Comparison of the LDH and MTT assays for quantifying cell death: validity for neuronal apoptosis?

The ruthenium complexes cis-(dichloro)tetramineruthenium(III) chloride and cis-tetraammine(oxalato)ruthenium(III) dithionate overcome resistance inducing apoptosis on human lung carcinoma cells (A549)

Lung cancer is one of the leading causes of death in the world, and non-small cell lung carcinoma accounts for approximately 75-85 % of all lung cancers. In the present work, we studied the antitumor activity of the compound cis-(dichloro)tetramineruthenium(III) chloride {cis-[RuCl2(NH3)4]Cl} against human lung carcinoma tumor cell line A549. The present study aimed to investigate the relationship between the expression of MDR1 and CYP450 genes in human lung carcinoma cell lines A549 treated with cisCarboPt, cisCRu(III) and cisDRu(III). The ruthenium-based coordinated complexes presented low cytotoxic and antiproliferative activities, with high IC50 values, 196 (±15.49), 472 (±20.29) and 175 (±1.41) for cisCarboPt, cisCRu(III) and cisDRu(III), respectively. The tested compounds induced apoptosis in A549 tumor cells as evidenced by caspase 3 activation, but only at high concentrations. Results also revealed that the amplification of P-gp gene is greater in A549 cells exposed to cisCarboPt and cisCRu(III) than cisDRu(III). Taken together all these results strongly demonstrate that MDR-1 over-expression in A549 cells could be associated to a MDR phenotype of these cells and moreover, it is also contributing to the platinum, and structurally-related compound, resistance in these cells. The identification and characterization of novel mechanisms of drug resistance will enable the development of a new generation of anti-cancer drugs that increase cancer sensitivity and/or represent more effective chemotherapeutic agents.

Cytotoxic response in human lung epithelial cells and ion characteristics of urban-air particles from Torino, a northern Italian city

Recently, much attention has been devoted to urban air pollution because epidemiological studies have reported health impacts related to particulate matter (PM). PM10 and PM2.5 were collected during different seasons in Torino, a northern Italian city, and were characterised by inorganic chemical species (secondary particulates and bio-available iron). The biological effects of aqueous and organic solvent PM extracts on human epithelial lung A549 were evaluated, and the effects on cell proliferation and lactate dehydrogenase (LDH) release were assayed. The average PM10 concentration during the sampling period was 47.9 ± 18.0 μg/m(3); the secondary particles accounted for 49 % ± 9 % of the PM10 total mass, and the bio-available iron concentration was 0.067 ± 0.045 μg/m(3). The PM2.5/PM10 ratio in Torino ranged from 0.47 to 0.90 and was higher in cold months than in warm months. The PM10 and PM2.5 extracts inhibited cell proliferation and induced LDH release in a dose-dependent manner with a seasonal trend. The PM10 extract had a stronger effect on LDH release, whereas the PM2.5 extract more strongly inhibited cell proliferation. No significant differences were observed in the effects induced by the two extracts, and no significant correlations were found between the biological effects and the PM components evaluated in this study, thus emphasising the importance of the entire mixture in inducing a cytotoxic response.

Anti-inflammatory potential of monogalactosyl diacylglycerols and a monoacylglycerol from the edible brown seaweed Fucus spiralis Linnaeus

A monoacylglycerol (1) and a 1:1 mixture of two monogalactosyl diacylglycerols (MGDGs) (2 and 3) were isolated from the brown seaweed Fucus spiralis Linnaeus. The structures were elucidated by spectroscopic means (NMR and MS) and by comparison with the literature. Compound 1 was composed of a glycerol moiety linked to oleic acid (C18:1 Ω9). Compounds 2 and 3 contained a glycerol moiety linked to a galactose unit and eicosapentaenoic acid (C20:5 Ω3) combined with octadecatetraenoic acid (C18:4 Ω3) or linolenic acid (C18:3 Ω3), respectively. The isolated compounds were tested for their cytotoxic and anti-inflammatory activity in RAW 264.7 macrophage cells. All of them inhibited NO production at non-cytotoxic concentrations. The fraction consisting of compounds 2 and 3, in a ratio of 1:1, was slightly more effective than compound 1 (IC₅₀ of 60.06 and 65.70 µg/mL, respectively). To our knowledge, this is the first report of these compounds from F. spiralis and on their anti-inflammatory capacity.

Downregulation of Homer1b/c improves neuronal survival after traumatic neuronal injury

Homer protein, a member of the post-synaptic density protein family, plays an important role in the neuronal synaptic activity and is extensively involved in neurological disorders. The present study investigates the role of Homer1b/c in modulating neuronal survival by using an in vitro traumatic neuronal injury model, which was achieved by using a punch device that consisted of 28 stainless steel blades joined together and produced 28 parallel cuts. Downregulation of Homer1b/c by specific siRNA significantly (p<0.05) alleviated the cytoplasmic calcium levels and neuron lactate dehydrogenase release, and ultimately decreased the apoptotic rate after traumatic neuronal injury compared with non-targeting siRNA control treatment in cultured rat cortical neurons. Moreover, the expression of metabotropic glutamate receptor 1a (mGluR1a) was significantly (p<0.05) reduced in the Homer1b/c siRNA-transfected neurons after injury. Therefore, Homer1b/c not only modulated the mGluR1a-inositol 1,4,5-triphosphate receptors-Ca(2+) signal transduction pathway, but also regulated the expression of mGluR1a in mechanical neuronal injury. These findings indicate that the suppression of Homer1b/c expression potentially protects neurons from glutamate excitotoxicity after injury and might be an effective intervention target in traumatic brain injury.

Neuroprotective action of deer bone extract against glutamate or Aβ₁₋₄₂-induced oxidative stress in mouse hippocampal cells

Water extracts of deer bone, called nokgol in Korean, and deer antlers have been traditionally used as anti-aging medicines. Deer antler extract is known to possess various activities, including anti-aging or anti-amnesic activity. However, there are no reports about the neuroprotective effect of deer bone extract (DBE). The objective of this study was to examine the neuroprotective effect of DBE on glutamate-induced cell death of mouse hippocampal cells (HT-22 cells) and to elucidate the mode of neuroprotective action of DBE. In this study, HT-22 cells was pretreated with DBE before stimulation with glutamate, and then, the effects of DBE on cell viability, oxidative stress markers, and MAP kinases were determined. Separately, the effect of DBE on H₂O₂ or amyloid beta peptide (1-42) (Aβ₁₋₄₂)-induced cytotoxicity of HT-22 cells was evaluated. DBE protected HT-22 cells from glutamate-induced cell death and prevented the increase in lactate dehydrogenase leakage in HT-22 cells. DBE also prevented glutamate-induced oxidative stress, as indicated by increased reactive oxygen species and lipid peroxidation as well as by decreases in glutathione (GSH) levels and GSH peroxidase activity. In addition, DBE inhibited glutamate-induced activation of c-Jun N-terminal kinases (JNK), p38, and extracellular signal-regulated kinase, indicators of oxidative stress-induced cell death. Furthermore, DBE also protected against H₂O₂ and Aβ₁₋₄₂-induced cytotoxicity. These results suggest that DBE may be a useful functional agent for the prevention against neurodegenerative disorders involving oxidative stress.

