A liver-specific gene expression panel predicts the differentiation status of in vitro hepatocyte models.

Alternative cell sources, such as three-dimensional organoids and induced pluripotent stem cell-derived cells, might provide a potentially effective approach for both drug development applications and clinical transplantation. For example, the development of cell sources for liver cell-based therapy has been increasingly needed, and liver transplantation is performed for the treatment for patients with severe end-stage liver disease. Differentiated liver cells and three-dimensional organoids are expected to provide new cell sources for tissue models and revolutionary clinical therapies. However, conventional experimental methods confirming the expression levels of liver-specific lineage markers cannot provide complete information regarding the differentiation status or degree of similarity between liver and differentiated cell sources. Therefore, in this study, to overcome several issues associated with the assessment of differentiated liver cells and organoids, we developed a liver-specific gene expression panel (LiGEP) algorithm that presents the degree of liver similarity as a "percentage." We demonstrated that the percentage calculated using the LiGEP algorithm was correlated with the developmental stages of in vivo liver tissues in mice, suggesting that LiGEP can correctly predict developmental stages. Moreover, three-dimensional cultured HepaRG cells and human pluripotent stem cell-derived hepatocyte-like cells showed liver similarity scores of 59.14% and 32%, respectively, although general liver-specific markers were detected. CONCLUSION: Our study describes a quantitative and predictive model for differentiated samples, particularly liver-specific cells or organoids; and this model can be further expanded to various tissue-specific organoids; our LiGEP can provide useful information and insights regarding the differentiation status of in vitro liver models. (Hepatology 2017;66:1662-1674).

Oleuropein isolated from Fraxinus rhynchophylla inhibits glutamate-induced neuronal cell death by attenuating mitochondrial dysfunction.

Glutamate-induced neurotoxicity is related to excessive oxidative stress accumulation and results in the increase of neuronal cell death. In addition, glutamate has been reported to lead to neurodegenerative diseases, including Parkinson's and Alzheimer's diseases.It is well known that Fraxinus rhynchophylla contains a significant level of oleuropein (Ole), which exerts various pharmacological effects. However, the mechanism of neuroprotective effects of Ole is still poorly defined. In this study, we aimed to investigate whether Ole prevents glutamate-induced toxicity in HT-22 hippocampal neuronal cells. The exposure of the glutamate treatment caused neuronal cell death through an alteration of Bax/Bcl-2 expression and translocation of mitochondrial apoptosis-inducing factor (AIF) to the cytoplasm of HT-22 cells. In addition, glutamate induced an increase in dephosphorylation of dynamin-related protein 1 (Drp1), mitochondrial fragmentation, and mitochondrial dysfunction. The pretreatment of Ole decreased Bax expression, increased Bcl-2 expression, and inhibited the translocation of mitochondrial AIF to the cytoplasm. Furthermore, Ole amended a glutamate-induced mitochondrial dynamic imbalance and reduced the number of cells with fragmented mitochondria, regulating the phosphorylation of Drp1 at amino acid residue serine 637. In conclusion, our results show that Ole has a preventive effect against glutamate-induced toxicity in HT-22 hippocampal neuronal cells. Therefore, these data imply that Ole may be an efficient approach for the treatment of neurodegenerative diseases.

Critical role of XBP1 in cancer signalling is regulated by PIN1.

XBP1 (X-box-binding protein 1) is activated in cancer and has a pivotal role in tumorigenesis and progression of human cancer. In particular, the XBP1 transcriptional regulatory network is well known to drive cancer development, but little is known about whether the stability of XBP1 is regulated and, if so, what controls the stability of XBP1. In the present study we show that PIN1 prolyl isomerase interacts with the active form of XBP1 (XBP1s) in a phosphorylation-dependent manner and promotes XBP1s-induced cell proliferation and transformation through the regulation of XBP1 stability. By contrast, depletion of Pin1 in cancer cells reduced XBP1s expression, which subsequently inhibits cell proliferation and transformation. Interestingly, XBP1s activates multiple oncogenic pathways including NF-κB (nuclear factor κB), AP1 (activator protein 1) and Myc, and down-regulates PIN1 transcription via a negative-feedback mechanism through p53 induction. Ultimately, reciprocal regulation of Pin1 and XBP1s is associated with the activation of oncogenic pathways, and the relationship of PIN1 and XBP1 may be an attractive target for novel therapy in cancers.

