Leptin alleviates endoplasmic reticulum stress induced by cerebral ischemia/reperfusion injury via the PI3K/Akt signaling pathway

Identification of endoplasmic reticulum stress-related genes as prognostic markers in colon cancer

Endoplasmic reticulum stress (ERS) has been implicated in the pathogenesis of various cancers, including colon cancer, by regulating tumor cell survival, growth, and immune response. However, the specific genes involved in ERS that could serve as prognostic markers in colon cancer remain underexplored. This study aims to identify and validate endoplasmic reticulum stress related genes (ERSRGs) in colon cancer that correlate with patient prognosis, thereby enhancing the understanding of ERS in oncological outcomes and potential therapeutic targeting. We utilized bioinformatics analyses to identify ERSRGs from publicly available colon cancer datasets. Differential expression analysis and survival analysis were performed to assess the prognostic significance of these genes. Validation was conducted through quantitative real-time PCR (RT-qPCR) on selected colon cancer cell lines. Our study identified nine ERS related genes (ASNS, ATF4, ATF6B, BOK, CLU, DDIT3, MANF, SLC39A14, TRAF2) involved in critical pathways including IL-12, PI3K-AKT, IL-7, and IL-23 signaling, and linked to 1-, 3-, and 5-year survival of patients with colon cancer. A multivariate Cox model based on these ERS related genes demonstrated significant prognostic power. Further, TRAF2 strong correlated with immune cells infiltration, suggesting its potential roles in modulating immune responses in the tumor microenvironment. The RT-qPCR validation confirmed the differential expression of these genes in human colon cancer cell lines versus human normal colonic epithelial cell line. The identified ERSRGs could serve as valuable prognostic markers and may offer new insights into the therapeutic targeting of ERS in colon cancer.

Leptin as a potential neuroprotective target in Parkinson's Disease: Exploring its role in Neuroinflammation, oxidative Stress, and dopaminergic neurodegeneration

Parkinson's disease (PD) is the second most commonneurodegenerative disease, characterized bybradykinesia, resting tremor, stiffness, and postural instabilityresulting due to the progressive loss ofdopaminergic neurons in the substantia nigra (SN). The pathophysiology of PDis extremely complex and involves mitochondrial dysfunction, oxidative stress, neuroinflammation, and disruption of protein homeostasis. Its progression is affected by both environmental and genetic factors, including mutations in the alpha-synuclein (SNCA), PTEN-induced kinase 1 (PINK1), and leucine-rich repeat kinase 2 (LRRK2) genes. Leptin, primarily secreted by the adipose tissue, has garnered significant interest for its involvement in neuroprotective mechanisms and potential role in the progression of PD. Its receptors located in the SN and hippocampus region indicate its role in neuronal survival and function. The role of leptin in the central nervous system (CNS) highlights its impact on neuroinflammation, oxidative stress, and synaptic plasticity. Recent studies indicate that through activation of Janus kinase/signal transducer and activator of transcription (JAK2/STAT3) and the phosphoinositide 3 kinase (PI3 K)/Akt pathways, leptin may exert a neuroprotective effect by preventing the degeneration of dopaminergic neurons, which marked as the hallmark in the pathophysiology of PD. Additionally, leptin's interaction with neurotrophic factors and its ability to enhance synaptic plasticity highlight its vital role in preserving neuronal health. This review summarizes the role of leptin as a neuroprotective mechanism in PD and explores its potential role as a therapeutic target for treatment to enhance neuroprotection and clinical outcome, by addressing the neurodegenerative characteristics associated with PD.

PI3K/AKT pathway: A potential therapeutic target in cerebral ischemia-reperfusion injury

Cerebral ischemia is a prevalent cerebrovascular disorder, with the restoration of blocked blood vessels serving as the current standard clinical treatment. However, reperfusion can exacerbate neuronal damage and neurological dysfunction, resulting in cerebral ischemia-reperfusion (I/R) injury. Presently, clinical treatment strategies for cerebral I/R injury are limited, creating an urgent need to identify new effective therapeutic targets. The PI3K/AKT signaling pathway, a pro-survival pathway associated with cerebral I/R injury, has garnered significant attention. We conducted a comprehensive review of the literature on the PI3K/AKT pathway in the context of cerebral I/R. Our findings indicate that activation of the PI3K/AKT signaling pathway following cerebral I/R can alleviate oxidative stress, reduce endoplasmic reticulum stress (ERS), inhibit inflammatory responses, decrease neuronal apoptosis, autophagy, and pyroptosis, mitigate blood-brain barrier (BBB) damage, and promote neurological function recovery. Consequently, this pathway ultimately reduces neuronal death, alleviates brain tissue damage, decreases the volume of cerebral infarction, and improves behavioral impairments. These results suggest that the PI3K/AKT signaling pathway is a promising therapeutic target for further research and drug development, holding significant potential for the treatment of cerebral I/R injury.

