ETS-Related Gene Activation Preserves Adherens Junctions and Permeability in Microvascular Endothelial Cells

ABSTRACT

ERG (ETS-related gene) is a member of the ETS (Erythroblast-transformation specific) family of transcription factors abundantly present in vascular endothelial cells. Recent studies demonstrate that ERG has important roles in blood vessel stability and angiogenesis. However, it is unclear how ERG is potentially involved in microvascular barrier functions and permeability. A wide variety of diseases and clinical conditions including trauma-hemorrhagic shock and burn injury are associated with microvascular dysfunctions, which causes excessive microvascular permeability, tissue edema and eventually, multiple organ dysfunction and death. The main purpose of this study was to determine the specific role of ERG in regulating microvascular permeability in human lung microvascular endothelial cells (HLMEC) and to evaluate if exogenous ERG will protect the barrier. The HLMECs were grown on Transwell inserts as monolayers and were transfected with ERG CRISPR/cas9 knockdown plasmid, ERG CRISPR activation plasmid, recombinant ERG protein or their respective controls. Recombinant vascular endothelial growth factor (VEGF) was used as an inducer of permeability for evaluating the effect of ERG activation on permeability. Changes in barrier integrity and permeability were studied using monolayer permeability assay and immunofluorescence of adherens junction proteins (VE-cadherin and β-catenin) respectively. CRISPR/cas9-based ERG knockdown as well as VEGF treatment induced monolayer hyperpermeability, VE-cadherin, and β-catenin junctional relocation and cytoskeletal F-actin stress fiber formation. CRISPR based ERG activation and recombinant ERG transfection attenuated VEGF-induced monolayer hyperpermeability. ERG activation preserved the adherens junctions and cytoskeleton. These results demonstrate that ERG is a potent regulator of barrier integrity and permeability in human lung microvascular endothelial cells and endogenously or exogenously enhancing ERG provides protection against barrier dysfunction and hyperpermeability.

Protective effects of FK 506 against haemorrhagic shock-induced microvascular hyperpermeability

Microvascular hyperpermeability, the excessive leakage of fluid and proteins from the intravascular space to the interstitium, is a devastating clinical concern in haemorrhagic shock (HS), sepsis, burn and so forth. Previous studies have shown that HS-induced microvascular hyperpermeability is associated with activation of the mitochondria-mediated 'intrinsic' apoptotic signalling cascade and caspase-3 mediated disruption of the endothelial cell barrier. In this study, our objective was to test if FK506, an immunomodulator that is also known to protect mitochondria, would protect barrier functions and decrease vascular hyperpermeability following HS by acting on this pathway. FK506 (25 µM) was given 10 minutes before the shock period in a rat model of HS. The HS model was a non-traumatic/fixed pressure model of hypovolemic shock developed by withdrawing blood to reduce the mean arterial pressure to 40 mm Hg for 60 minutes. The mesenteric post-capillary venules were monitored for changes in permeability using intravital microscopic imaging. The changes in mitochondrial transmembrane potential (MTP) were determined using the cationic dye 5,5',6,6' tetrachoro-1,1',3,3' tetraethyl benzimidazolyl carbocyanine iodide (JC-1), that was superfused on the mesenteric vasculature followed by intravital imaging. The mesenteric caspase-3 activity was measured fluorometrically. Haemorrhagic shock induced a significant increase in hyperpermeability compared to the sham-control group and FK506 treatment decreased HS-induced hyperpermeability significantly (P < .05). FK506 dampened HS-induced loss of MTP and elevation of caspase-3 activity significantly (P < .05). FK506 has protective effects against HS-induced microvascular hyperpermeability. The maintenance of the MTP and protection against caspase-3 mediated endothelial cell barrier disruption are possible mechanisms by which FK506 attenuates HS-induced hyperpermeability. FK506, currently used in clinical settings as an immunomodulator, needs to be explored further for its therapeutic usefulness against HS-induced vascular hyperpermeability and associated complications.

