Effects of Various Body Temperatures After Lipopolysaccharide-Induced Lung Injury in Rats

ZIF-8 as efficient carriers for polysaccharide from Tetrastigma Hemsleyanum Diels et Gilg in acute lung injury induced by lipopolysaccharides

Acute lung injury (ALI) is a critical respiratory syndrome significantly impacting patient health. Tetrastigma hemsleyanum Diels et Gilg (Sanyeqing, SYQ) is a traditional Chinese medicine and its polysaccharides (SYQP) have demonstrated efficacy in counteracting lipopolysaccharide-induced ALI. This study characterized the structure of SYQP and synthesized the SYQP@ZIF-8 composite using biomimetic mineralization, evaluating encapsulation and release efficiency. The biocompatibility of SYQP@ZIF-8 in vitro was assessed by the CCK-8 colorimetric assay and hemolytic activity. Inflammatory cytokine was measured to evaluate the therapeutic effect. The efficacy of SYQP@ZIF-8 in lung injury was assessed using a mice ALI model. Characterization showed SYQP as a homogeneous α-type polysaccharide, comprising galactose, mannose, glucuronide, glucose, galacturonide, and arabinose, with a molecular weight of 516.94 kDa. SYQP@ZIF-8 exhibited high encapsulation rate (> 90 %), rapid pH-responsive release (within 60 min up to ~100 %), low toxicity and favorable hemolytic characteristics. Furthermore, it demonstrated reduced inflammatory cytokine secretion compared to SYQP, along with a superior inhibitory effect. The outcomes of in vivo experiments, including a decrease in the W/D ratio and LDH activity, further confirmed the efficacy of SYQP@ZIF-8 in treating LPS-induced ALI. In conclusion, SYQP@ZIF-8 released SYQP in acidic inflammatory conditions, outperforming SYQP alone in treating ALI.

Successful use of mild therapeutic hypothermia as compassionate treatment for severe refractory hypoxemia in COVID-19

BACKGROUND

COVID-19 is a disease associated with an intense systemic inflammation that could induce severe acute respiratory distress syndrome (ARDS), with life-threatening hypoxia and hypercapnia. We present a case where mild therapeutic hypothermia was associated with improved gas exchange, facing other therapies' unavailability due to the pandemic.

CASE REPORT

A healthy 38-year-old male admitted for COVID-19 pneumonia developed extreme hypoxia (PaO₂/FiO₂ ratio 42 mmHg), respiratory acidosis, and hyperthermia, refractory to usual treatment (mechanical ventilation, neuromuscular blockade, and prone position), and advanced therapies were not available. Mild therapeutic hypothermia management (target 33-34 °C) was maintained for five days, with progressive gas exchange improvement, which allowed his recovery over the following weeks. He was discharged home after 68 days without significant ICU associated morbidity.

CONCLUSIONS

Mild hypothermia is a widely available therapy, that given some specific characteristics of COVID-19, may be explored as adjunctive therapy for life-threatening ARDS, especially during a shortage of other rescue therapies.

Induction of Chronic Subclinical Systemic Inflammation in Sprague-Dawley Rats Stimulated by Intermittent Bolus Injection of Lipopolysaccharide

Chronic subclinical systemic inflammation has a key role in stimulating several chronic conditions associated with cardiovascular diseases, cancer, rheumatoid arthritis, diabetes, and neurodegenerative diseases. Hence, developing in vivo models of chronic subclinical systemic inflammation are essential to the study of the pathophysiology and to measure the immunomodulatory agents involved. Male Sprague-Dawley rats were subjected to intraperitoneal, intermittent injection with saline, or lipopolysaccharide (LPS) (0.5, 1, 2 mg/kg) thrice a week for 30 days. Hematological, biochemical, and inflammatory mediators were measured at different timepoints and at the end of the study. The hearts, lungs, kidneys, and livers were harvested for histological evaluation. Significant elevation in peripheral blood leukocyte includes neutrophils, monocytes, and lymphocytes, as well as the neutrophils-to-lymphocyte ratio. The pro-inflammatory mediator levels [C-reactive protein, tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-1β, and IL-8] along with the biochemical profile (alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, creatine kinase, creatinine, and urea) were increased significantly (P < 0.05) and increased the expression of monocyte chemoattractant protein-1 and TNF-β. The histopathological changes of heart, lung, kidney, and liver tissues revealed degeneration, cellular infiltration of leukocyte in the inflammatory foci and interstitial space, edema, early signs of fibrosis, apoptosis, and necrosis. In conclusion, these results indicate that intermittent exposure to LPS produces chronic subclinical systemic inflammation in multiple organs leading to chronic conditions and supports this model to be a useful preclinical tool for developing immunotherapeutic agents that could prevent, or reduce, chronic inflammatory diseases associated with, or without, bacterial translocation.

