Depletion of cellular glutathione by conditions used for the passaging of adherent cultured cells

Bioactivity and antibacterial effects of zinc-containing bioactive glass on the surface of zirconia abutments

OBJECTIVES

This study aimed to enhance gingival fibroblast function and to achieve antibacterial activity around the implant abutment by using a zinc (Zn)-containing bioactive glass (BG) coating.

METHODS

45S5 BG containing 0, 5, and 10 wt.% Zn were coated on zirconia disks. The release of silica and Zn ions in physiological saline and their antibacterial effects were measured. The effects of BG coatings on human gingival fibroblasts (hGFs) were assessed using cytotoxicity assays and by analyzing the gene expression of various genes related to antioxidant enzymes, wound healing, and fibrosis.

RESULTS

BG coatings are capable of continuous degradation and simultaneous ion release. The antibacterial effect of BG coatings increased with the addition of Zn, while the cytotoxicity remained unchanged compared to the group without coatings. BG coating enhances the expression of angiogenesis genes, while the Zn-containing BG enhances the expression of antioxidant genes at an early time point. BG coating enhances the expression of collagen genes at later time points.

CONCLUSIONS

The antibacterial effect of BG improved with the increase in Zn concentration, without inducing cytotoxicity. BG coating enhances the expression of angiogenesis genes, and Zn-containing BG enhances the expression of antioxidant genes at an early time point. BG coating enhances the expression of collagen genes at later time points.

CLINICAL SIGNIFICANCE

Adding 10 wt% Zn to BG could enhance the environment around implant abutments by providing antibacterial, antioxidant, and anti-fibrotic effects, having potential for clinical use.

Modulation of hydrogel stiffness by external stimuli: soft materials for mechanotransduction studies

Mechanotransduction is an important process in determining cell survival, proliferation, migration and differentiation. The extracellular matrix (ECM) is the component of natural tissue that provides structural support and biochemical signals to adhering cells. The ECM is dynamic and undergoes physical and biochemical changes in response to various stimuli and there is an interest in understanding the effect of dynamic changes in stiffness on cell behaviour and fate. Therefore, stimuli-responsive hydrogels have been developed to mimic the cells' microenvironment in a controlled fashion. Herein, we review strategies for dynamic modulation of stiffness using various stimuli, such as light, temperature and pH. Special emphasis is placed on conducting polymer (CP) hydrogels and their fabrication procedures. We believe that the redox properties of CPs and hydrogels' biological properties make CPs hydrogels a promising substrate to investigate the effect of dynamic stiffness changes and mechanical actuation on cell fate in future studies.

Primary cultures of aspiration residual specimens predict outcomes of hepatocellular carcinoma patients receiving curative treatment

The utility of primary culture originated from the residual aspiration specimens to predict outcomes of hepatocellular carcinoma patients receiving curative treatment was investigated. A total of 105 American Joint Committee on Cancer TNM stage I or II patients were included. The culture results were determined at the 28th of culture and were divided into rapid proliferation of cancer cells alone, rapid proliferation of both cancer cells and cancer-associated fibroblasts, rapid proliferation of cancer-associated fibroblasts alone, slow proliferation, and no outgrowth of plating specimens. Our results showed that outgrowths of cultured cells from plated particles were achieved in 98.1% of patients. Sixty-nine patients (65.7%) showed rapid proliferation of cultured cells (11 rapid proliferation of cancer cells alone, 17 rapid proliferation of both cancer cells and cancer-associated fibroblasts, and 41 rapid proliferation of cancer-associated fibroblasts alone). There was no significant difference in the incidence of recurrence or survival between patients with normal and abnormal serum alpha-fetoprotein levels, chronic hepatitis B and chronic hepatitis C, TNM stage I and stage II, histological high-grade and low-grade hepatocellular carcinoma, and between patients treated by operative resection and local abrasion. Only patients with rapid proliferation of cancer cells ± rapid proliferation of cancer-associated fibroblasts showed significantly higher incidence of recurrence than patients with other growth types (P = .0482), but there was no significant difference in survival between two groups. In conclusion, primary culture using this method is clinically feasible and can be applied to predict recurrence of hepatocellular carcinoma patients receiving curative treatment.

