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NLRP3 Localizes to the Tubular Epithelium in Human Kidney and Correlates With Outcome in IgA Nephropathy.

Chun J, Chung H, Wang X, Barry R, Taheri ZM, Platnich JM, Ahmed SB, Trpkov K, Hemmelgarn B, Benediktsson H, James MT, Muruve DA - Sci Rep (2016)

Bottom Line: While NLRP3 expression in IgAN was detected in glomeruli, it remained largely confined to the tubular epithelial compartment.In vitro NLRP3 mRNA and protein expression were transiently induced in HPTC by TGF-β1 but subsequently diminished over time as cells lost their epithelial phenotype in a process regulated by transcription and ubiquitin-mediated degradation.Consistent with the in vitro data, low NLRP3 mRNA expression in kidney biopsies was associated with a linear trend of higher risk of composite endpoint of doubling serum creatinine and end stage renal disease in patients with IgAN.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta, Canada.

ABSTRACT
Nod-like receptor pyrin domain-containing-3 (NLRP3) has been implicated in the pathogenesis of experimental renal injury, yet its characterization in human kidney disease remains largely unexplored. NLRP3 expression was evaluated in human kidney biopsies, primary renal tubular cells (HPTC) and correlated to disease outcomes in patients with IgA nephropathy (IgAN). NLRP3 localized to renal tubules in normal human kidney tissue and to mitochondria within HPTC by immunohistochemistry and immunofluorescence microscopy. Compared to control kidneys, NLRP3 gene expression was increased in biopsies of patients with IgAN. While NLRP3 expression in IgAN was detected in glomeruli, it remained largely confined to the tubular epithelial compartment. In vitro NLRP3 mRNA and protein expression were transiently induced in HPTC by TGF-β1 but subsequently diminished over time as cells lost their epithelial phenotype in a process regulated by transcription and ubiquitin-mediated degradation. Consistent with the in vitro data, low NLRP3 mRNA expression in kidney biopsies was associated with a linear trend of higher risk of composite endpoint of doubling serum creatinine and end stage renal disease in patients with IgAN. Taken together, these data show that NLRP3 is primarily a kidney tubule-expressed protein that decreases in abundance in progressive IgAN.

No MeSH data available.


Related in: MedlinePlus

NLRP3 mRNA expression and renal outcome in IgAN.(a) NLRP3 mRNA expression by quantitative real-time PCR in patients with IgAN. RNA isolated from renal biopsies of patients with IgAN grouped into quartiles (Q1–4) based on NLRP3 mRNA expression levels standardized to normal kidney samples. Values are normalized to endogenous 18S mRNA expression levels. (b) Hazard ratio for NLRP3 quartiles based on the multivariable Cox model for the composite outcome of doubling serum Cr, ESRD or death. There is a significant linear trend towards lower risk of composite outcome with higher levels of NLRP3 (p = 0.047). (c) Product-limit survival estimates from each quartile. Quartile 1: low NLRP3; quartile 2: low-intermediate; quartile 3: high-intermediate; and quartile 4: high NLRP3. NLRP3 mRNA expression was analyzed as a logarithmic variable due to its non-normal distribution, and displayed as quartiles in a survival curve. (d) Correlation of NLRP3 mRNA expression with KIM-1 mRNA expression.
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f8: NLRP3 mRNA expression and renal outcome in IgAN.(a) NLRP3 mRNA expression by quantitative real-time PCR in patients with IgAN. RNA isolated from renal biopsies of patients with IgAN grouped into quartiles (Q1–4) based on NLRP3 mRNA expression levels standardized to normal kidney samples. Values are normalized to endogenous 18S mRNA expression levels. (b) Hazard ratio for NLRP3 quartiles based on the multivariable Cox model for the composite outcome of doubling serum Cr, ESRD or death. There is a significant linear trend towards lower risk of composite outcome with higher levels of NLRP3 (p = 0.047). (c) Product-limit survival estimates from each quartile. Quartile 1: low NLRP3; quartile 2: low-intermediate; quartile 3: high-intermediate; and quartile 4: high NLRP3. NLRP3 mRNA expression was analyzed as a logarithmic variable due to its non-normal distribution, and displayed as quartiles in a survival curve. (d) Correlation of NLRP3 mRNA expression with KIM-1 mRNA expression.

