Comparison of in vitro-activity of commonly used topical glucocorticoids on cytokine- and phospholipase inhibition.

Background And Objectives: Topical glucocorticoids (GCs) are potent inhibitors of cellular inflammatory mediator production. Differences in receptor binding activities are believed to correlate with inhibition of mediator release and anti-inflammatory efficacy in vivo. To further assess this hypothesis we compared in cultured human monocytes the inhibitory activity of classic synthetic GCs on leukotriene B4 (LTB4), prostaglandin E2 (PGE2), interleukin 1 beta (IL-1beta) and c-phospholipase A 2 activity (cPLA2).

Methods: Normal human monocytes (10(5) /ml) were tested for 20 hrs with increasing concentrations (range 10(-12) -10(-5) M) of triamcinolone acetonide (TAA) compared to beclomethasone dipropionate (BDP), budesonide (BUD), dexamethasone (DEX), or the ethanol diluent together with 10 microg/ml of lipopolysaccharide (LPS). Mediator production and spontaneous cPLA subset 2-activity was determined by direct enzyme immunoassay methods.

Results: TAA at therapeutically relevant concentration (10(-8) M) inhibited significantly (p<0.01, n = 9) mediator production of TNF-alpha > IL-1beta > TxB2 > LTB subset 4 in a dose dependent manner by 75%, 65%, 41%, and 33%. IL-1beta inhibition at 10(-8) M by TAA (65%)> BDP (52%)> BUD (47%) was not different (ANOVA, p>0.2). Also spontaneous cPLA2-activity at 10(-8) M was inhibited to a similar degree (ANOVA, p> 0.6) by BUD (17.3%) > TAA (11.4%) > BDP (8.6%). In the same culture conditions spontaneous PGE2-secretion was inhibited by BDP (28.8%) > BUD (24.2%) > TAA (11.4%) with no significant effect for TAA.

Conclusion: Clinically well established GCs have a similar inhibitory capacity on monocyte cytokine production and surprisingly only weak effects on AA-metabolism. Small receptor binding activity may account for the lack of cytokine inhibition by subtherapeutic (<10(-8) M) airway concentrations of TAA and BDP. Partial mediator inhibition by GCs at therapeutically known airway concentrations may be relevant to control bursts of airway inflammation during acute exacerbation but unfavourable to effectively delay progression of chronic airway inflammation.