Role of inducible nitric oxide synthase expressed by alveolar macrophages in high mobility group box 1--induced acute lung injury

The Effect and Regulatory Mechanism of High Mobility Group Box-1 Protein on Immune Cells in Inflammatory Diseases

High mobility group box-1 protein (HMGB1), a member of the high mobility group protein superfamily, is an abundant and ubiquitously expressed nuclear protein. Intracellular HMGB1 is released by immune and necrotic cells and secreted HMGB1 activates a range of immune cells, contributing to the excessive release of inflammatory cytokines and promoting processes such as cell migration and adhesion. Moreover, HMGB1 is a typical damage-associated molecular pattern molecule that participates in various inflammatory and immune responses. In these ways, it plays a critical role in the pathophysiology of inflammatory diseases. Herein, we review the effects of HMGB1 on various immune cell types and describe the molecular mechanisms by which it contributes to the development of inflammatory disorders. Finally, we address the therapeutic potential of targeting HMGB1.

The effect of high mobility group box-1 protein on cerebral edema, blood-brain barrier, oxidative stress and apoptosis in an experimental traumatic brain injury model

Traumatic brain injury (TBI) is one of the important reason of morbidity and mortality. While the primary injury due to mechanical impact is unavoidable, the secondary injury which is formed as a result of primary injury and thought to occur due to neuroinflammation in the forefront can be prevented and by this way mortality and morbidity can be reduced. High mobility group box-1 (HMGB1) is a protein that triggers the neuroinflammatory process by being released from the nucleus of necrotic tissues after primary injury. The aim of this study is to investigate the effects of HMGB1 on its receptors TLR4 and RAGE, cerebral edema, blood-brain barrier, oxidative stress and apoptosis causing secondary damage in an experimental traumatic brain injury model. Weighing between 280-320 g, 10 to 12 weeks-old, a total of 30 adult male Sprague-Dawley rats were used for the experiments. The rats were randomly assigned to 3 groups: 1) Control, 2) TBI and 3) TBI + ethyl pyruvate group (n = 10 per group). Right parietal cortical contusion was made by using a weight-dropping TBI method. Brain samples were harvested from pericontusional area at 24 h after TBI. HMGB1, TLR4, RAGE, occludin, claudin-5, ZO-1 levels are investigated by western blot analyses and immunohistochemistry examinations. HMGB-1, TLR4 and RAGE expressions increased after TBI. Major tight junction proteins in the blood-brain barrier: occludin, claudin-5 and ZO-1 expressions decreased after TBI. Brain edema increased after TBI. Also, proapoptotic bax and active caspase 3 expressions increased, antiapoptotic bcl-2 levels decreased after TBI. Total oxidant status and oxidative stress increased, total antioxidant status decreased after TBI. HMGB-1 protein plays a key role in the pathophysiology of traumatic brain injury.

The Role of HMGB1, a Nuclear Damage-Associated Molecular Pattern Molecule, in the Pathogenesis of Lung Diseases

Significance: High-mobility group protein box 1 (HMGB1), a ubiquitous nuclear protein, regulates chromatin structure and modulates the expression of many genes involved in the pathogenesis of lung cancer and many other lung diseases, including those that regulate cell cycle control, cell death, and DNA replication and repair. Extracellular HMGB1, whether passively released or actively secreted, is a danger signal that elicits proinflammatory responses, impairs macrophage phagocytosis and efferocytosis, and alters vascular remodeling. This can result in excessive pulmonary inflammation and compromised host defense against lung infections, causing a deleterious feedback cycle. Recent Advances: HMGB1 has been identified as a biomarker and mediator of the pathogenesis of numerous lung disorders. In addition, post-translational modifications of HMGB1, including acetylation, phosphorylation, and oxidation, have been postulated to affect its localization and physiological and pathophysiological effects, such as the initiation and progression of lung diseases. Critical Issues: The molecular mechanisms underlying how HMGB1 drives the pathogenesis of different lung diseases and novel therapeutic approaches targeting HMGB1 remain to be elucidated. Future Directions: Additional research is needed to identify the roles and functions of modified HMGB1 produced by different post-translational modifications and their significance in the pathogenesis of lung diseases. Such studies will provide information for novel approaches targeting HMGB1 as a treatment for lung diseases.

