Mechanism of cellular 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction

Poly-N-methylated amyloid beta-peptide (Abeta) C-terminal fragments reduce Abeta toxicity in vitro and in Drosophila melanogaster

Alzheimer's disease (AD), an age related neurodegenerative disorder, threatens to become a major health-economic problem. Assembly of 40- or 42-residue amyloid beta-peptides (Abeta) into neurotoxic oligo-/polymeric beta-sheet structures is an important pathogenic feature in AD, thus, inhibition of this process has been explored to prevent or treat AD. The C-terminal part plays an important role in Abeta aggregation, but most Abeta aggregation inhibitors have targeted the central region around residues 16-23. Herein, we synthesized hexapeptides with varying extents of N-methylation based on residues 32-37 of Abeta, to target its C-terminal region. We measured the peptides' abilities to retard beta-sheet and fibril formation of Abeta and to reduce Abeta neurotoxicity. A penta-N-methylated peptide was more efficient than peptides with 0, 2, or 3 N-methyl groups. This penta-N-methylated peptide moreover increased life span and locomotor activity in Drosophila melanogaster flies overexpressing human Abeta(1-42).

Induction of apoptotic cell death preferentially in reactive astrocytes by concanavalin A

When central nervous system is injured, reactive astrocytes form glial scar which prevents neuronal regeneration. We examined the effects of concanavalin A (ConA) in primary astrocytes, and found preferential apoptotic effect of ConA in migrating reactive astrocytes. Thus, ConA may be applicable for enhancing neuronal regeneration by preventing glial scar.

Protective effects of epigallocatechin gallate following 3-nitropropionic acid-induced brain damage: possible nitric oxide mechanisms

INTRODUCTION

The role of oxidative stress has been well known in neurodegenerative disorders. 3-Nitropropionic acid (3-NP) is a plant-based mycotoxin that produces HD like symptoms in animals. Oxidative stress and nitric oxide mechanisms have been recently proposed in the 3-NP-induced neurotoxicity. Epigallocatechin gallate (EGCG) is one of the major components of green tea, known for its potent antioxidant activity. Besides, neuroprotective effect of EGCG has also been suggested in different experimental models.

OBJECTIVES

The present study has been designed to examine possible effect of EGCG against 3-NP induced behavioral, oxidative stress, mitochondrial dysfunction, and striatal damage in rats and its possible interaction with nitric oxide modulators.

MATERIAL AND METHODS

Systemic 3-NP (10 mg/kg) administration for 14 days significantly reduced locomotor activity, body weight, grip strength, oxidative defense (raised levels of lipid peroxidation, nitrite concentration, depletion of antioxidant enzyme), and mitochondrial enzymes activity in striatum, cortex, and hippocampal regions of the brain.

RESULTS

Fourteen days of EGCG pretreatment (10, 20, and 40 mg/kg) significantly attenuated behavioral alterations, oxidative damage, mitochondrial complex enzymes dysfunction, and striatal damage in 3-NP-treated animals. L-arginine (50 mg/kg) pretreatment with sub-effective dose of EGCG (20 mg/kg) significantly reversed the protective behavioral, biochemical, cellular, and histological effects of EGCG. However, L-NAME (10 mg/kg) pretreatment with EGCG (20 mg/kg) significantly potentiated the protective effect of EGCG which was significant as compared to their effect per se.

CONCLUSION

The present study shows that EGCG attenuate 3-NP-induced neurotoxicity, and nitric oxide modulation might be involved in its protective action.

Impaired mitochondrial functions in organophosphate induced delayed neuropathy in rats

Acute exposure to organophosphates induces a delayed neurodegenerative condition known as organophosphate-induced delayed neuropathy (OPIDN). The mechanism of OPIDN has not been fully understood as it does not involve cholinergic crisis. The present study has been designed to evaluate the role of mitochondrial dysfunctions in the development of OPIDN. OPIDN was induced in rats by administering acute dose of monocrotophos (MCP, 20 mg/kg body weight, orally) or dichlorvos (DDVP, 200 mg/kg body weight, subcutaneously), 15-20 min after treatment with antidotes [atropine (20 mg/kg body weight) and 2-PAM (100 mg/kg body weight) intraperitoneally]. MDA levels were observed to be higher and thiol content was lower in mitochondria from brain regions of OP exposed animals. This was accompanied by decreased activities of the mitochondrial enzymes; NADH dehydrogenase, succinate dehydrogenase, and cytochrome oxidase. In addition, mitochondrial functions assessed by MTT reduction also confirmed mitochondrial dysfunctions following development of OPIDN. The spatial long-term memory evaluated using elevated plus-maze test was observed to be deficit in OPIDN. The results suggest impaired mitochondrial functions as a mechanism involved in the development of organophosphate induced delayed neuropathy.

Lycopene modulates nitric oxide pathways against 3-nitropropionic acid-induced neurotoxicity

AIM

The present study has been designed to investigate the involvement of the nitric oxide mechanism in the protective effect of lycopene against 3-nitropropionic acid-induced Huntington's disease-like symptoms in rats.

MAIN METHODS

The present experimental protocol design includes systemic 3-nitropropionic acid (10mg/kg i.p) treatment for 14 days. Lycopene (2.5, 5 and 10mg/kg) was given orally, once a day, 1h before 3-nitropropionic acid treatment for 14 days. Body weight and behavioral parameters (locomotor and rotarod activity) were assessed on 1st, 5th, 10th and 15th day post-3-nitropropionic acid administration. Malondialdehyde, nitrite concentration, superoxide dismutase and catalase levels were measured on the 15th day in the striatum, cortex and hippocampus. Mitochondrial enzyme complexes were also assessed in these brain areas. Systemic 3-nitropropionic acid treatment significantly reduced body weight, locomotor activity and oxidative defense. The mitochondrial enzyme activities were also significantly impaired in the examined brain regions in 3-nitropropionic acid-treated animals.

