title: Insulin protects against damage to pulmonary endothelial tight junctions after thermal injury: relationship with zonula occludens-1, F-actin, and AKT activity.
abstract: Intensive insulin therapy during critical illness protects the endothelium and thereby prevents organ failure. This study tested the hypothesis that insulin directly affects the attenuation of burn injury-induced damage to pulmonary endothelial tight junction and investigated the underlying mechanisms. Sprague Dawley rats with severe burn injury were randomized to treatment with insulin dissolved in normal saline (maintenance of blood glucose at a level between 5.0 and 7.0 mmol/L) or normal saline alone (in vivo treatment). Pulmonary damage was evaluated. Rat pulmonary microvascular endothelial cells were treated with 20% burn serum or 20% burn serum + insulin (in vitro treatment). Selected cultures were pretreated with phosphatidylinositol 3-kinase/protein kinase B (AKT) inhibitor (LY294002). Permeability was assessed by migration of bovine serum albumin across cell monolayers. Cells were stained with rhodamine phalloidin and were examined. Cell extracts were obtained to assess zonula occludens-1, occludin, and phosphorylated AKT levels by immunoblotting. Treatment with insulin attenuated the pulmonary edema, hemorrhage, and inflammatory cell infiltration of rats with severe burn injury. Burn serum significantly enhanced monolayer permeability to albumin, whereas treatment with insulin (10(-7 ) mol/L) limited this effect. Meanwhile, insulin (10(-7 ) mol/L) reduced burn serum-induced F-actin stress fiber formation and decreased zonula occludens-1 expression. LY294002 decreased cytoplasmic AKT phosphorylation and inhibited the protection effects of insulin. Through the phosphatidylinositol 3-kinase/AKT pathway, insulin independent of glucose toxicity can attenuate increased pulmonary endothelial permeability induced by burn injury. The effect is attributed to the attenuation of the architectural disruption of protein components of the endothelial tight junction. This result is useful in inhibiting multiple organ failure after burn injury.
authors.affiliation: Department of Burns and Cutaneous Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China.
authors.forename: Jun-Tao
authors.initials: JT
authors.lastname: Han
authors.forename: Wan-Fu
authors.initials: WF
authors.lastname: Zhang
authors.forename: Yun-Chuan
authors.initials: YC
authors.lastname: Wang
authors.forename: Wei-Xia
authors.initials: WX
authors.lastname: Cai
authors.forename: Gen-Fa
authors.initials: GF
authors.lastname: Lv
authors.forename: Da-Hai
authors.initials: DH
authors.lastname: Hu
mesh_terms: D000199:Actins / Q000096:biosynthesis / Q000378:metabolism*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002056:Burns / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology*; D042783:Endothelial Cells / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects / Q000473:pathology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006470:Hemorrhage / Q000517:prevention & control; D007328:Insulin / Q000494:pharmacology*; D009025:Morpholines / Q000494:pharmacology*; D009102:Multiple Organ Failure / Q000517:prevention & control; D051058:Oncogene Protein v-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D011654:Pulmonary Edema / Q000517:prevention & control; D051381:Rats; D017207:Rats, Sprague-Dawley; D020545:Respiratory Mucosa / Q000187:drug effects / Q000473:pathology*; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D014945:Wound Healing; D062826:Zonula Occludens-1 Protein / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: D000199:Actins; D001786:Blood Glucose; D002867:Chromones; D004791:Enzyme Inhibitors; D007328:Insulin; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D062826:Zonula Occludens-1 Protein; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D051058:Oncogene Protein v-akt