Effects of oxalate on the re-initiation of DNA synthesis in LLC-PK1 cells do not involve p42/44 MAP kinase activation

Koul, Sweaty; Chaturvedi, Lakshmi S.; Sekhon, Avtar; Bhandari, Akshay; Menon, Mani; Koul, Hari K.

doi:10.1046/j.1523-1755.2002.00163.x

Cited by 18 publications

(8 citation statements)

References 35 publications

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“…Though the functional significance of KIM-1 shedding is not known, Mitogen Activated Protein Kinases, especially ERK and p38 MAPK, have been shown to play an important role in this process [32]. Previous studies in our laboratory have identified activation of p38 MAPK in kidney epithelial cells exposed to Oxalate and COM-Crystals [7], [8], [17]. Based on these observations, it is tempting to speculate that signaling by p38 MAPK pathway may also play an important role in KIM-1 overexpression and shedding during hyperoxaluria mediated tubular injury, however, additional studies are need to support such conclusions.…”

Section: Discussionmentioning

confidence: 98%

Kidney Injury Molecule-1 Is Up-Regulated in Renal Epithelial Cells in Response to Oxalate In Vitro and in Renal Tissues in Response to Hyperoxaluria In Vivo

et al. 2012

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Oxalate is a metabolic end product excreted by the kidney. Mild increases in urinary oxalate are most commonly associated with Nephrolithiasis. Chronically high levels of urinary oxalate, as seen in patients with primary hyperoxaluria, are driving factor for recurrent renal stones, and ultimately lead to renal failure, calcification of soft tissue and premature death. In previous studies others and we have demonstrated that high levels of oxalate promote injury of renal epithelial cells. However, methods to monitor oxalate induced renal injury are limited. In the present study we evaluated changes in expression of Kidney Injury Molecule-1 (KIM-1) in response to oxalate in human renal cells (HK2 cells) in culture and in renal tissue and urine samples in hyperoxaluric animals which mimic in vitro and in vivo models of hyper-oxaluria. Results presented, herein demonstrate that oxalate exposure resulted in increased expression of KIM-1 m RNA as well as protein in HK2 cells. These effects were rapid and concentration dependent. Using in vivo models of hyperoxaluria we observed elevated expression of KIM-1 in renal tissues of hyperoxaluric rats as compared to normal controls. The increase in KIM-1 was both at protein and mRNA level, suggesting transcriptional activation of KIM-1 in response to oxalate exposure. Interestingly, in addition to increased KIM-1 expression, we observed increased levels of the ectodomain of KIM-1 in urine collected from hyperoxaluric rats. To the best of our knowledge our studies are the first direct demonstration of regulation of KIM-1 in response to oxalate exposure in renal epithelial cells in vitro and in vivo. Our results suggest that detection of KIM-1 over-expression and measurement of the ectodomain of KIM-1 in urine may hold promise as a marker to monitor oxalate nephrotoxicity in hyperoxaluria.

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Section: Discussionmentioning

confidence: 98%

Kidney Injury Molecule-1 Is Up-Regulated in Renal Epithelial Cells in Response to Oxalate In Vitro and in Renal Tissues in Response to Hyperoxaluria In Vivo

et al. 2012

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“…It is worthwhile to mention here that the previous study (10) from our laboratory has shown that the effects of oxalate and fetal bovine serum on the DNA synthesis were additive, suggesting involvement of independent signaling pathways in oxalate and fetal bovine serumstimulated DNA synthesis. These observations were further confirmed by evaluating the effects of various growth factors alone or in combination with oxalate on the re-initiation of DNA synthesis (73). The fact that oxalate induces re-initiation of the DNA synthesis without activating p42/44 MAP kinase suggests that oxalate-induced re-initiation of the DNA synthesis in renal epithelial cells follows signal transduction pathways that are distinct from serum-and growth factor-stimulated DNA synthesis.…”

Section: Discussionmentioning

confidence: 69%

Oxalate Selectively Activates p38 Mitogen-activated Protein Kinase and c-Jun N-terminal Kinase Signal Transduction Pathways in Renal Epithelial Cells

