Inhibitors of protein phosphatase 1 and 2A differentially regulate the expression of inducible nitric-oxide synthase in rat astrocytes and macrophages

In Vivo Biocompatibility of Synechococcus sp. PCC 7002-Integrated Scaffolds for Skin Regeneration

Cyanobacteria, commonly known as blue-green algae, are prevalent in freshwater systems and have gained interest for their potential in medical applications, particularly in skin regeneration. Among these, Synechococcus sp. strain PCC 7002 stands out because of its rapid proliferation and capacity to be genetically modified to produce growth factors. This study investigates the safety of Synechococcus sp. PCC 7002 when used in scaffolds for skin regeneration, focusing on systemic inflammatory responses in a murine model. We evaluated the following three groups: scaffolds colonized with genetically engineered bacteria producing hyaluronic acid, scaffolds with wild-type bacteria, and control scaffolds without bacteria. After seven days, we assessed systemic inflammation by measuring changes in cytokine profiles and lymphatic organ sizes. The results showed no significant differences in spleen, thymus, and lymph node weights, indicating a lack of overt systemic toxicity. Blood cytokine analysis revealed elevated levels of IL-6 and IL-1β in scaffolds with bacteria, suggesting a systemic inflammatory response, while TNF-α levels remained unaffected. Proteome profiling identified distinct cytokine patterns associated with bacterial colonization, including elevated inflammatory proteins and products, indicative of acute inflammation. Conversely, control scaffolds exhibited protein profiles suggestive of a rejection response, characterized by increased levels of cytokines involved in T and B cell activation. Our findings suggest that Synechococcus sp. PCC 7002 does not appear to cause significant systemic toxicity, supporting its potential use in biomedical applications. Further research is necessary to explore the long-term effects and clinical implications of these responses.

A Review of Common Cyanotoxins and Their Effects on Fish

Global warming and human-induced eutrophication drive the occurrence of various cyanotoxins in aquatic environments. These metabolites reveal diversified mechanisms of action, encompassing cyto-, neuro-, hepato-, nephro-, and neurotoxicity, and pose a threat to aquatic biota and human health. In the present paper, we review data on the occurrence of the most studied cyanotoxins, microcystins, nodularins, cylindrospermopsin, anatoxins, and saxitoxins, in the aquatic environment, as well as their potential bioaccumulation and toxicity in fish. Microcystins are the most studied among all known cyanotoxins, although other toxic cyanobacterial metabolites are also commonly identified in aquatic environments and can reveal high toxicity in fish. Except for primary toxicity signs, cyanotoxins adversely affect the antioxidant system and anti-/pro-oxidant balance. Cyanotoxins also negatively impact the mitochondrial and endoplasmic reticulum by increasing intracellular reactive oxygen species. Furthermore, fish exposed to microcystins and cylindrospermopsin exhibit various immunomodulatory, inflammatory, and endocrine responses. Even though cyanotoxins exert a complex pressure on fish, numerous aspects are yet to be the subject of in-depth investigation. Metabolites other than microcystins should be studied more thoroughly to understand the long-term effects in fish and provide a robust background for monitoring and management actions.

Protection of Mice from Controlled Cortical Impact Injury by Food Additive Glyceryl Tribenzoate

Despite intense investigations, no effective therapy is available to halt the pathogenesis of traumatic brain injury (TBI), a major health concern, which sometimes leads to long-term neurological disability, especially in war veterans and young adults. This study highlights the use of glyceryl tribenzoate (GTB), a flavoring ingredient, in ameliorating the disease process of controlled cortical impact (CCI)-induced TBI in mice. Oral administration of GTB decreased the activation of microglia and astrocytes to inhibit the expression of inducible nitric oxide synthase (iNOS) in hippocampus and cortex of TBI mice. Accordingly, GTB treatment protected and/or restored synaptic maturation in the hippocampus of TBI mice as revealed by the status of PSD-95, NR-2A and GluR1. Furthermore, oral GTB also reduced the size of lesion cavity in the brain of TBI mice. Finally, GTB treatment improved locomotor functions and protected spatial learning and memory in TBI mice. These results outline a novel neuroprotective property of GTB which may be beneficial in treatment of TBI.

Regression of Lung Cancer in Mice by Intranasal Administration of SARS-CoV-2 Spike S1

This study underlines the importance of SARS-CoV-2 spike S1 in prompting death in cultured non-small cell lung cancer (NSCLC) cells and in vivo in lung tumors in mice. Interestingly, we found that recombinant spike S1 treatment at very low doses led to death of human A549 NSCLC cells. On the other hand, boiled recombinant SARS-CoV-2 spike S1 remained unable to induce death, suggesting that the induction of cell death in A549 cells was due to native SARS-CoV-2 spike S1 protein. SARS-CoV-2 spike S1-induced A549 cell death was also inhibited by neutralizing antibodies against spike S1 and ACE2. Moreover, our newly designed wild type ACE2-interacting domain of SARS-CoV-2 (wtAIDS), but not mAIDS, peptide also attenuated SARS-CoV-2 spike S1-induced cell death, suggesting that SARS-CoV-2 spike S1-induced death in A549 NSCLC cells depends on its interaction with ACE2 receptor. Similarly, recombinant spike S1 treatment also led to death of human H1299 and H358 NSCLC cells. Finally, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) intoxication led to the formation tumors in lungs of A/J mice and alternate day intranasal treatment with low dose of recombinant SARS-CoV-2 spike S1 from 22-weeks of NNK insult (late stage) induced apoptosis and tumor regression in the lungs. These studies indicate that SARS-CoV-2 spike S1 may have implications for lung cancer treatment.

Antioxidant Therapy Significantly Attenuates Hepatotoxicity following Low Dose Exposure to Microcystin-LR in a Murine Model of Diet-Induced Non-Alcoholic Fatty Liver Disease

We have previously shown in a murine model of Non-alcoholic Fatty Liver Disease (NAFLD) that chronic, low-dose exposure to the Harmful Algal Bloom cyanotoxin microcystin-LR (MC-LR), resulted in significant hepatotoxicity including micro-vesicular lipid accumulation, impaired toxin metabolism as well as dysregulation of the key signaling pathways involved in inflammation, immune response and oxidative stress. On this background we hypothesized that augmentation of hepatic drug metabolism pathways with targeted antioxidant therapies would improve MC-LR metabolism and reduce hepatic injury in NAFLD mice exposed to MC-LR. We chose N-acetylcysteine (NAC, 40 mM), a known antioxidant that augments the glutathione detoxification pathway and a novel peptide (pNaKtide, 25 mg/kg) which is targeted to interrupting a specific Src-kinase mediated pro-oxidant amplification mechanism. Histological analysis showed significant increase in hepatic inflammation in NAFLD mice exposed to MC-LR which was attenuated on treatment with both NAC and pNaKtide (both p ≤ 0.05). Oxidative stress, as measured by 8-OHDG levels in urine and protein carbonylation in liver sections, was also significantly downregulated upon treatment with both antioxidants after MC-LR exposure. Genetic analysis of key drug transporters including Abcb1a, Phase I enzyme-Cyp3a11 and Phase II metabolic enzymes-Pkm (Pyruvate kinase, muscle), Pklr (Pyruvate kinase, liver, and red blood cell) and Gad1 (Glutamic acid decarboxylase) was significantly altered by MC-LR exposure as compared to the non-exposed control group (all p ≤ 0.05). These changes were significantly attenuated with both pNaKtide and NAC treatment. These results suggest that MC-LR metabolism and detoxification is significantly impaired in the setting of NAFLD, and that these pathways can potentially be reversed with targeted antioxidant treatment.

