Autophagy, Endoplasmic Reticulum Stress and the Unfolded Protein Response in Intracerebral Hemorrhage

The role of low-carbohydrate, high-fat diet in modulating autophagy and endoplasmic reticulum stress in aortic endothelial dysfunction of metabolic syndrome animal model

Background

Endothelial dysfunction (ED) is induced by insulin resistance, mediated by endoplasmic reticulum (ER) stress and disturbed autophagy. This study investigates the protective role of a low-carbohydrate, high-fat (LCHF) diet on ED, ER stress, and autophagy dysregulation in an experimental animal model of metabolic syndrome.

Methods

Forty male Sprague-Dawley rats were divided into four groups: a Control group (standard diet) and three Dexamethasone (DEX) treated groups. Group II continued the standard diet, Group III received an LCHF diet, and Group IV received a high-carbohydrate, low-fat (HCLF) diet. At the end of the experiment, aortic tissue samples were obtained and used for histological, immunohistochemical (Endothelin and PCNA, biochemical MDA, TCA, NO, 8-OH-dG, and Nrf2/ARE protein) and molecular (Endothelin, eNOS, Nrf-2 α, p62, LC3, BECN-1, PINK1, CHOP, BNIP3, PCNA) analysis.

Results

Oxidative stress, autophagy markers, and ED markers are increased in the metabolic syndrome group. LCHF diet mitigates the adverse effects of DEX on endothelial dysfunction and oxidative stress, as evidenced by reduced BMI, HOMA-IR, and improved histological and molecular parameters.

Conclusion

Oxidative stress, autophagy dysregulation, and ER stress play crucial roles in the pathogenesis of insulin resistance-induced endothelial dysfunction. An LCHF diet offers protective benefits against insulin resistance and related comorbidities, including endothelial dysfunction.

Pathological mechanisms and future therapeutic directions of thrombin in intracerebral hemorrhage: a systematic review

Intracerebral hemorrhage (ICH), a common subtype of hemorrhagic stroke, often causes severe disability or death. ICH induces adverse events that might lead to secondary brain injury (SBI), and there is currently a lack of specific effective treatment strategies. To provide a new direction for SBI treatment post-ICH, the systematic review discussed how thrombin impacts secondary injury after ICH through several potentially deleterious or protective mechanisms. We included 39 studies and evaluated them using SYRCLE's ROB tool. Subsequently, we explored the potential molecular mechanisms of thrombin-mediated effects on SBI post-ICH in terms of inflammation, iron deposition, autophagy, and angiogenesis. Furthermore, we described the effects of thrombin in endothelial cells, astrocytes, pericytes, microglia, and neurons, as well as the harmful and beneficial effects of high and low thrombin concentrations on ICH. Finally, we concluded the current research status of thrombin therapy for ICH, which will provide a basis for the future clinical application of thrombin in the treatment of ICH.

Interleukin-38 alleviates hepatic steatosis through AMPK/autophagy-mediated suppression of endoplasmic reticulum stress in obesity models

Interleukin-38 (IL-38), recently recognized as a cytokine with anti-inflammatory properties that mitigate type 2 diabetes, has been associated with indicators of insulin resistance and nonalcoholic fatty liver disease (NAFLD). This study investigated the impact of IL-38 on hepatic lipid metabolism and endoplasmic reticulum (ER) stress. We assessed protein expression levels using Western blot analysis, while monodansylcadaverine staining was employed to detect autophagosomes in hepatocytes. Oil red O staining was utilized to examine lipid deposition. The study revealed elevated serum IL-38 levels in high-fat diet (HFD)-fed mice and IL-38 secretion from mouse keratinocytes. IL-38 treatment attenuated lipogenic lipid accumulation and ER stress markers in hepatocytes exposed to palmitate. Furthermore, IL-38 treatment increased AMP-activated protein kinase (AMPK) phosphorylation and autophagy. The effects of IL-38 on lipogenic lipid deposition and ER stress were nullified in cultured hepatocytes by suppressing AMPK through small interfering (si) RNA or 3-methyladenine (3MA). In animal studies, IL-38 administration mitigated hepatic steatosis by suppressing the expression of lipogenic proteins and ER stress markers while reversing AMPK phosphorylation and autophagy markers in the livers of HFD-fed mice. Additionally, AMPK siRNA, but not 3MA, mitigated IL-38-enhanced fatty acid oxidation in hepatocytes. In summary, IL-38 alleviates hepatic steatosis through AMPK/autophagy signaling-dependent attenuation of ER stress and enhancement of fatty acid oxidation via the AMPK pathway, suggesting a therapeutic strategy for treating NAFLD.

The plant pathogenic bacterium Candidatus Liberibacter solanacearum induces calcium-regulated autophagy in midgut cells of its insect vector Bactericera trigonica

Autophagy plays an important role against pathogen infection in many organisms; however, little has been done with regard to vector-borne plant and animal pathogens, that sometimes replicate and cause deleterious effects in their vectors. Candidatus Liberibacter solanacearum (CLso) is a fastidious gram-negative phloem-restricted plant pathogen and vectored by the carrot psyllid, Bactericera trigonica. The plant disease caused by this bacterium is called carrot yellows and has recently gained much importance due to worldwide excessive economical losses. Here, we demonstrate that calcium ATPase, cytosolic calcium, and most importantly Beclin-1 have a role in regulating autophagy and its association with Liberibacter inside the psyllid. The presence of CLso generates reactive oxygen species and induces the expression of detoxification enzymes in the psyllid midguts, a main site for bacteria transmission. CLso also induces the expression of both sarco/endoplasmic reticulum Ca2+pump (SERCA) and 1,4,5-trisphosphate receptors (ITPR) in midguts, resulting in high levels of calcium in the cellular cytosol. Silencing these genes individually disrupted the calcium levels in the cytosol and resulted in direct effects on autophagy and subsequently on Liberibacter persistence and transmission. Inhibiting Beclin1-phosphorylation through different calcium-induced kinases altered the expression of autophagy and CLso titers and persistence. Based on our results obtained from the midgut, we suggest the existence of a direct correlation between cytosolic calcium levels, autophagy, and CLso persistence and transmission by the carrot psyllid. IMPORTANCE Plant diseases caused by vector-borne Liberibacter species are responsible for the most important economic losses in many agricultural sectors. Preventing these diseases relies mostly on chemical sprays against the insect vectors. Knowledge-based interference with the bacteria-vector interaction remains a promising approach as a sustainable solution. For unravelling how Liberibacter exploits molecular pathways in its insect vector for transmission, here, we show that the bacterium manipulates calcium levels on both sides of the endoplasmic reticulum membrane, resulting in manipulating autophagy. Silencing genes associated with these pathways disrupted the calcium levels in the cytosol and resulted in direct effects on autophagy and Liberibacter transmission. These results demonstrate major pathways that could be exploited for manipulating and controlling the disease transmission.

