Stress preconditioning attenuates oxidative injury to the alveolar epithelium of the lung following haemorrhage in rats

Genetic determinants of ammonia-induced acute lung injury in mice

In this study, a genetically diverse panel of 43 mouse strains was exposed to ammonia, and genome-wide association mapping was performed employing a single-nucleotide polymorphism (SNP) assembly. Transcriptomic analysis was used to help resolve the genetic determinants of ammonia-induced acute lung injury. The encoded proteins were prioritized based on molecular function, nonsynonymous SNP within a functional domain or SNP within the promoter region that altered expression. This integrative functional approach revealed 14 candidate genes that included Aatf, Avil, Cep162, Hrh4, Lama3, Plcb4, and Ube2cbp, which had significant SNP associations, and Aff1, Bcar3, Cntn4, Kcnq5, Prdm10, Ptcd3, and Snx19, which had suggestive SNP associations. Of these genes, Bcar3, Cep162, Hrh4, Kcnq5, and Lama3 are particularly noteworthy and had pathophysiological roles that could be associated with acute lung injury in several ways.

Exacerbation of Mild Hypoxia on Acute Radiation Syndrome and Subsequent Mortality

Mild hypoxia induced by 20% hemorrhage results in increases in few cytokine concentrations and sclerostin levels in blood, but shows no changes in bone formation, bone marrow cellularity, and gastrointestinal (GI) integrity and no systemic bacterial infection as well as no subsequent mortality. On the other hand, severe hypoxia induced by 40% hemorrhage causes significant increases in most cytokine concentrations, GI injury, lung injury, systemic bacterial infection, cellular ATP reduction and subsequent mortality. The severe hypoxia drastically damages GI and lung morphology, elevates cytokine concentrations in blood and increases inducible nitric oxide synthase (iNOS) expression in cells that is mediated by transcription factors NF-κB/NF-IL6, subsequently producing free radicals that disrupt mitochondria. ATP depletion, p53 phosphorylation, and caspase-3 activation are found, suggesting cell apoptosis. As a result, mortality occurs. However, when mild hypoxia follows ionizing radiation, the mild hypoxia significantly enhances radiation-induced mortality and acute radiation syndrome, including injury of bone marrow, GI, kidney, and lung. The synergism also occurs at the molecular level, resulting in alteration of microRNAs, amplification of iNOS expression, cytokine increases, sepsis, and ATP depletion. This is the first demonstration of synergistic effects between mild hypoxia and ionizing radiation.

Activation of heat shock response augments fibroblast growth factor-1 expression in wounded lung epithelium

We previously showed that coincident exposure to heat shock (HS; 42°C for 2 h) and TNF-α synergistically induces apoptosis in mouse lung epithelium. We extended this work by analyzing HS effects on human lung epithelial responses to clinically relevant injury. Cotreatment with TNF-α and HS induced little caspase-3 and poly(ADP-ribose) polymerase cleavage in human small airway epithelial cells, A549 cells, and BEAS2B cells. Scratch wound closure rates almost doubled when A549 and BEAS2B cells and air-liquid interface cultures of human bronchial epithelial cells were heat shocked immediately after wounding. Microarray, qRT-PCR, and immunoblotting showed fibroblast growth factor 1 (FGF1) to be synergistically induced by HS and wounding. Enhanced FGF1 expression in HS/wounded A549 was blocked by inhibitors of p38 MAPK (SB203580) or HS factor (HSF)-1 (KNK-437) and in HSF1 knockout BEAS2B cells. PCR demonstrated FGF1 to be expressed from the two most distal promoters in wounded/HS cells. Wound closure in HS A549 and BEAS2B cells was reduced by FGF receptor-1/3 inhibition (SU-5402) or FGF1 depletion. Exogenous FGF1 accelerated A549 wound closure in the absence but not presence of HS. In the presence of exogenous FGF1, HS slowed wound closure, suggesting that it increases FGF1 expression but impairs FGF1-stimulated wound closure. Frozen sections from normal and idiopathic pulmonary fibrosis (IPF) lung were analyzed for FGF1 and HSP70 by immunofluorescence confocal microscopy and qRT-PCR. FGF1 and HSP70 mRNA levels were 7.5- and 5.9-fold higher in IPF than normal lung, and the proteins colocalized to fibroblastic foci in IPF lung. We conclude that HS signaling may have an important impact on gene expression contributing to lung injury, healing, and fibrosis.

Impact of haemorrhagic shock intensity on the dynamic of alarmins release in porcine poly-trauma animal model

PURPOSE

Traumatic insults result in an altered inflammatory response, in which alarmins release has a central role. The impact of haemorrhagic shock intensity on the long-term kinetics of alarmins is not yet fully elucidated. We investigated these aspects in a combined trauma (chest, abdominal, and extremities injury) porcine model with different severities and durations of haemorrhagic shock.

METHODS

After induction of combined trauma (tibia fracture, lung contusion, and liver laceration), haemorrhagic shock was induced at different intensities: moderate haemorrhage (MH; n = 15): mean arterial pressure (MAP) <30 ± 5 mmHg [maximum loss of total blood volume (TBVmax): 45 %] for 90 min, and severe haemorrhage (SH; n = 10): MAP <25 ± 5 mmHg (TBVmax 50 %) for 120 min. Resuscitation was performed using a standardized crystalloid infusion protocol. Animals were mechanically ventilated and underwent ICU-monitoring for 48 h (MH) and 48.5 h (SH). Blood samples were collected over the clinical time course, and systemic levels of serum alarmins [High-Mobility Group Protein B-1 (HMGB-1) and Heat Shock Protein 70 (HSP70)] were measured using an ELISA kit.

RESULTS

Heart rate, systemic blood pressure, lactate, and base excess were significantly altered as a function of haemorrhagic shock in both trauma groups (MH and SH). Systemic HMGB-1 levels were significantly elevated in both trauma groups when compared to the sham group. Haemorrhagic shock severity and duration were positively correlated with HMGB-1 levels and compared to baseline values, concentrations remained significantly increased in SH when compared to MH. On the other hand, we observed a significant decrease in the systemic HSP70 levels of trauma groups (MH, and SH) when compared to the sham group, which was significantly decreased compared to baseline values in SH over the entire time course.

CONCLUSION

Our data show that haemorrhagic shock duration and severity affect the systemic levels of HMGB-1 and HSP70. This early alarmins release after trauma can be used to guide the treatment strategies (e.g. surgical procedures) of polytrauma patients.

Heat-shock response increases lung injury caused by Pseudomonas aeruginosa via an interleukin-10-dependent mechanism in mice

BACKGROUND

The heat-shock response (HSR) protects from insults, such as ischemia-reperfusion injury, by inhibiting signaling pathways activated by sterile inflammation. However, the mechanisms by which the HSR activation would modulate lung damage and host response to a bacterial lung infection remain unknown.

