The Role of Tamm‐Horsfall Protein in the Pathogenesis of Crystalline Nephropathy

Abstract

Acute crystalline nephropathy is closely related to glomerular and tubulointerstitial injury, but few studies have investigated the role of Tamm Horsfall protein (THP) in this condition. Thus, we hypothesize that THP can modulate the innate immune system and play a renoprotective role in physiological conditions. However, in crystalline‐induced AKI, reduced THP synthesis may induces inflammatory response. The aim of the current study is to understand the role of exogenous THP administration in an experimental model of crystalline‐induced AKI. Eight weeks old C57BL/6J mice were randomly allocated into four groups (n=5/group): 1. Control (received saline 0.9%); 2. THP (treated with exogenous THP – 5μg per animal, single injection i.p); 3. NaOx (treated with sodium oxalate – 9mg/100g of body weight, single injection i.p); 4. NaOx + THP. After the treatments, the animals were placed in metabolic cages for 24 hours for analysis of metabolic parameters and urinary protein expression. At the end of the period, blood and kidney samples were collected under the effect of anesthetics for further analysis. The experimental protocols, including euthanasia were conducted in accordance with CEUA (3894050221). The results presented as the mean ± S.D. were analyzed by two‐way ANOVA and a Bonferroni post hoc test using GraphPad Prism software. p < 0.05 was considered statistically significant. Our results revealed that the treatment with exogenous THP alone did not change any parameter analyzed in comparison to the control group. The treatment with NaOx did not change the body weight and urinary flow. However, multiple comparisons tests revealed that NaOx treated group exhibited significant decrease in food intake when compared to the control animals and this effect was attenuated in the cotreated group [(g) NaOx: 1.5±0.5 vs. Control: 7.0±0.8, p = 0.0081 and NaOx + THP: 4.0±1.5 vs. NaOx: 1.5±0.5, p = 0.0292]. Furthermore, the interaction between NaOx/THP was confirmed by two‐way ANOVA (p = 0.0236). The NaOx treatment resulted in increase of water intake [(mL/24h) NaOx: 4.4±0.5 vs. Control: 1.7±0.9, p= 0.0165], without interference of the THP in the cotreated group. The NaOx treatment resulted in albuminuria compared to the control group [(arbitrary units) NaOx: 101.613±35.415 vs. Control: 35.965±8,351, p = 0.0361], without significant interference of the THP in the cotreated group, while endogenous THP content in urine decreased in comparison to the control group [(arbitrary units) NaOx: 1.347±0.226 vs. Control: 1.924±0.162, p = 0.0065]. However, the cotreatment with exogenous THP recovered this parameter [(arbitrary units) NaOx + THP: 1.861±0.176 vs. NaOx: 1.347±0.226, p = 0.0216] and the interaction between NaOx/THP was confirmed by two‐way ANOVA (p = 0.0302). NaOx treatment resulted in increased kidney weight in comparison to the control group [(mg/g) NaOx: 8.8±0.3 vs. Control: 6.2±0.6, p = 0.0002] and this effect was attenuated in the cotreated group [(mg/g) NaOx + THP group: 7.1±1.0 vs. NaOx group: 8.8±0.3, p = 0.0150]. The interaction between NaOx/THP was confirmed by two‐way ANOVA (p = 0.0063). Thus, our preliminary results indicate that exogenous THP may have a renoprotective effect on crystalline‐induced AKI.