Protein persulfidation: Rewiring the hydrogen sulfide signaling in cell stress response

The past few decades have witnessed significant progress in the discovery of hydrogen sulfide (H₂S) as a ubiquitous gaseous signaling molecule in mammalian physiology, akin to nitric oxide and carbon monoxide. As the third gasotransmitter, H₂S is now known to exert a wide range of physiological and cytoprotective functions in the biological systems. However, endogenous H₂S concentrations are usually low, and its potential biologic mechanisms responsible have not yet been fully clarified. Recently, a growing body of evidence has demonstrated that protein persulfidation, a posttranslational modification of cysteine residues (RSH) to persulfides (RSSH) elicited by H₂S, is a fundamental mechanism of H₂S-mediated signaling pathways. Persulfidation, as a biological switch for protein function, plays an important role in the maintenance of cell homeostasis in response to various internal and external stress stimuli and is also implicated in numerous diseases, such as cardiovascular and neurodegenerative diseases and cancer. In this review, the biological significance of protein persulfidation by H₂S in cell stress response is reviewed providing a framework for understanding the multifaceted roles of H₂S. A mechanism-guided perspective can help open novel avenues for the exploitation of therapeutics based on H₂S-induced persulfidation in the context of diseases.

Autophagy and Apoptosis in Acute Brain Injuries: From Mechanism to Treatment

Significance: Autophagy and apoptosis are two important cellular mechanisms behind brain injuries, which are severe clinical situations with increasing incidences worldwide. To search for more and better treatments for brain injuries, it is essential to deepen the understanding of autophagy, apoptosis, and their interactions in brain injuries. This article first analyzes how autophagy and apoptosis participate in the pathogenetic processes of brain injuries respectively and mutually, then summarizes some promising treatments targeting autophagy and apoptosis to show the potential clinical applications in personalized medicine and precision medicine in the future. Recent Advances: Most current studies suggest that apoptosis is detrimental to brain recovery. Several studies indicate that autophagy can cause unnecessary death of neurons after brain injuries, while others show that autophagy is beneficial for acute brain injuries (ABIs) by facilitating the removal of damaged proteins and organelles. Whether autophagy is beneficial or detrimental in ABIs depends on many factors, and the results from different research groups are diverse or even controversial, making this topic more appealing to be explored further. Critical Issues: Neuronal autophagy and apoptosis are two primary pathological processes in ABIs. How they interact with each other and how their regulations affect the outcome and prognosis of brain injuries remain uncertain, making these answers more critical. Future Directions: Insights into the interplay between autophagy and apoptosis and the accurate regulations of their balance in ABIs may promote personalized and precise treatments in the field of brain injuries. Antioxid. Redox Signal. 38, 234-257.

Perspectives on benefit of early and prereperfusion hypothermia by pharmacological approach in stroke

Stroke kills or disables approximately 15 million people worldwide each year. It is the leading cause of brain injury, resulting in persistent neurological deficits and profound physical handicaps. In spite of over 100 clinical trials, stroke treatment modalities are limited in applicability and efficacy, and therefore, identification of new therapeutic modalities is required to combat this growing problem. Poststroke oxidative damage and lactic acidosis are widely-recognized forms of brain ischemia/reperfusion injury. However, treatments directed at these injury mechanisms have not been effective. In this review, we offer a novel approach combining these well-established damage mechanisms with new insights into brain glucose handling. Specifically, emerging evidence of brain gluconeogenesis provides a missing link for understanding oxidative injury and lactate toxicity after ischemia. Therefore, dysfunctional gluconeogenesis may substantially contribute to oxidative and lactate damage. We further review that hypothermia initiated early in ischemia and before reperfusion may ameliorate gluconeogenic dysfunction and subsequently provide an important mechanism of hypothermic protection. We will focus on the efficacy of pharmacologically assisted hypothermia and suggest a combination that minimizes side effects. Together, this study will advance our knowledge of basic mechanisms of ischemic damage and apply this knowledge to develop new therapeutic strategies that are desperately needed in the clinical treatment of stroke.

lncRNA H19 Aggravates Brain Injury in Rats following Experimental Intracerebral Hemorrhage via NF-κB Pathway

OBJECTIVE

To explore the effect of long noncoding RNA H19 (lncRNA H19) on brain injury in rats following experimental intracerebral hemorrhage (ICH).

METHODS

Rat ICH model was established with type IV collagenase. The neurological function scores were evaluated, and the water content in brain tissue was measured. The nerve injury indexes, inflammatory factors, and oxidative stress indexes were also measured. Moreover, the expression of lncRNA H19 was determined by qRT-PCR, and Western blot detected NF-κB pathway-related protein expression.

RESULTS

Compared with the sham group, the neurological function scores, the water content in brain tissue, and levels of injury indicators myelin basic protein (MBP), S-100B, and neuron-specific enolase (NSE) in the ICH rats were significantly increased. Meanwhile, the levels of TNF-α, IL-6, IL-1β, ROS, and MDA were significantly increased, but the levels of SOD were significantly decreased. In addition, the expression of lncRNA H19 in the brain tissue in the ICH group was significantly higher than that in the sham group. After further interference with lncRNA H19 expression (sh-H19 group), the levels of all the above indicators were reversed and the neurological damage was improved. Western blot results showed that the expression of NF-κBp65 and IKKβ was significantly higher, and IκBα expression was lower in the perivascular hematoma tissue in the ICH group compared with the sham group. Compared with the sh-NC group, NF-κBp65 and IKKβ expression were significantly lower and IκBα was significantly higher in the sh-H19 group.

CONCLUSION

lncRNA H19 exacerbated brain injury in rats with ICH by promoting neurological impairment, brain edema, and releasing inflammatory responses and oxidative stress. This may be related to the activation of NF-κB signaling pathway.

Scalp Acupuncture Attenuates Brain Damage After Intracerebral Hemorrhage Through Enhanced Mitophagy and Reduced Apoptosis in Rats

To study the effect of scalp acupuncture (SA) on the mitophagy signaling pathway in the caudate nucleus of Sprague-Dawley rats following intracerebral hemorrhage (ICH). An ICH model was established by injecting autologous arterial blood into the caudate nucleus in 200 male Sprague-Dawley rats, which were divided into five groups: sham, ICH, 3-methyladenine group (3-MA, 30 mg/kg), SA, and SA+3-MA. Animals were analyzed at 6 and 24 h as well as at 3 and 7 days. Composite neurological scale score was significantly higher in the SA group than in the ICH group. Transmission electron microscopy showed less structural damage and more autophagic vacuoles within brain in the SA group than in the ICH group. SA group showed higher levels of Beclin1, Parkin, PINK1, NIX protein, and a lower level of Caspase-9 in brain tissue. These animals consequently showed less neural cell apoptosis. Compared with the SA group, however, the neural function score and levels of mitophagy protein in the SA+3-MA group were decreased, neural cell apoptosis was increased with more severe structural damage, which suggested that 3-MA may antagonize the protective effect of SA on brain in rats with ICH. SA may mitigate the neurologic impairment after ICH by enhancing mitophagy and reducing apoptosis.

