c-Jun N-terminal kinase (JNK)-mediated modulation of brain mitochondria function: new target proteins for JNK signalling in mitochondrion-dependent apoptosis

Inhibition of histone methyltransferase promotes cognition and mitochondrial function in vascular dementia model

Vascular dementia (VD) is one of the most common forms of dementia worldwide, characterized by problems with reasoning, planning, judgment, and memory. This study investigated the effect of a histone methyltransferase inhibitor on cognition and mitochondrial function in a rat model of VD, as well as its impact on H2O2-induced neurotoxicity in hippocampal neuronal cultures. In the in vivo experiments, VD was induced by bilateral occlusion of the common carotid artery (CCA) for one month. The histone methyltransferase inhibitor, BIX01294, was administered intracerebroventricularly for one month (22.5 µg.kg-1 three times/week). On day 30, behavioral tests, including the novel object recognition test and elevated plus maze test, were conducted. Mitochondrial enzyme activities, including aconitase, α-ketoglutarate dehydrogenase (α-KG), complex I, and complex IV, were evaluated in the hippocampus of rats following CCA ligation. In the in vitro experiments, the effect of BIX01294 (50-600 μM) on H2O2 (400 µM)-induced cytotoxicity in hippocampal neuronal cells was assessed using the MTT assay. Flow cytometry was performed to evaluate apoptosis. Our findings revealed that BIX01294 effectively improved memory function, Krebs cycle enzyme activity, and mitochondrial function in the rat model of VD. Moreover, in vitro results showed that BIX01294 at a concentration of 100 µM significantly reversed the cytotoxicity and apoptosis induced by H2O2 in neuronal cells. These findings suggest that BIX01294 may have the potential to improve VD complications by reducing oxidative stress and inhibiting histone methylation.

Vernonia amygdalina Leaf Extract Induces Apoptosis in HeLa Cells: A Metabolomics and Proteomics Study

Medicinal plants produce various bioactive molecules with potential anti-cancer properties with favorable safety profiles. We aimed to investigate the comprehensive composition of Vernonia amygdalina leaf extract and its cytotoxic effects via apoptosis in HeLa cells. The metabolomics approach using LC-MS/MS was conducted to gather the metabolite profile of the extract. Proteomics was performed to understand the comprehensive mechanistic pathways of action. The apoptosis was visualized by cellular staining and the apoptotic proteins were evaluated. V. amygdalina leaf extract exhibited dose-dependent cytotoxic effects on both HeLa and Vero cells after 24 h of exposure in the MTT assay with the IC50 values of 0.767 ± 0.0334 and 4.043 ± 0.469 µg mL-1, respectively, which demonstrated a higher concentration required for Vero cell cytotoxicity. The metabolomic profile of 112 known metabolites specified that the majority of them were alkaloids, phenolic compounds, and steroids. Among these metabolites, deacetylvindoline and licochalcone B were suggested to implicate cytotoxicity. The cytotoxic pathways involved the response to stress and cell death which was similar to doxorubicin. The upstream regulatory proteins, phosphatase and tensin homolog deleted on chromosome ten (PTEN) and X-box binding protein 1 (XBP1), were significantly altered, supporting the regulation of apoptosis and cell death. The levels of apoptotic proteins, c-Jun N-terminal kinases (JNK), p53, and caspase-9 were significantly increased. The novel insights gained from the metabolomic profiling and proteomic pathway analysis of V. amygdalina leaf extract have identified crucial components related to apoptosis induction, highlighting its potential to develop future chemotherapy.

A comparative analysis of daunorubicin and its metabolite daunorubicinol interaction with apoptotic and drug resistance proteins using in silico approach

Daunorubicin (DNR) is a chemotherapeutic drug associated with multiple side effects, including drug resistance. As the molecular mechanism related to these side effects remain unclear and mostly hypothesized, this study addresses and compares the role of DNR and its metabolite Daunorubicinol (DAUNol) to induce apoptosis and drug resistance using molecular docking, Molecular Dynamics (MD) simulation, MM-PBSA and chemical pathway analysis. The results showed that DNR's interaction was stronger with Bax protein, Mcl-1:mNoxaB and Mcl-1:Bim protein complexes than DAUNol. On the other hand, contrasting results were obtained for drug resistance proteins where stronger interaction was obtained with DAUNol compared to DNR. Further, MD simulation performed for 100 ns provided the details of protein-ligand interaction. Most notable was the interaction of Bax protein with DNR, resulting in conformational changes at α-helices 5, 6 and 9, leading to Bax activation. Finally, the chemical signalling pathway analysis also revealed the regulation of different signalling pathways by DNR and DAUNol. It was observed that DNR majorly impacted the signalling associated with apoptosis while DAUNol mainly targeted pathways related to multidrug resistance and cardiotoxicity. Overall, the results highlight that DNR biotransformation reduces its capability to induce apoptosis while enhancing its ability to induce drug resistance and off-target toxicity.Communicated by Ramaswamy H. Sarma.

Dioscin induces osteosarcoma cell apoptosis by upregulating ROS-mediated P38 MAPK signaling

Osteosarcoma is the most common primary malignant bone tumor in children and adolescents. Many patients with osteosarcoma readily develop resistance to chemotherapy and have an extremely dismal prognosis. Dioscin, a saponin, is known to exhibit potent anticancer activities and induce cellular death of a variety of cancer types. However, the inhibitory effect of dioscin on osteosarcoma cells and its underlying mechanisms have not been fully elucidated. We investigated the responses of human U2-OS and MG63 osteosarcoma cells to dioscin with regard to proliferation, apoptosis, migration, and invasion, and studied the effect of dioscin on MAPK-related proteins by western blot analysis assays. Dioscin inhibited osteosarcoma cell proliferation, migration, and invasion. Moreover, it induced osteosarcoma cell apoptosis via reactive oxygen species (ROS)-dependent apoptotic signaling. N-acetylcysteine, a reactive oxygen species inhibitor, suppressed dioscin-induced apoptosis, indicating that ROS play an essential role in dioscin-induced apoptosis. Western blot analysis assays showed that p38 MAPK was upregulated after dioscin treatment, and that dioscin induced apoptosis by upregulating ROS-mediated p38 MAPK signaling. Our study suggests that dioscin possesses antitumor activities against human osteosarcoma cells, inhibits osteosarcoma cell proliferation, migration and invasion, and induces osteosarcoma cell apoptosis through upregulating ROS-mediated p38 MAPK signaling. This study may provide a new therapeutic strategy and potential clinical applications for the treatment of osteosarcoma.

Inhibition of TNF-α and JNK Signaling Pathway Can Reduce Paclitaxel-Induced Apoptosis of Mouse Cardiomyocytes

Paclitaxel (PTX) is a widely used chemotherapeutic drug for treating tumors. However, studies have shown that it can cause cardiac problems such as arrhythmia, myocarditis, chronic cardiomyopathy, and heart failure. Therefore, it is essential to study the mechanism behind the cardiotoxicity of PTX in tumor treatment. In this study, we initially injected PTX into mice to establish a myocardial cell apoptosis model to observe the degree of damage to mouse myocardium caused by PTX. Upon determining the levels of mouse myocardial creatine phosphokinase (CK), myokinase isoenzyme (CK-MB), aspartate transaminase (AST), and lactate dehydrogenase (LDH), we found that all of these levels showed apparent increases in mice treated with PTX. Further analyses of the TNF-α level and the expression of Jun N-terminal kinase (JNK) and Bcl-2 family-related proteins in myocardial tissue were performed. It was found that PTX increased the protein levels of TNF-α, Bax, p-JNK, and JNK in myocardial tissue but decreased the protein level of Bcl-2. After 1 month of PTX treatment in mice, we inhibited the expression of TNF-α and JNK proteins, which reduced the effect of paclitaxel on the apoptosis of mouse cardiomyocytes. The protein levels of Bax, p-JNK, and TNF-α in cardiomyocytes were reduced, while there was a relative increase in the Bcl-2 protein level. The findings suggested that inhibition of the NK signaling pathway and TNF-α can lessen the effect of PTX on mouse cardiomyocytes.

