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

Suppression of neuroinflammatory and apoptotic signaling cascade by curcumin alone and in combination with piperine in rat model of olfactory bulbectomy induced depression

Objectives

Bilateral destruction of the olfactory bulbs is known to cause behavioral changes analogous to symptoms of depression. Curcumin, a traditional Indian spice is currently being investigated in different psychiatric problems including depression. Dietary phytochemicals are currently used as an adjuvant therapy to accelerate their therapeutic efficacy. Therefore, the present study is an attempt to elucidate the neuroprotective mechanism of curcumin and its co-administration with piperine against olfactory bulbectomy induced depression in rats.

Methods

Rats undergone olfactory bulbs ablations were analyzed after post-surgical rehabilitation period of 2 weeks. Animals were then treated with different doses of curcumin (100, 200 and 400 mg/kg; p.o.), piperine (20 mg/kg; p.o.) and their combination daily for another 2 weeks. Imipramine (10 mg/kg; i.p.) served as a standard control. Various behavioral tests like forced swim test (FST), open field behaviour and sucrose preference test (SPT) were performed, followed by estimation of biochemical, mitochondrial, molecular and histopathological parameters in rat brain.

Results

Ablation of olfactory bulbs caused depression-like symptoms as evidenced by increased immobility time in FST, hyperactivity in open field arena, and anhedonic like response in SPT along with alterations in mitochondrial enzyme complexes, increased serum corticosterone levels and oxidative damage. These deficits were integrated with increased inflammatory cytokines (TNF-α) and apoptotic factor (caspase-3) levels along with a marked reduction in neurogenesis factor (BDNF) in the brain of olfactory bulbectomized (OBX) rats. Curcumin treatment significantly and dose-dependently restored all these behavioral, biochemical, mitochondrial, molecular and histopathological alterations associated with OBX induced depression. Further, co-administration of piperine with curcumin significantly potentiated their neuroprotective effects as compared to their effects alone.

Conclusions

The present study highlights that curcumin along with piperine exhibits neuroprotection against olfactory bulbectomy induced depression possibly by modulating oxidative-nitrosative stress induced neuroinflammation and apoptosis.

Anvirzel™ in combination with cisplatin in breast, colon, lung, prostate, melanoma and pancreatic cancer cell lines

Background

Platinum derivatives are used widely for the treatment of many cancers. However, the toxicity that is observed makes imperative the need for new drugs, or new combinations. Anvirzel™ is an extract which has been demonstrated with experimental data that displays anticancer activity. The aim of the present study is to determine whether the combination of Cisplatin and Anvirzel™ has a synergistic effect against different types of cancer.

Materials and methods

To measure the efficacy of treatment with Cisplatin and Anvirzel™, methyl-tetrazolium dye (MTT) chemosensitivity assays were used incorporating established human cancer cell lines. Measurements were performed in triplicates, three times, using different incubation times and different concentrations of the two formulations in combination or on their own. t-test was used for statistical analysis.

Results

In the majority of the cell lines tested, lower concentrations of Anvirzel™ induced a synergistic effect when combined with low concentrations of Cisplatin after an incubation period of 48 to 72 h. The combination of Anvirzel™/Cisplatin showed anti-proliferative effects against a wide range of tumours.

Conclusion

The results showed that the combination of Anvirzel™ and Cisplatin is more effective than monotherapy, even when administered at low concentrations; thus, undesirable toxic effects can be avoided.

MicroRNA 299-3p modulates replicative senescence in endothelial cells

MicroRNAs (miRNAs) regulate various cellular processes. While several genes associated with replicative senescence have been described in endothelial cells, miRNAs that regulate these genes remain largely unknown. The present study was designed to identify miRNAs associated with replicative senescence and their target genes in human umbilical vein endothelial cells (HUVECs). An integrated miRNA and gene profiling approach revealed that hsa-miR-299-3p is upregulated in senescent HUVECs compared with the young cells, and one of its target genes could be IGF1. IGF1 was upregulated in senescent compared with young HUVECs, and knockdown of hsa-miR-299-3p dose-dependently increased the mRNA expression of IGF1, more significantly observed in the presenescent cells (passage 19) compared with the senescent cells (passage 25). Knockdown of hsa-miR-299-3p also resulted in significant reduction in the percentage of cells positively stained for senescence-associated β-galactosidase and increases in cell viability measured by MTT assay but marginal increases in cell proliferation and cell migration capacity measured by real-time growth kinetics analysis. Moreover, knockdown of hsa-miR-299-3p also increased proliferation of cells treated with H2O2 to induce senescence. These findings suggest that hsa-miR-299-3p may delay or protect against replicative senescence by improving the metabolic activity of the senesced cells but does not stimulate growth of the remaining cells in senescent cultures. Hence, these findings provide an early insight into the role of hsa-miR-299-3p in the modulation of replicative senescence in HUVECs.

The sesquiterpene lactone dehydroleucodine triggers senescence and apoptosis in association with accumulation of DNA damage markers

Sesquiterpene lactones (SLs) are plant-derived compounds that display anti-cancer effects. Some SLs derivatives have a marked killing effect on cancer cells and have therefore reached clinical trials. Little is known regarding the mechanism of action of SLs. We studied the responses of human cancer cells exposed to various concentrations of dehydroleucodine (DhL), a SL of the guaianolide group isolated and purified from Artemisia douglasiana (Besser), a medicinal herb that is commonly used in Argentina. We demonstrate for the first time that treatment of cancer cells with DhL, promotes the accumulation of DNA damage markers such as phosphorylation of ATM and focal organization of γH2AX and 53BP1. This accumulation triggers cell senescence or apoptosis depending on the concentration of the DhL delivered to cells. Transient DhL treatment also induces marked accumulation of senescent cells. Our findings help elucidate the mechanism whereby DhL triggers cell cycle arrest and cell death and provide a basis for further exploration of the effects of DhL in in vivo cancer treatment models.

