Addressing the heterogeneity in liver diseases using biological networks.

The abnormalities in human metabolism have been implicated in the progression of several complex human diseases, including certain cancers. Hence, deciphering the underlying molecular mechanisms associated with metabolic reprogramming in a disease state can greatly assist in elucidating the disease aetiology. An invaluable tool for establishing connections between global metabolic reprogramming and disease development is the genome-scale metabolic model (GEM). Here, we review recent work on the reconstruction of cell/tissue-type and cancer-specific GEMs and their use in identifying metabolic changes occurring in response to liver disease development, stratification of the heterogeneous disease population and discovery of novel drug targets and biomarkers. We also discuss how GEMs can be integrated with other biological networks for generating more comprehensive cell/tissue models. In addition, we review the various biological network analyses that have been employed for the development of efficient treatment strategies. Finally, we present three case studies in which independent studies converged on conclusions underlying liver disease.

Vascular Endothelial Growth Factor-121 Administration Mitigates Halogen Inhalation-Induced Pulmonary Injury and Fetal Growth Restriction in Pregnant Mice.

Background Circulating levels of sFLT-1 (soluble fms-like tyrosine kinase 1), the extracellular domain of vascular endothelial growth factor (VEGF) receptor 1, and its ratio to levels of placental growth factor are markers of the occurrence and severity of preeclampsia. Methods and Results C57BL/6 pregnant mice on embryonic day 14.5 (E14.5), male, and non-pregnant female mice were exposed to air or to Br2 at 600 ppm for 30 minutes and were treated with vehicle or with VEGF-121 (100 µg/kg, subcutaneously) daily, starting 48 hours post-exposure. Plasma, bronchoalveolar lavage fluid, lungs, fetuses, and placentas were collected 120 hours post-exposure. In Br2-exposed pregnant mice, there was a time-dependent and significant increase in plasma levels of sFLT-1 which correlated with increases in mouse lung wet/dry weights and bronchoalveolar lavage fluid protein content. Supplementation of exogenous VEGF-121 improved survival and weight gain, reduced lung wet/dry weights, decreased bronchoalveolar lavage fluid protein levels, enhanced placental development, and improved fetal growth in pregnant mice exposed to Br2. Exogenous VEGF-121 administration had no effect in non-pregnant mice. Conclusions These results implicate inhibition of VEGF signaling driven by sFLT-1 overexpression as a mechanism of pregnancy-specific injury leading to lung edema, maternal mortality, and fetal growth restriction after bromine gas exposure.

Mechanisms and Treatment of Halogen Inhalation-Induced Pulmonary and Systemic Injuries in Pregnant Mice.

Inhalation of oxidant gases has been implicated in adverse outcomes in pregnancy, but animal models to address mechanisms and studies to identify potential pregnancy-specific therapies are lacking. Herein, we show that inhalation of bromine at 600 parts per million for 30 minutes by pregnant mice on the 15th day of embryonic development results in significantly lower survival after 96 hours than an identical level of exposure in nonpregnant mice. On the 19th embryonic day, bromine-exposed pregnant mice have increased systemic blood pressure, abnormal placental development, severe fetal growth restriction, systemic inflammation, increased levels of circulating antiangiogenic short fms-like tyrosine kinase-1, and evidence of pulmonary and cardiac injury. Treatment with tadalafil, an inhibitor of type 5 phosphodiesterase, by oral gavage 1 hour post-exposure and then once daily thereafter, attenuated systemic blood pressures, decreased inflammation, ameliorated pulmonary and cardiac injury, and improved maternal survival (from 36% to 80%) and fetal growth. These pathological changes resemble those seen in preeclampsia. Nonpregnant mice did not exhibit any of these pathological changes and were not affected by tadalafil. These findings suggest that pregnant women exposed to bromine may require particular attention and monitoring for signs of preeclampsia-like symptoms.

Nitrite therapy prevents chlorine gas toxicity in rabbits.

