Potential for using simulated altitude as a means of prehabilitation: a physiology study

The current pandemic of surgical complications necessitates urgent and pragmatic innovation to reduce postoperative morbidity and mortality, which are associated with poor pre-operative fitness and anaemia. Exercise prehabilitation is a compelling strategy, but it has proven difficult to establish that it improves outcomes either in isolation or as part of a multimodal approach. Simulated altitude exposure improves performance in athletes and offers a novel potential means of improving cardiorespiratory and metabolic fitness and alleviating anaemia within the prehabilitation window. We aimed to provide an initial physiological foundation for 'altitude prehabilitation' by determining the physiological effects of one week of simulated altitude (FI O2 15%, equivalent to approximately 2438 m (8000 ft)) in older sedentary volunteers. The study used a randomised, double-blind, sham-controlled crossover design. Eight participants spent counterbalanced normoxic and hypoxic weeks in a residential hypoxia facility and underwent repeated cardiopulmonary exercise tests. Mean (SD) age of participants was 64 (7) y and they were unfit, with mean (SD) baseline anaerobic threshold 12 (2) ml.kg-1 .min-1 and mean (SD) peak V̇O2 15 (3) ml.kg-1 .min-1 . Hypoxia was mild (mean (SD) Sp O2 93 (2) %, p < 0.001) and well-tolerated. Despite some indication of greater peak exercise capacity following hypoxia, overall there was no effect of simulated altitude on anaerobic threshold or peak V̇O2 . However, hypoxia induced a substantial increase in mean (SD) haemoglobin of 1.5 (2.7) g.dl-1 (13% increase, p = 0.028). This study has established the concept and feasibility of 'altitude prehabilitation' and demonstrated specific potential for improving haematological fitness. Physiologically, there is value in exploring a possible role for simulated altitude in pre-operative optimisation.

PGC-1α4 gene expression is suppressed by the IL-6-MEK-ERK 1/2 MAPK signalling axis and altered by resistance exercise, obesity and muscle injury

AIM

PGC-1α4 is a novel regulator of muscle hypertrophy; however, there is limited understanding of the regulation of its expression and role in many (patho)physiological conditions. Therefore, our purpose was to elicit signalling mechanisms regulating gene expression of Pgc1α4 and examine its response to (patho)physiological stimuli associated with altered muscle mass.

METHODS

IL-6 knockout mice and pharmacological experiments in C2C12 myocytes were used to identify regulation of Pgc1α4 transcription. To examine Pgc1α4 gene expression in (patho)physiological conditions, obese and lean Zucker rats with/without resistance exercise (RE), ageing mice and muscle regeneration from injury were examined.

RESULTS

In IL-6 knockout mice, Pgc1α4mRNA was ~sevenfold greater than wild type. In C2C12 cells, Pgc1α4mRNA was suppressed ~70% by IL-6. Suppression of Pgc1α4 by IL-6 was prevented by MEK-ERK-MAPK inhibition. RE led to ~260% greater Pgc1α4mRNA content in lean rats. However, obese Zucker rats exhibited ~270% greater Pgc1α4mRNA than lean, sedentary with no further augmentation by RE. No difference was seen in IL-6mRNA or ERK-MAPK phosphorylation in Zucker rats. Aged mice demonstrated ~50% lower Pgc1α4mRNA and ~fivefold greater ERK-MAPK phosphorylation than young despite unchanged Il-6mRNA. During muscle regeneration, Pgc1α4 content is ~30% and IL-6mRNA >threefold of uninjured controls 3 days following injury; at 5 days, Pgc1α4 was >twofold greater in injured mice with no difference in IL-6mRNA.

CONCLUSION

Our findings reveal a novel mechanism suppressing Pgc1α4 gene expression via IL-6-ERK-MAPK and suggest this signalling axis may inhibit Pgc1α4 in some, but not all, (patho)physiological conditions.

Reducing Stability of Support Structure for a Target Does Not Alter Reach Kinematics among Younger Adults

Investigation into the reach-to-grasp movement has indicated that this movement sequence is composed of two distinct movement components, independently influenced by the characteristics of the target. It remains undetermined whether properties other than those conveyed by the target also influence the strategy used to complete the task successfully. Here, we explored whether characteristics of the support structure influence reaching kinematics among younger adults. The purpose of the study was to assess whether support structure stability affected movement kinematics of the transport phase. Subjects were required to reach for a full glass of water on a stable or an unstable support structure. Kinematic measures of interest included transport time, peak transport velocity, peak transport acceleration, and timing of kinematic peaks. Analysis showed that reducing the stability of the support structure did not significantly affect any of the measures of interest. The results imply that stability of support structure does not influence transport kinematics among younger adults.

Translational machinery of mitochondrial mRNA is promoted by physical activity in Western diet-induced obese mice

AIM

Mitochondria-encoded proteins are necessary for oxidative phosphorylation; however, no report has examined how physical activity (PA) and obesity affect mitochondrial mRNA translation machinery. Our purpose was to determine whether Western diet (WD)-induced obesity and voluntary wheel running (VWR) impact mitochondrial mRNA translation machinery and whether expression of this machinery is dictated by oxidative phenotype.

METHODS

Obesity was induced with 8-wk WD feeding, and in the final 4 wks, half of mice were allowed VWR. Mitochondrial mRNA translation machinery including initiation factors (mtIF2/3), elongation factor Tu (TUFM) and translational activator (TACO1), and mitochondria-encoded proteins (CytB and ND4) was assessed by immunoblotting. The relation of mitochondrial mRNA translation to muscle oxidative phenotype was assessed using PGC-1α transgenic overexpression (MCK-PGC-1α vs. wild-type mice) and comparing across muscle groups in wild-type mice.

RESULTS

mtIF3 and TACO1 proteins were ~45% greater in VWR than sedentary (SED), and TACO1 and mtIF2 proteins were ~60% and 125% greater in WD than normal chow (NC). TUFM protein was ~50% lower in WD-SED than NC-SED, but ~50% greater in WD-VWR compared to NC-SED. CytB and ND4 were ~40% greater in VWR and ND4 was twofold greater with WD. TUFM, TACO1, ND4 and CytB were greater in MCK-PGC-1α compared to wild-type, and mtIF2/3 contents were not different. In oxidative muscle (soleus), mitochondrial translation machinery was elevated compared to mixed (gastrocnemius) or glycolytic (extensor digitorum longus) muscles.

CONCLUSION

These data suggest a novel mechanism promoting mitochondrial function by translation of mitochondrial protein following PA. This may act to promote muscle health by PA in obesity.

