Regulation of intrinsic prion protein by growth factors and TNF-alpha: the role of intracellular reactive oxygen species

Antiinflammatory effect of the ethanolic extract of Korean native herb Potentilla rugulosa Nakai in Bisphenol-a-stimulated A549 cells

Potentilla rugulosa Nakai (P. rugulosa) is a perennial herb in the Rosaceae family and found in the Korean mountains. Previously, our findings demonstrated that P. rugulosa contains numerous polyphenols and flavonoids exhibiting important antioxidant and anti-obesity bioactivities. Bisphenol A (BPA) is a xenoestrogen that was shown to produce pulmonary inflammation in humans. However, the mechanisms underlying BPA-induced inflammation remain to be determined. The aim of this study was to examine whether ethanolic extract of P. rugulosa exerted an inhibitory effect on BPA-induced inflammation utilizing an adenocarcinoma human alveolar basal epithelial cell line A549. The P. rugulosa extract inhibited BPA-mediated cytotoxicity by reducing levels of reactive oxygen species (ROS). Further, P. rugulosa extract suppressed the upregulation of various pro-inflammatory mediators induced by activation of the nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways. In addition, inhibition of the NF-κB and MAPK signaling pathways by P. rugulosa extract was found to occur via decrease in the transcriptional activity of NF-κB. Further, blockade of phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and stress-activated protein kinase/Jun N-terminal kinase (SAPK/JNK) was noted. Thus, our findings suggest that the ethanolic extract of P. rugulosa may act as a natural anti-inflammatory therapeutic agent.

Effects of clopidogrel bisulfate on B16-F10 cells and tumor development in a murine model of melanoma

Metastatic melanoma is a very aggressive skin cancer. Platelets are constituents of the tumor microenvironment and, when activated, contribute to cancer progression, especially metastasis and inflammation. P2Y12 is an adenosine diphosphate receptor that triggers platelet activation. Inhibition of P2Y12 by clopidogrel bisulfate (CB) decreases platelet activation, which is also controlled by the extracellular concentration and the metabolism of purines by purinergic enzymes. We evaluated the effects of CB on the viability and proliferation of cultured B16-F10 cells. We also used a metastatic melanoma model with C57BL-6 mice to evaluate cancer development and purine metabolism modulation in platelets. B16-F10 cells were administered intraperitoneally to the mice. Two days later, the animals underwent a 12-day treatment with CB (30 mg/kg by gavage). We have found that CB reduced cell viability and proliferation in B16-F10 culture in 72 h at concentrations above 30 µm. In vivo, CB decreased tumor nodule counts and lactate dehydrogenase levels and increased platelet purine metabolism. Our results showed that CB has significant effects on melanoma progression.

Evaluation of cytotoxicity, reactive oxygen species and nitrous oxide of nanochitosan from shrimp shell

This work aims to synthesize, characterize and evaluate the biological activity of nanochitosan (NQ) prepared from shrimp, showing an innovative character and correlating with sustainable development, in promoting an alternative to the solid waste (shrimp) shell and a biological application of the novel nanomaterial. The NQ synthesis was carried out by the alkaline deacetylation process of chitin obtained of the demineralization, deproteinization and deodorization steps from shrimp shells. NQ was characterized by X-ray Powder Diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), N₂ porosimetry (BET/BJH methods), zeta potential (ZP) and zero charge point (pH_ZCP). To evaluate the safety profile was carried out the cytotoxicity, DCFHA and NO tests in 293T and HaCat cell lines. Regarding the cell viability, NQ did not show toxicity for the tested cell lines. In the evaluation of the ROS production and NO tests, there was no increase in the levels of free radicals and between the negative control, respectively. Therefore, NQ does not present cytotoxicity in the cell lines tested (10, 30, 100 and 300 μg mL^-1), proposing new perspectives on the use of NQ as a potential nanomaterial for biomedical applications.

Insights of ethyl acetate fraction from Vassobia breviflora in multidrug-resistant bacteria and cancer cells: from biological to therapeutic

Cancer and infectious diseases are among the leading causes of death in the world. Despite the diverse array of treatments available, challenges posed by resistance, side effects, high costs, and inaccessibility persist. In the Solanaceae plant family, few studies with Vassobia breviflora species relating to biological activity are known, but promising results have emerged. The phytochemicals present in the ethyl acetate fraction were obtained using ESI-MS-QTOF, and the antioxidants assays 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) radical capture (ABTS), plasma ferric reduction capacity (FRAP), and total antioxidant capacity (TAC). Cytotoxic activity was evaluated by MTT, Neutral Red, and lactate dehydrogenase (LDH) released. The production of reactive oxygen species, nitric oxide, and purinergic enzymes was also investigated. Antibacterial activity was measured through minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and antibiofilm activity, in addition to genotoxicity in plasmid DNA. Five major masses were identified D-glucopyranose II, allyl disulfide, γ-lactones, pharbilignoside, and one mass was not identified. V. breviflora exhibited relevant antioxidant and cytotoxic activity against the HeLa cell line and enhanced expression effect in modulation of purinergic signaling. Antibacterial activities in the assays in 7 ATCC strains and 8 multidrug-resistant clinical isolates were found. V. breviflora blocked biofilm formation in producing bacteria at the highest concentrations tested. However, there was no plasmid DNA cleavage at the concentrations tested. Data demonstrated that V. breviflora exhibited an antioxidant effect through several methods and proved to be a promising therapeutic alternative for use against tumor cells via purinergic signaling and multidrug-resistant microorganisms, presenting an anti-biofilm effect.

Cytotoxic screening and antibacterial activity of Withaferin A

Cancer and bacterial infections are among the leading causes of death worldwide. Plant-derived bioactive compounds constitute promising alternatives for development of new therapeutics. This study aimed at evaluating the biological activity of Withaferin A using 6 tumor cell lines: A549 (lung cancer), U87MG (glioblastoma), SH-SY5Y (neuroblastoma), B16-F10 (mouse melanoma), HeLa (uterine colon cancer) and K562 (chronic myeloid leukemia). In addition, 17 other standard bacterial strains and several multidrug resistant bacteria (MDR) clinical isolates were examined. Cell viability was assessed using the following assays: MTT, neutral red, and dsDNA PicoGreen®. Further, oxidative stress was measured by quantification of reactive oxygen species (ROS) production. The activity against bacteria was determined by the minimum inhibitory concentration (MIC), minimum bacterial concentration (CBM) and antibiofilm activity in the production of strains. Withaferin A was effective, as evidenced by its cytotoxic activity in tumor cell lines, enhanced ROS production in tumor cells and bactericidal and antibiofilm activity. Data demonstrated that Withaferin A may be therapeutically considered as an antitumor and antibacterial agent.

