Journal Article

A multistep kinase-based Sertoli cell autocrine-amplifying loop regulates prostaglandins, their receptors, and cytokines

In Sertoli epithelial cells, the IL-1β induces prostaglandins (PG) PGE_2, PGF_2α and PGI_2 (7-, 11-, and 2-fold, respectively), but not PGD_2, production. Cyclohexamide pretreatment inhibiting protein synthesis prevents IL-1β increases in PG levels, indicating that induction requires de novo protein synthesis. IL-1β-regulated PGE_2 and PGF_2α production and cytokine expression require activation of cyclooxygenase-2 (COX-2) and c-Jun NH_2-terminal kinase, as shown using specific enzyme inhibition. PGE_2 and PGF_2α stimulate expression of IL-1α, -1β, and -6, findings consistent with PG involvement in IL signaling within the seminiferous tubule. PGE_2 and PGF_2α reverse COX-2-mediated inhibition of IL-1β induction of cytokine expression and PG production. Sertoli PG receptor expression was determined; four known E-prostanoid receptor (EP) subtypes (1–4) and the F-prostanoid and prostacyclin prostanoid receptors were demonstrated using RNA and protein analyses. Pharmacological characterization of Sertoli PG receptors associated with cytokine regulation was ascertained by quantitative real-time RT-PCR analyses. IL-1β regulates both EP_2 mRNA and protein levels, data consistent with a regulatory feedback loop. Butaprost (EP_2 agonist) and 11-deoxy PGE_1 (EP_2 and EP_4 agonist) treatments show that EP_2 receptor activation stimulates Sertoli cytokine expression. Consistent with EP_2-cAMP signaling, protein kinase A inhibition blocks both IL-1β- and PGE_2-induced cytokines. Together, the data indicate an autocrine-amplifying loop involving IL-1β-regulated Sertoli function mediated by COX-2-induced PGE_2 and PGF_2α production. PGE_2 activates EP_2 and/or EP_4 receptor(s) and the protein kinase A-cAMP pathway; PGF_2α activates F-prostanoid receptor-protein kinase C signaling. Further identification of the molecular mechanisms subserving these mediators may offer new insights into physiological events as well as proinflammatory-mediated pathogenesis in the testis.