Asparagine Endopeptidase Inhibition Attenuates Tissue Plasminogen Activator-Induced Brain Hemorrhagic Transformation After Ischemic Stroke

BACKGROUND

Thrombolytic treatment with tissue plasminogen activator (tPA) is one of the approved pharmacological therapies for acute ischemic stroke. However, the use of tPA is limited due to hemorrhagic transformation (HT) and the narrow therapeutic time window. Previous studies demonstrated that asparagine endopeptidase (AEP), a widely expressed pH-dependent endo-lysosomal cysteine protease, can induce neuronal death during ischemia-reperfusion injury. But whether AEP is engaged in HT during ischemia-reperfusion injury is unclear. In the current study, we expanded the role of AEP on HT after delayed tPA administration.

METHODS

In order to investigate the effects of AEP on HT after delayed tPA administration following ischemic stroke, the middle cerebral artery occlusion/reperfusion (MCAO/R) was performed in wild-type (WT) and AEP knockout (KO) transgenic mice, followed by delayed administration of tPA (10 mg/kg, 3 h after occlusion). Additionally, we explored the potential of R13, a specific TrkB agonist with a strong inhibitory impact on AEP, to mitigate injury induced by tPA. 24 h after tPA administration, the following parameters were assessed: infarct volume, behavioral tests, hemorrhagic levels, Evans blue leakage, tight and adherens junction protein expression, blood-brain barrier (BBB) function, cerebral vascular structure, matrix metalloproteinases (MMPs), and BBB-regulated protein low-density lipoprotein receptor-related protein 1 (LRP-1) expression. To construct an in vitro model to examine the effects of AEP on ischemia-reperfusion injury after tPA treatment, human umbilical vein endothelial cells (HUVECs) were exposed to 4 h of oxygen-glucose deprivation (OGD), followed by treatment with tPA (500 ng/mL). 7,8-dihydroxyflavone (7,8-DHF), a natural TrkB agonist with an inhibitory effect on AEP, was applied before OGD.

RESULTS

Compared with tPA-treated WT mice, AEP KO mice treated with tPA showed improved infarct volume, neurological function, brain edema, brain hemoglobin levels, Evans blue leakage, vascular tight junctions, and basement membrane structure combined with reduced AEP expression and activity within the peri-infarct area. In addition, the mice treated with R13 exhibited protective effects on the BBB. Furthermore, we found that the expression of MMP2, MMP9, and LRP-1 in the brain was inhibited by both AEP knockout and R13 treatment. Moreover, HUVECs treated with 7,8-DHF showed improvements in tight and adherens junction proteins and suppressed levels of MMP2, MMP9, and LRP-1.

CONCLUSION

Our findings demonstrate that AEP exacerbates HT induced by delayed tPA treatment in acute ischemic stroke by activating LRP-1, MMP2, and MMP9, which disrupts BBB integrity. We further confirmed R13 as a preventive therapy to attenuate HT induced by delayed tPA treatment in acute ischemic stroke. The present study suggests AEP inhibition may serve as a promising strategy to enhance the safety of delayed tPA thrombolysis for ischemic stroke.

Dexmedetomidine pretreatment alleviates brain injury in middle cerebral artery occlusion (MCAO) model rats by activating PI3K/AKT/NF-κB signaling pathway

Cerebral ischemia-reperfusion injury (CIRI) is a prevalent clinical complication associated with reperfusion following ischemic stroke resulting in neuronal damage and cognitive impairment. Dexmedetomidine (DEX), a highly selective α2-adrenoceptor agonist with sedative, and analgesic properties, is frequently utilized as a sedative anesthetic in clinical surgeries, and believed to play a crucial role in the prognosis of patients suffering from CIRI. However, the mechanism underlying DEX in CIRI remains to be determined. This study aimed to investigate the neuroprotective effects of Dex in rats suffering from CIRI. In the treatment group, DEX (50 µg/kg) was administered intraperitoneally 30 min prior to surgery. Middle cerebral artery occlusion (MCAO) used as a model of CIRI occurred with cerebral artery occlusion for 2 h was followed by reperfusion with blood for 24, 72, 120 or 168 h. Neurological function as assessed by the Longa neurological function score test demonstrated significantly reduced neurological scores and increased % infarct size in MCAO group which was blocked by DEX suggesting that DEX might be effective in treating ischemic stroke. In the MCAO animals, 2,3,5-triphenyltetrazolium chloride (TTC) showed large marked areas of cerebral infarction which were diminished in size by DEX. Using Western blot analysis, results showed that in MCAO rats protein expression levels of TNF-α and IL-6 were increased accompanied by reduced protein expression levels of PI3K/AKT signaling pathway. DEX pretreatment reversed the effects of MCAO as evidenced by decrease in protein expression levels of TNF-α and IL-6 associated with elevated protein expression levels of PI3K/AKT/NF-κB signaling pathway. Data demonstrated that DEX pretreatment improved the neuromotor performance and cognitive functions in animals suffering from consequences of MCAO by diminishing inflammation and activation of the PI3K/AKT/NF-κB signaling pathway.

