Activation of Akt by SC79 decreased cerebral infarct in early cerebral ischemia-reperfusion despite increased BBB disruption

Leucine Reduced Blood-Brain Barrier Disruption and Infarct Size in Early Cerebral Ischemia-Reperfusion

A disruption of the blood-brain barrier (BBB) is a crucial pathophysiological change that can impact the outcome of a stroke. Ribosomal protein S6 (S6) and protein kinase B (Akt) play significant roles in early cerebral ischemia-reperfusion injury. Studies have suggested that branched-chain amino acids (BCAAs) may have neuroprotective properties for spinal cord or brain injuries. Therefore, we conducted research to investigate if leucine, one of the BCAAs, could offer neuroprotection and alter BBB disruption, along with its effects on the phosphorylation of S6 and Akt during the early phase of cerebral ischemia-reperfusion, specifically within the thrombolytic therapy time window. In rats, ten min after left middle cerebral artery occlusion (MCAO), 5 µL of 20 mM L-leucine or normal saline was injected into the left lateral ventricle. After two hours of reperfusion following one hour of MCAO, we determined the transfer coefficient (Ki) of 14C-α-aminoisobutyric acid to assess the BBB disruption, infarct size, and phosphorylation of S6 and Akt. Ischemia-reperfusion increased the Ki (+143%, p < 0.001) and the intra-cerebroventricular injection of leucine lowered the Ki in the ischemic-reperfused cortex (-34%, p < 0.001). Leucine reduced the percentage of cortical infarct (-42%, p < 0.0001) out of the total cortical area. Ischemia-reperfusion alone significantly increased the phosphorylation of both S6 and Akt (p < 0.05). However, the administration of leucine had no further effect on the phosphorylation of S6 or Akt in the ischemic-reperfused cortex. This study suggests that an acute increase in leucine levels in the brain during early ischemia-reperfusion within a few hours of stroke may offer neuroprotection, possibly due to reduced BBB disruption being one of the major contributing factors. Leucine did not further increase the already elevated phosphorylation of S6 or Akt by ischemia-reperfusion under the current experimental conditions. Our data warrant further studies on the effects of leucine on neuronal survival and its mechanisms in the later stages of cerebral ischemia-reperfusion.

MiR-21 alleviates renal tubular epithelial cells injury induced by ischemia by targeting TLR4

Renal ischemia is the initial stage of kidney damage, leading to mitochondrial metabolism disorders and cell necrosis. In this study, we aimed to investigate the biological functions and potential mechanisms of miR-21 in protecting renal tubular epithelial cells from oxidative stress and apoptosis following oxygen glucose deprivation (OGD). Following an OGD injury, miR-21 levels increased in HK-2 renal tubular epithelial cells. Overexpression of miR-21 decreased the protein expressions of cleaved caspase-3, BAX, P53, cell apoptosis and increased Bcl-2 expression in HK-2 cells with OGD injury. In vivo studies found that miR-21 agomir reduced renal tissue apoptosis, while miR-21 antagomir increased it. In addition, overexpression of miR-21 reduced levels of reactive oxygen species (ROS), malondialdehyde (MDA) and lactate dehydrogenase (LDH) in HK-2 cells with OGD injury. However, miR-21 inhibition exhibited the opposite effect. A dual-luciferase reporter assay demonstrated that miR-21 directly regulates Toll-like receptor 4 (TLR4) by targeting the 3'-UTR of TLR4 mRNA. Overexpression of miR-21 led to decreased TLR4 protein expression, and TLR4 knockdown was shown to greatly increase AKT activity in HK-2 cells by in vitro kinase assay. Additionally, TLR4 knockdown promoted AKT phosphorylation and hypoxia-inducible factor-1α (HIF-1α) expression, while TLR4 overexpression inhibited these processes. Furthermore, AKT activation abolished the effect of TLR4 on HIF-1α, while AKT inhibition decreased the expression of TLR4 on HIF-1α in TLR4 knockdown HK-2 cells. Further study revealed that HIF-1α inhibition abolished the protective effect of miR-21 overexpression on ROS, LDH levels and cell apoptosis in HK-2 cells after OGD injury, which is indicated by increased levels of ROS and LDH, as well as increased cell apoptosis after HIF-1α inhibition in miR-21-treated HK-2 cells. In conclusion, miR-21 defends OGD-induced HK-2 cell injury via the TLR4/AKT/HIF-1α axis.