Lipopolysaccharide from the Cyanobacterium Geitlerinema sp. Induces Neutrophil Infiltration and Lung Inflammation

Glucocorticoid-resistant asthma, which predominates with neutrophils instead of eosinophils, is an increasing health concern. One potential source for the induction of neutrophil-predominant asthma is aerosolized lipopolysaccharide (LPS). Cyanobacteria have recently caused significant tidal blooms, and aerosolized cyanobacterial LPS has been detected near the cyanobacterial overgrowth. We hypothesized that cyanobacterial LPS contributes to lung inflammation by increasing factors that promote lung inflammation and neutrophil recruitment. To test this hypothesis, c57Bl/6 mice were exposed intranasally to LPS from the cyanobacterium member, Geitlerinema sp., in vivo to assess neutrophil infiltration and the production of pro-inflammatory cytokines and chemokines from the bronchoalveolar fluid by ELISA. Additionally, we exposed the airway epithelial cell line, A549, to Geitlerinema sp. LPS in vitro to confirm that airway epithelial cells were stimulated by this LPS to increase cytokine production and the expression of the adhesion molecule, ICAM-1. Our data demonstrate that Geitlerinema sp. LPS induces lung neutrophil infiltration, the production of pro-inflammatory cytokines such as Interleukin (IL)-6, Tumor necrosis factor-alpha, and Interferongamma as well as the chemokines IL-8 and RANTES. Additionally, we demonstrate that Geitlerinema sp. LPS directly activates airway epithelial cells to produce pro-inflammatory cytokines and the adhesion molecule, Intercellular Adhesion Molecule-1 (ICAM-1), in vitro using the airway epithelial cell line, A549. Based on our findings that use Geitlerinema sp. LPS as a model system, the data indicate that cyanobacteria LPS may contribute to the development of glucocorticoid-resistant asthma seen near water sources that contain high levels of cyanobacteria.

Immunotoxic Effects Induced by Microcystins and Cylindrospermopsin: A Review

Cyanotoxin occurrence is gaining importance due to anthropogenic activities, climate change and eutrophication. Among them, Microcystins (MCs) and Cylindrospermopsin (CYN) are the most frequently studied due to their ubiquity and toxicity. Although MCs are primary classified as hepatotoxins and CYN as a cytotoxin, they have been shown to induce deleterious effects in a wide range of organs. However, their effects on the immune system are as yet scarcely investigated. Thus, to know the impact of cyanotoxins on the immune system, due to its importance in organisms’ homeostasis, is considered of interest. A review of the scientific literature dealing with the immunotoxicity of MCs and CYN has been performed, and both in vitro and in vivo studies have been considered. Results have confirmed the scarcity of reports on the topic, particularly for CYN. Decreased cell viability, apoptosis or altered functions of immune cells, and changed levels and mRNA expression of cytokines are among the most common effects reported. Underlying mechanisms, however, are still not yet fully elucidated. Further research is needed in order to have a full picture of cyanotoxin immunotoxicity.

Screening-level evaluation of marine benthic dinoflagellates toxicity using mammalian cell lines

Complementary studies at different levels of the biological organization are fundamental to fully link environmental exposure to marine benthic dinoflagellate toxins and their effects. In order to contribute to this transdisciplinary evaluation, and for the first time, the present study aims to study the effects of Gambierdiscus excentricus, Ostreopsis cf. ovata, Prorocentrum hoffmannianum and Prorocentrum lima extracts on seven functionally different mammalian cell lines: HEK 293, HepG2, HNDF, H9c2(2-1), MC3T3-E1, Raw 264.7 and SH-SY5Y. All the cell lines presented cell mass decrease in a concentration-dependence of dinoflagellate extracts, exhibiting marked differences in cell toxicity. Gambierdiscus excentricus presented the highest effect, at very low concentrations with EC_50,24h (i.e., the concentration that gives half-maximal response after a 24-h exposure) between 1.3 and 13 cells mL^-1, followed by O. cf. ovata (EC_50,24h between 3.3 and 40 cells mL^-1), and Prorocentrum species (P. lima: EC_50,24h between 191 and 1027 cells mL^-1 and P. hoffmannianum: EC_50,24h between 152 and 783 cells mL^-1). Cellular specificities were also detected and rat cardiomyoblast H9c2(2-1) cells were in general the most sensitive to dinoflagellate toxic compounds, suggesting that this cell line is an animal-free potential model for dinoflagellate toxin testing. Finally, the sensitivity of cells expressing distinct phenotypes to each dinoflagellate extract exhibited low relation to human poisoning symptoms.

Chronic Low Dose Oral Exposure to Microcystin-LR Exacerbates Hepatic Injury in a Murine Model of Non-Alcoholic Fatty Liver Disease

Microcystins are potent hepatotoxins that have become a global health concern in recent years. Their actions in at-risk populations with pre-existing liver disease is unknown. We tested the hypothesis that the No Observed Adverse Effect Level (NOAEL) of Microcystin-LR (MC-LR) established in healthy mice would cause exacerbation of hepatic injury in a murine model (Lepr^db/J) of Non-alcoholic Fatty Liver Disease (NAFLD). Ten-week-old male Lepr^db/J mice were gavaged with 50 μg/kg, 100 μg/kg MC-LR or vehicle every 48 h for 4 weeks (n = 15–17 mice/group). Early mortality was observed in both the 50 μg/kg (1/17, 6%), and 100 μg/kg (3/17, 18%) MC-LR exposed mice. MC-LR exposure resulted in significant increases in circulating alkaline phosphatase levels, and histopathological markers of hepatic injury as well as significant upregulation of genes associated with hepatotoxicity, necrosis, nongenotoxic hepatocarcinogenicity and oxidative stress response. In addition, we observed exposure dependent changes in protein phosphorylation sites in pathways involved in inflammation, immune function, and response to oxidative stress. These results demonstrate that exposure to MC-LR at levels that are below the NOAEL established in healthy animals results in significant exacerbation of hepatic injury that is accompanied by genetic and phosphoproteomic dysregulation in key signaling pathways in the livers of NAFLD mice.

Chronic exposure to microcystin-LR affected mitochondrial DNA maintenance and caused pathological changes of lung tissue in mice

Microcystin-LR (MC-LR), an important variant of cyanotoxin family, was frequently encountered in the contaminated aquatic environment and taken as a potent hepatotoxin. However, a little was known on the association between the long-term MC-LR exposure and lung damage. In this study, we investigated the changes of the pulmonary histopathology, mitochondrial DNA (mtDNA) integrity and the expression of mtDNA encoded genes in the mice with chronic exposed to MC-LR at different concentrations (1, 5, 10, 20 and 40 μg/L) for 12 months. Our results showed that the long-term and persistent exposure to MC-LR disturbed the balance of redox system, influenced mtDNA stability, changed the expression of mitochondrial genes in the lung cells. Notably, MC-LR exposure influenced the level of inflammatory cytokines and resulted in thickening of the alveolar septa. In conclusion, chronic exposure to MC-LR affected mtDNA maintenance, and caused lung impairment in mice.

Sympathetic glial cells and macrophages develop different responses to Trypanosoma cruzi infection or lipopolysaccharide stimulation

Nitric oxide (NO) participates in neuronal lesions in the digestive form of Chagas disease and the proximity of parasitised glial cells and neurons in damaged myenteric ganglia is a frequent finding. Glial cells have crucial roles in many neuropathological situations and are potential sources of NO. Here, we investigate peripheral glial cell response to Trypanosoma cruzi infection to clarify the role of these cells in the neuronal lesion pathogenesis of Chagas disease. We used primary glial cell cultures from superior cervical ganglion to investigate cell activation and NO production after T. cruzi infection or lipopolysaccharide (LPS) exposure in comparison to peritoneal macrophages. T. cruzi infection was greater in glial cells, despite similar levels of NO production in both cell types. Glial cells responded similarly to T. cruzi and LPS, but were less responsive to LPS than macrophages were. Our observations contribute to the understanding of Chagas disease pathogenesis, as based on the high susceptibility of autonomic glial cells to T. cruzi infection with subsequent NO production. Moreover, our findings will facilitate future research into the immune responses and activation mechanisms of peripheral glial cells, which are important for understanding the paradoxical responses of this cell type in neuronal lesions and neuroprotection.

Hepatic and intestine alterations in mice after prolonged exposure to low oral doses of Microcystin-LR

Oral intake of Microcystin-LR (MC-LR) is the principal route of exposure to this toxin, with prolonged exposure leading to liver damage of unspecific symptomatology. The aim of the present paper was therefore to investigate the liver and intestine damage generated by prolonged oral exposure to low MC-LR doses (50 and 100 μg MC-LR/kg body weight, administrated every 48 h during a month) in a murine model. We found alterations in TBARS, SOD activity and glutathione content in liver and intestine of mice exposed to both doses of MC-LR. Furthermore, the presence of MC-LR was detected in both organs. We also found hepatic steatosis (3.6 ± 0.6% and 15.3 ± 1.6%) and a decrease in intraepithelial lymphocytes (28.7 ± 5.0% and 44.2 ± 8.7%) in intestine of 50- and 100-μg MC-LR/kg treated animals, respectively. This result could have important implications for mucosal immunity, since intraepithelial lymphocytes are the principal effectors of this system. Our results indicate that prolonged oral exposure at 50 μg MC-LR/kg every 48 h generates significant damage not only in liver but also in intestine. This finding calls for a re-appraisal of the currently accepted NOAEL (No Observed Adverse Effect Level), 40 μg MC-LR/kg body weight, used to derive the guideline value for MC-LR in drinking water.

