Recovery of hepatocellular ATP and "pericentral apoptosis" after hemorrhage and resuscitation

PGC-1 upregulation via estrogen receptors: a common mechanism of salutary effects of estrogen and flutamide on heart function after trauma-hemorrhage

Flutamide, an androgen receptor antagonist, is thought to improve cardiovascular function by blocking the androgen receptor after trauma-hemorrhage (T-H). Although 17β-estradiol (E2) and flutamide improve cardiac function after T-H, whether E2 and flutamide produce their salutary effect via the same or a different mechanism is unknown. We hypothesized that E2 and flutamide mediate their effects via estrogen receptor (ER)-mediated upregulation of peroxisome proliferator-activated receptor coactivator 1 (PGC-1). PGC-1, a key regulator of cardiac mitochondrial function, induces mitochondrial genes by activating transcription factors such as nuclear respiratory factor 2 (NRF-2), which regulates mitochondrial proteins [i.e., mitochondrial transcription factor A (Tfam), cytochrome- c oxidase subunit IV, and β-ATP synthase]. Adult male rats underwent T-H [5-cm midline incision and hemorrhage (blood pressure = 40 mmHg for ∼90 min)] and resuscitation. At the onset of resuscitation, rats received vehicle, flutamide (25 mg/kg), or E2 (50 μg/kg). Another group received the ER antagonist ICI-182780 (3 mg/kg) with or without flutamide. Flutamide or E2 administration after T-H restored depressed cardiac function. Moreover, E2 and flutamide normalized expression of cardiac PGC-1, NRF-2, Tfam, cytochrome- c oxidase subunit IV, and the mitochondrial DNA-encoded gene cytochrome- c oxidase subunit I and β-ATP synthase, mitochondrial ATP, and cytochrome- c oxidase activity. However, if the ER antagonist ICI-182780 was administered with flutamide, flutamide-mediated PGC-1 upregulation was totally abolished. These results indicate that E2 and flutamide upregulate PGC-1 via the ER. Thus PGC-1 upregulation appears to be the common mechanism by which E2 and flutamide mediate their salutary effects on cardiac function after T-H.

Hepatic apoptosis after hemorrhagic shock in rats can be reduced through modifications of conventional Ringer's solution

BACKGROUND

Resuscitation with racemic lactated Ringer's solution induces cellular apoptosis. This study was conducted to determine if the elimination of D-lactate isomer would attenuate apoptosis in the liver, and to investigate the possible mechanisms.

STUDY DESIGN

Sprague Dawley rats (n=30, 5 per group) were subjected to modified volume-controlled hemorrhage and randomized to the following groups: no hemorrhage (sham); no resuscitation (NR); resuscitation with racemic lactated Ringer's (DL-LR); L-isomer LR (L-LR); ketone (beta-hydroxybuturate) Ringer's (KR); or pyruvate Ringer's (PR). Animals were sacrificed 2 hours later and expressions of proapoptotic proteins (BAD), antiapoptotic (bcl-2) proteins, and poly-ADP ribose polymerase (PARP) cleavage in liver were analyzed by Western blotting. Contribution of the phosphatidylinositol 3-kinase/serine/threonine kinase (PI3k/Akt) pathway was assessed by measuring total and phosphorylated PI3K, Akt, BAD, and endothelial nitric oxide synthase (eNOS) proteins. The terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) assay was used to detect the apoptotic cells. Liver ATP levels were measured using a luciferase reaction assay.

RESULTS

Hemorrhage significantly decreased the hepatic ATP level and resuscitation improved it, but it returned to normal only in the L-isomer lactated Ringer's and ketone Ringer's groups. Expression of proapoptotic proteins was significantly lower in the pyruvate Ringer's and ketone Ringer's groups; L-isomer lactated Ringer's and pyruvate Ringer's resuscitation significantly increased bcl-2 expression. Poly-ADP ribose polymerase fragmentation and total number of apoptotic cells were significantly increased in the racemic lactated Ringer's group. There was no significant induction of Akt activity or changes in phosphorylated BAD, Akt, or eNOS levels.