Sodium danshensu attenuates cerebral ischemia–reperfusion injury by targeting AKT1

The beneficial properties of Sodium Danshensu (SDSS) for controlling cerebral ischemia and reperfusion injury (CIRI) are elucidated here both in vivo and in vitro. SDSS administration significantly improved the viability of P12 cells, reduced lactate dehydrogenase (LDH) leakage, and decreased the apoptosis rate following exposure to an oxygen-glucose deprivation/reoxygenation (OGD) environment. In addition, the results of a Huprot^TM human protein microarray and network pharmacology indicated that AKT1 is one of the main targets of SDSS. Moreover, functional experiments showed that SDSS intervention markedly increased the phosphorylation level of AKT1 and its downstream regulator, mTOR. The binding sites of SDSS to AKT1 protein were confirmed by Autodock software and a surface plasmon resonance experiment, the result of which imply that SDSS targets to the PH domain of AKT1 at ASN-53, ARG-86, and LYS-14 residues. Furthermore, knockdown of AKT1 significantly abolished the role of SDSS in protecting cells from apoptosis and necrosis. Finally, we investigated the curative effect of SDSS in a rat model of CIRI. The results suggest that administration of SDSS significantly reduces CIRI-induced necrosis and apoptosis in brain samples by activating AKT1 protein. In conclusion, SDSS exerts its positive role in alleviating CIRI by binding to the PH domain of AKT1 protein, further resulting in AKT1 activation.

Inhibition of serum and glucocorticoid regulated kinases by GSK650394 reduced infarct size in early cerebral ischemia-reperfusion with decreased BBB disruption

Blood-brain barrier (BBB) disruption is one of the most important pathological changes following cerebral ischemia-reperfusion. We tested whether inhibition of the serum and glucocorticoid regulated kinase 1 (SGK1) would decrease BBB disruption and contribute to decreasing infarct size in the first few hours of cerebral ischemia-reperfusion within the thrombolysis therapy time window. After transient middle cerebral artery occlusion (MCAO), an SGK1 inhibitor GSK650394, or vehicle was administered into the lateral ventricle of rats. After one hour of MCAO and two hours of reperfusion, we determined BBB disruption using the transfer coefficient (K_i) of ¹⁴C-α-aminoisobutyric acid, and also determined infarct size, phosphorylation of NDRG1, and MMP2 protein level. Ischemia-reperfusion increased (+34%, p < 0.05) and GSK650394 decreased (-25%, p < 0.05) the K_i in the ischemic-reperfused cortex. GSK650394 decreased the percentage of cortical infarct (-31%, p < 0.001). At the same time GSK650394 reduced NDRG1 phosphorylation and MMP2 protein level in the ischemic-reperfused cortex suggesting that SGK1 was inhibited by GSK650394 and that lower MMP2 could be one of the mechanisms of decreased BBB disruption. Collectively our data suggest that GSK650394 could be neuroprotective and one of the mechanisms of the neuroprotection could be decreased BBB disruption. SGK1 inhibition within the thrombolysis therapy time window might reduce cerebral ischemia-reperfusion injury.

