HSP70 Is a Critical Regulator of HSP90 Inhibitor's Effectiveness in Preventing HCl-Induced Chronic Lung Injury and Pulmonary Fibrosis

Exposure to hydrochloric acid (HCl) can provoke acute and chronic lung injury. Because of its extensive production for industrial use, frequent accidental exposures occur, making HCl one of the top five chemicals causing inhalation injuries. There are no Food and Drug Administration (FDA)-approved treatments for HCl exposure. Heat shock protein 90 (HSP90) inhibitors modulate transforming growth factor-β (TGF-β) signaling and the development of chemical-induced pulmonary fibrosis. However, little is known on the role of Heat Shock Protein 70 (HSP70) during injury and treatment with HSP90 inhibitors. We hypothesized that administration of geranylgeranyl-acetone (GGA), an HSP70 inducer, or gefitinib (GFT), an HSP70 suppressant, alone or in combination with the HSP90 inhibitor, TAS-116, would improve or worsen, respectively, HCl-induced chronic lung injury in vivo and endothelial barrier dysfunction in vitro. GGA, alone, improved HCl-induced human lung microvascular endothelial cells (HLMVEC) barrier dysfunction and, in combination with TAS-116, improved the protective effect of TAS-116. In mice, GGA reduced HCl toxicity and while TAS-116 alone blocked HCl-induced chronic lung injury, co-administration with GGA, resulted in further improvement. Conversely, GFT potentiated HCl-induced barrier dysfunction and impaired the antidotal effects of TAS-116. We conclude that combined treatments with HSP90 inhibitors and HSP70 inducers may represent a novel therapeutic approach to manage HCl-induced chronic lung injury and pulmonary fibrosis.

Growth hormone-releasing hormone antagonists protect against hydrochloric acid-induced endothelial injury in vitro

Growth hormone-releasing hormone (GHRH) regulates the synthesis of growth hormone from the anterior pituitary gland, and it is involved in inflammatory responses. On the other hand, GHRH antagonists (GHRHAnt) exhibit the opposite effects, resulting in endothelial barrier enhancement. Exposure to hydrochloric acid (HCL) is associated with acute and chronic lung injury. In this study, we investigate the effects of GHRHAnt in HCL-induced endothelial barrier dysfunction, utilizing commercially available bovine pulmonary artery endothelial cells (BPAEC). Cell viability was measured by utilizing 3-(4,5-dimethylthiazol2-yl)- 2,5-diphenyltetrazolium bromide (MTT) assay. Moreover, fluorescein isothiocyanate (FITC)-dextran was used to assess barrier function. Our observations suggest that GHRHAnt exert protective effects against HCL-induced endothelial breakdown, since those peptides counteract HCL-triggered paracellular hyperpermeability. Based on those findings, we propose that GHRHAnt represent a new therapeutic approach towards HCL-induced endothelial injury.

Germ cell apoptosis is critical to maintain Caenorhabditis elegans offspring viability in stressful environments

Maintaining reproduction in highly variable, often stressful, environments is an essential challenge for all organisms. Even transient exposure to mild environmental stress may directly damage germ cells or simply tax the physiology of an individual, making it difficult to produce quality gametes. In Caenorhabditis elegans, a large fraction of germ cells acts as nurse cells, supporting developing oocytes before eventually undergoing so-called physiological germ cell apoptosis. Although C. elegans apoptosis has been extensively studied, little is known about how germline apoptosis is influenced by ecologically relevant environmental stress. Moreover, it remains unclear to what extent germline apoptosis contributes to maintaining oocyte quality, and thus offspring viability, in such conditions. Here we show that exposure to diverse environmental stressors, likely occurring in the natural C. elegans habitat (starvation, ethanol, acid, and mild oxidative stress), increases germline apoptosis, consistent with previous reports on stress-induced apoptosis. Using loss-of-function mutant alleles of ced-3 and ced-4, we demonstrate that eliminating the core apoptotic machinery strongly reduces embryonic survival when mothers are exposed to such environmental stressors during early adult life. In contrast, mutations in ced-9 and egl-1 that primarily block apoptosis in the soma but not in the germline, did not exhibit such reduced embryonic survival under environmental stress. Therefore, C. elegans germ cell apoptosis plays an essential role in maintaining offspring fitness in adverse environments. Finally, we show that ced-3 and ced-4 mutants exhibit concomitant decreases in embryo size and changes in embryo shape when mothers are exposed to environmental stress. These observations may indicate inadequate oocyte provisioning due to the absence of germ cell apoptosis. Taken together, our results show that the central genes of the apoptosis pathway play a key role in maintaining gamete quality, and thus offspring fitness, under ecologically relevant environmental conditions.

Inhibition of Prostaglandin F2α Receptors Exaggerates HCl-Induced Lung Inflammation in Mice

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are severe respiratory disorders that are caused by aspiration, sepsis, trauma, and pneumonia. A clinical feature of ALI/ARDS is the acute onset of severe hypoxemia, and the mortality rate, which is estimated at 38-50%, remains high. Although prostaglandins (PGs) are detected in the bronchoalveolar lavage fluid of patients with ALI/ARDS, the role of PGF_2α in ALI remains unclear. We aimed to clarify the role of PGF_2α/PGF_2α receptor (FP) signaling in acid-induced ALI using an FP receptor antagonist, AL8810. Intratracheal injection of hydrochloric acid (HCl) increased neutrophil migration into the lungs, leading to respiratory dysfunction. Pre-administration of AL8810 further increased these features. Moreover, pre-treatment with AL8810 enhanced the HCl-induced expression of pro-inflammatory cytokines and neutrophil migratory factors in the lungs. Administration of HCl decreased the gene expression of lung surfactant proteins, which was further reduced by co-administration of AL8810. Administration of AL8810 also increased lung edema and reduced mRNA expression of epithelial sodium channel in the lungs, indicating that AL8810 reduced fluid clearance. Furthermore, AL8810 also increased lipopolysaccharide-induced expression of adhesion molecules such as intracellular adhesion molecule-1 and E-selectin in human umbilical vein endothelial cells. These results indicate that inhibition of FP receptors by AL8810 exacerbated HCl-induced ALI.

Age-Dependent Chronic Lung Injury and Pulmonary Fibrosis following Single Exposure to Hydrochloric Acid

Exposure to hydrochloric acid (HCl) represents a threat to public health. Children may inhale higher doses and develop greater injury because of their smaller airways and faster respiratory rate. We have developed a mouse model of pediatric exposure to HCl by intratracheally instilling p24 mice (mice 24 days old; 8-10 g) with 2 µL/g 0.1 N HCl, and compared the profile of lung injury to that in HCl-instilled adults (10 weeks old; 25-30 g) and their age-matched saline controls. After 30 days, alveolar inflammation was observed with increased proteinosis and mononuclear cells in the bronchoalveolar lavage fluid (BALF) in both HCl-instilled groups. Young p24 animals-but not adults-exhibited higher NLR family pyrin domain containing 3 (NLRP3) inflammasome levels. Increased amounts of Transforming Growth Factor-β (TGF-β) mRNA and its intracellular canonical and non-canonical pathways (p-Smad2 and p-ERK) were found in the lungs of both young and adult HCl-instilled mice. Constitutive age-related differences were observed in the levels of heat shock protein family (HSP70 and HSP90). HCl equally provoked the deposition of collagen and fibronectin; however, significant age-dependent differences were observed in the increase in elastin and tenascin C mRNA. HCl induced pulmonary fibrosis with an increased Ashcroft score, which was higher in adults, and a reduction in alveolar Mean Alveolar Linear Intercept (MALI). Young mice developed increased Newtonian resistance (Rn) and lower PV loops, while adults showed a higher respiratory system resistance and elastance. This data indicate that young p24 mice can suffer long-term complications from a single exposure to HCl, and can develop chronic lung injury characterized by a stronger persistent inflammation and lesser fibrotic pattern, mostly in the airways, differently from adults. Further data are required to characterize HCl time- and dose-dependent injury in young animals and to identify new key-molecular targets.

The HSP90 Inhibitor, AUY-922, Protects and Repairs Human Lung Microvascular Endothelial Cells from Hydrochloric Acid-Induced Endothelial Barrier Dysfunction

Exposure to hydrochloric acid (HCl) leads acutely to asthma-like symptoms, acute respiratory distress syndrome (ARDS), including compromised alveolo-capillary barrier, and respiratory failure. To better understand the direct effects of HCl on pulmonary endothelial function, we studied the characteristics of HCl-induced endothelial barrier dysfunction in primary cultures of human lung microvascular endothelial cells (HLMVEC), defined the involved molecular pathways, and tested the potentially beneficial effects of Heat Shock Protein 90 (HSP90) inhibitors. HCl impaired barrier function in a time- and concentration-dependent manner and was associated with activation of Protein Kinase B (AKT), Ras homolog family member A (RhoA) and myosin light chain 2 (MLC2), as well as loss of plasmalemmal VE-cadherin, rearrangement of cortical actin, and appearance of inter-endothelial gaps. Pre-treatment or post-treatment of HLMVEC with AUY-922, a third-generation HSP90 inhibitor, prevented and restored HCl-induced endothelial barrier dysfunction. AUY-922 increased the expression of HSP70 and inhibited the activation (phosphorylation) of extracellular-signal regulated kinase (ERK) and AKT. AUY-922 also prevented the HCl-induced activation of RhoA and MLC2 and the internalization of plasmalemmal VE-cadherin. We conclude that, by increasing the expression of cytoprotective proteins, interfering with actomyosin contractility, and enhancing the expression of junction proteins, inhibition of HSP90 may represent a useful approach for the management of HCl-induced endothelial dysfunction and acute lung injury.