Mitigation of ROS insults by Streptomyces secondary metabolites in primary cortical neurons

Oxidative stress is a common point in neurodegenerative diseases, widely connected with mitochondrial dysfunction. In this study, we screened seven natural products from Streptomyces sources against hydrogen peroxide insult in primary cortical neurons, an oxidative stress in vitro model. We showed the ability of these compounds to inhibit neuronal cytotoxicity and to reduce ROS release after 12 h treatment. Among the tested compounds, the quinone anhydroexfoliamycin and the red pyrrole-type pigment undecylprodigiosin stand out. These two compounds displayed the most complete protection against oxidative stress with mitochondrial function improvement, ROS production inhibition, and increase of antioxidant enzyme levels, glutathione and catalase. Further investigations confirmed that anhydroexfoliamycin acts over the Nrf2-ARE pathway, as a Nrf2 nuclear translocation inductor, and is able to strongly inhibit the effect of the mitochondrial uncoupler FCCP over cytosolic Ca(2+), pointing to mitochondria as a cellular target for this molecule. In addition, both compounds were able to reduce caspase-3 activity induced by the apoptotic enhancer staurosporine, but undecylprodigiosin failed to inhibit FCCP effects and it did not act over the Nrf2 pathway as was the case for anhydroexfoliamycin. These results show that Streptomyces metabolites could be useful for the development of new drugs for prevention of neurodegenerative disorders such as Parkinson's and Alzheimer's diseases and cerebral ischemia.

Cytoprotective effects of urinary trypsin inhibitor on astrocytes injured by sustained compression

Decreased cell membrane integrity is a primary pathological change observed in traumatic brain injury (TBI) that activates a number of complex intercellular and intracellular pathological events, leading to further neural injury. In this paper, we assessed the effects of urinary trypsin inhibitor (UTI) on astrocyte membrane integrity by determining the percentage of lactate dehydrogenase (LDH) released after sustained compression injury using a hydrostatic pressure model of mechanical-like TBI. Astrocytes isolated from SD rat pups were injured by sustained compression. At a pressure of 0.3 MPa for 5 min, a significant increase in LDH release was observed compared with control samples. Astrocytes displayed extensive structural disruption of mitochondrial cristae reflected in their swelling. Based on our initial results, injured astrocytes were treated with UTI at a final concentration of 500, 1,000, 3,000 or 5,000 U/ml for 24 h. The percentage of LDH released from injured astrocytes was significantly decreased when 1,000 and 3,000 U/ml of UTI were used. In a separate experiment, astrocytes were treated with UTI at a final concentration of 1,000 U/ml immediately, or at 30 min, 2, 6, or 24 h after sustained compression. The percentage of LDH release was significantly reduced (P < 0.05) when astrocytes were treated with UTI immediately or 30 min later. Together, our results suggest that UTI may have protective effects on astrocytes injured by sustained compression injury. Furthermore, the early administration (<2 h after injury) of UTI may result in a better outcome compared with delayed administration.

FGF-2 induces neuronal death through upregulation of system xc-

The cystine/glutamate antiporter (system xc-) transports cystine into cell in exchange for glutamate. Fibroblast growth factor-2 (FGF-2) upregulates system xc- selectively on astrocytes, which leads to increased cystine uptake, the substrate for glutathione production, and increased glutamate release. While increased intracellular glutathione can limit oxidative stress, the increased glutamate release can potentially lead to excitotoxicity to neurons. To test this hypothesis, mixed neuronal and glial cortical cultures were treated with FGF-2. Treatment with FGF-2 for 48 h caused a significant neuronal death in these cultures. Cell death was not observed in neuronal-enriched cultures, or astrocyte-enriched cultures, suggesting the toxicity was the result of neuron-glia interaction. Blocking system xc- eliminated the neuronal death as did the AMPA/kainate receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo[f]quinoxaline-2,3-dione (NBQX), but not the NMDA receptor antagonist memantine. When cultures were exposed directly to glutamate, both NBQX and memantine blocked the neuronal toxicity. The mechanism of this altered profile of glutamate receptor mediated toxicity by FGF-2 is unclear. The selective calcium permeable AMPA receptor antagonist 1-naphthyl acetyl spermine (NASPM) failed to offer protection. The most likely explanation for the results is that 48 h FGF-2 treatment induces AMPA/kainate receptor toxicity through increased system xc- function resulting in increased release of glutamate. At the same time, FGF-2 alters the sensitivity of the neurons to glutamate toxicity in a manner that promotes selective AMPA/kainate receptor mediated toxicity.

Hydroquinone induces oxidative and mitochondrial damage to human retinal Müller cells (MIO-M1)

PURPOSE

Smoking is a risk factor in the development of a variety of neuroretinal diseases. Therefore, we have investigated the effects of hydroquinone (HQ), a toxicant that is present in high concentrations in cigarette smoke, on a human retinal Müller cell line (MIO-M1).

METHODS

MIO-M1 cells were treated for 24h with four different concentrations of HQ (200μM, 100μM, 50μM, and 25μM). Assays were used to measure cell viability, reactive oxygen/nitrogen species (ROS/RNS), mitochondrial dehydrogenase activity (WST assay), caspase-3/7 activity and lactate dehydrogenase (LDH) levels. Western blot analyses with anti-LC3 and anti-GAPDH antibodies were performed on HQ-treated samples. Some cultures were treated with 4μM rapamycin, to induce autophagy, with and without the autophagy inhibitor 3-methyl-adenine (3MA), and levels of ROS/RNS and LDH were measured.

RESULTS

Our findings show that HQ reduced cell viability at four different concentrations tested (200, 100, 50 and 25μM); decreased mitochondrial function at concentrations of 200 and 100μM; increased ROS/RNS activity at all the concentrations tested and increased LDH levels at concentrations of 200, 100 and 50μM. Caspase-3/7 activities were not modified by HQ. However, treatment of these cells with this agent resulted in the appearance of the autophagy associated LC3-II band. Pre-treatment with 3MA reduced the ROS/RNS and LDH levels of the HQ-treated and rapamycin-treated cells.

CONCLUSION

Our study suggests that HQ damages the MIO-M1 cells through oxidative, mitochondrial and autophagic pathways and not caspase-related apoptosis.

