Effects of hydroxytyrosol on ISM-1, PODXL, p-mTOR, and p-AKT protein expression and 8-OHdG levels in doxorubicin-associated cardiac injury

Abstract

Doxorubicin (DOXO) is an effective chemotherapeutic agent used in various malignancies, but its clinical use is limited by cardiotoxicity. Hydroxytyrosol (HT), a natural polyphenol in olive oil, has strong antioxidant and anti-inflammatory properties with potential cardioprotective effects. However, whether HT modulates ISM-1, PODXL, and phosphorylated mechanistic target of rapamycin (p-mTOR)/ phosphorylated protein kinase B (p-AKT) signaling in DOXO-induced cardiotoxicity remains unclear, and the potential roles of these molecules in HT-associated cardiac responses have not been adequately investigated. This study investigated the effects of HT on serum 8-hydroxy-2’-deoxyguanosine (8-OHdG) levels and cardiac ISM-1, PODXL, p-mTOR, and p-AKT protein expression in a rat model of DOXO-induced cardiac injury. Four groups of rats ( n  = 7 per group) were used: Control (C), HT (100 mg/kg/day, orally for 4 weeks), DOXO (10 mg/kg, single dose, i.p., on day 1), and DOXO + HT (a single dose of DOXO (10 mg/kg, i.p.) on day 1, followed by oral HT (100 mg/kg/day) for 4 weeks, beginning 24 h after DOXO injection). Serum 8-OHdG levels were measured using ELISA. Cardiac ISM-1, PODXL, p-mTOR, and p-AKT expression, as well as histopathological alterations, were assessed using immunohistochemical methods. ISM-1, PODXL, p-mTOR, and p-AKT expression levels were significantly elevated in the DOXO group compared to controls ( p  < 0.001), accompanied by marked histopathological damage. Vacuolization, mononuclear cell infiltration, necrosis, and fibrosis scores were also significantly higher ( p  < 0.001). In the DOXO + HT group, p-mTOR and p-AKT expression, as well as intracytoplasmic vacuolization, mononuclear cell infiltration, and necrosis, were significantly reduced compared with the DOXO group. However, the reduction in fibrosis did not reach statistical significance ( p  = 0.590). Serum 8-OHdG levels increased in the DOXO group, whereas HT treatment mitigated this rise, resulting in a significant decrease in the DOXO + HT group. The findings show that DOXO induces marked oxidative stress, DNA damage, and histopathological deterioration in cardiac tissue. HT treatment was associated with a reduction in oxidative DNA damage by lowering 8-OHdG levels, modulation of ISM-1, PODXL, p-mTOR, and p-AKT expression, and attenuation of tissue injury. Given the limited sample size and lack of cardiac functional assessment, further studies are needed to confirm the cardioprotective effects of HT against DOXO-induced cardiotoxicity.