High glucose enhances LPS-stimulated human PMVEC hyperpermeability via the NO pathway

Abstract

Chronic hyperglycemia is an established risk factor for endothelial damage. It remains unclear, however, whether brief hyperglycemic exposure exacerbates the damage to vascular endothelial cells induced by endotoxin. We hypothesize that brief hyperglycemic exposure enhances the permeability of the endothelium following stimulation with lipopolysaccharide (LPS). Correlations between modulation of nitric oxide synthase (NOS) pathways and altered endothelial homeostasis have been studied and demonstrated in various pathophysiological conditions. NOS activities are regulated by endogenous inhibitors, including asymmetric dimethylarginine (ADMA), which is metabolized by dimethylarginine dimethylaminohydrolase (DDAH). Since previous data demonstrated that endothelial dysfunction may be related to reduced expression and/or activity of DDAH, in this study, we aimed to determine the effect of increased glucose levels on pulmonary microvascular endothelial cell (PMVEC) permeability, including effects on the NOS pathways. Human PMVECs were incubated with normal (5.5 mM) and high (33 mM) concentrations of D-glucose for 5 days to create a monolayer of cells prior to LPS stimulation (10 μg/ml) for 12 h. When stimulated with LPS, cells incubated with a high glucose (HG) concentration had significant microfilament rearrangement compared with cells incubated with a normal glucose concentration, as determined by immunofluorescence. Scanning electron microscopy revealed a larger average diameter and increased number of fenestrae on the hyperglycemic PMVECs when stimulated with LPS, compared with PMVECs cultured with a normal glucose concentration. The results demonstrated that a high concentration of glucose increases the LPS-stimulated horseradish peroxidase (HRP) permeability compared with a normal concentration of glucose. Furthermore, a HG concentration upregulated LPS-stimulated inducible NOS (iNOS) production and down-regulated endothelial NOS (eNOS) and DDAH-2 expression. Hyperglycemia significantly increased LPS-stimulated nitrite/nitrate production (stable NO end-products). Our results, thus, demonstrate that in vitro HG concentrations exacerbate LPS-stimulated cytoskeletal rearrangement and hyperpermeability of an endothelial monolayer, and cause further imbalance of the NO pathway. These results suggest that it is important to manage even short-term increases in blood glucose, particularly following acute infection.

Activation of the sweet taste receptor, T1R3, by the artificial sweetener sucralose regulates the pulmonary endothelium

“…We demonstrate that at a physiologically relevant high concentration of glucose (25 mM) vascular permeability was increased. Similar to previous studies, we also observed that high glucose exacerbates LPS-mediated barrier disruption ( 46 ); therefore, the protective effect of T1R3 activation with sucralose cannot be mimicked by glucose. Furthermore, while this study focused on the use of sucralose to activate T1R3, different artificial sweeteners demonstrate varying ability to bind T1R3 and stimulate downstream signaling ( 56 ).…”

Intermittent High Glucose Implements Stress-Induced Senescence in Human Vascular Endothelial Cells: Role of Superoxide Production by NADPH Oxidase

“…This finding suggests that the baneful effect of glucose fluctuation on endothelial cell senescence cannot be attributed to a substantial alteration in eNOS activation. Several papers have reported the expression of iNOS by high glucose in endothelial cells; however, the glucose concentration in those papers was higher (33 mM or more) than those in our finding (22 mM)[ 34 , 35 ], and inducers of iNOS, such as lipopolysaccharides, were simultaneously used in several experiments. Other papers have reported no induction of iNOS by high glucose in the cultured endothelium [ 36 ].…”

Hyperglycaemia Enhances Nitric Oxide Production in Diabetes: A Study from South Indian Patients

“…Similarly, high expression of iNOS was also associated with hyperglycemia [ 22 , 23 ]. Endothelial cells when treated with high glucose concentration can enhance iNOS expression [ 48 , 49 ]. Similarly, our present study also demonstrated higher gene expression of both eNOS and iNOS in HUVEC cells after treating with high glucose concentration.…”