Chlorine (Cl2) gas exposure and toxicity remains a concern in military and industrial sectors. While post-Cl2 exposure damage to the lungs and other tissues has been documented and major underlying mechanisms elucidated, no targeted therapeutics that are effective when administered post-exposure, and which are amenable to mass-casualty scenarios have been developed. Our recent studies show nitrite administered by intramuscular (IM) injection post-Cl2 exposure is effective in preventing acute lung injury and improving survival in rodent models. Our goal in this study was to develop a rabbit model of Cl2 toxicity and test whether nitrite affords protection in a non-rodent model. Exposure of New Zealand White rabbits to Cl2 gas (600ppm, 45min) caused significant increases in protein and neutrophil accumulation in the airways and ∼35% mortality over 18h. Nitrite administered 30min post Cl2 exposure by a single IM injection, at 1mg/kg or 10mg/kg, prevented indices of acute lung injury at 6h by up to 50%. Moreover, all rabbits that received nitrite survived over the study period. These data provide further rationale for developing nitrite as post-exposure therapeutic to mitigate against Cl2 gas exposure injury.

Formation of chlorinated lipids post-chlorine gas exposure.

Exposure to chlorine (Cl2) gas can occur during accidents and intentional release scenarios. However, biomarkers that specifically indicate Cl2 exposure and Cl2-derived products that mediate postexposure toxicity remain unclear. We hypothesized that chlorinated lipids (Cl-lipids) formed by direct reactions between Cl2 gas and plasmalogens serve as both biomarkers and mediators of post-Cl2 gas exposure toxicities. The 2-chloropalmitaldehyde (2-Cl-Pald), 2-chlorostearaldehyde (2-Cl-Sald), and their oxidized products, free- and esterified 2-chloropalmitic acid (2-Cl-PA) and 2-chlorostearic acid were detected in the lungs and plasma of mouse and rat models of Cl2 gas exposure. Levels of Cl-lipids were highest immediately post-Cl2 gas exposure, and then declined over 72 h with levels remaining 20- to 30-fold higher at 24 h compared with baseline. Glutathione adducts of 2-Cl-Pald and 2-Cl-Sald also increased with levels peaking at 4 h in plasma. Notably, 3-chlorotyrosine also increased after Cl2 gas exposure, but returned to baseline within 24 h. Intranasal administration of 2-Cl-PA or 2-Cl-Pald at doses similar to those formed in the lung after Cl2 gas exposure led to increased distal lung permeability and inflammation and systemic endothelial dysfunction characterized by loss of eNOS-dependent vasodilation. These data suggest that Cl-lipids could serve as biomarkers and mediators for Cl2 gas exposure and toxicity.

Upregulation of autophagy decreases chlorine-induced mitochondrial injury and lung inflammation.

The mechanisms of toxicity during exposure of the airways to chlorinated biomolecules generated during the course of inflammation and to chlorine (Cl2) gas are poorly understood. We hypothesized that lung epithelial cell mitochondria are damaged by Cl2 exposure and activation of autophagy mitigates this injury. To address this, NCI-H441 (human lung adenocarcinoma epithelial) cells were exposed to Cl2 (100 ppm/15 min) and bioenergetics were assessed. One hour after Cl2, cellular bioenergetic function and mitochondrial membrane potential were decreased. These changes were associated with increased MitoSOX signal, and treatment with the mitochondrial redox modulator MitoQ attenuated these bioenergetic defects. At 6h postexposure, there was significant increase in autophagy, which was associated with an improvement of mitochondrial function. Pretreatment of H441 cells with trehalose (an autophagy activator) improved bioenergetic function, whereas 3-methyladenine (an autophagy inhibitor) resulted in increased bioenergetic dysfunction 1h after Cl2 exposure. These data indicate that Cl2 induces bioenergetic dysfunction, and autophagy plays a protective role in vitro. Addition of trehalose (2 vol%) to the drinking water of C57BL/6 mice for 6 weeks, but not 1 week, before Cl2 (400 ppm/30 min) decreased white blood cells in the bronchoalveolar lavage fluid at 6h after Cl2 by 70%. Acute administration of trehalose delivered through inhalation 24 and 1h before the exposure decreased alveolar permeability but not cell infiltration. These data indicate that Cl2 induces bioenergetic dysfunction associated with lung inflammation and suggests that autophagy plays a protective role.

Hyaluronan mediates airway hyperresponsiveness in oxidative lung injury.

