IntroductionChemotherapy drugs are used in the treatment of various types of cancers. Their toxicities and minor risks are often overlooked as a result of their potential usefulness in treatment. In particular, testicular cells have been selected as targets by chemotherapeutic agents, as they enter various mitotic, meiotic, and morphological processes and therefore they are easily damaged [1]. Cis-diamminedichloroplatinum (II) or cisplatin (CP), a highly effective antineoplastic DNA alkylating agent, has been used to treat a wide variety of solid tumors, such as those in the testicles, ovaries, breast, lungs, bladder, head, and neck [2]. However, the use of the drug is limited due to side effects, such as testicular toxicity, cachexia, and testicular damage [2,3]. When CP is administered at a high cumulative dose, it can result in permanent azoospermia and then infertility in patients [3]. CP interacts with DNA to create cross-link and intra-chain cross-links. Since the DNA modified by CP cannot be sufficiently renewed, the DNA damage initiates apoptosis [4].Caffeic acid phenethyl ester (CAPE) is one of the active ingredients of the sharp and fragrant propolis substance found in the extract collected by bees from plants. CAPE has been used as a folk remedy for many years [5]. Antimicrobial, antiinflammatory, immunomodulatory, antimutagenic, antioxidant, and anticarcinogenic effects of propolis have been demonstrated by various studies. CAPE, one of the active ingredients of propolis, and has an important place in these beneficial effects [6,7]. Although CAPE is a pharmacologically safe compound, it also reduces lipid peroxidation and stimulates antioxidant enzyme activity [8].Background/aim: Cisplatin (CP), a chemotherapeutic drug, causes damage to spermatogenic serial cells, Sertoli cells, and Leydig cells in rat testicles. It was aimed to investigate the protective effect of caffeic acid phenethyl ester (CAPE), one of the active ingredients of propolis, in eliminating CP-induced testicular damage.Materials and methods: Group 1 (control group) was given physiological saline solution intraperitoneally (IP) throughout the experiment. Group 2 (CP group) was given a single dose of CP (7 mg/kg) IP on the day 7. Group 3 (CP + CAPE group), was given CAPE (10 µmol/kg/day) IP for 12 days and a single dose of CP (7 mg/kg) IP on day 7. Group 4 (CAPE group) was given CAPE (10 µmol/kg/day) IP for 12 days. On day 14 of the experiment, the rats were decapitated under xylazine and ketamine anesthesia and their testicles were removed. The sections obtained from the testicles were stained with hematoxylin-eosin and histopathological damage was evaluated. Malondialdehyde (MDA) levels, and superoxide dismutase (SOD) and catalase (CAT) enzymatic activities were measured in the testicular tissue samples. Testosterone (TES) levels were measured in the blood serum. The Johnsen testicular biopsy score (JTBS) was used to evaluate testicular tubules. DNA damage was evaluated in sperm samples taken from the ductus epididymis using the come...