Surfactant and inhaled nitric oxide in rats alleviate acute lung injury induced by intestinal ischemia and reperfusion

ATF3 Protects against LPS-Induced Inflammation in Mice via Inhibiting HMGB1 Expression

Lipopolysaccharide (LPS) triggers innate immunity mainly via TLR4 signaling. ATF3 is a negative regulator of TLR4 signaling. HMGB1 plays a critical role in the final step of sepsis. However, the mechanisms of ATF3 and the role of HMGB1 in regulating innate immunity-induced sepsis are incompletely understood. In this study, we found that serum HMGB1 levels were 10-fold higher in patients with sepsis than normal controls. We further demonstrated that ATF3 gene knockout in mice subjected to LPS-induced endotoxemia correlates with an increase in the mortality rate and the elevated expression of IL-6, TNF-α, NO, MCP-1, and HMGB1 in the lung tissues or serum. The biochemical effects of ATF3 were observed in in vitro macrophages and blocked by ATF3 siRNA treatment. We have also shown that adeno-associated virus-mediated ATF3 gene transfer protected ATF3 knockout mice from LPS-induced mortality. In addition, ATF3 knockdown increased LPS-induced release of HMGB1. In conclusion, upregulation of ATF3 contributes to the reduced release of inflammatory molecules, especially HMGB1, which induced lung injury and increased the survival rate of mice after LPS challenge. Therefore, suppressing LPS-induced inflammation with ATF3 induction or ATF3 mimetics may be an important strategy for sepsis therapy.

Pulmonary mechanical responses to intestinal ischaemia-reperfusion and endotoxin preconditioning

During intestinal ischaemia-reperfusion, endotoxin can be translocated. Pretreatment with sublethal doses of endotoxin develops tolerance to ischaemia-reperfusion in different organs; however, the tolerance to intestinal ischaemia-reperfusion in the lung has rarely been investigated. Our aim was to study the role of endotoxin pretreatment in the mechanical responses and inflammatory activation induced by intestinal ischaemia-reperfusion in the lung. Wistar rats were preconditioned with a sublethal dose of endotoxin on day -3 or -1. On day 0, anesthetized, paralyzed and mechanically ventilated rats were subjected to a 60-min occlusion of the superior mesenteric artery and a subsequent 240-min reperfusion. The low-frequency forced oscillation technique was employed to characterize the separate mechanical responses of the airways and respiratory tissues. Intestinal ischaemia-reperfusion caused a significant decrease in airway resistance and increases in tissue resistance and elastance, nitric oxide synthase and myeloperoxidase activities. Pretreatment with endotoxin modified both the pulmonary mechanical responses and the inflammatory markers in the lung during intestinal ischaemia-reperfusion. We conclude that endotoxin or the endotoxin-induced processes (and humoral mediators) have significant roles in the pathomechanism of the remote pulmonary effect of intestinal ischaemia-reperfusion.

Oroxylin-A rescues LPS-induced acute lung injury via regulation of NF-κB signaling pathway in rodents

BACKGROUND AND PURPOSE

Successful drug treatment for sepsis-related acute lung injury (ALI) remains a major clinical problem. This study was designed to assess the beneficial effects of post-treatment of oroxylin A (OroA), a flavonoid, in ameliorating lipopolysaccharides (LPS)-induced lung inflammation and fatality.

EXPERIMENTAL APPROACH

Rats were injected with LPS (10 mg/kg, iv) to induce ALI, and OroA was given (15 mg/kg, iv) 1 hr or 6 hrs after LPS challenge. Twenty four hrs after LPS challenge, biochemical changes in the blood and lung tissues, and morphological/histological alterations in the lung associated with inflammation and injury were examined. Therapeutic effect of OroA was assessed by measuring the survival rate in endotoxemic mice.

KEY RESULTS

LPS (10 mg/kg, iv) significantly altered WBC counts, elevated plasma tumor necrosis factor (TNF)-α and nitric oxide (NO), increased pulmonary edema, thickened alveolar septa, and decreased survival rate. These changes were ameliorated by OroA (15 mg/kg, iv) administered 1 hr or 6 hrs after LPS challenge. This post-treatment also significantly attenuated LPS-induced activation of nuclear factor-κB (NF-κB) and the release of high mobility group box 1 (HMGB1) in lung tissues. Furthermore, post-treatment with OroA (60 mg/kg, ip) administered 1 hr or 6 hrs after LPS challenge in mice significantly increased survival rate.