Regulation of the unfolded protein response transducer IRE1α by SERPINH1 aggravates periodontitis with diabetes mellitus via prolonged ER stress

The hyperglycemic microenvironment induced by diabetes mellitus aggravates the inflammatory response, in which the IRE1α signal transduction pathway of the unfolded protein response (UPR) participates. However, the mechanism by which hyperglycemia regulates the IRE1α signaling pathway and affects endoplasmic reticulum (ER) homeostasis in human gingival epithelium in periodontitis with diabetes mellitus remains unknown. Our current data provide evidence that diabetes mellitus causes a hyperinflammatory response in the gingival epithelium, which accelerates periodontal inflammation. Next, we assessed UPR-IRE1α signaling in periodontitis with diabetes mellitus by examining human clinical gingival epithelium samples from healthy subjects, subjects with periodontitis and subjects with periodontitis with diabetes mellitus and by in vitro challenge of human epithelial cells with a hyperglycemic microenvironment. The results showed that a hyperglycemic microenvironment inhibited the IRE1α/XBP1 axis, decreased the expression of a UPR target gene (GRP78), and ultimately impaired the UPR, causing ER stress to be prolonged or more severe in human gingival epithelium. Subsequently, RNA sequencing (RNA-seq) data was analyzed to investigate the expression of ER-related genes in human gingival epithelium. Experiments verified that the mechanism by which periodontitis is aggravated in individuals with diabetes mellitus may involve decreased SERPINH1 expression. Furthermore, experiments in SERPINH1-knockdown and SERPINH1-overexpression models established in vitro indicated that SERPINH1 might act as an activator of IRE1α, maintaining human gingival epithelium homeostasis and reducing proinflammatory cytokine expression by preventing prolonged ER stress induced by high-glucose conditions. In conclusion, regulation of the UPR transducer IRE1α by SERPINH1 alleviates periodontitis with diabetes mellitus by mitigating prolonged ER stress. This finding provides evidence for the further study of periodontitis with diabetes mellitus.

Chronobiological activity of cysteinyl leukotriene receptor 1 during basal and induced autophagy in the ARPE-19 retinal pigment epithelial cell line

Autophagy is an important cellular mechanism for maintaining cellular homeostasis, and its impairment correlates highly with age and age-related diseases. Retinal pigment epithelial (RPE) cells of the eye represent a crucial model for studying autophagy, as RPE functions and integrity are highly dependent on an efficient autophagic process. Cysteinyl leukotriene receptor 1 (CysLTR1) acts in immunoregulation and cellular stress responses and is a potential regulator of basal and adaptive autophagy. As basal autophagy is a dynamic process, the aim of this study was to define the role of CysLTR1 in autophagy regulation in a chronobiologic context using the ARPE-19 human RPE cell line.

Effects of CysLTR1 inhibition on basal autophagic activity were analyzed at inactive/low and high lysosomal degradation activity with the antagonists zafirlukast (ZTK) and montelukast (MTK) at a dosage of 100 nM for 3 hours. Abundances of the autophagy markers LC3-II and SQSTM1 and LC3B particles were analyzed in the absence and presence of lysosomal inhibitors using western blot analysis and immunofluorescence microscopy.

CysLTR1 antagonization revealed a biphasic effect of CysLTR1 on autophagosome formation and lysosomal degradation that depended on the autophagic activity of cells at treatment initiation. ZTK and MTK affected lysosomal degradation, but only ZTK regulated autophagosome formation. In addition, dexamethasone treatment and serum shock induced autophagy, which was repressed by CysLTR1 antagonization. As a newly identified autophagy modulator, CysLTR1 appears to be a key player in the chronobiological regulation of basal autophagy and adaptive autophagy in RPE cells.

Acupuncture inhibits mammalian target of rapamycin, promotes autophagy and attenuates neurological deficits in a rat model of hemorrhagic stroke

BACKGROUND

Intracerebral hemorrhage (ICH) accounts for approximately 15% of all stroke cases. Previous studies suggested that acupuncture may improve ICH-induced neurological deficits. Therefore, we investigated the effects of acupuncture on neurological deficits in an animal model of ICH.

METHODS

Adult male Sprague-Dawley rats were injected with autologous blood (50 μL) into the right caudate nucleus. Additional rats underwent sham surgery as controls. ICH rats either received acupuncture (GV20 through GB7 on the side of the lesion) or sham acupuncture (1 cm to the right side of the traditional acupuncture point locations). Some ICH rats received acupuncture plus rapamycin injection into the right lateral ventricle. Neurological deficits in the various groups were assessed based on composite neurological score. The perihemorrhagic penumbra was analyzed by histopathology following hematoxylin-eosin staining. Levels of autophagy-related proteins light chain (LC)3 and p62 as well as of mammalian target of rapamycin (mTOR)-related proteins, and phosphorylated (p)-mTOR and p-S6K1 (ribosomal protein S6 kinase beta-1), were assessed by Western blotting.

RESULTS

Acupuncture significantly improved composite neurological scores 7 days after ICH (17.7 ± 1.49 vs 14.8 ± 1.32, p < 0.01). Acupuncture augmented autophagosome and autolysosome accumulation based on transmission electron microscopy. Acupuncture significantly increased expression of LC3 (p < 0.01) but decreased expression of p62 (p < 0.01). Acupuncture also reduced levels of p-mTOR and p-S6K1 (both p < 0.01).

CONCLUSION

Acupuncture improved neurological deficits in a rat model of ICH, possibly by inhibiting the mTOR pathway and activating autophagy.