CONCLUSIONS

Resuscitation with racemic lactated Ringer's induces hepatic apoptosis, which is decreased if the D-isomer of lactate is eliminated. Apoptosis is reduced even more when lactate is substituted with beta-hydroxybutyrate or pyruvate. The beneficial effects are not through improvements in the energy status or activation of the PI3K/Akt pathway.

Inhibition of matrix metalloproteinase on hepatic transforming growth factor beta1 and caspase-3 activation in hemorrhage

OBJECTIVES

Hemorrhage initiates an inflammatory response that induces the systemic release of cytokines and sequestration of polymorphonuclear neutrophils. Sequestered polymorphonuclear neutrophils release proteases, including matrix metalloproteinases (MMPs) that degrade elements of the extracellular matrix, contributing to the morbidity and mortality seen from hemorrhage. Activation of MMPs may be associated with changes in transforming growth factor beta1 (TGF-beta1) and caspase-3 signaling pathways. In this study, the authors examined hemorrhage-induced changes in the expression of rat hepatic MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-l), TGF-beta1, and caspase-3 activities in the presence and absence of the MMP inhibitor hydroxamate.

METHODS

Hemorrhagic shock was induced in fasted, anesthetized, and cannulated rats by rapid phlebotomy to a mean arterial pressure level of 40 mm Hg, maintained for 90 minutes by withdrawal and infusion of blood, followed by a resuscitation period of lactated Ringer's infusion. Rats received either hydroxamate (25 mg/kg) or vehicle by gavage before hemorrhage. Twenty-four hours after resuscitation, plasma and liver samples were collected. Liver MMP-9, TGF-beta1, and caspase-3 levels were quantified by Western immunoblotting. Plasma glutamic oxaloacetic transaminase (GOT) and plasma glutamic pyruvic transaminase (GPT) were determined enzymatically.

RESULTS

Plasma GOT, plasma GPT, and liver MMP-9, TGF-beta1, and caspase-3 levels were all significantly elevated at 24 hours postresuscitation when compared with the control values. Hepatic TIMP-1, an in vivo inhibitor of MMP-9, was unaltered at 24 hours. Hydroxamate treatment reduced GOT, GPT, MMP-9, TGF-beta1, and caspase-3 levels at 24 hours. The mortality of hemorrhaged untreated rats was 29% after 24 hours, and pretreatment with hydroxamate reduced mortality to 0%.

CONCLUSIONS

These results indicate the beneficial effects of MMP inhibitor in preventing an increase in GOT, GPT, MMP-9, TGF-beta1, and caspase-3 activity with the potential for improvement of hepatic injury due to hemorrhage.

Inducible heat shock protein 70 kD and inducible nitric oxide synthase in hemorrhage/resuscitation-induced injury

Inducible head shock protein 70 kD (HSP-70i) has been shown to protect cells, tissues, and organs from harmful assaults in vivo and in vitro experimental models. Hemorrhagic shock followed by resuscitation is the principal cause of death among trauma patients and soldiers in the battlefield. Although the underlying mechanisms are still not fully understood, it has been shown that nitric oxide (NO) overproduction and inducible nitric oxide synthase (iNOS) overexpression play important roles in producing injury caused by hemorrhagic shock including increases in polymorphonuclear neutrophils (PMN) infiltration to injured tissues and leukotriene B(4) (LTB(4)) generation. Moreover, transcription factors responsible for iNOS expression are also altered by hemorrhage and resuscitation. It has been evident that either up-regulation of HSP-70i or down-regulation of iNOS can limit tissue injury caused by ischemia/reperfusion or hemorrhage/resuscitation. In our laboratory, geldanamycin, a member of ansamycin family, has been shown to induce HSP- 70i overexpression and then subsequently to inhibit iNOS expression, to reduce cellular caspase-3 activity, and to preserve cellular ATP levels. HSP-70i is found to couple to iNOS and its transcription factor. Therefore, the complex formation between HSP-70i and iNOS may be a novel mechanism for protection from hemorrhage/resuscitation-induced injury.

