Intracellular Ca2+ release through ryanodine receptors contributes to AMPA receptor-mediated mitochondrial dysfunction and ER stress in oligodendrocytes

From demyelination to remyelination: the road toward therapies for spinal cord injury

Myelin integrity is crucial for central nervous system (CNS) physiology while its preservation and regeneration after spinal cord injury (SCI) is key to functional restoration. Disturbance of nodal organization acutely after SCI exposes the axon and triggers conduction block in the absence of overt demyelination. Oligodendrocyte (OL) loss and myelin degradation follow as a consequence of secondary damage. Here, we provide an overview of the major biological events and underlying mechanisms leading to OL death and demyelination and discuss strategies to restrain these processes. Another aspect which is critical for SCI repair is the enhancement of endogenously occurring spontaneous remyelination. Recent findings have unveiled the complex roles of innate and adaptive immune responses in remyelination and the immunoregulatory potential of the glial scar. Moreover, the intimate crosstalk between neuronal activity, oligodendrogenesis and myelination emphasizes the contribution of rehabilitation to functional recovery. With a view toward clinical applications, several therapeutic strategies have been devised to target SCI pathology, including genetic manipulation, administration of small therapeutic molecules, immunomodulation, manipulation of the glial scar and cell transplantation. The implementation of new tools such as cellular reprogramming for conversion of one somatic cell type to another or the use of nanotechnology and tissue engineering products provides additional opportunities for SCI repair. Given the complexity of the spinal cord tissue after injury, it is becoming apparent that combinatorial strategies are needed to rescue OLs and myelin at early stages after SCI and support remyelination, paving the way toward clinical translation.

Protective Effects of Berberine on Oxygen-Glucose Deprivation/Reperfusion on Oligodendrocyte Cell Line (OLN-93)

BACKGROUND

Oligodendrocytes, the myelinating glial cells of central nervous system, are highly vulnerable to ischemic-induced excitotoxic insult, a phenomenon in which calcium overload triggers cell death. Berberine is an alkaloid extracted from medicinal herbs as Coptidis Rhizoma with several pharmacological effects like inhibition of neuronal apoptosis in cerebral ischemia.

METHODS

We examined the effects of berberine (0.5-4 μM) and glutamate receptors antagonists (MK-801 [10 μM] and NBQX [30 μM]) on OLN-93 cell line (a permanent immature rat oligodendrocyte) during (30, 60, 240 min) oxygen-glucose deprivation (OGD)/24 h reperfusion. The cells were cultured in 12-well plates. The cells were exposed to glucose-free medium and hypoxia in a small anaerobic chamber. Cell viability was evaluated by MTT (3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) assay. The intracellular calcium levels also were evaluated by Ca(2+)-sensitive indicator Fura-2/AM in presence or absence of berberine (2 μM) during 30 min chemical OGD by NaN3 (20 mM). Student's t-test and ANOVA were used for statistical analysis.

RESULTS

Berberine, MK-801and NBQX significantly increased oligodendrocyte viability in all 3 time-scheduled oxygen-glucose deprivation/reperfusion. Berberine at 2 μM produced peak of protection, and increased cell viability to 83%, 77%, and 79% during 30, 60, 240 min ischemic experiments, respectively (P < 0.001). Berberine significantly attenuated intracellular Ca(2+) rise induced by chemical ischemia, and this effect of berberine was significantly stronger than MK-801 and NBQX (P < 0.001).

CONCLUSIONS

We concluded that berberine protected OLN-93 oligodendrocyte against ischemic induced excitotoxic injury. Attenuation of intracellular Ca(2+) overload by berberine may be the key mechanism that saved OLN-93 from excitotoxicity damage.