Neuroprotective Effect of Luteolin-7-O-Glucoside against 6-OHDA-Induced Damage in Undifferentiated and RA-Differentiated SH-SY5Y Cells

Luteolin is one of the most common flavonoids present in edible plants and its potential benefits to the central nervous system include decrease of microglia activation, neuronal damage and high antioxidant properties. The aim of this research was to evaluate the neuroprotective, antioxidant and anti-inflammatory activities of luteolin-7-O-glucoside (Lut7). Undifferentiated and retinoic acid (RA)-differentiated SH-SY5Y cells were pretreated with Lut7 and incubated with 6-hydroxydopamine (6-OHDA). Cytotoxic and neuroprotective effects were determined by MTT assay. Antioxidant capacity was determined by DPPH, FRAP, and ORAC assays. ROS production, mitochondrial membrane potential (ΔΨm), Caspase–3 activity, acetylcholinesterase inhibition (AChEI) and nuclear damage were also determined in SH-SY5Y cells. TNF-α, IL-6 and IL-10 release were evaluated in LPS-induced RAW264.7 cells by ELISA. In undifferentiated SH-SY5Y cells, Lut7 increased cell viability after 24 h, while in RA-differentiated SH-SY5Y cells, Lut7 increased cell viability after 24 and 48 h. Lut7 showed a high antioxidant activity when compared with synthetic antioxidants. In undifferentiated cells, Lut7 prevented mitochondrial membrane depolarization induced by 6-OHDA treatment, decreased Caspase-3 and AChE activity, and inhibited nuclear condensation and fragmentation. In LPS-stimulated RAW264.7 cells, Lut7 treatment reduced TNF-α levels and increased IL-10 levels after 3 and 24 h, respectively. In summary, the results suggest that Lut7 has neuroprotective effects, thus, further studies should be considered to validate its pharmacological potential in more complex models, aiming the treatment of neurodegenerative diseases.

Roles of mitochondrial unfolded protein response in mammalian stem cells

The mitochondrial unfolded protein response (UPRmt) is an evolutionarily conserved adaptive mechanism for improving cell survival under mitochondrial stress. Under physiological and pathological conditions, the UPRmt is the key to maintaining intracellular homeostasis and proteostasis. Important roles of the UPRmt have been demonstrated in a variety of cell types and in cell development, metabolism, and immune processes. UPRmt dysfunction leads to a variety of pathologies, including cancer, inflammation, neurodegenerative disease, metabolic disease, and immune disease. Stem cells have a special ability to self-renew and differentiate into a variety of somatic cells and have been shown to exist in a variety of tissues. These cells are involved in development, tissue renewal, and some disease processes. Although the roles and regulatory mechanisms of the UPRmt in somatic cells have been widely reported, the roles of the UPRmt in stem cells are not fully understood. The roles and functions of the UPRmt depend on stem cell type. Therefore, this paper summarizes the potential significance of the UPRmt in embryonic stem cells, tissue stem cells, tumor stem cells, and induced pluripotent stem cells. The purpose of this review is to provide new insights into stem cell differentiation and tumor pathogenesis.

A Highly Selective In Vitro JNK3 Inhibitor, FMU200, Restores Mitochondrial Membrane Potential and Reduces Oxidative Stress and Apoptosis in SH-SY5Y Cells

Current treatments for neurodegenerative diseases (ND) are symptomatic and do not affect disease progression. Slowing this progression remains a crucial unmet need for patients and their families. c-Jun N-terminal kinase 3 (JNK3) are related to several ND hallmarks including apoptosis, oxidative stress, excitotoxicity, mitochondrial dysfunction, and neuroinflammation. JNK inhibitors can play an important role in addressing neuroprotection. This research aims to evaluate the neuroprotective, anti-inflammatory, and antioxidant effects of a synthetic compound (FMU200) with known JNK3 inhibitory activity in SH-SY5Y and RAW264.7 cell lines. SH-SY5Y cells were pretreated with FMU200 and cell damage was induced by 6-hydroxydopamine (6-OHDA) or hydrogen peroxide (H₂O₂). Cell viability and neuroprotective effect were assessed with an MTT assay. Flow cytometric analysis was performed to evaluate cell apoptosis. The H₂O₂-induced reactive oxygen species (ROS) generation and mitochondrial membrane potential (ΔΨm) were evaluated by DCFDA and JC-1 assays, respectively. The anti-inflammatory effect was determined in LPS-induced RAW264.7 cells by ELISA assay. In undifferentiated SH-SY5Y cells, FMU200 decreased neurotoxicity induced by 6-OHDA in approximately 20%. In RA-differentiated cells, FMU200 diminished cell death in approximately 40% and 90% after 24 and 48 h treatment, respectively. FMU200 reduced both early and late apoptotic cells, decreased ROS levels, restored mitochondrial membrane potential, and downregulated JNK phosphorylation after H₂O₂ exposure. In LPS-stimulated RAW264.7 cells, FMU200 reduced TNF-α levels after a 3 h treatment. FMU200 protects neuroblastoma SH-SY5Y cells against 6-OHDA- and H₂O₂-induced apoptosis, which may result from suppressing the JNK pathways. Our findings show that FMU200 can be a useful candidate for the treatment of neurodegenerative disorders.

Protection of apigenin against acrylonitrile-induced sperm and testis injury in rats: involvement of activation of ASK1-JNK/p38 signaling pathway

This study aims to clarify if apigenin (AP) could play a pivotal role in attenuating acrylonitrile (ACN)-induced sperm and testis injury by inhibiting ASK1-JNK/p38 signaling pathway. Male Sprague-Dawley rats were randomly divided into five groups: a control group (corn oil), an ACN group (ACN 46 mg kg^-1), an ACN + AP1 group (ACN + AP 117 mg kg^-1), an ACN + AP2 group (ACN + AP 234 mg kg^-1) and an ACN + AP3 group (ACN + AP 351 mg kg^-1). The ACN + AP groups were given ACN by gavage after a pretreatment with different dosages of AP for 30 min, whereas the rats in the control group received an equivalent volume of corn oil. The gavage was conducted for 6 days per week in 4 weeks. The results showed that AP reduced sperm deformity rate and DNA fragment index and attenuated the testicular injury induced by ACN. AP could also alleviate oxidative stress, downregulate ASK1-JNK/p38 signaling pathway and eventually inhibit mitochondria-mediated testicular apoptosis. In brief, AP could dampen oxidative stress thereby inhibiting testicular apoptosis mediated by ASK1-JNK/p38 signaling pathway, alleviating ACN-induced sperm and testis injury and exerting a protective effect on male reproductive system.

c-Jun N-Terminal Kinase Inhibitors as Potential Leads for New Therapeutics for Alzheimer's Diseases

Alzheimer's Disease (AD) is becoming more prevalent as the population lives longer. For individuals over 60 years of age, the prevalence of AD is estimated at 40.19% across the world. Regarding the cognitive decline caused by the disease, mitogen-activated protein kinases (MAPK) pathways such as the c-Jun N-terminal kinase (JNK) pathway are involved in the progressive loss of neurons and synapses, brain atrophy, and augmentation of the brain ventricles, being activated by synaptic dysfunction, oxidative stress, and excitotoxicity. Nowadays, AD symptoms are manageable, but the disease itself remains incurable, thus the inhibition of JNK3 has been explored as a possible therapeutic target, considering that JNK is best known for its involvement in propagating pro-apoptotic signals. This review aims to present biological aspects of JNK, focusing on JNK3 and how it relates to AD. It was also explored the recent development of inhibitors that could be used in AD treatment since several drugs/compounds in phase III clinical trials failed. General aspects of the MAPK family, therapeutic targets, and experimental treatment in models are described and discussed throughout this review.

Conditional Ablation of Myeloid TNF Improves Functional Outcome and Decreases Lesion Size after Spinal Cord Injury in Mice

Spinal cord injury (SCI) is a devastating condition consisting of an instant primary mechanical injury followed by a secondary injury that progresses for weeks to months. The cytokine tumor necrosis factor (TNF) plays an important role in the pathophysiology of SCI. We investigated the effect of myeloid TNF ablation (peripheral myeloid cells (macrophages and neutrophils) and microglia) versus central myeloid TNF ablation (microglia) in a SCI contusion model. We show that TNF ablation in macrophages and neutrophils leads to reduced lesion volume and improved functional outcome after SCI. In contrast, TNF ablation in microglia only or TNF deficiency in all cells had no effect. TNF levels tended to be decreased 3 h post-SCI in mice with peripheral myeloid TNF ablation and was significantly decreased 3 days after SCI. Leukocyte and microglia populations and all other cytokines (IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12, and IFNγ) and chemokines (CCL2, CCL5, and CXCL1) investigated, in addition to TNFR1 and TNFR2, were comparable between genotypes. Analysis of post-SCI signaling cascades demonstrated that the MAPK kinase SAPK/JNK decreased and neuronal Bcl-XL levels increased post-SCI in mice with ablation of TNF in peripheral myeloid cells. These findings demonstrate that peripheral myeloid cell-derived TNF is pathogenic in SCI.