Liver failure

PURPOSE OF REVIEW

Liver failure is a rare but life-threatening condition affecting a multitude of other organ systems, most notably the brain and kidneys, following severe hepatocellular injury. Liver failure may develop in the absence ('acute') or presence ('acute-on-chronic') of liver disease with substantial differences in pathophysiology and therapeutic options. Within the last 12 months substantial progress has been made in identifying patients who will potentially benefit from extracorporeal support of their failing liver.

RECENT FINDINGS

In addition to traditional 'static' laboratory tests to assess liver function, the significance of 'dynamic' tests, such as indocyanine green clearance, has been better defined, and these tests are becoming more easily available. Transplantation remains the treatment of choice for fulminant, acute and subacute liver failure with predicted unfavorable outcome according to King's College or Clichy criteria, most notably in the absence of pre-existing liver disease, and should be performed before extrahepatic complications emerge. Encouraging results have been obtained with the use of support systems in patients with acute and acute-on-chronic liver failure in relatively small patient collectives, making well-conducted randomized trials a necessity to define their role in this high-risk population. Current (pre)clinical data suggest that programmed cell death is an important mechanism for the pathogenesis of acute and acute-on-chronic liver failure and, thus, antiapoptotic strategies are promising pharmacologically.

SUMMARY

Although mortality remains high, substantial progress has been made in 2004 regarding the understanding of pathophysiology, and the monitoring and support of the patient presenting with a failing liver.

The role of the mitochondrion in trauma and shock

The mitochondrion of the eukaryotic cell is well known as a "power plant" whose energy is made available via the high-energy phosphate bonds of ATP. This indispensable and superbly adapted organelle appears to have originated as an endosymbiotic bacterium rather than as a eukaryotic creation per se. However, under the dangerous conditions of trauma and shock, the mitochondrion can become destabilized and harm its host cell in a variety of ways. These contrary traits may be, in part, vestiges from the bacterial origins of mitochondria. The mitochondrion can respond to the stress of trauma and shock by opening pores that leak contents into the host cell's cytoplasm, an event that can trigger programmed cell death or necrosis. In addition, the enormous oxygen consumption by mitochondria presents a two-edged sword in that a deranged mitochondrion can produce reactive oxygen species that damage genes and gene products, inflicting considerable harm to the mitochondrion and its host cell. However, although trauma and shock can cause the mitochondrion to wreak havoc in many ways, an adjuvant intervention with exogenous ATP-MgCl2 after trauma and shock appears useful for reducing cell and organ damage under those conditions.

Insights into the role of interleukin-6 in the induction of hepatic injury after trauma-hemorrhagic shock

Although systemic interleukin-6 (IL-6) level is elevated, hepatocellular function is impaired and liver injury occurs after trauma-hemorrhage (T-H), it remains unknown whether a causal relationship exists between elevated IL-6 levels and liver injury after T-H. We hypothesized that IL-6 is causative in the development of hepatic dysfunction and injury after T-H. To examine this, adult male Sprague-Dawley rats underwent a 5-cm midline laparotomy and were subjected to hemorrhagic shock (blood pressure = 35 mmHg for ∼90 min), followed by resuscitation (Ringer lactate, 4 times the shed blood volume). At 2, 5, and 24 h thereafter, blood samples were collected and the liver isolated and perfused for 60 min. Portal inflow pressure was measured, and perfusate samples were collected to measure IL-6, alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) levels. A significant positive correlation between plasma levels of IL-6 and ALT and perfusate levels of IL-6 and LDH levels was observed. In a second series of experiments, rats were treated with immunoglobulin G (IgG) or antibodies against rat IL-6 (anti-IL-6) at the onset of resuscitation. At 5 h after resuscitation, anti-IL-6 treatment attenuated the T-H induced increases in plasma ALT and thromboxane B2 (a thromboxane A2 metabolite) levels, and bile flow was normalized to sham levels. Perfusion of livers from normal rats with IL-6 did not alter portal pressure; however, perfusion of a stable thromboxane A2 analog dose dependently increased portal pressure. Thus IL-6 plays a significant role in the induction of hepatic dysfunction and liver injury after T-H that appears to be in part mediated by increased thromboxane A2 levels.