Fever and hypothermia in systemic inflammation

Systemic inflammation-associated syndromes (e.g., sepsis and septic shock) often have high mortality and remain a challenge in emergency medicine. Systemic inflammation is usually accompanied by changes in body temperature: fever or hypothermia. In animal studies, systemic inflammation is often modeled by administering bacterial lipopolysaccharide, which triggers autonomic and behavioral thermoeffector responses and causes either fever or hypothermia, depending on the dose and ambient temperature. Fever and hypothermia are regulated changes of body temperature, which correspond to mild and severe forms of systemic inflammation, respectively. Mediators of fever and hypothermia are called endogenous pyrogens and cryogens; they are produced when the innate immune system recognizes an infectious pathogen. Upon an inflammatory challenge, hepatic and pulmonary macrophages (and later brain endothelial cells) start to release lipid mediators, of which prostaglandin (PG) E₂ plays the key role, and cytokines. Blood PGE₂ enters the brain and triggers fever. At later stages of fever, PGE₂ synthesized within the blood-brain barrier maintains fever. In both cases, PGE₂ is synthesized by cyclooxygenase-2 and microsomal PGE₂synthase-1. Mediators of hypothermia are not well established. Both fever and hypothermia are beneficial host defense responses. Based on evidence from studies in laboratory animals and clinical trials in humans, fever is beneficial for fighting mild infection. Based mainly on animal studies, hypothermia is beneficial in severe systemic inflammation and infection.

Triptolide ameliorates lipopolysaccharide-induced acute lung injury in rats

Background

Acute lung injury (ALI) is a serious clinical syndrome with a high rate of mortality. In this study, the effects of triptolide on lipopolysaccharide (LPS)-induced ALI in rats were investigated.

Methods

Sixty-five male Sprague Dawley rats(approved by ethics committee of the First Affiliated Hospital of Soochow University) were randomly divided into five groups. The control group was injected with 2.5 mL saline/kg body weight via the tail vein and intraperitoneally with 1% dimethyl sulfoxide (DMSO) (n = 5). The L group was administered with 0.2% LPS dissolved in saline (5 mg/kg) to induce ALI via the tail vein (n = 15). The TP1, TP2, and TP3 groups were treated as rats in the L group and then intraperitoneally injected with 25, 50, and 100 μg triptolide/kg body weight, respectively (15 rats per group). Blood samples from the left heart artery were taken for blood gas analysis at 1 hour before injection and at 1, 3, 6, and 12 hours after saline and DMSO administration in the control group, LPS injection in the L group, and triptolide injection in the TP1, TP2, and TP3 groups. Lung wet-to-dry weight (W/D) ratio, diffuse alveolar damage (DAD) score, TNF-α levels, and mRNA and protein expression of toll-like receptor 4 (TLR4) were analyzed.

Results

Compared with the control group, the arterial partial pressure of oxygen (PaO₂) declined (P <0.05), the W/D ratio and DAD score increased (P <0.05), and TNF-α levels in serum and bronchoalveolar lavage fluid (BALF) and mRNA and protein expression of TLR4 were significantly increased in the L group (P <0.05). Compared with the L group, PaO₂ significantly increased in the TP2 and TP3 groups (P <0.05), while the W/D ratio and DAD score were significantly decreased in the TP2 and TP3 groups (P <0.05). TNF-α levels and mRNA and protein expression of TLR4 were significantly decreased in the TP2 and TP3 groups compared with the L group (P <0.05).

Conclusions

Triptolide can ameliorate LPS-induced ALI by reducing the release of the inflammatory mediator TNF-α and inhibiting TLR4 expression.

