Effects of γ-aminobutyric acid on the thymus tissue structure, antioxidant activity, cell apoptosis, and cytokine levels in chicks under heat stress

Abstract

ABSTRACT:This study aims to investigate the effect of dietary γ-aminobutyric acid (GABA) on the development of thymus tissue structure and function in chicks under heat stress. One-day-old male Wenchang chicks were randomly divided into control group (CK), heat stress group (HS), and GABA+HS group. The chicks from GABA+HS group were administered 0.2 ml of GABA solution daily by oral gavage (50 mg/kg of body weight). Chicks from HS and GABA+HS groups were subjected to heat stress treatment at 40 ± 0.5°C for 2 h every day. Blood and thymus tissue were collected from the chicks at the end of weeks 1-6. Results showed that the thymus weight and index, thickness of cortex, cortex/medulla ratio, number of lymphocytes, activity of superoxide dismutase, total antioxidant capacity, and glutathione peroxidase, and plasma level of tumor necrosis factor-α in HS group were significantly lower than in CK group (P < 0.05). The Toll-like receptor 2 (TLR2) expression in the late stage of heat stress, malondialdehyde (MDA) content, thymocyte apoptosis rate, number of lymphocytes in the S and G2/M phases, and plasma levels of interleukin-4 and interferon-γ in HS group were significantly higher than in CK group (P < 0.05). In contrast, the integrity of thymus tissue structure of GABA+HS group was improved compared with HS group. The TLR2 expression in the early stage of heat stress and the activity of antioxidant enzymes in GABA+HS group were significantly higher than in HS group (P < 0.05), and the MDA content, thymocyte apoptosis rate, number of lymphocytes in the S and G2/M phases, and plasma level of IL-4 and IFN-γ in GABA+HS group were significantly lower than in HS group (P < 0.05). We concluded that heat stress caused structure damage to thymus tissue of chicks, changed the plasma levels of cytokines, reduced the antioxidant activity, and increased cell apoptosis in chick thymus. GABA alleviated the negative effects on the development of chick thymus, improved the immune function of thymus, and played a protective role by regulating the plasma levels of cytokines and antioxidant activity of thymus tissue.

Effects of dietary fumaric acid on the growth performance, immune response, relative weight and antioxidant status of immune organs in broilers exposed to chronic heat stress

“…Shini et al (2010) reported that the cortical region of the bursa of Fabricius https://doi.org/10.17221/13/2020-CJAS increased while the medullary region decreased in broilers under stressful conditions. Moreover, the spleen and thymus are also atrophied in broilers under extreme HS (Park et al 2013;Liang et al 2016). The elevated levels of circulating corticosterone in heat-stressed broilers were reported to inhibit the growth and involution of immune organs (Aschbacher et al 2013).…”

Effects of Heat Stress on the Development of GABAergic Neurons in the HPG Axis of Wenchang Chicks

“…As an inhibitory neurotransmitter in the nervous system, GABA inhibits basal metabolism, regulates hormone levels, balances blood electrolytes, enhances antioxidant capacity, and helps overcome and alleviates adverse effects of a high-temperature environment in the poultry body in the summer (Chen et al, 2013;Liang et al, 2016). GABAergic neurons are neuronal cells that not only use GABA as a transmitter to participate in the regulation of metabolism, but also are inseparable from the egg development and sperm capacitation in the body (Watanabe et al, 2002;Geigerseder et al, 2004).…”

Effect of Heat Stress on Expression of Main Reproductive Hormone in Hypothalamic-Pituitary-Gonadal Axis of Wenchang Chicks

“…The Wenchang chicks in the HS group were placed in an artificial climate chamber (model LRH-800-GS, Tomorrow Environmental Protection Instrument, Shaoguan, China) daily for HS at 40 ± 0.5°C from 13:00 to 15:00, and the Wenchang chicks in the CK group were simultaneously placed in an unheated artificial climate chamber for 2 h of control treatment at 29.7 ± 2.3°C. After the HS or control treatment, all chicks were returned to their cages for routine feeding (Liang et al, 2016).…”