The protease Omi cleaves the mitogen-activated protein kinase kinase MEK1 to inhibit microglial activation

HTRA2/OMI-Mediated Mitochondrial Quality Control Alters Macrophage Polarization Affecting Systemic Chronic Inflammation

Systemic chronic inflammation (SCI) due to intrinsic immune over-activation is an important factor in the development of many noninfectious chronic diseases, such as neurodegenerative diseases and diabetes mellitus. Among these immune responses, macrophages are extensively involved in the regulation of inflammatory responses by virtue of their polarization plasticity; thus, dysregulation of macrophage polarization direction is one of the potential causes of the generation and maintenance of SCI. High-temperature demand protein A2 (HtrA2/Omi) is an important regulator of mitochondrial quality control, not only participating in the degradation of mis-accumulated proteins in the mitochondrial unfolded protein response (UPRmt) to maintain normal mitochondrial function through its enzymatic activity, but also participating in the regulation of mitochondrial dynamics-related protein interactions to maintain mitochondrial morphology. Recent studies have also reported the involvement of HtrA2/Omi as a novel inflammatory mediator in the regulation of the inflammatory response. HtrA2/Omi regulates the inflammatory response in BMDM by controlling TRAF2 stabilization in a collagen-induced arthritis mouse model; the lack of HtrA2 ameliorates pro-inflammatory cytokine expression in macrophages. In this review, we summarize the mechanisms by which HtrA2/Omi proteins are involved in macrophage polarization remodeling by influencing macrophage energy metabolism reprogramming through the regulation of inflammatory signaling pathways and mitochondrial quality control, elucidating the roles played by HtrA2/Omi proteins in inflammatory responses. In conclusion, interfering with HtrA2/Omi may become an important entry point for regulating macrophage polarization, providing new research space for developing HtrA2/Omi-based therapies for SCI.

RRx-001 Exerts Neuroprotection Against LPS-Induced Microglia Activation and Neuroinflammation Through Disturbing the TLR4 Pathway

Neuroinflammation plays an important role in the pathogenesis of many central nervous system diseases. Here, we investigated the effect of an anti-cancer compound RRx-001 on neuroinflammation and its possible new applications. BV2 cells and primary microglia cells were used to evaluate the role of RRx-001 in LPS-induced microglial activation and inflammatory response in vitro. And, we found that the increase in the synthesis and release of cytokines and the up-regulation of pro-inflammatory factors in LPS-treated microglial cells were significantly reduced by RRx-001 pretreatment. As the most classical inflammatory pathways, NF-κB and MAPK signaling pathways were activated by LPS, but were inhibited by RRx-001. Transcription of NLRP3 was also reduced by RRx-001. In addition, LPS induced oxidative stress by increasing the expression of Nox mediated by transcription factors NF-κB and AP-1, while RRx-001 pretreatment ameliorated Nox-mediated oxidative stress. LPS-induced activation of TAK1, an upstream regulator of NF-κB and MAPK pathways, was significantly inhibited by RRx-001 pretreatment, whereas recruitment of MyD88 to TLR4 was not affected by RRx-001. LPS-primed BV2 condition medium induced injury of primary neurons, and this effect was inhibited by RRx-001. Furthermore, we established a neuroinflammatory mouse model by stereotactic injection of LPS into the substantia nigra pars compacta (SNpc), and RRx-001 dose-dependently reduced LPS-induced microglial activation and loss of TH + neurons in the midbrain. In conclusion, the current study found that RRx-001 suppressed microglia activation and neuroinflammation through targeting TAK1, and may be a candidate for the treatment of neuroinflammation-related brain diseases.

