Fipronil is an insecticide that acts at the gamma-aminobutyric acid receptor and glutamate-gated chloride channels in the central nervous systems of target organisms. The use of fipronil is increasing across the globe. Presently, very little data exist on the potential impact of exposure to fipronil on the lungs. We studied the same by exposing mice to fipronil intranasally (N=8) or orally (N=7) for 7 days followed by collection of blood, broncho-alveolar lavage (BAL) fluid and lung tissues. Control mice were given corn oil (N=15). The oral and intranasal exposure routes were chosen because these are the most common routes of exposure for humans and animals. Hematoxylin-eosin stained lung sections showed normal histology in the control lungs compared to the thickened alveolar septa, disruption of the airways epithelium and damage to vascular endothelium in the intranasal and the oral groups. Lung sections stained for von Willebrand factor showed that mice exposed to fipronil either orally or intranasally had increased staining in the endothelium and septal capillaries. Compared to the control mice, TLR4 expression in lungs from animals treated orally with fipronil was reduced while animals exposed intranasally had increased TLR4 staining in the airway epithelium. Similarly, TLR9 stained lungs showed that orally treated animals had reduced TLR9 reaction in the airway epithelial cells but intranasally exposed animals had intense TLR9 staining in the alveolar septa and airway epithelium. The slides were also scored blindly to gain a quantitative understanding of the staining; there were a significantly higher number of TLR4 positive stained cells in the intranasal fipronil group (P=0.010) but no significant differences between treatments for TLR9 positive stained cells (P=0.226). The U937 cell line was employed to compliment the in vivo work. Cells were exposed to fipronil in DMSO at concentrations of 0.29 µm to 5.72 µm per 1 ml for various times from 3, 9 and 24 hours. Viability was assessed and western blots on Toll-like receptors 4 and 9 were completed in addition to immunofluorescence. Cell death was determined with trypan blue method. A significant increase in cell death was observed when the cell line was exposed to higher concentrations of fipronil (P<0.0001). Western blots on TLR4 and 9 revealed no significant differences (TLR4 {P=0.49}, TLR9 {P = 0.94}) between cells exposed to fipronil and those exposed to the control (DMSO). The data taken together show that fipronil causes cell dealth in vitro, and induces lung inflammation following oral or intranasal exposure but has different effects on the expression of TLR4 and TLR9 in vivo. Because of the central roles of TLR4 and TLR9 in lung inflammation, fipronil-induced changes in the expression of these receptors would alter the pulmonary response to bacterial infections in the host exposed to fipronil. Further studies are needed to examine the mechanisms through which fipronil regulates expression of immune receptors and also the pulmonary response of fipronil-exposed animals to subsequent microbial infections.

No description available.

No description available.

Introdução: Macrófagos de fenótipo M1 (ativação clássica) e M2 (ativação alternativa) estão relacionados com diversos processos patológicos como o câncer, a aterosclerose e doenças neurodegenerativas. No microambiente tumoral, os macrófagos associados ao tumor (TAM) têm atuação controversa na progressão da doença. Um modelo in vitro pode servir para avaliar a influência dessa alteração fenotípica em diversas patologias. A linhagem celular monocítica humana U937, sob estímulo de PMA (do inglês, Phorbol 12-myristate 13-acetate), se diferencia em macrófagos típicos. Estes adquirem fenótipos M1 e M2 quando estimulados, respectivamente, por LPS/IFN- e IL-4. Objetivo: Estabelecer um modelo in vitro para o estudo do papel dos macrófagos e seu envolvimento na progressão de doenças, bem como, sua caracterização fenotípica nesses eventos. Para tal, utilizamos: a) meta-análise de dois conjuntos de dados de micro-arranjos para avaliar os genes relacionados e b) análise de