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Inhibition of PGE2 production in macrophages from vitamin E-treated rats
W Sakamoto1, K Fujie, J Nishihira
1Department of Biochemistry, School of Dentistry, Hokkaido University, Sapporo, Japan.
Abstract:
Rat peritoneal macrophages from vitamin E-treated rats (5 mg per rat for 6 successive days) contained 403.3 +/- 90.7 ng alpha-tocopherol/10(6) cells, whereas control macrophages contained 1.2 +/- 0.4 ng. PGE2 production in the macrophages from vitamin E-treated rats was significantly suppressed when stimulated with PMA and calcium ionophore A23187. The mechanism of vitamin E inhibition of PGE2 production in macrophages was investigated. The release of (14C)-arachidonic acid from pre-labeled macrophages and the conversion of (14C)-arachidonic acid to PGE2 by the homogenate of the cells were remarkably reduced. These results strongly suggested that the inhibition of PGE2 production by vitamin E results from the inhibition of the activities of both phospholipase A2 and cyclooxygenase.
Insights
Vitamin E significantly suppresses prostaglandin E2 (PGE2) production in rat macrophages. This occurs by inhibiting key enzymes involved in PGE2 synthesis, namely phospholipase A2 and cyclooxygenase.
Area of Science:
- Immunology
- Nutritional Biochemistry
- Cellular Biology
Background:
- Macrophages play a crucial role in inflammatory processes, partly through the production of prostaglandins like PGE2.
- Vitamin E (alpha-tocopherol) is a well-known antioxidant with potential immunomodulatory effects.
- Elevated PGE2 levels are associated with various inflammatory conditions.
Purpose of the Study:
- To investigate the effect of vitamin E supplementation on PGE2 production in rat peritoneal macrophages.
- To elucidate the underlying molecular mechanisms by which vitamin E influences PGE2 synthesis.
Main Methods:
- Rats were treated with vitamin E (5 mg/day for 6 days), and peritoneal macrophages were isolated.
- Macrophages were stimulated with phorbol 12-myristate 13-acetate (PMA) and calcium ionophore A23187 to induce PGE2 production.
- The release of (14C)-arachidonic acid and its conversion to PGE2 in cell homogenates were measured to assess enzyme activity.
Main Results:
- Vitamin E-treated macrophages showed significantly higher alpha-tocopherol content compared to controls.
- PGE2 production was markedly suppressed in vitamin E-treated macrophages upon stimulation.
- The release of (14C)-arachidonic acid and its conversion to PGE2 were significantly reduced, indicating inhibition of phospholipase A2 and cyclooxygenase activities.
Conclusions:
- Vitamin E administration effectively increases alpha-tocopherol levels in rat macrophages.
- Vitamin E inhibits macrophage-derived PGE2 production.
- The inhibitory mechanism involves the suppression of both phospholipase A2 and cyclooxygenase activities, key enzymes in the prostaglandin synthesis pathway.