with inhibiting neuron apoptosis via p53 pathway, thereby ameliorating ischemic stroke.

The Sirtuin 5 Inhibitor MC3482 Ameliorates Microglia‑induced Neuroinflammation Following Ischaemic Stroke by Upregulating the Succinylation Level of Annexin-A1

In our previous study, we concluded that sirtuin 5 (SIRT5) was highly expressed in microglia following ischaemic stroke, which induced excessive neuroinflammation and neuronal injury. Therefore, SIRT5-targeting interventions should reduce neuroinflammation and protect against ischaemic brain injury. Here, we showed that treatment with a specific SIRT5 inhibitor, MC3482, alleviated microglia-induced neuroinflammation and improved long-term neurological function in a mouse model of stroke. The mice were administrated with either vehicle or 2 mg/kg MC3482 daily for 7 days via lateral ventricular injection following the onset of middle cerebral artery occlusion. The outcome was assessed by a panel of tests, including a neurological outcome score, declarative memory, sensorimotor tests, anxiety-like behavior and a series of inflammatory factors. We observed a significant reduction of infarct size and inflammatory factors, and the improvement of long-term neurological function in the early stages during ischaemic stroke when the mice were treated with MC3482. Mechanistically, the administration of MC3482 suppressed the desuccinylation of annexin-A1, thereby promoting its membrane recruitment and extracellular secretion, which in turn alleviated neuroinflammation during ischaemic stroke. Based on our findings, MC3482 offers promise as an anti-ischaemic stroke treatment that targets directly the disease's underlying factors.

Annexin A1 in the nervous and ocular systems

The therapeutic potential of Annexin A1, an important member of the Annexin superfamily, has become evident in results of experiments with multiple human systems and animal models. The anti-inflammatory and pro-resolving effects of Annexin A1 are characteristic of pathologies involving the nervous system. In this review, we initially describe the expression sites of Annexin A1, then outline the mechanisms by which Annexin A1 maintains the neurological homeostasis through either formyl peptide receptor 2 or other molecular approaches; and, finally, we discuss the neuroregenerative potential qualities of Annexin A1. The eye and the nervous system are anatomically and functionally connected, but the association between visual system pathogenesis, especially in the retina, and Annexin A1 alterations has not been well summarized. Therefore, we explain the beneficial effects of Annexin A1 for ocular diseases, especially for retinal diseases and glaucoma on the basis of published findings, and we explore present and future delivery strategies for Annexin A1 to the retina.

Multi-Omics Profiling Identifies Microglial Annexin A2 as a Key Mediator of NF-κB Pro-inflammatory Signaling in Ischemic Reperfusion Injury

Cerebral stroke is one of the leading causes of mortality and disability worldwide. Restoring the cerebral circulation following a period of occlusion and subsequent tissue oxygenation leads to reperfusion injury. Cerebral ischemic reperfusion (I/R) injury triggers immune and inflammatory responses, apoptosis, neuronal damage, and even death. However, the cellular function and molecular mechanisms underlying cerebral I/R-induced neuronal injury are incompletely understood. By integrating proteomic, phosphoproteomic, and transcriptomic profiling in mouse hippocampi after cerebral I/R, we revealed that the differentially expressed genes and proteins mainly fall into several immune inflammatory response-related pathways. We identified that Annexin 2 (Anxa2) was exclusively upregulated in microglial cells in response to cerebral I/R in vivo and oxygen-glucose deprivation and reoxygenation (OGD/R) in vitro. RNA-seq analysis revealed a critical role of Anxa2 in the expression of inflammation-related genes in microglia via the NF-κB signaling. Mechanistically, microglial Anxa2 is required for nuclear translocation of the p65 subunit of NF-κB and its transcriptional activity upon OGD/R in BV2 microglial cells. Anxa2 knockdown inhibited the OGD/R-induced microglia activation and markedly reduced the expression of pro-inflammatory factors, including TNF-α, IL-1β, and IL-6. Interestingly, conditional medium derived from Anxa2-depleted BV2 cell cultures with OGD/R treatment alleviated neuronal death in vitro. Altogether, our findings revealed that microglia Anxa2 plays a critical role in I/R injury by regulating NF-κB inflammatory responses in a non-cell-autonomous manner, which might be a potential target for the neuroprotection against cerebral I/R injury.

Vialinin A alleviates oxidative stress and neuronal injuries after ischaemic stroke by accelerating Keap1 degradation through inhibiting USP4-mediated deubiquitination

BACKGROUND

Oxidative stress is known as a hallmark of cerebral ischaemia‒reperfusion injury and it exacerbates the pathologic progression of ischaemic brain damage. Vialinin A, derived from a Chinese edible mushroom, possesses multiple pharmacological activities in cancer, Kawasaki disease, asthma and pathological scarring. Notably, vialinin A is an inhibitor of ubiquitin-specific peptidase 4 (USP4) that shows anti-inflammatory and antioxidative properties. However, the precise effect of vialinin A in ischaemic stroke, as well as its underlying mechanisms, remains largely unexplored.

PURPOSE

The present research focuses on the impacts of vialinin A on oxidative stress and explores the underlying mechanisms involved while also examining its potentiality as a therapeutic candidate for ischaemic stroke.

METHODS

Mouse ischaemic stroke was conducted by MCAO surgery. Vialinin A was administered via lateral ventricular injection at a dose of 2 mg/kg after reperfusion. Subsequent experiments were meticulously conducted at the appropriate time points. Stroke outcomes were evaluated by TTC staining, neurological score, Nissl staining and behavioural analysis. Co-IP assays were operated to examine the protein-protein interactions. Immunoblot analysis, qRT-PCR, and luciferase reporter assays were conducted to further investigate its underlying mechanisms.

RESULTS

In this study, we initially showed that administration of vialinin A alleviated cerebral ischaemia‒reperfusion injury-induced neurological deficits and neuronal apoptosis. Furthermore, vialinin A, which is an antioxidant, reduced oxidative stress injury, promoted the activation of the Keap1-Nrf2-ARE signaling pathway and increased the protein degradation of Keap1. The substantial neuroprotective effects of vialinin A against ischaemic stroke were compromised by the overexpression of USP4. Mechanistically, vialinin A inhibited the deubiquitinating enzymatic activity of USP4, leading to enhanced ubiquitination of Keap1 and subsequently promoting its degradation. This cascade caused the activation of Nrf2-dependent antioxidant response, culminating in a reduction of neuronal apoptosis and the amelioration of neurological dysfunction following ischaemic stroke.