Chlorine (Cl2) inhalation induces severe oxidative lung injury and airway hyperresponsiveness (AHR) that lead to asthmalike symptoms. When inhaled, Cl2 reacts with epithelial lining fluid, forming by-products that damage hyaluronan, a constituent of the extracellular matrix, causing the release of low-molecular-weight fragments (L-HA, <300 kDa), which initiate a series of proinflammatory events. Cl2 (400 ppm, 30 min) exposure to mice caused an increase of L-HA and its binding partner, inter-α-trypsin-inhibitor (IαI), in the bronchoalveolar lavage fluid. Airway resistance following methacholine challenge was increased 24 h post-Cl2 exposure. Intratracheal administration of high-molecular-weight hyaluronan (H-HA) or an antibody against IαI post-Cl2 exposure decreased AHR. Exposure of human airway smooth muscle (HASM) cells to Cl2 (100 ppm, 10 min) or incubation with Cl2-exposed H-HA (which fragments it to L-HA) increased membrane potential depolarization, intracellular Ca(2+), and RhoA activation. Inhibition of RhoA, chelation of intracellular Ca(2+), blockade of cation channels, as well as postexposure addition of H-HA, reversed membrane depolarization in HASM cells. We propose a paradigm in which oxidative lung injury generates reactive species and L-HA that activates RhoA and Ca(2+) channels of airway smooth muscle cells, increasing their contractility and thus causing AHR.

Nitrite therapy improves survival postexposure to chlorine gas.

Exposure to relatively high levels of chlorine (Cl2) gas can occur in mass-casualty scenarios associated with accidental or intentional release. Recent studies have shown a significant postexposure injury phase to the airways, pulmonary, and systemic vasculatures mediated in part by oxidative stress, inflammation, and dysfunction in endogenous nitric oxide homeostasis pathways. However, there is a need for therapeutics that are amenable to rapid and easy administration in the field and that display efficacy toward toxicity after chlorine exposure. In this study, we tested whether nitric oxide repletion using nitrite, by intramuscular injection after Cl2 exposure, could prevent Cl2 gas toxicity. C57bl/6 male mice were exposed to 600 parts per million Cl2 gas for 45 min, and 24-h survival was determined with or without postexposure intramuscular nitrite injection. A single injection of nitrite (10 mg/kg) administered either 30 or 60 min postexposure significantly improved 24-h survival (from ∼20% to 50%). Survival was associated with decreased neutrophil accumulation in the airways. Rendering mice neutropenic before Cl2 exposure improved survival and resulted in loss of nitrite-dependent survival protection. Interestingly, female mice were more sensitive to Cl2-induced toxicity compared with males and were also less responsive to postexposure nitrite therapy. These data provide evidence for efficacy and define therapeutic parameters for a single intramuscular injection of nitrite as a therapeutic after Cl2 gas exposure that is amenable to administration in mass-casualty scenarios.

Postexposure aerosolized heparin reduces lung injury in chlorine-exposed mice.

Chlorine (Cl2) is a highly reactive oxidant gas that, when inhaled, may cause acute lung injury culminating in death from respiratory failure. In this study, we tested the hypothesis that exposure of mice to Cl2 causes intra-alveolar and systemic activation of the coagulation cascade that plays an important role in development of lung injury. C57Bl/6 mice were exposed to Cl2 (400 for 30 min or 600 ppm for 45 min) in environmental chambers and then returned to room air for 1 or 6 h. Native coagulation (NATEM) parameters such as blood clotting time and clot formation time were measured in whole blood by the viscoelastic technique. D-dimers and thrombin-anti-thrombin complexes were measured in both plasma and bronchoalveolar lavage fluid (BALF) by ELISA. Our results indicate that mice exposed to Cl2 gas had significantly increased clotting time, clot formation time, and D-dimers compared with controls. The thrombin-anti-thrombin complexes were also increased in the BALF of Cl2 exposed animals. To test whether increased coagulation contributed to the development of acute lung injury, mice exposed to Cl2 and returned to room air were treated with aerosolized heparin or vehicle for 20 min. Aerosolized heparin significantly reduced protein levels and the number of inflammatory cells in the BALF at 6 h postexposure. These findings highlight the importance of coagulation abnormities in the development of Cl2-induced lung injury.

Chlorine gas exposure disrupts nitric oxide homeostasis in the pulmonary vasculature.

