Gadolinium blocks rat Kupffer cell calcium channels: relevance to calcium-dependent prostaglandin E2 synthesis and septic mortality.
Hepatic Kupffer cells (KC), the major tissue macrophage population, produce the septic response mediators, tumor necrosis factor alpha (TNF-alpha) and prostaglandin E2 (PGE2), and have been shown to internalize gadolinium chloride (GD), a rare earth metal of the lanthanide series. Because GD pretreatment of rats has been shown to inhibit the mortality of sepsis, we studied the secretory response to lipopolysaccharide (LPS) by KC isolated from rats injected with either saline or GD (7 mg/kg, intravenously) on the 2 days before KC isolation. Using culture conditions modified to reflect the intrasinusoidal milieu of arginine (RPMI-1640 media with 10 or 100 micromol/L arginine), KC from GD-treated rats responded to LPS (0. 0025 microg/mL) with significantly (P <.01) reduced PGE2 release. In contrast, TNF-alpha release by treated KC was significantly (P <.05) enhanced, consistent with the loss of PGE2 autocoid inhibition of TNF-alpha. Calcium flux is an early signaling event in eicosanoid synthesis, and GD is known to block calcium channels. Therefore, KC were loaded with fura-2-AM to study the effect of GD on KC calcium flux. GD prevented ionomycin and platelet-activating factor (PAF)-mediated [Ca++]i increase and calcium-dependent PGE2 synthesis, while GD did not affect PGE2 synthesis when protein kinase C (PKC) was directly activated with tetradecanoylphorbolacetate (TPA). The inhibition of calcium flux and calcium-dependent PGE2 synthesis in the major cell of the monocytic phagocytic system by GD may explain the previously reported ability of this lanthanide to prevent the mortality of endotoxemia.
Department of Surgery, Washington University School of Medicine, St. Louis, MO 63110, USA.
C R
CR
Roland
B
B
Naziruddin
T
T
Mohanakumar
M W
MW
Flye
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects*; D015232:Dinoprostone / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D005682:Gadolinium / Q000494:pharmacology*; D007239:Infections / Q000401:mortality; D015759:Ionomycin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D007476:Ionophores / Q000037:antagonists & inhibitors / Q000494:pharmacology; D007728:Kupffer Cells / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D007476:Ionophores; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D015759:Ionomycin; D005682:Gadolinium; D015232:Dinoprostone; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium