Up-regulated tumor necrosis factor-associated factor 6 level is correlated with apoptosis in the rat cerebral ischemia and reperfusion

Gene Therapy for Chronic Traumatic Brain Injury: Challenges in Resolving Long-term Consequences of Brain Damage

The gene therapy is alluring not only for CNS disorders but also for other pathological conditions. Gene therapy employs the insertion of a healthy gene into the identified genome to replace or replenish genes responsible for pathological disorder or damage due to trauma. The last decade has seen a drastic change in the understanding of vital aspects of gene therapy. Despite the complexity of traumatic brain injury (TBI), the advent of gene therapy in various neurodegenerative disorders has reinforced the ongoing efforts of alleviating TBI-related outcomes with gene therapy. The review highlights the genes modulated in response to TBI and evaluates their impact on the severity and duration of the injury. We have reviewed strategies that pinpointed the most relevant gene targets to restrict debilitating events of brain trauma and utilize vector of choice to deliver the gene of interest at the appropriate site. We have made an attempt to summarize the long-term neurobehavioral consequences of TBI due to numerous pathometabolic perturbations associated with a plethora of genes. Herein, we shed light on the basic pathological mechanisms of brain injury, genetic polymorphism in individuals susceptible to severe outcomes, modulation of gene expression due to TBI, and identification of genes for their possible use in gene therapy. The review also provides insights on the use of vectors and challenges in translations of this gene therapy to clinical practices.

Bone Marrow Mesenchymal Stem Cell Exosomal miR-345-3p Ameliorates Cerebral Ischemia-reperfusion Injury by Targeting TRAF6

INTRODUCTION

The purpose of this study was to investigate the effects of bone marrow mesenchymal stem cells (BMSCs) exosomal miR-345-3p and tumor necrosis factor receptorassociated factor 6 (TRAF6) on cerebral ischemia reperfusion (CIR) injury. Exosomes (Exos) derived from BMSCs were isolated and identified. PC12 (rat pheochromocytoma) cells were used to establish an oxygen and glucose deprivation/reoxygenation (OGD/R) model.

METHODS

Cell counting kit-8, TUNEL staining, lactate dehydrogenase staining, RT-qPCR, and western blotting were utilized for analyzing the functions of miR-345-3p about PC12 cells. Dualluciferase reporter experiment was then to confirm the link between miR-345-3p and TRAF6. Finally, using male SD rats, the middle cerebral artery occlusion (MCAO) model was constructed. Regulation of I/R damage in MCAO rats of miR-345-3p and TRAF6 were further explored in the changes of modified neurological severity score, cerebral infarction pictures, relative infarct volume, and histopathological changes. After OGD/R treatment, neuronal apoptosis was dramatically increased. After treatment with exosomal miR-345-3p, OGD/R-induced neuroapoptosis was dramatically inhibited. Exosomal miR-345-3p inhibited OGD/R-induced neuroapoptosis by downregulating the expression of TRAF6. However, the miR-345-3p inhibitor aggravated the changes caused by OGD/R.

RESULTS

The corresponding regulations of miR-345-3p were reversed with TRAF6 overexpression. The animal experiments in vivo further verified that miR-345-3p ameliorated brain I/R injury in MCAO rats by targeting TRAF6.

CONCLUSION

This study found that BMSCs-exosomal miR-345-3p protected against CIR injury by decreasing TRAF6.

Transcriptome-based biomarker gene screening and evaluation of the extracellular fatty acid-binding protein (Ex-FABP) on immune and angiogenesis-related genes in chicken erythrocytes of tibial dyschondroplasia

BACKGROUND

Tibial dyschondroplasia (TD) is a bone disorder in which dead chondrocytes accumulate as a result of apoptosis and non-vascularization in the tibial bone of broiler chickens. The pathogenicity of TD is under extensive research but is yet not fully understood. Several studies have linked it to apoptosis and non-vascularization in the tibial growth plate (GP). We conceived the idea to find the differentially expressed genes (DEGs) in chicken erythrocytes which vary in expression over time using a likelihood-ratio test (LRT). Thiram was used to induce TD in chickens, and then injected Ex-FABP protein at 0, 20, and 50 μg^.kg^-1 to evaluate its therapeutic effect on 30 screened immunity and angiogenesis-related genes using quantitative PCR (qPCR). The histopathology was also performed in TD chickens to explore the shape, circularity, arrangements of chondrocytes and blood vessels.