Oct-2 transcription factor binding activity and expression up-regulation in rat cerebral ischaemia is associated with a diminution of neuronal damage in vitro

Brain plasticity provides a mechanism to compensate for lesions produced as a result of stroke. The present study aims to identify new transcription factors (TFs) following focal cerebral ischaemia in rat as potential therapeutic targets. A transient focal cerebral ischaemia model was used for TF-binding activity and TF-TF interaction profile analysis. A permanent focal cerebral ischaemia model was used for the transcript gene analysis and for the protein study. The identification of TF variants, mRNA analysis, and protein study was performed using conventional polymerase chain reaction (PCR), qPCR, and Western blot and immunofluorescence, respectively. Rat cortical neurons were transfected with small interfering RNA against the TF in order to study its role. The TF-binding analysis revealed a differential binding activity of the octamer family in ischaemic brain in comparison with the control brain samples both in acute and late phases. In this study, we focused on Oct-2 TF. Five of the six putative Oct-2 transcript variants are expressed in both control and ischaemic rat brain, showing a significant increase in the late phase of ischaemia. Oct-2 protein showed neuronal localisation both in control and ischaemic rat brain cortical slices. Functional studies revealed that Oct-2 interacts with TFs involved in important brain processes (neuronal and vascular development) and basic cellular functions and that Oct-2 knockdown promotes neuronal injury. The present study shows that Oct-2 expression and binding activity increase in the late phase of cerebral ischaemia and finds Oct-2 to be involved in reducing ischaemic-mediated neuronal injury.

Dihydromyricetin reduced Bcl-2 expression via p53 in human hepatoma HepG2 cells

Dihydromyricetin (DHM) is a major active ingredient of flavonoids compounds. It exhibited anticancer activity and induced apoptosis in human hepatocellular carcinoma HepG2 cells according to our previous data. In this study, we investigated whether p53 is involved in DHM-triggered viability inhibition and apoptosis induction in cancer cells. MTT [3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] assay was employed to evaluate the viability of HepG2 cells after DHM treatment. Meanwhile, p53 small interfering RNA (siRNA) was adopted to silence p53 expression. Protein level of p53 and Bax/Bcl-2 were evaluated by western blot analysis. Cell counting assay showed that DHM inhibited HepG2 cell growth effectively in a time- and dose-dependent manner. P53 expression was significantly increased after DHM treatment, whereas Bcl-2 was reduced potently. Furthermore, after co-treatment with Pifithrin-α (PFT-α, p53 inhibitor), Bcl-2 expression was reversed. The expression of Bax was no significant change, which was also observed after p53 silence. These findings defined and supported a novel function that DHM could induce human hepatocellular carcinoma HepG2 cells apoptosis by up-regulating Bax/Bcl-2 expression via p53 signal pathway.

Δ-Tetrahydrocannabinol induces cytotoxicity in macrophage J774-1 cells: involvement of cannabinoid receptor 2 and p38 MAPK

Tetrahydrocannabinol (THC), a psychoactive component of marijuana, is known to exert cytotoxicity in immune cells. In the present study, we examined the cytotoxicity of Δ⁸-THC in mouse macrophage J774-1 cells and a possible involvement of cannabinoid receptors and stress-responsive mitogen-activated protein kinases (MAPKs) in the cytotoxic process. J774-1 cells were treated with Δ⁸-THC (0-20 μM) for up to 6 h. As measured by the MTT and LDH assays, Δ⁸-THC induced cell death of J774-1 cells in a concentration- and/or exposure time-dependent manner. Δ⁸-THC-induced cell damage was associated with vacuole formation, cell swelling, chromatin condensation, and nuclear fragmentation. The cytotoxic effect of Δ⁸-THC was significantly prevented by a caspase-1 inhibitor Ac-YVAD-cmk but not a caspase-3 inhibitor z-DEVD-fmk. The pretreatment with SR144528, a CB₂ receptor-selective antagonist, effectively suppressed Δ⁸-THC-induced cytotoxicity in J774-1 cells, which exclusively expressed CB₂ receptors as indicated by real-time polymerase chain reaction analysis. In contrast, AM251, a CB₁ receptor-selective antagonist, did not affect the cytotoxicity. Pertussis toxin and α-tocopherol significantly attenuated Δ⁸-THC-induced cytotoxicity suggesting that G(i/o) protein coupling signal transduction and oxidative stress are responsible for the cytotoxicity. Δ⁸-THC stimulated the phosphorylation of p38 MAPK and c-Jun N-terminal kinase (JNK) in J774-1 cells, which were effectively antagonized by the pretreatment with SR144528. In addition, SB203580, a p38 MARK inhibitor, significantly attenuated the cytotoxic effect of Δ⁸-THC, whereas SP600125, a JNK inhibitor, significantly enhanced the cytotoxicity. These results suggest that the cytotoxicity of Δ⁸-THC to J774-1 cells is exerted mediated through the CB₂ receptor followed by the activation of p38 MAPK.

Free radical scavenging and anti-oxidative activities of an ethanol-soluble pigment extract prepared from fermented Zijuan Pu-erh tea

An ethanol-soluble pigment extract was separated from fermented Zijuan Pu-erh tea. The compositions of the ethanol soluble pigment extract were analyzed by high-performance liquid chromatography-tandem mass spectroscopy (HPLC-MS/MS). The extract was prepared into a series of ethanol solutions and analyzed for free radical-scavenging activities (against two free radicals: 1,1-diphenyl-2-picrylhydrazyl (DPPH) and (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)) and in vitro anti-oxidative properties. Electron spin resonance spectroscopy showed that the peaks of DPPH and TEMPO decreased with increasing extract concentration, suggesting that the extract had excellent free radical-scavenging activities. In vitro cell culture suggested that, at 50-200 mg/L, the extract had no measurable effect on the viability of vascular endothelial cells (ECV340) but produced significant protective effects for cells that underwent oxidative injuries due to hydrogen peroxide (H₂O₂) treatment. Compared with the H₂O₂ treatment alone cells group, 200 mg/L of the extract increased the activity of superoxide dismutase (SOD) in cells by 397.3%, and decreased the concentration of malondialdehyde (MDA) and the activity of lactate acid dehydrogenase (LDH) by 47.8% and 69.6%, respectively. These results suggest that the extract has excellent free radical scavenging and anti-oxidative properties.

