Parathyroid Hormone-Related Protein Is a Mitogenic and a Survival Factor of Mesangial Cells from Male Mice: Role of Intracrine and Paracrine Pathways

Abstract

Glomerulonephritis is characterized by the proliferation and apoptosis of mesangial cells (MC). The parathyroid-hormone related protein (PTHrP) is a locally active cytokine that affects these phenomena in many cell types, through either paracrine or intracrine pathways. The aim of this study was to evaluate the effect of both PTHrP pathways on MC proliferation and apoptosis. In vitro studies were based on MC from male transgenic mice allowing PTHrP-gene excision by a CreLoxP system. MC were also transfected with different PTHrP constructs: wild type PTHrP, PTHrP devoid of its signal peptide, or of its nuclear localization sequence. The results showed that PTHrP deletion in MC reduced their proliferation even in the presence of serum and increased their apoptosis when serum-deprived. PTH1R activation by PTHrP(1-36) or PTH(1-34) had no effect on proliferation but improved MC survival. Transfection of MC with PTHrP devoid of its signal peptide significantly increased their proliferation and minimally reduced their apoptosis. Overexpression of PTHrP devoid of its nuclear localization sequence protected cells from apoptosis without changing their proliferation. Wild type PTHrP transfection conferred both mitogenic and survival effects, which seem independent of midregion and C-terminal PTHrP fragments. PTHrP-induced MC proliferation was associated with p27(Kip1) down-regulation and c-Myc/E2F1 up-regulation. PTHrP increased MC survival through the activation of cAMP/protein kinase A and PI3-K/Akt pathways. These results reveal that PTHrP is a cytokine of multiple roles in MC, acting as a mitogenic factor only through an intracrine pathway, and reducing apoptosis mainly through the paracrine pathway. Thus, PTHrP appears as a probable actor in MC injuries.

Molecular Mechanisms Associated With PTHrP‐Induced Proliferation of Colon Cancer Cells

“…Finally, we showed that ERK1/2, p38 MAPK, and PI3‐kinase inhibitors completely abolished the effect on PTHrP‐induced colonic cell proliferation. Several evidences demonstrate that these signaling pathways are involved in the anti‐apoptotic effects exerted by PTHrP through a paracrine pathway [Hochane et al, ; Lezcano et al, ]. Herein we prove the first evidence, to our knowledge, that ERK1/2, p38 MAPK, and PI3‐kinase are also involved in the mitogenic action of exogenous PTHrP (1–34) fragment on Caco‐2 cells.…”

Functional Roles of the Nuclear Localization Signal of Parathyroid Hormone-Related Protein (PTHrP) in Osteoblastic Cells

“…Also of note, antiapoptotic effects have been reported in the same osteoblastic cell type used herein, but stably transfected with a PTH1R plasmid construct (35). In addition, other studies have reported that cell protection by PTHrP may be conferred through the autocrine/ paracrine pathway in renal cells and other osteoblastic cell types (39,41,46). Consistent with previous findings in osteoblasts and other cell types (47,48), we here observed PTH1R protein down-regulation in PTHrP-overexpressing MC3T3-E1 cells, related to receptor internalization.…”

Suppressor of Cytokine Signaling-1/STAT1 Regulates Renal Inflammation in Mesangial Proliferative Glomerulonephritis Models

“…The mice and rats were sacrificed immediately after the Trimeresurus flavoviridis or OX-7 mAb injection at 3, 5, 7, or 14 days after GN induction. At each time point, following euthanasia, renal tissue was obtained, and glomeruli were isolated by differential sieving (22, 23). The cortex was subsequently cut off with a fine pair of surgical scissors and placed in a plastic Petri dish that contained PBS buffer.…”

“…The cortex was subsequently cut off with a fine pair of surgical scissors and placed in a plastic Petri dish that contained PBS buffer. The cortex was forced through sequential sieving (150, 106, and 75 μm for the rats; 125, 71, and 53 μm for the mice at room temperature (23, 24). The glomeruli were collected on the sieve (75 μm for the rats, 53 μm for the mice) using cold PBS buffer, centrifuged at 1,000 rpm for 5 min in a clinical centrifuge, resuspended in 5 ml of cold PBS buffer, and assessed for purity (more than 95% glomeruli, Figure S1) under the microscope.…”