Effects of heat pretreatment on histopathology, cytokine production, and surfactant in endotoxin-induced acute lung injury

Anti-inflammatory Role of Mesenchymal Stem Cells in an Acute Lung Injury Mouse Model

Background

Mesenchymal stem cells (MSCs) attenuate injury in various lung injury models through paracrine effects. We hypothesized that intratracheal transplantation of allogenic MSCs could attenuate lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice, mediated by anti-inflammatory responses.

Methods

Six-week-old male mice were randomized to either the control or the ALI group. ALI was induced by intratracheal LPS instillation. Four hours after LPS instillation, MSCs or phosphate-buffered saline was randomly intratracheally administered. Neutrophil count and protein concentration in bronchoalveolar lavage fluid (BALF); lung histology; levels of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and macrophage inflammatory protein-2; and the expression of proliferation cell nuclear antigen (PCNA), caspase-3, and caspase-9 were evaluated at 48 hours after injury.

Results

Treatment with MSCs attenuated lung injury in ALI mice by decreasing protein level and neutrophil recruitment into the BALF and improving the histologic change. MSCs also decreased the protein levels of proinflammatory cytokines including IL-1β, IL-6, and TNF-α, but had little effect on the protein expression of PCNA, caspase-3, and caspase-9.

Conclusions

Intratracheal injection of bone marrow-derived allogenic MSCs attenuates LPS-induced ALI via immunomodulatory effects.

Treadmill exercise preconditioning attenuates lung damage caused by systemic endotoxemia in type 1 diabetic rats

Endotoxemia induces a series of inflammatory responses that may result in lung injury. However, heat shock protein72 (HSP72) has the potential to protect the lungs from damage. The objective of this study was to determine whether prior exercise conditioning could increase the expression of HSP72 in the lungs and attenuate lung damage in diabetic rats receiving lipopolysaccharide (LPS). Streptozotocin was used to induce diabetes in adult male Wistar rats. Rats were randomly assigned to sedentary or exercise groups. Rats in the exercise condition ran on a treadmill 5 days/week, 30-60 min/day, with an intensity of 1.0 mile/hour over a 3-week period. Rats received an intravenous infusion of LPS after 24 hrs from the last training session. Elevated lavage tumor necrosis factor-alpha (TNF- α ) level in response to LPS was more marked in diabetic rats. HSP72 expression in lungs was significantly increased after exercise conditioning, but less pronounced in diabetic rats. After administration of LPS, exercised rats displayed higher survival rate as well as decreased lavage TNF- α level and lung edema in comparison to sedentary rats. Our findings suggest that exercise conditioning could attenuate the occurrence of inflammatory responses and lung damage, thereby reducing mortality rate in diabetic rats during endotoxemia.

Effects of propofol with hyperthermia in a rat model of endotoxemic shock

BACKGROUND

We aimed to investigate the effects of active mild hyperthermia and the effects of active mild hyperthermia with propofol on mortality and inflammatory responses during endotoxin-induced shock in rats.

METHODS

Intravenous Escherichia coli endotoxin (15 mg/kg over 2 min) was injected in 48 rats. The animals were randomly allocated to one of the following four groups (n = 12 per group): normothermia group (group N), rectal temperature maintained between 36 °C and 38 °C; hyperthermia group (group H), rectal temperature was moderate and maintained between 39 °C and 40 °C; propofol with normothermia group (group PN), propofol (10 mg/kg/h) was administered, and temperature was between 36 °C and 38 °C; Propofol with hyperthermia group (group PH), propofol (10 mg/kg/h) administrated, and temperatures were maintained between 39 °C and 40 °C. The primary outcome was mortality 8 h after endotoxin injection. Secondary outcomes included changes in haemodynamics, arterial blood gases and plasma cytokine concentrations for the 8-h observation period.

RESULTS

Mortality rates 8 h after endotoxin injection were 92%, 100%, 68% and 50% for N, H, PN and PH groups, respectively. There was no difference in hypotension, acidosis, and increase in plasma cytokine concentrations between N and H groups, but these parameters were attenuated in group PH.

CONCLUSION

The mortality rates in the present study were extremely high; further hypotension and elevations in plasma pro-inflammatory and anti-inflammatory cytokine concentrations after endotoxin injection were not attenuated by mild hyperthermia between 39 °C and 40 °C, but they were attenuated by propofol with mild hyperthermia.

The effect of post-treatment N-acetylcysteine in LPS-induced acute lung injury of rats

Background

Oxidation plays an important role in acute lung injury. This study was conducted in order to elucidate the effect of repetitive post-treatment of N-acetylcysteine (NAC) in lipopolysaccaride (LPS)-induced acute lung injury (ALI) of rats.

Methods

Six-week-old male Sprague-Dawley rats were divided into 4 groups. LPS (Escherichia coli 5 mg/kg) was administered intravenously via the tail vein. NAC (20 mg/kg) was injected intraperitoneally 3, 6, and 12 hours after LPS injection. Broncho-alveolar lavage fluid (BALF) and lung tissues were obtained to evaluate the ALI at 24 hours after LPS injection. The concentration of tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β) were measured in BALF. Nuclear factor κB (NF-κB), lipid peroxidation (LPO), and myeloperoxidase (MPO) were measured using lung tissues. Micro-computed tomography (micro-CT) images were examined in each group at 72 hours apart from the main experiments in order to observe the delayed effects of NAC.