CONCLUSIONS

This study demonstrates that inhibition of USP4 to activate Keap1-Nrf2-ARE signaling pathway may represent a mechanism by which vialinin A conferred protection against cerebral ischaemia‒reperfusion injury and sheds light on its promising prospects as a therapeutic intervention for ischaemic stroke.

A cell-penetrating peptide exerts therapeutic effects against ischemic stroke by mediating the lysosomal degradation of sirtuin 5

Stroke is a major public health concern worldwide. The lack of effective therapies heightens the need for new therapeutic agents. Previous study identified sirtuin 5 (SIRT5) as a positive regulator of microglia-induced excessive neuroinflammation following ischemic stroke. Interventions targeting SIRT5 should therefore alleviate neuroinflammation and protect against ischemic stroke. Here, we synthesized a membrane-permeable peptide specifically bound to SIRT5 through a chaperone-mediated autophagy targeting motif (Tat-SIRT5-CTM) and examined its therapeutic effect in vitro and in vivo. First, in primary microglia, Tat-SIRT5-CTM suppressed the binding of SIRT5 with annexin-A1 (ANXA1), leading to SIRT5 degradation and thus inhibition of SIRT5-mediated desuccinylation of ANXA1, followed by increased membrane accumulation and secretion of ANXA1. These changes, in turn, alleviated microglia-induced neuroinflammation. Moreover, following intravenous injection, Tat-SIRT5-CTM could efficiently pass through the blood‒brain barrier. Importantly, systemic administration of Tat-SIRT5-CTM reduced the brain infarct area and neuronal loss, mitigated neurological deficit scores, and improved long-term neurological functions in a mouse model of ischemic stroke. Furthermore, no toxicity was observed when high doses Tat-SIRT5-CTM were injected into nonischemic mice. Collectively, our study reveals the promising efficacy of the peptide-directed lysosomal degradation of SIRT5 and suggests it as an effective therapeutic approach for the treatment of ischemic stroke.

Cell-permeable peptide-based delivery vehicles useful for subcellular targeting and beyond

Personal medicine aims to provide tailor-made diagnostics and treatments and has been emerged as a promising but challenging strategy during the last years. This includes the active delivery and localization of a therapeutic compound to a targeted site of action within a cell. An example being targeting the interference of a distinct protein-protein interaction (PPI) within the cell nucleus, mitochondria or other subcellular location. Therefore, not only the cell membrane has to be overcome but also the final intracellular destination has to be reached. One approach which fulfills both requirements is to use short peptide sequences that are able to translocate into cells as targeting and delivery vehicles. In fact, recent progress in this field demonstrates how these tools can modulate the pharmacological parameters of a drug without compromising its biological activity. Beside classical targets that are addressed by various small molecule drugs such as receptors, enzymes, or ion channels, PPIs have received increasing attention as potential therapeutic targets. Within this review, we will provide a recent update on cell-permeable peptides targeting subcellular destinations. We include chimeric peptide probes that combine cell-penetrating peptides (CPPs) and a targeting sequence, as well peptides having intrinsic cell-permeability and which are often used to target PPIs.

SENP3-mediated deSUMOylation of c-Jun facilitates microglia-induced neuroinflammation after cerebral ischemia and reperfusion injury

Recent evidences have implicated that SENP3 is a deSUMOylase which possesses neuronal damage effects in cerebral ischemia. However, its role in microglia remains poorly understood. Here, we found that SENP3 was upregulated in the peri-infarct areas of mice following ischemic stroke. Furthermore, knockdown of SENP3 significantly inhibits the expression of proinflammatory cytokines and chemokines in microglial cells. Mechanistically, SENP3 can bind and then mediated the deSUMOylation of c-Jun, which activated its transcriptional activity, ultimately followed by the activation of MAPK/AP-1 signaling pathway. In addition, microglia-specific SENP3 knockdown alleviated ischemia-induced neuronal damage, and markedly diminished infract volume, ameliorated sensorimotor and cognitive function in animals subjected to ischemic stroke. These results indicated SENP3 functions as a novel regulator of microglia-induced neuroinflammation by activating the MAPK/AP-1 signaling pathway via mediating the deSUMOylation of c-Jun. Interventions of SENP3 expression or its interaction with c-Jun would be a new and promising therapeutic strategy for ischemic stroke.

TRIM67 alleviates cerebral ischemia‒reperfusion injury by protecting neurons and inhibiting neuroinflammation via targeting IκBα for K63-linked polyubiquitination

BACKGROUND

Excessive and unresolved neuroinflammation plays an important role in the pathophysiology of many neurological disorders, such as ischemic stroke, yet there are no effective treatments. Tripartite motif-containing 67 (TRIM67) plays a crucial role in the control of inflammatory disease and pathogen infection-induced inflammation; however, the role of TRIM67 in cerebral ischemia‒reperfusion injury remains poorly understood.

RESULTS

In the present study, we demonstrated that the expression level of TRIM67 was significantly reduced in middle cerebral artery occlusion and reperfusion (MCAO/R) mice and primary cultured microglia subjected to oxygen-glucose deprivation and reperfusion. Furthermore, a significant reduction in infarct size and neurological deficits was observed in mice after TRIM67 upregulation. Interestingly, TRIM67 upregulation alleviated neuroinflammation and cell death after cerebral ischemia‒reperfusion injury in MCAO/R mice. A mechanistic study showed that TRIM67 bound to IκBα, reduced K48-linked ubiquitination and increased K63-linked ubiquitination, thereby inhibiting its degradation and promoting the stability of IκBα, ultimately inhibiting NF-κB activity after cerebral ischemia.

CONCLUSION

Taken together, this study demonstrated a previously unidentified mechanism whereby TRIM67 regulates neuroinflammation and neuronal apoptosis and strongly indicates that upregulation of TRIM67 may provide therapeutic benefits for ischemic stroke.