Serine protease HtrA2/Omi regulates adaptive mitochondrial reprogramming in the brain cortex after ischemia/reperfusion injury via UCP2-SIRT3-PGC1 axis

This study is to investigate the underlying mechanisms of mitochondrial quality control (MQC) regulated by HtrA2/Omi during ischemia/reperfusion (I/R). We utilized the mnd2 mouse model, which has a missense mutation in HtrA2/Omi, to investigate the HtrA2/Omi regulation in mitochondria after I/R injury in the cerebral cortex. Compared to homozygous (HtrA2^mnd2) mice, heterozygous (HtrA2^Hetero) mice showed aging signs at a later age, increased HtrA2/Omi expression in the brain cortex, and lesser neurodegenerative signs. The brain cortex of HtrA2^Hetero mice had increased superoxide dismutase (SOD) activity; lower levels of malondialdehyde (MDA); higher expressions of mitochondrial unfolded protein response (mtUPR)-related proteins, NADH dehydrogenase [ubiquinone] iron-sulfur protein 7 (Ndufs7), and uncoupling protein 2 (UCP2) proteins; more mitochondrial fission; higher levels of ATP and mtDNA copies; elevated sirtuin 3 (SIRT3) activity; and increased NAD⁺/NADH ratio. After 1.5 h of I/R, the brain cortex of HtrA2^Hetero mice had a larger infarction size, reduced HtrA2/Omi expression, decreased S-X-linked inhibitor of apoptosis protein (XIAP), and increased C-Caspase3 than that of wild-type animals (WT). Mitochondria from the HtrA2^Hetero brain cortex showed decreased ATP production and MQC deficiency after 1.5 h I/R. Genipin pre-treatment reduced the aforementioned I/R injury in the HtrA2^Hetero brain cortex. In conclusion, mitochondrial function is compensated in the HtrA2^Hetero brain cortex via the upregulation of the UCP2-SIRT3-PGC1 axis. Decreased HtrA2/Omi function damages mitochondrial quality in the HtrA2^Hetero mouse brain cortex, leading to more brain I/R injury. Genipin pre-treatment ameliorates brain damages via the mitochondrial UCP2-SIRT3-PGC1 axis.

Loss of high-temperature requirement protein A2 protease activity induces mitonuclear imbalance via differential regulation of mitochondrial biogenesis in sarcopenia

Cellular homeostasis requires tight coordination between nucleus and mitochondria, organelles that each possesses their own genomes. Disrupted mitonuclear communication has been found to be implicated in many aging processes. However, little is known about mitonuclear signaling regulator in sarcopenia which is a major contributor to the risk of poor health-related quality of life, disability, and premature death in older people. High-temperature requirement protein A2 (HtrA2/Omi) is a mitochondrial protease and plays an important role in mitochondrial proteostasis. HtrA2^mnd2(-/-) mice harboring protease-deficient HtrA2/Omi Ser276Cys missense mutants exhibit premature aging phenotype. Additionally, HtrA2/Omi has been established as a signaling regulator in nervous system and tumors. We therefore asked whether HtrA2/Omi participates in mitonuclear signaling regulation in muscle degeneration. Using motor functional, histological, and molecular biological methods, we characterized the phenotype of HtrA2^mnd2(-/-) muscle. Furthermore, we isolated the gastrocnemius muscle of HtrA2^mnd2(-/-) mice and determined expression of genes in mitochondrial unfolded protein response (UPR^mt ), mitohormesis, electron transport chain (ETC), and mitochondrial biogenesis. Here, we showed that HtrA2/Omi protease deficiency induced denervation-independent skeletal muscle degeneration with sarcopenia phenotypes. Despite mitochondrial hypofunction, upregulation of UPR^mt and mitohormesis-related genes and elevated total reactive oxygen species (ROS) production were not observed in HtrA2^mnd2(-/-) mice, contrary to previous assumptions that loss of protease activity of HtrA2/Omi would lead to mitochondrial dysfunction as a result of proteostasis disturbance and ROS burst. Instead, we showed that HtrA2/Omi protease deficiency results in different changes between the expression of nuclear DNA- and mitochondrial DNA-encoded ETC subunits, which is in consistent with their transcription factors, nuclear respiratory factors 1 and 2, and coactivator peroxisome proliferator-activated receptor γ coactivator 1α. These results reveal that loss of HtrA2/Omi protease activity induces mitonuclear imbalance via differential regulation of mitochondrial biogenesis in sarcopenia. The novel mechanistic insights may be of importance in developing new therapeutic strategies for sarcopenia.