STAT1 regulates macrophage number and phenotype and prevents renal fibrosis after ischemia-reperfusion injury

Renal ischemia-reperfusion injury (IRI) leads to acute kidney injury or delayed allograft function, which predisposes to fibrosis in the native kidney or kidney transplant. Here we investigated the role of the signal transducer and activator of transcription 1 (STAT1) in inflammatory responses following renal IRI. Our study showed that a subsequent stimulation of Janus-activated kinase 2/STAT1 and Toll-like receptor 4 pathways led to greater STAT1 activation followed by increased cytokine transcription compared with single-pathway stimulation in murine renal tubular cells. Moreover, we observed increased activation of STAT1 under hypoxic conditions. In vivo, STAT1^-/- mice displayed less acute tubular necrosis and decreased macrophage infiltration 24 h after renal ischemia. However, investigation of the healing phase (30 days after IRI) revealed significantly more fibrosis in STAT1^-/- than in wild-type kidneys. In addition, we demonstrated increased macrophage infiltration in STAT1^-/- kidneys. Flow cytometry analysis revealed that STAT1 deficiency drives an alternatively activated macrophage phenotype, which is associated with downregulated cluster of differentiation 80 expression, decreased intracellular reactive oxygen species production, and enhanced ability for phagocytosis. Furthermore, we detected immunohistochemically enhanced STAT1 expression in human renal allograft biopsies with no interstitial fibrosis/tubular atrophy (IF/TA) compared with specimens with severe IF/TA without specific etiology. Thus, STAT1 activation drives macrophages toward an alternatively activated phenotype and enhances fibrogenesis indicating a potential STAT1-driven protective mechanism in tissue repair after ischemic injury.

Antioxidative biointerface: biocompatible materials scavenging reactive oxygen species

Oxidative stress caused by reactive oxygen species (ROS) occurs as events in which living tissues contact certain materials. These events include cell cultures and implantation of materials. Because of the high reactivity of ROS, they damage cells by oxidizing DNA, lipids, and proteins. Conversely, ROS also act as signaling molecules regulating cellular morphology. In particular, mitochondrial ROS are involved in the regulation of cellular physiology, including differentiation, autophagy, metabolic adaptation, apoptosis, and immunity. The balance between generation and elimination of ROS is essential for signaling pathways and proper cell function, and redox imbalance leads to cellular dysfunction and disturbs cellular homeostasis. To reduce oxidative stress, versatile antioxidants, including natural compounds, have been used; however, their poor bioavailability and pro-oxidant effects have limited the versatility of these antioxidants. Recent developments of antioxidative biointerfaces may represent a potent solution to this issue. Designed biointerfaces composed of polymer antioxidants eliminate excessive ROS at the interface between living tissues and materials, and do not disturb regulated redox balance inside cells, thus eliminating unexpected cell responses, such as inflammation and dysfunction.

Design of antioxidative biointerface for separation of hematopoietic stem cells with high maintenance of undifferentiated phenotype

During cell cultivation, excessively generated reactive oxygen species (ROS) affect cellular properties and functions. Although cell cultivation media contain several types of low-molecular-weight antioxidants, these small antioxidants are internalized into the mitochondria and they disrupt regulated redox balance. Here, we developed a novel biointerface that effectively eliminates ROS on a cell culture surface. Poly(ethylene glycol)-b-poly[4-(2,2,6,6-tetramethylpiperidine-1-oxyl)aminomethylstyrene] (PEG-b-PMNT) was synthesized and covalently coated on a carboxyl group-activated culture dish using sec-amino groups on a PMNT segment followed by immobilization of anti-CD34 antibodies. CD34-positive hematopoietic stem progenitor cells (HSPCs) were separated from mice fetal liver cells using our polymer-coated cell culture dish. The separated HSPCs possessed intact mitochondrial membrane potential compared with those in the conventional cell cultivation system. In addition, the expression level of CD34 was maintained for an extended period on our culture dish with the antioxidative biointerface. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2080-2085, 2016.

