Yinlong Liu

Melatonin attenuates traumatic brain injury-induced inflammation: a possible role for mitophagy.

Melatonin functions as a crucial mediator of sterile neuroinflammation; however, the underlying mechanisms remain poorly understood. Dysfunctional mitochondria, a main source of reactive oxygen species, are impacted in inflammation activation. This study aimed to examine the effect of melatonin on inflammation via elimination of damaged mitochondria after controlled cortical impact, an in vivo model of traumatic brain injury (TBI). Here, we demonstrated that inhibition of mitophagy, the selective degradation of damaged mitochondria by autophagy, markedly enhanced inflammation induced by TBI. Melatonin treatment activated mitophagy through the mTOR pathway, then to attenuate TBI‐induced inflammation. Furthermore, treatment with melatonin significantly ameliorated neuronal death and behavioral deficits after TBI, while 3‐methyladenine reversed this effect by inhibiting mitophagy. Taken together, these results highlight a role for melatonin in protecting against TBI‐triggered immunopathology, which is accomplished by negatively regulating inflammation activation and IL‐1β secretion via the autophagy of damaged mitochondria.

Omega-3 fatty acids regulate NLRP3 inflammasome activation and prevent behavior deficits after traumatic brain injury

&NA; Omega‐3 fatty acids (&ohgr; − 3 FAs) attenuate inflammation and improve neurological outcome in response to traumatic brain injury (TBI), but the specific anti‐inflammatory mechanisms remain to be elucidated. Here we found that NLRP3 inflammasome and subsequent pro‐inflammatory cytokines were activated in human brains after TBI. Rats treated with &ohgr; − 3 FAs had significantly less TBI‐induced caspase‐1 cleavage and IL‐1&bgr; secretion than those with vehicle. G protein‐coupled receptor 40 (GPR40) was observed to be involved in this anti‐inflammation. GW1100, a GPR40 inhibitor, eliminated the anti‐inflammatory effect of &ohgr; − 3 FAs after TBI. &bgr;‐Arrestin‐2 (ARRB2), a downstream scaffold protein of GPR40, was activated to inhibit inflammation via directly binding with NLRP3 in the &ohgr; − 3 FAs treatment group. Interestingly, we also observed that &ohgr; − 3 FAs prevented NLRP3 mitochondrial localization, which was reversed by GW1100. Furthermore, &ohgr; − 3 FAs markedly ameliorated neuronal death and behavioral deficits after TBI, while GW1100 significantly suppressed this effect. Collectively, these data indicate that the GPR40‐mediated pathway is involved in the inhibitory effects of &ohgr; − 3 FAs on TBI‐induced inflammation and ARRB2 is activated to interact with NLRP3. HighlightsInflammation was readily observed in human brains after TBI in comparison to control.&ohgr;‐3 FAs ameliorate TBI‐induced inflammation and behavior deficits in part by inhibiting NLRP3 inflammasome activation.ARRB2 functions as a key regulator to directly bind with NLRP3 in the &ohgr;‐3 FA‐mediated inflammation.

Extracellular Signal-Regulated Kinase/Nuclear Factor-Erythroid2-like2/Heme Oxygenase-1 Pathway-Mediated Mitophagy Alleviates Traumatic Brain Injury-Induced Intestinal Mucosa Damage and Epithelial Barrier Dysfunction.