Pivotal neuroinflammatory and therapeutic role of high mobility group box 1 in ischemic stroke

Stroke is a major cause of mortality and disability worldwide. Stroke is a frequent and severe neurovascular disorder. The main cause of stroke is atherosclerosis, and the most common risk factor for atherosclerosis is hypertension. Therefore, prevention and treatment of stroke are crucial issues in humans. High mobility group box 1 (HMGB1) is non-histone nuclear protein that is currently one of the crucial proinflammatory alarmins in ischemic stroke (IS). It is instantly released from necrotic cells in the ischemic core and activates an early inflammatory response. HMGB1 may signal via its putative receptors, such as receptor for advanced glycation end products (RAGE), toll-like receptors (TLRs) as well as matrix metalloproteinase (MMP) enzymes during IS. These receptors are expressed in brain cells. Additionally, brain-released HMGB1 can be redox modified in the circulation and activate peripheral immune cells. The role of HMGB1 may be more complex. HMGB1 possesses beneficial actions, such as endothelial activation, enhancement of neurite outgrowth, and neuronal survival. HMGB1 may also provide a novel link for brain-immune communication leading to post-stroke immunomodulation. Therefore, HMGB1 is new promising therapeutic intervention aimed at promoting neurovascular repair and remodeling after stroke. In this review, we look at the mechanisms of secretion of HMGB1, the role of receptors, MMP enzymes, hypoglycemia, atherosclerosis, edema, angiogenesis as well as neuroimmunological reactions and post-ischemic brain recovery in IS. We also outline therapeutic roles of HMGB1 in IS.

Artesunate Protects Against Sepsis-Induced Lung Injury Via Heme Oxygenase-1 Modulation

Artesunate, a derivative of artemisinin, has anti-inflammatory properties and exerts protective roles in sepsis. Heme oxygense-1 (HO-1) inhibits the inflammatory response through reduction of proinflammatory cytokines and leukocyte influx into tissues. The present study investigated the effects of artesunate on HO-1 and septic lung injury. Cecal ligation and puncture (CLP) was employed to induce septic lung injury. Mice pretreated with artesunate (AS) (15 mg/kg) exhibited decreased sepsis-induced mortality and lung injury and alleviated lung pathological changes and neutrophil infiltration. In addition, AS lowered the levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the serum and bronchoalveolar lavage fluid (BALF) and inhibited cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase isoform (iNOS) expression and NF-κB activation in lung tissue. In addition, AS enhanced NF-E2-related factor-2 (Nrf2) activation and HO-1 expression and enzymatic activity in lung tissue. However, the protective effects of AS on sepsis-induced lung injury were eliminated by ZnPP IX, an HO-1 competitive inhibitor. Therefore, AS plays protective roles in septic lung injury related to the upregulation of HO-1. These findings suggest an effective and applicable treatment to sepsis-induced lung injury and provide new insights into the molecular mechanisms and actions of AS.

Gadolinium chloride modulates bradykinin-induced pulmonary vasoconstriction and hypoxic pulmonary vasoconstriction during polymicrobial abdominal sepsis in rats

BACKGROUND

Macrophages importantly contribute to sepsis-induced lung injury. As their impact on pulmonary endothelial injury and dysregulation of hypoxic pulmonary vasoconstriction (HPV) remains unclear, we assessed pulmonary endothelial dysfunction and HPV by macrophage inhibition via gadolinium chloride (GC) pre-treatment in rats with peritonitis (cecal ligation and puncture [CLP]).

METHODS

The following four study groups were made: Group I: SHAM and group II: SHAM + GC (pre-treatment with NaCl 0.9% or GC 14 mg/kg body weight (b.w.) intravenously 24 hours prior to sham laparotomy); group III: CLP and group IV: CLP + GC (pre-treatment with NaCl 0.9% or GC 14 mg/kg b.w. 24 hours prior to induction of peritonitis). Exhaled nitric oxide (exNO), bradykinin-induced pulmonary vasoconstriction (=surrogate marker of endothelial dysfunction) and HPV were investigated in isolated and perfused lungs (n = 40). Using the same protocol wet to dry lung weight ratio and myeloperoxidase (MPO) activity were investigated in separate rats (n = 28). In additional rats (n = 12) of groups III and IV nitrite levels in alveolar macrophages (AM) were measured.

RESULTS

In sepsis, GC pre-treatment significantly attenuated exNO levels, AM-derived nitrite levels, lung MPO activity, and restored blunted HPV, but severely enhanced endothelial dysfunction in healthy and septic animals.

CONCLUSION

Macrophages exhibit a controversial role in sepsis-induced lung injury. The GC-induced restoration of inflammation parameters to sham levels is clearly limited by the negative impact on CLP-induced endothelial injury in this setting. The exact link between the GC-associated modulation of the NO pathway demonstrated and septic lung injury needs to be determined in future studies.

Postconditioning with simvastatin decreases myocardial injury in rats following acute myocardial ischemia

The aim of the present study was to investigate whether postconditioning with simvastatin attenuated myocardial ischemia reperfusion injury by inhibiting the expression of high mobility group box 1 (HMGB1) in rat myocardium following acute myocardial ischemia. In total, 30 male Sprague-Dawley rats were divided into sham operation (sham; n=10), acute myocardial infarction (AMI; n=10) and simvastatin (sim; n=10) groups. The AMI and sim groups were subjected to ischemia for 30 min, followed by reperfusion for 180 min. The rats in the sim group were administered 20 mg/kg simvastatin intravenously 5 min prior to reperfusion. Subsequently, the infarct size, serum cardiac troponin (c-TnI), tumor necrosis factor (TNF)-α and myocardial malondialdehyde (MDA) levels and superoxide dismutase (SOD) activity were measured. Western blot analysis was used to detect the protein expression of HMGB1. Postconditioning with simvastatin was shown to decrease the infarct size and HMGB1 expression levels in the myocardium following AMI (P<0.05). In addition, postconditioning with simvastatin not only decreased the serum levels of c-TnI and TNF-α (P<0.05), but also inhibited the increase in MDA levels and the reduction in SOD activity (P<0.05). Therefore, postconditioning with simvastatin was shown to attenuate myocardial injury. The underlying mechanism may be associated with the downregulation of HMGB1 expression in the ischemic myocardium.