Electroacupuncture at GV20‑GB7 regulates mitophagy to protect against neurological deficits following intracerebral hemorrhage via inhibition of apoptosis

The acupuncture penetrating line of Baihui (GV20) to Qubin (GB7) spans the parietal, frontal and temporal lobes. The present study aimed to elucidate the mechanism by which electroacupuncture (EA) at GV20‑GB7 regulates mitophagy in intracerebral hemorrhage (ICH) and whether it serves a neuroprotective role. A whole blood‑induced ICH model was used. Mitophagy‑regulating proteins, including BCL/adenovirus E1B 19 kDa‑interacting protein 3 (BNIP3), PTEN‑induced putative kinase 1 (PINK1), Parkin and apoptosis‑associated proteins were detected by western blotting; autophagy following ICH was evaluated by immunofluorescent techniques; morphological characteristics of mitophagy were observed using transmission electron microscopy; and TUNEL assay was performed to determine the number of apoptotic cells. Immunohistochemistry was used to detect p53 expression. The protective role of EA (GV20‑GB7) via enhanced mitophagy and suppressed apoptosis in ICH was further confirmed by decreased modified neurological severity score. The results showed that EA (GV20‑GB7) treatment upregulated mitochondrial autophagy following ICH and inhibited apoptotic cell death. The mechanism underlying EA (GV20‑GB7) treatment may involve inhibition of p53, an overlapping protein of autophagy and apoptosis. EA (GV20‑GB7) treatment decreased neurobehavioral deficits following ICH but pretreatment with 3‑methyladenine counteracted the beneficial effects of EA (GV20‑GB7) treatment. In conclusion, EA (GV20‑GB7) improved recovery from ICH by regulating the balance between mitophagy and apoptosis.

Moderate Ethanol Pre-treatment Mitigates ICH-Induced Injury via ER Stress Modulation in Rats

Intracerebral hemorrhage (ICH) is a life-threatening type of stroke that disrupts the normal neurological function of the brain. Clinical studies have reported a non-linear J-shaped association between alcohol consumption levels and the occurrence of cerebral stroke. Specifically, alcohol intoxication increases stroke incidence, while moderate alcohol pre-conditioning decreases stroke frequency and improves outcomes. Although alcohol pre-consumption is likely a crucial player in ICH, the underlying mechanism remains unclear. We performed 1-h alcohol pre-conditioning followed by ICH induction in Sprague-Dawley (SD) rats to investigate the role of alcohol pre-conditioning in ICH. Interestingly, behavioral test analysis found that ethanol intoxication (3 g/kg) aggravated ICH-induced neurological deficits, but moderate ethanol pre-conditioning (0.75 g/kg) ameliorated ICH-induced neurological deficits by reducing the oxidative stress and proinflammatory cytokines release. Moreover, we found that moderate ethanol pretreatment improved the striatal endoplasmic reticulum (ER) homeostasis by increasing the chaperone protein expression and reducing oxidative stress and apoptosis caused by ICH. Our findings show that the mechanism regulated by moderate ethanol pre-conditioning might be beneficial for ICH, indicating the importance of ER homeostasis, oxidative stress, and differential cytokines release in ICH.

Mechanisms of Oxidative Stress and Therapeutic Targets following Intracerebral Hemorrhage

Oxidative stress (OS) is induced by the accumulation of reactive oxygen species (ROS) following intracerebral hemorrhage (ICH) and plays an important role in secondary brain injury caused by the inflammatory response, apoptosis, autophagy, and blood-brain barrier (BBB) disruption. This review summarizes the current state of knowledge regarding the pathogenic mechanisms of brain injury after ICH, markers for detecting OS, and therapeutic strategies that target OS to mitigate brain injury.

The Blood Component Iron Causes Neuronal Apoptosis Following Intracerebral Hemorrhage via the PERK Pathway

PERK signaling pathway plays an important role in neuronal apoptosis after Intracerebral hemorrhage (ICH). ICH can cause the release of blood components into the brain. However, which component in the blood plays a major role still unclear. This study was designed to investigate the activation of the PERK pathway in different blood components after ICH and explore which components have major relationships with neuronal apoptosis. Eighty-five Sprague-Dawley rats were used to establish an ICH model. Western blot (WB) and immunofluorescence (IF) were used to evaluate the expression of the PERK pathway. TUNEL staining, FJC staining and neurological score were used to evaluate neuronal apoptosis and necrosis after ICH. The results showed that protein levels of p-PERK and p-eIF2α were upregulated following ICH with the injection of Fe³⁺ and Fe²⁺ after 48 h. Then, deferoxamine (DFX) was used to study the roles of Fe³⁺ in ICH through the PERK signaling pathway. The results showed that injection of DFX reversed increasing protein levels and prevented neuronal apoptosis. Thus, iron plays an important role in ICH through the PERK signaling pathway. Furthermore, the reduction of iron demonstrates neuroprotective effects in ICH. This suggests that targeting intervention of the iron and PERK pathway could be an effective treatment strategy to improve ICH prognosis.

Salubrinal Regulates the Apoptosis of Adrenocortical Carcinoma Cells via the PERK/eIF2α/ATF4 Signaling Pathway

The protein-kinase-R- (PKR-) like endoplasmic reticulum kinase (PERK) signaling pathway is a well-known promoter of cell apoptosis. In this study, we aimed to determine whether salubrinal (Sal), a selective activator of eukaryotic translation initiation factor 2 (eIF2α), can induce apoptosis of human adrenocortical carcinoma (ACC) cell via activating the PERK/eIF2α/ATF4 signaling pathway, and the potential mechanisms of this action were explored. The ACC cell lines, including SW-13 and NCI-H295 R, were used. 3-(4,5)-Dimethylthiazol(-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay, cell scratch experiments, flow cytometry, and JC-1 staining assays were performed to detect the cell viability, cell migration, and cell apoptosis. The expression of PERK/eIF2α/ATF4 signaling-pathway-related proteins and apoptosis-related proteins was detected by western blot (WB). Intracellular Ca²⁺ ion concentration was determined by a confocal laser scanning microscope. The results showed that Sal inhibited the migration and proliferation of ACC cells. Sal remarkably increased the influx of Ca²⁺ ion and the apoptosis rate of ACC cells in vitro. Furthermore, the expression levels of PERK/eIF2α/ATF4 signaling-related proteins and apoptosis-related proteins were upregulated in the treatment of Sal. The research demonstrated that Sal reduces the cell viability, increases the intracellular calcium concentration, and promotes the apoptosis of ACC cells in vitro through increasing the phosphorylation level of eIF2α and activating the PERK/eIF2α/ATF4 signaling. PERK/eIF2α/ATF4 is expected to act as a potential therapeutic target for the treatment of adrenocortical carcinoma.

