High-density lipoprotein and low-density lipoprotein-mediated signal transduction in cultured human skin fibroblasts.
The signalling mechanisms whereby high-density lipoproteins (HDL) and low-density lipoproteins (LDL) affect a number of cellular functions in fibroblasts are unclear. This study has analyzed the influence of HDL3 and LDL on the phosphatidylinositol specific phospholipase C pathway in human skin fibroblasts. Exposure of myo-[2-3H]-inositol prelabelled fibroblasts to HDL3 or LDL elicited major increases in IP1 and minor increases in IP2 and IP3 within 30 s. In fura-2 loaded suspended fibroblasts, HDL3 and LDL increased intracellular Ca2+ concentrations ([Ca2+]i) with comparable rapid, transient kinetics. The dose-profiles for HDL3- and LDL-induced increases in [Ca2+]i were also comparable, with half-maximally and maximally effective concentrations being approximately 15 micrograms/mL and approximately 50 micrograms/mL, respectively. HDL3- and LDL-induced increases in [Ca2+]i were diminished by approximately 60% (vs. control fibroblasts) in thapsigargin-pretreated fibroblasts, indicating that release of Ca2+ from intracellular pools is the major contributor toward lipoprotein-induced increases in [Ca2+]i. Pertussis toxin-pretreatment of cells completely abolished lipoprotein induced Ca(2+)-transient, indicating the involvement of a guanine nucleotide-binding protein in the signalling process. In [3H]-palmitic acid-prelabelled fibroblasts, both HDL3 and LDL were observed to stimulate production of DAG. Activation of protein kinase C (PKC) was analysed by determining the cytosol-to-membrane translocation of both enzymatic activity and immunoreactivity of specific PKC isoforms (alpha, delta, epsilon, and zeta). Stimulation with HDL3 and LDL evoked a rapid (within 2.5 min) translocation of PKC activity, with PKC alpha and PKC epsilon being the isoforms translocated. It is concluded that HDL3 and LDL acutely stimulate a phosphoinositide-specific phospholipase C pathway in human skin fibroblasts. However, the specific cell membrane events mediating this signal transduction remain to be further elucidated.
Institut für Klinische Chemie und Laboratoriumsmedizin, Universität Regensburg, Germany.
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Möllers
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Schmitz
D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D004075:Diglycerides / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D005456:Fluorescent Dyes; D016257:Fura-2; D006801:Humans; D007295:Inositol Phosphates / Q000096:biosynthesis; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D008075:Lipoproteins, HDL / Q000494:pharmacology*; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D037342:Pertussis Toxin; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D015290:Second Messenger Systems; D015398:Signal Transduction / Q000187:drug effects; D012867:Skin / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D010738:Type C Phospholipases / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
C011439:1,2-diacylglycerol; D004075:Diglycerides; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D007295:Inositol Phosphates; D007527:Isoenzymes; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D013729:Terpenes; D010566:Virulence Factors, Bordetella; D019284:Thapsigargin; D000242:Cyclic AMP; D037342:Pertussis Toxin; D011493:Protein Kinase C; D010738:Type C Phospholipases; D002118:Calcium; D016257:Fura-2