Cryotherapy reduces skeletal muscle damage after ischemia/reperfusion in rats

The aim of this study was to analyze the effects of cryotherapy on the biochemical and morphological changes in ischemic and reperfused (I/R) gastrocnemius muscle of rats. Forty male Wistar rats were divided into control and I/R groups, and divided based on whether or not the rats were submitted to cryotherapy. Following the reperfusion period, biochemical and morphological analyses were performed. Following cryotherapy, a reduction in thiobarbituric acid-reactive substances and dichlorofluorescein oxidation levels were observed in I/R muscle. Cryotherapy in I/R muscle also minimized effects such as decreased cellular viability, levels of non-protein thiols and calcium ATPase activity as well as increased catalase activity. Cryotherapy also limited mitochondrial dysfunction and decreased the presence of neutrophils in I/R muscle, an effect that was corroborated by reduced myeloperoxidase activity in I/R muscle treated with cryotherapy. The effects of cryotherapy are associated with a reduction in the intensity of the inflammatory response and also with a decrease in mitochondrial dysfunction.

MTT assay for cell viability: Intracellular localization of the formazan product is in lipid droplets

Although MTT is widely used to assess cytotoxicity and cell viability, the precise localization of its reduced formazan product is still unclear. In the present study the localization of MTT formazan was studied by direct microscopic observation of living HeLa cells and by colocalization analysis with organelle-selective fluorescent probes. MTT formazan granules did not colocalize with mitochondria as revealed by rhodamine 123 labeling or autofluorescence. Likewise, no colocalization was observed between MTT formazan granules and lysosomes labeled by neutral red. Taking into account the lipophilic character and lipid solubility of MTT formazan, an evaluation of the MTT reaction was performed after treatment of cells with sunflower oil emulsions to induce a massive occurrence of lipid droplets. Under this condition, lipid droplets revealed a large amount of MTT formazan deposits. Kinetic studies on the viability of MTT-treated cells showed no harmful effects at short times. Quantitative structure-activity relations (QSAR) models were used to predict and explain the localization of both the MTT tetrazolium salt and its formazan product. These predictions were in agreement with experimental observations on the accumulation of MTT formazan product in lipid droplets.

Degradation of islet amyloid polypeptide by neprilysin

AIMS/HYPOTHESIS

A progressive loss of pancreatic beta cell function, a decrease in beta cell mass and accumulation of islet amyloid is characteristic of type 2 diabetes mellitus. The main constituent of islet amyloid is islet amyloid polypeptide (IAPP). In this study, we examined the ability of the peptidase neprilysin to cleave IAPP and prevent human IAPP-induced pancreatic beta cell toxicity.

METHODS

Neprilysin and a catalytically compromised neprilysin mutant were tested for their ability to inhibit human IAPP fibrillisation and human IAPP-induced pancreatic beta cell cytotoxicity. Degradation of human IAPP by neprilysin was followed by HPLC, and the degradation products were identified by MS.

RESULTS

Neprilysin prevented IAPP fibrillisation by cleaving IAPP at Arg(11)-Leu(12), Leu(12)-Ala(13), Asn(14)-Phe(15), Phe(15)-Leu(16), Asn(22)-Phe(23) and Ala(25)-Ile(26). It also appears to prevent human IAPP fibrillisation through a non-catalytic interaction. Neprilysin protected against beta cell cytotoxicity induced by exogenously added or endogenously produced human IAPP.

CONCLUSIONS/INTERPRETATION

The data presented support a potential therapeutic role for neprilysin in preventing type 2 diabetes mellitus. This study supports the hypothesis that extracellular human IAPP contributes to human IAPP-induced beta cell cytotoxicity. Whether human IAPP exerts its cytotoxic effect through a totally extracellular mechanism or through a cellular reuptake mechanism is unclear at this time.

Cytotoxicity of esthetic, metallic, and nickel-free orthodontic brackets: cellular behavior and viability

INTRODUCTION

In this study, we evaluated the cellular viability of various esthetic, metallic, and nickel-free orthodontic brackets.

METHODS

The sample was divided into 11 groups (n = 8): cellular control, negative control, positive control, metallic, polycarbonate, 2 types of monocrystalline ceramic, 3 types of nickel free, and polycrystalline ceramic brackets. Cell culture (NIH/3T3-mice fibroblasts) was added to the plates of 96 wells containing the specimens and incubated in 5% carbon dioxide at 37°C for 24 hours. Cytotoxicity was analyzed qualitatively and quantitatively. Cell growth was analyzed with an inverted light microscope, photomicrographs were obtained, and the results were recorded as response rates based on modifications of the parameters of Stanford according to the size of diffusion halo of toxic substances. Cell viability was analyzed (MTT assay); a microplate reader recorded the cell viability through the mitochondrial activity in a length of 570 nm. The values were statistically analyzed.

RESULTS

All tested brackets had higher cytotoxicity values than did the negative control (P <0.05), with the exception Rematitan and Equilibrium (both, Dentaurum, Ispringen, Germany) (P >0.05), suggesting low toxicity effects. The values showed that only polycarbonate brackets were similar (P >0.05) to the positive control, suggesting high toxicity.