NTF4 plays a dual role in breast cancer in mammary tumorigenesis and metastatic progression

Breast cancer metastasis can happen even when the primary tumor is relatively small. But the mechanism for such early metastasis is poorly understood. Herein, we report that neurotrophin 4 (NTF4) plays a dual role in breast cancer proliferation and metastasis. Clinical data showed high levels of NTF4, especially in the early stage, to be associated with poor clinical outcomes, supporting the notion that metastasis, rather than primary cancer, was the major determinant of breast cancer mortality for patients. NTF4 promoted epithelial-mesenchymal transition (EMT), cell motility, and invasiveness of breast cancer cells in vitro and in vivo. Interestingly, NTF4 inhibited cell proliferation while promoting cellular apoptosis in vitro and inhibited xenograft tumorigenicity in vivo. Mechanistically, NTF4 elicited its pro-metastatic effects by activating PRKDC/AKT and ANXA1/NF-κB pathways to stabilize SNAIL protein, therefore decreasing the level of E-cadherin. Conversely, NTF4 increased ANXA1 phosphorylation and sumoylation and the interaction with importin β, leading to nuclear import and retention of ANXA1, which in turn activates the caspase-3 apoptosis cascade. Our findings identified an unexpected dual role for NTF4 in breast cancer which contributes to early metastasis of the disease. Therefore, NTF4 may serve as a prognostic marker and a potential therapeutic target for breast cancer.

Sirtuin 5 aggravates microglia-induced neuroinflammation following ischaemic stroke by modulating the desuccinylation of Annexin-A1

BACKGROUND

Microglia-induced excessive neuroinflammation plays a crucial role in the pathophysiology of multiple neurological diseases, such as ischaemic stroke. Controlling inflammatory responses is considered a promising therapeutic approach. Sirtuin 5 (SIRT5) mediates lysine desuccinylation, which is involved in various critical biological processes, but its role in ischaemic stroke remains poorly understood. This research systematically explored the function and potential mechanism of SIRT5 in microglia-induced neuroinflammation in ischaemic stroke.

METHODS

Mice subjected to middle cerebral artery occlusion were established as the animal model, and primary cultured microglia treated with oxygen-glucose deprivation and reperfusion were established as the cell model of ischaemic stroke. SIRT5 short hairpin RNA, adenovirus and adeno-associated virus techniques were employed to modulate SIRT5 expression in microglia both in vitro and in vivo. Coimmunoprecipitation, western blot and quantitative real-time PCR assays were performed to reveal the molecular mechanism.

RESULTS

In the current study, we showed that SIRT5 expression in microglia was increased in the early phase of ischaemic stroke. SIRT5 interacts with and desuccinylates Annexin A1 (ANXA1) at K166, which in turn decreases its SUMOylation level. Notably, the desuccinylation of ANXA1 blocks its membrane recruitment and extracellular secretion, resulting in the hyperactivation of microglia and excessive expression of proinflammatory cytokines and chemokines, ultimately leading to neuronal cell damage after ischaemic stroke. Further investigation showed that microglia-specific forced overexpression of SIRT5 worsened ischaemic brain injury, whereas downregulation of SIRT5 exhibited neuroprotective and cognitive-preserving effects against ischaemic brain injury, as proven by the decreased infarct area, reduced neurological deficit scores, and improved cognitive function.

CONCLUSIONS

Collectively, these data identify SIRT5 as a novel regulator of microglia-induced neuroinflammation and neuronal damage after cerebral ischaemia. Interventions targeting SIRT5 expression may represent a potential therapeutic target for ischaemic stroke.

SENP6 induces microglial polarization and neuroinflammation through de-SUMOylation of Annexin-A1 after cerebral ischaemia–reperfusion injury

Background

Previous data have reported that Sentrin/SUMO-specific protease 6 (SENP6) is involved in ischaemic brain injury and induces neuronal apoptosis after cerebral ischaemia, but the role of SENP6 in microglia-induced neuroinflammation and its underlying mechanism remain poorly understood. This research systematically explored the function and potential mechanism of SENP6 in microglia-induced neuroinflammation after ischaemic stroke.

Results

We first identified an increased protein level of SENP6 in microglia after cerebral ischaemia. Then, we demonstrated that SENP6 promoted detrimental microglial phenotype polarization. Specifically, SENP6-mediated de-SUMOylation of ANXA1 targeted the IκB kinase (IKK) complex and selectively inhibited the autophagic degradation of IKKα in an NBR1-dependent manner, activating the NF-κB pathway and enhancing proinflammatory cytokine expression. In addition, downregulation of SENP6 in microglia effectively reduced cocultured neuronal damage induced by ischaemic stroke. More importantly, we employed an AAV-based technique to specifically knockdown SENP6 in microglia/macrophages, and in vivo experiments showed that SENP6 inhibition in microglia/macrophages notably lessened brain ischaemic infarct size, decreased neurological deficit scores, and ameliorated motor and cognitive function in mice subjected to cerebral ischaemia surgery.

Conclusion

We demonstrated a previously unidentified mechanism by which SENP6-mediated ANXA1 de-SUMOylation regulates microglial polarization and our results strongly indicated that in microglia, inhibition of SENP6 may be a crucial beneficial therapeutic strategy for ischaemic stroke.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00850-2.

ANNEXIN A1: Roles in Placenta, Cell Survival, and Nucleus

The unbiased approaches of the last decade have enabled the collection of new data on the biology of annexin A1 (ANXA1) in a variety of scientific aspects, creating opportunities for new biomarkers and/or therapeutic purposes. ANXA1 is found in the plasma membrane, cytoplasm, and nucleus, being described at low levels in the nuclear and cytoplasmic compartments of placental cells related to gestational diabetic diseases, and its translocation from the cytoplasm to the nucleus has been associated with a response to DNA damage. The approaches presented here open pathways for reflection upon, and intrinsic clarification of, the modulating action of this protein in the response to genetic material damage, as well as its level of expression and cellular localization. The objective of this study is to arouse interest, with an emphasis on the mechanisms of nuclear translocation of ANXA1, which remain underexplored and may be beneficial in new inflammatory therapies.

