Activation of the Omega-3 Fatty Acid Receptor GPR120 Protects against Focal Cerebral Ischemic Injury by Preventing Inflammation and Apoptosis in Mice.

G protein-coupled receptor 120 (GPR120) has been shown to negatively regulate inflammation and apoptosis, but its role in cerebral ischemic injury remains unclear. Using an in vivo model of middle cerebral artery occlusion (MCAO) and an in vitro model of oxygen-glucose deprivation (OGD), we investigated the potential role and molecular mechanisms of GPR120 in focal cerebral ischemic injury. Increased GPR120 expression was observed in microglia and neurons following MCAO-induced ischemia in wild type C57BL/6 mice. Treatment with docosahexaenoic acid (DHA) inhibited OGD-induced inflammatory response in primary microglia and murine microglial BV2 cells, whereas silencing of GPR120 strongly exacerbated the inflammation induced by OGD and abolished the anti-inflammatory effects of DHA. Mechanistically, DHA inhibited OGD-induced inflammation through GPR120 interacting with ß-arrestin2. In addition to its anti-inflammatory function, GPR120 also played a role in apoptosis as its knockdown impaired the antiapoptotic effect of DHA in OGD-induced rat pheochromocytoma (PC12) cells. Finally, using MCAO mouse model, we demonstrated that GPR120 activation protected against focal cerebral ischemic injury by preventing inflammation and apoptosis. Our study indicated that pharmacological targeting of GPR120 may provide a novel approach for the treatment of patients with ischemic stroke.

ß-Arrestin-2-ERK1/2 cPLA2α axis mediates TLR4 signaling to influence eicosanoid induction in ischemic brain.

LPS has been shown to elicit neuroinflammation associated with the up-regulation of the eicosanoid pathway in animal models; however, the regulatory mechanisms of TLR4 in brain neuroinflammatory conditions remain elusive. ß-Arrestins are key regulators of the GPCR signaling pathway and are involved in the leukotriene B4-induced leukocyte migration to initiate inflammatory response. However, the roles of ß-arrestins in eicosanoid regulation and related diseases are not clear. To address this issue, we conducted a study to investigate the effect of TLR4 on the eicosanoid pathway in ischemic stroke brain and to explore the underlying molecular regulation mechanism. Cerebral ischemia was produced by occlusion of the middle cerebral artery, followed by reperfusion for 24 h. We demonstrated that knockout of TLR4 improves ischemic stroke brain associated with eicosanoid down-regulation. Interestingly, genetic disruption of ß-arrestin-2 failed to decrease neuroinflammation in the damaged brain of TLR4-/- mice, which indicates the requirement of ß-arrestin-2 for TLR4 knockdown protection. Further study showed that the negative regulation of phosphorylated (phospho-)ERK1/2 and phospho-cytosolic phospholipase A2 α (cPLA2α) by TLR4 deficiency was eliminated by genetic disruption of ß-arrestin-2. In addition, ß-arrestin-2 deficiency reversed the reduction of colocalization of phospho-ERK1/2 with phospho-cPLA2α in TLR4-/- mice following ischemic stroke. Mechanistic studies indicated that ß-arrestin-2 specifically colocalized and associated with ERK1/2 to prevent ERK1/2-dependent cPLA2α activation following ischemic injury, and ß-arrestin-2 deficiency blocked the negative regulation of phospho-ERK1/2, revived the association of phospho-ERK1/2 with phospho-cPLA2α, and subsequently increased the prostaglandin E2 and thromboxane A2 production remarkably. Our findings may provide novel insights that ß-arrestin-2 is responsible for ischemic brain improvement in TLR4-/- mice via negative regulation of eicosanoid production.-Xiang, Y., Wei, X., Du, P., Zhao, H., Liu, A., Chen, Y. ß-Arrestin-2-ERK1/2 cPLA2α axis mediates TLR4 signaling to influence eicosanoid induction in ischemic brain.

TREM2 deficiency aggravates α-synuclein-induced neurodegeneration and neuroinflammation in Parkinson's disease models.