METHODS

HSR was activated with whole-body hyperthermia or by intraperitoneal geldanamycin in mice that had their lungs instilled with Pseudomonas aeruginosa 24 h later (at least six mice per experimental group). Four hours after instillation, lung endothelial and epithelial permeability, bacterial counts, protein levels in bronchoalveolar lavage fluid, and lung myeloperoxidase activity were measured. Mortality rate 24 h after P. aeruginosa instillation was recorded. The HSR effect on the release of interleukin-10 and killing of P. aeruginosa bacteria by a mouse alveolar macrophage cell line and on neutrophil phagocytosis was also examined.

RESULTS

HSR activation worsened lung endothelial (42%) and epithelial permeability (50%) to protein, decreased lung bacterial clearance (71%), and increased mortality (50%) associated with P. aeruginosa pneumonia, an effect that was not observed in heat-shock protein-72-null mice. HSR-mediated decrease in neutrophil phagocytosis (69%) and bacterial killing (38%) by macrophages was interleukin-10 dependent, a mechanism confirmed by increased lung bacterial clearance and decreased mortality (70%) caused by P. aeruginosa pneumonia in heat-shocked interleukin-10-null mice.

CONCLUSIONS

Prior HSR activation worsens lung injury associated with P. aeruginosa pneumonia in mice via heat-shock protein-72- and interleukin-10-dependent mechanisms. These results provide a novel mechanism for the immunosuppression observed after severe trauma that is known to activate HSR in humans.

Lung preconditioning in anesthesia: Review of the literature

Lung injury can arise during or after anesthesia and can lead to a complicated postoperative course with great implications for the patient. Unfortunately, treatment of acute lung injury is at the moment mainly supportive and rates of recovery have not really improved in the recent years. In many cases, lung injury can be anticipated and preventive measures seem possible. This represents a unique challenge to the anesthesiologist, as some new opportunities to reduce the frequency and/or severity of lung injury seem now available. These chances may arise from the potency of preconditioning the lungs before the main injury, with smaller injurious insults. Although preconditioning began to be applicated first on the myocardium, experimental studies have shown potentially beneficial results also for the lungs. This review summarizes the main methods of lung preconditioning that have been tried in experimental studies in the literature and the main mechanisms that are perhaps involved. Emphasis is given in the two main methods of preconditioning that seem readily applicable in the clinical praxis, that is ischemic preconditioning, as well as preconditioning with volatile anesthetics. The few, but interesting clinical studies are also summarized and the future research points in this evolving field of anesthesia are stressed.

Activation of the heat shock response attenuates the interleukin 1β-mediated inhibition of the amiloride-sensitive alveolar epithelial ion transport

Acute lung injury (ALI) is a clinical syndrome characterized by hypoxia, which is caused by the breakdown of the alveolar capillary barrier. Interleukin 1β (IL-1β), a cytokine released within the airspace in ALI, downregulates the α subunit of the epithelial sodium channel (αENaC) transcription and protein expression via p38 MAP kinase-dependent signaling. Although induction of the heat shock response can restore alveolar fluid clearance compromised by IL-1β following the onset of severe hemorrhagic shock in rats, the mechanisms are not fully understood. In this study, we report that the induction of the heat shock response prevents IL-1β-dependent inhibition of αENaC mRNA expression and subsequent channel function. Heat shock results in IRAK1 detergent insolubility and a disruption of Hsp90 binding to IRAK1. Likewise, TAK1, another client protein of Hsp90 and signaling component of the IL-1β pathway, is also detergent insoluble after heat shock. Twenty-four hours after heat shock, both IRAK1 and TAK1 are again detergent soluble, which correlates with the IL-1β-dependent p38 activation. Remarkably, IL-1β-dependent p38 activation 24 h after heat shock did not result in an inhibition of αENaC mRNA expression and channel function. Further analysis demonstrates prolonged preservation of αENaC expression by the activation of the heat shock response that involves inducible Hsp70. Inhibition of Hsp70 at 24 h after heat shock results in p38-dependent IL-1β inhibition of αENaC mRNA expression, whereas overexpression of Hsp70 attenuates the p38-dependent IL-1β inhibition of αENaC mRNA expression. These studies demonstrate new mechanisms by which the induction of the heat shock response protects the barrier function of the alveolar epithelium in ALI.

Hyperthermia promotes and prevents respiratory epithelial apoptosis through distinct mechanisms

Hyperthermia has been shown to confer cytoprotection and to augment apoptosis in different experimental models. We analyzed the mechanisms of both effects in the same mouse lung epithelial (MLE) cell line (MLE15). Exposing MLE15 cells to heat shock (HS; 42°C, 2 h) or febrile-range hyperthermia (39.5°C) concurrent with activation of the death receptors, TNF receptor 1 or Fas, greatly accelerated apoptosis, which was detectable within 30 minutes and was associated with accelerated activation of caspase-2, -8, and -10, and the proapoptotic protein, Bcl2-interacting domain (Bid). Caspase-3 activation and cell death were partially blocked by inhibitors targeting all three initiator caspases. Cells expressing the IκB superrepessor were more susceptible than wild-type cells to TNF-α-induced apoptosis at 37°C, but HS and febrile-range hyperthermia still increased apoptosis in these cells. Delaying HS for 3 hours after TNF-α treatment abrogated its proapoptotic effect in wild-type cells, but not in IκB superrepressor-expression cells, suggesting that TNF-α stimulates delayed resistance to the proapoptotic effects of HS through an NF-κB-dependent mechanism. Pre-exposure to 2-hour HS beginning 6 to16 hours before TNF-α treatment or Fas activation reduced apoptosis in MLE15 cells. The antiapoptotic effects of HS pretreatment were reduced in TNF-α-treated embryonic fibroblasts from heat shock factor-1 (HSF1)-deficient mice, but the proapoptotic effects of concurrent HS were preserved. Thus, depending on the temperature and timing relative to death receptor activation, hyperthermia can exert pro- and antiapoptotic effects through distinct mechanisms.

The role of heat shock protein 90 in modulating ischemia-reperfusion injury in the kidney

INTRODUCTION

Kidney transplantation is the gold standard treatment for end-stage renal disease. Ischemia-reperfusion injury (IRI) is an unavoidable consequence of the transplantation procedure and is responsible for delayed graft function and poorer long-term outcomes.

AREAS COVERED

Pharmacological induction of heat shock protein (Hsp) expression is an emerging pre-conditioning strategy aimed at reducing IRI following renal transplantation. Hsp90 inhibition up-regulates protective Hsps (especially Hsp70) and potentially down-regulates NF-κB by disruption of the IκB kinase (IKK) complex. However, the clinical application of Hsp90 inhibitors is currently limited by their toxicity profile and the exact mechanism of protection conferred is unknown. Toll-like receptor 4 (TLR4) is a further regulator of NF-κB and recent studies suggest TLR4 plays a dominant role in mediating kidney damage following IRI. The full interaction of Hsps with TLRs is yet to be delineated and whether TLR4 signalling can be targeted by Hsp90 inhibition in IRI remains uncertain.