TRIM45 causes neuronal damage by aggravating microglia-mediated neuroinflammation upon cerebral ischemia and reperfusion injury

Excessive and unresolved neuroinflammation is a key component of the pathological cascade in brain injuries such as ischemic stroke. Tripartite motif-containing 45 (TRIM45) is a ubiquitin E3 ligase involved in various critical biological processes. However, the role of TRIM45 in cerebral ischemia remains unknown. Here, we found that the TRIM45 protein was highly expressed in the peri-infarct areas of mice subjected to cerebral ischemia and reperfusion injury induced by middle cerebral artery occlusion. This study systemically evaluated the putative role of TRIM45 in the regulation of neuroinflammation during ischemic injury and the potential underlying mechanisms. We found that TRIM45 knockdown significantly decreased proinflammatory cytokine and chemokine production in primary cultured microglia challenged with oxygen-glucose deprivation and reoxygenation (OGD/R) treatment. Mechanistically, we demonstrated that TRIM45 constitutively interacted with TAB2 and consequently facilitated the Lys-63-linked polyubiquitination of TAB2, leading to the formation of the TAB1-TAK1-TAB2 complex and activation of TAK1, which was ultimately followed by activation of the nuclear factor-kappa B (NF-κB) signaling pathway. In an in vitro coculture Transwell system, downregulation of TRIM45 expression also inhibited the OGD/R-induced activation of microglia and alleviated neuronal apoptosis. More importantly, microglia-specific knockdown of TRIM45 in mice significantly reduced the infarct size, mitigated neurological deficit scores, and improved cognitive function after ischemic stroke. Taken together, our study reveals that the TRIM45-TAB2 axis is a crucial checkpoint that controls NF-κB signaling in microglia during cerebral ischemia and reperfusion injury. Therefore, targeting TRIM45 may be an attractive therapeutic strategy.

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 Calcium Binding Protein S100A11 and Its Roles in Diseases

The calcium binding protein S100 family in humans contains 21 known members, with each possessing a molecular weight between 10 and 14 kDa. These proteins are characterized by a unique helix-loop-helix EF hand motif, and often form dimers and multimers. The S100 family mainly exists in vertebrates and exerts its biological functions both inside cells as a calcium sensor/binding protein, as well as outside cells. S100A11, a member of the S100 family, may mediate signal transduction in response to internal or external stimuli and it plays various roles in different diseases such as cancers, metabolic disease, neurological diseases, and vascular calcification. In addition, it can function as chemotactic agent in inflammatory disease. In this review, we first detail the discovery of S100 proteins and their structural features, and then specifically focus on the tissue and organ expression of S100A11. We also summarize its biological activities and roles in different disease and signaling pathways, providing an overview of S100A11 research thus far.

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.

Role of TRPM7 kinase in cancer

Cancer is the second leading cause of death worldwide and accounted for an estimated 9.6 million deaths, or 1 in 6 deaths, in 2018. Despite recent advances in cancer prevention, diagnosis, and treatment strategies, the burden of this disease continues to grow with each year, with dire physical, emotional, and economic consequences for all levels of society. Classic characteristics of cancer include rapid, uncontrolled cell proliferation and spread of cancerous cells to other parts of the body, a process known as metastasis. Transient receptor potential melastatin 7 (TRPM7), a Ca²⁺- and Mg²⁺-permeable nonselective divalent cation channel defined by the atypical presence of an α-kinase within its C-terminal domain, has been implicated, due to its modulation of Ca²⁺ and Mg²⁺ influx, in a wide variety of physiological and pathological processes, including cancer. TRPM7 is overexpressed in several cancer types and has been shown to variably increase cellular proliferation, migration, and invasion of tumour cells. However, the relative contribution of TRPM7 kinase domain activity to cancer as opposed to ion flux through its channel pore remains an area of active discovery. In this review, we describe the specific role of the TRPM7 kinase domain in cancer processes as well as mechanisms of regulation and inhibition of the kinase domain.

Ad- and AAV8-mediated ABCA1 gene therapy in a murine model with retinal ischemia/reperfusion injuries

The anti-inflammatory molecule annexin A1 (ANXA1) determines the ultimate fate of retinal ganglion cell (RGC) in glaucoma. Cytoplasmic and extracellular ANXA1 facilitate resolution of inflammation. However, the nuclear translocation of ANXA1 induces RGC apoptosis in a murine glaucoma model, and the maintenance of ANXA1 secreted in the extracellular environments remains unclear. In this study, we found that intravitreal injection of the recombinant adenovirus vector (Ad)-ATP-binding cassette transporter A1 (ABCA1; carrying full-length ABCA1) improved RGC survival in the ischemia reperfusion (IR) mice model. Upregulation of ABCA1 maintained ANXA1 cytoplasmic location and reduced ANXA1 nuclear translocation, which is due to the decreased binding of ANXA1 with importin β. Moreover, we found that amino acids 903 to 1,344 of ABCA1 interacted with ANXA1 and decreased its nuclear localization. Importantly, intravitreal injection of adenovirus-associated viral (AAV) vector AAV8-ABCA1 (carrying 903 to 1,344 fragments of ABCA1) maintained ANXA1 cytoplasmic location and improved RGC survival in the IR mice model. Thus, overexpression of ABCA1 protects against RGC apoptosis by partially blocking ANXA1 nuclear translocation. This study puts forth a potential gene treatment strategy to prevent RGC apoptosis in glaucoma.

Emerging Roles of TRIM8 in Health and Disease

The superfamily of TRIM (TRIpartite Motif-containing) proteins is one of the largest groups of E3 ubiquitin ligases. Among them, interest in TRIM8 has greatly increased in recent years. In this review, we analyze the regulation of TRIM8 gene expression and how it is involved in many cell reactions in response to different stimuli such as genotoxic stress and attacks by viruses or bacteria, playing a central role in the immune response and orchestrating various fundamental biological processes such as cell survival, carcinogenesis, autophagy, apoptosis, differentiation and inflammation. Moreover, we show how TRIM8 functions are not limited to ubiquitination, and contrasting data highlight its role either as an oncogene or as a tumor suppressor gene, acting as a “double-edged weapon”. This is linked to its involvement in the selective regulation of three pivotal cellular signaling pathways: the p53 tumor suppressor, NF-κB and JAK-STAT pathways. Lastly, we describe how TRIM8 dysfunctions are linked to inflammatory processes, autoimmune disorders, rare developmental and cardiovascular diseases, ischemia, intellectual disability and cancer.

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.

Annexin A1 promotes the nuclear localization of the epidermal growth factor receptor in castration-resistant prostate cancer

Epidermal growth factor receptor is a cancer driver whose nuclear localization has been associated with the progression of prostate cancer to the castration-resistant phenotype. Previous reports indicated a functional interaction between this receptor and the protein Annexin A1, which has also been associated with aggressive tumors. The molecular pathogenesis of castration-resistant prostate cancer remains largely unresolved, and herein we have demonstrated the correlation between the expression levels and localization of the epidermal growth factor receptor and Annexin A1 in prostate cancer samples and cell lines. Interestingly, a higher expression of both proteins was detected in castration-resistant prostate cancer cell lines and the strongest correlation was seen at the nuclear level. We verified that Annexin A1 interacts with the epidermal growth factor receptor, and by using prostate cancer cell lines knocked down for Annexin A1, we succeeded in demonstrating that Annexin A1 promotes the nuclear localization of epidermal growth factor receptor. Finally, we showed that Annexin A1 activates an autocrine signaling in castration-resistant prostate cells through the formyl peptide receptor 1. The inhibition of such signaling by Cyclosporin H inhibits the nuclear localization of epidermal growth factor receptor and its downstream signaling. The present work sheds light on the functional interaction between nuclear epidermal growth factor receptor and nuclear Annexin A1 in castration-resistant prostate cancer. Therefore, strategies to inhibit the nuclear localization of epidermal growth factor receptor through the suppression of the Annexin A1 autocrine loop could represent an important intervention strategy for castration-resistant prostate cancer.