CONCLUSIONS

The brackets demonstrated different ranges of cytotoxicity; nickel-free brackets had better biocompatibility than the others. On the other hand, polycarbonate brackets were made of a highly cytotoxic material for the cells analyzed.

Phosphorylation and subcellular localization of p27Kip1 regulated by hydrogen peroxide modulation in cancer cells

The Cyclin-dependent kinase inhibitor 1B (p27Kip1) is a key protein in the decision between proliferation and cell cycle exit. Quiescent cells show nuclear p27Kip1, but this protein is exported to the cytoplasm in response to proliferating signals. We recently reported that catalase treatment increases the levels of p27Kip1 in vitro and in vivo in a murine model. In order to characterize and broaden these findings, we evaluated the regulation of p27Kip1 by hydrogen peroxide (H(2)O(2)) in human melanoma cells and melanocytes. We observed a high percentage of p27Kip1 positive nuclei in melanoma cells overexpressing or treated with exogenous catalase, while non-treated controls showed a cytoplasmic localization of p27Kip1. Then we studied the levels of p27Kip1 phosphorylated (p27p) at serine 10 (S10) and at threonine 198 (T198) because phosphorylation at these sites enables nuclear exportation of this protein, leading to accumulation and stabilization of p27pT198 in the cytoplasm. We demonstrated by western blot a decrease in p27pS10 and p27pT198 levels in response to H(2)O(2) removal in melanoma cells, associated with nuclear p27Kip1. Melanocytes also exhibited nuclear p27Kip1 and lower levels of p27pS10 and p27pT198 than melanoma cells, which showed cytoplasmic p27Kip1. We also showed that the addition of H(2)O(2) (0.1 µM) to melanoma cells arrested in G1 by serum starvation induces proliferation and increases the levels of p27pS10 and p27pT198 leading to cytoplasmic localization of p27Kip1. Nuclear localization and post-translational modifications of p27Kip1 were also demonstrated by catalase treatment of colorectal carcinoma and neuroblastoma cells, extending our findings to these other human cancer types. In conclusion, we showed in the present work that H(2)O(2) scavenging prevents nuclear exportation of p27Kip1, allowing cell cycle arrest, suggesting that cancer cells take advantage of their intrinsic pro-oxidant state to favor cytoplasmic localization of p27Kip1.

Amyloid fibrils trigger the release of neutrophil extracellular traps (NETs), causing fibril fragmentation by NET-associated elastase

The accumulation of amyloid fibrils is a feature of amyloid diseases, where cell toxicity is due to soluble oligomeric species that precede fibril formation or are formed by fibril fragmentation, but the mechanism(s) of fragmentation is still unclear. Neutrophil-derived elastase and histones were found in amyloid deposits from patients with different systemic amyloidoses. Neutrophil extracellular traps (NETs) are key players in a death mechanism in which neutrophils release DNA traps decorated with proteins such as elastase and histones to entangle pathogens. Here, we asked whether NETs are triggered by amyloid fibrils, reasoning that because proteases are present in NETs, protease digestion of amyloid may generate soluble, cytotoxic species. We show that amyloid fibrils from three different sources (α-synuclein, Sup35, and transthyretin) induced NADPH oxidase-dependent NETs in vitro from human neutrophils. Surprisingly, NET-associated elastase digested amyloid fibrils into short species that were cytotoxic for BHK-21 and HepG2 cells. In tissue sections from patients with primary amyloidosis, we also observed the co-localization of NETs with amyloid deposits as well as with oligomers, which are probably derived from elastase-induced fibril degradation (amyloidolysis). These data reveal that release of NETs, so far described to be elicited by pathogens, can also be triggered by amyloid fibrils. Moreover, the involvement of NETs in amyloidoses might be crucial for the production of toxic species derived from fibril fragmentation.

Adhesive properties and inflammatory potential of citrullinated myelin basic protein peptide 45-89

Deimination of arginyl residue of myelin basic protein (MBP) reduces cationicity of MBP and impedes the normal myelin membrane assembly. Less ordered structure of MBP is more susceptible to proteolytic attack that may lead to the release of highly immunogenic deiminated peptides into extracellular milieu. We have studied the association of peptides 45-89 derived from citrullinated MBP (C8 isomer) and phosphorylated MBP (C3 isomer) with the myelin lipids in a model membrane system using optical waveguide lightmode spectrometry. The analysis of association/dissociation kinetics to planar lipids under controlled hydrodynamic conditions has shown that MBP 45-89 peptide from citrullinated C8 isomer is less effectively adsorbed on the lipid membrane, than peptide from phosphorylated C3 isomer and packing densities for phosphorylated 45-89 MBP peptide is higher than for citrullinated forms. On the other hand, our results shown that continuous (24 h) exposure of mixed oligodendrocyte/microglial cells to peptides 45-89 from MBP-C8 induces apoptosis via mitochondrial pathway. In addition, peptides 45-89 stimulated the secretion of nitric oxide from microglial cells via induction of iNOS and decreased the level of the inhibitory protein IkB, indicating involvement of the transcription factor NF-kB in these processes. Our results suggest that some citrullinated peptides, initially released from oligodendrocytes, might activate microglia, which produces reactive nitrogen species and generates in turn fatal feedbacks that kill oligodendrocytes.

Zerovalent bismuth nanoparticles inhibit Streptococcus mutans growth and formation of biofilm

Background and methods

Despite continuous efforts, the increasing prevalence of resistance among pathogenic bacteria to common antibiotics has become one of the most significant concerns in modern medicine. Nanostructured materials are used in many fields, including biological sciences and medicine. While some bismuth derivatives has been used in medicine to treat vomiting, nausea, diarrhea, and stomach pain, the biocidal activity of zerovalent bismuth nanoparticles has not yet been studied. The objective of this investigation was to analyze the antimicrobial activity of bismuth nanoparticles against oral bacteria and their antibiofilm capabilities.

