Association between group 2 innate lymphoid cells enrichment, nasal polyps and allergy in chronic rhinosinusitis

BACKGROUND

Group 2 innate lymphoid cells (ILC2s) were shown to be involved in the initiation and coordination of Th2-type immune responses in allergic disease animal models. Recently, ILC2s enrichment was noted in chronic rhinosinusitis (CRS) patients; however, the role of ILC2s in coordinating the Th2 response in CRS remains to be elucidated. Here, we characterize the ILC2 compartment in CRS by investigating the correlations between ILC2s, Th2 cells and Th2 cytokines expression in CRS patients.

METHODS

We used flow cytometric analysis of sinonasal mucosal tissues of 29 CRS patients and 5 controls to quantify ILC2s and Th2 cells. Messenger RNA expression levels of IL-5, IL-13, IL-25, IL-33, TSLP and GATA3 were determined using qRT-PCR.

RESULTS

ILC2s were significantly enriched in nasal polyps (CRSwNP) patients. Multivariate linear regression showed a significant positive association of ILC2 numbers with CRSwNP and allergic CRS and a negative association with the number of previous endoscopic sinus surgeries. Group 2 innate lymphoid cell numbers significantly correlated with Th2 cell frequencies. Messenger RNA expression levels of IL-5 and IL-13 were increased in CRSwNP compared with controls, while mRNA levels of IL-25 and GATA3 were significantly reduced.

CONCLUSIONS

Our results characterize the complex interactions between ILC2s and other Th2 response elements in the context of CRS and suggest that ILC2 enrichment occurs in CRSwNP and in allergic CRS patients.

Inflammasome gene expression alterations in Staphylococcus aureus biofilm-associated chronic rhinosinusitis

BACKGROUND

The role of inflammasomes in chronic inflammation has been the subject of intense research in recent years. Chronic rhinosinusitis (CRS), a persistent inflammatory disease, continues to be investigated hoping that a clearer pathophysiologic description will guide discovery of future treatment modalities. This study investigates the role of inflammasome complexes in CRS patients with Staphylococcus aureus biofilm infection, a key culprit associated with disease severity and recalcitrance.

METHODOLOGY

Sinonasal tissue samples were collected from CRS patients with (P+) and without (P-) polyps and controls. S. aureus biofilm status was obtained using fluorescence in situ hybridization and classified as biofilm positive (B+) or negative (B-). RNA was analysed using a Human Inflammasome PCR array, profiling the expression of 84 genes involved in inflammasome function.

RESULTS

Sixteen samples were obtained: 5 B+P+, 5 B-P- and 6 controls. Comparing B+P+ vs. controls showed the greatest number of differentially expressed genes. In particular, Absent in Melanoma 2 (AIM2) was consistently and significantly up-regulated in the B+P+ vs. B-P- and controls. In contrast, when comparing the B-P- vs. controls, no genes showed significant changes.

CONCLUSION

Our results indicate the involvement of inflammasome complexes and their signalling pathways in CRS patients with polyps and S. aureus biofilms. In particular, AIM2, activated by intracellular double-stranded DNA, is up-regulated in this group, implying that S. aureus may play a role in intracellular triggering of the inflammasome response. Studies with further patient stratification and assessing corresponding protein expression are needed to further characterize the role of inflammasomes in CRS.

Cell-type dependent response of melanoma cells to aloe emodin

Intrinsic characteristics of melanoma cells such as expression of inducible nitric oxide synthase (iNOS), redox status, and activity of signaling pathways involved in proliferation, differentiation and cell death define the response of the cells to the diverse treatments. In this context we compared the effectiveness of herbal antaquinone aloe emodin (AE) against mouse B16 melanoma and human A375, different in initial activity of ERK1/2, constitutive iNOS expression and basal level of reactive oxygen species (ROS). Both cell lines are sensitive to AE treatment. However, while the agent induces differentiation of B16 cells toward melanocytes, in A375 cells promoted massive apoptosis. Differentiation of B16 cells, characterized by enhanced melanin production and tyrosinase activity, was mediated by H(2)O(2) production synchronized with rapid p53 accumulation and enhanced expression of cyclins D1 and D3. Caspase mediated apoptosis triggered in A375 cells was accompanied with Bcl-2 but not iNOS down-regulation. In addition, opposite regulation of Akt-ERK1/2 axis in AE treated B16 and A375 cells correlated with different outcome of the treatment. However, AE in a dose-dependent manner rescued both B16 and A375 cells from doxorubicin- or paclitaxel-induced killing. These data indicate that caution is warranted when AE is administrated to the patients with conventional chemotherapy.

