Tamas Palkovics

Progesterone as an immunomodulatory molecule

Increased progesterone sensitivity of pregnancy lymphocytes is due to activation-induced appearance of progesterone binding sites in the lymphocytes. Following recognition of fetally derived antigens gamma/delta TCR+ cells develop progesterone receptors. Progesterone binding results in the synthesis of a mediator protein named the progesterone-induced blocking factor (PIBF). PIBF by acting on the phospholipase A2 enzyme interferes with arachidonic acid metabolism, induces a Th2 biased immune response, and by controlling NK activity exerts an anti-abortive effect.

The role of γ/δ T cells in progesterone-mediated immunomodulation during pregnancy: A review

PROBLEM: To determine if pregnancy is recognized by the immune system and if inadequate recognition of fetal antigens might result in failed pregnancy.

Progesterone-Induced Blocking Factor Activates STAT6 via Binding to a Novel IL-4 Receptor

Progesterone-induced blocking factor (PIBF) induces Th2-dominant cytokine production. Western blotting and EMSA revealed phosphorylation as well as nuclear translocation of STAT6 and inhibition of STAT4 phosphorylation in PIBF-treated cells. The silencing of STAT6 by small interfering RNA reduced the cytokine effects. Because the activation of the STAT6 pathway depends on the ligation of IL-4R, we tested the involvement of IL-4R in PIBF-induced STAT6 activation. Although PIBF does not bind to IL-4R, the blocking of the latter with an Ab abolished PIBF-induced STAT6 activation, whereas the blocking of the IL-13R had no effect. PIBF activated suppressor of cytokine signaling-3 and inhibited IL-12-induced suppressor of cytokine signaling-1 activation. The blocking of IL-4R counteracted all the described effects, suggesting that the PIBF receptor interacts with IL-4R α-chain, allowing PIBF to activate the STAT6 pathway. PIBF did not phosphorylate Jak3, suggesting that the γ-chain is not needed for PIBF signaling. Confocal microscopic analysis revealed a colocalization and at 37°C a cocapping of the FITC PIBF-activated PIBF receptor and PE anti-IL-4R-labeled IL-4R. After the digestion of the cells with phosphatidylinositol-specific phospholipase C, the STAT6-activating effect of PIBF was lost, whereas that of IL-4 remained unaltered. These data suggest the existence of a novel type of IL-4R composed of the IL-4R α-chain and the GPI-anchored PIBF receptor.

Progesterone-dependent immunomodulation

The biological effects of progesterone are mediated by a 34-kDa protein named the progesterone-induced blocking factor (PIBF). PIBF, synthesized by lymphocytes of healthy pregnant women in the presence of progesterone, inhibits arachidonic acid release as well as NK activity, and modifies the cytokine balance. Within the cell the full-length PIBF is associated with the centrosome, while secretion of shorter forms is induced by activation of the cell. PIBF induces nuclear translocation of STAT6 as well as PKC phosphorylation and exerts a negative effect on STAT4 phosphorylation. The concentration of PIBF in pregnancy urine is related to the positive or negative outcome of pregnancy; furthermore, premature pregnancy termination is predictable by lower than normal pregnancy PIBF values. In vivo data suggest the biological importance of the above findings. Treatment of pregnant Balb/c mice with the antiprogesterone RU 486 results in an increased resorption rate, which is associated with the inability of spleen cells to produce PIBF. High resorption rates induced by progesterone receptor block as well as those due to high NK activity are corrected by simultaneous PIBF treatment.

Suppressing LPS-induced early signal transduction in macrophages by a polyphenol degradation product: a critical role of MKP-1

Macrophages represent the first defense line against bacterial infection and therefore, play a crucial role in early inflammatory response. In this study, we investigated the role of MAPKs and MKP‐1 activation in regulation of an early inflammatory response in RAW 264.7 macrophage cells. We induced the inflammatory response by treating the macrophages with LPS and inhibited an early inflammatory response by using ferulaldehyde, a water‐soluble end‐product of dietary polyphenol degradation that we found previously to exert its beneficial anti‐inflammatory effects during the early phase of in vivo inflammation. We found that LPS‐induced ROS and nitrogen species formations were reduced by ferulaldehyde in a concentration‐dependent manner, and ferulaldehyde protected mitochondria against LPS‐induced rapid and massive membrane depolarization. LPS induced early suppression of MKP‐1, which was accompanied by activation of JNK, ERK, and p38 MAPK. By reversing LPS‐induced early suppression of MKP‐1, ferulaldehyde diminished MAPK activation, thereby inhibiting NF‐κB activation, mitochondrial depolarization, and ROS production. Taken together, our data suggest that ferulaldehyde exerts its early anti‐inflammatory effect by preserving the mitochondrial membrane integrity and shifting the expression of MKP‐1 forward in time in macrophages.

The progesterone-induced blocking factor modulates the balance of PKC and intracellular Ca.

Problem  Progesterone‐induced blocking factor (PIBF) induces Th2 biased cytokine production; therefore, this study investigates the effects of PIBF on the protein kinase C (PKC)/Ca++ system – which plays a key role in Th1/Th2 differentiation.