Diet-induced obesity alters anabolic signalling in mice at the onset of skeletal muscle regeneration

AIM

Obesity is classified as a metabolic disorder that is associated with delayed muscle regeneration following damage. For optimal skeletal muscle regeneration, inflammation along with extracellular matrix remodelling and muscle growth must be tightly regulated. Moreover, the regenerative process is dependent on the activation of myogenic regulatory factors (MRFs) for myoblast proliferation and differentiation. The purpose of this study was to determine how obesity alters inflammatory and protein synthetic signalling and MRF expression at the onset of muscle regeneration in mice.

METHODS

Forty-eight male C57BL/6J mice (3 weeks old) were randomly assigned to either a high-fat diet (HFD, 60% fat) or a lean diet (10% fat) for 12 weeks. At 15 weeks, bupivacaine was injected into the tibialis anterior (TA) of the injured group (n = 5-8/group) and PBS was injected into the control (n = 5-6). The TA was excised 3 or 28 days after injection.

RESULTS

We demonstrated impaired muscle regeneration in obese mice. The obese mice had reduced IL-6, MyoD and IGF-1 mRNA abundance compared to the lean mice (P < 0.05). Three days following muscle damage, TNF-α mRNA and protein levels of P-STAT3 and P-Akt were 14-fold, fourfold and fivefold greater in the lean mice respectively. However, there were no differences observed in the obese injured group compared to the uninjured group. Moreover, p70S6K1 was threefold greater in lean injured mice compared to uninjured but was reduced by 28% in the obese injured mice.

CONCLUSION

Obese mice have impaired inflammatory and protein synthetic signalling that may negatively influence muscle regeneration.

A lack of functional NK1 receptors explains most, but not all, abnormal behaviours of NK1R-/- mice(1)

Mice lacking functional neurokinin-1 receptors (NK1R-/-) display abnormal behaviours seen in Attention Deficit Hyperactivity Disorder (hyperactivity, impulsivity and inattentiveness). These abnormalities were evident when comparing the behaviour of separate (inbred: 'Hom') wildtype and NK1R-/- mouse strains. Here, we investigated whether the inbreeding protocol could influence their phenotype by comparing the behaviour of these mice with that of wildtype (NK1R+/+) and NK1R-/- progeny of heterozygous parents ('Het', derived from the same inbred strains). First, we recorded the spontaneous motor activity of the two colonies/genotypes, over 7 days. This continuous monitoring also enabled us to investigate whether the diurnal rhythm in motor activity differs in the two colonies/genotypes. NK1R-/- mice from both colonies were hyperactive compared with their wildtypes and their diurnal rhythm was also disrupted. Next, we evaluated the performance of the four groups of mice in the 5-Choice Serial Reaction-Time Task (5-CSRTT). During training, NK1R-/- mice from both colonies expressed more impulsive and perseverative behaviour than their wildtypes. During testing, only NK1R-/- mice from the Hom colony were more impulsive than their wildtypes, but NK1R-/- mice from both colonies were more perseverative. There were no colony differences in inattentiveness. Moreover, a genotype difference in this measure depended on time of day. We conclude that the hyperactivity, perseveration and, possibly, inattentiveness of NK1R-/- mice is a direct consequence of a lack of functional NK1R. However, the greater impulsivity of NK1R-/- mice depended on an interaction between a functional deficit of NK1R and other (possibly environmental and/or epigenetic) factors.

TEMPERATURE CHARACTERISTICS FOR DURATION OF AN INSTAR IN CLADOCERANS

1. The temperature characteristics for the rate of development during a well defined instar were determined for three species of Cladocera, and found to be of the same general magnitudes as those obtained for rates of development and of O₂ consumption in other arthropods. 2. Critical temperatures were found to occur at points most frequently critical in quite diverse vital phenomena as determined by abrupt changes in the relationship between rate and temperature. 3. A suggestion is made that, since the values of µ and the positions of critical temperatures obtained for the different species are not the same, some relation may exist between the occurrence of these forms in nature and their relative rates of development as controlled by temperatures.

THE RATE OF KILLING OF CLADOCERANS AT HIGHER TEMPERATURES

In spite of obvious possible sources of disturbance, the "velocity of killing" of organisms at supranormal temperatures, properly determined, tends to adhere to the Arrhenius equation for relation to temperature. Over certain ranges of temperature the relationship between log velocity of killing and 1/T degrees abs. is linear. Interpreted as due to the thermal denaturing of protein, it is possible that differences between the temperature characteristics for the killing process in closely related forms may be suggestive in regard to the mechanism of the denaturing. The temperature limits within which the linear relationships appear may be classed among those temperature levels which are critical temperatures for protoplasmic organization.

ON THE NATURE OF THE EQUATION FOR GROWTH PROCESSES

An analysis of the growth curves of a cladoceran for one adult instar at each of two temperatures is made by comparing the apparent gains or losses in time when the animals are transferred from one of these temperatures to the other during the course of the developmental period. Since the curves for the two temperatures when brought together at their end-point do not coincide, the equation used to describe growth must have at least two velocity constants unequally affected by changes in temperature.

Effect of Nutritional Status on the Lung Surfactant System: Food Deprivation and Caloric Restriction

It has been reported that food deprivation may result in decreased synthesis of lung surfactant phospholipids while the ratio of saturated and unsaturated fatty acids of phosphatidylcholine is maintained. To further investigate this effect, rats were deprived of diet for 24, 48, 72, or 96 hr or fed a nutritionally complete but calorie-deficient diet for 48, 96, 144, and 192 hr. The surfactant was separated into extracellular and intracellular fractions, with the remaining lung tissue pooled as a nonsurfactant fraction. The total phospholipids, phosphatidylcholine, phosphatidylglycerol, and disaturated phosphatidylcholine of each surfactant fraction and the remaining lung tissue were analyzed. The data suggest that on a DNA basis, food and caloric deprivation results temporarily in an altered quantity of pulmonary phospholipids. By 96 hr of fasting or 192 hr of calorie-deficient diet, the pool sizes were replenished and no longer significantly different from the control state. In addition, the distribution of phosphatidylglycerol and phosphatidylcholine was modified in extracellular and intracellular surfactant fractions and in the nonsurfactant tissue fraction. Although the percentage of total phospholipids found as phosphatidylcholine was decreased, the relationship between saturated and unsaturated phosphatidylcholine was preserved in the extracellular surfactant fraction. These results demonstrate that during food and caloric deprivation, the lung quickly adapts to maintain the quality and quantity of surfactant on the alveolar surface.

Insights into the dynamics of hereditary diffuse leukoencephalopathy with axonal spheroids

OBJECTIVE

To report a new American family with hereditary diffuse leukoencephalopathy with spheroids (HDLS), including serial, presymptomatic and symptomatic, cranial MRIs from the proband.

METHODS

We report clinical and genealogic investigations of an HDLS family, sequential brain MRIs of the proband, and autopsy slides of brain tissue from the proband's father.