RESULTS

Clinical lameness was observed in TD chickens, which decreased with the injection of Ex-FABP. Histopathological findings support Ex-FABP as a therapeutic agent for the morphology and vascularization of affected chondrocytes in TD chickens. qPCR results of 10 immunity (TLR2, TLR3, TLR4, TLR5, TLR7, TLR15, IL-7, MyD88, MHCII, and TRAF6) and 20 angiogenesis-related genes (ITGAV, ITGA2, ITGB2, ITGB3, ITGA5, IL1R1, TBXA2R, RPL17, F13A1, CLU, RAC2, RAP1B, GIT1, FYN, IQGAP2, PTCH1, NCOR2, VAV-like, PTPN11, MAML3) regulated when Ex-FABP is injected to TD chickens.

CONCLUSION

Immunity and angiogenesis-related genes can be responsible for apoptosis of chondrocytes and vascularization in tibial GP. Injection of Ex-FABP protein to thiram induced TD chickens decrease the chondrocytes damage and improves vascularization.

The circular RNA circ_0099630/miR-940/receptor-associated factor 6 regulation cascade modulates the pathogenesis of periodontitis

Background/purpose

Materials and methods

Results

Conclusion

Do pyroptosis, apoptosis, and necroptosis (PANoptosis) exist in cerebral ischemia? Evidence from cell and rodent studies

Some scholars have recently developed the concept of PANoptosis in the study of infectious diseases where pyroptosis, apoptosis and necroptosis act in consort in a multimeric protein complex, PANoptosome. This allows all the components of PANoptosis to be regulated simultaneously. PANoptosis provides a new way to study the regulation of cell death, in that different types of cell death may be regulated at the same time. To test whether PANoptosis exists in diseases other than infectious diseases, we chose cerebral ischemia/reperfusion injury as the research model, collected articles researching cerebral ischemia/reperfusion from three major databases, obtained the original research data from these articles by bibliometrics, data mining and other methods, then integrated and analyzed these data. We selected papers that investigated at least two of the components of PANoptosis to check its occurrence in ischemia/reperfusion. In the cell model simulating ischemic brain injury, pyroptosis, apoptosis and necroptosis occur together and this phenomenon exists widely in different passage cell lines or primary neurons. Pyroptosis, apoptosis and necroptosis also occurred in rat and mouse models of ischemia/reperfusion injury. This confirms that PANoptosis is observed in ischemic brain injury and indicates that PANoptosis can be a target in the regulation of various central nervous system diseases.

Screening of toll-like receptor signaling pathway-related genes and the response of recombinant glutathione S-transferase A3 protein to thiram induced apoptosis in chicken erythrocytes

The expression of genes related to the Toll-like receptors (TLRs) signaling pathway were determined. Group A, B and C fed with basal diet and group D, E and F induced TD by feeding a basal diet containing 100 mg·kg-1 thiram. rGSTA3 protein was injected at 20 μg·kg-1 in group B, E and at 50 μg·kg-1 in C, F. Results suggested that lameness and death of chondrocytes were significant on day 14. TLRs signaling pathway related genes were screened based on the transcriptome enrichment, and validated on qPCR. IL-7, TLR2, 3, 4, 5, 7, 15, MyD88, MHC-II, MDA5 and TRAF6 were significantly (p < 0.05) expressed in group E and F as compared to group D on day 14 and 23. IL-7, MHCII, TRAF6, TLR3, TLR5, TLR7, and TLR15 determined insignificant in group D compared to group A on day 23. TD occur in an early phase and alleviated in the later period. rGSTA3 protein can prevent apoptosis and repair degraded chondrocytes.

Gas6/Axl signaling attenuates alveolar inflammation in ischemia-reperfusion-induced acute lung injury by up-regulating SOCS3-mediated pathway

Background

Axl is a cell surface receptor tyrosine kinase, and activation of the Axl attenuates inflammation induced by various stimuli. Growth arrest-specific 6 (Gas6) has high affinity for Axl receptor. The role of Gas6/Axl signaling in ischemia-reperfusion-induced acute lung injury (IR-ALI) has not been explored previously. We hypothesized that Gas6/Axl signaling regulates IR-induced alveolar inflammation via a pathway mediated by suppressor of cytokine signaling 3 (SOCS3).

