Redox regulation of endothelial barrier integrity

Intestinal ischemia-reperfusion is associated with the generation of reactive oxygen metabolites as well as remote, oxidant-mediated lung injury. Oxidants elicit endothelial redox imbalance and loss of vascular integrity by disorganizing several junctional proteins that contribute to the maintenance and regulation of the endothelial barrier. To determine the specific effect of redox imbalance on pulmonary vascular barrier integrity, microvascular permeability was determined in lungs of animals subjected to chemically induced redox imbalance. The effect of redox imbalance on microvascular permeability and endothelial junctional integrity in cultured lung microvascular cells was also determined. Whole lung and cultured pulmonary endothelial cell permeability both increased significantly in response to chemical redox imbalance. Thiol depletion also resulted in decreased endothelial cadherin content and disruption of the endothelial barrier. These deleterious effects of intracellular redox imbalance were blocked by pretreatment with exogenous glutathione. The results of this study suggest that redox imbalance contributes to pulmonary microvascular dysfunction by altering the content and/or spatial distribution of endothelial junctional proteins.

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SARS-CoV-2 Spike Protein Induces Degradation of Junctional Proteins That Maintain Endothelial Barrier Integrity

Frontiers in Cardiovascular Medicine ◽

10.3389/fcvm.2021.687783 ◽

2021 ◽

Vol 8 ◽

Author(s):

Somasundaram Raghavan ◽

Divya Borsandra Kenchappa ◽

M. Dennis Leo

Keyword(s):

Endothelial Cells ◽

Angiotensin Converting Enzyme ◽

Spike Protein ◽

Endothelial Barrier ◽

Converting Enzyme ◽

Angiotensin Converting Enzyme 2 ◽

Barrier Integrity ◽

Junctional Proteins ◽

Junction Protein ◽

Junctional Protein

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) uses the Angiotensin converting enzyme 2 (ACE2) receptor present on the cell surface to enter cells. Angiotensin converting enzyme 2 is present in many cell types including endothelial cells, where it functions to protect against oxidative damage. There is growing evidence to suggest that coronavirus disease (COVID-19) patients exhibit a wide range of post-recovery symptoms and shows signs related to cardiovascular and specifically, endothelial damage. We hypothesized that these vascular symptoms might be associated with disrupted endothelial barrier integrity. This was investigated in vitro using endothelial cell culture and recombinant SARS-CoV-2 spike protein S1 Receptor-Binding Domain (Spike). Mouse brain microvascular endothelial cells from normal (C57BL/6 mice) and diabetic (db/db) mice were used. An endothelial transwell permeability assay revealed increased permeability in diabetic cells as well as after Spike treatment. The expression of VE-Cadherin, an endothelial adherens junction protein, JAM-A, a tight junctional protein, Connexin-43, a gap junctional protein, and PECAM-1, were all decreased significantly after Spike treatment in control and to a greater extent, in diabetic cells. In control cells, Spike treatment increased association of endothelial junctional proteins with Rab5a, a mediator of the endocytic trafficking compartment. In cerebral arteries isolated from control and diabetic animals, Spike protein had a greater effect in downregulating expression of endothelial junctional proteins in arteries from diabetic animals than from control animals. In conclusion, these experiments reveal that Spike-induced degradation of endothelial junctional proteins affects endothelial barrier function and is the likely cause of vascular damage observed in COVID-19 affected individuals.

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Microvascular ischemia-reperfusion injury in striated muscle: significance of "reflow paradox"

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1992.263.6.h1901 ◽

1992 ◽

Vol 263 (6) ◽

pp. H1901-H1906 ◽

Cited By ~ 18

Author(s):

M. D. Menger ◽

S. Pelikan ◽

D. Steiner ◽

K. Messmer

Keyword(s):