KEY FINDINGS

Lycopene (2.5, 5 and 10mg/kg) treatment significantly attenuated the impairment in behavioral, biochemical and mitochondrial enzyme activities as compared to the 3-nitropropionic acid-treated group. l-arginine (50mg/kg) pretreatment with a sub-effective dose of lycopene (5mg/kg) significantly attenuated the protective effect of lycopene. Furthermore, L-NAME (10mg/kg) pretreatment with a sub-effective dose of lycopene (5mg/kg) for 14 days significantly potentiated the protective effect.

SIGNIFICANCE

The results of the present study suggest that the nitric oxide modulation is involved in the protective effect of lycopene against 3-NP-induced behavioral, biochemical and cellular alterations in rats.

Gap junction inhibitors modulate S100B secretion in astrocyte cultures and acute hippocampal slices

Astrocytes sense, integrate, and respond to stimuli generated by neurons or neural injury; this response involves gap junction (GJ) communication. Neuronal vulnerability to injury increased when cocultures of astrocytes and neurons were exposed to GJ inhibitors. However, GJ uncoupling could limit the extension of a lesion. We investigated a possible link between GJ communication and S100B secretion. S100B is a calcium-binding protein of 21 kDa that is predominantly expressed and secreted by astrocytes, which has trophic paracrine activity on neurite growth, glial proliferation, and neuronal survival. GJ inhibitors were analyzed in isolated astrocytes in primary cultures from hippocampus, acute hippocampal slices, and C6 glioma cells, which were used as a negative control. Our data indicate that GJ blocking stimulates S100B secretion in astrocyte cultures and acute hippocampal slices. Different assays were used to confirm cell integrity during exposure to GJ inhibitors. S100B secretion was observed with different types of GJ inhibitors; the resulting event was dependent on time, the nature of the inhibitor, its putative molecular target of GJ blocking, and/or the cell preparation used. Only carbenoxolone induced a fast and persistent increase in S100B secretion in both preparations. Endothelin-1 increased S100B secretion in astrocyte cultures at 1 hr, but a decrease was observed at 6 hr or in acute hippocampal slices. Physiologically, a local GJ closure associated with release of S100B in injury conditions favors the idea of a common mechanism available to limit the extension of lesion and increase the chances of cell survival.

Evaluation of cryopreserved donor skin viability: the experience of the regional tissue bank of Verona

BACKGROUND

Allogeneic human skin removed from cadaveric donors is the covering of choice for deep burns, since it accelerates the re-epithelialisation of autologous skin. In this study we evaluated the cellular viability of cryopreserved skin at the regional tissue bank of Verona (Italy).

METHODS

From 1st June 2007 to 30th September 2007, tests of cutaneous cell viability were carried out on 21 consecutive skin donors using the MTT (tetrazolium salt) method on samples prior to freezing and on thawed samples after a period of cryopreservation.

RESULTS

The mean percentage viability was 45.1% (+/-20.1%), which is similar to results obtained in other tissue banks. It was noted that viability decreased with increasing age of the donor.

CONCLUSIONS

The results of the evaluation of cutaneous cell viability document the validity of the skin cryopreservation procedure in use at the tissue bank in Verona.

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces calcium influx through T-type calcium channel and enhances lysosomal exocytosis and insulin secretion in INS-1 cells

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been associated with diabetes in several epidemiological studies. However, the diabetogenic action of TCDD on pancreatic cells is unclear. Here, we investigated the direct toxic effects of TCDD on a rat insulin-secreting beta cell line. We found that TCDD enhances exocytosis of MTT formazan and lysosomal proteins such as beta-hexosaminindase and Lamp-1. This TCDD-induced exocytosis was abrogated by T-type calcium channel blockers (mibefradil, flunarizine) but not by an aryl hydrocarbon receptor antagonist (alpha-naphtoflavone). Indeed, cytosolic calcium levels were increased by TCDD. Furthermore, TCDD stimulated insulin secretion, which was inhibited by flunarizine. Taken together, our results suggest that TCDD-induced calcium influx via T-type channels regulates vesicular trafficking, such as lysosomal and secretory granule exocytosis, and that TCDD might exert adverse effects on beta cells by continuous insulin release followed by beta cell exhaustion. This could contribute to the link between TCDD exposure and the risk of developing diabetes.

Cholinoceptive and cholinergic properties of cardiomyocytes involving an amplification mechanism for vagal efferent effects in sparsely innervated ventricular myocardium

Our recent studies have shown that, as indicated by vagal stimulation, an acetylcholinesterase inhibitor donepezil, an anti-Alzheimer's disease drug, prevents progression of heart failure in rats with myocardial infarction, and activates a common cell survival signal shared by acetylcholine (ACh) in vitro. On the basis of this and evidence that vagal innervation is extremely poor in the left ventricle, we assessed the hypothesis that ACh is produced by cardiomyocytes, which promotes its synthesis via a positive feedback mechanism. Rat cardiomyocytes expressed choline acetyltransferase (ChAT) in the cytoplasm and vesicular acetylcholine transporter with the vesicular structure identified by immunogold electron microscopy, suggesting that cardiomyocytes possess components for ACh synthesis. Intracellular ACh in rat cardiomyocytes was identified with physostigmine or donepezil. However, with atropine, the basal ACh content was reduced. In response to exogenous ACh or pilocarpine, cardiomyocytes increased the transcriptional activity of the ChAT gene through a muscarinic receptor and ChAT protein expression, and, finally, the intracellular ACh level was upregulated by pilocarpine. Knockdown of ChAT by small interfering RNA accelerated cellular energy metabolism, which is suppressed by ACh. Although physostigmine had a minimal effect on the ChAT promoter activity by inhibiting acetylcholinesterase, donepezil resulted in elevation of the activity, protein expression and intracellular ACh level even in the presence of sufficient physostigmine. Orally administered donepezil in mice increased the ChAT promoter activity in a reporter gene-transferred quadriceps femoris muscle and the amount of cardiac ChAT protein. These findings suggest that cardiomyocytes possess an ACh synthesis system, which is positively modulated by cholinergic stimuli. Such an amplification system in cardiomyocytes may contribute to the beneficial effects of vagal stimulation on the ventricles.

