We report herein a novel mechanism, unraveled by proteomics and validated by in vitro and in vivo studies, of the aberrant aging-associated upregulation of ovarian transferrin and ferritin in rat ovaries. The ovarian mass and serum estradiol titer plummeted while the ovarian labile ferrous iron and total iron levels escalated with age in rats. Oxidative stress markers, such as nitrite/nitrate, 3-nitrotyrosine, and 4-hydroxy-2-nonenal, accumulated in the aging ovaries due to an aberrant upregulation of the ovarian transferrin, ferritin light/heavy chains, and iron regulatory protein 2(IRP2)-mediated transferrin receptor 1 (TfR1). Ferritin inhibited estradiol biosynthesis in ovarian granulosa cells in vitro via the upregulation of a nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and p65/p50-induced oxidative and inflammatory factor inducible nitric oxide synthase (iNOS). An in vivo study demonstrated how the age-associated activation of NF-κB induced the upregulation of iNOS and the tumor necrosis factor α (TNFα). The downregulation of the keap1-mediated nuclear factor erythroid 2-related factor 2 (Nrf2), that induced a decrease in glutathione peroxidase 4 (GPX4), was observed. The aberrant transferrin and ferritin upregulation triggered an iron accumulation via the upregulation of an IRP2-induced TfR1. This culminates in NF-κB-iNOS-mediated ovarian oxi-inflamm-aging and serum estradiol decrement in naturally aging rats. The iron accumulation and the effect on ferroptosis-related proteins including the GPX4, TfR1, Nrf2, Keap1, and ferritin heavy chain, as in testicular ferroptosis, indicated the triggering of ferroptosis. In young rats, an intraovarian injection of an adenovirus, which expressed iron regulatory proteins, upregulated the ovarian NF-κB/iNOS and downregulated the GPX4. These novel findings have contributed to a prompt translational research on the ovarian aging-associated iron metabolism and aging-associated ovarian diseases.

Polyphyllin II (PPII) is a natural steroidal saponin occurring in Rhizoma Paridis. It has been demonstrated to exhibit anti-cancer activity against a variety of cancer cells. However, the anti-colorectal cancer (CRC) effects and mechanism of action of PPII are rarely reported. In the present study, we showed that PPII inhibited the proliferation of HCT116 and SW620 cells. Moreover, PPII induced G2/M-phase cell cycle arrest and apoptosis, as well as protective autophagy, in CRC cells. We found that PPII-induced autophagy was associated with the inhibition of PI3K/AKT/mTOR signaling. Western blotting results further revealed that PPII lowered the protein levels of phospho-Src (Tyr416), phospho-JAK2 (Tyr1007/1008), phospho-STAT3 (Tyr705), and STAT3-targeted molecules in CRC cells. The overactivation of STAT3 attenuated the cytotoxicity of PPII against HCT116 cells, indicating the involvement of STAT3 inhibition in the anti-CRC effects of PPII. PPII (0.5 mg/kg or 1 mg/kg, i.p. once every 3 days) suppressed HCT116 tumor growth in nude mice. In alignment with the in vitro results, PPII inhibited proliferation, induced apoptosis, and lowered the protein levels of phospho-STAT3, phospho-AKT, and phospho-mTOR in xenografts. These data suggest that PPII could be a potent therapeutic agent for the treatment of CRC.

We discuss the diverse biological activities, therapeutic potential, and clinical applications of peptides and proteins isolated from various yams species including Dioscorea opposita Thunb (Chinese yam), D alata, D japonica (Japanese yam), D pseudojaponica, D batatas (Korea yam), and D cayenensis. Yam peptides and proteins have many pharmacological activities including immunomodulatory, antioxidant, estrogen-stimulating, osteogenic, angiotensin I-converting enzyme inhibiting, carbonic anhydrase and trypsin inhibiting, chitinase, anti-insect, anti-dust mite, lectin, and anti-proliferative activities. Yam peptides and proteins have therapeutic potential for treating cardiovascular diseases, inflammatory diseases, cancers, aging disorders, menopause, and osteoporosis.