Spine venom of crown-of-thorns starfish (Acanthaster planci) induces antiproliferation and apoptosis of human melanoma cells (A375.S2)

The crown-of-thorns starfish (Acanthaster planci) is a venomous starfish. In this study, the extraction of A. planci spine venom (ASV) was performed by phosphate saline buffer, followed by assaying the cytotoxicity on human normal and tumor cells. It was found that human melanoma cells (A375.S2) were the most sensitive to the ASV solution. The cells, after incubation with ASV, significantly appeared to decrease cell viability and increase lactate dehydrogenase (LDH) release with a dose-dependent relationship. The extract of spine promoted loss of mitochondrial membrane potential (ΔΨm) and induced inter-nucleosomal DNA fragmentation in human melanoma cells. The cells exhibited apoptosis by using propidium iodide (PI) staining of DNA fragmentation; it was then determined by flow cytometry (sub-G1 peak). The molecular cytotoxicity of ASV was tested through evaluation of the apoptosis/necrosis ratio by double staining with annexin V and PI assay. The A. planci spine venom showed significant antiproliferation. The human melanoma cells revealed apoptosis at low dose (1.25 μg/ml), and necrosis occurred at high dose (5 μg/ml).

Neurotransmitter signaling in white matter

White matter (WM) tracts are bundles of myelinated axons that provide for rapid communication throughout the CNS and integration in grey matter (GM). The main cells in myelinated tracts are oligodendrocytes and astrocytes, with small populations of microglia and oligodendrocyte precursor cells. The prominence of neurotransmitter signaling in WM, which largely exclude neuronal cell bodies, indicates it must have physiological functions other than neuron-to-neuron communication. A surprising aspect is the diversity of neurotransmitter signaling in WM, with evidence for glutamatergic, purinergic (ATP and adenosine), GABAergic, glycinergic, adrenergic, cholinergic, dopaminergic and serotonergic signaling, acting via a wide range of ionotropic and metabotropic receptors. Both axons and glia are potential sources of neurotransmitters and may express the respective receptors. The physiological functions of neurotransmitter signaling in WM are subject to debate, but glutamate and ATP-mediated signaling have been shown to evoke Ca(2+) signals in glia and modulate axonal conduction. Experimental findings support a model of neurotransmitters being released from axons during action potential propagation acting on glial receptors to regulate the homeostatic functions of astrocytes and myelination by oligodendrocytes. Astrocytes also release neurotransmitters, which act on axonal receptors to strengthen action potential propagation, maintaining signaling along potentially long axon tracts. The co-existence of multiple neurotransmitters in WM tracts suggests they may have diverse functions that are important for information processing. Furthermore, the neurotransmitter signaling phenomena described in WM most likely apply to myelinated axons of the cerebral cortex and GM areas, where they are doubtless important for higher cognitive function.

Isoflurane induces endoplasmic reticulum stress and caspase activation through ryanodine receptors

BACKGROUND

Isoflurane has been reported to induce caspase-3 activation, which may induce neurotoxicity and contribute to the pathogenesis of Alzheimer's disease. However, the underlying mechanism is largely unknown, especially whether or not isoflurane can induce ryanodine receptors (RyRs)-associated endoplasmic reticulum (ER) stress, leading to caspase-3 activation. We therefore assessed the effects of isoflurane on RyRs-associated ER stress.

METHODS

We treated primary neurones from wild-type (C57BL/6J) mice with 1% and 2% isoflurane for 1, 3, or 6 h. We then measured levels of C/EBP homologous protein (CHOP) and caspase-12, two ER stress markers, using immunocytochemistry staining and western blotting analysis. Dantrolene (5 μM), the antagonist of RyRs, was used to investigate the role of RyRs in the isoflurane-induced ER stress and caspase-3 activation.

RESULTS

Isoflurane 2% for 6 h treatment increased the levels of CHOP (876% vs 100%, P=0.00009) and caspase-12 (276% vs 100%, P=0.006), and induced caspase-3 activation in the neurones. The administration of 2% isoflurane for 3 h (shorter duration), however, only increased the levels of CHOP (309% vs 100%, P=0.003) and caspase-12 (266% vs 100%, P=0.001), without causing caspase-3 activation. The isoflurane-induced ER stress (CHOP: F=16.64, P=0.0022; caspase-12: F=6.13, P=0.0383) and caspase-3 activation (F=32.06, P=0.0005) were attenuated by the dantrolene treatment.