RESULTS

We identified seven affected family members (five deceased). The mean age at symptomatic disease onset was 35 years (range: 20-57), and the mean disease duration was 16 years (range: 3-46). Five affected individuals initially manifested memory disturbance and behavioral changes, whereas two experienced a mood disorder as their presenting symptom. Our proband's father had been diagnosed clinically with vascular dementia, but his brain autopsy was consistent with HDLS. The proband had a cranial MRI prior to symptom onset, with two subsequent MRIs performed during follow-up. These serial images reveal a progressive, confluent, frontal-predominant leukoencephalopathy with symmetric cortical atrophy.

CONCLUSIONS

The proband of our newly identified hereditary diffuse leukoencephalopathy with spheroids (HDLS) kindred had subtle evidence of an incipient leukoencephalopathy on a presymptomatic cranial MRI. Conceivably, MRI may facilitate identifying affected presymptomatic individuals within known HDLS kindreds, increasing the likelihood of isolating the causative genes.

Anxiety-mediated gait adaptations reduce errors of obstacle negotiation among younger and older adults: implications for fall risk

The purpose of this study was to determine if anxiety-mediated gait adaptations can reduce the risk for falling among younger and older adults. Fourteen younger adults (23.14+/-3.08 years) and 14 older adults (69.28+/-5.41 years) participated in this study. Participants were asked to walk the length of a 7.20m walkway and avoid contact with an obstacle that appeared suddenly underfoot at either 25% or 75% of the gait cycle duration. Testing was conducted in four conditions of postural threat. The obstacle was presented as a light beam and did not jeopardize balance when contacted. Fall risk was inferred from the frequency of obstacle contacts. Our findings indicated that obstacle contact frequency decreased when conservative gait patterns emerged. These findings imply that anxiety-mediated gait adaptations are beneficial in reducing the risk for falling among older adults and present the possibility that fear of falling may offer protective benefits for postural control. One possibility is that the beneficial effects of anxiety can only be realized among older adults who do not fear falling.

Contributions from Caenorhabditis elegans functional genetics to antiparasitic drug target identification and validation: nicotinic acetylcholine receptors, a case study

Following the complete sequencing of the genome of the free-living nematode, Caenorhabditis elegans, in 1998, rapid advances have been made in assigning functions to many genes. Forward and reverse genetics have been used to identify novel components of synaptic transmission as well as determine the key components of antiparasitic drug targets. The nicotinic acetylcholine receptors (nAChRs) are prototypical ligand-gated ion channels. The functions of these transmembrane proteins and the roles of the different members of their extensive subunit families are increasingly well characterised. The simple nervous system of C. elegans possesses one of the largest nicotinic acetylcholine receptor gene families known for any organism and a combination of genetic, microarray, physiological and reporter gene expression studies have added greatly to our understanding of the components of nematode muscle and neuronal nAChR subtypes. Chemistry-to-gene screens have identified five subunits that are components of nAChRs sensitive to the antiparasitic drug, levamisole. A novel, validated target acting downstream of the levamisole-sensitive nAChR has also been identified in such screens. Physiology and molecular biology studies on nAChRs of parasitic nematodes have also identified levamisole-sensitive and insensitive subtypes and further subdivisions are under investigation.

Neuronal activity-related coupling in cortical arterioles: involvement of astrocyte-derived factors

Neuronal activity-evoked dilatation was investigated in cortical arterioles in brain slices from mature rats maintained in vitro at 31-33 degrees C. In the presence of the thromboxane A2 agonist U46619 (75 nM) to preconstrict vessels, internal diameter decreased by 14.2% and rhythmic contractile activity (vasomotion) developed. Addition of the epoxygenase inhibitor miconazole (20 microm) produced a further decrease in diameter and increase in the frequency of vasomotion, suggesting that tonic release of epoxygenase products maintains a level of cerebrovascular dilator tone. Addition of 1 mum AMPA for 5 min evoked a 15.4 +/- 3.7% increase in diameter and the frequency of vasomotion decreased by -6.7 +/- 1.4 contractions min(-1). The response persisted in the presence of 1 mum TTX, indicating that it was independent of neuronal activity and thus likely to have been evoked by activation of AMPA receptors on astrocytes rather than neurones. The response to the brief (5 min) application of AMPA remained unchanged in the presence of miconazole (20 microm). Prolonged (30 min) application of AMPA produced a +12.1 +/- 1.5% increase in internal diameter and reduction in vasomotion (-8.4 +/- 1.7 contractions min(-1)) that were sustained throughout the stimulation period. However, when AMPA was applied in the presence of miconazole (20 microm) it evoked only a transient increase in diameter (+9.8 +/- 3.1%) and decrease in vasomotion (-6.6 +/- 1.5 contractions min(-1)) that lasted for less than 10 min despite continued application of AMPA. The results suggest that products of epoxygenase activity, probably epoxyeicosatrienoic acids (EETs) are involved in activity-related dilatation in cortical arterioles. Whilst epoxygenase activity is not required to initiate dilatation, it appears to be involved in sustaining the response. Thus EETs released from membrane stores could contribute to the initial stages, but once these have been depleted de novo synthesis of EETs is required to maintain the effect.

Inhaled benzo(a)pyrene impairs long-term potentiation in the F1 generation rat dentate gyrus

The purpose of this study is to provide a point of reference regarding the neurotoxic effects resulting from exposure to environmental contaminants. Benzo(a)pyrene is a member of the polycyclic aromatic hydrocarbon (PAH) family and it is a by-product of combustion processes. Thus, persons living near factories or hazardous waste sites face the danger of exposure through contact with contaminated air, water and soil. In an effort to understand the impact of environmental contaminants, we have investigated the effects of gestational B(a)P aerosol exposure on long-term potentiation (LTP), a cellular correlate of learning and memory in the F1 generation. Briefly, timed-pregnant rats were exposed to B(a)P via nose-only inhalation on gestation days 11-21 for 4 hr per day. Dams were maintained to term and pups were weaned on postnatal day 30. Subsequent electrophysiological studies during postnatal days 60-70 revealed a diminution in LTP across the perforant path-granular cells synapses in the hippocampus of F1 generation animals that were transplacentally exposed to B(a)P aerosol relative to unexposed controls. Additionally, NMDA receptor subunit 1 (NR1) protein was found to be downregulated in the hippocampus of B(a)P exposed F1 generation animals. Taken together, our results suggest that gestational exposure to B(a)P aerosol attenuates the capacity for LTP in the F1 generation.