Role of nitric oxide in the genotoxic response to chronic microcystin-LR exposure in human-hamster hybrid cells

Microcystin-LR (MC-LR) is the most abundant and toxic microcystin congener and has been classified as a potential human carcinogen (Group 2B) by the International Agency for Research on Cancer. However, the mechanisms underlying the genotoxic effects of MC-LR during chronic exposure are still poorly understood. In the present study, human-hamster hybrid (AL) cells were exposed to MC-LR for varying lengths of time to investigate the role of nitrogen radicals in MC-LR-induced genotoxicity. The mutagenic potential at the CD59 locus was more than 2-fold higher (p<0.01) in AL cells exposed to a cytotoxic concentration (1 μmol/L) of MC-LR for 30 days than in untreated control cells, which was consistent with the formation of micronucleus. MC-LR caused a dose-dependent increase in nitric oxide (NO) production in treated cells. Moreover, this was blocked by concurrent treatment with the NO synthase inhibitor NG-methyl-L-arginine (L-NMMA), which suppressed MC-LR-induced mutations as well. The survival of mitochondrial DNA-depleted (ρ0) AL cells was markedly decreased by MC-LR treatment compared to that in AL cells, while the CD59 mutant fraction was unaltered. These results provided clear evidence that the genotoxicity associated with chronic MC-LR exposure in mammalian cells was mediated by NO and might be considered as a basis for the development of therapeutics that prevent carcinogenesis.

Alterations in neurobehaviors and inflammation in hippocampus of rats induced by oral administration of microcystin-LR

Microcystin-LR (MC-LR) is a widely studied toxic peptide secreted by certain water blooms of cyanobacteria that exhibit hepatotoxicity and neural toxicity. This study aimed to observe the neurotoxic effects of low-dose MC-LR exposure by oral administration. Male Sprague-Dawley (SD) rats were administered orally every 2 days for 8 weeks with pure water and 0.2, 1.0, and 5.0 μg/kg MC-LR. The Morris water maze test was used to assess the spatial learning and memory capability of rats. The activation of astrocytes and nitric oxide synthase (NOS) was evaluated by immunohistochemistry, and concentrations of nitric oxide (NO) in rat hippocampus were analyzed. Slight liver dysfunction was observed in the 5.0 μg/kg MC-LR-treated rats. Impairment of spatial learning and memory was also observed in the 5.0 μg/kg MC-LR-treated rats. Astrocytes in the hippocampus of the 5.0 μg/kg MC-LR-treated rats showed enhanced activation and cell density; the inflammatory indicators, NOS and NO, increased in accordance with astrocyte activation. This study showed that oral exposure of MC-LR had adverse affects on neurobehaviors, and induced inflammation in memory-related brain regions.

Okadaic Acid, a Bioactive Fatty Acid from Halichondria okadai, Stimulates Lipolysis in Rat Adipocytes: The Pivotal Role of Perilipin Translocation

Lipid metabolism in visceral fat cells is correlated with metabolic syndrome and cardiovascular diseases. Okadaic-acid, a 38-carbon fatty acid isolated from the black sponge Halichondria okadai, can stimulate lipolysis by promoting the phosphorylation of several proteins in adipocytes. However, the mechanism of okadaic acid-induced lipolysis and the effects of okadaic acid on lipid-droplet-associated proteins (perilipins and beta-actin) remain unclear. We isolated adipocytes from rat epididymal fat pads and treated them with isoproterenol and/or okadaic acid to estimate lipolysis by measuring glycerol release. Incubating adipocytes with okadaic acid stimulated time-dependent lipolysis. Lipid-droplet-associated perilipins and beta-actin were analyzed by immunoblotting and immunofluorescence, and the association of perilipin A and B was found to be decreased in response to isoproterenol or okadaic acid treatment. Moreover, okadaic-acid treatment could enhance isoproterenol-mediated lipolysis, whereas treatment of several inhibitors such as KT-5720 (PKA inhibitor), calphostin C (PKC inhibitor), or KT-5823 (PKG inhibitor) did not attenuate okadaic-acid-induced lipolysis. By contrast, vanadyl acetylacetonate (tyrosine phosphatase inhibitor) blocked okadaic-acid-dependent lipolysis. These results suggest that okadaic acid induces the phosphorylation and detachment of lipid-droplet-associated perilipin A and B from the lipid droplet surface and thereby leads to accelerated lipolysis.

Identification and expression profiles of IL-8 in bighead carp (Aristichthys nobilis) in response to microcystin-LR

Microcystin-LR (MCLR) is a widespread cyanotoxin and has immunotoxicity to animals, including fish. Chemokines are considered to play important roles in inflammatory response induced by MCLR. In this study, we cloned the full-length cDNA of interleukin-8 (IL-8) from bighead carp (Aristichthys nobilis) for the first time. The full-length IL-8 cDNA was 552 bp and contained a 297-bp open-reading frame that encoded for a 98-amino acid protein. The deduced IL-8 protein had a typical aspartic acid (D)-leucine (L)-arginine (R) and a CXC motif at the N-terminal, which were conserved in most fish species. Phylogenetic analysis showed that bighead carp IL-8 protein was grouped in the teleost IL-8 lineage 2. Under normal conditions, the expression of IL-8 is constitutive and weak in all tested tissues. However, MCLR treatment could significantly increase the transcription of IL-8 in bighead carp in a temporal- and dose-dependent pattern. The present study will help us to understand more about the evolution of IL-8 and its function in the MCLR induced proinflammatory response in bighead carp.

Different expression patterns of Phactr family members in normal and injured mouse brain

Phosphatase and actin regulators (Phactrs) are a novel family of proteins expressed in the brain, and they exhibit both strong modulatory activity of protein phosphatase 1 and actin-binding activity. Phactrs are comprised of four family members (Phactr1-4), but their detailed expression patterns during embryonic and postnatal development are not well understood. We found that these family members exhibit different spatiotemporal mRNA expression patterns. Phactr4 mRNA was found in neural stem cells in the developing and adult brains, whereas Phactr1 and 3 appeared to be expressed in post-mitotic neurons. Following traumatic brain injury which promotes neurogenesis in the neurogenic region and gliogenesis in the injury penumbra, the mRNA expression of phactr2 and 4 was progressively increased in the injury penumbra, and phactr4 mRNA and protein induction was observed in reactive astrocytes. These differential expression patterns of phactrs imply specific functions for each protein during development, and the importance of Phactr4 in the reactive gliosis following brain injury.

In vivo studies on the immunotoxic effects of microcystins on rabbit

Microcystins (MCs) are the toxic molecules produced by common cyanobacterium in freshwater blooms. Their toxicities raise severe health issues in livestock and human beings. In current study, the immunotoxic effects of MC-LR were investigated in rabbit through evaluating the dynamics of white blood cell (WBC) numbers and cytokine production such as interleukin-3 (IL-3), IL-4, IL-6, interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α). MCs at the high dose (50 μg MC-LReq kg(-1) ) significantly induced increase in the WBC number but decrease in the Th1 (IFN-γ, TNF-α) and Th2 (IL-3, IL-4, IL-6) production. In the low dose group(12.5 μg MC-LReq kg(-1) ), the number of WBC and the production of IFN-γ, IFN-α, IL-4, IL-3, and IL-6 increased gradually in first 12 h, reach the peaks at 12 h, and dropped after 24 h. Significantly positive correlations were found between the cytokines production of IL-4 and IL-6, IFN-γ and IFN-α, or IL-4 and IFN-γ. In conclusion, MC-LR is able to disturb the rabbit immune system and there exists time-dose response relationship in the MC-LR-eliciting perturbation, which probably give a better insight into investigating the immunotoxicity mechanisms of MCs in vivo. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2012.