Murine brain endothelial cells differently modulate interferon-γ and interleukin-17 production in vitro

Brain endothelial cells (BEC) are the major constituents of the blood-brain barrier (BBB), the structure that controls entrance of immune cells into CNS parenchyma. Our aim was to investigate the influence of BEC on production of IL-17 and IFN-?-cytokines that are important for CNS inflammation. To that end, co-cultivations of the bEnd.3 brain endothelial cell line and lymph node cells (LNC) were performed, and gene expression and production of IL-17 and IFN-? were determined. It was found that bEnd.3 cells inhibited expression and production of IFN-?, but not of IL-17. Additionally, bEnd.3 cells also reduced production of the major IFN-?-promoting cytokine - IL-12 - in LNC. The observed variation in modulation of pro-inflammatory cytokines by BEC could be of importance for the understanding of CNS inflammation.

Predictors of infarct artery patency after prehospital thrombolysis: the multicentre, prospective, observational OPTIMAL study

OBJECTIVE

To identify predictors of early TIMI 3 flow patency of the infarct-related artery after prehospital thrombolysis in patients with ST-segment elevation myocardial infarction (STEMI) using data from a "real-world" population, and to develop a nomogram for triaging patients to emergency angiography.

DESIGN

Multicentre, observational, prospective, cohort study.

SETTING

79 Hospitals in France with a prehospital mobile intensive care unit and a coronary care unit with 24 h access to coronary angiography.

PATIENTS

997 Patients with STEMI.

INTERVENTIONS

All patients received prehospital thrombolysis within 6 h of symptom onset and angiography was performed within 6 h of thrombolysis.

MAIN OUTCOME MEASURES

Coronary patency (TIMI flow).

RESULTS

The median age of the population was 59 years and the sample comprised 18% women. After multivariable logistic regression analysis, predictors of TIMI 3 flow in the infarct-related artery were current/previous smoking (odds ratio (OR) = 1.60, 95% confidence interval 1.15 to 2.22), < or =5 leads with ST-segment elevation before thrombolysis (OR = 1.59, 1.12 to 2.25), Killip class I (OR = 1.96, 1.05 to 3.67), chest pain relief (OR = 1.62, 1.17 to 2.25) and ST-segment resolution > or =70% (OR = 1.76, 1.29 to 2.38). A nomogram was developed to assess the probability of TIMI 3 flow, according to smoking status, number of leads with ST elevation before thrombolysis, Killip class, chest pain relief and ST-segment resolution.

CONCLUSIONS

This study provides quantitative data for predicting success of prehospital thrombolysis. The nomogram is a simple tool for predicting likelihood of coronary patency, based on clinical and electrocardiographic data. It may help to identify patients who require emergency angiography and rescue percutaneous coronary intervention.

Are there good and bad responders to prehospital thrombolysis in the acute phase of myocardial infarction? OPTIMAL study rationale

The effectiveness of thrombolytics has been clearly demonstrated in more than half the cases in the large cohorts of patients selected for trials during the acute phase of myocardial infarction. At individual level, thrombolysis will clinically either succeed or fail so, for the medical team managing the patient, choice of treatment may be likened to a gamble which in the best of cases (most often) leads to an uncomplicated success and, in the worst of cases, failure worsened by a severe complication. OPTIMAL is a multidisciplinary and multicentre, prospective cohort study associating mobile medical teams and interventional cardiology units to test the hypothesis that the outcome of prehospital thrombolysis does not depend on chance alone but also varies according to demographic, etiological, clinical and logistic factors involved in the occurrence and management of myocardial infarction. The primary objective of this French study, conducted over one year on more than 800 subjects, is to identify the predictors of the results of prehospital thrombolysis from a very early angiographic evaluation. The results for this cohort may be useful for setting up appropriate management strategies for acute myocardial infarction, from the prehospital phase (thrombolysis or not) up to in-hospital orientation of the patients (angiography room or Intensive Care Unit) and to determine the most judicious time for coronary angiography. OPTIMAL is to date the largest prospective serie of prehospital thrombolysis evaluated by an early angiographic control.