Mentions: We previously demonstrated that NLRP3 mRNA expression in the kidney is increased in a limited number of patients with IgAN compared to normal6. To determine if NLRP3 expression correlated with IgAN disease outcome and progression, kidney NLRP3 mRNA expression was analyzed by real-time PCR in an expanded cohort of patients with IgAN and correlated to clinical outcomes. Fifty-four consecutive patients with a primary diagnosis of IgAN were selected for analysis from a pool of kidney biopsies performed between 2003 and 2007. The baseline characteristics of the cohort are shown in Table 1. Consistent with our previous study6 and the variable clinical presentation of IgAN, NLRP3 mRNA expression in kidney biopsies varied from two to several hundred-fold above normal controls (Fig. 8a). NLRP3 mRNA expression levels in IgAN patients were arbitrarily categorized into quartiles and correlated to the time to event of the composite endpoint of doubling of serum creatinine, ESRD or death. Interestingly, there was a trend towards for a lower risk of the composite endpoint in IgAN patients with high expression of NLRP3 (Fig. 8b). In a multivariable Cox model for the composite outcome of doubling of serum creatinine, ESRD or death adjusted for histopathological features according to the Oxford classification, there was a significant linear trend (p-value 0.047) towards lower risk of the composite outcome among patients with higher quartiles of NLRP3 (Fig. 8c). Similar to results reported by other groups3031, the multivariable Cox model also demonstrated a significantly increased risk of the composite outcome associated with a tubular atrophy/interstitial fibrosis score of T = 2 by the Oxford classification (p-value 0.01, Table 2). Given that NLRP3 is localized primarily to the tubular compartment, these observations suggest that NLRP3 expression in the kidney decreases during tubular atrophy/interstitial fibrosis observed in progressive IgAN that is associated with a worse clinical outcome. Consistent with this premise, NLRP3 mRNA expression in IgAN directly correlated with KIM-1 (also a tubular activation marker) with an R-squared value of 0.782 (Fig. 8d).


NLRP3 Localizes to the Tubular Epithelium in Human Kidney and Correlates With Outcome in IgA Nephropathy.

Chun J, Chung H, Wang X, Barry R, Taheri ZM, Platnich JM, Ahmed SB, Trpkov K, Hemmelgarn B, Benediktsson H, James MT, Muruve DA - Sci Rep (2016)

NLRP3 mRNA expression and renal outcome in IgAN.(a) NLRP3 mRNA expression by quantitative real-time PCR in patients with IgAN. RNA isolated from renal biopsies of patients with IgAN grouped into quartiles (Q1–4) based on NLRP3 mRNA expression levels standardized to normal kidney samples. Values are normalized to endogenous 18S mRNA expression levels. (b) Hazard ratio for NLRP3 quartiles based on the multivariable Cox model for the composite outcome of doubling serum Cr, ESRD or death. There is a significant linear trend towards lower risk of composite outcome with higher levels of NLRP3 (p = 0.047). (c) Product-limit survival estimates from each quartile. Quartile 1: low NLRP3; quartile 2: low-intermediate; quartile 3: high-intermediate; and quartile 4: high NLRP3. NLRP3 mRNA expression was analyzed as a logarithmic variable due to its non-normal distribution, and displayed as quartiles in a survival curve. (d) Correlation of NLRP3 mRNA expression with KIM-1 mRNA expression.
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Related In: Results  -  Collection

