Beta2-adrenoceptor activation inhibits Shiga toxin2-induced apoptosis of renal tubular epithelial cells.
Apoptosis is regulated by several pathways, such as caspases, mitogen activated protein kinase (MAPK) and cAMP/cAMP-dependent protein kinase A (PKA) cascade. This study investigated the effect of beta(2)-adrenoceptor activation on Shiga toxin (Stx)2-induced apoptosis in renal tubular cells and the contribution of these signalling pathways. Cultured human adenocarcinoma-derived tubular cells were exposed to Stx2 (64 pg/mL) for 2-24hr following the addition of the beta(2)-adrenoceptor agonist (terbutaline) to the incubation medium. Stx2-induced apoptosis and its amelioration by beta(2)-adrenoceptor activation was confirmed using DNA degradation assays and by flow cytometry for annexin V, mitochondrial membrane potential and caspase(-3 and -7) activity. Exposure of cells to Stx2 for 24hr increased the DNA fragmentation to 11.6+/-0.9%, compared to 3.3+/-0.2% in control cells (P<0.05) but was decreased to approximately 5-7% (P<0.05) in the presence of terbutaline. Furthermore, Stx2-stimulated apoptosis, detected by TUNEL, annexin V and mitochondrial potential, was inhibited by terbutaline (P<0.05) which was prevented by cAMP-PKA inhibitors and a beta(2)-adrenoceptor antagonist. However, inhibition of Stx2-mediated caspase activity by terbutaline was partially blocked by cAMP-PKA inhibitors. On the other hand, p38MAPK inhibition by terbutaline prevented Stx2-induced apoptosis and caspase activity through a cAMP-independent pathway via beta(2)-adrenoceptor. These data indicate that beta(2)-adrenoceptor activation can inhibit Stx2-induced apoptosis of the cells, which may be caused by a reduction in caspase activity through cAMP-PKA activation and the p38MAPK pathway.
Nakamura
Akio
A
Department of Paediatrics, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, Tokyo 173, Japan. akio@med.teikyo-u.ac.jp
Imaizumi
Akira
A
Yanagawa
Yukishige
Y
Niimi
Ryo
R
Kohsaka
Takao
T
Johns
Edward J
EJ
D017304:Annexin A5 / Q000494:pharmacology; D017209:Apoptosis; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases; D004247:DNA / Q000378:metabolism; D004587:Electrophoresis, Agar Gel; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects*; D006801:Humans; D020287:In Situ Nick-End Labeling; D007685:Kidney Tubules, Collecting / Q000166:cytology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism / Q000502:physiology*; D022641:Shiga Toxin 2 / Q000494:pharmacology*
D017304:Annexin A5; D018343:Receptors, Adrenergic, beta-2; D022641:Shiga Toxin 2; D004247:DNA; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020169:Caspases