Caspase inhibition does not protect against liver damage in hemorrhagic shock

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.

Identification of Fibrinogen as a Key Anti-Apoptotic Factor in Human Fresh Frozen Plasma for Protecting Endothelial Cells In Vitro

Resuscitation with human fresh frozen plasma (FFP) in hemorrhagic shock (HS) patients is associated with improved clinical outcomes. Our group has demonstrated that the beneficial effect of FFP is due to its blockade on endothelial hyperpermeability, thereby improving vascular barrier function. The current study aimed to investigate HS-induced endothelial cell apoptosis, a potential major contributor to the endothelial hyperpermeability, and to determine the effect and the key components/factors of FFP on protecting endothelial cells from apoptosis. We first measured and demonstrated an increase in apoptotic endothelial microparticles (CD146AnnexinV) in patients in shock compared to normal subjects, indicating the induction of endothelial cell activation and apoptosis in shock patients. We then transfused HS rats with FFP and showed that FFP blocked HS-induced endothelial cell apoptosis in gut tissue. To identify the anti-apoptotic factors in FFP, we utilized high-performance liquid chromatography, fractionated FFP, and screened the fractions in vitro for the anti-apoptotic effects. We selected the most effective fractions, performed mass spectrometry, and identified fibrinogen as a potent anti-apoptotic factor. Taken together, our findings suggest that HS-induced endothelial apoptosis may constitute a major mechanism underlying the vascular hyperpermeability. Furthermore, the identified anti-apoptotic factor fibrinogen may contribute to the beneficial effects of FFP resuscitation, and therefore, may have therapeutic potential for HS.

TUDCA Ameliorates Liver Injury Via Activation of SIRT1-FXR Signaling in a Rat Hemorrhagic Shock Model

OBJECTIVE

The aim of this study was to investigate the changes of bile acids in the liver during hemorrhagic shock (HS) and their potential to attenuate liver injury via activation of SIRT1 (sirtuin 1)-FXR (farnesoid X receptor) signaling.

METHODS

A Sprague-Dawley (SD) rat HS model was established, whereas HepG2 cells were hypoxically cultured to simulate HS in vitro. Liver bile acids (BA) were profiled with ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). FXR expression was detected by western blot and immunohistochemistry. The mRNA levels of SIRT1 and FXR were detected by polymerase chain reaction. Protein expression of SIRT1, FoxM1, NF-κB, acetyl-NF-κB, p53, and acetyl-p53 was analyzed by western blot. Hepatocyte apoptosis and proliferation were measured by TUNEL assay and Ki-67 staining, respectively. Serum and supernatant cytokines were analyzed using ELISA assays. Liver injury was also assessed. To investigate the possible mechanisms, SIRT1 agonist (SRT1720), SIRT1 inhibitor (EX527), and FXR inhibitor (Z-guggulsterone) were used.

RESULTS

Tauroursodeoxycholic acid (TUDCA) in the liver decreased significantly after HS. SIRT1 and FXR expression was time-dependently downregulated by HS or hypoxia condition. TUDCA upregulated SIRT1-FXR activity, which inhibited expression and acetylation of NF-κB and p53 and increased FoxM1 expression, leading to decreased inflammatory response and apoptosis and increased proliferative capacity in hepatocytes, and attenuation of liver injury. EX527 pretreatment reversed the protective effect of TUDCA. Moreover, Z-guggulsterone supplementation decreased the protective effect of TUDCA in vitro.

CONCLUSION

TUDCA in the liver decreased during HS. TUDCA supplementation might attenuate HS-induced liver injury by upregulating SIRT1-FXR signaling.

Caspase-(8/3) activation and organ inflammation in a rat model of resuscitated hemorrhagic shock: A role for uric acid

BACKGROUND

Multiple organ failure can develop after hemorrhagic shock (HS). Uric acid (UA) is released from dying cells and can be proinflammatory. We hypothesized that UA could be an alternative mediator of organ apoptosis and inflammation after HS.

METHODS

Ventilated male Wistar rats were used for the HS model. Two durations of shock (5 minutes vs. 60 minutes) were compared, and shams were instrumented only; animals were resuscitated and observed for 24 hours/72 hours. Caspases-(8/3), myeloperoxidase (MPO), TNF-α were measured in lungs and kidneys. Plasma UA and cytokine (IL-1β, IL-18, TNF-α) were measured. A second set of animals were randomized to vehicle versus Rasburicase intraperitoneal intervention (to degrade UA) during resuscitation. Another group received exogenous UA intraperitoneally without HS. Measures mentioned above, in addition to organs UA, were performed at 24 hours. In vitro, caspases-(8/3) activity was tested in epithelial cells exposed to UA.

RESULTS

Hemorrhagic shock increased organ (kidney and lung) TNF-α, MPO, and caspases activity in various patterns while caspase-8 remained elevated over time. Hemorrhagic shock led to increased plasma UA at 2 hours, which remained high until 72 hours; TNF-α and IL-18 were elevated at 24 hours. The exogenous UA administration in sham animals reproduced the activation of caspase-8 and MPO in organs, and TNF-α in the lung. The increased plasma and organ UA levels, plasma and lung TNF-α, as well as organ caspase-(8/3) and MPO, observed at 24 hours after HS, were prevented by the administration of Rasburicase during resuscitation. In vitro, soluble UA induced caspases-(3/8) activity in epithelial cells.

