A Multistep Kinase-Based Sertoli Cell Autocrine-Amplifying Loop Regulates Prostaglandins, Their Receptors, and Cytokines
In Sertoli epithelial cells, the interleukin (IL)-1β induces prostaglandins (PG) PGE 2 , PGF 2α and cPGI 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 cJun-N-terminal kinase, as shown using specific
... me inhibition. PGE 2 and PGF 2α stimulate expression of IL-1α, -1β, and -6, findings consistent with PG involvement in interleukin 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 prostaglandin receptor expression was determined; four known EP subtypes (1-4), and the FP and IP 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 (PKA) 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 PKA-cAMP pathway; PGF 2α activates FP receptor-PKC signalling. Further identification of the molecular Ishikawa and Morris -4 mechanisms subserving these mediators may offer new insights into physiological events as well as pro-inflammatory-mediated pathogenesis in the testis.