Role of PGC-1α in Mitochondrial Quality Control in Neurodegenerative Diseases

As one of the major cell organelles responsible for ATP production, it is important that neurons maintain mitochondria with structural and functional integrity; this is especially true for neurons with high metabolic requirements. When mitochondrial damage occurs, mitochondria are able to maintain a steady state of functioning through molecular and organellar quality control, thus ensuring neuronal function. And when mitochondrial quality control (MQC) fails, mitochondria mediate apoptosis. An apparently key molecule in MQC is the transcriptional coactivator peroxisome proliferator activated receptor γ coactivator-1α (PGC-1α). Recent findings have demonstrated that upregulation of PGC-1α expression in neurons can modulate MQC to prevent mitochondrial dysfunction in certain in vivo and in vitro aging or neurodegenerative encephalopathy models, such as Huntington's disease, Alzheimer's disease, and Parkinson's disease. Because mitochondrial function and quality control disorders are the basis of pathogenesis in almost all neurodegenerative diseases (NDDs), the role of PGC-1α may make it a viable entry point for the treatment of such diseases. This review focuses on multi-level MQC in neurons, as well as the regulation of MQC by PGC-1α in these major NDDs.

LP induced/mediated PGE2 synthesis through activation of the ERK/NF-κB pathway contributes to inflammatory damage triggered by Escherichia coli-infection in bovine endometrial tissue

The bovine endometrium is constantly challenged with pathogenic bacteria, especially with Escherichia coli. In previous studies, we showed that prostaglandin E₂ (PGE₂) synthesis was increased in E. coli-infected bovine endometrial tissue, which promoted the development of inflammatory damage. However, the molecular mechanism underlying this accumulation of PGE₂ remained undefined. Lipoprotein (LP) is one of critical outer membrane protein in E. coli, which regulates inflammatory response. In this study, we determined the role of LP in PGE₂ accumulation in bovine endometrial tissue by infecting the tissue with wild endometrial pathogenic E. coli and E. coli LP deletion mutant (JE5505) strains. We demonstrate that JE5505 was less effective than pathogenic E. coli in inducing the production of PGE_2,IL-6, TNF-α, HMGB-1, and HABP1 and that the induction of cytokines was dependent on the activation of MAPKs, as revealed by rapid phosphorylation of ERK1/2/NF-κB in the endometrial tissues, furthermore, LP also induced PGE₂ synthessis and cytokine secretion. Additionally, ERK and NF-κB inhibitors significantly inhibited PGE₂ production and cytokine secretion and reduced or attenuated tissue damage in JE5505-infected and LP induced endometrial tissues. What is more important, we reported PGE₂ introduction increased the expression of pro-inflammatory factors and DAMPs in E. coli-infected bovine endometrial tissue. Taken together, these results indicate that LP is involved in the accumulation of PGE₂ through the activation of the ERK/NF-κB pathway that induces the production of pro-inflammatory factors and damage-associated molecular patterns (DAMPs) in E. coli-infected bovine endometrial tissue. These results should help in better understanding and management of postpartum inflammatory diseases in dairy cows.

P7C3 Inhibits LPS-Induced Microglial Activation to Protect Dopaminergic Neurons Against Inflammatory Factor-Induced Cell Death in vitro and in vivo

