5-Fluorouracil disrupts ovarian preantral follicles in young C57BL6J mice

The therapeutic effect of silibinin against 5-fluorouracil-induced ovarian toxicity in rats

5-Fluorouracil (5-FU) is a fluoropyrimidine group antineoplastic drug with antimetabolite properties and ovotoxicity is one of the most important side effects. Silibinin (SLB) is a natural compound that is used worldwide and stands out with its antioxidant and anti-inflammatory properties. The aim of this study was to evaluate the therapeutic effect of SLB in 5-FU-induced ovototoxicity using biochemical and histological analysis. This study was carried out in five main groups containing six rats in each group: control, SLB (5 mg/kg), 5-FU (100 mg/kg), 5-FU + SLB (2.5 mg/kg), and 5-FU + SLB (5 mg/kg). The levels of ovarian malondialdehyde (MDA), total oxidant status (TOS), total antioxidant status (TAS), superoxide dismutase (SOD), catalase (CAT), 8-hydroxy-2'-deoxyguanosine (8-OHdG), tumor necrosis factor-alpha (TNF-α), myeloperoxidase (MPO), and caspase-3 were determined using spectrophotometric methods. Hematoxylin and eosin staining method was employed for histopathological examination. MDA, TOS, 8-OHdG, TNF-α, MPO, and caspase-3 levels in 5-FU group were significantly increased compared with the control group, while the levels of TAS, SOD, and CAT were decreased (p < 0.05). SLB treatments statistically significantly restored this damage in a dose-dependent manner (p < 0.05). Although vascular congestion, edema, hemorrhage, follicular degeneration, and leukocyte infiltration were significantly higher in the 5-FU group compared with the control group, SLB treatments also statistically significantly restored these damages (p < 0.05). In conclusion, SLB has a therapeutic effect on the ovarian damage induced by 5-FU via decreasing the levels of oxidative stress, inflammation, and apoptosis. It may be helpful to consider the usefulness of SLB as an adjuvant therapy to counteract the side effects of chemotherapy.

5-Flourouracil-induced toxicity in both male and female reproductive systems: A narrative review

The chemotherapeutic drug 5-flourouracil (5FU) is frequently used to treat a wide range of solid malignant tumors, such as colorectal, pancreatic, gastric, breast, and head and neck cancers. Its antitumoral effects are achieved by interfering with the synthesis of RNA and DNA and by inhibiting thymidylate synthase in both malignant and non-malignant cells. Therefore, it can be responsible for severe toxicities in crucial body organs, including heart, liver, kidney, and reproductive system. Given the fact that 5FU-induced reproductive toxicity may limit the clinical application of this drug, in this study, we aimed to discuss the main locations and mechanisms of the 5FU-induced reproductive toxicity. Initially, we discussed the impact of 5FU on the male reproductive system, which leads to damage of the seminiferous epithelial cells and the development of vacuoles in Sertoli cells. Although no noticeable changes occur at the histopathological level, there is a decrease in the weight of the prostate. Additionally, 5FU causes significant abnormalities in spermatogenesis, including germ cell shedding, spermatid halo formation, polynucleated giant cells, and decreased sperm count. Finally, in females, 5FU-induced reproductive toxicity is characterized by the presence of atretic secondary and antral follicles with reduced numbers of growing follicles, ovarian weight, and maturity impairment.

Reproductive and developmental toxicities of 5-fluorouracil in model organisms and humans

Chemotherapy, as an important clinical treatment, has greatly enhanced survival in cancer patients, but the side effects and long-term sequelae bother both patients and clinicians. 5-Fluorouracil (5-FU) has been widely used as a chemotherapeutic agent in the clinical treatment of various cancers, but several studies showed its adverse effects on reproduction. Reproductive toxicity of 5-FU often associates with developmental block, malformation and ovarian damage in the females. In males, 5-FU administration alters the morphology of sexual organs, the levels of reproductive endocrine hormones and the progression of spermatogenesis, ultimately reducing sperm numbers. Mechanistically, 5-FU exerts its effect through incorporating the active metabolites into nucleic acids directly, or inhibiting thymidylate synthase to disrupt the function of DNA and RNA, leading to profound effects on cellular metabolism and viability. However, some studies suggested that the toxicity of 5-FU on reproduction is reversible and certain drugs used in combination with 5-FU during chemotherapy could protect reproductive systems from 5-FU damage both in females and males. Herein, we summarise the recent findings and discuss underlying mechanisms of the 5-FU-induced reproductive toxicity, providing a reference for future research and clinical treatments.

In vitro cytotoxic effects of 5-Fluorouracil on isolated murine ovarian preantral follicles

5 fluorouracil (5FU), an antineoplastic drug, is often utilized in the therapeutic regimen for several types of cancer, including the hepatoblastoma in children. The effects of 5FU on the population of ovarian preantral follicles, which is the largest oocyte reservoir, is still poorly understood. The integrity of the ovarian preantral follicle pool is important for lifelong fertility. The better understanding of such effects may favor intervention strategies to protect fertility in 5FU-treated children and women coping with cancer. To analyze the effects of 5FU on isolated murine secondary follicles in vitro, ovaries were collected from young mice (28-30 days old), and secondary follicles were isolated and cultured for 12 days in basic culture medium, with or without 5FU at concentrations of 0.3 mM, 1 mM, 3 mM, 10 mM, and 30 mM. In the in vitro study, we analyzed the percentage of morphologically normal follicles, antrum formation, follicular diameter, and hormone production. On day 12, oocytes were recovered for in vitro maturation. 5FU treatment did not alter the percentage of morphologically normal follicles. On day 12, only 1, 10, and 30 mM 5FU significantly reduced the percentage of antrum. From day 4 onwards, 5FU treatments significantly reduced follicle diameter. The meiosis resumption rate was significantly lower in all 5FU treatments. 5FU concentrations ≥3 mM reduced estradiol levels. In conclusion, 5FU does not affect follicular morphology. However, 5FU deleteriously affects follicular growth, estradiol production, and oocyte maturation in isolated ovarian follicles.

Varied effects of doxorubicin (DOX) on the corpus luteum of C57BL/6 mice during early pregnancy

Certain chemotherapeutic drugs are toxic to ovarian follicles. The corpus luteum (CL) is normally developed from an ovulated follicle for producing progesterone (P4) to support early pregnancy. To fill in the knowledge gap about effects of chemotherapy on the CL, we tested the hypothesis that chemotherapy may target endothelial cells and/or luteal cells in the CL to impair CL function in P4 steroidogenesis using doxorubicin (DOX) as a representative chemotherapeutic drug in mice. In both mixed background mice and C57BL/6 mice, a single intraperitoneal injection of DOX (10 mg/kg) on 0.5 days post coitum (D0.5, post-ovulation) led to ~58% D3.5 mice with serum P4 levels lower than the serum P4 range in the PBS-treated control mice. Further studies in the C57BL/6 ovaries revealed that CLs from DOX-treated mice with low P4 levels had less defined luteal cords and disrupted collagen IV expression pattern, indicating disrupted capillary, accompanied with less differentiated luteal cells that had smaller cytoplasm and reduced StAR expression. DOX-treated ovaries had increased granulosa cell death in the growing follicles, reduced PCNA-positive endothelial cells in the CLs, enlarged lipid droplets and disrupted F-actin in the luteal cells. These novel data suggest that the proliferating endothelial cells in the developing CL may be the primary target of DOX to impair the vascular support for luteal cell differentiation and subsequently P4 steroidogenesis. This study fills in the knowledge gap about the toxic effects of chemotherapy on the CL and provides critical information for risk assessment of chemotherapy in premenopausal patients.