Interleukin-17 stimulates inducible nitric oxide synthase-dependent toxicity in mouse beta cells

The influence of the proinflammatory cytokine interleukin (IL)-17 on inducible nitric oxide (NO) synthase (iNOS)-mediated NO release was investigated in the mouse insulinoma cell line MIN6 and mouse pancreatic islets. IL-17 markedly augmented iNOS mRNA/protein expression and subsequent NO production induced in MIN6 cells or pancreatic islets by different combinations of interferon-gamma, tumor necrosis factor-alpha, and IL-1beta. The induction of iNOS by IL-17 was preceded by phosphorylation of p38 mitogen-activated protein kinase (MAPK), and inhibition of p38 MAPK activation completely abolished IL-17-stimulated NO release. IL-17 enhanced the NO-dependent toxicity of proinflammatory cytokines toward MIN6 cells, while IL-17-specific neutralizing antibody partially reduced the NO production and rescued insulinoma cells and pancreatic islets from NO-dependent damage induced by activated T cells. Finally, a significant increase in blood IL-17 levels was observed in a multiple low-dose streptozotocin model of diabetes, suggesting that T cell-derived IL-17 might be involved in NO-dependent damage of beta cells in this disease.

Aloe emodin decreases the ERK-dependent anticancer activity of cisplatin

The present study describes the ability of an anthraquinone derivative aloe emodin (AE) to reduce the cytotoxic activity of the platinum(II)-based anticancer agent cisplatin toward murine L929 fibrosarcoma and C6 glioma cell lines. The protective effect of AE was demonstrated by MTT and crystal violet assays for cell viability, and involved supression of cisplatin-induced apoptosis and necrosis, as assessed by lactate dehydrogenase release and flow cytometric analysis of DNA fragmentation or phosphatidylserine exposure. Cell-based ELISA and Western blot analysis revealed that AE abolished cisplatin-triggered activation of extracellular signal-regulated kinase (ERK) in tumor cells, while activation of c-Jun N-terminal kinase was not significantly altered. A selective blockade of ERK activation with PD98059 mimicked the protective effect of AE treatment in both tumor cell lines. Moreover, AE failed to protect tumor cells against the ERK-independent toxicity of the Pt(IV)-based complex tetrachloro(O,O-dibutyl-ethylenediamine-N,N'-di-3-propanoate)platinum(IV). Taken together, these data indicate that herbal anthraquinone AE can downregulate the anticancer activity of cisplatin by blocking the activation of ERK in tumor cells.

Anti-glioma action of aloe emodin: the role of ERK inhibition

The effect of aloe emodin (AE), a herbal anthraquinone derivative, on the rat C6 glioma cell line was investigated. In addition to cell cycle block and caspasedependent apoptosis, AE led to the formation of intracytoplasmic acidic vesicles indicative for autophagic cell death. Moreover, differentiation of surviving cells toward the astrocytic lineage was confirmed by typical morphological changes and increased expression of glial fibrillary acidic protein (GFAP). AE did not affect the activation of mitogen-activated protein kinase p38, Jun-N-terminal kinase, or transcription factor NF-kappaB, but markedly inhibited the activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in C6 cells. A selective inhibitor of ERK activation, PD98059, mimicked the effects of AE on glioma cell morphology and GFAP expression, but failed to induce either apoptosis or autophagy. Taken together, these results indicate that the anti-glioma action of AE involves ERK-independent induction of both apoptosis and autophagy, as well as ERK inhibition-mediated differentiation of glioma cells.

Inducible nitric oxide synthase inhibition by mycophenolic acid

The focus of this review is the influence of an immunosuppressive xenobiotic drug mycophenolic acid on the induction of nitric oxide production in various cell types. The potential therapeutic significance of the cell-specific fine-tuning of nitric oxide release by mycophenolic acid, as well as the mechanisms behind the drug action are discussed.