Evaluation of non-surgical therapy on glutathione levels in chronic periodontitis

Objective:

To compare the levels of glutathione (GSH), both oxidized and reduced forms in patients with and without chronic periodontitis in gingival crevicular fluid (GCF).

Materials and Methods:

Twenty GCF samples from maxillary quadrants were collected using capillary micropipettes from the chronic periodontitis patients (test group) at baseline before treatment, at 1-month, 3 months, and 6 months after scaling and root planing and samples from 20 patients without chronic periodontitis (control group) from maxillary quadrants were also collected. GSH, oxidized glutathione (GSSG) levels and GSH: GSSG ratios were determined using the spectrophotometric method.

Statistical Analysis:

Results were concluded for the test over control groups using paired Student's t-test.

Results:

Lower concentrations of GSH (P < 0.001) and GSSG (P < 0.001) were detected in GCF in patients with chronic periodontitis (test group) than patients without chronic periodontitis (control group) at baseline. Treatment had a significant effect in improving the GSH and reducing GSSG levels postscaling and root planing at 1-month and 3 months but not significant effect at 6 months. Scaling and root planing increased the GSH: GSSG ratio (P < 0.001) in the test group as compared to the control group (P < 0.001).

Conclusions:

The concentrations of GSH within GCF are reduced in chronic periodontitis patients. Scaling and root planing (nonsurgical therapy) restores GSH concentration in GCF post 1-month and 3 months along with redox balance (GSH: GSSG ratio), but at 6 months the balance is not maintained. Adjunctive use of micronutritional supplements to boost antioxidant concentration in tissues by preserving GSH or by elevating its level at the inflamed sites is recommended, as nonsurgical periodontal therapy alone is not able to maintain redox balance for longer duration.

A thermoresponsive, micro-roughened cell culture surface

Surface topography has been shown to play a major role in cell behavior, but has yet to be seriously exploited in the field of cell surface engineering. In the present work, surface roughness has been used in combination with the thermoresponsive polymer polyisopropylacrylamide (PIPAAm) to generate cell sheets with tailored biochemical properties. Micro-roughened polystyrene (PS) with 1.5-5.5 μm features was derivatized with PIPAAm to form a cell culture surface for the growth of human fibroblast cell sheets that exhibit a modified cytoskeleton and extracellular matrix. Fibroblasts cell sheets cultured on the rough surfaces had fewer actin stress fibers and twice the average fibronectin (FN) fibril formation when compared to cell sheets on flat substrates. The cell sheets harvested from the roughened PS were collected after only 2 days of culture and detached from the PIPAAm grafted surface in <1h after cooling the culture system. The simple and rapid method for generating cell sheets with increased FN fibril formation has applications in tissue grafts or wound repair and has demonstrated that the thermoresponsive surface can be used for reliable cell sheet formation.

Clinical utility of a simple primary culture method in hepatocellular carcinoma patients

BACKGROUND AND AIM

The clinical utility of our designed primary culture method in patients with hepatocellular carcinoma was investigated.

METHODS

Specimens obtained from ultrasound-guided fine-needle aspiration of 108 hepatocellular carcinoma patients were cultured. The associations of the cellular proliferative speeds with cancer invasiveness and 1-year survivals were analyzed.

RESULTS

Successful cultures were achieved in 105 patients (97.2%). Ten hepatocellular carcinoma and nine cancer-associated fibroblast cell lines were established. The cells obtained from patients with American Joint Committee on Cancer TNM staging ≥ IIIB upon entering the study had higher proportion of rapidly proliferative cancer cells than those from patients with staging ≤ IIIA (P < 0.005). For Barcelona Clinic Liver Cancer classification A or B patients receiving palliative transcatheter chemoembolization, patients with rapidly proliferative cancer-associated fibroblasts showed higher incidence of cancer-related death than patients with other proliferative patterns (P = 0.0385). The influence of the presence of rapidly proliferative cancer cells on survivals in this group could not be calculated due to a very small number of this kind of patients (9.5%). For Barcelona Clinic Liver Cancer classification C patients receiving non-curative treatment, the incidence of rapidly proliferative cancer cells was 45.2%. Patients with rapidly proliferative cancer cells showed higher incidence of cancer-related death than patients with other proliferative patterns in patients receiving chemoembolization (P = 0.0452) and in patients receiving conservative treatment (P = 0.0206).

