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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 expression in human IgAN.Immunofluorescence confocal microscopy in frozen sections of normal kidney tissue (obtained from a representative human nephrectomy sample) (a) or a representative kidney biopsy from a patient with IgAN (b). Dual labeling probing for NLRP3 (green) and PDGFR-β (red) or kidney injury molecule-1 (KIM-1, red); NLRP3 (red) with alpha smooth muscle actin (α-SMA, green). Nuclear stain using DAPI (blue) is shown in merged images. Magnified views of the indicated regions outlined from the merged images. Scale bars 100 μm. Arrows point to areas of yellow indicating colocalization of green and red channels. Images are representative of experiments performed at least 3 independent times.
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f2: NLRP3 expression in human IgAN.Immunofluorescence confocal microscopy in frozen sections of normal kidney tissue (obtained from a representative human nephrectomy sample) (a) or a representative kidney biopsy from a patient with IgAN (b). Dual labeling probing for NLRP3 (green) and PDGFR-β (red) or kidney injury molecule-1 (KIM-1, red); NLRP3 (red) with alpha smooth muscle actin (α-SMA, green). Nuclear stain using DAPI (blue) is shown in merged images. Magnified views of the indicated regions outlined from the merged images. Scale bars 100 μm. Arrows point to areas of yellow indicating colocalization of green and red channels. Images are representative of experiments performed at least 3 independent times.

Mentions: We have previously identified significant NLRP3 mRNA expression in the kidneys of a small number of patients with IgAN6. Thus, immunostaining experiments were performed in biopsies from patients with IgAN to further characterize NLRP3 in this cohort. Similar to normal kidney tissue, NLRP3 once again localized primarily to the tubular epithelium in patients with IgAN (Fig. 2a,b). Not surprisingly, with renal injury and disease, tissue from patients with IgAN also demonstrated increased KIM-1 expression, a tubule-restricted activation marker that colocalized with NLRP3 (Fig. 2b). In glomeruli, NLRP3 expression became detectable in IgAN and colocalized to PDGFR-β positive areas (Fig. 2b). NLRP3 staining was absent in fibrotic areas and did not colocalize with α-SMA in the interstitium ruling out NLRP3 expression in myofibroblasts. These results show that in IgAN, NLRP3 remains predominately expressed in tubules with lesser expression at glomeruli.


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 expression in human IgAN.Immunofluorescence confocal microscopy in frozen sections of normal kidney tissue (obtained from a representative human nephrectomy sample) (a) or a representative kidney biopsy from a patient with IgAN (b). Dual labeling probing for NLRP3 (green) and PDGFR-β (red) or kidney injury molecule-1 (KIM-1, red); NLRP3 (red) with alpha smooth muscle actin (α-SMA, green). Nuclear stain using DAPI (blue) is shown in merged images. Magnified views of the indicated regions outlined from the merged images. Scale bars 100 μm. Arrows point to areas of yellow indicating colocalization of green and red channels. Images are representative of experiments performed at least 3 independent times.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837396&req=5

f2: NLRP3 expression in human IgAN.Immunofluorescence confocal microscopy in frozen sections of normal kidney tissue (obtained from a representative human nephrectomy sample) (a) or a representative kidney biopsy from a patient with IgAN (b). Dual labeling probing for NLRP3 (green) and PDGFR-β (red) or kidney injury molecule-1 (KIM-1, red); NLRP3 (red) with alpha smooth muscle actin (α-SMA, green). Nuclear stain using DAPI (blue) is shown in merged images. Magnified views of the indicated regions outlined from the merged images. Scale bars 100 μm. Arrows point to areas of yellow indicating colocalization of green and red channels. Images are representative of experiments performed at least 3 independent times.
Mentions: We have previously identified significant NLRP3 mRNA expression in the kidneys of a small number of patients with IgAN6. Thus, immunostaining experiments were performed in biopsies from patients with IgAN to further characterize NLRP3 in this cohort. Similar to normal kidney tissue, NLRP3 once again localized primarily to the tubular epithelium in patients with IgAN (Fig. 2a,b). Not surprisingly, with renal injury and disease, tissue from patients with IgAN also demonstrated increased KIM-1 expression, a tubule-restricted activation marker that colocalized with NLRP3 (Fig. 2b). In glomeruli, NLRP3 expression became detectable in IgAN and colocalized to PDGFR-β positive areas (Fig. 2b). NLRP3 staining was absent in fibrotic areas and did not colocalize with α-SMA in the interstitium ruling out NLRP3 expression in myofibroblasts. These results show that in IgAN, NLRP3 remains predominately expressed in tubules with lesser expression at glomeruli.

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