Iron down-regulates macrophage anti-tumour activity by blocking nitric oxide production

Although the inhibitory effect of iron on macrophage production of tumoricidal free radical nitric oxide (NO) has been reported, its possible influence on macrophage anti-tumour activity has not been established. In the present study, FeSO4 markedly reduced IFN-gamma + LPS-induced NO synthesis in mouse and rat macrophages. The effect of iron coincided with the loss of macrophage cytotoxic activity against NO-sensitive C6 rat astrocytoma and L929 mouse fibrosarcoma cell lines, as measured by MTT assay for cellular respiration and the crystal violet test for cell viability. Tumour cell survival did not improve further in the presence of FeSO4 if macrophage NO release and cytotoxicity were already blocked by aminoguanidine. In accordance with the results obtained with exogenous iron, cell membrane permeable iron chelator o-phenanthroline enhanced both macrophage NO release and anti-tumour activity. Iron also down-regulated NO production and increased the viability of L929 fibrosarcoma cells stimulated with IFN-gamma + LPS in the absence of macrophages. However, neither NO release nor cell viability was affected by iron addition to cultures of the C6 astrocytoma cell line. Iron was unable to prevent L929 and C6 cell death induced by the NO releasing chemicals SNP and SIN-1, indicating that iron-mediated inhibition of NO synthesis, rather than interference with its cytotoxic action, was responsible for the protection of tumour cells. Collectively, these results indicate that iron might protect tumour cells by reducing both macrophage and tumour cell-derived NO release.

Taxol activates inducible nitric oxide synthase in rat astrocytes: the role of MAP kinases and NF-kappaB

Taxol is a microtubule-stabilizing agent that has recently been shown effective in the treatment of experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. As astrocytes could modulate central nervous system (CNS) autoimmunity through inducible nitric oxide synthase (iNOS)-mediated production of immunoregulatory free radical nitric oxide (NO), we investigated the effect of taxol on NO synthesis in rat astrocytes. Taxol, either alone or in combination with interferon-gamma, induced NO generation in primary astrocytes and astrocytoma C6 cells in a dose- and time-dependent manner. Accordingly, the drug markedly up-regulated the expression of both iNOS mRNA and protein in astrocytes. The observed effect of taxol was mediated through induction of iNOS transcription factors NF-kappaB and IRF-1, and required the activation of p38 MAP kinase and JNK. Finally, NO release by taxol-stimulated astrocytes was blocked with the microtubule-depolymerizing agent colchicine, suggesting the involvement of a microtubule-stabilizing activity of taxol in the observed effect.

Aloe-emodin prevents cytokine-induced tumor cell death: the inhibition of auto-toxic nitric oxide release as a potential mechanism

Aloe-emodin (AE) is a plant-derived hydroxyanthraquinone with potential anticancer activity. We investigated the ability of AE to modulate survival of mouse L929 fibrosarcoma and rat C6 astrocytoma cells through interference with the activation of inducible nitric oxide (NO) synthase (NOS) and subsequent production of tumoricidal free radical NO. Somewhat surprisingly, AE in a dose-dependent manner rescued interferon-gamma + interleukin-1-stimulated L929 cells from NO-dependent killing by reducing their autotoxic NO release. The observed protective effect was less pronounced in C6 cells, due to their higher sensitivity to a direct toxic action of the drug. AE-mediated inhibition of tumor cell NO release coincided with a reduction in cytokine-induced accumulation of transcription and translation products of genes encoding inducible NOS and its transcription factor IRF-1, while activation of NF-kappaB remained unaltered. These data indicate that the influence of AE on tumor growth might be more complex that previously recognized, the net effect being determined by the balance between the two opposing actions of the drug: its capacity to directly kill tumor cells, but also to protect them from NO-mediated toxicity.

5-Aza-2'-deoxycytidine stimulates inducible nitric oxide synthase induction in C6 astrocytoma cells

The influence of a nucleoside analog 5-aza-2'-deoxycytidine (5-AzadC) on inducible nitric oxide synthase (iNOS)-dependent nitric oxide (NO) production in various rat cell types was investigated. In C6 astrocytoma cell line and primary astrocytes, 5-AzadC enhanced proinflammatory cytokine (IFN-gamma, TNF-alpha, IL-1)-triggered NO synthesis in a time- and dose-dependent manner. In contrast, 5-AzadC did not potentiate NO production in IFN-gamma-stimulated macrophages, fibroblasts, or endothelial cells. Blockade of transcription or translation in C6 cells abolished the observed effect, suggesting the iNOS gene expression, rather than its catalytic activity, as a target for the drug action. Accordingly, 5-AzadC upregulated IFN-gamma-induced expression of iNOS mRNA in C6 astrocytes. The effect of 5-AzadC on astrocyte NO release was blocked by the inhibitor of p44/42 mitogen activated protein kinase-dependent signaling. Finally, the observed stimulatory effect of 5-AzadC on iNOS expression was apparently independent of DNA demethylation, as DNA digestion with methylation-sensitive restriction enzyme HpaII showed that 5-AzadC failed to demethylate cellular DNA in conditions used for iNOS induction.