Targeting PI3K/Akt in Cerebral Ischemia Reperfusion Injury Alleviation: From Signaling Networks to Targeted Therapy

Ischemia/reperfusion (I/R) injury is a pathological event that results in reperfusion due to low blood flow to an organ. Cerebral ischemia is a common cerebrovascular disease with high mortality, and reperfusion is the current standard intervention. However, reperfusion may further induce cellular damage and dysfunction known as cerebral ischemia/reperfusion injury (CIRI). Currently, strategies for the clinical management of CIRI are limited, necessitating the exploration of novel and efficacious treatment modalities for the benefit of patients. PI3K/Akt signaling pathway is an important cellular process associated with the disease. Stimulation of the PI3K/Akt pathway enhances I/R injury in multiple organs such as heart, brain, lung, and liver. It stands as a pivotal signaling pathway crucial for diminishing cerebral infarction size and safeguarding the functionality of brain tissue after CIRI. During CIRI, activation of the PI3K/Akt pathway exhibits a protective effect on CIRI. Furthermore, activation of the PI3K/Akt pathway has the potential to augment the activity of antioxidant enzymes, resulting in a decrease in reactive oxygen species (ROS) and the associated oxidative stress. Meanwhile, PI3K/Akt plays a neuroprotective role by inhibiting inflammatory responses and apoptosis. For example, PI3K/Akt interacts with NF-κB, Nrf2, and MAPK signaling pathways to mitigate CIRI. This article is aimed to explore the pivotal role and underlying mechanism of PI3K/Akt in ameliorating CIRI and investigate the influence of ischemic preconditioning and post-processing, as well as the impact of pertinent drugs or activators targeting the PI3K/Akt pathway on CIRI. The primary objective is to furnish compelling evidence supporting the activation of PI3K/Akt in the context of CIRI, elucidating its mechanistic intricacies. By doing so, the paper aims to underscore the critical contribution of PI3K/Akt in mitigating CIRI, providing a theoretical foundation for considering the PI3K/Akt pathway as a viable target for CIRI treatment.

[Exogenous leptin improves cerebral ischemia-reperfusion-induced glutamate excitotoxic injury in mice by up-regulating GLT-1 and GLAST expression in astrocytes]

OBJECTIVE

To investigate the protective effect of exogenous leptin against focal cerebral ischemia-reperfusion (I/R) injury in mice and explore the underlying mechanism.

METHODS

A total of 100 C57BL/6 mice were randomly divided into 5 groups, including a sham-operated group, cerebral I/R model group, and 3 leptin treatment groups with intraperitoneal injections of 0.5, 1.0 or 2.0 leptin immediately after occlusion of the internal carotid artery. At 24 h after reperfusion, neurological function scores of the mice were assessed, and TTC staining was used to determine the area of cerebral infarction. The pathological changes in the cortical brain tissue of the mice were observed using HE staining, and degenerative damage of the cortical neurons were assessed with Fluoro-Jade C staining. The expression of glial fibrillary acidic protein in cortical brain tissues was detected using immunohistochemistry and Western blotting. In another 45 C57BL/6 mice with sham operation, I/R modeling, or leptin (1 mg/kg) treatment, glutamic acid in the cortical brain tissue was detected using glutamate assay, and cortical glutamate-aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) protein expressions were detected using immunohistochemistry.

RESULTS

Compared with the I/R model mice, the leptin-treated mice had significantly lower neurological deficit scores, smaller cerebral infarct area, milder pathologies in the cortical brain tissue, and lessened cortical neuronal damage with normal morphology and less excessive proliferation of the astrocytes. Leptin treatment significantly up-regulated the expressions of GLT-1 and GLAST and lowered the content of glutamic acid in the brain tissue of the I/R mice.

CONCLUSION

Exogenous leptin has obvious neuroprotective effect against cerebral I/R injury in mice, mediated probably by controlling excessive astrocyte proliferation and up-regulating cortical GLT-1 and GLAST expressions to reduce glutamate-mediated excitotoxic injury of the astrocytes.

