Showing papers by "Pál Gergely published in 2004"

Effects of poly(ADP-ribose) polymerase inhibition on inflammatory cell migration in a murine model of asthma

Abstract: BACKGROUND Poly(ADP-ribose) polymerase-1 (PARP-1), a monomeric nuclear enzyme present in eukaryotes, plays a role in cell death, inflammatory mediator expression, and mononuclear cell recruitment in various experimental models of inflammation and reperfusion injury. Part of the molecular mechanism of this function involves the regulation of cytokine and chemokine production. Since chemokines are principal regulators of mononuclear and polymorphonuclear cell trafficking in asthma, we investigated the possibility whether PARP modulates chemokine production and cell recruitment in a murine model of asthma. MATERIAL/METHODS We studied ovalbumin-sensitized mice challenged with a single dose of ovalbumin. RESULTS PARP inhibition with the phenanthridinone-based PARP inhibitor PJ34 suppressed inflammatory cell migration. These effects were associated with downregulation of the CC chemokine MIP-1alpha, but not the CXC chemokine MIP-2. The production of TNF- alpha and IL-12, but not IL-5 or IL-13, was also suppressed by PARP inhibition. CONCLUSIONS Our results demonstrate the pathogenetic role of PARP activation in a murine model of asthma. PARP selectively regulates the production of certain chemokines and cytokines in this experimental model, which may be responsible for some of the observed protective effects seen in the current murine asthma model.

Localization of myosin phosphatase target subunit 1 in rat brain and in primary cultures of neuronal cells

Abstract: Myosin phosphatase (PP1M) is composed of the delta isoform of the PP1 catalytic subunit (PP1cdelta), the myosin phosphatase target subunit (MYPT), and a 20 kDa subunit. Western blots detected higher amounts of the MYPT1 isoform compared to MYPT2 in whole brain extracts. The localization of MYPT1 was studied in rat brain and in primary cell cultures of neurons using specific antibodies. Analysis of lysates of brain regions for MYPT1 and PP1M by Western blots using anti-MYPT1 antibodies and by phosphatase assays with myosin as substrate suggested a ubiquitous distribution. Immunohistochemistry of tissue sections revealed that MYPT1 was distributed in all areas of the brain, with staining observed in many different cell types. Depending on the method used for fixation, the MYPT1 appeared with varying intensity in nuclei, in nucleoli, and in the cytoplasm. In primary hippocampal cultures, MYPT1 was identified by confocal microscopy in the cytoplasm and in the nucleus, whereas a predominantly cytoplasmic localization was found in cochlear nucleus cells. In cultured cells, MYPT1 and PP1cdelta colocalized with synaptophysin. PP1M activity was high in synaptosomes isolated from the cerebral cortex, but was relatively low in the postsynaptic densities. The interaction of MYPT1 with synaptophysin and with known partners (Rho-kinase, PP1cdelta) in brain extracts was shown by immunoprecipitation with anti-MYPT1. Pull-down assays from synaptosomes, using GST-MYPT1, also confirmed these interactions. In conclusion, the widespread cellular and subcellular localization of MYPT1 implies that PP1M may play an important role in the dephosphorylation of key regulatory proteins in neuronal cells.

Cytoprotective effect of gallotannin in oxidatively stressed HaCaT keratinocytes: the role of poly(ADP-ribose) metabolism.

Abstract: Oxidative stress-induced cytotoxicity is mediated in part by accelerated poly-ADP ribosylation. Peroxynitrite and hydrogen peroxide cause DNA breakage triggering the activation of the DNA nick sensor enzyme poly(ADP-ribose) polymerase-1 (PARP-1). Overactivation of PARP-1 leads to cell dysfunction and cell death mainly due to depletion of NAD(+) (the substrate of PARP-1) and ATP. PARP-1 attaches most ADP-ribose residues onto itself, leading to downregulation of enzyme activity. Here, we have investigated the role of poly(ADP-ribose) glycohydrolase (PARG), the poly(ADP-ribose)-catabolyzing enzyme in oxidative stress-induced cytotoxicity in HaCaT cells. We have found that inhibition of PARG by gallotannin (GT) (50 microM) provided significant cytoprotection to peroxynitrite- or hydrogen peroxide-treated HaCaT cells, as assessed by lactate dehydrogenase release and propidium iodide uptake (parameters of necrotic cell death) as well as caspase activation (apoptotic parameter). GT pretreatment has also inhibited the depletion of cellular NAD(+) pools in hydrogen peroxide- or peroxynitrite-treated HaCaT cells. GT caused the accumulation of poly(ADP-ribose) and concomitant inhibition in cellular PARP activity in oxidatively stressed cells. Therefore, PARG is likely to contribute to maintaining the active state of PARP-1 by continuously removing inhibitory ADP-ribose residues from PARP-1.

Abnormal Cell-Specific Expressions of Certain Protein Kinase C Isoenzymes in Peripheral Mononuclear Cells of Patients with Systemic Lupus Erythematosus: Effect of Corticosteroid Application

Abstract: We have studied the expressions of various protein kinase C (PKC) isoenzymes in T cells and monocytes from patients with systemic lupus erythematosus (SLE), in comparison to those of healthy controls and patients with other immunological disorders. As measured by Western blotting, the levels of PKCβ, δ, η, e, θ and ζ (but not of PKCα) significantly decreased in T cells of SLE patients. In monocytes, however, we observed marked suppressions only in the expressions of PKCδ, e and ζ but not in the expressions of other PKC isoforms. In vivo corticosteroid application, as well as in vitro steroid treatment of monocytes, elevated the expressions of most isoforms close to normal values; however, the decreased levels of PKCθ and ζ were not affected by steroid application. These alterations were characteristic to SLE because we could not detect any changes in the PKC levels in mononuclear cells of primary Sjogren's syndrome and mixed connective tissue disease patients. These results suggest that impaired PKC isoenzyme pattern may exist in the T cells and monocytes of SLE patients. Furthermore, the clinically efficient glucocorticoid application in SLE can increase the expression of some members of PKC system.