Homer1a Attenuates Endoplasmic Reticulum Stress-Induced Mitochondrial Stress After Ischemic Reperfusion Injury by Inhibiting the PERK Pathway

Lipocalin-2 inhibition alleviates neural injury by microglia ferroptosis suppression after experimental intracerebral hemorrhage in mice via enhancing ferritin light chain expression

INTRODUCTION

Microglia play pivotal roles in post-intracerebral hemorrhage (ICH) neural injury. Iron metabolism, which is dysregulated after ICH, participates in microglial dysfunction. Previous studies have shown that iron metabolism-related lipocalin-2 (LCN2) is involved in regulating microglial function following ICH. In this study, we investigated the role of LCN2 in microglial function following ICH.

METHODS

The BV2 (microglia) cell line, transfected with LCN2 for overexpression/interference, received a blood infusion from C57BL/6 mice in vitro. For the in vivo study of LCN2 function, an LCN2 knockout was conducted in mice. Liproxstatin-1 and RSL3 were used to manipulate ferroptosis and to study the effects of LCN2 on microglia after ICH. A BV2 (microglia) cell line, transfected with ferritin light chain (FTL) for overexpression/interference, was co-cultured with primary cultured neurons for a study on the mechanism of LCN2. Behavioral tests were conducted pre-ICH and on days 3, 7, and 28 post-ICH, and the brains and cultured cells were collected for protein, histological, and morphological studies.

RESULTS

Brain LCN2 expression was upregulated in microglia, astrocytes, and neurons and played hazardous roles after ICH. In microglia, LCN2 promoted ferroptosis, which facilitated neural injury after ICH. LCN2-mediated FTL deficiency was shown to be responsible for microglial ferroptosis-induced neural injury.

CONCLUSION

Our study suggests that LCN2-enhanced microglial ferroptosis plays a detrimental role by inducing FTL deficiency after ICH. The current study reveals a novel molecular mechanism involved in the pathophysiological progression of ICH.

ROS induced pyroptosis in inflammatory disease and cancer

Pyroptosis, a form of caspase-1-dependent cell death, also known as inflammation-dependent death, plays a crucial role in diseases such as stroke, heart disease, or tumors. Since its elucidation, pyroptosis has attracted widespread attention from various sectors. Reactive oxygen species (ROS) can regulate numerous cellular signaling pathways. Through further research on ROS and pyroptosis, the level of ROS has been revealed to be pivotal for the occurrence of pyroptosis, establishing a close relationship between the two. This review primarily focuses on the molecular mechanisms of ROS and pyroptosis in tumors and inflammatory diseases, exploring key proteins that may serve as drug targets linking ROS and pyroptosis and emerging fields targeting pyroptosis. Additionally, the potential future development of compounds and proteins that influence ROS-regulated cell pyroptosis is anticipated, aiming to provide insights for the development of anti-tumor and anti-inflammatory drugs.

Homer1a reduces inflammatory response after retinal ischemia/reperfusion injury

JOURNAL/nrgr/04.03/01300535-202407000-00042/figure1/v/2023-11-20T171125Z/r/image-tiff

Elevated intraocular pressure (IOP) is one of the causes of retinal ischemia/reperfusion injury, which results in NLRP3 inflammasome activation and leads to visual damage. Homer1a is reported to play a protective role in neuroinflammation in the cerebrum. However, the effects of Homer1a on NLRP3 inflammasomes in retinal ischemia/reperfusion injury caused by elevated IOP remain unknown. In our study, animal models were constructed using C57BL/6J and Homer1flox/ –/Homer1a+/ –/Nestin-Cre+/ – mice with elevated IOP-induced retinal ischemia/reperfusion injury. For in vitro experiments, the oxygen-glucose deprivation/reperfusion injury model was constructed with Müller cells. We found that Homer1a overexpression ameliorated the decreases in retinal thickness and Müller cell viability after ischemia/reperfusion injury. Furthermore, Homer1a knockdown promoted NF-κB P65Ser536 activation via caspase-8, NF-κB P65 nuclear translocation, NLRP3 inflammasome formation, and the production and processing of interleukin-1β and interleukin-18. The opposite results were observed with Homer1a overexpression. Finally, the combined administration of Homer1a protein and JSH-23 significantly inhibited the reduction in retinal thickness in Homer1flox/ –/Homer1a+/ –/Nestin-Cre+/ – mice and apoptosis in Müller cells after ischemia/reperfusion injury. Taken together, these studies demonstrate that Homer1a exerts protective effects on retinal tissue and Müller cells via the caspase-8/NF-κB P65/NLRP3 pathway after I/R injury.