Syk/NF-κB-targeted anti-inflammatory activity of Melicope accedens (Blume) T.G. Hartley methanol extract

ETHNOPHARMACOLOGICAL RELEVANCE

Melicope accedens (Blume) Thomas G. Hartley is a plant included in the family Rutaceae and genus Melicope. It is a native plant from Vietnam that has been used for ethnopharmacology. In Indonesia and Malaysia, the leaves of M. accedens are applied externally to decrease fever.

AIM OF THE STUDY

The molecular mechanisms of the anti-inflammatory properties of M. accedens are not yet understood. Therefore, we examined those mechanisms using a methanol extract of M. accedens (Ma-ME) and determined the target molecule in macrophages.

MATERIALS AND METHODS

We evaluated the anti-inflammatory effects of Ma-ME in lipopolysaccharide (LPS)-stimulated RAW264.7 cells and in an HCl/EtOH-triggered gastritis model in mice. To investigate the anti-inflammatory activity, we performed a nitric oxide (NO) production assay and ELISA assay for prostaglandin E2 (PGE₂). RT-PCR, luciferase gene reporter assays, western blotting analyses, and a cellular thermal shift assay (CETSA) were conducted to identify the mechanism and target molecule of Ma-ME. The phytochemical composition of Ma-ME was analyzed by HPLC and LC-MS/MS.

RESULTS

Ma-ME suppressed the production of NO and PGE₂ and the mRNA expression of proinflammatory genes (iNOS, IL-1β, and COX-2) in LPS-stimulated RAW264.7 cells without cytotoxicity. Ma-ME inhibited NF-κB activation by suppressing signaling molecules such as IκBα, Akt, Src, and Syk. Moreover, the CETSA assay revealed that Ma-ME binds to Syk, the most upstream molecule in the NF-κB signal pathway. Oral administration of Ma-ME not only alleviated inflammatory lesions, but also reduced the gene expression of IL-1β and p-Syk in mice with HCl/EtOH-induced gastritis. HPLC and LC-MS/MS analyses confirmed that Ma-ME contains various anti-inflammatory flavonoids, including quercetin, daidzein, and nevadensin.

CONCLUSIONS

Ma-ME exhibited anti-inflammatory activities in vitro and in vivo by targeting Syk in the NF-κB signaling pathway. Therefore, we propose that Ma-ME could be used to treat inflammatory diseases such as gastritis.

Gastroprotective effects of irsogladine maleate on ethanol/hydrochloric acid induced gastric ulcers in mice

BACKGROUND/AIMS

This study was conducted to investigate the inhibitory effect of irsogladine maleate (IM) on gastric ulcers induced by ethanol and hydrochloric acid (HCl).

METHODS

Mice were pretreated with IM for 1 hours before ulcer induction. Gastric ulcers were induced by oral administration of an ethanol/HCl mixture. To clarify the action mechanism of IM, the roles of 3'5'-cyclic adenosine monophosphate (cAMP), nitric oxide (NO), adenosine triphosphate-sensitive potassium (KATP) channels, prostaglandins and transient receptor potential cation channel subfamily V member 1 (TRPV1) were investigated, and lipid peroxidation in the stomach of IM-treated and -untreated animals was also measured.

RESULTS

IM significantly reduced the extent of ethanol/HCl mixture-induced gastric ulceration. It exhibited dose-related gastroprotection against the ethanol/ HCl-induced lesions, while pretreatment with glibenclamide but not N(ω)-nitro- L-arginine methyl ester, reversed this action. While pretreatment with the TRPV1 antagonist capsazepine failed to effectively block the gastroprotective effect of IM, the non-selective cyclooxygenase inhibitor indomethacin almost abolished it. IM also decreased the level of thiobarbituric acid reactive substances.

CONCLUSION

We concluded that IM exhibited significant gastroprotective effects in an ethanol/HCl-induced ulcer model, which appear to be mediated, at least in part, by NO, cAMP, endogenous prostaglandins, KATP channel opening, activation of TRPV1 channels, and antioxidant properties.

Antiulcer Activity of Steamed Ginger Extract against Ethanol/HCl-Induced Gastric Mucosal Injury in Rats

Ginger (Zingiber officianale), the most widely consumed species, is traditionally used as a folk medicine to treat some inflammatory diseases in China and Korea. However, the functional activity of steamed ginger extract on gastric ulcers has not been previously explored. The present study aimed to investigate antiulcer activity of steamed ginger extract (GGE03) against ethanol (EtOH)/HCl-induced gastric ulcers in a rat model. GGE03 (100 mg/kg) was orally administered for 14 days to rats before oral intubation of an EtOH/HCl mixture to induce gastric damage. Pretreatment with GGE03 markedly protected the formation of microscopic pathological damage in the gastric mucosa. Further, administration of GGE03 significantly increased mucosal total nitrate/nitrite production in gastric tissues, and elevated total GSH content, catalase activity and superoxide dismutase (SOD) expression as well as decreasing lipid peroxidation and myeloperoxidase (MPO) activity. Underlying protective mechanisms were examined by assessing inflammation-related genes, including nuclear factor-κB (NF-κB), prostaglandin E2 (PGE2), and pro-inflammatory cytokines levels. GGE03 administration significantly reduced the expression of NF-κB and pro-inflammatory cytokines. Our findings suggest that GGE03 possesses antiulcer activity by attenuating oxidative stress and inflammatory responses.

A comparison of four different models of acute respiratory distress syndrome in sheep

BACKGROUND

Acute respiratory distress syndrome (ARDS) can have various causes. The study objective was to investigate whether different pathophysiologic models of ARDS would show different respiratory, cardiovascular and inflammatory outcomes.

METHODS

We performed a prospective, randomized study in 27 ventilated ewes inducing ARDS using three different techniques to mimic the pulmonary causes of ARDS (ARDSp): warm saline lavage (n = 6), intratracheal hydrochloric acid (HCl; n = 6), intratracheal albumin (n = 10), and one technique to mimic an extrapulmonary cause of ARDS (ARDSexp): intravenous lipopolysaccharide (LPS iv; n = 5). ARDS was defined when PaO2 was < 15 kPa (112 mmHg) when ventilated with PEEP 10 cm H2O and FiO2 = 1.0. The effects on gas exchange were investigated by calculating the oxygenation index (OI) and the ventilation efficacy index (VEI) every 30 min for a period of 4 h. Post mortem lung lavage was performed to obtain broncho-alveolar lavage fluid (BALF) to assess lung injury and inflammation. Lung injury and inflammation were assessed by measuring the total number and differentiation of leukocytes, the concentration of protein and disaturated phospholipids, and interleukine-6 and -8 in the BALF. Histology of the lung was evaluated by measuring the mean alveolar size, alveolar wall thickness and the lung injury score system by Matute-Bello et al., as markers of lung injury. The concentration of interleukin-6 was determined in plasma, as a marker of systematic inflammation.

RESULTS

The OI and VEI were most affected in the LPS iv group and thereafter the HCl group, after meeting the ARDS criteria. Diastolic blood pressure was lowest in the LPS iv group. There were no significant differences found in the total number and differentiation of leukocytes, the concentration of protein and disaturated phospholipids, or interleukin-8 in the BALF, histology of the lung and the lung injury score. IL-6 in BALF and plasma was highest in the LPS iv group, but no significant differences were found between the other groups. It took a significantly longer period of time to meet the ARDS criteria in the LPS iv group.

CONCLUSIONS

The LPS model caused the most severe pulmonary and cardiovascular insufficiency. Surprisingly, there were limited significant differences in lung injury and inflammatory markers, despite the different pathophysiological models, when the clinical definition of ARDS was applied.

Alisma canaliculatum ethanol extract suppresses inflammatory responses in LPS-stimulated macrophages, HCl/EtOH-induced gastritis, and DSS-triggered colitis by targeting Src/Syk and TAK1 activities

ETHNOPHARMACOLOGICAL RELEVANCE

Alisma canaliculatum A.Braun & C.D.Bouché, distributed in Korea, Japan, China, and Taiwan, is a traditional medicine. In particular, the stem and root of Alisma canaliculatum A.Braun & C.D.Bouché are prescribed to relieve various inflammatory symptoms resulting from nephritis, cystitis, urethritis, and dropsy.

AIM OF STUDY

However, the curative mechanism of Alisma canaliculatum A.Braun & C.D.Bouché with respect to inflammatory symptoms is poorly understood. In this study, the curative roles of this plant in various inflammatory conditions as well as its inhibitory mechanism were aimed to examine using an ethanol extract (Ac-EE).

