Neuronal nitric oxide synthase and its interaction with soluble guanylate cyclase is a key factor for the vascular dysfunction of experimental sepsis.
OBJECTIVE
Vascular dysfunction plays a central role in sepsis, and it is characterized by hypotension and hyporesponsiveness to vasoconstrictors. Nitric oxide is regarded as a central element of sepsis vascular dysfunction. The high amounts of nitric oxide produced during sepsis are mainly derived from the inducible isoform of nitric oxide synthase 2. We have previously shown that nitric oxide synthase 2 levels decrease in later stages of sepsis, whereas levels and activity of soluble guanylate cyclase increase. Therefore, we studied the putative role of other relevant nitric oxide sources, namely, the neuronal (nitric oxide synthase 1) isoform, in sepsis and its relationship with soluble guanylate cyclase. We also studied the consequences of nitric oxide synthase 1 blockade in the hyporesponsiveness to vasoconstrictors.


METHODS
Randomized controlled prospective experimental study.


METHODS
Academic research laboratory.


METHODS
Female Wistar rats submitted to cecal ligation and puncture method.


METHODS
1) Six, 12, and 24 hours after cecal ligation and puncture, vascular reactivity to phenylephrine (3 and 30 nmol/kg) before and after 7-nitroindazole (45 μmol/kg, s.c.) or aminoguanidine (30 μmol/kg, s.c.) administration was evaluated. 2) Protein levels and interaction between nitric oxide synthase 1 and soluble guanylate cyclase were determined. 3) Six, 12, and 24 hours after cecal ligation and puncture, thoracic aorta segments were stimulated with phenylephrine in the presence or absence of 7-nitroindazole and cyclic guanosine monophosphate accumulation was determined. 4) After 24 hours of cecal ligation and puncture, norepinephrine was infused (10 μg/kg/min) in the presence or absence of 7-nitroindazole or S-methyl-L-thiocitrulline (1 μmol/kg, IV) and mean arterial pressure was registered.


RESULTS
1) Both nitric oxide synthase 1 and soluble guanylate cyclase are expressed in higher levels in vascular tissues during sepsis; 2) both proteins physically interact and nitric oxide synthase 1 blockade inhibits cyclic guanosine monophosphate production; 3) pharmacological blockade of nitric oxide synthase 1 using 7-nitroindazole or S-methyl-L-thiocitrulline reverts the hyporesponsiveness to phenylephrine and increases the vasoconstrictor effect of norepinephrine and phenylephrine.


CONCLUSIONS
Sepsis induces increased expression and physical association of nitric oxide synthase 1/soluble guanylate cyclase and a higher production of cyclic guanosine monophosphate that together may help explain sepsis-induced vascular dysfunction. In addition, selective inhibition of nitric oxide synthase 1 restores the responsiveness to vasoconstrictors. Therefore, inhibition of nitric oxide synthase 1 (and possibly soluble guanylate cyclase) may represent a valuable alternative to restore the effectiveness of vasopressor agents during late sepsis.
1Department of Pharmacology, Biological Sciences Center, Universidade Federal de Santa Catarina, Santa Catarina, Brazil. 2Laboratory of Pharmacology, Area of Biological and Health Science, Universidade do Oeste de Santa Catarina, Santa Catarina, Brazil. 3Department of Cell Biology, Embryology and Genetics, Biological Sciences Center, Universidade Federal de Santa Catarina, Santa Catarina, Brazil.
Geisson M
GM
Nardi
Karin
K
Scheschowitsch
Dib
D
Ammar
Simone Kobe
SK
de Oliveira
Thais B
TB
Arruda
Jamil
J
Assreuy
D000818:Animals; D001011:Aorta / Q000378:metabolism; D062186:Arterial Pressure; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006162:Guanylate Cyclase / Q000378:metabolism*; D007022:Hypotension / Q000209:etiology*; D009569:Nitric Oxide / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology*; D010656:Phenylephrine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D018805:Sepsis / Q000150:complications* / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I; D017869:Cyclic GMP-Dependent Protein Kinases; D006162:Guanylate Cyclase; D009638:Norepinephrine