Methods

IR-ALI was induced by producing 30 min of ischemia followed by 90 min of reperfusion in situ in an isolated and perfused rat lung model. The rats were randomly allotted to a control group and IR groups, which were treated with three different doses of Gas6. Mouse alveolar epithelium MLE-12 cells were cultured in control and hypoxia-reoxygenation (HR) conditions with or without Gas6 and Axl inhibitor R428 pretreatment.

Results

We found that Gas6 attenuated IR-induced lung edema, the production of proinflammatory cytokines in perfusates, and the severity of ALI ex vivo. IR down-regulated SOCS3 expression and up-regulated NF-κB, and Gas6 restored this process. In the model of MLE-12 cells with HR, Gas6 suppressed the activation of TRAF6 and NF-κB by up-regulating SOCS3. Axl expression of alveolar epithelium was suppressed in IR-ALI but Gas6 restored phosphorylation of Axl. The anti-inflammatory effect of Gas6 was antagonized by R428, which highlighted that phosphorylation of Axl mediated the protective role of Gas6 in IR-ALI.

Conclusions

Gas6 up-regulates phosphorylation of Axl on alveolar epithelium in IR-ALI. The Gas6/Axl signaling activates the SOCS3-mediated pathway and attenuates IR-related inflammation and injury.

TRAF6-p38/JNK-ATF2 axis promotes microglial inflammatory activation

Activating transcription factor 2 (ATF2), a member of the alkaline-leucine zipper family, is widely expressed in various tissues, and reportedly involved in inflammatory responses to various irritates, but its role in the central nervous system (CNS) remains unclear. This study aimed to investigate the expression and biological function of ATF2 in CNS inflammation. Utilizing the LPS-induced neuroinflammation model on mice, we first found ATF2 up-regulation and its co-localization with microglia in inflamed mice brain. In vitro, we revealed an increased expression, phosphorylation, and nuclear accumulation of ATF2 in LPS-treated BV2 microglia cells. Inhibiting ATF2 significantly decreased the expression of pro-inflammatory factors in LPS-treated microglia, and alleviated neuronal apoptosis induced by the conditioned medium of activated microglia. Knocking down TRAF6, an important adaptor of the TLR4/MAPK/NF-κB signaling pathway, suppressed the LPS-induced ATF2 expression and phosphorylation, accompanied by the decreased p38/JNK phosphorylation, in microglia. Blocking p38 or JNK signaling pathway by the specific inhibitors reversed the TRAF6-overexpression mediated ATF2 activation. Taken together, our data first proved the pro-inflammatory function of ATF2 in microglia, and suggested that the TRAF6-JNK/p38-ATF2 axis might promote microglial inflammatory activation and thus aggravate neuronal injury in brain, which might become a potential therapeutic target for CNS diseases.

Roles of TRAF6 in Central Nervous System

Tumor necrosis factor receptor-associated factor (TRAF) is an important binding protein of tumor necrosis factor (TNF) superfamily and the toll/IL-1 receptor (TIR) superfamily, which play an important role in innate immunity and acquired immunity. TRAFs family have 7 members (TRAF1-7), and TRAF6 has its special facture and biological function. TRAF6 has two special domains: C-terminal domain and N-terminal domain, which could integrate with multiple kinases and regulate signaling pathway function as an E3 ubiquitin ligase. Studies have increasingly found that TRAF6 is closely related to central nervous system diseases, such as stroke, Traumatic brain injury, neurodegenerative diseases and neuropathic pain. Further research on the pathophysiological mechanism may be expected to become the new targets for the treatment of central nervous system diseases.

The Ubiquitin E3 Ligase TRAF6 Exacerbates Ischemic Stroke by Ubiquitinating and Activating Rac1