MTT assays cannot be utilized to study the effects of STI571/Gleevec on the viability of solid tumor cell lines

PURPOSE

This study will determine whether MTT assays accurately assess the effect of STI571 (Gleevec; Abl kinase inhibitor) on the viability of cancer cells containing highly active Abl kinases.

METHODS

Growth kinetics, tritiated thymidine, fluorescent caspase, MTT, and Cell Titer Glo (CTG) assays were used to determine the effect of STI571 on growth, proliferation, apoptosis, and viability of melanoma and breast cancer cells.

RESULTS

STI571 inhibited growth and proliferation, and increased apoptosis. However, MTT assays indicated that STI571 increased cell viability. In contrast, STI571 induced a dose-dependent decrease in viability using CTG assays.

CONCLUSIONS

Doses of STI571 (1-10 microM) required to inhibit endogenous Abl kinases interfere with the MTT assay, and therefore MTT cannot be used to determine the effect of STI571 on viability using these doses. Additionally, caution should be utilized when interpreting the results of MTT assays used to screen kinase inhibitors for anti-cancer activity, as drug effectiveness may be minimized.

The effects of fluoride on cell migration, cell proliferation, and cell metabolism in GH4C1 pituitary tumour cells

The consumption of drinking water rich in fluoride has toxic effects on the central nervous system. In cell biology research, fluoride is currently used as a phosphatase inhibitor. The aim of the present study was to evaluate the effect of fluoride on different physiological processes in GH4C1 pituitary tumour cells. We used a range of different fluoride concentrations, from levels below normal human serum concentrations (0.23 and 1.2 micromol/L) to those observed in chronically exposed persons (10.7 micromol/L) and above (107 and 1072 micromol/L). Treatment of 10.7 micromol/L fluoride resulted in a discrete induction of DNA synthesis, without a change in cell number. Cell migration, a behaviour stimulated by growth factors, was increased in cells treated with 2.4 micromol/L. At this fluoride concentration, changes in phosphorylation status of both cytoskeletal and cytosolic protein fractions, as well as in actin cytoskeletal arrangements were observed. The GH4C1 fluoride treated cells had significantly less cellular protein than control cells, suggesting an effect of fluoride on hormone secretion and protein synthesis in this endocrine cell. The bioreduction of MTT was significantly increased with a wide range of fluoride concentrations. With the highest fluoride concentration, 1072 micromol/L, all of the analysed parameters were significantly reduced, suggesting that this dose is highly toxic in GH4C1 cells. Our results show that biologically relevant concentrations of fluoride are capable of increasing cell migration in tumour cells, suggesting that exposure to fluoride could stimulate tumour invasion.

Evidence for an ATP-sensitive K+ channel in mitoplasts isolated from Trypanosoma cruzi and Crithidia fasciculata

Mammalian mitochondria, as well as rat, plant and Caenorhabditis elegans mitochondria, possess an ATP-sensitive K+ channel (mitoK(ATP)) that has been pharmacologically characterised. Opening of mitoK(ATP) and the subsequent K+ entry into the matrix was shown to have three effects on mitochondria physiology: (i) an increase in matrix volume (swelling), (ii) an acceleration of respiration, and (iii) an increase in reactive oxygen species (ROS) production. These effects on mitochondria bioenergetics have been shown to be part of distinct intracellular signalling pathways, to protect against cell death and to modulate gene transcription. To date, such a channel or its activity has not been described in trypanosomatids. In the present study, we show pharmacological evidence for the presence of a mitoK(ATP) in trypanosomatids. Cells were incubated in a hypotonic medium followed by mild detergent exposure to isolate mitoplasts from Trypanosoma cruzi and Crithidia fasciculata. Mitoplasts swelled when incubated in KCl medium due to respiration-driven K+ entry into the matrix. Swelling was sensitive to the presence of ATP when the mitoplast suspension was incubated in K+ -containing, but not in K+ -free, medium. The ATP inhibition of swelling was reversed by the mitoK(ATP) agonist diazoxide and the diazoxide-induced swelling was inhibited by the mitoK(ATP) blockers 5-hydroxydecanoate (5HD) or glibenclamide. Similar to mammalian and rat mitochondria, trypanosomatid mitoK(ATP) activity was modulated by the general protein kinase C (PKC) agonist phorbol 12-myristate 13-acetate (PMA) and antagonist chelerythrine. As expected, the potassium ionophore valinomycin could also reverse the ATP-inhibited state but this reversal was not sensitive to 5HD or glibenclamide. Dose response curves for ATP, diazoxide and 5HD are presented. These results provide strong evidence for the presence of an ATP-sensitive K+ in trypanosomatid mitochondria.

Hybrid peptides attenuate cytotoxicity of beta-amyloid by inhibiting its oligomerization: implication from solvent effects

Abnormal assembly of monomeric beta-amyloid (Abeta) in Alzheimer's disease leads to the formation of most neurotoxic oligomers in vivo. In this study, we explored a linking strategy to design hybrid peptides, by combining the Abeta recognition motif and the solvent disruptive sequences. We found that in vitro all synthetic peptides with the recognition motif can affect Abeta fibrillization and alter the morphology of Abeta aggregates variously, different from those without the recognition motif. The effects of peptides containing recognition motif on Abeta aggregation correlate with their abilities to change the surface tension of solutions. In addition, compounds with the recognition motif, not those without such motif, can inhibit cytotoxicity of Abeta in cell culture probably by decreasing the amount of toxic Abeta oligomers. These results indicate that recognition domain and solvent effect should be considered as important factors when designing molecules to target Abeta aggregation.