Molecular Correlates of Hemorrhage and Edema Volumes Following Human Intracerebral Hemorrhage Implicate Inflammation, Autophagy, mRNA Splicing, and T Cell Receptor Signaling

Intracerebral hemorrhage (ICH) and perihematomal edema (PHE) volumes are major determinants of ICH outcomes as is the immune system which plays a significant role in damage and repair. Thus, we performed whole-transcriptome analyses of 18 ICH patients to delineate peripheral blood genes and networks associated with ICH volume, absolute perihematomal edema (aPHE) volume, and relative PHE (aPHE/ICH; rPHE). We found 440, 266, and 391 genes correlated with ICH and aPHE volumes and rPHE, respectively (p < 0.005, partial-correlation > |0.6|). These mainly represented inflammatory pathways including NF-κB, TREM1, and Neuroinflammation Signaling-most activated with larger volumes. Weighted Gene Co-Expression Network Analysis identified seven modules significantly correlated with these measures (p < 0.05). Most modules were enriched in neutrophil, monocyte, erythroblast, and/or T cell-specific genes. Autophagy, apoptosis, HIF-1α, inflammatory and neuroinflammatory response (including Toll-like receptors), cell adhesion (including MMP9), platelet activation, T cell receptor signaling, and mRNA splicing were represented in these modules (FDR p < 0.05). Module hub genes, potential master regulators, were enriched in neutrophil-specific genes in three modules. Hub genes included NCF2, NCF4, STX3, and CSF3R, and involved immune response, autophagy, and neutrophil chemotaxis. One module that correlated negatively with ICH volume correlated positively with rPHE. Its genes and hubs were enriched in T cell-specific genes including hubs LCK and ITK, Src family tyrosine kinases whose modulation improved outcomes and reduced BBB dysfunction following experimental ICH. This study uncovers molecular underpinnings associated with ICH and PHE volumes and pathophysiology in human ICH, where knowledge is scarce. The identified pathways and hub genes may represent novel therapeutic targets.

TRPM2 channel-mediated cell death: An important mechanism linking oxidative stress-inducing pathological factors to associated pathological conditions

Oxidative stress resulting from the accumulation of high levels of reactive oxygen species is a salient feature of, and a well-recognised pathological factor for, diverse pathologies. One common mechanism for oxidative stress damage is via the disruption of intracellular ion homeostasis to induce cell death. TRPM2 is a non-selective Ca2+-permeable cation channel with a wide distribution throughout the body and is highly sensitive to activation by oxidative stress. Recent studies have collected abundant evidence to show its important role in mediating cell death induced by miscellaneous oxidative stress-inducing pathological factors, both endogenous and exogenous, including ischemia/reperfusion and the neurotoxicants amyloid-β peptides and MPTP/MPP+ that cause neuronal demise in the brain, myocardial ischemia/reperfusion, proinflammatory mediators that disrupt endothelial function, diabetogenic agent streptozotocin and diabetes risk factor free fatty acids that induce loss of pancreatic β-cells, bile acids that damage pancreatic acinar cells, renal ischemia/reperfusion and albuminuria that are detrimental to kidney cells, acetaminophen that triggers hepatocyte death, and nanoparticles that injure pericytes. Studies have also shed light on the signalling mechanisms by which these pathological factors activate the TRPM2 channel to alter intracellular ion homeostasis leading to aberrant initiation of various cell death pathways. TRPM2-mediated cell death thus emerges as an important mechanism in the pathogenesis of conditions including ischemic stroke, neurodegenerative diseases, cardiovascular diseases, diabetes, pancreatitis, chronic kidney disease, liver damage and neurovascular injury. These findings raise the exciting perspective of targeting the TRPM2 channel as a novel therapeutic strategy to treat such oxidative stress-associated diseases.

Inhibiting ER Stress Weakens Neuronal Pyroptosis in a Mouse Acute Hemorrhagic Stroke Model

Intracerebral hemorrhage (ICH) is a form of stroke, characterized by high morbidity and mortality and currently lacks specific therapy. ICH leads to endoplasmic reticulum (ER) stress, which can induce neurological impairment through crosstalk with programmed cell death (PCD). Pyroptosis, a newly discovered form of PCD, has received attention because of its close relationship with some certain diseases, such as traumatic brain injury and ischemic and hemorrhagic stroke. However, the relationship between ER stress and pyroptosis in ICH remains unclear. In this study, we investigated the role of ER stress in evoking neuronal pyroptosis and related mechanisms in a mouse ICH model. We used tauroursodeoxycholic acid (TUDCA) to inhibit ER stress and observed that TUDCA reduces neuronal pyroptosis and has a neuroprotective role. We explored the potential mechanisms underlying the regulation of neuronal pyroptosis by ER stress through testing the expression of interleukin-13 (IL-13). We found that ER stress inhibition alleviates neuronal pyroptosis through decreasing the expression of IL-13 after ICH. In summary, this study revealed that IL-13 is involved in ER stress-induced neuronal pyroptosis after ICH, pointing to IL-13 as a novel therapeutic target for ICH treatment.

Heme Induces BECN1/ATG5-Mediated Autophagic Cell Death via ER Stress in Neurons

Intracerebral hemorrhage (ICH) is a serious medical problem, and effective treatment is limited. Hemorrhaged blood is highly toxic to the brain, and heme, which is mainly released from hemoglobin, plays a vital role in neurotoxicity. However, the specific mechanism involved in heme-mediated neurotoxicity has not been well studied. In this study, we investigated the neurotoxicity of heme in neurons. Neurons were treated with heme, and cell death, autophagy, and endoplasmic reticulum (ER) stress were analyzed. In addition, the relationship between autophagy and apoptosis in heme-induced cell death and the downstream effects were also assessed. We showed that heme induced cell death and autophagy in neurons. The suppression of autophagy using either pharmacological inhibitors (3-methyladenine) or RNA interference of essential autophagy genes (BECN1 and ATG5) decreased heme-induced cell death in neurons. Moreover, the ER stress activator thapsigargin increased cell autophagy and the cell death ratio following heme treatment. Autophagy promoted heme-induced cell apoptosis and cell death through the BECN1/ATG5 pathway. Our findings suggest that heme potentiates neuronal autophagy via ER stress, which in turn induces cell death via the BECN1/ATG5 pathway. Targeting ER stress-mediated autophagy might be a promising therapeutic strategy for ICH.

CircRNA_0001449 disturbs phosphatidylinositol homeostasis and AKT activity by enhancing Osbpl5 translation in transient cerebral ischemia

Phosphatidylinositol-3,4,5-trisphosphate [PI(3,4,5)P3] is a phosphorylated derivative of phosphatidylinositol 4-phosphate [PI(4)P] and phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], which recruit and activate AKT in the plasma membrane (PM) to promote cellular survival. ORP5 anchors at the endoplasmic reticulum (ER)-PM contact sites and acts as a PI(4)P and PI(4,5)P2/phosphatidylserine (PS) exchanger. Here, a lipidomics analysis of the sensorimotor cortex revealed that transient middle cerebral artery occlusion (tMCAO) disturbs the homeostasis of phosphatidylinositols (PIs) and PS between the PM and ER. Conditional knockout mice showed that ORP5 contributes to this abnormal distribution. Abolishing the ORP5 gene significantly inhibited apoptosis and autophagy. RNA sequencing and RNA pull down analyses confirmed a competing endogenous RNA pathway in which circ_0001449 sponges miR-124-3p and miR-32-5p to promote Osbpl5 translation. Our data showed that circRNA_0001449 regulates membrane homeostasis via ORP5 and is involved in the AKT survival pathway.

