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Multiple Mechanisms are Involved in Salt-Sensitive Hypertension-Induced Renal Injury and Interstitial Fibrosis

View Article: PubMed Central - PubMed

ABSTRACT

Salt-sensitive hypertension (SSHT) leads to kidney interstitial fibrosis. However, the potential mechanisms leading to renal fibrosis have not been well investigated. In present study, Dahl salt-sensitive (DS) rats were divided into three groups: normal salt diet (DSN), high salt diet (DSH) and high salt diet treated with hydrochlorothiazide (HCTZ) (DSH + HCTZ). A significant increase in systolic blood pressure (SBP) was observed 3 weeks after initiating the high salt diet, and marked histological alterations were observed in DSH rats. DSH rats showed obvious podocyte injury, peritubular capillary (PTC) loss, macrophage infiltration, and changes in apoptosis and cell proliferation. Moreover, Wnt/β-catenin signaling was significantly activated in DSH rats. However, HCTZ administration attenuated these changes with decreased SBP. In addition, increased renal and urinary Wnt4 expression was detected with time in DSH rats and was closely correlated with histopathological alterations. Furthermore, these alterations were also confirmed by clinical study. In conclusion, the present study provides novel insight into the mechanisms related to PTC loss, macrophage infiltration and Wnt/β-catenin signaling in SSHT-induced renal injury and fibrosis. Therefore, multi-target therapeutic strategies may be the most effective in preventing these pathological processes. Moreover, urinary Wnt4 may be a noninvasive biomarker for monitoring renal injury after hypertension.

No MeSH data available.


Related in: MedlinePlus

Wnt/β-catenin signaling activation and urinary Wnt4 excretion in DS rats fed a high salt diet.(a) Representative immunofluorescence micrographs of the time-dependent induction of β-catenin after high salt loading at various time points (magnification, 200X). Arrows indicate β-catenin-positive cells in the interstitium. (b) The chart of the quantification of β-catenin fluorescence intensity. (c–g) Quantitative RT-PCR was used to determine the mRNA levels of β-catenin signaling ligands at the time point with the highest β-catenin expression after high salt loading. Relative mRNA levels were determined after normalization to GAPDH, and the data are presented as the fold induction compared with the DSN group. (h) A dramatic increase in renal β-catenin and Wnt4 expression was observed by western blot analysis. (i–j) The quantitative data are presented, and relative β-catenin and Wnt4 protein levels (fold induction compared with the DSN group) are reported after normalization to β-actin. (k) Representative immunofluorescence micrographs of the time-dependent induction of Wnt4 after high salt loading in each group (magnification, 200X). (l) Quantification of immunofluorescence staining of Wnt4 in each group. (m) Representative western blot analyses of the dynamic changes in urinary Wnt4 expression. (n) Quantification of urinary Wnt4 excretion by western blot analysis in each group. (o) Correlation between kidney Wnt4 expression by immunofluorescence and urinary Wnt4 expression by western blot. (p) Relationship between kidney Wnt4 expression by immunofluorescence and tubular injury index. (q) Correlation between urinary Wnt4 expression by western blot and tubular injury index. The gels were run under the same experimental conditions. Cropped blots are shown (full-sized blots are presented in Supplementary Fig. S1). *p < 0.05, **p < 0.01 versus DSN group. #p < 0.05, ##p < 0.01: DSH + HCTZ group versus DSH group.
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f6: Wnt/β-catenin signaling activation and urinary Wnt4 excretion in DS rats fed a high salt diet.(a) Representative immunofluorescence micrographs of the time-dependent induction of β-catenin after high salt loading at various time points (magnification, 200X). Arrows indicate β-catenin-positive cells in the interstitium. (b) The chart of the quantification of β-catenin fluorescence intensity. (c–g) Quantitative RT-PCR was used to determine the mRNA levels of β-catenin signaling ligands at the time point with the highest β-catenin expression after high salt loading. Relative mRNA levels were determined after normalization to GAPDH, and the data are presented as the fold induction compared with the DSN group. (h) A dramatic increase in renal β-catenin and Wnt4 expression was observed by western blot analysis. (i–j) The quantitative data are presented, and relative β-catenin and Wnt4 protein levels (fold induction compared with the DSN group) are reported after normalization to β-actin. (k) Representative immunofluorescence micrographs of the time-dependent induction of Wnt4 after high salt loading in each group (magnification, 200X). (l) Quantification of immunofluorescence staining of Wnt4 in each group. (m) Representative western blot analyses of the dynamic changes in urinary Wnt4 expression. (n) Quantification of urinary Wnt4 excretion by western blot analysis in each group. (o) Correlation between kidney Wnt4 expression by immunofluorescence and urinary Wnt4 expression by western blot. (p) Relationship between kidney Wnt4 expression by immunofluorescence and tubular injury index. (q) Correlation between urinary Wnt4 expression by western blot and tubular injury index. The gels were run under the same experimental conditions. Cropped blots are shown (full-sized blots are presented in Supplementary Fig. S1). *p < 0.05, **p < 0.01 versus DSN group. #p < 0.05, ##p < 0.01: DSH + HCTZ group versus DSH group.