Hydrogen sulfide donor NaHS reduces organ injury in a rat model of pneumococcal pneumosepsis, associated with improved bio-energetic status

Sepsis is characterized by a generalized inflammatory response and organ failure, associated with mitochondrial dysfunction. Hydrogen sulfide donor NaHS has anti-inflammatory properties, is able to reduce metabolism and can preserve mitochondrial morphology and function. Rats were challenged with live Streptococcus pneumonia or saline and infused with NaHS (36 µmol/kg/h) or vehicle. Lung and kidney injury markers were measured as well as mitochondrial function, viability and biogenesis. Infusion of NaHS reduced heart rate and body temperature, indicative of a hypo-metabolic state. NaHS infusion reduced sepsis-related lung and kidney injury, while host defense remained intact, as reflected by unchanged bacterial outgrowth. The reduction in organ injury was associated with a reversal of a fall in active oxidative phosphorylation with a concomitant decrease in ATP levels and ATP/ADP ratio. Preservation of mitochondrial respiration was associated with increased mitochondrial expression of α-tubulin and protein kinase C-ε, which acts as regulators of respiration. Mitochondrial damage was decreased by NaHS, as suggested by a reduction in mitochondrial DNA leakage in the lung. Also, NaHS treatment was associated with upregulation of peroxisome proliferator-activated receptor-γ coactivator 1α, with a subsequent increase in transcription of mitochondrial respiratory subunits. These findings indicate that NaHS reduces organ injury in pneumosepsis, possibly via preservation of oxidative phosphorylation and thereby ATP synthesis as well as by promoting mitochondrial biogenesis. Further studies on the involvement of mitochondria in sepsis are required.

Pretreatment with pentoxifylline attenuates lung injury induced by intestinal ischemia/reperfusion in rats

PURPOSE

To investigate the protective effect of pentoxifylline against the lung injury observed after intestinal ischemia (I) followed by a period of reperfusion (R).

METHODS

Twenty-eight male Wistar rats were equally divided into 4 experimental groups and operated under ketamine-xylazine anesthesia. (1) Sham: falsely-operated animals; (2) SS+IR: intestinal ischemia was accomplished by clipping the superior mesenteric artery during 60 minutes, with an administration of a standard volume of saline solution (SS) 5 min before the end of the ischemia period; the clip was then releases or a 120-min period of reperfusion; (3) I+PTX+R: ischemia as above, PTX was administered (25 mg/kg) and the gut reperfused as above; (4) PTX+I+PTX+R: Five minutes before arterial occlusion PTX was administered; the superior mesenteric artery was then clipped for 60 minutes. After 55-min ischemia, an additional dosis of PTX was administered; the clip was removed for reperfusion as above. At the 60th min of reperfusion a third dosis of PTX was administered.

RESULTS

PTX markedly attenuated lung injury as manifested by significant decreases (all P<0.001 as compared with the SS+IR group) of pulmonary wet/dry tissue weight ratio, total protein content, myeloperoxidase activity and tumor necrosis factor-alpha. Moreover, it was apparent that in the group PTX+I+PTX+R the improvements have been even more significant.

CONCLUSION

PTX exerted a protective effect on the lung from the injuries caused by intestinal ischemia/reperfusion.

Therapeutic Effects of Baicalin on Lipopolysaccharide-Induced Acute Lung Injury in Rats

Baicalin is a flavonoid present in many traditional Chinese medicines. A number of studies show that baicalin has anti-inflammatory actions and protects against a variety of tissue and organ injuries. The effect of baicalin in lipopolysaccharide (LPS)-induced acute lung injury is not well studied. In this study, typically acute lung injury was induced in rat by intratracheal injection of LPS, which increased lactate dehydrogenase activity and protein content in bronchoalveolar lavage fluid, wet/dry lung weight ratio, Evan's blue dye leakage, and neutrophil infiltration. Baicalin (20 mg/kg) was administrated 1 hour before or 30 min after LPS injection. Both pre and post-treatment with baicalin attenuated the increase of these parameters and improved histological finding. Our results suggest that baicalin has a therapeutic effect on LPS-induced acute lung injury.

Plasminogen activator inhibitor type-1 deficiency exaggerates LPS-induced acute lung injury through enhancing Toll-like receptor 4 signaling pathway