Results

Our results showed that stable colloidal bismuth nanoparticles had 69% antimicrobial activity against Streptococcus mutans growth and achieved complete inhibition of biofilm formation. These results are similar to those obtained with chlorhexidine, the most commonly used oral antiseptic agent. The minimal inhibitory concentration of bismuth nanoparticles that interfered with S. mutans growth was 0.5 mM.

Conclusion

These results suggest that zerovalent bismuth nanoparticles could be an interesting antimicrobial agent to be incorporated into an oral antiseptic preparation.

Hesperidin ameliorates immobilization-stress-induced behavioral and biochemical alterations and mitochondrial dysfunction in mice by modulating nitrergic pathway

The present study was aimed to evaluate the protective effect of hesperidin against immobilization-stress-induced alterations in biochemical, behavioral, and mitochondrial functions in mice. In many instances neuroscientists have reported that acute immobilization stress for 6 h resulted in anxiety and impaired locomotor activity due to excess oxidative-nitrergic stress, depletion of antioxidant defense mechanisms, and mitochondrial dysfunction in animals. In the present study, 6 h of acute immobilization stress had significantly altered the behavioral (anxiety and memory) and biochemical parameters coupled with mitochondrial dysfunction in Swiss albino mice. Fourteen days of pretreatment with Hesperidin (50 and 100 mg/kg, p.o.) significantly and dose-dependently inhibited the behavioral and biochemical alterations and mitochondrial dysfunction caused by acute immobilization stress. Furthermore, pre-treatment of l-arginine (50 mg/kg, i.p.), a nitric oxide precursor, reversed the protective effect of Hesperidin (50 and 100 mg/kg) (P < 0.05). In contrast, pretreatment of l-NAME (5 mg/kg, i.p.), a nitric oxide synthase inhibitor, potentiated the protective effect of Hesperidin (P < 0.05). These results suggest the possible involvement of nitrergic pathway in the protective effect Hesperidin against immobilization-stress-induced behavioral, biochemical, and mitochondrial dysfunction in mice.

Validation of a new metabolic marker to assess the vascular viability of vitrified whole sheep ovaries

BACKGROUND

Whole ovary cryopreservation has been suggested as a means to preserve fertility. In animal models, autologous cryopreserved ovary transplants frequently undergo thrombosis and a method to assess the vascular viability of cryopreserved ovaries would be valuable. We developed a staining method using methylthiazolyl blue tetrazolium (MTT, a metabolic marker) to assess the pedicle metabolism of whole ovaries vitrified using cryoprotectant called 'VS4'.

METHODS

Whole sheep ovaries were perfused with MTT (1 g/l). In one group, ovarian tissue lesions were induced by immersing the ovarian pedicle in medium at 53°C or 65°C or in liquid nitrogen prior to MTT perfusion. In the second group, several metabolic substrates (d-glucose, l-glucose and pyruvic acid) and inhibitors [2-deoxy-d-glucose for d-glucose metabolism, azide for mitochondrial respiration and diphenyleneiodonium (DPI) for NADPH oxidase (an effector of the pentose phosphate pathway)] were added to the MTT stain. The third group was subjected to VS4 ± vitrification/warming prior to MTT perfusion. Pedicle MTT staining was assessed qualitatively by histological examination of frozen sections or quantified at 564 nm after solubilization in alcohol.

RESULTS

MTT strongly and reproducibly stained the vascular smooth muscle. Heating at 53°C or 65°C or cooling in liquid nitrogen significantly diminished MTT staining by 48% (P = 0.001, n = 10), 94% (P = 0.0002, n = 10) and 94% (P = 0.0002, n = 10), respectively. MTT staining was affected by d-glucose metabolism: absence of d-glucose, substitution of unmetabolized l-glucose for d-glucose or addition of 2-deoxy-d-glucose significantly decreased MTT staining by 44% (P < 0.01, n = 10), 45% (P < 0.01, n = 10) and 29% (P < 0.01, n = 10), respectively. Pyruvic acid failed to correct the MTT staining decrease induced by d-glucose deprivation and azide did not decrease MTT staining, suggesting that MTT staining could be independent of mitochondrial metabolism. Adding DPI significantly inhibited MTT staining by 25% (P < 0.001, n = 10), suggesting involvement of the pentose phosphate pathway's effectors. Compared with controls, VS4-vitrified/warmed pedicles showed significantly less MTT staining (-30%, P < 0.005, n = 10), with unstained foci, whereas unvitrified VS4-exposed pedicles showed no difference.

CONCLUSIONS

MTT can serve as a qualitative and quantitative vascular viability marker.VS4 vitrification caused alterations in ovarian vascular metabolism. MTT staining should allow accurate comparisons of whole-organ cryoprotection protocols.