CONCLUSIONS

These data imply that isoflurane might induce caspase-3 activation by causing ER stress through RyRs, and dantrolene could attenuate the isoflurane-induced ER stress and caspase-3 activation. Further investigations of the potential neurotoxicity of isoflurane are needed.

Proteomics and phosphoproteomics provide insights into the mechanism of action of a novel pyrazolo[3,4-d]pyrimidine Src inhibitor in human osteosarcoma

Osteosarcoma (OS) is a highly malignant bone tumour, affecting mainly children and young adults between 10 and 20 years of age. It represents the most frequent primitive malignant tumour of the skeletal system and is characterized by an extremely aggressive clinical course, with rapid development of lung metastases. In the last few years, targeting Src in the treatment of OS has become one of the major challenges in the development of new drugs, since an elevated Src kinase activity has been associated with the development and the maintenance of the OS malignant phenotype. Recently, SI-83, a novel pyrazolo[3,4-d]pyrimidine derivate Src inhibitor, was selected as a promising OS therapeutic drug because of its elevated anti-tumour effects toward human OS. In the present study, gel-based proteomics and phosphoproteomics revealed significant changes in proteins involved in many cancer related processes. We got insight into SI-83 proapoptotic and antiproliferative properties (overrepresentation of GRIA1, GRP78, and CALR and underrepresentation of NPM1, RCN, and P4HB). Nevertheless, the most significant findings of our work are the SI-83 induced dephosphorylation of ARPC5L, a subunit of the actin related Arp2/3 complex, and the decrease of other cytoskeleton proteins. These data, together with a dramatic impairment of SaOS-2 cell migration and adhesion, suggest that SI-83 may have antimetastatic features that enhance its use as a potent OS chemotherapeutic drug.

Modulation of oxidative stress, apoptosis, and calcium entry in leukocytes of patients with multiple sclerosis by Hypericum perforatum

OBJECTIVES

Hypericum perfortarum (HP, St John's wort) is a modulator of Ca(2+) entry in neutrophils and it may modulate intracellular free Ca(2+) ([Ca(2+)]i) entry in leukocytes of patients with multiple sclerosis (MS). We investigated effects of HP on oxidative stress, apoptosis, and [Ca(2+)]i concentrations in serum and leukocytes of patients with MS.

METHODS

Neutrophils of nine newly diagnosed MS patients and nine healthy subjects within four subgroups were used in the study. The first group was a control; the second group was patients with MS. The neutrophils from patient group were incubated non-specific TRPM2 channel blocker (2-APB), voltage-gated calcium channel blockers, verapamil and diltiazem (V + D) with HP before N-formyl-L-methionyl-L-leucyl-L-phenylalanine stimulation, respectively.

RESULTS

Neutrophil and serum lipid peroxidation, neutrophil apoptosis and [Ca(2+)]i levels in patients with MS were higher than in control although their levels were decreased by HP, 2-APB, and V + D incubations. The modulator role of V + D in MS and MS + HP groups was higher than in the 2-APB group. Neutrophilic glutathione peroxidase (GSH-Px) and serum vitamin A and E concentrations were lower in the MS group than in control. However, the neutrophil GSH-Px activity was increased by HP incubation. The neutrophil reduced glutathione, serum vitamin C and β-carotene concentrations did not change in control and patients.

DISCUSSION

We observed that HP-induced protective effects on oxidative stress and [Ca(2+)]i concentrations by modulating transient receptor potential and voltage gated calcium channel in the patients with MS. Thus, it may provide useful treatment of neutrophil activity in the patients.