Rapalink-1 Increased Infarct Size in Early Cerebral Ischemia-Reperfusion With Increased Blood-Brain Barrier Disruption

It has been reported that the mechanistic target of rapamycin (mTOR) pathway is involved in cerebral ischemia–reperfusion injury. One of the important pathological changes during reperfusion after cerebral ischemia is disruption of blood–brain barrier (BBB). Rapamycin, a first-generation mTOR inhibitor, produces divergent effects on neuronal survival and alteration in BBB disruption. In this study, we investigated how Rapalink-1, a third-generation mTOR inhibitor, would affect neuronal survival and BBB disruption in the very early stage of cerebral ischemia–reperfusion that is within the time window of thrombolysis therapy. The middle cerebral artery occlusion (MCAO) was performed in rats under isoflurane anesthesia with controlled ventilation. Of note, 2 mg/kg of Rapalink-1 or vehicle was administered intraperitoneally 10 min after MCAO. After 1 h of MCAO and 2 h of reperfusion, the transfer coefficient (K_i) of ¹⁴C-α-aminoisobutyric acid (104 Da) and the volume of ³H-dextran (70,000 Da) distribution were determined to assess the degree of BBB disruption. At the same time points, phosphorylated S6 (Ser240/244) and Akt (Ser473) as well as matrix metalloproteinase-2 (MMP2) protein level were determined by Western blot along with the infarct size using tetrazolium stain. Rapalink-1 increased the K_i in the ischemic-reperfused cortex (IR-C, +23%, p < 0.05) without a significant change in the volume of dextran distribution. Rapalink-1 increased the percentage of cortical infarct out of the total cortical area (+41%, p < 0.005). Rapalink-1 significantly decreased phosphorylated S6 and Akt to half the level of the control rats in the IR-C, which suggests that both of the mechanistic target of rapamycin complex 1 and 2 (mTORC1 and mTORC2) were inhibited. The MMP2 level was increased suggesting that BBB disruption could be aggravated by Rapalink-1. Taken together, our data suggest that inhibiting both mTORC1 and mTORC2 by Rapalink-1 could worsen the neuronal damage in the early stage of cerebral ischemia–reperfusion and that the aggravation of BBB disruption could be one of the contributing factors.

Brain-Specific Serine-47 Modification of Cytochrome c Regulates Cytochrome c Oxidase Activity Attenuating ROS Production and Cell Death: Implications for Ischemia/Reperfusion Injury and Akt Signaling

We previously reported that serine-47 (S47) phosphorylation of cytochrome c (Cytc) in the brain results in lower cytochrome c oxidase (COX) activity and caspase-3 activity in vitro. We here analyze the effect of S47 modification in fibroblast cell lines stably expressing S47E phosphomimetic Cytc, unphosphorylated WT, or S47A Cytc. Our results show that S47E Cytc results in partial inhibition of mitochondrial respiration corresponding with lower mitochondrial membrane potentials (ΔΨm) and reduced reactive oxygen species (ROS) production. When exposed to an oxygen-glucose deprivation/reoxygenation (OGD/R) model simulating ischemia/reperfusion injury, the Cytc S47E phosphomimetic cell line showed minimal ROS generation compared to the unphosphorylated WT Cytc cell line that generated high levels of ROS upon reoxygenation. Consequently, the S47E Cytc cell line also resulted in significantly lower cell death upon exposure to OGD/R, confirming the cytoprotective role of S47 phosphorylation of Cytc. S47E Cytc also resulted in lower cell death upon H2O2 treatment. Finally, we propose that pro-survival kinase Akt (protein kinase B) is a likely mediator of the S47 phosphorylation of Cytc in the brain. Akt inhibitor wortmannin abolished S47 phosphorylation of Cytc, while the Akt activator SC79 maintained S47 phosphorylation of Cytc. Overall, our results suggest that loss of S47 phosphorylation of Cytc during brain ischemia drives reperfusion injury through maximal electron transport chain flux, ΔΨm hyperpolarization, and ROS-triggered cell death.