Parkinson’s disease (PD) is the second most common neurodegenerative disorder. Although its pathogenesis remains unclear, growing evidencce suggests that microglia-mediated neuroinflammation contributes greatly to the progression of PD. P7C3, an aminopropyl carbazole, possesses significant neuroprotective effects in several neurodegenerative disease animal models, including PD. In this study, we designed to investigate the effects of P7C3 on neuroinflammation. We showed that P7C3 specially suppressed the expression of lipopolysaccharide (LPS)-induced pro-inflammatory factors but not influenced the anti-inflammatory factors in microglia. The inhibition of the nuclear factor κB (NF-κB) signaling pathway was involved in the mechanisms of the anti-inflammatory effects by P7C3. LPS-induced activation of IκB kinase (IKK), degradation of the inhibitory κB alpha (IκBα) and nuclear translocation of NF-κB can be attenuated by the pretreatment of P7C3 in microglia. Furthermore, in LPS-treated microglia, P7C3-pretreatment decreased the toxicity of conditioned media to MES23.5 cells (a dopaminergic (DA) cell line). Most importantly, the anti-inflammatory effects of P7C3 were observed in LPS-stimulated mouse model. In general, our study demonstrates that P7C3 inhibits LPS-induced microglial activation through repressing the NF-κB pathway both in vivo and in vitro, providing a theoretical basis for P7C3 in anti-inflammation.

The mitochondrial protease HtrA2 restricts the NLRP3 and AIM2 inflammasomes

Activation of the inflammasome pathway is crucial for effective intracellular host defense. The mitochondrial network plays an important role in inflammasome regulation but the mechanisms linking mitochondrial homeostasis to attenuation of inflammasome activation are not fully understood. Here, we report that the Parkinson’s disease-associated mitochondrial serine protease HtrA2 restricts the activation of ASC-dependent NLRP3 and AIM2 inflammasomes, in a protease activity-dependent manner. Consistently, disruption of the protease activity of HtrA2 results in exacerbated NLRP3 and AIM2 inflammasome responses in macrophages ex vivo and systemically in vivo. Mechanistically, we show that the HtrA2 protease activity regulates autophagy and controls the magnitude and duration of inflammasome signaling by preventing prolonged accumulation of the inflammasome adaptor ASC. Our findings identify HtrA2 as a non-redundant mitochondrial quality control effector that keeps NLRP3 and AIM2 inflammasomes in check.

HSV‑TK/GCV can induce cytotoxicity of retinoblastoma cells through autophagy inhibition by activating MAPK/ERK

Retinoblastoma is an severe ophthalmic disease and the most common type intraocular malignant tumor, particularly in infants. Currently, few drugs and therapies are available. Gene therapy has been considered to be a potential treatment to cure cancer effectively and Herpes simplex virus type 1 thymidine kinase/ganciclovir (HSV-TK/GCV) is one type of suicide gene therapy that has been extensively studied. Numerous in vitro and in vivo studied have shown that this system can kill tumor cells, including liver and lung cancer cells. GCV is used as an antiviral drug, and the thymidine kinase, HSV-TK can phosphorylate GCV to GCV-TP, a competitive inhibitor of DNA synthesis, instead of guanine-5′-triphosphate in the process of DNA synthesis. This process prevents DNA chain elongation causing cell death via apoptosis. However, the toxic effects of HSV-TK/GCV on retinoblastoma cells remain unknown, and the molecular mechanisms of its therapeutic effects have not been fully elucidated. Our results suggest that HSV-TK/GCV can significantly cause the death of retinoblastoma cell lines, HXO-RB44 and Y79. Further studies have reported that this cell death is induced by the inhibition of autophagy by activating the MAPK/ERK (mitogen-activated protein kinase/ERK) signaling pathway. The mTOR inhibitor Torin1 can partially block the toxic effects of HSV-TK/GCV on HXO-RB44 cells. The above results demonstrate that the mechanism undertaken by HSV-TK/GCV to exhibit therapeutic effects mechanism may inhibit autophagy by activating MAPK/ERK. The findings of the present study may provide novel insight for the exploration of HSV-TK/GCV in the treatment of retinoblastoma.

Vitamin K2 suppresses rotenone-induced microglial activation in vitro

AIM

Increasing evidence has shown that environmental factors such as rotenone and paraquat induce neuroinflammation, which contributes to the pathogenesis of Parkinson's disease (PD). In this study, we investigated the molecular mechanisms underlying the repression by menaquinone-4 (MK-4), a subtype of vitamin K2, of rotenone-induced microglial activation in vitro.