MATERIALS AND METHODS

Anti-inflammatory effects of Ac-EE were evaluated in lipopolysaccharide (LPS)-induced macrophages in vitro and HCl/EtOH-stimulated mouse model of gastritis and DSS-treated mouse model of colitis. To determine the potentially active anti-inflammatory components in this extracts, we employed HPLC. We also used kinase assays, reporter gene assay, immunoprecipitation analysis and target enzyme overexpressing cell analysis to analyze the molecular mechanisms and the target molecules.

RESULTS

This extract dose-dependently inhibited the production of nitric oxide (NO) and prostaglandin E₂ (PGE₂) from RAW264.7 cells and peritoneal macrophages activated by lipopolysaccharide (LPS). Additionally, Ac-EE ameliorated inflammatory symptoms resulting from gastritis and colitis. Ac-EE down-regulated the mRNA levels of inducible NO synthase (iNOS), tumor necrosis factor (TNF)-α, and cyclooxygenase-2 (COX-2). Ac-EE also blocked the nuclear translocation of nuclear factor (NF)-κB and activator protein (AP)- 1 in LPS-stimulated RAW264.7 cells. By analyzing the target signaling molecules activating these transcription factors, we found that Src and Syk, as well as molecular association between TAK1 and mitogen-activated protein kinase kinase 4/7 (MKK4/7), were targeted by Ac-EE.

CONCLUSIONS

Our data suggest that the Ac-EE NF-κB/AP-1-targeted anti-inflammatory potential is mediated by suppression of Src and Syk as well as the complex formation between TAK1 and its substrate proteins MKK4/7.

Detrimental ELAVL-1/HuR-dependent GSK3β mRNA stabilization impairs resolution in acute respiratory distress syndrome

A hallmark of acute respiratory distress syndrome (ARDS) is accumulation of protein-rich edema in the distal airspaces and its removal is critical for patient survival. Previous studies have shown a detrimental role of Glycogen Synthase Kinase (GSK) 3β during ARDS via inhibition of alveolar epithelial protein transport. We hypothesized that post-transcriptional regulation of GSK3β could play a functional role in ARDS resolution. To address this hypothesis, we performed an in silico analysis to identify regulatory genes whose expression correlation to GSK3β messenger RNA utilizing two lung cancer cell line array datasets. Among potential regulatory partners of GSK3β, these studies identified the RNA-binding protein ELAVL-1/HuR (Embryonic Lethal, Abnormal Vision, Drosophila-Like) as a central component in a likely GSK3β signaling network. ELAVL-1/HuR is a RNA-binding protein that selectively binds to AU-rich elements of mRNA and enhances its stability thereby increasing target gene expression. Subsequent studies with siRNA suppression of ELAVL-1/HuR demonstrated deceased GSK3β mRNA and protein expression and improved clearance of FITC-albumin in A549 cells. Conversely, stabilization of ELAVL-1/HuR with the proteasome inhibitor MG-132 resulted in induction of GSK3β at mRNA and protein level and attenuated FITC-albumin clearance. Utilizing ventilator-induced lung injury or intra-tracheal installation of hydrochloric acid to induce ARDS in mice, we observed increased mRNA and protein expression of ELAVL-1/HuR and GSK3β. Together, our findings indicate a previously unknown interaction between GSK3β and ELAV-1 during ARDS, and suggest the inhibition of the ELAV-1- GSK3β pathways as a novel ARDS treatment approach.

Antiulcer activity and subacute toxicity of trans-dehydrocrotonin from Croton cajucara

The antiulcerogenic activity of trans-dehydrocrotonin (DHC), a nor-clerodane diterpene isolated from Croton cajucara Benth. (Euphorbiaceae), and its subacute (35 days) toxicity were studied in mice and rats, respectively. For the antiulcerogenic tests, models of gastric ulcers induced in mice by ethanol/HCl or stress were used. In both models, an oral dose of DHC (100 mg/kg) significantly reduced (P <0.01) the formation of gastric lesions. DHC was also tested for its ability to scavenge free radicals, but no such action was observed in rat liver mitochondria. To assess the subacute toxicity, rats were treated orally with DHC (25, 50 and 100 mg/kg) for 5 weeks. A significant increase in liver weight was observed in male and female rats at highest doses, whereas a significant reduction in plasma alkaline phosphatase and cholesterol levels and an increase in gamma glutamyl transpeptidase were observed only at the highest dose (100 mg/kg) in female rats. DHC caused histopathological alterations in the liver that included a turbid tumefaction, microvacuolar degeneration and nuclear alterations. Despite the beneficial antiulcerogenic activity of DHC, our results suggest that the long-term use of this compound may induce liver damage.

Acute respiratory distress syndrome: we can't miss regional lung perfusion!

In adult respiratory distress syndrome (ARDS), life-threatening hypoxemia may occur, dictating the need for differentiated ventilator strategies. Pronounced consolidation and/or atelectasis have been well documented in ARDS, but the contribution of regional perfusion to oxygenation has been poorly addressed. Evidence has accumulated that, in ARDS, regional perfusion is extremely variable and may affect oxygenation, independently from the amount of atelectatic-consolidated lung regions. Thus, the response in oxygenation to different ventilatory settings, both during controlled and assisted mechanical ventilation, should be interpreted with caution. In fact, gas exchange may be not determined solely by changes in aeration, but also redistribution of perfusion. Furthermore, regional perfusion can play an important role in worsening of lung injury due to increased transmural pressures. In addition, distribution of perfusion in lungs might affect the delivery of drugs through the pulmonary circulation, including antibiotics. In recent years, several techniques have been developed to determine pulmonary blood flow with increasing level of spatial resolution, allowing a better understanding of normal physiology and various pathophysiological conditions, but most of them are restricted to experimental or clinical research. Lung ultrasound and novel algorithms for electrical impedance tomography represent new promising techniques that could enable physicians to assess the distribution of pulmonary blood flow at the bedside. In ARDS, we cannot afford missing regional lung perfusion! Please see related article: http://dx.doi.org/10.1186/s12871-015-0013-0.

Combined effects of ventilation mode and positive end-expiratory pressure on mechanics, gas exchange and the epithelium in mice with acute lung injury

The accepted protocol to ventilate patients with acute lung injury is to use low tidal volume (V(T)) in combination with recruitment maneuvers or positive end-expiratory pressure (PEEP). However, an important aspect of mechanical ventilation has not been considered: the combined effects of PEEP and ventilation modes on the integrity of the epithelium. Additionally, it is implicitly assumed that the best PEEP-V(T) combination also protects the epithelium. We aimed to investigate the effects of ventilation mode and PEEP on respiratory mechanics, peak airway pressures and gas exchange as well as on lung surfactant and epithelial cell integrity in mice with acute lung injury. HCl-injured mice were ventilated at PEEPs of 3 and 6 cmH(2)O with conventional ventilation (CV), CV with intermittent large breaths (CV(LB)) to promote recruitment, and a new mode, variable ventilation, optimized for mice (VV(N)). Mechanics and gas exchange were measured during ventilation and surfactant protein (SP)-B, proSP-B and E-cadherin levels were determined from lavage and lung homogenate. PEEP had a significant effect on mechanics, gas exchange and the epithelium. The higher PEEP reduced lung collapse and improved mechanics and gas exchange but it also down regulated surfactant release and production and increased epithelial cell injury. While CV(LB) was better than CV, VV(N) outperformed CV(LB) in recruitment, reduced epithelial injury and, via a dynamic mechanotransduction, it also triggered increased release and production of surfactant. For long-term outcome, selection of optimal PEEP and ventilation mode may be based on balancing lung physiology with epithelial injury.

Gastric acid induces mitochondrial superoxide production and lipid peroxidation in gastric epithelial cells

BACKGROUND

Gastric hydrochloric acid (HCl) has been regarded as an inciting factor in gastric mucosal injuries and has been reported to induce lipid peroxidation in vitro. However, because HCl is not an oxidant per se, the exact mechanism by which the acid induces lipid peroxidation is unknown. We hypothesized that gastric acid may disrupt mitochondrial transmembrane potential and induce the production of superoxide in mitochondria, which subsequently may induce lipid peroxidation and apoptosis in gastric mucosal cells.

METHODS

Firstly we treated gastric epithelial RGM1 cells with solutions containing various concentrations of HCl (i.e., of varying pH), and examined cellular injury, lipid peroxidation, and apoptosis with specific fluorescent dyes. Secondly, we performed electron paramagnetic resonance (EPR) spectroscopy of isolated, acid-exposed mitochondria from the cells, using a spin-trapping reagent for superoxide, 5-(2,2-dimethyl-1,3-propoxy cyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO). Finally, we established novel RGM1 cells that overexpressed manganese superoxide dismutase (MnSOD), which removes superoxide from mitochondria, and examined the effect of acid treatment on cellular membrane lipid peroxidation.

RESULTS

The results indicated that the exposure to acid indeed induced cellular injury, cellular lipid peroxidation, apoptosis, and the demonstration of the exact superoxide spectra on EPR spectroscopy in gastric epithelial cells, and that overexpression of MnSOD decreased superoxide production and prevented cellular lipid peroxidation.

CONCLUSION

These results suggested that gastric acid, like nonsteroidal anti-inflammatory drugs (NSAIDs), induces mitochondrial superoxide production, which induces gastric cellular injury by triggering cellular lipid peroxidation and apoptosis.