Acute toxicity evaluation, antibacterial, antioxidant and immunomodulatory effects of Melastoma malabathricum

Melastoma malabathricum (MM) is a well-known plant in Malaysian traditional medicine, locally known as senduduk. Its ethanol and aqueous extracts have been used in the present investigation to study the immunomodulatory role on human peripheral blood mononuclear cell (PBMC), and the DPPH, ABTS and FRAP free radical scavenging activities were also measured. Total flavonoids and total phenolic contents were assayed and the antibacterial effect was tested against four species of bacteria; two Gram-positive (Staphylococcus aureus and Streptococcus agalactiae) and two Gram-negative (Escherichia coli and Klebsilla pneumonia). The tests were carried out using the disc diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. Moreover, the acute toxicity was evaluated in vivo on the ethanol extract of MM to establish its safety when administered orally. In our results, both extracts of MM showed abilities to scavenge DPPH and ABTS free radicals, IC₅₀ values: (11.599 ± 0.84, 10.573 ± 0.58 µmol/L) and (62.657 ± 0.78, 63.939 ± 0.48 µmol/L) for ethanol and aqueous extracts respectively. Indeed the ethanol extract evidenced high phenolic content (384.33 ± 0.005 mg/g), flavonoids contents (85.8 ± 0.009 mg/g) and ferric reducing antioxidant power (33,590 ± 0.038 mmol/g), with high activity against S. aureus and S. agalactiae (11 ± 0.3 and 12 ± 0.6 mm inhibition zones). Likewise, the percentage of peripheral blood mononuclear cells (PBMC) viability was increased in response to MM, IC₅₀ values (1.781 ± 1.2 and 6.545 ± 0.93 µg/mL) for ethanol and aqueous extracts, respectively. In addition, our results showed that the MM extract is safe even at a high dose of 5,000 mg/kg and has no oral toxicity. These findings suggest the excellent medicinal bioactivity of MM and explain the popularity of this plant in the folk medicine as a remedy for different illnesses.

Role of LOX/COX pathways in 3-nitropropionic acid-induced Huntington's disease-like symptoms in rats: protective effect of licofelone

BACKGROUND AND PURPOSE

Huntington's disease (HD) is a progressive neurodegenerative disorder characterized by a degeneration of striatal neurons. The possible role of COX and lipoxygenase (LOX) pathways has been well-documented in the pathology of several neurodegenerative disorders including HD. Licofelone is a competitive inhibitor of COX-1- and COX-2 and 5-LOX isoenzymes. Therefore, the present study was designed to investigate possible neuroinflammatory and apoptotic mechanisms in the neuroprotective effect of licofelone against 3-nitropropionic acid (3-NP)-induced HD-like symptoms in rats.

EXPERIMENTAL APPROACH

Rats were administered 3-NP (10 mg·kg⁻¹ day⁻¹, i.p.) for 14 days. Licofelone (2.5, 5 and 10 mg·kg⁻¹, p.o.) was given once a day, 1 h before 3-NP treatment for 14 days. Body weight and behavioural parameters (locomotor and rotarod activity) were assessed on the 1st, 5th, 10th and 15th day post-3-NP administration. Malondialdehyde, nitrite concentration, endogenous antioxidant enzymes (superoxide dismutase and catalase levels), mitochondrial enzyme complexes, pro-inflammatory compounds (TNF-α, IL-6, NF-κB), PGs (PGE₂ and PGF(2α)) and caspase-3 activity were measured on day 15 in the striatum.

KEY RESULTS

Systemic 3-NP treatment significantly reduced body weight, locomotor activity, oxidative defence, mitochondrial enzyme complex activities and increased TNF-α, IL-6, caspase-3 activity, NF-κB and PGE₂ and PGF(2α) levels in the striatum. Licofelone (2.5, 5 and 10 mg·kg⁻¹) significantly attenuated the impairment in behavioural, biochemical and mitochondrial, pro-inflammatory and pro-apoptotic markers as compared with vehicle-treated group.

CONCLUSIONS AND IMPLICATIONS

The results demonstrate the involvement of pro-inflammatory compounds and the apoptotic cascade in the neuroprotective effect of licofelone against 3-NP-induced neurotoxicity.

Amyloid β1-42 oligomer inhibits myelin sheet formation in vitro

Accumulating evidence indicates that white matter degeneration contributes to the neural disconnections that underlie Alzheimer's disease pathophysiology. Although this white matter degeneration is partly attributable to axonopathy associated with neuronal degeneration, amyloid β (Aβ) protein-mediated damage to oligodendrocytes could be another mechanism. To test this hypothesis, we studied effects of soluble Aβ in oligomeric form on survival and differentiation of cells of the oligodendroglial lineage using highly purified oligodendroglial cultures from rats at different developmental stages. Aβ oligomer at 10 μM or higher reduced survival of mature oligodendrocytes, whereas oligodendroglial progenitor cells (OPCs) were relatively resistant to the Aβ oligomer-mediated cytotoxicity. Further study revealed that Aβ oligomer even at 1 μM accelerated 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) formazan exocytosis in mature oligodendrocytes, and, more significantly, inhibited myelin sheet formation after induction of in vitro differentiation of OPCs. These results imply a novel pathogenetic mechanism underlying Aβ oligomer-mediated white matter degeneration, which could impair myelin maintenance and remyelination by adult OPCs, resulting in accumulating damage to myelinating axons thereby contributing to neural disconnections.

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.

Acylated mono-, bis- and tris- cinchona-based amines containing ferrocene or organic residues: synthesis, structure and in vitro antitumor activity on selected human cancer cell lines

A series of novel functionalized mono-, bis- and tris-(S)-{[(2S,4R,8R)-8-ethyl-quinuclidin-2-yl](6-methoxyquinolin-4-yl)}methanamines including ferrocene-containing derivatives was obtained by the reaction of the precursor amine with a variety of acylation agents. Their in vitro antitumor activity was investigated against human leukemia (HL-60), human neuroblastoma (SH-SY5Y), human hepatoma (HepG2) and human breast cancer (MCF-7) cells by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)-assay and the 50% inhibitory concentration (IC₅₀) values were determined. Our data indicate that the precursor amine has no antitumor activity in vitro, but the bis-methanamines with ureido-, thioureido and amide-type linkers display attractive in vitro cytotoxicity and cytostatic effects on HL-60, HepG2, MCF-7 and SH-SY5Y cells. Besides ¹H- and ¹³C-NMR methods the structures of the new model compounds were also studied by DFT calculations.