HMGB1 in health and disease

Complex genetic and physiological variations as well as environmental factors that drive emergence of chromosomal instability, development of unscheduled cell death, skewed differentiation, and altered metabolism are central to the pathogenesis of human diseases and disorders. Understanding the molecular bases for these processes is important for the development of new diagnostic biomarkers, and for identifying new therapeutic targets. In 1973, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and termed high-mobility group (HMG) proteins. The HMG proteins include three superfamilies termed HMGB, HMGN, and HMGA. High-mobility group box 1 (HMGB1), the most abundant and well-studied HMG protein, senses and coordinates the cellular stress response and plays a critical role not only inside of the cell as a DNA chaperone, chromosome guardian, autophagy sustainer, and protector from apoptotic cell death, but also outside the cell as the prototypic damage associated molecular pattern molecule (DAMP). This DAMP, in conjunction with other factors, thus has cytokine, chemokine, and growth factor activity, orchestrating the inflammatory and immune response. All of these characteristics make HMGB1 a critical molecular target in multiple human diseases including infectious diseases, ischemia, immune disorders, neurodegenerative diseases, metabolic disorders, and cancer. Indeed, a number of emergent strategies have been used to inhibit HMGB1 expression, release, and activity in vitro and in vivo. These include antibodies, peptide inhibitors, RNAi, anti-coagulants, endogenous hormones, various chemical compounds, HMGB1-receptor and signaling pathway inhibition, artificial DNAs, physical strategies including vagus nerve stimulation and other surgical approaches. Future work further investigating the details of HMGB1 localization, structure, post-translational modification, and identification of additional partners will undoubtedly uncover additional secrets regarding HMGB1's multiple functions.

Identification and functional characterization of the goldfish (Carassius auratus L.) high mobility group box 1 (HMGB1) chromatin-binding protein

We report on the identification and functional characterization of HMGB1 of the goldfish. Quantitative analysis indicated the highest expression of goldfish HMGB1 in the brain, with lower mRNA levels in spleen, intestine, kidney, gill and heart. HMGB1 was also differentially expressed in goldfish immune cell populations with highest mRNA levels present in splenocytes and neutrophils. We generated and functionally characterized the recombinant HMGB1 (rgHMGB1). The rgHMGB1 primed the respiratory burst response in monocytes and induced nitric oxide production of primary goldfish macrophages. Treatment of goldfish macrophages with heat-killed Mycobacterium marinum and Aeromonas salmonicida elevated the expression of HMGB1 and resulted in higher HMGB1 protein levels. The rgHMGB1 induced a dose-dependent production of TNFα-2 and IL-1β1 of goldfish macrophages. Furthermore, the dual luciferase reporter assay revealed that goldfish HMGB1 induced the activation of the NF-κB signaling pathway. Our results indicate that goldfish HMGB1 is a critical regulatory cytokine of inflammatory and antimicrobial response of the goldfish.

Protective effect of glycyrrhizin, a direct HMGB1 inhibitor, on focal cerebral ischemia/reperfusion-induced inflammation, oxidative stress, and apoptosis in rats

Aim

Glycyrrhizin (GL) has been reported to protect against ischemia and reperfusion (I/R)-induced injury by inhibiting the cytokine activity of high mobility group box 1 (HMGB1). In the present study, the protective effects of GL against I/R injury, as well as the related molecular mechanisms, were investigated in rat brains.

Methods

Focal cerebral I/R injury was induced by intraluminal filamentous occlusion of the middle cerebral artery (MCA) in Male Sprague-Dawley rats. GL alone or GL and rHMGB1 were administered intravenously at the time of reperfusion. Serum levels of HMGB1 and inflammatory mediators were quantified via enzyme-linked immunosorbent assay (ELISA). Histopathological examination, immunofluorescence, RT-PCR and western blotting analyses were performed to investigate the protective and anti-apoptotic effects and related molecular mechanisms of GL against I/R injury in rat brains.

Results

Pre-treatment with GL significantly reduced infarct volume and improved the accompanying neurological deficits in locomotor function. The release of HMGB1 from the cerebral cortex into the serum was inhibited by GL administration. Moreover, pre-treatment with GL alleviated apoptotic injury resulting from cerebral I/R through the inhibition of cytochrome C release and caspase 3 activity. The expression levels of inflammation- and oxidative stress-related molecules including TNF-α, iNOS, IL-1β, and IL-6, which were over-expressed in I/R, were decreased by GL. P38 and P-JNK signalling were involved in this process. All of the protective effects of GL could be reversed by rHMGB1 administration.