Exploring the intricacies of calcium dysregulation in ischemic stroke: Insights into neuronal cell death and therapeutic strategies

Calcium ion (Ca2+) dysregulation is one of the main causes of neuronal cell death and brain damage after cerebral ischemia. During ischemic stroke, the ability of neurons to maintain Ca2+ homeostasis is compromised. Ca2+ regulates various functions of the nervous system, including neuronal activity and adenosine triphosphate (ATP) production. Disruptions in Ca2+ homeostasis can trigger a cascade of events, including activation of the unfolded protein response (UPR) pathway, which is associated with endoplasmic reticulum (ER) stress and mitochondrial dysfunction. This response occurs when the cell is unable to manage protein folding within the ER due to various stressors, such as a high influx of Ca2+. Consequently, the UPR is initiated to restore ER function and alleviate stress, but prolonged activation can lead to mitochondrial dysfunction and, ultimately, cell death. Hence, precise regulation of Ca2+ within the cell is mandatory. The ER and mitochondria are two such organelles that maintain intracellular Ca2+ homeostasis through various calcium-operating channels, including ryanodine receptors (RyRs), inositol trisphosphate receptors (IP3Rs), sarco/endoplasmic reticulum calcium ATPases (SERCAs), the mitochondrial Na+/Ca2+ exchanger (NCLX), the mitochondrial calcium uniporter (MCU) and voltage-dependent anion channels (VDACs). These channels utilize Ca2+ sequestering and release mechanisms to maintain intracellular Ca2+ homeostasis and ensure proper cellular function and survival. The present review critically evaluates the significance of Ca2+ and its physiological role in cerebral ischemia. We have compiled recent findings on calcium's role and emerging treatment strategies, particularly targeting mitochondria and the endoplasmic reticulum, to address Ca2+ overload in cerebral ischemia.

Serum Homer1 is a Novel Biomarker for Predicting the Clinical Outcomes of Acute Ischemic Stroke Patients

Purpose

We aim to explore the relationship between Homer1 and the outcomes of AIS patients at 3 months.

Patients and Methods

This prospective cohort study was conducted from May 2022 to March 2023. In this study, we investigated the association between serum Homer1 levels by enzyme-linked immunosorbent assay at admission and functional outcomes of patients at 3 months after AIS.

Results

Overall, 89 AIS patients (48 good outcomes and 41 poor outcomes) and 83 healthy controls were included. The median serum Homer1 level of patients at admission with poor outcomes was significantly higher than that of patients with good outcomes (39.33 vs 33.15, P<0.001). Serum Homer1 levels at admission were positively correlated with the severity of AIS (r = 0.488, P<0.001). The optimal cutoff of serum Homer1 level as an indicator for an auxiliary diagnosis of 3 months functional outcomes was 35.07 pg/mL, with a sensitivity of 75.0% and a specificity of 92.7% (AUC 0.837; 95% CI [0.744-0.907]; P<0 0.001). The odds ratio of MRS > 2 predicted by the level of serum Homer1 after 3 months was 1.665 (1.306-2.122; P<0.001).

Conclusion

Serum concentrations of Homer1 have a high predictive value for neurobehavioral outcomes after acute ischemic stroke. Higher serum Homer1 levels (>35.07 pg/mL) were positively associated with poor functional outcomes of patients 3 months post-stroke.

Phenothiazines reduced autophagy in ischemic stroke through endoplasmic reticulum (ER) stress-associated PERK-eIF2α pathway

BACKGROUND

Neuroprotective effects have been the main focus of new treatment modalities for ischemic stroke. Phenothiazines, or chlorpromazine plus promethazine (C + P), are known to prevent the generation of free radicals and uptake of Ca2+ by plasma membrane; they have a potential as a treatment for acute ischemic stroke (AIS). This study aims to investigate the role of endoplasmic reticulum (ER) stress-associated PERK-eIF2α pathway underlying the phenothiazine-induced neuroprotective effects after cerebral ischemia/reperfusion (I/R) injury.

METHODS

A total of 49 male Sprague Dawley rats (280-320 g) were randomly divided into 4 groups (n = 7 per group): (1) sham, (2) I/R that received 2 h of middle cerebral artery occlusion (MCAO), followed by 6 or 24 h of reperfusion, (3) MCAO treated by C + P without temperature control and (4) MCAO treated by C + P with temperature control. Human neuroblastoma (SH-SY5Y) cells were used in 5 groups: (1) control, (2) oxygen-glucose deprivation (OGD) for 2 h followed by reoxygenation (OGD/R), (3) OGD/R with C + P; (4) OGD/R with PERK inhibitor, GSK2656157, and (5) OGD/R with C + P and GSK2656157. The molecules of ER stress, unfolded protein response (UPR) (Bip, PERK, p-PERK, p-PERK/PERK, eIF2α, p-eIF2α, p-eIF2α/eIF2α), autophagy (ATG12, LC3II/I), and apoptosis (BAX, Bcl-XL) were measured at mRNA levels by real time PCR and protein levels by Western blotting.

RESULTS

In ischemic rats followed by reperfusion, expression of Bip, p-PERK/PERK, p-eIF2α/eIF2α, ATG12, and LC3II/I, as well as BAX were all significantly increased. These markers were significantly reduced by C + P at both 6 and 24 h of reperfusion. Anti-apoptotic Bcl-XL expression was increased, while pro-apoptotic BAX expression was decreased by C + P. In SH-SY5Y cell lines, both C + P and GSK2656157 significantly reduced the level of autophagy and apoptosis after I/R, respectively. The combination of GSK2656157 and C + P did not promote the same effect, suggesting that C + P did not induce any neuroprotective effect by inhibiting autophagy and apoptosis through the PERK-eIF2α pathway when this pathway was already blocked by GSK2656157. In general, the reduction in body temperature by phenothiazines was associated with better neuroprotection but it did not reach significant levels.