C-terminal turn stability determines assembly differences between Aβ40 and Aβ42

Oligomerization of the amyloid β-protein (Aβ) is a seminal event in Alzheimer's disease. Aβ42, which is only two amino acids longer than Aβ40, is particularly pathogenic. Why this is so has not been elucidated fully. We report here results of computational and experimental studies revealing a C-terminal turn at Val36-Gly37 in Aβ42 that is not present in Aβ40. The dihedral angles of residues 36 and 37 in an Ile31-Ala42 peptide were consistent with β-turns, and a β-hairpin-like structure was indeed observed that was stabilized by hydrogen bonds and by hydrophobic interactions between residues 31-35 and residues 38-42. In contrast, Aβ(31-40) mainly existed as a statistical coil. To study the system experimentally, we chemically synthesized Aβ peptides containing amino acid substitutions designed to stabilize or destabilize the hairpin. The triple substitution Gly33Val-Val36Pro-Gly38Val ("VPV") facilitated Aβ42 hexamer and nonamer formation, while inhibiting formation of classical amyloid-type fibrils. These assemblies were as toxic as were assemblies from wild-type Aβ42. When substituted into Aβ40, the VPV substitution caused the peptide to oligomerize similarly to Aβ42. The modified Aβ40 was significantly more toxic than Aβ40. The double substitution d-Pro36-l-Pro37 abolished hexamer and dodecamer formation by Aβ42 and produced an oligomer size distribution similar to that of Aβ40. Our data suggest that the Val36-Gly37 turn could be the sine qua non of Aβ42. If true, this structure would be an exceptionally important therapeutic target.

Proteasome inhibition leads to early loss of synaptic proteins in neuronal culture

A dysfunctional ubiquitin proteasome system may be a mediating factor of disease progression in Lewy body dementia (LBD). The effects of proteasome inhibition using lactacystin and epoxomicin in primary neuronal culture were studied to assess the validity of this model to reflect the cortical pathology of LBD. Treatment of primary cortical neurons with 5 μM lactacystin for 24 h led to a 38 % reduction in the levels of β-III-tubulin (p < 0.05), a 48 % reduction in the levels of synaptophysin (p < 0.05) and a 74 % reduction in the levels of drebrin (p < 0.01), when compared to controls. Results for epoxomicin were similar. The loss of neuronal protein occurred prior to any loss of mitochondrial activity or cell death. The results are reflective of the loss of synapses and the synaptic changes observed in LBD, which may be an early event in the neurodegeneration of LBD. The similarities with the pathological changes in LBD highlight the possibility that this model can potentially provide a platform to test novel treatments.

The inotropic effects of ammonia on isolated perfused rat hearts and the mechanisms involved

Ammonia (NH(3)) is a common exogenous gas in the atmosphere, as well as an endogenous chemical produced by amino acid catabolism and other pathways in vivo. Physiological and pathophysiological roles of NH(3) in the nervous system have been studied. Recently, endogenous NH(3) has been suggested to be a gas transmitter. However, so far the role of NH(3) in cardiovascular functions has not been reported. The present study was designed to investigate the inotropic effects of NH(3) on isolated perfused rat hearts and the possible mechanisms involved in these effects. The results showed that NH(3) had a positive inotropic effect in a concentration-dependent manner and produced a higher positive effect than NaOH and NH(4)Cl. At low concentrations, the effect of NH(3) on cardiac function was caused by NH(3) molecules; at high concentrations, the effect of NH(3) on hearts may be partly correlated with a change of pH value, but was mainly caused by NH(3) molecules. The mechanisms involved in the NH(3)-induced positive inotropic effect may be related to the ATP-sensitive K(+) (K(ATP)) channel and the nitric oxide (NO)-cyclic GMP (cGMP) signaling pathway. In addition, at a concentration of 1.5 mmol l(-1), NH(3) significantly increased the activity of creatine kinase (CK) and lactate dehydrogenase (LDH) in the coronary perfusate and decreased the activity of Na(+),K(+)-ATPase and Ca(2+),Mg(2+)-ATPase in the hearts. These results indicate that NH(3) at physiological or low concentrations may play a modulatory role in heart function, but at high concentrations had a damaging effect on isolated rat hearts.

Exocytosis of MTT formazan could exacerbate cell injury

MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] method is one of the most widely used methods to analyze cell proliferation and viability. It is taken up through endocytosis and is reduced by mitochondrial enzymes as well as endosomal/lysosomal compartments, then is transported to cell surfaces to form needle-like MTT formazans; however the effect of MTT itself still remains elusive. Our objective was to investigate the direct effects of MTT on in vitro SH-SY5Y cells. Results showed that the endocytosis of MTT did not cause obvious lesion and induce cell death, but the metabolism and exocytosis of MTT could dramatically damage cells. Our results also indicated that MTT could activate apoptosis related factors such as caspase-8, caspase-3 or accelerate the leakage of cell contents after the appearance of MTT formazan crystals. The present data suggest MTT method should be carefully chosen; otherwise the cell viability would be underestimated and incomparable.

Size-dependent cellular toxicity of silver nanoparticles

Silver nanoparticles (AgNPs) have found a variety of uses including biomedical materials; however, studies of the cytotoxicity of AgNPs by size effects are only in the beginning stage. In this study, we examined the size-dependent cellular toxicity of AgNPs using three different characteristic sizes (∼ 10, 50, and 100 nm) against several cell lines including MC3T3-E1 and PC12. The cytotoxic effect determined based on the cell viability, intracellular reactive oxygen species generation, lactate dehydrogenase release, ultrastructural changes in cell morphology, and upregulation of stress-related genes (ho-1 and MMP-3) was fairly size- and dose-dependent. In particular, AgNPs stimulated apoptosis in the MC3T3-E1 cells, but induced necrotic cell death in the PC12 cells. Furthermore, the smallest sized AgNPs (10 nm size) had a greater ability to induce apoptosis in the MC3T3-E1 cells than the other sized AgNPs (50 and 100 nm). These data suggest that the AgNPs-induced cytotoxic effects against tissue cells are particle size-dependent, and thus, the particle size needs careful consideration in the design of the nanoparticles for biomedical uses.

Establishing the links between Aβ aggregation and cytotoxicity in vitro using biophysical approaches

Aggregation and fibril formation of the amyloid-β (Aβ) peptides play a pivotal role in the pathogenesis of Alzheimer's disease (AD). The missing links on the pathway to Aβ oligomerization, fibril formation, and neurotoxicity in AD remain the identity of the toxic Aβ species and mechanism(s) of their toxicity. Such information is crucial for the development of mechanism-based therapeutics to treat AD and tools to diagnose and/or monitor the disease progression. Herein, we describe a simple approach that combines standard biophysical methods with cell biology assays to correlate the aggregation state of Aβ peptides with their cytotoxicity in vitro. The individual assays are well-established, commonly used, rely on easily accessible materials and can be performed within 24 h.

