ABSTRACT
Poly(ADP-ribosyl)ation is an essential post-translational modification with the biopolymer poly(ADP-ribose) (PAR). The reaction is catalyzed by poly(ADP-ribose) polymerases (PARPs) and plays key roles in cellular physiology and stress response. PARP inhibitors are currently being tested in clinical cancer treatment, in combination therapy, or as monotherapeutic agents by inducing synthetic lethality. We have developed an accurate and sensitive bioanalytical platform based on isotope dilution mass spectrometry in order to quantify steady-state and stress-induced PAR levels in cells and tissues and to characterize pharmacological properties of PARP inhibitors. In contrast to existing PAR-detection techniques, the LC-MS/MS method uses authentic isotope-labeled standards, which provide unequivocal chemical specificity to quantify cellular PAR in absolute terms with femtomol sensitivity. Using this platform we analyzed steady-state levels as well as stress-induced dynamics of poly(ADP-ribosyl)ation in a series of biological systems including cancer cell lines, mouse tissues, and primary human lymphocytes. Our results demonstrate a rapid and transient stress-induced increase in PAR levels by >100-fold in a dose- and time-dependent manner with significant differences between cell types and individual human lymphocyte donors. Furthermore, ex vivo pharmacodynamic studies in human lymphocytes provide new insight into pharmacological properties of clinically relevant PARP inhibitors. Finally, we adapted the LC-MS/MS method to quantify poly(ADP-ribosyl)ation in solid tissues and identified tissue-dependent associations between PARP1 expression and PAR levels in a series of different mouse organs. In conclusion, this study demonstrates that mass spectrometric quantification of cellular poly(ADP-ribosyl)ation has a wide range of applications in basic research as well as in drug development.
Subject(s)
Isotopes , Poly(ADP-ribose) Polymerases/physiology , Stress, Physiological , Animals , Cell Line, Tumor , Chromatography, High Pressure Liquid , Dose-Response Relationship, Drug , Enzyme Inhibitors/chemistry , Fluorescent Antibody Technique , Humans , Limit of Detection , Lymphocytes/enzymology , Mass Spectrometry , Mice , Molecular Structure , Poly(ADP-ribose) Polymerase InhibitorsABSTRACT
Mitochondrial reactive oxygen species (ROS) are indispensible for T cell activation-induced expression of interleukin 2 (IL-2) and CD95 ligand (CD95L, FasL/Apo-1L) genes, and in turn, for CD95L-mediated activation-induced cell death (AICD). Here, we show that manganese superoxide dismutase (MnSOD/SOD2), a major mitochondrial antioxidative enzyme, constitutes an important control switch in the process of activation-induced oxidative signal generation in T cells. Analysis of the kinetics of T cell receptor (TCR)-triggered ROS production revealed a temporal association between higher MnSOD abundance/activity and a shut-down phase of oxidative signal generation. Transient or inducible MnSOD overexpression abrogated T cell activation-triggered mitochondrial ROS production as well as NF-κB- and AP-1-mediated transcription. Consequently, lowered expression of IL-2 and CD95L genes resulted in decreased IL-2 secretion and CD95L-dependent AICD. Moreover, upregulation of the mitochondrial MnSOD level is dependent on oxidation-sensitive transcription and not on the increase of mitochondrial mass. Thus, MnSOD-mediated negative feedback regulation of activation-induced mitochondrial ROS generation exemplifies a process of retrograde mitochondria-to-nucleus communication. Our finding underlines the critical role for MnSOD and mitochondria in the regulation of human T cell activation.
Subject(s)
Lymphocyte Activation/immunology , Signal Transduction/immunology , Superoxide Dismutase/metabolism , T-Lymphocytes/cytology , T-Lymphocytes/enzymology , Cell Death/immunology , Fas Ligand Protein/metabolism , Gene Expression Regulation , Humans , Jurkat Cells , Mitochondria/metabolism , Models, Immunological , Oxidation-Reduction , Reactive Oxygen Species/metabolism , Superoxide Dismutase/genetics , T-Lymphocytes/immunology , Transcription, GeneticABSTRACT
There is growing evidence that immunocompetent cells are involved in the pathogenesis of chronic pancreatitis. Using a model of chronic pancreatitis induced by dibutyltin dichloride (DBTC) in rats, we have immunohistochemically phenotyped the infiltrating T lymphocytes, CD45RC+ cells, macrophages, as well as the IL-2 receptor as an activation marker during a time course of two months. In addition, the expression of CD44, of the integrin component CD18, and of MHC class II was determined. Furthermore, the isoforms of CD45 which are generated by alternative mRNA splicing were analysed using reverse transcription followed by the polymerase chain reaction-technique (RT-PCR). The pattern of the local leukocytes in the DBTC pancreatitis suggests that the acute unspecific inflammation is followed by an activation of T lymphocytes resulting in the chronic course of the disease.
