OBJECTIVETo investigate the effects of zinc deficiency on the relevant immune function in rats with LPS-induced sepsis.

METHODSSixty rats were divided into low zinc group (LZ), normal zinc pair-fed group (NP), and normal zinc control group (NC) according to the random number table, with 20 rats in each group. The rats in group LZ were fed with low zinc diet, and the rats in group NP were fed with normal zinc diet, with the same intake as that of group LZ by manual control, and the rats in group NC were fed with normal zinc diet freely. After being fed for 7 d, the rats all fasted and were further divide into the below subgroups named LZ-LPS, LZ-normal saline (NS), NP-LPS, NP-NS, NC-LPS, and NC-NS according to the random number table, with 10 rats in each subgroup. Rats in the LPS subgroups were intraperitoneally injected with 1 mg/mL LPS solution with the dosage of 5 mg/kg, rats in the corresponding NS subgroups were intraperitoneally injected with equivalent NS. The rats were sacrificed at post injection hour 6 to collect blood, spleen, and thymus. The serum level of zinc was detected by inductively coupled plasma mass spectrometry, and the serum alkaline phosphatase (ALP) activity was detected by automatic blood biochemical analyzer. The body weight and weight of spleen and thymus of rats were weighed, and the indices of spleen and thymus were calculated. Six routine blood indices were examined by automatic blood cell analyzer. The serum levels of interferon gamma (IFN-γ), TNF-α, IL-4, and IL-10 were determined with ELISA, and the ratio of IFN-γ to IL-4 was calculated. Data were processed with one-way analysis of variance and SNK test.

RESULTS(1) Serum levels of zinc and ALP activity in the LPS subgroups were significantly lower than those in the corresponding NS subgroups (with P values below 0.05). The two former indices in subgroups NP-NS and NC-NS were significantly higher than those in subgroup LZ-NS (with P values below 0.05). The two former indices in subgroups NP-LPS and NC-LPS were significantly higher than those in subgroup LZ-LPS (with P values below 0.05). (2) Body weight, spleen and thymus weight, indices of spleen and thymus in the LPS subgroups were similar with those in the corresponding NS subgroups (with P values above 0.05). The 4 former indices, except for body weight, in subgroups NP-NS and NC-NS were significantly higher than those in subgroup LZ-NS (with P values below 0.05). The 4 former indices, except for body weight, in subgroups NP-LPS and NC-LPS were significantly higher than those in subgroup LZ-LPS (with P values below 0.05). (3) Levels of leucocyte count in subgroups LZ-LPS and NP-LPS were significantly higher than those in the corresponding NS subgroups (with P values below 0.05). Level of leucocyte count in subgroup NC-NS was significantly higher than that in subgroup LZ-NS (P<0.05). Level of leucocyte count in subgroup NC-LPS was significantly lower than that in subgroup LZ-LPS (P<0.05). Levels of neutrophilic granulocyte count (NGC) and NG in the LPS subgroups were significantly higher than those in the corresponding NS subgroups (with P values below 0.05). The two former indices in subgroup NC-LPS were significantly lower than those in subgroup LZ-LPS (with P values below 0.05). Level of NG in subgroup NC-NS was significantly lower than that in subgroup LZ-NS (P<0.05). Levels of lymphocyte count and lymphocyte in subgroups LZ-NS, LZ-LPS, NP-NS, NP-LPS, NC-NS, and NC-LPS were respectively (1.8 ± 0.4) × 10⁹/L, (1.0 ± 0.3)× 10⁹/L, (2.6 ± 0.7) × 10⁹/L, (1.4 ± 0.4) × 10⁹/L, (3.3 ± 0.6) × 10⁹/L, (1.5 ± 0.5) × 10⁹/L, and 0.39 ± 0.10, 0.11 ± 0.03, 0.47 ± 0.12, 0.14 ± 0.04, 0.50 ± 0.09, 0.24 ± 0.07. The two former indices in the LPS subgroups were significantly lower than those in the corresponding NS subgroups (with P values below 0.05). The two former indices in subgroup NC-NS were significantly higher than those in subgroup LZ-NS (with P values below 0.05). The two former indices in subgroups NP-LPS and NC-LPS were significantly higher than those in subgroup LZ-LPS (with P values below 0.05). Level of lymphocyte count in subgroup NP-NS was significantly higher than that in subgroup LZ-NS (P<0.05). Levels of platelet count (PC) in subgroups NP-LPS and NC-LPS were significantly lower than those in the corresponding NS subgroups (with P values below 0.05). Levels of PC in subgroups NP-NS and NC-NS were significantly higher than those in subgroup LZ-NS (with P values below 0.05). Level of PC in subgroup NC-LPS was significantly higher than that in subgroup LZ-LPS (P<0.05). (4) Serum levels of TNF-α, IL-4, and IL-10 in each subgroup showed no significant differences (with P values above 0.05). Serum levels of IFN-γ and ratios of IFN-γ to IL-4 in subgroups LZ-NS, LZ-LPS, NP-NS, NP-LPS, NC-NS, and NC-LPS were respectively (75 ± 21), (233 ± 40), (80 ± 14), (345 ± 74), (66 ± 7), (821 ± 189) pg/mL, and 3.1 ± 1.0, 6.6 ± 1.7, 3.9 ± 1.7, 20.2 ± 8.3, 3.4 ± 1.5, 45.7 ± 7.6. The two former indices in the LPS subgroups were significantly higher than those in the corresponding NS subgroups (with P values below 0.05). The two former indices in subgroups NP-NS and NC-NS were similar with those in subgroup LZ-NS (with P values above 0.05). The two former indices in subgroups NP-LPS and NC-LPS were significantly higher than those in subgroup LZ-LPS (with P values below 0.05).

CONCLUSIONSZinc deficiency can induce the atrophy of spleen and thymus, and reduction of peripheral blood lymphocyte. In sepsis, zinc deficiency can further decrease the production of IFN-γ, thus making the cytokines of Th1/Th2 shift to Th2 and the immune imbalance worse.