Green Nanoarchitectonics of Silver Nanoparticles for Antimicrobial Activity Against Resistant Pathogens

Antimicrobial resistance represents a serious concern to public health, being responsible for hospital infections, affecting mainly immunosuppressed patients. Thus, nanotechnology appears as an alternative to solve this problem, through the application of metallic nanoparticles with antimicrobial activity. The present work aims to synthesize and characterize AgNPs from Klebsiella pneumoniae (AgNPs-KP) and Aloe vera extract (AgNPs-AV), evaluating the antimicrobial activity against Klebsiella pneumoniae carbapenemase (KpC) and the cytotoxicity in the L929 cell line. AgNPs were prepared by the biosynthetic method using Klebsiella pneumoniae and were characterized by XRD, FTIR and SEM–EDS. Antimicrobial activity was tested using the MIC and MBC. The cytotoxicity was evaluated by the MTT method and neutral red. The production of ROS and nitrogen RNS tests were performed in the L929 cell line. Thus, it was possible to confirm the production of AgNPs-KP, through morphological, structural and elemental analysis. AgNPs from Klebsiella pneumoniae had potent antimicrobial activity in low concentration against antimicrobial resistant pathogens with MIC 9.76 µg mL⁻¹ and MBC 9.06 µg mL⁻¹. Moreover, AgNPs-KP in concentrations of 10, 30 and 100 µg mL⁻¹ did not show cytotoxic properties for the L929 fibroblast, where only the cytotoxic effect was observed in high concentrations (300 µg mL⁻¹). AgNPs-KP did not produce ROS about the analyzed concentrations and RNS production was only in the highest concentration of 3000 µg mL⁻¹. Therefore, AgNPs biosynthesized by Klebsiella pneumoniae have potential medical applicability as a promising antimicrobial agent, using a simple and low-cost method, correlating nanomedicine as nanostructured materials.

Synthesis and evaluation of multi-target-directed ligands with BACE-1 inhibitory and Nrf2 agonist activities as potential agents against Alzheimer's disease

Cumulative evidence suggests that β-amyloid and oxidative stress are closely related with each other and play key roles in the process of Alzheimer's disease (AD). Multitarget regulation of both pathways might represent a promising therapeutic strategy. Here, a series of selenium-containing compounds based on ebselen and verubecestat were designed and synthesized. Biological evaluation showed that 13f exhibited good BACE-1 inhibitory activity (IC₅₀ = 1.06 μΜ) and potent GPx-like activity (ν₀ = 183.0 μM min^-1). Aβ production experiment indicated that 13f could reduce the secretion of Aβ1-40 in HEK APPswe 293T cells. Moreover, 13f exerted a cytoprotective effect against the H₂O₂ or 6-OHDA caused cell damage via alleviation of intracellular ROS, mitochondrial dysfunction, Ca²⁺ overload and cell apoptosis. The mechanism studies indicated that 13f exhibited cytoprotective effect by activating the Keap1-Nrf2-ARE pathway and stimulating downstream anti-oxidant protein including HO-1, NQO1, TrxR1, GCLC, and GCLM. In addition, 13f significantly reduced the production of NO and IL-6 induced by LPS in BV2 cells, which confirmed its anti-inflammatory activity as a Nrf2 activator. The BBB permeation assay predicted that 13f was able to cross the BBB. In summary, 13f might be a promising multi-target-directed ligand for the treatment of AD.

In vitro cytotoxicity of co-exposure to superparamagnetic iron oxide and solid lipid nanoparticles

Increased production and use of different types of nanoparticles (NPs) in the last decades has led to increased environmental release of these NPs with potential detrimental effects on both the environment and public health. Information is scarce in the literature on the cytotoxic effect of co-exposure to many NPs as this concern is relatively recent. Thus, in this study, we hypothesized scenarios of cell's co-exposure to two kinds of NPs, solid lipid nanoparticles (SLNs) and superparamagnetic iron oxide nanoparticles (SPIONs), to assess the potential cytotoxicity of exposure to NPs combination. Cytotoxicity of SPIONs, SLNs, and their 1:1 mixture (MIX) in six tumor and six non-tumor cell lines was investigated. The mechanisms underlining the induced cytotoxicity were studied through cell cycle analysis, detection of reactive oxygen species (ROS), and alterations in mitochondrial membrane potential (ΔΨM). Double staining with acridine orange and ethidium bromide was also used to confirm cell morphology alterations. The results showed that SPIONs induced low cytotoxicity compared to SLNs. However, the mixture of SPIONs and SLNs showed synergistic, antagonistic, and additive effects based on distinct tests such as viability assay, ROS generation, ΔΨM, and DNA damage, depending on the cell line. Apoptosis triggered by ROS and disturbances in ΔΨM are the most probable related mechanisms of action. As was postulated, there is possible cytotoxic interaction between the two kinds of NPs.

Involvement of the Prion Protein in the Protection of the Human Bronchial Epithelial Barrier Against Oxidative Stress

Aim: Bronchial epithelium acts as a defensive barrier against inhaled pollutants and microorganisms. This barrier is often compromised in inflammatory airway diseases that are characterized by excessive oxidative stress responses, leading to bronchial epithelial shedding, barrier failure, and increased bronchial epithelium permeability. Among proteins expressed in the junctional barrier and participating to the regulation of the response to oxidative and to environmental stresses is the cellular prion protein (PrP^C). However, the role of PrP^C is still unknown in the bronchial epithelium. Herein, we investigated the cellular mechanisms by which PrP^C protein participates into the junctional complexes formation, regulation, and oxidative protection in human bronchial epithelium. Results: Both PrP^C messenger RNA and mature protein were expressed in human epithelial bronchial cells. PrP^C was localized in the apical domain and became lateral, at high degree of cell polarization, where it colocalized and interacted with adherens (E-cadherin/γ-catenin) and desmosomal (desmoglein/desmoplakin) junctional proteins. No interaction was detected with tight junction proteins. Disruption of such interactions induced the loss of the epithelial barrier. Moreover, we demonstrated that PrP^C protection against copper-associated oxidative stress was involved in multiple processes, including the stability of adherens and desmosomal junctional proteins. Innovation: PrP^C is a pivotal protein in the protection against oxidative stress that is associated with the degradation of adherens and desmosomal junctional proteins. Conclusion: Altogether, these results demonstrate that the loss of the integrity of the epithelial barrier by oxidative stress is attenuated by the activation of PrP^C expression, where deregulation might be associated with respiratory diseases.