marcadores de diferenciação celular, taxa de adesão, alterações morfológicas e níveis de espécies reativas. Métodos: Cultura Celular: Linhagem celular humana U937, cultivada com meio de cultura RPMI 1640 e tratada com 10nM de PMA, por 12, 24, 48 e 72 horas. Quantificação de Espécies Reativas de Oxigênio: Células U937 diferenciadas e indiferenciadas incubadas com a sonda DCF para avaliar a formação de espécies reativas, medida fluorescência por 1h. Ensaio de MTT e Adesão Celular: Células U937 diferenciadas e indiferenciadas foram incubadas com solução de MTT por 1h, para análise da viabilidade celular, foi medida absorbância em 560nm e índice de adesão por método de SRB. Produção de óxido Nítrico: Quantificado pelo método de Griess, a 540nm. Análise Morfológica por meio de Imagens das Células: Imagens obtidas após tempos de tratamento com PMA em 0, 12, 24, 48 e 72 horas. Bioinformática: a) obtidos dois conjuntos de dados de micro-arranjos do Gene Expression Omnibus (GEO) - GSE5099 e GSE15038; b) criamos redes de genes para o fenótipo M1 e M2, com ferramenta on-line STRING e software MEDUSA; c) rede de genes e informações dos micro-arranjos foram combinados e plotados em gráficos de acordo com a sua topologia, com software ViaComplex. Resultados: As imagens mostraram alteração morfológica característica da célula monocítica U937 (célula proliferativa) para macrófago (célula aderida na placa), quando tratadas com PMA. Quanto aos níveis de espécies reativas formadas e a taxa de aderência medida, foi maior nas células tratadas, no decorrer do tempo de tratamento. A taxa de proliferação da célula controle U937 aumentou com o tempo, enquanto que, observamos uma diminuição na proliferação das células tratadas com PMA. A análise bioinformática mostrou um aumento na expressão, tratadas x controle, de genes do fenótipo M1 e M2, nas células U937 diferenciadas por PMA e polarizadas com LPS/IFN gama e IL-4, respectivamente. O fenótipo M1 mostrou aumento na formação de ER e de NO quando tratado com LPS + IFN-gamacombinados. Houve uma diminuição de NO no fenótipo M2 quando ativadas por IL-4. Conclusão: Nosso trabalho descreve um método válido de diferenciação macrofágica da linhagem humana U937 e a possibilidade de sua polarização ao fenótipo M1 e M2 quando estimulada com PMA e posteriormente com LPS/IFN gama e IL-4, respectivamente. A compreensão das relações entre as alterações fenotípicas dos macrófagos e do microambiente gerado é importante para o desenvolvimento de pesquisas para combater/atenuar a agressividade das patologias. / Introduction: In vitro model of macrophages (MF) can be used to evaluate the influence of these cells in human pathologies. Objective: To establish an in vitro model to study macrophages and it’s evaluating M1/M2 polarization. Methods: The human U937 cell line was grown in medium RPMI 1640 and differentiated into functional macrophages by 10 nM phorbol 12-myristate 13-acetate (PMA)-treatment, with M1 or M2 phenotypes with LPS/IFNg and IL-4, respectively. Reactive Oxigen Species (ROS) (time course of DCF oxidation), nitric oxide (NO) (Griess method), cell proliferation (MTT assay) and adherence (SRB method), and change in cellular morphology were determined. Moreover, two microarray data sets from Gene Expression Omnibus (GEO) (GSE5099 and GSE15038) were used to analyze differential M1/M2 gene expression with the online bioinformatics tools STRING, MEDUSA and Via Complex. Results: Time course experiments (0, 24, 48 and 72h) showed decreased cell proliferation with increase in morphological changes, cell adherence and ROS generation in PMA-treated U937 cells compatible with the acquisition of a macrophage-like phenotype. Bioinformatics approach showed increased expression in M1/M2 genes by PMA-treatment. 24h of LPS/IFNg- treatment induced increased NO, ROS, and the expression of M1 genes (classical activation MF), while 24h IL-4-treatment induced the expression of M2genes (alternative activation MF). Conclusion: This simple human macrophage-like differentiation and M1/M2 activation protocol could be used in vitro to establish the role of these cells in human pathologies.