An acute case of intoxication with cyanobacteria and cyanotoxins in recreational water in Salto Grande Dam, Argentina

Cyanobacterial blooms and hepatotoxic microcystins (MCs) usually occur in summer, constituting a sanitary and environmental problem in Salto Grande Dam, Argentina. Water sports and recreational activities take place in summer in this lake. We reported an acute case of cyanobacterial poisoning in Salto Grande dam, Argentina, which occurred in January 2007. Accidentally, a young man was immersed in an intense bloom of Microcystis spp. A level of 48.6 μg·L(-1) of microcystin-LR was detected in water samples. Four hours after exposure, the patient showed nausea, abdominal pain and fever. Three days later, dyspnea and respiratory distress were reported. The patient was hospitalized in intensive care and diagnosed with an atypical pneumonia. Finally, a week after the exposure, the patient developed a hepatotoxicosis with a significant increase of hepatic damage biomarkers (ALT, AST and γGT). Complete recovery took place within 20 days. This is the first study to show an acute intoxication with microcystin-producing cyanobacteria blooms in recreational water.

Activated astroglia during chronic inflammation in Alzheimer's disease--do they neglect their neurosupportive roles?

Alzheimer's disease (AD) is a neurodegenerative disorder, characterized histopathologically by the extracellular deposition of beta-amyloid peptide in senile plaques, as well as intracellular neurofibrillary tangles (NFT) of hyperphosphorylated tau protein, extensive neuronal loss and synaptic changes in the hippocampus and cerebral cortex. In addition, the AD brain shows chronic inflammation characterized by an abundance of reactive astrocytes and activated microglia. In the healthy brain, astrocytes provide essential services for brain homeostasis and neuronal function, including metabolic support for neurons in the form of lactate, glutamate uptake and conversion into glutamine, and synthesis of glutathione and its precursors. In AD, a large body of evidence now suggests that by transforming from a basal to a reactive state, astrocytes neglect their neurosupportive functions, thus rendering neurons vulnerable to neurotoxins including pro-inflammatory cytokines and reactive oxygen species. This review will explain the normal functions of astrocytes, and how these cells might be activated to turn into inflammatory cells, actively contributing to neurodegeneration and neglecting their neurosupportive roles ("neuro-neglect hypothesis"). Furthermore, it is proposed that astrocytes might be promising target of therapeutic intervention for Alzheimer's disease, if these compromised functions can be normalized with pharmacological agents that are specifically designed to return astrocytes to a quiescent phenotype or supplement factors which activated astrocytes lack to produce.

Activated astrocytes: a therapeutic target in Alzheimer's disease?

Astrocytes become activated in Alzheimer's disease, contributing to and reinforcing an inflammatory cascade. A large body of evidence suggests that by transforming from a basal to a reactive state, astrocytes neglect their neurosupportive functions, thus rendering neurons vulnerable to neurotoxins, including proinflammatory cytokines and reactive oxygen species. This review highlights three important astrocytic functions that may be impaired in neurodegenerative diseases such as Alzheimer's disease. These are: the uptake of glucose and release of lactate; the uptake of glutamate and release of glutamine; and the uptake of glutathione precursors and release of glutathione. Astrocytes could become promising targets of therapeutic intervention for Alzheimer's disease, if these compromised functions can be normalized with pharmacological agents that are specifically designed to return astrocytes to a quiescent phenotype or to supplement any factors that activated astrocytes fail to produce.

Toll-like receptor 9 ligand blocks osteoclast differentiation through induction of phosphatase

CpG-ODN, in addition to stimulation of osteoclastogenic signals in early osteoclast precursors, also induces phosphatase, shifting the pattern of ERK phosphorylation from sustained to transient. This shift results in the degradation of c-fos, an essential molecule for osteoclast differentiation. Therefore, CpG-ODN blocks osteoclast differentiation.

INTRODUCTION

Activation of either Toll-like receptor 9 (TLR9) or RANK induces similar responses in osteoclast precursors. Paradoxically, activation of TLR9 results in inhibition of RANKL-induced osteoclastogenesis.

MATERIALS AND METHODS

We used bone marrow-derived osteoclast precursors. Analyses of signaling molecules phosphorylation were performed using Western blotting. Different levels of gene expression analyses were performed using RT-PCR, Northern, and run-on analyses (for RNA), and EMSA, Western, and pulse-chase experiments (for protein). Phosphatase activity was measured spectrophotometrically.

RESULTS

We found that RANKL and TLR9 ligand, oligodeoxynucleotides containing unmethylated CpG dinucleotides (CpG-ODN), induce sustained and transient extracellular signal-regulated kinase (ERK) phosphorylation, respectively. Furthermore, together they induce a transient phosphorylation of ERK. The duration of ERK phosphorylation is a key factor in determining induction of c-fos, a protein critical for osteoclastogenesis. Indeed, we found that CpG-ODN does not induce c-fos and inhibits its induction by RANKL by enhancing c-fos mRNA and protein degradation. Our observation that CpG-ODN, but not RANKL, induces the expression of the phosphatase PP2A suggests that CpG-ODN exerts its inhibitory activity by induction of ERK dephosphorylation. Moreover, together with the phosphatase inhibitor okadaic acid, CpG-ODN induces sustained ERK phosphorylation and c-fos expression.

CONCLUSIONS

Our findings suggest that the increased rate of c-fos degradation by the TLR9 ligand mediates the inhibition of RANKL-induced osteoclast differentiation. The TLR9 ligand, through induction of dephosphorylation, prevents the sustained ERK phosphorylation needed for maintaining high c-fos levels that are essential for osteoclast differentiation.

Interleukin 10 and TNFalpha synergistically enhance the expression of the G protein-coupled formylpeptide receptor 2 in microglia

Microglia are important participants in inflammatory responses in the central nervous system. We previously observed that tumor necrosis factor alpha (TNFalpha) induces the expression of the formylpeptide receptor mFPR2 on microglial cells. This chemoattractant receptor mediates microglial cell chemotaxis in response to a variety of peptides, including amyloid beta peptide (Abeta(42)), a major pathogenic factor in Alzheimer's disease (AD). In search for agents that regulate microglial activation, we unexpectedly found that IL-10 enhanced the expression of mFPR2 on TNFalpha-activated microglia. This was associated with a markedly increased microglial chemotaxis to Abeta(42) and its endocytosis via mFPR2. Mechanistic studies revealed that the synergistic effect of IL-10 on TNFalpha-induction of mFPR2 in microglia was dependent on activation of p38 MAPK. Our results suggest that IL-10 may affect the pathogenic process of AD by up-regulating mFPR2 and thus favoring the recognition and internalization of Abeta(42) by activated microglial cells.

Multiple inhibitory pathways for lipopolysaccharide- and pro-inflammatory cytokine-induced nitric oxide production in cultured astrocytes

We previously showed that lipopolysaccharide (LPS) and pro-inflammatory cytokines utilized different mechanisms for the production of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) in cultured rat astrocytes. To further characterize these regulatory pathways, we tested the effects of inhibitory factors (anti-inflammatory cytokines, cellular cAMP, and glucocorticoid) on aspects of iNOS expression (from transcription to enzyme activity) during LPS- and cytokine-induced astrocyte NO production. Anti-inflammatory cytokines (transforming growth factor-beta and interleukin-4) suppressed both LPS- and cytokine-induced NO production by reducing iNOS protein expression without affecting mRNA levels. Increased cellular cAMP levels, induced by noradrenaline or forskolin, suppressed LPS-induced, but not cytokine-induced, NO production without affecting iNOS protein expression. The glucocorticoid analog, dexamethasone, suppressed LPS-induced, but not cytokine-induced, NO production by reducing iNOS promoter activity. These different mechanisms would allow the fine control of NO concentration in the brain, as well as accounting for the multiple roles of NO in brain physiology and pathology. Moreover, these mechanisms provide useful therapeutic targets for the treatment of neurodegenerative diseases.

The effects of phorbol 12-myristate 13-acetate, cholera toxin, prostaglandin E2 and norepinephrine on inducible nitric oxide synthase activation induced by lipopolysaccharide in C6 cells

Nitric oxide (NO) plays a significant role in the pathophysiology of the central nervous system including inflammatory, ischemic and traumatic injuries. We demonstrated the possible involvement of protein kinase C (PKC) as well as protein kinase A (PKA) in the regulation of NO synthesis induced by lipopolysaccharide (LPS) treatment. In this study, the role of phorbol 12-myristate 13-acetate (PMA), cholera toxin (CTX), pertussis toxin (PTX), prostaglandin E(2) (PGE(2)) and norepinephrine (NE) in the regulation of NO synthesis was examined in C6 glioma cells. Stimulation with LPS (1 microg/ml) evoked increases in NO production in C6 glioma cells. LPS-induced NO production was enhanced by pretreatment with PMA, CTX and PGE(2). PTX pretreatment had no effect on NO production induced by LPS. In addition, NE inhibited NO production elicited by LPS treatment. These results suggest that NO production induced by LPS in C6 glioma cells is regulated by several kinds of pathways in which CTX-specific G protein, PKC, prostanoid EP(4) receptor and adrenergic receptor may play important roles.