CONCLUSION

The combined treatment of C + P plays a crucial role in stroke therapy by inhibiting ER stress-mediated autophagy, thereby leading to reduced apoptosis and increased neuroprotection. Our findings highlight the PERK-eIF2α pathway as a central mechanism through which C + P exerts its beneficial effects. The results from this study may pave the way for the development of more targeted and effective treatments for stroke patients.

Blockage of calcium-sensing receptor improves chronic intermittent hypoxia-induced cognitive impairment by PERK-ATF4-CHOP pathway

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is involved in cognitive impairment of children. Chronic intermittent hypoxia (CIH) is considered as the critical pathophysiological mechanism of OSAHS. Calcium sensitive receptor (CaSR) mediated apoptosis in many neurological disease models by endoplasmic reticulum stress (ERS)-related pathway. However, little is known about the role of CaSR in OSAHS-induced cognitive dysfunction. In this study, we explored the effect of CaSR on CIH-induced cognitive impairment and possible mechanisms on regulation of PERK-ATF4-CHOP pathway in vivo and in vitro. CIH exposed for 9 h in PC12 cells and resulted in the cell apoptosis, simulating OSAHS-induced neuronal injury. CIH upregulated the level of CaSR, p-PERK, ATF4 and CHOP, contributing to the cell apoptosis. Treated with CaSR inhibitor (NPS-2143) or p-PERK inhibitor (GSK2656157) before CIH exposure, CIH-induced PC12 cell apoptosis was alleviated via inhibition of CaSR by downregulating p-PERK, ATF4 and CHOP. In addition, we established CIH mice model. With CIH exposure for 4 weeks in mice, more spatial memory errors were observed during 8-arm radial maze test. CIH significantly increased apoptotic cells in hippocampus via upregulating cleaved Caspase-3 and downregulating ratio of Bcl-2 to Bax. Besides, treatment of CaSR inhibitor alleviated the hippocampal neuronal apoptosis following CIH with downregulated p-PERK, ATF4 and CHOP, suggesting that CaSR contributed to CIH-induced neuronal apoptosis in hippocampus via ERS pathway. Sum up, our results demonstrated that CaSR accelerated hippocampal apoptosis via PERK-ATF4-CHOP pathway, holding a critical function on CIH-mediated cognitive impairment. Conversely, inhibition of CaSR suppressed PERK-ATF4-CHOP pathway and alleviated cognitive impairment.

The protective role of sulforaphane and Homer1a in retinal ischemia-reperfusion injury: Unraveling the neuroprotective interplay

AIMS

Retinal ischemia/reperfusion (I/R) injury is a common pathological basis for various ophthalmic diseases. This study aimed to investigate the potential of sulforaphane (SFN) and Homer1a in regulating cell apoptosis induced by retinal I/R injury and to explore the underlying regulatory mechanism between them.

MATERIALS AND METHODS

In in vivo experiments, C57BL/6J mice and Homer1flox/-/Homer1a+/-/Nestin-Cre+/- mice were used to construct retinal I/R injury models. In vitro experiments utilized the oxygen-glucose deprivation-reperfusion (OGD/R) injury model with primary retinal ganglion cells (RGCs). The effects of Homer1a and SFN on cell apoptosis were observed through pathological analyses, flow cytometry, and visual electrophysiological assessments.

KEY FINDINGS

We discovered that after OGD/R injury, apoptosis of RGCs and intracellular Ca2+ activity significantly increased. However, these changes were reversed upon the addition of SFN, and similar observations were reproduced in in vivo studies. Furthermore, both in vivo and in vitro studies confirmed the upregulation of Homer1a after I/R, which could be further enhanced by the administration of SFN. Moreover, upregulation of Homer1a resulted in a reduction in cell apoptosis and pro-apoptotic proteins, while downregulation of Homer1a had the opposite effect. Flash visual evoked potential, oscillatory potentials, and escape latency measurements in mice supported these findings. Furthermore, the addition of SFN strengthened the neuroprotective effects in the OGD/R + H+ group but weakened them in Homer1flox/-/Homer1a+/-/Nestin-Cre+/- mice.

SIGNIFICANCE

These results indicate that Homer1a plays a significant role in the therapeutic potential of sulforaphane for retinal I/R injury, thereby providing a theoretical basis for clinical treatment.

