Modulace funkce plazmacytoidních dendritických buněk: role immunoreceptorů TIM-3 a BDCA-2

Albert Font Haro ABSTRAKT Modulace funkce plazmacytoidních dendritických buněk: role immunoreceptorů TIM-3 a BDCA-2 Plasmacytoidní dendritické buňky (pDC) hrají klíčovou roli v antivirovou odpověd a propojení vrozené a adaptivní imunity. Tyto buňky exprimují endozomální toll-like receptory 7 a 9 detekující ssRNA a DNA postrádající methylaci CpG dinukleotidů. Díky stálé expresi transkripčního faktoru IRF7 jsou pDC schopny rychlé produkce velkého množství interferonů typu I (IFN-I; α, β, ω), typu III (IFN-III; 1, 2, 3, 4) a prozánětlivých cytokinů jako jsou IL-1, IL-6 a TNF-α. Po dozrání pDC také fungují jako buňky prezentující antigeny. I přes intenzivní výzkum je mechanizmus produkce a regulace IFN a prozánětlivých cytokinů málo prozkoumaný. S použitím buněčné linie GEN2.2 a primárních lidských pDC jsme popsali roli kináz MEK a SYK v produkci a regulaci produkce IFN-I. Zjistili jsme, že SYK se účastní nejen regulace regulačním receptorem (RR) řízené BCR-like dráhy působící negativně na sekreci IFN-I a IFN-III, ale také v pozitivní signalizaci pomocí TLR7/9 signální dráhy vedoucí k produkci IFN-I. Dále jsme zjistili že také MEK hraje důležitou roli v inhibiční RR dráze. Další výzkum pomocí farmakologického cílení kináz SYK a MEK může posloužit ke zmírnění symptomů nemocí jako je systémový lupus...Albert Font Haro ABSTRACT Modulation of plasmacytoid dendritic cell function: role of immunoreceptors TIM-3 and BDCA-2 Plasmacytoid dendritic cells (pDCs) are key players in the antiviral response as well as in linking innate and adaptive immune response. They express endosomal toll-like receptors 7 and 9, which can detect ssRNA and unmethylated CpG DNA, respectively. Due to the constitutive expression of the transcription factor IRF7, pDCs are able to rapidly produce massive quantities of type I (α, β, ω) and type III (1, 2, 3, 4) interferons (IFN-I and IFN-III) as well as pro- inflammatory cytokines such as IL-1, IL-6 and TNF-α. After maturation, they also function as antigen-presenting cells. Despite intense research, the mechanisms of IFN and pro-inflammatory cytokines production and regulation are still poorly understood. Using the pDC cell line GEN2.2 and also primary human pDCs, we shed light on the role of kinases MEK and SYK in IFN-I production and regulation. We found that SYK is not only involved in the regulatory receptor (RR)-mediated BCR-like pathway that represents the negative regulation of IFN-I and IFN-III secretion but also in the positive TLR7/9-mediated signal transduction pathway that leads to IFN-I production, representing the immunogenic function. We also found that MEK plays a...Department of Genetics and MicrobiologyKatedra genetiky a mikrobiologiePřírodovědecká fakultaFaculty of Scienc

Modulation of plasmacytoid dendritic cell function: role of immunoreceptors TIM-3 and BDCA-2

Albert Font Haro ABSTRACT Modulation of plasmacytoid dendritic cell function: role of immunoreceptors TIM-3 and BDCA-2 Plasmacytoid dendritic cells (pDCs) are key players in the antiviral response as well as in linking innate and adaptive immune response. They express endosomal toll-like receptors 7 and 9, which can detect ssRNA and unmethylated CpG DNA, respectively. Due to the constitutive expression of the transcription factor IRF7, pDCs are able to rapidly produce massive quantities of type I (α, β, ω) and type III (1, 2, 3, 4) interferons (IFN-I and IFN-III) as well as pro- inflammatory cytokines such as IL-1, IL-6 and TNF-α. After maturation, they also function as antigen-presenting cells. Despite intense research, the mechanisms of IFN and pro-inflammatory cytokines production and regulation are still poorly understood. Using the pDC cell line GEN2.2 and also primary human pDCs, we shed light on the role of kinases MEK and SYK in IFN-I production and regulation. We found that SYK is not only involved in the regulatory receptor (RR)-mediated BCR-like pathway that represents the negative regulation of IFN-I and IFN-III secretion but also in the positive TLR7/9-mediated signal transduction pathway that leads to IFN-I production, representing the immunogenic function. We also found that MEK plays a..