The dynamics of recycled acetylcholine receptors at the neuromuscular junction in vivo

At the peripheral neuromuscular junction (NMJ), a significant number of nicotinic acetylcholine receptors (AChRs) recycle back into the postsynaptic membrane after internalization to intermingle with not-yet-internalized ;pre-existing' AChRs. However, the way in which these receptor pools are maintained and regulated at the NMJ in living animals remains unknown. Here, we demonstrate that recycled receptors in functional synapses are removed approximately four times faster than pre-existing receptors, and that most removed recycled receptors are replaced by new recycled ones. In denervated NMJs, the recycling of AChRs is significantly depressed and their removal rate increased, whereas direct muscle stimulation prevents their loss. Furthermore, we show that protein tyrosine phosphatase inhibitors cause the selective accumulation of recycled AChRs in the peri-synaptic membrane without affecting the pre-existing AChR pool. The inhibition of serine/threonine phosphatases, however, has no effect on AChR recycling. These data show that recycled receptors are remarkably dynamic, and suggest a potential role for tyrosine dephosphorylation in the insertion and maintenance of recycled AChRs at the postsynaptic membrane. These findings may provide insights into long-term recycling processes at less accessible synapses in the central nervous system in vivo.

Role of MAPK in the regulation of double-stranded RNA- and encephalomyocarditis virus-induced cyclooxygenase-2 expression by macrophages

In response to virus infection or treatment with dsRNA, macrophages express the inducible form of cyclooxygenase-2 (COX-2) and produce proinflammatory prostaglandins. Recently, we have shown that NF-kappaB is required for encephalomyocarditis virus (EMCV)- and dsRNA-stimulated COX-2 expression in mouse macrophages. The dsRNA-dependent protein kinase R is not required for EMCV-stimulated COX-2 expression, suggesting the presence of protein kinase R-independent pathways in the regulation of this antiviral gene. In this study, the role of MAPK in the regulation of macrophage expression of cyclooxygenase-2 (COX)-2 in response to EMCV infection was examined. Treatment of mouse macrophages or RAW-264.7 cells with dsRNA or infection with EMCV stimulates the rapid activation of the MAPKs p38, JNK, and ERK. Inhibition of p38 and JNK activity results in attenuation while ERK inhibition does not modulate dsRNA- and EMCV-induced COX-2 expression and PGE2 production by macrophages. JNK and p38 appear to selectively regulate COX-2 expression, as inhibition of either kinase fails to prevent dsRNA- or EMCV-stimulated inducible NO synthase expression by macrophages. Using macrophages isolated from TLR3-deficient mice, we show that p38 and JNK activation and COX-2 expression in response to EMCV or poly(IC) does not require the presence the dsRNA receptor TLR3. These findings support a role for p38 and JNK in the selective regulation of COX-2 expression by macrophages in response to virus infection.

Signals for the induction of nitric oxide synthase in astrocytes

Nitric oxide (NO), being a double-edged sword depending on its concentration in the microenvironment, is involved in both physiological and pathological processes of many organ systems including brain and spinal cord. It is now well-documented that once inducible nitric oxide synthase (iNOS) is expressed in CNS in a signal-dependent fashion, NO in excess of physiological thresholds is produced and this excess NO then plays a role in the pathogenesis of stroke, demyelination and other neurodegenerative diseases. Therefore, a keen interest has been generated in recent years in comprehending the regulation of this enzyme in brain cells. The present review summarizes our current understanding of signaling mechanisms leading to transcription of the iNOS gene in activated astrocytes. We attempt this comprehension with a hope to identify potential targets to intervene NO-mediated CNS disorders.

Regulation of inducible nitric oxide synthase gene in glial cells

Elevated levels of NO produced within the central nervous system (CNS) are associated with the pathogenesis of neuroinflammatory and neurodegenerative human diseases such as multiple sclerosis, HIV dementia, brain ischemia, trauma, Parkinson's disease, and Alzheimer's disease. Resident glial cells in the CNS (astroglia and microglia) express inducible nitric oxide synthase (iNOS) and produce high levels of NO in response to a wide variety of proinflammatory and degenerative stimuli. Although pathways resulting in the expression of iNOS may vary in two different glial cells of different species, the intracellular signaling events required for the expression of iNOS in these cells are slowly becoming clear. Various signaling cascades converge to activate several transcription factors that control the transcription of iNOS in glial cells. The present review summarizes different results and discusses current understandings about signaling mechanisms for the induction of iNOS expression in activated glial cells. A complete understanding of the regulation of iNOS expression in glial cells is expected to identify novel targets for therapeutic intervention in NO-mediated neurological disorders.

Ganoderma lucidum mycelia enhance innate immunity by activating NF-kappaB

Ganoderma lucidum is a popular medicinal mushroom in China and Japan for its immunomodulatory and antitumor effects. The goal of this research is to investigate the effect of dried mycelia of Ganoderma lucidum produced by submerged cultivation on the enhancement of innate immune response. We found that Ganoderma lucidum mycelia (0.2-1.6 mg/ml) stimulated TNF-alpha and IL-6 production after 8h treatment in human whole blood. IFN-gamma release from human whole blood was also enhanced after 3 day-culture with Ganoderma lucidum mycelia (0.2-1.0mg/ml). However, Ganoderma lucidum mycelia did not potentiate nitric oxide production in RAW264.7 cells. To better understand the possible immuno-enhancement mechanisms involved, we focused on nuclear factor (NF)-kappaB activation. Electrophoretic mobility shift assay revealed that the Ganoderma lucidum mycelia (1.6 mg/ml) activated kappaB DNA binding activity in RAW264.7 cells. These results provide supporting evidences for the immunomodulatory effect of Ganoderma lucidum mycelia.

Effects of ketamine and propofol on inflammatory responses of primary glial cell cultures stimulated with lipopolysaccharide

BACKGROUND

Ketamine has been reported to exert anti-inflammatory effects on macrophages stimulated with lipopolysaccharide (LPS) in vitro and in vivo. Several studies have reported conflicting results regarding the effects of propofol on cytokine production from immune cells. However, there have been no reports of the effects of these agents on inflammatory responses in glial cells. We investigated the effects of ketamine and propofol on LPS-induced production of nitric oxide, tumour necrosis factor-alpha (TNF-alpha) and prostaglandin E(2) (PGE(2)) from primary cultures of rat glial cells in vitro.

METHODS

Glial cells were stimulated with LPS in the absence and presence of various concentrations of ketamine (30-1000 microM) or propofol (30 and 300 microM). Nitric oxide released into the culture media was determined by measuring nitrite using the Griess reaction, and concentrations of TNF-alpha and PGE(2) were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Ketamine reduced LPS-induced TNF-alpha production without significant inhibition of nitrite release in mixed glial cells, astrocyte cultures and microglial cultures. Ketamine also inhibited LPS-induced production of PGE(2) in astrocyte cultures. In contrast, propofol had no effect on LPS-induced nitrite or TNF-alpha production in mixed glial cells.

CONCLUSIONS

The data demonstrate that ketamine inhibited some of the inflammatory responses of both astrocytes and microglial cells treated with LPS without causing major change in nitric oxide release. Propofol had no effect on the production of nitric oxide or TNF-alpha from LPS-stimulated glial cells.