Mentions: Recent findings have indicated that Wnt protein ligands promote renal interstitial fibrosis by interacting with their receptors in the Wnt/β-catenin pathway17. Renal fibrosis is significantly associated with elevated β-catenin activity25. For these reasons, the role of the Wnt/β-catenin pathway in SSHT needs to be clarified. As shown in Fig. 6a, β-catenin protein levels markedly increased in DSH rats, and HCTZ administration decreased β-catenin expression (Fig. 6a,b). Next, we used real-time PCR (RT-PCR) to analyze the mRNA levels of Wnt ligands. As shown in Fig. 6c–g, the mRNA levels of Wnt2b, Wnt4, Wnt5b, Wnt7b, and Wnt10a were increased in the DSH group compared with the DSN group, whereas HCTZ administration decreased the overexpression of Wnt4, Wnt7b, and Wnt10a but did not significantly influence Wnt2b and Wnt5b expression. These results were confirmed by western blot analyses (Fig. 6h,i).


Multiple Mechanisms are Involved in Salt-Sensitive Hypertension-Induced Renal Injury and Interstitial Fibrosis
Wnt/β-catenin signaling activation and urinary Wnt4 excretion in DS rats fed a high salt diet.(a) Representative immunofluorescence micrographs of the time-dependent induction of β-catenin after high salt loading at various time points (magnification, 200X). Arrows indicate β-catenin-positive cells in the interstitium. (b) The chart of the quantification of β-catenin fluorescence intensity. (c–g) Quantitative RT-PCR was used to determine the mRNA levels of β-catenin signaling ligands at the time point with the highest β-catenin expression after high salt loading. Relative mRNA levels were determined after normalization to GAPDH, and the data are presented as the fold induction compared with the DSN group. (h) A dramatic increase in renal β-catenin and Wnt4 expression was observed by western blot analysis. (i–j) The quantitative data are presented, and relative β-catenin and Wnt4 protein levels (fold induction compared with the DSN group) are reported after normalization to β-actin. (k) Representative immunofluorescence micrographs of the time-dependent induction of Wnt4 after high salt loading in each group (magnification, 200X). (l) Quantification of immunofluorescence staining of Wnt4 in each group. (m) Representative western blot analyses of the dynamic changes in urinary Wnt4 expression. (n) Quantification of urinary Wnt4 excretion by western blot analysis in each group. (o) Correlation between kidney Wnt4 expression by immunofluorescence and urinary Wnt4 expression by western blot. (p) Relationship between kidney Wnt4 expression by immunofluorescence and tubular injury index. (q) Correlation between urinary Wnt4 expression by western blot and tubular injury index. The gels were run under the same experimental conditions. Cropped blots are shown (full-sized blots are presented in Supplementary Fig. S1). *p < 0.05, **p < 0.01 versus DSN group. #p < 0.05, ##p < 0.01: DSH + HCTZ group versus DSH group.
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f6: Wnt/β-catenin signaling activation and urinary Wnt4 excretion in DS rats fed a high salt diet.(a) Representative immunofluorescence micrographs of the time-dependent induction of β-catenin after high salt loading at various time points (magnification, 200X). Arrows indicate β-catenin-positive cells in the interstitium. (b) The chart of the quantification of β-catenin fluorescence intensity. (c–g) Quantitative RT-PCR was used to determine the mRNA levels of β-catenin signaling ligands at the time point with the highest β-catenin expression after high salt loading. Relative mRNA levels were determined after normalization to GAPDH, and the data are presented as the fold induction compared with the DSN group. (h) A