XingNaoJing injections protect against cerebral ischemia/reperfusion injury and alleviate blood-brain barrier disruption in rats, through an underlying mechanism of NLRP3 inflammasomes suppression

The aim of this study was to explore the neuroprotective effect and mechanism of XingNaoJing injections (XNJ) on cerebral ischemia injury and blood-brain barrier (BBB) disruption. Middle cerebral artery occlusion (MCAO) method was applicated to establish the model of cerebral ischemia/reperfusion (I/R) injury in rats. BBB permeability after I/R injury was assessed with the leaking amount of Evans Blue and the expression of occludin and ZO-1. The expression of NOD-like receptor family, pyrin domain containing (NLRP3) was checked to explore the inhibition of inflammation by XNJ. The results showed that XNJ could significantly increase the survival percent, decrease the infarct area and ameliorate neurological deficits and brain damage after I/R injury. Leaking amount of Evans Blue was reduced by XNJ, and the expression of tight junction protein, occludin and ZO-1 was also up-regulated by XNJ, which showed a role of protection on BBB disruption. The expression of NLRP3 was inhibited after exposure of XNJ, which was associated with inhibition of the inflammatory response. In summary, XNJ could suppress NLRP3 inflammasomes and improve BBB disruption and brain damage in rats after cerebral I/R injury, which provided a beneficial insight to further explore XNJ.

Discovery and Validation of Circulating Hsa-miR-210-3p as a Potential Biomarker for Primary Open-Angle Glaucoma

Purpose

Blood-based examination tools for glaucoma diagnosis in clinical practice, which can be useful for screening patients when traditional ophthalmic examinations cannot be utilized, are not available thus far. This study aimed to identify circulating microRNAs (miRNAs) associated with primary open-angle glaucoma (POAG) and explore their utility as diagnostic markers.

Methods

A total of 136 POAG patients and controls were enrolled. Next-generation RNA sequencing was used to explore the expression profile of circulating miRNAs in the sequencing set, and potential miRNAs from independent samples in both the screening and validation sets were validated by quantitative real-time polymerase chain reaction (qRT-PCR). Receiver operating characteristic (ROC) analysis was used to evaluate the ability of certain miRNAs to distinguish POAG patients from control subjects.

Results

Using sequencing and qRT-PCR, hsa-miR-210-3p was found to be elevated in POAG patients in all sets. ROC analysis of the screening and validation sets revealed that hsa-miR-210-3p differentiated between POAG patients and matched controls with an area under the curve (AUC) of 0.846 (sensitivity: 84.6%; specificity: 80.8%) and 0.813 (sensitivity: 84.8%; specificity: 69.7%), respectively. In case of all nonsequencing participants, analysis revealed that hsa-miR-210-3p differentiated between severe POAG patients and controls with an AUC of 0.880 (sensitivity: 85.4%; specificity: 85.7%). In addition, the expression of hsa-miR-210-3p was associated with visual field defects of |mean deviation| (β = 0.237; P = 0.022) and average retinal nerve fiber layer thickness (β = -5.792; P = 0.014).

Conclusions

Circulating hsa-miR-210-3p may serve as a potential diagnostic marker for POAG (especially for severe POAG patients).

Advances on fluid shear stress regulating blood-brain barrier

The integrity of structure and function of blood-brain barrier (BBB) plays a central role in maintaining the homeostasis of the central nervous system. Patients with severe cerebrovascular stenosis often undergo cerebrovascular bypass surgery. However, the sharply increased fluid shear stress (FSS) after cerebrovascular bypass disrupts the physiological function of brain microvascular endothelial cells (BMECs) at the lesion site, damaging BBB and inducing intracerebral hemorrhage eventually. At present, there are great interests in cerebral vascular flow regulating the structure and function of BBB under physiological and pathological conditions, and most of studies have highlighted the importance of BMECs in BBB. Understanding of how FSS regulating BBB can promote the development of new protective and restorative cerebral vascular interventional therapy.

