TY - JOUR
T1 - Activation of endothelial nitric oxide synthase by the pro-apoptotic drug embelin
T2 - Striking discrepancy between nitric oxide-mediated cyclic GMP accumulation and l-citrulline formation
AU - Schmidt, Kurt
AU - Martens-Lobenhoffer, Jens
AU - Meinitzer, Andreas
AU - Graier, Wolfgang F.
AU - Torres, Christina M.
AU - Venema, Richard C
AU - Mayer, Bernd
N1 - Copyright:
Copyright 2010 Elsevier B.V., All rights reserved.
PY - 2010/5/15
Y1 - 2010/5/15
N2 - The benzoquinone derivative embelin is a multifunctional drug that not only induces apoptosis by inhibiting XIAP, the X chromosome-linked inhibitor of apoptosis protein, but also blocks nuclear factor-κB signaling pathways, thereby leading to down-regulation of a variety of gene products involved in tumor cell survival, proliferation, invasion, angiogenesis, and inflammation. Here, we report that embelin activates and modulates l-arginine/nitric oxide/cyclic GMP signaling in cultured endothelial cells. Embelin elicited a rapid increase of intracellular free Ca2+, leading to activation of endothelial nitric oxide synthase (eNOS) and NO-induced cGMP accumulation. While the cGMP response was comparable to that caused by other Ca2+-mobilizing agents, the stimulatory effect of embelin on l-citrulline formation (∼4-fold) was substantially lower than that observed upon activation of eNOS with the Ca2+ ionophore A23187 (∼18-fold), the receptor agonist ATP (∼16-fold) or the sarco-endoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin (∼14-fold). The apparent discrepancy between NO/cGMP and l-citrulline formation in embelin-treated cells was not due to enhanced metabolism and/or efflux of l-citrulline, increased NO bioavailability, inhibition of cGMP hydrolysis, sensitization of soluble guanylate cyclase (sGC) to NO, or enhanced formation of a sGC/eNOS complex. Our puzzling observations suggest that embelin improves coupling of endothelial NO synthesis to sGC activation through mobilization of an as yet unrecognized signaling pathway.
AB - The benzoquinone derivative embelin is a multifunctional drug that not only induces apoptosis by inhibiting XIAP, the X chromosome-linked inhibitor of apoptosis protein, but also blocks nuclear factor-κB signaling pathways, thereby leading to down-regulation of a variety of gene products involved in tumor cell survival, proliferation, invasion, angiogenesis, and inflammation. Here, we report that embelin activates and modulates l-arginine/nitric oxide/cyclic GMP signaling in cultured endothelial cells. Embelin elicited a rapid increase of intracellular free Ca2+, leading to activation of endothelial nitric oxide synthase (eNOS) and NO-induced cGMP accumulation. While the cGMP response was comparable to that caused by other Ca2+-mobilizing agents, the stimulatory effect of embelin on l-citrulline formation (∼4-fold) was substantially lower than that observed upon activation of eNOS with the Ca2+ ionophore A23187 (∼18-fold), the receptor agonist ATP (∼16-fold) or the sarco-endoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin (∼14-fold). The apparent discrepancy between NO/cGMP and l-citrulline formation in embelin-treated cells was not due to enhanced metabolism and/or efflux of l-citrulline, increased NO bioavailability, inhibition of cGMP hydrolysis, sensitization of soluble guanylate cyclase (sGC) to NO, or enhanced formation of a sGC/eNOS complex. Our puzzling observations suggest that embelin improves coupling of endothelial NO synthesis to sGC activation through mobilization of an as yet unrecognized signaling pathway.
KW - Embelin
KW - Endothelial nitric oxide synthase
KW - Nitric oxide
KW - Soluble guanylate cyclase
KW - cGMP
KW - l-Citrulline
UR - http://www.scopus.com/inward/record.url?scp=77949915404&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=77949915404&partnerID=8YFLogxK
U2 - 10.1016/j.niox.2010.02.001
DO - 10.1016/j.niox.2010.02.001
M3 - Article
C2 - 20144727
AN - SCOPUS:77949915404
SN - 1089-8603
VL - 22
SP - 281
EP - 289
JO - Nitric Oxide - Biology and Chemistry
JF - Nitric Oxide - Biology and Chemistry
IS - 4
ER -