Downregulation of TRB3 protects neurons against apoptosis induced by global cerebral ischemia and reperfusion injury in rats

Interfering TRIB3 protects the blood brain barrier through PI3K/Akt pathway to alleviate cerebral ischemia-reperfusion injury in diabetes mellitus mice

This study aimed to treat diabetic cerebral ischemia-reperfusion injury (CI/RI) by affecting blood brain barrier (BBB) permeability and integrity. The CI/RI model in DM mice and a high glucose (HG) treated oxygen and glucose deprivation/reoxygenation (OGD/R) brain endothelial cell model were established for the study. Evans blue (EB) staining was used to evaluate the permeability of BBB in vivo. TTC staining was used to analyze cerebral infarction. The location and expression of tribbles homolog 3 (TRIB3) in endothelial cells were detected by immunofluorescence. Western blotting was used to detect the protein expressions of TRIB3, tight junction molecules, adhesion molecules, phosphorylated protein kinase B (p-AKT) and AKT. The levels of pro-inflammatory cytokines were detected by qRT-PCR. Trans-epithelial electrical resistance (TEER) and fluorescein isothiocyanate (FITC)-dextran were used to measure vascular permeability in vitro. TRIB3 ubiquitination and acetylation levels were detected. Acetyltransferase bound to TRIB3 were identified by immunoprecipitation. TRIB3 was localized in cerebral endothelial cells and was highly expressed in diabetic CI/R mice. The BBB permeability in diabetic CI/R mice and HG-treated OGD/R cells was increased, while the junction integrity was decreased. Interference with TRIB3 in vitro reduces BBB permeability and increases junction integrity. In vivo interfering with TRIB3 reduced cerebral infarction volume, BBB permeability and inflammation levels, and upregulated p-AKT levels. The phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin reversed the effects of TRIB3-interfering plasmid. In vitro HG treatment induced TRIB3 acetylation through acetyltransferase p300, which in turn reduced ubiquitination and stabilized TRIB3. Interfering TRIB3 protects BBB by activating PI3K/AKT pathway and alleviates brain injury, which provides a new target for diabetic CI/RI.

Multi-parametric MRI assessment of melatonin regulating the polarization of microglia in rats after cerebral ischemia/reperfusion injury

OBJECTIVES

Multi-parametric magnetic resonance imaging (MRI) can provide comprehensive and valuable information for precise diagnosis and treatment evaluation of a number of diseases. In this study, the neuroprotective effects of melatonin (Mel) on a rat model of cerebral ischemia/reperfusion injury (CIRI) were assessed by multi-parametric MRI combined with histopathological techniques for longitudinal monitoring of the lesion microenvironment.

METHODS

Sixty Sprague Dawley (SD) rats were randomly divided into three groups: the Sham, CIRI and CIRI + Mel groups. At multiple time points after ischemia, MRI scanning was performed on a 7.0 Tesla MRI scanner. Multi-parametric MRI includes T2-weighted imaging (T2WI), diffusion weighted imaging (DWI), and chemical exchange saturation transfer (CEST)-MRI. CEST effects were calculated by the Lorentzian difference method, 3.5 ppm indicates amide protons of mobile proteins/peptide (Amide-CEST) and 2.0 ppm indicates amine protons (Guan-CEST). Multiple histopathological techniques were used to examine the histopathological changes and explore the therapeutic effects of Mel.

RESULTS

T2WI and DWI-MRI could localize the infarct foci and areas in CIRI rats, which was further validated by staining, 2, 3, 5-triphenyl tetrazolium chloride (TTC) staining, hematoxylin and eosin (H&E) staining, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labelling (TUNEL) staining. After Mel treatment, T2WI and DWI-MRI showed smaller infarct volume, and neurons displayed improved morphology with less apoptosis rates. Notably, Amide-CEST and Guan-CEST signal decreased as early as 2 h after CIRI (all P <0.001), reflecting the change of pH after ischemia. After Mel treatment, both Amide-CEST and Guan-CEST signal increased in ischemic cortex and striatum compared with control group (all P < 0.001). The immunofluorescence staining and western blotting analysis suggested the expression of M2 microglia increased after Mel treatment; While，after Mel treatment the inflammatory factor interleukin-1β (IL-1β) decreased compared with control CIRI rats.

CONCLUSIONS

Multi-parametric MRI was shown to be an effective method to monitor the brain damage in a rat model of CIRI and assess the therapeutic effects of Mel treatment. Amide-CEST and Guan-CEST were especially sensitive to the changes in brain microenvironment during the early stage after CIRI. Furthermore, the neuroprotective effect of Mel treatment is associated with its promotion of the microglia polarized to M2 type in CIRI rats.

