Activation of phosphoinositide 3-kinase, protein kinase C, and extracellular signal-regulated kinase is required for oridonin-enhanced phagocytosis of apoptotic bodies in human macrophage-like U937 cells.
Our previous study showed that oridonin isolated from Rabdosia rubescens enhanced phagocytosis of apoptotic cells by macrophage-like U937 cells through tumor necrosis factor (TNF) alpha and interleukin (IL)-1beta release. In this study, we further investigated signaling events involved in oridonin-augmented phagocytosis. Phagocytic stimulation was significantly suppressed by inhibitors, including a phosphoinositide 3-kinases (PI3K) inhibitor (wortmannin), a protein kinase C (PKC) inhibitor (stauroporine), and a phospholipase C (PLC) inhibitor (U73122). Exposure of U937 cells to oridonin caused an increase in PKC activity time- dependently, which was prevented by pretreatment with inhibitors of PI3K and PLC. Simultaneously, the activation of protein kinase B (PKB/Akt) and the increased expression of PLCgamma2 were also blocked by wortmannin. In addition, an extracellular signal-regulated kinase (ERK) MAPK inhibitor, PD98059, suppressed oridonin-augmented phagocytosis, whereas the p38 MAPK inhibitor (SB203580) and c-Jun N-terminal kinase (JNK) MAPK inhibitor (SP98059) had no inhibitory effect. Furthermore, pretreatment of U937 cells with anti-TNFalpha and anti-IL-1beta antibodies blocked oridonin-induced phagocytic stimulation as well as phosphorylation of ERK, but did not block the activation of PKC, indicating that these signaling events are triggered by oridonin, whereas secreted TNFalpha or IL-1beta only activate the ERK-dependent pathway. Taken together, oridonin is suggested to enhance phagocytosis of apoptotic bodies by activating PI3K, PKC, and ERK-dependent pathways.
Liu
Yan-Qiu
YQ
China-Japan Research Institute of Medical and Pharmaceutical Sciences, Shenyang Pharmaceutical University, Shenyang 110016, China.
You
Song
S
Tashiro
Shin-Ichi
S
Onodera
Satoshi
S
Ikejima
Takashi
T
D000730:Androstadienes / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects; D015153:Blotting, Western; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D002851:Chromatography, High Pressure Liquid; D004224:Diterpenes / Q000737:chemistry / Q000494:pharmacology*; D045786:Diterpenes, Kaurane; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D015394:Molecular Structure; D010587:Phagocytosis / Q000187:drug effects*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011760:Pyrrolidinones / Q000494:pharmacology; D019311:Staurosporine / Q000494:pharmacology; D013997:Time Factors; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D020298:U937 Cells; D014466:Ultraviolet Rays; D000077191:Wortmannin
D000730:Androstadienes; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D004224:Diterpenes; D045786:Diterpenes, Kaurane; D004791:Enzyme Inhibitors; D004963:Estrenes; D048049:Extracellular Signal-Regulated MAP Kinases; D005419:Flavonoids; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D011760:Pyrrolidinones; D019311:Staurosporine; D010738:Type C Phospholipases; D000077191:Wortmannin; C011959:oridonin; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one