Regulation of inducible nitric oxide synthase by cAMP-elevating phospho-diesterase inhibitors

Among the numerous genes controlled by cyclic adenosine monophosphate (cAMP)/protein kinase A signalling machinery is the gene encoding the inducible nitric oxide synthase (iNOS), an enzyme catalyzing the synthesis of a highly reactive free radical nitric oxide (NO). While being a major microbicidal and tumoricidal molecule, iNOS-derived NO has also been implicated in tissue destruction, as well as in regulation of inflammatory/immune cell function in various disorders associated with excessive inflammation. A feasible way for cAMP-dependent therapeutic control of inflammation, including iNOS-mediated NO synthesis, could involve the administration of drugs that block the enzymatic activity of cAMP-degrading phosphodiesterases (PDE). Indeed, cAMP-elevating PDE inhibitors can influence iNOS activation in different cell types in vitro, and their potent anti-inflammatory effects in experimental disease models and clinical studies were frequently accompanied with profound modulation of NO production. A set of conflicting data has been generated over the years, ranging from strong suppression to marked enhancement of NO release by cAMP-increasing PDE inhibitors, depending on cell-type, iNOS stimuli, and/or the agents used. The present review summarizes the data on iNOS modulation by cAMP-elevating PDE inhibitors and possible mechanisms behind it, speculating on its contribution to the therapeutic effects of these drugs.

Mycophenolic acid inhibits activation of inducible nitric oxide synthase in rodent fibroblasts

Mycophenolate mofetil (MMF) is an immunosuppressive drug that acts as a selective inhibitor of inosine monophosphate dehydrogenase (IMPDH). MMF has recently been shown to inhibit the enzymatic activity of inducible NO synthase (iNOS) and subsequent production of the cytotoxic free radical nitric oxide (NO) in endothelial cells. We here investigated the effect of bioactive MMF compound mycophenolic acid (MPA) on iNOS-mediated NO synthesis in fibroblasts, which are important source of NO in rheumatoid arthritis and during rejection of solid organ transplants. MPA exerted dose-dependent inhibition of NO synthesis, measured as nitrite accumulation, in IFN-gamma + LPS-stimulated L929 mouse fibroblast cell line and rat primary fibroblasts. The effect of MPA was not mediated through interference with IMPDH-dependent synthesis of iNOS co-factor BH4 and subsequent suppression of iNOS enzymatic activity, as direct BH4 precursor sepiapterin failed to block the action of the drug. MPA suppressed the IFN-gamma + LPS-induced expression of fibroblast iNOS protein, as well as mRNA for iNOS and its transcription factor IRF-1, as assessed by cell-based ELISA and semiquantitative RT-PCR, respectively. MPA suppression of fibroblast NO release, iNOS, and IRF-1 activation, was efficiently prevented by exogenous guanosine, indicating that the drug acted through reduction of IMPDH-dependent synthesis of guanosine nucleotides. These results suggest that MPA inhibits NO production in fibroblasts by blocking guanosine nucleotide-dependent expression of iNOS gene, through mechanisms that might involve the interference with the induction of iNOS transcription factor IRF-1.

Immunosuppressants leflunomide and mycophenolic acid inhibit fibroblast IL-6 production by distinct mechanisms

Mycophenolic acid (MPA) and A77 1726, the active components of the immunosuppressants mycophenolate mophetil and leflunomide, respectively, in a dose-dependent manner inhibited interferon (IFN)-gamma/LPS-induced interleukin (IL)-6 release in confluent cultures of mouse L929 fibrosarcoma cells. In addition, both drugs markedly reduced the production of the free radical gas nitric oxide (NO), without affecting the viability of L929 cells. The inhibitors of NO synthase, aminoguanidine and L-NMMA, but not L-NMMA inactive counterpart D-NMMA, mimicked the effects of A77 1726 and MPA on IL-6 generation in L929 fibroblasts. Furthermore, NO-releasing substance SNP completely reverted IL-6 accumulation in L929 cultures treated with A77 1726, while only partial recovery of IL-6 production was observed in the presence of MPA. MPA, but not A77 1726, significantly suppressed NO-independent IL-6 release triggered by cAMP-elevating agent rolipram. Thus, while A77 1726 effect on IL-6 production was mediated through concomitant reduction of NO synthesis, MPA action was mainly independent of the interference with NO generation. Finally, both agents inhibited IFN-gamma/LPS-triggered IL-6 production in mouse primary fibroblasts, but not in mouse peritoneal macrophages, indicating cell-specificity of this novel anti-inflammatory action of A77 1726 and MPA.