CONCLUSION

Uric acid is persistently high after HS and leads to the activation of caspases-8 and organ inflammation; these can be prevented by an intervention to degrade UA. Therefore, UA is an important biomarker and mediator that could be considered a therapeutic target during HS resuscitation in human.

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.

Oxidative stress and cell damage in a model of precancerous lesions and advanced hepatocellular carcinoma in rats

Hepatocellular carcinoma (HCC) is the third most frequent cause of cancer deaths throughout the world. This study was aimed to analyze oxidative stress and cell damage in a multistage model of liver carcinogenesis induced by diethylnitrosamine (DEN) in rats. Male Wistar rats weighing 145–150 g were divided into three groups: control, precancerous lesions (PL) (which received 100 mg DEN once a week every 6 weeks up to 28 weeks), and advanced HCC (50 mg DEN once/twice per week up to 19 weeks). Lipid peroxidation (TBARS), superoxide dismutase (SOD) activity, and expression of transforming growth factor-1 beta (TGF)-1β, endothelial and inducible nitric oxide syntahese (eNOS, iNOS), NADPH quinone oxireductase (NQO)-1, nuclear factor erythroid 2-related factor (NrF)2, kelch-like ECH-associated protein (Keap)1 and heat shock protein (HSP)70 were measured. TBARS concentration was augmented in the PL and advanced HCC groups. SOD activity, TGF-1β and Nrf2 expression were higher in animals with precancerous lesions. In advanced HCC, expression of NQO1 and iNOS increased while there was a decrease in HPS70 expression. Data obtained provide evidence for the differential activation of proteins involved in oxidative stress and cell damage during progression of carcinogenesis in an animal model of HCC.

The MnSOD Ala16Val SNP: relevance to human diseases and interaction with environmental factors

The relevance of reactive oxygen species (ROS) production relies on the dual role shown by these molecules in aerobes. ROS are known to modulate several physiological phenomena, such as immune response and cell growth and differentiation; on the other hand, uncontrolled ROS production may cause important tissue and cell damage, such as deoxyribonucleic acid oxidation, lipid peroxidation, and protein carbonylation. The manganese superoxide dismutase (MnSOD) antioxidant enzyme affords the major defense against ROS within the mitochondria, which is considered the main ROS production locus in aerobes. Structural and/or functional single nucleotide polymorphisms (SNP) within the MnSOD encoding gene may be relevant for ROS detoxification. Specifically, the MnSOD Ala16Val SNP has been shown to alter the enzyme localization and mitochondrial transportation, affecting the redox status balance. Oxidative stress may contribute to the development of type 2 diabetes, cardiovascular diseases, various inflammatory conditions, or cancer. The Ala16Val MnSOD SNP has been associated with these and other chronic diseases; however, inconsistent findings between studies have made difficult drawing definitive conclusions. Environmental factors, such as dietary antioxidant intake and exercise have been shown to affect ROS metabolism through antioxidant enzyme regulation and may contribute to explain inconsistencies in the literature. Nevertheless, whether environmental factors may be associated to the Ala16Val genotypes in human diseases still needs to be clarified.

Melatonin modulates the autophagic response in acute liver failure induced by the rabbit hemorrhagic disease virus

Autophagy is an important survival pathway and participates in the host response to infection. Beneficial effects of melatonin have been previously reported in an animal model of acute liver failure (ALF) induced by the rabbit hemorrhagic disease virus (RHDV). This study was aimed to investigate whether melatonin protection against liver injury induced by the RHDV associates to modulation of autophagy. Rabbits were infected with 2 × 10(4) hemagglutination units of a RHDV isolate and received 20 mg/kg melatonin at 0, 12, and 24 hr postinfection. RHDV induced autophagy, with increased expression of beclin-1, ubiquitin-like autophagy-related (Atg)5, Atg12, Atg16L1 and sequestrosome 1 (p62/SQSTM1), protein 1 light chain 3 (LC3) staining, and conversion of LC3-I to autophagosome-associated LC3-II. These effects reached a maximum at 24 hr postinfection, in parallel to extensive colocalization of LC3 and lysosome-associated membrane protein (LAMP)-1. The autophagic response induced by RHDV infection was significantly inhibited by melatonin administration. Melatonin treatment also resulted in decreased immunoreactivity for RHDV viral VP60 antigen and a significantly reduction in RHDV VP60 mRNA levels, oxidized to reduced glutathione ratio (GSSG/GSH), caspase-3 activity, and immunoglobulin-heavy-chain-binding protein (BiP) and CCAAT/enhancer-binding protein homologous protein (CHOP) expression. Results indicate that, in addition to its antioxidant and antiapoptotic effects, and the suppression of ER stress, melatonin induces a decrease in autophagy associated with RHDV infection and inhibits RHDV RNA replication. Results obtained reveal novel molecular pathways accounting for the protective effect of melatonin in this animal model of ALF.