Gastroprotective activity of epitaondiol and sargaol

The effects of epitaondiol (1) and sargaol (2), isolated from the brown alga Stypopodium flabelliforme on HCl/ethanol-induced gastric lesions in mice were evaluated and compared with that of lansoprazole. Epitaondiol and sargaol (6.25 - 50 mg/kg) dose-dependently inhibited the appearance of gastric lesions in mice, displaying similar values to lansoprazole at 20 mg/kg. Both epitaondiol and sargaol showed gastroprotective activity with ED50 values of 40 mg/kg and 35 mg/kg, respectively. The results suggest that epitaondiol and sargaol protect the gastric mucosa in the HCl/EtOH model in mice.

Hydrochloric acid: an overlooked driver of environmental change

Research on the ecosystem impacts of acidifying pollutants, and measures to control them, has focused almost exclusively on sulfur (S) and nitrogen (N) compounds. Hydrochloric acid (HCl), although emitted by coal burning, has been overlooked as a driver of ecosystem change because most of it was considered to redeposit close to emission sources rather than in remote natural ecosystems. Despite receiving little regulatory attention, measures to reduce S emissions, and changes in energy supply, have led to a 95% reduction in United Kingdom HCl emissions within 20 years. Long-term precipitation, surface water, and soil solution data suggest that the near-disappearance of HCl from deposition could account for 30-40% of chemical recovery from acidification during this time, affecting both near-source and remote areas. Because HCl is highly mobile in reducing environments, it is a more potent acidifier of wetlands than S or N, and HCl may have been the major driver of past peatland acidification. Reduced HCl loadings could therefore have affected the peatland carbon cycle, contributing to increases in dissolved organic carbon leaching to surface waters. With many regions increasingly reliant on coal for power generation, HCl should be recognized as a potentially significant constituent of resulting emissions, with distinctive ecosystem impacts.

Hemodynamic effects of PEEP in a porcine model of HCl-induced mild acute lung injury

BACKGROUND

Positive end-expiratory pressure (PEEP) and sustained inspiratory insufflations (SI) during acute lung injury (ALI) are suggested to improve oxygenation and respiratory mechanics. We aimed to investigate the hemodynamic effects of PEEP with and without alveolar recruiting maneuver in a mild ALI model induced by inhalation of hydrochloric acid.

METHODS

Thirty-two pigs were randomly allocated into four groups (Control-PEEP, Control-SI, ALI-PEEP and ALI-SI). ALI was induced by intratracheal instillation of hydrochloric acid. PEEP values were progressively increased and decreased from 5, 10, 15 and 20 cmH2O in all groups. Three SIs maneuvers of 30 cmH2O for 20 s were applied to the assignable groups between each PEEP level. Transesophageal echocardiography (TEE), global hemodynamics, oxygenation indexes and gastric tonometry were measured 5 min after the maneuvers had been concluded and at each established value of PEEP (5, 10, 15 and 20 cmH2O).

RESULTS

The cardiac index, ejection fraction and end-diastolic volume of right ventricle were significantly (P < 0.001) decreased with PEEP in both Control and ALI groups. Left ventricle echocardiography showed a significant decrease in end-diastolic volume at 20 cmH2O of PEEP (P < 0.001). SIs did not exert any significant hemodynamic effects either early (after 5 min) or late (after 3 h).

CONCLUSIONS

In a mild ALI model induced by inhalation of hydrochloric acid, significant hemodynamic impairment characterized by cardiac function deterioration occurred during PEEP increment, but SI, probably due to low applied values (30 cmH2O), did not exert further negative hemodynamic effects. PEEP should be used cautiously in ALI caused by acid gastric content inhalation.

Underlying mechanism of ASIC1a involved in acidosis-induced cytotoxicity in rat C6 glioma cells

AIM

To investigate the underlying mechanism of acid-sensing ion channel (ASIC) 1a involved in the acidosis-induced cytotoxicity of rat C6 glioma cells.

METHODS

The stable ASIC1a-silenced C6 cells built with the RNA interference technology were confirmed by RT-PCR and Western blot analysis. Intracellular calcium ([Ca2+]i) in both the wild-type rat C6 glioma cells and the ASIC1a-silenced C6 cells were analyzed before and after acid application/exposure with the calcium imaging experiment.

RESULTS

The rapid extracellular pH drop induced the increase of [Ca2+]i in the wild-type C6 cells, but not in the ASIC1a-silenced C6 cells. During the prolonged acid exposure, [Ca2+]i was lower in the ASIC1a-silenced C6 cells than that in the control cells.

CONCLUSION

The resultant toxicity of [Ca2+]i might contribute to the acidosis-induced cytotoxicity.

Cannabinoid CB2 receptor activation prevents bronchoconstriction and airway oedema in a model of gastro-oesophageal reflux

Cannabinoids have been shown to inhibit sensory nerve activation in guinea-pigs and humans. Their effects are mediated by specific activation of two types of receptors, named CB(1) and CB(2). The purpose of this study was to investigate the effects of WIN 55,212-2, (R)-(+)-[2,3-dihydro-5methyl-3-[(4-morpholino)methyl]pyrrolo-[1,2,3-de]-1,4-benzoxazin-6-yl](1-naphthyl)methanone, a non selective agonist of cannabinoid receptors, and JWH 133, (6aR,10aR)-3-(1,1-dimethylbutyl)-6a,7,10,10a-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]pyran a selective cannabinoid CB(2) receptor agonist, on the sensory nerve component of intraoesophageal (i.oe.) HCl-induced airway microvascular leakage and bronchoconstriction in guinea-pigs. We also tested the effect of WIN 55,212-2 on substance P-induced plasma extravasation and bronchoconstriction. Airway microvascular leakage and bronchoconstriction induced by i.oe. HCl was inhibited by the cannabinoid CB(1)/CB(2) agonist WIN 55,212-2 (0.3-3 mg/kg i.p.) in a dose-dependent manner (maximal inhibition at the dose of 3 mg kg(-1), P<0.01). The effect of WIN 55,212-2 was inhibited by a cannabinoid CB(2) receptor antagonist SR 144528, [N-[(1S)-endo-1,3,3-trimethylbicyclo[2,2,1] heptan-2yl]-5-(-4-chloro-3-methylphenyl)-1-(4-methylbenzyl)pyrazole-3-carboxamide], but not by a CB(1) receptor antagonist, SR 141716, [N-(piperidin-1yl)-5-(-4-chlorophenyl)-1-(2,4dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride]. The cannabinoid CB(2) agonist JWH 133 (0.3-3 mg/kg i.p.) mimicked the inhibitory effect of WIN 55,212-2 on HCl-induced microvascular leakage. Under similar conditions, WIN 55,212-2 (1 mg kg (-1) i.p.) was unable to counteract the airway microvascular leakage and bronchoconstriction induced by substance P. These results suggest that inhibition by WIN 55,212-2 of airway plasma extravasation and bronchoconstriction induced by i.oe. HCl instillation in guinea-pigs is mediated through cannabinoid CB(2) receptor activation.

Protective effect of raloxifene on lipopolysaccharide and acid- induced acute lung injury in rats

AIM

To evaluate the protective effect of oral raloxifene on acute lung injury.

METHODS

Thirty adult, male Sprague-Dawley rats each weighing 180-210 g were used and divided into 3 groups: the raloxifene-lipopolysaccharide (LPS)-HCl group (n=10), the LPS-raloxifene-HCl group (n=10), and the placebo group (n=10). All the rats were injected intraperitoneally (ip) with 5 mg/kg LPS, and raloxifene (30 mg/kg) was orally administered 1 h before and 14 h after LPS injection into the raloxifene-LPS-HCl and the LPS-raloxifene-HCl groups, respectively; the placebo group received nothing. Sixteen hours after LPS injection, all the animals were anesthetized and the femoral artery was cannulated. All the rats received a direct intratracheal (IT) injection of HCl (pH 1.2; 0.5 mL/kg). The mean arterial pressure (MAP) and blood gas concentrations were measured. Fifteen rats (5 in each group, respectively) underwent a micro positron emission tomography (microPET) scan of the thorax 4 h after HCl instillation. The wet/dry (W/D) weight ratio determination and histopathological examination were also performed.

RESULTS

The rats in the LPS-raloxifene-HCl group had a lower [18F]fluorodeoxyglucose uptake compared with the rats in the placebo group (4.67+/-1.33 vs 9.01+/-1.58, respectively, P<0.01). The rats in the LPS-raloxifene-HCl group also had a lower histological lung injury score (8.20+/-1.23 vs 12.6+/-0.97, respectively, P<0.01) and W/D weight ratio (5.335+/-0.198 vs 5.886+/-0.257, respectively, P<0.01) compared to the placebo group. The rats in this group also showed better pulmonary gas exchange and more stable mean arterial pressure (MAP) compared to the placebo group.

CONCLUSION

Raloxifene provides a significant protective effect on acute lung injury in rats induced first by LPS ip injection and then by HCl IT instillation.

