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

Objective: To investigate the mechanism of regulatory T cells (Treg) in heat stroke (HS)-induced acute kidney injury (AKI).

Methods: 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 1×10 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.

Results: 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].

Conclusions: Treg might be involved in HS-AKI, possibly via down-regulation of pro-inflammatory cytokines and infiltration of inflammatory cells.