METHODS

A microglial cell line (BV2) was exposed to rotenone (1 μmol/L) with or without MK-4 treatment. The levels of TNF-α or IL-1β in 100 μL of cultured media of BV2 cells were measured using ELISA kits. BV2 cells treated with rotenone with or without MK4 were subjected to mitochondrial membrane potential, ROS production, immunofluorescence or immunoblot assays. The neuroblastoma SH-SY5Y cells were treated with conditioned media (CM) of BV2 cells that were exposed to rotenone with or without MK-4 treatment, and the cell viability was assessed using MTT assay.

RESULTS

In rotenone-treated BV2 cells, MK-4 (0.5-20 μmol/L) dose-dependently suppressed the upregulation in the expression of iNOS and COX-2 in the cells, as well as the production of TNF-α and IL-1β in the cultured media. MK-4 (5-20 μmol/L) significantly inhibited rotenone-induced nuclear translocation of NF-κB in BV2 cells. MK-4 (5-20 μmol/L) significantly inhibited rotenone-induced p38 activation, ROS production, and caspase-1 activation in BV2 cells. MK-4 (5-20 μmol/L) also restored the mitochondrial membrane potential that had been damaged by rotenone. Exposure to CM from rotenone-treated BV2 cells markedly decreased the viability of SH-SY5Y cells. However, this rotenone-activated microglia-mediated death of SH-SY5Y cells was significantly attenuated when the BV2 cells were co-treated with MK-4 (5-20 μmol/L).

CONCLUSION

Vitamin K2 can directly suppress rotenone-induced activation of microglial BV2 cells in vitro by repressing ROS production and p38 activation.

Mitochondrial dysfunction in Parkinson's disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease, which is characterized by loss of dopaminergic (DA) neurons in the substantia nigra pars compacta and the formation of Lewy bodies and Lewy neurites in surviving DA neurons in most cases. Although the cause of PD is still unclear, the remarkable advances have been made in understanding the possible causative mechanisms of PD pathogenesis. Numerous studies showed that dysfunction of mitochondria may play key roles in DA neuronal loss. Both genetic and environmental factors that are associated with PD contribute to mitochondrial dysfunction and PD pathogenesis. The induction of PD by neurotoxins that inhibit mitochondrial complex I provides direct evidence linking mitochondrial dysfunction to PD. Decrease of mitochondrial complex I activity is present in PD brain and in neurotoxin- or genetic factor-induced PD cellular and animal models. Moreover, PINK1 and parkin, two autosomal recessive PD gene products, have important roles in mitophagy, a cellular process to clear damaged mitochondria. PINK1 activates parkin to ubiquitinate outer mitochondrial membrane proteins to induce a selective degradation of damaged mitochondria by autophagy. In this review, we summarize the factors associated with PD and recent advances in understanding mitochondrial dysfunction in PD.

ESE1 is Associated with Neuronal Apoptosis in Lipopolysaccharide Induced Neuroinflammation

Neuronal apoptosis induced by the over-activation of microglia during neuroinflammation contributes to the pathology of central nervous system (CNS) degenerative diseases. ESE1 regulates apoptosis of intestinal epithelial cells in ulcerative colitis via accelerating NF-κB activation. NF-κB activation participates in neuronal apoptosis. However, the expression and functions of ESE1 in neuronal apoptosis during CNS inflammatory response remain unclear. In present study, ESE1 expression significantly increased in cerebral cortex after lipopolysaccharide (LPS) intracerebroventricular injection. Immunofluorescence staining indicated that ESE1 was located in neurons. Furthermore, there was a concomitant up-regulation of apoptotic markers including active caspase-3, BAX and decreased expression of anti-apoptosis protein Bcl-2. In vitro, ESE1 depletion in cortical primary neurons inhibited active caspase-3 and BAX expression as well as lactate dehydrogenase (LDH) release with up-regulation of Bcl-2, while ESE1 overexpression can exert opposite effects, indicating that ESE1 promoted neuronal apoptosis induced by LPS or LPS exposed microglia conditioned media (CM). ESE1 accelerated NF-κB activation in neurons with CM treatment. Collectively, all these data suggested that ESE1 might boost neuronal apoptosis during neuroinflammation via up-regulating NF-κB activation. These findings have implications on the potential target of ESE1 in CNS inflammation treatment.