Inhibition of the mitochondrial enzyme ABAD restores the amyloid-β-mediated deregulation of estradiol

Alzheimer's disease (AD) is a conformational disease that is characterized by amyloid-β (Aβ) deposition in the brain. Aβ exerts its toxicity in part by receptor-mediated interactions that cause down-stream protein misfolding and aggregation, as well as mitochondrial dysfunction. Recent reports indicate that Aβ may also interact directly with intracellular proteins such as the mitochondrial enzyme ABAD (Aβ binding alcohol dehydrogenase) in executing its toxic effects. Mitochondrial dysfunction occurs early in AD, and Aβ's toxicity is in part mediated by inhibition of ABAD as shown previously with an ABAD decoy peptide. Here, we employed AG18051, a novel small ABAD-specific compound inhibitor, to investigate the role of ABAD in Aβ toxicity. Using SH-SY5Y neuroblastoma cells, we found that AG18051 partially blocked the Aβ-ABAD interaction in a pull-down assay while it also prevented the Aβ42-induced down-regulation of ABAD activity, as measured by levels of estradiol, a known hormone and product of ABAD activity. Furthermore, AG18051 is protective against Aβ42 toxicity, as measured by LDH release and MTT absorbance. Specifically, AG18051 reduced Aβ42-induced impairment of mitochondrial respiration and oxidative stress as shown by reduced ROS (reactive oxygen species) levels. Guided by our previous finding of shared aspects of the toxicity of Aβ and human amylin (HA), with the latter forming aggregates in Type 2 diabetes mellitus (T2DM) pancreas, we determined whether AG18051 would also confer protection from HA toxicity. We found that the inhibitor conferred only partial protection from HA toxicity indicating distinct pathomechanisms of the two amyloidogenic agents. Taken together, our results present the inhibition of ABAD by compounds such as AG18051 as a promising therapeutic strategy for the prevention and treatment of AD, and suggest levels of estradiol as a suitable read-out.

Iron accumulation and neurotoxicity in cortical cultures treated with holotransferrin

Nonheme iron accumulates in CNS tissue after ischemic and hemorrhagic insults and may contribute to cell loss. The source of this iron has not been precisely defined. After blood-brain barrier disruption, CNS cells may be exposed to plasma concentrations of transferrin-bound iron (TBI), which exceed that in the CSF by over 50-fold. In this study, the hypothesis that these concentrations of TBI produce cell iron accumulation and neurotoxicity was tested in primary cortical cultures. Treatment with 0.5-3mg/ml holotransferrin for 24h resulted in the loss of 20-40% of neurons, associated with increases in malondialdehyde, ferritin, heme oxygenase-1, and iron; transferrin receptor-1 expression was reduced by about 50%. Deferoxamine, 2,2'-bipyridyl, Trolox, and ascorbate prevented all injury, but apotransferrin was ineffective. Cell TBI accumulation was significantly reduced by deferoxamine, 2,2'-bipyridyl, and apotransferrin, but not by ascorbate or Trolox. After treatment with (55)Fe-transferrin, approximately 40% of cell iron was exported within 16h. Net export was increased by deferoxamine and 2,2'-bipyridyl, but not by apotransferrin. These results suggest that downregulation of transferrin receptor-1 expression is insufficient to prevent iron-mediated death when neurons are exposed to plasma concentrations of TBI. Chelator therapy may be beneficial for acute CNS injuries associated with loss of blood-brain barrier integrity.

Activation of Akt rescues endoplasmic reticulum stress-impaired murine cardiac contractile function via glycogen synthase kinase-3β-mediated suppression of mitochondrial permeation pore opening

AIMS

The present study was designed to examine the impact of chronic Akt activation on endoplasmic reticulum (ER) stress-induced cardiac mechanical anomalies, if any, and the underlying mechanism involved.

RESULTS

Wild-type and transgenic mice with cardiac-specific overexpression of the active mutant of Akt (Myr-Akt) were subjected to the ER stress inducer tunicamycin (1 or 3 mg/kg). ER stress led to compromised echocardiographic (elevated left ventricular end-systolic diameter and reduced fractional shortening) and cardiomyocyte contractile function, intracellular Ca(2+) mishandling, and cell survival in wild-type mice associated with mitochondrial damage. In vitro ER stress induction in murine cardiomyocytes upregulated the ER stress proteins Gadd153, GRP78, and phospho-eIF2α, and promoted reactive oxygen species production, carbonyl formation, apoptosis, mitochondrial membrane potential loss, and mitochondrial permeation pore (mPTP) opening associated with overtly impaired cardiomyocyte contractile and intracellular Ca(2+) properties. Interestingly, these anomalies were mitigated by chronic Akt activation or the ER chaperon tauroursodeoxycholic acid (TUDCA). Treatment with tunicamycin also dephosphorylated Akt and its downstream signal glycogen synthase kinase 3β (GSK3β) (leading to activation of GSK3β), the effect of which was abrogated by Akt activation and TUDCA. The ER stress-induced cardiomyocyte contractile and mitochondrial anomalies were obliterated by the mPTP inhibitor cyclosporin A, GSK3β inhibitor SB216763, and ER stress inhibitor TUDCA.

INNOVATION

This research reported the direct relationship between ER stress and cardiomyocyte contractile and mitochondrial anomalies for the first time.

CONCLUSION

Taken together, these data suggest that ER stress may compromise cardiac contractile and intracellular Ca(2+) properties, possibly through the Akt/GSK3β-dependent impairment of mitochondrial integrity.

Proteases inhibition assessment on PC12 and NGF treated cells after oxygen and glucose deprivation reveals a distinct role for aspartyl proteases

Hypoxia is a severe stressful condition and induces cell death leading to neuronal loss both to the developing and adult nervous system. Central theme to cellular death is the activation of different classes of proteases such as caspases calpains and cathepsins. In the present study we investigated the involvement of these proteases, in the hypoxia-induced PC12 cell death. Rat PC12 is a model cell line for experimentation relevant to the nervous system and several protocols have been developed for either lethal hypoxia (oxygen and glucose deprivation OGD) or ischemic preconditioning (IPS). Nerve Growth Factor (NGF) treated PC12 differentiate to a sympathetic phenotype, expressing neurites and excitability. Lethal hypoxia was established by exposing undifferentiated and NGF-treated PC12 cells to a mixture of N₂/CO₂ (93:5%) in DMEM depleted of glucose and sodium pyruvate for 16 h. The involvement of caspases, calpains and lysosomal cathepsins D and E to the cell death induced by lethal OGD was investigated employing protease specific inhibitors such as z-VAD-fmk for the caspases, MDL28170 for the calpains and pepstatin A for the cathepsins D and E. Our findings show that pepstatin A provides statistically significant protection from cell death of both naive and NGF treated PC12 cells exposed to lethal OGD. We propose that apart from the established processes of apoptosis and necrosis that are integral components of lethal OGD, the activation of cathepsins D and E launches additional cell death pathways in which these proteases are key partners.