CONCLUSION AND IMPLICATION

OroA administered after induction of ALI by LPS significantly prevent and revere lung tissues injuries with increased survival rate. Positive post-treatment effects of OroA suggest that OroA is a potentially useful candidate for managing lung inflammation in LPS-induced endotoxemia and septic shock.

The effect of curcumin on lung injuries in a rat model induced by aspirating gastrointestinal decontamination agents

BACKGROUND

Aspiration is one of the most feared complications of gastrointestinal decontamination procedures with nonabsorbed polyethylene glycol (PEG) solution and activated charcoal (AC). We aimed to investigate the protective effects of curcumin (CUR) on lung injury in rats induced by aspiration of these agents.

METHODS

Experimental rats were divided randomly into 6 groups (n = 7): a saline-aspirated control (group I), sterile saline aspirated with CUR treatment (group II), PEG aspirated (group III), PEG aspirated with CUR treatment (group IV), AC aspirated (group V), and AC aspirated with CUR treatment (group VI). After aspiration, treatment groups II, IV, and VI were given 150 mg/kg CUR intraperitoneally once a day for 7 days. After 7 days, the rats were humanely killed, and both the lungs and serum specimens from all groups were evaluated histopathologically, immunohistochemically, and biochemically.

RESULTS

Aspiration of gastrointestinal decontamination agents produced histopathologic changes, elevated levels of malondialdehyde and surfactant protein D, reduced levels of antioxidant enzymes, and increased expression of inflammatory cytokines interleukin-1β and tumor necrosis factor α. Curcumin treatments effectively attenuated the rats' pulmonary inflammation responses (as shown by reduced alveolar damage), decreased serum malondialdehyde and surfactant protein D levels, and inhibited the expressions of tumor necrosis factor α and interleukin-1β.

CONCLUSIONS

Because of its anti-inflammatory effects, CUR treatment may have preventive effects on lung injuries induced by aspirating gastrointestinal decontamination agents.

Surfactant therapy for acute lung injury and acute respiratory distress syndrome

This article examines exogenous lung surfactant replacement therapy and its usefulness in mitigating clinical acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS). Surfactant therapy is beneficial in term infants with pneumonia and meconium aspiration lung injury, and in children up to age 21 years with direct pulmonary forms of ALI/ARDS. However, extension of exogenous surfactant therapy to adults with respiratory failure and clinical ALI/ARDS remains a challenge. This article reviews clinical studies of surfactant therapy in pediatric and adult patients with ALI/ARDS, focusing on its potential advantages in patients with direct pulmonary forms of these syndromes.

High tidal volume ventilation induces lung injury after hepatic ischemia-reperfusion

Ischemia-reperfusion not only damages the affected organ but also leads to remote organ injuries. Hepatic inflow interruption usually occurs during hepatic surgery. To investigate the influence of liver ischemia-reperfusion on lung injury and to determine the contribution of tidal volume settings on liver ischemia-reperfusion-induced lung injury, we studied anesthetized and mechanically ventilated rats in which the hepatic inflow was transiently interrupted twice for 15 min. Two tidal volumes, 6 ml/kg as a low tidal volume (IR-LT) and 24 ml/kg as a high tidal volume (IR-HT), were assessed after liver ischemia-reperfusion, as well as after a sham operation, 6 ml/kg (NC-LT) and 24 ml/kg (NC-HT). Both the IR-HT and IR-LT groups had a gradual decline in the systemic blood pressure and a significant increase in plasma TNF-α concentrations. Of the four groups, only the IR-HT group developed lung injury, as assessed by an increase in the lung wet-to-dry weight ratio, the presence of significant histopathological changes, such as perivascular edema and intravascular leukocyte aggregation, and an increase in the bronchoalveolar lavage fluid TNF-α concentration. Furthermore, only in the IR-HT group was airway pressure increased significantly during the 6-h reperfusion period. These findings suggest that liver ischemia-reperfusion caused systemic inflammation and that lung injury is triggered when high tidal volume ventilation follows liver ischemia-reperfusion.