CRISPR/Cas9-mediated whole genomic wide knockout screening identifies mitochondrial ribosomal proteins involving in oxygen-glucose deprivation/reperfusion resistance

Recanalization therapy by intravenous thrombolysis or endovascular therapy is critical for the treatment of cerebral infarction. However, the recanalization treatment will also exacerbate acute brain injury and even severely threatens human life due to the reperfusion injury. So far, the underlying mechanisms for cerebral ischaemia-reperfusion injury are poorly understood and effective therapeutic interventions are yet to be discovered. Therefore, in the research, we subjected SK-N-BE(2) cells to oxygen-glucose deprivation/reperfusion (OGDR) insult and performed a pooled genome-wide CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 (CRISPR-associated protein 9) knockout screen to discover new potential therapeutic targets for cerebral ischaemia-reperfusion injury. We used Metascape to identify candidate genes which might involve in OGDR resistance. We found that the genes contributed to OGDR resistance were primarily involved in neutrophil degranulation, mitochondrial translation, and regulation of cysteine-type endopeptidase activity involved in apoptotic process and response to oxidative stress. We then knocked down some of the identified candidate genes individually. We demonstrated that MRPL19, MRPL32, MRPL52 and MRPL51 inhibition increased cell viability and attenuated OGDR-induced apoptosis. We also demonstrated that OGDR down-regulated the expression of MRPL19 and MRPL51 protein. Taken together, our data suggest that genome-scale screening with Cas9 is a reliable tool to analyse the cellular systems that respond to OGDR injury. MRPL19 and MRPL51 contribute to OGDR resistance and are supposed to be promising targets for the treatment of cerebral ischaemia-reperfusion damage.

Cisplatin treatment modulates Annexin A1 and inhibitor of differentiation to DNA 1 expression in cervical cancer cells

Cisplatin (Cis) is a choice chemotherapy approach to cervical cancer by inducing DNA adducts and subsequent apoptosis. We have investigated the effects of Cis on Annexin A1 (ANXA1) and inhibitor of DNA binding 1 (ID1) proteins expression to elucidate further mechanisms of Cis actions. Human cervical tissue samples from twenty-four patients, with Cervical Intraepithelial Neoplasia (CIN, stage I, II and III), were evaluated to quantified ANXA1 and ID1 expressions. In vitro, human epidermoid carcinoma of the cervix (SiHa cell line) were treated with Annexin A1 peptide (ANXA1_2-26), Cis or Cis + ANXA1_2-26 to evaluate cell proliferation and migration, cytotoxicity of treatments as well as ANXA1 and ID1 modulations by mRNA and protein expression. Our findings showed expression of ID1 and ANXA1 proteins in tissue samples from Cervical Intraepithelial Neoplasia (CIN) patients, with intense immunological identification of ID1 in the CIN III stage. In SiHa cells, treatments with Cis alone or Cis + ANXA1_2-26, increase mRNA expressions of the ANXA1 and reduced the ID1. In agreement, Cis + ANXA1_2-26 enhanced ANXA1 protein expression and Cis or Cis + ANXA1_2-26 abolished ID1 protein expression. Cell proliferation was reduced after treatment with ANXA1_2-26 peptide and more significant after Cis or Cis + ANXA1_2-26 treatments. These two last treatments reduced cell viability, by inducing late apoptosis, and impaired cell migration. Together, our data highlight endogenous ANXA1 is involved in Cis therapy for cervical cancer.

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.

HDAC4 Levels Control Sensibility toward Cisplatin in Gastric Cancer via the p53-p73/BIK Pathway

Gastric cancer (GC) remains a health issue due to the low efficiency of therapies, such as cisplatin. This unsatisfactory situation highlights the necessity of finding factors impacting GC sensibility to therapies. We analyzed the cisplatin pangenomic response in cancer cells and found HDAC4 as a major epigenetic regulator being inhibited. HDAC4 mRNA repression was partly mediated by the cisplatin-induced expression of miR-140. At a functional level, HDAC4 inhibition favored cisplatin cytotoxicity and reduced tumor growth. Inversely, overexpression of HDAC4 inhibits cisplatin cytotoxicity. Importantly, HDAC4 expression was found to be elevated in gastric tumors compared to healthy tissues, and in particular in specific molecular subgroups. Furthermore, mutations in HDAC4 correlate with good prognosis. Pathway analysis of genes whose expression in patients correlated strongly with HDAC4 highlighted DNA damage, p53 stabilization, and apoptosis as processes downregulated by HDAC4. This was further confirmed by silencing of HDAC4, which favored cisplatin-induced apoptosis characterized by cleavage of caspase 3 and induction of proapoptotic genes, such as BIK, in part via a p53-dependent mechanism. Altogether, these results reveal HDAC4 as a resistance factor for cisplatin in GC cells that impacts on patients' survival.

The Extracellular Matrix Receptor Discoidin Domain Receptor 1 Regulates Collagen Transcription by Translocating to the Nucleus

BACKGROUND

The discoidin domain receptor 1 (DDR1) is activated by collagens, upregulated in injured and fibrotic kidneys, and contributes to fibrosis by regulating extracellular matrix production, but how DDR1 controls fibrosis is poorly understood. DDR1 is a receptor tyrosine kinase (RTK). RTKs can translocate to the nucleus via a nuclear localization sequence (NLS) present on the receptor itself or a ligand it is bound to. In the nucleus, RTKs regulate gene expression by binding chromatin directly or by interacting with transcription factors.

METHODS

To determine whether DDR1 translocates to the nucleus and whether this event is mediated by collagen-induced DDR1 activation, we generated renal cells expressing wild-type or mutant forms of DDR1 no longer able to bind collagen. Then, we determined the location of the DDR1 upon collagen stimulation. Using both biochemical assays and immunofluorescence, we analyzed the steps involved in DDR1 nuclear translocation.