Ammonium chloride enhances cisplatin cytotoxicity through DNA double-strand breaks in human cervical cancer cells

Cisplatin (cis-diamminedichloroplatinum II, CDDP) acts as a therapeutic agent by initiating cellular apoptosis. However, side-effects and drug resistance limit the clinical use of cisplatin. Numerous studies have focused on the drug-target interactions, cellular pharmacology and pharmacokinetics of cisplatin. Newly developed treatment strategies are needed in order to be used in combination with cisplatin, with the aim to minimize toxicity and to circumvent cisplatin resistance. Ammonium chloride (NH4Cl) is widely used in various areas, but its use as a combination agent with cisplatin for the treatment of cancer cells has not been previously reported. In the present study, we showed that NH4Cl could be potentially used as an effective agent in cisplatin combination treatment of HeLa human cervical cancer (HCC) cells. Cisplatin was found to inhibit cell growth, as well as to induce cell apoptosis and DNA double-strand breaks. In addition, treatment with NH4Cl increased the rate of cell apoptosis and the activation of caspase-3. Particularly, we found that NH4Cl treatment increased cisplatin‑induced phosphorylation of H2AX. In conclusion, our data indicate that NH4Cl enhances cisplatin cytotoxicity through increased DNA damage in HeLa HCC cells.

Deregulation of excitatory neurotransmission underlying synapse failure in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia in the elderly. Memory loss in AD is increasingly attributed to soluble oligomers of the amyloid-β peptide (AβOs), toxins that accumulate in AD brains and target particular synapses. Glutamate receptors appear to be centrally involved in synaptic targeting by AβOs. Once bound to neurons, AβOs dysregulate the activity and reduce the surface expression of both N-methyl-D-aspartate (NMDA) and 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propanoic acid (AMPA) types of glutamate receptors, impairing signaling pathways involved in synaptic plasticity. In the extracellular milieu, AβOs promote accumulation of the excitatory amino acids, glutamate and D-serine. This leads to overactivation of glutamate receptors, triggering abnormal calcium signals with noxious impacts on neurons. Here, we review key findings linking AβOs to deregulated glutamate neurotransmission and implicating this as a primary mechanism of synapse failure in AD. We also discuss strategies to counteract the impact of AβOs on excitatory neurotransmission. In particular, we review evidence showing that inducing neuronal hyperpolarization via activation of inhibitory GABA(A) receptors prevents AβO-induced excitotoxicity, suggesting that this could comprise a possible therapeutic approach in AD.

Restoring endoplasmic reticulum homeostasis improves functional recovery after spinal cord injury

The endoplasmic reticulum (ER) stress response (ERSR) is activated to maintain protein homeostasis or induce apoptosis in the ER in response to distinct cellular insults including hypoxia, inflammation, and oxidative damage. Recently, we showed ERSR activation in a mouse model of a contusive spinal cord injury (SCI) and an improved hindlimb locomotor function following SCI when the pro-apoptotic arm of ERSR was genetically inhibited. The objective of the current study was to explore if the pharmacological enhancement of the homeostatic arm of the ERSR pathway can improve the functional outcome after SCI. Salubrinal enhances the homeostatic arm of the ERSR by increasing phosphorylation of eIF2α. Salubrinal significantly enhanced the levels of phosphorylated eIF2α protein and modulated the downstream ERSR effectors assessed at the lesion epicenter 6h post-SCI. Hindlimb locomotion showed significant improvement in animals treated with salubrinal. Treadmill-based-gait assessment showed a significant increase in maximum speed of coordinated walking and a decrease in rear stance time and stride length in salubrinal-treated animals. This improved functional recovery corresponded with increased white matter sparing and decreased oligodendrocyte apoptosis. In addition, salubrinal protected cultured mouse oligodendrocyte progenitor cells against the ER stress-inducing toxin tunicamycin. These data suggest that boosting the homeostatic arm of the ERSR reduces oligodendrocyte loss after traumatic SCI and support the contention that pharmacological targeting of the ERSR after CNS trauma is a therapeutically viable approach.

