Mitochondrial Ca(2+)homeostasis in the regulation of apoptotic and necrotic cell deaths

Toxicity assessment of polyethylene microplastics in combination with a mix of emerging pollutants on Physalaemus cuvieri tadpoles

Studies in recent years have shown that aquatic pollution by microplastics (MPs) can be considered to pose additional stress to amphibian populations. However, our knowledge of how MPs affect amphibians is very rudimentary, and even more limited is our understanding of their effects in combination with other emerging pollutants. Thus, we aimed to evaluate the possible toxicity of polyethylene MPs (PE-MPs) (alone or in combination with a mix of pollutants) on the health of Physalaemus cuvieri tadpoles. After 30 days of exposure, multiple biomarkers were measured, including morphological, biometric, and developmental indices, behavioral parameters, mutagenicity, cytotoxicity, antioxidant and cholinesterase responses, as well as the uptake and accumulation of PE-MPs in animals. Based on the results, there was no significant change in any of the parameters measured in tadpoles exposed to treatments, but induced stress was observed in tadpoles exposed to PE-MPs combined with the mixture of pollutants, reflecting significant changes in physiological and biochemical responses. Through principal component analysis (PCA) and integrated biomarker response (IBR) assessment, effects induced by pollutants in each test group were distinguished, confirming that the exposure of P. cuvieri tadpoles to the PE-MPs in combination with a mix of emerging pollutants induces an enhanced stress response, although the uptake and accumulation of PE-MPs in these animals was reduced. Thus, our study provides new insight into the danger to amphibians of MPs coexisting with other pollutants in aquatic environments.

Protein kinase CK2 – diverse roles in cancer cell biology and therapeutic promise

The association of protein kinase CK2 (formerly casein kinase II or 2) with cell growth and proliferation in cells was apparent at early stages of its investigation. A cancer-specific role for CK2 remained unclear until it was determined that CK2 was also a potent suppressor of cell death (apoptosis); the latter characteristic differentiated its function in normal versus malignant cells because dysregulation of both cell growth and cell death is a universal feature of cancer cells. Over time, it became evident that CK2 exerts its influence on a diverse range of cell functions in normal as well as in transformed cells. As such, CK2 and its substrates are localized in various compartments of the cell. The dysregulation of CK2 is documented in a wide range of malignancies; notably, by increased CK2 protein and activity levels with relatively moderate change in its RNA abundance. High levels of CK2 are associated with poor prognosis in multiple cancer types, and CK2 is a target for active research and testing for cancer therapy. Aspects of CK2 cellular roles and targeting in cancer are discussed in the present review, with focus on nuclear and mitochondrial functions and prostate, breast and head and neck malignancies.

Mitochondrial Calcium: Effects of Its Imbalance in Disease

Calcium is used in many cellular processes and is maintained within the cell as free calcium at low concentrations (approximately 100 nM), compared with extracellular (millimolar) concentrations, to avoid adverse effects such as phosphate precipitation. For this reason, cells have adapted buffering strategies by compartmentalizing calcium into mitochondria and the endoplasmic reticulum (ER). In mitochondria, the calcium concentration is in the millimolar range, as it is in the ER. Mitochondria actively contribute to buffering cellular calcium, but if matrix calcium increases beyond physiological demands, it can promote the opening of the mitochondrial permeability transition pore (mPTP) and, consequently, trigger apoptotic or necrotic cell death. The pathophysiological implications of mPTP opening in ischemia-reperfusion, liver, muscle, and lysosomal storage diseases, as well as those affecting the central nervous system, for example, Parkinson’s disease (PD), Alzheimer’s disease (AD), Huntington’s disease (HD), and amyotrophic lateral sclerosis (ALS) have been reported. In this review, we present an updated overview of the main cellular mechanisms of mitochondrial calcium regulation. We specially focus on neurodegenerative diseases related to imbalances in calcium homeostasis and summarize some proposed therapies studied to attenuate these diseases.

Recent Advancements in Colorimetric and Fluorescent pH Chemosensors: From Design Principles to Applications

Due to the immense biological significance of pH in diverse living systems, the design, synthesis, and development of pH chemosensors for pH monitoring has been a very active research field in recent times. In this review, we summarize the designing strategies, sensing mechanisms, biological and environmental applications of fluorogenic and chromogenic pH chemosensors of the last three years (2018-2020). We categorized these pH probes into seven types based on their applications, including 1) Cancer cell discriminating pH probes; 2) Lysosome targetable pH probes; 3) Mitochondria targetable pH probes; 4) Golgi body targetable pH probes; 5) Endoplasmic reticulum targetable pH probes; 6) pH probes used in nonspecific cell imaging; and 7) pH probes without cell imaging. All these different categories exhibit diverse applications of pH probes in biological and environmental fields.

The Role of Osteoclast Energy Metabolism in the Occurrence and Development of Osteoporosis

In recent decades, the mechanism underlying bone metabolic disorders based on energy metabolism has been heavily researched. Bone resorption by osteoclasts plays an important role in the occurrence and development of osteoporosis. However, the mechanism underlying the osteoclast energy metabolism disorder that interferes with bone homeostasis has not been determined. Bone resorption by osteoclasts is a process that consumes large amounts of adenosine triphosphate (ATP) produced by glycolysis and oxidative phosphorylation. In addition to glucose, fatty acids and amino acids can also be used as substrates to produce energy through oxidative phosphorylation. In this review, we summarize and analyze the energy-based phenotypic changes, epigenetic regulation, and coupling with systemic energy metabolism of osteoclasts during the development and progression of osteoporosis. At the same time, we propose a hypothesis, the compensatory recovery mechanism (involving the balance between osteoclast survival and functional activation), which may provide a new approach for the treatment of osteoporosis.

Effects of advanced glycation end products on dental pulp calcification

OBJECTIVE

The main aim of this study was to elucidate the effects of advanced glycation end products (AGEs) on the calcification of cultured rat dental pulp cells (RDPCs) and to investigate the crystallisation ability of glycated collagen.

MATERIALS AND METHODS

AGEs were prepared via non-enzymatic glycation of a dish coated with type I collagen using dl-glyceraldehyde. To investigate the effects of AGEs on RDPCs, we performed WST-1 and lactate dehydrogenase assays; alkaline phosphatase, Alizarin Red S and immunohistochemical staining; and real-time quantitative reverse transcription PCR. In addition, we performed crystallisation experiments on glycated collagen. All microstructures were analysed using scanning electron microscopy/energy-dispersive X-ray spectroscopy and transmission electron microscopy/diffraction pattern analysis.

RESULTS

AGEs did not affect the proliferation or differentiation of RDPCs, but enhanced the calcification rate and cytotoxicity. No major calcification-related genes or proteins were involved in these calcifications, and glycated collagen was found to exhibit a negative polarity and form calcium phosphate crystals. Cytotoxicity due to drastic changes in the concentration of pericellular ions led to dystrophic calcification, assumed to represent an aspect of diabetic pulp calcifications.

CONCLUSION

Glycated collagen-containing AGEs provide a nurturing environment for crystallisation and have a significant effect on the early calcification of RDPCs.