Laparoscopic transhiatal esophago-gastrectomy after corrosive injury

Esophago-gastric necrosis is a surgical emergency associated with high morbidity and mortality. We report a laparoscopic transhiatal esophago-gastrectomy performed on a 43-year-old male, presenting two hours after hydrochloric acid ingestion. A gastroscopy showed several oral mucosal ulcers, a significant edema of the pharynx and larynx, a necrosis of the middle and lower esophagus and of the gastric fundus and antrum. A conservative strategy with intensive care observation was initially followed. After a change of clinical signs, chest-abdominal computed tomography was realized and a pneumoperitoneum with free fluid in the left subphrenic space and bilateral pleural effusions was in evidence. A laparoscopic exploration was proposed to the patient, and confirmed the presence of free peritoneal fluid and necrosis with perforation of the upper part of the stomach. A laparoscopic total gastrectomy with subtotal esophagectomy was performed; the procedure finished with an esophagostomy on the left side of the neck and a laparoscopic feeding jejunostomy (video). Total operative time was 235 minutes. After six months a digestive reconstruction with esophagocoloplasty by laparotomy and cervicotomy was easily realized thanks to the advantages (few adhesions, bloodless, and simple colic mobilization) of the previous minimally invasive surgery.

New concept for a toxicity assay based on multiple indexes from the wave shape of damped metabolic oscillation induced in living yeast cells (part II): application to analytical toxicology

An ideal toxicity assay should utilize multiple indexes obtained from transient changes of metabolic activities. Here, we demonstrate the possibility for a novel toxicity bioassay using the damped glycolytic oscillation phenomenon occurring in starved yeast cells. In a previous study, the phenomenon was characterized in detail. Under optimum conditions to induce the phenomenon, the wave shapes of the damped glycolytic oscillations were changed by the instantaneous addition of both glucose and chemicals and by changing the chemical concentration. We estimated the changes in the oscillation wave shapes as six indexes, i.e., the number of wave cycles, maximum amplitude, oscillation frequency, attenuation coefficient, initial peak height, and non-steady-state time. These index changes were obtained from several kinds of chemicals. The chemicals, especially those for acids (0.01-100 mM HCl and 0.01-50 mM citric acid), bases (0.001-50 mM KOH), heavy metal ions (1-1,000 mg L(-1); Cu(2+), Pb(2+), Cd(2+), Hg(2+)), respiratory inhibitors (3-500 mg L(-1) NaN(3)), dissolved oxygen removers (10-300 mg L(-1) NaSO(3)), surfactants (10-200 mg L(-1) benzalkonium chloride), and aldehyde (10-1,000 mg L(-1) acetaldehyde), showed characteristic patterns depending on each chemical and its concentration. These significant results demonstrate the possibilities of new methods for both toxicity qualification and quantification.

Gastroprotective activity and cytotoxic effect of cyperenoic acid derivatives

The gastroprotective effect of the sesquiterpene cyperenoic acid and seven semi-synthetic derivatives was assessed in the HCl/ethanol-induced gastric ulcer model in mice. At doses of 25, 50 and 100 mg kg(-1), cyperenoic acid showed a dose-dependent gastroprotective effect reducing the lesions by 45 and 75% at 50 and 100 mg kg(-1), respectively. Seven derivatives of the sesquiterpene were prepared and their gastroprotective activity compared at 50 mg kg(-1). The cytotoxicity of the compounds was evaluated in fibroblasts and AGS cells. At 50 mg kg(-1), patchoulan-15-oic acid (compound 8) presented the best gastroprotective effect, reducing the gastric lesions by 86%, with a similar effect to lansoprazole at 20 mg kg(-1). The gastroprotective effect of cyperenol, cyperenoic acid methyl ester and the ethylamide and butylamide from cyperenoic acid were in the same range, reducing the gastric lesions by 72-77%. Cyperenol and cyperenoic acid methyl ester, however, were more cytotoxic with IC50 (concentration that produces a 50% inhibitory effect) values of 44 and 75, 48 and 75 microM against AGS cells and fibroblasts, respectively. The best gastroprotective effect with lower cytotoxicity was found for the compound 8, cyperenoic acid and the p-anisidyl derivative 7.

Activation of the alpha7 nAChR reduces acid-induced acute lung injury in mice and rats

New evidence indicates that neural mechanisms can down-regulate acute inflammation. In these studies, we tested the potential role of the alpha7 nicotinic acetylcholine receptor (alpha7 nAChR) in a rodent model of acid-induced acute lung injury. We first determined that the alpha7 nAChR was expressed by alveolar macrophages and lung epithelial cells. Then, using an acid-induced acute lung injury mouse model, we found that nicotine, choline, and PNU-282,987 (a specific alpha7 nAChR agonist) decreased excess lung water and lung vascular permeability, and reduced protein concentration in the bronchoalveolar lavage (BAL). Deficiency of alpha7 nAChR resulted in a 2-fold increase in excess lung water and lung vascular permeability. The reduction of proinflammatory cytokines (macrophage inflammatory protein-2 and TNF-alpha) in the BAL with nicotine probably resulted from the suppression of NF-kappaB activation in alveolar macrophages. The beneficial effect of nicotine was also tested in rat model of acid-induced acute lung injury in which BAL protein and receptor for advanced glycation end products (RAGE), a marker of type I cell injury, were reduced by nicotine treatment. These results indicate that activation of alpha7 nAChR may provide a new therapeutic pathway for the treatment of acute lung injury.

In vitro effects of hydrochloric acid and various concentrations of acetic, propionic, butyric, or valeric acids on bioelectric properties of equine gastric squamous mucosa

OBJECTIVE

To compare the effects of hydrochloric acid (HCl) and various concentrations of volatile fatty acids (VFAs) on tissue bioelectric properties of equine stomach nonglandular (NG) mucosa.

SAMPLE POPULATION

Gastric tissues obtained from 48 adult horses.

PROCEDURES

NG gastric mucosa was studied by use of Ussing chambers. Short-circuit current (Isc) and potential difference (PD) were measured and electrical resistance (R) and conductance calculated for tissues after addition of HCl and VFAs (5, 10, 20, and 40 mM) in normal Ringer's solution (NRS).

RESULTS

Mucosa exposed to HCl in NRS (pH of 1.5 and, to a lesser extent, 4.0) had a significant decrease in Isc, PD, and R, whereas tissues exposed to acetic acid at a pH of < 4.0, propionic and butyric acids at a pH of <or= 4.0, and valeric acid at a pH of <or= 7.0 induced a concentration-dependent effect on reduction in these same values. Values for Isc returned to baseline (recovery of sodium transport) after addition of calcium carbonate in tissues exposed to all concentrations of VFAs except the higher concentrations of valeric acid at a pH of <or= 4.0. Histologic examination revealed cell swelling in the mucosal layers below and adjacent to the stratum corneum in tissues exposed to HCl and VFAs at a pH of <or= 4.0.

CONCLUSIONS AND CLINICAL RELEVANCE

The VFAs, especially acetic acid, in the presence of HCl at a pH of <or= 4.0 appear to be important in the pathogenesis of NG mucosal ulcers in horses.

Attenuation of indomethacin- and HCl/ethanol-induced oxidative gastric mucosa damage in rats by kolaviron, a natural biflavonoid of Garcinia kola seed

Reactive oxygen species (ROS) have been implicated in the aetiology of HCl/ethanol- and indomethacin gastric mucosal damage. This study investigated the protective effects of kolaviron, a natural antioxidant from the seed of Garcinia kola, on oxidative gastric mucosal damage induced by HCl/ethanol, and indomethacin.A HCl/ethanol mixture (1.5 mL of 0.15 n HCl in 70% ethanol) and indomethacin (IND) caused severe gastric damage with an ulcer index of 2.90 +/- 0.8 and 2.5 +/- 0.4, respectively, and significant reductions in the gastric mucosal content of catalase (CAT), superoxide dismutase (SOD) and glutathione (GSH) (p < 0.001).Pre-treatment of animals with kolaviron (100 mg/kg) orally 1 h and once daily for 3 days prior to ulcer induction significantly reduced the formation of ulcers induced by HCl/ethanol with preventive ratios of 65 and 72, respectively, while rats treated with kolaviron 1 day and for 7 days prior to IND treatment attenuated ulcer formation by 59% and 77%. Pre-treatment with ranitidine 1 h prior to ulcer induction (50 mg/kg) elicited preventive ulcer ratio of 55. Kolaviron pre-treatment 1 h before ulcer induction attenuated the HCl/ethanol reduction in CAT, SOD and GSH by 43%, 42% and 30%, respectively, and 67%, 68% and 64% following 72 h treatment with kolaviron. Ranitidine elicited 24%, 41% and 29% protective effects, respectively.Similarly, kolaviron administered to rats 1 day and for 7 days before IND treatment attenuated the drug-induced inhibition of CAT by 44% and 70%; SOD by 23% and 43% and GSH by 32% and 55%, respectively. In a 1 h and 3-day treatment with kolaviron before HCl/ethanol administration, MDA was reduced by 35% and 55%, respectively, while kolaviron administration 1 day and for 7 days before IND elicited a 39% and 58% reduction in MDA. Ranitidine elicited 39% and 50% reduction in MDA following HCl/ethanol and IND treatment. The results indicate the gastroprotective activity of kolaviron, which may be linked to its intrinsic antioxidant properties.