Gastrointestinal dysfunction is one of several physiologic complications in patients with traumatic brain injury (TBI). TBI can result in increased intestinal permeability resulting from apoptosis of intestinal epithelial cells, which contain a large number of mitochondria for persisting barrier function. Autophagy of damaged mitochondria (mitophagy) controls the quality of the mitochondria and regulates cellular homeostasis. However, the exact mechanism of mitophagy that underlies the pathological changes induced by TBI is unknown. Here, we report that mitophagy decreases the intestinal epithelial cell damage and apoptosis that are activated in a rat model of controlled cortical impact (CCI). CCI-induced mitophagy is associated with an increase in 3-nitrotyrosine and 4-hydroxynonenal, indicating that oxidative stress may increase in response to mitochondrial disturbance. CCI also results in the expression of the tight junction proteins zonula occludens-1 (ZO-1) and occludin, which may regulate the in vivo intestinal hyperpermeability induced by CCI. Additionally, CCI-induced mitophagy was shown to be mediated by the oxidative stress-related extracellular signal-regulated kinase (ERK)/nuclear factor-erythroid2-like2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway, which may serve to reduce the apoptosis induced by oxidative stress. These results suggest that CCI-induced mitophagy serves to diminish apoptosis-mediated intestinal epithelial cell damage and to improve intestinal permeability, via ERK/Nrf2/HO-1 signaling. These findings may be useful in the design of rational approaches for the prevention and treatment of symptoms associated with TBI.

CBX7 negatively regulates migration and invasion in glioma via Wnt/β-catenin pathway inactivation

CBX7, a member of the Polycomb-group proteins, plays a significant role in normal and cancerous tissues and has been defined as a tumor suppressor in thyroid, breast and pancreatic cancers. However, its function in glioma remains undefined. CBX7 expression is decreased in glioma, especially in higher grade cases, according to data in the CGGA, GSE16001 and TCGA databases. Further experimental evidence has shown that exogenous CBX7 overexpression induced apoptosis and inhibited cell proliferation, colony formation and migration of glioma cells. In this study, we show that the invasive ability of glioma cells was decreased following CBX7 overexpression and CBX7 overexpression was associated with Wnt/β-catenin pathway inhibition, which also decreased downstream expression of ZEB1, a core epithelial-to-mesenchymal transition factor. This reduction in Wnt signaling is controlled by DKK1, a specific Wnt/β-catenin inhibitor. CBX7 enhances DKK1 expression by binding the DKK1 promoter, as shown in Luciferase reporter assays. Our data confirm that CBX7 inhibits EMT and invasion in glioma, which is manifested by influencing the expression of MMP2, MMP9, E-cadherin, N-cadherin and Vimentin in LN229, T98G cells and primary glioma cells (PGC). Furthermore, as a tumor suppressor, CBX7 expression is pivotal to reduce tumor invasion and evaluate prognosis.

ERK1/2/mTOR/Stat3 pathway-mediated autophagy alleviates traumatic brain injury-induced acute lung injury

Acute lung injury (ALI) is one of several complications in patients with traumatic brain injury (TBI). Autophagy is a primary homeostatic process that promotes cell survival under stress. Accumulating evidence implicates autophagy in the pathogenesis of ALI under various conditions. However, the role of autophagy in TBI-induced ALI remains unknown. The aim of this study was to adjust autophagy with pharmacological agents to determine its functional significance in TBI-induced ALI. Rats were preconditioned with autophagy promoter rapamycin or inhibitor 3-methyladenine before they were challenged with TBI. Extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor U0126, mechanistic target of rapamycin (mTOR) inhibitor rapamycin, and signal transducer and activator of transcription 3 (Stat3) inhibitor S31-201 were used to test the role of ERK1/2/mTOR/Stat3 signaling pathway in regulating autophagy. Autophagy is activated in lung tissues after TBI. Enhancement of autophagy suppressed apoptosis, inflammation and oxidative stress in lung tissues, which were activated after TBI, whereas inhibition of autophagy aggravated these critical pathological changes. Autophagy also improved TBI-induced impairment in pulmonary barrier function, oxygenation function and static compliance. Furthermore, TBI-induced autophagy was mediated by ERK1/2/mTOR/Stat3 pathway, which may serve to reduce ALI and improve pulmonary barrier function, oxygenation function and static compliance. These findings are important for the prevention and treatment of TBI-induced ALI.

