Noncyclooxygenase metabolites of arachidonic acid amplify the vasopressin-induced Ca2+ signal in glomerular mesangial cells by releasing Ca2+ from intracellular stores.
Noncyclooxygenase metabolites of arachidonic acid may be potent modulators of the mitogenic response of renal mesangial cells to the mitogenic vasoactive peptide arginine vasopressin (AVP). Since Ca2+ is a critical second messenger in the response of mesangial cells to AVP, and Ca2+ has been implicated in the regulation of growth, we determined whether noncyclooxygenase metabolites altered the phospholipase C-Ca2+ signalling cascade which is activated by AVP. Pretreatment of mesangial cells for 10 min with lipoxygenase and cytochrome P450 monooxygenase inhibitors, nordihydroguaiaretic acid (NDGA, 10(-5) M) or SKF-525A (2.5 x 10(-5) M), but not the cyclooxygenase inhibitor indomethacin (2 x 10(-5) M), reduced the magnitude of the AVP (10(-8) and 10(-7) M)-induced increase in cytosolic free Ca2+ concentration ([Ca2+]i) without affecting inositol trisphosphate production. With 10(-8) M AVP, [Ca2+]i increased to 250 +/- 47 nM in NDGA-treated cells versus 401 +/- 59 nM in control cells (p less than 0.01). [Ca2+]i, measured 2 min after exposure to AVP, was also lower with NDGA (152 +/- 21 nM) when compared with AVP alone (220 +/- 22 nM, p less than 0.01). 14,15-epoxyeicosatrienoic acid (EET) (10(-8) M), which had no effect on inositol trisphosphate production, completely reversed the NDGA-induced inhibition of the [Ca2+]i transient, whereas 5-hydroperoxyeicosatetraenoic acid (HPETE) (5 x 10(-7) M) did not. Pretreatment with higher concentrations of 14,15-EET (10(-7)-10(-6) M) markedly potentiated the AVP-induced increase in [Ca2+]i. NDGA-induced inhibition of the AVP-generated [Ca2+]i transient was also observed when cells were incubated in low Ca2+ media ([Ca2+] less than 5 x 10(-8) M), suggesting that NDGA pretreatment impaired intracellular release of Ca2+. Since NDGA had no direct effect on inositol 1,4,5-trisphosphate-induced Ca2+ release, we postulated that NDGA blocked production of a metabolite that releases Ca2+ from intracellular stores. 14,15-EET and 15-HPETE, but not 15-hydroxyeicosatetraenoic acid (each at 3 x 10(-7) M), raised [Ca2+]i when added directly to cells in low Ca2+ media. In permeabilized cells 14,15-EET and 15-HPETE (10(-7) M) potently released Ca2+ from intracellular stores. In summary, noncyclooxygenase metabolites of arachidonic acid, and in particular P450 metabolites, are potent endogenous amplifiers of the AVP-induced [Ca2+]i signal by mechanisms not directly involving phospholipase C activation. This effect is mediated, at least in part, by enhanced release of Ca2+ from intracellular storage sites by an inositol 1,4,5-trisphosphate-independent mechanism.
Force
T
T
Department of Preventive Medicine, Massachusetts General Hospital, Boston.
Hyman
G
G
Hajjar
R
R
Sellmayer
A
A
Bonventre
J V
JV
D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D001127:Arginine Vasopressin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002478:Cells, Cultured; D015232:Dinoprostone / Q000494:pharmacology; D015777:Eicosanoids / Q000502:physiology; D015118:Eicosapentaenoic Acid / Q000494:pharmacology; D005920:Glomerular Mesangium / Q000502:physiology*; D006893:Hydroxyeicosatetraenoic Acids / Q000494:pharmacology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D015289:Leukotrienes / Q000494:pharmacology; D008054:Lipid Peroxides / Q000494:pharmacology; D009637:Masoprocol / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000502:physiology*
D001095:Arachidonic Acids; D015777:Eicosanoids; D006893:Hydroxyeicosatetraenoic Acids; D007295:Inositol Phosphates; D015289:Leukotrienes; D008054:Lipid Peroxides; D011725:Pyridines; D001127:Arginine Vasopressin; C013109:metapyrone; D016718:Arachidonic Acid; C025086:15-hydroperoxy-5,8,11,13-eicosatetraenoic acid; C025984:15-hydroxy-5,8,11,13-eicosatetraenoic acid; D009637:Masoprocol; C046782:14,15-epoxy-5,8,11-eicosatrienoic acid; D015118:Eicosapentaenoic Acid; D010738:Type C Phospholipases; D015126:8,11,14-Eicosatrienoic Acid; D015232:Dinoprostone; D002118:Calcium; D007213:Indomethacin