Effect of Bovine Lactoferrin Treatment Followed by Acute Stress on the IgA-Response in Small Intestine of BALB/c Mice

Secretory IgA (SIgA) has a pivotal role in gut homeostasis, which can be disturbed by stress. SIgA is formed by IgA-dimers (associated by the J-chain) and the secretory component, a protein derivative of polymeric immunoglobulin receptor (pIgR). Given the gut immuno-modulatory properties of bovine lactoferrin (bLf), the aim of this study was to compare, after bLf treatment followed by acute stress, the IgA response and IgA-associated parameters in proximal versus distal small intestine. Male BALB/c mice (n = 6) were orally treated with bLf (50, 500, and 5000 μg) for 7 days, then stressed by immobilization for 1 h, and sacrificed. In proximal and distal segments, levels were determined of IgA in gut secretions (enzyme-linked immunosorbent assay [ELISA]), the α-/J-chain and pIgR proteins in epithelial cells (Western-blot), and mRNA expression of the α-/J-chain, pIgR, and interleukins (ILs) in mucosa (RT-PCR). Data were compared by two-way analysis of variance (ANOVA) (significance at P < 0.05). Under acute stress, bLf triggered higher levels of IgA, SIgA, and anti-bLf-IgA as well as greater mRNA expression of pIgR, IL-4, and IL-6 (500 µg) in proximal intestine, while inducing higher levels of the total IgA, α-/J-chain, and pIgR proteins as well as greater mRNA expression of the α-chain and IL-4 (5000 µg) in distal intestine. Compared to unstressed/bLf-untreated mice, plasma corticosterone (a stress biomarker, measured by ELISA) increased in stressed/bLf-treated (0, 50 and 500 µg) and unstressed/bLf-treated (5000 µg) mice. The interplay of corticosterone with gut neuroendocrine factors may have elicited signals creating anti-inflammatory conditions for an IgA-response profile in each intestinal region, according to the bLf concentration administered.