Glycosylation end products mediate damage and apoptosis of periodontal ligament stem cells induced by the JNK-mitochondrial pathway

Background: Recent studies have confirmed the bidirectional relationship between the two and the exacerbation of periodontitis by type II diabetes mellitus (T2DM), the pathogenic mechanism has not yet been clarified, AGEs has been linked to the pathogenesis of both periodontitis and T2DM, JNK signaling pathway might play a important role to explain the inner mechanism.

Objectives: To study advanced glycation end products (AGEs) activate the innate immune system of the host by activating oxidative stress and affecting cellular signal transduction in periodontal ligament stem cells (PDLSCs);

Results: TNF-α and/or AGEs can induce the formation of endogenous ROS in PDLSCs, thereby activating the downstream JNK signalling pathway, leading to the initiation of the mitochondria-mediated apoptotic pathway and the induction of PDLSC apoptosis.

Conclusion: we hypothesized that the JNK pathway is a key link in the apoptosis of PDLSCs mediated by TNF-α and/or AGEs.

Materials and Methods: PDLSCs from healthy volunteers were extracted, cultured and stimulated with TNF-a and/or AGEs, Flow cytometry, CCK-8, multidifferential assay, RT-PCR, apoptosis assay, Transmission electron microscopy and Western blotting were recruit to detect the internal relations between AGEs and PDLSCs.

Hinokiflavone induces apoptosis via activating mitochondrial ROS/JNK/caspase pathway and inhibiting NF-κB activity in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the sixth most common malignancy with limited treatment options. Hinokiflavone (HF), a natural biflavonoid, has shown to inhibit the proliferation of melanoma, whereas its antitumour effect against HCC and the underlying mechanisms remain elusive. Here, we aimed at evaluating its antitumour effect against HCC in both in vitro and in vivo. Cell counting kit 8, colony formation assay, PI/RNase staining and Western blotting revealed that HF inhibited the proliferation of HCC cells via G0/G1 cell cycle arrest with p21/p53 up-regulation. DAPI staining, Annexin V-FITC/PI staining and Western blotting confirmed that HF triggered caspase-dependent apoptosis. Moreover, HF increased the levels of mitochondrial reactive oxygen species (mtROS) and activated c-Jun N-terminal kinase (JNK) pathway, as measured by MitoSOX Red staining and Western blotting. After respectively inhibiting mtROS (Mito-TEMPO) and JNK (SP600125), HF-induced apoptosis was reversed. Additionally, Western blotting documented that HF suppressed nuclear factor kappa B (NF-κB) activity and the anti-apoptotic genes downstream, contributing to cell apoptosis. Finally, in vivo studies demonstrated that HF significantly impaired tumour growth in HCC xenograft. Collectively, these findings suggested that HF induced apoptosis through activating mtROS/JNK/caspase pathway and inhibiting NF-κB signalling, which may represent a novel therapeutic agent for treating HCC.

Blockage of Autophagic Flux and Induction of Mitochondria Fragmentation by Paroxetine Hydrochloride in Lung Cancer Cells Promotes Apoptosis via the ROS-MAPK Pathway

Cancer cells are characterized by malignant proliferation and aberrant metabolism and are thereby liable to the depletion of nutrients and accumulation of metabolic waste. To maintain cellular homeostasis, cancer cells are prone to upregulating the canonical autophagy pathway. Here, we identified paroxetine hydrochloride (Paxil) as a late autophagy inhibitor and investigated its killing effect on lung cancer cells and with a xenograft mouse model in vivo. Upregulated LC3-II and p62 expression indicated that Paxil inhibited autophagy. Acid-sensitive dyes (e.g., LysoTracker and AO staining) indicated reduced lysosomal acidity following Paxil treatment; consequently, the maturation of the pH-dependent hydroxylases (e.g., cathepsin B and D) substantially declined. Paxil also induced the fragmentation of mitochondria and further intensified ROS overproduction. Since the autophagy pathway was blocked, ROS rapidly accumulated, which activated JNK and p38 kinase. Such activity promoted the localization of Bax, which led to increased mitochondrial outer membrane permeability. The release of Cytochrome c with the loss of the membrane potential triggered a caspase cascade, ultimately leading to apoptosis. In contrast, the clearance of ROS by its scavenger, NAC, rescued Paxil-induced apoptosis accompanied by reduced p38 and JNK activation. Thus, Paxil blocked the autophagic flux and induced the mitochondria-dependent apoptosis via the ROS-MAPK pathway.

Neoantimycin F, a Streptomyces-Derived Natural Product Induces Mitochondria-Related Apoptotic Death in Human Non-Small Cell Lung Cancer Cells

Streptomyces-derived natural products have been become a major focus of anti-tumor drug discovery studies. Neoantimycin F (NAT-F), was isolated from Streptomyces conglobatus by our group. Here, we examined the anti-cancer activities and its underlying molecular mechanisms implicated in NAT-F-induced apoptosis of non-small cell lung cancer (NSCLC) cells. Our results showed that NAT-F exerted excellent growth-inhibitory activity against PC9 and H1299 cells in a concentration-dependent manner. NAT-F-induced cell cycle arrest at S and G₀/G₁ phase in PC9 and H1299 cells, respectively. Further investigation revealed that the key proteins (including cyclinD1, cyclinE1, cyclinB1, CDK2, and CDK4) were involved in the cell regulation by NAT-F. Additionally, NAT-F significantly increased the production of reactive oxygen species (ROS), induced DNA damage, nuclear condensation, and cell apoptosis in both cell lines. Moreover, loss of the mitochondrial membrane potential (MMP) was markedly induced by NAT-F. Additional results revealed that NAT-F could up-regulate pro-apoptotic protein Bax and down-regulate anti-apoptotic protein Bcl-2, Mcl-1, and Bcl-x_L, resulting in cytochrome c release from mitochondria and sequential activation of caspase-9 and -3, as well as the cleavage of poly (ADP-ribose) polymerase. Meanwhile, c-Jun N-terminal kinase (JNK), p38 MAPK (p38), and extracellular signal-regulated kinase (ERK) signaling pathway were also involved in anti-cancer activity of NAT-F in NSCLC cells. Taken together, these findings indicated that NAT-F possessed anti-proliferative effect and induced apoptosis in NSCLC cells in vitro and may be conducive to promote the development of novel anti-NSCLC agents.

N-Methylparoxetine Blocked Autophagic Flux and Induced Apoptosis by Activating ROS-MAPK Pathway in Non-Small Cell Lung Cancer Cells

The main mechanistic function of most chemotherapeutic drugs is mediated by inducing mitochondria-dependent apoptosis. Tumor cells usually respond to upregulate autophagy to eliminate impaired mitochondria for survival. Hypothetically, inhibiting autophagy might promote mitochondria-dependent apoptosis, thus enhancing the efficacy of chemotherapeutic therapies. We previously identified N-methylparoxetine (NMP) as an inducer of mitochondrial fragmentation with subsequent apoptosis in non-small cell lung cancer (NSCLC) cells. We discovered that ROS was accumulated in NMP-treated NSCLC cells, followed by c-Jun N-terminal kinase (JNK) and p38 MAP kinase (p38) activation. This was reversed by the application of a reactive oxygen species (ROS) scavenger, N-acetylcysteine (NAC), leading to a reduction in apoptosis. Our data suggested that NMP induced apoptosis in NSCLC cells by activating mitogen-activated protein kinase (MAPK) pathway. We further speculated that the remarkable increase of ROS in NMP-treated NSCLC cells might result from an inhibition of autophagy. Our current data confirmed that NMP blocked autophagy flux at late stage wherein lysosomal acidification was inhibited. Taken together, this study demonstrated that NMP could exert dual apoptotic functions—mitochondria impairment and, concomitantly, autophagy inhibition. NMP-related excessive ROS accumulation induced apoptosis by activating the MAPK pathway in NSCLC cells.

Paeoniflorin inhibits tributyltin chloride-induced apoptosis in hypothalamic neurons via inhibition of MKK4-JNK signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Paeoniflorin (PF) exerts a significant protective effect against neurotoxicity and mitochondrial damage in neurons. However, the mechanisms underlying PF-mediated rescue remain elusive. Therefore, we endeavored to further research the molecular mechanisms underlying PF-mediated inhibition of tributyltin chloride (TBTC)-induced apoptosis of neurons.

AIM OF THE STUDY

To investigate the influence and possible mechanism of action of PF in TBTC-induced neurodegenerative disease.