Loblolly pine and slash pine responses to acute aluminum and acid exposures

In response to concerns about aluminum and HCl exposure associated with rocket motor testing and launches, survival and growth of full-sib families of loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) were evaluated in a nursery bed experiment. Each species was exposed to a single soil application of aluminum chloride (0.33 M AlCl(3), pH 2.5), hydrochloric acid (0.39 M HCl, pH 0.6) or water, with or without mycorrhizal inoculation with Pisolithus tinctorius (Coker and Couch). After 20 weeks without inoculation, survival in AlCl(3) and HCl treatments averaged 52% for loblolly pine and 72% for slash pine. Inoculation improved survival of loblolly pine, receiving HCl from 49 to 73%, and of those receiving AlCl3, from 55 to 90%. Inoculation also resulted in improved survival and growth of individual families in AlCl(3), but not in HCl treatments. Results illustrate the relative resistance of both pine species to the acute treatments supplied, the improvement in resistance associated with mycorrhizal inoculation and the importance of field testing, following hydroponic screening, to verify the resistance to soil-supplied stresses.

Effect of Acid and Pepsin on Glottic Wound Healing

OBJECTIVE

To evaluate the effects of acid and pepsin on the healing of traumatized vocal folds in a simulated reflux model. Gastroesophageal reflux is related to various laryngeal manifestations. However, there is a lack of established reflux animal models that would ensure longer observation periods.

DESIGN

A prospective randomized animal study.

INTERVENTIONS

Forty-two rabbits underwent a stripping procedure of the unilateral glottis and catheter insertion under transoral endoscopic guidance. The animals were randomly assigned to a control group (n = 21; isotonic sodium chloride was used) or a reflux group (n = 21, acid and pepsin were used). They received intrapharyngeal catheter irrigation with 3 mL of isotonic sodium chloride or a solution of acid with a pH of 3 and pepsin, 0.3 mg/mL, twice daily for 4 or 8 weeks after surgery.

MAIN OUTCOME MEASURES

Gross and histologic findings of the preinjured glottides of the 2 groups were compared.

RESULTS

The catheter extrusion rate was significantly low (6%), and any catheter problems were immediately solved by reinsertion or reconnection. The extent of glottic scarring and frequency of granulation formation were higher in the reflux group compared with the control group (P<.05). Histologic inflammation scores and collagen deposition were significantly greater in the reflux group compared with the control group (P<.05).

CONCLUSIONS

Our data suggest that glottic wound healing is significantly affected by acid and pepsin. Antireflux treatment can be advocated to minimize further injury caused by gastroesophageal reflux in patients who undergo laryngeal surgery.

Comparison of systemic and local effects of nitric acid and hydrochloric acid: an experimental study in a rat model

BACKGROUND

We aimed to determine the local and systemic effects of widely available household cleaners, namely 45% nitric acid (NHO(3)), and 18% hydrochloric acid (HCl), in a rat model.

METHODS

This prospective, experimental, placebo-controlled trial was carried out in the Animal Research Laboratory of Akdeniz University hospital. Commonly available solution of 45% NHO(3) and 18% HCl were tested against normal saline. Each solution was administrated orally to groups consisting of ten rats. The metabolic changes were determined by measuring the pH and calcium (Ca) levels before and after the administration of solutions. In addition, the pathological changes and mortality rates were determined for each group.

RESULTS

There was a statistically significant increase in the post-ingestion (30 minutes later) Ca levels and a decrease in the post-ingestion pH levels after the administration of test solution in the NHO(3) (p=0.006 for Ca increase, p=0.001 for pH decrease) and HCl (p=0.007 for Ca increase, p=0.023 for pH decrease) groups. There was also a statistically significant difference between groups for Ca increase (p=0.000) and pH decrease (p=0.006). In post hoc analysis, the difference between the groups was found to be originated from the placebo group. In the pathological evaluation of esophagus and stomach, there was a statistically significant difference between groups (p=0.009 (E) and p=0.016 (S)) and the difference was found to be originated from the control group (p=0.543 (E), p=0.244 (S) for NHO(3) and HCl). The 30-minute mortality rates were 0,2 in the NHO(3) group, 0,6 in the HCl group and 0 in the control group.

CONCLUSION

Serious metabolic and mild local pathological changes can occur after the ingestion of household NHO3 and HCl solutions. Further studies should be performed to elucidate the causes of death following oral ingestion of these compounds and appropriate public health warnings should be taken.

An internal dose model of incapacitation and lethality risk from inhalation of fire gases

A mathematical model for estimating the likelihood of incapacitation and lethality from the inhalation of toxic gases is presented. The model computes an internal dose, equal to retained toxic gas per body mass, which is used to extrapolate outcomes across species. Account is taken for ventilation changes due to species, activity, and chemical response. The internal dose is correlated with each outcome using a cumulative, log-normal, probability distribution, which allows the estimation of tolerances for any population incidence. No internal interactions of gases are modeled and probabilities are combined independently. The model compares favorably with combined gas and large animal data.

Can the aqueous decoction of mango flowers be used as an antiulcer agent?

This study was designed to determine the effect of Mangifera indica flowers decoction, on the acute and subacute models of induced ulcer in mice and rats. A single oral administration of the aqueous decoction (AD) from M. indica up to a dose of 5 g/kg, p.o. did not produce any signs or symptom of toxicity in the treated animals. The oral pre-treatment with AD (250, 500 and 1000 mg/kg) in rats with gastric lesions induced by ethanol, decreased the gastric lesions from 89.0+/-6.71 (control group) to 9.25+/-2.75, 4.50+/-3.30 and 0, respectively. Pretreatment with AD (250, 500 and 1000 mg/kg) to mice with HCl/ethanol- or stress-induced gastric lesions resulted in a dose-dependent significant decrease of lesion index. In the piroxicam-induced gastric lesions, the gastroprotective effect of AD was reducing with the increase of the AD dose. In the pylorus-ligature, AD (p.o.) significantly decreased the acid output indicating the antisecretory property involved in the gastroprotective effect of M. indica. Treatment with AD during 14 consecutive days significantly accelerated the healing process in subacute gastric ulcer induced by acetic acid in rats. Pretreatment with N-nitro-l-arginine methyl ester (l-NAME), an inhibitor of NO-synthase, did not abolish the gastroprotective effects (99% with saline versus 80% with l-NAME) of AD against ethanol-induced gastric lesions. Pretreatment with N-ethylmaleimide (NEM), a blocker of endogenous sulphydryl group, significantly abolished the protective effects of AD against ethanol-induced gastric ulcers (95% with saline versus 47% with NEM). Phytochemical screening showed the presence of steroids, triterpenes, phenolic compounds and flavonoids. Estimation of the global polyphenol content in the AD was performed by Folin-Ciocalteu method and showed approximately 53% of total phenolic on this extract. These findings indicate the potential gastroprotective and ulcer-healing properties of aqueous decoction of M. indica flowers and further support its popular use in gastrointestinal disorders in Caribbean.

Lipoxin A(4) regulates bronchial epithelial cell responses to acid injury

Aspiration of gastric acid commonly injures airway epithelium and, if severe, can lead to respiratory failure from acute respiratory distress syndrome. Recently, we identified cyclooxygenase-2 (COX-2)-derived prostaglandin E(2) (PGE(2)) and lipoxin A(4) (LXA(4)) as pivotal mediators in vivo for resolution of acid-initiated acute lung injury. To examine protective mechanisms for these mediators in the airway, we developed an in vitro model of acid injury by transiently exposing well-differentiated normal human bronchial epithelial cells to hydrochloric acid. Transmission electron microscopy revealed selective injury to superficial epithelial cells with disruption of cell attachments and cell shedding. The morphological features of injury were substantially resolved within 6 hours. Acid triggered and early marked increases in COX-2 expression and PGE(2) production, and acid-induced PGE(2) significantly increased epithelial LXA(4) receptor (ALX) expression. LXA(4) is generated in vivo during acute lung injury, and we observed that nanomolar quantities increased basal epithelial cell proliferation and potently blocked acid-triggered interleukin-6 release and neutrophil transmigration across well-differentiated normal human bronchial epithelial cells. Expression of recombinant human ALX in A549 airway epithelial cells uncovered ALX-dependent inhibition of cytokine release by LXA(4). Together, these findings indicate that injured bronchial epithelial cells up-regulate ALX in a COX-2-dependent manner to promote LXA(4)-mediated resolution of airway inflammation.