Protease Omi cleaving Hax-1 protein contributes to OGD/R-induced mitochondrial damage in neuroblastoma N2a cells and cerebral injury in MCAO mice

AIM

In the penumbra after focal cerebral ischemia, an increase of protease Omi is linked to a decrease of Hs1-associated protein X-1 (Hax-1), a protein belonging to the Bcl-2 family. In this study we investigated the mechanisms underlying the regulation of Hax-1 by protease Omi in cerebral ischemia/reperfusion (I/R) injury.

METHODS

Mouse neuroblastoma N2a cells were subjected to oxygen-glucose deprivation and reoxygenation (OGD/R); cell viability was assessed with MTT assay. Mice underwent 2-h middle cerebral artery occlusion (MCAO) and reperfusion, and the infarct volume was determined with TTC staining. The expression of Omi and Hax-1 was detected using immunoblot and immunofluorescence assays. The mitochondrial membrane potential was measured using TMRM staining.

RESULTS

In the brains of MCAO mice, the protein level of Omi was significantly increased, while the protein level of Hax-1 was decreased. Similar changes were observed in OGD/R-treated N2a cells, but the mRNA level of Hax-1 was not changed. Furthermore, in OGD/R-treated N2a cells, knockdown of Omi significantly increased Hax-1 protein level. Immunofluorescence assay showed that Omi and Hax-1 were co-localized in mitochondria of N2a cells. OGD/R caused marked mitochondrial damage and apoptosis in N2a cells, while inhibition of Omi protease activity with UCF-101 (10 μmol/L) or overexpression of Hax-1 could restore the mitochondrial membrane potential and attenuate cell apoptosis. Moreover, pretreatment of MCAO mice with UCF-101 (7.15 mg/kg, ip) could restore Hax-1 expression, inhibit caspase activation, and significantly reduce the infarct volume.

CONCLUSION

Protease Omi impairs mitochondrial function by cleaving Hax-1, which induces apoptosis in OGD/R-treated N2a cells and causes I/R injury in MCAO mice.

Resveratrol attenuates HMGB1 signaling and inflammation in house dust mite-induced atopic dermatitis in mice

Resveratrol is a polyphenol abundantly found in red grape skin and is effective against antiaging and anti-inflammation associated with immune responses. In this study, we have investigated the effect of resveratrol on skin lesion, high mobility group box (HMGB)1 and inflammation pathway in an atopic dermatitis (AD) mouse model. AD-like lesion was induced by the application of house dust mite extract to the dorsal skin of NC/Nga mouse. After AD induction, resveratrol (20 mg/kg, p.o.) was administered daily for 2 weeks. We evaluated dermatitis severity, histopathological changes, serum levels of T helper (Th) cytokines (interferon (IFN)γ, interleukin (IL)-4) and changes in protein expression by Western blotting for HMGB1, receptor for advanced glycation end products (RAGE), toll like receptor (TLR)4, nuclear factor (NF)κB, phosphatidylinositide 3-kinase (PI3K), extracellular signal-regulated kinase (ERK)1/2, cyclooxygenase (COX)2, tumor necrosis factor (TNF)α, IL-1β, IL-2Rα and other inflammatory markers in the skin of AD mice. Treatment of resveratrol inhibited the development of the AD-like skin lesions. Histological analysis showed that resveratrol inhibited hypertrophy, intracellular edema, mast cells and infiltration of inflammatory cells. Furthermore, resveratrol treatment down-regulated HMGB1, RAGE, p-NFκB, p-PI3K, p-ERK1/2, COX2, TNFα, IL-1β, IL-2Rα, IFNγ and IL-4. Considering all these findings together, the HMGB1 pathway might be a potential therapeutic target in skin inflammation, and resveratrol treatment could have beneficial effects on AD by modulating the HMGB1 protein expression.

