The role of nitric oxide and related synthase in thermal injury was investigated by using models of experimental burn to evaluate severity from the aspect of vascular permeability. Thermal injuries were produced in the murine right ear by pinching with a pair of preheated tweezers. Immediately thereafter, Evans blue dye was intravenously administered, and the mice injured with burns were sacrificed at various times. The burned ears were collected and hydrolyzed, and the level of extracted dye was measured as an indicator of inflammation. Vascular hyperpermeability was suppressed by the administration of nitric oxide synthase inhibitors. LNAME not only suppressed vascular hyperpermeability in thermal injuries in a dose-dependent manner but was also effective with either prophylactic or therapeutic administration. Although aminoguanidine also suppressed the inflammatory response, it had no effect on the early inflammatory phase. Nitric oxide synthase is well known to have two types of isozymes. Aminoguanidine, an inhibitor specific to inducible nitric oxide synthase, suppressed the late phase 6 h after injury, suggesting that inducible nitric oxide synthase is involved in inflammatory responses of thermal injuries. These results also demonstrated that inducible nitric oxide synthase-like protein stained the burned region immunohistochemically. Therefore, both types of enzymes mediating nitric oxide affect inflammatory responses, i.e., vascular hyperpermeability, and their regulation may lead to the development of new therapy for thermal injuries.
"Endothelial nitric oxide synthase (eNOS) is a constitutive enzyme of endothelial cells found in the choroid plexus and brain parenchyma. Elevated levels of nitric oxide (NO) increase the vascular permeability of endothelial cells [13, 14]. Recent studies have demonstrated that NO can influence vascular permeability by regulating endothelial cell shape and intercellular junction formation [15, 16]. "
[Show abstract][Hide abstract] ABSTRACT: In this study, expressions of aquaporin (AQP) 1, AQP4, endothelial nitric oxide synthase (eNOS), and vascular endothelial growth factor in blood-cerebrospinal fluid (CSF) barrier and blood-brain barrier (BBB) are examined in rat choroid plexus and peri-infarcted hippocampal formation (HF) following systemic hyponatremia (SH) and permanent middle cerebral artery occlusion (pMCAO). These events are thought to cause the development of hydrocephalic and vasogenic edemas. The importance of CSF overproduction and intact blood-CSF barrier during hydrocephalic edema formation is demonstrated by the high expression of AQP1 (329.86±10.2%, n=4 , P<0.01) and trapped plasma immunoglobulin G (IgG) in choroid plexus epithelium after 24 hours of SH. However, the increased eNOS expression in peri-infarcted HF (130±3%, n=4, P<0.01) and extravasation of plasma IgG into the extravascular compartment after 24 hours of pMCAO suggest that increased microvascular permeability, probably due to elevated levels of nitric oxide, leads to development of vasogenic brain edema via BBB breakdown. Based on these findings, the authors suggest that modulation of different protein expression, dependent on the type of brain edema, is required for primary (pMCAO) and secondary (SH) brain injuries to attenuate brain edema and neuronal degeneration.
"Several signaling transduction pathways including nitric oxide  , protein kinase C , calcium  are involved in burn-induced vascular hyperpermeability. However, until now there is no direct evidence that Rho/Rho kinase signaling transduction pathway is involved. "
[Show abstract][Hide abstract] ABSTRACT: To investigate the role of the Small GTPase Rho and endothelial cytoskeleton in the increased vascular permeability of rat skin after scalding.
Rats were subjected to scalding local ventral skin and a venule was isolated from scalded skin and cannulated by micropipette. The venular permeability was measured with a fluorescence ratio technique and expressed with the permeability coefficient to albumin (P(a)). The venular F-actin filaments were observed by staining with rhodamine phalloidin and laser confocal scanning microscopy. A specific Rho kinase inhibitor Y-27632 was added into vessel bathing solution or preincubated with vessels to evaluate the role of Rho kinase in regulating of vascular barrier function.
Scalding increased P(a) value of skin venule about threefold compared to normal skin venules (P<0.01) and was maintained for 120 min. Inhibition of Rho kinase with Y-27632 (30 micromol/l in low-concentration group; 60 micromol/l in high-concentration group) significantly attenuated the hyperpermeability responses to scalding in a dose dependent fashion. A prominent peripheral actin rim (PAR) existed at the outer area of endothelial cells and apparently delineated the cell-to-cell borders. In the control group, the PARs were arranged smoothly and fairly continuously. However, occasionally PARs did show focal interruption with focal fluorescein isothiocyanate (FITC)-albumin leakage. In the burned group, PARs were less organized and accompanied by a large amount of FITC-albumin leakage. Inhibition of Rho kinase with Y-27632 dramatically reduced P(a) value with recovery of actin filament arrangement in venule after scalding.
Burn leads to dermal venular permeability increase with endothelial cytoskeleton depolymerization and disruption. Rho signal transduction pathway is involved in these responses.
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