Chronic restraint stress exacerbates neurological deficits and disrupts the remodeling of the neurovascular unit in a mouse intracerebral hemorrhage model

Growing evidences have shown that patients recovering from stroke experience high and unremitting stress. Chronic restraint stress (CRS) has been found to exacerbate neurological impairments in an experimental focal cortical ischemia model. However, there have been no studies reporting the effect and mechanism of CRS on intracerebral hemorrhage (ICH). This study aimed to evaluate the effect of CRS on a mouse ICH model. Adult male C57BL mice were subjected to infusion of collagenase IV (to induce ICH) or saline (for sham) into the left striatum. After ICH, animals were stressed with application of CRS protocol for 21 days. Our results showed that CRS significantly exacerbated neurological deficits (Garcia test, corner turn test, and wire grip test) and the ipsilateral brain atrophy and reduced body weight gain after ICH. Immunofluorescence staining indicated that CRS exerted significant suppressive effects on neuron, astrocyte, vascular endothelial cell and pericyte and excessively activated microglia post ICH. All of the key cellular components mentioned above are involved in the neurovascular unit (NVU) remodeling in the peri-hemorrhagic region after ICH. Western blot results showed that matrix metalloproteinase (MMP)-9 and tight junction (TJ) proteins including zonula occludens-1, occludin and claudin-5 were increased after ICH, but MMP-9 protein was further up-regulated and TJ-related proteins were down-regulated by CRS. In addition, ICH-induced activation of endoplasmic reticulum stress and apoptosis were further strengthened by CRS. Collectively, CRS exacerbates neurological deficits and disrupts the remodeling of the peri-hemorrhagic NVU after ICH, which may be associated with TJ proteins degradation and excessive activation of MMP-9 and endoplasmic reticulum stress-apoptosis.LAY SUMMARYCRS exacerbates neurological deficits and disrupts the remodeling of the NVU in the recovery stage after ICH, which suggest that monitoring chronic stress levels in patients recovering from ICH may merit consideration in the future.

A Role for Endoplasmic Reticulum Stress in Intracerebral Hemorrhage

The endoplasmic reticulum (ER) is an intracellular organelle that performs multiple functions, such as lipid biosynthesis, protein folding, and maintaining intracellular calcium homeostasis. Thus, conditions wherein the ER is unable to fold proteins is defined as ER stress, and an inbuilt quality control mechanism, called the unfolded protein response (UPR), is activated during ER stress, which serves as a recovery system that inhibits protein synthesis. Further, based on the severity of ER stress, the response could involve both proapoptotic and antiapoptotic phases. Intracerebral hemorrhage (ICH) is the second most common subtype of cerebral stroke and many lines of evidence have suggested a role for the ER in major neurological disorders. The injury mechanism during ICH includes hematoma formation, which in turn leads to inflammation, elevated intracranial pressure, and edema. A proper understanding of the injury mechanism(s) is required to effectively treat ICH and closing the gap between our current understanding of ER stress mechanisms and ICH injury can lead to valuable advances in the clinical management of ICH.

Neuroprotection by trans-resveratrol against collagenase-induced neurological and neurobehavioural deficits in rats involves adenosine A1 receptors

Objective: Trans-resveratrol has been shown to have neuroprotective effects and could be a promising therapeutic agent in the treatment of intracerebral haemorrhage (ICH). This study aimed to investigate the involvement of the adenosine A1 receptor (A1R) in trans-resveratrol-induced neuroprotection in rats with collagenase-induced ICH.Methods: Sixty male Sprague-Dawley rats weighing 330-380 g were randomly divided into five groups (n = 12): (i) control, (ii) sham-operated rats, (iii) ICH rats pretreated with vehicle (0.1% DMSO saline, i.c.v.), (iv) ICH rats pretreated with trans-resveratrol (0.9 µg, i.c.v.) and (v) ICH rats pretreated with trans-resveratrol (0.9 µg) and the A1R antagonist, DPCPX (2.5 µg, i.c.v.). Thirty minutes after pretreatment, ICH was induced by intrastriatal injection of collagenase (0.04 U). Forty-eight hours after ICH, the rats were assessed using a variety of neurobehavioural tests. Subsequently, rats were sacrificed and brains were subjected to gross morphological examination of the haematoma area and histological examination of the damaged area.Results: Severe neurobehavioural deficits and haematoma with diffuse oedema were observed after intrastriatal collagenase injection. Pretreatment with trans-resveratrol partially restored general locomotor activity, muscle strength and coordination, which was accompanied with reduction of haematoma volume by 73.22% (P < 0.05) and damaged area by 60.77% (P < 0.05) in comparison to the vehicle-pretreated ICH group. The trans-resveratrol-induced improvement in neurobehavioural outcomes and morphological features of brain tissues was inhibited by DPCPX pretreatment.Conclusion: This study demonstrates that the A1R activation is possibly the mechanism underlying the trans-resveratrol-induced neurological and neurobehavioural protection in rats with ICH.

The PERK Pathway Plays a Neuroprotective Role During the Early Phase of Secondary Brain Injury Induced by Experimental Intracerebral Hemorrhage

The protein kinase RNA-like endoplasmic reticulum kinase (PERK) pathway, which is a branch of the unfolded protein response, participates in a range of pathophysiological processes of neurological diseases. However, few studies have investigated the role of the PERK in intracerebral hemorrhage (ICH). The present study evaluated the role of the PERK pathway during the early phase of ICH-induced secondary brain injury (SBI) and its potential mechanisms. An autologous whole blood ICH model was established in rats, and cultured primary cortical neurons were treated with oxyhemoglobin to mimic ICH in vitro. We found that levels of phosphorylated alpha subunit of eukaryotic translation initiation factor 2 (p-eIF2α) and activating transcription factor 4 (ATF4) increased significantly and peaked at 12 h during the early phase of the ICH. To further elucidate the role of the PERK pathway, we assessed the effects of the PERK inhibitor, GSK2606414, and the eIF2α dephosphorylation antagonist, salubrinal, at 12 h after ICH both in vivo and in vitro. Inhibition of PERK with GSK2606414 suppressed the protein levels of p-eIF2α and ATF4, resulting in increase of transcriptional activator CCAAT/enhancer-binding protein homologous protein (CHOP) and caspase-12, which promoted apoptosis and reduced neuronal survival. Treatment with salubrinal yielded opposite results, which suggested that activation of the PERK pathway could promote neuronal survival and reduce apoptosis. In conclusion, the present study has demonstrated the neuroprotective effects of the PERK pathway during the early phase of ICH-induced SBI. These findings highlight the potential value of PERK pathway as a therapeutic target for ICH.