Impedance measurement for real time detection of neuronal cell death

Detection of neuronal cell death is a standard requirement in cell culture models of neurodegenerative diseases. Although plenty of viability assays are available for in vitro applications, most of these are endpoint measurements providing only little information on the kinetics of cell death. Here, we validated the xCELLigence system based on impedance measurement for real-time detection of cell death in a neuronal cell line of immortalized hippocampal neurons (HT-22 cells), neuronal progenitor cells (NPC) and differentiated primary cortical neurons. We found a good correlation between impedance measurements and endpoint viability assays in HT-22 cells and NPC, for detecting proliferation, cell death kinetics and also neuroprotective effects of pharmacological inhibitors of apoptosis. In primary neurons we could not detect dendritic outgrowth during differentiation of the cells. Cell death in primary neurons was detectable by the xCELLigence system, however, the changes in the cell index on the basis of impedance measurements depended to a great extent on the severity of the insult. Cell death induced by ionomycin, e.g. shows as a fast paced process involving a strong cellular disintegration, which allows for impedance-based detection. Cell death accompanied by less pronounced morphological changes like glutamate induced cell death, however, is not well accessible by this approach. In conclusion, our data show that impedance measurement is a convenient and reliable method for the detection of proliferation and kinetics of cell death in neuronal cell lines, whereas this method is less suitable for the assessment of neuronal differentiation and viability of primary neurons.

Effects of Buthus martensii Karsch Venom on Cell Proliferation and Cytotoxicity in Hela Cells

This paper focuses on the effect of the venom of the scorpion Buthus martensii on the proliferation of human cervical carcinoma Hela cell line and the related molecular mechanism. MTT test showed that the scorpion venom inhibited proliferation of Hela cells in time-dependent and concentration-dependent manner with 50% inhibitory concentration (IC50) of 34.5 μg/mL(48 h). By using flow cytometry, it was found that the scorpion venom could induce apoptosis and necrosis in Hela cells. RT-PCR and Western blot indicated there were obviously up-regulated in the expressions of p21 protein but the expression of p21 mRNA showed no significant difference in the Hela cell by the scorpion venom. These results suggest that the possible mechanism of the scorpion venom is to activate the expressions of p21 protein and to cause Hela cell apoptosis.

Is nitric oxide decrease observed with naphthoquinones in LPS stimulated RAW 264.7 macrophages a beneficial property?

The search of new anti-inflammatory drugs has been a current preoccupation, due to the need of effective drugs, with less adverse reactions than those used nowadays. Several naphthoquinones (plumbagin, naphthazarin, juglone, menadione, diosquinone and 1,4-naphthoquinone), plus p-hydroquinone and p-benzoquinone were evaluated for their ability to cause a reduction of nitric oxide (NO) production, when RAW 264.7 macrophages were stimulated with lipopolysaccharide (LPS). Dexamethasone was used as positive control. Among the tested compounds, diosquinone was the only one that caused a NO reduction with statistical importance and without cytotoxicity: an IC₂₅ of 1.09±0.24 µM was found, with 38.25±6.50% (p<0.001) NO reduction at 1.5 µM. In order to elucidate if this NO decrease resulted from the interference of diosquinone with cellular defence mechanisms against LPS or to its conversion into peroxynitrite, by reaction with superoxide radical formed by naphthoquinones redox cycling, 3-nitrotyrosine and superoxide determination was also performed. None of these parameters showed significant changes relative to control. Furthermore, diosquinone caused a decrease in the pro-inflammatory cytokines: tumour necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6). Therefore, according to the results obtained, diosquinone, studied for its anti-inflammatory potential for the first time herein, has beneficial effects in inflammation control. This study enlightens the mechanisms of action of naphthoquinones in inflammatory models, by checking for the first time the contribution of oxidative stress generated by naphthoquinones to NO reduction.

Pre-conditioning induces the precocious differentiation of neonatal astrocytes to enhance their neuroprotective properties

Hypoxic preconditioning reprogrammes the brain's response to subsequent H/I (hypoxia–ischaemia) injury by enhancing neuroprotective mechanisms. Given that astrocytes normally support neuronal survival and function, the purpose of the present study was to test the hypothesis that a hypoxic preconditioning stimulus would activate an adaptive astrocytic response. We analysed several functional parameters 24 h after exposing rat pups to 3 h of systemic hypoxia (8% O₂). Hypoxia increased neocortical astrocyte maturation as evidenced by the loss of GFAP (glial fibrillary acidic protein)-positive cells with radial morphologies and the acquisition of multipolar GFAP-positive cells. Interestingly, many of these astrocytes had nuclear S100B. Accompanying their differentiation, there was increased expression of GFAP, GS (glutamine synthetase), EAAT-1 (excitatory amino acid transporter-1; also known as GLAST), MCT-1 (monocarboxylate transporter-1) and ceruloplasmin. A subsequent H/I insult did not result in any further astrocyte activation. Some responses were cell autonomous, as levels of GS and MCT-1 increased subsequent to hypoxia in cultured forebrain astrocytes. In contrast, the expression of GFAP, GLAST and ceruloplasmin remained unaltered. Additional experiments utilized astrocytes exposed to exogenous dbcAMP (dibutyryl-cAMP), which mimicked several aspects of the preconditioning response, to determine whether activated astrocytes could protect neurons from subsequent excitotoxic injury. dbcAMP treatment increased GS and glutamate transporter expression and function, and as hypothesized, protected neurons from glutamate excitotoxicity. Taken altogether, these results indicate that a preconditioning stimulus causes the precocious differentiation of astrocytes and increases the acquisition of multiple astrocytic functions that will contribute to the neuroprotection conferred by a sublethal preconditioning stress.

Purification and neuroprotective effects of polysaccharides from Opuntia Milpa Alta in cultured cortical neurons

Opuntia is a traditional plant from China with medicinal applications. In this experiment, polysaccharides from Opuntia Milpa Alta (MAPs) were analyzed using gas chromatograph-mass spectrometer (GC-MS) method and result showed that MAPs contained mannose (6.37%), rhamnose (14.94%), xylose (1.99%), arabinose (24.07%), galactose (38.25%), ribose (2.63%) and glucose (11.48%). The neuroprotective effects of MAPs were evaluated at the mechanistic level in vitro models of cerebral ischemic injury. In vitro oxygen/glucose deprivation (OGD) model, MAPs (0.5 μg/ml, 5 μg/ml, 50 μg/ml) effectively increased cell viability by methyl thiazolyl tetrazolium (MTT) assay, inhibited cell cytotoxicity by lactate dehydrogenase (LDH) assay, reduced neuronal cell death, suppressed the production of intracellular reactive oxygen species (ROS), decreased of intracellular free Ca(2+) concentrations ([Ca(2+)](i)), and reduced extracellular glutamate level. Therefore, MAPs might prevent intracellular calcium overload and decreased glutamate excitotoxicity, both of which can cause neuronal injury and death in vitro models of cerebral ischemic injury.