EXPERT OPINION

Pharmacological pre-conditioning by Hsp90 inhibition involves direct treatment to the kidney donor and/or organ, which aims to reduce injury prior to the onset of ischemia. The major challenges going forward are to establish the exact mechanism of protection offered by these drugs and the investgiation of less toxic analogues that could be safely translated into human studies.

Combination therapy with HSP90 inhibitor 17-DMAG reconditions the tumor microenvironment to improve recruitment of therapeutic T cells

Ineffective recognition of tumor cells by CD8+ T cells is a limitation of cancer immunotherapy. Therefore, treatment regimens that coordinately promote enhanced antitumor CD8+ T-cell activation, delivery, and target cell recognition should yield greater clinical benefit. Using an MCA205 sarcoma model, we show that in vitro treatment of tumor cells with the HSP90 inhibitor 17-DMAG results in the transient (proteasome-dependent) degradation of the HSP90 client protein EphA2 and the subsequent increased recognition of tumor cells by Type-1 anti-EphA2 CD8+ T cells. In vivo administration of 17-DMAG to tumor-bearing mice led to slowed tumor growth, enhanced/prolonged recognition of tumor cells by anti-EphA2 CD8+ T cells, reduced levels of myeloid-derived suppressor cells and regulatory T cells in the tumor microenvironment, and activation of tumor-associated vascular endothelial cells in association with elevated levels of Type-1 tumor-infiltrating lymphocytes. When combined with EphA2-specific active vaccination or the adoptive transfer of EphA2-specific CD8+ T cells, 17-DMAG cotreatment yielded a superior tumor therapeutic regimen that was capable of rendering animals free of disease. Taken together, our findings indicate that 17-DMAG functions as an immune adjuvant in the context of vaccines targeting EphA2.

Nadph oxidase regulates alveolar epithelial sodium channel activity and lung fluid balance in vivo via O⁻₂ signaling

To define roles for reactive oxygen species (ROS) and epithelial sodium channel (ENaC) in maintaining lung fluid balance in vivo, we used two novel whole animal imaging approaches. Live X-ray fluoroscopy enabled quantification of air space fluid content of C57BL/6J mouse lungs challenged by intratracheal (IT) instillation of saline; results were confirmed by using conventional lung wet-to-dry weight ratios and Evans blue as measures of pulmonary edema. Visualization and quantification of ROS produced in lungs was performed in mice that had been administered a redox-sensitive dye, hydro-Cy7, by IT instillation. We found that inhibition of NADPH oxidase with a Rac-1 inhibitor, NSC23766, resulted in alveolar flooding, which correlated with a decrease in lung ROS production in vivo. Consistent with a role for Nox2 in alveolar fluid balance, Nox2(-/-) mice showed increased retention of air space fluid compared with wild-type controls. Interestingly, fluoroscopic analysis of C57BL/6J lungs IT instilled with LPS showed an acute stimulation of lung fluid clearance and ROS production in vivo that was abrogated by the ROS scavenger tetramethylpiperidine-N-oxyl (TEMPO). Acute application of LPS increased the activity of 20 pS nonselective ENaC channels in rat type 1 cells; the average number of channel and single-channel open probability (NPo) increased from 0.14 ± 0.04 to 0.62 ± 0.23. Application of TEMPO to the same cell-attached recording caused an immediate significant decrease in ENaC NPo to 0.04 ± 0.03. These data demonstrate that, in vivo, ROS has the capacity to stimulate lung fluid clearance by increasing ENaC activity.

17-DMAG diminishes hemorrhage-induced small intestine injury by elevating Bcl-2 protein and inhibiting iNOS pathway, TNF-α increase, and caspase-3 activation

BACKGROUND

Hemorrhage increases inducible nitric oxide synthase (iNOS) and depletes ATP levels in various tissues. Previous studies have shown that geldanamycin, an inducer of heat shock protein 70kDa (HSP-70) and inhibitor of iNOS, limits both processes. Reduction in NO production limits lipid peroxidation, apoptosome formation, and caspase-3 activation, thereby increasing cellular survival and reducing the sequelae of hemorrhage. The poor solubility of geldanamycin in aqueous solutions, however, limits its effectiveness as a drug. 17-DMAG is a water-soluble analog of geldanamycin that might have greater therapeutic utility. This study investigated the effectiveness of 17-DMAG at reducing hemorrhagic injury in mouse small intestine.

RESULTS

In mice, the hemorrhage-induced iNOS increase correlated with increases in Kruppel-like factor 6 (KLF6) and NF-kB and a decrease in KLF4. As a result, increases in NO production and lipid peroxidation occurred. Moreover, hemorrhage also resulted in decreased Bcl-2 and increased TNF-α, IL-6, and IL-10 concentrations, p53 protein, caspase-3 activation, and cellular ATP depletion. A shortening and widening of villi in the small intestine was also observed. Treatment with 17-DMAG significantly reduced the hemorrhage-induced increases in iNOS protein, jejunal alteration, and TNF-α and IL-10 concentrations, but 17-DMAG did not affect the hemorrhage-induced increases in p53 and IL-6 concentration. 17-DMAG treatment by itself upregulated HSP-70, Bcl-2, and p53.

CONCLUSION

Since 17-DMAG is water soluble, bioactive, and not toxic, 17-DMAG may prove useful as a prophylactic drug for hemorrhage.

Activation of the stress protein response inhibits the STAT1 signalling pathway and iNOS function in alveolar macrophages: role of Hsp90 and Hsp70

BACKGROUND AND AIM

Alveolar fluid clearance is impaired by inducible nitric oxide synthase (iNOS)/nitric oxide (NO)-dependent mechanisms in acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). The activation of the stress protein response (SPR) in alveolar macrophages on iNOS-dependent NO production in response to interferon gamma (IFNgamma), a major cytokine present in the airspace of patients with ALI, was investigated.

METHODS

The SPR was activated in murine and primary human alveolar macrophages prior to analysis of signal transducer and activator of transcription factor 1 (STAT1) activation, iNOS mRNA and protein synthesis, and NO production.

RESULTS

SPR activation resulted in inhibition of IFNgamma-mediated NO production (p=0.001) with >95% detergent insolubilisation of the STAT1 protein. Its subsequent proteasomal degradation was partially reversed with pretreatment of cells with the chemical chaperone glycerol. This early effect of the SPR was caused by the complete disruption of heat shock protein 90 (Hsp90)-STAT1 binding, as shown by immunoprecipitation. Recovery of STAT1 activation and recovery of iNOS synthesis occurred within 12 h after SPR activation (p=0.02). NO production (as compared with non-SPR controls) did not occur until 48 h later (p=0.02). SPR-induced Hsp70 (Hsp70i) expression caused a late inhibition of NO production (p=0.02). Inhibiting >50% Hsp70i expression recovered NO production to control levels whereas overexpressing Hsp70i in the absence of the SPR inhibited NO production (p=0.02).