Inflammatory mediators reduce surface PrPc on human BMVEC resulting in decreased barrier integrity

The cellular prion protein (PrP^c) is a surface adhesion molecule expressed at junctions of various cell types including brain microvascular endothelial cells (BMVEC) that are important components of the blood-brain barrier (BBB). PrP^c is involved in several physiological processes including regulation of epithelial cell barrier function and monocyte migration across BMVEC. BBB dysfunction and disruption are significant events in central nervous system (CNS) inflammatory processes including HIV neuropathogenesis. Tumor necrosis factor (TNF)-α and vascular endothelial growth factor (VEGF) are two inflammatory factors that have been implicated in the processes that affect BBB integrity. To examine the effect of inflammation on PrP^c expression in BMVEC, we used these mediators and found that TNF-α and VEGF decrease surface PrP^c on primary human BMVEC. We also showed that these factors decrease total PrP^c protein as well as mRNA, indicating that they regulate expression of this protein by de novo synthesis. To determine the effect of PrP^c loss from the surface of BMVEC on barrier integrity, we used small hairpin RNAs to knockdown PrP^c. We found that the absence of PrP^c from BMVEC causes increased permeability as determined by a fluorescein isothiocyanate (FITC)-dextran permeability assay. This suggests that cell surface PrP^c is essential for endothelial monolayer integrity. To determine the mechanism by which PrP^c downregulation leads to increased permeability of an endothelial monolayer, we examined changes in expression and localization of tight junction proteins, occludin and claudin-5, and found that decreased PrP^c leads to decreased total and membrane-associated occludin and claudin-5. We propose that an additional mechanism by which inflammatory factors affect endothelial monolayer permeability is by decreasing cell-associated PrP^c. This increase in permeability may have subsequent consequences that lead to CNS damage.

Solid lipid nanoparticles improve octyl gallate antimetastatic activity and ameliorate its renal and hepatic toxic effects

Metastasis is the main cause of cancer-related death and requires the development of effective treatments with reduced toxicity and effective anticancer activity. Gallic acid derivatives have shown significant biological properties including antitumoral activity as shown in a previous study with octyl gallate (G8) in vitro. Thus, the aim of this work was to evaluate the antimetastatic effect of free and solid lipid nanoparticle-loaded G8 in mice in a lung metastasis model. Animals inoculated with melanoma cells presented metastasis in lungs, which was significantly inhibited by treatment with G8 and solid lipid nanoparticle-loaded G8, named G8-NVM. However, G8-treated mice showed an increase in several toxicological parameters, which were almost completely circumvented by G8-NVM treatment. This study supports the need for pharmacological studies on new potential medicinal plants to treat cancer and can provide new perspectives on using nanotechnology to improve biological activities while decreasing the chemotherapy toxicological effects of anticancer drugs.

Role of hypoxia‑mediated cellular prion protein functional change in stem cells and potential application in angiogenesis (Review)

Cellular prion protein (PrP^C) can replace other pivotal molecules due to its interaction with several partners in performing a variety of important biological functions that may differ between embryonic and mature stem cells. Recent studies have revealed major advances in elucidating the putative role of PrP^C in the regulation of stem cells and its application in stem cell therapy. What is special about PrP^C is that its expression may be regulated by hypoxia-inducible factor (HIF)-1α, which is the transcriptional factor of cellular response to hypoxia. Hypoxic conditions have been known to drive cellular responses that can enhance cell survival, differentiation and angiogenesis through adaptive processes. Our group recently reported hypoxia-enhanced vascular repair of endothelial colony-forming cells on ischemic injury. Hypoxia-induced AKT/signal transducer and activator of transcription 3 phosphorylation eventually increases neovasculogenesis. In stem cell biology, hypoxia promotes the expression of growth factors. According to other studies, aspects of tissue regeneration and cell function are influenced by hypoxia, which serves an essential role in stem cell HIF-1α signaling. All these data suggest the possibility that hypoxia-mediated PrP^C serves an important role in angiogenesis. Therefore, the present review summarizes the characteristics of PrP^C, which is produced by HIF-1α in hypoxia, as it relates to angiogenesis.

Morphine Withdrawal Modifies Prion Protein Expression in Rat Hippocampus

The hippocampus is a vulnerable brain structure susceptible to damage during aging and chronic stress. Repeated exposure to opioids may alter the brain so that it functions normally when the drugs are present, thus, a prolonged withdrawal might lead to homeostatic changes headed for the restoration of the physiological state. Abuse of morphine may lead to Reacting Oxygen Species-induced neurodegeneration and apoptosis. It has been proposed that during morphine withdrawal, stress responses might be responsible, at least in part, for long-term changes of hippocampal plasticity. Since prion protein is involved in both, Reacting Oxygen Species mediated stress responses and synaptic plasticity, in this work we investigate the effect of opiate withdrawal in rats after morphine treatment. We hypothesize that stressful stimuli induced by opiate withdrawal, and the subsequent long-term homeostatic changes in hippocampal plasticity, might modulate the Prion protein expression. Our results indicate that abstinence from the opiate induced a time-dependent and region-specific modification in Prion protein content, indeed during morphine withdrawal a selective unbalance of hippocampal Prion Protein is observable. Moreover, Prion protein overexpression in hippocampal tissue seems to generate a dimeric structure of Prion protein and α-cleavage at the hydrophobic domain. Stress factors or toxic insults can induce cytosolic dimerization of Prion Protein through the hydrophobic domain, which in turn, it stimulates the α-cleavage and the production of neuroprotective Prion protein fragments. We speculate that this might be the mechanism by which stressful stimuli induced by opiate withdrawal and the subsequent long-term homeostatic changes in hippocampal plasticity, modulate the expression and the dynamics of Prion protein.

Oxidative stress in primiparous cows in relation to dietary starch and the progress of lactation

