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) PGE2, PGF2α and PGI2 (7-, 11-, and 2-fold, respectively), but not PGD2, production. Cyclohexamide pretreatment inhibiting protein synthesis prevents IL-1β increases in PG levels, indicating that induction requires de novo protein synthesis. IL-1β-regulated PGE2 and PGF2α production and cytokine expression require activation of cyclooxygenase-2 (COX-2) and c-Jun NH2-terminal kinase, as shown using specific enzyme inhibition. PGE2 and PGF2α stimulate expression of IL-1α, -1β, and -6, findings consistent with PG involvement in IL signaling within the seminiferous tubule. PGE2 and PGF2α 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 EP2 mRNA and protein levels, data consistent with a regulatory feedback loop. Butaprost (EP2 agonist) and 11-deoxy PGE1 (EP2 and EP4 agonist) treatments show that EP2 receptor activation stimulates Sertoli cytokine expression. Consistent with EP2-cAMP signaling, protein kinase A inhibition blocks both IL-1β- and PGE2-induced cytokines. Together, the data indicate an autocrine-amplifying loop involving IL-1β-regulated Sertoli function mediated by COX-2-induced PGE2 and PGF2α production. PGE2 activates EP2 and/or EP4 receptor(s) and the protein kinase A-cAMP pathway; PGF2α 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.
Ishikawa, Tomomoto and Patricia L. Morris. 2006. "A multistep kinase-based Sertoli cell autocrine-amplifying loop regulates prostaglandins, their receptors, and cytokines," Endocrinology 147(4): 1706–1716.