Activation of Pak1/Akt/eNOS signaling following sphingosine-1-phosphate release as part of a mechanism protecting cardiomyocytes against ischemic cell injury

We investigated whether plasma long-chain sphingoid base (LCSB) concentrations are altered by transient cardiac ischemia during percutaneous coronary intervention (PCI) in humans and examined the signaling through the sphingosine-1-phosphate (S1P) cascade as a mechanism underlying the S1P cardioprotective effect in cardiac myocytes. Venous samples were collected from either the coronary sinus (n = 7) or femoral vein (n = 24) of 31 patients at 1 and 5 min and 12 h, following induction of transient myocardial ischemia during elective PCI. Coronary sinus levels of LCSB were increased by 1,072% at 1 min and 941% at 5 min (n = 7), while peripheral blood levels of LCSB were increased by 579% at 1 min, 617% at 5 min, and 436% at 12 h (n = 24). In cultured cardiac myocytes, S1P, sphingosine (SPH), and FTY720, a sphingolipid drug candidate, showed protective effects against CoCl induced hypoxia/ischemic cell injury by reducing lactate dehydrogenase activity. Twenty-five nanomolars of FTY720 significantly increased phospho-Pak1 and phospho-Akt levels by 56 and 65.6% in cells treated with this drug for 15 min. Further experiments demonstrated that FTY720 triggered nitric oxide release from cardiac myocytes is through pertussis toxin-sensitive phosphatidylinositol 3-kinase/Akt/endothelial nitric oxide synthase signaling. In ex vivo hearts, ischemic preconditioning was cardioprotective in wild-type control mice (Pak1^f/f), but this protection appeared to be ineffective in cardiomyocyte-specific Pak1 knockout (Pak1^cko) hearts. The present study provides the first direct evidence of the behavior of plasma sphingolipids following transient cardiac ischemia with dramatic and early increases in LCSB in humans. We also demonstrated that S1P, SPH, and FTY720 have protective effects against hypoxic/ischemic cell injury, likely a Pak1/Akt1 signaling cascade and nitric oxide release. Further study on a mouse model of cardiac specific deletion of Pak1 demonstrates a crucial role of Pak1 in cardiac protection against ischemia/reperfusion injury.

Insulin-like growth factor 1 and transforming growth factor-β stimulate cystine/glutamate exchange activity in dental pulp cells

INTRODUCTION

The growth factors insulin-like growth factor (IGF-1) and transforming growth factor-β (TGF-β) are protective to dental pulp cells in culture against the toxicity of the composite materials Durafill VS and Flow Line (Henry Schein Inc, New York, NY). Because the toxicity of these materials is mediated by oxidative stress, it seemed possible that the protective effects of IGF-1 and TGF-β were through the enhancement of an endogenous antioxidant mechanism.

METHODS

We used cultured dental pulp cells to determine the mechanism of the protective effects of IGF-1 and TGF-β, focusing on the glutathione system and the role of cystine/glutamate exchange (system xc-).

RESULTS

We found that the toxicity of Durafill VS and Flow Line was attenuated by the addition of glutathione monoethylester, suggesting a specific role for the cellular antioxidant glutathione. Supporting this hypothesis, we found that IGF-1 and TGF-β were protective against the toxicity of the glutathione synthesis inhibitor buthionine sulfoximine. Because levels of cellular cystine are the limiting factor in the production of glutathione, we tested the effects of IGF-1 and TGF-β on cystine uptake. Both growth factors stimulated system xc-mediated cystine uptake. Furthermore, they attenuated the glutathione depletion induced by Durafill VS and Flow Line.

CONCLUSIONS

The results suggest that IGF-1 and TGF-β are protective through the stimulation of system xc-mediated cystine uptake, leading to maintenance of cellular glutathione. This novel action of growth factors on dental pulp cells has implications not only for preventing toxicity of dental materials but also for the general function of these cells.

Manganese induces oxidative stress, redox state unbalance and disrupts membrane bound ATPases on murine neuroblastoma cells in vitro: protective role of silymarin

Manganese (Mn) is an essential trace element required for ubiquitous enzymatic reactions. Chronic overexposure to this metal may promote potent neurotoxic effects. The mechanism of Mn toxicity is not well established, but several studies indicate that oxidative stress play major roles in the Mn-induced neurodegenerative processes. Silymarin (SIL) has antioxidant properties and stabilizes intracellular antioxidant defense systems. The aim of this study was to evaluate the toxic effects of MnCl₂ on the mouse neuroblastoma cell lines (Neuro-2A), to characterize the toxic mechanism associated with Mn exposure and to investigate whether SIL could efficiently protect against neurotoxicity induced by Mn. A significant increase in LDH release activity was observed in Neuro-2A cells associated with a significant decrease in cellular viability upon 24 h exposure to MnCl₂ at concentrations of 200 and 800 μM (P < 0.05) when compared with control unexposed cells. In addition, exposure cells to MnCl₂ (200 and 800 μM), increases oxidant biomarkers and alters enzymatic and non enzymatic antioxidant systems. SIL treatment significantly reduced the levels of LDH, nitric oxide, reactive oxygen species and the oxidants/antioxidants balance in Neuro-2A cells as compared to Mn-exposed cells. These results suggested that silymarin is a powerful antioxidant through a mechanism related to its antioxidant activity, able to interfere with radical-mediated cell death. SIL may be useful in diseases known to be aggravated by reactive oxygen species and in the development of novel treatments for neurodegenerative disorders such as Alzheimer or Parkinson diseases.

The RNA-binding protein RBM3 is involved in hypothermia induced neuroprotection

Induced hypothermia is the only therapy with proven efficacy to reduce brain damage after perinatal asphyxia. While hypothermia down-regulates global protein synthesis and cell metabolism, low temperature induces a small subset of proteins that includes the RNA-binding protein RBM3 (RNA-binding motif protein 3), which has recently been implicated in cell survival. Here, immunohistochemistry of the developing postnatal murine brain revealed a spatio-temporal neuronal RBM3 expression pattern very similar to that of doublecortin, a marker of neuronal precursor cells. Mild hypothermia (32°C) profoundly promoted RBM3 expression and rescued neuronal cells from forced apoptosis as studied in primary neurons, PC12 cells, and cortical organotypic slice cultures. Blocking RBM3 expression in neuronal cells by specific siRNAs significantly diminished the neuroprotective effect of hypothermia while vector-driven RBM3 over-expression reduced cleavage of PARP, prevented internucleosomal DNA fragmentation, and LDH release also in the absence of hypothermia. Together, neuronal RBM3 up-regulation in response to hypothermia apparently accounts for a substantial proportion of hypothermia-induced neuroprotection.

Vitamin D inhibits captopril-induced cell detachment and apoptosis in keratinocytes

BACKGROUND

Captopril, an angiotensin I-converting enzyme inhibitor, is a commonly prescribed antihypertensive drug. Its cutaneous side-effects include pemphigus vulgaris acantholysis and bullous pemphigoid-like cell-matrix detachment. This medication also triggers apoptosis in human keratinocytes. Calcitriol, the hormonally active vitamin D metabolite, protects keratinocytes from programmed cell death induced by various noxious stimuli.

OBJECTIVES

To examine if calcitriol protects proliferating keratinocytes from the damage inflicted by captopril.