MATERIALS AND METHODS

First, primary hypothalamic neurons were treated with tributyltin chloride (150 μg/L) and PF (25, 50, and 100 μM). 17β-estradiol (1 nM) was used as a positive control. Subsequently, CCK-8 assay was performed. The level of apoptosis was examined by flow cytometry and the function of mitochondria was reflected by MMP levels. The mRNA expression levels of B-cell lymphoma-2 (Bcl-2), together with Bax, were examined using qRT-PCR. The protein levels of mitogen-activated protein kinase kinase 4 (MKK4), c-Jun N-terminal kinase (JNK), Bcl-2, Bax, and Caspase-3 were examined using western blotting. Finally, pretreatment with JNK agonist, anisomycin, was done to observe the change in expressions of MKK4 and JNK.

RESULTS

Paeoniflorin treatment reduced TBTC-induced damage and neuron loss in a dose-dependent manner. Decrease in mitogen-activated protein kinase (MAPK) as well as JNK levels were reversed by treatment with paeoniflorin via inhibition of JNK activation. Furthermore, ratio of levels of Bcl-2/Bax increased while the activation of caspase-3 was suppressed. In addition, pretreatment with JNK agonist, anisomycin effectively suppressed TBTC-induced cytotoxicity in hypothalamic neuron.

CONCLUSIONS

PF can potentially be used to prevent and/or treat neurodegenerative diseases and neural injury by inhibiting MKK4-JNK signaling pathway.

Redox inhibition of protein phosphatase PP2A: Potential implications in oncogenesis and its progression

Cellular processes are dictated by the active signaling of proteins relaying messages to regulate cell proliferation, apoptosis, signal transduction and cell communications. An intricate web of protein kinases and phosphatases are critical to the proper transmission of signals across such cascades. By governing 30–50% of all protein dephosphorylation in the cell, with prominent substrate proteins being key regulators of signaling cascades, the phosphatase PP2A has emerged as a celebrated player in various developmental and tumorigenic pathways, thereby posing as an attractive target for therapeutic intervention in various pathologies wherein its activity is deregulated. This review is mainly focused on refreshing our understanding of the structural and functional complexity that cocoons the PP2A phosphatase, and its expression in cancers. Additionally, we focus on its physiological regulation as well as into recent advents and strategies that have shown promise in countering the deregulation of the phosphatase through its targeted reactivation. Finally, we dwell upon one of the key regulators of PP2A in cancer cells-cellular redox status-its multifarious nature, and its integration into the reactome of PP2A, highlighting some of the significant impacts that ROS can inflict on the structural modifications and functional aspect of PP2A.

Sab concentrations indicate chemotherapeutic susceptibility in ovarian cancer cell lines

The occurrence of chemotherapy-resistant tumors makes ovarian cancer (OC) the most lethal gynecological malignancy. While many factors may contribute to chemoresistance, the mechanisms responsible for regulating tumor vulnerability are under investigation. Our analysis of gene expression data revealed that Sab, a mitochondrial outer membrane (MOM) scaffold protein, was down-regulated in OC patients. Sab-mediated signaling induces cell death, suggesting that this apoptotic pathway is diminished in OC. We examined Sab expression in a panel of OC cell lines and found that the magnitude of Sab expression correlated to chemo-responsiveness; wherein, OC cells with low Sab levels were chemoresistant. The Sab levels were reflected by a corresponding amount of stress-induced c-Jun N-terminal kinase (JNK) on the MOM. BH3 profiling and examination of Bcl-2 and BH3-only protein concentrations revealed that cells with high Sab concentrations were primed for apoptosis, as determined by the decrease in pro-survival Bcl-2 proteins and an increase in pro-apoptotic BH3-only proteins on mitochondria. Furthermore, overexpression of Sab in chemoresistant cells enhanced apoptotic priming and restored cellular vulnerability to a combination treatment of cisplatin and paclitaxel. Contrariwise, inhibiting Sab-mediated signaling or silencing Sab expression in a chemosensitive cell line resulted in decreased apoptotic priming and increased resistance. The effects of silencing on Sab on the resistance to chemotherapeutic agents were emulated by the silencing or inhibition of JNK, which could be attributed to changes in Bcl-2 protein concentrations induced by sub-chronic JNK inhibition. We propose that Sab may be a prognostic biomarker to discern personalized treatments for OC patients.

Poly(adenosine diphosphate-ribose) polymerase as therapeutic target: lessons learned from its inhibitors

Poly(ADP-ribose) polymerases are a family of DNA-dependent nuclear enzymes catalyzing the transfer of ADP-ribose moieties from cellular nicotinamide-adenine-dinucleotide to a variety of target proteins. Although they have been considered as resident nuclear elements of the DNA repair machinery, recent works revealed a more intricate physiologic role of poly(ADP-ribose) polymerases with numerous extranuclear activities. Indeed, poly(ADP-ribose) polymerases participate in fundamental cellular processes like chromatin remodelling, transcription or regulation of the cell-cycle. These new insight into the physiologic roles of poly(ADP-ribose) polymerases widens the range of human pathologies in which pharmacologic inhibition of these enzymes might have a therapeutic potential. Here, we overview our current knowledge on extranuclear functions of poly(ADP-ribose) polymerases with a particular focus on the mitochondrial ones and discuss potential fields of future clinical applications.

Triptolide induces Sertoli cell apoptosis in mice via ROS/JNK-dependent activation of the mitochondrial pathway and inhibition of Nrf2-mediated antioxidant response

Triptolide (TP), an oxygenated diterpene, has a variety of beneficial pharmacodynamic activities but its clinical applications are restricted due to severe testicular injury. This study aimed to delineate the molecular mechanisms of TP-induced testicular injury in vitro and in vivo. TP (5-50000 nmol/L) dose-dependently decreased the viability of TM4 Sertoli cells with an IC₅₀ value of 669.5-269.45 nmol/L at 24 h. TP (125, 250, and 500 nmol/L) dose-dependently increased the accumulation of ROS, the phosphorylation of JNK, mitochondrial dysfunction and activation of the intrinsic apoptosis pathway in TM4 cells. These processes were attenuated by co-treatment with the antioxidant N-acetyl cysteine (NAC, 1 mmol/L). Furthermore, TP treatment inhibited the translocation of Nrf2 from cytoplasm into the nucleus as well as the expression of downstream genes NAD(P)H quinone oxidoreductase1 (NQO1), catalase (CAT) and hemeoxygenase 1 (HO-1), thus abrogating Nrf2-mediated defense mechanisms against oxidative stress. Moreover, siRNA knockdown of Nrf2 significantly potentiated TP-induced apoptosis of TM4 cells. The above results from in vitro experiments were further validated in male mice after oral administration of TP (30, 60, and 120 mg·kg^-1·d^-1, for 14 d), as evidenced by the detected indexes, including dose-dependently decreased SDH activity, increased MDA concentration, altered testicle histomorphology, elevated caspase-3 activation, apoptosis induction, increased phosphorylation of JNK, and decreased gene expression of NQO1, CAT and HO-1 as well as nuclear protein expression of Nrf2 in testicular tissue. Our results demonstrate that TP activates apoptosis of Sertoli cells and injury of the testis via the ROS/JNK-mediated mitochondrial-dependent apoptosis pathway and down-regulates Nrf2 activation.

Novel derivative of Paeonol, Paeononlsilatie sodium, alleviates behavioral damage and hippocampal dendritic injury in Alzheimer's disease concurrent with cofilin1/phosphorylated-cofilin1 and RAC1/CDC42 alterations in rats

Alzheimer’s disease (AD) is a typical hippocampal amnesia and the most common senile dementia. Many studies suggest that cognitive impairments are more closely correlated with synaptic loss than the burden of amyloid deposits in AD progression. To date, there is no effective treatment for this disease. Paeonol has been widely employed in traditional Chinese medicine. This compound improves learning behavior in an animal model; however, the mechanism remains unclear. In this study, Paeononlsilatie sodium (Pa), a derivative of Paeonol, attenuated D-galactose (D-gal) and AlCl₃-induced behavioral damages in rats based on evaluations of the open field test (OFT), elevated plus maze test (EPMT), and Morris water maze test (MWMT). Pa increased the dendritic complexity and the density of dendritic spines. Correlation analysis indicated that morphological changes in neuronal dendrites are closely correlated with behavioral changes. Pa treatment reduced the production of Aβ, affected the phosphorylation and redistribution of cofilin1 and inhibited rod-like formation in hippocampal neurons. The induction of D-gal and AlCl₃ promoted the expression of RAC1/CDC42 expression; however, the tendency of gene expression was inhibited by pretreatment with Pa. Taken together, our results suggest that Pa may represent a novel therapeutic agent for the improvement of cognitive and emotional behaviors and dendritic morphology in an AD animal model.