Chrysophanol Suppressed Glutamate-Induced Hippocampal Neuronal Cell Death via Regulation of Dynamin-Related Protein 1-Dependent Mitochondrial Fission.

Chrysophanic acid, or chrysophanol, is an anthraquinone found in Rheum palmatum, which was used in the preparation of oriental medicine in ancient China. The hippocampus plays a major role in controlling the activities of the short- and long-term memory. It is one of the major regions affected by excessive cell death in Alzheimer's disease. Therefore, neuronal cell-death modulation in the hippocampus is important for maintaining neuronal function. We investigated chrysophanol's effects on glutamate-induced hippocampal neuronal cell death. Chrysophanol reduced glutamate-induced cell death via suppression of proapoptotic factors and reactive oxygen species generation. Furthermore, it downregulated glutamate-induced mitochondrial fission by inhibiting dynamin-related protein 1 (Drp1) dephosphorylation. Thus, chrysophanol suppressed hippocampal neuronal cell death via inhibition of Drp1-dependent mitochondrial fission, and can be used as a therapeutic agent for treating neuronal cell death-mediated neurodegenerative diseases.

Chrysophanol suppresses pro-inflammatory response in microglia via regulation of Drp1-dependent mitochondrial fission.

OBJECTIVES: Chrysophanol, also called chrysophanic acid, is a natural anthraquinone compound found in Rheum palmatum. R. palmatum has been used in oriental medicine in ancient East Asia. Microglial cells represent not only the forefront immune defense in the central nervous system but also the most reactive sensors to various threats. However, activated microglia can exert neurotoxic effects via excessive production of cytotoxic molecules and proinflammatory cytokines. Therefore, modulation of microglial cell activation is important for maintaining neuronal function. MATERIALS AND METHODS: Pretreatment of chrysophanol in BV-2 murein microglial cells was carried out for 1 hour, followed by stimulation with 1 µg/mL LPS. Level of proteins and RNAs were detected by western blotting and Reverse Transcriptase PCR. DsRed2-Mito-expressing cells were used for detecting mitochondrial morphology. RESULTS: In this study, we determined the effects of chrysophanol on lipopolysaccharide (LPS)-induced microglial activation. Chrysophanol inhibited the LPS-induced production of proinflammatory mediators and cytokines via suppression of mitogen-activated protein kinase/nuclear factor kappa-B activation and reactive oxygen species generation. In addition, chrysophanol downregulated LPS-induced mitochondrial fission by diminishing dynamin-related protein 1 (Drp1) dephosphorylation. Taken together, chrysophanol suppressed the proinflammatory response of activated microglia via inhibition of Drp1-dependent mitochondrial fission. CONCLUSION: Our findings can provide the basis for the use of chrysophanol in microglial inflammatory response-mediated neurodegenerative diseases. Furthermore, our study can contribute to the production of new drugs for inflammatory response-mediated neurodegenerative diseases by purification of chrysophanol.

Loss of mitofusin 2 links beta-amyloid-mediated mitochondrial fragmentation and Cdk5-induced oxidative stress in neuron cells.

Mitochondrial dysfunction is implicated in age-related degenerative disorders such as Alzheimer's disease (AD). Maintenance of mitochondrial dynamics is essential for regulating mitochondrial function. Aß oligomers (AßOs), the typical cause of AD, lead to mitochondrial dysfunction and neuronal loss. AßOs have been shown to induce mitochondrial fragmentation, and their inhibition suppresses mitochondrial dysfunction and neuronal cell death. Oxidative stress is one of the earliest hallmarks of AD. Cyclin-dependent kinase 5 (Cdk5) may cause oxidative stress by disrupting the antioxidant system, including Prx2. Cdk5 is also regarded as a modulator of mitochondrial fission; however, a precise mechanistic link between Cdk5 and mitochondrial dynamics is lacking. We estimated mitochondrial morphology and alterations in mitochondrial morphology-related proteins in Neuro-2a (N2a) cells stably expressing the Swedish mutation of amyloid precursor protein (APP), which is known to increase AßO production. We demonstrated that mitochondrial fragmentation by AßOs accompanies reduced mitofusin 1 and 2 (Mfn1/2) levels. Interestingly, the Cdk5 pathway, including phosphorylation of the Prx2-related oxidative stress, has been shown to regulate Mfn1 and Mfn2 levels. Furthermore, Mfn2, but not Mfn1, over-expression significantly inhibits the AßO-mediated cell death pathway. Therefore, these results indicate that AßO-mediated oxidative stress triggers mitochondrial fragmentation via decreased Mfn2 expression by activating Cdk5-induced Prx2 phosphorylation. Mitochondrial fragmentation induced by amyloid-beta oligomer (AßOs) which is generated from the Swedish mutation of amyloid precursor protein (APP) accompanies reduced Mfn1/2 levels. Interestingly, the Cdk5 pathway, including phosphorylation of the Prx2-related oxidative stress, has been shown to regulate Mfn1/2. Furthermore, Mfn2 over-expression significantly inhibits the AßO-mediated neuronal cells death pathway, but not Mfn1 over-expression. Therefore, these results indicate that AßO-mediated oxidative stress triggers mitochondrial fragmentation via decreased Mfn2 expression by activating Cdk5-induced Prx2 phosphorylation. ATP, adenosine triphosphate; Bax, Bcl-2-associated X protein; Bcl-2, B-cell lymphoma 2; Cdk5, Cyclin-dependent kinase; Cyt C, cytochrome C; Mfn2, mitofusin 2; Prx2, peroxiredoxin 2; ROS, reactive oxygen species.