Duck enteritis virus infection suppresses viability and induces apoptosis and endoplasmic reticulum stress in duck embryo fibroblast cells via the regulation of Ca2

Duck viral enteritis (DVE) is a lethal viral disease caused by duck enteritis virus (DEV) via an unknown mechanism. This study explores the relationship between Chinese standard challenge strain DEV (DEV-CSC)-induced apoptosis and endoplasmic reticulum stress (ERS) in duck embryo fibroblast (DEF) cells. Here we examined changes in Ca²⁺ concentration, cell proliferation, apoptosis, and the differential expression of C/EBP homologous protein (CHOP), glucose regulatory protein 78 (GRP78), and activating transcription factor 6 (ATF6) in infected cells. The results revealed that DEV-CSC infection significantly decreased Ca²⁺ concentration, suppressed cell viability, and induced apoptosis in DEF cells. Further experiments also demonstrated that DEV-CSC infection significantly upregulates CHOP, GRP78, and ATF6 expression. In addition, we show that the addition of ethylenediaminetetraacetic acid (EDTA) reverses the induction of apoptosis and the ERS mediated inhibition of cell viability in DEF cells associated with DEV-CSC infection. Therefore, we can conclude that infection with DEV-CSC induces apoptosis and ERS reducing the viability of DEF cells via the regulation of Ca²⁺. These findings may provide a new target for the treatment of DVE.

The lncRNA LOC102549805 (U1) modulates neurotoxicity of HIV-1 Tat protein

HIV-1 Tat is a potent neurotoxic protein that is released by HIV-1 infected cells in the brain and perturbs neuronal homeostasis, causing a broad range of neurological disorders in people living with HIV-1. Furthermore, the effects of Tat have been addressed in numerous studies to investigate the molecular events associated with neuronal cells survival and death. Here, we discovered that exposure of rat primary neurons to Tat resulted in the up-regulation of an uncharacterized long non-coding RNA (lncRNA), LOC102549805 (lncRNA-U1). Our observations showed that increased expression of lncRNA-U1 in neurons disrupts bioenergetic pathways by dysregulating homeostasis of Ca²⁺, mitigating mitochondrial oxygen reduction, and decreasing ATP production, all of which point mitochondrial impairment in neurons via the Tat-mediated lncRNA-U1 induction. These changes were associated with imbalances in autophagy and apoptosis pathways. Additionally, this study showed the ability of Tat to modulate expression of the neuropeptide B/W receptor 1 (NPBWR1) gene via up-regulation of lncRNA-U1. Collectively, our results identified Tat-mediated lncRNA-U1 upregulation resulting in disruption of neuronal homeostasis.

Aspirin Induces Mitochondrial Ca2+ Remodeling in Tumor Cells via ROS‒Depolarization‒Voltage-Gated Ca2+ Entry

Aspirin (acetylsalicylic acid) and its metabolite salicylate, have an anti-melanoma effect by evoking mitochondrial dysfunction through poorly understood mechanisms. Depolarization of the plasma membrane potential leads to voltage-gated Ca²⁺ entry (VGCE) and caspase-3 activation. In the present study, we investigated the role of depolarization and VGCE in aspirin’s anti-melanoma effect. Aspirin and to a lesser extent, salicylate (≥2.5 mM) induced a rapid (within seconds) depolarization, while they caused comparable levels of depolarization with a lag of 2~4 h. Reactive oxygen species (ROS) generation also occurred in the two-time points, and antioxidants abolished the early ROS generation and depolarization. At the same concentrations, the two drugs induced apoptotic and necrotic cell death in a caspase-independent manner, and antioxidants and Ca²⁺ channel blockers prevented cell death. Besides ROS generation, reduced mitochondrial Ca²⁺ (Ca²⁺_m) and mitochondrial membrane potential preceded cell death. Moreover, the cells expressed the Ca_v1.2 isoform of l-type Ca²⁺ channel, and knockdown of Ca_v1.2 abolished the decrease in Ca²⁺_m. Our findings suggest that aspirin and salicylate induce Ca²⁺_m remodeling, mitochondrial dysfunction, and cell death via ROS-dependent depolarization and VGCE activation.

The Mitochondrial Ca2+ Overload via Voltage-Gated Ca2+ Entry Contributes to an Anti-Melanoma Effect of Diallyl Trisulfide

Allium vegetables such as garlic (Allium sativum L.) are rich in organosulfur compounds that prevent human chronic diseases, including cancer. Of these, diallyl trisulfide (DATS) exhibits anticancer effects against a variety of tumors, including malignant melanoma. Although previous studies have shown that DATS increases intracellular calcium (Ca2+) in different cancer cell types, the role of Ca2+ in the anticancer effect is obscure. In the present study, we investigated the Ca2+ pathways involved in the anti-melanoma effect. We used melittin, the bee venom that can activate a store-operated Ca2+ entry (SOCE) and apoptosis, as a reference. DATS increased apoptosis in human melanoma cell lines in a Ca2+-dependent manner. It also induced mitochondrial Ca2+ (Ca2+mit) overload through intracellular and extracellular Ca2+ fluxes independently of SOCE. Strikingly, acidification augmented Ca2+mit overload, and Ca2+ channel blockers reduced the effect more significantly under acidic pH conditions. On the contrary, acidification mitigated SOCE and Ca2+mit overload caused by melittin. Finally, Ca2+ channel blockers entirely inhibited the anti-melanoma effect of DATS. Our findings suggest that DATS explicitly evokes Ca2+mit overload via a non-SOCE, thereby displaying the anti-melanoma effect.

Effects of Rubiadin isolated from Prismatomeris connata on anti-hepatitis B virus activity in vitro

Prismatomeris connata was a kind of Rubiaceae plant for treatment of hepatitis, hepatic fibrosis and silicosis. Whereas, the effective components of Prismatomeris connata remains unexplored. The aim of this study was to investigate the inhibitory effects and mechanisms of Rubiadin isolated from Prismatomeris connata against HBV using HepG2.2.15 cells. The levels of hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), and hepatitis B core antigen (HBcAg) in the supernatants or cytoplasm were examined using by enzyme-linked immunosorbent assay. HBV DNA was qualified q-PCR. Rubiadin was isolated by silica gel column. The structure of the compound was elucidated by HPLC, FT-IR, ¹ H-NMR, ¹³ C-NMR and identified as 1,3-Dihydroxy-2-methyl-9, 10-anthraquinone. Rubiadin significantly decreased HBeAg,HBcAg secretion level and inhibit HBV DNA replication. Rubiadin inhibits the proliferation of the cells and HBx protein expression in a dose-dependent manner. The intracellular calcium concentration was significantly reduced. These results demonstrated that Rubiadin could inhibit HepG2.2.15 cells proliferation, reduce the level of HBx expression, and intracellular free calcium, which might become a novel anti-HBV drug candidate.

Effect of Clonazepam on Raynaud's Phenomenon and Fingertip Ulcers in Scleroderma

Objective:

To report the novel finding of a significant improvement in Raynaud's phenomenon symptoms with clonazepam in a patient with systemic sclerosis.

Case Summary:

A 45-year-old female with limited scleroderma and chronic renal failure was admitted to our hospital due to hyponatremia (sodium 103 mEq/L). Her hyponatremia was treated by intravenous infusion of NaCI 3%. Clonazepam, which had been prescribed previously for anxiety and insomnia, was discontinued. Three weeks after she was discharged from the hospital, the patient presented with the complaint of increased severity of Raynaud's phenomenon and digital ulcers. She told us that her fingertip ulcers had been healed while she was taking clonazepam and that episodes of Raynaud's phenomenon had increased after discontinuation of the drug. Clonazepam 1 mg twice daily was restarted, and Raynaud's phenomenon and fingertip ulcers resolved within a month. On 2 occasions after that time, we discontinued clonazepam and replaced it with alprazolam, as the patient believed alprazolam was more beneficial in alleviating anxiety. Episodes of Raynaud's phenomenon and new digital ulcers recurred on both of these occasions, and clonazepam was restarted. At the time of writing, no severe episodes of Raynaud's phenomenon or fingertip ulcers have occurred with clonazepam treatment.