The effect of sucrose esters on a culture model of the nasal barrier

Sucrose esters are effective solubilizers and there is an interest to use them as pharmaceutical excipients for nasal drug delivery. We have determined for the first time the non-toxic doses of laurate and myristate sucrose esters by four independent methods, and their effects on epithelial permeability using RPMI 2650 human nasal epithelial cell line. Based on real-time cell electronic sensing, MTT dye conversion and lactate dehydrogenase release methods reference surfactant Cremophor RH40 proved to be the least toxic excipient, and could be used at 5mg/mL concentration for 1h in epithelial cells without cellular damage. The non-toxic dose of Tween 80 was 1 mg/mL, while the dose of laurate and myristate sucrose esters that could be safely used on cells for 1 h was 0.1 mg/mL. Both the reference surfactants and the sucrose esters significantly enhanced the permeability of epithelial cell layers for the paracellular marker FITC-labelled 4.4 kDa dextran at 0.1 mg/mL concentration. The effects of sucrose esters on epithelial permeability were dose-dependent. These data indicate that laurate and myristate sucrose esters can be potentially used as permeability enhancers in nasal formulations to augment drug delivery to the systemic circulation.

Signaling mechanisms downstream of quinolinic acid targeting the cytoskeleton of rat striatal neurons and astrocytes

The studies of signaling mechanisms involved in the disruption of the cytoskeleton homeostasis were performed in a model of quinolinic acid (QUIN) neurotoxicity in vitro. This investigation focused on the phosphorylation level of intermediate filament (IF) subunits of astrocytes (glial fibrillary acidic protein - GFAP) and neurons (low, medium and high molecular weight neurofilament subunits - NFL, NFM and NFH, respectively). The activity of the phosphorylating system associated with the IFs was investigated in striatal slices of rat exposed to QUIN or treated simultaneously with QUIN plus glutamate receptor antagonists, calcium channel blockers or kinase inhibitors. Results showed that in astrocytes, the action of 100 μM QUIN was mainly due to increased Ca(2+) influx through NMDA and L-type voltage-dependent Ca(2+) channels (L-VDCC). In neuronal cells QUIN acted through metabotropic glutamate receptor (mGluR) activation and influx of Ca(2+) through NMDA receptors and L-VDCC, as well as Ca(2+) release from intracellular stores. These mechanisms then set off a cascade of events including activation of PKA, PKCaMII and PKC, which phosphorylate head domain sites on GFAP and NFL. Also, Cdk5 was activated downstream of mGluR5, phosphorylating the KSP repeats on NFM and NFH. mGluR1 was upstream of phospholipase C (PLC) which, in turn, produced diacylglycerol (DAG) and inositol 3,4,5 triphosphate (IP3). DAG is important to activate PKC and phosphorylate NFL, while IP(3) contributed to Ca(2+) release from internal stores promoting hyperphosphorylation of KSP repeats on the tail domain of NFM and NFH. The present study supports the concept of glutamate and Ca(2+) contribution in excitotoxic neuronal damage provoked by QUIN associated to dysfunction of the cytoskeleton homeostasis and highlights the differential signaling mechanisms elicited in striatal astrocytes and neurons.

Neuroprotective potentials of candesartan, atorvastatin and their combination against stroke induced motor dysfunction

Cerebral ischaemia is a leading cause of death and disability. The objective of the present investigation was to explore the neuroprotective potentials of candesartan and atorvastatin alone and their combination against the cerebral ischaemia induced behavioral, biochemical, and mitochondrial dysfunction. Male Wistar rats (200-220 g) were subjected to bilateral common carotid artery occlusion for 30 min followed by 24 h reperfusion. Candesartan (0.1 and 0.3 mg/kg) and atorvastatin (10 and 20 mg/kg) were pretreated for 7 days before animals were subjected to ischaemia reperfusion injury. Various behavioral tests (locomotor activity and rotarod performance), biochemical parameters (Malondialdehyde levels, nitrite concentration, superoxide dismutase and catalase activity, redox ratio, and GST) and mitochondrial enzyme (Complex I, II, III, and IV) dysfunctions were measured in cerebral cortex, striatum and hippocampus of the ischaemic brain. Seven days candesartan (0.1 and 0.3 mg/kg) or atorvastatin (10 and 20 mg/kg) pretreatment significantly attenuated neurobehavioral alterations, oxidative damage and restored mitochondrial enzyme dysfunction as compared to control (I/R) group. Further, combined treatment of candesartan (0.1 mg/kg) and atorvastatin (10 mg/kg) significantly potentiated their protective effect which was significant as compared to their effect alone. Present study suggests the protective effect of candesartan and atorvastatin and their combination against ischaemia reperfusion induced behavioral and biochemical alterations in rats.