The MEK1/2-ERK Pathway Inhibits Type I IFN Production in Plasmacytoid Dendritic Cells

Recent studies have reported that the crosslinking of regulatory receptors (RRs), such as blood dendritic cell antigen 2 (BDCA-2) (CD303) or ILT7 (CD85g), of plasmacytoid dendritic cells (pDCs) efficiently suppresses the production of type I interferons (IFN-I, α/β/ω) and other cytokines in response to toll-like receptor 7 and 9 (TLR7/9) ligands. The exact mechanism of how this B cell receptor (BCR)-like signaling blocks TLR7/9-mediated IFN-I production is unknown. Here, we stimulated BCR-like signaling by ligation of RRs with BDCA-2 and ILT7 mAbs, hepatitis C virus particles, or BST2 expressing cells. We compared BCR-like signaling in proliferating pDC cell line GEN2.2 and in primary pDCs from healthy donors, and addressed the question of whether pharmacological targeting of BCR-like signaling can antagonize RR-induced pDC inhibition. To this end, we tested the TLR9-mediated production of IFN-I and proinflammatory cytokines in pDCs exposed to a panel of inhibitors of signaling molecules involved in BCR-like, MAPK, NF-ĸB, and calcium signaling pathways. We found that MEK1/2 inhibitors, PD0325901 and U0126 potentiated TLR9-mediated production of IFN-I in GEN2.2 cells. More importantly, MEK1/2 inhibitors significantly increased the TLR9-mediated IFN-I production blocked in both GEN2.2 cells and primary pDCs upon stimulation of BCR-like or phorbol 12-myristate 13-acetate-induced protein kinase C (PKC) signaling. Triggering of BCR-like and PKC signaling in pDCs resulted in an upregulation of the expression and phoshorylation of c-FOS, a downstream gene product of the MEK1/2-ERK pathway. We found that the total level of c-FOS was higher in proliferating GEN2.2 cells than in the resting primary pDCs. The PD0325901-facilitated restoration of the TLR9-mediated IFN-I production correlated with the abrogation of MEK1/2-ERK-c-FOS signaling. These results indicate that the MEK1/2-ERK pathway inhibits TLR9-mediated type I IFN production in pDCs and that pharmacological targeting of MEK1/2-ERK signaling could be a strategy to overcome immunotolerance of pDCs and re-establish their immunogenic activity

The MEK1/2-ERK Pathway Inhibits Type I IFN Production in Plasmacytoid Dendritic Cells