RECOMBINANT BCL-XL ATTENUATES VASCULAR HYPERPERMEABILITY IN A RAT MODEL OF HEMORRHAGIC SHOCK

Following hemorrhagic shock (HS), vascular hyperpermeability, that is, the leakage of fluid, nutrients and proteins into the extravascular space occurs primarily due to the disruption of the endothelial cell–cell adherens junctional complex. Studies from our laboratory demonstrate that activation of the mitochondria-mediated ‘intrinsic’ apoptotic signaling cascade has a significant role in modulating HS-induced hyperpermeability. Here we report the novel use of recombinant Bcl-xL, an anti-apoptotic protein, to control HS-induced vascular hyperpermeability. Our results corroborate involvement of vascular hyperpermeability and apoptotic signaling. HS (the mean arterial pressure (MAP) was reduced to 40 mm Hg for 60 min followed by resuscitation to 90 mm Hg for 60 min) in rats resulted in vascular hyperpermeability as determined by intravital microscopy. Treatment of Bcl-xL (2.5 µg/ml of rat blood in non-lipid cationic polymer, i.v.) before, during and even after HS attenuated or reversed HS-induced vascular hyperpermeability significantly (P<0.05). Conversely, treatment using Bcl-xL inhibitors, 2-methoxy antimycin (2-OMeAA) and ABT 737, significantly increased vascular hyperpermeability compared with sham (P<0.05). Bcl-xL treatment also decreased the amount of fluid volume required to maintain a MAP of 90 mm Hg during resuscitation (P<0.05). HS resulted in an increased mitochondrial reactive oxygen species formation, reduction of ΔΨm, mitochondrial release of cytochrome c and significant activation of caspase-3 (P<0.05). All of these effects were significantly inhibited by Bcl-xL pre-treatment (P<0.05). Our results show that recombinant Bcl-xL is effective against HS-induced vascular hyperpermeability that appears to be mediated through the preservation of ΔΨm and subsequent prevention of caspase-3 activation.

Tumor necrosis factor-α-induced microvascular endothelial cell hyperpermeability: role of intrinsic apoptotic signaling

Tumor necrosis factor-α (TNF-α), a pro-apoptotic cytokine, is involved in vascular hyperpermeability, tissue edema, and inflammation. We hypothesized that TNF-α induces microvascular hyperpermeability through the mitochondria-mediated intrinsic apoptotic signaling pathway. Rat lung microvascular endothelial cells grown on Transwell inserts, chamber slides, or dishes were treated with recombinant TNF-α (10 ng/ml) in the presence or absence of a caspase-3 inhibitor, Z-DEVD-FMK (100 μM). Fluorescein isothiocyanate (FITC)-albumin (5 mg/ml) was used as a marker of monolayer permeability. Mitochondrial reactive oxygen species (ROS) was determined using dihydrorhodamine 123 and mitochondrial transmembrane potential using JC-1. The adherens junction integrity and actin cytoskeletal organization were studied using β-catenin immunofluorescence and rhodamine phalloidin, respectively. Caspase-3 activity was measured fluorometrically. The pretreatment with Z-DEVD-FMK (100 μM) attenuated TNF-α-induced (10 ng/ml) disruption of the adherens junctions, actin stress fiber formation, increased caspase-3 activity, and monolayer hyperpermeability (p < 0.05). TNF-α (10 ng/ml) treatment resulted in increased mitochondrial ROS formation and decreased mitochondrial transmembrane potential. Intrinsic apoptotic signaling-mediated caspase-3 activation plays an important role in regulating TNF-α-induced endothelial cell hyperpermeability.

The role of intrinsic apoptotic signaling in hemorrhagic shock-induced microvascular endothelial cell barrier dysfunction

Hemorrhagic shock leads to endothelial cell barrier dysfunction resulting in microvascular hyperpermeability. Hemorrhagic shock-induced microvascular hyperpermeability is associated with worse clinical outcomes in patients with traumatic injuries. The results from our laboratory have illustrated a possible pathophysiological mechanism showing involvement of mitochondria-mediated "intrinsic" apoptotic signaling in regulating hemorrhagic shock-induced microvascular hyperpermeability. Hemorrhagic shock results in overexpression of Bcl-2 family of pro-apoptotic protein, BAK, in the microvascular endothelial cells. The increase in BAK initiates "intrinsic" apoptotic signaling cascade with the release of mitochondrial cytochrome c in the cytoplasm and activation of downstream effector caspase-3, leading to loss of endothelial cell barrier integrity. Thus, this review article offers a brief overview of important findings from our past and present research work along with new leads for future research. The summary of our research work will provide information leading to different avenues in developing novel strategies against microvascular hyperpermeability following hemorrhagic shock.

Regulation of tumor necrosis factor-α-induced microvascular endothelial cell hyperpermeability by recombinant B-cell lymphoma-extra large

BACKGROUND

Tumor necrosis factor-α (TNF-α), a cytotoxic cytokine, induces endothelial cell barrier dysfunction and microvascular hyperpermeability, leading to tissue edema, a hallmark of traumatic injuries. The objective of the present study was to determine whether B-cell lymphoma-extra large (Bcl-xL), an antiapoptotic protein, would regulate and protect against TNF-α-mediated endothelial cell barrier dysfunction and microvascular hyperpermeability.