Ca(2+) -dependent endoplasmic reticulum stress correlates with astrogliosis in oligomeric amyloid β-treated astrocytes and in a model of Alzheimer's disease

Neurotoxic effects of amyloid β peptides are mediated through deregulation of intracellular Ca(2+) homeostasis and signaling, but relatively little is known about amyloid β modulation of Ca(2+) homeostasis and its pathological influence on glia. Here, we found that amyloid β oligomers caused a cytoplasmic Ca(2+) increase in cultured astrocytes, which was reduced by inhibitors of PLC and ER Ca(2+) release. Furthermore, amyloid β peptides triggered increased expression of glial fibrillary acidic protein (GFAP), as well as oxidative and ER stress, as indicated by eIF2α phosphorylation and overexpression of chaperone GRP78. These effects were decreased by ryanodine and 2APB, inhibitors of ryanodine receptors and InsP3 receptors, respectively, in both primary cultured astrocytes and organotypic cultures of hippocampus and entorhinal cortex. Importantly, intracerebroventricular injection of amyloid β oligomers triggered overexpression of GFAP and GRP78 in astrocytes of the hippocampal dentate gyrus. These data were validated in a triple-transgenic mouse model of Alzheimer's disease (AD). Overexpression of GFAP and GRP78 in the hippocampal astrocytes correlated with the amyloid β oligomer load in 12-month-old mice, suggesting that this parameter drives astrocytic ER stress and astrogliosis in vivo. Together, these results provide evidence that amyloid β oligomers disrupt ER Ca(2+) homeostasis, which induces ER stress that leads to astrogliosis; this mechanism may be relevant to AD pathophysiology.

Excitatory amino acid changes in the brains of rhesus monkeys following selective cerebral deep hypothermia and blood flow occlusion

Selective cerebral deep hypothermia and blood flow occlusion can enhance brain tolerance to ischemia and hypoxia and reduce cardiopulmonary complications in monkeys. Excitotoxicity induced by the release of a large amount of excitatory amino acids after cerebral ischemia is the major mechanism underlying ischemic brain injury and nerve cell death. In the present study, we used selective cerebral deep hypothermia and blood flow occlusion to block the bilateral common carotid arteries and/or bilateral vertebral arteries in rhesus monkey, followed by reperfusion using Ringer's solution at 4°C. Microdialysis and transmission electron microscope results showed that selective cerebral deep hypothermia and blood flow occlusion inhibited the release of glutamic acid into the extracellular fluid in the brain frontal lobe and relieved pathological injury in terms of the ultrastructure of brain tissues after severe cerebral ischemia. These findings indicate that cerebral deep hypothermia and blood flow occlusion can inhibit cytotoxic effects and attenuate ischemic/hypoxic brain injury through decreasing the release of excitatory amino acids, such as glutamic acid.

Osteoblasts detect pericellular calcium concentration increase via neomycin-sensitive voltage gated calcium channels

The mechanisms underlying the detection of critically loaded or micro-damaged regions of bone by bone cells are still a matter of debate. Our previous studies showed that calcium efflux originates from pre-failure regions of bone matrix and MC3T3-E1 osteoblasts respond to such efflux by an increase in the intracellular calcium concentration. The mechanisms by which the intracellular calcium concentration increases in response to an increase in the pericellular calcium concentration are unknown. Elevation of the intracellular calcium may occur via release from the internal calcium stores of the cell and/or via the membrane bound channels. The current study applied a wide range of pharmaceutical inhibitors to identify the calcium entry pathways involved in the process: internal calcium release from endoplasmic reticulum (ER, inhibited by thapsigargin and TMB-8), calcium receptor (CaSR, inhibited by calhex), stretch-activated calcium channel (SACC, inhibited by gadolinium), voltage-gated calcium channels (VGCC, inhibited by nifedipine, verapamil, neomycin, and ω-conotoxin), and calcium-induced-calcium-release channel (CICRC, inhibited by ryanodine and dantrolene). These inhibitors were screened for their effectiveness to block intracellular calcium increase by using a concentration gradient induced calcium efflux model which mimics calcium diffusion from the basal aspect of cells. The inhibitor(s) which reduced the intracellular calcium response was further tested on osteoblasts seeded on mechanically loaded notched cortical bone wafers undergoing damage. The results showed that only neomycin reduced the intracellular calcium response in osteoblasts, by 27%, upon extracellular calcium stimulus induced by concentration gradient. The inhibitory effect of neomycin was more pronounced (75% reduction in maximum fluorescence) for osteoblasts seeded on notched cortical bone wafers loaded mechanically to damaging load levels. These results imply that the increase in intracellular calcium occurs by the entry of extracellular calcium ions through VGCCs which are sensitive to neomycin. N-type and P-type VGCCs are potential candidates because they are observed in osteoblasts and they are sensitive to neomycin. The calcium channels identified in this study provide new insight into mechanisms underlying the targeted repair process which is essential to bone adaptation.

