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TNFα signaling regulates cystic epithelial cell proliferation through Akt/mTOR and ERK/MAPK/Cdk2 mediated Id2 signaling.

Zhou JX, Fan LX, Li X, Calvet JP, Li X - PLoS ONE (2015)

Bottom Line: However, the cross-talk between TNFα and PKD associated signaling pathways remains elusive.In this study, we found that stimulation of renal epithelial cells with TNFα or RANKL (receptor activator of NF-κB ligand), a member of the TNFα cytokine family, activated either the PI3K pathway, leading to AKT and mTOR mediated the increase of Id2 protein, or MAPK and Cdk2 to induce Id2 nuclear translocation.The effects of TNFα/RANKL on increasing Id2 protein and its nuclear translocation caused significantly decreased mRNA and protein levels of the Cdk inhibitor p21, allowing increased cell proliferation.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, University of Kansas Medical Center, Kansas City, KS 66160, United States of America; Kidney Institute, University of Kansas Medical Center, Kansas City, KS 66160, United States of America.

ABSTRACT
Tumor necrosis factor alpha (TNFα) is present in cyst fluid and promotes cyst growth in autosomal dominant polycystic kidney disease (ADPKD). However, the cross-talk between TNFα and PKD associated signaling pathways remains elusive. In this study, we found that stimulation of renal epithelial cells with TNFα or RANKL (receptor activator of NF-κB ligand), a member of the TNFα cytokine family, activated either the PI3K pathway, leading to AKT and mTOR mediated the increase of Id2 protein, or MAPK and Cdk2 to induce Id2 nuclear translocation. The effects of TNFα/RANKL on increasing Id2 protein and its nuclear translocation caused significantly decreased mRNA and protein levels of the Cdk inhibitor p21, allowing increased cell proliferation. TNFα levels increase in cystic kidneys in response to macrophage infiltration and thus might contribute to cyst growth and enlargement during the progression of disease. As such, this study elucidates a novel mechanism for TNFα signaling in regulating cystic renal epithelial cell proliferation in ADPKD.

No MeSH data available.


Related in: MedlinePlus

RANKL stimulation increases the expression of TNFα in renal epithelial cells.(A) The mRNA levels of TNFα in Pkd1 wild type and Pkd1  MEK cells treated with RANKL, SN50, RANKL plus SN50, Bay-11-7085, Bay-11-7085 plus RANKL and vehicle control, respectively, for 6 hours were analyzed by qRT-PCR. The expression levels of TNFα were normalized to the expression levels of actin. n = 3, ANOVA, p < 0.01. (B and C) Western blot analysis of the expression of I-κBα from whole cell lysates of Pkd1 wild-type and Pkd1  MEK cells treated with RANKL (100 ng/ml) at indicated time point (B) and at indicated concentration for 45 mins (C). The numbers at the bottom indicate the relative intensities of the bands, which are normalized to Actin.
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pone.0131043.g001: RANKL stimulation increases the expression of TNFα in renal epithelial cells.(A) The mRNA levels of TNFα in Pkd1 wild type and Pkd1 MEK cells treated with RANKL, SN50, RANKL plus SN50, Bay-11-7085, Bay-11-7085 plus RANKL and vehicle control, respectively, for 6 hours were analyzed by qRT-PCR. The expression levels of TNFα were normalized to the expression levels of actin. n = 3, ANOVA, p < 0.01. (B and C) Western blot analysis of the expression of I-κBα from whole cell lysates of Pkd1 wild-type and Pkd1 MEK cells treated with RANKL (100 ng/ml) at indicated time point (B) and at indicated concentration for 45 mins (C). The numbers at the bottom indicate the relative intensities of the bands, which are normalized to Actin.

Mentions: Our previous studies showed that TNFα mRNA was increased in Pkd1 mutant renal epithelial cells, and that TNFα mRNA induces its own transcription through activating canonical NF-κB signaling [4]. RANKL, a TNFα family molecule, can also activate NF-κB signaling and transcriptionally regulate TNFα in osteoclasts and cancer cells [23, 24]. Therefore, we examined whether RANKL also regulated TNFα transcription in renal epithelial cells. We found that TNFα mRNA was increased in response to RANKL stimulation in Pkd1 wild type and mutant mouse embryonic kidney (MEK) cells as analyzed by quantitative reverse transcription PCR (qRT-PCR) (Fig 1A). RANKL treatment decreased the expression of IκBα in a time-dependent (Fig 1B) and dose-dependent manner (Fig 1C), suggesting the activation of NF-κB signaling. We further found that two NF-κB inhibitors, SN50 and Bay-11-7085 [25], blocked the upregulation of TNFα mRNA induced by RANKL (Fig 1A), suggesting that RANKL induced TNFα upregulation is mediated by NF-κB signaling.