Stroke is one of the leading causes of morbidity and mortality worldwide. Inflammation, oxidative stress, apoptosis, and excitotoxicity contribute to neuronal death during ischemic stroke; however, the mechanisms underlying these complicated pathophysiological processes remain to be fully elucidated. Here, we found that the expression of tumor necrosis factor receptor-associated factor 6 (TRAF6) was markedly increased after cerebral ischemia/reperfusion (I/R) in mice. TRAF6 ablation in male mice decreased the infarct volume and neurological deficit scores and decreased proinflammatory signaling, oxidative stress, and neuronal death after cerebral I/R, whereas transgenic overexpression of TRAF6 in male mice exhibited the opposite effects. Mechanistically, we demonstrated that TRAF6 induced Rac1 activation and consequently promoted I/R injury by directly binding and ubiquitinating Rac1. Either functionally mutating the TRAF6 ubiquitination site on Rac1 or inactivating Rac1 with a specific inhibitor reversed the deleterious effects of TRAF6 overexpression during I/R injury. In conclusion, our study demonstrated that TRAF6 is a key promoter of ischemic signaling cascades and neuronal death after cerebral I/R injury. Therefore, the TRAF6/Rac1 pathway might be a promising target to attenuate cerebral I/R injury.SIGNIFICANCE STATEMENT Stroke is one of the most severe and devastating neurological diseases globally. The complicated pathophysiological processes restrict the translation of potential therapeutic targets into medicine. Further elucidating the molecular mechanisms underlying cerebral ischemia/reperfusion injury may open a new window for pharmacological interventions to promote recovery from stroke. Our study revealed that ischemia-induced tumor necrosis factor receptor-associated factor 6 (TRAF6) upregulation binds and ubiquitinates Rac1 directly, which promotes neuron death through neuroinflammation and neuro-oxidative signals. Therefore, precisely targeting the TRAF6-Rac1 axis may provide a novel therapeutic strategy for stroke recovery.

Socs1 and Socs3 degrades Traf6 via polyubiquitination in LPS-induced acute necrotizing pancreatitis

Mechanisms involved in inflammatory development during acute pancreatitis (AP) are largely vague, especially in the transformation of acute edematous pancreatitis (AEP) into acute necrotizing pancreatitis (ANP). This current study aims to investigate the functions of Traf6 in different AP models in vitro and in vivo, and to identify the possible regulatory mechanism in the progression of inflammation from mild to severe. Our data revealed that the level of Traf6 expression was significantly increased in the mild AP induced by caerulein, and the upregulation of Traf6 played a protective role in acinar cells against caerulein-induced apoptosis. In contrast, only Traf6 protein but not mRNA was downregulated in the severe ANP induced by combination treatment of caerulein and LPS. Mechanistic studies showed that LPS upregulated the levels of Socs1 and Socs3 expressions in acinar cells, Socs1 and Socs3 interacted Traf6 directly and degraded Traf6 protein via polyubiquitination, thereby counteracted the protective function of Traf6. In vivo study further showed that combination treatment of caerulein and LPS failed to induce an ANP model in the TLR4 knockout mice, and the level of Traf6 expression in the pancreatic tissues remained the same as that from the acute edematous pancreatitis (AEP) mouse. Taken together, our study reveals that Traf6 functioned as a protective factor in the progression of AP, and LPS-induced Socs1 and Socs3 exacerbate mild AP to severe AP, which provides evidence for developing a new therapeutic target to combat AP.

Association Between TRAF6 Gene Polymorphisms and Susceptibility of Ischemic Stroke in Southern Chinese Han Population

The tumor necrosis factor receptor-associated factor 6 (TRAF6) gene encodes a protein that acts downstream of the Toll-like receptor (TLR) pathway. TLRs activate inflammatory cascades and mediate inflammatory injury after cerebral ischemia. However, the role of TFAR6 gene polymorphisms in ischemic stroke (IS) remains unknown. This study aims to investigate the associations of TRAF6 gene polymorphisms with susceptibility to IS and IS-related quantitative traits in Southern Chinese Han population. A total of 816 IS cases and 816 age- and gender-matched controls were included. Two variants of the TRAF6 gene (rs5030411 and rs5030416) were genotyped using the Sequenom MassARRAY iPLEX platform. Our study showed that rs5030416 was significantly associated with increased susceptibility to IS in the additive model [ORadj 1.25(1.04-1.51), P adj = 0.019, P Bc = 0.038] and dominant model [ORadj 1.23(1.04-1.60), P adj = 0.021, P Bc = 0.042] after adjusting by age and sex and applying a Bonferroni correction. No significant association was found between rs5030411 and IS susceptibility (all P > 0.05). The haplotype rs5030416 (allele C)-rs5030411 (allele C) was significantly associated with IS susceptibility (P adj = 0.015). Moreover, a significant association of rs5030411 with TC levels in IS patients under the additive model [β 0.16(0.01-0.30), P adj = 0.034] and recessive model [β 0.45(0.12-0.78), P adj = 0.007] was observed after adjustment by age and sex. This association remained statistically significant under the recessive model (P Bc = 0.042) after Bonferroni correction. Our results suggest that TRAF6 gene polymorphisms may be involved in the pathogenesis of IS.