Nonfibrillar Abeta 1-42 inhibits glutamate uptake and phosphorylates p38 in human fibroblasts

Alzheimer disease (AD) is the most prevalent neurodegenerative disease, characterized by an increased deposition of β-amyloid (Abeta) within the central nervous system, leading to neuronal death. The availability of effective models, in which confirming novel pathogenic hypotheses and developing therapeutic targets, represents a very important goal for the field of AD. Fibroblasts from these patients may be relevant models in which addressing these issues, as they display biochemical alterations mirroring SNC ones. In this work, fibroblasts obtained from controls were studied after exposure to nonfibrillar Abeta 1-42, showing decreased glutamate uptake, similar to that observed in AD cells, in absence of transporters modifications. Nonfibrillar Abeta 1-42 was able to induce in control cells mitochondrial alterations and p38-phosphorylation, mirroring similar alterations found in AD fibroblasts. Under our experimental conditions, this treatment induced neither apoptosis nor necrosis. To investigate a putative role of p38-modulation in mediating nonfibrillar Abeta 1-42 toxicity, fibroblasts from controls were pretreated with retinoic-acid, and SB203580, a p38-inhibitor. These pretreatments prevented both p38-phosphorylation and glutamate uptake inhibition. Our results suggest that nonfibrillar Abeta 1-42 downregulates glutamate transporters activity interfering with p38-activation and mitochondrial stress. Thus, modulating complex kinase signaling pathway might represent a future therapeutic target in AD.

Altered glutamate receptor function in the cerebellum of the Ppt1-/- mouse, a murine model of infantile neuronal ceroid lipofuscinosis

The neuronal ceroid lipofuscinoses (NCLs) are a family of devastating pediatric neurodegenerative disorders and currently represent the most common form of pediatric-onset neurodegeneration. Infantile NCL (INCL), the most aggressive of these disorders, is caused by mutations in the CLN1 gene that encodes the enzyme palmitoyl protein thioesterase 1 (PPT1). Previous studies have suggested that glutamatergic neurotransmission may be disrupted in INCL, so the present study investigates glutamate receptor function in the Ppt1(-/-) mouse model of INCL by comparing the sensitivity of cultured wild-type (WT) and Ppt1(-/-) cerebellar granule cells to glutamate receptor-mediated toxicity. Ppt1(-/-) neurons were significantly less sensitive to AMPA receptor-mediated toxicity but markedly more vulnerable to NMDA receptor-mediated cell death. Because glutamate receptor function is regulated primarily by the surface expression level of the receptor, the surface level of AMPA and NMDA receptor subunits in the cerebella of WT and Ppt1(-/-) mice was also examined. Western blotting of surface cross-linked cerebellar samples showed a significantly lower surface level of the GluR4 AMPA receptor subunit in Ppt1(-/-) mice, providing a plausible explanation for the decreased vulnerability of Ppt1(-/-) cerebellar neurons to AMPA receptor-mediated cell death. The surface expression of the NR1, NR2A, and NR2B NMDA receptor subunits was similar in the cerebella of WT and Ppt1(-/-) mice, indicating that there is another mechanism behind the increased sensitivity of Ppt1(-/-) cerebellar granule cells to NMDA toxicity. Our results indicate an AMPA receptor hypofunction and NMDA receptor hyperfunction phenotype in Ppt1(-/-) neurons and provide new therapeutic targets for INCL.

Engineering nanosilver as an antibacterial, biosensor and bioimaging material

The capacity of nanosilver (Ag nanoparticles) to destroy infectious micro-organisms makes it one of the most powerful antimicrobial agents, an attractive feature against "super-bugs" resistant to antibiotics. Furthermore, its plasmonic properties facilitate its employment as a biosensor or bioimaging agent. Here, the interaction of nanosilver with biological systems including bacteria and mammalian cells is reviewed. The toxicity of nanosilver is discussed focusing on Ag⁺ ion release in liquid solutions. Biomedical applications of nanosilver are also presented capitalizing on its antimicrobial and plasmonic properties and summarizing its advantages, limitations and challenges. Though a lot needs to be learned about the toxicity of nanosilver, enough is known to safely use it in a spectrum of applications with minimal impact to the environment and human health.

Novel protective mechanisms of antidepressants against 3-nitropropionic acid induced Huntington's-like symptoms: a comparative study

Huntington's disease (HD) is characterized by progressive degeneration of neurons in the striatum, cortex and other parts of the brain, causing motor and cognitive dysfunction. 3-Nitropropionic acid (3-NP) is a well-known mycotoxin that significantly induces motor dysfunction in animals. Studies suggested the involvement of oxidative stress and nitric oxide mechanisms in HD pathogenesis. Clinical reports have also indicated the neuroprotective potential of antidepressants. Therefore, the present study has been designed to elucidate and compare the mechanistic role of different antidepressants (sertraline, venlafaxine, imipramine and trazodone) and their interaction with nitric oxide modulators if any, against 3-NP-induced neurotoxicity. Systemic 3-NP (10 mg/kg) administration for 14 days significantly reduced locomotor activity, body weight, motor coordination, oxidative defense and impaired mitochondrial complex enzyme activities in the striatum. Sertraline, venlafaxine, imipramine and trazodone treatments significantly improved behavioral, oxidative defense and mitochondrial complex enzyme activities as compared with the 3-NP-treated group. Systemic L-arginine (50 mg/kg) pretreatment with sub-effective dose of sertraline (10 mg/kg), venlafaxine (10 mg/kg), imipramine (10 mg/kg) and trazodone (10 mg/kg) for 14 days significantly attenuated their protective effect. Similarly, L-nitro-arginine methyl ester (L-NAME) (10 mg/kg) pretreatment with sub-effective dose of sertraline (10 mg/kg), venlafaxine (10 mg/kg), imipramine (10 mg/kg) and trazodone (10 mg/kg) for 14 days significantly potentiated their protective effects which were significant as compared with their effect alone, respectively. The results of the present study suggest that a nitric oxide mechanism might be involved in their protective effect against 3-NP-induced neurotoxicity.

