Inflammatory response under zinc deficiency is exacerbated by dysfunction of the T helper type 2 lymphocyte-M2...

Nutritional zinc deficiency leads to immune dysfunction and aggravates inflammation. However, the underlying mechanism remains unknown. In this study, the relationship between macrophage subtypes (M1 and M2) and helper T lymphocytes (Th1 and Th2) was investigated using the spleen from rats fed zinc-deficient or standard diet. In experiment I, 5-week-old male Sprague-Dawley rats were fed a zinc-deficient diet (without zinc additives) or a standard diet (containing 0·01% zinc) for 6 weeks. In experiment II, the rats were divided into four groups: one group was fed a standard diet for 6 weeks; two groups were fed zinc-deficient diets and were injected three times a week with either saline or interleukin-4 (IL-4) (zinc-deficient/IL-4 i.p.); a fourth group (zinc-deficient/standard) was fed a zinc-deficient diet for 6 weeks followed by a standard diet for 4 weeks. In experiment I; GATA-binding protein 3 (GATA-3) protein level, M2 macrophage, CD3⁺  CD8⁺ cells, and IL-4/IL-13-positive cells significantly decreased in the spleens of the zinc-deficient group. Additionally, IL-1β and macrophage inflammatory protein-1α (MIP-1α) mRNA levels significantly increased in the splenic macrophages of the zinc-deficient group. In experiment II; M2 macrophages, CD3⁺  CD8⁺ cells, IL-4/IL-13-positive cells, and GATA-3 protein levels significantly increased in the spleens of the zinc-deficient/IL-4 i.p. and zinc-deficient/standard groups. Furthermore, IL-1β and MIP-1α mRNA levels decreased in the splenic macrophages of the zinc-deficient/IL-4 i.p. and zinc-deficient/standard groups. Zinc deficiency-induced aggravated inflammation is related to Th2 lymphocytes and followed by the association with loss of GATA-3, IL-4 and anti-inflammatory M2 macrophages. Importantly, IL-4 injection or zinc supplementation can reverse the effects of zinc deficiency on immune function.