Introdução: Macrófagos de fenótipo M1 (ativação clássica) e M2 (ativação alternativa) estão relacionados com diversos processos patológicos como o câncer, a aterosclerose e doenças neurodegenerativas. No microambiente tumoral, os macrófagos associados ao tumor (TAM) têm atuação controversa na progressão da doença. Um modelo in vitro pode servir para avaliar a influência dessa alteração fenotípica em diversas patologias. A linhagem celular monocítica humana U937, sob estímulo de PMA (do inglês, Phorbol 12-myristate 13-acetate), se diferencia em macrófagos típicos. Estes adquirem fenótipos M1 e M2 quando estimulados, respectivamente, por LPS/IFN- e IL-4. Objetivo: Estabelecer um modelo in vitro para o estudo do papel dos macrófagos e seu envolvimento na progressão de doenças, bem como, sua caracterização fenotípica nesses eventos. Para tal, utilizamos: a) meta-análise de dois conjuntos de dados de micro-arranjos para avaliar os genes relacionados e b) análise de marcadores de diferenciação celular, taxa de adesão, alterações morfológicas e níveis de espécies reativas. Métodos: Cultura Celular: Linhagem celular humana U937, cultivada com meio de cultura RPMI 1640 e tratada com 10nM de PMA, por 12, 24, 48 e 72 horas. Quantificação de Espécies Reativas de Oxigênio: Células U937 diferenciadas e indiferenciadas incubadas com a sonda DCF para avaliar a formação de espécies reativas, medida fluorescência por 1h. Ensaio de MTT e Adesão Celular: Células U937 diferenciadas e indiferenciadas foram incubadas com solução de MTT por 1h, para análise da viabilidade celular, foi medida absorbância em 560nm e índice de adesão por método de SRB. Produção de óxido Nítrico: Quantificado pelo método de Griess, a 540nm. Análise Morfológica por meio de Imagens das Células: Imagens obtidas após tempos de tratamento com PMA em 0, 12, 24, 48 e 72 horas. Bioinformática: a) obtidos dois conjuntos de dados de micro-arranjos do Gene Expression Omnibus (GEO) - GSE5099 e GSE15038; b) criamos redes de genes para o fenótipo M1 e M2, com ferramenta on-line STRING e software MEDUSA; c) rede de genes e informações dos micro-arranjos foram combinados e plotados em gráficos de acordo com a sua topologia, com software ViaComplex. Resultados: As imagens mostraram alteração morfológica característica da célula monocítica U937 (célula proliferativa) para macrófago (célula aderida na placa), quando tratadas com PMA. Quanto aos níveis de espécies reativas formadas e a taxa de aderência medida, foi maior nas células tratadas, no decorrer do tempo de tratamento. A taxa de proliferação da célula controle U937 aumentou com o tempo, enquanto que, observamos uma diminuição na proliferação das células tratadas com PMA. A análise bioinformática mostrou um aumento na expressão, tratadas x controle, de genes do fenótipo M1 e M2, nas células U937 diferenciadas por PMA e polarizadas com LPS/IFN gama e IL-4, respectivamente. O fenótipo M1 mostrou aumento na formação de ER e de NO quando tratado com LPS + IFN-gamacombinados. Houve uma diminuição de NO no fenótipo M2 quando ativadas por IL-4. Conclusão: Nosso trabalho descreve um método válido de diferenciação macrofágica da linhagem humana U937 e a possibilidade de sua polarização ao fenótipo M1 e M2 quando estimulada com PMA e posteriormente com LPS/IFN gama e IL-4, respectivamente. A compreensão das relações entre as alterações fenotípicas dos macrófagos e do microambiente