CONCLUSION

Our method can provide cells from individual patient for researches and predict outcomes in patients receiving non-curative treatment of hepatocellular carcinoma.

Parylene mobile microplates integrated with an enzymatic release for handling of single adherent cells

An approach for manipulating single adherent cells is developed that is integrated with an enzymatic batch release. This strategy uses an array of releasable microfabricated mobile substrates, termed microplates, formed from a biocompatible polymer, parylene. A parylene microplate array of 10-70 μm in diameter can be formed on an alginate hydrogel sacrificial layer by using a standard photolithographic process. The parylene surfaces are modified with fibronectin to enhance cell attachment, growth, and stretching. To load single cells onto these microplates, cells are initially placed in suspension at an optimized seeding density and are allowed to settle, stretch, and grow on individual microplates. The sacrificial layer underneath the microplate array can be dissolved on a time-scale of several seconds without cytotoxicity. This system allows the inspection of selected single adherent cells. The ability to assess single cells while maintaining their adhesive properties will broaden the examination of a variety of attributes, such as cell shape and cytoskeletal properties.

Thermally reversible colloidal gels for three-dimensional chondrocyte culture

Healthy cells are required in large numbers to form a tissue-engineered construct and primary cells must therefore be increased in number in a process termed 'expansion'. There are significant problems with existing procedures, including cell injury and an associated loss of phenotype, but three-dimensional culture has been reported to offer a solution. Reversible gels, which allow for the recovery of cells after expansion would therefore have great value in the expansion of chondrocytes for tissue engineering applications, but they have received relatively little attention to date. In this study, we examined the synthesis and use of thermoresponsive polymers that form reversible three-dimensional gels for chondrocyte cell culture. A series of polymers comprising N-isopropylacrylamide (NIPAM) and styrene was synthesized before studying their thermoresponsive solution behaviour and gelation. A poly(NIPAM-co-styrene-graft-N-vinylpyrrolidone) variant was also synthesized in order to provide increased water content. Both random- and graft-copolymers formed particulate gels above the lower critical solution temperature and, on cooling, re-dissolved to allow enzyme-free cell recovery. Chondrocytes remained viable in all of these materials for 24 days, increased in number and produced collagen type II and glycosaminoglycans.

Thiols stabilize cobblestone morphology of cultured mesothelial cells

Cellular thiols including GSH (glutathione) and L-Cys (L-cysteine) are essential for cell signalling, growth and differentiation. L-Cys is derived from the extracellular thiol pool and is the rate-limiting compound for intracellular GSH biosynthesis. The present study investigated the effect of thiol-supplemented medium on cell growth, phenotype and total GSH of cultured hPMCs (human peritoneal mesothelial cells). Cells were cultured in medium M199 supplemented with 2% serum, with 'plus' or without 'minus' L-Cys and compared with medium supplemented with either β-ME (β-mercaptoethanol) (0.25 mmol/l) or the receptor tyrosine kinase ligand EGF (epidermal growth factor, 100 ng/ml). β-ME produced a disproportionate increase in total GSH compared with L-Cys and other thiols tested [(procysteine (2-oxothiazolidine-4-carboxylic acid) or NAC (N-acetyl-L-cysteine)], while growth and morphology were identical. Cell behaviour of primary hPMCs is characterized by the transition of fibroblastoid to cobblestone morphology during early passage. L-Cys and β-ME promoted a rapid MET (mesenchymal-to-epithelial transition) within 3 days of culture, confirmed by the presence of cobblestone cells, intact organelles, abundant microvilli, primary cilia and cortical actin. In contrast, EGF produced a biphasic response consisting of delayed growth and retention of a fibroblastoid morphology. During a rapid log phase of growth, MET was accompanied by rapid catch-up growth. Thiols may stabilize the epithelial phenotype by engaging redox-sensitive receptors and transcription factors that modulate differentiation. These data may benefit researchers working on thiol-mediated cell differentiation and strategies to regenerate damage to serosal membranes.