The uprooting of people, migration, and labor force experiences: Ecuador 1982 and 1990

"Moving beyond traditional theories of migration, this paper considers how actual economic, socio-political, and natural events impacted uprooting of people in Ecuador since the 1950s. Major eras of economic growth and economic devolution are represented by Census data for 1982 and 1990. Through these, individual labor force experiences of migrants and stayers, and gender differentials within each group, are considered. Uprooting of people persists forty to fifty years after events initiating its occurrence, and differentially impacts each population group. Gender differentials are noticeably significant among occupational sectors of employment, less so for economic sectors. Predominance and continual growth of informal activities also is apparent, a trend which impacts women more strongly." (SUMMARY IN GER)

Inhibition of vasomotion in hippocampal cerebral arterioles during increases in neuronal activity

The activity of small arterioles, internal diameter 9.9 +/- 0.8 microm (SEM), was investigated in the CA1 region of hippocampal slices maintained in vitro at 34 degrees C. Under resting conditions, the vessels were quiescent. However, in the presence of the thromboxane A2 agonist U46619 (75-100 nM), rhythmic contractile activity (vasomotion, 1.1-9.9 min(-1), mean 4.1 +/- 0.7 min(-1) SEM) developed in the smooth muscle cells of the vessel walls. Electrical stimulation of the Schaffer collateral fibre pathway was used to evoke increases in neuronal activity in CA1 in the vicinity of the vessels under investigation. A 3-min period of electrical stimulation of the Schaffer collateral fibre pathway produced a significant reduction in vasomotion in 8/8 vessels. During stimulation, vasomotion either ceased completely (n = 5) or the frequency decreased from 7.1, 3.3 and 3.2 min(-1) to 1.2, 0.4 and 0.6 min(-1), respectively (n = 3). In addition, the amplitude of the residual contractions was reduced by 66%, 12% and 52%. In the presence of 1 microM tetrodotoxin (TTX) (n = 4) to block the generation of action potentials, vasomotion was still present. However, the inhibition of vasomotion evoked by increased neuronal activity was blocked concomitant with the abolition of the field potentials recorded in CA1 in response to the stimulation of the Schaffer collaterals. These findings suggest that a reduction in vasomotion may contribute to the local hyperaemia, which accompanies increases in synaptic activity in the brain.

The translating platform paradigm: perturbation displacement waveform alters the postural response

The translating platform paradigm is widely used to investigate the regulation of upright standing and locomotion. This study investigated how the displacement waveform characteristics underlying the translating platform perturbation are revealed in the resulting postural response. Eight participants experienced a series of backward-directed perturbations using a hydraulically driven forceplate. Two ranges of platform displacement (5 and 15 cm) in combination with two peak velocities (40 and 60 cm/s) were achieved using three distinct waveforms for platform displacement: (a) RAMP: ramp onset and ramp offset, (b) Ramp-to-Parabola (R-P): ramp onset with parabolic offset and (c) SINE: sine-wave onset with sine wave offset. Our findings indicated that the unique and distinctive acceleration and deceleration characteristics that result from the three different platform displacement waveforms significantly altered the postural response to the perturbation.

Compensatory stepping: the biomechanics of a preferred response among older adults

The purpose of this study was to evaluate age-related differences in the mechanics of the compensatory stepping response to balance threats. A moving platform was used to disturb the balance of 16 younger (21 to 35 years) and 19 older (68 to 88 years) adults. Backward platform translations consisted of 15-cm displacements with peak accelerations ranging from 9.4 to 15.2 m/s2. Older adults were more likely to use a step to recover balance and stepped at lower perturbation magnitudes than younger adults. Group differences were not found in time to step initiation or segmental momentum. The lack of group differences in momentum revealed that lower perturbation accelerations created an equivalent or greater magnitude of body motion in older adults compared to higher accelerations experienced by younger adults. Older adults also showed a reduced ability to attenuate the input acceleration and experienced significantly greater linear acceleration of the head.

Implantable cardioverter-defibrillator endocarditis secondary to Candida albicans

The implantable cardioverter-defibrillator (ICD) represents an important advance in the treatment of ventricular arrhythmias, but infection has remained a serious complication of device implantation. Fungal infections associated with these devices are uncommon, with only 4 cases previously reported. We describe a case of ICD-associated endocarditis caused by Candida albicans that was successfully treated with complete device explantation and prolonged antifungal therapy, and we review the features of ICD-related fungal infections.

Chronic ethanol ingestion potentiates TNF-alpha-mediated oxidative stress and apoptosis in rat type II cells

In septic patients, chronic alcohol abuse increases the incidence of the acute respiratory distress syndrome (ARDS). Because alveolar type II cell viability is critical for epithelial repair, our objective was to determine if chronic ethanol ingestion increased the sensitivity of type II cells to the inflammatory mediators upregulated during sepsis. In rats chronically fed ethanol, type II cell mitochondrial GSH was depleted, and tumor necrosis factor-alpha (TNF-alpha)-induced generation of mitochondrial reactive oxygen species (ROS) and apoptosis were potentiated. When added to the ethanol diet, the GSH precursor (-)-2-oxo-4-thiazolidinecarboxylic acid (Procysteine; Pro) but not N-acetylcysteine (NAC) normalized type II cell mitochondrial GSH. Likewise, Pro but not NAC normalized TNF-alpha-induced mitochondrial ROS and apoptosis. This suggested that chronic ethanol ingestion potentiated TNF-alpha-induced apoptosis in type II cells via mitochondrial GSH depletion. This may be particularly relevant in ARDS when type II cell viability is critical to repair of the damaged alveolar epithelium and may have important ramifications for the treatment of ARDS patients with a history of alcohol abuse.

Effect of chronic ethanol ingestion on alveolar type II cell: glutathione and inflammatory mediator-induced apoptosis

BACKGROUND

In septic patients, chronic alcohol abuse increases the incidence of the acute respiratory distress syndrome, a syndrome that requires alveolar type II cell proliferation and differentiation for repair of the damaged alveolar epithelium. We previously showed in a rat model that chronic ethanol ingestion decreased the antioxidant glutathione (GSH) in type II cells and exacerbated endotoxin-mediated acute lung injury. We hypothesized that this GSH depletion by ethanol, particularly mitochondrial GSH, predisposed type II cells to inflammatory mediator-induced apoptosis.

METHODS

Adult male rats were fed the Lieber-DeCarli diet for 2, 6, or 16 weeks. Alveolar type II cells were then isolated and treated with hydrogen peroxide or TNF-alpha. The effect on glutathione (cytosolic and mitochondrial), apoptotic events, and necrosis were determined. In other studies, rats were fed ethanol for 6 weeks and were treated with endotoxin and apoptosis of type II cells determined by the TUNEL method.

RESULTS

Chronic ethanol ingestion alone resulted in a progressive decrease in mitochondrial GSH and a progressive increase in the basal apoptosis and necrosis rate (p < or = 0.05). Furthermore, there was a progressive increase in the sensitivity of the cells to H2O2 or TNF-alpha induced cytochrome c release, caspase 3 activation, apoptosis, and necrosis (p < or = 0.05). Finally, there was a 2-fold increase in apoptotic type II cells in vivo when chronic ethanol ingestion was superimposed on endotoxemia.