METHODS

Autonomously proliferating HaCaT keratinocytes, used as a model for basal layer keratinocytes, were exposed to captopril. Cell detachment was examined visually by light microscopy. Cytotoxicity was assessed by Hoechst 33342 staining and lactate dehydrogenase release. Apoptotic death was assessed by monitoring caspase 3-like activity.

RESULTS

Cells exposed to captopril detached and became round. This process was accompanied by programmed cell death. From time-dependent monitoring of cell detachment and apoptosis, and examination of pan-caspase inhibitor effects on cell detachment we concluded that cell death is the consequence of cell detachment from the culture plate and not vice versa. Pretreatment with calcitriol significantly attenuated these events. The effects of calcitriol were already evident at 1 nmol L(-1) concentration of the hormone.

CONCLUSIONS

The results of this study show that calcitriol protects keratinocytes from captopril-induced cell detachment and apoptosis.

Comparison of methods for measuring viable E. coli cells during cultivation: great differences in the early and late exponential growth phases

Four methods, namely enumeration of colony-forming units (CFU), aerobic respiration, MTT reduction capacity and succinate dehydrogenase activity were compared to determine the viability of E. coli cells at the early and late exponential growth phases. Our results revealed that great differences in cell viability existed between these methods and that the choice of method to determine cell viability must be made with caution.

Morphological behavior and attachment of p19 neural cells to root-end filling materials

Some techniques and instruments like stereomicroscopy and confocal microscopy used for observing neural cells are too complicated and dependent on preparation and cell fixation methods. This may question the results of these methods. Though, we have used scanning electron microscopy on replicated specimens to observe p19 neural cells and their cellular extensions. This manuscript has shown the feasibility of using replica (indirect) method instead of direct methods for observing morphological characteristics of this high sensitive cell line. As neural cells are very sensitive to fixation solutions and processes, we have used replica mode and observed neural cells with a novel indirect method. We have used replica mode in this study to indirectly and noninvasively evaluate the state of p19 neural cells and their cellular extensions.

Endothelin as a neuroprotective factor in the olfactory epithelium

In mammals, the olfactory sensory neurons are the only ones directly in contact with an aggressive environment. Thus, the olfactory mucosa is one of the few neuronal zones which are continuously renewed during adulthood. We have previously shown that endothelin is locally matured in the olfactory mucosa and that olfactory sensory neurons preferentially express ETB receptors, while ETA receptors are rather present in non neuronal olfactory mucosa cells. In addition to its vasoactive effect, the endothelin system is known for its pleiotropic effects including the modulation of cell population dynamics. We thus examined its potential neuroprotective effect in the olfactory mucosa using a primary culture of olfactory sensory neurons lying on non neuronal cells. While a serum deprivation led to a massive decrease of the density of olfactory sensory neurons in the primary cultures, endothelin 1 (ET-1) rescued part of the neuronal population through both ETA and ETB receptors. This effect was mainly anti-apoptotic as it reduced cleaved caspase-3 signal and nuclear condensation. Furthermore, the olfactory epithelium of ETB-deficient rats displayed increased apoptosis. These results strongly suggest that ET-1 acts as an anti-apoptotic factor on olfactory sensory neurons, directly through ETB and indirectly by limiting non neuronal cells death through ETA.

PEX13 deficiency in mouse brain as a model of Zellweger syndrome: abnormal cerebellum formation, reactive gliosis and oxidative stress

Delayed cerebellar development is a hallmark of Zellweger syndrome (ZS), a severe neonatal neurodegenerative disorder. ZS is caused by mutations in PEX genes, such as PEX13, which encodes a protein required for import of proteins into the peroxisome. The molecular basis of ZS pathogenesis is not known. We have created a conditional mouse mutant with brain-restricted deficiency of PEX13 that exhibits cerebellar morphological defects. PEX13 brain mutants survive into the postnatal period, with the majority dying by 35 days, and with survival inversely related to litter size and weaning body weight. The impact on peroxisomal metabolism in the mutant brain is mixed: plasmalogen content is reduced, but very-long-chain fatty acids are normal. PEX13 brain mutants exhibit defects in reflex and motor development that correlate with impaired cerebellar fissure and cortical layer formation, granule cell migration and Purkinje cell layer development. Astrogliosis and microgliosis are prominent features of the mutant cerebellum. At the molecular level, cultured cerebellar neurons from E19 PEX13-null mice exhibit elevated levels of reactive oxygen species and mitochondrial superoxide dismutase-2 (MnSOD), and show enhanced apoptosis together with mitochondrial dysfunction. PEX13 brain mutants show increased levels of MnSOD in cerebellum. Our findings suggest that PEX13 deficiency leads to mitochondria-mediated oxidative stress, neuronal cell death and impairment of cerebellar development. Thus, PEX13-deficient mice provide a valuable animal model for investigating the molecular basis and treatment of ZS cerebellar pathology.

ER-targeted Bcl-2 and inhibition of ER-associated caspase-12 rescue cultured immortalized cells from ethanol toxicity

Alcohol abuse, known for promoting apoptosis in the liver and nervous system, is a major public health concern. Despite significant morbidity and mortality resulting from ethanol consumption, the precise cellular mechanism of its toxicity remains unknown. Previous work has shown that wild-type Bcl-2 is protective against ethanol. The present study investigated whether protection from ethanol toxicity involves mitochondrial Bcl-2 or endoplasmic reticulum (ER) Bcl-2, and whether mitochondria-associated or ER-associated caspases are involved in ethanol toxicity. Chinese hamster ovary (CHO695) cells were transiently transfected with cDNA constructs encoding wild-type Bcl-2, mitochondria-targeted Bcl-2, or ER-targeted Bcl-2. MTT assay was used to measure cell viability in response to ethanol. Ethanol treatments of 1 and 2.5 M reduced cell viability at 5, 10, and 24 h. Wild-type Bcl-2, localized both to mitochondria and ER, provided significant rescue for CHO695 cells treated with 1M ethanol for 24 h, but did not rescue toxicity at 2.5 M. ER-targeted Bcl-2, however, provided significant and robust rescue following 24 h of 1 and 2.5 M ethanol. Mitochondria-targeted Bcl-2 offered no protection at any ethanol concentration and generally reduced cell viability. To follow up these experiments, we used a peptide inhibitor approach to investigate which caspases were responsible for ethanol-induced apoptosis. Caspase-9 and caspase-12 are known to be downstream of mitochondria and the ER, respectively. CHO695 cells were treated with a pan-caspase inhibitor, a caspase-9 or caspase-12 inhibitor along with 1.5 M ethanol, followed by MTT cell viability assay. Treatment with the pan-caspase inhibitor provided significant rescue from ethanol, whereas inhibition of caspase-9 did not. Inhibition of ER-associated caspase-12, however, conferred significant protection from ethanol toxicity, similar to the pan inhibitor. These findings are consistent with our transfection data and, taken together, suggest a significant role for the ER in ethanol toxicity.