Oxidative stress may be important in early lactation cows due to high metabolic demands. Modifying dietary starch may alter glucose utilization, modify oxidative metabolism and, consequently, increase oxidative stress. To test this hypothesis, early lactation primiparous cows underwent a short-term dietary starch restriction followed by realimentation. At calving, 10 Friesian primiparous cows were randomly assigned to two groups and given a basal starch diet (BSD, 249 g/kg of starch dry matter (DM)) in the form of a total mixed ration until 42 days in milk (DIM). Afterwards, five cows (CTR) continued to receive the same diet and five cows (EXP) were allotted to experimental diets: low starch diet (LSD, 210 g/kg starch DM) from 43 to 65 DIM followed by high starch diet (HSD, 283 g/kg starch DM) from 66 to 85 DIM and BSD from 86 to 94 DIM. Blood samples were collected at 37, 50, 60, 70, 80, and 94 DIM to measure total plasma glutathione (GSH), thiobarbituric acid reactive substances (TBARS), and erythrocyte glutathione peroxidase (GPx) activity as indicators of oxidative stress, N-acetyl-ß-D glucosaminidase (NAGase), lysosyme, and white blood cell counts as indicators of immune response. Metabolic adaptations were evaluated by glucose, non-esterified fatty acids (NEFA), beta-hydroxy-butyrate (BOHB), insulin, and GH concentrations, and the acid/base balance. Milk yield was not significantly different between groups throughout the experiment and was correlated with TBARS (r 0·284; P 0·05) and GSH (r = 0·294; P 0·05). Estimated energy intake was significantly higher in the EXP group at 70 DIM only (P 0·05). Plasma glucose was significantly lower in the EXP group at 50, 60 (P 0·001) and 80 DIM (P 0·05), and was correlated with GSH (r = 0·348; P 0·01) and TBARS (r = 0·367; P 0·01). Plasma NEFA decreased overall in both groups (P 0·01). EXP was lower than CTR in concentrations of plasma BOHB at 70 DIM (P 0·05) and plasma insulin at 60 (P 0·001), 80 and 94 (P 0·05) DIM. Plasma TBARS, GSH and GPx increased throughout (P 0·01) in both groups. This was delayed in the EXP group following introduction of LSD; significant differences between groups at 60 (P 0·01), 80 and 95 (P 0·05) DIM for TBARS, and at 70 (P 0·01) and 80 (P 0·05) DIM for GPx. Indicators of immune response and plasma bicarbonates did not differ between groups. Blood pH was significantly lower in the EXP group at 80 and 94 DIM (P 0·001). Blood pCO2 was significantly lower at 80 and 94 DIM (P 0·05) in the CTR group. While recovering from the negative energy balance, cellular metabolism probably shifted towards oxidative phosphorylation, with a consequent oxidative stress increase. LSD delayed this recovery in the EXP group and thus reduced GSH synthesis. In conclusion, the diet starch content may alter the control of oxidative stress and expose animals to oxidative injuries.

Neuroprotective Effects Against POCD by Photobiomodulation: Evidence from Assembly/Disassembly of the Cytoskeleton

Postoperative cognitive dysfunction (POCD) is a decline in memory following anaesthesia and surgery in elderly patients. While often reversible, it consumes medical resources, compromises patient well-being, and possibly accelerates progression into Alzheimer's disease. Anesthetics have been implicated in POCD, as has neuroinflammation, as indicated by cytokine inflammatory markers. Photobiomodulation (PBM) is an effective treatment for a number of conditions, including inflammation. PBM also has a direct effect on microtubule disassembly in neurons with the formation of small, reversible varicosities, which cause neural blockade and alleviation of pain symptoms. This mimics endogenously formed varicosities that are neuroprotective against damage, toxins, and the formation of larger, destructive varicosities and focal swellings. It is proposed that PBM may be effective as a preconditioning treatment against POCD; similar to the PBM treatment, protective and abscopal effects that have been demonstrated in experimental models of macular degeneration, neurological, and cardiac conditions.

Cytokine profiles and the role of cellular prion protein in patients with vascular dementia and vascular encephalopathy

Understanding inflammatory mechanisms in vascular dementia (VD) is pivotal for achieving better insights into changes in brain metabolism. We performed cytokine profiling and measured levels of the cellular prion protein (PrP(C)) in serum and cerebrospinal fluid (CSF) samples from patients with VD and with vascular encephalopathy (VE). Significant changes were observed for interleukin (IL)-1β, IL-4, IL-5, tumor necrosis factor alpha, interferon gamma, granulocyte-colony stimulating factor, monocyte chemotactic protein 1, and macrophage inflammatory protein 1 beta in serum and for IL-6 and granulocyte macrophage colony-stimulating factor in CSF of VD and VE patients, suggesting that most of immune markers depend on vascular lesions, while only IL-6 was related to dementia. In VD patients, the severity of dementia as defined by the Mini-Mental Status Test or Cambridge Cognitive Examination battery test was significantly correlated with the levels of IL-8 (CSF) and macrophage inflammatory protein 1 beta (serum and CSF). Additionally, in CSF of VD patients, our data revealed a correlation between immune and neurodegenerative marker proteins. Both indicate an association of neuroinflammation and cognitive decline. Levels of PrP(C) were regulated differentially in VD and VE patients compared with Alzheimer's disease patients and controls. Moreover, we observed a significant negative correlation between cytokine levels and PrP(C) in VD patients in CSF and serum, as well as a correlation between PrP(C) expression with levels of neurodegenerative marker proteins in CSF (in VD and VE patients). Our data suggest that immunological modifiers play a role in VD and VE patients and provide evidence for an association of PrP(C) with immune and neurodegenerative markers.

Relationships between cobalamin, epidermal growth factor, and normal prions in the myelin maintenance of central nervous system

Cobalamin (Cbl), epidermal growth factor (EGF), and prions (PrPs) are key molecules for myelin maintenance in the central and peripheral nervous systems. Cbl and EGF increase normal prion (PrP(C)) synthesis and PrP(C) levels in rat spinal cord (SC) and elsewhere. Cbl deficiency increases PrP(C) levels in rat SC and cerebrospinal fluid (CSF), and decreases PrP(C)-mRNA levels in rat SC. The administration of anti-octapeptide repeat PrP(C) region antibodies (Abs) to Cbl-deficient (Cbl-D) rats prevents SC myelin lesions and a local increase in tumor necrosis factor (TNF)-α levels, whereas anti-TNF-α Abs prevent SC myelin lesions and the increase in SC and CSF PrP(C) levels. As it is known that both Cbl and EGF regulate SC PrP(C) synthesis independently, and that Cbl regulates SC EGF synthesis, EGF may play both Cbl-independent and Cbl-dependent roles. When Cbl-D rats undergo Cbl replacement therapy, SC PrP(C) levels are similar to those observed in Cbl-D rats. In rat frontal cortex (which is marginally affected by Cbl deficiency in histological terms), Cbl deficiency decreases PrP(C) levels and the increase induced by Cbl replacement leads to their normalization. Increased nerve PrP(C) levels are detected in the myelin lesions of the peripheral neuropathy of Cbl-D rats, and CSF PrP(C) levels are also increased in Cbl-D patients (but not in patients with Cbl-unrelated neurological diseases). Various common steps in the downstream signaling pathway of Cbl, EGF, and PrP(C) underlines the close relationship between the three molecules in keeping myelin normal.

