Effect of carvacrol to induce autophagy and apoptosis and its interaction with Newcastle disease virus in the chicken embryo model.

Newcastle disease (ND) is an important disease and a significant concern in the poultry industry. The ND virus (NDV) is oncolytic and considered as a potential treatment for cancer treatment. Carvacrol (CVC) is a plant monoterpene known for its antimicrobial and anti-cancer properties. The effects of CVC on embryos and NDV have not been investigated yet. Chicken embryonated eggs were treated with different doses of CVC. Some were sampled on hatching day, while others were bred and immunized with ND vaccine. In another experiment, NDV was pretreated with 100, 1000 and 10,000 ppm CVC before being inoculated in ovo. Additionally, some embryonated eggs were treated with 10,000 ppm CVC and then inoculated with 100 EID50 NDV. The most damages were observed in the brain, tissue at 1000 and 10,000 ppm. LC3 staining in the brain showed autophagy at both doses, while TUNEL staining confirmed the occurrence of apoptosis at 10,000 ppm. Furthermore, in heart and renal tissues pathological alterations were detected at high dose administration. The virus yield increased in embryos pretreated with 10,000 ppm CVC. However, in the experiment where NDV was pretreated with CVC, only 10,000 ppm was virucidal, with other doses leading to an increase in virus yield. Treatment of embryos with CVC had no significant effect on the HI antibody response to the ND vaccine in the breeding period. Based on our findings, the enhancing effects of CVC on NDV proliferation and its impact on apoptosis and autophagy at high doses could be a new area of research for potential cancer treatment in resistant cancer cells.