Putative roles of mitochondrial Voltage-Dependent Anion Channel, Bcl-2 family proteins and c-Jun N-terminal Kinases in ischemic stroke associated apoptosis

There is a constant need for better stroke treatments. Neurons at the periphery of an ischemic stroke affected brain tissue remains metabolically active for several hours or days after stroke onset. They later undergo mitochondrion-mediated apoptosis. It has been found that inhibiting apoptosis in the peripheral ischemic neurons could be very effective in the prevention of stroke progression. During stroke associated apoptosis, cytosolic c-Jun N-terminal Kinases (JNKs) and Bcl-2 family proteins translocate towards mitochondria and promote cytochrome c release by interacting with the outer mitochondrion membrane associated proteins. This review provides an overview of the plausible interactions of the outer mitochondrial membrane Voltage Dependent Anion Channel, Bcl-2 family proteins and JNKs in cytochrome c release in the peripheral ischemic stroke associated apoptotic neurons. The review ends with a note on designing new anti-stroke treatments.

Furanodienone induces G0/G1 arrest and causes apoptosis via the ROS/MAPKs-mediated caspase-dependent pathway in human colorectal cancer cells: a study in vitro and in vivo

Furanodienone, a major bioactive constituents of sesquiterpene derived from Rhizoma Curcumae, has been proven to possess the potent anticancer efficacy on human breast cancer cells. Here, we investigated the cytotoxicity of furanodienone on human colorectal carcinoma cell lines in vitro and in vivo, as well as its underlying molecular mechanisms in the induction of apoptosis. In this study, we found that furanodienone significantly inhibited proliferation of RKO and HT-29 cells, induced mitochondrial dysfunction characterized by collapse of mitochondrial transmembrane potential and reduction of ATP level, and promoted the production of reactive oxygen species (ROS) that functions upstream of caspase-dependent apoptosis. The antioxidant N-acetyl cysteine, a ROS scavenger, abolished this apoptosis induced by furanodienone. In addition, furanodienone elevated the expression of p-p38, p-JNK, but decreased p-ERK, as a result of the produced ROS. The specific inhibitors U0126, SP600125 and SB202190 attenuated the expression of MAPKs, and regulated the expression of cleaved caspase-8, -9 and -3. Furthermore, the potential inhibitory effect of furanodienone on CRC cells was also corroborated in mouse xenograft model. In conclusion, the results demonstrated that furanodienone-triggered ROS plays a pivotal role in apoptosis as an upstream molecule-modulating activity of caspases in mitochondrial pathway via stimulating MAPKs signaling pathway. Our finding may provide a novel candidate for development of antitumor drugs targeting on colorectal cancer.

Hepatoprotective Effect of Polyphenol-Enriched Fraction from Folium Microcos on Oxidative Stress and Apoptosis in Acetaminophen-Induced Liver Injury in Mice

Folium Microcos (FM), the leaves of Microcos paniculata L., shows various biological functions including antioxidant activity and α-glucosidase inhibitory effect. However, its therapeutic potential in acute liver injury is still unknown. This study investigated the hepatoprotective effect and underlying mechanisms of the polyphenol-enriched fraction (FMF) from Folium Microcos. FMF exhibited strong free radical scavenging activities and prevented HepG2/Hepa1-6 cells from hydrogen peroxide- (H₂O₂-) induced ROS production and apoptosis in vitro. Antioxidant activity and cytoprotective effects were further verified by alleviating APAP-induced hepatotoxicity in mice. Western blot analysis revealed that FMF pretreatment significantly abrogated APAP-mediated phosphorylation of MAPKs, activation of proapoptotic protein caspase-3/9 and Bax, and restored expression of antiapoptotic protein Bcl2. APAP-intoxicated mice pretreated with FMF showed increased nuclear accumulation of nuclear factor erythroid 2-related factor (Nrf2) and elevated hepatic expression of its target genes, NAD(P)H:quinine oxidoreductase 1 (NQO1) and hemeoxygenase-1(HO-1). HPLC analysis revealed the four predominantly phenolic compounds present in FMF: narcissin, isorhamnetin-3-O-β-D-glucoside, isovitexin, and vitexin. Consequently, these findings indicate that FMF possesses a hepatoprotective effect against APAP-induced hepatotoxicity mainly through dual modification of ROS/MAPKs/apoptosis axis and Nrf2-mediated antioxidant response, which may be attributed to the strong antioxidant activity of phenolic components.

Unexpected Neuroprotective Effects of Loganin on 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine-Induced Neurotoxicity and Cell Death in Zebrafish

1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP), which induces the pathological characteristics of Parkinson's disease in rodents, also specifically targets dopaminergic neurons in zebrafish embryos and larvae. Loganin, a traditional Chinese drug, was reported to regulate immune function and possess anti-inflammatory and anti-shock effects. Here, we investigate the role of loganin in MPTP-induced Parkinson-like abnormalities in zebrafish. MPTP treatment-induced abnormal development, in larvae, such as pericardium edema, increased yolk color, yolk sac edema, and retarded yolk sac resorption, as well as defects in brain development. Loganin could block MPTP-induced defects, with little toxicity to the eggs. Results of whole mount in situ hybridization showed loganin prevented the loss of both dopaminergic neurons and locomotor activity, exhibited by larvae treated with MPTP. In addition, loganin significantly rescued MPTP-induced neurotoxicity on PC12 cells, possibly through the suppression of PI3K/Akt/mTOR axis and JNK signaling pathways. In conclusion, loganin blocks MPTP-induced neurotoxicity and abnormal development in zebrafish. J. Cell. Biochem. 118: 615-628, 2017. © 2016 Wiley Periodicals, Inc.

Amorphous silica nanoparticles trigger vascular endothelial cell injury through apoptosis and autophagy via reactive oxygen species-mediated MAPK/Bcl-2 and PI3K/Akt/mTOR signaling

Environmental exposure to silica nanoparticles (SiNPs) is inevitable due to their widespread application in industrial, commercial, and biomedical fields. In recent years, most investigators focus on the evaluation of cardiovascular effects of SiNPs in vivo and in vitro. Endothelial injury and dysfunction is now hypothesized to be a dominant mechanism in the development of cardiovascular diseases. This study aimed to explore interaction of SiNPs with endothelial cells, and extensively investigate the exact effects of reactive oxygen species (ROS) on the signaling molecules and cytotoxicity involved in SiNPs-induced endothelial injury. Significant induction of cytotoxicity as well as oxidative stress, apoptosis, and autophagy was observed in human umbilical vein endothelial cells following the SiNPs exposure (P<0.05). The oxidative stress was induced by ROS generation, leading to redox imbalance and lipid peroxidation. SiNPs induced mitochondrial dysfunction, characterized by membrane potential collapse, and elevated Bax and declined bcl-2 expression, ultimately leading to apoptosis, and also increased number of autophagosomes and autophagy marker proteins, such as LC3 and p62. Phosphorylated ERK, PI3K, Akt, and mTOR were significantly decreased, but phosphorylated JNK and p38 MAPK were increased in SiNPs-exposed endothelial cells. In contrast, all of these stimulation phenomena were effectively inhibited by N-acetylcysteine. The N-acetylcysteine supplement attenuated SiNPs-induced endothelial toxicity through inhibition of apoptosis and autophagy via MAPK/Bcl-2 and PI3K/Akt/mTOR signaling, as well as suppression of intracellular ROS property via activating antioxidant enzyme and Nrf2 signaling. In summary, the results demonstrated that SiNPs triggered autophagy and apoptosis via ROS-mediated MAPK/Bcl-2 and PI3K/Akt/mTOR signaling in endothelial cells, and subsequently disturbed the endothelial homeostasis and impaired endothelium. Our findings may provide experimental evidence and explanation for cardiovascular diseases triggered by SiNPs. Furthermore, results hint that the application of antioxidant may provide a novel way for safer use of nanomaterials.

Subchronic administration of ascorbic acid elicits antidepressant-like effect and modulates cell survival signaling pathways in mice

In this study, we examined the ability of subchronic ascorbic acid administration to produce an antidepressant-like effect in the mouse tail suspension test (TST). Moreover, we investigated the effect of this vitamin on hippocampal and cerebrocortical brain-derived neurotrophic factor (BDNF) immunocontent, phosphorylation of protein kinase B (AKT), extracellular signal-regulated kinase (ERK), p38^MAPK and c-Jun. N-terminal kinase (JNK). Fluoxetine (10 mg/kg, positive control, po) or ascorbic acid (0.1 and 1 mg/kg, po), administered once daily for 21 days, produced a significant antidepressant-like effect in the TST. The significant effects obtained in protein immunocontents were: administration of ascorbic acid at 1 mg/kg induced an increase in AKT phosphorylation in cerebral cortex of mice. Ascorbic acid treatment (1 mg/kg), similar to fluoxetine, decreased hippocampal p38^MAPK but did not alter ERK or JNK phosphorylation. These results extend the data about the antidepressant-like effect of ascorbic acid by exploring, for the first time, the intracellular pathways involved in its antidepressant properties after subchronic administration.