METHODS

Rat lung microvascular endothelial cells were grown as monolayers on Transwell membranes, and fluorescein isothiocyanate-bovine albumin flux (5 mg/mL) across the monolayer was measured fluorometrically to indicate changes in monolayer permeability. The rat lung microvascular endothelial cell adherens junctional integrity and actin cytoskeleton was studied using β-catenin immunofluorescence and rhodamine phalloidin dye, respectively. Pretreatment of caspase-8 inhibitor (Z-IETD-FMK, 100 μM) for 1 hour and transfection of Bcl-2-homology domain 3-interacting domain death agonist small interfering RNA (10 μM) for 48 hours were performed to study their respective effects on TNF-α-induced (10 ng/mL; 1-hour treatment) monolayer permeability. Recombinant Bcl-xL protein (2.5 μg/ml) was transfected in rat lung microvascular endothelial cells for 1 hour, and its effect on permeability was demonstrated using a permeability assay. Caspase-3 activity was assayed fluorometrically.

RESULTS

Z-IETD-FMK pretreatment protected the adherens junctions and decreased TNF-α-induced monolayer hyperpermeability. Bcl-2-homology domain 3-interacting domain death agonist small interfering RNA transfection attenuated the TNF-α-induced increase in monolayer permeability. Recombinant Bcl-xL protein showed protection against TNF-α-induced actin stress fiber formation, an increase in caspase-3 activity, and monolayer hyperpermeability.

CONCLUSIONS

Our results have demonstrated the protective effects of recombinant Bcl-xL protein against TNF-α-induced endothelial cell adherens junction damage and microvascular endothelial cell hyperpermeability. These findings support the potential for Bcl-xL-based drug development against microvascular hyperpermeability and tissue edema.

Microvascular endothelial cell hyperpermeability induced by endogenous caspase 3 activator staurosporine

BACKGROUND

Microvascular hyperpermeability following conditions such as hemorrhagic shock occurs mainly owing to disruption of the adherens junctional protein complex in endothelial cells. The objective of this study was to examine the action of staurosporine, a potent activator of endogenous caspase 3 on the adherens junction and the cellular pathway through which it causes possible endothelial cell barrier dysfunction.

METHODS

Rat lung microvascular endothelial cell (RLMEC) permeability was measured by fluorescein isothiocyanate-albumin flux across the monolayer in a Transwell plate. Integrity of the endothelial cell adherens junctions was studied using immunofluorescence of β-catenin and vascular endothelial-cadherin. Mitochondrial reactive oxygen species formation was determined by using dihydrorhodamine 123 and mitochondrial transmembrane potential by JC-1 fluorescent probe and flow cytometry. Caspase 3 enzyme activity was assayed fluorometrically. Cell death assay in RLMECs was performed using propidium iodide staining and analyzed by flow cytometry.

RESULTS

Staurosporine (1 µM)-treated RLMEC monolayers showed significant increase in permeability, which was decreased by pretreatment with caspase 3 specific inhibitor, Z-DEVD-FMK (p < 0.05). Immunofluorescence studies showed staurosporine induced disruption of the adherens junction, which was reversed by Z-DEVD-FMK. Staurosporine treatment led to an increase in mitochondrial reactive oxygen species formation and a decrease in mitochondrial transmembrane potential. Furthermore, staurosporine induced a significant increase in caspase 3 activity (p < 0.05) but not cell death in RLMECs (p < 0.05).

CONCLUSION

Staurosporine-induced disruption of the adherens junction and microvascular endothelial cell hyperpermeability is associated with the activation of mitochondrial "intrinsic" apoptotic signaling cascade but without causing endothelial cell death. Our results suggest that prevention of mitochondrial-mediated activation of caspase 3 has therapeutic potential against microvascular hyperpermeability.

Cyclosporine A--protection against microvascular hyperpermeability is calcineurin independent

BACKGROUND

Mitochondria-mediated apoptotic signaling contributes to microvascular hyperpermeability. We hypothesized that cyclosporine A (CsA), which protects mitochondrial transition pores, would attenuate hyperpermeability independent of its calcineurin inhibitory property.

METHODS

Hyperpermeability was induced in microvascular endothelial cell monolayers using proapoptotic BAK or active caspase-3 after CsA or a specific calcineurin inhibitor, calcineurin autoinhibitory peptide (CIP), treatment. Permeability was measured based on fluorescein isothiocyanate-albumin flux across the monolayers. Mitochondrial transmembrane potential (MTP) was determined using 5,5',6,6'-tetrachoro-1,1',3,3'-tetraethylbenzimidazolyl carbocyanine iodide. Mitochondrial release of cytochrome c was measured using an enzyme-linked immunosorbent assay and caspase-3 activity fluorometrically.