Ca2+ store depletion and endoplasmic reticulum stress are involved in P2X7 receptor-mediated neurotoxicity in differentiated NG108-15 cells

P2X7 receptor (P2X7R) activation by extracellular ATP triggers influx of Na(+) and Ca(2+), cytosolic Ca(2+) overload and consequently cytotoxicity. Whether disturbances in endoplasmic reticulum (ER) Ca(2+) homeostasis and ER stress are involved in P2X7R-mediated cell death is unknown. In this study, a P2X7R agonist (BzATP) was used to activate P2X7R in differentiated NG108-15 neuronal cells. In a concentration-dependent manner, application of BzATP (10-100 µM) immediately raised cytosolic Ca(2+) concentration ([Ca(2+)]i) and caused cell death after a 24-h incubation. P2X7R activation for 2 h did not cause cell death but resulted in a sustained reduction in ER Ca2+ pool size, as evidenced by a diminished cyclopiazonic acid-induced Ca(2+) discharge (fura 2 assay) and a lower fluorescent signal in cells loaded with Mag-fura 2 (ER-specific Ca(2+)-fluorescent dye). Furthermore, P2X7R activation (2 h) led to the appearance of markers of ER stress [phosphorylated α subunit of eukaryotic initiation factor 2 (p-eIF2α) and C/EBP homologous protein (CHOP)] and apoptosis (cleaved caspase 3). Xestospongin C (XeC), an antagonist of inositol-1,4,5-trisphosphate (IP3) receptor (IP3R), strongly inhibited BzATP-triggered [Ca(2+)]i elevation, suggesting that the latter involved Ca(2+) release via IP3R. XeC pretreatment not only attenuated the reduction in Ca(2+) pool size in BzATP-treated cells, but also rescued cell death and prevented BzATP-induced appearance of ER stress and apoptotic markers. These novel observations suggest that P2X7R activation caused not only Ca(2+) overload, but also Ca(2+) release via IP3R, sustained Ca(2+) store depletion, ER stress and eventually apoptotic cell death.

Roles of white matter in central nervous system pathophysiologies

The phylogenetic enlargement of cerebral cortex culminating in the human brain imposed greater communication needs that have been met by the massive expansion of WM (white matter). Damage to WM alters brain function, and numerous neurological diseases feature WM involvement. In the current review, we discuss the major features of WM, the contributions of WM compromise to brain pathophysiology, and some of the mechanisms mediating WM injury. We will emphasize the newly appreciated importance of neurotransmitter signalling in WM, particularly glutamate and ATP signalling, to understanding both normal and abnormal brain functions. A deeper understanding of the mechanisms leading to WM damage will generate much-needed insights for developing therapies for acute and chronic diseases with WM involvement.

Ablation of junctin or triadin is associated with increased cardiac injury following ischaemia/reperfusion

AIMS

Junctin and triadin are calsequestrin-binding proteins that regulate sarcoplasmic reticulum (SR) Ca(2+) release by interacting with the ryanodine receptor. The levels of these proteins are significantly down-regulated in failing human hearts. However, the significance of such decreases is currently unknown. Here, we addressed the functional role of these accessory proteins in the heart's responses to ischaemia/reperfusion (I/R) injury.