Protective role of fructose in the metabolism of astroglial C6 cells exposed to hydrogen peroxide

Astroglial cells represent the main line of defence against oxidative damage related to neurodegeneration. Therefore, protection of astroglia from an excess of reactive oxygen species could represent an important target of the treatment of such conditions. The aim of our study was to compare the abilities of glucose and fructose, the two monosaccharides used in diet and infusion, to protect C6 cells from hydrogen peroxide (H(2)O(2))-mediated oxidative stress. It was observed using confocal microscopy with fluorescent labels and the MTT test that fructose prevents changes of oxidative status of the cells exposed to H(2)O(2) and preserves their viability. Even more pronounced protective effects were observed for fructose 1,6-bis(phosphate). We propose that fructose and its intracellular forms prevent H(2)O(2) from participating in the Fenton reaction via iron sequestration. As fructose and fructose 1,6-bis(phosphate) are able to pass the blood-brain barrier, they could provide antioxidative protection of nervous tissue in vivo. So, in contrast to the well-known negative effects of frequent consumption of fructose under physiological conditions, acute infusion or ingestion of fructose or fructose 1,6-bis(phosphate) could be of benefit in the cytoprotective therapy of neurodegenerative disorders related to oxidative stress.

Compound FLZ inhibits lipopolysaccharide-induced inflammatory effects via down-regulation of the TAK-IKK and TAK-JNK/p38MAPK pathways in RAW264.7 macrophages

AIM

The aim of this study was to investigate the effect of the squamosamide derivative FLZ (N-2-(4-hydroxy-phenyl)-ethyl-2-(2,5-dimethoxy-phenyl)-3-(3-methoxy-4-hydroxy-phenyl)-acrylamide) on lipopolysaccharide (LPS)-induced inflammatory mediator production and the underlying mechanism in RAW264.7 macrophages.

METHODS

RAW264.7 cells were preincubated with non-toxic concentrations of compound FLZ (1, 5, and 10 micromol/L) for 30 min and then stimulated with 10 microg/L LPS. The production of nitric oxide (NO), the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2), and the activation of nuclear factor kappa-B (NF-kappaB) and mitogen-activated protein kinase (MAPK) pathways were examined.

RESULTS

FLZ significantly inhibited the LPS-induced production of NO, as well as the expression of iNOS and COX-2 at both the RNA and the protein levels in RAW264.7 cells. The LPS-induced increase in the DNA binding activity of NF-kappaB and activator protein 1 (AP-1), the nuclear translocation of NF-kappaB p65, the degradation of the inhibitory kappaBalpha protein (IkappaBalpha) and the phosphorylation of IkappaBalpha, IkappaB kinase (IKK) alpha/beta, c-Jun NH(2)-terminal kinase (JNK) and p38 MAPKs were all suppressed by FLZ. However, the phosphorylation of extracellular signal-regulated kinase (ERK) was not affected. Further study revealed that FLZ inhibited the phosphorylation of transforming growth factor-beta (TGF-beta)-activated kinase 1 (TAK1), which is an upstream signaling molecule required for IKKalpha/beta, JNK and p38 activation.

CONCLUSION

FLZ inhibited the LPS-induced production of inflammatory mediators at least partly through the downregulation of the TAK-IKK and TAK-JNK/p38MAPK pathways.

Sesamol attenuate 3-nitropropionic acid-induced Huntington-like behavioral, biochemical, and cellular alterations in rats

Sesamol (SML) obtained from sesame seeds (Sesamum indicum, Linn, Pedaliaceae) has been used as a traditional health food in India and other countries since a long time. Besides its good antioxidant activity, SML is currently receiving considerable attention in relation to neurological disorders. Therefore, the present study has been designed to explore the protective role of SML in 3-nitropropionic acid (3-NP)-induced neurotoxicity in animals. Male rats were given 3-NP (10 mg/kg) treatment for 14 days. Various behavioral observations (body weight, locomotor activity), oxidative damage (lipid peroxidation, nitrite level, superoxide dismutase, and catalase enzyme), and mitochondrial enzyme complex functions were also assessed in the striatum, cortex, and hippocampal regions of the brain. 3-NP treatment significantly impaired locomotor activity, motor coordination, body weight, oxidative damage, and mitochondrial enzyme complex functions as compared with vehicle-treated groups. SML (5, 10, and 20 mg/kg) pre-treatment significantly improved body weight, locomotor activity, motor coordination, and attenuated oxidative damage in different regions of rat brain. Besides these, SML treatment also significantly improved mitochondrial enzymes in all regions of the brain as compared with the respective control (3-NP) group. The present study suggests that SML could be used as effective agents in the management of Huntington's disease.

Effect of polycyclic aromatic hydrocarbons and carbon black particles on pro-inflammatory cytokine secretion: impact of PAH coating onto particles

It has been suggested that the organic fraction of particulate matter in air pollution has a major role in the toxicity of this pollutant, notably via its effects on inflammation. The major organic compounds adsorbed onto these particles are polycyclic aromatic hydrocarbons (PAH), among which benzo[a]pyrene (B[a]P), benzo[b]fluoranthene (B[b]F), and pyrene (Pyr) are quantitatively the most important. Generally, cells or organisms are exposed to organic extracts of the particles rather than the native particles in order to study the effects of these PAH. In this study, B[a]P, B[b]F, and Pyr were tested alone and/or adsorbed onto carbon black (CB) particles differing in size in order to evaluate their impact on cytokine production (with or without LPS stimulation) by THP-1 macrophage-like cells. PAH induced significant secretion of IL-1beta, IL-8, and IL-12 after 24 or 48 hr of treatment, an effect reinforced by LPS stimulation; no effect on IL-10 secretion was noted. Fine CB particles (260 nm diameter) induced secretion of each cytokine. In general, coating the CB with PAH did not modify the effect of the CB alone; the exception was that LPS-induced IL-1beta secretion was reduced. In contrast, ultrafine CB (14 nm diameter: ufCB) caused a decrease in cytokine secretion; this effect was modified by PAH coating. For example, PAH coating on ufCB amplified the inhibitory effect of ufCB against IL-1beta secretion but did not modify IL-8 formation. Moreover, PAH coating on ufCB tended to minimize the effect of LPS stimulation; this included (i) inhibition of the decrease in IL-12 secretion induced by uncoated ufCB and (ii) stimulation of IL-10 production. It was concluded that adsorption of PAH onto these particles could decrease their bioavailability and so their abilities to affect cell cytokine production. The results also showed that when PAH were adsorbed onto the fine particles, any observed increases in cytokine secretion consistently appeared to be due to the particles themselves. In contrast, while ufCB alone almost uniformly led to decreases in cytokine formation by the cells, the added presence of the test PAHs led to variable effects - depending on whether stimulation with LPS took place or not. Thus, while some PAHs likely to be associated with PM are clearly immunomodulants, their ultimate effects in situ will likely depend on the properties of the particles themselves, in particular, their size.