Mice lacking plasminogen activator inhibitor-1 (PAI-1) did not affect lung injury induced by gram-positive bacteria pneumococcal pneumonia but worsened lung injury induced by gram-negative bacteria Klebsiella. The exact mechanisms have not been completely elucidated. In this study, we examined the signaling pathway of Toll-like receptor 4 (TLR4) with/without PAI-1 in acute lung injury (ALI) induced by lipopolysaccharides (LPS) in mice. PAI-1 knockout mice (n=60) and wild-type mice (n=60) were exposed to LPS intratracheal instillation. Different groups of mice were then sacrificed at 0 and 8 h after LPS instillation. PAI-1-/- mice showed increased excess lung water and elevated cytokines production and release. In addition, expression of TLR4 was up-regulated and the phosphorylation activation of extracellular regulating kinase (ERK) and c-Jun N-terminal kinase (JNK) were also increased in PAI-1 knockout mice compared to wild-type mice. Inversely, interleukin (IL)-1 receptor-associated kinase-M (IRAK-M) and suppressor of cytokine signaling 1 (SOCS1) were both significantly reduced in PAI-1-/-mice after LPS challenge. PAI-1 deletion increased lung injury induced by LPS through up-regulation of TLR4, ERK and C-JNK and down-regulation of TLR4 negative regulators.

Hypobaric hypoxia preconditioning attenuates acute lung injury during high-altitude exposure in rats via up-regulating heat-shock protein 70

HHP (hypobaric hypoxia preconditioning) induces the overexpression of HSP70 (heat-shock protein 70), as well as tolerance to cerebral ischaemia. In the present study, we hypothesized that HHP would protect against HAE (high-altitude exposure)-induced acute lung injury and oedema via promoting the expression of HSP70 in lungs prior to the onset of HAE. At 2 weeks after the start of HHP, animals were exposed to a simulated HAE of 6000 m in a hypobaric chamber for 24 h. Immediately after being returned to ambient pressure, the non-HHP animals had higher scores of alveolar oedema, neutrophil infiltration and haemorrhage, acute pleurisy (e.g. increased exudate volume, increased numbers of polymorphonuclear cells and increased lung myeloperoxidase activity), increased pro-inflammatory cytokines [e.g. TNF-α (tumour necrosis factor-α), IL (interleukin)-1β and IL-6], and increased cellular ischaemia (i.e. glutamate and lactate/pyruvate ratio) and oxidative damage [glycerol, NOx (combined nitrate+nitrite) and 2,3-dihydroxybenzoic acid] markers in the BALF (bronchoalveolar fluid). HHP, in addition to inducing overexpression of HSP70 in the lungs, significantly attenuated HAE-induced pulmonary oedema, inflammation, and ischaemic and oxidative damage in the lungs. The beneficial effects of HHP in preventing the occurrence of HAE-induced pulmonary oedema, inflammation, and ischaemic and oxidative damage was reduced significantly by pretreatment with a neutralizing anti-HSP70 antibody. In conclusion, HHP may attenuate the occurrence of pulmonary oedema, inflammation, and ischaemic and oxidative damage caused by HAE in part via up-regulating HSP70 in the lungs.

Oral melatonin attenuates lung inflammation and airway hyperreactivity induced by inhalation of aerosolized pancreatic fluid in rats

Melatonin is a free radical scavenger with potent antioxidant properties and immunomodulatory effects. The purpose of this study was to determine the effects of orally administered melatonin in a pancreatic fluid (PF)-induced lung inflammation and airway hyperreactivity model. Aerosolized PF was introduced into airways to induce inflammation in rats. Animals were randomized into three experimental groups: sham treated; PF treated (200 μL/kg); and PF with melatonin (10 mg/kg) pretreatment. Airway reactivity to methacholine, airflow and airway resistance, bronchoalveolar lavage (BAL) cellular differential, the tumor necrosis factor α (TNFα) level, lavage nitric oxide, hydroxyl radical, and lactic dehydrogenase (LDH) were compared among groups. mRNA expressions of inducible nitric oxide synthase (iNOS) and TNFα in lung tissues were determined by real-time polymerase chain reaction. Protein expressions of iNOS and nitrotyrosine and lung tissue myeloperoxidase (MPO) activity were determined using an ELISA assay. Oral melatonin treatment indicated anti-inflammatory efficacy as evidenced by decreased methacholine sensitivity by 24% and airway obstruction by 28%, reduction in BAL eosinophil (P < 0.01) and neutrophil counts (P < 0.05), LDH (P < 0.05), and TNFα concentrations (P < 0.05) when compared to levels in sham-treated rats. Melatonin-treated animals also had reduced nitric oxide and hydroxyl radical concentrations (P < 0.05) in lavage fluid. Oral melatonin significantly reduced mRNA and protein expression of iNOS (P < 0.05 and P < 0.01, respectively), TNFα (P < 0.05), nitrotyrosine (P < 0.05), and MPO activity (P < 0.05) in lung tissues when compared with the sham-treated animals. These results suggest that oral treatment with melatonin had a beneficial effect on PF-induced obstructive ventilatory insufficiency by attenuating nitrosative and oxidative stress.