Over-Activated Proteasome Mediates Neuroinflammation on Acute Intracerebral Hemorrhage in Rats

Background: Neuroinflammation is a hallmark in intracerebral hemorrhage (ICH) that induces secondary brain injury, leading to neuronal cell death. ER stress-triggered apoptosis and proteostasis disruption caused neuroinflammation to play an important role in various neurological disorders. The consequences of ER stress and proteostasis disruption have rarely been studied during the course of ICH development. Methods: ICH was induced by collagenase VII-S intrastriatal infusion. Animals were sacrificed at 0, 3, 6, 24, and 72 h post-ICH. Rats were determined for body weight changes, hematoma volume, and neurological deficits. Brain tissues were harvested for molecular signaling analysis either for ELISA, immunoblotting, immunoprecipitation, RT-qPCR, protein aggregation, or for histological examination. A non-selective proteasome inhibitor, MG132, was administered into the right striatum three hours prior to ICH induction. Results: ICH-induced acute proteasome over-activation caused the early degradation of the endoplasmic reticulum (ER) chaperone GRP78 and IκB protein. These exacerbations were accompanied by the elevation of pro-apoptotic CCAAT-enhancer-binding protein homologous protein (CHOP) and pro-inflammatory cytokines expression via nuclear factor-kappa B (NF-κB) signal activation. Pre-treatment with proteasome inhibitor MG132 significantly ameliorated the ICH-induced ER stress/proteostasis disruption, pro-inflammatory cytokines, neuronal cells apoptosis, and neurological deficits. Conclusions: ICH induced rapid proteasome over-activation, leading to an exaggeration of the ER stress/proteostasis disruption, and neuroinflammation might be a critical event in acute ICH pathology.

Tension induces intervertebral disc degeneration via endoplasmic reticulum stress-mediated autophagy

Background: Intervertebral disc degeneration is a common degenerative disease. The present study aimed to explore the role and mechanism of tension-induced endoplasmic reticulum stress in intervertebral disc degeneration.

Methods: Intervertebral disc degeneration models of SD rat were analyzed for apoptosis, the expression of Poly(ADP-ribose) polymerase (PARP), Caspase-12, Caspase-3, LC3, Beclin-1 and CHOP using immunohistochemistry, qPCR and Western blot analysis. Annulus fibrosus cells of intervertebral disc were isolated, subjected to cyclic deformation stress and analyzed for ROS and apoptosis, lysosome activity and expression of genes. The cells were knockdown with siRNA or treated with endoplasmic reticulum stress inhibitor 4-PBA and assayed for ROS, apoptosis, lysosome activity and gene expression.

Results: Compared with the controls, intervertebral disc degeneration was observed through X-rays examinations and HS staining. Apoptosis and expression of PARP, Caspase-12, Caspase-3, LC3, Beclin-1 and CHOP were significantly increased in the intervertebral disc tissue of the models. In mechanic mimic experiments, the primary annulus fibrosus cells were subjected to 18% cyclic deformation, ROS and apoptosis as well as the activity of lysosome were increased. Similarly, the expression of PARP, Caspase-12, Caspase-3, LC3, Beclin-1 and CHOP was also increased significantly after deformation treatment. On other hand, when the cells were treated with 9 mM 4-PBA and/or CHOP-siRNA4, the apoptosis rate, ROS level, lysosome activity and expression of PARP, Caspase-12, Caspase-3, LC3, Beclin-1 and CHOP were significantly reduced.

Conclusions: Autophagy reaction mediated by endoplasmic reticulum stress plays important rale in tension-induced intervertebral disc degeneration. Intervertebral disc degeneration likely results from interactions between autophagy, apoptosis and reticulum stress, and is ROS-dependent.

A Rhenium Isonitrile Complex Induces Unfolded Protein Response-Mediated Apoptosis in Cancer Cells

Complexes of the element Re have recently been shown to possess promising anticancer activity through mechanisms of action that are distinct from the conventional metal-based drug cisplatin. In this study, we report our investigations on the anticancer activity of the complex [Re(CO)₃ (dmphen)(p-tol-ICN)]⁺ (TRIP) in which dmphen=2,9-dimethyl-1,10-phenanthroline and p-tol-ICN=para-tolyl isonitrile. TRIP was synthesized by literature methods and exhaustively characterized. This compound exhibited potent in vitro anticancer activity in a wide variety of cell lines. Flow cytometry and immunostaining experiments indicated that TRIP induces intrinsic apoptosis. Comprehensive biological mechanistic studies demonstrated that this compound triggers the accumulation of misfolded proteins, which causes endoplasmic reticulum (ER) stress, the unfolded protein response, and apoptotic cell death. Furthermore, TRIP induced hyperphosphorylation of eIF2α, translation inhibition, mitochondrial fission, and expression of proapoptotic ATF4 and CHOP. These results establish TRIP as a promising anticancer agent based on its potent cytotoxic activity and ability to induce ER stress.

Cordycepin-induced unfolded protein response-dependent cell death, and AKT/MAPK-mediated drug resistance in mouse testicular tumor cells

Testicular cancer is the most commonly diagnosed cancer in men at 15-44 years of age, and radical orchidectomy combined with chemotherapy is currently considered as the standard treatment. However, drugs resistance and side effects that impact the quality of life for patients with testicular cancer have not been markedly improved in recent decades. In this study, we characterized the pharmacological exacerbation of the unfolded protein response (UPR), which is an effective approach to kill testicular cancer cells, by carrying out a clustering analysis of mRNA expression profiles and the immunobloting examination of cordycepin-treated MA-10 cells. The UPR is executed in response to endoplasmic reticulum stress to complement by an apoptotic response if the defect cannot be resolved. Results showed that cordycepin significantly modulated FoxO/P15/P27, PERK-eIF2α (apoptotic), and the IRE1-XBP1 (adaptive) UPR pathways. Interestingly, a fraction of MA-10 cells survived after cordycepin treatment, the AKT, LC3 I/II, and MAPK signaling pathways were highly induced in attached cells as compared to the suspended cells, illustrating the drug resistance to cordycepin via activating AKT and MAPK pathways in MA-10 cells. In summary, PERK-eIF2α signaling pathway is required for pro-apoptotic UPR in MA-10 cell death following cordycepin treatment, suggesting a potential therapeutic application in treating testicular cancer. However, activation of AKT and MAPK pathways could possibly result in drug resistance to cordycepin in MA-10 cells.

Inflammatory, regulatory, and autophagy co-expression modules and hub genes underlie the peripheral immune response to human intracerebral hemorrhage

BACKGROUND

Intracerebral hemorrhage (ICH) has a high morbidity and mortality. The peripheral immune system and cross-talk between peripheral blood and brain have been implicated in the ICH immune response. Thus, we delineated the gene networks associated with human ICH in the peripheral blood transcriptome. We also compared the differentially expressed genes in blood following ICH to a prior human study of perihematomal brain tissue.

