Effect of central injection of tumor-necrosis factor-like cytokine 1A and interferons on food intake in chicks

In mammals, anorexia accompanying infection is thought to be mediated via cytokines including interleukins, interferons (IFNs), and tumor necrosis factor (TNF). However, there is a lack of related knowledge on birds. Therefore, the purpose of the present study was to determine if cytokines are associated with reduced food intake in chicks (Gallus gallus). Specifically, we evaluated the effects of TNF-like cytokine 1A (TL1A), a member of the TNF family, interferon-α (IFN-α), and interferon-γ (IFN-γ) on food intake. Additionally, the effect of lipopolysaccharide (LPS) and polyinosinic:polycytidylic acid (poly I:C) on cytokine mRNA expression in the diencephalon and spleen was also measured. Intracerebroventricular (ICV) injection of 0.05 or 0.5 μg TL1A, IFN-α, and IFN-γ had no effect on food intake. However, when 1.0 μg each of these factors was evaluated, TL1A significantly decreased food intake at 180 and 240 min after the injection, but IFN-α and IFN-γ had no effect. When chicks received intraperitoneal (IP) injections of 100 μg LPS or 400 μg poly I:C, their food intake was reduced. Diencephalic mRNA expression of TL1A was significantly decreased following IP injection of LPS or poly I:C. Additionally, diencephalic mRNA expression of IFN-γ mRNA was significantly increased by IP injection of LPS but decreased by IP injection of poly I:C. For the spleen, IP injection of LPS and poly I:C both significantly increased TL1A and IFN-γ mRNA expression. In sum, we have provided evidence that central TL1A but not IFN-α or IFN-γ are related to reduction of food intake in chicks, but the role of these cytokines for mediating anorexia associated with infections may differ from mammals.