Mechanism of regulatory T cells in heat stroke-induced acute kidney injury

Abstract

To investigate the mechanism of regulatory T cells (Treg) in heat stroke (HS)-induced acute kidney injury (AKI). Male SPF Balb/c mice were randomly divided into control group, HS group (HS+Rat IgG), HS+PC61 group, and HS+Treg group (n = 6). The HS mice model was established by making the body temperature of the mice reach 42.7 centigrade at room temperature 39.5 centigrade with relative humidity 60% for 1 hour. In HS+PC61 group, 100 μg PC61 antibody (anti-CD25) was injected through the tail vein in consecutive 2 days before the model was established to eliminate Tregs. Mice in HS+Treg group was injected with 1×106 Treg via tail vein immediately after successful modeling. The proportion of Treg infiltrated in the kidney, serum creatinine (SCr) and histopathology, levels of interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) both in the serum and kidney tissue, as well as proportion of neutrophils and macrophages located in the kidney were observed at 24 hours after HS. HS dampened renal function and exaggerated kidney injury, up-regulated levels of inflammatory cytokines both in local kidney and circulation, and increased infiltration of neutrophils and macrophages to the injured kidneys. The proportion of Treg (Treg/CD4+) infiltrated in kidney was significantly decreased in HS group, compared with control group [(3.40±0.46)% vs. (7.67±0.82)%, P < 0.01]. Compared with HS group, local Tregs in kidney were almost completely depleted via PC61 antibody [(0.77±0.12)% vs. (3.40±0.46)%, P < 0.01]. Depletion of Tregs could exacerbate HS-AKI, indicating by increased serum creatinine [SCr (mmol/L): 348.22±35.36 vs. 254.42±27.40, P < 0.01] and pathological injury (Paller score: 4.70±0.20 vs. 3.60±0.20, P < 0.01), incremental levels of IFN-γand TNF-α both in injured kidney and serum [serum IFN-γ (ng/L): 747.70±64.52 vs. 508.46±44.79, serum TNF-α (ng/L): 647.41±26.62 vs. 464.53±41.80, both P < 0.01], and more infiltrated neutrophils and macrophages in the injured kidney [neutrophil proportion: (6.63±0.67)% vs. (4.37±0.43)%, macrophage proportion: (38.70±1.66)% vs. (33.19±1.55)%, both P < 0.01]. On the contrast, adoptive transfer of Tregs could reverse the aforementioned effects of Treg depletion, indicating by incremental proportion of Tregs in the injured kidney [(10.58±1.19)% vs. (3.40±0.46)%, P < 0.01], decreased serum creatinine [SCr (mmol/L): 168.24±40.56 vs. 254.42±27.40, P < 0.01] and pathological injury (Paller score: 2.73±0.11 vs. 3.60±0.20, P < 0.01), reduced levels of IFN-γ and TNF-α both in injured kidney and serum [serum IFN-γ (ng/L): 262.62±22.68 vs. 508.46±44.79, serum TNF-α (ng/L): 206.41±22.58 vs. 464.53±41.80, both P < 0.01], and less infiltrated neutrophils and macrophages in the injured kidney [neutrophil proportion: (3.04±0.33)% vs. (4.37±0.43)%, macrophage proportion: (25.68±1.93)% vs. (33.19±1.55)%, both P < 0.01]. Treg might be involved in HS-AKI, possibly via down-regulation of pro-inflammatory cytokines and infiltration of inflammatory cells.