Alterations of ciliate phosducin phosphorylation in Blepharisma japonicum cells

We have previously reported that motile photophobic response in ciliate Blepharisma japonicum correlates with dephosphorylation of a cytosolic 28 kDa phosphoprotein (PP28) exhibiting properties similar to those of phosducin. Here we demonstrate in in vivo phosphorylation assay that the light-elicited dephosphorylation of the PP28 is significantly modified by cell incubation with substances known to modulate protein phosphatase and kinase activities. Immunoblot analyses showed that incubation of ciliates with okadaic acid and calyculin A, potent inhibitors of type 1 or 2A protein phosphatases, distinctly increased phosphorylation of PP28 in dark-adapted cells and markedly weakened dephosphorylation of the ciliate phosducin following cell illumination. An enhancement of PP28 phosphorylation was also observed in dark-adapted ciliates exposed to 8-Br-cAMP and 8-Br-cGMP, slowly hydrolysable cyclic nucleotide analogs and 3-isobutyryl-1-methylxanthine (IBMX), a non-specific cyclic nucleotide phosphodiesterase (PDEs) inhibitor. Only slight changes in light-evoked dephosphorylation levels of PP28 were observed in cells treated with the cyclic nucleotide analogs and IBMX. Incubation of ciliates with H 89 or KT 5823, highly selective inhibitor of cAMP-dependent protein kinase (PKA) and cGMP-dependent protein kinase (PKG), respectively, decreased PP28 phosphorylation levels in dark-adapted cells, whereas the extent of light-evoked dephosphorylation of the phosphoprotein was only slightly influenced. Cell treatment with higher Ca2+ concentration together with ionophore A23187 in culture medium resulted in marked increase in PP28 phosphorylation levels, while quite an opposite effect was observed in cells exposed to Ca2+ chelators, EGTA or BAPTA/AM as well as calmodulin antagonists, such as trifluoperazine (TFP), W-7 or calmidazolium. Light-dependent dephosphorylation was not considerably affected by these treatments. The experimental findings presented here suggest that an endogenous light-dependent protein kinase-phosphatase system may be engaged in the alteration of phosducin phosphorylation in ciliate B. japonicum thereby to modulate the cell motile photophobic behavior.

Phosphatase-1 and -2A inhibition modulates apoptosis in human osteoarthritis chondrocytes independently of nitric oxide production

OBJECTIVE

To characterise the role of phosphatase-1 and -2A (PP1/2A) in the modulation of apoptosis in human osteoarthritis (OA) chondrocytes.

METHODS

Human OA chondrocytes were isolated from cartilage obtained from the femoral heads of patients undergoing joint replacement surgery. Cell viability was evaluated by MTT assay. Apoptosis was quantified by ELISA, which measures DNA fragmentation. Nitric oxide (NO) production was evaluated by the Greiss method, and inducible nitric oxide synthase (iNOS) protein synthesis was studied by western blotting.

RESULTS

Inhibition of PP1/2A by the specific inhibitor okadaic acid (OKA) dose and time dependently caused a reduction of cell viability (OKA at 50 nmol/l: a reduction to 60% and 43% at 48 and 72 hours, respectively). Genomic DNA from chondrocytes treated with OKA at 50 and 100 nmol/l for 48 hours displayed increased internucleosomal DNA fragmentation by 11 and 13 fields, respectively. Light microscopy and DAPI studies showed that OKA induced DNA condensation and fragmentation, typical of death by apoptosis. The caspase inhibitors Z-VAD-FMK and Z-DEVD-FMK increased cell viability, reduced by OKA at 50 nmol/l to 87% and 73%, respectively. OKA did not increase iNOS protein synthesis or NO production.

CONCLUSION

PP1/2A modulate apoptosis in human OA chondrocytes; this is independent of NO production but dependent on caspases.

Regulation of inducible nitric oxide synthase in proinflammatory cytokine-stimulated human primary astrocytes

The present study was undertaken to investigate the mechanism of expression of inducible nitric oxide synthase (iNOS) in human primary astrocytes. Among IL-1beta, TNF-alpha, and IFN-gamma, only IL-1beta alone was capable of inducing iNOS. Similarly, among different cytokine combinations, the combinations involving only IL-1beta as a partner were capable of inducing iNOS. The combination of IL-1beta and IFN-gamma (IL-IF) induced the expression of iNOS at the highest level. All three cytokines alone induced the activation of AP-1 while IL-1beta and TNF-alpha but not IFN-gamma induced the activation of NF-kappaB. However, among the three cytokines, only IL-1beta was capable of inducing the activation of CCAAT/enhancer-binding proteinbeta (C/EBPbeta), suggesting an essential role of C/EBPbeta in the expression of iNOS in astrocytes. Although IL-1beta and IFN-gamma alone induced the activation of AP-1, the combination of these two cytokines (IL-IF) markedly inhibited the activation of AP-1. Consistently, JNK-I, a specific inhibitor of JNK, inhibited IL-1beta-mediated activation of AP-1 and expression of iNOS. On the other hand, JNK-I had no effect on (IL-IF)-induced expression of iNOS, suggesting that the activation of AP-1 is involved only during the low level of iNOS induction by IL-1beta but not during the high level of induction by IL-IF. In contrast, the activation of gamma-activation site (GAS) was involved only during the high level of induction by IL-IF but not during the low level of induction by IL-1beta. However, the activation of NF-kappaB and C/EBPbeta was involved in the induction of iNOS by IL-1beta as well as by IL-IF.

Effects of microcystin-LR on patterns of iNOS and cytokine mRNA expression in macrophages in vitro

The presence of cyanobacterial toxins in drinking and recreational waters represent a potential health hazard to the public. Microcystin-LR (MC-LR) is the most commonly encountered toxin and is a potent cyclic heptapeptide hepatotoxin produced by cyanobacteria. In this study, the immunomodulation by MC-LR of BALB/c mice peritoneal macrophages was investigated in vitro on mRNA levels of induced nitric oxide synthase and multiple cytokines by reverse-transcription polymerase chain reaction (RT-PCR). Lavaged peritoneal macrophages were incubated for 6 h with lipopolysaccharide (LPS) at a concentration of 100 microg/L and MC-LR at doses of 1, 10, 100, and 1000 nmol/L. Total RNA was extracted from the incubated macrophages, and then the levels of mRNA for induced nitric oxide synthase (iNOS), IL-1beta, TNF-alpha, GM-CSF, and IFN-gamma were detected. The results showed that expression of mRNA for iNOS, IL-1beta, TNF-alpha, GM-CSF, and IFN-gamma decreased significantly compared to the positive control (LPS only). These results have led us to propose the need for the establishment of a survey of the immunotoxicity of microcystins.

In vitro Assessment of Renal Toxicity and Inflammatory Events of Two Protein Phosphatase Inhibitors Cantharidin and Nor-Cantharidin*

In China, cantharidin has been reported to be active against various human cancers, but with severe side effects such as nephrotoxicity. In order to reduce this toxicity, its demethylated analogue nor-cantharidin has been synthesized and used in cancer therapy, but with only few data regarding safety assessment. The aim of this study was to compare the in vitro effects of cantharidin and nor-cantharidin on renal toxicity and on inflammatory events associated with tumoural process where protein phosphatases could be involved (energy status, prostanoid production, glutathione and nitrite contents) on RAW 264.7 and LLC-PK1 cells. In macrophages, both cantharidin and nor-cantharidin decreased cell viability, in a concentration- and time-dependent manner. However, IC50 was lower with cantharidin than with nor-cantharidin. These two drugs significantly decreased the ATP level after 24 hr incubation. However, ATP decreased much more with cantharidin (up to 4 times) than with nor-cantharidin. When control macrophages were activated with lipopolysaccharide+interferon-gamma for 24 hr a significant increase in nitrite content and in prostanoids were observed. Addition of either drug decreased nitrite generation and prostanoids, however these decreases were greater with cantharidin than with nor-cantharidin. In LLC-PK1 cells, incubated with either cantharidin or nor-cantharidin, our results show significant differences between the two drugs, similar to those observed in peritoneal macrophages, except for GSH content with opposite variations in both cells. We provide a better understanding of the various mechanisms of cantharidin side effects, allowing an easier comparison with nor-cantharidin which could be an attractive therapeutic potential in cancer chemotherapy in western countries.

Expression modulation of multiple cytokines in vivo by cyanobacteria blooms extract from taihu lake, China

Cyanobacterial blooms that generate microcystins (MCs) are being increasingly recognized as a potent health hazard in aquatic ecosystems. However, immunomodulation induced by cyanotoxins has not been well documented. This paper reports the in vivo data on the immune disorder caused by crude microcystin (MC) extract of cyanobacteria blooms collected from Taihu Lake, China, with respect to cytokine mRNA levels. Using reverse-transcriptional polymerase chain reaction (RT-PCR), the expression of multiple cytokines, including proinflammatory (IL-1beta, TNF-alpha, and IL-6) and Th1/Th2-related cytokines (IL-2, IL-4 and IL-10), was evaluated following the cyanobacteria blooms extract containing MCs (CBE) exposure at four doses of 23, 38, 77, 115 mg lyophilized algae cells/kg body weight. The results showed that the mRNA levels of TNF-alpha, IL-1beta, IL-2 and IL-4 decreased significantly following injection of all doses as compared to the control (LPS or ConA only), while the IL-6 level was unaffected. Contrast to this decrease, the level of IL-10 mRNA was, however, transiently up regulated following injection of the lowest dose of CBE. The distinct patterns of expression of these cytokines suggested a modulation of cytokine network, the essential component of the host immune system. We further developed a mathematical model to simulate the interaction of T helper cell subsets and related cytokines, which proved to be a good approach to study the kinetics of the interaction of cells and cytokines in microcystin immunosuppression.