Discussion:

Raynaud's phenomenon and recurrent digital ulcers are a manifestation of vascular disease in patients with systemic sclerosis and lead to pain, impaired function, and tissue loss. Few drugs have previously been shown to affect digital ulcers in the setting of scleroderma. Our patient experienced a significant and sustained improvement in Raynaud's phenomenon and digital ulcers following the initiation of clonazepam. To our knowledge, as of March 2007, this is the first reported use of clonazepam in Raynaud's phenomenon and digital ulcer. While its therapeutic mechanism remains unclear, clonazepam may offer some advantages compared with current agents.

Conclusions:

We report a case of Raynaud's phenomenon and digital ulcers responding to clonazepam. Further research is warranted to test the robustness of this preliminary finding.

Silibinin induces mitochondrial NOX4-mediated endoplasmic reticulum stress response and its subsequent apoptosis

Background

Silibinin, a biologically active compound of milk thistle, has chemopreventive effects on cancer cell lines. Recently it was reported that silibinin inhibited tumor growth through activation of the apoptotic signaling pathway. Although various evidences showed multiple signaling pathways of silibinin in apoptosis, there were no reports to address the clear mechanism of ROS-mediated pathway in prostate cancer PC-3 cells. Several studies suggested that reactive oxygen species (ROS) play an important role in various signaling cascades, but the primary source of ROS was currently unclear.

Methods

The effect of silibinin was investigated on cell growth of prostate cell lines by MTT assay. We examined whether silibinin induced apoptosis through production of ROS using flow cytometry. Expression of apoptosis-, endoplasmic reticulum (ER)-related protein and gene were determined by western blotting and RT-PCR, respectively.

Results

Results showed that silibinin triggered mitochondrial ROS production through NOX4 expression and finally led to induce apoptosis. In addition, mitochondrial ROS caused ER stress through disruption of Ca²⁺ homeostasis. Co-treatment of ROS inhibitor reduced the silibinin-induced apoptosis through the inhibition of NOX4 expression, resulting in reduction of both Ca²⁺ level and ER stress response.

Conclusions

Taken together, silibinin induced mitochondrial ROS-dependent apoptosis through NOX4, which is associated with disruption of Ca²⁺ homeostasis and ER stress response. Therefore, the regulation of NOX4, mitochondrial ROS producer, could be a potential target for the treatment of prostate cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2516-6) contains supplementary material, which is available to authorized users.

A genome-wide association study of non-HPV-related head and neck squamous cell carcinoma identifies prognostic genetic sequence variants in the MAP-kinase and hormone pathways

BACKGROUND

Carcinomas of the oral cavity, pharynx and larynx are referred to as head and neck cancers (HNC); together they account for 2-3% of all newly diagnosed cancers in North America. Between 40-50% of HNC are early diagnosed at stages I-II. The 5-year and 10-year relative survival rates are 61% and 50%, respectively. Germline genetic sequence variants (GSV) have become increasingly found to have prognostic implications in a variety of cancers. Identifying these variants may have important clinical and biological implications.

METHODS

We conducted a genome-wide association study (GWAS) in 531 Stage I-II radiation-treated HNC patients (originally recruited for α-tocopherol/β-carotene placebo-controlled secondary prevention study) and used a replication cohort of 566 HNC patients of all stages, of mostly non-HPV-related cancers. Survival rates were estimated by the Kaplan-Meier method. Cox proportional hazards models adjusted for potential clinical factors and principal components were used to test for associations between the GSV and overall survival (OS) in these tumors.

RESULTS

The median follow-up time for OS was 9.21 years (GWAS cohort) and 2.37 years (replication cohort). In both cohorts, CACNA2D1:rs2299187, ESRRG:rs946465 and ESRRG:rs1416612 were each individually significantly associated with survival. In silico analysis of ESRRG:rs946465 identifies that it produces a splice variant in ESRRG. Variant alleles of CACNA2D1:rs2299187 and ESRRG:rs946465 were associated with higher expression of the corresponding protein.

CONCLUSIONS

Putatively functional polymorphisms in the MAP-Kinase and estrogen pathways, identified through GWAS and replicated in an independent dataset were associated with the survival of HNC patients.

The calcium uniporter regulates the permeability transition pore in isolated cortical mitochondria

To investigate the influence of the mitochondrial calcium uniporter on the mitochondrial permeability transition pore, the present study observed mitochondrial morphology in cortical neurons isolated from adult rats using transmission electron microscopy, and confirmed the morphology and activity of isolated mitochondria by detecting succinic dehydrogenase and monoamine oxidase, two mitochondrial enzymes. Isolated mitochondria were treated with either ruthenium red, an inhibitor of the uniporter, spermine, an activator of the uniporter, or in combination with cyclosporin A, an inhibitor of the mitochondrial permeability transition pore. Results showed that ruthenium red inhibited CaCl2-induced mitochondrial permeability transition pore opening, spermine enhanced opening, and cyclosporin A attenuated the effects of spermine. Results demonstrated that the mitochondrial calcium uniporter plays a role in regulating the mitochondrial permeability transition pore in mitochondria isolated from the rat brain cortex.

Transcriptome profiling of brain edemas caused by influenza infection and lipopolysaccharide treatment

Influenza A virus-associated encephalopathy triggered by influenza virus infection often occurs in children aged five and younger in Japan. However, the mechanisms behind Influenza A virus-associated encephalopathy are not yet well understood. This study developed an Influenza A virus-associated encephalopathy-like model using mice infected with Influenza A virus and given lipopolysaccharide treatment. The results showed that the mice used in the model suffered from brain edemas nearly three times more severe, as well as having higher cytokine levels in sera compared to those of the control groups. Using gene expression profiling, cytokine-related genes were found not to be up-regulated in the brain in situ, while protein coding genes, which are known to be involved in blood-brain barrier disruption, were up-regulated. Categorizing the functional groups using gene ontology revealed the terms "ion channels," "calcium oscillation," and "membrane transporter activities." The blood-brain barrier disruption found in this Influenza A virus-associated encephalopathy model can therefore be assumed to be due to a cellular electrolyte imbalance of the neuronal tissue, in addition to a cytokine storm.

Neuroprotective effects of total saikosaponins of Bupleurum yinchowense on corticosterone-induced apoptosis in PC12 cells

ETHNOPHARMACOLOGICAL RELEVANCE

The root of Bupleurum yinchowense Shan et Y. Li, a well-known medicinal plant in China, was originally documented in the "Shennong's Herbal", which is the oldest Chinese materia medica monographs. It has the action of soothing liver and relieving constraint for improving symptoms of emotional instability such as depression, anxiety and phobia. The in vivo experiment of our previous study has showed an efficacy of Total Saikosaponins (TSS) from Bupleurum yinchowense in acute stress and chronic unpredictable mild stress models. Nevertheless, there are no studies on the cytoprotection and potential mechanisms of TSS on corticosterone-induced apoptosis in PC12 cells. The present study focuses on cytoprotection against corticosterone-induced neurotoxicity in PC12 cells and its underlying molecule mechanisms of the antidepressant-like effect of TSS.