CONCLUSION

Early inhibition of STAT1 following its dissociation from Hsp90, and later inhibition of iNOS activity by Hsp70i, represent novel mechanisms by which SPR activation modulates the IFNgamma signalling in alveolar macrophages. These results highlight a potential clinical application for Hsp90 inhibitors in modulating NO signalling during the early phase of acute lung injury.

Induced hypothermia attenuates the acute lung injury in hemorrhagic shock

BACKGROUND

In previous animal studies, induction of therapeutic hypothermia (HT) in hemorrhagic shock (HS) had beneficial effects on the hemodynamic and metabolic parameters and on the survival. However, the effect of induced HT on acute lung injury (ALI) in HS has not been investigated. We sought to determine the effects of HT on ALI in HS.

METHODS

Male Sprague-Dawley rats (350-390 g; n = 8 per group) were randomized to the normothermia (NT; 36-37 degrees C) group or the moderate HT (27-30 degrees C) group and were subjected to volume-controlled (2 mL/100 g weight) HS (90 minutes) followed by 90 minutes of resuscitation. ALI score, lung malondialdehyde content, and myeloperoxidase activity were measured. The expression of glycogen synthase kinase 3beta (GSK-3beta), phosphorylated GSK-3beta, inducible nitric oxide synthase (iNOS), heat shock protein (HSP) 72, and nuclear factor-kappaB (NF-kappaB) in the lung were compared.

RESULTS

ALI score, lung malondialdehyde content, and myeloperoxidase were lower in the HT group. GSK-3beta and iNOS gene expressions in lung tissue were significantly decreased in the HT group (p < 0.05). On the contrary, the expression of phosphorylated GSK-3beta was increased in the HT group (p < 0.001). HSP 72 was expressed in the HT group but not in the NT group. The activated p65 NF-kappaB levels in lung nuclear extract were significantly lower in the NT group (p = 0.03).

CONCLUSIONS

HT attenuates HS-induced ALI in rats by the modulation of GSK, HSP 72, iNOS, and NF-kappaB.

Geldanamycin analog 17-DMAG inhibits iNOS and caspases in gamma-irradiated human T cells

Inducible nitric oxide synthase (iNOS) expression and NO production increase after radiation exposure. We showed previously that inhibiting iNOS expression prevents hemorrhage injury; we therefore investigated whether inhibiting iNOS expression also limits radiation injury. Human Jurkat T cells were exposed to gamma radiation (2, 4, 6 or 8 Gy), and cell lysates were collected for analysis at selected times afterward. Radiation exposure increased iNOS expression within 4 h postirradiation by increasing the levels of the iNOS transcription factors NF-kappaB and KLF6. By 24 h postirradiation cell viability was reduced. In these cells, NO production, lipid peroxidation, protein nitration, apoptosomes (formed by cytochrome c, caspase 9 and Apaf-1), and caspase 3 activity were significantly elevated, suggesting that the iNOS pathway had been activated. Treatment with the iNOS inhibitors 17-DMAG or L-NIL-6 24 h prior to irradiation limited these changes, as did treatment with iNOS siRNA to silence the iNOS gene. These results suggest radiation injury involves the iNOS pathway, and iNOS-mediated NO produced endogenously in the T cell alters overall T-cell function and results in apoptosis and cell lethality. Control of iNOS expression may represent a useful approach for protecting T cells from radiation injury.

Heat shock protein 90-binding agents protect renal cells from oxidative stress and reduce kidney ischemia-reperfusion injury

Heat shock proteins (Hsps) are protective in models of transplantation, yet practical strategies to upregulate them remain elusive. The heat shock protein 90-binding agent (HBA) geldanamycin and its analogs (17-AAG and 17-DMAG) are known to upregulate Hsps and confer cellular protection but have not been investigated in a model relevant to transplantation. We examined the ability of HBAs to upregulate Hsp expression and confer protection in renal adenocarcinoma (ACHN) cells in vitro and in a mouse model of kidney ischemia-reperfusion (I/R) injury. Hsp70 gene expression was increased 30-40 times in ACHN cells treated with HBAs, and trimerization and DNA binding of heat shock transcription factor-1 (HSF1) were demonstrated. A three- and twofold increase in Hsp70 and Hsp27 protein expression, respectively, was found in ACHN cells treated with HBAs. HBAs protected ACHN cells from an H2O2-mediated oxidative stress, and HSF1 short interfering RNA was found to abrogate HBA-mediated Hsp induction and protection. In vivo, Hsp70 was upregulated in the kidneys, liver, lungs, and heart of HBA-treated mice. This was associated with a functional and morphological renal protection from I/R injury. Therefore, HBAs mediate upregulation of protective Hsps in mouse kidneys which are associated with reduced I/R injury and may be useful in reducing transplant-associated kidney injury.

Mechanical ventilation and hemorrhagic shock-resuscitation interact to increase inflammatory cytokine release in rats

OBJECTIVE

To determine whether hemorrhagic shock and resuscitation (HSR) and high lung stress during mechanical ventilation interact to augment lung and systemic inflammatory responses and whether their sequence affects these responses.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

Research laboratory.

SUBJECTS

Fifty-six male Wistar rats.

INTERVENTIONS

Controls were immediately killed after anesthesia. High lung stress was produced by mechanical ventilation with high tidal volume of 30 mL/kg and no positive end-expiratory pressure (HV) for 2 hrs. HSR consisted of lessening systemic arterial pressure to 30 mm Hg for 1 hr followed by reinjection of the withdrawn blood. Experimental groups consisted of HSR only and HSR preceded or followed by HV or conventional mechanical ventilation.

MEASUREMENTS AND MAIN RESULTS

Interleukin-1beta, interleukin-6, and macrophage inhibitory protein 2 were determined in lung homogenate, bronchoalveolar lavage fluid, and plasma. HV ventilation alone did not increase plasma or lung cytokine content compared with controls. HSR significantly increased all mediators in lungs and plasma but not macrophage inhibitory protein 2 in plasma. Conventional ventilation, applied either before or after HSR, did not influence lung or systemic mediator release, whereas HV significantly increased mediator release when combined with HSR whatever the sequence of injuries. Lung mediator content was significantly higher in animals ventilated with HV before the HSR stress than in animals submitted to HSR and then ventilated with HV. Plasma macrophage inhibitory protein 2 concentrations followed the same pattern.

CONCLUSIONS

This study shows that HSR and high lung tissue stress interact to increase lung and systemic release of inflammatory mediators in a way that depends on their sequence. Previous injury may sensitize lungs to inadequate mechanical ventilation, but inadequate mechanical ventilation may also sensitize lungs to postoperative complications.