Inhibition of acute lung inflammation and injury is a target of brain cooling after heatstroke injury

BACKGROUND

Although brain cooling has recently been reported as effective in improving the survival after heatstroke generation in rats, the mechanisms underlying the therapeutic effects of brain cooling are not fully elucidated. This study was conducted to test whether the acute lung inflammation and damage that might occur during heatstroke could be affected by brain cooling.

METHODS

Anesthetized rats were randomized into four groups as follows: (a) normothermic controls (n = 8); (b) heatstroke rats without saline delivery (n = 8); (c) heatstroke rats treated with 36°C saline via retrograde jugular vein (n = 8); and (d) heatstroke rats treated with 4°C saline via retrograde jugular vein (n = 8). Heatstroke was induced by putting the animals in a folded heating pad of 42°C for 68 minutes controlled by circulating hot water. The core temperatures of normothermic groups were maintained at about 36°C. The cardiovascular parameters and core temperatures were monitored for all experiments. Bronchoalveolar lavage (BAL) was done in the left lung 20 minutes after termination of heat stress for determination of cellular ischemia markers (e.g., glutamate, lactate-to-pyruvate ratio), proinflammatory cytokines (interleukin-1, tumor necrosis factor-alpha), and nitric oxide metabolites. Parts of the right lung were excised for meloperoxidase measurement, whereas the rest was collected for lung damage score assessments.

RESULTS

When compared with those of normothermic controls, untreated or 36°C saline-treated heatstroke rats had higher values of BAL fluid levels of cellular ischemia markers, proinflammatory cytokines, nitric oxide metabolites, lung meroperoxidase activity, lung damage score, and neutrophil infiltration. Brain cooling causes by 4°C saline infusion significantly reduced the heat-induced increased BAL levels of cellular ischemia markers, proinflammatory cytokines, and nitric oxide metabolites, and reduced lung damage score and neutrophil infiltration.

CONCLUSIONS

These experimental data indicate that acute lung inflammation and damage is a target of brain cooling after heatstroke injury.

The role of mild hypothermia in air embolism-induced acute lung injury

BACKGROUND

Mild hypothermia has become an important treatment for ischemic brain injury. However, the role of mild hypothermia in air embolism-induced lung injury has not been explored. In this study, we investigated whether treatment with mild hypothermia before and synchronous with air infusion can attenuate acute lung injury induced by air embolism.

METHODS

In this rat model study (Sprague-Dawley rats), pulmonary air embolism was induced by venous infusion of air at a rate of 25 microL/min for 40 minutes. Control animals received no air infusion. The rats were randomly assigned to 2 control groups of normothermia (37 degrees C) and mild hypothermia (34 degrees C) and 3 air embolism groups of mild hypothermia induced before air infusion, normothermia with air infusion, and mild hypothermia induced synchronous with air infusion. At the end of the experiment, the variables of lung injury were assessed.

RESULTS

Air infusion elicited a significant increase in lung wet/dry weight ratio and protein, lactate dehydrogenase, and tumor necrosis factor-alpha concentration of the bronchoalveolar lavage fluid. Myeloperoxidase activity, neutrophil infiltration, and interstitial edema in lung tissue were also significantly increased. In addition, nuclear factor-kappaB activity was significantly increased in the lungs. Treatment with mild hypothermia before air infusion reduced increases in these variables, whereas mild hypothermia synchronous with air infusion had no significant effect on them.

CONCLUSIONS

Our study suggests that mild hypothermia before air infusion decreases air embolism-induced acute lung injury. The protective mechanism seems to be the inhibition of inflammation.

Hypothermia increases interleukin-6 and interleukin-10 in juvenile endotoxemic mice

OBJECTIVE

To develop a juvenile mouse model to establish effects of in vivo hypothermia on expression of the inflammation-modulating cytokines tumor necrosis factor-alpha, interleukin-1beta, interleukin-6, and interleukin-10. Although induced hypothermia is neuroprotective in some patients, the mechanisms of protection are not well understood and concerns remain over potential detrimental effects, particularly in the setting of infection. We previously showed that in vitro hypothermia increases production of tumor necrosis factor-alpha and interleukin-1beta in lipopolysaccharide-treated monocytes.

DESIGN

: Laboratory investigation.