RESULTS

CsA-attenuated (10 nmol/L) but not CIP-attenuated (100 mumol/L) BAK induced hyperpermeability (P < .05), CsA- but not CIP-attenuated BAK induced a decrease in MTP and an increase in cytochrome c levels and caspase-3 activity (P < .05). CsA and CIP were ineffective against caspase-3-induced hyperpermeability.

CONCLUSIONS

CsA attenuated hyperpermeability by protecting MTP, thus preventing mitochondria-mediated apoptotic signaling. The protective effect of CsA is independent of calcineurin inhibition.

(-)-Deprenyl inhibits vascular hyperpermeability after hemorrhagic shock

Recent studies from our laboratory demonstrated the involvement of endothelial cell reactive oxygen species (ROS) formation and activation of apoptotic signaling in vascular hyperpermeability after hemorrhagic shock (HS). The objective of this study was to determine if (-)-deprenyl, an antioxidant with antiapoptotic properties, would attenuate HS-induced vascular hyperpermeability. In rats, HS was induced by withdrawing blood to reduce the MAP to 40 mmHg for 60 min followed by resuscitation for 60 min. To study hyperpermeability, we injected the rats with fluorescein isothiocyanate--albumin (50 mg/kg), and the changes in integrated optical intensity of the mesenteric postcapillary venules were obtained intravascularly and extravascularly using intravital microscopy. Mitochondrial ROS formation and mitochondrial transmembrane potential (DeltaPsim) were studied using dihydrorhodamine 123 and JC-1, respectively. Mitochondrial release of cytochrome c was determined using enzyme-linked immunosorbent assay and caspase-3 activity by a fluorometric assay. Parallel studies were performed in rat lung microvascular endothelial cells using proapoptotic BAK as inducer of hyperpermeability. Hemorrhagic shock induced vascular hyperpermeability, mitochondrial ROS formation, DeltaPsim decrease, cytochrome c release, and caspase-3 activation (P G 0.05). (-)-Deprenyl (0.15 mg/kg) attenuated all these effects (P < 0.05). Similarly in rat lung microvascular endothelial cells, (-)-deprenyl attenuated BAK peptide-induced monolayer hyperpermeability (P < 0.05), ROS formation, DeltaPsim decrease, cytochrome c release (P<0.05), and caspase-3 activation (P < 0.05). The protective effects of (-)-deprenyl on vascular barrier functions may be due to its protective effects on DeltaPsim, thereby preventing mitochondrial release of cytochrome c and caspase-3--mediated disruption of endothelial adherens junctions.

17beta-estradiol mediates protection against microvascular endothelial cell hyperpermeability

BACKGROUND

Previous work from our laboratory demonstrated the involvement of "intrinsic" mitochondrial apoptotic signaling in vascular hyperpermeability. The objective of this study was to determine if 17beta-estradiol, a known inhibitor of apoptosis, would attenuate microvascular endothelial cell hyperpermeability.

METHODS

Rat lung microvascular endothelial cell monolayers were treated with 17beta-estradiol or estrogen-receptor antagonist ICI 182780 after transfection with BAK peptide (5 microg/mL). Fluorescein isothiocyanate (FITC)-albumin was used to determine the change in permeability. Mitochondrial reactive oxygen species (ROS) formation and transmembrane potential were determined using 123 dihydrorhodamine and JC-1, respectively. Cytosolic cytochrome c levels and caspase-3 activity were determined using enzyme-linked immunosorbent assay and fluorometric assay respectively.

RESULTS

17beta-estradiol (10 nm) attenuated BAK-induced hyperpermeability (P < .05), ROS formation, cytochrome c release, and caspase-3 activation. The estrogen receptor antagonist ICI 182780 blocked the protective effect of 17beta-estradiol on hyperpermeability (P < .05).

CONCLUSIONS

17beta-estradiol attenuates BAK-induced hyperpermeability in rat lung microvascular endothelial cells by way of an estrogen-receptor mediated pathway.

Vascular leak in a rat model of preeclampsia

BACKGROUND/AIMS

Preeclampsia is a hypertensive disorder which develops de novo in women during pregnancy. The urinary excretion of the cardiotonic steroid, marinobufagenin (MBG), is increased prior to the development of hypertension. Preeclamptic patients are volume expanded but much of the excess salt and water appears to be located primarily in the interstitial space. Therefore, 'capillary leak' syndrome has been postulated in this disorder.

METHODS

We evaluated the vascular leakage in normal rats following MBG injection and in a rat model of human preeclampsia. We measured the changes in light intensity comparing that in the intravascular to the extravascular space by assessing 'leak' of fluorescein-labeled albumin (FITC-albumin) from mesenteric postcapillary venules.