Conclusions

GL has a protective effect on ischemia-reperfusion injury in rat brains through the inhibition of inflammation, oxidative stress and apoptotic injury by antagonising the cytokine activity of HMGB1.

The protective effect of melatonin and S-methylisothiourea treatments in nitrogen mustard induced lung toxicity in rats

OBJECTIVES

Mustard is highly toxic to the lung. Its toxic effects are associated with inflammatory cell accumulation and increased pro-inflammatory cytokines as well as reactive oxygen and nitrogen species. In this study, we aimed to investigate the efficiency of melatonin (MEL) and S-methylisothiourea (SMT) on mechlorethamine (MEC) induced lung toxicity.

METHODS

Thirty-six male rats were randomly divided into four groups: control, MEC, MEC+MEL, and MEC+SMT. Control group was given saline only via transdermal route. Other groups were exposured to a single dose of MEC (3.5 mg/kg) via transdermal route. MEL (100 mg/kg) was administered intraperitoneally 30 min after the application of MEC, and after the same dose of MEL was given every 12 h for a total of six doses. SMT (50 mg/kg) was also given intraperitoneally 30 min after the application of MEC.

RESULTS

MEC injection resulted in alveolar epithelial injury, hemorrhage, inflammation, edema and interalveolar septal thickening in the lung tissues. The tissue TNF-α, IL-1β, and nitrate/nitrite (NOx) levels were found significantly different for all groups (p<0.001). TNF-α and IL-1β levels increased significantly with MEC exposure, and MEL and SMT ameliorated these increases in lung tissues. MEC also elevated NOx levels in lung tissue. Melatonin showed meaningful protection against lung injury. But protection of SMT was weaker.

CONCLUSION

Inflammation plays an important role in the MEC induced lung toxicity as well as oxidative and nitrosative stress. Melatonin has also anti-inflammatory properties similar to SMT, as well as anti-oxidant properties. But melatonin treatment was found more efficient than SMT treatment.

High mobility group box 1 can enhance NF-κB activation and act as a pro-inflammatory molecule in the Pacific oyster, Crassostrea gigas

High-mobility group box 1 (HMGB1), a highly conserved DNA-binding protein, is involved in nucleosome formation and transcriptional regulation, and can also act as an extracellular cytokine to trigger inflammation and immune responses. In this study, we identified a HMGB1 gene (hereafter designated as CgHMGB1) in the Pacific oyster Crassostrea gigas. The full-length CgHMGB1 cDNA is 833 bp including 5' and 3'-untranslated regions (UTRs) of 145 and 79 bp, respectively, and an open reading frame (ORF) of 609 bp. The gene encodes a 202 amino acid polypeptide with an estimated molecular mass of 23.3 kDa. Sequence alignment shows that CgHMGB1 contains two basic HMG boxes and a highly acidic C-terminal domain. Recombinant CgHMGB1 proteins can enhance the mRNA level of various inflammatory cytokines in vivo. Typically, CgHMGB1 is localized in the nucleus, though lipopolysaccharide can induce its release to cytoplasm. Moreover, luciferase reporter assays reveal that CgHMGB1 cannot stimulate Nuclear Factor-κB reporter activity alone, but it can enhance Rel-dependent NF-κB activation in a dose-dependent manner. CgHMGB1 is highly expressed in hemocytes and its transcripts are significantly more abundant following bacterial challenge. Our results suggest that CgHMGB1 plays an essential role in innate defense by enhancing Rel-activated NF-κB activity and inducing the expression of inflammatory cytokines.

Relationship between vascular reactivity and expression of HMGB1 in a rat model of septic aorta

Intruoduction

High mobility group box 1 (HMGB1), a ubiquitous nuclear protein, induces several inflammatory diseases and functions as a fatal factor when released extracellularly. The effect of HMGB1 on vascular reactivity during sepsis remains to be clarified.

Methods

A rat model of abdominal sepsis was produced by cecal ligation and puncture (CLP) under sevoflurane anesthesia (n = 28). Anti-HMGB1 antibody at a dose of 4 or 0.4 mg/kg, or normal saline was injected twice intravenously, i.e., immediately after the CLP surgery and 4 h thereafter. Rats in the sham group underwent laparotomy, and the cecum was manipulated but not ligated or punctured. The descending thoracic aorta was excised 12 h after the CLP surgery and cut into rings of approximately 3 mm in length. Changes in the expression of HMGB1 and vascular reactivity were examined in the rings shortly after harvest and 4 h thereafter.