SETTING

Research laboratory.

SUBJECTS

Juvenile (4-wk) male C57BL/6 mice.

INTERVENTIONS

: Mice were given chlorpromazine to suspend thermoregulation and lipopolysaccharide to stimulate cytokine production. Core temperature was maintained at 32 degrees C or 37 degrees C for 6 hrs by adjusting environmental temperature. In separate experiments, lipopolysaccharide-treated mice were kept in a cooling chamber without chlorpromazine treatment.

MEASUREMENTS AND MAIN RESULTS

Plasma and organs were collected for cytokine quantitation. Chlorpromazine-treated hypothermic mice had 2.3-fold and 1.8-fold higher plasma interleukin-6 and interleukin-10 levels at 6 hrs compared with identically treated normothermic mice (p < .05), whereas plasma tumor necrosis factor-alpha and interleukin-1beta were not significantly different at 2 hrs or 6 hrs. Liver tumor necrosis factor-alpha and interleukin-6 were significantly higher in hypothermic vs. normothermic mice, but lung and brain cytokines were not different. Lipopolysaccharide-treated mice kept in a cooling chamber without chlorpromazine treatment developed varying degrees of hypothermia with associated increases in plasma interleukin-6 and interleukin-10. A nonspecific marker of stress (plasma corticosterone) was not affected by hypothermia in lipopolysaccharide-treated mice.

CONCLUSION

Further studies are necessary to determine the mechanism and physiologic consequences of augmented systemic interleukin-6 and interleukin-10 expression during induced hypothermia.

Baicalin attenuates air embolism-induced acute lung injury in rat isolated lungs

BACKGROUND AND PURPOSE

Baicalin has been reported to have anti-inflammatory effects and protect against various tissue injuries. However, the effect of baicalin on air embolism-induced acute lung injury has not been tested yet.

EXPERIMENTAL APPROACH

Acute lung injury was induced by infusion of air at a rate of 0.25 mL.min(-1) for 1 min into the pulmonary artery of rat isolated lungs. At the end of the experiment, samples were collected for assessment of lung injury, biochemical analysis and histology. Different doses of baicalin (1, 2 and 4 mg.kg(-1)) were given into the perfusate before air infusion.

KEY RESULTS

Air embolism elicited a significant increase in microvascular permeability (K(f)), lung weight gain, wet/dry weight ratio, pulmonary artery pressure and protein concentration in the bronchoalveolar lavage fluid. Levels of the cytokines, tumour necrosis factor alpha and cytokine-induced neutrophil chemoattractant-1 in perfusate, and malondialdehyde levels and myeloperoxidase activities in lung tissue were also significantly increased. In addition, histological examination showed increased neutrophil infiltration in lung tissues. Furthermore, nuclear factor-kappaB activity and degradation of IkappaB-alpha were significantly increased in lungs. Pretreatment of the lungs with baicalin (4 mg.kg(-1)) showed a statistically significant difference in all of the assessed parameters, except for alteration in the pulmonary artery pressure.

CONCLUSIONS AND IMPLICATIONS

Our study suggests that baicalin attenuated air embolism-induced acute lung injury and may be considered a useful adjunct drug therapy in this clinical condition.

Intrapulmonary delivery of bone marrow-derived mesenchymal stem cells improves survival and attenuates endotoxin-induced acute lung injury in mice

Recent in vivo and in vitro work suggests that mesenchymal stem cells (MSC) have anti-inflammatory properties. In this study, we tested the effect of administering MSC directly into the airspaces of the lung 4 h after the intrapulmonary administration of Escherichia coli endotoxin (5 mg/kg). MSC increased survival compared with PBS-treated control mice at 48 h (80 vs 42%; p < 0.01). There was also a significant decrease in excess lung water, a measure of pulmonary edema (145 +/- 50 vs 87 +/- 20 microl; p < 0.01), and bronchoalveolar lavage protein, a measure of endothelial and alveolar epithelial permeability (3.1 +/- 0.4 vs 2.2 +/- 0.8 mg/ml; p < 0.01), in the MSC-treated mice. These protective effects were not replicated by the use of further controls including fibroblasts and apoptotic MSC. The beneficial effect of MSC was independent of the ability of the cells to engraft in the lung and was not related to clearance of the endotoxin by the MSC. MSC administration mediated a down-regulation of proinflammatory responses to endotoxin (reducing TNF-alpha and MIP-2 in the bronchoalveolar lavage and plasma) while increasing the anti-inflammatory cytokine IL-10. In vitro coculture studies of MSC with alveolar macrophages provided evidence that the anti-inflammatory effect was paracrine and was not cell contact dependent. In conclusion, treatment with intrapulmonary MSC markedly decreases the severity of endotoxin-induced acute lung injury and improves survival in mice.