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f8: NLRP3 mRNA expression and renal outcome in IgAN.(a) NLRP3 mRNA expression by quantitative real-time PCR in patients with IgAN. RNA isolated from renal biopsies of patients with IgAN grouped into quartiles (Q1–4) based on NLRP3 mRNA expression levels standardized to normal kidney samples. Values are normalized to endogenous 18S mRNA expression levels. (b) Hazard ratio for NLRP3 quartiles based on the multivariable Cox model for the composite outcome of doubling serum Cr, ESRD or death. There is a significant linear trend towards lower risk of composite outcome with higher levels of NLRP3 (p = 0.047). (c) Product-limit survival estimates from each quartile. Quartile 1: low NLRP3; quartile 2: low-intermediate; quartile 3: high-intermediate; and quartile 4: high NLRP3. NLRP3 mRNA expression was analyzed as a logarithmic variable due to its non-normal distribution, and displayed as quartiles in a survival curve. (d) Correlation of NLRP3 mRNA expression with KIM-1 mRNA expression.
Mentions: We previously demonstrated that NLRP3 mRNA expression in the kidney is increased in a limited number of patients with IgAN compared to normal6. To determine if NLRP3 expression correlated with IgAN disease outcome and progression, kidney NLRP3 mRNA expression was analyzed by real-time PCR in an expanded cohort of patients with IgAN and correlated to clinical outcomes. Fifty-four consecutive patients with a primary diagnosis of IgAN were selected for analysis from a pool of kidney biopsies performed between 2003 and 2007. The baseline characteristics of the cohort are shown in Table 1. Consistent with our previous study6 and the variable clinical presentation of IgAN, NLRP3 mRNA expression in kidney biopsies varied from two to several hundred-fold above normal controls (Fig. 8a). NLRP3 mRNA expression levels in IgAN patients were arbitrarily categorized into quartiles and correlated to the time to event of the composite endpoint of doubling of serum creatinine, ESRD or death. Interestingly, there was a trend towards for a lower risk of the composite endpoint in IgAN patients with high expression of NLRP3 (Fig. 8b). In a multivariable Cox model for the composite outcome of doubling of serum creatinine, ESRD or death adjusted for histopathological features according to the Oxford classification, there was a significant linear trend (p-value 0.047) towards lower risk of the composite outcome among patients with higher quartiles of NLRP3 (Fig. 8c). Similar to results reported by other groups3031, the multivariable Cox model also demonstrated a significantly increased risk of the composite outcome associated with a tubular atrophy/interstitial fibrosis score of T = 2 by the Oxford classification (p-value 0.01, Table 2). Given that NLRP3 is localized primarily to the tubular compartment, these observations suggest that NLRP3 expression in the kidney decreases during tubular atrophy/interstitial fibrosis observed in progressive IgAN that is associated with a worse clinical outcome. Consistent with this premise, NLRP3 mRNA expression in IgAN directly correlated with KIM-1 (also a tubular activation marker) with an R-squared value of 0.782 (Fig. 8d).

Bottom Line: While NLRP3 expression in IgAN was detected in glomeruli, it remained largely confined to the tubular epithelial compartment.In vitro NLRP3 mRNA and protein expression were transiently induced in HPTC by TGF-β1 but subsequently diminished over time as cells lost their epithelial phenotype in a process regulated by transcription and ubiquitin-mediated degradation.Consistent with the in vitro data, low NLRP3 mRNA expression in kidney biopsies was associated with a linear trend of higher risk of composite endpoint of doubling serum creatinine and end stage renal disease in patients with IgAN.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta, Canada.

ABSTRACT
Nod-like receptor pyrin domain-containing-3 (NLRP3) has been implicated in the pathogenesis of experimental renal injury, yet its characterization in human kidney disease remains largely unexplored. NLRP3 expression was evaluated in human kidney biopsies, primary renal tubular cells (HPTC) and correlated to disease outcomes in patients with IgA nephropathy (IgAN). NLRP3 localized to renal tubules in normal human kidney tissue and to mitochondria within HPTC by immunohistochemistry and immunofluorescence microscopy. Compared to control kidneys, NLRP3 gene expression was increased in biopsies of patients with IgAN. While NLRP3 expression in IgAN was detected in glomeruli, it remained largely confined to the tubular epithelial compartment. In vitro NLRP3 mRNA and protein expression were transiently induced in HPTC by TGF-β1 but subsequently diminished over time as cells lost their epithelial phenotype in a process regulated by transcription and ubiquitin-mediated degradation. Consistent with the in vitro data, low NLRP3 mRNA expression in kidney biopsies was associated with a linear trend of higher risk of composite endpoint of doubling serum creatinine and end stage renal disease in patients with IgAN. Taken together, these data show that NLRP3 is primarily a kidney tubule-expressed protein that decreases in abundance in progressive IgAN.

No MeSH data available.


Related in: MedlinePlus