RESULTS

FITC-albumin extravasation continued to increase in a time-dependent fashion after MBG infusion and was significant (p < 0.05) at 60 min of observation when compared to sham rats. We also observed a significant difference in 'vascular leakage' in preeclamptic rats compared to control non-pregnant and normal pregnant groups starting at 20 min after the FITC-albumin infusion.

CONCLUSION

We propose that MBG is involved in the production of a 'vascular leak' in our rat model of preeclampsia.

Angiopoietin-1 inhibits intrinsic apoptotic signaling and vascular hyperpermeability following hemorrhagic shock

Studies from our laboratory demonstrated the involvement of intrinsic apoptotic signaling in hyperpermeability following hemorrhagic shock (HS). Angiopoietin 1 (Ang-1), a potent inhibitor of hyperpermeability, was recently shown to inhibit apoptosis. The purpose of our study was to determine the effectiveness of Ang-1 in attenuating HS-induced hyperpermeability and its relationship to apoptotic signaling. HS was induced in rats by withdrawing blood to reduce the mean arterial pressure to 40 mmHg for 1 h, followed by reperfusion. Mesenteric postcapillary venules were examined for changes in hyperpermeability by intravital microscopy. Mitochondrial release of second mitochondrial derived activator of caspases (smac) and cytochrome c were determined by Western blot and ELISA, respectively. Caspase-3 activity was determined by fluorometric assay. Parallel studies were performed in rat lung microvascular endothelial cell (RLMEC) monolayers, utilizing HS serum and the proapoptotic Bcl-2 homologous antagonist/killer [BAK (BH3)] peptide as inducers of hyperpermeability. In rats, Ang-1 (200 ng/ml) attenuated HS-induced hyperpermeability versus the HS group ( P < 0.05). Ang-1 prevented HS-induced collapse of mitochondrial transmembrane potential (ΔΨm), smac and cytochrome c release, and caspase-3 activity ( P < 0.05). In RLMEC monolayers, HS serum and BAK (BH3) peptide both induced hyperpermeability that was inhibited by Ang-1 ( P < 0.05). Ang-1 attenuated HS and BAK (BH3) peptide-induced collapse of ΔΨm, smac release, cytochrome c release, activation of caspase-3, and vascular hyperpermeability. In vivo, BAK (BH3) induced vascular hyperpermeability that was attenuated by Ang-1 ( P < 0.05). These findings suggest that Ang-1's role in maintaining microvascular endothelial barrier integrity involves the intrinsic apoptotic signaling cascade.

PKC and MLCK-dependent, cytokine-induced rat coronary endothelial dysfunction

BACKGROUND

Heart disease is one of the leading causes of death in the United States, killing nearly one million people every year. Inflammatory mediators or cytokines are released following myocardial infarction and ischemia/reperfusion injury. These cytokines, of which interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha (TNF-alpha) are among the most important, propagate the activation of a multitude of signaling pathways, such as the protein kinase C (PKC) and myosin light chain kinase (MLCK) pathways, which lead to deleterious changes in the structure and function of the coronary microvascular endothelium.

METHODS

The effects of cytokines on rat heart microvascular endothelial cell monolayer integrity, PKC activity, and adherens junction protein alteration were examined. Further, an in vivo rat coronary ischemia/reperfusion injury model was used to determine vascular leakage and TNF-alpha release.

RESULTS

Administration of the above mentioned cytokines to cell monolayers resulted in significant increases in PKC activation, gap formation, and hyperpermeability across the monolayer and beta-catenin phosphorylation/reorganization. Inhibition of conventional PKC and MLCK attenuated permeability increases. Ischemia/reperfusion injury to the left ventricle resulted in TNF-alpha release as well as conventional PKC- and MLCK-dependent protein extravasation from the circulation to the heart tissue.

CONCLUSION

These results identify the conventional PKC and MLCK pathways as important factors in coronary endothelial dysfunction elicited by IR injury and cytokine release. Further examination of these molecular signaling cascades has the potential of identifying targets for therapeutic intervention following ischemic events in the heart.

Apoptotic signaling induces hyperpermeability following hemorrhagic shock

Hemorrhagic shock (HS) disrupts the endothelial cell barrier, resulting in microvascular hyperpermeability. Recent studies have also demonstrated that activation of the apoptotic signaling cascade is involved in endothelial dysfunction, which may result in hyperpermeability. Here we report involvement of the mitochondrial "intrinsic" pathway in microvascular hyperpermeability following HS in rats. HS resulted in the activation of the mitochondrial intrinsic pathway, as is evident from an increase in the proapoptotic Bcl-2 family member BAK, release of mitochondrial cytochrome c into the cytoplasm, and activation of caspase-3. This, along with the in vivo transfection of the proapoptotic peptide BAK (BH3), resulted in hyperpermeability (as visualized by intravital microscopy), release of mitochondrial cytochrome c into the cytoplasm, and activation of caspase-3. Conversely, transfection of the BAK (BH3) mutant had no effect on hyperpermeability. Together, these results demonstrate involvement of the mitochondrial intrinsic apoptotic pathway in HS-induced hyperpermeability and that the attenuation of this pathway may provide an alternative strategy in preserving vascular barrier integrity.