Variants in the gene encoding the triggering receptor expressed on myeloid cells 2 (TREM2) are known to increase the risk of developing Alzheimer disease and Parkinson's disease (PD). However, the potential role of TREM2 effect on synucleinopathy has not been characterized. In this study, we investigated whether loss of TREM2 function affects α-synucleinopathy both in vitro and in vivo. In vitro, BV2 microglial cells were exposed to α-synuclein (α-syn) in the presence or absence of TREM2 small interference RNA. For in vivo studies, wild-type controls and TREM2 gene knockout mice were intracranially injected in the substantia nigra with adeno-associated viral vectors expressing human α-syn (AAV-SYN) to induce PD. Our results revealed that knockdown of TREM2 aggravated α-syn-induced inflammatory responses in BV2 cells and caused greater apoptosis in SH-SY5Y cells treated with BV2-conditioned medium. In mice, TREM2 knockout exacerbated dopaminergic neuron loss in response to AAV-SYN. Moreover, both in vitro and in vivo TREM2 deficiency induced a shift from an anti-inflammatory toward a proinflammatory activation status of microglia. These data suggest that impairing microglial TREM2 signaling aggravates proinflammatory responses to α-syn and exacerbates α-syn-induced neurodegeneration by modulating microglial activation state.-Guo, Y., Wei, X., Yan, H., Qin, Y., Yan, S., Liu, J., Zhao, Y., Jiang, F., Lou, H. TREM2 deficiency aggravates α-synuclein-induced neurodegeneration and neuroinflammation in Parkinson's disease models.

ß-arrestin 2 negatively regulates NOD2 signalling pathway through association with TRAF6 in microglia after cerebral ischaemia/reperfusion injury.

We previously reported that nucleotide-binding oligomerization domain-containing protein (NOD) 2 was involved in the inflammatory responses to cerebral ischaemia/reperfusion (I/R) insult. However, the mechanism by which NOD2 participates in brain ischaemic injury and the regulation of NOD2 in the process are still obscure. Increased ß-arrestin 2 (ARRB2) expression was observed in microglia following cerebral I/R in wild-type mice besides the up-regulation of NOD2 and TRAF6. Stimulation of NOD2 by muramyl dipeptide (MDP) in BV2 cells induced the activation of NF-κB by the phosphorylation of p65 subunit and the degradation of IκBα. Meanwhile, the protein level of Cyclooxygenase-2 (COX-2), the protein expression and activity of MMP-9 were significantly increased in BV2 cells after administration of MDP. Furthermore, overexpression of ARRB2 significantly suppressed the inflammation induced by MDP, silence of ARRB2 significantly enhanced the inflammation induced by MDP in BV2 cells. In addition, we observed endogenous interaction of TRAF6 and ARRB2 after stimulation of MDP or cerebral I/R insult, indicating ARRB2 negatively regulates NOD2-triggered inflammatory signalling pathway by associating with TRAF6 in microglia after cerebral I/R injury. Finally, the in vivo study clearly confirmed that ARRB2 negatively regulated NOD2-induced inflammatory response, as ARRB2 deficiency exacerbated stroke outcomes and aggravated the NF-κB signalling pathway induced by NOD2 stimulation after cerebral I/R injury. These findings revealed ARRB2 negatively regulated NOD2 signalling pathway through the association with TRAF6 in cerebral I/R injury.

TIPE1 suppresses invasion and migration through down-regulating Wnt/ß-catenin pathway in gastric cancer.