Neuroglobin protects against cerebral ischemia/reperfusion injury in rats by suppressing mitochondrial dysfunction and endoplasmic reticulum stress-mediated neuronal apoptosis through synaptotagmin-1

Cerebral ischemia/reperfusion (I/R) injury remains a grievous health threat, and herein effective therapy is urgently needed. This study explored the protection of neuroglobin (Ngb) in rats with cerebral I/R injury. The focal cerebral I/R rat models were established by middle cerebral artery occlusion (MCAO) and neuronal injury models were established by oxygen-glucose deprivation/reoxygenation (OGD/R) treatment. The brain injury of rats was assessed. Levels of Ngb, Bcl-2, Bax, endoplasmic reticulum stress (ERS)-related markers, and Syt1 were measured by immunofluorescence staining and Western blotting. The cytotoxicity in neurons was assessed by lactate dehydrogenase (LDH) release assay. Levels of intracellular Ca²⁺ and mitochondrial function-related indicators were determined. The binding between Ngb and Syt1 was detected by co-immunoprecipitation. Ngb was upregulated in cerebral I/R rats and its overexpression alleviated brain injury. In OGD/R-induced neurons, Ngb overexpression decreased LDH level and neuronal apoptosis, decreased Ca²⁺ content, and mitigated mitochondrial dysfunction and ERS-related apoptosis. However, Ngb silencing imposed the opposite effects. Importantly, Ngb could bind to Syt1. Syt1 knockdown partially counteracted the alleviation of Ngb on OGD/R-induced injury in neurons and cerebral I/R injury in rats. Briefly, Ngb extenuated cerebral I/R injury by repressing mitochondrial dysfunction and endoplasmic reticulum stress-mediated neuronal apoptosis through Syt1.

PERK inhibitor, GSK2606414, ameliorates neuropathological damage, memory and motor functional impairments in cerebral ischemia via PERK/p-eIF2ɑ/ATF4/CHOP signaling

The protein kinase R-like endoplasmic reticulum kinase/eukaryotic initiation factor 2ɑ (PERK/eIF2α), the branch of unfolded protein response (UPR), is responsible for transient arrest in translation to counter the enhanced levels of misfolded or unfolded proteins in the endoplasmic reticulum (ER) following any acute condition. In neurological disorders, overactivation of PERK-P/eIF2-P signaling, leads to a prolonged decline in global protein synthesis resulting in synaptic failure and neuronal death. Our study has shown, PERK/ATF4/CHOP pathway gets activated following cerebral ischemia in rats. We have further demonstrated, PERK inhibitor, GSK2606414 ameliorates ischemia induced neuronal damage by preventing additional neuronal loss, minimizing brain infarct, reducing brain edema, and preventing neurological symptoms from appearing. GSK2606414 was found to improve the neurobehavioral deficits and reduce the pyknotic neurons in ischemic rats. Also, it decreased glial activation and apoptotic protein mRNA expression while enhanced the synaptic protein mRNA expression in rat brain following cerebral ischemia. In conclusion, our findings suggest that PERK/ATF4/CHOP activation play a vital role in cerebral ischemia. Thus, PERK inhibitor, GSK2606414 might be a potential neuroprotective agent in cerebral ischemia.

Remembering and forgetting in sleep: Selective synaptic plasticity during sleep driven by scaling factors Homer1a and Arc

Sleep is a conserved and essential process that supports learning and memory. Synapses are a major target of sleep function and a locus of sleep need. Evidence in the literature suggests that the need for sleep has a cellular or microcircuit level basis, and that sleep need can accumulate within localized brain regions as a function of waking activity. Activation of sleep promoting kinases and accumulation of synaptic phosphorylation was recently shown to be part of the molecular basis for the localized sleep need. A prominent hypothesis in the field suggests that some benefits of sleep are mediated by a broad but selective weakening, or scaling-down, of synaptic strength during sleep in order to offset increased excitability from synaptic potentiation during wake. The literature also shows that synapses can be strengthened during sleep, raising the question of what molecular mechanisms may allow for selection of synaptic plasticity types during sleep. Here I describe mechanisms of action of the scaling factors Arc and Homer1a in selective plasticity and links with sleep need. Arc and Homer1a are induced in neurons in response to waking neuronal activity and accumulate with time spent awake. I suggest that during sleep, Arc and Homer1a drive broad weakening of synapses through homeostatic scaling-down, but in a manner that is sensitive to the plasticity history of individual synapses, based on patterned phosphorylation of synaptic proteins. Therefore, Arc and Homer1a may offer insights into the intricate links between a cellular basis of sleep need and memory consolidation during sleep.

Sodium formononetin-3'-sulphonate alleviates cerebral ischemia-reperfusion injury in rats via suppressing endoplasmic reticulum stress-mediated apoptosis

BACKGROUND

Sodium formononetin-3'-sulphonate (Sul-F) may alleviate I/R injury in vivo with uncertain mechanism. Endoplasmic reticulum (ER) stress-mediated apoptosis participates in the process of cerebral ischemia-reperfusion (I/R) injury. Our aim is to figure out the effect of Sul-F on cerebral I/R injury and to verify whether it works through suppressing ER stress-mediated apoptosis.