The role of interleukin-17 in inducible nitric oxide synthase-mediated nitric oxide production in endothelial cells

The effect of interleukin (IL)-17 on the activation of inducible nitric oxide (NO) synthase (iNOS) and subsequent production of NO was investigated. IL-17 induced NO production in both mouse and rat endothelial cells in a dose- and time-dependent manner. This was paralleled by the induction of mRNA for iNOS, which was markedly down-regulated by specific antagonists of protein tyrosine kinase, p38 MAP kinase or iNOS transcription factor NF-kappaB. The expression of iNOS transcription factor IRF-1 was also induced by IL-17 and blocked by all three inhibitors, suggesting that the induction of iNOS by IL-17 might be partly exerted through IRF-1 activation. Neutralization with the specific antibody showed that endogenous IL-17 is involved in T cell-mediated NO production in endothelial cells and NO-dependent suppression of T cell growth. These data indicate that IL-17-triggered iNOS activation in endothelial cells might participate in regulation of the T cell-dependent inflammatory response.

Nitric oxide metabolites and interleukin-6 in cerebrospinal fluid from multiple sclerosis patients

Interleukin-6 (IL-6) and nitric oxide (NO) are implicated in the pathology of multiple sclerosis (MS). We have investigated the levels of these mediators in the cerebrospinal fluid (CSF) from 50 patients with MS and 23 control subjects. Mean CSF IL-6 level was higher in the total MS group in comparison with controls, but not significantly, whilst the difference between patients with stable MS and controls reached the level of statistical significance. Mean CSF nitrite/nitrate level was significantly higher in the total MS group compared with the control group, as well as in active MS patients versus controls. There was significant difference neither in the mean CSF IL-6 nor in nitrite/nitrate levels between active and stable MS patients. Interestingly, we observed a significant negative correlation between IL-6 and nitrite/nitrate levels in the CSF in the total MS group. Such a trend existed in both subgroups with active and stable MS, but without reaching the level of statistical significance. Our data further support the involvement of IL-6 and NO in ongoing pathological processes in MS, suggesting their potential interplay within the central nervous system in this disease.

Interleukin-17 stimulates inducible nitric oxide synthase activation in rodent astrocytes

The effect of interleukin-17 (IL-17) on production of nitric oxide (NO) in rodent astrocytes was investigated. While IL-17 by itself did not induce NO production, it caused a dose-dependent enhancement of IFN-gamma-triggered NO synthesis in both mouse and rat primary astrocytes. In contrast, IL-17 was unable to stimulate NO synthesis in either murine or rat macrophages. IFN-gamma-triggered expression of mRNA for iNOS, but not for its transcription factor interferon regulatory factor-1 (IRF-1), was markedly elevated in IL-17-treated astrocytes. The induction of iNOS mRNA by IL-17 in IFN-gamma-pretreated astrocytes was abolished by antagonists of nuclear factor-kappaB (NF-kappaB) activation--a proteasome inhibitor MG132 and an antioxidant agent PDTC, as well as with specific p38 MAP kinase inhibitor SB203580. While IL-17 stimulated both IL-1beta and IL-6 production in astrocytes, only IL-1 was partly responsible for IL-17-induced NO release. Finally, IL-17 synergized with exogenous IL-1beta and TNF-alpha for astrocyte NO production. Having in mind a well-known neurotoxic action of NO, these results suggest a possible role for IL-17 in the inflammatory diseases of the CNS.