TNFα signaling regulates cystic epithelial cell proliferation through Akt/mTOR and ERK/MAPK/Cdk2 mediated Id2 signaling.

Zhou JX, Fan LX, Li X, Calvet JP, Li X - PLoS ONE (2015)

RANKL stimulation increases the expression of TNFα in renal epithelial cells.(A) The mRNA levels of TNFα in Pkd1 wild type and Pkd1  MEK cells treated with RANKL, SN50, RANKL plus SN50, Bay-11-7085, Bay-11-7085 plus RANKL and vehicle control, respectively, for 6 hours were analyzed by qRT-PCR. The expression levels of TNFα were normalized to the expression levels of actin. n = 3, ANOVA, p < 0.01. (B and C) Western blot analysis of the expression of I-κBα from whole cell lysates of Pkd1 wild-type and Pkd1  MEK cells treated with RANKL (100 ng/ml) at indicated time point (B) and at indicated concentration for 45 mins (C). The numbers at the bottom indicate the relative intensities of the bands, which are normalized to Actin.
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pone.0131043.g001: RANKL stimulation increases the expression of TNFα in renal epithelial cells.(A) The mRNA levels of TNFα in Pkd1 wild type and Pkd1 MEK cells treated with RANKL, SN50, RANKL plus SN50, Bay-11-7085, Bay-11-7085 plus RANKL and vehicle control, respectively, for 6 hours were analyzed by qRT-PCR. The expression levels of TNFα were normalized to the expression levels of actin. n = 3, ANOVA, p < 0.01. (B and C) Western blot analysis of the expression of I-κBα from whole cell lysates of Pkd1 wild-type and Pkd1 MEK cells treated with RANKL (100 ng/ml) at indicated time point (B) and at indicated concentration for 45 mins (C). The numbers at the bottom indicate the relative intensities of the bands, which are normalized to Actin.
Mentions: Our previous studies showed that TNFα mRNA was increased in Pkd1 mutant renal epithelial cells, and that TNFα mRNA induces its own transcription through activating canonical NF-κB signaling [4]. RANKL, a TNFα family molecule, can also activate NF-κB signaling and transcriptionally regulate TNFα in osteoclasts and cancer cells [23, 24]. Therefore, we examined whether RANKL also regulated TNFα transcription in renal epithelial cells. We found that TNFα mRNA was increased in response to RANKL stimulation in Pkd1 wild type and mutant mouse embryonic kidney (MEK) cells as analyzed by quantitative reverse transcription PCR (qRT-PCR) (Fig 1A). RANKL treatment decreased the expression of IκBα in a time-dependent (Fig 1B) and dose-dependent manner (Fig 1C), suggesting the activation of NF-κB signaling. We further found that two NF-κB inhibitors, SN50 and Bay-11-7085 [25], blocked the upregulation of TNFα mRNA induced by RANKL (Fig 1A), suggesting that RANKL induced TNFα upregulation is mediated by NF-κB signaling.

Bottom Line: However, the cross-talk between TNFα and PKD associated signaling pathways remains elusive.In this study, we found that stimulation of renal epithelial cells with TNFα or RANKL (receptor activator of NF-κB ligand), a member of the TNFα cytokine family, activated either the PI3K pathway, leading to AKT and mTOR mediated the increase of Id2 protein, or MAPK and Cdk2 to induce Id2 nuclear translocation.The effects of TNFα/RANKL on increasing Id2 protein and its nuclear translocation caused significantly decreased mRNA and protein levels of the Cdk inhibitor p21, allowing increased cell proliferation.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, University of Kansas Medical Center, Kansas City, KS 66160, United States of America; Kidney Institute, University of Kansas Medical Center, Kansas City, KS 66160, United States of America.

ABSTRACT
Tumor necrosis factor alpha (TNFα) is present in cyst fluid and promotes cyst growth in autosomal dominant polycystic kidney disease (ADPKD). However, the cross-talk between TNFα and PKD associated signaling pathways remains elusive. In this study, we found that stimulation of renal epithelial cells with TNFα or RANKL (receptor activator of NF-κB ligand), a member of the TNFα cytokine family, activated either the PI3K pathway, leading to AKT and mTOR mediated the increase of Id2 protein, or MAPK and Cdk2 to induce Id2 nuclear translocation. The effects of TNFα/RANKL on increasing Id2 protein and its nuclear translocation caused significantly decreased mRNA and protein levels of the Cdk inhibitor p21, allowing increased cell proliferation. TNFα levels increase in cystic kidneys in response to macrophage infiltration and thus might contribute to cyst growth and enlargement during the progression of disease. As such, this study elucidates a novel mechanism for TNFα signaling in regulating cystic renal epithelial cell proliferation in ADPKD.

No MeSH data available.


Related in: MedlinePlus