Chaturvedi¹,

Koul²,

Sekhon³

et al. 2002

Journal of Biological Chemistry

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Oxalate, a metabolic end product, is an important factor in the pathogenesis of renal stone disease. Oxalate exposure to renal epithelial cells results in re-initiation of the DNA synthesis, altered gene expression, and apoptosis, but the signaling pathways involved in these diverse effects have not been evaluated. The effects of oxalate on mitogen-and stress-activated protein kinase signaling pathways were studied in LLC-PK1 cells. Exposure to oxalate (1 mM) rapidly stimulated robust phosphorylation and activation of p38 MAPK. Oxalate exposure also induced modest activation of JNK, as monitored by phosphorylation of c-Jun. In contrast, oxalate exposure had no effect on phosphorylation and enzyme activity of p42/44 MAPK. We also show that specific inhibition of p38 MAPK by 4(4-(fluorophenyl)-2-(4-methylsulfonylphenyl)-5-(4-pyridyl)imidazole (SB203580) or by overexpression of a kinase-dead dominant negative mutant of p38 MAPK abolishes oxalate induced re-initiation of DNA synthesis in LLC-PK1 cells. The inhibition is dose-dependent and correlates with in situ activity of native p38 MAP kinase, determined as MAPK-activated protein kinase-2 activity in cell extracts. Thus, this study not only provides the first demonstration of selective activation of p38 MAPK and JNK signaling pathways by oxalate but also suggests that p38 MAPK activity is essential for the effects of oxalate on re-initiation of DNA synthesis.

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“…This unprecedented suppression of a large number of genes in renal epithelial cells suggests a program of the suppression of transcriptional activity. However, previous studies by have shown that the exposure of renal epithelial cells to oxalate results in the up-regulation of several genes [12], [15], [18], [20], [20], [22,23]. Thus, the notion of a general transcriptional repression is too simplistic of an explanation.…”

Section: Discussionmentioning

confidence: 98%

Genome Wide Analysis of Differentially Expressed Genes in HK-2 Cells, a Line of Human Kidney Epithelial Cells in Response to Oxalate

et al. 2012

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Nephrolithiasis is a multi-factorial disease which, in the majority of cases, involves the renal deposition of calcium oxalate. Oxalate is a metabolic end product excreted primarily by the kidney. Previous studies have shown that elevated levels of oxalate are detrimental to the renal epithelial cells; however, oxalate renal epithelial cell interactions are not completely understood. In this study, we utilized an unbiased approach of gene expression profiling using Affymetrix HG_U133_plus2 gene chips to understand the global gene expression changes in human renal epithelial cells [HK-2] after exposure to oxalate. We analyzed the expression of 47,000 transcripts and variants, including 38,500 well characterized human genes, in the HK2 cells after 4 hours and 24 hours of oxalate exposure. Gene expression was compared among replicates as per the Affymetrix statistical program. Gene expression among various groups was compared using various analytical tools, and differentially expressed genes were classified according to the Gene Ontology Functional Category. The results from this study show that oxalate exposure induces significant expression changes in many genes. We show for the first time that oxalate exposure induces as well as shuts off genes differentially. We found 750 up-regulated and 2276 down-regulated genes which have not been reported before. Our results also show that renal cells exposed to oxalate results in the regulation of genes that are associated with specific molecular function, biological processes, and other cellular components. In addition we have identified a set of 20 genes that is differentially regulated by oxalate irrespective of duration of exposure and may be useful in monitoring oxalate nephrotoxicity. Taken together our studies profile global gene expression changes and provide a unique insight into oxalate renal cell interactions and oxalate nephrotoxicity.

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Effects of oxalate on the re-initiation of DNA synthesis in LLC-PK1 cells do not involve p42/44 MAP kinase activation

Abstract: These findings demonstrate that oxalate does not activate the p42/44 MAP kinase pathway, and the effects of oxalate are mediated by pathways that are distinct from those of EGF, PDGF and insulin.

Cited by 18 publications

References 35 publications

Kidney Injury Molecule-1 Is Up-Regulated in Renal Epithelial Cells in Response to Oxalate In Vitro and in Renal Tissues in Response to Hyperoxaluria In Vivo

Kidney Injury Molecule-1 Is Up-Regulated in Renal Epithelial Cells in Response to Oxalate In Vitro and in Renal Tissues in Response to Hyperoxaluria In Vivo

Oxalate Selectively Activates p38 Mitogen-activated Protein Kinase and c-Jun N-terminal Kinase Signal Transduction Pathways in Renal Epithelial Cells

Genome Wide Analysis of Differentially Expressed Genes in HK-2 Cells, a Line of Human Kidney Epithelial Cells in Response to Oxalate

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