Effects of thermal preconditioning on the ischemia-reperfusion-induced acute lung injury in minipigs

Lung ischemia-reperfusion (I/R) injury plays an important role in many clinical issues. A series of mechanisms after I/R has been uncovered after numerous related studies. Organ preconditioning (PC) is a process whereby a brief antecedent event, such as transient ischemia, oxidative stress, temperature change, or drug administration, bestows on an organ an early or delayed tolerance to further insults by the same or different stressors. In this study, we want to uncover the optimal thermal PC patterns that cause maximal early or delayed protective effect on the subsequent pulmonary I/R with the use of miniature pig model. Twenty-eight 15- to 20-kg weight Lanyu miniature pigs are used and divided into four groups (seven sham operation control [NC], seven PC only [PC], seven I/R [I/R], and seven PC followed by I/R [PC + I/R]). The PC was performed with the animals being anesthetized and, using an alternative hyperthermic (40 degrees C) and normothermic moist air to ventilate their lungs for 15 min, respectively, for 2 cycles, followed by I/R, which consists of 90 min of blocking the perfusion and ventilation of the left lung followed by 240 min of reperfusion. Control animals had a thoracotomy with hilar dissection only. Indicators of lung injury included hemodynamic parameters, blood gas analysis, histopathological (lung pathology, wet/dry weight ratio, myeloperoxidase assay), and molecular biological profiles (interleukin-1beta [IL-1beta], IL-6, tumor necrosis factor-alpha by enzyme-linked immunosorbent assay analysis). Lung tissue heat shock protein 70 (HSP-70) expression was also detected by Western blotting. This model of lung I/R induced significant lung injury with pulmonary hypertension, increased pulmonary vascular resistance, and pulmonary venous hypoxemia at the ischemia side, increased pulmonary tissue injury score and neutrophil infiltration, increased wet/dry ratio, myeloperoxidase assay, tumor necrosis factor-alpha, IL-1beta, and IL-6 assay. This type of thermal PC would not injure the lung parenchyma or tracheal epithelium. Moreover, it could attenuate the I/R-related lung injury, with some of these parameters improved significantly. Increased expression of HSP-70 was also found in the group of PC plus I/R than the I/R only. Less prominent and transient increase in expression of HSP-70 was found in the PC group. We concluded that the intratracheal thermal PC can effectively attenuate I/R-induced lung injury through various mechanisms, including the decrease of various proinflammatory cytokines. The mechanism of its protective effect might be related to the increased expression of HSP-70.

Inhibition of inducible nitric-oxide synthase protects human T cells from hypoxia-induced apoptosis

Sodium cyanide-induced chemical hypoxia triggers a series of biochemical alterations leading to apoptosis in many cell types, including T cells. It is known that chemical hypoxia promotes inducible nitric-oxide synthase (iNOS) gene transcription by activating its transcription factors. To determine whether iNOS and NO production are responsible for chemical hypoxia-induced apoptosis, we exposed human Jurkat T cells to sodium cyanide in the presence or absence of iNOS inhibitors. We found that iNOS expression is necessary for hypoxia-induced lipid peroxidation and leukotriene B(4) generation. The inhibition of iNOS limited T-cell apoptosis by decreasing the activity of caspase-3 without affecting the expression of Fas/Apo-1/CD95 on the surface membrane of T cells. These data suggest iNOS-mediated NO produced endogenously in the T cell alters overall T-cell function and results in apoptosis. Proper control of iNOS expressed in the T cell may represent a useful approach to immunomodulation.

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.

Hypertonic saline solution increases the expression of heat shock protein 70 and improves lung inflammation early after reperfusion in a rodent model of controlled hemorrhage

Hypertonic saline solution (HS solution, NaCl 7.5%) has shown to restore hemodynamic parameters in hemorrhagic shock and to decrease the inflammation triggered by ischemia-reperfusion injury (I-R). Therefore, our objective was to investigate the effects of HS solution on the mechanisms involved in I-R, in an experimental model of controlled hemorrhagic shock. Wistar rats (280-350 g) were submitted to controlled bleeding, keeping the mean arterial pressure around 40 mmHg, for 1 h. After that, rats were randomized and treated with HS solution (4 mL/kg) or normal saline (34 mL/kg). There were no differences in hemodynamic parameters between both groups for at least 2 h after shock. No difference either was observed in reactive oxygen species generation (measured indirectly by malondialdehyde concentration) or cytokines (interleukins 6 and 10) production (measured by enzyme-linked immunosorbent assay). Quantitative analysis of lung tissue showed a smaller neutrophil infiltration in animals that received HS solution. Moreover, the animals in the HS group showed an increased expression of heat shock protein 70. Therefore, we concluded that treatment of hemorrhagic shock with HS solution can decrease pulmonary inflammation and increase cellular protection by up-regulating heat shock protein 70 expression.

Genetic evidence for a protective role of heat shock factor 1 against irritant-induced gastric lesions

Gastric lesions result from an imbalance between aggressive and defensive factors. Indirect lines of evidence suggest that heat shock proteins (HSPs) induced by various aggressive factors provide a major protective mechanism. In this study, we compared gastric ulcerogenic response in wild-type mice and in those lacking heat shock factor 1 (HSF1), a transcription factor for hsp genes. The severity of gastric lesions induced by ethanol or hydrochloric acid was worsened in HSF1-null mice. Immunoblotting, real-time reverse transcription-polymerase chain reaction, immunohistochemical analysis, and terminal deoxynucleotidyl transferase dUTP nick-end labeling assay revealed that the ethanol administration up-regulated gastric mucosal HSPs, in particular HSP70, in an HSF1-dependent manner, and more apoptotic cells were observed in the gastric mucosa of HSF1-null mice than in wild-type mice. In contrast, other parameters governing the gastric ulcerogenic response, including gastric acid secretion, gastric mucosal blood flow, and prostaglandin E(2) levels, were not significantly affected by the absence of the hsf1 gene. Geranylgeranylacetone (GGA), a clinically used antiulcer drug with HSP-inducing activity, suppressed ethanol-induced gastric lesions in wild-type mice but not in heat shock factor 1 (HSF1)-null mice. The results suggest that the aggravation of irritant-induced gastric lesions in HSF1-null mice is due to their inability to up-regulate HSPs, leading to apoptosis. It is also suggested that the HSP-inducing activity of GGA contributes to the drug's antiulcer activity. This study provides direct genetic evidence that HSPs, after their HSF1-dependent up-regulation, confer gastric protection against the irritant-induced lesions.

Glutamine attenuation of cell death and inducible nitric oxide synthase expression following inflammatory cytokine-induced injury is dependent on heat shock factor-1 expression

BACKGROUND

Glutamine (GLN) has been shown to improve outcome after experimental and clinical models of critical illness. Enhanced expression of heat shock protein (HSP) has been hypothesized to be responsible for this protection. The heat shock response has been shown to inhibit inducible nitric oxide synthase (iNOS) gene expression and nitric oxide (NO) production. This study tested the hypothesis that GLN-mediated activation of the HSP pathway is responsible for improved survival and attenuation of iNOS expression after an inflammatory cytokine-induced injury.