Regulation and function of the two-pore-domain (K2P) potassium channel Trek-1 in alveolar epithelial cells

Hyperoxia can lead to a myriad of deleterious effects in the lung including epithelial damage and diffuse inflammation. The specific mechanisms by which hyperoxia promotes these pathological changes are not completely understood. Activation of ion channels has been proposed as one of the mechanisms required for cell activation and mediator secretion. The two-pore-domain K(+) channel (K2P) Trek-1 has recently been described in lung epithelial cells, but its function remains elusive. In this study we hypothesized that hyperoxia affects expression of Trek-1 in alveolar epithelial cells and that Trek-1 is involved in regulation of cell proliferation and cytokine secretion. We found gene expression of several K2P channels in mouse alveolar epithelial cells (MLE-12), and expression of Trek-1 was significantly downregulated in cultured cells and lungs of mice exposed to hyperoxia. Similarly, proliferation cell nuclear antigen (PCNA) and Cyclin D1 expression were downregulated by exposure to hyperoxia. We developed an MLE-12 cell line deficient in Trek-1 expression using shRNA and found that Trek-1 deficiency resulted in increased cell proliferation and upregulation of PCNA but not Cyclin D1. Furthermore, IL-6 and regulated on activation normal T-expressed and presumably secreted (RANTES) secretion was decreased in Trek-1-deficient cells, whereas release of monocyte chemoattractant protein-1 was increased. Release of KC/IL-8 was not affected by Trek-1 deficiency. Overall, deficiency of Trek-1 had a more pronounced effect on mediator secretion than exposure to hyperoxia. This is the first report suggesting that the K(+) channel Trek-1 could be involved in regulation of alveolar epithelial cell proliferation and cytokine secretion, but a direct association with hyperoxia-induced changes in Trek-1 levels remains elusive.

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.

Translating promising preclinical neuroprotective therapies to human stroke trials

Stroke is the third leading cause of mortality and carries the greatest socioeconomic burden of disease in North America. Despite several promising therapies discovered in the preclinical setting, there have been no positive results in human stroke clinical trials to date. In this article, we review the potential causes for failure and discuss strategies that have been proposed to overcome the barrier to translation of stroke therapies. To improve the chance of success in future human stroke trials, we propose that therapies be tested in stroke models that closely resemble the human condition with molecular, imaging and functional outcomes that relate to outcomes utilized in clinical trials. These strategies include higher-order, old-world, nonhuman primate models of stroke with clinically relevant outcome measures. Although stroke neuroprotection has been looked upon pessimistically given the many failures in clinical trials to date, we propose that neuroprotection in humans is feasible and will be realized with rigorous translational science.

Minocycline exerts uncoupling and inhibiting effects on mitochondrial respiration through adenine nucleotide translocase inhibition

The present study was aimed to provide a better understanding of the mitochondria-targeted actions of minocycline (MC), a second-generation tetracycline which has cytoprotective effects. Although the specific mechanisms underlying its activity remained elusive, considerable amounts of data indicated mitochondria as the primary pharmacological target of MC. Previous reports have shown that MC affects the oxygen-uptake rate by isolated mitochondria in different respiratory states. Here, we report on the effect of MC, in the range 50-200μM, on mitochondrial respiration. State 3 respiration titration with carboxyatractyloside revealed that MC inhibits the adenine nucleotide translocase. Furthermore, we analyze MC channel-forming capacity in the lipid membrane bilayer. Our results confirmed the crucial role of Δψ and showed a dependence on Ca(2+) for MC to have an effect on mitochondria. Our data also indicated that outer and inner mitochondrial membranes contribute differently to this effect, involving the presence of Δψ (the inner membrane) and VDAC (the outer membrane). Data from three isosmotic media indicate that MC does not increase the permeability of the inner membrane to protons or potassium. In addition, by using mitoplasts and ruthenium red, we showed that Ca(2+) uptake is not involved in the MC effect, suggesting involvement of VDAC in the MC interaction with the outer membrane. Our data contribute to unravel the mechanisms behind the mitochondria-targeted activity of the cytoprotective drug MC.

Comparative sensitivity of tumor and non-tumor cell lines as a reliable approach for in vitro cytotoxicity screening of lysine-based surfactants with potential pharmaceutical applications

Surfactants are used as additives in topical pharmaceuticals and drug delivery systems. The biocompatibility of amino acid-based surfactants makes them highly suitable for use in these fields, but tests are needed to evaluate their potential toxicity. Here we addressed the sensitivity of tumor (HeLa, MCF-7) and non-tumor (3T3, 3T6, HaCaT, NCTC 2544) cell lines to the toxic effects of lysine-based surfactants by means of two in vitro endpoints (MTT and NRU). This comparative assay may serve as a reliable approach for predictive toxicity screening of chemicals prior to pharmaceutical applications. After 24-h of cell exposure to surfactants, differing toxic responses were observed. NCTC 2544 and 3T6 cell lines were the most sensitive, while both tumor cells and 3T3 fibroblasts were more resistant to the cytotoxic effects of surfactants. IC(50)-values revealed that cytotoxicity was detected earlier by MTT assay than by NRU assay, regardless of the compound or cell line. The overall results showed that surfactants with organic counterions were less cytotoxic than those with inorganic counterions. Our findings highlight the relevance of the correct choice and combination of cell lines and bioassays in toxicity studies for a safe and reliable screen of chemicals with potential interest in pharmaceutical industry.