Autophagic response in the Rabbit Hemorrhagic Disease, an animal model of virally-induced fulminant hepatic failure

The Rabbit Hemorrhagic Disease Virus (RHDV) induces a severe disease that fulfils many requirements of an animal model of fulminant hepatic failure. However, a better knowledge of molecular mechanisms contributing to liver damage is required, and it is unknown whether the RHDV induces liver autophagy and how it relates to apoptosis. In this study, we attempted to explore which signalling pathways were involved in the autophagic response induced by the RHDV and to characterize their role in the context of RHDV pathogenesis. Rabbits were infected with 2 × 10⁴ hemmaglutination units of a RHDV isolate. The autophagic response was measured as presence of autophagic vesicles, LC3 staining, conversion of LC3-I to autophagosome-associated LC3-II and changes in expression of beclin-1, UVRAG, Atg5, Atg12, Atg16L1 and p62/SQSTM1. RHDV-triggered autophagy reached a maximum at 24 hours post-infection (hpi) and declined at 30 and 36 hpi. Phosphorylation of mTOR also augmented in early periods of infection and there was an increase in the expression of the endoplasmic reticulum chaperones BiP/GRP78, CHOP and GRP94. Apoptosis, measured as caspase-3 activity and expression of PARP-1, increased significantly at 30 and 36 hpi in parallel to the maximal expression of the RHDV capsid protein VP60. These data indicate that RHDV infection initiates a rapid autophagic response, perhaps in an attempt to protect liver, which associates to ER stress development and is independent from downregulation of the major autophagy suppressor mTOR. As the infection continues and the autophagic response declines, cells begin to exhibit apoptosis.

Melatonin treatment reduces endoplasmic reticulum stress and modulates the unfolded protein response in rabbits with lethal fulminant hepatitis of viral origin

Hepatocyte apoptosis plays an important role in the development of fulminant hepatic failure (FHF). The objective of this study was to investigate whether endoplasmic reticulum (ER) stress and unfolded protein response (UPR) inhibition is an underlying mechanism of melatonin anti-apoptotic effects in an animal model of FHF of viral origin induced by the rabbit hemorrhagic disease virus (RHDV). Rabbits were experimentally infected with 2 × 10(4) hemagglutination units of a RHDV isolate and received melatonin at two concentrations of 10 mg/kg and 20 mg/kg at 0 hr, 12 hr and 24 hr postinfection. RHDV infection induced increased expression of CCAAT/enhancer-binding protein homologous protein (CHOP), immunoglobulin heavy chain binding protein (BiP/GRP78), glucose-regulated protein 94 (GRP94), phospho-c-Jun N-terminal kinase (JNK) and caspase-12. These effects were attenuated by melatonin. Double immunofluorescence staining showed colocalization of CHOP and cleaved caspase-3 in liver sections of RHDV-infected rabbits, while immunostaining decreased markedly with melatonin treatment. RHDV infection resulted in significant increases in the mRNA levels of activating transcription factor 6 (ATF6), ATF4, inositol-requiring enzyme 1 (IRE1), spliced X-box binding protein-1 (XBP1s) and tumor necrosis factor receptor-associated factor 2 (TRAF2). Melatonin attenuated the extent of the changes. Data obtained provide evidence that in rabbits with experimental infection by RHDV, reduction in apoptotic liver damage by melatonin is associated with attenuation of ER stress through a modulation of the three arms of UPR signaling and further support a potential hepatoprotective role of melatonin in FHF.

Glutamine treatment attenuates endoplasmic reticulum stress and apoptosis in TNBS-induced colitis

Endoplasmic reticulum (ER) stress and apoptotic cell death play an important role in the pathogenesis and perpetuation of inflammatory bowel disease (IBD). We aimed to explore the potential of glutamine to reduce ER stress and apoptosis in a rat model of experimental IBD. Colitis was induced in male Wistar rats by intracolonic administration of 30 mg of 2,4,6-trinitrobenzene sulfonic acid (TNBS). Glutamine (25 mg/dL) was given by rectal route daily for 2 d or 7 d. Both oxidative stress (TBARS concentration and oxidised/reduced glutathione ratio) and ER stress markers (CHOP, BiP, calpain-1 and caspase-12 expression) increased significantly within 48 h of TNBS instillation, and glutamine attenuated the extent of the changes. Glutamine also inhibited the significant increases of ATF6, ATF4 and spliced XBP-1 mRNA levels induced by TNBS instillation. TNBS-colitis resulted in a significant increase in p53 and cytochrome c expression, and a reduced Bcl-xL expression and Bax/Bcl-2 ratio. These effects were significantly inhibited by glutamine. Treatment with the amino acid also resulted in significant decreases of caspase-9, caspase-8 and caspase-3 activities. Double immunofluorescence staining showed co-localization of CHOP and cleaved caspase-3 in colon sections. Phospho-JNK and PARP-1 expression was also significantly higher in TNBS-treated rats, and treatment with glutamine significantly decreased JNK phosphorylation and PARP-1 proteolysis. To directly address the effect of glutamine on ER stress and apoptosis in epithelial cells, the ER stress inducers brefeldin A and tunicamycin were added to Caco-2 cells that were treated with glutamine (5 mM and 10 mM). The significant enhancement in PERK, ATF6 phosphorylated IRE1, BiP and cleaved caspase-3 expression induced by brefeldin A and tunicamycin was partly prevented by glutamine. Data obtained indicated that modulation of ER stress signalling and anti-apoptotic effects contribute to protection by glutamine against damage in TNBS-induced colitis.