Mitochondrial dynamics modulate the expression of pro-inflammatory mediators in microglial cells.

Over-activation of microglia cells in the brain contributes to neurodegenerative processes promoted by the production of various neurotoxic factors including pro-inflammatory cytokines and nitric oxide. Recently, accumulating evidence has suggested that mitochondrial dynamics are an important constituent of cellular quality control and function. However, the role of mitochondrial dynamics in microglial activation is still largely unknown. In this study, we determined whether mitochondrial dynamics are associated with the production of pro-inflammatory mediators in lipopolysaccharide (LPS)-stimulated immortalization of murine microglial cells (BV-2) by a v-raf/v-myc carrying retrovirus (J2). Excessive mitochondrial fission was observed in lentivirus-transfected BV-2 cells stably expressing DsRed2-mito following LPS stimulation. Furthermore, mitochondrial localization of dynamin-related protein 1 (Drp1) (a key regulator of mitochondrial fission) was increased and accompanied by de-phosphorylation of Ser637 in Drp1. Interestingly, inhibition of LPS-induced mitochondrial fission and reactive oxygen species (ROS) generation by Mdivi-1 and Drp1 knock-down attenuated the production of pro-inflammatory mediators via reduced nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and mitogen-activated protein kinase (MAPK) signaling. Our results demonstrated for the first time that mitochondrial fission regulates mitochondrial ROS production in activated microglial cells and influences the expression of pro-inflammatory mediators through the activation of NF-κB and MAPK. We therefore suggest that mitochondrial dynamics may be essential for understanding pro-inflammatory mediator expression in activated microglial cells. This could represent a new therapeutic approach for preventing neurodegenerative diseases.

Isoliquiritigenin isolated from Glycyrrhiza uralensis protects neuronal cells against glutamate-induced mitochondrial dysfunction.

Glutamate-mediated excitotoxicity, which is associated with reactive oxygen species (ROS), is hypothesized to be a major contributor to pathological cell death in the mammalian central nervous system, and to be involved in many acute and chronic brain diseases. Here, we showed that isoliquiritigenin (ISL) isolated from Glycyrrhiza uralensis (Gu), one of the most frequently prescribed oriental herbal medicines, protected HT22 hippocampal neuronal cells from glutamate-induced oxidative stress. In addition, we clarified the molecular mechanisms by which it protects against glutamate-induced neuronal cell death. ISL reversed glutamate-induced ROS production and mitochondrial depolarization, as well as glutamate-induced changes in expression of the apoptotic regulators Bcl-2 and Bax. Pretreatment of HT22 cells with ISL suppresses the release of apoptosis-inducing factor from mitochondria into the cytosol. Taken together, our results suggest that ISL may protect against mitochondrial dysfunction by limiting glutamate-induced oxidative stress. In conclusion, our results demonstrated that ISL isolated from Gu has protective effects against glutamate-induced mitochondrial damage and hippocampal neuronal cell death. We expect ISL to be useful in the development of drugs to prevent or treat neurodegenerative diseases.

Microglial peroxiredoxin V acts as an inducible anti-inflammatory antioxidant through cooperation with redox signaling cascades.

