Abstract
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 μM) 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 μM NDGA and abolished that induced by 10 μM NDGA. In Ca2+-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 μM) and the endoplasmic reticulum (ER) Ca2+ pump inhibitor thapsigargin (1 μM). However, 0.1 mM NDGA still increased [Ca2+](i) after Ca2+ stores had been depleted by pretreating with 2 μM CCCP, 1 μM thapsigargin and 0.1 mM cyclopiazonic acid. NDGA (50 μM) activated Mn2+ quench of fura-2 fluorescence at 360 nm excitation wavelength, which was almost abolished by 50 μm La3+. This implies NDGA induced Ca2+ influx mainly via a La3+-sensitive pathway. Consistently, 50 μM 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 Ca2+-free medium, suggesting NDGA activated capacitative Ca2+ entry. Pretreatment with 0.1 mM NDGA for 200 s prior to Ca2+ did not alter 1 μM thapsigargin-induced capacitative Ca2+ entry. Pretreatment with 40 μM aristolochic acid to inhibit phospholipase A2 reduced 0.1 mM NDGA-induced Ca2+ release by 65%, but inhibiting phospholipase C with 2 μM 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.
Original language | English |
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Pages (from-to) | 1753-1762 |
Number of pages | 10 |
Journal | Life Sciences |
Volume | 66 |
Issue number | 18 |
DOIs | |
State | Published - 24 03 2000 |
Externally published | Yes |
Keywords
- Ca signaling
- Capacitative Ca entry
- MDCK cells
- Nordihydroguaiaretic acid