Attenuating Oxidative Stress by Paeonol Protected against Acetaminophen-Induced Hepatotoxicity in Mice

Acetaminophen (APAP) overdose is the most frequent cause of drug-induced acute liver failure. The purpose of this study was to investigate whether paeonol protected against APAP-induced hepatotoxicity. Mice treated with paeonol (25, 50, 100 mg/kg) received 400 mg/kg acetaminophen intraperitoneally (i.p.) and hepatotoxicity was assessed. Pre-treatment with paeonol for 6 and 24 h ameliorated APAP-induced hepatic necrosis and significantly reduced the serum alanine aminotransferase (ALT) and aspartate transaminase (AST) levels in a dose-dependent manner. Post-treatment with 100 mg/kg paeonol ameliorated APAP-induced hepatic necrosis and reduced AST and ALT levels in the serum after APAP administration for 24 h. Western blot revealed that paeonol inhibited APAP-induced phosphorylated JNK protein expression but not p38 and Erk1/2. Moreover, paeonol showed anti-oxidant activities with reducing hepatic MDA contents and increasing hepatic SOD, GSH-PX and GSH levels. Paeonol dose-dependently prevented against H2O2 or APAP-induced LDH releasing and ROS production in primary mouse hepatocytes. In addition, the mRNA levels of pro-inflammatory genes such as TNF-α, MCP-1, IL-1β and IL-6 in the liver were dose-dependently reduced by paeonol pre-treatment. Pre-treatment with paeonol significantly inhibited IKKα/β, IκBα and p65 phosphorylation which contributed to ameliorating APAP-induced hepatic inflammation. Collectively, the present study demonstrates paeonol has a protective ability against APAP-induced hepatotoxicity and might be an effective candidate compound against drug-induced acute liver failure.

Mitochondrial dysfunction and cell death in neurodegenerative diseases through nitroxidative stress

Mitochondria are important for providing cellular energy ATP through the oxidative phosphorylation pathway. They are also critical in regulating many cellular functions including the fatty acid oxidation, the metabolism of glutamate and urea, the anti-oxidant defense, and the apoptosis pathway. Mitochondria are an important source of reactive oxygen species leaked from the electron transport chain while they are susceptible to oxidative damage, leading to mitochondrial dysfunction and tissue injury. In fact, impaired mitochondrial function is commonly observed in many types of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, alcoholic dementia, brain ischemia-reperfusion related injury, and others, although many of these neurological disorders have unique etiological factors. Mitochondrial dysfunction under many pathological conditions is likely to be promoted by increased nitroxidative stress, which can stimulate post-translational modifications (PTMs) of mitochondrial proteins and/or oxidative damage to mitochondrial DNA and lipids. Furthermore, recent studies have demonstrated that various antioxidants, including naturally occurring flavonoids and polyphenols as well as synthetic compounds, can block the formation of reactive oxygen and/or nitrogen species, and thus ultimately prevent the PTMs of many proteins with improved disease conditions. Therefore, the present review is aimed to describe the recent research developments in the molecular mechanisms for mitochondrial dysfunction and tissue injury in neurodegenerative diseases and discuss translational research opportunities.

Hyperosmotic Shock Engages Two Positive Feedback Loops through Caspase-3-dependent Proteolysis of JNK1-2 and Bid

Hyperosmotic shock induces early calpain activation, Smac/DIABLO release from the mitochondria, and p38/JNK activation in Xenopus oocytes. These pathways regulate late cytochrome c release and caspase-3 activation. Here, we show that JNK1-1 and JNK1-2 are activated early by osmostress, and sustained activation of both isoforms accelerates the apoptotic program. When caspase-3 is activated, JNK1-2 is proteolyzed at Asp-385 increasing the release of cytochrome c and caspase-3 activity, thereby creating a positive feedback loop. Expression of Bcl-xL markedly reduces hyperosmotic shock-induced apoptosis. In contrast, expression of Bid induces rapid caspase-3 activation, even in the absence of osmostress, which is blocked by Bcl-xL co-expression. In these conditions a significant amount of Bid in the cytosol is mono- and bi-ubiquitinated. Caspase-3 activation by hyperosmotic shock induces proteolysis of Bid and mono-ubiquitinated Bid at Asp-52 increasing the release of cytochrome c and caspase-3 activation, and thus creating a second positive feedback loop. Revealing the JNK isoforms and the loops activated by osmostress could help to design better treatments for human diseases caused by perturbations in fluid osmolarity.

Critical role of c-jun N-terminal protein kinase in promoting mitochondrial dysfunction and acute liver injury

The mechanism by which c-Jun N-terminal protein kinase (JNK) promotes tissue injury is poorly understood. Thus we aimed at studying the roles of JNK and its phospho-target proteins in mouse models of acute liver injury. Young male mice were exposed to a single dose of CCl₄ (50 mg/kg, IP) and euthanized at different time points. Liver histology, blood alanine aminotransferase, and other enzyme activities were measured in CCl₄-exposed mice without or with the highly-specific JNK inhibitors. Phosphoproteins were purified from control or CCl₄-exposed mice and analyzed by differential mass-spectrometry followed by further characterizations of immunoprecipitation and activity measurements. JNK was activated within 1 h while liver damage was maximal at 24 h post-CCl₄ injection. Markedly increased phosphorylation of many mitochondrial proteins was observed between 1 and 8 h following CCl₄ exposure. Pretreatment with the selective JNK inhibitor SU3327 or the mitochondria-targeted antioxidant mito-TEMPO markedly reduced the levels of p-JNK, mitochondrial phosphoproteins and liver damage in CCl₄-exposed mice. Differential proteomic analysis identified many phosphorylated mitochondrial proteins involved in anti-oxidant defense, electron transfer, energy supply, fatty acid oxidation, etc. Aldehyde dehydrogenase, NADH-ubiquinone oxidoreductase, and α-ketoglutarate dehydrogenase were phosphorylated in CCl₄-exposed mice but dephosphorylated after SU3327 pretreatment. Consistently, the suppressed activities of these enzymes were restored by SU3327 pretreatment in CCl₄-exposed mice. These data provide a novel mechanism by which JNK, rapidly activated by CCl₄, promotes mitochondrial dysfunction and acute hepatotoxicity through robust phosphorylation of numerous mitochondrial proteins.

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JNK was rapidly activated after carbon tetrachloride (CCl₄) exposure.

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Activated JNK was translocated to mitochondria and phosphorylated many proteins.

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Many mitochondrial phosphoproteins were identified by mass-spec analysis.

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Mitochondrial ALDH2, α-KGDH, and complex I were inactivated by phosphorylation.

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JNK inhibition reduced phosphorylation of mitochondrial proteins and hepatotoxicity.

Antiproliferative and Apoptotic Activity of Chamaecyparis obtusa Leaf Extract against the HCT116 Human Colorectal Cancer Cell Line and Investigation of the Bioactive Compound by Gas Chromatography-Mass Spectrometry-Based Metabolomics

Chamaecyparis obtusa (CO) belongs to the Cupressaceae family, and it is found widely distributed in Japan and Korea. In this study, the anti-proliferative activities of the methanol and water extracts of CO leaves against a human colorectal cancer cell line (HCT116) were investigated. The methanol extract of CO leaves, at a concentration of 1.25 µg/mL, exhibited anti-proliferative activity against HCT116 cells, while displaying no cytotoxicity against Chang liver cells. Comparative global metabolite profiling was performed using gas chromatography-mass spectrometry coupled with multivariate statistical analysis, and it was revealed that anthricin was the major compound contributing to the anti-proliferative activity. The activation of c-Jun N-terminal kinases played a key role in the apoptotic effect of the methanol extract of CO leaves in HCT116 human colon cancer cells. These results suggest that the methanol extract and anthricin derived from CO leaves might be useful in the development of medicines with anti-colorectal cancer activity.