Amyloid-β and proinflammatory cytokines utilize a prion protein-dependent pathway to activate NADPH oxidase and induce cofilin-actin rods in hippocampal neurons

Neurites of neurons under acute or chronic stress form bundles of filaments (rods) containing 1∶1 cofilin∶actin, which impair transport and synaptic function. Rods contain disulfide cross-linked cofilin and are induced by treatments resulting in oxidative stress. Rods form rapidly (5-30 min) in >80% of cultured hippocampal or cortical neurons treated with excitotoxic levels of glutamate or energy depleted (hypoxia/ischemia or mitochondrial inhibitors). In contrast, slow rod formation (50% of maximum response in ∼6 h) occurs in a subpopulation (∼20%) of hippocampal neurons upon exposure to soluble human amyloid-β dimer/trimer (Aβd/t) at subnanomolar concentrations. Here we show that proinflammatory cytokines (TNFα, IL-1β, IL-6) also induce rods at the same rate and within the same neuronal population as Aβd/t. Neurons from prion (PrP(C))-null mice form rods in response to glutamate or antimycin A, but not in response to proinflammatory cytokines or Aβd/t. Two pathways inducing rod formation were confirmed by demonstrating that NADPH-oxidase (NOX) activity is required for prion-dependent rod formation, but not for rods induced by glutamate or energy depletion. Surprisingly, overexpression of PrP(C) is by itself sufficient to induce rods in over 40% of hippocampal neurons through the NOX-dependent pathway. Persistence of PrP(C)-dependent rods requires the continuous activity of NOX. Removing inducers or inhibiting NOX activity in cells containing PrP(C)-dependent rods causes rod disappearance with a half-life of about 36 min. Cofilin-actin rods provide a mechanism for synapse loss bridging the amyloid and cytokine hypotheses for Alzheimer disease, and may explain how functionally diverse Aβ-binding membrane proteins induce synaptic dysfunction.

Electronic waste leachate-mediated DNA fragmentation and cell death by apoptosis in mouse fibroblast (NIH/3T3) cell line

This study investigated the apoptotic effect of electronic waste on fibroblast cell line. Cells were treated with different concentrations of the leachate for 24h. Cell viability was detected by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test, nuclear morphology of cells was explored by acridine orange (AO)/ethidium bromide (EB) double staining, mitochondrial membrane potential was evaluated using JC-1 probe while cell cycle analysis was conducted using flow cytometry. The oxidative status was detected using DCFH-DA (dichlorofluorescin diacetate) probe and the relationship between cell death and ROS (reactive oxygen species) was investigated using N-acetylcysteine. Results showed an increased cell death as detected by MTT assay and AO/EB staining. Cell cycle analysis indicated an induction of sub/G1 events while JC-1 probe showed significant disruption of mitochondrial membrane potential. There was significant induction of ROS, while N-acetylcysteine protected the cells from DNA damage. These suggest apoptotic pathway as a possible mechanism of e-waste induced cyto-genotoxicity.

Cobalamin and normal prions: a new horizon for cobalamin neurotrophism

It is known that cobalamin (Cbl) deficiency damages myelin by increasing tumor necrosis factor (TNF)-α and decreasing epidermal growth factor (EGF) levels in rat central nervous system (CNS), and affects the peripheral nervous system (PNS) morphologically and functionally. It is also known that some polyneuropathies not due to Cbl deficiency are connected with increased TNF-α levels, and that various cytokines (including TNF-α) and growth factors regulate the in vitro synthesis of normal prions (PrP(C)s). Given that there is extensive evidence that PrP(C)s play a key role in the maintenance of CNS and PNS myelin, we investigated whether the PrP(C) octapeptide repeat (OR) region is involved in the pathogenesis of rat Cbl-deficient (Cbl-D) polyneuropathy. After intracerebroventricularly administering antibodies (Abs) against the OR region (OR-Abs) to Cbl-D rats to prevent myelin damage and maximum nerve conduction velocity (MNCV) abnormalities, and PrP(C)s to otherwise normal rats to reproduce PNS Cbl-D-like lesions, we measured PrP(C) levels and MNCV of the sciatic and tibial nerves. PrP(C) and TNF-α levels were increased in sciatic and tibial nerves of Cbl-D and saline-treated rats, and the OR-Abs normalized the myelin ultrastructure, TNF-α levels, and MNCV values of the sciatic and tibial nerves of Cbl-D rats. The same peripheral nerves of the otherwise normal PrP(C)-treated rats showed typical Cbl-D myelin lesions, significantly increased TNF-α levels, and significantly decreased MNCV values. These findings demonstrate that Cbl deficiency induces excess PrP(C)s and thereby excess OR regions, which seem to be responsible for the PNS myelin damage, as has recently been found in the case of CNS myelin damage [66]. Furthermore, excess TNF-α is also involved in the pathogenesis of Cbl-D polyneuropathy. In conclusion, we have extended the list of prion diseases by adding one caused by excess PrP(C)s and the polyneuropathies related to excess TNF-α.

Neuroimmunoendocrine regulation of the prion protein in neutrophils

The prion protein (PrP(C)) is a cell surface protein expressed mainly in the nervous system. In addition to the role of its abnormal conformer in transmissible spongiform encephalopathies, normal PrP(C) may be implicated in other degenerative conditions often associated with inflammation. PrP(C) is also present in cells of hematopoietic origin, including T cells, dendritic cells, and macrophages, and it has been shown to modulate their functions. Here, we investigated the impact of inflammation and stress on the expression and function of PrP(C) in neutrophils, a cell type critically involved in both acute and chronic inflammation. We found that systemic injection of LPS induced transcription and translation of PrP(C) in mouse neutrophils. Up-regulation of PrP(C) was dependent on the serum content of TGF-β and glucocorticoids (GC), which, in turn, are contingent on the activation of the hypothalamic-pituitary-adrenal axis in response to systemic inflammation. GC and TGF-β, either alone or in combination, directly up-regulated PrP(C) in neutrophils, and accordingly, the blockade of GC receptors in vivo curtailed the LPS-induced increase in the content of PrP(C). Moreover, GC also mediated up-regulation of PrP(C) in neutrophils following noninflammatory restraint stress. Finally, neutrophils with up-regulated PrP(C) presented enhanced peroxide-dependent cytotoxicity to endothelial cells. The data demonstrate a novel interplay of the nervous, endocrine, and immune systems upon both the expression and function of PrP(C) in neutrophils, which may have a broad impact upon the physiology and pathology of various organs and systems.