METHODS

Heat shock factor-1 (HSF-1) wild-type and knockout mouse embryonic fibroblasts (HSF-1+/+ and HSF-1-/-) were used in all experiments. Cells were treated with 0 mmol/L or 8 mmol/L GLN and cytomix (tumor necrosis factor-alpha, lipopolysaccharide, and interferon-gamma) in a concurrent treatment model once they had reached confluence. Cell viability was assayed with MTS/PMS mixture. Apoptosis and necrosis were assayed via immunohistochemistry. iNOS and HSP-70 expression were detected via Western blotting. NO production was measured using the Griess reagent.

RESULTS

GLN treatment significantly attenuated inflammatory cytokine-induced cell death and apoptosis in HSF-1+/+ cells vs 0 mmol/L GLN treatment; however, GLN's cellular protection was lost in HSF-1-/- cells. GLN supplementation attenuated cytomix-induced iNOS expression and NO production only in HSF-1+/+ cells. Further, GLN induced HSP-70 expression only in HSF-1+/+ cells.

CONCLUSIONS

This is the first demonstration that GLN-mediated cellular protection after inflammatory cytokine injury is due to HSF-1 expression and cellular capacity to activate an HSP response.

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.

Alveolar macrophages contribute to alveolar barrier dysfunction in ventilator-induced lung injury

In patients requiring mechanical ventilation for acute lung injury or acute respiratory distress syndrome (ARDS), tidal volume reduction decreases mortality, but the mechanisms of the protective effect have not been fully explored. To test the hypothesis that alveolar macrophage activation is an early and critical event in the initiation of ventilator-induced lung injury (VILI), rats were ventilated with high tidal volume (HV(T)) for 10 min to 4 h. Alveolar macrophage counts in bronchoalveolar lavage (BAL) fluid decreased 45% by 20 min of HV(T) (P < 0.05) consistent with activation-associated adhesion. Depletion of alveolar macrophages in vivo with liposomal clodronate significantly decreased permeability and pulmonary edema following 4 h of HV(T) (P < 0.05). BAL fluid from rats exposed to 20 min of HV(T) increased nitric oxide synthase activity nearly threefold in naïve primary alveolar macrophages (P < 0.05) indicating that soluble factors present in the air spaces contribute to macrophage activation in VILI. Media from cocultures of alveolar epithelial cell monolayers and alveolar macrophages exposed to 30 min of stretch in vitro also significantly increased nitrite production in naïve macrophages (P < 0.05), but media from stretched alveolar epithelial cells or primary alveolar macrophages alone did not, suggesting alveolar epithelial cell-macrophage interaction was required for the subsequent macrophage activation observed. These data demonstrate that injurious mechanical ventilation rapidly activates alveolar macrophages and that alveolar macrophages play an important role in the initial pathogenesis of VILI.

Geldanamycin prevents hemorrhage-induced ATP loss by overexpressing inducible HSP70 and activating pyruvate dehydrogenase

Hemorrhage in mice results in decreased ATP levels in the jejunum, lung, kidney, heart, and brain but not in liver tissue lysates, albeit at variable levels and time kinetics. The decreased protein expression and activity of pyruvate dehydrogenase (PDH) accounted for the hemorrhage-induced ATP loss. Treatment with geldanamycin (GA; 1 microg/g body wt), a known inducer of heat shock protein (HSP)70, inhibited the hemorrhage-induced ATP loss in the jejunum, lung, heart, kidney, and brain. GA was found to increase PDH protein, preserve PDH enzymatic activity, and inhibit mucosal injury in jejunum tissues. GA-induced HSP70i was found to form complexes with PDH protein. HSP70 gene transfer into intestinal epithelial cells promoted PDH and ATP levels, whereas HSP70 short interfering RNA limited them. We conclude that agents able to increase the expression of HSP70 and PDH may be of value in reducing pathology resulting from hemorrhage-associated ATP loss.

Activation of the stress protein response prevents the development of pulmonary edema by inhibiting VEGF cell signaling in a model of lung ischemia-reperfusion injury in rats

Lung endothelial damage is a characteristic morphological feature of ischemia-reperfusion (I/R) injury, although the molecular steps involved in the loss of endothelial integrity are still poorly understood. We tested the hypothesis that the activation of vascular endothelial growth factor (VEGF) cell signaling would be responsible for the increase in lung vascular permeability seen early after the onset of I/R in rats. Furthermore, we hypothesized that the I/R-induced pulmonary edema would be significantly attenuated in rats by the activation of the stress protein response. Pretreatment with Ad Flk-1, an adenovirus encoding for the soluble VEGF receptor type II, prevented I/R-mediated increase in lung vascular permeability in rats. Furthermore, the I/R-induced lung injury was significantly decreased by prior activation of the stress protein response with geldanamycin or pyrrolidine dithiocarbamate. In vitro studies demonstrated that VEGF caused an increase in protein permeability across primary cultures of bovine macro- and microvascular lung endothelial cell monolayers that were associated with a phosphorylation of VE- and E-cadherin and the formation of actin stress fibers. Activation of the stress protein response prevented the VEGF-mediated changes in protein permeability across these cell monolayers and reduced the phosphorylation of VE-and E-cadherins, as well as the formation of actin stress fibers in these cells.

Extracellular heat shock protein 72 is a marker of the stress protein response in acute lung injury

Previous studies have shown that heat shock protein 72 (Hsp72) is found in the extracellular space (eHsp72) and that eHsp72 has potent immunomodulatory effects. However, whether eHsp72 is present in the distal air spaces and whether eHsp72 could modulate removal of alveolar edema is unknown. The first objective was to determine whether Hsp72 is released within air spaces and whether Hsp72 levels in pulmonary edema fluid would correlate with the capacity of the alveolar epithelium to remove alveolar edema fluid in patients with ALI/ARDS. Patients with hydrostatic edema served as controls. The second objective was to determine whether activation of the stress protein response (SPR) caused the release of Hsp72 into the extracellular space in vivo and in vitro and to determine whether SPR activation and/or eHsp72 itself would prevent the IL-1beta-mediated inhibition of the vectorial fluid transport across alveolar type II cells. We found that eHsp72 was present in plasma and pulmonary edema fluid of ALI patients and that eHsp72 was significantly higher in pulmonary edema fluid from patients with preserved alveolar epithelial fluid clearance. Furthermore, SPR activation in vivo in mice and in vitro in lung endothelial, epithelial, and macrophage cells caused intracellular expression and extracellular release of Hsp72. Finally, SPR activation, but not eHsp72 itself, prevented the decrease in alveolar epithelial ion transport induced by exposure to IL-1beta. Thus SPR may protect the alveolar epithelium against oxidative stress associated with experimental ALI, and eHsp72 may serve as a marker of SPR activation in the distal air spaces of patients with ALI.