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.

Reduced oncotic necrosis in Fas receptor-deficient C57BL/6J-lpr mice after bile duct ligation

Neutrophils aggravate cholestatic liver injury after bile duct ligation (BDL). Recently, it was suggested that hepatocellular apoptosis might be critical for liver injury in this model. To test the hypothesis that apoptosis could be a signal for neutrophil extravasation and injury, we assessed parameters of apoptosis and inflammation after BDL using 2 different approaches: (1) wild-type and Fas receptor-deficient lpr mice of the C57BL/6J or C3H/HeJ strains, and (2) treatment with the pancaspase inhibitor z-Val-Ala-Asp-fluoromethylketone (z-VAD-fmk)in C3HeB/FeJ mice. After BDL for 3 days, total cell death was estimated to be between 10% and 50% of all cells evaluated. However, less than 0.1% of hepatocytes showed apoptotic morphology in all 3 strains. Processing of procaspase-3, caspase-3 enzyme activities, and immunohistochemical staining for cytokeratin 18 cleavage products indicated no activation of caspases. Real-time reverse-transcriptase polymerase chain reaction analysis revealed increased expression of many inflammatory mediators but no effect on proapoptotic genes. More than 50% of all accumulated neutrophils were extravasated and colocalized with foci of oncotic hepatocytes and chlorotyrosine adducts. z-VAD-fmk treatment had no effect on apoptosis or liver injury after BDL but eliminated apoptosis after galactosamine/endotoxin in C3HeB/FeJ mice. In Fas receptor-deficient lpr mice (C57BL/6J), expression of inflammatory mediators, neutrophil accumulation and extravasation, chlorotyrosine adduct formation, and liver injury were reduced. This protection was not observed in lpr mice of the endotoxin-resistant C3H/HeJ strain. In conclusion, liver injury (oncotic necrosis) after BDL correlated with the severity of the inflammatory response. The minimal amount of apoptosis had no effect on inflammation or on the overall injury.

Apoptosis versus oncotic necrosis in hepatic ischemia/reperfusion injury

Warm and cold hepatic ischemia followed by reperfusion leads to necrotic cell death (oncosis), which often occurs within minutes of reperfusion. Recent studies also suggest a large component of apoptosis after ischemia/reperfusion. Here, we review the mechanisms underlying adenosine triphosphate depletion-dependent oncotic necrosis and caspase-dependent apoptosis, with emphasis on shared features and pathways. Although apoptosis causes internucleosomal DNA degradation that can be detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and related assays, DNA degradation also occurs after oncotic necrosis and leads to pervasive terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining far in excess of that for apoptosis. Similarly, although apoptosis can occur in a physiological setting without inflammation, in pathophysiological settings apoptosis frequently induces inflammation because of the onset of secondary necrosis and stimulation of cytokine and chemokine formation. In liver, the mitochondrial permeability transition represents a shared pathway that leads to both oncotic necrosis and apoptosis. When the mitochondrial permeability transition causes severe adenosine triphosphate depletion, plasma membrane failure and necrosis ensue. If adenosine triphosphate is preserved, at least in part, cytochrome c release after the mitochondrial permeability transition activates caspase-dependent apoptosis. Mitochondrial permeability transition-dependent cell death illustrates the concept of necrapoptosis, whereby common pathways lead to both necrosis and apoptosis. In conclusion, oncotic necrosis and apoptosis can share features and mechanisms, which sometimes makes discrimination between the 2 forms of cell death difficult. However, elucidation of critical cell death pathways under clinically relevant conditions will show potentially important therapeutic intervention strategies in hepatic ischemia/reperfusion injury.