The mechanism of Ningxin-Tongyu-Zishen formula regulating probdnf/mbdnf balance through PAI-1/tPA signaling pathway in the treatment of premature ovarian insufficiency.

Background: Premature ovarian insufficiency (POI) is a refractory gynecological endocrine disorder. Ningxin-Tongyu-Zishen formula (NTZF), developed based on the 'simultaneous heart-kidney regulation' principle, exhibits therapeutic efficacy in treating POI, potentially through regulating proBDNF/mBDNF balance. This study aimed to elucidate the molecular mechanism by which NTZF treats POI via proBDNF/mBDNF modulation.

Methods: POI rat models were established using cyclophosphamide (CTX). The therapeutic effects of NTZF were evaluated by analyzing estrous cycles, ovarian indices, follicular development, serum sex hormone levels (FSH, E₂, AMH), and ovarian granulosa cells (OGCs) apoptosis. Following immunofluorescence staining to localize BDNF receptors, proBDNF/mBDNF protein expression was quantified in brain and ovarian tissues. The active metabolite of CTX, phosphoramide mustard (PM), was employed to induce damage in KGN cells. The regulatory effect of NTZF on proBDNF/mBDNF was investigated and compared with recombinant mBDNF protein. tPA and PAI-1 was screened, and their interactions with NTZF were analyzed. mRNA and protein expression of tPA, PAI-1, and tPA-PAI-1 complexes were assessed via q-PCR and Western Blot.

Results: NTZF composition was characterized and shown to improve ovarian function in POI rats. Its mechanism involves correcting proBDNF/mBDNF imbalance in both brain and ovarian tissues. NTZF achieved this correction through the PAI-1/tPA signaling pathway, thereby inhibiting apoptosis in damaged KGN cells.

Conclusion: Our findings demonstrate that NTZF attenuates PAI-1 expression, diminishes tPA-PAI-1 complex formation, and potentiates tPA-dependent proteolysis of proBDNF into mBDNF, thereby restoring their balance. This restores proBDNF/mBDNF balance, suppresses OGCs apoptosis, and ultimately ameliorates POI.