Reactive oxygen species (ROS) actively participate in microglia-mediated pathogenesis as pro-inflammatory molecules. However, little is known about the involvement of specific antioxidants in maintaining the microglial oxidative balance. We demonstrate that microglial peroxiredoxin (Prx) 5 expression is up-regulated by lipopolysaccharide (LPS) through activation of the ROS-sensitive signaling pathway and is involved in attenuation of both microglial activation and nitric oxide (NO) generation. Unlike in stimulation of oxidative insults with paraquat and hydrogen peroxide, Prx V expression is highly sensitive to LPS-stimulation in microglia. Reduction of ROS level by treatment with either NADPH oxidase inhibitor or antioxidant ablates LPS-mediated Prx V up-regulation in BV-2 microglial cells and is closely associated with the activation of the c-jun N-terminal kinase (JNK) signaling pathway. This suggests the involvement of ROS/JNK signaling in LPS-mediated Prx V induction. Furthermore, NO induces Prx V up-regulation that is ablated by the addition of inducible nitric oxide synthase inhibitor or deleted mutation of inducible nitric oxide synthase in LPS-stimulated microglia. Therefore, these results suggest that Prx V is induced by cooperative action among the ROS, RNS, and JNK signaling cascades. Interestingly, knockdown of Prx V expression causes the acceleration of microglia activation, including augmented ROS generation and JNK-dependent NO production. In summary, we demonstrate that Prx V plays a key role in the microglial activation process through modulation of the balance between ROS/NO generation and the corresponding JNK cascade activation.

A Novel X-Linked Variant of IQSEC2 is Associated with Lennox-Gastaut Syndrome and Mild Intellectual Disability in Three Generations of a Korean Family.

Aim: Lennox-Gastaut syndrome (LGS) is a severe type of childhood-onset epilepsy with multiple types of seizures, specific discharges on electroencephalography, and intellectual disability. However, LGS-related genes are largely unknown. To identify causative genes related to LGS, we collected and analyzed data from a three-generation Korean family in which one member had LGS and two had intellectual disability. Methods: Genomic DNAs were extracted from blood samples of all participants and used in whole-exome sequencing (WES). Genetic variants were detected by the Genome Analysis Toolkit and confirmed by Sanger sequencing. Variant pathogenicity was evaluated by prediction programs and the American College of Medical Genetics criteria. The LGS patient had generalized slow spike-and-wave discharges, multiple types of seizures, and developmental delay. Results: Analyses of the WES data from the family revealed a novel variant (c.1048G>A, p.Ala350Thr) in the IQ motif and Sec7 domain 2 (IQSEC2). This variant is within a highly evolutionarily conserved IQ-like motif, indicating a decrease in the calmodulin-binding capacity or α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid transmission. The hemizygous variant in the male with LGS was a maternally inherited X-linked variant from the heterozygous maternal grandmother and mother, both of whom had intellectual disability. Conclusion: These findings indicate that the variant of IQSEC2 triggered both LGS and intellectual disability dependent on sex in this family. We report a novel X-linked inherited IQSEC2 variant for LGS and intellectual disability, which enhances the spectrum of variants in the IQ-like motif of IQSEC2.

Coiled-coil domain containing 50-V2 protein positively regulates neurite outgrowth.

The coiled-coil domain containing 50 (CCDC50) protein is a phosphotyrosine-dependent signalling protein stimulated by epidermal growth factor. It is highly expressed in neuronal cells in the central nervous system; however, the roles of CCDC50 in neuronal development are largely unknown. In this study, we showed that the depletion of CCDC50-V2 impeded the neuronal development process, including arbor formation, spine density development, and axonal outgrowth, in primary neurons. Mechanistic studies revealed that CCDC50-V2 positively regulated the nerve growth factor receptor, while it downregulated the epidermal growth factor receptor pathway. Importantly, JNK/c-Jun activation was found to be induced by the CCDC50-V2 overexpression, in which the interaction between CCDC50-V2 and JNK2 was also observed. Overall, the present study demonstrates a novel mechanism of CCDC50 function in neuronal development and provides new insight into the link between CCDC50 function and the aetiology of neurological disorders.

Isoliquiritigenin attenuates glutamate-induced mitochondrial fission via calcineurin-mediated Drp1 dephosphorylation in HT22 hippocampal neuron cells.

