Apoptosis induction by oxidized glycated LDL in human retinal capillary pericytes is independent of activation of MAPK signaling pathways

Mol Vis. 2009;15:135-45. Epub 2009 Jan 19.

Abstract

Background: Pericyte loss is a cardinal feature of early diabetic retinopathy. We previously reported that highly oxidized-glycated low density lipoprotein (HOG-LDL) induces pericyte apoptosis in vitro. In this study, we investigated the role of the mitogen-activated protein kinase (MAPK) signaling pathways in HOG-LDL-induced apoptosis in human pericytes.

Methods: Human retinal capillary pericytes (HRCP) were exposed to native LDL (N-LDL) and HOG-LDL, and apoptosis was measured using flow cytometry. Time- and dose-dependent responses of extracellular signal-regulated kinase (ERK), p38, and Jun N-terminal kinase (JNK) following exposure to N-LDL or HOG-LDL were determined using western blotting. U0126 (ERK inhibitor), SB203580 (p38 inhibitor), and SP600125 (JNK inhibitor) were used to determine the role of MAPK signaling in HOG-LDL-induced apoptosis.

Results: HOG-LDL induced apoptosis in HRCP in a dose-dependent manner at concentrations from 5 to 50 mg/l, with a constant effect from 50 to 200 mg/l. When compared to serum-free medium (SFM), this effect of HOG-LDL was found to be significant at all doses above 10 mg/l. In contrast, N-LDL at 200 mg/l did not induce apoptosis compared with SFM. Exposure to N-LDL versus HOG-LDL induced similar phosphorylation of ERK, p38, and JNK, peaking at 5 min, with similar dose-dependent responses up to 25 mg/l that were constant from 25 to 100 mg/l. Blocking of the ERK, p38, and JNK pathways did not inhibit pericyte apoptosis induced by HOG-LDL.

Conclusions: Our data suggest that apoptosis induced by HOG-LDL in HRCP is independent of the activation of MAPK signaling pathways.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anthracenes / pharmacology
  • Apoptosis / drug effects*
  • Butadienes / pharmacology
  • Capillaries / cytology
  • Capillaries / drug effects
  • Capillaries / enzymology
  • Extracellular Signal-Regulated MAP Kinases / antagonists & inhibitors
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Humans
  • Imidazoles / pharmacology
  • JNK Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • Lipoproteins, LDL / pharmacology*
  • MAP Kinase Signaling System / drug effects
  • Nitriles / pharmacology
  • Pericytes / cytology*
  • Pericytes / drug effects*
  • Pericytes / enzymology
  • Phosphorylation
  • Protein Kinase Inhibitors / pharmacology
  • Pyridines / pharmacology
  • Retinal Vessels / cytology*
  • Time Factors
  • p38 Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • Anthracenes
  • Butadienes
  • Imidazoles
  • Lipoproteins, LDL
  • Nitriles
  • Protein Kinase Inhibitors
  • Pyridines
  • U 0126
  • glycosylated lipoproteins, LDL
  • oxidized low density lipoprotein
  • pyrazolanthrone
  • Extracellular Signal-Regulated MAP Kinases
  • JNK Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases
  • SB 203580