Exposure to chlorine (Cl2) gas during industrial accidents or chemical warfare leads to significant airway and distal lung epithelial injury that continues post exposure. While lung epithelial injury is prevalent, relatively little is known about whether Cl2 gas also promotes injury to the pulmonary vasculature. To determine this, rats were subjected to a sub-lethal Cl2 gas exposure (400 ppm, 30 min) and then brought back to room air. Pulmonary arteries (PA) were isolated from rats at various times post-exposure and contractile (phenylephrine) and nitric oxide (NO)-dependent vasodilation (acetylcholine and mahmanonoate) responses measured ex vivo. PA contractility did not change, however significant inhibition of NO-dependent vasodilation was observed that was maximal at 24-48 h post exposure. Superoxide dismutase restored NO-dependent vasodilation suggesting a role for increased superoxide formation. This was supported by ∼2-fold increase in superoxide formation (measured using 2-hydroethidine oxidation to 2-OH-E+) from PA isolated from Cl2 exposed rats. We next measured PA pressures in anesthetized rats. Surprisingly, PA pressures were significantly (∼4 mmHg) lower in rats that had been exposed to Cl2 gas 24 h earlier suggesting that deficit in NO-signaling observed in isolated PA experiments did not manifest as increased PA pressures in vivo. Administration of the iNOS selective inhibitor 1400W, restored PA pressures to normal in Cl2 exposed, but not control rats suggesting that any deficit in NO-signaling due to increased superoxide formation in the PA, is offset by increased NO-formation from iNOS. These data indicate that disruption of endogenous NO-signaling mechanisms that maintain PA tone is an important aspect of post-Cl2 gas exposure toxicity.

Chlorine gas exposure increases susceptibility to invasive lung fungal infection.

Chlorine (Cl2) is a highly irritating and reactive gas with potential occupational and environmental hazards. Acute exposure to Cl2 induces severe epithelial damage, airway hyperreactivity, impaired alveolar fluid clearance, and pulmonary edema in the presence of heightened inflammation and significant neutrophil accumulation in the lungs. Herein, we investigated whether Cl2 exposure affected the lung antimicrobial immune response leading to increased susceptibility to opportunistic infections. Mice exposed to Cl2 and challenged intratracheally 24 h thereafter with the opportunistic mold Aspergillus fumigatus demonstrated an >500-fold increase in A. fumigatus lung burden 72 h postchallenge compared with A. fumigatus mice exposed to room air. Cl2-exposed A. fumigatus challenged mice also demonstrated significantly higher lung resistance following methacholine challenge and increased levels of plasma proteins (albumin and IgG) in the bronchoalveolar lavage fluid. Despite enhanced recruitment of inflammatory cells to the lungs of Cl2-exposed A. fumigatus challenged mice, these cells (>60% of which were neutrophils) demonstrated a profound impairment in generating superoxide. Significantly higher A. fumigatus burden in the lungs of Cl2 exposed mice correlated with enhanced production of IL-6, TNF-α, CXCL1, CCL2, and CCL3. Surprisingly, however, Cl2-exposed A. fumigatus challenged mice had a specific impairment in the production of IL-17A and IL-22 in the lungs compared with mice exposed to room air and challenged with A. fumigatus. In summary, our results indicate that Cl2 exposure markedly impairs the antimicrobial activity and inflammatory reactivity of myeloid cells in the lung leading to increased susceptibility to opportunistic pathogens.

Administration of nitrite after chlorine gas exposure prevents lung injury: effect of administration modality.