MATERIALS AND METHODS

The PC12 cells were treated with 250 μM corticosterone in the absence or presence of different concentrations of TSS for 24 h, then the cell viability, lactate dehydrogenase (LDH) release, Hoechst 33342 and propidium iodide (PI) double staining and the DNA fragmentation of the apoptotic PC12 cells were determined. The mitochondrial permeability transition pore (mPTP), mitochondrial membrane potential (MMP), intracellular Ca(2+) ([Ca(2+)]i) concentration and western blot analysis of caspase-3, glucose-regulated protein 78 (GRP78), growth arrest and DNA damage inducible proteins 153 (GADD-153), X-box DNA-binding protein-1 (XBP-1), Bax, Bcl-2 were investigated.

RESULTS

Pretreatment of PC12 cells with TSS (3.125, 6.25, 12.5, 25 μg/ml) partly reversed corticosterone-induced neurotoxicity in a dose dependent manner. TSS (25 =g/ml) reversed the increase of dead cells in the Hoechst 33342 stain, the accumulation in LDH leakage and the number of TUNEL positive cells induced by corticosterone to PC12 cells. Moreover, the cytoprotection of TSS was proved to be associated with the homeostasis of intracellular Ca(2+), the stabilization of ER stress via the down-regulation of GRP78, GADD-153, XBP-1, and the restoration of mitochondrial function, which included mPTP, MMP and caspase-3 activity. Furthermore, TSS (25 μg/ml) markedly ameliorated up-regulation of Bax and down-regulation of Bcl-2 in corticosterone-induced PC12 cells.

CONCLUSION

The result depicted that antidepressant-like effect of TSS in vivo may be associated with the cytoprotection of neuron, and the neuroprotective mechanisms were correlated with inhibiting the ER stress and the mitochondrial apoptotic pathways.

Deranged calcium signaling in Purkinje cells and pathogenesis in spinocerebellar ataxia 2 (SCA2) and other ataxias

Spinocerebellar ataxias (SCAs) constitute a heterogeneous group of more than 30 autosomal-dominant genetic and neurodegenerative disorders. SCAs are generally characterized by progressive ataxia and cerebellar atrophy. Although all SCA patients present with the phenotypic overlap of cerebellar atrophy and ataxia, 17 different gene loci have so far been implicated as culprits in these SCAs. It is not currently understood how mutations in these 17 proteins lead to the cerebellar atrophy and ataxia. Several pathogenic mechanisms have been studied in SCAs but there is yet to be a promising target for successful treatment of SCAs. Emerging research suggests that a fundamental cellular signaling pathway is disrupted by a majority of these mutated genes, which could explain the characteristic death of Purkinje cells, cerebellar atrophy, and ataxia that occur in many SCAs. We propose that mutations in SCA genes cause disruptions in multiple cellular pathways but the characteristic SCA pathogenesis does not begin until calcium signaling pathways are disrupted in cerebellar Purkinje cells either as a result of an excitotoxic increase or a compensatory suppression of calcium signaling. We argue that disruptions in Purkinje cell calcium signaling lead to initial cerebellar dysfunction and ataxic sympoms and eventually proceed to Purkinje cell death. Here, we discuss a calcium hypothesis of Purkinje cell neurodegeneration in SCAs by primarily focusing on an example of spinocerebellar ataxia 2 (SCA2). We will also present evidence linking deranged calcium signaling to the pathogenesis of other SCAs (SCA1, 3, 5, 6, 14, 15/16) that lead to significant Purkinje cell dysfunction and loss in patients.

Imipramine protects mouse hippocampus against tunicamycin-induced cell death

Endoplasmic reticulum (ER) stress is implicated in various diseases. Recently, some reports have suggested that the sigma-1 receptor may play a role in ER stress, and many antidepressants have a high affinity for the sigma-1 receptor. In the present study, we focused on imipramine, a widely used antidepressant, and investigated whether it might protect against the neuronal cell death induced by tunicamycin, an ER stress inducer. In mouse cultured hippocampal HT22 cells, imipramine inhibited cell death and caspase-3 activation induced by tunicamycin, although it did not alter the elevated expressions of 78 kDa glucose-regulated protein (GRP78) and C/EBP-homologous protein (CHOP). Interestingly, in such cells application of imipramine normalized the expression of the sigma-1 receptor, which was decreased by treatment with tunicamycin alone. Additionally, NE-100, a selective sigma-1 receptor antagonist, abolished the protective effect of imipramine against such tunicamycin-induced cell death. Imipramine inhibited the reduction of mitochondrial membrane potential induced by tunicamycin, and NE-100 blocked this modulating effect of imipramine. Furthermore, in anesthetized mice intracerebroventricular administration of tunicamycin decreased the number of neuronal cells in the hippocampus, particularly in the CA1 and dentate gyrus (DG) areas, and 7 days' imipramine treatment (10mg/kg/day; i.p.) significantly suppressed these reductions in CA1 and DG. These findings suggest that imipramine protects against ER stress-induced hippocampal neuronal cell death both in vitro and in vivo. Such protection may be partly due to the sigma-1 receptor.

Corticosterone suppresses the proliferation of BV2 microglia cells via glucocorticoid, but not mineralocorticoid receptor

AIMS

Corticosterone (CORT), which is often referred to as the stress hormone, is a well-known regulator of peripheral immune responses and also shows anti-inflammatory properties in the brain. Microglia play a key role in immune response and inflammation in the brain. However, it is still unclear how CORT affects microglia. In this study, we focused on the effects of CORT on the proliferation and survival of microglia using mouse microglia cell line BV2.

MAIN METHODS

We used WST-8 and LDH (lactate dehydrogenase) assays to check the effects of CORT for the proliferation and survival in BV2 microglia cells. We also analyzed the expression pattern of proteins which related to CORT signal cascades using western blotting analysis.

KEY FINDINGS

Under treatment with 0.1, 1 and 10μM CORT for 24h, the BV2 proliferation rate decreased to 83, 77 and 70% of that in the control. Moreover, this inhibition was blocked by treatment with mifepristone, a glucocorticoid receptor (GR) antagonist, but not by spironolactone, a mineralocorticoid receptor (MR) antagonist. Moreover, an LDH assay showed that CORT was dose-dependently cytotoxic toward BV2 microglia cells and this cytotoxicity was partially abolished by treatment with mifepristone. In addition, treatment with CORT resulted in the translocation of GR, but not MR, from the cytosol to the nucleus.

SIGNIFICANCE

Our findings suggested that CORT suppresses the proliferation of BV2 microglia cells accompanied with a cytotoxic effect that is induced by the formation of a CORT-GR complex.

CIBZ, a novel BTB domain-containing protein, is involved in mouse spinal cord injury via mitochondrial pathway independent of p53 gene

Spinal cord injury (SCI) induces both primary uncontrollable mechanical injury and secondary controllable degeneration, which further results in the activation of cell death cascades that mediate delayed tissue damage. To alleviate its impairments and seek for an effective remedy, mRNA differential display was used to investigate gene mRNA expression profiling in mice following SCI. A specific Zinc finger and BTB domain-containing protein, CIBZ, was discovered to implicate in the SCI process for the first time. Further researches indicated that CIBZ was extensively distributed in various tissues, and the expression level was highest in muscle, followed by spinal cord, large intestine, kidney, spleen, thymus, lung, cerebrum, stomach, ovary and heart, respectively. After injury, the CIBZ expression decreased dramatically and reached the lowest level at 8 h, but it gradually increased to the maximal level at 7 d. Caspase-3 and C-terminal-binding protein (CtBP), two CIBZ-related proteins, showed similar tendency. Interestingly, p53 expression remained constant in all groups. Via flow cytometry (FCM) analysis, it was found that the cell death rate in SCI group markedly increased and reached the highest value 1 d after surgery and the mitochondrial transmembrane potential (ΔΨm) at 1 d was the lowest in all groups. Taken together, it is suggested that: (i) in the presence of CtBP, CIBZ gene is involved in secondary injury process and trigger the activation of apoptotic caspase-3 and bax genes independent of p53; (ii) abrupt down-regulation of CtBP at 8 h is a sign of mitochondria dysfunction and the onset of cell death; (iii) it could be used as an inhibitor or target drug of caspase-3 gene to improve spinal cord function.

