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Subacute treatment of rats with dexamethasone reduces ICAM-1 levels on circulating monocytes
A Tailor1, A M Das, S J Getting
1Department of Biochemical Pharmacology, William Harvey Research Institute, London, United Kingdom.
Abstract:
We report for the first time that in vivo treatment with dexamethasone (DEX) reduces levels of intercellular adhesion molecule-1 (ICAM-1) expression on rat circulating unstimulated monocytes (-55%) and peritoneal macrophages (-26%). This effect was present following sub-acute (5 days) treatment with a low dose (0.1 mg/kg per day), but not after single administration of a high dose (1 mg/kg, -2 h), of the steroid. Both acute and sub-acute treatment with DEX failed to modify either basal or up-regulated CD11b expression on peripheral blood monocytes and neutrophils, elastase release from neutrophils, and beta-glucuronidase release from cultured macrophages. The lack of alteration of CD11b expression on circulating leukocytes suggests that the effect of DEX on ICAM-1 expression is secondary to gene repression rather than a non-specific blockade of cell differentiation. These data promote the concept that different dose-regimens with glucocorticoids affect distinct molecular targets and indicate that clinically-related protocols of DEX may reveal new mechanism(s) of action.
Insights
Dexamethasone (DEX) treatment in rats reduces intercellular adhesion molecule-1 (ICAM-1) on monocytes and macrophages. This effect depends on the dose and duration of DEX administration, suggesting specific molecular targets for glucocorticoids.
Area of Science:
- Immunology
- Pharmacology
Background:
- Intercellular adhesion molecule-1 (ICAM-1) plays a crucial role in immune cell trafficking and inflammatory responses.
- Glucocorticoids, like dexamethasone (DEX), are potent anti-inflammatory agents with complex mechanisms of action.
Purpose of the Study:
- To investigate the effect of dexamethasone (DEX) on intercellular adhesion molecule-1 (ICAM-1) expression in vivo.
- To determine if DEX influences other immune cell markers and functions.
- To explore the relationship between DEX dosage, treatment duration, and its impact on ICAM-1 expression.
Main Methods:
- In vivo administration of dexamethasone (DEX) to rats at varying doses and durations.
- Flow cytometry analysis of ICAM-1 and CD11b expression on circulating monocytes, peritoneal macrophages, and neutrophils.
- Assays for elastase release from neutrophils and beta-glucuronidase release from macrophages.
Main Results:
- Sub-acute, low-dose DEX treatment significantly reduced ICAM-1 expression on rat monocytes (-55%) and peritoneal macrophages (-26%).
- Acute, high-dose DEX administration did not alter ICAM-1 levels.
- DEX treatment did not affect CD11b expression, neutrophil elastase release, or macrophage beta-glucuronidase release.
Conclusions:
- Dexamethasone's reduction of ICAM-1 expression is dose- and duration-dependent, suggesting specific molecular targets.
- The effect on ICAM-1 appears to be mediated by gene repression rather than non-specific effects on cell differentiation.
- Different glucocorticoid dosing regimens may target distinct molecular pathways, offering insights into novel mechanisms of action for clinical applications.