METHODS AND RESULTS

Isolated mouse hearts were subjected to global I/R, and contractile parameters were assessed in wild-type (WT), junctin-knockout (JKO), and triadin-knockout (TKO) hearts. Both JKO and TKO were associated with significantly depressed post-I/R contractile recovery. However, ablation of triadin resulted in the most severe post-I/R phenotype. The additional contractile impairment of TKO hearts was not related to a mitochondrial death pathway, but attributed to endoplasmic reticulum (ER) stress-mediated apoptosis. Activation of the X-box-binding protein-1 and transcriptional up-regulation of C/EBP-homologous protein (CHOP) provided a molecular mechanism of caspase-12-dependent apoptosis in myocytes. In addition, elevation of cytosolic Ca(2+) during reperfusion was associated with the activation of calpain proteases and troponin I breakdown. Accordingly, treatment with the calpain inhibitor MDL-28170 significantly ameliorated post-I/R impairment of contractile recovery in intact hearts.

CONCLUSION

These findings indicate that deficiency of either junctin or triadin impairs the contractile recovery in post-ischaemic hearts, which appears to be primarily attributed to increased ER stress and activation of calpain.

Increased expression of ER stress- and hypoxia-associated molecules in grey matter lesions in multiple sclerosis

BACKGROUND

The endoplasmic reticulum (ER) stress pathway may play a role in the pathogenesis multiple sclerosis (MS), and while ER stress-associated molecules have been demonstrated in white matter (WM) lesions, these have not been analysed in grey matter (GM) demyelination.

OBJECTIVE

The objective was to characterise the type and frequency of GM lesions and establish expression profiles of ER stress- and hypoxia-associated markers.

METHODS

Sections from 16 MS cases and 12 non-MS controls were stained for ER stress molecules (BiP and CHOP) and hypoxia-associated D110 antigen.

RESULTS

Of the GM lesions analysed, 24% were type 1 (continuous between GM and WM), 22% were type 2 (entirely within GM) and the majority (54%) were type 3 (extending from pia mater). Comparison of GM lesions, MS normal-appearing grey matter (NAGM) and non-MS control tissue showed that NAGM, type 1 and type 3 lesions all had significantly increased levels of CHOP compared to controls. According to morphological and dual-labelling criteria, the majority of CHOP-positive cells were microglia. Approximately 50% of GM lesions contained D110-positive cells.

CONCLUSION

These data suggest that ER stress plays an important role in GM lesion development and may be critical in activation of microglia in pre-lesional NAGM. The high number of lesions containing D110-positive cells suggests a role for hypoxic-like insult in GM lesion development.

Hormesis, cell death and aging

Frequently, low doses of toxins and other stressors not only are harmless but also activate an adaptive stress response that raise the resistance of the organism against high doses of the same agent. This phenomenon, which is known as "hormesis", is best represented by ischemic preconditioning, the situation in which short ischemic episodes protect the brain and the heart against prolonged shortage of oxygen and nutrients. Many molecules that cause cell death also elicit autophagy, a cytoprotective mechanism relying on the digestion of potentially harmful intracellular structures, notably mitochondria. When high doses of these agents are employed, cells undergo mitochondrial outer membrane permeabilization and die. In contrast, low doses of such cytotoxic agents can activate hormesis in several paradigms, and this may explain the lifespan-prolonging potential of autophagy inducers including resveratrol and caloric restriction.

Role of the promyelocytic leukaemia protein in cell death regulation

The promyelocytic leukaemia gene PML was originally identified at the t(15;17) translocation of acute promyelocytic leukaemia, which generates the oncogene PML-retinoic acid receptor α. PML epitomises a subnuclear structure called PML nuclear body. Current models propose that PML through its scaffold properties is able to control cell growth and survival at many different levels. Here we discuss the current literature and propose new avenues for investigation.

