High doses of dietary zinc induce cytokines, chemokines, and apoptosis in reproductive tissues during regression

Abstract

In chickens, high levels of dietary zinc cause molting, and the reproductive system undergoes complete remodeling concomitant to feather replacement. In the present study, the expression profiles of cytokines and chemokines were investigated in the ovary and oviduct of control hens and of hens induced to molt by zinc feeding. The zinc-induced feed-intake suppression, the changes in corticosterone levels, the immune cell populations in the reproductive tract, and the apoptosis of reproductive tissues were analyzed. The expression of mRNAs for interleukin-6 (IL-6), interferon-gamma (IFN-gamma), the avian ortholog of mammalian IL-8 (chCXCLi2), and a chicken MIP-1beta-like chemokine (chCCLi2) in the ovary and of mRNAs for IL-1beta, IL-6, IFN-gamma, transforming growth factor-beta2, chCXCLi2, and chCCLi2 in the oviduct were upregulated significantly during zinc-induced molting. A simultaneous feed-intake reduction was observed with higher expression of cytokines and chemokines. The results of the present investigation also suggested that the upregulation of corticosterone was closely associated with the increased expression of cytokines and chemokines. An increase in apoptosis within reproductive tissue during tissue regression was also noted. We had previously observed the upregulation of these cytokines expression in an earlier study (molting by feed withdrawal). However, the pattern and the level of expression were different among these two methods. These findings indicate that cytokines might be a common mediator of tissue regression during molting induced by diverse methods, although the pattern of induction is different. Thus, a high dose of dietary zinc seems to induce reproductive regression via the upregulation of cytokines and chemokines, the suppression of feed intake, and the increase in serum corticosterone, resulting finally in the apoptosis of reproductive tissues.

Characterisation of basal expression of selected cytokines in the liver, spleen, and respiratory, reproductive and intestinal tract of hens

“…However, as we did not observe any signs of infection, we considered the notion that IL-18 expression was high in magnum due to the presence of an unknown infection as quite unlikely and instead, this cytokine may have a yet unknown role in the control of reproduction, similar to IL-6 in mammals (Robertson et al, 2010;Thomakos et al, 2010). Concerning IL-6, its expression in the reproductive tract of hens has been described (Sundaresan et al, 2007(Sundaresan et al, , 2008. Unfortunately, these studies were focused on the expression of IL-6 and other cytokines in the reproductive tract only and the authors did not therefore report on the expression of IL-6 in the reproductive tract relative to other tissues.…”

“…Although cytokines are mostly associated with control of the host's immune response to different foreign antigens (Berndt et al, 2007;Shaughnessy et al, 2009), they also contribute to processes not directly associated with infection, e.g., remodelling of the reproductive system in molting hens (Sundaresan et al, 2007(Sundaresan et al, , 2008 or control of the menstrual cycle in women (Laird et al, 1994). Tight control of their expression is therefore critical for both immune response to infection and maintenance of internal body homeostasis.…”

Effects of lipopolysaccharide on the expression of proinflammatory cytokines and chemokines and the subsequent recruitment of immunocompetent cells in the oviduct of laying and molting hens

“…Analysis of the phenotypes of CD8+ T cells and their functions may show further information on the property of oviductal mucosal immunity in future studies. Sundaresan et al (2007Sundaresan et al ( , 2008 suggested that the increase in cytokine expression may play a major role in the regression of the ovary and oviduct during induced molting in chickens. The results of the current study support their observation because expression of proinflammatory cytokines and chemokines were generally higher in molting hens than in laying hens.…”

“…In the regressed oviduct of molting hens induced by feed withdrawal, the immunocompetent cell frequencies tended to decrease in the surface and subepithelial stroma of the mucosa, whereas increased in the middle part of the stroma (Yoshimura et al, 1997). Sundaresan et al (2008) reported that expression of proinflammatory cytokines, IL-6 and GXGLi2, were upregulated in the oviduct to play roles in the regression of tissues during induced molting. However, it is unknown whether there is a difference in the induction of proinflammatory cytokine and chemokine expression and T cell recruitment in response to LPS between laying and molting hens.…”

Multi-Element Analysis of Blood Samples in a Passerine Species: Excesses and Deficiencies of Trace Elements in an Urbanization Study

“…They affect enzymatic activity and antioxidant defenses (Powell, 2000;Sahin et al, 2005) and play an important role in embryo development and nestling growth (Park et al, 2004). Their concentration can exceptionally raise toxicity thresholds (Sundaresan et al, 2008), but, more likely for vertebrates that are very tolerant to these elements, they may impact physiological performances if their concentrations do not meet homeostatic requirements (deficiencies) (Keen et al, 1998). Despite the crucial role of essential elements in nestling growth, and in bird physiology more generally, very few studies have focused on the potential deficiencies in these elements in urbanization studies.…”