Chronic treatment with electroconvulsive shock may modulate the immune function of macrophages

OBJECTIVE

To determine the effect of single and chronic electroconvulsive shock (ECS) administration on the immunoregulatory functions of macrophages.

METHODS

Male Wistar rats received single or chronic treatment with ECS (150 mA, 50 Hz, 0.5 seconds) delivered through ear clips, once a day for 10 consecutive days, or sham ECS administered likewise. The rats were killed 24 hours after the last treatment, and peritoneal macrophages were cultured in vitro for 3 or 36 hours for a subsequent determination of their metabolic activity. The ability of macrophages to reduce Alamar Blue, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT), and nitrotetrazolium blue chloride and pinocytosis, adherence, and vitality, as well as synthesis of nitric oxide and arginase activity, was assessed.

RESULTS

We found statistically significant changes in the biological properties of macrophages which occurred after 36 hours of incubation, especially in cultures stimulated with lipopolysaccharide; in contrast, no differences were observed between groups assessed after 3 hours of incubation. Rats receiving chronic 10-fold ECS showed a substantial increase in the metabolic activity of macrophages, reflected as their ability to reduce Alamar Blue and MTT and to increase arginase activity, accompanied with a marked but statistically insignificant decrease in nitric oxide synthesis compared with respective controls.

CONCLUSIONS

Our results suggest that chronic treatment with ECS may induce long-lasting changes in the activity of peritoneal macrophages. Attenuation of their proinflammatory properties indicates that ECS can change the primarily immunoregulatory functions of macrophages.

Age-related changes in cerebellar phosphatase-1 reduce Na,K-ATPase activity

We evaluated whether changes in protein content and activity of PP-1 and PP-2A were the mechanism underneath the basal age-related reduction in alpha(2/3)-Na,K-ATPase activity in rats cerebella and whether this occurred through the cyclic GMP-PKG pathway. PP1 activity, but not its expression, increased with age, whereas PP-2 was not changed. The activity of alpha(2/3)-Na,K-ATPase varied with age, and there was a negative association between the PP-1 and alpha(2/3)-Na,K-ATPase activities. In young rats, the inhibition of PP-1 and PP-2A by okadaic acid (OA) increased in a dose-dependent manner alpha(1)- and alpha(2/3)-Na,K-ATPase, but had no effect on Mg-ATPase activity. A direct stimulation of PKG with 8-Br-cyclic GMP did not surmount the effect of OA. This analogue of cyclic GMP inhibited PP-1 activity only, indicating that at least part of the increase in alpha(1)- and alpha(2/3)-Na,K-ATPase activity induced by OA was mediated by the cyclic GMP-PKG-PP-1 cascade. Taking into account that PP1 inhibition increased alpha(2/3)-Na,K-ATPase activity, we propose that an age-related increase in PP-1 activity due to a decrease in cyclic GMP-PKG modulation plays a role for the age-related reduction of alpha(2/3)-Na,K-ATPase activity in rat cerebellum.

Mitochondrial oxidative stress and dysfunction in rat brain induced by carbofuran exposure

Repeated low-dose exposure to carbofuran exerts its neurotoxic effects by non-cholinergic mechanisms. Emerging evidence indicates that oxidative stress plays an important role in carbofuran neurotoxicity after sub-chronic exposure. The purpose of the present study is to evaluate the role of mitochondrial oxidative stress and dysfunction as a primary event responsible for neurotoxic effects observed after sub-chronic carbofuran exposure. Carbofuran was administered to rats at a dose of 1 mg/kg orally for a period of 28 days. There was a significant inhibition in the activity of acetylcholinesterase (66.6%) in brain samples after 28 days of carbofuran exposure. Mitochondrial respiratory chain functions were assessed in terms of MTT (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) reduction and activity of succinate dehydrogenase in isolated mitochondria. It was observed that carbofuran exposure significantly inhibited MTT reduction (31%) and succinate dehydrogenase activity (57%). This was accompanied by decrease in low-molecular weight thiols (66.6%) and total thiols (37.4%) and an increase in lipid peroxidation (43.7%) in the mitochondria isolated from carbofuran-exposed rat brain. The changes in mitochondrial oxidative stress and functions were associated with impaired cognitive and motor functions in the animals exposed to carbofuran as compared to the control animals. Based on these results, it is clear that carbofuran exerts its neurotoxicity by impairing mitochondrial functions leading to oxidative stress and neurobehavioral deficits.

