We investigated the role of
arachidonic acid-derived
eicosanoids in
staphylococcal alpha-toxin (alpha-T)-induced
lung injury. Bolus injection of 200 and 500 micrograms alpha-T into isolated perfused rat lungs resulted in increased pulmonary perfusion pressure followed by lung
weight gain. Inhibition of pressure change with
papaverine (10(-4) M) failed to abolish lung
edema. Furthermore, alpha-T increased the permeability-surface area product in
papaverine-treated lungs and caused marked endothelial cell injury and interstitial
edema as documented by electron microscopy. alpha-T dose dependently increased lung tissue
thromboxane B2 (TxB2) levels and
leukotriene C4 levels. In lungs given 0, 200, and 500 micrograms of alpha-T, TxB2 (in micrograms/g
wet lung) values were 16.3 +/- 2.8, 25.0 +/- 3.0, and 54.2 +/- 6.2; and
leukotriene C4 values were 4.6 +/- 1.1, 6.7 +/- 1.2, and 22.1 +/- 3.8, respectively. Inhibition of
cyclooxygenase enzyme with
indomethacin (10(-5) M) or
lipoxygenase enzyme with 2(12-hydroxydodeca-5,10-dinyl)-3,5,6-trimethyl-1,4-benzoq uin one (
AA861, 10(-5) M) attenuated the vasoconstriction and prevented lung
edema due to low dose (200 micrograms) but not high dose (500 micrograms) alpha-T. The protective effect of these inhibitors on lung
edema is in part due to decreases in alpha-T-stimulated venoconstriction because alpha-T-induced increase in lung microvascular pressure was attenuated by
indomethacin and
AA861 pretreatment. We conclude that both
eicosanoid-dependent and
eicosanoid-independent mechanisms contribute to alpha-T-induced lung
edema in the rat.