Mitochondrial dysfunction and tissue injury by alcohol, high fat, nonalcoholic substances and pathological conditions through post-translational protein modifications

Mitochondria are critically important in providing cellular energy ATP as well as their involvement in anti-oxidant defense, fat oxidation, intermediary metabolism and cell death processes. It is well-established that mitochondrial functions are suppressed when living cells or organisms are exposed to potentially toxic agents including alcohol, high fat diets, smoking and certain drugs or in many pathophysiological states through increased levels of oxidative/nitrative stress. Under elevated nitroxidative stress, cellular macromolecules proteins, DNA, and lipids can undergo different oxidative modifications, leading to disruption of their normal, sometimes critical, physiological functions. Recent reports also indicated that many mitochondrial proteins are modified via various post-translation modifications (PTMs) and primarily inactivated. Because of the recently-emerging information, in this review, we specifically focus on the mechanisms and roles of five major PTMs (namely oxidation, nitration, phosphorylation, acetylation, and adduct formation with lipid-peroxides, reactive metabolites, or advanced glycation end products) in experimental models of alcoholic and nonalcoholic fatty liver disease as well as acute hepatic injury caused by toxic compounds. We also highlight the role of the ethanol-inducible cytochrome P450-2E1 (CYP2E1) in some of these PTM changes. Finally, we discuss translational research opportunities with natural and/or synthetic anti-oxidants, which can prevent or delay the onset of mitochondrial dysfunction, fat accumulation and tissue injury.

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Hepatotoxic agents including alcohol and high fat elevate nitroxidative stress.

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Increased nitroxidative stress promotes post-translational protein modifications.

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Post-translational protein modifications of many proteins lead to their inactivation.

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Inactivation of mitochondrial proteins contributes to mitochondrial dysfunction.

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Mitochondrial dysfunction contributes to necrotic or apoptotic tissue injury.

Acrylamide induces mitochondrial dysfunction and apoptosis in BV-2 microglial cells

Acrylamide (ACR), a potent neurotoxin, can be produced during food processing at high temperature. This study examined the redox-dependent apoptotic and inflammatory responses of ACR in an immortalized mouse microglia cell line BV2. The exposure of BV2 cells to ACR reduced cell viability and induced apoptosis in a concentration-dependent manner. ACR impaired cell energy metabolism by decreasing mitochondrial respiration, anaerobic glycolysis, and lowering expression of the complex I, III, and IV subunits. Mitochondrial dysfunction was associated with a decrease of the mitochondrial membrane potential and the Bcl-2/Bax ratio, thus resulting in activation of the mitochondrion-driven apoptotic signaling. This was accompanied by (a) the modulation of redox-sensitive signaling, suppressed Akt activation and increased JNK and p38 activation, and (b) increased expression of NFκB and downstream inducible nitric oxide synthase (iNOS) and nitric oxide generation, thus supporting indirectly a proinflammatory effect of ACR. Nrf2 expression was also increased but not its translocation to the nucleus. Expectedly, the electrophilic attack of ACR on GSH resulted in substantial loss of GSH with a minor GSSG formation. These changes in the cell׳s redox status elicited by ACR resulted in increased H2O2 formation. The changes in mitochondrial functionality and complex subunit expression caused by ACR were reversed by N-acetyl-L-cysteine (NAC). Likewise, NAC restored the cell׳s redox status by increasing GSH levels with concomitant attenuation of H2O2 generation; these effects resulted in decreased apoptotic cell death and inflammatory responses. ACR-mediated mitochondrial dysfunction along with a more oxidized redox status seems to be critical events leading to activation of the intrinsic apoptotic pathway and inflammatory responses.

Gamma-aminobutyric acid induces tumor cells apoptosis via GABABR1·β-arrestins·JNKs signaling module

Gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter in central nervous system, has yet been found to widely exist in tumor tissues to regulate tumor cells growth. However, the function of GABA on inducing tumor cells apoptosis and the potential mechanism are still unclear. In order to detect whether GABA via GABAB receptor GABABR1 would activate c-Jun N-terminal kinases (JNKs) to promote tumor cells apoptosis, co-immunoprecipitation assay was used to investigate the association of β-arrestins with GABABR1 and JNKs in the different four cancer cell lines. Our observation demonstrated that β-arrestins, in addition to their role in G protein-coupled receptors desensitization, had an additional function as adapter proteins to recruit JNKs to GABABR1, thereby conferring distinct enzymatic activities upon the receptor, which may trigger JNKs signal pathway involved in the regulation of cellular growth. Activated JNKs subsequently phosphorylated downstream c-Jun to transcribe a wide variety of pro-apoptotic genes. Additionally, GABA up-regulated the ratio of pro-apoptotic protein Bax to anti-apoptotic protein Bcl-2, and thus facilitated caspase-3 cleavage, leading to tumor cells apoptosis in a mitochondrial-dependent pathway. In contrast, GABABR antagonist CGP35348 reversed GABA-induced JNKs phosphorylation and its downstream proteins activation, which consequently restrained tumor cells apoptosis. Taken together, our study suggested that GABA via its receptor GABABR1 recruited β-arrestins to facilitate the activation of JNKs cascade, resulting in tumor cells growth inhibition.

Oleuropein induced apoptosis in HeLa cells via a mitochondrial apoptotic cascade associated with activation of the c-Jun NH2-terminal kinase

Oleuropein could inhibit growth and/or induce apoptosis in several cancer cell lines. In this study, we investigate how oleuropein strongly induces apoptotic cell death in HeLa human cervical carcinoma cells. Oleuropein induced HeLa cells apoptosis as demonstrated by induction of a sub-G(1) peak in flow cytometry and apoptosis-related morphological changes observed by fluorescence microscopy after being stained by Hoechst 33324. The results also showed that 150 - 200 μM oleuropein&ndash;treated HeLa cells were arrested at the G(2)/M phase. Western blot analysis revealed that the phosphorylated ATF-2, c-Jun NH(2)-terminal kinase (JNK) protein, p53, p21, Bax, and cytochrome c protein in the cytoplasm significantly increased in a dose-dependent manner after treatment of oleuropein for 24 h. Additionally, increasing levels of Bax in response to JNK/SPAK signaling, which formed mitochondrial membrane channels, accounted for releasing of cytochrome c and activation of caspase-9 and -3. SP600125 (20 μM), a JNK(1/2) inhibitor, markedly suppressed the formation of apoptotic bodies and JNK activation induced by oleuropein at 200 μM. Thus, oleuropein-induced apoptosis was activated by the JNK/SPAK signal pathway. The result shows that oleuropein holds promise as a potential chemotherapeutic agent for the treatment of HeLa cells.

Pathways involved in acetaminophen hepatotoxicity with specific targets for inhibition/downregulation

Insights on molecular/immunological mechanisms involve in APAP hepatotoxicity and pave way for researchers/clinicians/pharma bodies to identify novel biomarkers, effective bioactive candidates and fruitful therapy against APAP hepatotoxicity.

The neurotoxicity of 5-S-cysteinyldopamine is mediated by the early activation of ERK1/2 followed by the subsequent activation of ASK1/JNK1/2 pro-apoptotic signalling

5-S-cysteinyldopamine is an endogenous neurotoxin with relevance to Parkinson's disease. The present study shows for the first time that the endogenous formation of 5-S-cysteinyldopamine in the Parkinsonian brain may be causally related to nigrostriatal tract degeneration.

Energy crisis: the role of oxidative phosphorylation in acute inflammation and sepsis

Mitochondrial dysfunction is increasingly recognized as an accomplice in most of the common human diseases including cancer, neurodegeneration, diabetes, ischemia/reperfusion injury as seen in myocardial infarction and stroke, and sepsis. Inflammatory conditions, both acute and chronic, have recently been shown to affect mitochondrial function. We here discuss the role of oxidative phosphorylation (OxPhos), focusing on acute inflammatory conditions, in particular sepsis and experimental sepsis models. We discuss mitochondrial alterations, specifically the suppression of oxidative metabolism and the role of mitochondrial reactive oxygen species in disease pathology. Several signaling pathways including metabolic, proliferative, and cytokine signaling affect mitochondrial function and appear to be important in inflammatory disease conditions. Cytochrome c oxidase (COX) and cytochrome c, the latter of which plays a central role in apoptosis in addition to mitochondrial respiration, serve as examples for the entire OxPhos system since they have been studied in more detail with respect to cell signaling. We propose a model in which inflammatory signaling leads to changes in the phosphorylation state of mitochondrial proteins, including Tyr304 phosphorylation of COX catalytic subunit I. This results in an inhibition of OxPhos, a reduction of the mitochondrial membrane potential, and consequently a lack of energy, which can cause organ failure and death as seen in septic patients.

Mark4 promotes adipogenesis and triggers apoptosis in 3T3-L1 adipocytes by activating JNK1 and inhibiting p38MAPK pathways

BACKGROUND INFORMATION

Microtubule affinity-regulating kinase 4 (MARK4) deficiency has been reported to negatively regulate diet-induced obesity and to mitigate insulin resistance in knockout mice, and thus may play a role in metabolic syndrome. However, the details of the molecular mechanism have yet to be revealed and the impacts of MARK4 on apoptosis remain unexplored. This study investigated the role of Mark4 in the regulation of lipid accumulation and apoptosis in adipocytes and analysed signalling pathways involved.