miR-146a ameliorates liver ischemia/reperfusion injury by suppressing IRAK1 and TRAF6

A critical role of the Toll-like receptor(TLR) and its downstream molecules, including IL-1 receptor-associated kinase 1(IRAK1) and tumor necrosis factor receptor- associated factor 6(TRAF6), in the pathogenesis of liver ischemia/reperfusion (I/R) injury has been documented. Recently a microRNA, miR-146a, was identified as a potent negative regulator of the TLR signaling pathway. In this study, we investigated the role of miR-146a to attenuate TLR signaling and liver I/R injury in vivo and in vitro. miR-146a was decreased in mice Kupffer cells following hepatic I/R, whereas IRAK1 and TRAF6 increased. Overexpression of miR-146a directly decreased IRAK1 and TRAF6 expression and attenuated the release of proinflammatory cytokines through the inactivation of NF-κB P65 in hypoxia/reoxygenation (H/R)-induced macrophages, RAW264.7 cells. Knockdown experiments demonstrated that IRAK1 and TRAF6 are two potential targets for reducing the release of proinflammatory cytokines. Moreover, co-culture assays indicated that miR-146a decreases the apoptosis of hepatocytes after H/R. In vivo administration of Ago-miR-146a, a stable version of miR-146a in vivo, protected against liver injury in mice after I/R via inactivation of the TLR signaling pathway. We conclude that miR-146a ameliorates liver ischemia/reperfusion injury in vivo and hypoxia/reoxygenation injury in vitro by directly suppressing IRAK1 and TRAF6.

Neuroprotective effect of hydrogen-rich saline against neurologic damage and apoptosis in early brain injury following subarachnoid hemorrhage: possible role of the Akt/GSK3β signaling pathway

Backgrounds

Early brain injury (EBI) plays a key role in the pathogenesis of subarachnoid hemorrhage (SAH). Neuronal apoptosis is involved in the pathological process of EBI. Hydrogen can inhibit neuronal apoptosis and attenuate EBI following SAH. However, the molecular mechanism underlying hydrogen-mediated anti-apoptotic effects in SAH has not been elucidated. In the present study, we aimed to evaluate whether hydrogen alleviates EBI after SAH, specifically neuronal apoptosis, partially via the Akt/GSK3β signaling pathway.

Methods

Sprague-Dawley rats (n = 85) were randomly divided into the following groups: sham group (n = 17), SAH group (n = 17), SAH + saline group (n = 17), SAH + hydrogen-rich saline (HS) group (n = 17) and SAH + HS + Ly294002 (n = 17) group. HS or an equal volume of physiological saline was administered immediately after surgery and repeated 8 hours later. The PI3K inhibitor, Ly294002, was applied to manipulate the proposed pathway. Neurological score and SAH grade were assessed at 24 hours after SAH. Western blot was used for the quantification of Akt, pAkt, GSK3β, pGSK3β, Bcl-2, Bax and cleaved caspase-3 proteins. Neuronal apoptosis was identified by double staining of terminal deoxynucleotidyl transferase mediated nick end labeling (TUNEL) staining and NeuN, and quantified by apoptosis index. Immunohistochemistry and immunofluorescent double-labeling staining was performed to clarify the relationships between neuronal apoptosis and pAkt or pGSK3β.

Results

HS significantly reduced neuronal apoptosis and improved neurological function at 24 hours after SAH. The levels of pAkt and pGSK3β, mainly expressed in neurons, were markedly up-regulated. Additionally, Bcl-2 was significantly increased while Bax and cleaved caspase-3 was decreased by HS treatment. Double staining of pAkt and TUNEL showed few colocalization of pAkt-positive cells and TUNEL-positive cells. The inhibitor of PI3K, Ly294002, suppressed the beneficial effects of HS.

Conclusions

HS could attenuate neuronal apoptosis in EBI and improve the neurofunctional outcome after SAH, partially via the Akt/GSK3β pathway.