gerado é importante para o desenvolvimento de pesquisas para combater/atenuar a agressividade das patologias. / Introduction: In vitro model of macrophages (MF) can be used to evaluate the influence of these cells in human pathologies. Objective: To establish an in vitro model to study macrophages and it’s evaluating M1/M2 polarization. Methods: The human U937 cell line was grown in medium RPMI 1640 and differentiated into functional macrophages by 10 nM phorbol 12-myristate 13-acetate (PMA)-treatment, with M1 or M2 phenotypes with LPS/IFNg and IL-4, respectively. Reactive Oxigen Species (ROS) (time course of DCF oxidation), nitric oxide (NO) (Griess method), cell proliferation (MTT assay) and adherence (SRB method), and change in cellular morphology were determined. Moreover, two microarray data sets from Gene Expression Omnibus (GEO) (GSE5099 and GSE15038) were used to analyze differential M1/M2 gene expression with the online bioinformatics tools STRING, MEDUSA and Via Complex. Results: Time course experiments (0, 24, 48 and 72h) showed decreased cell proliferation with increase in morphological changes, cell adherence and ROS generation in PMA-treated U937 cells compatible with the acquisition of a macrophage-like phenotype. Bioinformatics approach showed increased expression in M1/M2 genes by PMA-treatment. 24h of LPS/IFNg- treatment induced increased NO, ROS, and the expression of M1 genes (classical activation MF), while 24h IL-4-treatment induced the expression of M2genes (alternative activation MF). Conclusion: This simple human macrophage-like differentiation and M1/M2 activation protocol could be used in vitro to establish the role of these cells in human pathologies.

Introdução: Macrófagos de fenótipo M1 (ativação clássica) e M2 (ativação alternativa) estão relacionados com diversos processos patológicos como o câncer, a aterosclerose e doenças neurodegenerativas. No microambiente tumoral, os macrófagos associados ao tumor (TAM) têm atuação controversa na progressão da doença. Um modelo in vitro pode servir para avaliar a influência dessa alteração fenotípica em diversas patologias. A linhagem celular monocítica humana U937, sob estímulo de PMA (do inglês, Phorbol 12-myristate 13-acetate), se diferencia em macrófagos típicos. Estes adquirem fenótipos M1 e M2 quando estimulados, respectivamente, por LPS/IFN- e IL-4. Objetivo: Estabelecer um modelo in vitro para o estudo do papel dos macrófagos e seu envolvimento na progressão de doenças, bem como, sua caracterização fenotípica nesses eventos. Para tal, utilizamos: a) meta-análise de dois conjuntos de dados de micro-arranjos para avaliar os genes relacionados e b) análise de marcadores de diferenciação celular, taxa de adesão, alterações morfológicas e níveis de espécies reativas. Métodos: Cultura Celular: Linhagem celular humana U937, cultivada com meio de cultura RPMI 1640 e tratada com 10nM de PMA, por 12, 24, 48 e 72 horas. Quantificação de Espécies Reativas de Oxigênio: Células U937 diferenciadas e indiferenciadas incubadas com a sonda DCF para avaliar a formação de espécies reativas, medida fluorescência por 1h. Ensaio de MTT e Adesão Celular: Células U937 diferenciadas e indiferenciadas foram incubadas com solução de MTT por 1h, para análise da viabilidade celular, foi medida absorbância em 560nm e índice de adesão por método de SRB. Produção de óxido Nítrico: Quantificado pelo método de