Morphine Sulfate Attenuates Hemorrhagic Shock- Induced Hyperpermeability

Morphine sulfate is often administered for patients requiring surgical intervention for the control of hemorrhage. Recent data implicate morphine as an immune modulator that affects white blood cells and increases infection rates. In addition, morphine releases histamine, an inflammatory mediator that increases microvascular permeability. Both of these actions of morphine could aggravate the inflammatory progress after hemorrhagic shock. In this study, we evaluated the role of morphine sulfate on microvascular permeability and its effects on leukocyte adherence after hemorrhagic shock. After a control period, blood was withdrawn to reduce the mean arterial blood pressure to 40 mm Hg for 1 h in urethane-anesthetized Sprague-Dawley rats. Mesenteric postcapillary venules in a transilluminated segment of small intestine were examined to quantify changes in permeability and leukocyte adherence. The rats received an IV injection of fluorescein isothiocyanate-bovine albumin during the control period. The fluorescent light intensity emitted from the fluorescein isothiocyanate-bovine albumin was recorded with digital microscopy within the lumen of the microvasculature and compared with the intensity of light in the extraluminal space over time. These images were downloaded to a computerized image analysis program that quantitates changes in light intensity. This change in light intensity represents albumin extravasation. In addition, bright-field images were recorded on compact disk for playback to determine leukocyte adherence. Leukocytes stationary for more than 30 s or longer in a 100-micron segment of venule was considered adherent. Our results demonstrated a marked increase in fluorescein isothiocyanate-bovine albumin leakage into the extravascular space after hemorrhagic shock. Hemorrhagic shock was also associated with an increase in leukocytes adhering to the postcapillary venular endothelium. Morphine sulfate 10 microg/kg given before the shock period, attenuated both the hyperpermeability (P < 0.05) and the increase in leukocyte adherence (P < 0.05) after hemorrhagic shock. These results suggest that instead of aggravating the inflammatory response after hemorrhagic shock, morphine may provide protection to the microvasculature.

Evidence of transcellular albumin transport after hemorrhagic shock

Hemorrhagic shock-induced ischemia-reperfusion injury is characterized by an increase in microvascular permeability. This increase in permeability is thought to occur mainly via passive transport through interendothelial cell junctions. However, recent data have suggested that a transcellular (caveolae) transport mechanism(s) may also play a role after shock. The purpose of our study was to investigate the role of caveolae transport after hemorrhagic shock. After a control period, blood was withdrawn to reduce the mean arterial pressure to 40 mmHg for 1 h in urethane-anesthetized Sprague-Dawley rats. Mesenteric postcapillary venules in a transilluminated segment of small intestine were examined to determine changes in permeability. Rats received an intravenous injection of fluorescein isothiocyanate-bovine albumin during the control period. The fluorescent light intensity emitted from the fluorescein isothiocyanate-bovine albumin was recorded with digital microscopy within the lumen of the microvasculature and was compared with the intensity of light in the extravascular space. The images were downloaded to a computerized image analysis program that quantitates changes in light intensity. This change in light intensity represents albumin extravasation. Our results demonstrated a marked increase in albumin leak after hemorrhagic shock that was significantly attenuated with two different inhibitors of transcellular transport, N-ethylmaleimide and methyl-beta-cyclodextrin. These data suggest that caveolae transport plays a significant role in microvascular permeability after hemorrhagic shock.

Hypothermia reduces microvascular permeability and reactive oxygen species expression after hemorrhagic shock

BACKGROUND

Hypothermia is a frequent manifestation after trauma-induced hemorrhagic shock. Clinical studies have suggested that hypothermia is an independent risk variable predisposing patients to an increase in morbidity. Thus, most of the current goal-directed resuscitation protocols are aimed at the establishment of euthermia. However, recent data suggest that hypothermia may provide protection by attenuating the inflammatory response after hemorrhagic shock. The purpose of this study was twofold: to examine the effects of mild to moderate hypothermia on barrier function after hemorrhagic shock, and to determine the role of reactive oxygen species (ROS) in this process.