Salutary effects of estrogen receptor-β agonist on lung injury after trauma-hemorrhage

Although 17β-estradiol (E2) administration after trauma-hemorrhage attenuates lung injury in male rodents, it is not known whether the salutary effects are mediated via estrogen receptor (ER)-α or ER-β. We hypothesized that the salutary effects of E2 lung are mediated via ER-β. Male Sprague-Dawley rats underwent trauma-hemorrhage (mean blood pressure 40 mmHg for 90 min, then resuscitation). E2 (50 μg/kg), ER-α agonist propyl pyrazole triol (PPT; 5 μg/kg), ER-β agonist diarylpropiolnitrile (DPN; 5 μg/kg), or vehicle (10% DMSO) was injected subcutaneously during resuscitation. At 24 h after trauma-hemorrhage or sham operation, bronchoalveolar fluid (BALF) was collected for protein concentration, LDH activity, and nitrate/nitrite and IL-6 levels. Moreover, lung tissue was used for inducible nitric oxide synthase (iNOS) mRNA/protein expression, nitrate/nitrite and IL-6 levels, and wet/dry weight ratio ( n = 6 rats/group). One-way ANOVA and Tukey's test were used for statistical analysis. The results indicated that E2 downregulated lung iNOS expression after trauma-hemorrhage. Protein concentration, LDH activity, and nitrate/nitrite and IL-6 levels in BALF and nitrate/nitrite and IL-6 levels in the lung increased significantly after trauma-hemorrhage; however, administration of DPN but not PPT significantly improved all parameters. Moreover, DPN treatment attenuated trauma-hemorrhage-mediated increase in iNOS mRNA/protein expression in the lung. In contrast, no significant change in the above parameters was observed with PPT. Thus the salutary effects of E2 on attenuation of lung injury are mediated via ER-β, and ER-β-induced downregulation of iNOS likely plays a significant role in the DPN-mediated lung protection after trauma-hemorrhage.

Organ preconditioning: the past, current status, and related lung studies

Preconditioning (PC) has emerged as a powerful method for experimentally and clinically attenuating various types of organ injuries. In this paper related clinical and basic research issues on organ preconditioning issues were systemically reviewed. Since lung injuries, including ischemia-reperfusion and others, play important roles in many clinical results, including thromboembolism, trauma, thermal injury, hypovolemic and endotoxin shock, reimplantation response after organ transplantation, and many respiratory diseases in critical care. It is of interest to uncover methods, including the PCs, to protect the lung from the above injuries. However, related studies on pulmonary PC are relatively rare and still being developed, so we will review previous literature on experimental and clinical studies on pulmonary PC in the following paragraphs.

Serum Levels of Hsp60 Correlate with the Development of Acute Lung Injury after Trauma1

BACKGROUND

Previous studies have shown that heat shock protein 60 (Hsp60) is a danger signal for the immune system and appears to be a key endogenous inflammatory mediator that activates the toll-like receptors and causes the release of proinflammatory cytokines and nitric oxide by immune competent cells, but no data are available for trauma patients. The purpose of this study was to determine whether Hsp60 could be detected in the serum of patients early after severe trauma and whether its serum level might correlate with the development of acute lung injury (ALI) in trauma patients.

METHODS

Clinical data were collected prospectively during a 12-month period for trauma patients who were ventilated mechanically for more than 24 h and who met the following inclusion criteria: Injury Severity Score > or =16, age >18 years. Physiological data for quantitative assessment of organ dysfunction were collected for each patient. Hsp60 levels were measured in the serum of trauma patients.

RESULTS

Sixty-four patients with severe trauma were enrolled in the study. Eighteen patients developed ALI (28%). Trauma patients who later developed ALI had significantly higher serum values of Hsp60 than those who did not (4.21 +/- 2.24 ng/mL versus 0.73 +/- 0.26 ng/mL, P < 0.05, mean +/- SE). Furthermore, immature but not mature recombinant Hsp60 induced in vitro the release of nitric oxide (NO) from RAW 264.7 murine macrophages.

CONCLUSION

Serum levels of Hsp60 detected within 30 min after trauma correlate with the development of ALI. Immature but mature Hsp60 causes in vitro the release of NO by macrophages, suggesting that the extracellular release of the immature Hsp60 associated with traumatic cell necrosis could be involved in the release of NO by immune competent cells, leading to an activation of the inflammatory response within the lung or other organs.

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.

Febrile-range hyperthermia augments neutrophil accumulation and enhances lung injury in experimental gram-negative bacterial pneumonia

We previously demonstrated that exposure to febrile-range hyperthermia (FRH) accelerates pathogen clearance and increases survival in murine experimental Klebsiella pneumoniae peritonitis. However, FRH accelerates lethal lung injury in a mouse model of pulmonary oxygen toxicity, suggesting that the lung may be particularly susceptible to injurious effects of FRH. In the present study, we tested the hypothesis that, in contrast with the salutary effect of FRH in Gram-negative peritonitis, FRH would be detrimental in multilobar Gram-negative pneumonia. Using a conscious, temperature-clamped mouse model and intratracheal inoculation with K. pneumoniae Caroli strain, we showed that FRH tended to reduce survival despite reducing the 3 day-postinoculation pulmonary pathogen burden by 400-fold. We showed that antibiotic treatment rescued the euthermic mice, but did not reduce lethality in the FRH mice. Using an intratracheal bacterial endotoxin LPS challenge model, we found that the reduced survival in FRH-treated mice was accompanied by increased pulmonary vascular endothelial injury, enhanced pulmonary accumulation of neutrophils, increased levels of IL-1beta, MIP-2/CXCL213, GM-CSF, and KC/CXCL1 in the bronchoalveolar lavage fluid, and bronchiolar epithelial necrosis. These results suggest that FRH enhances innate host defense against infection, in part, by augmenting polymorphonuclear cell delivery to the site of infection. The ultimate effect of FRH is determined by the balance between accelerated pathogen clearance and collateral tissue injury, which is determined, in part, by the site of infection.

Heat shock treatment protects against angiotensin II-induced hypertension and inflammation in aorta

Angiotensin II (Ang II) is a potent vasoconstrictor and induces inflammation and end-organ injury through its activation of the proinflammatory transcription factor, nuclear factor-kappaB (NF-kappaB). Heat shock (HS) treatment with subsequent expression of heat shock proteins (Hsps) is an effective strategy for tissue protection against oxidative injuries. Recently, HS and Hsps have been shown to interact with NF-kappaB in tissue injury. In this study, we investigated whether HS could protect against Ang II-induced hypertension and inflammation by inhibiting NF-kappaB. Sprague-Dawley rats were divided into control and HS groups. Control and 24-hour post-heat shocked rats were treated with Ang II. At days 1, 3, 5, 7, 11, and 14 after Ang II administration, systolic blood pressures were measured by tail-cuff plethysmography, and aorta tissues were collected. Aorta NF-kappaB deoxyribonucleic acid-binding activity was measured by electrophoretic mobility shift assay, and NF-kappaB p65 subunit, Hsp70, Hsp27, and interleukin-6 (IL-6) expressions were measured by Western analysis. HS treatment significantly decreased Ang II-induced hypertension. The activation of NF-kappaB in aorta by Ang II was suppressed by HS treatment. The elevated expression of IL-6 induced by Ang II treatment was also decreased by HS treatment. Although Ang II treatment induced an increase in Hsp70 and Hsp27, HS treatment induced a greater elevation of Hsp70 and Hsp27 expression. HS treatment protects against Ang II-induced hypertension and inflammation. This protection may relate to the interaction of Hsps and the NF-kappaB pathway.