RESULTS

We found that Mark4 significantly up-regulated the expression of gene sterol regulatory element binding protein-1c (SREBP-1c), fatty acid synthase (FAS), acetyl-CoA carboxylase-α (ACCα) and peroxisome proliferator activated receptor-γ (PPARγ); and reduced the protein contents of adipose triglyceride lipase (ATGL), as evidenced by the dramatic increasing lipid droplet accumulation in 3T3-L1 cells. Furthermore, a terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) apoptosis assay showed that Mark4 triggered apoptosis of adipocytes; and apoptosis was confirmed by the decreased protein contents of B-cell lymphoma-2 (Bcl-2), full-length caspase-3 and full-length caspase-9, as well as the increased expression of Bax, cleaved caspase-3 and cleaved caspase-9. Analysis of special inhibitors allowed us to offer the following explanation for these impacts of Mark4: activation of Jun N-terminal kinase1 (JNK1) promoted both apoptosis and adipogenesis, whereas inhibition of the p38 mitogen-activated protein kinase (p38MAPK) pathway contributed to lipid accumulation alone.

CONCLUSIONS

Mark4 promotes adipogenesis in 3T3-L1 adipocytes by activating the JNK1 and inhibiting the p38MAPK pathway, and triggers apoptosis by activating the JNK1 pathway. We conclude that anti-Mark4 therapy targetted to inhibit lipid accumulation and apoptosis of adipocytes shows potential as a novel therapeutic strategy for treatment of obesity-associated metabolic complications.

Regulation of spontaneous eosinophil apoptosis-a neglected area of importance

Asthma is characterized by the accumulation of eosinophils in the airways in most phenotypes. Eosinophils are inflammatory cells that require an external survival-prolonging stimulus such as granulocyte macrophage-colony-stimulating factor (GM-CSF), interleukin (IL)-5, or IL-3 for survival. In their absence, eosinophils are programmed to die by spontaneous apoptosis in a few days. Eosinophil apoptosis can be accelerated by Fas ligation or by pharmacological agents such as glucocorticoids. Evidence exists for the relevance of these survival-prolonging and pro-apoptotic agents in the regulation of eosinophilic inflammation in inflamed airways. Much less is known about the physiological significance and mechanisms of spontaneous eosinophil apoptosis even though it forms the basis of regulation of eosinophil longevity by pathophysiological factors and pharmacological agents. This review concentrates on discussing the mechanisms of spontaneous eosinophil apoptosis compared to those of glucocorticoid- and Fas-induced apoptosis. We aim to answer the question whether the external apoptotic stimuli only augment the ongoing pathway of spontaneous apoptosis or truly activate a specific pathway.

Fucoidan induces caspase-dependent apoptosis in MC3 human mucoepidermoid carcinoma cells

Fucoidan is a sulfated polysaccharide present in brown algae that has been identified to exhibit multiple biological effects. In this study, the apoptotic effects of fucoidan in MC3 human mucoepidermoid carcinoma (MEC) cells were investigated. The apoptotic effects of fucoidan on MC3 MEC cells were evaluated by cell proliferation assay, 4′,6-diamidino-2-phenylindole staining and western blot analysis. The results showed that fucoidan decreased cell proliferation and induced caspase-dependent apoptosis in MC3 MEC cells. Fucoidan downregulated the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2, whereas phospho-p38 mitogen-activated protein kinase or phospho-c-Jun NH₂-terminal kinase (JNK) levels were not altered. In addition, fucoidan significantly decreased the expression levels of myeloid cell leukemia-1 (Mcl-1). These results suggest that fucoidan is able to modulate the ERK1/2 pathway and thereby regulate Mcl-1 protein expression and induce apoptosis in MC3 MEC cells. Therefore, fucoidan may be a promising agent for the treatment of human MEC.

FTY720 protects neuronal cells from damage induced by human prion protein by inactivating the JNK pathway

Prion diseases affect the central nervous system (CNS) in humans and animals, and are associated with the conversion of the cellular prion protein (PrPC) to the misfolded isoform (PrPSc). FTY720, an immune modulator and synthetic analogue of sphingosine-1-phosphate (S1P), activates S1P receptors and has been shown to be effective in experimental models of transplantation and autoimmunity, including multiple sclerosis. Whereas the immune modulatory functions of FTY720 have been extensively investigated, the other functions of FTY720 are not yet well understood. In this study, we investigated the effects of FTY720 phosphate (FTY720-p) on prion protein-mediated neuronal cell death, as well as its effects on intracellular apoptotic pathways. Treatment with FTY720-p protected neuronal cells from synthetic human prion protein peptide [PrP (106‑126)]-mediated damage and prevented mitochondrial dysfunction by inhibiting the activation of c-jun N-terminal kinase. Moreover, FTY720-p prevented the PrP (106‑126)-induced reduction in mitochondrial potential, the translocation of Bax to the mitochondria and the release of cytochrome c. To the best of our knowledge, this study is the first to demonstrate the effects of FTY720 on prion protein-mediated neurotoxicity and to suggest that FTY720 has therapeutic potential in prion diseases.

Oxidative stress: the mitochondria-dependent and mitochondria-independent pathways of apoptosis

Oxidative stress basically defines a condition in which prooxidant-antioxidant balance in the cell is disturbed; cellular biomolecules undergo severe oxidative damage, ultimately compromising cells viability. In recent years, a number of studies have shown that oxidative stress could cause cellular apoptosis via both the mitochondria-dependent and mitochondria-independent pathways. Since these pathways are directly related to the survival or death of various cell types in normal as well as pathophysiological situations, a clear picture of these pathways for various active molecules in their biological functions would help designing novel therapeutic strategy. This review highlights the basic mechanisms of ROS production and their sites of formation; detail mechanism of both mitochondria-dependent and mitochondria-independent pathways of apoptosis as well as their regulation by ROS. Emphasis has been given on the redox-sensitive ASK1 signalosome and its downstream JNK pathway. This review also describes the involvement of oxidative stress under various environmental toxin- and drug-induced organ pathophysiology and diabetes-mediated apoptosis. We believe that this review would provide useful information about the most recent progress in understanding the mechanism of oxidative stress-mediated regulation of apoptotic pathways. It will also help to figure out the complex cross-talks between these pathways and their modulations by oxidative stress. The literature will also shed a light on the blind alleys of this field to be explored. Finally, readers would know about the ROS-regulated and apoptosis-mediated organ pathophysiology which might help to find their probable remedies in future.

Neuronal inputs and outputs of aging and longevity

An animal’s survival strongly depends on its ability to maintain homeostasis in response to the changing quality of its external and internal environment. This is achieved through intracellular and intercellular communication within and among different tissues. One of the organ systems that plays a major role in this communication and the maintenance of homeostasis is the nervous system. Here we highlight different aspects of the neuronal inputs and outputs of pathways that affect aging and longevity. Accordingly, we discuss how sensory inputs influence homeostasis and lifespan through the modulation of different types of neuronal signals, which reflects the complexity of the environmental cues that affect physiology. We also describe feedback, compensatory, and feed-forward mechanisms in these longevity-modulating pathways that are necessary for homeostasis. Finally, we consider the temporal requirements for these neuronal processes and the potential role of natural genetic variation in shaping the neurobiology of aging.

Magnolol protects against oxidative stress-mediated neural cell damage by modulating mitochondrial dysfunction and PI3K/Akt signaling

Magnolol, an orally available compound from Magnolia officinalis used widely in traditional herbal medicine against a variety of neuronal diseases, possesses potent antioxidant properties and protects the brain against oxidative damage. The aim of the work is to examine the protective mechanisms of magnolol on human neuroblastoma SH-SY5Y cells against apoptosis induced by the neurotoxin acrolein, which can cause neurodegenerative disorders by inducing oxidative stress. By investigating the effect of magnolol on neural cell damage induced by the neurotoxin acrolein, we found that magnolol pretreatment significantly attenuated acrolein-induced oxidative stress through inhibiting reactive oxygen species accumulation caused by intracellular glutathione depletion and nicotinamide adenine dinucleotide phosphate oxidase activation. We next examined the signaling cascade(s) involved in magnolol-mediated antiapoptotic effects. The results showed that acrolein induced SH-SY5Y cell apoptosis by activating mitochondria/caspase and MEK/ERK signaling pathways. Our findings provide the first evidence that magnolol protects SH-SY5Y cells against acrolein-induced oxidative stress and prolongs SH-SY5Y cell survival through regulating JNK/mitochondria/caspase, PI3K/MEK/ERK, and PI3K/Akt/FoxO1 signaling pathways.