Numerous studies suggest that glutamate toxicity is a major contributor to neuronal dysfunction and death in several neurodegenerative diseases. In our previous study, isoliquiritigenin (ISL) isolated from Glycyrrhiza uralensis showed neuroprotective effects against neuronal cell death mediated by intracellular reactive oxygen species (ROS) generation and loss of mitochondrial membrane potential. However, the mechanisms by which ISL protects against glutamate-induced oxidative stress are unknown. In the present study, we focused on the cellular and molecular mechanisms underlying the inhibition of ROS production and induction of mitochondrial dysfunction by ISL in glutamate-stimulated HT22 mouse hippocampal neuron cells. The results revealed that ISL inhibited glutamate-induced mitochondrial ROS production and decline of glutathione levels and ATP generation in HT22 cells. Interestingly, we discovered that ISL prevents glutamate-induced mitochondrial fission by inhibiting the dephosphorylation of Drp1 at the serine 637 residue, which is a regulatory factor of mitochondrial dynamics, and both a S637D mutation of Drp1, which resulted in a phosphorylation-mimetic form of Drp1 at Ser637, and mitochondria-targeted antioxidant Mito-TEMPO inhibited glutamate-induced mitochondrial fission. Furthermore, ISL also prevented the increase of intracellular calcium accompanied by activation of calcineurin, which is a key regulator of dephosphorylation of Drp1 (Ser637), in glutamate-treated HT22 cells. Taken together, our results demonstrated that ISL protects against glutamate-induced mitochondrial fission by inhibiting the increase of mitochondrial ROS and intracellular calcium, which are accompanied by dephosphorylation of Drp1 (Ser637), and consequently attenuates glutamate-induced neuronal cell death. Therefore, these findings suggest that ISL exhibits the potential for protection against glutamate toxicity. These results may contribute to the development of new drugs and novel strategies for the treatment of neurodegenerative disorders related to glutamate toxicity.

Anti-inflammatory effect of oleuropein on microglia through regulation of Drp1-dependent mitochondrial fission.

Oleuropein is a primary phenolic compound found in olive leaf and Fraxinus rhynchophylla. Here, we investigated the impact of oleuropein on LPS-induced BV-2 microglial cells. Oleuropein suppressed the LPS-induced increase in pro-inflammatory mediators, such as nitric oxide, and pro-inflammatory cytokines, via inhibition of ERK/p38/NF-κB activation and reactive oxygen species (ROS) generation. Furthermore, it suppressed LPS-induced excessive mitochondrial fission, which regulates mitochondrial ROS generation and pro-inflammatory response by diminishing Drp1 dephosphorylation. Collectively, we demonstrated that oleuropein suppresses pro-inflammatory response of microglia by inhibiting Drp1-dependent mitochondrial fission. Our findings suggest a potential role of oleuropein in microglial inflammation-mediated neurodegenerative disorders.

Novel indazole-based small compounds enhance TRAIL-induced apoptosis by inhibiting the MKK7-TIPRL interaction in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is one of the most malignant tumors. Although various treatments, such as surgery and chemotherapy, have been developed, a novel alternative therapeutic approach for HCC therapy is urgently needed. Tumor necrosis factor-related apoptosis inducing ligand (TRAIL) is a promising anti-cancer agent, but many cancer cells are resistant to TRAIL-induced apoptosis. To help overcome TRAIL resistance in HCC cancer cells, we have identified novel chemical compounds that act as TRAIL sensitizers. We first identified the hit compound, TRT-0002, from a chemical library of 6,000 compounds using a previously developed high-throughput enzyme-linked immunosorbent assay (ELISA) screening system, which was based on the interaction of mitogen-activated protein kinase kinase 7 (MKK7) and TOR signaling pathway regulator-like (TIPRL) proteins and a cell viability assay. To increase the efficacy of this TRAIL sensitizer, we synthesized 280 analogs of TRT-0002 and finally identified two lead compounds (TRT-0029 and TRT-0173). Co-treating cultured Huh7 cells with either TRT-0029 or TRT-0173 and TRAIL resulted in TRAIL-induced apoptosis due to the inhibition of the MKK7-TIPRL interaction and subsequent phosphorylation of MKK7 and c-Jun N-terminal kinase (JNK). In vivo, injection of these compounds and TRAIL into HCC xenograft tumors resulted in tumor regression. Taken together, our results suggest that the identified lead compounds serve as TRAIL sensitizers and represent a novel strategy to overcome TRAIL resistance in HCC.

Plasma glutamate carboxypeptidase is a negative regulator in liver cancer metastasis.