Stress-Induced Inhibition of the NF-κB Signaling Pathway Results from the Insolubilization of the IκB Kinase Complex following Its Dissociation from Heat Shock Protein 90

Activation of the stress response attenuates proinflammatory responses by suppressing cytokine-stimulated activation of the NF-kappaB signaling pathway. In this study, we show that the activation of the cellular stress response, either by heat shock treatment or after exposure to sodium arsenite, leads to a transient inhibition of IkappaBalpha phosphorylation. Inhibition of IkappaBalpha phosphorylation after stress was associated with the detergent insolubilization of the upstream kinases, IkappaB kinase alpha (IKKalpha) and IkappaB kinase beta, components involved in IkappaBalpha phosphorylation. Pretreatment of cells with glycerol, a chemical chaperone that reduces the extent of stress-induced protein denaturation, reduced the stress-dependent detergent insolubility of the IKK complex and restored the cytokine-stimulated phosphorylation of IkappaB. The stress-dependent insolubility of the IKK complex appeared reversible; as the cells recovered from the heat shock treatment, the IKK complex reappeared within the soluble fraction of cells and was again capable of mediating the phosphorylation of IkappaBalpha in response to added cytokines. Treatment of cells with geldanamycin, an inhibitor of heat shock protein 90 (Hsp90) function, also resulted in IKK detergent insolubility and proteasome-mediated degradation of the IKK complex. Furthermore, while IKKalpha coprecipitated with Hsp90 in control cells, coprecipitation of the two proteins was greatly reduced in those cells early after stress or following exposure to geldanamycin. Stress-induced transient insolubilization of the IkappaB kinase complex following its dissociation from Hsp90 represents a novel mechanism by which the activation of the stress response inhibits the NF-kappaB signaling pathway in response to proinflammatory stimuli.

HO-1 induction restores c-AMP-dependent lung epithelial fluid transport following severe hemorrhage in rats

Inhibition of cAMP-dependent stimulation of the vectorial fluid transport across the lung epithelium following hemorrhagic shock is mediated by NO released within the airspaces of the lung. We tested here the hypothesis that prior induction of HO-1 would attenuate the release of NO in the airspaces, thus preventing the inhibition of the c-AMP stimulation of alveolar fluid clearance (ALC) in rats. Indeed, HO-1 induction restored the cAMP-mediated up-regulation of ALC after hemorrhage by decreasing NO released within the airspaces of the lung. In vitro studies demonstrated that HO-1 induction significantly reduced the iNOS-mediated release of NO by alveolar macrophages stimulated with endotoxin for 24 h. This effect is explained in part by a HO-1-dependent attenuation of the LPS-mediated nuclear translocation of NF-kappaB. In addition, HO-1 induction also significantly reduced the iNOS-mediated release of NO by MH-S cells that were stimulated with interferon-gamma by decreasing the phosphorylation of STAT 1, another transcription factor important for the activation of the iNOS promoter. In contrast, HO-1 induction did not affect the production of NO by rat alveolar epithelial type II cells that were stimulated with cytomix (a mixture of TNF-alpha, IL-1beta, and IFN-gamma) for 24 h. In summary, these results provide the first in vivo evidence that the induction of HO-1 in the lung restores a normal fluid transport capacity of the alveolar epithelium following hemorrhagic shock by inhibiting the iNOS-mediated release of NO by alveolar macrophages.

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.

Geldanamycin treatment inhibits hemorrhage-induced increases in KLF6 and iNOS expression in unresuscitated mouse organs: role of inducible HSP70

The aim of this study was to determine whether hemorrhage affects the levels of a variety of stress-related proteins and whether changes can be inhibited by drugs reported to provide protection from ischemia and reperfusion injury. Male Swiss Webster mice were subjected to a 40% hemorrhage without resuscitation. Western blot analysis indicated that c-Jun (an AP-1 protein), Kruppel-like factor 6 (KFL6), and inducible nitric oxide synthase (iNOS) were upregulated sequentially in that order. Pretreatment of mice with geldanamycin (GA) 16 h before hemorrhage effectively inhibited the expression of the proteins KLF6 and iNOS, whereas caffeic acid phenethyl ester did not. GA pretreatment increased inducible heat shock protein (HSP) 70 but not HSP90 in both sham and hemorrhagic tissues. The overexpressed inducible HSP70 formed complexes with KLF6 and iNOS. These results suggest that GA may be therapeutically useful for reducing hemorrhage-induced injury when used as a presurgical treatment or when added to resuscitation fluids.

Use of Hsf1−/− mice reveals an essential role for HSF1 to protect lung against cadmium-induced injury

Cadmium (Cd) is known to activate heat shock (HS) response, which is characterized by overexpression of heat shock proteins (Hsps) under the control of heat shock factor 1 (HSF1). The potential protection provided by the HS response, induced by increasing the body temperature of animals before Cd exposure or by Cd itself, against pathophysiological changes occurring after Cd intranasal instillation (1 to 100 microg/mouse) was examined. HSF1-deficient mice were used to evaluate the role of this factor in lung protection. Cd instillation caused dose- and time-dependent changes in the respiratory pattern measured by plethysmography (Penh), and significant increases in lactate dehydrogenase (LDH) activity as well as macrophage and neutrophil counts in bronchoalveolar lavage fluids. HS preconditioning induced Hsp overexpression and reduced the Penh (-30%), LDH (-25%), and neutrophil (-55%) responses to subsequent administration of the highest Cd doses (50 and 100 microg) in wild-type mice. HSF1 deficiency abolished the HS response and its protective effect. In the absence of preconditioning, Hsf1(-/-) mice exhibited higher values of Penh (+70%) and LDH activity (+42%) compared with wild-type animals when exposed to the lowest Cd doses. Higher macrophage (+80%) and neutrophil counts (+115%) were recorded whatever the dose. Western blot analyses indicated that lung protection might be related to the kinetics of HSF1-dependent Hsp70 expression. Altogether, our data demonstrate that HS response elicited both by prior HS and by Cd itself moderates pulmonary injuries due to Cd instillation, and that HSF1 is a major mediator in this protection.