Thrombin induces endocytosis of endoglin and type-II TGF-beta receptor and down-regulation of TGF-beta signaling in endothelial cells

Thrombin activates protease-activated receptor 1 (PAR1) on endothelial cells (ECs) and is critical for angiogenesis and vascular development. However, the mechanism underlying the proangiogenic effect of thrombin has not been elucidated yet. Here, we report the discovery of a novel functional link between thrombin-PAR1 and transforming growth factor-beta (TGF-beta) signaling pathways. We showed that thrombin via PAR1 induced the internalization of endoglin and type-II TGF-beta receptor (TbetaRII) but not type-I receptors in human ECs. This effect was mediated by protein kinase C-zeta (PKC-zeta) since specific inhibition of PKC-zeta caused an aggregation of endoglin or TbetaRII on cell surface and blocked their internalization by thrombin. Furthermore, acute and long-term pretreatment of ECs with thrombin or PAR1 peptide agonist suppressed the TGF-beta-induced serine phosphorylation of Smad2, a critical mediator of TGF-beta signaling. Moreover, activation of PAR1 led to a profound and spread cytosolic clustering formation of Smad2/3 and markedly prevented Smad2/3 nuclear translocation evoked by TGF-beta1. Since TGF-beta plays a crucial role in the resolution phase of angiogenesis, the down-regulation of TGF-beta signaling by thrombin-PAR1 pathway may provide a new insight into the mechanism of the proangiogenic effect of thrombin.

Analysis of immunomodulating nitric oxide, iNOS and cytokines mRNA in mouse macrophages induced by microcystin-LR

Microcystins (MCs) are the toxic molecules produced by common cyanobacterium in freshwater blooms. Their toxicities have brought severe health issues to livestock and human being. Microcystin-LR (MC-LR) is one of the most toxic MCs. This paper presents the profile of the immunomodulation of MC-LR to BALB/c mice peritoneal macrophages. Macrophages were stimulated with 100microg/l lipopolysaccharide (LPS) and MC-LR at dose of 1, 10, 100, 1000nmol/l, respectively, for 24h. Nitric oxide (NO) production in cell culture supernatants was quantified by using Griess reagent method. Total RNA was extracted from incubated macrophages then the mRNA abundance of induced nitric oxide synthase (iNOS), IL-1beta, TNF-alpha, GM-CSF, IFN-gamma was monitored by using reverse-transcriptional polymerase chain reaction (RT-PCR). The results demonstrated that NO production, mRNA levels of iNOS, IL-1beta, TNF-alpha were down regulated by MC-LR dose-dependently and mRNA levels of GM-CSF and IFN-gamma were also decreased but in dose-independent manner. Our results illustrated the involvement of NO production, iNOS and some cytokines in mice immune system in microcystin shock.

IL-4 down-regulates lipopolysaccharide-induced formyl peptide receptor 2 in murine microglial cells by inhibiting the activation of mitogen-activated protein kinases

Microglial cells actively participate in proinflammatory responses in the CNS. Upon stimulation with the bacterial LPS, microglial cells express a functional formyl peptide receptor 2 which mediates the chemotactic and activating effects of a variety of polypeptide agonists including amyloid beta (Abeta(1-42)), a critical pathogenic agent in Alzheimer's disease. In the present study, we found that LPS-induced expression and function of formyl peptide receptor 2 in microglial cells was markedly inhibited by IL-4, a Th2-type cytokine. Our effort to elucidate the mechanistic basis revealed that IL-4 attenuated LPS-stimulated activation of NF-kappaB, extracellular signal-regulated kinase, and p38 mitogen-activated protein kinase, and the effect of IL-4 was associated with a phosphoinositide 3-kinase pathway-dependent increase in serine/threonine phosphatase activity. These results suggest that IL-4 may play an important role in the maintenance of homeostasis of CNS and in the regulation of the disease process characterized by microglial activation in response to proinflammatory stimulants.

Regulation of alpha(1)-adrenoceptor-linked phosphoinositide metabolism in cultured glia: involvement of protein phosphatases and kinases

Noradrenaline-stimulated phosphoinositide breakdown in cultured glia was found to be mediated by alpha(1A)-adrenoceptors. The alpha(1A)-selective agonist A61603 was as effective as noradrenaline in eliciting 3H-inositol phosphate (IP) accumulation but was approximately 50-fold more potent. In addition, the use of selective antagonists revealed a clear rank order of potency in the ability of these drugs to reverse the effect of noradrenaline on phosphoinositide breakdown: RS17053 (alpha(1A)-selective) >>AH11110A (alpha(1B)-selective)>BMY7378 (alpha(1D)-selective). Pre-treatment of cultured glia with the protein phosphatase inhibitor okadaic acid resulted in a concentration- and time-dependent reduction in noradrenaline-evoked 3H-IP accumulation. This effect was mimicked by, but was not additive with, a phorbol ester, was reversed by protein kinase C (PKC) inhibitors and was not evident in cells which had been PKC depleted. The ability of cell extracts to dephosphorylate radiolabelled glycogen phosphorylase revealed the presence of the phosphatases PP1 and PP2A in almost equal abundance. Okadaic acid pre-treatment of intact cultures elicited a marked reduction in total phosphatase activity, particularly that mediated by PP2A. We also determined the effect of okadaic acid pre-treatment on PKC and cyclic AMP-dependent protein kinase (PKA) activities in these cells. PKC and PKA activities in cell extracts were assessed by determining the incorporation of 32P into histone and kemptide, respectively. Okadaic acid elicited increases in both Ca(2+)-dependent and Ca(2+)-independent PKC activity; in addition, increases in both initial and total PKA activities were also recorded. The effect of okadaic acid on noradrenaline-stimulated 3H-IP accumulation were not, however, mimicked by either forskolin or 8-bromo-cyclic AMP, suggesting that this event is not regulated by PKA. Our data point to roles for both PKC and PP2A in the regulation of alpha(1A)-adrenoceptor-linked phosphoinositide metabolism in cultured cortical glia.

Regulation of the Expression of Inducible Nitric Oxide Synthase

Nitric oxide (NO), generated by the inducible isoform of nitric oxide synthase (iNOS), has been described to have beneficial microbicidal, antiviral, antiparasital, immunomodulatory, and antitumoral effects. However, aberrant iNOS induction at the wrong place or at the wrong time has detrimental consequences and seems to be involved in the pathophysiology of several human diseases. iNOS is primarily regulated at the expression level by transcriptional and post-transcriptional mechanisms. iNOS expression can be induced in many cell types with suitable agents such as bacterial lipopolysaccharides (LPS), cytokines, and other compounds. Pathways resulting in the induction of iNOS expression may vary in different cells or different species. Activation of the transcription factors NF-kappaB and STAT-1alpha, and thereby activation of the iNOS promoter, seems to be an essential step for iNOS induction in most cells. However, at least in the human system, also post-transcriptional mechanism are critically involved in the regulation of iNOS expression. The induction of iNOS can be inhibited by a wide variety of immunomodulatory compounds acting at the transcriptional levels and/or post-transcriptionally.