Metalloprotease vsm is the major determinant of toxicity for extracellular products of Vibrio splendidus

Genomic data combined with reverse genetic approaches have contributed to the characterization of major virulence factors of Vibrio species; however, these studies have targeted primarily human pathogens. Here, we investigate virulence factors in the oyster pathogen Vibrio splendidus LGP32 and show that toxicity is correlated to the presence of a metalloprotease and its corresponding vsm gene. Comparative genomics showed that an avirulent strain closely related to LGP32 lacked the metalloprotease. The toxicity of LGP32 metalloprotease was confirmed by exposing mollusk and mouse fibroblastic cell lines to extracellular products (ECPs) of the wild type (wt) and a vsm deletion mutant (Deltavsm mutant). The ECPs of the wt induced a strong cytopathic effect whose severity was cell type dependent, while those of the Deltavsm mutant were much less toxic, and exposure to purified protein demonstrated the direct toxicity of the Vsm metalloprotease. Finally, to investigate Vsm molecular targets, a proteomic analysis of the ECPs of both LGP32 and the Deltavsm mutant was performed, revealing a number of differentially expressed and/or processed proteins. One of these, the VSA1062 metalloprotease, was found to have significant identity to the immune inhibitor A precursor, a virulence factor of Bacillus thuringiensis. Deletion mutants corresponding to several of the major proteins were constructed by allelic exchange, and the ECPs of these mutants proved to be toxic to both cell cultures and animals. Taken together, these data demonstrate that Vsm is the major toxicity factor in the ECPs of V. splendidus.

Bid-induced release of AIF from mitochondria causes immediate neuronal cell death

Mitochondrial dysfunction and release of pro-apoptotic factors such as cytochrome c or apoptosis-inducing factor (AIF) from mitochondria are key features of neuronal cell death. The precise mechanisms of how these proteins are released from mitochondria and their particular role in neuronal cell death signaling are however largely unknown. Here, we demonstrate by fluorescence video microscopy that 8-10 h after induction of glutamate toxicity, AIF rapidly translocates from mitochondria to the nucleus and induces nuclear fragmentation and cell death within only a few minutes. This markedly fast translocation of AIF to the nucleus is preceded by increasing translocation of the pro-apoptotic bcl-2 family member Bid (BH3-interacting domain death agonist) to mitochondria, perinuclear accumulation of Bid-loaded mitochondria, and loss of mitochondrial membrane integrity. A small molecule Bid inhibitor preserved mitochondrial membrane potential, prevented nuclear translocation of AIF, and abrogated glutamate-induced neuronal cell death, as shown by experiments using Bid small interfering RNA (siRNA). Cell death induced by truncated Bid was inhibited by AIF siRNA, indicating that caspase-independent AIF signaling is the main pathway through which Bid mediates cell death. This was further supported by experiments showing that although caspase-3 was activated, specific caspase-3 inhibition did not protect neuronal cells against glutamate toxicity. In conclusion, Bid-mediated mitochondrial release of AIF followed by rapid nuclear translocation is a major mechanism of glutamate-induced neuronal death.

An endoplasmic reticulum (ER) stress-suppressive compound and its analogues from the mushroom Hericium erinaceum

Three new compounds, 3-hydroxyhericenone F (1), hericenone I (2), and hericenone J (3), were isolated from the mushroom Hericium erinaceum. The structures of 1-3 were determined by the interpretation of spectral data. Compound 1 showed the protective activity against endoplasmic reticulum (ER) stress-dependent Neuro2a cell death, however, compounds 2 and 3 did not.

A human spinal cord cell promotes motoneuron survival and maturation in vitro

Primary cultures of motoneurons represent a good experimental model for studying mechanisms underlying certain spinal cord pathologies, such as amyotrophic lateral sclerosis and spinal bulbar muscular atrophy (Kennedy's disease). However, a major problem with such culture systems is the relatively short cell survival times, which limits the extent of motoneuronal maturation. In spite of supplementing culture media with various growth factors, it remains difficult to maintain motoneurons viable longer than 10 days in vitro. This study employs a new approach, in which rat motoneurons are plated on a layer of cultured cells derived from newborn human spinal cord. For all culture periods, more motoneurons remain viable in such cocultures compared with control monocultures. Moreover, although no motoneurons survive in control cultures after 22 days, viable motoneurons were observed in cocultures even after 7 weeks. Although no significant difference in neurite length was observed between 8-day mono- and cocultures, after 22 and 50 days in coculture motoneurons had a very mature morphology. They extended extremely robust, very long neurites, which formed impressive branched networks. Data obtained using a system in which the spinal cord cultures were separated from motoneurons by a porous polycarbonate filter suggest that soluble factors released from the supporting cells are in part responsible for the beneficial effects on motoneurons. Several approaches, including immunocytochemistry, immunoblotting, and electron microscopy, indicated that these supporting cells, capable of extending motoneuron survival and enhancing neurite growth, had an undifferentiated or poorly differentiated, possibly mesenchymal phenotype.

Impairment of mitochondrial energy metabolism in different regions of rat brain following chronic exposure to aluminium

The present study was designed with an aim to evaluate the effects of chronic aluminium exposure (10 mg/kg b.wt, intragastrically for 12 weeks) on mitochondrial energy metabolism in different regions of rat brain in vivo. Mitochondrial preparations from aluminium treated rats revealed significant decrease in the activity of various electron transport complexes viz. cytochrome oxidase, NADH cytochrome c reductase and succinic dehydrogenase as well, in the hippocampus region. The decrease in the activity of these respiratory complexes was also seen in the other two regions viz. corpus striatum and cerebral cortex, but to a lesser extent. This decrease in the activities of electron transport complexes in turn affected the ATP synthesis and ATP levels adversely in the mitochondria isolated from aluminium treated rat brain regions. We also studied the spectral properties of the mitochondrial cytochromes viz. cyt a, cyt b, cyt c1, and cyt c in both control and treated rat brains. The various cytochrome levels were found to be decreased following 12 weeks of aluminium exposure. Further, these impairments in mitochondrial functions may also be responsible for the production of reactive oxygen species and impaired antioxidant defense system as observed in our study. The electron micrographs of neuronal cells depicted morphological changes in mitochondria as well as nucleus only from hippocampus and corpus striatum regions following 12 weeks exposure to aluminium. The present study thus highlights the significance of altered mitochondrial energy metabolism and increased ROS production as a result of chronic aluminium exposure in different regions of the rat brain.

