Fas and Fas-associated death domain protein regulate monocyte chemoattractant protein-1 expression by human smooth muscle cells through caspase- and calpain-dependent release of interleukin-1alpha.
We previously reported that treatment of human vascular smooth muscle cells (SMCs) with proapoptotic stimuli, including Fas ligand plus cycloheximide (FasL/Chx), or overexpression of Fas-associated death domain protein (FADD) result in increased expression of monocyte chemoattractant protein-1 (MCP-1) and other proinflammatory genes. In this study, we demonstrate that Fas/FADD-induced MCP-1 upregulation is driven by an autocrine/paracrine signaling loop in which interleukin (IL)-1alpha synthesis and release are activated through caspase- and calpain-dependent processes. Untreated SMCs contain very little IL-1alpha protein or transcript. Both were increased greatly in response to Fas/FADD activation, primarily through an autocrine/paracrine pathway in which secreted IL-1alpha stimulated additional IL-1alpha synthesis and release. Caspase 8 (Csp8) activity increased in response to FasL/Chx treatment, and Csp8 inhibitors markedly reduced IL-1alpha release and MCP-1 upregulation. In contrast, Csp8 activity was not significantly increased in response to FADD overexpression and caspase inhibitors did not effect FADD-induced MCP-1 upregulation. Both FasL/Chx treatment and FADD overexpression increased the activity of calpains. Calpain inhibitors reduced IL-1alpha release and MCP-1 upregulation in both FADD-overexpressing SMCs and FasL/Chx-treated SMCs without blocking Csp8 activity. This indicates that calpains are not required for activation of caspases and that caspase activation is not sufficient for IL-1alpha release and MCP-1 upregulation. These data suggest that calpains play a dominant role in Fas/FADD-induced IL-1alpha release and MCP-1 upregulation and that caspase activation may function to amplify the effects of calpain activation.
Schaub
Friedemann J
FJ
Department of Pathology, University of Washington, Box 357470, Seattle, Wash 98195-7470, USA.
Liles
W Conrad
WC
Ferri
Nicola
N
Sayson
Kirsten
K
Seifert
Ronald A
RA
Bowen-Pope
Daniel F
DF
D048868:Adaptor Proteins, Signal Transducing; D002154:Calpain / Q000378:metabolism / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000096:biosynthesis* / Q000235:genetics; D003513:Cycloheximide / Q000494:pharmacology; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D005786:Gene Expression Regulation; D006801:Humans; D007375:Interleukin-1 / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology / Q000276:immunology*; D015398:Signal Transduction; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018932:Chemokine CCL2; C505533:FADD protein, human; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D007375:Interleukin-1; D008562:Membrane Glycoproteins; D003513:Cycloheximide; D002154:Calpain; D020169:Caspases