RESULTS

The cerebral lesions of middle cerebral artery occlusion (MCAO) model in SD rats were aggravated after 24 h of reperfusion, including impaired neurological function, increased infarct volume, intensified inflammatory response and poor cell morphology. After intervention, the edaravone (EDA, 3 mg/kg) group and Sul-F high-dose (Sul-F-H, 80 mg/kg) group significantly alleviated I/R injury via decreasing neurological score, infarct volume and the serum levels of inflammatory factors (TNF-α, IL-1β and IL-6), as well as alleviating pathological injury. Furthermore, the ER stress level and apoptosis rate were elevated in the ischemic penumbra of MCAO group, and were significantly blocked by EDA and Sul-F-H. In addition, EDA and Sul-F-H significantly down-regulated the ER stress related PERK/eIF2α/ATF4 and IRE1 signal pathways, which led to reduced cell apoptosis rate compared with the MCAO group. Furthermore, there was no difference between the EDA and Sul-F-H group in terms of therapeutic effect on cerebral I/R injury, indicating a therapeutic potential of Sul-F for ischemic stroke.

CONCLUSIONS

Sul-F-H can significantly protects against cerebral I/R injury through inhibiting ER stress-mediated apoptosis in the ischemic penumbra, which might be a novel therapeutic target for ischemic stroke.

Protective role of TLR9-induced macrophage/microglia phagocytosis after experimental intracerebral hemorrhage in mice

INTRODUCTION

Intracerebral hemorrhage (ICH) causes devastating morbidity and mortality, and studies have shown that the toxic components of hematomas play key roles in brain damage after ICH. Recent studies have found that TLR9 participates in regulating the phagocytosis of peripheral macrophages. The current study examined the role of TLR9 in macrophage/microglial (M/M) function after ICH.

METHODS

RAW264.7 (macrophage), BV2 (microglia), and HT22# (neurons) cell lines were transfected with lentivirus for TLR9 overexpression. Whole blood from C57BL/6 or EGFP^Tg/+ mice was infused for phagocytosis and injury experiments, and brusatol was used for the experiments. Intraperitoneal injection of the TLR9 agonist ODN1826 or control ODN2138 was performed on days 1, 3, 5, 7, and 28 after ICH to study the effects of TLR9 in mice. In addition, clodronate was coinjected in M/M elimination experiments. The brains were collected for histological and protein experiments at different time points after ICH induction. Cellular and histological methods were used to measure hematoma/iron residual, M/Ms variation, neural injury, and brain tissue loss. Behavioral tests were performed premodeling and on days 1, 3, 7, and 28 post-ICH.

RESULTS

Overexpression of TLR9 facilitated M/M phagocytosis and protected neurons from blood-derived hazards in vitro. Furthermore, ODN1826 boosted M/M activation and phagocytic function, facilitated hematoma/iron resolution, reduced brain injury, and improved neurological function recovery in ICH mice, which were abolished by clodronate injection. The experimental results indicated that the Nrf2/CD204 pathway participated in TLR9-induced M/M phagocytosis after ICH.

CONCLUSION

Our study suggests a protective role for TLR9-enhanced M/M phagocytosis via the Nrf2/CD204 pathway after ICH. Our findings may serve as potential targets for ICH treatment.

Intertwined Relation between the Endoplasmic Reticulum and Mitochondria in Ischemic Stroke

In ischemic stroke (IS), accumulation of the misfolded proteins in the endoplasmic reticulum (ER) and mitochondria-induced oxidative stress (OS) has been identified as the indispensable inducers of secondary brain injury. With the increasing recognition of an association between ER stress and OS with ischemic stroke and with the improved understanding of the underlying molecular mechanism, novel targets for drug therapy and new strategies for therapeutic interventions are surfacing. This review discusses the molecular mechanism underlying ER stress and OS response as both causes and consequences of ischemic stroke. We also summarize the latest advances in understanding the importance of ER stress and OS in the pathogenesis of ischemic stroke and discuss potential strategies and clinical trials explicitly aiming to restore mitochondria and ER dynamics after IS.

Endoplasmic Reticulum Stress and the Unfolded Protein Response in Cerebral Ischemia/Reperfusion Injury

Ischemic stroke is an acute cerebrovascular disease characterized by sudden interruption of blood flow in a certain part of the brain, leading to serious disability and death. At present, treatment methods for ischemic stroke are limited to thrombolysis or thrombus removal, but the treatment window is very narrow. However, recovery of cerebral blood circulation further causes cerebral ischemia/reperfusion injury (CIRI). The endoplasmic reticulum (ER) plays an important role in protein secretion, membrane protein folding, transportation, and maintenance of intracellular calcium homeostasis. Endoplasmic reticulum stress (ERS) plays a crucial role in cerebral ischemia pathophysiology. Mild ERS helps improve cell tolerance and restore cell homeostasis; however, excessive or long-term ERS causes apoptotic pathway activation. Specifically, the protein kinase R-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), and inositol-requiring enzyme 1 (IRE1) pathways are significantly activated following initiation of the unfolded protein response (UPR). CIRI-induced apoptosis leads to nerve cell death, which ultimately aggravates neurological deficits in patients. Therefore, it is necessary and important to comprehensively explore the mechanism of ERS in CIRI to identify methods for preserving brain cells and neuronal function after ischemia.

