The mechanisms contributing to
sepsis vascular dysfunction are not well known. We tested the hypothesis that
peroxynitrite scavenging ameliorates
sepsis-induced macrovascular and microvascular dysfunction. Male Sprague-Dawley rats were killed 48 h after cecal
ligation (n = 15) and
puncture or
sham procedure (n = 15). Their aortas and mesenteric vessels were mounted in organ
baths for isometric tension recording. We studied contraction in resting vessels (
norepinephrine 1 nM-10 μM and 10 nM-10 μM) and endothelium-dependent relaxation (
acetylcholine, 10 nM-10 μM and 1 nM-10 μM) for aortas and microvessels, respectively.
Vascular rings were preincubated for 30 min with the
superoxide scavenger
Cu-Zn-superoxide dismutase (SOD) (100 U/mL), the SOD mimetic and
peroxynitrite scavenger
tempol (10 M), the
NO synthase inhibitor N-nitro-
l-arginine methyl ester (10 M), or the
peroxynitrite decomposition catalyst
manganese tetrakis(4-N-methylpyridyl)porphyrin (
MnTMPyP) (10 M). Fluorescence to
3-nitrotyrosine, oxidized
dihydroethidium, and NOS2 was assessed in vascular tissue. Vascular NOS2,
endothelial nitric oxide synthase (NOS1), NADPH-oxidase-1 (NOX-1), and SOD expression was analyzed by reverse transcription-polymerase chain reaction.
Sepsis induced (i) in macrovessels, impairment of
norepinephrine-induced contractions; (ii) in microvessels, impairment in
norepinephrine-induced contractions and
acetylcholine-induced relaxations; (iii) aortic and microvascular tissue increased reactivity to
3-nitrotyrosine, oxidized
dihydroethidium, NOS2, and increased expression of NOS2, as well as increased expression of NOX-1 in microvascular tissue. Contractile responses in aortic and microvascular rings improved by ex vivo treatment with
MnTMPyP and
tempol, whereas vascular relaxation in microvessels improved only with
MnTMPyP.
Peroxynitrite scavenging protects from vascular dysfunction in
sepsis.