CONCLUSIONS

These results suggested that chronic ethanol ingestion resulted in a progressive depletion of mitochondrial GSH and sensitization of type II cells to inflammatory mediator-induced apoptosis and necrosis. These effects may be particularly relevant during acute stress when proliferation and differentiation of these cells are critical to repair of the damaged alveolar epithelium and may have important ramifications for the treatment of acute respiratory distress syndrome in patients with a history of alcohol abuse.

Cholesterol embolism causing delayed healing of a foot ulcer

A cholesterol embolism presents with various systemic and local manifestations giving rise to a diagnostic dilemma. We report a case of cholesterol embolism of the leg that delayed the healing of a foot ulcer, necessitating a toe amputation. This report points to the potential of cholesterol emboli to cause a significant compromise in the vascular supply.

TGF-beta is a critical mediator of acute lung injury

We have shown that the integrin alphavbeta6 activates latent TGF-beta in the lungs and skin. We show here that mice lacking this integrin are completely protected from pulmonary edema in a model of bleomycin-induced acute lung injury (ALI). Pharmacologic inhibition of TGF-beta also protected wild-type mice from pulmonary edema induced by bleomycin or Escherichia coli endotoxin. TGF-beta directly increased alveolar epithelial permeability in vitro by a mechanism that involved depletion of intracellular glutathione. These data suggest that integrin-mediated local activation of TGF-beta is critical to the development of pulmonary edema in ALI and that blocking TGF-beta or its activation could be effective treatments for this currently untreatable disorder.

Expression of highly selective sodium channels in alveolar type II cells is determined by culture conditions

Alveolar fluid clearance in the developing and mature lungs is believed to be mediated by some form of epithelial Na channels (ENaC). However, single-channel studies using isolated alveolar type II (ATII) cells have failed to demonstrate consistently the presence of highly selective Na+ channels that would be expected from ENaC expression. We postulated that in vitro culture conditions might be responsible for alterations in the biophysical properties of Na+ conductances observed in cultured ATII cells. When ATII cells were grown on glass plates submerged in media that lacked steroids, the predominant channel was a 21-pS nonselective cation channel (NSC) with a Na+-to-K+ selectivity of 1; however, when grown on permeable supports in the presence of steroids and air interface, the predominant channel was a low-conductance (6.6 +/- 3.4 pS, n = 94), highly Na+-selective channel (HSC) with a P(Na)/P(K) >80 that is inhibited by submicromolar concentrations of amiloride (K(0.5) = 37 nM) and is similar in biophysical properties to ENaC channels described in other epithelia. To establish the relationship of this HSC channel to the cloned ENaC, we employed antisense oligonucleotide methods to inhibit the individual subunit proteins of ENaC (alpha, beta, and gamma) and used patch-clamp techniques to determine the density of this channel in apical membrane patches of ATII cells. Overnight treatment of cells with antisense oligonucleotides to any of the three subunits of ENaC resulted in a significant decrease in the density of HSC channels in the apical membrane cell-attached patches. Taken together, these results show that when grown on permeable supports in the presence of steroids and air interface, the predominant channels expressed in ATII cells have single-channel characteristics resembling channels that are associated with the coexpression of the three cloned ENaC subunits alpha-, beta-, and gamma-ENaC.

S-nitrosoglutathione inhibits TNF-alpha-induced NFkappaB activation in neutrophils

OBJECTIVE AND DESIGN

Cytokine expression is controlled by transcription factors including NFkappaB, which has recently been found to exist in human neutrophils. We previously showed that exogenous nitric oxide (NO) induces neutrophil apoptosis and hypothesized that this NO effect could be mediated by inhibition of NFkappaB activation.

MATERIALS AND METHODS

Isolated human neutrophils were incubated with or without S-nitrosoglutathione (GSNO 0.1 mM-5 mM; Sigma) for 2 h. Neutrophils were either unstimulated or stimulated with TNFalphalpha or n-formyl methionyl leucine phenylalanine (fMLP). Viability was assessed by vital dye cytotoxicity assay. After nuclear extraction and measurement of protein concentration, NFkappaB binding was determined by electrophoretic mobility shift assay. Effects of GSNO on activation of IkappaB alpha, which inhibits intranuclear translocation of NFkappaB, were measured by Western immunoblot technique. For comparison, experiments were also performed in the presence of the NFkappaB inhibitor PDTC.

RESULTS

TNFalpha increased nuclear NFkappaB activity compared to unstimulated neutrophils (p < 0.001, n = 5). GSNO (500 microM) decreased TNFalpha-induced NFkappaB activity (p<0.05) and inhibited NFkappaB activity whether given prior to or during TNFalpha exposure. IkappaB alpha was significantly degraded at 30 and 120 min of TNFalpha exposure compared to control neutrophils (p < 0.05). GSNO exposure (500 microM) inhibited IkappaB alpha degradation in the presence of TNFalpha. PDTC enhanced neutrophil cell death and DNA fragmentation, in association with decreased NFkappaB activity, similar to GSNO effects.

CONCLUSION

Neutrophils possess NFkappaB activity that is increased by stimulation with TNFalpha. GSNO inhibits NFkappaB activity in association with inhibiting TNFalpha-induced degradation of IkappaB alpha. GSNO effects are similar to those seen with NFkappaB inhibition by PDTC. Inhibition of NF kappaB could represent a potential anti-inflammatory effect of GSNO.

Neutrophils induce apoptosis of lung epithelial cells via release of soluble Fas ligand

Neutrophils release soluble Fas ligand (sFasL), which can induce apoptosis in certain Fas-bearing cell types (Liles WC, Kiener PA, Ledbetter JA, Aruffo A, and Klebanoff SJ. J Exp Med 184: 429-440, 1996). We hypothesized that neutrophils could induce alveolar epithelial apoptosis via release of sFasL. A549 pulmonary adenocarcinoma cells expressed surface Fas and underwent cell death (10 +/- 7% viability) and DNA fragmentation (354 +/- 98% of control cells) when incubated with agonistic CD95/Fas monoclonal antibody (P < 0.05). Coincubation with human neutrophils induced significant A549 cell death at 48 (51 +/- 9% viability; P < 0.05) and 72 h (25 +/- 10%; P < 0.05) and increased DNA fragmentation (178 +/- 42% of control cells; P < 0.05), with morphological characteristics of apoptosis. The addition of antioxidants did not inhibit apoptosis. sFasL concentrations were maximally increased in coculture medium at 24 h (4.9 +/- 0.7 ng/ml; P < 0.05). Neutrophil-induced A549 cell apoptosis was blocked by inhibitory anti-Fas (42 +/- 6% of control cells; P < 0.05) and anti-FasL monoclonal antibodies (29 +/- 3%; P < 0.05). Human neutrophils and Fas similarly affected murine primary alveolar epithelial cell bilayers, and caspase activation occurred in response to Fas exposure. We conclude that neutrophils undergoing spontaneous apoptosis induce A549 cell death and DNA fragmentation, independent of the oxidative burst, that is mediated by sFasL.