Epithelial-mesenchymal transition (EMT) plays an important role in the invasiveness and metastasis of gastric cancer. Therefore, identifying key molecules involved in EMT will provide new therapeutic strategy for treating patients with gastric cancer. TIPE1 is a newly identified member of the TIPE (TNFAIP8) family, and its contributions to progression and metastasis have not been evaluated. In this study, we found that the levels of TIPE1 were significantly reduced and inversely correlated with differentiation status and distant metastasis in primary gastric cancer tissues. We further observed overexpression of TIPE1 in aggressive gastric cancer cell lines decreased their metastatic properties both in vitro and in vivo as demonstrated by markedly inhibiting EMT and metastasis of gastric cancer cells in nude mice. Consistently, gene silencing of TIPE1 in well-differentiated gastric cancer cell line (AGS) inhibited these processes. Mechanistically, we found that TIPE1-medicated Wnt/ß-catenin signalling was one of the critical signal transduction pathways that link TIPE1 to EMT inhibition. Importantly, TIPE1 dramatically restrained the expression and activities of MMP2 and MMP9 which are demonstrated to promote tumour progression and are implicated in EMT. Collectively, these findings provide new evidence for a better understanding of the biological activities of TIPE1 in progression and metastasis of gastric cancer and suggest that TIPE1 may be an innovative diagnostic and therapeutic target of gastric cancer.

NOD2 promotes dopaminergic degeneration regulated by NADPH oxidase 2 in 6-hydroxydopamine model of Parkinson's disease.

BACKGROUND: In Parkinson's disease (PD), loss of striatal dopaminergic (DA) terminals and degeneration of DA neurons in the substantia nigra (SN) are associated with inflammation. Nucleotide-binding oligomerization domain-containing protein (NOD)2, one of the first discovered NOD-like receptors, plays an important role in inflammation. However, the role of NOD2 has not been elucidated in PD. METHODS: NOD2 mRNA and protein expression in the SN and the striatum of C57BL/6 mice treated with 6-hydroxydopamine (6-OHDA) was measured. We next investigated the potential contribution of the NOD2-dependent pathway to 6-OHDA-induced DA degeneration using NOD2-deficient (NOD2-/-) mice. Assays examining DA degeneration and inflammation include HPLC, Western blot, immunohistochemistry, TUNEL staining, and cytometric bead array. To further explore a possible link between NADPH oxidase 2 (NOX2) and NOD2 signaling in PD, microglia were transfected with shRNA specific to NOX2 in vitro and apocynin were given to mice subjected to 6-OHDA and muramyl dipeptide (MDP) striatal injection. RESULTS: The expression of NOD2 was upregulated in an experimental PD model induced by the neurotoxin 6-OHDA. NOD2 deficiency resulted in a protective effect against 6-OHDA-induced DA degeneration and neuronal death, which was associated with the attenuated inflammatory response. Moreover, silencing of NOX2 in microglia suppressed the expression of NOD2 and the inflammatory response induced by 6-OHDA and attenuated the toxicity of conditioned medium from 6-OHDA or MDP-stimulated microglia to neuronal cells. Furthermore, apocynin treatment inhibited NOD2 upregulation and DA degeneration in the SN of WT mice induced by 6-OHDA and MDP. CONCLUSION: This study provides the direct evidence that NOD2 is related to 6-OHDA-induced DA degeneration through NOX2-mediated oxidative stress, indicating NOD2 is a novel innate immune signaling molecule participating in PD inflammatory response.

FTY720 Attenuates 6-OHDA-Associated Dopaminergic Degeneration in Cellular and Mouse Parkinsonian Models.

FTY720 (fingolimod) is the first oral drug approved for treating relapsing-remitting forms of multiple sclerosis. It is also protective in other neurological models including ischemia, Alzheimer's disease, Huntington disease and Rett syndrome. However, whether it might protect in a 6-hydroxydopamine (6-OHDA) mouse model associated with the dopaminergic pathology of Parkinson's disease (PD), has not been explored. Therefore, in the present study, we investigated the effects of FTY720 on 6-OHDA-induced neurotoxicity in cell cultures and mice. Here we show that FTY720 protected against 6-OHDA cytotoxicity and apoptosis in SH-SY5Y cells. We also show that prior administration of FTY720 to 6-OHDA lesioned mice ameliorated both motor deficits and nigral dopaminergic neurotoxicity, while also reducing 6-OHDA-associated inflammation. The protective effects of FTY720 were associated with activation of AKT and ERK1/2 pro-survival pathways and an increase in brain derived neurotrophic factor (BDNF) expression in vitro and in vivo. These findings suggest that FTY720 holds promise as a PD therapeutic acting, at least in part, through AKT/ERK1/2/P-CREB-associated BDNF expression.