Results

HMGB1 was identified immunohistochemically and by Western blotting in the nuclei of vascular endothelial and smooth muscle cells in all groups shortly after excision of the aorta, but its expression was augmented only in the CLP groups 4 h thereafter. Degenerated smooth muscle cells were also observed after CLP. Anti-HMGB1 antibody dose-dependently inhibited the augmentation of HMGB1 expression and the morphological changes induced by CLP. The expression of HMGB1 partly correlated with suppression of vascular reactivity.

Conclusion

The present results strongly suggest that HMGB1 plays an important role in vascular malfunction from an early phase of sepsis.

Synergistic effects of antibodies against high-mobility group box 1 and tumor necrosis factor-α antibodies on D-(+)-galactosamine hydrochloride/lipopolysaccharide-induced acute liver failure

High-mobility group box 1 (HMGB1) protein is released into the serum after tissue damage, and serves as a warning signal to enhance the inflammatory response. Acute liver injury is one of the diseases that starts with tissue damage and ends with systemic inflammation. We used D-(+)-galactosamine hydrochloride (D-GalN)/lipopolysaccharide (LPS)-treated mice as an acute liver injury model to explore the functions of HMGB1 in more detail. HMGB1 is released into the serum at a very early stage of D-GalN/LPS-induced acute liver injury. It upregulates the expression of tumor necrosis factor-α (TNF-α), interleukin-6, inducible nitric oxide synthase, and tissue factor. TNF-α and HMGB1 form a positive feedback loop to amplify the downstream signals. mAbs against HMGB1 and TNF-α have synergistic effects in protecting mice from D-GalN/LPS-induced acute liver failure. The results suggest that HMGB1 is a key mediator in D-GalN/LPS-induced acute liver injury. Tissue damage and cell necrosis shortly after administration of D-GalN and LPS lead to early HMGB1 release, and HMGB1 acts synergistically with TNF-α to promote pathological processes in acute liver failure.

Danger-associated molecular patterns (DAMPs) in acute lung injury

Danger-associated molecular patterns (DAMPs) are host-derived molecules that can function to regulate the activation of pathogen recognition receptors (PRRs). These molecules play a critical role in modulating the lung injury response. DAMPs originate from multiple sources, including injured and dying cells, the extracellular matrix, or exist as immunomodulatory proteins within the airspace and interstitium. DAMPs can function as either toll-like receptor (TLR) agonists or antagonists, and can modulate both TLR and nod-like receptor (NLR) signalling cascades. Collectively, this diverse group of molecules may represent important therapeutic targets in the prevention and/or treatment of acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS).

Honokiol attenuates the severity of acute pancreatitis and associated lung injury via acceleration of acinar cell apoptosis

Severe acute pancreatitis remains a life-threatening disease with a high mortality rate among a defined proportion of those affected. Apoptosis has been hypothesized to be a beneficial form of cell death in acute pancreatitis. Honokiol, a low-molecular-weight natural product, possesses the ability of anti-inflammation and apoptosis induction. Here, we investigate whether honokiol can ameliorate severe acute pancreatitis and the associated acute lung injury in a mouse model. Mice received six injections of cerulein at 1-h intervals, then given one intraperitoneal injection of bacterial lipopolysaccharide for the induction of severe acute pancreatitis. Moreover, mice were intraperitoneally given vehicle or honokiol 10 min after the first cerulein injection. Honokiol protected against the severity of acute pancreatitis in terms of increased serum amylase and lipase levels, pancreas pathological injury, and associated acute lung injury. Honokiol significantly reduced the increases in serum tumor necrosis factor-α, interleukin 1, and nitric oxide levels 3 h and serum high-mobility group box 1 24 h after acute pancreatitis induction. Honokiol also significantly decreased myeloperoxidase activities in the pancreas and the lungs. Endoplasmic reticulum stress-related molecules eIF2α (phosphorylated) and CHOP protein expressions, apoptosis, and caspase-3 activity were increased in the pancreas of mice with severe acute pancreatitis, which was unexpectedly enhanced by honokiol treatment. These results suggest that honokiol protects against acute pancreatitis and limits the spread of inflammatory damage to the lung in a severe acute pancreatitis mouse model. The acceleration of pancreatic cell apoptosis by honokiol may play a pivotal role.

Temporal and spatial expression of high-mobility group box 1 in surgically injured rat vocal folds

OBJECTIVES/HYPOTHESIS

High-mobility group box 1 (HMGB1) protein has been identified as a principal instigator of injury-induced inflammation in many organ systems. Physiologically, HMGB1 binds to chromatin in cell nucleus. Upon injury, cells release HMGB1 to extracellular milieu, triggering a destructive inflammatory response. Neutralizing or removing HMGB1 has been shown to control inflammation. Unfortunately, the role of HMGB1 in laryngeal inflammation and healing has yet to be defined. The purpose of this study was to determine spatial and temporal patterns of HMGB1 expression in surgically injured rat vocal folds up to 2 weeks after injury.

STUDY DESIGN

Prospective animal study.