Inhaled nitric oxide attenuates hyperoxic and inflammatory injury without alteration of phosphatidylcholine synthesis in rat lungs

We hypothesized that inhaled nitric oxide (iNO), a selective vasodilator for pulmonary hypertension, may exacerbate hyperoxia-related lung inflammatory injury by alteration of phosphatidylcholine (PC) synthesis in mature lungs. Healthy adult rats were allocated to 4 groups and exposed to: 95% oxygen, or 20ppm iNO, or both (ONO), or room air, all for 48h. (3)H-choline chloride was injected i.v. at 10min, 8, 16, and 24h prior to the end of 48h exposure and the animal lungs were processed. In oxygen group, oxidative damage and inflammation were significantly induced compared to the room air group. In ONO group there were significantly elevated glutathione, attenuated malondialdehyde, myeloperoxidase, and wet-to-dry lung weight ratio in lung parenchyma, decreased white cell counts and vascular-to-alveolar leakage of albumin in bronchoalveolar lavage fluid. In both oxygen and ONO groups both total phospholipids and surfactant protein-A were significantly increased compared with the room air group. Newly synthesized (3)H-PC was low in the lungs of NO group but high over time in both oxygen and ONO groups. Morphologically, lung injury was mild in ONO, but moderate in both oxygen and NO groups. We conclude that iNO alleviated oxidative damage and inflammation, and reduced alveolar leakage in hyperoxic injury of the mature lungs. Hyperoxia enhanced production of surfactant, whereas iNO did not attenuate this effect.

Extrapulmonary effects of inhaled nitric oxide: role of reversible S-nitrosylation of erythrocytic hemoglobin

Early applications of inhaled nitric oxide (iNO), typically in the treatment of diseases marked by acute pulmonary hypertension, were met by great enthusiasm regarding the purported specificity of iNO: vasodilation by iNO was specific to the lung (without a change in systemic vascular resistance), and within the lung, NO activity was said to be confined spatially and temporally by Hb within the vascular lumen. Underlying these claims were classical views of NO as a short-lived paracrine hormone that acts largely through the heme groups of soluble guanylate cyclase, and whose potential activity is terminated on encountering the hemes of red blood cell (RBC) Hb. These classical views are yielding to a broader paradigm, in which NO-related signaling is achieved through redox-related NO adducts that endow NO synthase products with the ability to act at a distance in space and time from NO synthase itself. Evidence supporting the biological importance of such stable NO adducts is probably strongest for S-nitrosothiols (SNOs), in which NO binds to critical cysteine residues in proteins or peptides. The circulating RBC is a major SNO reservoir, and RBC Hb releases SNO-related bioactivity peripherally on O2 desaturation. These new paradigms describing NO transport also provide a plausible mechanistic understanding of the increasingly recognized peripheral effects of inhaled NO. An explanation for the peripheral actions of inhaled NO is discussed here, and the rationale and results of attempts to exploit the "NO delivery" function of the RBC are reviewed.

Protective effects of S-nitrosoalbumin on lung injury induced by hypoxia-reoxygenation in mouse model of sickle cell disease

Nitric oxide (NO) is a potential new therapeutic agent for sickle cell disease (SCD). We investigated the effects of NO donor on hypoxia-induced acute lung injury that occurs when transgenic sickle cell SAD mice are exposed to chronic hypoxia, a model for lung vasoocclusive sickle cell events. In wild-type and SAD mice, intraperitoneal injection of S-nitrosoalbumin (NO-Alb) produced no significant hematologic changes under room air conditions, whereas it induced mild temporary hypotension and inhibition of platelet aggregation. NO-Alb administration (300 mg/kg ip twice a day, equivalent to 7.5 microM NO) in wild-type and SAD mice exposed to 46 h of hypoxia (8% oxygen) followed by 2 h of normoxia resulted in 1) reduction of the hypoxia-induced increase in blood neutrophil count, 2) prevention of hypoxia-induced increased IL-6 and IL-1beta levels in bronchoalveolar lavage, 3) reduction of the lung injury induced by hypoxia-reoxygenation, 4) prevention of thrombus formation, and 5) prevention of hypoxia-induced increase of lung matrix metalloproteinase-9 gene expression. These effects provide new insights into the possible use of NO-Alb in the treatment of acute lung injury in SCD.