Tetramethylpyrazine Analogue CXC195 Protects Against Dopaminergic Neuronal Apoptosis via Activation of PI3K/Akt/GSK3ß Signaling Pathway in 6-OHDA-Induced Parkinson's Disease Mice.

Parkinson's disease (PD) is a progressive neurodegenerative disorder and characterized by motor system disorders resulting in loss of dopaminergic (DA) neurons. CXC195, a novel tetramethylpyrazine derivative, has been shown strongest neuroprotective effects due to its anti-apoptotic activity. However, whether CXC195 protects against DA neuronal damage in PD and the mechanisms underlying its beneficial effects are unknown. The purpose of our study was to investigate the potential neuroprotective role of CXC195 and to elucidate its mechanism of action against 6-hydroxydopamine (6-OHDA)-induced mouse model of PD. CXC195 administration improved DA neurodegeneration in PD mice induced by 6-OHDA. Our further findings confirmed treatment of CXC195 at the dose of 10 mg/kg significantly inhibited the apoptosis by decreasing the level of cleaved caspase-3 and Bax, and increasing the level of Bcl-2 in 6-OHDA-lesioned mice. Meanwhile, 6-OHDA also decreased the amount of phosphorylated Akt while increased GSK-3ß activity (the amount of phosphorylated GSK-3ß at Ser9 was decreased) which was prevented by CXC195. Wortmannin, a specific PI3K inhibitor, dramatically abolished the changes induced by CXC195. Our study firstly demonstrated that CXC195 protected against DA neurodegeneration in 6-OHDA-induced PD model by its anti-apoptotic properties and PI3K/Akt/GSK3ß signaling pathway was involved in it.

HDAC9 exacerbates endothelial injury in cerebral ischaemia/reperfusion injury.

Histone deacetylase (HDAC) 9, a member of class II HDACs, regulates a wide variety of normal and abnormal physiological functions, which is usually expressed at high levels in the brain and skeletal muscle. Although studies have highlighted the importance of HDAC-mediated epigenetic processes in the development of ischaemic stroke and very recent genome-wide association studies have identified a variant in HDAC9 associated with large-vessel ischemic stroke, the molecular events by which HDAC9 induces cerebral injury keep unclear. In this study, we found that HDAC9 was up-regulated in the ischaemic cerebral hemisphere after cerebral ischaemia/reperfusion (I/R) injury in rats and in vivo gene silencing of HDAC9 by recombinated lentivirus infection in the brain reduced cerebral injury in experimental stroke. We further demonstrated that HDAC9 contributed to oxygen-glucose deprivation-induced brain microvessel endothelial cell dysfunction as demonstrated by the increased inflammatory responses, cellular apoptosis and endothelial cell permeability dysfunction accompanied by reduced expression of tight-junction proteins. We further found that HDAC9 suppressed autophagy, which was associated with endothelial dysfunction. This study for the first time provides direct evidence that HDAC9 contributes to endothelial cell injury and demonstrates that HDAC9 is one of critical components of a signal transduction pathway that links cerebral injury to epigenetic modification in the brain.

NLRP2 is highly expressed in a mouse model of ischemic stroke.

Nucleotide binding oligomerization domain (NOD)-like receptors (NLRs) are a class of cytoplasmic pattern-recognition receptors with a major role in innate immunity. Fourteen of the twenty-two human NLRs contain a pyrin domain and form the NLRP subfamily (NLRPs). Among NLRPs, NLRP2 is less well-understood in aspects of distribution and functions, especially in central nervous system (CNS). This study was the first to explore the expression of NLRP2 in central nervous system both under normal conditions and in ischemic stroke models. We found NLRP2 protein had a basal level of expression in CNS, mainly in astrocytes and was significantly elevated in ischemic brains in vivo or oxygen-glucose deprivation-treated cells in vitro. And silencing of NLRP2 genes could reduce the apoptotic rate of oxygen-glucose deprivation-treated cells. Thus high expression of NLRP2, especially in astrocytes, may play important roles in the pathophysiological process of ischemic stroke and has potential clinical value for the treatment of ischemic stroke.