Griess, a 540nm. Análise Morfológica por meio de Imagens das Células: Imagens obtidas após tempos de tratamento com PMA em 0, 12, 24, 48 e 72 horas. Bioinformática: a) obtidos dois conjuntos de dados de micro-arranjos do Gene Expression Omnibus (GEO) - GSE5099 e GSE15038; b) criamos redes de genes para o fenótipo M1 e M2, com ferramenta on-line STRING e software MEDUSA; c) rede de genes e informações dos micro-arranjos foram combinados e plotados em gráficos de acordo com a sua topologia, com software ViaComplex. Resultados: As imagens mostraram alteração morfológica característica da célula monocítica U937 (célula proliferativa) para macrófago (célula aderida na placa), quando tratadas com PMA. Quanto aos níveis de espécies reativas formadas e a taxa de aderência medida, foi maior nas células tratadas, no decorrer do tempo de tratamento. A taxa de proliferação da célula controle U937 aumentou com o tempo, enquanto que, observamos uma diminuição na proliferação das células tratadas com PMA. A análise bioinformática mostrou um aumento na expressão, tratadas x controle, de genes do fenótipo M1 e M2, nas células U937 diferenciadas por PMA e polarizadas com LPS/IFN gama e IL-4, respectivamente. O fenótipo M1 mostrou aumento na formação de ER e de NO quando tratado com LPS + IFN-gamacombinados. Houve uma diminuição de NO no fenótipo M2 quando ativadas por IL-4. Conclusão: Nosso trabalho descreve um método válido de diferenciação macrofágica da linhagem humana U937 e a possibilidade de sua polarização ao fenótipo M1 e M2 quando estimulada com PMA e posteriormente com LPS/IFN gama e IL-4, respectivamente. A compreensão das relações entre as alterações fenotípicas dos macrófagos e do microambiente gerado é importante para o desenvolvimento de pesquisas para combater/atenuar a agressividade das patologias. / Introduction: In vitro model of macrophages (MF) can be used to evaluate the influence of these cells in human pathologies. Objective: To establish an in vitro model to study macrophages and it’s evaluating M1/M2 polarization. Methods: The human U937 cell line was grown in medium RPMI 1640 and differentiated into functional macrophages by 10 nM phorbol 12-myristate 13-acetate (PMA)-treatment, with M1 or M2 phenotypes with LPS/IFNg and IL-4, respectively. Reactive Oxigen Species (ROS) (time course of DCF oxidation), nitric oxide (NO) (Griess method), cell proliferation (MTT assay) and adherence (SRB method), and change in cellular morphology were determined. Moreover, two microarray data sets from Gene Expression Omnibus (GEO) (GSE5099 and GSE15038) were used to analyze differential M1/M2 gene expression with the online bioinformatics tools STRING, MEDUSA and Via Complex. Results: Time course experiments (0, 24, 48 and 72h) showed decreased cell proliferation with increase in morphological changes, cell adherence and ROS generation in PMA-treated U937 cells compatible with the acquisition of a macrophage-like phenotype. Bioinformatics approach showed increased expression in M1/M2 genes by PMA-treatment. 24h of LPS/IFNg- treatment induced increased NO, ROS, and the expression of M1 genes (classical activation MF), while 24h IL-4-treatment induced the expression of M2genes (alternative activation MF). Conclusion: This simple human macrophage-like differentiation and M1/M2 activation protocol could be used in vitro to establish the role of these cells in human pathologies.