Derivation, characterization and expansion of fetal chondrocytes on different microcarriers

Fetal chondrocytes (FCs) have recently been identified as an alternative cell source for cartilage tissue engineering applications because of their partially chondrogenically differentiated phenotype and developmental plasticity. In this study, chondrocytes derived from fetal bovine cartilage were characterized and then cultured on commercially available Cytodex-1 and Biosilon microcarriers and thermosensitive poly(hydroxyethylmethacrylate)-poly(N-isopropylacrylamide) (PHEMA-PNIPAAm) beads produced by us. Growth kinetics of FCs were estimated by means of specific growth rate and metabolic activity assay. Cell detachment from thermosensitive microcarriers was induced by cold treatment at 4 °C for 20 min or enzymatic treatment was applied for the detachment of cells from Cytodex-1 and Biosilon. Although attachment efficiency and proliferation of FCs on PHEMA-PNIPAAm beads were lower than that of commercial Cytodex-1 and Biosilon microcarriers, these beads also supported growth of FCs. Detached cells from thermosensitive beads by cold induction exhibited a normal proliferative activity. Our results indicated that Cytodex-1 microcarrier was the most suitable material for the production of FCs in high capacity, however, 'thermosensitive microcarrier model' could be considered as an attractive solution to the process scale up for cartilage tissue engineering by improving surface characteristics of PHEMA-PNIPAAm beads.

Thermally responsive polymeric hydrogel brushes: synthesis, physical properties and use for the culture of chondrocytes

Hydrogel brushes are materials composed of a water-swollen network, which contains polymer chains that are grafted with another polymer. Using a thermally responsive polymer, poly(N-isopropyl acrylamide) (polyNIPAM), as the graft component we are able to maintain the critical solution temperature (Tcrit), independent of the overall composition of the material, at approximately 32 degrees C. The change in swelling at Tcrit is a function of the amount of polyNIPAM in the system. However, there is a much smaller change in the surface contact angles at Tcrit. PolyNIPAM-based materials have generated considerable interest, as 'smart' substrates for the culture of cells and here, we show the utility of hydrogel brushes in cell culture. Chondrocytes attached to the hydrogel brushes and yielded viable cell cultures. Moreover, the chondrocytes could be released from the hydrogel brushes without the use of proteases by reducing the temperature of the cultures to below Tcrit to induce a change in the conformation of the polyNIPAM chain at Tcrit. The importance of the crosslink hydrogel component is illustrated by significant changes in cell attachment/cell viability as the crosslink density is changed.

Discordant influence of amphotericin B on epirubicin cytotoxicity in primary hepatic malignant cells collected by a new primary culture technique

BACKGROUND

The purpose of this prospective study was to investigate whether amphotericin B (AmB) had any potential role in the systemic chemotherapy of primary hepatic malignancy using cancer cells collected by the authors' method of primary culture.

METHODS

The specimens obtained by ultrasound-guided fine-needle aspiration biopsy (22 G) from 15 patients with hepatocellular carcinoma (HCC) and one with cholangiocarcinoma were plated into culture flask without disaggregation by trypsin-ethylenediamine tetra-acetic acid solution. Six patients with HCC and one patient with cholangiocarcinoma (7/16, 44%) had successful culture and the cancer cells at the 4th passage were continuously exposed to therapeutic ranges of epirubicin (0, 0.5, 1.0, 1.5, 2.0 microg/mL) with or without the combination of 2.5 microg/mL AmB for 24 h. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was applied to evaluate the effects of the drugs. A human HCC cell line (HA 22T/VGH) was studied for comparison.