17beta-estradiol mediated protection against vascular leak after hemorrhagic shock: role of estrogen receptors and apoptotic signaling

Vascular hyperpermeability is a clinical complication associated with hemorrhagic shock (HS) and occurs mainly because of the disruption of the adherens junctional complex. The objective of this study was to understand the role of 17beta-estradiol in HS-induced hyperpermeability particularly focusing on estrogen receptors. In male Sprague-Dawley rats, HS was induced by withdrawing blood to reduce the mean arterial pressure to 40 mmHg for 1 hour followed by 1 hour of resuscitation to 90 mmHg. The study groups were 17beta-estradiol, tamoxifen, fulvestrant plus 17beta-estradiol, propyl pyrazole triol plus 17beta-estradiol, and diarylpropionitrile plus 17beta-estradiol. Intravital microscopy was used to study changes in mesenteric postcapillary venules. Mitochondrial reactive oxygen species formation was studied in vivo using dihydrorhodamine 123. The mitochondrial transmembrane potential was studied using the fluorescent cationic probe 5,5',6,6'tetrachloro-1,1',3,3'tetraethylbenzimidazolyl carbocyanine iodide (JC-1). The mesenteric microvasculature was analyzed for cytochrome c levels by enzyme-linked immunosorbent assay and caspase-3 activity by a fluorometric assay. Our results demonstrated that 17beta-estradiol attenuated HS-induced hyperpermeability. Fulvestrant reversed this protective effect (P < 0.05). Tamoxifen 5 mg/kg attenuated HS-induced hyperpermeability, whereas 10 mg/kg induced permeability (P < 0.05). Both alpha and beta estrogen receptor agonists inhibited HS-induced hyperpermeability (P < 0.05). 17beta-Estradiol decreased HS-induced reactive oxygen species formation and restored mitochondrial transmembrane potential. 17beta-Estradiol decreased both cytosolic cytochrome c level and activation of caspase-3 (P < 0.05). These findings suggest that 17beta-estradiol protects the microvasculature after HS, and that this protection may be mediated through the alpha and beta estrogen receptors.

Melatonin attenuates apoptotic liver damage in fulminant hepatic failure induced by the rabbit hemorrhagic disease virus

Hepatocyte apoptosis plays an important role in the development of fulminant hepatic failure (FHF). The objective of this study was to investigate the antiapoptotic effect of melatonin in an animal model of FHF of viral origin induced by the rabbit hemorrhagic disease virus (RHDV). Rabbits were experimentally infected with 2 × 10(4) hemagglutination units of a RHDV isolate and received melatonin at two concentrations of 10 and 20 mg/kg at 0, 12, and 24 hr postinfection. RHDV infection induced liver apoptosis, with increased caspase-3 immunoexpression and activity and poly(ADP-ribose)polymerase-1 (PARP-1) proteolysis. These effects were attenuated by melatonin in a concentration-dependent manner. Antiapoptotic effects of melatonin were related to a reduced expression of Bax and cytosolic cytochrome c release, increased expression of Bcl-2 and Bcl-xL, and inhibition of caspase-9 activity. Increased thiobarbituric reactive acid substances concentration and oxidized-to-reduced glutathione ratio were significantly prevented by melatonin administration. Melatonin treatment also resulted in a reduction in caspase-8 activity, tumor necrosis factor receptor-1 (TNF-R1) expression, and phosphorylated Janus kinase (JNK) expression, and increased expression of cellular FLICE-inhibitory protein (c-FLIP). Our findings show that inhibition of apoptotic mechanisms contributes to the beneficial effects of melatonin in rabbits with experimental infection by RHDV and supports a potential hepatoprotective role of melatonin in FHF.

(-)-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.

Cyclosporine A prevents vascular hyperpermeability after hemorrhagic shock by inhibiting apoptotic signaling

BACKGROUND

Hemorrhagic shock (HS) is associated with the activation of caspase-dependent or -independent apoptotic signaling pathways, disruption of endothelial cell adherens junctions, and vascular hyperpermeability. Recent studies have suggested that the vascular hyperpermeability observed after HS is associated with activation of the intrinsic apoptotic signaling cascade resulting in caspase-mediated cleavage of endothelial cell adherens proteins and subsequent cell-cell detachment. We hypothesized that cyclosporine A (CsA) would attenuate vascular hyperpermeability after HS by protecting mitochondrial transition pores and thereby preventing the activation of caspase-mediated apoptotic signaling. The objective of this study was to determine the effect of CsA on, HS-induced hyperpermeability, mitochondrial membrane depolarization, mitochondrial release of cytochrome c, and caspase 3 activation.