Protective effect of edaravone on blood-brain barrier by affecting NRF-2/HO-1 signaling pathway

Protective effect of edaravone on blood-brain barrier (BBB) in experimental cerebral infarction rats was investigated. SD rats were prepared as the permanent middle cerebral artery occlusion model and randomly divided into 4 groups: cerebral infarction model group, edaravone low, medium and high dose groups. Healthy rats only for operation and no filament were selected as the sham operation control group. Rats in the cerebral infarction model group and the control group were given normal saline, and those in the edaravone low, medium and high dose groups were given edaravone 10, 15 and 20 mg/kg, respectively. The survival status, the body weight and neurological function score before and after treatment, the brain water content and the permeability of the blood-brain barrier after treatment were measured. The expression levels of NFE2-related factor 2 (NRF2) and hemeoxygenase 1 (HO-1) in rat brain tissue were detected by western blotting. Levels of peripheral blood malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione (GSH) were detected by ELISA. The state of the rats in three edaravone groups was improved compared with that of the cerebral infarction group. Compared with the cerebral infarction model group, the body weight was significantly increased after treatment and the neurological function score, brain tissue water content and BBB permeability were significantly decreased in three edaravone groups (P<0.05). Compared with the model group of cerebral infarction, the expression of NRF-2 and HO-1 in the brain of the three edaravone groups was significantly higher (P<0.05). Compared with the model group of cerebral infarction, the expression of MDA and GSH in the three edaravone groups was significantly decreased, GSH and SOD was increased (P<0.05), in a dose-dependent manner. Edaravone might play a protective role in the BBB by activating the NRF-2/HO-1 signaling pathway.

Inhibition of p70 ribosomal S6 kinase 1 (S6K1) by PF-4708671 decreased infarct size in early cerebral ischemia-reperfusion with decreased BBB permeability

It is not clear whether inhibition of p70 ribosomal S6 kinase 1 (S6K1) is neuroprotective in cerebral ischemia-reperfusion. Decreasing blood-brain barrier (BBB) disruption has been associated with a better neuronal outcome in cerebral ischemia. We hypothesized that inhibition of S6K1 would decrease BBB disruption and infarct size in the early stage of cerebral ischemia-reperfusion. Middle cerebral artery occlusion (MCAO) was performed in rats under isoflurane anesthesia with controlled ventilation. 75 mg/kg of PF-4708671, an S6K1 inhibitor, was administered intraperitoneally 15 min after MCAO. After 1 h of MCAO and 2 h of reperfusion, the transfer coefficient (K_i) of ¹⁴C-α-aminoisobutyric acid and the volume of ³H-dextran distribution were determined to assess the degree of BBB disruption. At the same time point, phosphorylated Rictor (pT1135) and the infarct size were measured to evaluate S6K1 activity. In the PF-4708671 treated rats, the K_i of the ischemic-reperfused cortex was lower than the untreated rats (-22%, P < 0.05) and the volume of dextran distribution was significantly lower in most brain regions. With PF-4708671, a significant decrease in pT1135 Rictor was observed and the percentage of cortical infarct out of total cortical area was decreased (11.6 ± 2.0% vs 7.2 ± 1.1%, P < 0.0001). Our data demonstrate that PF-4708671 decreased the size of the cortical infarct in the ischemic-reperfused cortex with a decrease in BBB disruption suggesting that inhibition of S6K1 may induce neuronal survival in early cerebral ischemia-reperfusion and that a decrease of BBB disruption could be one of the contributing factors.

Di-n-butyl phthalate epigenetically induces reproductive toxicity via the PTEN/AKT pathway

Di-n-butyl phthalate (DBP) is a kind of ubiquitous chemical linked to hormonal disruptions that affects male reproductive system. However, the mechanism of DBP-induced germ cells toxicity remains unclear. Here, we demonstrate that DBP induces reduction of proliferation, increase of apoptosis and DNA damage dependent on the PTEN/AKT pathway. Mechanistically, DBP decreases PTEN promoter methylation and increases its transcriptional activity, leading to increased PTEN expression. Notably, DNMT3b is confirmed as a target of miR-29b and miR-29b-mediated status of PTEN methylation is involved in the effects of DBP treatment. Meanwhile, DBP decreases AKT pathway expression via increasing PTEN expression. In addition, the fact that DBP decreases the sperm number and the percentage of motile and progressive sperm is associated with downregulated AKT pathway and sperm flagellum-related genes. Collectively, these findings indicate that DBP induces aberrant PTEN demethylation, leading to inhibition of the AKT pathway, which contributes to the reproductive toxicity.