Lipopolysaccharide regulates both serotonin- and thrombin-induced intracellular calcium mobilization in rat C6 glioma cells: possible involvement of nitric oxide synthase-mediated pathway.
To investigate the mechanisms by which lipopolysaccharide (LPS) affects Ca2+ signaling systems, we studied the effects of LPS on the serotonin (5-HT)- or thrombin-induced intracellular Ca2+ ([Ca2+]i) increase in rat C6 glioma cells. Pretreatment of the cells with 1 microg/ml LPS for 24 hr significantly inhibited [Ca2+]i increase induced by 10 microM 5-HT- or 0.5 U/ml thrombin. Its inhibitory effects were both dose- and time-dependent. Treatment with 1 mM dibutyryl cGMP (dbcGMP) for 30 min also significantly inhibited the 5-HT- and thrombin-induced [Ca2+]i increase to approximately 60-70% of control. However, simultaneous pretreatment with LPS and dbcGMP did not show any synergistic inhibition. The simultaneous pretreatment with LPS and the potent cGMP-dependent protein kinase (PKG) inhibitors H-8 and KT5823 for 24 hr significantly antagonized the inhibitory effect of LPS. Pretreatment of the cells with 1 microg/ml LPS for 24 hr significantly enhanced cGMP accumulation, while dexamethasone and NMMA (NOS inhibitors) significantly attenuated the LPS-induced enhancement in cGMP accumulation. In addition, pretreatment of the cells with 100 nM dexamethasone for 24 hr significantly suppressed LPS-induced inducible nitric oxide synthase (iNOS; type II NOS, NOS-II) protein expression. These results indicate that LPS may inhibit both 5-HT- and thrombin-induced [Ca2+]i increase via iNOS expression and PKG activation pathway in rat C6 glioma cells.
Tawara
Y
Y
Department of Psychiatry and Neurosciences, Hiroshima University School of Medicine, Japan.
Kagaya
A
A
Uchitomi
Y
Y
Horiguchi
J
J
Yamawaki
S
S
D000818:Animals; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006152:Cyclic GMP / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D003995:Dibutyryl Cyclic GMP / Q000494:pharmacology; D005910:Glioma; D007424:Intracellular Fluid / Q000502:physiology; D007546:Isoquinolines / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D009599:Nitroprusside / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D012701:Serotonin / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D013917:Thrombin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D007546:Isoquinolines; D008070:Lipopolysaccharides; D009599:Nitroprusside; D003995:Dibutyryl Cyclic GMP; D012701:Serotonin; D003907:Dexamethasone; C053177:N-(2-(methylamino)ethyl)-5-isoquinolinesulfonamide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D011493:Protein Kinase C; D013917:Thrombin; D006152:Cyclic GMP; D002118:Calcium