RESULTS

Addition of AmB showed no influence on epirubicin cytotoxicity in two patients (one partial resistant HCC and one epirubicin-sensitive cholangiocarcinoma; 25%), augmentation of the epirubicin cytotoxicity in two patients (one total resistant HCC, partial resistant HA 22T/VGH cell line and one epirubicin-sensitive HCC; 37.5%), and decrease of epirubicin cytotoxicity in the remaining three (one partial resistant and two epirubicin-sensitive HCC; 37.5%).

CONCLUSIONS

Amphotericin B has a discordant influence on epirubicin cytotoxicity in primary cultured hepatic malignant cells. Application of AmB in the systemic chemotherapy of primary hepatic malignancy should be limited to patients with positive AmB effect evaluated by an in vitro sensitivity test such as the present method.

From cells to ageing: a review of models and mechanisms of cellular senescence and their impact on human ageing

Given the duration of ageing in humans, cell culture studies are a promising approach to the study of human ageing. It is reasonable to assume that human ageing has, at least partly, a cellular origin. The question is how we can replicate in vitro the age-related changes that occur in human cells in vivo. In this review, widely used models for studying ageing in cell culture, such as Hayflick's, are interpreted in the context of the human ageing process. The mechanisms behind cellular senescence such as telomere disruption and DNA damage are reviewed and their relation to human ageing debated. A system-level examination of these mechanisms suggests that cell culture models are useful for studying cancer and certain age-related pathologies. There is little evidence, however, that cellular senescence is a significant factor in human ageing or that the mechanisms responsible for in vitro cellular senescence are a causative factor in human ageing in vivo. Therefore, novel approaches for studying human ageing at a cellular level are necessary and some suggestions are put forward.

HL-1 myocytes exhibit PKC and K ATP channel-dependent delta opioid preconditioning 1,2 1This was presented at the annual meeting of the Association for Academic Surgery, Boston, MA, November 7–9, 2002. 2The present study was supported by a grant from the National Institutes of Health-NHLBI, HL58781

BACKGROUND

Opioid preconditioning protects the myocardium against ischemia/reperfusion (IR) injury. By enhancing cardiomyocyte viability, opioids can enhance cardiac function and recovery from IR injury during acute cardiac care. The myocyte model HL-1 is an immortalized, mouse atrial cell line that expresses functional delta-opioid receptors. The HL-1 myocyte may be useful for IR injury research exploring opioid cardioprotection.

MATERIALS AND METHODS

In study I, microplates of HL-1 were subjected to 10 min pre-treatment with either basal media, delta-opioid agonist DADLE(10uM), or DADLE(10uM) + delta-antagonist naltrindole (10uM). Study II treatment groups included PKC inhibitor chelerythrine (2uM), K(ATP) channel closer glybenclamide (100uM), or mitochondrial K(ATP) channel opener diazoxide (100uM) administered in various combinations followed by DADLE (10uM) or control. Microplates were subjected to normal oxygen/substrate conditions or ischemic (<1% 0(2)) and substrate deficient (10 uM 2-Deoxyglucose versus 10 mM glucose) conditions, then reperfused with normal oxygen and glucose-containing media. Microplate supernatants were subjected to lactate dehydrogenase (LDH) assay.

RESULTS

Compared to untreated control, the LDH assay showed significant reduction in opioid-only pretreated groups at all time points. These effects were attenuated with delta-opioid antagonist co-administration. Co-administration of non-selective K(ATP) channel closer glybenclamide and DADLE abolished DADLE cytoprotection, while selective mitochondrial K(ATP) opener diazoxide mimicked DADLE cytoprotection Co-administration of chelerythrine and DADLE significantly reduced chelerythrine cytotoxicity.

CONCLUSION

Delta-opioid preconditioning of HL-1 myocytes significantly decreased necrosis from in vitro simulated ischemia/reperfusion as measured by LDH release; this effect was reversed by delta-antagonist naltrindole. Cytoprotection was PKC and K(ATP) channel-dependent. HL-1 myocytes exhibit opioid-induced cytoprotection from IR injury, and present a novel model of pharmacologic preconditioning.

