Parathyroid hormone‐related protein is a hypertrophy factor for human mesangial cells: Implications for diabetic nephropathy

Abstract

Hypertrophy of human mesangial cells (HMC) is among the earliest characteristics in patients with diabetic nephropathy (DN). Recently, we observed the upregulation of parathyroid hormone (PTH)-related protein (PTHrP) in experimental DN, associated with renal hypertrophy. Herein, we first examined whether PTHrP was overexpressed in human DN, and next assessed the putative role of this protein on high glucose (HG)-induced HMC hypertrophy. As previously found in mice, kidneys from diabetic patients showed an increased tubular and glomerular immunostaining for PTHrP. In HMC, HG medium increased PTHrP protein expression associated with the development of hypertrophy as assessed by cell protein content. This effect was also induced by PTHrP(1-36). HG and PTHrP(1-36)-induced hypertrophy were associated with an increase in cyclin D1 and p27Kip1 protein expression, a decreased cyclin E expression, and the prevention of cyclin E/cdk2 complex activation. Both PTHrP neutralizing antiserum (α-PTHrP) and the PTH/PTHrP receptor antagonist (JB4250) were able to abolish HG induction of hypertrophy, the aforementioned changes in cell cycle proteins, and also TGF-β1 up-regulation. Moreover, the capability of both HG and PTHrP(1-36) to induce HMC hypertrophy was abolished by α-TGFβ1. These data show for the first time that PTHrP is upregulated in the kidney of patients with DN. Our findings also demonstrate that PTHrP acts as an important mediator of HG-induced HMC hypertrophy by modulating cell cycle regulatory proteins and TGF-β1.

Bisphenol‐A Induces Podocytopathy With Proteinuria in Mice

“…Equal numbers of cells were lysed in RIPA buffer (0.1% SDS, 0.5% sodium deoxycholate, 1.0% Nonidet P‐40, in PBS) and the total protein content was determined by the Bradford's method (Pierce, Rockford, IL), using BSA as standard. Total protein was expressed as percentage of hypertrophy index (micrograms of protein per 10 4 cells) as previously reported (Romero et al, ; Ortega et al, ). To determine [H 3 ]‐leucine incorporation, podocytes were pulsed with 2 μCi/mL [H 3 ] leucine, washed with PBS, solubilized with 0.1% sodium dodecyl sulfate (SDS) and transferred into a tube containing 10% bovine serum albumin (BSA).…”

Parathyroid Hormone–Related Protein Contributes to Early Healing of Habu Snake Venom–Induced Glomerulonephritis in Mice

“…There were not enough proteins in the isolated glomeruli to ascertain PTHrP overexpression by Western blot analysis. We and others previously documented that PTHrP can be expressed in activated mesangial cells in vivo and mesangial cells in culture, 11,15,30 as well as in podocytes 31 and endothelial cells. 32 Infiltrating macrophages and T lymphocytes in HSV-damaged glomeruli may be another source of PTHrP, according to previous reports.…”

“…A late (day 7) and moderate increase in TGF-b1 mRNA also appeared insensitive to the treatment of mice with PTHrP-neutralizing antibody ( Figure 3B). (24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) antibody (C13 antiserum) was used for PTHrP immunostaining (green), and a monoclonal mouse anti-human asmooth muscle actin (a-SMA) antibody was used for a-SMA detection (red). Nuclei (blue) were stained by bisbenzimide H33342.…”

Dual roles of parathyroid hormone related protein in TGF-β1 signaling and fibronectin up-regulation in mesangial cells

“…Little is known about the cross-talk between PTHrP and TGF-β1 in the kidney. Previous studies showed that continuous expression of or incubation with PTHrP induced TGF-β up-regulation in MCs and podocytes [ 31 , 32 ]. The present study for the first time demonstrated the dual roles of PTHrP on TGF-β1 signaling.…”

“…It has been reported that prolonged exposure of cultured human MCs to PTHrP in the absence of exogenous growth factors induces a proliferative effect (24 h) followed by hypertrophy at 72 h [ 31 , 33 , 34 ], which is mediated by TGF-β1 [ 31 ]. The biological responses elicited by short PTHrP treatment are as yet unclear.…”