Fluorescent imaging of nitric oxide production in neuronal varicosities associated with intraparenchymal arterioles in rat hippocampal slices

The fluorescent indicator 4,5-diaminofluorescein (DAF-2) has been used to investigate the production of nitric oxide in the vicinity of intraparenchymal cerebral blood vessels. Slices of rat hippocampus 300-350 microm thick, were loaded with 5 microM DAF-2 diacetate. On exposure to light of 450-490 nm wavelength, point sources of fluorescence, 1.8+/-0.2 microm in diameter (mean+/-SEM), were observed in close apposition to the outer surface of the vascular smooth muscle wall of 10/15 arterioles. In fixed slices, resectioned and processed for nicotinamide adenine dinucleotide phosphate-dependent diaphorase, stained varicose fibres were also seen in close association with the smooth muscle wall of small arterioles. These findings suggest that tonic activity in perivascular nitrergic nerve fibres lying in close proximity to intraparenchymal microvessels may be a source of dilator tone within the parenchyma.

Adenovirus-mediated transfer of an Na+/K+-ATPase beta1 subunit gene improves alveolar fluid clearance and survival in hyperoxic rats

Pulmonary edema is cleared via active Na(+) transport by alveolar epithelial Na(+)/K(+)-ATPases and Na(+) channels. Rats exposed to acute hyperoxia have a high mortality rate, decreased Na(+)/K(+)-ATPase function, and decreased alveolar fluid clearance (AFC). We hypothesized that Na(+)/K(+)-ATPase subunit gene overexpression could improve AFC in rats exposed to hyperoxia. We delivered 4 x 10(9) PFU of recombinant adenoviruses containing rat alpha(1) and beta(1) Na(+)/K(+)-ATPase subunit cDNAs (adalpha(1) and adbeta(1), respectively) to rat lungs 7 days prior to exposure to 100% O(2) for 64 hr. As compared with controls and ad alpha(1), AFC in the adbeta(1) rats was increased by >300%. Permeability for large solutes was less in the ad beta(1) than in the other hyperoxia groups. Glutathione oxidation, but not superoxide dismutase activity, was increased only in the adbeta(1) group. Survival through 14 days of hyperoxia was 100% in the adbeta(1) group but was not different from hyperoxic controls in animals given adalpha(1). Our data show that overexpression of a beta(1) Na(+)/K(+)-ATPase subunit augments AFC and improves survival in this model of acute lung injury via antioxidant-independent mechanisms. Conceivably, restoration of AFC via gene transfer of Na(+)/K(+)-ATPase subunit genes may prove useful for the treatment of acute lung injury and pulmonary edema.

Focal bacterial nephritis (lobar nephronia) presenting as renal mass

A focal infection of the kidney can cause a diagnostic dilemma by mimicking a neoplasm. We describe a case of focal bacterial nephritis (acute lobar nephronia) caused by Escherichia coli in which the diagnosis was confirmed only after surgical exploration. Although the patient had fever on admission, urine and blood cultures were negative and fine needle aspiration of the kidney could not rule out a well-differentiated carcinoma.

Ethanol ingestion via glutathione depletion impairs alveolar epithelial barrier function in rats

We determined that rats fed a liquid diet containing ethanol (36% of calories) for 6 wk had decreased (P < 0.05) net vectorial fluid transport and increased (P < 0.05) bidirectional protein permeability across the alveolar epithelium in vivo compared with rats fed a control diet. However, both groups increased (P < 0.05) fluid transport in response to epinephrine (10(-5) M) stimulation, indicating that transcellular sodium transport was intact. In parallel, type II cells isolated from ethanol-fed rats and cultured for 8 days formed a more permeable monolayer as reflected by increased (P < 0.05) leak of [(14)C]inulin. However, type II cells from ethanol-fed rats had more sodium-permeant channels in their apical membranes than type II cells isolated from control-fed rats, consistent with the preserved response to epinephrine in vivo. Finally, the alveolar epithelium of ethanol-fed rats supplemented with L-2-oxothiaxolidine-4-carboxylate (Procysteine), a glutathione precursor, had the same (P < 0.05) net vectorial fluid transport and bidirectional protein permeability in vivo and permeability to [(14)C]inulin in vitro as control-fed rats. We conclude that chronic ethanol ingestion via glutathione deficiency increases alveolar epithelial intercellular permeability and, despite preserved or even enhanced transcellular sodium transport, renders the alveolar epithelium susceptible to acute edematous injury.

Mitochondrial glutathione replacement restores surfactant synthesis and secretion in alveolar epithelial cells of ethanol-fed rats

BACKGROUND

Chronic alcohol abuse increases the incidence and severity of acute lung injury in critically ill patients. Previously we determined that ethanol ingestion in rats dramatically decreased alveolar epithelial cellular levels of glutathione and surfactant synthesis and secretion in vitro. Previous studies in alcoholic liver disease suggest that mitochondrial glutathione levels, and not cellular levels per se, are involved in the pathogenesis of ethanol-mediated hepatotoxicity. Therefore, we hypothesized that alveolar epithelial mitochondrial glutathione depletion mediates the observed defects in surfactant synthesis and secretion in ethanol-fed rats.

METHODS

Male Sprague-Dawley rats were fed the Lieber-DeCarli liquid diet with or without ethanol (36% of total calories) for 6 weeks. In some experiments, ethanol-fed rats were then switched to the control diet for 1 week, with or without glutathione supplementation with either N-acetylcysteine (NAC) or procysteine (PRO). Alveolar epithelial type II cells were then isolated and glutathione levels (cytosolic and mitochondrial) and surfactant production (synthesis and secretion) were determined.

RESULTS

Ethanol ingestion decreased (p < 0.05) mitochondrial and cytosolic levels of glutathione, and surfactant synthesis and secretion in isolated type II cells when compared to cells from control-fed rats. NAC treatment restored (p < 0.05) cytosolic but not mitochondrial glutathione levels (p > 0.05), and had no effect (p > 0.05) on surfactant synthesis and secretion in type II cells isolated from ethanol-fed rats. In contrast, PRO treatment restored (p < 0.05) cytosolic and mitochondrial glutathione levels, and normalized (p < 0.05) surfactant synthesis and secretion in type II cells isolated from ethanol-fed rats.

CONCLUSIONS

These results suggest that mitochondrial, and not simply cytosolic, replacement of glutathione is necessary to improve surfactant function in critically ill patients with a history of alcohol abuse.

Application of cDNA microarrays in determining molecular phenotype in cardiac growth, development, and response to injury

BACKGROUND

Normal myocardial development and the tissue response to cardiac stress are accompanied by marked changes in gene expression; however, the extent of these changes and their significance remain to be fully explored. We used cDNA microarrays for gene expression profiling in rat cardiac tissue samples to study developmental transitions and the response to myocardial infarction (MI).