Neuroprotective Effects of Tanshinone I Against 6-OHDA-Induced Oxidative Stress in Cellular and Mouse Model of Parkinson's Disease Through Upregulating Nrf2.

In this study, we investigated whether tanshinone I (T-I) has therapeutic effects in cellular and animal model of Parkinson's disease (PD), and explore its possible mechanism. For this purpose, human neuroblastoma SH-SY5Y cells were cultured and exposed to 100 µM 6-hydroxydopamine (6-OHDA) in the absence or presence of T-I (1, 2.5 and 5 µM). The results revealed that 6-OHDA-induced cell death was reduced by T-I pretreatment as measured by MTT assay, lactate dehydrogenase release and flow cytomety analysis of cell apoptosis. The increase in the reactive oxygen species caused by 6-OHDA treatment was also attenuated by T-I in SH-SY5Y cells. T-I pretreatment was also shown to result in an increase in nuclear factor erythroid-2-related factor 2 (Nrf2) protein levels and its transcriptional activity as well as the upregulation of Nrf2-dependent genes encoding the antioxidant enzymes heme oxygenase-1, glutathione cysteine ligase regulatory subunit and glutathione cysteine ligase modulatory subunit in SH-SY5Y cells. Moreover, in the in vivo experiment, T-I treatment significantly attenuated 6-OHDA-induced striatal oxidative stress and ameliorated dopaminergic neurotoxicity in 6-OHDA-lesioned mice, as evidenced by western blot analysis of tyrosine hydroxylase (TH) and TH immunostaining of dopaminergic neurons in the substantia nigra and the striatum. Taken together, the results suggest that T-I may be beneficial for the treatment of neurodegenerative diseases like PD.

S-allyl cysteine activates the Nrf2-dependent antioxidant response and protects neurons against ischemic injury in vitro and in vivo.

Stroke is a devastating clinical condition for which an effective neuroprotective treatment is currently unavailable. S-allyl cysteine (SAC), the most abundant organosulfur compound in aged garlic extract, has been reported to possess neuroprotective effects against stroke. However, the mechanisms underlying its beneficial effects remain poorly defined. The present study tests the hypothesis that SAC attenuates ischemic neuronal injury by activating the nuclear factor erythroid-2-related factor 2 (Nrf2)-dependent antioxidant response in both in vitro and in vivo models. Our findings demonstrate that SAC treatment resulted in an increase in Nrf2 protein levels and subsequent activation of antioxidant response element pathway genes in primary cultured neurons and mice. Exposure of primary neurons to SAC provided protection against oxygen and glucose deprivation-induced oxidative insults. In wild-type (Nrf2(+/+) ) mice, systemic administration of SAC attenuated middle cerebral artery occlusion-induced ischemic damage, a protective effect not observed in Nrf2 knockout (Nrf2(-/-) ) mice. Taken together, these findings provide the first evidence that activation of the Nrf2 antioxidant response by SAC is strongly associated with its neuroprotective effects against experimental stroke and suggest that targeting the Nrf2 pathway may provide therapeutic benefit for the treatment of stroke. The transcription factor Nrf2 is involved in cerebral ischemic disease and may be a promising target for the treatment of stroke. We provide novel evidence that SAC confers neuroprotection against ischemic stroke by activating the antioxidant Nrf2 signaling pathway. ARE, antioxidant response element; GCLC, glutathione cysteine ligase regulatory subunit; GCLM, glutathione cysteine ligase modulatory subunit; HO-1, heme oxygenase-1; JNK, c-Jun N-terminal kinase; Keap1, Kelch-like ECH-associated protein 1; Maf, musculoaponeurotic fibrosarcoma; Nrf2, nuclear factor erythroid-2-related factor 2; SAC, S-allyl cysteine; ROS, reactive oxygen species.