METHODS

Bilateral vocal fold injury was performed on 70 Sprague-Dawley rats. An additional 14 rats served as uninjured controls. Animals were sacrificed at 1 day, 3 days, 5 days, 1 week, and 2 weeks following surgery. Immunohistochemistry staining and enzyme-linked immunosorbent assay (ELISA) were performed to determine the spatial distribution and temporal expression, respectively, of HMGB1 in vocal fold tissue. Hematoxylin-and-eosin staining for cell counting was performed to evaluate cell infiltration.

RESULTS

Cell number peaked significantly 5 days after injury. HMGB1 was positively stained in the nuclear, cytoplasmic, and extracellular compartments from days 1 to 7 after injury, whereas a strict nuclear staining was observed in uninjured controls and week 2 animals. Staining results were corroborated by ELISA.

CONCLUSIONS

Spatial and temporal changes of HMGB1 expression were shown in injured vocal fold tissue, indicating this protein may be one of the principal drivers of inflammation and healing response to surgical injury in the larynx.

Role of Apoptosis in Amplifying Inflammatory Responses in Lung Diseases

Apoptosis is an important contributor to the pathophysiology of lung diseases such as acute lung injury (ALI) and chronic obstructive pulmonary disease (COPD). Furthermore, the cellular environment of these acute and chronic lung diseases favors the delayed clearance of apoptotic cells. This dysfunctional efferocytosis predisposes to the release of endogenous ligands from dying cells. These so-called damage-associated molecular patterns (DAMPs) play an important role in the stimulation of innate immunity as well as in the induction of adaptive immunity, potentially against autoantigens. In this review, we explore the role of apoptosis in ALI and COPD, with particular attention to the contribution of DAMP release in augmenting the inflammatory response in these disease states.

Effects of pneumonectomy on nitric oxide synthase expression and perivascular edema in the remaining lung of rats

Pneumonectomy is associated with high mortality and high rates of complications. Postpneumonectomy pulmonary edema is one of the leading causes of mortality. Little is known about its etiologic factors and its association with the inflammatory process. The purpose of the present study was to evaluate the role of pneumonectomy as a cause of pulmonary edema and its association with gas exchange, inflammation, nitric oxide synthase (NOS) expression and vasoconstriction. Forty-two non-specific pathogen-free Wistar rats were included in the study. Eleven animals died during or after the procedure, 21 were submitted to left pneumonectomy and 10 to sham operation. These animals were sacrificed after 48 or 72 h. Perivascular pulmonary edema was more intense in pneumonectomized rats at 72 h (P = 0.0131). Neutrophil density was lower after pneumonectomy in both groups (P = 0.0168). There was higher immunohistochemical expression of eNOS in the pneumonectomy group (P = 0.0208), but no statistically significant difference in the expression of iNOS. The lumen-wall ratio and pO(2)/FiO(2) ratio did not differ between the operated and sham groups after pneumonectomy. Left pneumonectomy caused perivascular pulmonary edema with no elevation of immunohistochemical expression of iNOS or neutrophil density, suggesting the absence of correlation with the inflammatory process or oxidative stress. The increased expression of eNOS may suggest an intrinsic production of NO without signs of vascular reactivity.

Involvement of nitric oxide in acute lung inflammation induced by cigarette smoke in the mouse

Short-term exposure to cigarette smoke (CS) leads to acute lung inflammation (ALI) by disturbing oxidant/antioxidant balance. Both CS exposure and lung inflammation are important risk factors in the pathogenesis of chronic obstructive pulmonary disease. Nitric oxide (NO) is an oxidant both present in CS and produced in the inflammatory response, but its role in the effects of CS exposure is unclear. Our aim was to study involvement of NO in a model of CS exposure. Groups of mice (male C57BL/6) exposed to CS (six cigarettes per day over five days) were simultaneously subjected to treatment with vehicle (CS), 60mg/kg/day omega-nitro-l-arginine methyl ester (CS+l-NAME), 20mg/kg/day nitroglycerine (CS+NTG), or 120mg/kg/day l-arginine (CS+l-arg). Bronchoalveolar lavage fluid was then aspirated to perform cell counts, and malondialdehyde (MDA), nitrite, catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) levels were measured in lung homogenates. Macrophage and neutrophil counts were increased in the CS (p<0.001) and CS+l-NAME groups (p<0.05 and p<0.01, respectively); the CS+NTG and CS+l-arg groups showed no differences from the control group. MDA was increased in the CS (p<0.05) and CS+l-NAME (p<0.01) groups when compared to the control group. Nitrite levels were decreased in the CS and CS+l-NAME groups (p<0.001) and increased in the CS+NTG (p<0.001) and CS+l-arg (p<0.01) groups when compared to the control. CAT, SOD and GPx activities in the CS and CS+l-NAME groups were all significantly increased compared to the control group. Our results suggest that administration of NO donors or substrates may be a useful therapy in the treatment of ALI caused by CS.