Striated Muscle ◽

Ischemia Reperfusion Injury ◽

Ischemia Reperfusion ◽

Reactive Oxygen ◽

Microvascular Permeability ◽

Leukocyte Rolling ◽

Reactive Oxygen Metabolites ◽

Oxygen Metabolites ◽

Reflow Paradox

Ischemia-reperfusion (I/R)-induced microvascular injury is characterized by capillary “no-reflow” and reflow-associated events, termed “reflow paradox,” including leukocyte-endothelium interaction and increase in microvascular permeability. The major objectives of this study were 1) to elucidate the significance of reflow paradox after 4 h of tourniquet-induced ischemia in striated muscle and 2) to determine the role of reactive oxygen metabolites in the pathogenesis of reflow paradox-dependent microcirculatory alterations. By use of in vivo fluorescence microscopy in a striated muscle preparation of hamsters, leukocyte-endothelium interaction in postcapillary venules and macromolecular extravasation from capillaries and venules were quantified before ischemia and after 30 min, 2 h, and 24 h of reperfusion. I/R elicited marked enhancement (P < 0.01) of leukocyte rolling during initial reperfusion and a 20-fold increase of leukocyte adherence (P < 0.01) lasting for the entire postischemic reperfusion period (n = 7). These phenomena were accompanied by significant leakage (P< 0.01) of macromolecules from capillaries and in particular from postcapillary venules (n = 9). Both superoxide dismutase (SOD, 20 mg/kg body wt, n = 7) and allopurinol (50 mg/kg body wt, n = 7) were effective in attenuating I/R-induced leukocyte rolling and adherence. In addition, microvascular leakage was significantly reduced by allopurinol (n = 9) and completely abolished by SOD (n = 9) (P < 0.01). These results support the concept that reactive oxygen metabolites contribute to I/R-induced reflow paradox, resulting in leukocyte accumulation, adherence, and increase in microvascular permeability.

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Reversal of pulmonary capillary ischemia-reperfusion injury by rolipram, a cAMP phosphodiesterase inhibitor

Journal of Applied Physiology ◽

10.1152/jappl.1994.77.2.774 ◽

1994 ◽

Vol 77 (2) ◽

pp. 774-781 ◽

Cited By ~ 55

Author(s):

J. W. Barnard ◽

A. F. Seibert ◽

V. R. Prasad ◽

D. A. Smart ◽

S. J. Strada ◽

...

Keyword(s):

Ischemia Reperfusion Injury ◽

Ischemia Reperfusion ◽

Phosphodiesterase Inhibitor ◽

Dry Weight ◽

Close Correlation ◽

Microvascular Permeability ◽

Lung Model ◽

Cell Permeability ◽

Camp Accumulation ◽

Camp Phosphodiesterase

Isoproterenol (ISO) and forskolin, agents that increase adenosine 3′,5′-cyclic monophosphate (cAMP) via adenylyl cyclase activation, reverse lung injury associated with increased microvascular permeability. We studied the role of rolipram, a relatively isozyme-selective cAMP phosphodiesterase (PDE) inhibitor, in reversing increased capillary permeability due to ischemia-reperfusion (I/R), a form of oxidant injury in the lung, by using the isolated perfused rat lung model. Rolipram (2 microM) administered after 45 min of ischemia and 45 min of reperfusion reduced I/R-increased permeability as measured by the capillary filtration coefficient to control lung values. Computer image analysis of air space edema and perivascular cuffing, as well as wet-to-dry weight ratios, confirms the permeability reversal by rolipram administration. Rolipram inhibition of cAMP PDE in the lung was assessed by using [3H]adenine prelabeling adapted for the whole lung and perfusate [3H]cAMP accumulation. Rolipram failed to increase perfusate cAMP alone but dramatically increased perfusate cAMP above ISO alone. Dose-response relationships of ISO or rolipram show a close correlation of the half-maximal effective dose (ED50) for injury reversal and perfusate cAMP production. The combination of rolipram and ISO produced synergistic reversal of I/R injury. We conclude that reversal of I/R-induced increased microvascular permeability can be achieved with rolipram and that the mechanism of action of rolipram is probably through PDE isozyme-selective inhibition. The similarity of the ED50 values for cAMP efflux and reversal of permeability increases also supports a close coupling between cAMP accumulation and endothelial cell permeability.

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