METHODS

After a control period, blood was withdrawn to reduce the mean arterial pressure to 40 mm Hg for 1 hour in urethane-anesthetized rats. Mesenteric postcapillary venules in a transilluminated segment of small intestine were examined to quantitate changes in permeability and ROS expression. Sprague-Dawley rats received an intravenous injection of fluorescein isothiocyanate (FITC)-albumin during the control period. The fluorescent light intensity emitted from the FITC-albumin was recorded with digital microscopy within the lumen of the microvasculature and compared with the intensity of light in the extravascular space. The images were downloaded to a computerized image analysis program that quantitates changes in light intensity. This change in light intensity represents albumin-FITC extravasation.

RESULTS

Our results demonstrated a marked increase in albumin leakage after hemorrhagic shock that was significantly attenuated with mild (34 degrees C) and moderate (30 degrees C) hypothermia. In addition, hypothermia attenuated ROS expression after hemorrhagic shock.

CONCLUSION

These data suggest that hypothermia may protect barrier integrity after hemorrhagic shock by inhibition of oxygen radical expression.

In vivo visualization of reactive oxidants and leukocyte-endothelial adherence following hemorrhagic shock

The generation of oxygen radicals during leukocyte-endothelial cell interaction is considered to represent one of the fundamental steps of microvascular injury following ischemia and reperfusion. Indirect evidence also suggests that this relationship may be important following hemorrhagic shock. The purpose of this study was to characterize the temporal changes of reactive oxygen species (ROS) in the mesenteric microvascular endothelium, in vivo, as a consequence of hemorrhagic shock and reperfusion, and to correlate this ROS production to leukocyte adherence. Following a control period, blood was withdrawn to reduce the mean arterial pressure to 40 mmHg for 1 h in urethane-anesthetized rats. Mesenteric venules in a transilluminated segment of small intestine were examined to quantitate changes in ROS generation and leukocyte adherence. Sprague-Dawley rats were injected with dihydrorhodamine 123, a hydroperoxide-sensitive fluorescent probe that is trapped within viable cells as a nonfluorescent form and then converted to the mitochondrion-selective form rhodamine 123 by hydroperoxides. The fluorescent light emission from rhodamine 123 was recorded with digital microscopy and downloaded to a computerized image analysis program. Our results demonstrated an 80% increase in ROS generation beginning within 5 min into resuscitation and a 10-fold increase in leukocyte adherence that occurred at 10 min after resuscitation. Both ROS generation and leukocyte adherence were attenuated with pre-shock administration of platelet activating factor (PAF) antagonist, WEB 2086, and the CD11/CD18a antibody, anti-LFA-1beta. Our findings suggest that ROS production in endothelial cells is increased during reperfusion following hemorrhagic shock and that the mechanism of expression is mediated in part by both PAF expression and subsequent leukocyte adherence.

Leukocyte adherence and sequestration following hemorrhagic shock and total ischemia in rats

The pathogenesis of generalized microvascular injury following hemorrhagic shock and total ischemia appears to be dependent on leukocytes interacting with the venular endothelium. The purpose of this study was to compare leukocyte adherence and sequestration following hemorrhagic shock with that of total ischemia in the small bowel mesentery of rats. Leukocyte adherence and sequestration was measured by direct visualization in vivo using intravital microscopy. In addition, sequestration was also quantitated by measuring tissue levels of myeloperoxidase, a marker of leukocyte infiltration. Mean arterial blood pressure was decreased to 40 mm Hg for 30 min (hemorrhagic shock group). In the total ischemia group, both the superior and inferior mesenteric arteries were clamped for 30 min followed by reperfusion. Hemorrhagic shock (9.4+/-1.5 cell/100 microm) and total ischemia (8.3+/-3 cell/100 microm) caused a statistically significant increases in leukocyte adherence 60 min postinsult as compared with controls (.9+/-1.5 cell/100 microm). However, the increase in leukocyte adherence appeared earlier and to a greater degree initially following total ischemia. Leukocyte sequestration as measured by intravital microscopy was significant only after total ischemia [(24.6+/-1.7 cell/(100 microm)2; p<.01] and not hemorrhagic shock [3.4+/-.6 cell/(100 microm)2] versus controls [2.2+/-.2 cell/(100 microm)2]. This difference in sequestration was also confirmed by tissue levels of myeloperoxidase. The results of this study suggest that the microvascular response following hemorrhagic shock is different than that of total ischemia, and caution is warranted when extrapolating the experimental results of one to the other.