Atherosclerosis is a complex inflammation condition involving the accumulation of lipid-filled macrophages within the artery wall. Progression of the initial fatty streak to an advanced atherosclerotic plaque is characterized by the development of a necrotic core region containing cholesterol and dead cells. The oxidation of low-density lipoprotein (LDL) to oxidized LDL (oxLDL) and its subsequent uptake by macrophages to form foam cells are the key process in plaque formation. OxLDL is found within atherosclerotic plaque, and it is cytotoxic to a range of cells including macrophages through the generation of reactive oxygen species (ROS) and induction of oxidative stress. The aim of this study was to examine the cytotoxic effects of oxLDL to U937 human monocyte-like cells. OxLDL caused a rapid concentration-dependent cell viability loss in U937 cells within 6 hours. The progression of oxLDL-induced cell death was found to be strongly correlated with the intracellular ROS production and intracellular glutathione (GSH) loss. OxLDL also caused a rapid loss of intracellular aconitase activity, indicating the impairment of the cellular metabolic function. The cytosolic calcium ion (Ca²⁺) level was also elevated by oxLDL, which could be from both intra- and extra-cellular sources. OxLDL also activated plasma membrane superoxide generation complex NADPH oxidase (NOX), and the progression of oxLDL-induced NOX activation was correlated with oxLDL-mediated ROS production, suggesting NOX is the major source of ROS. Further investigations using NOX inhibitors apocynin or diphenyleneiodonium (DPI) found that inhibition of NOX prevented oxLDL-induced cell viability loss, ROS production, GSH loss and aconitase activity decrease. The cytosolic Ca²⁺ elevation caused by oxLDL was also suppressed slightly by inhibiting NOX activity. These results clearly show that NOX is the major site of oxidative stress upon oxLDL activation, contributing to the oxLDL-induced cell death. This study also examined the protective effect of 7,8-dihydroneopterin (7,8-NP) on oxLDL-induced oxidative stress. 7,8-NP dramatically protected cells from oxLDL-induced cell viability loss, ROS generation and aconitase activity loss. 7,8-NP also inhibited oxLDL-induced cytosolic Ca²⁺ influx particularly after 3 hours. 7,8-NP did not inhibited mitochondrial aconitase activity decrease caused by oxLDL, nor inhibited mitochondrial ROS production. This indicates the protective effect of 7,8-NP against oxLDL damage could primarily in cytoplasm. The failure of 7,8-NP protection from oxLDL activating NOX suggests that the protection of 7,8-NP against oxLDL-induced oxidative stress was not due to the inhibition of NOX activation, but by radical scavenging activity of the NOX products.

Intracellular oxidative stress is induced by oxidised low density lipoprotein (oxLDL) in macrophages. In the atherosclerotic lesions, this oxLDL dependent oxidative stress appears to cause macrophage cell death, a key process in the development of the necrotic core within the complex plaque. Macrophages are activated by γ-interferon to synthesise and release a potent antioxidant, 7,8-dihydroneopterin (7,8-NP), which has been previously shown to protect human monocyte-like U937 cells and human monocyte-derived macrophage (HMDM) cells from oxLDL cytotoxicity. This study examined whether oxLDL causes the loss of cellular metabolic function and whether 7,8-dihydroneopterin can prevent this loss of metabolic activity in U937 cells and HMDM cells. OxLDL prepared by copper oxidation caused cell death in both U937 and HMDM cells at concentrations of 0.5 and 2.0 mg/ml, respectively. Cell morphology showed the oxLDL caused a necrotic like death in both cells as indicated by cell swelling and lysis. The decrease in cell viability was only observed after the loss of intracellular glutathione (GSH) which occurred in the first 3 hours in U937 cells following oxLDL addition. The loss of GSH appeared to be due to the production of intracellular oxidants generated in response to the presence of the oxLDL. Within 3 hours of oxLDL addition to both cell types, there was a rapid and progressive shutdown of cell metabolism indicated by a significant decrease in the enzymatic activity of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and a fall in lactate production and intracellular ATP levels. GAPDH activity was found to be inactivated rather than being lost from the cell. Gel electrophoresis with specific staining for oxidised proteins showed that the GAPDH had been oxidatively inactivated