METHODS AND RESULTS

Microarrays with rat cDNAs for 86 known genes and 989 anonymous cDNAs obtained by molecular subtraction (representational difference analysis) of mRNA from sham-operated and 6-week post-MI samples were used in 2-color hybridization experiments. Twelve known genes previously associated with myocardial development were identified together with 10 uncharacterized expressed sequence tags and 36 genes not previously associated with cardiac development. After MI, genes associated with myocardial stress and wound healing exhibited differences in magnitude and expression kinetics, and 14 genes not previously associated with MI were identified. In situ hybridization revealed mRNA localization characteristic of wound healing and vascular and cardiomyocyte reactivity.

CONCLUSIONS

Tissue analysis of gene expression with cDNA microarrays provides a measure of transcriptional or posttranscriptional regulation and cellular recruitment. Our results demonstrate the complexity of gene regulation in the developing myocardium and show that cDNA microarrays can be used to monitor the evolution of the cardiac stress-inducible phenotype.

Digital analysis of light microscope immunofluorescence: high-resolution co-localization of synaptic proteins in cultured neurons

A protocol is presented for determining the subcellular distribution of fluorescently labeled proteins in neurons using deconvolved images gathered with a wide-field microscope. The protocol includes optimal settings for the numerical algorithm used to deconvolve the images and an objective method for thresholding the deconvolved images to retain only high-intensity, specific labeling. The effectiveness of the protocol is demonstrated using a fluorescent antibody stain directed towards the alpha1 subunit of the GABA(A) receptor in cultured neurons. We also show, using an antibody against the presynaptic vesicular protein synaptophysin, that the technique can detect presumptive regions of synaptic contact between neurons. Double-labeling with the anti-alpha1 and anti-synaptophysin antibodies in a cultured neuron reveals regions of both synaptic and non-synaptic alpha1 labeling. Thus, numerical postprocessing of wide-field images can be used to efficiently locate receptor proteins in neurons in relation to functionally important structures. This confocal-like functionality is attained without the excessive bleaching and phototoxicity associated with the intense laser excitation light used in confocal techniques.

Cognitive influence on postural stability: a neuromuscular analysis in young and older adults

BACKGROUND

Previous literature indicates that attentional resources are required for recovery of postural stability. Previous studies have also examined the effect of aging on the performance of a static postural task while a secondary cognitive task is being conducted. This study describes the effect of a cognitive task on the neuromuscular response characteristics underlying reactive balance control in young versus older adults.

METHODS

The attentional demand on the neuromuscular system was examined in 14 young and 12 healthy older adults by analysis of the integrated electromyography activity while the adults were performing a dual-task paradigm. The primary task involved standing platform perturbations and the secondary task was a math task that involved subtraction by threes. Integrated electromyography activity was compared between the cognitive (math and balance) task versus control (balance only) task.

RESULTS

For both groups of subjects, onset latency of postural muscle responses did not change under dual-task conditions. In contrast, the amplitude of postural muscle activity was significantly affected by performance of a secondary task. When electromyography data were combined for both young and older adults, there was a decrease in muscle response amplitude in both agonist (gastrocnemius) and antagonist (tibialis anterior) muscles when the cognitive math task was performed. This was apparent at 350-500 milliseconds from plate onset for the gastrocnemius and between 150 and 500 for the tibialis anterior. When young and older adults were compared, an age by task interaction effect was seen in muscle response amplitude for the agonist (gastrocnemius) muscle between 350 to 500 milliseconds, with older adults showing a significantly greater reduction than young adults.

CONCLUSION

The decline of muscle activity when the secondary task was performed suggests that less attentional processing capacity was available for balance control during the dual-task paradigm. The results also indicate that the dual-task activity has a greater impact on balance control in the older adults than in the young adults.

The effects of chronic alcohol abuse on pulmonary glutathione homeostasis

The incidence and severity of the acute respiratory distress syndrome (ARDS) is increased in critically ill patients with a prior history of chronic alcohol abuse; however, the specific mechanisms responsible for this association are unknown. Recently, we determined that chronic ethanol ingestion in rats decreased the alveolar epithelial lining fluid (ELF) concentration of the antioxidant glutathione (GSH), which is a characteristic finding in patients with ARDS. However, the effects of chronic alcohol abuse on the human alveolar epithelium are essentially unknown. Therefore, as a first step we asked if chronic alcohol abuse, independent of other comorbid conditions, decreases the concentration of GSH in the human lung. We determined that otherwise healthy chronic alcoholics had significantly decreased ELF concentrations of GSH compared with nonalcoholic control subjects (79 micromol [48 to 118 micromol] versus 576 micromol [493 to 728 mmol], p < 0.001). Furthermore, the percentage of GSH in the oxidized form was higher in the chronic alcoholics (9.8% [2.2 to 14.8%] versus 2.8% [0.4 to 4.0%] p = 0.05), indicative of increased utilization of GSH. This is the first report that chronic alcohol abuse alters GSH homeostasis in the human lung, and suggests a potential mechanism by which chronic alcohol abuse predisposes susceptible patients to develop ARDS.

Insights into early vasculogenesis revealed by expression of the ETS-domain transcription factor Fli-1 in wild-type and mutant zebrafish embryos

Fli-1 is an ETS-domain transcription factor whose locus is disrupted in Ewing's Sarcoma and F-MuLV induced erythroleukaemia. To gain a better understanding of its normal function, we have isolated the zebrafish homologue. Similarities with other vertebrates, in the amino acid sequence and DNA binding properties of Fli-1 from zebrafish, suggest that its function has been conserved during vertebrate evolution. The initial expression of zebrafish fli-1 in the posterior lateral mesoderm overlaps with that of gata2 in a potential haemangioblast population which likely contains precursors of blood and endothelium. Subsequently, fli-1 and gata2 expression patterns diverge, with separate fli-1 and gata2 expression domains arising in the developing vasculature and in sites of blood formation respectively. Elsewhere in the embryo, fli-1 is expressed in sites of vasculogenesis. The expression of fli-1 was investigated in a number of zebrafish mutants, which affect the circulatory system. In cloche, endothelium is absent and blood is drastically reduced. In contrast to the blood and endothelial markers that have been studied previously, fli-1 expression was initiated normally in cloche embryos, indicating that induction of fli-1 is one of the earliest indicators of haemangioblast formation. Furthermore, although fli-1 expression in the trunk was not maintained, the normal expression pattern in the anterior half of the embryo was retained. These anterior cells did not, however, condense to form blood vessels. These data indicate that cloche has previously unsuspected roles at multiple stages in the formation of the vasculature. Analysis of fli-1 expression in midline patterning mutants floating head and squint, confirms a requirement for the notochord in the formation of the dorsal-aorta. The formation of endothelium in one-eyed pinhead, cyclops and squint embryos indicates a novel role for the endoderm in the formation of the axial vein. The phenotype of sonic-you mutants implies a likely role for Sonic Hedgehog in mediating these processes.