In vitro biocompatibility of solid lipid nanoparticles

This study was undertaken to address the current deficient knowledge of cellular response to solid lipid nanoparticles (SLNs) exposure. We investigated the cytotoxicity of several SLNs formulations in two fibroblast cell lineages, Vero and MDCK. Several methods were used to explore the mechanisms involved in this cytotoxic process, including cell viability assays, flow cytometry and ROS generation assessment. Among nanoparticles tested, two of them (F4 and F5) demonstrated more cytotoxic effects in both cell lineages. The cell viability assays suggested that F4 and F5 interfere in cell mitochondrial metabolism and in lysosomal activity. In addition, F5 decreased the percentage of MDCK cells in G0/G1 and G2/M phases, with a marked increase in the Sub/G1 population, suggesting DNA fragmentation. Regarding F4, although IC(50) was higher (~700 μg/mL), this formulation affected mitochondrial membrane potential for Vero cells. However, the IC(50) of F5 was around 250 μg/mL, suggesting the effect of SDS (sodium dodecyl sulfate) present in the formulation. In summary, the nanoparticles tested here appears to be biocompatible, with the exception of F5. Further studies are required to elucidate the in vivo effects of these nanoscale structures, in order to evaluate or predict the connotation of their increased and widespread use.

In vivo manganese exposure modulates Erk, Akt and Darpp-32 in the striatum of developing rats, and impairs their motor function

Manganese (Mn) is an essential metal for development and metabolism. However, exposures to high Mn levels may be toxic, especially to the central nervous system (CNS). Neurotoxicity is commonly due to occupational or environmental exposures leading to Mn accumulation in the basal ganglia and a Parkinsonian-like disorder. Younger individuals are more susceptible to Mn toxicity. Moreover, early exposure may represent a risk factor for the development of neurodegenerative diseases later in life. The present study was undertaken to investigate the developmental neurotoxicity in an in vivo model of immature rats exposed to Mn (5, 10 and 20 mg/kg; i.p.) from postnatal day 8 (PN8) to PN12. Neurochemical analysis was carried out on PN14. We focused on striatal alterations in intracellular signaling pathways, oxidative stress and cell death. Moreover, motor alterations as a result of early Mn exposure (PN8-12) were evaluated later in life at 3-, 4- and 5-weeks-of-age. Mn altered in a dose-dependent manner the activity of key cell signaling elements. Specifically, Mn increased the phosphorylation of DARPP-32-Thr-34, ERK1/2 and AKT. Additionally, Mn increased reactive oxygen species (ROS) production and caspase activity, and altered mitochondrial respiratory chain complexes I and II activities. Mn (10 and 20 mg/kg) also impaired motor coordination in the 3^rd, 4^th and 5^th week of life. Trolox™, an antioxidant, reversed several of the Mn altered parameters, including the increased ROS production and ERK1/2 phosphorylation. However, Trolox™ failed to reverse the Mn (20 mg/kg)-induced increase in AKT phosphorylation and motor deficits. Additionally, Mn (20 mg/kg) decreased the distance, speed and grooming frequency in an open field test; Trolox™ blocked only the decrease of grooming frequency. Taken together, these results establish that short-term exposure to Mn during a specific developmental window (PN8-12) induces metabolic and neurochemical alterations in the striatum that may modulate later-life behavioral changes. Furthermore, some of the molecular and behavioral events, which are perturbed by early Mn exposure are not directly related to the production of oxidative stress.

Prion protein: From physiology to cancer biology

Prion protein (PrPc) was originally viewed solely as being involved in prion disease, but now several intriguing lines of evidence have emerged indicating that it plays a fundamental role not only in the nervous system, but also throughout the human body. PrPc is expressed most abundantly in the brain, but has also been detected in other non-neuronal tissues as diverse as lymphoid cells, lung, heart, kidney, gastrointestinal tract, muscle, and mammary glands. Recent data indicate that PrPc may be implicated in biology of glioblastoma, breast cancer, prostate and gastric cancer. Over expression of PrPc is correlated to the acquisition by tumor cells of a phenotype for resistance to cell death induced by TNF alpha and TRAIL or antitumor drugs such as paclitaxel and anthracyclines. PrPc may promote tumorigenesis, proliferation and G1/S transition in gastric cancer cells. This review revisits the physiological functions of PrPc, and its possible implications for cancer biology.

Overexpression of cFLIPs inhibits oxaliplatin-mediated apoptosis through enhanced XIAP stability and Akt activation in human renal cancer cells

cFLIP inhibits caspase 8 recruitment and processing at the death-inducing signaling complex (DISC), which is known to inhibits apoptosis mediated by death receptors such as Fas and death receptor 5 (DR5) as well as apoptosis mediated by anticancer therapeutic drugs. We observed that oxaliplatin induced apoptosis, the activation of DEVDase activity, DNA fragmentation, and cleavage of PLC-gamma1 and degradation of XIAP protein in dose-dependent manners, which was prevented by pretreatment with z-VAD or NAC, suggesting that oxaliplatin-induced apoptosis was mediated by caspase- or reactive oxygen species (ROS)-dependent pathways. Furthermore, ectopic expression of cFLIPs potently attenuated oxaliplatin-induced apoptosis, whereas cFLIP(L) had less effect. Interestingly, we found that the protein level of XIAP was sustained in oxaliplatin-treated cFLIPs overexpressing cell, which was caused by the increased XIAP protein stability and that the phospho-Akt level was high compared to vector-transfected cell. The increased XIAP protein stability was lessened by PI3K inhibitor LY294002 treatment in cFLIPs overexpressing cells. Thus, our findings imply that the anti-apoptotic functions of cFLIPs may be attributed to inhibit oxaliplatin-induced apoptosis through the sustained XIAP protein level and Akt activation.

The octarepeat region of prion protein, but not the TM1 domain, is important for the antioxidant effect of prion protein

The cellular prion protein (PrP(c)) plays a crucial role in the pathogenesis of prion diseases, but its physiological function is far from understood. Several candidate functions have been proposed including binding and internalization of metal ions, a superoxide dismutase-like activity, regulation of cellular antioxidant activities, and signal transduction. The transmembrane (TM1) region of PrP(c) (residues 110-135) is particularly interesting because of its very high evolutionary conservation. We investigated a possible role of TM1 in the antioxidant defense, by assessing the impact of overexpressing wt-PrP or deletion mutants in N(2)A mouse neuroblastoma cells on intracellular reactive oxygen species (ROS) levels. Under conditions of oxidative stress, intracellular ROS levels were significantly lowered in cells overexpressing either wild-type PrP(c) (wt-PrP) or a deletion mutant affecting TM1 (Delta8TM1-PrP), but, as expected, not in cultures overexpressing a deletion mutant lacking the octapeptide region (Deltaocta-PrP). Overexpression of wt-PrP, Delta8TM1-PrP, or Deltaocta-PrP did not affect basal ROS levels. Interestingly, the mitochondrial membrane potential was significantly lowered in Deltaocta-PrP-transfected cultures in the absence of oxidative stress. We conclude that the protective effect of PrP(c) against oxidative stress involves the octarepeat region but not the TM1 domain nor the high-affinity copper binding site described for human residues His96/His111.