Prion protein complexed to N2a cellular RNAs through its N-terminal domain forms aggregates and is toxic to murine neuroblastoma cells

Conversion of the cellular prion protein (PrP^C) into its altered conformation, PrP^Sc, is believed to be the major cause of prion diseases. Although PrP is the only identified agent for these diseases, there is increasing evidence that other molecules can modulate the conversion. We have found that interaction of PrP with double-stranded DNA leads to a protein with higher β-sheet content and characteristics similar to those of PrP^Sc. RNA molecules can also interact with PrP and potentially modulate PrP^C to PrP^Sc conversion or even bind differentially to both PrP isoforms. Here, we investigated the interaction of recombinant murine PrP with synthetic RNA sequences and with total RNA extracted from cultured neuroblastoma cells (N2aRNA). We found that PrP interacts with N2aRNA with nanomolar affinity, aggregates upon this interaction, and forms species partially resistant to proteolysis. RNA does not bind to N-terminal deletion mutants of PrP, indicating that the N-terminal region is important for this process. Cell viability assays showed that only the N2aRNA extract induces PrP-RNA aggregates that can alter the homeostasis of cultured cells. Small RNAs bound to PrP give rise to nontoxic small oligomers. Nuclear magnetic resonance measurements of the PrP-RNA complex revealed structural changes in PrP, but most of its native fold is maintained. These results indicate that there is selectivity in the species generated by interaction with different molecules of RNA. The catalytic effect of RNA on the PrP^C→PrP^Sc conversion depends on the RNA sequence, and small RNA molecules may exert a protective effect.

In vitro behaviour of osteoblast cells seeded into a COL/β-TCP composite scaffold

The purpose of the present study was to investigate the effect of a collagen/β-tricalcium phosphate (COL/β-TCP) composite on osteoblast growth and proliferation. The COL/β-TCP composite was prepared by mixing COL type I with β-TCP, in 1:1 (w/w) ratio and conditioned as sponge by freeze-drying. The osteoblast culture was obtained from rat calvaria bones by enzymatic digestion and cells were seeded in the COL/β-TCP composite. The cell morphology and viability, alkaline phosphatase and osteocalcin, as markers of osteoblast proliferation were evaluated at 3, 7 and 25 days of culture. Histological sections revealed that cell colonization progressively increased inside the COL/β-TCP scaffold, and osteoblasts had a random distribution throughout the scaffold. Cells cultured into the COL/β-TCP scaffold presented osteoblast phenotype, intense staining of alkaline phosphatase and increased production of osteocalcin. Transmission electron micrographs revealed intimate contacts between osteoblasts and the scaffold. MTT test indicated that the viability of the cells cultivated in the presence of COL/β-TCP scaffold was similar to that of the control. All these results show that our COL/β-TCP composite act as a good substrate for rat osteoblast proliferation and migration and could be a promising substitute for bone repair.

Characterization of oxidized low-density lipoprotein-induced hormesis-like effects in osteoblastic cells

Epidemiological studies indicate that patients suffering from atherosclerosis are predisposed to develop osteoporosis. Atherogenic determinants such as oxidized low-density lipoprotein (oxLDL) particles have been shown both to stimulate the proliferation and promote apoptosis of bone-forming osteoblasts. Given such opposite responses, we characterized the oxLDL-induced hormesis-like effects in osteoblasts. Biphasic 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reductive activity responses were induced by oxLDL where low concentrations (10-50 microg/ml) increased and high concentrations (from 150 microg/ml) reduced the MTT activity. Cell proliferation stimulation by oxLDL partially accounted for the increased MTT activity. No alteration of mitochondria mass was noticed, whereas low concentrations of oxLDL induced mitochondria hyperpolarization and increased the cellular levels of reactive oxygen species (ROS). The oxLDL-induced MTT activity was not related to intracellular ROS levels. OxLDL increased NAD(P)H-associated cellular fluorescence and flavoenzyme inhibitor diphenyleneiodonium reduced basal and oxLDL-induced MTT activity, suggesting an enhancement of NAD(P)H-dependent cellular reduction potential. Low concentrations of oxLDL reduced cellular thiol content and increased metallothionein expression, suggesting the induction of compensatory mechanisms for the maintenance of cell redox state. These concentrations of oxLDL reduced osteoblast alkaline phosphatase activity and cell migration. Our results indicate that oxLDL particles cause hormesis-like response with the stimulation of both proliferation and cellular NAD(P)H-dependent reduction potential by low concentrations, whereas high concentrations lead to reduction of MTT activity associated with the cell death. Given the effects of low concentrations of oxLDL on osteoblast functions, oxLDL may contribute to the impairment of bone remodeling equilibrium.

Lack of robust protective effect of quercetin in two types of 6-hydroxydopamine-induced parkinsonian models in rats and dopaminergic cell cultures

In the present study, we examined the ability of a flavonoid quercetin to prevent 6-hydroxydopamine (6-OHDA)-induced oxygen radical formation and cytotoxicity in vitro and neurotoxicity in vivo. Quercetin (10-100 microM) had an acute significant antioxidant effect against the 6-OHDA-induced (30 microM) oxygen radical formation in catecholaminergic SH-SY5Y neuroblastoma cells. Moreover, in these cells, quercetin at 10-50 microM had a significant protective effect against 6-OHDA though at 100 microM it was itself harmful to the cells. The possible effect of quercetin in preventing neurotoxicity in unilateral medial forebrain bundle (full nigral lesion) or striatal (partial lesion) 6-OHDA rat lesion models of Parkinson's disease was studied in three treatment schedules: a 7-day pre- or post-treatment or their combination. Rotational responses to apomorphine (0.1 mg/kg, subcutaneously) and d-amphetamine (2.5 mg/kg, intraperitoneally) were assessed at weeks 1 and 2 post-lesion. Quercetin had no consistent neuroprotective effect in either model at 50-200 mg/kg once a day or 100 mg/kg twice a day. Furthermore, no protection was observed in tyrosine hydroxylase positive nigral cell numbers, striatal fiber density or in striatal levels of dopamine. These in vitro and in vivo results cast doubt on the theory that quercetin exerts reliable neuroprotective effects against 6-OHDA-induced toxicity. In vitro, quercetin seems to be protective at low doses but damaging at high doses.