TNFα in myocardial ischemia/reperfusion, remodeling and heart failure

TNFα is crucially involved in the pathogenesis and progression of myocardial ischemia/reperfusion injury and heart failure. The formation and release of TNFα and its downstream signal transduction cascade following activation of its two receptor subtypes are characterized. Myocardial TNFα and TNF receptor activation have an ambivalent role in myocardial ischemia/reperfusion injury and protection from it. Excessive TNFα expression and subsequent cardiomyocyte TNF receptor type 1 stimulation induce contractile dysfunction, hypertrophy, fibrosis and cell death, while a lower TNFα concentration and subsequent cardiomyocyte TNF receptor type 2 stimulation are protective. Apart from its concentration and receptor subtype, the myocardial action of TNFα depends on the duration of its exposure and its localization. While detrimental during sustained ischemia, TNFα contributes to ischemic preconditioning protection, no matter whether it is the first, second or third window of protection, and both TNF receptors are involved in the protective signal transduction cascade. Finally, the available clinical attempts to antagonize TNFα in cardiovascular disease, notably heart failure, are critically discussed.

Role of inositol 1,4,5-trisphosphate receptors in pathogenesis of Huntington's disease and spinocerebellar ataxias

Huntington's disease (HD) and spinocerebellar ataxias (SCAs) are autosomal-dominant neurodegenerative disorders. HD is caused by polyglutamine (polyQ) expansion in the amino-terminal region of a protein huntingtin (Htt) and primarily affects medium spiny striatal neurons (MSN). Many SCAs are caused by polyQ-expansion in ataxin proteins and primarily affect cerebellar Purkinje cells. The reasons for neuronal dysfunction and death in HD and SCAs remain poorly understood and no cure is available for the patients. Our laboratory discovered that mutant huntingtin, ataxin-2 and ataxin-3 proteins specifically bind to the carboxy-terminal region of the type 1 inositol 1,4,5-trisphosphate receptor (IP(3)R1), an intracellular Ca(2+) release channel. Moreover, we found that association of mutant huntingtin or ataxins with IP(3)R1 causes sensitization of IP(3)R1 to activation by IP(3) in planar lipid bilayers and in neuronal cells. These results suggested that deranged neuronal Ca(2+) signaling might play an important role in pathogenesis of HD, SCA2 and SCA3. In support of this idea, we demonstrated a connection between abnormal Ca(2+) signaling and neuronal cell death in experiments with HD, SCA2 and SCA3 transgenic mouse models. Additional data in the literature indicate that abnormal neuronal Ca(2+) signaling may also play an important role in pathogenesis of SCAl, SCA5, SCA6, SCA14 and SCA15/16. Based on these results I propose that IP(3)R and other Ca(2+) signaling proteins should be considered as potential therapeutic targets for treatment of HD and SCAs.

Ca2+ overload and mitochondrial permeability transition pore activation in living delta-sarcoglycan-deficient cardiomyocytes

Muscular dystrophies are often associated with significant cardiac disease that can be the prominent feature associated with gene mutations in sarcoglycan. Cardiac cell death is a main feature of cardiomyopathy in sarcoglycan deficiency and may arise as a cardiomyocyte intrinsic process that remains unclear. Deficiency of delta-sarcoglycan (delta-SG) induces disruption of the dystrophin-associated glycoprotein complex, a known cause of membrane instability that may explain cardiomyocytes cytosolic Ca2+ increase. In this study we assessed the hypothesis that cytosolic Ca2+ increase triggers cardiomyocyte death through mitochondrial Ca2+ overload and dysfunction in the delta-SG-deficient CHF147 hamster. We showed that virtually all isolated CHF147 ventricular myocytes exhibited elevated cytosolic and mitochondrial Ca2+ levels by the use of the Fura-2 and Rhod-2 fluorescent probes. Observation of living cells with Mito-Tracker red lead to the conclusion that approximately 15% of isolated CHF147 cardiomyocytes had disorganized mitochondria. Transmission electron microscope imaging showed mitochondrial swelling associated with crest and membrane disruption. Analysis of the mitochondrial permeability transition pore (MPTP) activity using calcein revealed that mitochondria of CHF147 ventricular cells were twofold leakier than wild types, whereas reactive oxygen species production was unchanged. Bax, Bcl-2, and LC3 expression analysis by Western blot indicated that the intrinsic apoptosis and the cell death associated to autophagy pathways were not significantly activated in CHF147 hearts. Our results lead to conclusion that cardiomyocytes death in delta-SG-deficient animals is an intrinsic phenomenon, likely related to Ca2+-induced necrosis. In this process Ca2+ overload-induced MPTP activation and mitochondrial disorganization may have an important role.

NSAIDs, Mitochondria and Calcium Signaling: Special Focus on Aspirin/Salicylates

Aspirin (acetylsalicylic acid) is a well-known nonsteroidal anti-inflammatory drug (NSAID) that has long been used as an anti-pyretic and analgesic drug. Recently, much attention has been paid to the chemopreventive and apoptosis-inducing effects of NSAIDs in cancer cells. These effects have been thought to be primarily attributed to the inhibition of cyclooxygenase activity and prostaglandin synthesis. However, recent studies have demonstrated unequivocally that certain NSAIDs, including aspirin and its metabolite salicylic acid, exert their anti-inflammatory and chemopreventive effects independently of cyclooxygenase activity and prostaglandin synthesis inhibition. It is becoming increasingly evident that two potential common targets of NSAIDs are mitochondria and the Ca²⁺ signaling pathway. In this review, we provide an overview of the current knowledge regarding the roles of mitochondria and Ca²⁺ in the apoptosis-inducing effects as well as some side effects of aspirin, salicylates and other NSAIDs, and introducing the emerging role of L-type Ca²⁺ channels, a new Ca²⁺ entry pathway in non-excitable cells that is up-regulated in human cancer cells.

Cardioprotection via modulation of calcium homeostasis by thiopental in hypoxia-reoxygenated neonatal rat cardiomyocytes

PURPOSE

Ca(2+) homeostasis plays an important role in myocardial cell injury induced by hypoxia-reoxygenation, and prevention of intracellular Ca(2+) overload is key to cardioprotection. Even though thiopental is a frequently used anesthetic agent, little is known about its cardioprotective effects, particularly in association with Ca(2+) homeostasis. We investigated whether thiopental protects cardiomyocytes against hypoxia-reoxygenation injury by regulating Ca(2+) homeostasis.