Progranulin protects against renal ischemia/reperfusion injury in mice.

Progranulin (PGRN), an autocrine growth factor, has multiple physiological functions and is widely involved in the pathogenesis of many types of diseases. The pivotal anti-inflammatory function of PGRN in rheumatoid arthritis encouraged us to examine the role of PGRN in acute kidney injury (AKI). We found that levels of PGRN were significantly reduced in the kidney in a mouse model of renal ischemia/reperfusion injury. We also observed that PGRN deficiency (Grn(-/-) mice) significantly aggravated renal injury as evidenced by higher serum creatinine, more severe morphological injury, increased tubular epithelial cell death, and tubulointerstitial neutrophil and macrophage infiltration versus wild-type mice. In vitro, we found that recombinant human PGRN attenuated hypoxia-induced inflammatory actions and apoptosis in proximal tubule epithelial cells, at least in part associated with a nucleotide-binding oligomerization domain containing 2 (NOD2)-mediated immune response. Importantly, pretreatment with or delayed administration of recombinant human PGRN protected against or promoted recovery from renal ischemia/reperfusion injury in wild-type and Grn(-/-) mice. Similar protective effects were also found in cisplatin-induced AKI. Thus, our findings provide a better understanding of the biological activities of PGRN in the kidney and suggest that PGRN may be an innovative therapeutic strategy for treating patients with AKI.

Tetramethylpyrazine analogue CXC195 ameliorates cerebral ischemia-reperfusion injury by regulating endothelial nitric oxide synthase phosphorylation via PI3K/Akt signaling.

A novel tetramethylpyrazine derivative, CXC195, has been recently shown to protect against cerebral ischemia-reperfusion (I/R) injury. However, the detailed mechanisms underlying the neuroprotection of CXC195 are still unclear. The aim of the present study was to investigate the effects of CXC195 on the phosphorylation of endothelial nitric oxide synthase (eNOS) in response to cerebral I/R and to determine whether phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway might be involved. An in vitro model of oxygen glucose deprivation (OGD) which was performed on primary cultured human aortic endothelial cells (HAECs) and an in vivo middle cerebral artery occlusion (MCAO) model that was performed on Wistar rats were used in this study. CXC195 increased nitric oxide (NO) production and the phosphorylation but not the protein level of eNOS in HAECs subjected to 1 h OGD followed by reperfusion. In addition, CXC195 increased the phosphorylation of Akt; inhibition of PI3K/Akt pathway by a specific inhibitor, wortmannin, suppressed CXC195-induced NO release in HAECs. Consistently, CXC195 treatment significantly restored the phosphorylations of eNOS and Akt in the cortical penumbra of rats subjected to 2 h MCAO followed by reperfusion. Moreover, wortmannin abolished CXC195-induced eNOS phosphorylation and neuroprotection as evidenced by a reversal of the reduction in infarct volume and neurobehavioral outcomes. In conclusion, CXC195 induced phosphorylation of eNOS by activation of PI3K/Akt signaling under pathological cerebral I/R conditions, which provided a novel explanation for the neuroprotective effect of CXC195.

Eriodictyol Attenuates ß-Amyloid 25-35 Peptide-Induced Oxidative Cell Death in Primary Cultured Neurons by Activation of Nrf2.

Oxidative stress plays an important role in the pathogenesis of neurodegenerative diseases, including Alzheimer's disease (AD). Eriodictyol, a flavonoid isolated from the Chinese herb Dracocephalum rupestre, has long been established as an antioxidant. The present study was designed to investigate the effect of eriodictyol on ß-amyloid 25-35 peptide (Aß25-35)-induced oxidative cell death in primary neurons and to explore the role of the nuclear factor erythroid-2-related factor 2/antioxidant response element (Nrf2/ARE) pathway in this process. For this purpose, primary cultures of cortical neurons were exposed to 15 µM Aß25-35 in the absence or presence of eriodictyol (20, 40 and 80 µM). The results revealed that Aß25-35-induced cytotoxicity and apoptotic characteristics such as activation of JNK/p38 apoptotic signaling pathway were effectively attenuated by eriodictyol pretreatment. Eriodictyol treatment also resulted in an increase in Nrf2 protein levels and subsequent activation of ARE pathway genes in primary cultured neurons. The protective effects of eriodictyol were attenuated by RNA interference-mediated knockdown of Nrf2 expression. Taken together, these results clearly demonstrate that eriodictyol protects neurons against Aß25-35-induced cell death partially through Nrf2/ARE signaling pathway, which further supports that eriodictyol might be a promising novel therapeutic agent for AD.

