Immune-induced activation of the hypothalamus-pituitary-adrenal axis is mediated by cyclooxygenase derived prostaglandins. Here we examined the role of cyclooxygenase-1 in this response, by using genetically modified mice as well as pharmacological inhibition. We found that mice with a deletion of the gene encoding cyclooxygenase-1, in contrast to wild type mice, did not show increased plasma corticosterone at 1h after immune challenge by peripheral injection of bacterial wall lipopolysaccharide, whereas the corticosterone levels were similarly elevated in both genotypes at 6h post-injection. Pretreatment of mice with the selective cyclooxygenase-1 inhibitor SC-560, given orally, likewise inhibited the rapid corticosterone response. These findings, taken together with our recent demonstration that the delayed stress hormone response to immune challenge is dependent on cyclooxygenase-2, show that the two cyclooxygenase isoforms play distinct, but temporally supplementary roles for the stress hormone response to inflammation.
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