MATERIALS AND METHODS

Neonatal rat cardiomyocytes were isolated. Cardiomyocytes were exposed to different concentrations of thiopental and immediately replaced in the hypoxic chamber to maintain hypoxia. After 1 hour of exposure, a culture dish was transferred to the CO(2) incubator and cells were incubated at 37 for 5 hours. At the end of the experiments, the authors assessed cell protection using immunoblot analysis and caspase activity. The mRNA of genes involved in Ca(2+) homeostasis, mitochondrial membrane potential, and cellular Ca(2+) levels were examined.

RESULTS

In thiopental-treated cardiomyocytes, there was a decrease in expression of the proapoptotic protein Bax, caspase-3 activation, and intracellular Ca(2+) content. In addition, both enhancement of anti-apoptotic protein Bcl-2 and activation of Erk concerned with survival were shown. Furthermore, thiopental attenuated alterations of genes involving Ca(2+) regulation and significantly modulated abnormal changes of NCX and SERCA2a genes in hypoxia-reoxygenated neonatal cardiomyocytes. Thiopental suppressed disruption of mitochondrial membrane potential (DeltaPsi(m)) induced by hypoxia-reoxygenation.

CONCLUSION

Thiopental is likely to modulate expression of genes that regulate Ca(2+) homeostasis, which reduces apoptotic cell death and results in cardioprotection.

L-type Ca2+ channels: a new player in the regulation of Ca2+ signaling, cell activation and cell survival in immune cells

Ca(2+) is a highly versatile intracellular second messenger in many cell types, and regulates many complicated cellular processes, including cell activation, proliferation and apoptosis. Influx of Ca(2+) from the extracellular fluid is required for sustained elevation of the cytosolic Ca(2+) concentration and full activation of Ca(2+)-dependent processes. It is widely accepted that Ca(2+) release-activated Ca(2+) channels are the major routes of Ca(2+) influx in electrically non-excitable cells, including hematopoietic cells, whereas voltage-gated Ca(2+) channels such as L-type Ca(2+) channels (LTCCs) serve as the principal routes of Ca(2+) entry into electrically excitable cells such as neurons and myocytes. However, recent pharmacological and molecular genetic studies have revealed the existence of functional LTCCs and/or LTCC-like channels in a variety of immune cells including mast cells. In this article, we review recent advances in our understanding of Ca(2+) signaling in immune cells with a special interest in mast cells. We highlight roles for LTCCs in antigen receptor-mediated mast cell activation and survival.

The relationship between calcium accumulation in osteoclast mitochondrial granules and bone resorption

In the process of bone resorption, calcium is considered to be transported within vesicles in osteoclasts and eventually released. We studied the ultramicromorphology of calcium (Ca) transport in osteoclasts by preparing samples of osteoclasts collected from rat femurs in which calcium was maximally preserved and subjected them to high-pressure quick-freezing and freeze-substitution. We then examined the localization of calcium by Electron Energy Loss Spectroscopy (EELS). The structures of cell membranes were preserved, suggesting the suitability of this high-pressure quick-freezing and freeze-substitution technique. Osteoclast mitochondria adjacent to the ruffled border were rich in mitochondrial granules and contained a large amount of Ca. In contrast, mitochondria in the basolateral region contained few granules. Moreover, by an osteoclast-culturing experiment, differences in the morphology of mitochondrial granules were noted between culturing on a dentin slice and that on a gold plate, i.e., few mitochondrial granules were noted in osteoclasts cultured on a non-dentin plate. These findings suggest an association between the morphology of mitochondrial granules in osteoclasts and bone resorption as well as a new transport route for Ca resorbed by osteoclasts. We propose that Ca accumulates in mitochondria granules to prevent increased Ca concentration in cytoplasm of osteoclasts during bone resorption.

Caspase-cleaved tau expression induces mitochondrial dysfunction in immortalized cortical neurons: implications for the pathogenesis of Alzheimer disease

In Alzheimer disease (AD) mitochondrial abnormalities occur early in the pathogenic process and likely play a significant role in disease progression. Tau is a microtubule-associated protein that is abnormally processed in AD, and a connection between tau pathology and mitochondrial impairment has been proposed. However, few studies have examined the relationship between pathological forms of tau and mitochondrial dysfunction. We recently demonstrated that inducible expression of tau truncated at Asp-421 to mimic caspase cleavage (T4C3) was toxic to immortalized cortical neurons compared with a full-length tau isoform (T4). In this study we investigated the effects of T4C3 on mitochondrial function. Expression of T4C3 induced mitochondrial fragmentation and elevated oxidative stress levels in comparison with T4-expressing cells. Thapsigargin treatment of T4 or T4C3 cells, which causes an increase in intracellular calcium levels, resulted in a significant decrease in mitochondrial potential and loss of mitochondrial membrane integrity in T4C3 cells when compared with cells expressing T4. The mitochondrial fragmentation and mitochondrial membrane damage were ameliorated in T4C3 cells by pretreatment with cyclosporine A or FK506, implicating the calcium-dependent phosphatase calcineurin in these pathogenic events. Increased calcineurin activity has been reported in AD brain, and thus, inhibition of this phosphatase may provide a therapeutic target for the treatment of AD.

Ca v 1.2 L-type Ca2+ channel protects mast cells against activation-induced cell death by preventing mitochondrial integrity disruption

In non-excitable cells, store-operated Ca(2+) channels (SOCs) are the principal routes of Ca(2+) entry. Recently, store-independent Ca(2+) channels which are pharmacologically and/or immunologically similar to L-type Ca(2+) channels (LTCCs) have been shown to exist in various hematopoietic cells, including T cells, B cells and neutrophils. We previously reported that mast cells express LTCCs which regulate mast cell effector responses in a distinct manner from SOCs. In the present study, we examined the possible role for LTCCs in mast cell survival. Both RBL-2H3 mast cells and bone marrow-derived mast cells underwent considerable apoptosis after treatment with thapsigargin (Tg) but not stimulation through the high-affinity IgE receptor (Fc epsilon RI). The LTCC-selective antagonists such as nifedipine greatly augmented Fc epsilon RI-mediated apoptosis, while the LTCC-selective agonist (S)-BayK8644 blocked Tg-induced apoptosis. The modulation of apoptosis was accompanied by altered mitochondrial integrity, as measured with the mitochondrial membrane potential, cytochrome c release and caspase-3/7 activation. Fc epsilon RI stimulation induced mitochondrial Ca(2+) ([Ca(2+)](m)) entry through both SOCs and LTCCs, while Tg evoked [Ca(2+)](m) entry through LTCCs but not SOCs. The LTCC-selective antagonists blocked [Ca(2+)](m) entry, whereas (S)-BayK8644 augmented Tg-induced [Ca(2+)](m) entry. Moreover, blockade of the expression of the alpha(1C) subunit of Ca(v)1.2 LTCC using small-interfering RNA strongly augmented Fc epsilon RI-mediated apoptosis, mitochondrial integrity, and mitochondrial Ca(2+) collapse, and abolished the protective effects of (S)-BayK8644 against Tg-induced apoptosis. These findings suggest that Ca(v)1.2 LTCC protects mast cells against activation-induced cell death by preventing mitochondrial integrity disruption.