Cl(2) gas toxicity is complex and occurs during and after exposure, leading to acute lung injury (ALI) and reactive airway syndrome (RAS). Moreover, Cl(2) exposure can occur in diverse situations encompassing mass casualty scenarios, highlighting the need for postexposure therapies that are efficacious and amenable to rapid and easy administration. In this study, we assessed the efficacy of a single dose of nitrite (1 mg/kg) to decrease ALI when administered to rats via intraperitoneal (ip) or intramuscular (im) injection 30 min after Cl(2) exposure. Exposure of rats to Cl(2) gas (400 ppm, 30 min) significantly increased ALI and caused RAS 6-24h postexposure as indexed by BAL sampling of lung surface protein and polymorphonucleocytes (PMNs) and increased airway resistance and elastance before and after methacholine challenge. Intraperitoneal nitrite decreased Cl(2)-dependent increases in BAL protein but not PMNs. In contrast im nitrite decreased BAL PMN levels without decreasing BAL protein in a xanthine oxidoreductase-dependent manner. Histological evaluation of airways 6h postexposure showed significant bronchial epithelium exfoliation and inflammatory injury in Cl(2)-exposed rats. Both ip and im nitrite improved airway histology compared to Cl(2) gas alone, but more coverage of the airway by cuboidal or columnar epithelium was observed with im compared to ip nitrite. Airways were rendered more sensitive to methacholine-induced resistance and elastance after Cl(2) gas exposure. Interestingly, im nitrite, but not ip nitrite, significantly decreased airway sensitivity to methacholine challenge. Further evaluation and comparison of im and ip therapy showed a twofold increase in circulating nitrite levels with the former, which was associated with reversal of post-Cl(2) exposure-dependent increases in circulating leukocytes. Halving the im nitrite dose resulted in no effect in PMN accumulation but significant reduction of BAL protein levels, indicating a distinct nitrite dose dependence for inhibition of Cl(2)-dependent lung permeability and inflammation. These data highlight the potential for nitrite as a postexposure therapeutic for Cl(2) gas-induced lung injury and also suggest that administration modality is a key consideration in nitrite therapeutics.

Targeted aerosolized delivery of ascorbate in the lungs of chlorine-exposed rats.

BACKGROUND: Chlorine (Cl(2))-induced lung injury is a serious public health threat that may result from industrial and household accidents. Post-Cl(2) administration of aerosolized ascorbate in rodents decreased lung injury and mortality. However, the extent to which aerosolized ascorbate augments depleted ascorbate stores in distal lung compartments has not been assessed. METHODS: We exposed rats to Cl(2) (300 ppm for 30 min) and returned them to room air. Within 15-30 min postexposure, rats breathed aerosolized ascorbate and desferal or vehicle (mean particle size 3.3 µm) through a nose-only exposure system for 60 min and were euthanized. We measured the concentrations of reduced ascorbate in the bronchoalveolar lavage (BAL), plasma, and lung tissues with high-pressure liquid chromatography, protein plasma concentration in the BAL, and the volume of the epithelia lining fluid (ELF). RESULTS: Cl(2)-exposed rats that breathed aerosolized vehicle had lower values of ascorbate in their BAL, ELF, and lung tissues compared to air-breathing rats. Delivery of aerosolized ascorbate increased reduced ascorbate in BAL, ELF, lung tissues, and plasma of both Cl(2) and air-exposed rats without causing lung injury. Based on mean diameter of aerosolized particles and airway sizes we calculated that approximately 5% and 1% of inhaled ascorbate was deposited in distal lung regions of air and Cl(2)-exposed rats, respectively. Significantly higher ascorbate levels were present in the BAL of Cl(2)-exposed rats when aerosol delivery was initiated 1 h post-Cl(2). CONCLUSIONS: Aerosol administration is an effective, safe, and noninvasive method for the delivery of low molecular weight antioxidants to the lungs of Cl(2)-exposed individuals for the purpose of decreasing morbidity and mortality. Delivery is most effective when initiated 1 h postexposure when the effects of Cl(2) on minute ventilation subside.

Post-exposure antioxidant treatment in rats decreases airway hyperplasia and hyperreactivity due to chlorine inhalation.

We assessed the safety and efficacy of combined intravenous and aerosolized antioxidant administration to attenuate chlorine gas-induced airway alterations when administered after exposure. Adult male Sprague-Dawley rats were exposed to air or 400 parts per million (ppm) chlorine (a concentration likely to be encountered in the vicinity of industrial accidents) in environmental chambers for 30 minutes, and returned to room air, and they then received a single intravenous injection of ascorbic acid and deferoxamine or saline. At 1 hour and 15 hours after chlorine exposure, the rats were treated with aerosolized ascorbate and deferoxamine or vehicle. Lung antioxidant profiles, plasma ascorbate concentrations, airway morphology, and airway reactivity were evaluated at 24 hours and 7 days after chlorine exposure. At 24 hours after exposure, chlorine-exposed rats had significantly lower pulmonary ascorbate and reduced glutathione concentrations. Treatment with antioxidants restored depleted ascorbate in lungs and plasma. At 7 days after exposure, in chlorine-exposed, vehicle-treated rats, the thickness of the proximal airways was 60% greater than in control rats, with twice the amount of mucosubstances. Airway resistance in response to methacholine challenge was also significantly elevated. Combined treatment with intravenous and aerosolized antioxidants restored airway morphology, the amount of airway mucosubstances, and airway reactivity to control levels by 7 days after chlorine exposure. Our results demonstrate for the first time, to the best of our knowledge, that severe injury to major airways in rats exposed to chlorine, as characterized by epithelial hyperplasia, mucus accumulation, and airway hyperreactivity, can be reversed in a safe and efficacious manner by the post-exposure administration of ascorbate and deferoxamine.