Induction of COX-2-PGE2 synthesis by activation of the MAPK/ERK pathway contributes to neuronal death triggered by TDP-43-depleted microglia

Neuroinflammation is a striking hallmark of amyotrophic lateral sclerosis (ALS) and other neurodegenerative disorders. Previous studies have shown the contribution of glial cells such as astrocytes in TDP-43-linked ALS. However, the role of microglia in TDP-43-mediated motor neuron degeneration remains poorly understood. In this study, we show that depletion of TDP-43 in microglia, but not in astrocytes, strikingly upregulates cyclooxygenase-2 (COX-2) expression and prostaglandin E2 (PGE2) production through the activation of MAPK/ERK signaling and initiates neurotoxicity. Moreover, we find that administration of celecoxib, a specific COX-2 inhibitor, greatly diminishes the neurotoxicity triggered by TDP-43-depleted microglia. Taken together, our results reveal a previously unrecognized non-cell-autonomous mechanism in TDP-43-mediated neurodegeneration, identifying COX-2-PGE2 as the molecular events of microglia- but not astrocyte-initiated neurotoxicity and identifying celecoxib as a novel potential therapy for TDP-43-linked ALS and possibly other types of ALS.

The protease Omi regulates mitochondrial biogenesis through the GSK3β/PGC-1α pathway

Loss of the mitochondrial protease activity of Omi causes mitochondrial dysfunction, neurodegeneration with parkinsonian features and premature death in mnd2 (motor neuron degeneration 2) mice. However, the detailed mechanisms underlying this pathology remain largely unknown. Here, we report that Omi participates in the process of mitochondrial biogenesis, which has been linked to several neurodegenerative diseases. The mitochondrial biogenesis is deficit in mnd2 mice, evidenced by severe decreases of mitochondrial components, mitochondrial DNA and mitochondrial density. Omi cleaves glycogen synthase kinase 3β (GSK3β), a kinase promoting PPARγ coactivator-1α (PGC-1α) degradation, to regulate PGC-1α, a factor important for the mitochondrial biogenesis. In mnd2 mice, GSK3β abundance is increased and PGC-1α abundance is decreased significantly. Inhibition of GSK3β by SB216763 or overexpression of PGC-1α can restore mitochondrial biogenesis in mnd2 mice or Omi-knockdown N2a cells. Furthermore, there is a significant improvement of the movement ability of mnd2 mice after SB216763 treatment. Thus, our study identified Omi as a novel regulator of mitochondrial biogenesis, involving in Omi protease-deficient-induced neurodegeneration.

The anti-inflammation effect of Moutan Cortex on advanced glycation end products-induced rat mesangial cells dysfunction and High-glucose-fat diet and streptozotocin-induced diabetic nephropathy rats

ETHNOPHARMACOLOGICAL RELEVANCE

Moutan Cortex (MC, family: Paeonia suffruticosa Andr.) is a well-known traditional herbal medicine that has been shown to hold a protective effect on inflammation in several diseases. However, its anti-inflammatory activity on diabetic nephropathy (DN) has been less reported. The present study was conducted to evaluate the potential attenuation activities of MC on inflammation in AGEs-induced rat mesangial cells dysfunction and high-glucose-fat diet and streptozotocin (STZ)-induced DN rats and explore the possible mechanism underlying its DN effect.

MATERIALS AND METHODS

The inflammation in mesangial cells (HBZY-1) was induced by 200 μg/ml advanced glycation end products (AGEs). DN rats model was established by an administration high-glucose-fat diet and an intraperitoneal injection of STZ (30 mg/kg). Interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) level in cell supernatant and rats serum were detected by appropriate kits. A co-culture system of mesangial cells and macrophages was performed to evaluate the migration of macrophages. Immunohistochemical assay was applied to examine transforming growth factor beta1 (TGF-β1), IL-6, MCP-1 and intercellular adhesion molecule-1 (ICAM-1) expression in kidney tissues of rats. Furthermore, western blot analysis was carried out to examine TGF-β1, IL-6, MCP-1, ICAM-1 and RAGE protein expressions in mesangial cells.