Increased PrPC expression correlates with endoglin (CD105) positive microvessels in advanced carotid lesions

Normal cellular prion protein (PrP(C)) has multiple functions but its role in the development of atherosclerosis has not been studied. Our pilot microarray data showed increased expression of PrP(C) in tissue samples of complicated carotid lesions. Therefore in this study, we aimed to investigate its localisation within atherosclerotic arteries and its concentration in patient plasma. PrP(C) expression was examined using an enzyme immunometric assay (EIA) in plasma from patients undergoing endarterectomy. Carotid specimens and control vascular transplants were studied for PrP(C) and CD105 (endoglin, a marker of active vessels) expression by immunohistochemistry and real-time PCR. Patients with carotid disease had higher levels of plasma PrP(C) than the control group [4.35 ng/ml (n = 22; 3.1-5.3) vs. 1.95 ng/ml (n = 21; 1.1-2.5), P < 0.001]. Furthermore, CD105-positive plaques had higher PrP(C) expression which colocalized with CD105 in neovessels. There was a significant correlation between mRNA expression of PrP(C) and CD105 in tested plaques (P < 0.001; r = 0.7) supporting our immunohistochemical findings. We conclude that PrP(C) is expressed in carotid specimens and may be associated with neovessel growth or survival in these plaques. Our results suggest a role for PrP(C) in modulating neovessel formation in complicated plaques.

P2Y receptor-activating nucleotides modulate cellular reactive oxygen species production in dissociated hippocampal astrocytes and neurons in culture independent of parallel cytosolic Ca(2+) rise and change in mitochondrial potential

With mixed cultures of hippocampal astrocytes and neurons, we investigated the influence of nucleotides on cytosolic Ca(2+) level, generation of reactive oxygen species (ROS), and mitochondrial potential. We employed ATP and four purine/pyrimidine derivates, which are P2Y receptor subtype-preferring agonists. Stimulation with ATP, a P2Y(1/2/4) receptor agonist in rat, caused a large cytosolic Ca(2+) increase in astrocytes and a considerably smaller Ca(2+) response in neighboring neurons. The P2Y(1) receptor antagonist MRS2179 completely blocked the ATP-induced Ca(2+) response in astrocytes and neurons. Application of ATP significantly reduced the mitochondrial potential in neurons, which was not inhibited by MRS2179. Interestingly, MRS2179 mediated a mitochondrial depolarization without affecting the cytosolic Ca(2+) level. Stimulation with UDP, a P2Y(6) receptor agonist; UTP, a P2Y(2/4) receptor agonist; 2MeSATP, a P2Y(1) receptor agonist; or 2MeSADP, a P2Y(1/12/13) receptor agonist, evoked significant Ca(2+) responses in astrocytes but small Ca(2+) responses in neurons. In astrocytes, there was an inverse relationship between the amplitude of the cytosolic Ca(2+) peak and the rate of ROS generation in response to nucleotide application. Activation with UDP resulted in the highest ROS generation that we detected, whereas 2MeSADP and 2MeSATP reduced the ROS generation below the basal level. 2MeSADP and UDP caused mitochondrial depolarization of comparable size. Thus, neither in astrocytes nor in neurons did the degree of mitochondrial depolarization correlate with ROS generation. Nucleotides acting via P2Y receptors can modulate ROS generation of hippocampal neurons without acutely changing the cytosolic Ca(2+) level. Thus, ROS might function as a signaling molecule upon nucleotide-induced P2Y receptor activation in brain.

Three-colour flow cytometric detection of PrP in ovine leukocytes

PrP(c) (cellular prion protein, CD230) expression by subpopulations of lymphoid cells has been widely investigated in a variety of species, possibly because of the possible link between transmissible spongiform encephalopathies (TSE) transmission and blood transfusion. However, the role of the immune cells in the transmission of the disease is still unclear. Here we describe the optimisation and standardisation of a three-colour staining procedure to detect PrP in association with phenotypic and activation markers in ovine immune cells. We demonstrate a reproducible, flexible and sensitive method and that the combination of isotype-specific antibodies and Fab fragments is feasible. To our knowledge, this is the first report of such labelling of ovine cells. Using this method, we were able to detect differences in levels of PrP expression between blood and lymph node cells of the same animal, and considerable variability between animals. Moreover, we were able to explore possible associations between PrP expression and cellular activation and to identify cell subsets with different labelling patterns. We are currently employing this approach to evaluate variations in immunological parameters during experimental infection in sheep.

Helicobacter pylori upregulates prion protein expression in gastric mucosa: a possible link to prion disease

AIM

Pathological prion protein (PrP(sc)) is responsible for the development of transmissible spongiform encephalopathies (TSE). While PrPc enters the organism via the oral route, less data is available to know about its uptake and the role of gastrointestinal inflammation on the expression of prion precursor PrPc, which is constitutively expressed in the gastric mucosa.

METHODS

We studied PrPc expression in the gastric mucosa of 10 Helicobacter pylori-positive patients before and after successful H pylori eradication compared to non-infected controls using RT-PCR and Western blotting. The effect of central mediators of gastric inflammation, i.e., gastrin, prostaglandin E(2) (PGE(2)), tumor necrosis factor alpha (TNF-alpha) and interleukin 1 beta (IL-1beta) on PrPc expression was analyzed in gastric cell lines.

RESULTS

PrPc expression was increased in H pylori-infection compared with non-infected controls and decreased to normal after successful eradication. Gastrin, PGE(2), and IL-1beta dose-dependently upregulated PrPc in gastric cells, while TNF-alpha had no effect.

CONCLUSION

H pylori infection leads to the upregulation of gastric PrPc expression. This can be linked to H pylori induced hypergastrinemia and increased mucosal PGE(2) and IL-1beta synthesis. H pylori creates a milieu for enhanced propagation of prions in the gastrointestinal tract.