MicroRNA-98 Attenuates Cell Migration and Invasion in Glioma by Directly Targeting Pre-B Cell Leukemia Homeobox 3

Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults. The extraordinary invasion of human GBM into adjacent normal brain tissues contributes to treatment failure. However, the mechanisms that control this process remain poorly understood. Increasing evidence has demonstrated that microRNAs are strongly implicated in the migration and invasion of GBM. In this study, we found that microRNA-98 (miR-98) was markedly downregulated in human glioma tissues and cell lines. Functional experiments indicated that restored expression of miR-98 attenuated glioma cell invasion and migration, whereas depletion of miR-98 promoted glioma cell invasion and migration. Subsequent investigation showed that pre-B-cell leukemia homeobox 3 (PBX3), an important transcription factor that controls tumor invasion, was a direct and functional target of miR-98 in GBM cells. Consistently, an orthotopic mouse model also demonstrated the suppressive effects of miR-98 overexpression on tumor invasion and PBX3 expression. Silencing of PBX3 using small interfering RNA inhibited the migratory and invasive capacities of glioma cells, whereas reintroduction of PBX3 into glioma cells reversed the anti-invasive function of miR-98. Furthermore, depletion of PBX3 phenocopied the effects of miR-98 overexpression in vivo. Finally, quantitative real-time polymerase chain reaction results showed that miR-98 was negatively correlated with PBX3 expression in 24 glioma tissues. Thus, we propose that PBX3 modulation by miR-98 has an important role in regulating GBM invasion and may serve as therapeutic target for GBM.

Sex-related differences in striatal dopaminergic system after traumatic brain injury.

Several studies have demonstrated alterations in the dopamine (DA) system after traumatic brain injury (TBI). Additionally, the existence of significant sex-related differences in the dopaminergic system has long been recognized. Accordingly, the purpose of the present study was to investigate whether TBI would differentially alter, in female and male mice, the expression and the function of the striatal vesicular monoamine transporter-2 (VMAT-2), an important DA transporter. After controlled cortical impact (CCI) injury, female mice showed significantly lower striatal DA concentrations and K(+)-evoked DA output. By contrast, no significant sex-related differences were observed in the mRNA and protein levels of striatal dopamine transporter (DAT) and VMAT-2 and the methamphetamine (MA)-evoked DA output. These results demonstrated clear sex-related differences in striatal VMAT-2 function in response to TBI and suggested that female mice may be more sensitive to the TBI-induced inhibition of the VMAT-2 function, as indicated by the greater degree of deficits observed when the VMAT-2 DA-storage function was inhibited by TBI. Moreover, the TBI-induced suppression of locomotion was more pronounced than female mice. Such findings highlight the need for sex-specific considerations when examining differences among brain injury conditions.

PBX3/MEK/ERK1/2/LIN28/let-7b positive feedback loop enhances mesenchymal phenotype to promote glioblastoma migration and invasion

BackgroundBrain invasion by glioblastoma (GBM) determines recurrence and prognosis in patients, which is, in part, attributed to increased mesenchymal transition. Here, we report evidence favoring such a role for the Pre-B-cell leukemia homebox (PBX) family member PBX3.MethodsWestern blot, immunohistochemistry, qRT-PCR and datasets mining were used to determined proteins or genes expression levels. Wound-healing and transwell assays were used to examine the invasive abilities of GBM cells. Dual-luciferase reporter assays were used to determine how let-7b regulates PBX3. Chromatin-immunoprecipitation (ChIP) and rescue experiments were performed to investigate the involved molecular mechanisms. Orthotopic mouse models were used to assess the role of PBX3 in vivo.ResultsWe found that PBX3 expression levels positively correlated with glioma mesenchymal markers. Ectopic expression of PBX3 promoted invasive phenotypes and triggered the expression of mesenchymal markers, whereas depletion of PBX3 reduced GBM cell invasive abilities and decreased the expression of mesenchymal markers. In addition, inhibition of PBX3 attenuated transforming growth factor-β (TGFβ)-induced GBM mesenchymal transition. Mechanistic studies revealed that PBX3 mediated GBM mesenchymal transition through activation of MEK/ERK1/2, leading to increased expression of LIN28 by c-myc. Increased LIN28 inhibited let-7b biogenesis, which then promoted the pro-invasive genes, such as HMGA2 and IL-6. Furthermore, let-7b suppressed PBX3 by directly targeting 3′-UTR of PBX3. Thus, repressed let-7b by PBX3 amplifies PBX3 signaling and forms a positive feedback loop to promote GBM mesenchymal transition.ConclusionsThese data highlight the importance of PBX3 as a key driver of mesenchymal transition and potential therapeutic target.