Loss of microglial ramification in microglia-astrocyte cocultures: involvement of adenylate cyclase, calcium, phosphatase, and Gi-protein systems

Reduction in microglial branching is a common feature in brain pathology and culminates in the transformation into small, rounded, microglia-derived phagocytes in the presence of neural debris. The molecular factors responsible for this transformation are unknown. Here we explored the effect of different classes of intra- and extracellular stimuli in vitro on the morphology of ramified microglia cultured on a confluent astrocyte substrate. These studies showed a strong dose-dependent effect for the Ca(2+) ionophore calcimycine/A21837 (50 microM) and for dibutyryl-cAMP (1 mM), with a loss of microglial ramification. Direct activation of the adenylate cyclase with forskolin (0.1 mM) also led to the disappearance of microglial branching. Okadaic acid (70 nM), the inhibitor of protein phosphatases 1 and 2A (PP1/PP2A), and pertussis toxin (12.5 microg/ml), a G(i)-protein inhibitor, also showed similar effects. No effect was observed for dibutyryl-cGMP or for UTP; addition of ATP had a moderate effect, but only at very high, probably nonphysiological concentrations (100 mM). Extracellular matrix components such as keratatan-sulfate, integrin receptor blockers, the disintegrins kistrin, echistatin, and flavoridin, or the serine protease thrombin all had no effect. Addition of prostaglandin D(2) (PGD(2)), a molecule produced by activated microglial cells, had a transforming effect, but at concentrations two orders of magnitude higher than that of established PGD(2) receptors. In summary, addition of agents causing intracellular elevation of Ca(2+) and cAMP or inhibition of G(i)-proteins and phosphatases to ramified microglia cultured on top of confluent astrocytes leads to a rapid loss of microglial branching. Signaling cascades controlled by these molecules may play an important role in the regulation of this common physiological process in the injured brain.

Michael adducts of palmitoylascorbic acid: effects on the oxidative burst of neutrophils and the production of tumor necrosis factor-alpha in monocytes

The effects of Michael adducts of 6-O-palmitoyl-L-ascorbic acid (compounds 1-4) on the phosphorylation-dependent response of stimulated monocytes and neutrophils was investigated. The pyranosyl derivative 3 increased the production of tumor necrosis factor-alpha in human monocytes stimulated with lipopolysaccharide (LPS). Compound 3 also enhanced the release of tumor necrosis factor-alpha from nonstimulated monocytes. Michael adducts 1-4 inhibited the formation of reactive oxygen species in fMLP-stimulated human neutrophils as measured by luminol chemiluminescence. Treatment with 6-O-palmitoyl-L-ascorbic acid (compound 5) also led to a decreased luminescence response of neutrophils. Results are discussed with respect to the inhibitory activity of Michael adducts of ascorbic acids towards protein phosphatases PP1/PP2A.

Myelin basic protein-primed T cells induce nitric oxide synthase in microglial cells. Implications for multiple sclerosis

The presence of autoreactive T cells recognizing self myelin antigens is necessary for the development of central nervous system autoimmune diseases such as multiple sclerosis (MS). The present study was undertaken to investigate the role of myelin basic protein (MBP)-primed T cells in the expression of inducible nitric oxide synthase (iNOS) in microglial cells. MBP-primed T cells alone markedly induced the production of NO and the expression of iNOS protein and mRNA in mouse BV-2 microglial cells. Similarly, MBP-primed T cells also induced the production of NO in mouse primary microglia. This induction of NO production was primarily dependent on the contact between MBP-primed T cells and microglia. The expression of very late antigen-4 (VLA-4) on the surface of MBP-primed T cells and inhibition of MBP-primed T cell-induced microglial NO production by functional blocking of antibodies to the alpha(4) chain of VLA-4 (CD49d) suggest that VLA-4 integrin on MBP-primed T cells plays an important role in contact-mediated induction of iNOS. Since IFN-beta has been used to treat MS patients, we examined the effect of IFN-beta on MBP-primed T cell-induced the production of NO. Surprisingly, IFN-beta alone induced the production of NO in microglial cells. However, the pretreatment of MBP-primed T cells with IFN-beta inhibited the expression of VLA-4 integrin on the surface of MBP-primed T cells and thereby inhibited the ability of those T cells to induce the production of NO in microglial cells. This study illustrates a novel role of neuroantigen-primed T cells in inducing contact-mediated expression of iNOS in microglial cells that may participate in the pathogenesis of MS.

Human immunodeficiency virus type 1 (HIV-1) tat induces nitric-oxide synthase in human astroglia

Human immunodeficiency virus type 1 (HIV-1) infection is known to cause neuronal injury and dementia in a significant proportion of patients. However, the mechanism by which HIV-1 mediates its deleterious effects in the brain is poorly defined. The present study was undertaken to investigate the effect of the HIV-1 tat gene on the expression of inducible nitric-oxide synthase (iNOS) in human U373MG astroglial cells and primary astroglia. Expression of the tat gene as RSV-tat but not that of the CAT gene as RSV-CAT in U373MG astroglial cells led to the induction of NO production and the expression of iNOS protein and mRNA. Induction of NO production by recombinant HIV-1 Tat protein and inhibition of RSV-tat-induced NO production by anti-Tat antibodies suggest that RSV-tat-induced production of NO is dependent on Tat and that Tat is secreted from RSV-tat-transfected astroglia. Similar to U373MG astroglial cells, RSV-tat also induced the production of NO in human primary astroglia. The induction of human iNOS promoter-derived luciferase activity by the expression of RSV-tat suggests that RSV-tat induces the transcription of iNOS. To understand the mechanism of induction of iNOS, we investigated the role of NF-kappaB and C/EBPbeta, transcription factors responsible for the induction of iNOS. Activation of NF-kappaB as well as C/EBPbeta by RSV-tat, stimulation of RSV-tat-induced production of NO by the wild type of p65 and C/EBPbeta, and inhibition of RSV-tat-induced production of NO by deltap65, a dominant-negative mutant of p65, and deltaC/EBPbeta, a dominant-negative mutant of C/EBPbeta, suggest that RSV-tat induces iNOS through the activation of NF-kappaB and C/EBPbeta. In addition, we show that extracellular signal-regulated kinase (ERK) but not that p38 mitogen-activated protein kinase (MAPK) is involved in RSV-tat induced production of NO. Interestingly, PD98059, an inhibitor of the ERK pathway, and deltaERK2, a dominant-negative mutant of ERK2, inhibited RSV-tat-induced production of NO through the inhibition of C/EBPbeta but not that of NF-kappaB. This study illustrates a novel role for HIV-1 tat in inducing the expression of iNOS in human astrocytes that may participate in the pathogenesis of HIV-associated dementia.

Gemfibrozil, a lipid-lowering drug, inhibits the induction of nitric-oxide synthase in human astrocytes

Gemfibrozil, a lipid-lowering drug, inhibited cytokine-induced production of NO and the expression of inducible nitric-oxide synthase (iNOS) in human U373MG astroglial cells and primary astrocytes. Similar to gemfibrozil, clofibrate, another fibrate drug, also inhibited the expression of iNOS. Inhibition of human iNOS promoter-driven luciferase activity by gemfibrozil in cytokine-stimulated U373MG astroglial cells suggests that this compound inhibits the transcription of iNOS. Since gemfibrozil is known to activate peroxisome proliferator-activated receptor-alpha (PPAR-alpha), we investigated the role of PPAR-alpha in gemfibrozil-mediated inhibition of iNOS. Gemfibrozil induced peroxisome proliferator-responsive element (PPRE)-dependent luciferase activity, which was inhibited by the expression of DeltahPPAR-alpha, the dominant-negative mutant of human PPAR-alpha. However, DeltahPPAR-alpha was unable to abrogate gemfibrozil-mediated inhibition of iNOS suggesting that gemfibrozil inhibits iNOS independent of PPAR-alpha. The human iNOS promoter contains consensus sequences for the binding of transcription factors, including interferon-gamma (IFN-gamma) regulatory factor-1 (IRF-1) binding to interferon-stimulated responsive element (ISRE), signal transducer and activator of transcription (STAT) binding to gamma-activation site (GAS), nuclear factor-kappaB (NF-kappaB), activator protein-1 (AP-1), and CCAAT/enhancer-binding protein beta (C/EBPbeta); therefore, we investigated the effect of gemfibrozil on the activation of these transcription factors. The combination of interleukin (IL)-1beta and IFN-gamma induced the activation of NF-kappaB, AP-1, C/EBPbeta, and GAS but not that of ISRE, suggesting that IRF-1 may not be involved in cytokine-induced expression of iNOS in human astrocytes. Interestingly, gemfibrozil strongly inhibited the activation of NF-kappaB, AP-1, and C/EBPbeta but not that of GAS in cytokine-stimulated astroglial cells. These results suggest that gemfibrozil inhibits the induction of iNOS probably by inhibiting the activation of NF-kappaB, AP-1, and C/EBPbeta and that gemfibrozil, a prescribed drug for humans, may further find its therapeutic use in neuroinflammatory diseases.