Feto-maternal immune regulation by TIM-3/galectin-9 pathway and PD-1 molecule in mice at day 14.5 of pregnancy

INTRODUCTION Immunoregulation implies the activation of negative pathways leading to the modulation of specific immune responses. Co-inhibitory receptors (such as PD-1 and TIM-3) represent possible tools for this purpose. PD-1 and TIM-3 have been demonstrated to be present on immune cells suggesting general involvement in immunosuppression such as fetomaternal tolerance. The aim of our study was to investigate the expression pattern of PD-1, TIM-3, and its ligand Gal-9 on different immune cell subsets in the peripheral blood and at the fetomaternal interface in pregnant mice. METHODS TIM-3 and PD-1 expression by peripheral and decidual immune cells from pregnant BALB-c mice in 2 weeks of gestational age were measures by flow cytometry. Placental galectin-9 expression was determined by immunohistochemically and RT-PCR. RESULTS Gal-9 was found to be present in the spongiotrophoblast layer of the haemochorial placenta. Decidual NK, NKT and γ/δ T cells showed increased PD-1 expression and reduced cytotoxic potential when compared to the periphery. TIM-3 expression by NK cells and γ/δ T cells is similar both in the periphery and in the decidua, notably, their relative TIM-3 expression is increased locally which is associated with reduced lytic activity. Decidual NKT cells exhibit a reduced TIM-3 expression with increased relative receptor expression and a slightly increased cytotoxicity when compared to the periphery. DISCUSSION Our data reveals a particularly complex, tissue and cell type specific immunoregulatory mechanism by the investigated co-inhibitory receptors at the fetomaternal interface.

Antimicrobial and Virulence-Modulating Effects of Clove Essential Oil on the Foodborne Pathogen Campylobacter jejuni

ABSTRACT Our study investigated the antimicrobial action of clove (Syzygium aromaticum) essential oil (EO) on the zoonotic pathogen Campylobacter jejuni. After confirming the clove essential oils general antibacterial effect, we analyzed the reference strain Campylobacter jejuni NCTC 11168. Phenotypic, proteomic, and transcriptomic methods were used to reveal changes in cell morphology and functions when exposed to sublethal concentrations of clove EO. The normally curved cells showed markedly straightened and shrunken morphology on the scanning electron micrographs as a result of stress. Although, oxidative stress, as a generally accepted response to essential oils, was also present, the dominance of a general stress response was demonstrated by reverse transcription-PCR (RT-PCR). The results of RT-PCR and two-dimensional (2D) PAGE revealed that clove oil perturbs the expression of virulence-associated genes taking part in the synthesis of flagella, PEB1, PEB4, lipopolysaccharide (LPS), and serine protease. Loss of motility was also detected by a phenotypic test. Bioautographic analysis revealed that besides its major component, eugenol, at least four other spots of clove EO possessed bactericidal activity against C. jejuni. Our findings show that clove EO has a marked antibacterial and potential virulence-modulating effect on C. jejuni. IMPORTANCE This study demonstrates that the components of clove essential oil influence not only the expression of general stress genes but also the expression of virulence-associated genes. Based on this finding, alternative strategies can be worked on to control this important foodborne pathogen.

Oxidative stress effect on progesterone-induced blocking factor (PIBF) binding to PIBF-receptor in lymphocytes

Receptor-ligand binding is an essential interaction for biological function. Oxidative stress can modify receptors and/or membrane lipid dynamics, thus altering cell physiological functions. The aim of this study is to analyze how oxidative stress may alter receptor-ligand binding and lipid domain distribution in the case of progesterone-induced blocking factor/progesterone-induced blocking factor-receptor. For membrane fluidity regionalization analysis of MEC-1 lymphocytes, two-photon microscopy was used in individual living cells. Lymphocytes were also double stained with AlexaFluor647/progesterone-induced blocking factor and Laurdan to evaluate -induced blocking factor/progesterone-induced blocking factor-receptor distribution in the different membrane domains, under oxidative stress. A new procedure has been developed which quantitatively analyzes the regionalization of a membrane receptor among the lipid domains of different fluidity in the plasma membrane. We have been able to establish a new tool which detects and evaluates lipid raft clustering from two-photon microscopy images of individual living cells. We show that binding of progesterone-induced blocking factor to progesterone-induced blocking factor-receptor causes a rigidification of plasma membrane which is related to an increase of lipid raft clustering. However, this clustering is inhibited under oxidative stress conditions. In conclusion, oxidative stress decreases membrane fluidity, impairs receptor-ligand binding and reduces lipid raft clustering.

Nonspecific Immunological Mechanisms and Hormones

Pregnancy lymphocytes express progesterone receptors (PR). The regulation of lymphocyte PR expression is activation dependent, but hormone independent. There are at least two possible ways of recognition of fetally derived antigens by the maternal immune system. Shed antigens that appear in maternal circulation can be recognized by α/βT cells, or alternatively, antigens presented by the trophoblast might be recognized by γ/δT cells.