dramatic increase in renal β-catenin and Wnt4 expression was observed by western blot analysis. (i–j) The quantitative data are presented, and relative β-catenin and Wnt4 protein levels (fold induction compared with the DSN group) are reported after normalization to β-actin. (k) Representative immunofluorescence micrographs of the time-dependent induction of Wnt4 after high salt loading in each group (magnification, 200X). (l) Quantification of immunofluorescence staining of Wnt4 in each group. (m) Representative western blot analyses of the dynamic changes in urinary Wnt4 expression. (n) Quantification of urinary Wnt4 excretion by western blot analysis in each group. (o) Correlation between kidney Wnt4 expression by immunofluorescence and urinary Wnt4 expression by western blot. (p) Relationship between kidney Wnt4 expression by immunofluorescence and tubular injury index. (q) Correlation between urinary Wnt4 expression by western blot and tubular injury index. The gels were run under the same experimental conditions. Cropped blots are shown (full-sized blots are presented in Supplementary Fig. S1). *p < 0.05, **p < 0.01 versus DSN group. #p < 0.05, ##p < 0.01: DSH + HCTZ group versus DSH group.
Mentions: Recent findings have indicated that Wnt protein ligands promote renal interstitial fibrosis by interacting with their receptors in the Wnt/β-catenin pathway17. Renal fibrosis is significantly associated with elevated β-catenin activity25. For these reasons, the role of the Wnt/β-catenin pathway in SSHT needs to be clarified. As shown in Fig. 6a, β-catenin protein levels markedly increased in DSH rats, and HCTZ administration decreased β-catenin expression (Fig. 6a,b). Next, we used real-time PCR (RT-PCR) to analyze the mRNA levels of Wnt ligands. As shown in Fig. 6c–g, the mRNA levels of Wnt2b, Wnt4, Wnt5b, Wnt7b, and Wnt10a were increased in the DSH group compared with the DSN group, whereas HCTZ administration decreased the overexpression of Wnt4, Wnt7b, and Wnt10a but did not significantly influence Wnt2b and Wnt5b expression. These results were confirmed by western blot analyses (Fig. 6h,i).

View Article: PubMed Central - PubMed

ABSTRACT

Salt-sensitive hypertension (SSHT) leads to kidney interstitial fibrosis. However, the potential mechanisms leading to renal fibrosis have not been well investigated. In present study, Dahl salt-sensitive (DS) rats were divided into three groups: normal salt diet (DSN), high salt diet (DSH) and high salt diet treated with hydrochlorothiazide (HCTZ) (DSH&thinsp;+&thinsp;HCTZ). A significant increase in systolic blood pressure (SBP) was observed 3 weeks after initiating the high salt diet, and marked histological alterations were observed in DSH rats. DSH rats showed obvious podocyte injury, peritubular capillary (PTC) loss, macrophage infiltration, and changes in apoptosis and cell proliferation. Moreover, Wnt/&beta;-catenin signaling was significantly activated in DSH rats. However, HCTZ administration attenuated these changes with decreased SBP. In addition, increased renal and urinary Wnt4 expression was detected with time in DSH rats and was closely correlated with histopathological alterations. Furthermore, these alterations were also confirmed by clinical study. In conclusion, the present study provides novel insight into the mechanisms related to PTC loss, macrophage infiltration and Wnt/&beta;-catenin signaling in SSHT-induced renal injury and fibrosis. Therefore, multi-target therapeutic strategies may be the most effective in preventing these pathological processes. Moreover, urinary Wnt4 may be a noninvasive biomarker for monitoring renal injury after hypertension.

No MeSH data available.


Related in: MedlinePlus