Bee venom induces apoptosis through intracellular Ca2+ -modulated intrinsic death pathway in human bladder cancer cells

OBJECTIVES

To focus on bee venom-induced apoptosis in human bladder cancer TSGH-8301 cells and to investigate its signaling pathway to ascertain whether intracellular calcium iron (Ca(2+)) is involved in this effect.

METHODS

Bee venom-induced cytotoxic effects, productions of reactive oxygen species and Ca(2+) and the level of mitochondrial membrane potential (ΔΨm) were analyzed by flow cytometry. Apoptosis-associated proteins were examined by Western blot analysis and confocal laser microscopy.

RESULTS

Bee venom-induced cell morphological changes and decreased cell viability through the induction of apoptosis in TSGH-8301 cell were found. Bee venom promoted the protein levels of Bax, caspase-9, caspase-3 and endonuclease G. The enhancements of endoplasmic reticulum stress-related protein levels were shown in bee venom-provoked apoptosis of TSGH-8301 cells. Bee venom promoted the activities of caspase-3, caspase-8, and caspase-9, increased Ca(2+) release and decreased the level of ΔΨm. Co-localization of immunofluorescence analysis showed the releases of endonuclease G and apoptosis-inducing factor trafficking to nuclei for bee venom-mediated apoptosis. The images revealed evidence of nuclear condensation and formation of apoptotic bodies by 4',6-diamidino-2-phenylindole staining and DNA gel electrophoresis showed the DNA fragmentation in TSGH-8301 cells.

CONCLUSIONS

Bee venom treatment induces both caspase-dependent and caspase-independent apoptotic death through intracellular Ca(2+) -modulated intrinsic death pathway in TSGH-8301 cells.

Neurodegenerative processes in Huntington's disease

Huntington's disease (HD) is a complex and severe disorder characterized by the gradual and the progressive loss of neurons, predominantly in the striatum, which leads to the typical motor and cognitive impairments associated with this pathology. HD is caused by a highly polymorphic CAG trinucleotide repeat expansion in the exon-1 of the gene encoding for huntingtin protein. Since the first discovery of the huntingtin gene, investigations with a consistent number of in-vitro and in-vivo models have provided insights into the toxic events related to the expression of the mutant protein. In this review, we will summarize the progress made in characterizing the signaling pathways that contribute to neuronal degeneration in HD. We will highlight the age-dependent loss of proteostasis that is primarily responsible for the formation of aggregates observed in HD patients. The most promising molecular targets for the development of pharmacological interventions will also be discussed.

Inhibition of autophagy enhances cisplatin cytotoxicity through endoplasmic reticulum stress in human cervical cancer cells

The function of autophagy in cisplatin-treated cancer cells is not fully understood. Cisplatin treatment induced degradation of ubiquitinated proteins by autophagy, which reduced apoptosis induced by endoplasmic reticulum (ER) stress and downregulated the mitochondrial pathway of apoptosis. Inhibition of autophagy using 3-methyladenine (3-MA) or chloroquine (CQ) increased the levels of intracellular misfolded proteins, which enhanced cellular apoptosis. We found that tunicamycin, an ER stress inducer, augmented cisplatin cytotoxicity by upregulating ER stress-mediated apoptosis. Our data indicates that autophagy plays an important role in preventing cisplatin-induced apoptosis in HeLa cells, thus inhibition of autophagy may improve cisplatin chemotherapy.

Cell death in disease: from 2010 onwards

The strong interest in cell death, and the shift in emphasis from basic mechanisms to translational aspects fostered the launch last year of the new sister journal of Cell Death and Differentiation, named Cell Death and Disease, to reflect its stronger focus towards clinical applications. Here, we review that first year of activity, which reflects an enthusiastic response by the scientific community. On the basis of this, we now launch two novel initiatives, the start of a new section dedicated to cancer metabolism and the opening of a new editorial office in Shanghai.