in the cells when oxLDL was present. Unlike GAPDH, lactate dehydrogenase (LDH) was not inactivated by the oxidation but was lost from the cells due to cell lysis. The observed rate of glycolysis failure was similar in both cell types except the HMDM cells did not lose lactate, LDH activity and cell viability until 6 hours compared to 3 hours with the U937 cells. The rate of oxygen consumption (VO2) was measured in U937 cells by taking cells at set time points and placing them in the respirometers to measure the VO2. U937 cells were found to increase their VO2 with incubation but this increase was inhibited in the presence of oxLDL within 3 hours. The addition of the 7,8 dihydroneopterin above 100 μM to both the U937 and HMDM cells significantly inhibited the oxLDL-induced loss of cell viability. GAPDH activity loss was also inhibited while lactate production was maintained. The 7,8-dihydroneopterin also prevented the decrease in the VO2 in oxLDL-treated U937 cells. OxLDL was labelled with fluorescent DiI to measure the uptake of oxLDL by HMDM cells. The incorporation of DiI into oxLDL was found to make it non-cytotoxic, possibly due to DiI’s antioxidant properties. Studies were therefore conducted using either a mixture of oxLDL and DiI labelled oxLDL (DiI-oxLDL) at non-protective concentrations or low concentration of DiI-oxLDL alone. These studies showed that 7,8-dihydroneopterin downregulated the oxLDL uptake in oxLDL-treated HMDM cells. Surprisingly the uptake rates also suggested that there was no relationship between oxLDL uptake and cell death assuming oxLDL and DiI-oxLDL are taken up by the same mechanism. This research showed that oxLDL-induced oxidative stress in macrophage cells causes a rapid oxidative loss of GAPDH activity which leads to the loss of glycolytic activity and a fall in ATP levels. The failure of cell metabolism appears to be a key event in the death mechanism triggered by the oxLDL. The radical scavenging activity of 7,8-dihydroneopterin appears to prevent the oxidative stress as indicated by the protection of the GSH pool. Without the oxidative stress, GAPDH remains functioning, glycolytic activity is maintained and both the U937 cells and HMDM cells did not die. This suggests that within the atherosclerotic plaque, 7,8-dihydroneopterin may act to stabilise the metabolism of macrophage cells in the presence of oxLDL and downregulate the oxLDL uptake.

Les sensibilisants de contact sont des molécules réactives électrophiles qui ont la capacité de modifier des protéines de la peau pour former un antigène. Au delà de ce mécanisme d'hapténisation, le signal de danger induit par les sensibilisants conduisant à l'activation des cellules dendritiques (DC) est un élément déterminant dans l'induction de cellules T spécifiques de l'haptène. Dans le contexte du 7ième amendement à la directive cosmétique européenne, la mise en place d'une batterie de tests in vitro permettant de prédire le potentiel sensibilisant de molécules est indispensable pour l'industrie cosmétique. Tandis que la plupart des études in vitro étudient les signaux de danger induits par les sensibilisants dans des modèles homéostasiques, nous nous sommes intéressés à l'effet des sensibilisants sur la mise en place d'une réponse inflammatoire. Lorsque la lignée U937 est différenciée avec du PMA et stimulée avec du LPS, les facteurs de transcription NF-κB et Nrf2 sont activés et l'acide arachidonique (AA) est métabolisé au travers de la cascade cPLA2 / COX-2. L'ensemble de ces voies activées conduit à la production par les U937 d'un grand nombre de médiateurs inflammatoires (IL-1β, TNF-α, IL-6, IL-10, IL-8, PGE2, PGD2, TxB2). Dans ce modèle, nous avons analysé l'effet de 6 sensibilisants de potentiels variés (DNCB, PPD, HQ, PG, CIN, EUG) et montré que de façon inattendue, tous les sensibilisants étudiés diminuent significativement et de façon spécifique la production de tous les prostanoïdes et en particulier de PGE2 induite par PMA/LPS. Nous avons de plus démontré que selon les sensibilisants, les cibles de cette inhibition au sein de la cascade métabolique de l'AA diffèrent, même si elles se focalisent la plupart du temps (sauf pour le DNCB) sur l'enzyme COX-2 (inhibition de son expression et/ou de son activité). Pour le DNCB, le mécanisme d'inhibition semble plutôt impliquer sa capacité à réagir fortement avec les groupements résidus thiols, ce qui se traduit en particulier par la déplétion du GSH intracellulaire et engendrerait l'inhibition des synthases dépendantes du GSH pour leurs activités. En parallèle