Leflunomide inhibits activation of inducible nitric oxide synthase in rat astrocytes

Highly reactive gaseous free radical nitric oxide (NO), generated by astrocytes and infiltrating macrophages is implicated in inflammatory destruction of brain tissue, including that occurring in multiple sclerosis. Therefore, the influence of immunosuppressive drug leflunomide on inducible nitric oxide synthase (iNOS)-dependent NO production in rat astrocytes and macrophages was investigated. Under the same cultivating conditions, leflunomide's active metabolite A77 1726 caused a dose-dependent decrease of NO production in IFN-gamma+LPS-stimulated primary astrocytes, but not in macrophages. While A77 1726 did not alter iNOS enzymatic activity, it markedly suppressed IFN-gamma+LPS-triggered expression of iNOS mRNA in astrocytes. In the presence of transcription inhibitor actinomycin D, A77 1726 failed to inhibit astrocyte NO production, suggesting transcriptional regulation of iNOS by leflunomide. This assumption was further supported by the ability of A77 1726 to inhibit IFN-gamma+LPS-induced expression of mRNA for an important iNOS transcription factor IRF-1. PD98059, a specific inhibitor of mitogen-activated protein kinase kinase (MAPKK/MEK), but not genistein, an unselective protein tyrosine kinase inhibitor, completely mimicked cell type-specific inhibition of NO synthesis by A77 1726. Therefore, previously described inhibition of MEK/MAP pathway by leflunomide could present a possible mechanism for A77 1726-mediated suppression of iNOS activation in astrocytes. Accordingly to results obtained with primary astrocytes, both A77 1726 and PD98059 significantly reduced IFN-gamma+LPS-induced NO synthesis in the cultures of rat astrocytoma cell line C6. The ability to suppress iNOS induction in astrocytes supports potential use of leflunomide in the treatment of multiple sclerosis and other NO-dependent inflammatory brain disorders.

High expression, purification, and properties of recombinant homocysteine alpha, gamma-lyase

Homocysteine alpha,gamma-lyase from the anaerobic protozoan parasite Trichomonas vaginalis has been cloned from genomic DNA using PCR methods and expressed in Escherichia coli with a vector containing the T7 promoter. The recombinant homocysteine alpha,gamma-lyase (rHCYase) is expressed as the major protein in the host E. coli cells. The enzyme was purified to approximately 90% purity using heat treatment at 50 degreesC, precipitation steps with polyethyleneimine, polyethylene glycol 8000, and high sodium chloride, DEAE-Sepharose FF chromatography, and phenyl-Sepharose 6 FF chromatography. The final yield was greater than 50%, which encompassed an approximate 18-fold purification. The enzyme is a homotetramer with a monomer molecular weight of 43K and contains pyridoxal phosphate. The Trichomonas rHCYase is selective for homocysteine with respect to very low cysteinase activity in contrast to the alpha,gamma-lyase from Pseudomonas putida, which has very high cysteinase activity with respect to homocysteine. The T. vaginalis and P. putida alpha,gamma-lyases readily separate on a phenyl-Sepharose 6 FF column with the T. vaginalis enzyme eluting first. rHCYase is stable up to 50 degreesC and active over a pH range of 6-8. These properties of high recombinant expression in E. coli, a simple and effective high-yield purification procedure and high relative specificity for homocysteine with respect to cysteine, make rHCYase a promising candidate to use for the diagnosis of hyperhomocystenemia, which has been demonstrated to be a major risk factor for the onset and mortality of cardiovascular disease of all types.

New sensitive discovery histoculture model for growth-inhibition studies in prostate cancer and BPH

BACKGROUND

A new, total-immersion three-dimensional histoculture (TIH) method was developed to evaluate growth of tissue containing a mixture of benign prostate hyperplasia (BPH) and prostate cancer in vitro.

METHODS

Efficacy of inhibitors, such as genistein, was determined by measuring 3H-thymidine incorporation per microgram protein. Inhibitory effects obtained in TIH were compared to those in sponge-gel supported histoculture (SSH).

RESULTS

3H-thymidine incorporation was 2-5-fold higher in tissue cultured in TIH than in SSH. The average inhibition by genistein at a concentration of 18 JIM was 73% in TIH, vs. 31% in SSH. TIH also appeared to be more sensitive, since the lowest concentration of genistein that significantly inhibited growth of BPH mixed with prostate cancer tissue was 2.3 IJM, while in SSH the lowest concentration was 9.2 F,M. Although the within-assay coefficient of variation (CV) was similar for both TIH and SSH, the between-assay CV was better in TIH.

CONCLUSIONS

These data suggest that TIH can be used as a discovery model for screening and evaluating inhibitors of prostate tissue growth in vitro.