METHODS

HS was induced in Sprague-Dawley rats by withdrawing blood to reduce the mean arterial pressure to 40 mm Hg for 60 minutes. CsA (10 microL/mL) was given 10 minutes before the shock period. The mesenteric postcapillary venules of the proximal ileum were monitored for permeability changes using intravital microscopy. The changes in mitochondrial transmembrane potential were determined using the cationic dye JC-1. Mitochondrial release of cytochrome c in to the cytosol was detected using ELISA. Caspase-3 activity was measured using a fluorometric assay.

RESULTS

HS induced vascular hyperpermeability, release of cytochrome c, and activation of caspase-3 (p < 0.05). CsA (10 microL/mL) attenuated HS-induced hyperpermeability (p < 0.05) and prevented HS-induced decrease in mitochondrial transmembrane potential. CsA treatment decreased the HS-induced rise in cytosolic cytochrome c levels and caspase-3 activity (p < 0.05).

CONCLUSIONS

These findings demonstrate that CsA protects mitochondrial permeability transition pores to prevent HS-induced release of cytochrome c and caspase-3 activation.

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.

When apoptosis meets autophagy: deciding cell fate after trauma and sepsis

Apoptotic cell death is considered to be an underlying mechanism in immunosuppression and multiple organ dysfunction after trauma-hemorrhage and sepsis. Although studied intensively over the last decade, the role of other cell death mechanisms under similar pathophysiological conditions has remained elusive. Recently, autophagy has emerged as an important mediator of programmed cell death pathways. Here, we review recent advances in our understanding of apoptosis and autophagy and the crosstalk between these processes. We explore the coexistence of these two processes and the effects of autophagy on apoptosis after trauma-hemorrhage and sepsis. The inter-relationship between autophagy and apoptosis might unveil novel therapeutic approaches for the detection and treatment of trauma-hemorrhage and sepsis.

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.

High-fat nutrition reduces hepatic damage following exposure to bacterial DNA and hemorrhagic shock

BACKGROUND/AIMS

Bacterial infection combined with hypotension results in exacerbation of the inflammatory response with release of interferon (IFN) gamma. This excessive inflammation may lead to development of hepatic damage and liver failure. This study investigates the effect of dietary lipids on release of IFN-gamma and development of hepatic damage following exposure to synthetic bacterial DNA (CpG-ODN) and hemorrhagic shock.

METHODS

Rats were exposed to CpG-ODN 18h before hemorrhagic shock. Samples were taken 4h following shock. High-fat nutrition was administered at 18h, 2h and 45min before induction of shock.

RESULTS

Enteral high-fat strongly reduced circulating IFN-gamma (0.2ng/ml, P<0.01) following exposure to CpG-ODN and hemorrhagic shock compared with fasted rats (2.7ng/ml). Concomitantly, plasma L-FABP was reduced (437+/-22ng/ml, P<0.01), and F-actin distribution was preserved. Furthermore, high-fat nutrition reduced apoptosis in the liver and preserved expression of the hepatoprotective protein ABIN-1. Interestingly, administration of anti-IFN-gamma antibodies was associated with reduced expression of ABIN-1.

CONCLUSIONS

This study shows that enteral high-fat reduces IFN-gamma and decreases CpG-enhanced liver injury following hemorrhagic shock. Administration of high-fat nutrition may be an important new therapeutic strategy to reduce liver damage in a clinical setting of bacterial infection combined with hypotension.

Apoptosis and haemorrhagic shock

Abstract

This is a review paper that provides an overview of current information on programmed cell death in haemorrhagic shock, including the identification of different molecular receptor signals. A PubMed search for all dates was undertaken using the search terms apoptosis, trauma and haemorrhagic shock. Original research, sentinel and review papers from peer-reviewed journals were included for identification of key concepts. Haemorrhagic shock remains a primary cause of death in civilian and military trauma. Apoptosis is accelerated following haemorrhagic shock. Many methods are used to detect and quantify apoptosis. Fluid resuscitation regimens vary in their effect on the extent of apoptosis. Investigators are examining the effects of haemorrhagic shock and fluid resuscitation on apoptotic signalling pathways. Molecular information is becoming available and being applied to the care of patients experiencing haemorrhagic shock, making it essential for nurses and other health care providers to consider the mechanisms and consequences of apoptosis.

