Plasmin cleaves tumor necrosis factor α exodomain from sheep follicular endothelium:: Implication in the ovulatory process

Ovulation in the sheep is predicated on plasmin up-regulation at the ovarian surface-follicular interface, release of tumor necrosis factor (TNF) alpha from contiguous endothelium, and ap. optotic cell death, The objectives of this investigation were to determine whether plasmin elicits TNF alpha secretion from thecal endothelium of ovine follicles, to characterize the site(s) of enzymatic attack, and to assess the physiological consequence of soluble TNF alpha action, Endothelial cells of thecal tissues isolated from antral follicles of eCG-primed anestrous ewes shed (histochemical depletion) TNF alpha into incubation medium (ovarian cell DNA fragmentation bioassay, Western blot detection) upon exposure to plasmin, immunopurification and N-terminal sequence analysis indicated that TNF alpha was excised from its transmembrane precursor at the Arg79-Ser80 and Lys88-Pro89 linkages. Microinjection of TNF alpha into the apical wall of explanted follicles induced cellular apoptosis and stigma development. We suggest that plasmin-mediated cleavage of TNF alpha exodomain from its membrane anchor along thecal endothelium is a determinant of tissue dissolution within the formative ovulatory rupture site of ewes.