International audienceRecent studies have reported that the crosslinking of regulatory receptors (RRs), such as blood dendritic cell antigen 2 (BDCA-2) (CD303) or ILT7 (CD85g), of plasmacytoid dendritic cells (pDCs) efficiently suppresses the production of type I interferons (IFN-I, α/β/ω) and other cytokines in response to toll-like receptor 7 and 9 (TLR7/9) ligands. The exact mechanism of how this B cell receptor (BCR)-like signaling blocks TLR7/9-mediated IFN-I production is unknown. Here, we stimulated BCR-like signaling by ligation of RRs with BDCA-2 and ILT7 mAbs, hepatitis C virus particles, or BST2 expressing cells. We compared BCR-like signaling in proliferating pDC cell line GEN2.2 and in primary pDCs from healthy donors, and addressed the question of whether pharmacological targeting of BCR-like signaling can antagonize RR-induced pDC inhibition. To this end, we tested the TLR9-mediated production of IFN-I and proinflammatory cytokines in pDCs exposed to a panel of inhibitors of signaling molecules involved in BCR-like, MAPK, NF-ĸB, and calcium signaling pathways. We found that MEK1/2 inhibitors, PD0325901 and U0126 potentiated TLR9-mediated production of IFN-I in GEN2.2 cells. More importantly, MEK1/2 inhibitors significantly increased the TLR9-mediated IFN-I production blocked in both GEN2.2 cells and primary pDCs upon stimulation of BCR-like or phorbol 12-myristate 13-acetate-induced protein kinase C (PKC) signaling. Triggering of BCR-like and PKC signaling in pDCs resulted in an upregulation of the expression and phoshorylation of c-FOS, a downstream gene product of the MEK1/2-ERK pathway. We found that the total level of c-FOS was higher in proliferating GEN2.2 cells than in the resting primary pDCs. The PD0325901-facilitated restoration of the TLR9-mediated IFN-I production correlated with the abrogation of MEK1/2-ERK-c-FOS signaling. These results indicate that the MEK1/2-ERK pathway inhibits TLR9-mediated type I IFN production in pDCs and that pharmacological targeting of MEK1/2-ERK signaling could be a strategy to overcome immunotolerance of pDCs and re-establish their immunogenic activity

Expression of TIM-3 on Plasmacytoid Dendritic Cells as a Predictive Biomarker of Decline in HIV-1 RNA Level during ART

Depletion and functional impairment of circulating plasmacytoid dendritic cells (pDCs) are characteristic attributes of HIV-1-infection. The mechanism of dysfunction of pDCs is unclear. Here, we studied the development of phenotype of pDCs in a cohort of HIV-1-infected individuals monitored before the initiation and during a 9-month follow up with antiretroviral therapy (ART). Using polychromatic flow cytometry, we detected significantly higher pDC-surface expression of the HIV-1 receptor CD4, regulatory receptor BDCA-2, Fcγ receptor CD32, pDC dysfunction marker TIM-3, and the marker of killer pDC, TRAIL, in treatment-naïve HIV-1-infected individuals before initiation of ART when compared to healthy donors. After 9 months of ART, all of these markers approached but did not reach the expression levels observed in healthy donors. We found that the rate of decline in HIV-1 RNA level over the first 3 months of ART negatively correlated with the expression of TIM-3 on pDCs. We conclude that immunogenic phenotype of pDCs is not significantly restored after sustained suppression of HIV-1 RNA level in ART-treated patients and that the level of the TIM-3 expressed on pDCs in treatment naïve patients could be a predictive marker of the rate of decline in the HIV-1 RNA level during ART

Dual Role of the Tyrosine Kinase Syk in Regulation of Toll-Like Receptor Signaling in Plasmacytoid Dendritic Cells

International audienceCrosslinking of regulatory immunoreceptors (RR), such as BDCA-2 (CD303) or ILT7 (CD85g), of plasmacytoid dendritic cells (pDCs) efficiently suppresses production of type-I interferon (IFN)-α/β and other cytokines in response to Toll-like receptor (TLR) 7/9 ligands. This cytokine-inhibitory pathway is mediated by spleen tyrosine kinase (Syk) associated with the ITAM-containing adapter of RR. Here we demonstrate by pharmacological targeting of Syk that in addition to the negative regulation of TLR7/9 signaling via RR, Syk also positively regulates the TLR7/9 pathway in human pDCs. Novel highly specific Syk inhibitor AB8779 suppressed IFN-α, TNF-α and IL-6 production induced by TLR7/9 agonists in primary pDCs and in the pDC cell line GEN2.2. Triggering of TLR9 or RR signaling induced a differential kinetics of phosphorylation at Y352 and Y525/526 of Syk and a differential sensitivity to AB8779. Consistent with the different roles of Syk in TLR7/9 and RR signaling, a concentration of AB8779 insufficient to block TLR7/9 signaling still released the block of IFN-α production triggered via the RR pathway, including that induced by hepatitis B and C viruses. Thus, pharmacological targeting of Syk partially restored the main pDC function-IFN-α production. Opposing roles of Syk in TLR7/9 and RR pathways may regulate the innate immune response to weaken inflammation reaction