Histone deacetylase 4 selectively contributes to podocyte injury in diabetic nephropathy.

Studies have highlighted the importance of histone deacetylase (HDAC)-mediated epigenetic processes in the development of diabetic complications. Inhibitors of HDAC are a novel class of therapeutic agents in diabetic nephropathy, but currently available inhibitors are mostly nonselective inhibit multiple HDACs, and different HDACs serve very distinct functions. Therefore, it is essential to determine the role of individual HDACs in diabetic nephropathy and develop HDAC inhibitors with improved specificity. First, we identified the expression patterns of HDACs and found that, among zinc-dependent HDACs, HDAC2/4/5 were upregulated in the kidney from streptozotocin-induced diabetic rats, diabetic db/db mice, and in kidney biopsies from diabetic patients. Podocytes treated with high glucose, advanced glycation end products, or transforming growth factor-ß (common detrimental factors in diabetic nephropathy) selectively increased HDAC4 expression. The role of HDAC4 was evaluated by in vivo gene silencing by intrarenal lentiviral gene delivery and found to reduce renal injury in diabetic rats. Podocyte injury was associated with suppressing autophagy and exacerbating inflammation by HDAC4-STAT1 signaling in vitro. Thus, HDAC4 contributes to podocyte injury and is one of critical components of a signal transduction pathway that links renal injury to autophagy in diabetic nephropathy.

HDAC4/5-HMGB1 signalling mediated by NADPH oxidase activity contributes to cerebral ischaemia/reperfusion injury.

Histone deacetylases (HDACs)-mediated epigenetic mechanisms play critical roles in the homeostasis of histone acetylation and gene transcription. HDAC inhibitors have displayed neuroprotective properties in animal models for various neurological diseases including Alzheimer's disease and ischaemic stroke. However, some studies have also reported that HDAC enzymes exert protective effects in several pathological conditions including ischaemic stress. The mixed results indicate the specific roles of each HDAC protein in different diseased states. However, the subtypes of HDACs associated with ischaemic stroke keep unclear. Therefore, in this study, we used an in vivo middle cerebral artery occlusion (MCAO) model and in vitro cell cultures by the model of oxygen glucose deprivation to investigate the expression patterns of HDACs and explore the roles of individual HDACs in ischaemic stroke. Our results showed that inhibition of NADPH oxidase activity ameliorated cerebral ischaemia/reperfusion (I/R) injury and among Zn(2+) -dependent HDACs, HDAC4 and HDAC5 were significantly decreased both in vivo and in vitro, which can be reversed by NADPH oxidase inhibitor apocynin. We further found that both HDAC4 and HDAC5 increased cell viability through inhibition of HMGB1, a central mediator of tissue damage following acute injury, expression and release in PC12 cells. Our results for the first time provide evidence that NADPH oxidase-mediated HDAC4 and HDAC5 expression contributes to cerebral ischaemia injury via HMGB1 signalling pathway, suggesting that it is important to elucidate the role of individual HDACs within the brain, and the development of HDAC inhibitors with improved specificity is required to develop effective therapeutic strategies to treat stroke.

TIPE2, a novel regulator of immunity, protects against experimental stroke.