Danhong injection alleviates cerebral ischemia-reperfusion injury by inhibiting mitochondria-dependent apoptosis pathway and improving mitochondrial function in hyperlipidemia rats

Cerebral ischemia threatens human health and life. Hyperlipidemia is a risk of cerebral ischemia. Danhong injection (DHI) is a traditional Chinese medical preparation for the treatment of cerebrovascular diseases. However, the effects of DHI on mitochondria-dependent apoptosis and mitochondrial function following cerebral ischemia in hyperlipidemia rats are not clear. In this study, SD rats were fed by high-fat diet for six weeks to establish the hyperlipidemia model, except for the sham and ischemia-reperfusion (I/R) groups. Hyperlipidemia rats were assigned into I/R + high-fat diet (HFD) group, DHI 1 mL/kg group, and DHI 2 mL/kg group. DHI was administrated to the drug group via caudal vein for seven consecutive days (once per day). Subsequently, rats underwent middle cerebral artery occlusion (MCAO) for 1 h and reperfusion for 24 h. The results showed that DHI significantly reduced cerebral infarction volume, ameliorated neurological function, improved pathological changes, and inhibited apoptosis. DHI could significantly restore the levels of mitochondrial respiratory chain complexes I-IV, increase the ATP content and COX activity, and decrease the level of OFR in the ischemic brain mitochondria of hyperlipidemia rats after I/R. DHI significantly regulated the levels of cytochrome c (Cyt c), Apaf1, Bax, Bcl-2, Caspase-3, and Caspase-9 in brain tissue, and improved mitochondrial dynamics (Mfn1, Mfn2, OPA1, Drp1, and Fis1). The results indicate that DHI could alleviate ischemic brain injury in hyperlipidemia rats, and the mechanism may be to improve mitochondrial function by restoring the mitochondrial respiratory chain and changing the protein balance of mitochondrial fusion and fission, and inhibiting mitochondria-dependent apoptosis.

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.

Longxuetongluo Capsule protects against cerebral ischemia/reperfusion injury through endoplasmic reticulum stress and MAPK-mediated mechanisms

Introduction

Longxuetongluo Capsule (LTC) is wildly applied to treat ischemic stroke in clinical practice in China. However, the pharmacological mechanism of LTC on ischemic stroke is still unstated.

Objective

Our research was designed to study the protective effect of LTC against cerebral ischemia–reperfusion (I/R) injury and reveal the underlying mechanism both in vivo and in vitro.

Methods

PC12 cells treated with glucose deprivation/reperfusion (OGD/R) were used to simulate in vitro ischemia/reperfusion (I/R) injury. The cell viability, apoptosis rate, and protein expressions of PC12 cells were evaluated. In vivo validation of the protective effect of LTC was carried out by middle cerebral artery occlusion (MCAO)/reperfusion treatment, and the underlying mechanism of its anti-apoptosis ability was further revealed by immunohistochemistry staining and Western blotting.

Results

In the current study, we observed that LTC effectively inhibited oxygen-glucose deprivation/reperfusion (OGD/R) induced apoptosis of PC12 cells through suppressing the cleavage of poly ADP-ribose polymerase (PARP), caspase-3, and caspase-9. Further investigation revealed that OGD/R insult remarkably triggered the endoplasmic reticulum stress responses (ER stress) to induce PC12 cell apoptosis. LTC treatment alleviated OGD/R induced ER stress by inhibiting the activation of protein kinase RNA (PKR)-like ER kinase (PERK)/eukaryotic translation initiation factor 2 (eIF2α) and inositol requiring enzyme 1 (IRE1)/tumor necrosis factor receptor-associated factor 2 (TRAF2) pathways. Additionally, LTC also restrained the OGD/R-induced PC12 cell apoptosis by reversing the activated mitogen-activated protein kinase (MAPK) through IRE1/TRAF2 pathway. Animal studies demonstrated LTC significantly restricted the infarct region induced by middle cerebral artery occlusion (MCAO)/reperfusion, the activation of ER stress and apoptosis of neuronal cells had also been suppressed by LTC in the penumbra region.

Conclusion

LTC protects the cerebral neuronal cell against ischemia/reperfusion injury through ER stress and MAPK-mediated mechanisms.

Neuroprotective Effects of Celastrol on Transient Global Cerebral Ischemia Rats via Regulating HMGB1/NF-κB Signaling Pathway

