Heat-Induced Oxidative Stress and Use of Astaxanthin on the NF-kB, NFE2L2 Transcription Factors and Cytoprotective Capacity in the Thymus of Broilers

The thymus, a central lymphoid organ in animals serves as the site for T cell development, differentiation and maturation, vital to adaptive immunity. Thymus is critical for maintaining tissue homeostasis providing protection against tumors and tissue damage. Overactive or prolonged immune response can lead to oxidative stress due to increased production of reactive oxygen species. Heat stress induces oxidative stress and overwhelms the natural antioxidant defense mechanisms. The objectives of the study were to investigate the protective properties of astaxanthin against heat-induced oxidative stress and apoptosis in the chicken thymus, by comparing the growth performance and gene signaling pathways among three groups- thermal neutral, heat stress and heat stress with astaxanthin, under two temperature conditions of 21-22°C and 32-35°C. Both treatments under heat stress experienced reduced growth performance, while the group treated with astaxanthin showed a slightly lesser decline. The inflammatory response and antioxidant defense system were activated by the upregulation of the NF-kB, NFE2L2, PPARα, cytoprotective capacity and apoptotic gene pathways in the heat stress compared to the thermal neutral group. Conversely, expression levels were without significance between the thermal neutral and heat stress with antioxidant groups, suggesting astaxanthin antioxidant effectiveness to mitigate inflammation and oxidative stress damage.