The inflammatory responses accompanying stroke are recognized to contribute to secondary ischemic injury. TIPE2 is a very recently identified negative regulator of inflammation that maintains immune homeostasis. However, it is unknown whether TIPE2 is expressed in the brain and contributes to the regulation of cerebral diseases. In this study, we explored the potential roles of TIPE2 in cerebral ischemia/reperfusion injury. TIPE2(-/-) mice were used to assess whether TIPE2 provides neuroprotection following cerebral ischemia/reperfusion induced by middle cerebral artery occlusion (MCAO), and in vitro primary cerebral cell cultures were used to investigate the expression and regulation of TIPE2. Our results show that genetic ablation of the Tipe2 gene significantly increased the cerebral volume of infarction and neurological dysfunction in mice subjected to MCAO. Flow cytometric analysis revealed more infiltrating macrophages, neutrophils, and lymphocytes in the ischemic hemisphere of TIPE2(-/-) mice. The responses to inflammatory cytokines and chemokines were significantly increased in TIPE2(-/-) mouse brain after MCAO. We further observed that TIPE2 was highly induced in WT mice after cerebral ischemia and was expressed mainly in microglia/macrophages, but not in neurons and astrocytes. Finally, we found that regulation of TIPE2 expression was associated with NADPH oxidase activity. These findings demonstrate, for the first time, that TIPE2 is involved in the pathogenesis of stroke and suggest that TIPE2 plays an essential role in a signal transduction pathway that links the inflammatory immune response to specific conditions after cerebral ischemia. Targeting TIPE2 may be a new therapeutic strategy for stroke treatment.

NOD2 promotes renal injury by exacerbating inflammation and podocyte insulin resistance in diabetic nephropathy.

An increasing number of clinical and animal model studies indicate that activation of the innate immune system and inflammatory mechanisms are important in the pathogenesis of diabetic nephropathy. Nucleotide-binding oligomerization domain containing 2 (NOD2), a member of the NOD-like receptor family, plays an important role in innate immune response. Here we explore the contribution of NOD2 to the pathogenesis of diabetic nephropathy and found that it was upregulated in kidney biopsies from diabetic patients and high-fat diet/streptozotocin-induced diabetic mice. Further, NOD2 deficiency ameliorated renal injury in diabetic mice. In vitro, NOD2 induced proinflammatory response and impaired insulin signaling and insulin-induced glucose uptake in podocytes. Moreover, podocytes treated with high glucose, advanced glycation end-products, tumor necrosis factor-α, or transforming growth factor-ß (common detrimental factors in diabetic nephropathy) significantly increased NOD2 expression. NOD2 knockout diabetic mice were protected from the hyperglycemia-induced reduction in nephrin expression. Further, knockdown of NOD2 expression attenuated high glucose-induced nephrin downregulation in vitro, supporting an essential role of NOD2 in mediating hyperglycemia-induced podocyte dysfunction. Thus, NOD2 is one of the critical components of a signal transduction pathway that links renal injury to inflammation and podocyte insulin resistance in diabetic nephropathy.

NOD2 deficiency protects against cardiac remodeling after myocardial infarction in mice.

BACKGROUND/AIMS: Although the pathogenesis of myocardial infarction (MI) is multifactorial, activation of innate immune system to induce inflammation has emerged as a key pathophysiological process in MI. NOD2, one member of the NOD-like receptor (NLR) family, plays an important role in the innate immune response. This study was to examine the role of NOD2 during MI. METHODS: MI was induced by permanent ligation of the left coronary artery in wild type and NOD2(-/-) mice and cardiac fibroblasts were isolated. RESULTS: NOD2 expression was significantly increased in myocardium in post-MI mice. NOD2 deficiency improved cardiac dysfunction and remodeling after MI as evidenced by echocardiographic analysis, reduced the levels of cytokines, inflammatory cell infiltration and matrix metalloproteinase-9 (MMP-9) activity. In vitro, we further found that NOD2 activation induced the activation of MAPK signaling pathways, production of proinflammatory mediators and MMP-9 activity in cardiac fibroblasts. CONCLUSIONS: Our studies demonstrate that NOD2 is a critical component of a signal transduction pathway that links cardiac injury by exacerbation of inflammation and MMP-9 activity. Pharmacological targeting of NOD2-mediated signaling pathways may provide a novel approach to treatment of cardiovascular diseases.