Endothelial cells protect against lipopolysaccharide-induced caspase-3-mediated pericyte apoptosis in a coculture system.
BACKGROUND
Cells that comprise the pulmonary capillary walls, the pericytes and endothelial cells, may undergo apoptosis in inflammatory states. This study examined the effects of lipopolysaccharide (LPS) on apoptosis in pericytes and endothelial cells, both individually and grown together in a coculture system.


METHODS
Pericytes and endothelial cells were isolated and cultured separately and in coculture as previously described. The cells were subsequently exposed to LPS for 12, 24, 48, and 72 hours. The cellular contents were then examined by Western blot analysis for products of apoptosis. TUNEL staining was also performed to analyze for apoptosis.


RESULTS
Pericytes alone exposed to LPS showed increased levels of p11 and p17, which are activated fragments of capase-3, a cysteine effector protease involved in cleaving cytoskeletal and nuclear proteins to induce apoptosis. When grown in coculture with endothelial cells and exposed to LPS in coculture but harvested independently, pericytes showed decreased levels of p11 and p17 and increased levels of Bcl-xL, an antiapoptotic protein that protects the integrity of mitochondria, and prevents cytochrome c release and subsequent caspase-9 activation.


CONCLUSIONS
In response to LPS, pericytes undergo apoptosis involving the caspase-3 pathway. Endothelial cells may decrease this effect through the expression of a soluble mediator.
Department of Surgery, Wayne State University School of Medicine, Detroit, MI, USA.
Jason M
JM
Blocksom
Jing
J
Huang
Sid
S
Kerkar
Carl
C
Hinshaw
Mallory
M
Williams
James G
JG
Tyburski
Arthur M
AM
Carlin
Christopher P
CP
Steffes
Robert F
RF
Wilson
D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000502:physiology*; D018920:Coculture Techniques; D019610:Cytoprotection; D042783:Endothelial Cells / Q000502:physiology*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D020286:Pericytes / Q000166:cytology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D019311:Staurosporine / Q000494:pharmacology; D051020:bcl-X Protein
C494813:Bcl2l1 protein, rat; D008070:Lipopolysaccharides; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D019311:Staurosporine