de cette étude mécanistique, nous avons appréhendé la problématique du point de vue statistique et vérifié sur un set plus important et diversifié de molécules (160 molécules) que le paramètre « inhibition de PGE2 » pouvait être un bon test de prédiction de l'HSRC. L'étude statistique a permis de déterminer le modèle prédictif du test PGE2 et de mettre en évidence de bonnes performances (78%) par rapport aux prédictions du LLNA. Au-delà, une certaine complémentarité du test PGE2 avec d'autres tests in vitro (MUSST, Nrf2-HTS) a pu être mise en évidence. En conclusion, au travers de cette étude, nous avons pu mettre en évidence de nouvelles propriétés biochimiques des sensibilisants. Même si la signification biologique de la diminution de PGE2 par les sensibilisants de contact demeure complexe d'interprétation, ce paramètre a permis le développement d'un test qui prédit avec de bonnes performances le caractère sensibilisant de molécules et dont la position au sein d'une batterie prédictive d'évaluation de l'allergie de contact reste à être précisée. / Contact sensitizers are defined as reactive molecules (electrophilic) which have the ability to modify skin proteins to form an antigen (hapten). In addition to the haptenation mechanism, danger signals, leading to the activation of dendritic cells, are described to be crucial for the effective induction of an hapten-specific T cell immune response. In the context of the 7th amendment to the Cosmetic Directive, the cosmetic industry is concerned by the challenge of finding non-animal approaches to assess the sensitizing potential of chemicals. While danger signals induced by sensitizers in steady-state conditions have already been analyzed, we chose to investigate the impact of sensitizers on the course of an inflammatory response. For this purpose we used the U937 cell line differentiated with PMA and activated with LPS. In these conditions, cells produce a large amount of inflammatory mediators (IL-β, TNF-α, IL-6, IL-10, IL-8, PGE2, PGD2, TxB2) through the activation of pathways leading to the activation of the transcription factors NF-κB and Nrf2 and through AA metabolism by the cPLA2/COX-2 cascade. Interestingly, we showed that 6 contact sensitizers with various potential (DNCB, PPD, HQ, PG, CIN, EUG) significally and specifically decrease the production of prostanoïds and in particular of PGE2 induced by PMA/LPS. We further demonstrated that there is no unique inhibition profile of the sensitizers even if the majority (except for DNCB) of the effects applies on COX-2 (i.e. inhibition of the expression and/or activity). For DNCB, inhibition mechanism appears to be dependant of its capacity to react with thiols residues and in particular to deplete intracellular glutathione possibly leading to the inactivation of the PG-synthases. In parallel, we assess a statistical analysis on 160 molecules that allow us to define the test parameters (a molecule is a sensitizer if the PGE2 inhibition at 24h is more than 60%) and to calculate the test performance toward LLNA (78%). Moreover we demonstrated that the PGE2 test could be complementary to other already existing in vitro tests like MUSST or Nrf2-HTS. In summary, we add here a new insight into the multiple biochemical effects described so far for sensitizers. Even if the underlying biological relevance remains unclear, the parameter “PGE2 inhibition” is good test for skin sensitization evaluation. Further studies will precise how this parameter could be implemented into an alternative testing strategy for the evaluation of skin sensitization.

Phylloquinone is a natural analog of vitamin K that has been shown to both inhibit cancer cell growth and induce apoptosis in several cancer cell lines. This study examined these effects in a non-Hodgkin lymphoma cell line, known as U937. Cell growth inhibition and apoptosis were assessed through the quantification of cell density and area, following treatment with several concentrations of phylloquinone. In addition, apoptosis was detected and quantified using immunofluorescent markers of apoptosis (i.e. annexin V, APO-BrdU). Treatment with phylloquinone resulted in reduced overall cell density, increased overall cell area, and an increased frequency of apoptosis in U937 cells. Increasing both phylloquinone concentration and treatment time enhanced these effects. These results are significant because they document the anti-cancer effects of this analog of vitamin K, as well as provide insight into the morphological changes that occur during apoptosis in U937 cells.