Tumor metastasis is the leading cause of cancer death. In the metastatic process, EMT is a unique phenotypic change that plays an important role in cell invasion and changes in cell morphology. Despite the clinical significance, the mechanism underlying tumor metastasis is still poorly understood. Here we report a novel mechanism by which secreted plasma glutamate carboxypeptidase(PGCP) negatively involves Wnt/ß-catenin signaling by DKK4 regulation in liver cancer metastasis. Pathway analysis of the RNA sequencing data showed that PGCP knockdown in liver cancer cell lines enriched the functions of cell migration, motility and mesenchymal cell differentiation. Depletion of PGCP promoted cell migration and invasion via activation of Wnt/ß-catenin signaling pathway components such as phospho-LRP6 and ß-catenin. Also, addition of DKK4 antagonized the Wnt/ß-catenin signaling cascade in a thyroxine (T4)-dependent manner. In an in vivo study, metastatic nodules were observed in the lungs of the mice after injection of shPGCP stable cell lines. Our findings suggest that PGCP negatively associates with Wnt/ß-catenin signaling during metastasis. Targeting this regulation may represent a novel and effective therapeutic option for liver cancer by preventing metastatic activity of primary tumor cells.

Mitochondrial ROS govern the LPS-induced pro-inflammatory response in microglia cells by regulating MAPK and NF-κB pathways.

Activation of microglia cells in the brain contributes to neurodegenerative processes promoted by many neurotoxic factors such as pro-inflammatory cytokines and nitric oxide (NO). Reactive oxygen species (ROS) actively affect microglia-associated neurodegenerative diseases through their role as pro-inflammatory molecules and modulators of pro-inflammatory processes. Although the ROS which involved in microglia activation are thought to be generated primarily by NADPH oxidase (NOX) and involved in the immune response, mitochondrial ROS have also been proposed as important regulators of the inflammatory response in the innate immune system. However, the role of mitochondrial ROS in microglial activation has yet to be fully elucidated. In this study, we demonstrate that inhibition of mitochondrial ROS by treatment with Mito-TEMPO effectively suppressed the level of mitochondrial and intracellular ROS. Mito-TEMPO treatment also significantly prevented LPS-induced increase in the TNF-α, IL-1ß, IL-6, iNOS and Cox-2 in BV-2 and primary microglia cells. Furthermore, LPS-induced suppression of mitochondrial ROS generation not only affected LPS-stimulated activation of MAPKs, including ERK, JNK, and p38, but also regulated IκB activation and NF-κB nuclear localization. These results indicate that mitochondria constitute a major source of ROS generation in LPS-mediated activated microglia cells. Additionally, suppression of LPS-induced mitochondrial ROS plays a role in modulating the production of pro-inflammatory mediators by preventing MAPK and NF-κB activation in microglia cells. Our findings suggest that a potential strategy in the development of therapy for inflammation-associated degenerative neurological diseases involves targeting the regulation of mitochondrial ROS in microglial cells.

Peroxiredoxin I is a ROS/p38 MAPK-dependent inducible antioxidant that regulates NF-κB-mediated iNOS induction and microglial activation.

Reactive oxygen species (ROS) function as modulators of pro-inflammatory processes in microglia-associated neurodegenerative diseases. However, little is known about the involvement of specific antioxidants in regulating the microglial redox status. Here, we demonstrated that peroxiredoxin (Prx) I activity was induced by lipopolysaccharide (LPS), but not paraquat and hydrogen peroxide, through activation of the ROS/p38 MAPK signal pathway, and participated in alleviating the microglial activation and generation of nitric oxide (NO). Interestingly, a null mutation of Prx I accelerated NF-κB-mediated iNOS induction and subsequent NO secretion in LPS-stimulated microglia. Furthermore, F4/80 expression as microglial activation marker was notably up-regulated in primary cultures of microglia, hippocampal sections, and cerebral cortex of 15-month-old Prx I(-/-) mouse. Taken together, the results of our study indicated that Prx I is an antioxidant that is up-regulated in a ROS/p38 MAPK-dependent manner and governs the progression of neuroinflammation by suppressing microglial activation. In addition, Prx I deficiency increased the nuclear translocation of NF-κB mediated-iNOS induction as pro-inflammatory mediators. The findings of our work suggest possible strategies for developing novel therapies to treat inflammation-associated degenerative neurological diseases by targeting the induction of Prx I in microglial cells.