Cerebral ischemia is a major cause of brain dysfunction, neuroinflammation and oxidative stress have been implicated in the pathophysiological process of cerebral ischemia/reperfusion injury. Celastrol is a potent inhibitor of inflammation and oxidative stress that has little toxicity. The present study was designed to evaluate whether celastrol has neuroprotective effects through anti-inflammatory and antioxidant actions, and to elucidate the possible involved mechanisms in transient global cerebral ischemia reperfusion (tGCI/R) rats. Celastrol (1, 2, or 4 mg/kg) was administrated intraperitoneally immediately after reperfusion and the effect of celastrol on reverting spatial learning and memory impairment was determined by Morris water maze (MWM) task. Inflammatory response and oxidative stress, hippocampal neuronal damage and glial activation, and HMGB1/NF-κB signaling pathway proteins were also examined. Our results indicated that celastrol dose-dependently reduced hippocampal and serum concentration of pro-inflammatory markers (TNF-α, IL-1β, and IL-6) and oxidative stress marker (MDA), whereas the anti-inflammatory marker IL-10 and antioxidant markers (GSH, SOD, and CAT) were increased significantly in celastrol treated tGCI/R rats. Celastrol alleviated apoptotic neuronal death, inhibited reactive glial activation and proliferation and improved ischemia-induced neurological deficits. Simultaneously, we found that mechanisms responsible for the neuroprotective effect of celastrol could be attributed to its anti-inflammatory and antioxidant actions via inhibiting HMGB1/NF-κB signaling pathway. These findings provide a proof of concept for the further validation that celastrol may be a superior candidate for the treatment of severe cerebral ischemic patients in clinical practice in the future.

The Chemical Biology of Ferroptosis in the Central Nervous System

Over the past five decades, thanatology has come to include the study of how individual cells in our bodies die appropriately and inappropriately in response to physiological and pathological stimuli. Morphological and biochemical criteria have been painstakingly established to create clarity around definitions of distinct types of cell death and mechanisms for their activation. Among these, ferroptosis has emerged as a unique, oxidative stress-induced cell death pathway with implications for diseases as diverse as traumatic brain injury, hemorrhagic stroke, Alzheimer's disease, cancer, renal ischemia, and heat stress in plants. In this review, I highlight some of the formative studies that fostered its recognition in the nervous system and describe how chemical biological tools have been essential in defining events necessary for its execution. Finally, I discuss emerging opportunities for antiferroptotic agents as therapeutic agents in neurological diseases.

Inhibition of TRIB3 Protects Against Neurotoxic Injury Induced by Kainic Acid in Rats

Epilepsy refers to a group of neurological disorders of varying etiologies characterized by recurrent seizures, resulting in brain dysfunction. Endoplasmic reticulum (ER) stress is highly activated in the process of epilepsy-related brain injury. However, the mechanisms by which ER stress triggers neuronal apoptosis remain to be fully elucidated. Tribbles pseudokinase 3 (TRIB3) is a pseudokinase that affects a number of cellular functions, and its expression is increased during ER stress. Here, we sought to clarify the role of TRIB3 in neuronal apoptosis mediated by ER stress. In the kainic acid (KA) (10 mg/kg)-induced rat seizure model, we characterized neuronal injury and apoptosis after KA injection. KA induced an ER stress response, as indicated by elevated expression of glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP). TRIB3 protein was upregulated concomitantly with the downregulation of phosphorylated-protein kinase B (p-AKT) in rats following KA administration. In rat cortical neurons treated with KA, TRIB3 knockdown by siRNA reduced the number of dying neurons, decreased the induction of GRP78 and CHOP and the activation of caspase-3, and blocked the dephosphorylation of AKT after KA treatment. Our findings indicate that TRIB3 is involved in neuronal apoptosis occurring after KA-induced seizure. The knockdown of TRIB3 effectively protects against neuronal apoptosis in vitro, suggesting that TRIB3 may be a potential therapeutic target for the treatment of epilepsy.

Cdh1 overexpression improves emotion and cognitive-related behaviors via regulating hippocampal neuroplasticity in global cerebral ischemia rats

Post-stroke survivors exhibited cognitive deficits and performed emotional impairment. However, the effect of global cerebral ischemia on standard behavioral measures of emotionality and underlying mechanism remain largely unknown. Our previous work identified that down-regulation of Cdh1 contributed to ischemic neuronal death in rat, thus we hypothesized that Cdh1 exerts a role in emotionality after cerebral ischemia, and we investigated the effect of Cdh1 overexpression on neurogenic behaviors and possible mechanisms in transient global cerebral ischemia reperfusion (tGCI/R) rats. A series of behavioral tests were used to evaluate emotion and cognitive related behaviors, and molecular biological techniques were employed to investigate hippocampal neuroplasticity. The results showed that tGCI/R rats displayed anxiety- and depression-like behaviors and a certain degree of cognitive impairment, and these abnormal behaviors accompanied with a loss of hippocampal synapses and dendritic spines, disruption of dendrite arborization and decline in the level of GAP-43, synaptophysin, synapsin and PSD-95. However, Cdh1 overexpression improved negative emotionality, ameliorated cognitive deficits, rescued hippocampal synapses loss, prevented dendritic network disorganization, and increased the level of synaptic-associated proteins after tGCI/R. Taken together, these findings suggest that Cdh1 overexpression exerts a neuroprotective effect by regulating hippocampal neuroplasticity thus improving negative emotionality and cognitive deficits after tGCI/R.