Homer1 promotes the conversion of A1 astrocytes to A2 astrocytes and improves the recovery of transgenic mice after intracerebral hemorrhage

Background

Inflammation induced by intracerebral hemorrhage (ICH) is one of the main causes of the high mortality and poor prognosis of patients with ICH. A1 astrocytes are closely associated with neuroinflammation and neurotoxicity, whereas A2 astrocytes are neuroprotective. Homer scaffolding protein 1 (Homer1) plays a protective role in ischemic encephalopathy and neurodegenerative diseases. However, the role of Homer1 in ICH-induced inflammation and the effect of Homer1 on the phenotypic conversion of astrocytes remain unknown.

Methods

Femoral artery autologous blood from C57BL/6 mice was used to create an ICH model. We use the A1 phenotype marker C3 and A2 phenotype marker S100A10 to detect astrocyte conversion after ICH. Homer1 overexpression/knock-down mice were constructed by adeno-associated virus (AAV) infection to explore the role of Homer1 and its mechanism of action after ICH. Finally, Homer1 protein and selumetinib were injected into in situ hemorrhage sites in the brains of Homer1^flox/flox/Nestin-Cre^+/− mice to study the efficacy of Homer1 in the treatment of ICH by using a mouse cytokine array to explore the potential mechanism.

Results

The expression of Homer1 peaked on the third day after ICH and colocalized with astrocytes. Homer1 promotes A1 phenotypic conversion in astrocytes in vivo and in vitro. Overexpression of Homer1 inhibits the activation of MAPK signaling, whereas Homer1 knock-down increases the expression of pathway-related proteins. The Homer1 protein and selumetinib, a non-ATP competitive MEK1/2 inhibitor, improved the outcome in ICH in Homer1^flox/flox/Nestin-Cre^+/− mice. The efficacy of Homer1 in the treatment of ICH is associated with reduced expression of the inflammatory factor TNFSF10 and increased expression of the anti-inflammatory factors activin A, persephin, and TWEAK.

Conclusions

Homer1 plays an important role in inhibiting inflammation after ICH by suppressing the A1 phenotype conversion in astrocytes. In situ injection of Homer1 protein may be a novel and effective method for the treatment of inflammation after ICH.

Emerging Roles and Mechanisms of lncRNA FOXD3-AS1 in Human Diseases

Numerous long noncoding RNAs (lncRNAs) have been identified as powerful regulators of human diseases. The lncRNA FOXD3-AS1 is a novel lncRNA that was recently shown to exert imperative roles in the initialization and progression of several diseases. Emerging studies have shown aberrant expression of FOXD3-AS1 and close correlation with pathophysiological traits of numerous diseases, particularly cancers. More importantly, FOXD3-AS1 was also found to ubiquitously impact a range of biological functions. This study aims to summarize the expression, associated clinicopathological features, major functions and molecular mechanisms of FOXD3-AS1 in human diseases and to explore its possible clinical applications.

Homer signaling pathways as effective therapeutic targets for ischemic and traumatic brain injuries and retinal lesions

Ischemic and traumatic insults to the central nervous system account for most serious acute and fatal brain injuries and are usually characterized by primary and secondary damage. Secondary damage presents the greatest challenge for medical staff; however, there are currently few effective therapeutic targets for secondary damage. Homer proteins are postsynaptic scaffolding proteins that have been implicated in ischemic and traumatic insults to the central nervous system. Homer signaling can exert either positive or negative effects during such insults, depending on the specific subtype of Homer protein. Homer 1b/c couples with other proteins to form postsynaptic densities, which form the basis of synaptic transmission, while Homer1a expression can be induced by harmful external factors. Homer 1c is used as a unique biomarker to reveal alterations in synaptic connectivity before and during the early stages of apoptosis in retinal ganglion cells, mediated or affected by extracellular or intracellular signaling or cytoskeletal processes. This review summarizes the structural features, related signaling pathways, and diverse roles of Homer proteins in physiological and pathological processes. Upregulating Homer1a or downregulating Homer1b/c may play a neuroprotective role in secondary brain injuries. Homer also plays an important role in the formation of photoreceptor synapses. These findings confirm the neuroprotective effects of Homer, and support the future design of therapeutic drug targets or gene therapies for ischemic and traumatic brain injuries and retinal disorders based on Homer proteins.

CTRP1 Attenuates Cerebral Ischemia/Reperfusion Injury via the PERK Signaling Pathway

Cerebral ischemic stroke is one of the leading causes of death worldwide. Previous studies have shown that circulating levels of CTRP1 are upregulated in patients with acute ischemic stroke. However, the function of CTRP1 in neurons remains unclear. The purpose of this study was to explore the role of CTRP1 in cerebral ischemia reperfusion injury (CIRI) and to elucidate the underlying mechanism. Middle cerebral artery occlusion/reperfusion (MCAO/R) and oxygen-glucose deprivation/reoxygenation (OGD/R) models were used to simulate cerebral ischemic stroke in vivo and in vitro, respectively. CTRP1 overexpression lentivirus and CTRP1 siRNA were used to observe the effect of CTRP1 expression, and the PERK selective activator CCT020312 was used to activate the PERK signaling pathway. We found the decreased expression of CTRP1 in the cortex of MCAO/R-treated rats and OGD/R-treated primary cortical neurons. CTRP1 overexpression attenuated CIRI, accompanied by the reduction of apoptosis and suppression of the PERK signaling pathway. Interference with CTRP1 expression in vitro aggravated apoptotic activity and increased the expression of proteins involved in the PERK signaling pathway. Moreover, activating the PERK signaling pathway abolished the protective effects of CTRP1 on neuron injury induced by CIRI in vivo and in vitro. In conclusion, CTRP1 protects against CIRI by reducing apoptosis and endoplasmic reticulum stress (ERS) through inhibiting the PERK-dependent signaling pathway, suggesting that CTRP1 plays a crucial role in the pathogenesis of CIRI.