Trauma-hemorrhagic shock-induced pulmonary epithelial and endothelial cell injury utilizes different programmed cell death signaling pathways

Intestinal ischemia after trauma-hemorrhagic shock (T/HS) results in gut barrier dysfunction and the production/release of biologically active and tissue injurious factors in the mesenteric lymph, which, in turn, causes acute lung injury and a systemic inflammatory state. Since T/HS-induced lung injury is associated with pulmonary endothelial and epithelial cell programmed cell death (PCD) and was abrogated by mesenteric lymph duct ligation, we sought to investigate the cellular pathways involved. Compared with trauma-sham shock (T/SS) rats, a significant increase in caspase-3 and M30 expression was detected in the pulmonary epithelial cells undergoing PCD, whereas apoptosis-inducing factor (AIF), but not caspase-3, was detected in endothelial cells undergoing PCD. This AIF-mediated pulmonary endothelial PCD response was validated in an in situ femoral vein assay where endothelial cells were found to express AIF but not caspase-3. To complement these studies, human umbilical vein endothelial cell (HUVEC), human lung microvascular endothelial cell (HLMEC), and human alveolar type II epithelial cell (A549) lines were used as in vitro models. T/HS lymph induced the nuclear translocation of AIF in HUVEC and HLMEC, and caspase inhibition in these cells did not afford any cytoprotection. For proof of principle, AIF silencing in HUVEC reversed the cytotoxic effects of T/HS on cell viability and DNA fragmentation. In A549 cells, T/HS lymph activated caspase-3-mediated apoptosis, which was partially abrogated by N-benzyloxycarbonyl-Val-Ala-Asp (zVAD). Additionally, T/HS lymph did not cause the nuclear translocation of AIF in A549 cells. Collectively, T/HS-induced pulmonary endothelial PCD occurs via an AIF-dependent caspase-independent pathway, whereas epithelial cells undergo apoptosis by a caspase-dependent pathway.

Sesame oil does not show accumulatively enhanced protection against oxidative stress-associated hepatic injury in septic rats

BACKGROUND

Sepsis is one of the major causes of death reported in intensive care units. A daily supplement of sesame oil for 1 week significantly attenuates oxidative stress-associated hepatic injury in septic rats. However, the excess intake of sesame oil may be associated with a health risk. This study investigates the effect of accumulative sesame oil on oxidative stress-associated hepatic injury after cecal ligation and puncture in rats.

METHODS

Sesame oil was administered daily (4 mL/kg/d, orally) to rats, and the total intake of sesame oil ranged from 0 (control) to 140 mL/kg before cecal ligation and puncture in 9 groups of rats. Oxidative stress was examined by determining the levels of lipid peroxidation and glutathione. Hepatic injury was evaluated by measuring serum levels of aspartate aminotransferase and alkaline phosphatase.

RESULTS

Rats that received sesame oil for 4 and 5 weeks had a lower body weight gain compared with those that received saline. Lipid peroxidation was decreased in the 20-mL/kg and 28-mL/kg groups, but it was increased in the 140-mL/kg group compared with the control group. Glutathione levels were increased in the < or =28-mL/kg groups compared with the control group. Serum levels of aspartate aminotransferase and alkaline phosphatase were reduced in the < or =28-mL/kg groups compared with the control group.

CONCLUSION

Sesame oil does not demonstrate accumulatively enhanced protection against oxidative stress-associated hepatic injury after cecal ligation and puncture in rats.

Effects of dimethyl sulfoxide, pyrrolidine dithiocarbamate, and methylprednisolone on nuclear factor-kappaB and heat shock protein 70 in a rat model of hemorrhagic shock

BACKGROUND

Nuclear factor kappa B (NF-kappaB) is a transcription factor involved in the inflammatory response. Heat shock protein 70 (HSP70) is involved in the cell protection from various stresses. The aim of this study was to evaluate the effects of dimethyl sulfoxide (DMSO), pyrrolidine dithiocarbamate (PDTC), and methylprednisolone (MP) on liver, renal, and intestinal activation of NF-kappaB and HSP70 in a rat model of hemorrhagic shock (HS).

METHODS

Sixty rats were randomized in 6 groups: sham-operated; only HS; HS and resuscitation with blood plus normal saline (NS); HS and resuscitation with blood/NS and 6 mg/kg DMSO; HS and resuscitation with blood/NS and 100 mg/kg PDTC; HS and resuscitation with blood/NS and 30 mg/kg MP. Rats were subjected to HS by blood removal to a mean arterial pressure of 35 to 40 mm Hg through the femoral artery. After 1-hour shock-period, the animals were resuscitated according to the experimental protocol. NF-kappaB and HSP70 expression in liver, kidney, and small intestine was analyzed 1 and 3 hours after resuscitation by immunohistochemistry.

RESULTS

HS upregulated NF-kappaB activation and HSP70 expression (p < 0.05). Resuscitation was not associated with a further increase in NF-kappaB and HSP70 activation. DMSO, PDTC, and MP administration resulted in a decreased liver, renal, and intestinal activation of NF-kappaB associated with an increase of HSP70 expression (p < 0.05).

CONCLUSIONS

Our results suggest that treatment with DMSO, PDTC, and MP can modulate the expression of NF-kappaB and HSP70 after HS in rats. This modulation may have potential effects in HS through inhibition of the NF-kappaB-dependent production of proinflammatory mediators.