Extracellular divalent cations modulate aminoglycoside-induced hair cell death in the zebrafish lateral line

Aminoglycoside antibiotics cause death of sensory hair cells. Research over the past decade has identified several key players in the intracellular cascade. However, the role of the extracellular environment in aminoglycoside ototoxicity has received comparatively little attention. The present study uses the zebrafish lateral line to demonstrate that extracellular calcium and magnesium ions modulate hair cell death from neomycin and gentamicin in vivo, with high levels of either divalent cation providing significant protection. Imaging experiments with fluorescently-tagged gentamicin show that drug uptake is reduced under high calcium conditions. Treating fish with the hair cell transduction blocker amiloride also reduces aminoglycoside uptake, preventing the toxicity, and experiments with variable calcium and amiloride concentrations suggest complementary effects between the two protectants. Elevated magnesium, in contrast, does not appear to significantly attenuate drug uptake, suggesting that the two divalent cations may protect hair cells from aminoglycoside damage through different mechanisms. These results provide additional evidence for calcium- and transduction-dependent aminoglycoside uptake. Divalent cations provided differential protection from neomycin and gentamicin, with high cation concentrations almost completely protecting hair cells from neomycin and acute gentamicin toxicity, but offering reduced protection from continuous (6 h) gentamicin exposure. These experiments lend further support to the hypothesis that aminoglycoside toxicity occurs via multiple pathways in a both a drug and time course-specific manner.

Rosiglitazone treatment prevents mitochondrial dysfunction in mutant huntingtin-expressing cells: possible role of peroxisome proliferator-activated receptor-gamma (PPARgamma) in the pathogenesis of Huntington disease

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a member of the PPAR family of transcription factors. Synthetic PPARgamma agonists are used as oral anti-hyperglycemic drugs for the treatment of non-insulin-dependent diabetes. However, emerging evidence indicates that PPARgamma activators can also prevent or attenuate neurodegeneration. Given these previous findings, the focus of this report is on the potential neuroprotective role of PPARgamma activation in preventing the loss of mitochondrial function in Huntington disease (HD). For these studies we used striatal cells that express wild-type (STHdh(Q7/Q7)) or mutant (STHdh(Q111/Q111)) huntingtin protein at physiological levels. Treatment of mutant cells with thapsigargin resulted in a significant decrease in mitochondrial calcium uptake, an increase in reactive oxygen species production, and a significant decrease in mitochondrial membrane potential. PPARgamma activation by rosiglitazone prevented the mitochondrial dysfunction and oxidative stress that occurred when mutant striatal cells were challenged with pathological increases in calcium. The beneficial effects of rosiglitazone were likely mediated by activation of PPARgamma, as all protective effects were prevented by the PPARgamma antagonist GW9662. Additionally, the PPARgamma signaling pathway was significantly impaired in the mutant striatal cells with decreases in PPARgamma expression and reduced PPARgamma transcriptional activity. Treatment with rosiglitazone increased mitochondrial mass levels, suggesting a role for the PPARgamma pathway in mitochondrial function in striatal cells. Altogether, this evidence indicates that PPARgamma activation by rosiglitazone attenuates mitochondrial dysfunction in mutant huntingtin-expressing striatal cells, and this could be an important therapeutic avenue to ameliorate the mitochondrial dysfunction that occurs in HD.

Extracellular superoxide released from mitochondria mediates mast cell death by advanced glycation end products

Advanced glycation end products (AGEs) accumulate during aging and to higher extents under pathological conditions such as diabetes. Since we previously showed that mast cells expressed the AGE-binding protein, receptor for AGEs (RAGE) on their cell surface, we examined whether AGE affected mast cell survival. Herein, we demonstrate that mast cells undergo apoptosis in response to AGE. Glycated albumin (GA), an AGE, but not stimulation with the high-affinity IgE receptor (FcepsilonRI), can induce mast cell death, as measured by annexin V/propidium iodide double-staining. GA (> or =0.1 mg/ml) exhibited this pro-apoptotic activity in a concentration-dependent manner. GA and FcepsilonRI stimulation increased the cytosolic Ca(2+) levels to a similar extent, whereas GA, but not FcepsilonRI stimulation, caused mitochondrial Ca(2+) overload and membrane potential collapse, resulting in mitochondrial integrity disruption, cytochrome c release and caspase-3/7 activation. In addition, GA, but not FcepsilonRI stimulation, induced extracellular release of superoxide from mitochondria, and this release played a key role in the disruption of Ca(2+) homeostasis. Knockdown of RAGE expression using small interfering RNA abolished GA-induced apoptosis, mitochondrial Ca(2+) overload, and superoxide release, demonstrating that RAGE mediates the GA-induced mitochondrial death pathway. AGE-induced mast cell apoptosis may contribute to the immunocompromised and inflammatory conditions.

Toward biologically targeted therapy of calcium cycling defects in heart failure

A growing body of evidence indicates that heart failure progression is tightly associated with dysregulation of phosphorylation of Ca2+ regulators localized in the sub-cellular microdomain of the sarcoplasmic reticulum. Chemical or genetic correction of abnormalities in cardiac phosphorylation cascades is emerging as a potential target in the treatment of heart failure. Here, we review how specific kinases and phosphatases finely tune Ca2+ cycling and regulate excitation-contraction (E-C) coupling in cardiomyocytes.

Survival signaling by C-RAF: mitochondrial reactive oxygen species and Ca2+ are critical targets

Survival signaling by RAF occurs through largely unknown mechanisms. Here we provide evidence for the first time that RAF controls cell survival by maintaining permissive levels of mitochondrial reactive oxygen species (ROS) and Ca(2+). Interleukin-3 (IL-3) withdrawal from 32D cells resulted in ROS production, which was suppressed by activated C-RAF. Oncogenic C-RAF decreased the percentage of apoptotic cells following treatment with staurosporine or the oxidative stress-inducing agent tert-butyl hydroperoxide. However, it was also the case that in parental 32D cells growing in the presence of IL-3, inhibition of RAF signaling resulted in elevated mitochondrial ROS and Ca(2+) levels. Cell death is preceded by a ROS-dependent increase in mitochondrial Ca(2+), which was absent from cells expressing transforming C-RAF. Prevention of mitochondrial Ca(2+) overload after IL-3 deprivation increased cell viability. MEK was essential for the mitochondrial effects of RAF. In summary, our data show that survival control by C-RAF involves controlling ROS production, which otherwise perturbs mitochondrial Ca(2+) homeostasis.

Regulation of hypoxic neuronal death signaling by neuroglobin

The signal transduction pathways involved in neuronal death are not well understood. Neuroglobin (Ngb), a recently discovered vertebrate globin expressed predominantly in the brain, shows increased expression in neurons in response to oxygen deprivation and protects neurons from ischemic and hypoxic death. The mechanism of this neuroprotection is unclear. We examined the surface distribution of raft membrane microdomains in cortical neuron cultures during hypoxia using the raft marker cholera toxin B (CTx-B) subunit. Mechanistically, we demonstrate that hypoxia induces rapid polarization of somal membranes and aggregation of microdomains with the subjacent mitochondrial network. This signaling complex is formed well before neurons commit to die, consistent with an early role in death signal transduction. Neurons from Ngb-overexpressing transgenic (Ngb-Tg) mice do not undergo microdomain polarization or mitochondrial aggregation in response to, and are resistant to death from hypoxia. We link the protective actions of Ngb to inhibition of Pak1 kinase activity and Rac1-GDP-dissociation inhibitor disassociation, and inhibition of actin assembly and death-signaling module polarization.