Oxidative stress in cell culture: an under-appreciated problem?

Cell culture studies have given much valuable information about mechanisms of metabolism and signal transduction and of regulation of gene expression, proliferation, senescence, and death. However, cells in culture may behave differently from cells in vivo in many ways. One of these is that cell culture imposes a state of oxidative stress on cells. I argue that cells that survive and grow in culture might use ROS-dependent signal transduction pathways that rarely or never operate in vivo. A further problem is that cell culture media can catalyse the oxidation of compounds added to them, resulting in apparent cellular effects that are in fact due to oxidation products such as ROS. Such artefacts may have affected many studies on the effects of ascorbate, thiols, flavonoids and other polyphenolic compounds on cells in culture.

Release of cytochrome c and activation of pro-caspase-9 following lysosomal photodamage involves Bid cleavage

Photodynamic therapy (PDT) protocols employing lysosomal sensitizers induce apoptosis via a mechanism that causes cytochrome c release prior to loss of mitochondrial membrane potential (DeltaPsi(m)). The current study was designed to determine how lysosomal photodamage initiates mitochondrial-mediated apoptosis in murine hepatoma 1c1c7 cells. Fluorescence microscopy demonstrated that the photosensitizer N-aspartyl chlorin e6 (NPe6) localized to the lysosomes. Irradiation of cultures preloaded with NPe6 induced the rapid destruction of lysosomes, and subsequent cleavage/activation of Bid, pro-caspases-9 and -3. Pro-caspase-8 was not activated. Release of cytochrome c occurred at about the time of Bid cleavage and preceded the loss of DeltaPsi(m). Extracts of purified lysosomes catalyzed the in vitro cleavage of cytosolic Bid, but not pro-caspase-3 activation. Pharmacological inhibition of cathepsin B, L and D activities did not suppress Bid cleavage or pro-caspases-9 and -3 activation. These studies demonstrate that photodamaged lysosomes trigger the mitochondrial apoptotic pathway by releasing proteases that activate Bid.

Effect of diquat on the antioxidant system and cell growth in human neuroblastoma cells

Oxidative stress elicits an adaptive antioxidant response, which varies with tissue type. Diquat, a potent redox cycler that generates reactive oxygen species, has been used to study oxidative stress; however, its effect on the antioxidant system has not been characterized in neuronal cells. Accordingly, we measured antioxidant parameters and cell growth in human neuroblastoma SH-SY5Y cells cultured for 48 h in medium containing 5, 10, or 25 microM diquat dibromide or phosphate-buffered saline. Viable cells were assayed for glutathione (GSH) and activities of catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), glutathione peroxidase (GPX), and glucose-6-phosphate dehydrogenase (GPDH). Mitochondrial function was evaluated by glutamate dehydrogenase (GDH) activity and MTT reduction. Diquat caused a marked concentration-related decrease in viable cell count ( by 26, 51, and 87% at 5, 10, and 25 microM diquat). Cell viability was only affected at 10 and 25 microM diquat and did not fully account for the decreased viable cell count. Concentration-related increases also occurred with GSH levels and a majority of antioxidant enzymes activities; however, the mode and magnitude varied with parameter. Increases in GSH, CAT, SOD, and GR were maximal at 25 microM diquat (to 3-, 6-, 2-, and 1.5-fold control values, respectively). GPDH activity was maximal at 10 microM diquat and then decreased to 86% of control activity at 25 microM diquat. GPX activity showed a concentration-related decrease (to 35% of control). Activity of the mitochondrial enzyme GDH increased 3-fold at 25 microM diquat, along with a lesser increase in MTT reduction. We conclude that diquat reduces cell growth in neuroblastoma cells and induces an adaptive antioxidant response, which are concentration dependent and occur at sublethal concentrations. At higher concentrations, diquat alters mitochondrial function and becomes increasingly toxic.