Lowered iPLA 2 γ activity causes increased mitochondrial lipid peroxidation and mitochondrial dysfunction in a rotenone-induced model of Parkinson's disease

ABSTRACT iPLA2&ggr;, calcium‐independent phospholipase A2&ggr;, discerningly hydrolyses glycerophospholipids to liberate free fatty acids. iPLA2&ggr;‐deficiency has been associated with abnormal mitochondrial function. More importantly, the iPLA2 family is causative proteins in mitochondrial neurodegenerative disorders such as parkinsonian disorders. However, the mechanisms by which iPLA2&ggr; affects Parkinsons disease (PD) remain unknown. Mitochondrion stress has a key part in rotenone‐induced dopaminergic neuronal degeneration. The present evaluation revealed that lowered iPLA2&ggr; function provokes the parkinsonian phenotype and leads to the reduction of dopamine and its metabolites, lowered survival, locomotor deficiencies, and organismal hypersensitivity to rotenone‐induced oxidative stress. In addition, lowered iPLA2&ggr; function escalated the amount of mitochondrial irregularities, including mitochondrial reactive oxygen species (ROS) regeneration, reduced ATP synthesis, reduced glutathione levels, and abnormal mitochondrial morphology. Further, lowered iPLA2&ggr; function was tightly linked with strengthened lipid peroxidation and mitochondrial membrane flaws following rotenone treatment, which can cause cytochrome c release and eventually apoptosis. These results confirmed the important role of iPLA2&ggr;, whereby decreasing iPLA2&ggr; activity aggravates mitochondrial degeneration to induce neurodegenerative disorders in a rotenone rat model of Parkinsons disease. These findings may be useful in the design of rational approaches for the prevention and treatment of PD‐associated symptoms. HighlightsDecreasing iPLA2&ggr; activity deteriorated the outcome of rats and worsened PDsymptoms after rotenone treatment.Decreasing iPLA2&ggr; activity increased oxidative stress, which was accompanied by mitochondria disorders and apoptosis.iPLA2&ggr; functions as a protective enzyme in the midbrain during oxidative stress.

Activation of bradykinin B2 receptor induced the inflammatory responses of cytosolic phospholipase A2 after the early traumatic brain injury

Phospholipase A2 is a known aggravator of inflammation and deteriorates neurological outcomes after traumatic brain injury (TBI), however the exact inflammatory mechanisms remain unknown. This study investigated the role of bradykinin and its receptor, which are known initial mediators within inflammation activation, as well as the mechanisms of the cytosolic phospholipase A2 (cPLA2)-related inflammatory responses after TBI. We found that cPLA2 and bradykinin B2 receptor were upregulated after a TBI. Rats treated with the bradykinin B2 receptor inhibitor LF 16-0687 exhibited significantly less cPLA2 expression and related inflammatory responses in the brain cortex after sustaining a controlled cortical impact (CCI) injury. Both the cPLA2 inhibitor and the LF16-0687 improved CCI rat outcomes by decreasing neuron death and reducing brain edema. The following TBI model utilized both primary astrocytes and primary neurons in order to gain further understanding of the inflammation mechanisms of the B2 bradykinin receptor and the cPLA2 in the central nervous system. There was a stronger reaction from the astrocytes as well as a protective effect of LF16-0687 after the stretch injury and bradykinin treatment. The protein kinase C pathway was thought to be involved in the B2 bradykinin receptor as well as the cPLA2-related inflammatory responses. Rottlerin, a Protein Kinase C (PKC) δ inhibitor, decreased the activity of the cPLA2 activity post-injury, and LF16-0687 suppressed both the PKC pathway and the cPLA2 activity within the astrocytes. These results indicated that the bradykinin B2 receptor-mediated pathway is involved in the cPLA2-related inflammatory response from the PKC pathway.