RESULTS

We show that although DDR1 and its natural ligand, collagen, lack an NLS, DDR1 is present in the nucleus of injured human and mouse kidney proximal tubules. We show that DDR1 nuclear translocation requires collagen-mediated receptor activation and interaction of DDR1 with SEC61B, a component of the Sec61 translocon, and nonmuscle myosin IIA and β-actin. Once in the nucleus, DDR1 binds to chromatin to increase the transcription of collagen IV, a major collagen upregulated in fibrosis.

CONCLUSIONS

These findings reveal a novel mechanism whereby activated DDR1 translates to the nucleus to regulate synthesis of profibrotic molecules.

The C-terminal domain of p53 orchestrates the interplay between non-covalent and covalent poly(ADP-ribosyl)ation of p53 by PARP1

The post-translational modification poly(ADP-ribosyl)ation (PARylation) plays key roles in genome maintenance and transcription. Both non-covalent poly(ADP-ribose) binding and covalent PARylation control protein functions, however, it is unknown how the two modes of modification crosstalk mechanistically. Employing the tumor suppressor p53 as a model substrate, this study provides detailed insights into the interplay between non-covalent and covalent PARylation and unravels its functional significance in the regulation of p53. We reveal that the multifunctional C-terminal domain (CTD) of p53 acts as the central hub in the PARylation-dependent regulation of p53. Specifically, p53 bound to auto-PARylated PARP1 via highly specific non–covalent PAR-CTD interaction, which conveyed target specificity for its covalent PARylation by PARP1. Strikingly, fusing the p53-CTD to a protein that is normally not PARylated, renders this a target for covalent PARylation as well. Functional studies revealed that the p53–PAR interaction had substantial implications on molecular and cellular levels. Thus, PAR significantly influenced the complex p53–DNA binding properties and controlled p53 functions, with major implications on the p53-dependent interactome, transcription, and replication-associated recombination. Remarkably, this mechanism potentially also applies to other PARylation targets, since a bioinformatics analysis revealed that CTD-like regions are highly enriched in the PARylated proteome.

Reduced Annexin A1 Secretion by ABCA1 Causes Retinal Inflammation and Ganglion Cell Apoptosis in a Murine Glaucoma Model

Variants near the ATP-binding cassette transporter A1 (ABCA1) gene are associated with elevated intraocular pressure and newly discovered risk factors for glaucoma. Previous studies have shown an association between ABCA1 deficiency and retinal inflammation. Using a mouse model of ischemia-reperfusion (IR) induced by acute intraocular pressure elevation, we found that the retinal expression of ABCA1 protein was decreased. An induction of ABCA1 expression by liver X receptor agonist TO901317 reduced retinal ganglion cell (RGC) apoptosis after IR and promoted membrane translocation and secretion of the anti-inflammatory factor annexin A1 (ANXA1). Moreover, ABCA1 and ANXA1 co-localized in cell membranes, and the interaction domain is amino acid 196 to 274 of ANXA1 fragment. TO901317 also reduced microglia migration and activation and decreased the expression of pro-inflammatory cytokines interleukin (IL)-17A and IL-1β, which could be reversed by the ANXA1 receptor blocker Boc2. Overexpression of TANK-binding kinase 1 (TBK1) increased ABCA1 degradation, which was reversed by the proteasome inhibitor carbobenzoxy-L-leucyl-L-leucyl-L-leucinal (MG132). Silencing Tbk1 with siRNA increased ABCA1 expression and promoted ANXA1 membrane translocation. These results indicate a novel IR mechanism, that leads via TBK1 activation to ABCA1 ubiquitination. This degradation decreases ANXA1 secretion, thus facilitating retinal inflammation and RGC apoptosis. Our findings suggest a potential treatment strategy to prevent RGC apoptosis in retinal ischemia and glaucoma.

Inhibition of the AnxA1/FPR1 autocrine axis reduces MDA-MB-231 breast cancer cell growth and aggressiveness in vitro and in vivo

Breast Cancer (BC) is a highly heterogeneous disease whose most aggressive behavior is displayed by triple-negative breast cancer (TNBC), which lacks an efficient targeted therapy. Despite its controversial role, one of the proteins that having been linked with BC is Annexin A1 (AnxA1), which is a Ca⁺² binding protein that acts modulating the immune system, cell membrane organization and vesicular trafficking. In this work we analyzed tissue microarrays of BC samples and observed a higher expression of AnxA1 in TNBCs and in lymph node metastasis. We also observed a positive correlation in primary tumors between expression levels of AnxA1 and its receptor, FPR1. Despite displaying a lesser strength, this correlation also exists in BC lymph node metastasis. In agreement, we have found that AnxA1 was highly expressed and secreted in the TNBC cell line MDA-MB-231 that also expressed high levels of FPR1. Furthermore, we demonstrated, by using the specific FPR1 inhibitor Cyclosporin H (CsH) and the immunosuppressive drug Cyclosporin A (CsA), the existence of an autocrine signaling of AnxA1 through the FPR1. Such signaling, elicited by AnxA1 upon its secretion, increased the aggressiveness and survival of MDA-MB-231 cells. In this manner, we demonstrated that CsA works very efficiently as an FPR1 inhibitor. Finally, by using CsA, we demonstrated that FPR1 inhibition decreased MDA-MB-231 tumor growth and metastasis formation in nude mice. These results indicate that FPR1 inhibition could be a potential intervention strategy to manage TNBCs displaying the characteristics of MDA-MB-231 cells. FPR1 inhibition can be efficiently achieved by CsA.