Septic pulmonary microvascular endothelial cell injury: role of alveolar macrophage NADPH oxidase

A significant role for alveolar macrophages (AM) in the pathophysiology of sepsis-induced acute lung injury (ALI) has been shown; however, the mechanisms behind AM-related lung injury remain relatively uncertain. We examined the role of AM nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in pulmonary endothelial cell septic injury. NADPH oxidase is one of the major sources of cellular reactive oxygen species and has been implicated in endothelial injury in ALI. Pulmonary microvascular endothelial cells (PMVEC) monolayers were grown on Transwell inserts and incubated with wild-type and NADPH oxidase-deficient AM in the presence or absence of cytomix (equimolar TNF-alpha, IL-1beta, and IFN-gamma). Injury to the monolayers was assessed by trans-PMVEC Evans blue (EB)-labeled albumin flux. We found AM under cytomix stimulation caused significant EB-albumin flux across the PMVEC monolayers, and this effect was attenuated by the genetic deletion of AM NADPH oxidase. The pharmacological inhibition of AM NADPH oxidase with apocynin and PR-39 also significantly reduced AM-dependent PMVEC injury. In the AM-PMVEC cocultures, we also assessed PMVEC injury through measurement of protein oxidation and lipid peroxidation. AM were shown to cause a significant increase in these markers of PMVEC injury, which was also attenuated by the inhibition of NADPH oxidase or through the use of NADPH oxidase-deficient AM. PMVEC NADPH oxidase was shown not to significantly contribute to PMVEC injury in our studies. From our findings we have concluded that AM NADPH oxidase is crucial for the septic increase in pulmonary vascular permeability.

HMGB1: endogenous danger signaling

While foreign pathogens and their products have long been known to activate the innate immune system, the recent recognition of a group of endogenous molecules that serve a similar function has provided a framework for understanding the overlap between the inflammatory responses activated by pathogens and injury. These endogenous molecules, termed alarmins, are normal cell constituents that can be released into the extracellular milieu during states of cellular stress or damage and subsequently activate the immune system. One nuclear protein, High mobility group box-1 (HMGB1), has received particular attention as fulfilling the functions of an alarmin by being involved in both infectious and non-infectious inflammatory conditions. Once released, HMGB1 signals through various receptors to activate immune cells involved in the immune process. Although initial studies demonstrated HMGB1 as a late mediator of sepsis, recent findings indicate HMGB1 to have an important role in models of non-infectious inflammation, such as autoimmunity, cancer, trauma, and ischemia reperfusion injury. Furthermore, in contrast to its pro-inflammatory functions, there is evidence that HMGB1 also has restorative effects leading to tissue repair and regeneration. The complex functions of HMGB1 as an archetypical alarmin are outlined here to review our current understanding of a molecule that holds the potential for treatment in many important human conditions.

Clinical significance of serum HMGB-1 and sRAGE levels in systemic sclerosis: association with disease severity

INTRODUCTION

The high mobility group box 1 protein (HMGB-1)/advanced glycation end products (RAGE) system is recently shown to play an important part in immune/inflammatory disorders. However, the association of this system in systemic sclerosis (SSc) remains unknown.

MATERIALS AND METHODS

To determine clinical association of serum levels of HMGB-1 and soluble RAGE (sRAGE) in patients with SSc, sera from 70 patients with SSc and 25 healthy controls were examined by enzyme-linked immunosorbent assay. Sera from tight-skin mice and bleomycin-induced scleroderma mice, animal models for SSc, were also examined. Skin HMGB-1 and RAGE expression was assessed by immunohistochemistry.

RESULTS AND DISCUSSION

Serum HMGB-1 and sRAGE levels in SSc were higher than those in controls. Similarly, HMGB-1 and sRAGE levels in animal SSc models were higher than those in control mice. SSc patients with elevated HMGB-1 and sRAGE levels had more frequent involvement of several organs and immunological abnormalities compared to those with normal levels. Furthermore, HMGB-1 and sRAGE levels correlated positively with modified Rodnan total skin thickness score and negatively with pulmonary function test.

CONCLUSIONS

HMGB-1 and sRAGE expression in the sclerotic skin was more intense than normal skin. These results suggest that elevated serum HMGB-1 and sRAGE levels are associated with the disease severity and immunological abnormalities in SSc.

Alveolar macrophage inducible nitric oxide synthase-dependent pulmonary microvascular endothelial cell septic barrier dysfunction

