Induction of proinflammatory cytokines and nitric oxide by Trypanosoma cruzi in renal cells

Defective Treg response in acute kidney injury was caused by a reduction in TIM-3+ Treg cells

BACKGROUND

Despite years of research, the treatment of acute kidney injury (AKI) remains a significant challenge. Animal studies presented causal links between elevated regulatory T cell (Treg) response and better prognosis in AKI. Previous studies in mice and humans showed that TIM-3+ Treg cells were more potent than TIM-3- Treg cells. In this study, we investigated the role of TIM-3 in Treg in AKI patients.

METHODS

Peripheral blood from AKI patients and healthy controls were gathered, and TIM-3+ Treg subset was examined.

RESULTS

Compared to healthy controls, the AKI patients presented a significant upregulation in the frequency of circulating CD4+CD25+ T cells; however, the majority of this increase was from the CD4+CD25+TIM-3- subset, and the frequency of CD4+CD25+TIM-3+ T cells was downregulated in AKI patients. In both healthy controls and AKI patients, the CD4+CD25+TIM-3+ T cells expressed higher levels of Foxp3, and were more potent at expressing LFA-1, LAG-3, CTLA-4, IL-10 and TGF-β. In addition, the CD4+CD25+TIM-3+ T cells from both healthy controls and AKI patients presented higher capacity to suppress CD4+CD25- T cell proliferation than the CD4+CD25+TIM-3- T cells. Interestingly, the total CD4+CD25+ T cells from AKI patients presented significantly lower inhibitory capacity than those from healthy controls, indicating that the low frequency of CD4+CD25+TIM-3+ T cells was restricting the efficacy of the Treg responses in AKI patients.

CONCLUSIONS

We demonstrated that TIM-3 downregulation impaired the function of Treg cells in AKI. The therapeutic potential of CD4+CD25+TIM-3+ T cells in AKI should be investigated in future studies.

Influence of parasite load on renal function in mice acutely infected with Trypanosoma cruzi

BACKGROUND

Chagas disease is a neglected tropical disease caused by Trypanosoma cruzi. Despite the vast number of studies evaluating the pathophysiological mechanisms of the disease, the influence of parasite burden on kidney lesions remains unclear. Thus, the main goal of this work was to evaluate the effect of T. cruzi infection on renal function and determine whether there was a correlation between parasite load and renal injury using an acute experimental model of the disease.

METHODOLOGY/PRINCIPAL FINDINGS

Low, medium and high parasite loads were generated by infecting C57BL/6 mice with 300 (low), 3,000 (medium) or 30,000 (high) numbers of "Y" strain trypomastigotes. We found that mice infected with T. cruzi trypomastigotes show increased renal injury. The infection resulted in reduced urinary excretion and creatinine clearance. We also observed a marked elevation in the ratio of urine volume to kidney and body weight, blood urea nitrogen, chloride ion, nitric oxide, pro- and anti-inflammatory cytokines and the number of leukocytes in the blood and/or renal tissues of infected mice. Additionally, we observed the presence of the parasite in the cortical/medullary and peri-renal region, an increase of inflammatory infiltrate and of vascular permeability of the kidney. Overall, most renal changes occurred mainly in animals infected with high parasitic loads.

CONCLUSIONS/SIGNIFICANCE

These data demonstrate that T. cruzi impairs kidney function, and this impairment is more evident in mice infected with high parasitic loads. Moreover, these data suggest that, in addition to the extensively studied cardiovascular effects, renal injury should be regarded as an important indicator for better understanding the pan-infectivity of the parasite and consequently for understanding the disease in experimental models.