Presentation_1.PDF

<p>Recent studies have reported that the crosslinking of regulatory receptors (RRs), such as blood dendritic cell antigen 2 (BDCA-2) (CD303) or ILT7 (CD85g), of plasmacytoid dendritic cells (pDCs) efficiently suppresses the production of type I interferons (IFN-I, α/β/ω) and other cytokines in response to toll-like receptor 7 and 9 (TLR7/9) ligands. The exact mechanism of how this B cell receptor (BCR)-like signaling blocks TLR7/9-mediated IFN-I production is unknown. Here, we stimulated BCR-like signaling by ligation of RRs with BDCA-2 and ILT7 mAbs, hepatitis C virus particles, or BST2 expressing cells. We compared BCR-like signaling in proliferating pDC cell line GEN2.2 and in primary pDCs from healthy donors, and addressed the question of whether pharmacological targeting of BCR-like signaling can antagonize RR-induced pDC inhibition. To this end, we tested the TLR9-mediated production of IFN-I and proinflammatory cytokines in pDCs exposed to a panel of inhibitors of signaling molecules involved in BCR-like, MAPK, NF-ĸB, and calcium signaling pathways. We found that MEK1/2 inhibitors, PD0325901 and U0126 potentiated TLR9-mediated production of IFN-I in GEN2.2 cells. More importantly, MEK1/2 inhibitors significantly increased the TLR9-mediated IFN-I production blocked in both GEN2.2 cells and primary pDCs upon stimulation of BCR-like or phorbol 12-myristate 13-acetate-induced protein kinase C (PKC) signaling. Triggering of BCR-like and PKC signaling in pDCs resulted in an upregulation of the expression and phoshorylation of c-FOS, a downstream gene product of the MEK1/2-ERK pathway. We found that the total level of c-FOS was higher in proliferating GEN2.2 cells than in the resting primary pDCs. The PD0325901-facilitated restoration of the TLR9-mediated IFN-I production correlated with the abrogation of MEK1/2-ERK-c-FOS signaling. These results indicate that the MEK1/2-ERK pathway inhibits TLR9-mediated type I IFN production in pDCs and that pharmacological targeting of MEK1/2-ERK signaling could be a strategy to overcome immunotolerance of pDCs and re-establish their immunogenic activity.</p

Effect of Syk inhibitor AB8779 on production of IFN-α TNF-α and IL-6 in pDCs.

<p>(A) Experimental outline. GEN2.2 cells (B), or primary pDC (C) were incubated with different concentrations of Syk inhibitor AB8779 for 1 hr before stimulation with CpG-A, CpG-B and PMA (N = 3) (B), or CpG-A and R848 (N = 2) (<b>C</b>). After 16 hr culture, IFN-α TNF-α and IL-6 production in GEN2.2 cells (B) or in primary pDCs (C) was determined in cell-free supernatants by ELISA and the results expressed as a multiple of control with the matching concentration of DMSO.</p

Subliminal concentrations of Syk inhibitor partially restore IFN-α production in GEN2.2 pDC cell line.

<p>(A) Experimental outline. After separation from MS-5 feeder cells, GEN2.2 cells were incubated with 0.01 μM AB8779 or with a matching concentration of DMSO for 1 hr before exposure ILT7 or BDCA-2 mAb or HCV or HBV particles and stimulation with CpG-A. (B) After 16 hr culture, IFN-α production was determined in GEN2.2 cell-free supernatants by ELISA, and the results were standardized to the quantity of IFN-α produced by GEN2.2 exposed to isotype control Ab or mock-infected culture in the absence of AB8779 (N = 3). (C) IFN-α production determined in GEN2.2 exposed to ILT7 or BDCA-2 mAb or HCV or HBV particles (shown in B) was normalized to IFN-α production in the absence of AB8779 *, <i>p</i> ≤0.05; **, <i>p</i> <0.01.</p