Effect of caspase inhibition on thymic apoptosis in hemorrhagic shock

In hemorrhagic shock (HS) an increased thymic apoptosis (TA) was described. The aim of this study was to evaluate the effect of administration of the caspase inhibitor N-benzyloxy-carbonil-Val-Ala-Asp-fluoromethylketone (Z-VAD-FMK) during the resuscitation phase on TA, organ dysfunctions, and tumor necrosis factor (TNF)-alpha release in HS. Forty rats were randomly assigned to four groups: no HS/resuscitation (sham); HS/resuscitation with shed blood and normal saline (control); HS/resuscitation with shed blood and phosphate-buffered solution (PBS) (vehicle); and HS/resuscitation with shed blood and Z-VAD-FMK (inhibitor). Rats were subjected to HS by blood removal to a MAP of 35-40 mmHg. After a 1-h shock period, the animals were resuscitated according to the protocol. At 1 and 3 h after resuscitation, transaminases, creatinine, urea, lipase, TNF-alpha, and TA were evaluated. Our study showed that a nonlethal HS is early able to induce organ dysfunctions and increased TA. Administration of Z-VAD-FMK did not significantly decrease organ dysfunctions, while it induced a significant TNF-alpha release. TA was significantly reduced by Z-VAD-FMK after 1 h, but not after 3 h. Our results suggest that postinjury caspase inhibition does not attenuate organ dysfunctions, and also does not permanently reduce TA induced by HS and resuscitation in rats.

N-acetyl-cysteine protects liver from apoptotic death in an animal model of fulminant hepatic failure

BACKGROUND

This work was undertaken to investigate whether treatment with N-acetyl-cysteine (NAC) prevents oxidative stress and inhibits the apoptotic pathways in an animal model of fulminant hepatic failure.

METHODS

Rabbits were experimentally infected with 2x10(4) hemagglutination units of a rabbit hemorrhagic disease virus isolate.

RESULTS

The spontaneous mortality rate of infected animals was 67% at 36 h post infection (pi) and 90% at 48 h pi. This percentage decreased significantly in animals receiving an i.p. injection of NAC (150 mg/kg body way/daily), for 7 days prior to infection. From 36 h pi marked increases were detected in blood levels of transaminases, lactate dehydrogenase, bilirubin and the oxidised/reduced glutathione ratio. All these effects were significantly prevented by NAC treatment. The Bax to Bcl-2 relative expression, the expression of FasL, cytochrome c and PARP-1, and the activity of caspase 3 were significantly increased at 36 and 48 h pi in infected animals. These changes were markedly reduced in animals treated with NAC, with the exception of FasL.

CONCLUSION

Our results suggest a potential hepatoprotective role of NAC in fulminant hepatic failure, mediated partially through the modulation of the intrinsic pathway of apoptosis.

Geldanamycin inhibits hemorrhage-induced increases in caspase-3 activity: role of inducible nitric oxide synthase

Hemorrhage has been shown to increase inducible nitric oxide synthase (iNOS) and deplete ATP levels in tissues and geldanamycin limits both processes. Moreover, it is evident that inhibition of iNOS reduces caspase-3 and increases survival. Thus we sought to identify the molecular events responsible for the beneficial effect of geldanamycin. Hemorrhage in mice significantly increased caspase-3 activity and protein while treatment with geldanamycin significantly limited these increases. Similarly, geldanamycin inhibited increases in proteins forming the apoptosome (a complex of caspase-9, cytochrome c, and Apaf-1). Modulation of the expression of iNOS by iNOS gene transfection or siRNA treatment demonstrated that the level of iNOS correlates with caspase-3 activity. Our data indicate that geldanamycin limits caspase-3 expression and protects from organ injury by suppressing iNOS expression and apoptosome formation. Geldanamycin, therefore, may prove useful as an adjuvant in fluids used to treat patients suffering blood loss.

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.

Androstenediol inhibits the trauma-hemorrhage-induced increase in caspase-3 by downregulating the inducible nitric oxide synthase pathway

Soft tissue trauma and hemorrhage (T-H) diminishes various aspects of liver function, while it increases hepatic nitrate/nitrite, inducible nitric oxide synthase (iNOS), and endothelin-1 levels. Treatment with androstenediol (AED) inhibits the T-H-induced alterations of the above parameters. We sought to identify the molecular events underlying the beneficial effect of AED. Exposure of rats to T-H significantly increased the caspase-3 activity and protein, whereas treatment with AED significantly limited these increases. AED treatment also suppressed the T-H-induced increase in iNOS by effectively altering the levels of key transcription factors involved in the regulation of iNOS expression. Immunoprecipitation and immunoblotting analyses indicate that T-H increased apoptosome formation, and AED treatment significantly decreased it. Modulating the iNOS protein by transfecting cells with iNOS gene or small interfering RNA further confirmed the correlation between iNOS and caspase-3. Our data indicate that AED limits caspase-3 expression by suppressing the expression of transcription factors involved in the production of iNOS, resulting in decreased apoptosome. AED can potentially be a useful adjuvant for limiting liver apoptosis following T-H shock.