METHODS

We performed peripheral blood whole-transcriptome analysis of ICH and matched vascular risk factor control subjects (n = 66). Gene co-expression network analysis identified groups of co-expressed genes (modules) associated with ICH and their most interconnected genes (hubs). Mixed-effects regression identified differentially expressed genes in ICH compared to controls.

RESULTS

Of seven ICH-associated modules, six were enriched with cell-specific genes: one neutrophil module, one neutrophil plus monocyte module, one T cell module, one Natural Killer cell module, and two erythroblast modules. The neutrophil/monocyte modules were enriched in inflammatory/immune pathways; the T cell module in T cell receptor signaling genes; and the Natural Killer cell module in genes regulating alternative splicing, epigenetic, and post-translational modifications. One erythroblast module was enriched in autophagy pathways implicated in experimental ICH, and NRF2 signaling implicated in hematoma clearance. Many hub genes or module members, such as IARS, mTOR, S1PR1, LCK, FYN, SKAP1, ITK, AMBRA1, NLRC4, IL6R, IL17RA, GAB2, MXD1, PIK3CD, NUMB, MAPK14, DDX24, EVL, TDP1, ATG3, WDFY3, GSK3B, STAT3, STX3, CSF3R, PIP4K2A, ANXA3, DGAT2, LRP10, FLOT2, ANK1, CR1, SLC4A1, and DYSF, have been implicated in neuroinflammation, cell death, transcriptional regulation, and some as experimental ICH therapeutic targets. Gene-level analysis revealed 1225 genes (FDR p < 0.05, fold-change > |1.2|) have altered expression in ICH in peripheral blood. There was significant overlap of the 1225 genes with dysregulated genes in human perihematomal brain tissue (p = 7 × 10-3). Overlapping genes were enriched for neutrophil-specific genes (p = 6.4 × 10-08) involved in interleukin, neuroinflammation, apoptosis, and PPAR signaling.

CONCLUSIONS

This study delineates key processes underlying ICH pathophysiology, complements experimental ICH findings, and the hub genes significantly expand the list of novel ICH therapeutic targets. The overlap between blood and brain gene responses underscores the importance of examining blood-brain interactions in human ICH.

miR-181b regulates ER stress induced neuron death through targeting Heat Shock Protein A5 following intracerebral haemorrhage

Endoplasmic reticulum (ER) stress acts as a protein folding and contributes to neuronal damage and neurological deterioration following intracerebral hemorrhage (ICH). Heat Shock Protein A5 (HSPA5) serves as an essential regulator of the endoplasmic reticulum (ER) stress response. However, the specific mechanism has not been will identified. Primary cortical neurons from C57BL/6 mice were subjected to erythrocyte lysates. Cell viability, microRNA and HSPA5 levels, and ER stress was detected. The interaction between microRNA and the target HSPA5 was identified by dual luciferase reporter gene assay. In addition, inflammatory cytokines, brain edema, and neurological functions in ICH mice were also assessed. Erythrocyte lysates induced ER stress and neuron damage, downregulated miR-181b and upregulated HSPA5 levels. MiR-181b suppressed HSPA5 expression by directly binding its 3'-untranslated region. Correspondingly, our data demonstrated that overexpression of miR-181b attenuated erythrocyte lysates induced neuronal necrosis and apoptosis. In vivo, downregulated miR-181b increased the HSPA5 level, along with significant elevations of pro-inflammatory cytokines, brain edema, and neurological injury following ICH. HSPA5 pathway plays an important role in ER stress induced brain damage following ICH. In addition, miR-181b has neuroprotective effects that alleviates neurological injury and represents a promising therapeutic strategy in ICH.

Melatonin Protects Against Neuronal Apoptosis via Suppression of the ATF6/CHOP Pathway in a Rat Model of Intracerebral Hemorrhage

Neuronal apoptosis is an important factor accounting for the poor outcomes of intracerebral hemorrhage (ICH). This study first showed that inhibition of activating transcription factor 6 (ATF6) could alleviate secondary brain injury through anti-apoptosis after ICH in rats. Melatonin, ATF6 and CCAAT/enhancer-binding protein homologous protein (CHOP) siRNAs were applied in this study. Brain edema, neurological functions, blood-brain barrier (BBB) integrity were evaluated at 24 h after ICH. Western blot analysis was used to evaluate the protein level of target proteins (ATF6, CHOP, Bip, Bcl-2, Bax, and cleaved caspase-3). Reverse transcription-polymerase chain reaction (RT-PCR) was used to assess the mRNA level of ATF6, CHOP and cleaved caspase-3. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and caspase-3 immunofluorescence staining were applied to evaluate the neuronal cell death. The results suggested that the levels of ATF6 and its downstream protein, CHOP, were upregulated and reached the peak at 24 h after ICH. ATF6 was highly expressed in neurons. The administration of melatonin significantly decreased the mRNA and protein levels of ATF6, and its downstream targets, CHOP and cleaved caspase-3, but increased the Bcl-2/Bax ratio, which ameliorated the neurological functions. The CHOP siRNA significantly reversed the pro-apoptotic effect induced by the increased ATF6 level after ICH. Melatonin could protect against neuronal apoptosis via suppression of ATF6/CHOP arm of ER-stress-response pathway.

PERK Pathway Activation Promotes Intracerebral Hemorrhage Induced Secondary Brain Injury by Inducing Neuronal Apoptosis Both in Vivo and in Vitro

The protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK) signaling pathway was reported to exert an important role in neuronal apoptosis. The present study was designed to investigate the roles of the PERK signaling pathway in the secondary brain injury (SBI) induced by intracerebral hemorrhage (ICH) and its potential mechanisms. Sprague-Dawley rats were used to establish ICH models by injecting autologous blood (100 μl), and cultured primary rat cortical neurons were exposed to oxyhemoglobin (10 μM) to mimic ICH in vitro. The PERK antagonist, GSK2606414, and inhibitor of eukaryotic translation initiation factor 2 subunit α (eIF2α) dephosphorylation, salubrinal, were used to study the roles of PERK signaling pathway in ICH-induced SBI. Our results showed that the protein levels of p-eIF2α and ATF4 were upregulated following ICH, peaking at 48 h. Application of GSK2606414 reversed this increase in vivo and in vitro, thereby preventing ICH-induced neuronal apoptosis. On the contrary, salubrinal inhibited the dephosphorylation of eIF2α, resulting in the elevation of p-eIF2α, which could activate downstream of PERK signaling and induce neuronal apoptosis and necrosis following ICH in vitro and in vivo. Thus, PERK signaling pathway plays an important role in ICH-induced apoptosis and blocking its activation has neuroprotective effects that alleviates SBI, suggesting that targeting this pathway could be a promising therapeutic strategy for improving patient outcome after ICH.