Obesity as a Limiting Factor for Remote Ischemic Postconditioning-Mediated Neuroprotection after Stroke

Background

Remote ischemic postconditioning (RIPostC) may protect the brain from ischemia/reperfusion (I/R) injury. The association between RIPostC and obesity has not yet been extensively studied.

Methods

Twelve-week-old male Zucker diabetic fatty (ZDF; n=68) and Zucker diabetic lean (ZDL; n=51) rats were subjected to focal cerebral ischemia for 90 minutes, followed by 24 hours of reperfusion. RIPostC was performed with 5-minute I/R cycles using a tourniquet on the right hind limb.

Results

The results showed a negative association between obesity and neurological impairment in ischemic animals. We observed a 70% greater infarct size in ZDF rats compared with their lean counterparts, as evaluated by 2,3,5-triphenyltetrazolium chloride staining. To measure the total fragmented DNA in peripheral lymphocytes, comet assay was performed. Obese rats exhibited higher levels of DNA damage (by approximately 135%) in peripheral blood lymphocytes even before the induction of stroke. RIPostC did not attenuate oxidative stress in the blood in obese rats subjected to ischemia. Focal cerebral ischemia increased core and penumbra tissue glutamate release in the brain and decreased it in the blood of ischemic ZDL rats, and these changes improved following RIPostC treatment. However, changes in blood and tissue glutamate content were not detected in ischemic ZDF rats or after RIPostC intervention.

Conclusion

Our findings suggest that obese animals respond more severely to ischemia-reperfusion brain injury. However, obese animals did not achieve neuroprotective benefits of RIPostC treatment.

Xingnaojing injection alleviates cerebral ischemia/reperfusion injury through regulating endoplasmic reticulum stress in Vivo and in Vitro

Background

Xingnaojing (XNJ) injection, an extract derived from traditional Chinese medicine, is commonly used to treat ischemic stroke (IS). Previous studies have shown that XNJ has the ability to alleviate apoptosis in cerebral ischemia-reperfusion injury. However, the potential mechanisms have not been clarified.

Objective

To identify the neuroprotective effect of XNJ and explore whether XNJ inhibits cell apoptosis associated with endoplasmic reticulum stress (ERS) after IS.

Methods

In this study, cultured hippocampal neurons from mouse embryos and Sprague-Dawley rats were assigned randomly to four groups: sham, model, XNJ, and edaravone. The treatment groups were administered 2 h after modelling. Neurological deficit scores and motor performance tests were performed after 24 h of modelling. Additionally, pathomorphology, cell apoptosis and calcium content were evaluated. To ascertain the expression of ERS proteins, western blotting and polymerase chain reaction were employed.

Results

The results indicated that XNJ treatment resulted in a notable decrease in infarct volume, apoptosis and missteps compared with the model group. XNJ also exhibited improvements in neurological function, grip strength and motor time. The calcium content significantly reduced in XNJ group. The XNJ administration resulted in a reduction in the levels of proteins associated with ERS including CHOP, GRP78, Bax, caspase-12, caspase-9, and cleaved-caspase-3, but an increase of the Bcl-2/Bax ratio. Furthermore, the downregulation of mRNA expression of CHOP, GRP78, caspase-12, caspase-9, and caspase-3 was confirmed in both cultured neurons and rat model.

Conclusion

These findings suggest that XNJ may alleviate apoptosis by modulating the ERS-induced apoptosis pathway, making it a potential novel therapeutic approach for ischemic stroke.

Recent Advances in the Knowledge of the Mechanisms of Leptin Physiology and Actions in Neurological and Metabolic Pathologies

Excess body weight is frequently associated with low-grade inflammation. Evidence indicates a relationship between obesity and cancer, as well as with other diseases, such as diabetes and non-alcoholic fatty liver disease, in which inflammation and the actions of various adipokines play a role in the pathological mechanisms involved in these disorders. Leptin is mainly produced by adipose tissue in proportion to fat stores, but it is also synthesized in other organs, where leptin receptors are expressed. This hormone performs numerous actions in the brain, mainly related to the control of energy homeostasis. It is also involved in neurogenesis and neuroprotection, and central leptin resistance is related to some neurological disorders, e.g., Parkinson's and Alzheimer's diseases. In peripheral tissues, leptin is implicated in the regulation of metabolism, as well as of bone density and muscle mass. All these actions can be affected by changes in leptin levels and the mechanisms associated with resistance to this hormone. This review will present recent advances in the molecular mechanisms of leptin action and their underlying roles in pathological situations, which may be of interest for revealing new approaches for the treatment of diseases where the actions of this adipokine might be compromised.