Molecular characterization of a zebrafish TCF ETS-domain transcription factor

The ternary complex factor (TCF) subfamily of ETS-transcription factors represent key nuclear targets of the MAP kinase pathways. Members of this subfamily are classified by the presence of several conserved domains for DNA binding, interaction with SRF, interaction with MAP kinases and transcriptional activation. In this study we have isolated a further member of this subfamily (TCF-1) from zebrafish. The protein product of zebrafish TCF-1 (zTCF-1), shares sequence similarity with the mammalian TCFs in all four conserved domains, with highest overall similarity to SAP-1. Zebrafish TCF-1 is expressed throughout zebrafish embryonic development and exhibits typical TCF DNA binding characteristics, with the B-box being required for interaction with SRF. Of the mammalian TCFs, its DNA binding specificity resembles Elk-1. zTCF-1 is a target for both the growth factor/mitogen-activated and stress-activated MAP kinase cascades in vitro and in vivo. However, differential targeting occurs, with the profile of its activation closely resembling that of mammalian SAP-1. Together, our results demonstrate that the TCFs have been functionally conserved during vertebrate development.

Bio-imaging of nitric oxide-producing neurones in slices of rat brain using 4,5-diaminofluorescein

4,5-Diaminofluorescein (DAF-2) was used to identify individual nitric oxide (NO)-producing neurones in brain slices in vitro. Coronal slices of midbrain or hippocampus, 300 microm thick from young adult rats, were incubated for 30 min in 1 microM DAF-2 diacetate (DAF-2 DA) and maintained in ACSF at 33 degrees C. Illumination at 450-490 nm revealed punctate fluorescence in neurones in the lateral tegmental nucleus, dorsal raphe nucleus, dorsolateral periaqueductal grey matter, deep collicular layers and cortical areas. Neurones in the hippocampal pyramidal cell layer, molecular layer of the dentate gyrus and the hilus fluoresced also. The fluorescence was abolished by pre-incubation of slices with L-NAME (100 microM-1 mM), the inhibitor of constitutive nitric oxide synthase (NOS), but not by D-NAME (100 microM) or L-NIL (5-50 microM), an inhibitor of inducible NOS. In some superficially located arterioles, there were small regions of bright fluorescence close to the outer smooth muscle wall and diffuse fluorescence within the adjacent smooth muscle cells. A diffuse fluorescence was also seen in some superficially located capillaries. Basal production of NO was not seen within deeper blood vessels. DAF-2 DA offers a sensitive indicator for visualising basal production of NO with high spatial resolution and could provide a means of identifying NOS-containing neurones in brain slices in vitro prior to neurophysiological study.

Ethanol ingestion increases activation of matrix metalloproteinases in rat lungs during acute endotoxemia

Previously we reported that alcohol abuse increases the incidence of the acute respiratory distress syndrome (ARDS) in septic patients, and that chronic ethanol ingestion in rats depletes alveolar epithelial glutathione and increases endotoxin-mediated lung edema. In this study we examined a potential mechanism by which ethanol-induced glutathione depletion could predispose to acute lung injury. We hypothesized that glutathione depletion activates matrix metalloproteinases (MMPs), thereby increasing degradation of the alveolar extracellular matrix (ECM) during sepsis. Ethanol-fed rats (20% vol/vol in water for 6 wk) were given endotoxin (2 mg/kg, intraperitoneally) followed 2 h later by lung isolation and ex vivo perfusion with n-formyl-methionyl-leucyl-phenylalanine (fMLP) (10(-)(7) M). Ethanol ingestion increased (p < 0.05) MMP-9 and MMP-2 activity, as determined by zymography, in the lung tissue and lavage fluid compared with control-fed rats, and increased (p < 0.05) levels of the 7S fragment of type IV collagen in the lung lavage fluid. Ethanol ingestion increased activation, but not production, of the MMP-9 and MMP-2 zymogens. Finally, although concomitant ingestion of N-acetylcysteine had no effect (p > 0.05) on MMP production, it increased (p > 0.05) lung glutathione levels, blocked (p < 0.05) MMP-9 and MMP-2 activation, and decreased (p < 0.05) levels of the 7S fragment of type IV collagen. We conclude that chronic ethanol ingestion, via glutathione depletion, activates MMPs during sepsis, thereby increasing degradation of the alveolar epithelial ECM. Lois M, Brown LAS, Moss IM, Roman J, Guidot DM. Ethanol ingestion increases activation of matrix metalloproteinases in rat lungs during acute endotoxemia.

Effects of exogenous nitric oxide and hyperoxia on lung fibroblast viability and DNA fragmentation

Effective lung repair after acute injury requires elimination of proliferating mesenchymal and inflammatory cells without inducing an acute inflammatory response or disturbing concomitant repair of lung microvasculature. Previous studies have shown that endogenous NO regulates programmed cell death in fibroblasts and can modulate wound fibroblast synthetic function. We hypothesized that exposure of human lung fibroblasts to NO gas would decrease viability and induce apoptotic cell death. Primary cultures of normal human lung fibroblasts were exposed for 4 h to room air (RA), 80% oxygen, NO (at either 20 or 50 ppm) blended with RA, or NO blended with 80% O(2), then incubated for 24 to 72 h. Cell viability was determined by fluorescence viability/cytotoxicity assay and DNA fragmentation by TUNEL assay. Peroxynitrite formation was assessed using immunoblotting for S-nitrosotyrosine. NO plus O(2) induced significant cell death at 20 and 50 ppm NO when compared to either RA or O(2) alone at both 24 and 72 h (p < 0.05). Incubation with superoxide dismutase (SOD), catalase (CAT) or SOD + CAT significantly decreased cell death in fibroblasts treated with NO(20)/O(2) and NO(50)/O(2) compared with controls (p < 0.05). NO(20)/O(2) and NO(50)/O(2) exposure significantly increased TUNEL mean fluorescence intensity (MFI), consistent with increased DNA fragmentation, compared to RA at 24 and 72 h (p < 0.05). Antioxidants decreased MFI in cells exposed to NO(20)/O(2) (CAT and SOD + CAT) compared to controls at 24 h (p < 0.05). Western blot analysis for S-nitrosotyrosine showed increased signal intensity in fibroblasts exposed to NO at 20 and 50 ppm plus O(2) compared to RA or O(2) alone. Incubation with SOD + CAT reduced signal intensity for peroxynitrite in cells exposed to NO(20)/O(2). We conclude that NO in hyperoxic conditions induces fibroblast cell death and DNA fragmentation, which could be partially mediated by peroxynitrite synthesis.