Different viabilities and toxicity types after 6-OHDA and Ara-C exposure evaluated by four assays in five cell lines

Cell viability studies are useful when screening novel drugs for the diseases that are related to either increased cell death or enhanced cell survival. There are numerous assays but the results that they produce are rarely unanimous. Here we compared the performance of (1) morphological microscopic assay with double DNA staining, (2) propidium iodide-digitonin assay, (3) MTT-assay, and (4) ATP-assay in human neuroblastoma (SH-SY5Y), rat glioma (C6), rabbit smooth muscle (SMC), Chinese hamster ovary (CHO) and monkey fibroblast cells (CV1-P) exposed to cytosine arabinoside (Ara-C) and 6-hydroxydopamine (6-OHDA). We found that neuronal SH-SY5Y cells were most sensitive to both toxins and the results in all viability tests correlated well. All the other cell lines were much more resistant, particularly to Ara-C but also to 6-OHDA. Toxicity of the compounds was best revealed by MTT and ATP assays, measuring the metabolic activity of the cells, and only occasionally by morphological observations or with the propidium iodide-digitonin assay which is based on the cell membrane integrity. In this research, Ara-C induced pure apoptosis whereas the toxicity type of 6-OHDA was dose-dependent. The use of several viability tests and cell lines is recommended when studying cell death, particularly apoptosis, and performance of antiapoptotic compounds.

Ethanol exposure of neonatal rats does not increase biomarkers of oxidative stress in isolated cerebellar granule neurons

Oxidative stress is a candidate mechanism for ethanol neuropathology in fetal alcohol spectrum disorders. Oxidative stress often involves production of reactive oxygen species (ROS), deterioration of the mitochondrial membrane potential (MMP), and cell death. Previous studies have produced conflicting results regarding the role of oxidative stress and the benefit of antioxidants in ethanol neuropathology in the developing brain. This study investigated the hypothesis that ethanol neurotoxicity involves production of ROS with negative downstream consequences for MMP and neuron survival. This was modeled in neonatal rats at postnatal day 4 (P4) and P14. It is well established that granule neurons in the rat cerebellar cortex are more vulnerable to ethanol neurotoxicity on P4 than at later ages. Thus, it was hypothesized that ethanol produces more oxidative stress and its negative consequences on P4 than on P14. A novel experimental approach was used in which ethanol was administered to animals in vivo (gavage 6g/kg), granule neurons were isolated 2-24h post-treatment, and ROS production and relative MMP were immediately assessed in the viable cells. Cells were also placed in culture and survival was measured 24h later. The results revealed that ethanol did not induce granule cells to produce ROS, cause deterioration of neuronal MMP, or cause neuron death when compared to vehicle controls. Further, granule neurons from neither P4 nor P14 animals mounted an oxidative response to ethanol. These findings do not support the hypothesis that oxidative stress is obligate to granule neuron death after ethanol exposure in the neonatal rat brain. Other investigators have reached a similar conclusion using either brain homogenates or cell cultures. In this context, it is likely that oxidative stress is not the sole and perhaps not the principal mechanism of ethanol neurotoxicity for cerebellar granule neurons during this stage of brain development.

A stirred microchamber for oxygen consumption rate measurements with pancreatic islets

Improvements in pancreatic islet transplantation for treatment of diabetes are hindered by the absence of meaningful islet quality assessment methods. Oxygen consumption rate (OCR) has previously been used to assess the quality of organs and primary tissue for transplantation. In this study, we describe and characterize a stirred microchamber for measuring OCR with small quantities of islets. The device has a titanium body with a chamber volume of about 200 microL and is magnetically stirred and water jacketed for temperature control. Oxygen partial pressure (pO(2)) is measured by fluorescence quenching with a fiber optic probe, and OCR is determined from the linear decrease of pO(2) with time. We demonstrate that measurements can be made rapidly and with high precision. Measurements with betaTC3 cells and islets show that OCR is directly proportional to the number of viable cells in mixtures of live and dead cells and correlate linearly with membrane integrity measurements made with cells that have been cultured for 24 h under various stressful conditions.

Photodynamic therapy with a new photosensitizing agent

OBJECTIVE

The aim of this study was to investigate the cytotoxicity of octal-bromide zinc phthalocyanine (ZnPcBr(8)) before and after irradiation with a low-power laser (AsGaAl) and analyze the effects of photodynamic therapy (PDT) on the nucleus of L929 cells.

BACKGROUND DATA

One of the most recent and promising applications of phthalocyanine in medicine is in the detection and cure of tumors. We studied the ZnPcBr(8) in agreement with the development of new photosensitizing agents for curing tumors.

METHODS

L929 cells were cultivated at standard conditions, incubated with ZnPcBr(8) for 1 h at different concentrations, irradiated with a semiconductor laser, and incubated in MEM medium for 1, 12, or 24 h. Cells were analyzed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) technique and fluorescence microscopy.

RESULTS

The results demonstrated that ZnPcBr(8) at 1 microM was the most effective concentration for PDT, with a decrease of 63% after 1 h, 99% after 12 h, and 100% after 24 h in relation to the control group. The fluorescence microscopy results showed that ZnPcBr(8) was localized in the perinuclear region when analyzed 1 h after incubation. Nucleus staining with DAPI made it possible to observe that nuclear fragmentation occurred 24 h after PDT, cytoplasm retraction at 1, 12, and 24 h after PDT, and vacuoles along the cytoplasm at 12 and 24 h after PDT.

CONCLUSION

According to the results obtained in this study, L929 cell death caused by PDT with ZnPcBr(8) possesses characteristics of apoptosis mediated by the mitochondria, due to the decrease in cells viability, the subcellular localization, and the photodamage found.