Insulin prevents oxidant-induced endothelial cell barrier dysfunction via nitric oxide-dependent pathway.
BACKGROUND
The rigorous maintenance of normoglycemia by the administration of insulin is beneficial to critically ill patients. Because insulin induces endothelial nitric oxide (NO) release, and the constitutive release of NO maintains normal microvascular permeability, the authors postulated that insulin would prevent peroxide (H(2)O(2))-induced endothelial barrier dysfunction, an effect dependent on endothelial NO synthase (eNOS) activity.


METHODS
Murine lung microvascular endothelial cells (LMEC) grown to confluence on 8 micro pore polyethylene filters were exposed to media (control), H(2)O(2) (20 to 500 micromol/L), insulin (1 to 1,000 nmol/L) or insulin (100 nmol/L) + H(2)O(2) (10(-4)mol/L). Endothelial monolayer permeability was quantitated by measuring the transendothelial electrical resistance at 15-minute intervals for 120 minutes. Other cells were exposed to H(2)O(2) and insulin after pretreatment with a NO scavenger (PTIO), an eNOS inhibitor (L-NIO), or a phosphoinositol-3-kinase inhibitor (LY-294002).


RESULTS
H(2)O(2) caused a concentration- and time-dependent reduction in electrical resistance consistent with an increase in monolayer permeability. This effect was prevented by insulin. Inhibiting NO release (L-NIO, LY-294002) or scavenging NO (PTIO) abolished this protective effect.


CONCLUSIONS
These data suggest that insulin may modulate endothelial barrier function during oxidant stress by inducing the release of NO.
Rath
Siddhartha
S
Department of Surgery, LSU Health Sciences Center in Shreveport, 1501 Kings Highway, Shreveport, LA 71130, USA.
Kalogeris
Theodore
T
Mai
Nicholas
N
Zibari
Gazi
G
Alexander
J Steven
JS
Lefer
David
D
Turnage
Richard H
RH
D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D003470:Culture Media; D003497:Cyclic N-Oxides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D017097:Electric Impedance; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism* / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000008:administration & dosage / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D008833:Microcirculation / Q000187:drug effects; D009025:Morpholines / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009952:Ornithine / Q000031:analogs & derivatives / Q000494:pharmacology; D009994:Osmolar Concentration; D016877:Oxidants / Q000008:administration & dosage / Q000494:pharmacology*; D011817:Rabbits; D013997:Time Factors
D002867:Chromones; D003470:Culture Media; D003497:Cyclic N-Oxides; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D007093:Imidazoles; D007328:Insulin; D009025:Morpholines; D016877:Oxidants; C079391:2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; D009569:Nitric Oxide; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C065027:N(G)-iminoethylornithine; D006861:Hydrogen Peroxide; D009952:Ornithine; D019001:Nitric Oxide Synthase; D005947:Glucose