Oxidative and nitrative injury in periventricular leukomalacia: a review

Periventricular leukomalacia (PVL) is the major substrate of cerebral palsy in survivors of prematurity. Its pathogenesis is complex and likely involves ischemia/reperfusion in the critically ill premature infant, with impaired regulation of cerebral blood flow, as well as inflammatory mechanisms associated with maternal and/or fetal infection. During the peak period of vulnerability for PVL, developing oligodendrocytes (OLs) predominate in the white matter. We hypothesize that free radical injury to the developing OLs underlies, in part, the pathogenesis of PVL and the hypomyelination seen in long-term survivors. In human PVL, free radical injury is supported by evidence of oxidative and nitrative stress with markers to lipid peroxidation and nitrotyrosine, respectively. Evidence in normal human cerebral white matter suggests an underlying vulnerability of the premature infant to free radical injury resulting from a developmental mismatch of antioxidant enzymes (AOE) and subsequent imbalance in oxidant metabolism. In vitro studies using rodent OLs suggest that maturational susceptibility to reactive oxygen species is dependent, not only on levels of individual AOE, but also on specific interactions between these enzymes. Rodent in vitro data further suggest 2 mechanisms of nitric oxide damage: one involving the direct effect of nitric oxide on OL mitochondrial integrity and function, and the other involving an activation of microglia and subsequent release of reactive nitrogen species. The latter mechanism, while important in rodent studies, remains to be determined in the pathogenesis of human PVL. These observations together expand our knowledge of the role that free radical injury plays in the pathogenesis of PVL, and may contribute to the eventual development of therapeutic strategies to alleviate the burden of oxidative and nitrative injury in the premature infant at risk for PVL.

Reactive oxygen species contribute to the presynaptic action of extracellular ATP at the frog neuromuscular junction

During normal cell metabolism the production of intracellular ATP is associated with the generation of reactive oxygen species (ROS), which appear to be important signalling molecules. Both ATP and ROS can be released extracellularly by skeletal muscle during intense activity. Using voltage clamp recording combined with imaging and biochemical assay of ROS, we tested the hypothesis that at the neuromuscular junction extracellular ATP generates ROS to inhibit transmitter release from motor nerve endings. We found that ATP produced the presynaptic inhibitory action on multiquantal end-plate currents. The inhibitory action of ATP (but not that of adenosine) was significantly reduced by several antioxidants or extracellular catalase, which breaks down H2O2. Consistent with these data, the depressant effect of ATP was dramatically potentiated by the pro-oxidant Fe2+. Exogenous H2O2 reproduced the depressant effects of ATP and showed similar sensitivity to anti- and pro-oxidants. While NO also inhibited synaptic transmission, inhibitors of the NO-producing cascade did not prevent the depressant action of ATP. The ferrous oxidation in xylenol orange assay showed the increase of ROS production by ATP and 2-MeSADP but not by adenosine. Suramin, a non-selective antagonist of P2 receptors, and pertussis toxin prevented the action of ATP on ROS production. Likewise, imaging with the ROS-sensitive dye carboxy-2',7'-dichlorodihydrofluorescein revealed increased production of ROS in the muscle treated with ATP or ADP while UTP or adenosine had no effect. Thus, generation of ROS contributed to the ATP-mediated negative feedback mechanism controlling quantal secretion of ACh from the motor nerve endings.

Chronic ethanol enhances ectodomain shedding in T cells and monocytes

BACKGROUND

Chronic ethanol (EtOH) has been shown to augment tumor necrosis factor (TNF)-alpha production, and this has been associated with EtOH-induced liver injury. We have recently described a chronic in vitro cell culture model where chronic ethanol exposure results in significantly augmented TNF production in Mono Mac 6 cells, a human monocytic cell line. This enhanced TNF production was redox regulated and associated with increased levels of TNF messenger RNA (mRNA) as well as increased processing of TNF by TNF converting enzyme (TACE), the enzymatic activity of which is regulated by the cellular redox state. We hypothesized that chronic ethanol through oxidative stress activates TACE-mediated ectodomain shedding of the preformed substrates p75 and p55 TNF receptors in Mono Mac 6 cells and L-selectin in Jurkat T cells.

METHODS

Mono Mac 6 or Jurkat T cells were treated with EtOH (0, 50, or 100 mM) for 4 to 6 days. Shedding of p75 and p55 TNF receptors (Mono Mac 6 cells) or L-selectin (Jurkat T cells) was induced by stimulation with lipopolysaccharide and phorbol myristate acetate for Mono Mac 6 cells and PMA alone for Jurkat T cells. Shedding was assessed by enzyme-linked immunosorbent assay for shed molecules in the cell supernatant as well as the cell-associated proteins recovered from cell pellets. Steady-state mRNA levels for p75 TNF receptor and L-selectin were determined by ribonuclease protection assay. Cell surface L-selectin and TACE were measured by flow cytometry, and cell associated p55 and p75 TNF receptors were measured by enzyme-linked immunosorbent assay.

RESULTS

Chronic EtOH exposure for 6 days resulted in a significant dose-dependent increase in shedding of p75 and p55 TNF receptors from Mono Mac 6 cells and L-selectin from Jurkat T-cells. The enhanced shedding was correlated with an alcohol-induced increase in mRNA levels and cell surface protein levels for these TACE substrates. Although chronic EtOH exposure increased the total amount of p75 and p55 TNF receptor and L-selectin shed into the media, the efficiency of shedding was suppressed by EtOH. In the case of Mono Mac 6 cells, the EtOH exposure increased superoxide production. Inhibition of nicotinamide adenine dinucleotide phosphate (reduced form) oxidase and hydrogen peroxide partially prevented the increased production of p75 TNF receptor in these cells.

CONCLUSIONS

These results suggest that chronic EtOH up-regulates p75 and p55 TNF receptors on monocytes and L-selectin on T-cells. However, the TACE-mediated shedding efficiency of these substrates may be inhibited in the presence of EtOH. These results may have implications in monocyte signaling and T-cell trafficking, which may, in part, contribute to immune dysregulation associated with chronic ethanol.

Phospholipase A2 Inhibitors or Platelet-activating Factor Antagonists Prevent Prion Replication

A key feature of prion diseases is the conversion of the cellular prion protein (PrP(C)) into disease-related isoforms (PrP(Sc)), the deposition of which is thought to lead to neurodegeneration. In this study a pharmacological approach was used to determine the metabolic pathways involved in the formation of protease-resistant PrP (PrP(res)) in three prion-infected cell lines (ScN2a, SMB, and ScGT1 cells). Daily treatment of these cells with phospholipase A(2) (PLA(2)) inhibitors for 7 days prevented the accumulation of PrP(res). Glucocorticoids with anti-PLA(2) activity also prevented the formation of PrP(res) and reduced the infectivity of SMB cells. Treatment with platelet-activating factor (PAF) antagonists also reduced the PrP(res) content of cells, while the addition of PAF reversed the inhibitory effect of PLA(2) inhibitors on PrP(res) formation. ScGT1 cells treated with PLA(2) inhibitors or PAF antagonists for 7 days remained clear of detectable (PrPres) when grown in control medium for a further 12 weeks. Treatment of non-infected cells with PLA(2) inhibitors or PAF antagonists reduced PrP(C) levels suggesting that limiting cellular PrP(C) may restrict prion formation in infected cells. These data indicate a pivotal role for PLA(2) and PAF in controlling PrP(res) formation and identify them as potential therapeutic agents.