S100A11 protects against neuronal cell apoptosis induced by cerebral ischemia via inhibiting the nuclear translocation of annexin A1

The subcellular location of annexin A1 (ANXA1) determines the ultimate fate of neurons after ischemic stroke. ANXA1 nuclear translocation is involved in neuronal apoptosis after cerebral ischemia, and extracellular ANXA1 is also associated with regulation of inflammatory responses. As the factors and mechanism that influence ANXA1 subcellular translocation remain unclear, studies aiming to determine and clarify the role of ANXA1 as a cell fate ‘regulator’ within cells are critically needed. In this study, we found that intracerebroventricular injection of the recombinant adenovirus vector Ad-S100A11 (carrying S100A11) strongly improved cognitive function and induced robust neuroprotective effects after ischemic stroke in vivo. Furthermore, upregulation of S100A11 protected against neuronal apoptosis induced by oxygen-glucose deprivation and reoxygenation (OGD/R) in vitro. Surprisingly, S100A11 overexpression markedly decreased ANXA1 nuclear translocation and subsequently alleviated OGD/R-induced neuronal apoptosis. Notably, S100A11 exerted its neuroprotective effect by directly binding ANXA1. Importantly, S100A11 directly interacted with ANXA1 through the nuclear translocation signal (NTS) of ANXA1, which is essential for ANXA1 to import into the nucleus. Consistent with our previous studies, ANXA1 nuclear translocation after OGD/R promoted p53 transcriptional activity, induced mRNA expression of the pro-apoptotic Bid gene, and activated the caspase-3 apoptotic pathway, which was almost completely reversed by S100A11 overexpression. Thus, S100A11 protects against cell apoptosis by inhibiting OGD/R-induced ANXA1 nuclear translocation. This study provides a novel mechanism whereby S100A11 protects against neuronal cells apoptosis, suggesting the potential for a previously unidentified treatment strategy in minimizing apoptosis after ischemic stroke.

A novel cell-penetrating peptide protects against neuron apoptosis after cerebral ischemia by inhibiting the nuclear translocation of annexin A1

Nuclear translocation of annexin A1 (ANXA1) has recently been reported to participate in neuronal apoptosis after cerebral ischemia. Prevention of the nuclear translocation of ANXA1 should therefore inhibit neuronal apoptosis and protect against cerebral stroke. Here, we found that, in the repeat III domain of ANXA1, the amino-acid residues from R228 to F237 function as a unique nuclear translocation signal (NTS) and are required for nuclear translocation of ANXA1. Intriguingly, we synthesized a cell-penetrating peptide derived by conjugating the trans-activator of transcription (Tat) domain to the NTS sequence. This Tat-NTS peptide specifically blocked the interaction of ANXA1 with importin β and, consequently, the nuclear translocation of ANXA1 without affecting the nucleocytoplasmic shuttling of other proteins. The Tat-NTS peptide inhibited the transcriptional activity of p53, decreased Bid expression, suppressed activation of the caspase-3 apoptosis pathway and improved the survival of hippocampal neurons subjected to oxygen-glucose deprivation and reperfusion in vitro. Moreover, using a focal brain ischemia animal model, we showed that the Tat-NTS peptide could be efficiently infused into the ischemic hippocampus and cortex by unilateral intracerebroventricular injection. Injection of the Tat-NTS peptide alleviated neuronal apoptosis in the ischemic zone. Importantly, further work revealed that administration of the Tat-NTS peptide resulted in a dramatic reduction in infarct volume and that this was correlated with a parallel improvement in neurological function after reperfusion. Interestingly, the effects of Tat-NTS were injury specific, with little impact on neuronal apoptosis or cognitive function in sham-treated nonischemic animals. In conclusion, based on its profound neuroprotective and cognitive-preserving effects, it is suggested that the Tat-NTS peptide represents a novel and potentially promising new therapeutic candidate for the treatment of ischemic stroke.

Ac2-26 Induces IKKβ Degradation Through Chaperone-Mediated Autophagy Via HSPB1 in NCM-Treated Microglia

Annexin A1 (ANXA1) is an endogenous protein with potent anti-inflammatory properties in the brain. Although ANXA1 has been predominantly studied for its binding to formyl peptide receptors (FPRs) on plasma membranes, little is known regarding whether this protein has an anti-inflammatory effect in the cytosol. Here, we investigated the mechanism by which the ANXA1 peptide Ac2-26 decreases high TNF-α production and IKKβ activity, which was caused by oxygen glucose deprivation/reperfusion (OGD/R)-induced neuronal conditioned medium (NCM) in microglia. We found that exogenous Ac2-26 crosses into the cytoplasm of microglia and inhibits both gene expression and protein secretion of TNF-α. Ac2-26 also causes a decrease in IKKβ protein but not IKKβ mRNA, and this effect is inverted by lysosome inhibitor NH₄CL. Furthermore, we demonstrate that Ac2-26 induces IKKβ accumulation in lysosomes and that lysosomal-associated membrane protein 2A (LAMP-2A), not LC-3, is enhanced in microglia exposed to Ac2-26. We hypothesize that Ac2-26 mediates IKKβ degradation in lysosomes through chaperone-mediated autophagy (CMA). Interestingly, ANXA1 in the cytoplasm does not interact with IKKβ but with HSPB1, and Ac2-26 promotes HSPB1 binding to IKKβ. Furthermore, both ANXA1 and HSPB1 can interact with Hsc70 and LAMP-2A, but IKKβ only associates with LAMP-2A. Downregulation of HSPB1 or LAMP-2A reverses the degradation of IKKβ induced by Ac2-26. Taken together, these findings define an essential role of exogenous Ac2-26 in microglia and demonstrate that Ac2-26 is associated with HSPB1 and promotes HSPB1 binding to IKKβ, which is degraded by CMA, thereby reducing TNF-α expression.

Annexin A1 is elevated in patients with COPD and affects lung fibroblast function

Purpose

Fibrosis in peripheral airways is responsible for airflow limitation in chronic obstructive pulmonary disease (COPD). Annexin A1 modulates several key biological events during inflammation. However, little is known about its role in airway fibrosis in COPD. We investigated whether levels of Annexin A1 were upregulated in patients with COPD, and whether it promoted airway fibrosis.

Methods

We quantified serum Annexin A1 levels in never-smokers (n=12), smokers without COPD (n=11), and smokers with COPD (n=22). Correlations between Annexin A1 expression and clinical indicators (eg, lung function) were assessed. In vitro, human bronchial epithelial (HBE) cells were exposed to cigarette smoke extract (CSE) and Annexin A1 expression was assessed. Primary human lung fibroblasts were isolated from patients with COPD and effects of Annexin A1 on fibrotic deposition of lung fibroblasts were evaluated.

Results

Serum Annexin A1 was significantly higher in patients with Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines stage III or IV than in those with GOLD stages I or II (12.8±0.8 ng/mL versus 9.8±0.7 ng/mL; p=0.016). Annexin A1 expression was negatively associated with airflow obstruction (forced expiratory volume in one second % predicted; r=−0.72, p<0.001). In vitro, Annexin A1 was significantly increased in CSE-exposed HBE cells in a time- and concentration-dependent manner. Annexin A1 promoted lung fibroblasts proliferation, migration, differentiation, and collagen deposition via the ERK1/2 and p38 mitogen-activated protein kinase pathways.