Inducible nitric oxide (NO) synthase (iNOS) from neutrophils and alveolar macrophages (AM) contributes to the pathophysiology of murine septic acute lung injury (ALI). It is not known if AM iNOS has a direct effect on septic pulmonary microvascular endothelial cell (PMVEC) permeability. We hypothesized that AM iNOS mediates PMVEC permeability in vitro under septic conditions through NO and peroxynitrite. 100,000 confluent PMVEC on cell-culture inserts were co-incubated with iNOS+/+ vs. iNOS-/- AM, in various ratios of AM to PMVEC. PMVEC injury was assessed by trans-PMVEC Evans Blue-labelled albumin flux in the presence or absence of cytomix (equimolar TNF-alpha, IL-1beta and IFN-gamma). Cytomix stimulation dose-dependently increased trans-PMVEC EB-albumin flux, which was exaggerated (1.4+/-0.1% vs. 0.4+/-0.1% in unstimulated PMVEC, p<0.05) in the presence of iNOS+/+, but not iNOS-/-, AM in the upper compartment. Similarly, iNOS+/+, but not iNOS-/-, AM in the lower compartment also enhanced septic trans-PMVEC albumin leak. The mechanism of iNOS-dependent septic PMVEC permeability was pursued through pharmacologic studies with inhibitors of NOS, and scavengers of NO, superoxide, and peroxynitrite, and treatment of PMVEC with the NO donor, DETA-NONOate. Septic iNOS+/+ AM-dependent trans-PMVEC albumin leak was significantly attenuated by pharmacologic iNOS inhibition (L-NAME and 1400W), and scavenging of either NO (oxyhemoglobin), superoxide (PEG-SOD), or peroxynitrite (FeTPPS). Exogenous NO (DETA-NONOate) had no effect on PMVEC permeability. These data are consistent with a direct role of AM iNOS in septic PMVEC barrier dysfunction, which is likely mediated, in part, through peroxynitrite.

Hepatic transcription factor activation and proinflammatory mediator production is attenuated by hypertonic saline and pentoxifylline resuscitation after hemorrhagic shock

BACKGROUND

Fluid resuscitation can contribute to postshock inflammation and the development of end organ injury. We have previously observed an attenuation in pulmonary and ileal inflammation when hypertonic saline and pentoxifylline (HSPTX) were concomitantly administered after hemorrhage. We hypothesized that the attenuation in hepatic injury observed with HSPTX is associated with the reduction of transcription factor activation and proinflammatory mediator production when compared with Ringer's lactate (RL).

METHODS

Male Sprague-Dawley rats were resuscitated with racemic RL (32 mL/kg) or HSPTX (4 mL/kg 7.5% NaCl + PTX 25 mg/kg) and killed at 4 hours and 24 hours after resuscitation. Liver injury was determined by histology and serum aminotransferases. Nitrite, tumor necrosis factor-alpha, interleukin (IL)-1beta, and IL-6 were measured with enzyme-linked immunosorbent assay. High mobility group box 1, inducible nitric oxide synthase, nuclear factor (NF)-kappaB phosphorylation, and signal transducers and activators of transcription-3 phosphorylation were determined by Western blot. Transcription factor activation was verified with Electrophoretic Mobility Shift Assay.

RESULTS

RL resuscitation led to significant increases all measured parameters when compared with control. In contrast, HSPTX did not induce elevations in histologic liver injury or alanine aminotransferase levels. HSPTX attenuated inducible nitric oxide synthase by 23% (p < 0.01), nitrite by 25% (p < 0.05), tumor necrosis factor-alpha by 25% (p < 0.05), IL-1 by 63% (p < 0.01), IL-6 by 35% (p < 0.05), and high mobility group box 1 by 39% (p < 0.05) when compared with RL. HSPTX reduced IkappaB-alpha phosphorylation by 34% (p < 0.05), NF-kappaB p65 phosphorylation by 75% (p < 0.01), and signal transducers and activators of transcription-3 phosphorylation by 52% (p < 0.01).

CONCLUSIONS

The reduction in liver injury observed with HSPTX resuscitation after hemorrhage is associated with attenuation transcription factor activation and proinflammatory mediators. HSPTX has the potential to be a superior resuscitation fluid with significant immunomodulatory properties.

Anti-high mobility group box 1 monoclonal antibody ameliorates brain infarction induced by transient ischemia in rats

The high mobility group box-1 (HMGB1), originally identified as an architectural nuclear protein, exhibits an inflammatory cytokine-like activity in the extracellular space. Here we show that treatment with neutralizing anti-HMGB1 monoclonal antibody (mAb; 200 microg, twice) remarkably ameliorated brain infarction induced by 2-h occlusion of the middle cerebral artery in rats, even when the mAb was administered after the start of reperfusion. Consistent with the 90% reduction in infarct size, the accompanying neurological deficits in locomotor function were significantly improved. Anti-HMGB1 mAb inhibited the increased permeability of the blood-brain barrier, the activation of microglia, the expression of TNF-alpha and iNOS, and suppressed the activity of MMP-9, whereas it had little effect on blood flow. Intracerebroventricular injection of HMGB1 increased the severity of infarction. Immunohistochemical study revealed that HMGB1 immunoreactivity in the cell nuclei decreased or disappeared in the affected areas, suggesting the release of HMGB1 into the extracellular space. These results indicate that HMGB1 plays a critical role in the development of brain infarction through the amplification of plural inflammatory responses in the ischemic region and could be an outstandingly suitable target for the treatment. Intravenous injection of neutralizing anti-HMGB1 mAb provides a novel therapeutic strategy for ischemic stroke.