Mitigation of chlorine gas lung injury in rats by postexposure administration of sodium nitrite.

Nitrite (NO(2)(-)) has been shown to limit injury to the heart, liver, and kidneys in various models of ischemia-reperfusion injury. Potential protective effects of systemic NO(2)(-) in limiting lung injury or enhancing repair have not been documented. We assessed the efficacy and mechanisms by which postexposure intraperitoneal injections of NO(2)(-) mitigate chlorine (Cl(2))-induced lung injury in rats. Rats were exposed to Cl(2) (400 ppm) for 30 min and returned to room air. NO(2)(-) (1 mg/kg) or saline was administered intraperitoneally at 10 min and 2, 4, and 6 h after exposure. Rats were killed at 6 or 24 h. Injury to airway and alveolar epithelia was assessed by quantitative morphology, protein concentrations, number of cells in bronchoalveolar lavage (BAL), and wet-to-dry lung weight ratio. Lipid peroxidation was assessed by measurement of lung F(2)-isoprostanes. Rats developed severe, but transient, hypoxemia. A significant increase of protein concentration, neutrophil numbers, airway epithelia in the BAL, and lung wet-to-dry weight ratio was evident at 6 h after Cl(2) exposure. Quantitative morphology revealed extensive lung injury in the upper airways. Airway epithelial cells stained positive for terminal deoxynucleotidyl-mediated dUTP nick end labeling (TUNEL), but not caspase-3. Administration of NO(2)(-) resulted in lower BAL protein levels, significant reduction in the intensity of the TUNEL-positive cells, and normal lung wet-to-dry weight ratios. F(2)-isoprostane levels increased at 6 and 24 h after Cl(2) exposure in NO(2)(-)- and saline-injected rats. This is the first demonstration that systemic NO(2)(-) administration mitigates airway and epithelial injury.

Mechanisms and modification of chlorine-induced lung injury in animals.

Chlorine (Cl(2)) is a reactive oxidant gas used extensively in industrial processes. Exposure of both humans and animals to high concentrations of Cl(2) results in acute lung injury, which may resolve spontaneously or progress to acute respiratory failure. Injury to airway and alveolar epithelium may result from chemical reactions of Cl(2), from HOCl (the hydrolysis product of Cl(2)), and/or from the various reaction products, such as chloramines, that are formed from the reactions of these chlorinating species with biological molecules. Subsequent reactions may initiate self-propagating reactions and induce the production of inflammatory mediators compounding injury to pulmonary surfactant, ion channels, and components of lung epithelial and airway cells. Low-molecular-weight antioxidants, such as ascorbate, glutathione, and urate, present in the lung epithelial lining fluid and tissue, remove Cl(2) and HOCl and thus decrease injury to critical target biological targets. However, levels of lung antioxidants of animals exposed to Cl(2) in concentrations likely to be encountered in the vicinity of industrial accidents decrease rapidly and irreversibly. Our measurements show that prophylactic administration of a mixture containing ascorbate and desferal N-acetyl-cysteine, a precursor of reduced glutathione, prevents Cl(2)-induced injury to the alveolar epithelium of rats exposed to Cl(2). The clinical challenge is to deliver sufficient quantities of antioxidants noninvasively, after Cl(2) exposure, to decrease morbidity and mortality.

Mitigation of chlorine-induced lung injury by low-molecular-weight antioxidants.