Conclusion

Annexin A1 expression is upregulated in patients with COPD and affects lung fibroblast function. However, more studies are needed to clarify the role of Annexin A1 in airway fibrosis of COPD.

The protective effect of PFTα on alcohol-induced osteonecrosis of the femoral head

Epidemiologic studies have shown alcohol plays a pivotal role in the development of osteonecrosis of the femoral head (ONFH). The aim of this study was to explore the underlying mechanism of alcohol-induced ONFH and the protective effect of pifithrin-α (PFTα). In vitro, we found ethanol treatment significantly activated p53, suppressed Wnt/β-catenin signaling and inhibited osteogenic-related proteins. Furthermore, by separating the cytoplasmic and nuclear proteins, we found ethanol inhibited osteogenesis by impairing the accumulation of β-catenin in both the cytoplasm and nucleus in human bone mesenchymal stem cells (hBMSCs), which resulted from activating glycogen synthase kinase-3β (GSK-3β). Therefore, PFTα, a p53 inhibitor, was introduced in this study to block the ethanol-triggered activation of p53 in hBMSCs and alcohol-induced ONFH in a rat model. In vivo, we established alcohol-induced ONFH in rats and investigated the protective effect of PFTα. Hematoxylin & eosin (H&E) staining combined with TdT-mediated dUTP nick end labeling (TUNEL), cleaved caspase-3 immunohistochemical staining, and micro-CT images revealed substantial ONFH in the alcohol-administered rats, whereas significantly less osteonecrosis developed in the rats injected with PFTα. Osteogenic-related proteins, including osteocalcin, osteopontin and collagen I, were significantly decreased in the alcohol-administered rats, whereas these results were reversed in the PFTα-injected rats. Fluorochrome labeling similarly showed that alcohol significantly reduced the osteogenic activity in the rat femoral head, which was blocked by the injection of PFTα. In conclusion, PFTα had an antagonistic effect against the effects of ethanol on hBMSCs and could be a clinical strategy to prevent the development of alcohol-induced ONFH.

p73 Regulates Primary Cortical Neuron Metabolism: a Global Metabolic Profile

The transcription factor p73 has been demonstrated to play a significant role in survival and differentiation of neuronal stem cells. In this report, by employing comprehensive metabolic profile and mitochondrial bioenergetics analysis, we have explored the metabolic alterations in cortical neurons isolated from p73 N-terminal isoform specific knockout animals. We found that loss of the TAp73 or ΔNp73 triggers selective biochemical changes. In particular, p73 isoforms regulate sphingolipid and phospholipid biochemical pathway signaling. Indeed, sphinganine and sphingosine levels were reduced in p73-depleted cortical neurons, and decreased levels of several membrane phospholipids were also observed. Moreover, in line with the complexity associated with p73 functions, loss of the TAp73 seems to increase glycolysis, whereas on the contrary, loss of ΔNp73 isoform reduces glucose metabolism, indicating an isoform-specific differential effect on glycolysis. These changes in glycolytic flux were not reflected by parallel alterations of mitochondrial respiration, as only a slight increase of mitochondrial maximal respiration was observed in p73-depleted cortical neurons. Overall, our findings reinforce the key role of p73 in regulating cellular metabolism and point out that p73 exerts its functions in neuronal biology at least partially through the regulation of metabolic pathways.

14-3-3 Isoforms Differentially Regulate NFκB Signaling in the Brain After Ischemia-Reperfusion

Mammalian 14-3-3 isoforms exist predominantly in the brain and are heavily involved in neurological diseases. However, the isoform-specific role of 14-3-3 proteins in the brain remains largely unclear. Here, we investigated the role of 14-3-3 isoforms in rat brains after transient middle cerebral artery occlusion and reperfusion. 14-3-3β, η, γ and ζ but not ε or τ were selectively upregulated in cerebral cortical neurons after ischemia-reperfusion (I/R). Selectively, 14-3-3β, γ and ζ were translocated from cytoplasm into the nuclei of neurons after I/R. 14-3-3 bound to p65 and suppressed p65 expression in N2a cells. In the brain, 14-3-3 could either colocalize with p65 in the nuclei of neurons or segregate from p65 expression in cortical neurons after I/R. All evidence together suggests that 14-3-3 isoforms are differentially induced to enter into the nuclei of neurons after I/R, which might regulate NFκB signaling directly or indirectly. Since 14-3-3 proteins are essential for cell survival and NFκB is a key transcriptional factor, our data suggest that the 14-3-3/p65 signaling pathway might be a potential therapeutic target for stroke.

Annexins as Overlooked Regulators of Membrane Trafficking in Plant Cells

Annexins are an evolutionary conserved superfamily of proteins able to bind membrane phospholipids in a calcium-dependent manner. Their physiological roles are still being intensively examined and it seems that, despite their general structural similarity, individual proteins are specialized toward specific functions. However, due to their general ability to coordinate membranes in a calcium-sensitive fashion they are thought to participate in membrane flow. In this review, we present a summary of the current understanding of cellular transport in plant cells and consider the possible roles of annexins in different stages of vesicular transport.

Annexin A1 nuclear translocation induces retinal ganglion cell apoptosis after ischemia-reperfusion injury through the p65/IL-1β pathway

The degeneration of retinal ganglion cells (RGCs) has been identified as a major problem in glaucoma. Previous studies have indicated an association between annexin A1 (ANXA1) and neuronal cell apoptosis, and RGCs apoptosis in acute ischemia-reperfusion was attributed to an increased production of IL-1β. We found that the expression and nuclear translocation of ANXA1 were upregulated in models of acute ischemia-reperfusion in RGCs in vivo. ANXA1 was found to have a promoting effect on the expression of IL-1β in primary cultured RGCs, which could be inhibited by treatment with ANXA1 shRNA or the p65 inhibitor BAY 11-7082. ANXA1 interacted with p65, and recruited it into the nucleus. Chromatin immunoprecipitation assay revealed that ANXA1 accumulated at the IL-1β gene promoter. The reduction of p65 nuclear translocation using a membrane-permeable ANXA1 peptide containing a Ser5Ala mutation led to a decrease in the expression of IL-1β, and acute ischemia-reperfusion induced RGCs apoptosis in vivo. These results indicate that in RGCs, ANXA1 increases IL-1β expression by recruiting p65 to the nucleus, which induces cell apoptosis. The obtained results may help the development of a novel treatment strategy against RGCs apoptosis in acute ischemia-reperfusion injury.