VEGF-C promotes survival in podocytes.
Vascular endothelial growth factor (VEGF)-A is an autocrine survival factor for podocytes, which express two VEGF receptors, VEGF-R1 and VEGF-R3. As VEGF-A is not a known ligand for VEGF-R3, the aim of this investigation was to examine whether VEGF-C, a known ligand for VEGF-R3, served a function in podocyte biology and whether this was VEGF-R3 dependent. VEGF-C protein expression was localized to podocytes in contrast to VEGF-D, which was expressed in parietal epithelial cells. Intracellular calcium ([Ca2+]i) experiments demonstrated that VEGF-C induced a 0.74+/-0.09-fold reduction in [Ca2+]i compared with baseline in human conditionally immortalized podocytes (hCIPs; P<0.05, one sample t-test, n=8). Cytotoxicity experiments revealed that in hCIPs VEGF-C reduced cytotoxicity to 81.4+/-1.9% of serum-starved conditions (P<0.001, paired t-test, n=16), similar to VEGF-A (82.8+/-4.5% of serum-starved conditions, P<0.05, paired t-test). MAZ51 (a VEGF-R3 kinase inhibitor) inhibited the VEGF-C-induced reduction in cytotoxicity (106.2+/-2.1% of serum-starved conditions), whereas MAZ51 by itself had no cytotoxic effects on hCIPs. VEGF-C was also shown to induce a 0.5+/-0.13-fold reduction in levels of MAPK phosphorylation compared with VEGF-A and VEGF-A-Mab treatment (P<0.05, ANOVA, n=4), yet had no effect on Akt phosphorylation. Surprisingly, immunoprecipitation studies detected no VEGF-C-induced autophosphorylation of VEGF-R3 in hCIPs but did so in HMVECs. Moreover, SU-5416, a tyrosine kinase inhibitor, blocked the VEGF-C-induced reduction in cytotoxicity (106+/-2.8% of serum-starved conditions) at concentrations specific for VEGF-R1. Together, these results suggest for the first time that VEGF-C acts in an autocrine manner in cultured podocytes to promote survival, although the receptor or receptor complex activated has yet to be elucidated.
Foster
R R
RR
Microvascular Research Laboratories, Department of Physiology, and Academic Renal Unit, Southmead Hospital, University of Bristol, Bristol BS2 8EJ, UK.
Satchell
S C
SC
Seckley
J
J
Emmett
M S
MS
Joory
K
K
Xing
C Y
CY
Saleem
M A
MA
Mathieson
P W
PW
Bates
D O
DO
Harper
S J
SJ
D002118:Calcium / Q000032:analysis / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects* / Q000502:physiology*; D042783:Endothelial Cells / Q000737:chemistry / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D006801:Humans; D047468:Immunoprecipitation; D007211:Indoles / Q000494:pharmacology; D007678:Kidney Glomerulus / Q000737:chemistry; D020929:Mitogen-Activated Protein Kinase Kinases / Q000032:analysis / Q000502:physiology; D009281:Naphthalenes / Q000494:pharmacology; D010766:Phosphorylation; D050199:Podocytes / Q000737:chemistry / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000032:analysis / Q000502:physiology; D011758:Pyrroles / Q000494:pharmacology; D040262:Receptors, Vascular Endothelial Growth Factor / Q000032:analysis / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A / Q000032:analysis / Q000502:physiology; D042582:Vascular Endothelial Growth Factor C / Q000502:physiology*; D042643:Vascular Endothelial Growth Factor D / Q000032:analysis / Q000502:physiology
C441602:3-(4-dimethylamino-naphthalen-1-ylmethylene)-1,3-dihydro-indol-2-one; D007211:Indoles; D009281:Naphthalenes; D047428:Protein Kinase Inhibitors; D011758:Pyrroles; D042461:Vascular Endothelial Growth Factor A; D042582:Vascular Endothelial Growth Factor C; D042643:Vascular Endothelial Growth Factor D; C116890:Semaxinib; D040262:Receptors, Vascular Endothelial Growth Factor; D051057:Proto-Oncogene Proteins c-akt; D020929:Mitogen-Activated Protein Kinase Kinases; D002118:Calcium