Resuscitation with lactated Ringer solution limits the expression of molecular events associated with lung injury after hemorrhage

The aim of this study was to determine whether hemorrhage altered the caspase-3 activity and the ATP levels in rat lung and ileum tissues and determine whether resuscitation with lactated Ringer solution (LR) or whole blood (WB) reversed these changes. Male Sprague-Dawley rats were briefly anesthetized with isoflurane, and their mean arterial blood pressure was reduced from 110 to 40 mmHg by bleeding. The bled rat was then resuscitated with LR or autologous WB to bring mean arterial blood pressure back to 80 mmHg. Lung and ileum tissues were removed at the end of hemorrhage or at the end of the resuscitation period for specified bioassays. Hemorrhage increased cellular caspase-3 activity in the lung and the ileum. After the hemorrhaged rats received LR or WB, caspase-3 activity returned to the basal level in the lung and ileum, respectively. Likewise, hemorrhage decreased cellular ATP levels in lung and ileum. After LR or WB resuscitation, the cellular ATP level returned to the basal level only in the lung resuscitated with LR. The increased caspase-3 activity was associated with the increased expression of caspase-3 mRNA, which also returned to normal levels after either resuscitation. Similarly, hemorrhage increased the expression of inducible nitric oxide synthase and Kruppel-like factor 6 and decreased expression of Kruppel-like factor 4. Subsequent LR resuscitation normalized the expression of these genes in the lung tissue. Our results demonstrate that resuscitation with LR can reverse the expression of genes and their products that are thought to contribute to hemorrhage-induced lung injury.

ERYTHROPOIETIN ATTENUATES THE TISSUE INJURY ASSOCIATED WITH HEMORRHAGIC SHOCK AND MYOCARDIAL ISCHEMIA

Here we investigate the effects of erythropoietin (EPO) on the tissue/organ injury caused by hemorrhagic shock (HS), endotoxic shock, and regional myocardial ischemia and reperfusion in anesthetized rats. Male Wistar rats were anesthetized with thiopental sodium (85 mg/kg i.p.) and subjected to hemorrhagic shock (HS; i.e., mean arterial blood pressure reduced to 45 mmHg for 90 min, followed by resuscitation with shed blood for 4 h), endotoxemia (for 6 h), or left anterior descending coronary artery occlusion (25 min) and reperfusion (2 h). HS and endotoxemia resulted in renal dysfunction and liver injury. Administration of EPO (300 IU/kg i.v., n = 10) before resuscitation abolished the renal dysfunction and liver injury in hemorrhagic, but not endotoxic, shock. HS also resulted in significant increases in the kidney of the activities of caspases 3, 8, and 9. This increase in caspase activity was not seen in HS rats treated with EPO. In cultured human proximal tubule cells, EPO concentration-dependently reduced the cell death and increase in caspase-3 activity caused by either ATP depletion (simulated ischemia) or hydrogen peroxide (oxidative stress). In the heart, administration of EPO (300 IU/kg i.v., n = 10) before reperfusion also caused a significant reduction in infarct size. In cultured rat cardiac myoblasts (H9C2 cells), EPO also reduced the increase in DNA fragmentation caused by either serum deprivation (simulated ischemia) or hydrogen peroxide (oxidative stress). We propose that the acute administration of EPO on reperfusion and/or resuscitation will reduce the tissue injury caused by ischemia-reperfusion of the heart (and other organs) and hemorrhagic shock.

CALPAIN INHIBITORS IMPROVE MYOCARDIAL DYSFUNCTION AND INFLAMMATION INDUCED BY ENDOTOXIN IN RATS

Excessive activation of calpains has been implicated in the pathophysiology of inflammation, trauma, and ischemia reperfusion injury. Here, we investigated the effects of calpain inhibition on myocardial dysfunction and inflammation induced by endotoxin in rats. Rats were treated i.v. with endotoxin (10 mg/kg) or endotoxin plus calpain inhibitors and were then prepared after 4 h for myocardial contractility assessment, detection of endothelium leukocyte interactions, and plasma TNF-alpha, nitrite/nitrate, and endocan levels. Compared with vehicle-treated rats, hearts from endotoxin-treated rats had reduced systolic performance that was partially prevented by calpain inhibitors, i.e., acetyl-leucyl-leucyl-arginal (leupeptin), carbobenzoxy-valyl-phenylalanial (calpain inhibitor III), and N-acetyl-leucinyl-leucinyl-norleucinal (ALLN). Leupeptin and calpain inhibitor III reduced plasma TNF-alpha levels in endotoxin-treated rats. ALLN reduced plasma TNF-alpha and nitrite/nitrate levels in endotoxin-treated rats. Endotoxin treatment increased mesenteric venule leukocyte rolling (10 +/- 3 leukocytes/min vs. 44 +/- 10 leukocytes/min; P < 0.01) and adhesion (2 +/- 2 leukocytes/min vs. 15 +/- 3 leukocytes/min; P < 0.01), which was reduced by calpain inhibitors. Attenuation of leukocyte endothelium interactions observed in calpain inhibitor-treated rats with sepsis was associated with increases in plasma anti-adhesion molecule endocan. In conclusion, calpain inhibitors improved endotoxin-induced cardiac dysfunction, which may be attributed to the modulation of endothelium leukocyte interactions in the inflamed vasculature.