Autophagy protects against cerebral ischemic reperfusion injury by inhibiting neuroinflammation

OBJECTIVE

To examine the effect of autophagy on cerebral damage caused by different models and test the hypothesis that its protection mechanism acts via inhibiting expression of neuroinflammatory mediators.

METHODS

Autophagy was induced by rapamycin treatment. Cerebral damage was induced using models of IL-6 treatment, oxygen glucose deprivation/reoxygenation (OGD/R) in vitro, and middle cerebral artery occlusion (MCAO) in vivo. The effect and mechanism of autophagy was examined and assessed in terms of cell viability, infarction size in brain tissue, neurological score, production of inflammatory mediators IL-1β and IL-6, transcription and protein expression of autophagy markers beclin-1 and LC-3II in different experimental groups.

RESULTS

Autophagy triggered by rapamycin could protect neurons from IL-6-induced injury and astrocytes from OGD/R-induced injury in vitro and in rat brain tissue from MCAO in vivo. Autophagy significantly increased cell viability, attenuated cerebral infarction and improved neurological scores. It also inhibited production of the IL-1β and IL-6 and elevated the expression of beclin-1 and LC-3II.

CONCLUSIONS

Autophagy can inhibit the inflammatory response and reduce cerebral I/R injury. There was a relationship between the extent of protection and (i) the level of the autophagic response, (ii) the stage of the cerebral I/R injury, and (iii) the time of intervention.

Ischemic-hypoxic preconditioning enhances the mitochondrial function recovery of transplanted olfactory mucosa mesenchymal stem cells via miR-181a signaling in ischemic stroke

Cerebral ischemia/reperfusion injury causes a series of intricate cascade reactions in brain tissue causing apoptosis and proinflammatory programmed cell death known as pyroptosis of nerve cells. The dysfunction of target organelle mitochondria plays a key role in the process of neuronal apoptosis and pyroptosis. Mesenchymal stem cells (MSCs) have been widely used in the experimental or clinical treatment of various ischemic diseases, but the therapeutic efficacy of MSCs on cerebral ischemia-reperfusion injury need to be improved. We successfully cultured olfactory mucosa MSCs (OM-MSCs) to obtain a better source of seed cells. In this way, the therapeutic potential of OM-MSCs transplantation has been evaluated for ischemic stroke using an optimized culture scheme in vitro. Ischemic-hypoxic preconditioned OM-MSCs (IhOM-MSCs) were used to treat a neuron model of oxygen-glucose deprivation/reperfusion and the middle cerebral artery occlusion in rats. These results demonstrated that IhOM-MSCs mediated the upregulation of the downstream target genes GRP78 and Bcl-2 by miR-181a to protect mitochondrial function and inhibit apoptosis and pyroptosis of neurons in the ischemia/reperfusion injury model. Thus, IhOM-MSCs transplantation may be an effective therapy of ischemic stroke in the future.

Neuroprotective Effects of Exercise Postconditioning After Stroke via SIRT1-Mediated Suppression of Endoplasmic Reticulum (ER) Stress

While it is well-known that pre-stroke exercise conditioning reduces the incidence of stroke and the development of comorbidities, it is unclear whether post-stroke exercise conditioning is also neuroprotective. The present study investigated whether exercise postconditioning (PostE) induced neuroprotection and elucidated the involvement of SIRT1 regulation on the ROS/ER stress pathway. Adult rats were subjected to middle cerebral artery occlusion (MCAO) followed by either: (1) resting; (2) mild exercise postconditioning (MPostE); or (3) intense exercise postconditioning (IPostE). PostE was initiated 24 h after reperfusion and performed on a treadmill. At 1 and 3 days thereafter, we determined infarct volumes, neurological defects, brain edema, apoptotic cell death through measuring pro- (BAX and Caspase-3) and anti-apoptotic (Bcl-2) proteins, and ER stress through the measurement of glucose-regulated protein 78 (GRP78), inositol-requiring 1α (IRE1α), protein kinase RNA-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), C/EBP homologous protein (CHOP), Caspase-12, and SIRT1. Proteins were measured by Western blot. ROS production was detected by flow cytometry.Compared to resting rats, both MPostE and IPostE significantly decreased brain infarct volumes and edema, neurological deficits, ROS production, and apoptotic cell death. MPostE further increased Bcl-2 expression and Bcl-2/BAX ratio as well as BAX and Caspase-3 expressions and ROS production (*p < 0.05). Both PostE groups saw decreases in ER stress proteins, while MPostE demonstrated a further reduction in GRP78 (***p < 0.001) and Caspase-12 (*p < 0.05) expressions at 1 day and IRE1α (**p < 0.01) and CHOP (*p < 0.05) expressions at 3 days. Additionally, both PostE groups saw significant increases in SIRT1 expression.In this study, both mild and intense PostE levels induced neuroprotection after stroke through SIRT1 and ROS/ER stress pathway. Additionally, the results may provide a base for our future study regarding the regulation of SIRT1 on the ROS/ER stress pathway in the biochemical processes underlying post-stroke neuroprotection. The results suggest that mild exercise postconditioning might play a similar neuroprotective role as intensive exercise and could be an effective exercise strategy as well.