Isolation, characterization, and amino-terminal amino acid sequence analysis of human neutrophil cathepsin G from normal donors

Human neutrophil cathepsin G from normal donors has been purified 82-fold using an isolation procedure which included sequential sodium chloride extraction, Aprotonin-Sepharose affinity chromatography, CM-cellulose ion-exchange chromatography, and AcA44 gel filtration chromatography. The inclusion of this last purification step was crucial for separating inactive lower molecular weight species from the active forms of neutrophil cathepsin G and resulted in a higher specific activity of the final preparation. SDS polyacrylamide gradient gel electrophoresis of the purified reduced protein demonstrated three discrete polypeptides of Mr 31,000, 30,000, and 29,500. Peptide analysis of tryptic digests indicated that these three polypeptides are structurally related to each other and represent microheterogeneity of the purified protein. The cathepsin G peptide maps were distinctly different from the peptide maps of neutrophil elastase. The apparent isoelectric points of these forms as determined by two-dimensional electrophoresis was approximately 8.0. Utilizing microsequencing techniques, the first 25 residues of normal neutrophil cathepsin G have been determined and shown to be identical (except for residue 11) with the sequence of 21 residues of cathepsin G isolated from leukemic myeloid cells. A high degree of homology was found when the amino-terminal regions of neutrophil cathepsin G, rat mast cell protease II (65%) and two human serine proteinases, factor D (52%) and neutrophil elastase (48%), were compared. A precipitating monospecific antiserum to cathepsin G was produced by repeated immunizations of guinea pigs. This antiserum has been used in immunoblotting experiments to demonstrate that the intracellular form(s) of this enzyme is the same approximate Mr as the purified enzyme, and to develop a solid-phase radioimmunoassay for measuring neutrophil cathepsin G in the range 5-50 ng/ml.

Isolation, characterization, and amino-terminal amino acid sequence analysis of human neutrophil elastase from normal donors

Human neutrophil elastase from normal donors has been purified using an isolation procedure which included sequential sodium chloride extraction, Aprotinin-Sepharose affinity chromatography, CM-cellulose ion-exchange chromatography, and AcA44 gel filtration chromatography. The inclusion of this last purification step was crucial for separating inactive lower molecular weight species from the active forms of neutrophil elastase and resulted in a higher specific activity of the final preparation. Sodium dodecyl sulfate-polyacrylamide gradient gel electrophoresis of the reduced purified protein demonstrated three polypeptides of Mr 31,000, 28,000, and 27,500. Four polypeptides were resolved on acid gel electrophoresis; each of the four possessed amidolytic activity. Furthermore, peptide analysis of Staphylococcus aureus V8 protease digests indicated that these polypeptides are structurally related to each other and represent microheterogeneity of the purified protein. The apparent isoelectric points of these four forms as determined by two-dimensional electrophoresis range from 6.1 to 6.7. By utilizing microsequencing techniques, the first 40 residues of neutrophil elastase have been determined and compared with the reported sequence of elastase isolated from leukemic myeloid cells. In addition, a high degree of homology was found within the amino-terminal regions of neutrophil elastase and the serine proteinases porcine elastase, bovine chymotrypsin, human factor D, and the beta chain of plasmin.

Monoclonal and allospecific H-2Kk antisera precipitate a high molecular weight protein

A protein with an apparent m.w. of 68,000 has been observed in immunoprecipitations of NP-40 solubilized BW5147 thymoma cells by using monoclonal or polyclonal allospecific H-2Kk antisera. By contrast, H-2Dk alloantisera precipitated a 45,000 m.w. protein from the same membrane preparations. The 68,000 m.w. protein is expressed on the plasma membrane as determined by vectoral labeling. Extensive clearing experiments and the use of monoclonal antibody demonstrate that the protein does not bear group-specific C-type viral determinants.

Monoclonal and allospecific H-2Kk antisera precipitate a high molecular weight protein

A protein with an apparent m.w. of 68,000 has been observed in immunoprecipitations of NP-40 solubilized BW5147 thymoma cells by using monoclonal or polyclonal allospecific H-2Kk antisera. By contrast, H-2Dk alloantisera precipitated a 45,000 m.w. protein from the same membrane preparations. The 68,000 m.w. protein is expressed on the plasma membrane as determined by vectoral labeling. Extensive clearing experiments and the use of monoclonal antibody demonstrate that the protein does not bear group-specific C-type viral determinants.

PRoperties of the low-temperature photosystem I primary reaction in the P-700-chlorophyll alpha-protein

The Photosystem I primary reaction, as measured by electron paramagnetic resonance changes of P-700 and a bound iron-sulfur center, has been studied at 15 degrees K in P-700-chlorophyll alpha-protein complexes isolated from a blue-green alga. One complex, prepared with sodium dodecyl sulfate shows P-700 photooxidation only at 300 degrees K, whereas a second complex, prepared with Triton X-100, is photochemically active at 15 degrees K as well as at 300 degrees K. Analysis of these two preparations shows that the absence of low-temperature photoactivity in the sodium dodecyl sulfate complex reflects a lack of bound iron-sulfur centers in this preparation and supports the assignment of an iron-sulfur center as the primary electron acceptor of Photosystem I.