Electrochemical analysis of the effect of Ca2+ on cardiolipin–cytochrome c interaction

Mitochondrial Ca2+ has been considered a trigger for the release of cytochrome c, which is a critical and early event in the induction of cell apoptosis, although the molecular mechanism underlying this effect is still not fully understood. Here we investigate the interaction between cytochrome c and cardiolipin and the effect of Ca2+ on this interaction using electrochemical methods. Experimental results revealed that modification of cardiolipin onto the surface of a pyrolytic graphite electrode could lead to a rapid direct electron transfer of cytochrome c through the electrostatic interaction between the protein and the cardiolipin. Addition of Ca2+ to the test solution containing cytochrome c could cause the decrease of the redox peaks of the protein, and the peaks could be recovered when Ca2+ was chelated by ethylenediaminetetraacetate. The cardiolipin-cytochrome c interaction and the Ca2+ effect were also investigated with the variation of the charges of lipids, buffer solutions, reaction time, and valencies of cations for comparison.

Suppression of IP3-mediated calcium release and apoptosis by Bcl-2 involves the participation of protein phosphatase 1

The involvement and potential interdependence of inositol trisphosphate (IP3) receptors and Bcl-2 in the regulation of Ca2+ signaling is not clear. Here, we have explored the mechanism(s) of how Bcl-2 suppresses the IP3-sensitive Ca2+ release in MCF-7 cells focusing on the possible role of protein phosphatase 1 (PP1). We found that through influences on protein-protein interaction, Bcl-2 may alter the balance between the effects of phosphatase (PP1) and kinase (PKA) on the IP3 R1 signaling complex. Using various experimental approaches including phosphatase inhibition and RNAi, we show that Bcl-2 by competing with IP3R1 for the binding of PP1 can reduce the IP3-mediated calcium signal and protect cells from mitochondrial dysfunction and cell death.

An antioxidant treatment potentially protects myocardial energy metabolism by regulating uncoupling protein 2 expression in a chronic β-adrenergic stimulation rat model

Excessive beta-adrenergic stimulation causes cardiac toxicity, which also contributes to cardiac oxidative stress. Although uncoupling protein 2 (UCP2), a member of the mitochondrial inner membrane carrier family, can regulate energy efficiency and oxidative stress in mitochondria, little data exist regarding interactions between UCP2 expression and beta-adrenergic stimulation induced cardiac oxidative damage. We investigated whether chronic beta-adrenergic stimulation induces myocardial energy metabolism abnormality via oxidative stress, including any role of UCP2. We also examined whether 3-methyl-1-phenyl-2-pyrazolin-5-one (MIC-186; edaravone), a potent free radical scavenger, has cardioprotective effects against beta-adrenergic stimulation. Male Sprague-Dawley rats received isoproterenol (1.2 mg/kg/day) subcutaneously or/and edaravone (30 mg/kg/day) orally. Isoproterenol increased the heart/body weight ratio, accompanied by an increase in the level of myocardial thiobarbituric acid reactive substances (TBARS) and a decreased phosphocreatine (PCr) to adenosine triphosphate (ATP) ratio. Isoproterenol also markedly increased expressions of UCP2 mRNA (1.74 fold vs. non-isoproterenol) and protein (1.93 fold vs. non-isoproterenol). Edaravone had no apparent effect in hypertrophic responses, but significantly prevented both increases in TBARS and decreases in the PCr/ATP ratio. Edaravone also prevented increases in UCP2 mRNA (0.76 fold vs. isoproterenol) and protein (0.62 fold vs. isoproterenol) expressions against isoproterenol administration. Our results suggest that chronic beta-adrenergic stimulation induces myocardial energy inefficiency via excessive oxidative stress. The antioxidant effect of edaravone has potential to improve energy metabolism abnormalities against beta-adrenergic stimulation. Adequate regulation of UCP2 expression through artificial reduction of oxidative stress may play an important role in protection of the myocardial energy metabolism.

Chloroacetaldehyde- and acrolein-induced death of human proximal tubule cells

Ifosfamide (ifo) is a commonly used drug in chemotherapy. It is metabolized to acrolein (acro) and chloroacetaldehyde (CAA), which are thought to be responsible for renal side effects. We studied the effects of ifo and cyclophosphamide (cyclo) as well as their metabolites, acro and CAA, on cellular protein content, necrosis, apoptosis and cytosolic calcium concentration using a human proximal tubule cell line. The protein content decreased during acro or CAA administration (15 to 300 micromol/l), but not during ifo or cyclo exposure over a time period of up to 72 h. Mild apoptosis was induced only by high acro (150, 300 micromol/l) and low CAA concentrations (15, 75 micromol/l) and only in a narrow time window (24 h). Necrosis was increased after exposure to acro or CAA at all concentrations. CAA was more potent than acro. Ifo and cyclo did not induce necrosis or apoptosis. Glutathione abolished CAA-induced cell death. Cytosolic calcium concentrations increased after acro or CAA administration and showed an oscillating pattern. Cytosolic Ca(2+) chelation did not prevent necrosis. We conclude that neither ifo nor cyclo induce cell damage, but that their metabolites acro and CAA induce cell death. This cell death occurs mainly by necrosis and not by apoptosis.

Molecular research technologies in mitochondrial diseases: The microarray approach

Mitochondria are ubiquitous in eukaryotic cells where they generate much of the cellular energy by the process of oxidative phosphorylation (OXPHOS). The approximately 1500 genes of the mitochondrial genome are distributed between the cytoplasmic, maternally-inherited, mitochondrial DNA (mtDNA) which encodes 37 genes and the nuclear DNA (nDNA) which encompasses the remaining mitochondrial genes. The interplay between the mtDNA and nDNA encoded mitochondrial genes and their role in mitochondrial disorders is still largely unclear. One approach for elucidating the pathophysiology of mitochondrial diseases has been to look at changes in the expression of mtDNA and nDNA-encoded genes in response to specific mitochondrial genetic defects. Initial studies of gene expression changes in response to mtDNA defect employed blot technologies to analyze changes in the expression of individual genes one at a time. While Southern/Northern blot experiments confirmed the importance of nDNA-mtDNA interactions in the pathophysiology of mitochondrial myopathy, the methodology used limited the number of genes that could be analyzed from each patient. This barrier has been overcome, in part by the advent of DNA microarray technology. In DNA microarrays gene sequences or oligonucleotides homologous to gene sequences are arrayed on a solid support. The RNA from the subject is then isolated, the mRNA converted to cDNA and the cDNA labeled with a fluorescent probe. The labeled cDNA is hybridized on the microarray and the fluorescence bound to each array is then quantified. Recently, these technologies have been applied to mitochondrial disease patient tissues and the presence of coordinate changes in mitochondrial gene expression confirmed.

Zonal necrosis prevented by transduction of the artificial anti-death FNK protein

Protection of cells from necrosis would be important for many medical applications. Here, we show protein transduction domain (PTD)-FNK therapeutics based on protein transduction to prevent necrosis and acute hepatic injury with zonal death induced by carbon tetrachloride (CCl4). PTD-FNK is a fusion protein comprising the HIV/Tat PTD and FNK, a gain-of-function mutant of anti-apoptotic Bcl-x(L). PTD-FNK protected hepatoma HepG2 from necrotic death induced by CCl4, and additionally, increased the apoptotic population among cells treated with CCl4. A concomitant treatment with a pan-caspase inhibitor Z-VAD-FMK (N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone), which alone could not prevent the necrosis, protected these cells from the apoptosis. When pre-injected intraperitoneally, PTD-FNK markedly reduced zonal liver necrosis caused by CCl4. Moreover, injection of PTD-FNK accompanied by Z-VAD-FMK suppressed necrotic injury even after CCl4 administration. These results suggest that PTD-FNK has great potential for clinical applications to prevent cell death, whether from apoptosis or necrosis, and organ failure.