Trans, trans-2,4-decadienal (tt-DDE), a composition of cooking oil fumes, induces oxidative stress and endoplasmic reticulum stress in human corneal epithelial cells

Indoor pollution with cooking oil fumes (COF) as one of the main components is closely related to ocular surface disorders. However, as the most abundant aldehyde in COF, the toxicity of trans, trans-2,4-decadienal (tt-DDE) on human cornea has not been explored before. In the present study, we observed a time- and dose-dependent cytotoxicity induced by tt-DDE in human corneal epithelial (HCE) cells, as evidenced by decreased cell viability, altered cell morphology, and increased proportion of apoptotic cells. Exposure to tt-DDE also led to an increase in reactive oxygen species (ROS) production, MMP loss, and a decrease in intracellular ATP levels. In addition, after exposure to tt-DDE, the expression of endoplasmic reticulum (ER) stress-related proteins (Bip, pIRE1, XBP1, pPERK, peIF2α, ATF4, and CHOP) increased, indicating that ER stress was activated. Moreover, pretreatment of HCE cells with two ER stress inhibitors (200 nM ISRIB or 1 mM 4-PBA) effectively attenuated oxidative stress induced by tt-DDE. These results suggested that tt-DDE could cause damage to HCE cells by triggering oxidative stress and ER stress. Furthermore, regulation of ER stress can be considered as a potential protective method for tt-DDE-induced ocular surface disorders.

CTCF inhibits endoplasmic reticulum stress and apoptosis in cardiomyocytes by upregulating RYR2 via inhibiting S100A1

AIMS

Pediatric heart failure is a common cardiovascular disease in clinical pediatrics. CCCTC-binding factor (CTCF), a novel transcriptional repressor, was reported to participate in the occurrence of various cardiovascular diseases. The present study focuses on exploring the effects of CTCF on tunicamycin (TM)-induced endoplasmic reticulum (ER) stress, and investigating the underlying mechanisms.

MATERIALS AND METHOD

Expression of CTCF in blood samples of heart failure children and TM-induced cardiomyocytes were evaluated by real-time quantitative PCR (RT-qPCR). Apoptotic rate of cardiomyocytes was detected by Annexin v assay. Western blotting and enzyme-linked immunosorbent assay (ELISA) were applied to examine the effect of CTCF on ER stress. Co-immunoprecipitation and western blotting were devoted to explore the mechanism by which CTCF contributes to ER stress.

KEY FINDINGS

We proved that CTCF was lowly expressed in blood samples of heart failure children and TM-induced cardiomyocytes, and overexpression of CTCF weaken the TM-induced ER stress. Using co-immunoprecipitation and protein blots, we demonstrated that CTCF upregulates RYR2 by inhibiting S100A1, thus mediating the PERK signaling pathway and regulating ER stress.

SIGNIFICANCE

Our data revealed that CTCF protects cardiomyocytes from ER stress through S100A1-RYR2 axis, and can be applied as a therapeutic target for the treatment of pediatric heart failure in future.

Iduna protects HT22 cells by inhibiting parthanatos: The role of the p53-MDM2 pathway

Traumatic brain injury (TBI) is common and often fatal in current times. The role of poly(adenosine diphosphate-ribose) polymerase (PARP)-induced cell death (parthanatos) in TBI has not been well studied. Our past study showed that oxidative stress-induced cell death includes parthanatos by confirming the occurrence of PARP activation and nuclear translocation of apoptosis-inducing factor (AIF). As oxidative stress plays a key role in pathological progression after TBI, we believe TBI may also be alleviated by the expression of Iduna, which is the only known endogenous regulator of parthanatos. Thus, a transection model in HT-22 cells was established for present study. Downregulation of Iduna aggravated the cell damage caused by mechanical cell injury, whereas upregulation of Iduna reduced mitochondrial dysfunction induced by mechanical cell injury but exerted no effect on apoptosis associated with mitochondrial dysfunction. By contrast, Iduna prevented parthanatos by reducing PARP activation and nuclear translocation of AIF. We also investigated 2 novel p53-MDM2 pathway inhibitors, AMG 232 and Nutlin-3, which substantially reduced the protective effects of Iduna. These findings indicate that Iduna might prevent TBI by specifically inhibiting parthanatos and promoting mitochondrial function, with the p53-MDM2 pathway playing a critical role.