RESULTS

Pretreatment with MC could significantly inhibit AGEs-induced migration of macrophages in the co-culture system of mesangial cell and macrophage. MC could decrease IL-6 and MCP-1 levels in serum of DN rats in a dose-dependent manner. Furthermore, MC also improved the blood glucose, serum creatinine and urine protein levels. Both immunocytochemistry analysis and western blot analysis showed that MC decreased significantly the over-expression of IL-6, MCP-1, TGF-β1, ICAM-1 and RAGE in mesangial cells or kidney tissues. Additionally, the protein expression of proinflammatory cytokine could also be down-regulated by the pretreatment of RAGE-Ab (5 μg/ml).

CONCLUSION

These findings indicated that the extract of MC had an amelioration activity on the inflammation in AGEs-induced mesangial cells dysfunction and high-glucose-fat diet and STZ-induced DN rats. The protective effect might be associated with the intervention of MC via target of RAGE. These findings suggested that MC might be a benefit agent for the prevention and treatment of DN.

Rotenone directly induces BV2 cell activation via the p38 MAPK pathway

Parkinson’s disease (PD) is the second most common neurodegenerative disease. Although its pathogenesis is still unclear, increasing evidence suggests that mitochondrial dysfunction induced by environmental toxins, such as mitochondrial complex I inhibitors, plays a significant role in the disease process. The microglia in PD brains are highly activated, and inflammation is also an essential element in PD pathogenesis. However, the means by which these toxins activate microglia is still unclear. In the present study, we found that rotenone, a mitochondrial complex I inhibitor, could directly activate microglia via the nuclear factor kappa B (NF-κB) signaling pathway, thereby inducing significantly increased expression of inflammatory cytokines. We further observed that rotenone induced caspase-1 activation and mature IL-1β release, both of which are strictly dependent on p38 mitogen-activated protein kinase (MAPK). The activation of p38 is associated with the presence of reactive oxygen species (ROS) produced by rotenone. Removal of these ROS abrogated the activation of the microglia. Therefore, our data suggest that the environmental toxin rotenone can directly activate microglia through the p38 MAPK pathway.

Amelioration of compound 4,4'-diphenylmethane-bis(methyl)carbamate on high mobility group box1-mediated inflammation and oxidant stress responses in human umbilical vein endothelial cells via RAGE/ERK1/2/NF-κB pathway

High mobility group box-1 (HMGB1), a secreted nuclear protein, acts as an inflammatory mediator and has been implicated in pathophysiological damage of diabetic vascular complications. A compound 4,4'-diphenylmethane-bis(methyl) carbamate (CM1) has a protective activity on advanced glycation end products (AGEs)-induced endothelial dysfunction in our previous study. The aim of this study was to investigate whether CM1 could attenuate HMGB1-induced endothelial dysfunction in human umbilical vein endothelial cells (HUVECs), and also elucidate the possible underlying mechanism. The pre-treatment of CM1 (10(-9)M) could inhibit significantly the migration of macrophages in co-incubation with HUVECs system. HMGB1 stimulated intercellular adhesion molecule-1 (ICAM-1), transforming growth factor-beta1 (TGF-β1) and receptor for advanced glycation end products (RAGE) protein expression in HUVECs, which were inhibited by pretreatment with CM1. Furthermore, it also reduced significantly reactive oxygen species (ROS) generation and inflammatory cytokine interleukin-6 (IL-6) level in co-incubation system. Immunofluorescence and Western blotting assays showed that CM1 could attenuate HMGB1-induced intracellular ERK1/2 and NF-kB activation in HUVECs. Our findings indicated that CM1 attenuated HMGB1-mediated endothelial activation by ameliorating inflammation and oxidant stress responses via RAGE/ERK1/2/NF-κB pathway.

Science Signaling Podcast: 28 August 2012

A protease can help protect against neurodegeneration by preventing inflammation in microglia.