Polymyxin B immobilized column is effective for hydrochloric acid-induced lung injury in rats

The purpose of this study was to examine whether hemoperfusion using polymyxin B (PMX) immobilized column improves hydrochloric acid (HCl)-induced lung injury. Rats weighing 350 g underwent hemoperfusion for 30 min at a flow rate of 120 ml/h after the intratracheal instillation of hydrochloric acid or water. Rats were divided into those that underwent hemoperfusion, with or without polymyxin B column, 30 min after HCl instillation ("HCl+PMX" and "HCl"), and hemoperfusion with or without polymyxin B column 30 min after water instillation ("Aqua+PMX" and "Aqua"). Systolic blood pressure, arterial blood gas analysis and white blood cell count and neutrophils were measured before, 1 and 3h after hemoperfusion. Plasma and bronchoalveolar lavage fluid concentrations of growth-related oncogene/cytokine-induced neutrophils chemoattractant-1 (GRO/CINC-1) were measured at 1 and 3h after hemoperfusion. Arterial oxygen concentrations were higher in the "HCl+PMX" group than in the "HCl" group. The total numbers of cells and neutrophils in the bronchoalveolar lavage fluid were significantly higher in the "HCl" group than in the others. The GRO/CINC-1 concentrations in the plasma and bronchoalveolar lavage fluid and the albumin ratio in the "HCl+PMX" group were significantly lower than in the "HCl" group. Direct hemoperfusion using polymyxin B immobilized column treatment affects the recruitment of circulating neutrophils to the lungs due to the decrease in mediators for non-endotoxic lung injury.

Centers for Disease Control and Prevention (CDC). Improper disposal of hazardous substances and resulting injuries--selected States, January 2001-March 2005

Many consumer and industrial products, including fuels, solvents, fertilizers, pesticides, paints, and household cleaning disinfectants, contain hazardous substances. Improper disposal of these materials can lead to unexpected releases of toxins that are hazardous to humans and harmful to the environment. This report summarizes all known events involving improper disposal of hazardous substances reported to the Agency for Toxic Substances and Disease Registry (ATSDR) during January 2001-March 2005, describes four illustrative case reports, and provides recommendations for preventing injury resulting from improper disposal.

Effect of cyclooxygenase-2 inhibitor pretreatment on gas exchange after hydrochloric acid aspiration in rats

The present study was carried out to determine the effect of cyclooxygenase-2 (COX-2) inhibitor on acid aspiration-induced lung injury in rats. Rats were allocated into one of four groups. Group H received intratracheal instillation of HCl. Group S received saline intratracheally. Group HC received COX-2 inhibitor (celecoxib) 10 mg/kg intravenously 30 min before intratracheal instillation of HCl. Group C underwent bronchoalveolar lavage (BAL) only. All rats were mechanically ventilated for 30 min before BAL. Arterial blood gas analysis was done immediately before BAL. Groups H, S, and HC were subdivided to each two groups. Groups H-1, S-1, and HC-1 underwent BAL 1 h after instillation, whereas groups H-8, S-8, and HC-8 underwent BAL 8 h after instillation. The BAL fluid was used to measure the prostaglandin E2 (PGE2) concentration. Intratracheal HCl resulted in impaired oxygenation. COX-2 inhibitor attenuated the impairment of oxygenation 8 h after instillation but not after 1 h. Intratracheal HCl caused an increase in PGE2 concentration. COX-2 inhibitor attenuated an increase in PGE2 concentration 8 h after instillation but not after 1 h. The results show that COX-2 inhibitor attenuates the oxygenation impairment and the increase in alveolar PGE2 concentration during the inflammatory phase of acid aspiration-induced lung injury in rats.

Activated protein C attenuates acid-aspiration lung injury in rats

Acid aspiration causes direct lung damage and secondary inflammatory response involving several cytokines and accumulation of neutrophils. Activated protein C (APC) exhibits antithrombotic and anti-inflammatory properties. We examined the effect and mechanism of pre-treatment APC on acid-aspirated lung injury in rats. Anesthetized rats were instilled intratracheally with normal saline (NS, 2 ml kg(-1)) or hydrochloric acid (HCl, 0.1 N, 2 ml kg(-1)). Thirty minutes before HCl instillation, APC (200 U kg(-1) h(-1)) was infused continuously into the right jugular vein. Animals were ventilated during the experiments. Five hours after HCl or NS instillation, bronchoalveolar lavage fluid (BALF) and lung tissue samples were obtained. Total and differential cell count, absorbance, albumin concentration, concentrations of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6 and cytokine-induced neutrophil chemoattractant (CINC) in BALF, wet and dry weight (W/D) ratio were measured. Platelet count and fibrin degradation product (FDP) in peripheral blood were also measured. HCl instillation markedly increased these values in BALF as well as W/D ratio. APC attenuated the parameters increased by HCl-induced lung injury in rats. However, HCl instillation and APC treatment did not cause significant changes in platelet count and FDP compared with the control. We conclude that APC treatment protected the rats against HCl-induced lung injury and that this action seemed to be due to the anti-inflammatory properties of this protein rather than its anti-coagulant effects.

Irritative action of alcoholic beverages in rat stomachs: A comparative study with ethanol

The mucosal irritative action of alcoholic beverages such as white wine, Japanese sake and whisky was examined in rat stomachs in vivo and in vitro, in comparison with ethanol. The concentration of ethanol in these alcoholic beverages was 15%. Mucosal application of ethanol (15%) and whisky in the chambered stomach caused a decrease in gastric potential difference (PD), while that of Japanese sake and white wine caused a slight increase but not decrease in PD. Likewise, both ethanol and whisky markedly reduced the cell viability of RGM1 cells after 5 min incubation, whereas neither Japanese sake nor white wine had any effect. In addition, supplementation of glucose, one of the non-alcoholic ingredients of white wine and Japanese sake, antagonized a reduction in both PD and cell viability caused by ethanol. These results suggest that the mucosal irritative action of Japanese sake and white wine is much less than that of ethanol or whisky and that these properties may be, at least partly, due to the glucose contained in these alcoholic beverages.

Acid-induced pain and its modulation in humans

Despite the discovery of ion channels that are activated by protons, we still know relatively little about the signaling of acid pain. We used a novel technique, iontophoresis of protons, to investigate acid-induced pain in human volunteers. We found that transdermal iontophoresis of protons consistently caused moderate pain that was dose-dependent. A marked desensitization occurred with persistent stimulation, with a time constant of approximately 3 min. Recovery from desensitization occurred slowly, over many hours. Acid-induced pain was significantly augmented in skin sensitized by acute topical application of capsaicin. However, skin desensitized by repeated capsaicin application showed no significant reduction in acid-induced pain, suggesting that both capsaicin-sensitive and insensitive sensory neurons contribute to acid pain. Furthermore, topical application of non-steroidal anti-inflammatory drugs (NSAIDs) significantly attenuated acid-evoked pain but did not affect the heat pain threshold, suggesting a specific interaction between NSAIDs and peripheral acid sensors. Subcutaneous injection of amiloride (1 mm) also significantly inhibited the pain induced by iontophoresis of acid, suggesting an involvement of acid-sensing ion channel (ASIC) receptors. Conversely, iontophoresis of acid over a wide range of skin temperatures from 4 to 40 degrees C produced only minor changes in the induced pain. Together these data suggest a prominent role for ASIC channels and only a minor role for transient receptor potential vanilloid receptor-1 as mediators of cutaneous acid-induced pain.

[Prophylactic effect of ambroxol on acute hydrochloric acid aspiration - induced lung injury]

OBJECTIVE

To evaluate the protective effect of ambroxol, a muco-active drug, on acute hydrochloric acid-induced lung injury in rats.

METHODS

Thirty pathogen-free SD rats were randomly divided into three groups: group A (n=10) and group B (n=10) were injected normal saline (NS) intraperitoneally (6.7 ml/kg), and group C with ambroxol (50 mg/kg), once a day for 3 consecutive days. Then animals received in tracheal instillation of NS (group A, pH 5.3, 1.2 ml/kg) or hydrochloric acid/NS (group B and C, pH 1.25, 1.2 ml/kg). Five hours after instillation of the injury vehicle, the arterial gas was determined, and the extent of lung injury was assessed by measuring the ratio of wet to dry weight (W/D) and evaluation of pathological change in lung tissue.

RESULTS

(1)Partial pressure of oxygen in arterial blood (PaO(2)) was significantly lower in group B than in groups A and C, although pH and partial pressure of carbon dioxide in arterial blood (PaCO(2)) in three groups showed little difference (all P<0.01). (2)The W/D was the highest in group B and the lowest in group A. (3)Severe acute lung injuries were detected in group B by pathological examination, the extent of injury was less in group C than in group B, but more severe than in group A (group A vs. B and B vs. C in mean pathologic score, P<0.01 and P<0.05, respectively).

CONCLUSION

Hydrochloric-acid aspiration may induce an acute and diffuse lung injury, with manifestations of hyperpnea, lower PaO(2) and severe pathological changes in lung tissues. Ambroxol may have a protective effect against lung injury induced by hydrochloric acid.

Cyclooxygenase 2 Plays a Pivotal Role in the Resolution of Acute Lung Injury

Acute lung injury (ALI) is a severe illness with excess mortality and no specific therapy. In its early exudative phase, neutrophil activation and accumulation in the lung lead to hypoxemia, widespread tissue damage, and respiratory failure. In clinical trials, inhibition of proinflammatory mediators has not proven effective. In this study, we pursued a new investigative strategy that emphasizes mediators promoting resolution from lung injury. A new spontaneously resolving experimental murine model of ALI from acid aspiration was developed to identify endogenous proresolving mechanisms. ALI increased cyclooxygenase 2 (COX-2) expression in murine lung. Selective pharmacologic inhibition or gene disruption of COX-2 blocked resolution of ALI. COX-2-derived products increased levels of the proresolving lipid mediators lipoxin A4 (LXA4) and, in the presence of aspirin, 15-epi-LXA4. Both LXA4 and 15-epi-LXA4 interact with the LXA4 receptor (ALX) to mediate anti-inflammatory actions. ALX expression was markedly induced by acid injury and transgenic mice with increased ALX expression displayed dramatic protection from ALI. Together, these findings indicate a protective role in ALI for COX-2-derived mediators, in part via enhanced lipoxin signaling, and carry potential therapeutic implications for this devastating clinical disorder.