Chlorine (Cl(2)) is a highly reactive oxidant gas used extensively in a number of industrial processes. Exposure to high concentrations of Cl(2) results in acute lung injury that may either resolve spontaneously or progress to acute respiratory failure. Presently, the pathophysiological sequelae associated with Cl(2)-induced acute lung injury in conscious animals, as well as the cellular and biochemical mechanisms involved, have not been elucidated. We exposed conscious Sprague-Dawley rats to Cl(2) gas (184 or 400 ppm) for 30 min in environmental chambers and then returned them to room air. At 1 h after exposure, rats showed evidence of arterial hypoxemia, respiratory acidosis, increased levels of albumin, IgG, and IgM in bronchoalveolar lavage fluid (BALF), increased BALF surfactant surface tension, and significant histological injury to airway and alveolar epithelia. These changes were more pronounced in the 400-ppm-exposed rats. Concomitant decreases of ascorbate (AA) and reduced glutathione (GSH) were also detected in both BALF and lung tissues. In contrast, heart tissue AA and GSH content remained unchanged. These abnormalities persisted 24 h after exposure in rats exposed to 400 ppm Cl(2). Rats injected systemically with a mixture of AA, deferoxamine, and N-acetyl-L-cysteine before exposure to 184 ppm Cl(2) had normal levels of AA, lower levels of BALF albumin and normal arterial Po(2) and Pco(2) values. These findings suggest that Cl(2) inhalation damages both airway and alveolar epithelial tissues and that resulting effects were ameliorated by prophylactic administration of low-molecular-weight antioxidants.

Single-dose vs multiple-dose antibiotic prophylaxis in instrumented lumbar fusion--a prospective study.

BACKGROUND: This prospective investigation was designed to determine if the postoperative infection rate in instrumented lumbar spinal fusion is affected by postoperative antibiotic use. METHODS: Two hundred sixty-nine patients were randomized into either a preoperative only protocol or preoperative with an extended postoperative antibiotic protocol. The preoperative only protocol received a single dose of cefazolin IV. The extended postoperative antibiotic protocol received the same preoperative dose plus postoperative cefazolin IV every 8 hours for 3 days followed by oral cephalexin every 6 hours for 7 days. Because of untoward drug reaction or deviation from the antibiotic protocol, 36 of the 269 patients were eliminated from the study. Therefore, 233 patients completed the entire study. RESULTS: There was no significant difference in infection rates between the 2 antibiotic protocols. The postoperative infection rates were 4.3% for the preoperative only protocol and 1.7% for the preoperative with extended antibiotic protocol. The overall postoperative infection rate was 3%. However, 5 variables of blood transfusion, electrophysiologic monitoring, increased height, increased weight, and increased body mass index appeared to demonstrate a trend toward increase in infection rate. Increased tobacco use trended toward a lower infection rate. CONCLUSION: Statistical significance was not proven in this prospective study comparing single-dose preoperative antibiotic protocol vs preoperative with an extended postoperative antibiotic protocol. A larger study of 1400 patients would possibly provide more statistically significant information.

Abdominal pseudocyst: predisposing factors and treatment algorithm.

Abdominal pseudocyst (APC) is an uncommon complication of ventriculoperitoneal shunts. Various predisposing factors have been attributed to it, including the presence of infection and multiple shunt revisions. We reviewed the records of shunt revisions performed over a 20-year period. During that time, 64 cases of APC were found in 36 patients. The records were then reviewed for the presence of infection, history of necrotizing enterocolitis, prior abdominal surgery, and treatment performed. Of the cases of APC, 46 were primary and 18 were recurrent. A history of prior abdominal surgery other than shunt revision was found in 47% of patients and a history of necrotizing enterocolitis was found in 19% of patients. The average number of prior shunt revisions was 4.1 per patient. Shunt infection as defined by positive cultures of either cerebrospinal fluid or abdominal fluid was present in only 23% of cases of APC. A history of prior shunt infection was present in 30% of patients. Infection was treated by shunt removal, external ventricular drainage, and appropriate antibiotics. After the infection was cleared or if no infection was present, treatment consisted of: (1) repositioning the distal catheter into the peritoneum, (2) repositioning the distal catheter into the pleural space, the atrium, or the gallbladder, (3) exploratory laparotomy with lysis of adhesions and repositioning the peritoneal catheter, (4) APC aspiration only, or (5) shunt removal or disconnection. Because of the complexity of APC management, we analyzed the outcomes of our cases and outlined an algorithm to simplify this process.