Mechanisms of nordihydroguaiaretic acid-induced [Ca2+]i increases in MDCK cells.
The effect of nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, on Ca2+ signaling in Madin Darby canine kidney (MDCK) cells has been investigated. NDGA (10-100 microM) increased [Ca2+]i concentration-dependently. The [Ca2+]i increase comprised an initial slow rise and a plateau over a time period of 5 min. Ca2+ removal partly inhibited the Ca2+ signals induced by 25-100 microM NDGA and abolished that induced by 10 microM NDGA. In Ca(2+)-free medium, pretreatment with 0.1 mM NDGA for 12 min abolished the [Ca2+]i increase induced by the mitochondrial uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP; 2 microM) and the endoplasmic reticulum (ER) Ca2+ pump inhibitor thapsigargin (1 microM). However, 0.1 mM NDGA still increased [Ca2+]i after Ca2+ stores had been depleted by pretreating with 2 microM CCCP, 1 microM thapsigargin and 0.1 mM cyclopiazonic acid. NDGA (50 microM) activated Mn2+ quench of fura-2 fluorescence at 360 nm excitation wavelength, which was almost abolished by 50 microM La3+. This implies NDGA induced Ca2+ influx mainly via a La(3+)-sensitive pathway. Consistently, 50 microM La3+ pretreatment inhibited 0.1 mM NDGA-induced [Ca2+]i increase. Adding 3 mM Ca2+ increased [Ca2+]i in cells pretreated with 0.1 mM NDGA in Ca(2+)-free medium, suggesting NDGA activated capacitative Ca2+ entry. Pretreatment with 0.1 mM NDGA for 200 s prior to Ca2+ did not alter 1 microM thapsigargin-induced capacitative Ca2+ entry. Pretreatment with 40 microM aristolochic acid to inhibit phospholipase A2 reduced 0.1 mM NDGA-induced Ca2+ release by 65%, but inhibiting phospholipase C with 2 microM U73122 had little effect. This suggests NDGA-induced Ca2+ release was independent of inositol 1,4,5-trisphosphate (IP3), but was modulated by phospholipase A2.
Jan
C R
CR
Department of Medical Education and Research, Veterans General Hospital-Kaohsiung, Taiwan. crjan@isca.vghks.gov.tw
Tseng
C J
CJ
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002460:Cell Line; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009637:Masoprocol / Q000494:pharmacology*; D008674:Metals, Rare Earth / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology
D000975:Antioxidants; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D008674:Metals, Rare Earth; D019284:Thapsigargin; D009637:Masoprocol; D002118:Calcium; D016257:Fura-2