The effects of hypothermia on endotoxin-primed lung

BACKGROUND

Hypothermia may be effective for endotoxin-induced acute lung injury. In most studies, hypothermia was induced before the development of neutrophilic inflammation, which would be clinically irrelevant. We investigated whether hypothermia induced after the onset of such neutrophilic inflammation reduces acute lung injury.

METHODS

In the first experiment, rats were allocated to one of four groups: intratracheal saline instillation/killed at 1 h (saline), intratracheal lipopolysaccharide (LPS) instillation/killed at 1 h (LPS-primed), intratracheal LPS instillation/killed at 6 h (LPS-NT), all under normothermia (NT) (37 +/- 0.5 degrees C) throughout study, and intratracheal LPS instillation/killed at 6 h with hypothermia (HT) (32 +/- 0.5 degrees C) for the last 5 h of study (LPS-HT). Lungs were lavaged for biochemical measurements. In the second experiment in 26 additional rats, we followed exactly the same protocol as described above for the saline group (n = 2), LPS-NT (n = 12), and LPS-HT (n = 12), and obtained a fresh pool of alveolar neutrophils to assess oxidative burst.

RESULTS

Compared with the LPS-primed group, the neutrophil count, protein level, and lactate dehydrogenase activity in the bronchoalveolar lavage fluid, and myeloperoxidase activity of the lung were all higher in the LPS-NT group. Compared with this LPS-NT group, the neutrophil count, protein level, and lactate dehydrogenase activity in the bronchoalveolar lavage fluid, and microscopic scores for alveolar neutrophilic infiltration were all lower in the LPS-HT group. The stimulated production of hydrogen peroxide in neutrophils was lower in the LPS-HT group than in the LPS-NT group.

CONCLUSION

Hypothermia, applied even after the onset of neutrophilic inflammation, was effective in reducing endotoxin-induced acute lung injury.

Modulating cofactors of acute lung injury 2005–2006: any closer to ‘prime time’?

PURPOSE OF REVIEW

Considerable progress has recently been made in understanding the modulation of acute lung injury by cofactors that are not traditionally considered 'pulmonary' in nature. We will review findings regarding some of these extrapulmonary cofactors, focusing on those most readily manipulated in the current clinical setting.

RECENT FINDINGS

Recent studies have demonstrated that limiting fluid administration in the setting of acute lung injury might improve surrogate outcomes; that hypercapnea and induced hypothermia might protect against or attenuate acute lung injury; that corticosteroids can improve mechanics but not mortality in acute respiratory distress syndrome; a potential role for concomitant administration of colloid and diuretic in acute lung injury; and the potential benefits of inhaled beta agonists in acute lung injury.

SUMMARY

There are a number of simple, low-cost, and rapidly deployable approaches to reducing the severity of acute lung injury that are not directly pulmonary in origin. These interventions could be rapidly implemented in any intensive care unit, once evidence for their efficacy and safety is adequate.

Acute but not chronic stimulation of glial cells in rat spinal cord by systemic injection of lipopolysaccharide is associated with hyperalgesia

We have analyzed development of mechanical hyperalgesia after repeated systemic lipopolysaccharide (LPS) injections and correlated these findings with stimulation of astrocytes and microglia in spinal cord. Male Lewis rats received a single or seven intraperitoneal injections of LPS. Mechanical hyperalgesia was measured as rat hindpaw withdrawal thresholds (PWTs). We observed that a single LPS injection elicited a specific change of PWTs while stimulated spinal glial activation was identified by immunoreactivities of specific markers, ED1, P2X4 receptor, endothelial monocyte activating polypeptide II (EMAP II) and glial fibrillary acidic protein (GFAP), respectively; multiple LPS treatments induced tolerance to mechanical hyperalgesia, whereas expression of ED1 and GFAP were further increased. In conclusion, we have demonstrated that the number of activated spinal glial cells was increased as an acute effect of LPS correlating with increased sensitivity to mechanical stimulation. However chronic exposure to LPS can develop a tolerance to mechanical hyperalgesia despite ongoing signs of CNS glial activation.