Acid and particulate-induced aspiration lung injury in mice: importance of MCP-1

A model of aspiration lung injury was developed in WT C57BL/6 mice to exploit genetically modified animals on this background, i.e., MCP-1(-/-) mice. Mice were given intratracheal hydrochloric acid (ACID, pH 1.25), small nonacidified gastric particles (SNAP), or combined acid plus small gastric particles (CASP). As reported previously in rats, lung injury in WT mice was most severe for "two-hit" aspiration from CASP (40 mg/ml particulates) based on the levels of albumin, leukocytes, TNF-alpha, IL-1beta, IL-6, MCP-1, KC, and MIP-2 in bronchoalveolar lavage (BAL) at 5, 24, and 48 h. MCP-1(-/-) mice given 40 mg/ml CASP had significantly decreased survival compared with WT mice (32% vs. 80% survival at 24 h and 0% vs. 72% survival at 48 h). MCP-1(-/-) mice also had decreased survival compared with WT mice for CASP aspirates containing reduced particulate doses of 10-20 mg/ml. MCP-1(-/-) mice given 5 mg/ml CASP had survival similar to WT mice given 40 mg/ml CASP. MCP-1(-/-) mice also had differing responses from WT mice for several inflammatory mediators in BAL (KC or IL-6 depending on the particle dose of CASP and time of injury). Histopathology of WT mice with CASP (40 mg particles/ml) showed microscopic areas of compartmentalization with prominent granuloma formation by 24 h, whereas lung tissue from MCP-1(-/-) mice had severe diffuse pneumonia without granulomas. These results indicate that MCP-1 is important for survival in murine aspiration pneumonitis and appears to act partly to protect uninjured lung regions by promoting isolation and compartmentalization of tissue with active inflammation.

Early treatment with pentoxifylline reduces lung injury induced by acid aspiration in rats

STUDY OBJECTIVES

To evaluate the effect of pentoxifylline treatment on gas exchange and mortality immediately after bilateral instillation of hydrochloric acid.

DESIGN

Randomized, prospective, placebo-controlled trial.

SETTING

Animal laboratory of a university hospital.

SUBJECTS

Twenty-four, adult, male Sprague-Dawley rats.

METHODS

Sevoflurane-anesthetized rats (n = 12 in each group) underwent tracheostomy and insertion of a cannula into a hind paw vein and the left carotid artery. All animals received volume-controlled mechanical ventilation (zero positive end-expiratory pressure; fraction of inspired oxygen, 0.21). Acute lung injury was induced by instillation of 0.4 mL/kg 0.1 mol/L hydrochloric acid. The animals were randomized into two groups. The pentoxifylline group (n = 12) received a bolus of 20 mg/kg IV pentoxifylline after aspiration, followed by a continuous infusion of 6 mg/kg/h. The placebo group (n = 12) received an equivalent volume of saline solution. Arterial blood samples were collected for blood gas analysis 15 min and 0 min prior to aspiration and 30, 90, 180, 270, and 360 min after aspiration. Hemodynamic parameters, temperature, and ECG were recorded simultaneously. The primary end point was 6 h after aspiration. All surviving rats were killed by IV administration of pentobarbital. To assess morphologic changes due to lung injury, all animals underwent CT in inspiratory hold at the end of the experiment.

MEASUREMENTS AND RESULTS

No difference in baseline measurements was observed. In pentoxifylline-treated rats, Pao(2) was significantly increased (p < 0.05) at 30, 90, 180, 270, and 360 min. Mortality at 6 h was 17% in the pentoxifylline group vs 67% in the placebo group. Placebo-treated rats showed significant abnormalities in CT lung scans compared with the pentoxifylline group.

CONCLUSIONS

Acid aspiration impairs gas exchange and induces hypotension. Pentoxifylline administration shortly after acid instillation results in significant alleviation of impaired oxygenation, stabilization of BP with higher heart rates, and improved survival after 6 h.

The use of a retrievable self-expanding stent in treating childhood benign esophageal strictures

BACKGROUND/PURPOSE

Esophageal stenting is a popular form of treatment of esophageal strictures in adults but is not widely used in children. The aim of the current study was to investigate whether esophageal stents could be used safely and effectively in the treatment of esophageal stenosis in children.

METHODS

Covered retrievable expandable nitinol stents were placed in 8 children with corrosive esophageal stenosis. The stents were removed 1 to 4 weeks after insertion.

RESULTS

The stents were placed in all patients without complications and were later removed successfully. After stent placement, all patients could take solid food without dysphagia. Stent migration occurred in one patient and so the insertion procedure was repeated to reposition the stent. During the 3-month follow-up period after stent removal, all children could eat satisfactorily. After 6 months, 2 children required balloon dilation (3 times in one and 5 times in the other). The dysphagia score improved in all patients.

CONCLUSIONS

The use of the covered retrievable expandable stent is an effective and safe method in treating childhood corrosive esophageal stenosis.

Differential effects of sustained inflation recruitment maneuvers on alveolar epithelial and lung endothelial injury

OBJECTIVE

The role of recruitment maneuvers in mechanical ventilation for patients with the acute respiratory distress syndrome and acute lung injury remains uncertain in part due to a lack of data on the effects of specific recruitment maneuvers on lung injury severity. The primary objective of this study was to determine the effect of one type of recruitment maneuver--sustained inflation--on alveolar epithelial and lung endothelial injury in experimental acute lung injury.

DESIGN

Randomized experimental study.

SETTING

Academic research laboratory.

SUBJECTS

Forty-nine Sprague-Dawley rats.

INTERVENTIONS

Lung injury was induced in anesthetized, ventilated rats by instillation of acid (pH 1.5) into the airspaces. Rats were ventilated with a tidal volume of 6 mL/kg and a positive end-expiratory pressure of 5 cm H(2)O with or without a sustained inflation recruitment maneuver repeated every 30 mins. Each recruitment maneuver consisted of two 30-sec inflations to total lung capacity (30 cm H(2)O) 1 min apart.

MEASUREMENTS AND MAIN RESULTS

The use of recruitment maneuvers significantly improved oxygenation, compliance, end-expiratory lung volume, functional residual capacity, and deadspace fraction. Recruitment maneuvers reduced extravascular lung water and lung endothelial injury as measured by protein permeability (217 +/- 28 vs. 314 +/- 70 extravascular plasma equivalents [microL], p < .05). However, recruitment maneuvers did not prevent alveolar epithelial injury. Epithelial permeability and bronchoalveolar lavage RTI40 levels, a marker of type I cell injury, were similar with or without recruitment maneuvers. Recruitment maneuvers decreased epithelial fluid transport, a functional marker of epithelial injury. Recruitment maneuvers did not reduce markers of airspace inflammation.

CONCLUSIONS

Sustained inflation recruitment maneuvers improve respiratory mechanics and oxygenation and may protect the lung endothelium but do not reduce alveolar epithelial injury. Because of the differential effects of recruitment maneuvers on the lung endothelium and alveolar epithelium, the net effect in clinical acute lung injury may not be beneficial. Additional clinical studies will be needed to assess the net impact of recruitment maneuvers in patients with acute lung injury.

COX expression and PGE2 and PGD2 production in experimental acute and chronic gastric lesions

Prostaglandin E(2) and D(2) (PGE(2) and PGD(2)) production and cyclooxygenase-2 (COX-2) expression during the resolution of acute and chronic gastric inflammatory lesions in Wistar rats have been investigated. Differences between ibuprofen, nonselective COX inhibitor, and rofecoxib, specific COX-2 inhibitor, on the development of the induced responses were also analysed. In an acute model, by instillation of HCL, the greatest injury was observed early with a rapid and progressive restoration. Maximal up-regulation of COX-2 protein was detected at 6 h and was accompanied by increase of PGE(2) synthesis but not PGD(2). Both drugs stimulated COX-2 expression in accordance to their capacity of inhibiting this enzymatic activity, driving to delay in the healing. In a chronic model, by acetic acid-induced gastric ulcers, COX-2 was expressed at 7 days and was also associated with PGE(2) increase. Ibuprofen and rofecoxib also augmented COX-2 protein and inhibited PGE(2) levels. However, PGD(2) production was augmented when none signal of COX-2 protein could be detected. Together, this study confirms the role played by COX-2 enzyme in the resolution of acute and chronic gastric inflammatory process, PGE(2) being the principal product. The antiinflammatory effect of nonsteroidal antiinflammatory drugs (NSAIDs) could be mediated not only through the inhibition of COX activity but also through the induction of antiinflammatory PGs production-such as PGD(2)-although further studies would be needed to clarify the mechanisms of this activity and the possible implicated processes.