Results

TNF-α and IL-1β concentration in BALF were not different between LPS and NAC treatment groups. The concentration of LPO in NAC treatment group was significantly lower than that of LPS group (5.5±2.8 nmol/mL vs. 16.5±1.6 nmol/mL) (p=0.001). The activity of MPO in NAC treatment group was significantly lower than that of LPS group (6.4±1.8 unit/g vs. 11.2±6.3 unit/g, tissue) (p<0.048). The concentration of NF-κB in NAC treatment group was significantly lower than that of LPS group (0.3±0.1 ng/µL vs. 0.4±0.2 ng/µL) (p=0.0001). Micro-CT showed less extent of lung injury in NAC treatment than LPS group.

Conclusion

After induction of ALI with lipopolysaccharide, the therapeutic administration of NAC partially attenuated the extent of ALI through the inhibition of NF-κB activation.

Exercise pretraining attenuates endotoxin-induced hemodynamic alteration in type I diabetic rats

Higher expression of heat shock protein 72 (HSP72) reduces the mortality rate and organ damage in septic shock and prevents cardiac mitochondrial dysfunction due to lipopolysaccharide (LPS). Our hypothesis is that exercise preconditioning may increase the expression of HSP72 in heart and the nucleus tractus solitarii (NTS) of the brain to alleviate the cardiovascular dysfunction in type I diabetic rats receiving endotoxin. Wistar rats were randomly assigned to the following groups: sedentary normal, sedentary type I diabetic rats, and type I diabetic rats with exercise training. The trained rats ran on a treadmill 5 d.week-1, 30-60 min.d-1, at an intensity of 1.0 mile.h-1 (1 mile = 1.6 km) over a 3 week period. Twenty-four hours after the last training session, we compared the temporal profiles of mean arterial pressure, heart rate, cardiac output, stroke volume, and serum tumor necrosis factor alpha level in rats receiving an injection of LPS. In addition, HSP72 expression in heart and NTS from each group was determined. We found that HSP72 expression in the heart and NTS was significantly increased in diabetic rats with exercise training. After administration of LPS, the survival time was significantly longer in diabetic rats with exercise training. Additionaly, serum tumor necrosis factor alpha levels decreased as compared with those rats not receiving exercise training. Exercise training also diminished cardiovascular dysfunction in diabetic rats during endotoxemia. These data suggest that exercise may increase the expression of HSP72 in the heart and NTS to protect against the high mortality rate and attenuate cardiovascular dysfunction in diabetic rats during endotoxemia.

Heat stress protects against lung injury in the neutropenic, endotoxemic rat

The objective of this study is to determine if heat stress prior to endotoxemia diminishes cardiopulmonary dysfunction by attenuating the cytokine inflammatory response. Rats were assigned to either: 1) neutropenia; 2) heat; 3) neutropenia, LPS; or 4) heat, neutropenia, LPS. Heart rate, blood gases, and blood, lung lavage, and lung mRNA for tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and macrophage inflammatory protein (MIP)-2 were measured. Heat given before LPS resulted in a similar A-a O(2) gradient as the heat-alone and neutropenic groups (8 +/- 8 versus 8 +/- 7 versus 4 +/- 3 mm Hg) and a lower A-a O(2) gradient when compared to the neutropenic, LPS rats (8 +/- 8 versus 22 +/- 8 mm Hg, p < 0.003). Blood, lung lavage, and lung mRNA for TNF-alpha, IL-1beta, and MIP-2 were similar in the LPS rats regardless of heat. Heart rate was similar in both LPS groups but higher than non-LPS groups. Heat pretreatment attenuates lung injury in the neutropenic, endotoxemic rat but not by decreasing TNF-alpha, IL-1beta, or MIP-2 in the lung. Heat prior to LPS did not prevent cardiac dysfunction in neutropenic rats.

Heat stress attenuates air bubble-induced acute lung injury: a novel mechanism of diving acclimatization

Diving acclimatization refers to a reduced susceptibility to acute decompression sickness (DCS) in individuals undergoing repeated compression-decompression cycles. We postulated that mechanisms responsible for the acclimatization are similar to that of a stress preconditioning. In this study, we investigated the protective effect of prior heat shock treatment on air embolism-induced lung injury and on the incidence of DCS in rats. We exposed rats (n = 31) to a pressure cycle that induced signs of severe DCS in 48% of the rats, greater wet-to-dry ratio (W/D) of lung weight compared with the control group (5.48 +/- 0.69 vs. 4.70 +/- 0.17), and higher protein concentration in bronchoalveolar lavage (BAL) fluid (362 +/- 184 vs. 209 +/- 78 mg/l) compared with the control group. Rats with DCS expressed more heat shock protein 70 (HSP70) in the lungs than those without signs of disease. Prior heat shock (n = 12) increased the expression of HSP70 in the lung and attenuated the elevation of W/D of lung weight (5.03 +/- 0.17) after the identical decompression protocol. Prior heat shock reduced the incidence of severe DCS by 23%, but this failed to reach statistical significant (chi(2) = 1.94, P = 0.163). Venous air infusion (1.0 ml/40 min) caused profound hypoxemia (54.5 +/- 3.8 vs. 83.8 +/- 3.2 Torr at baseline; n = 6), greater W/D of lung weight (5.98 +/- 0.45), and high protein concentration in BAL fluid (595 +/- 129 mg/l). Prior heat shock (n = 6) did not alter the level of hypoxemia caused by air embolism, but it accelerated the recovery to normoxemia after air infusion was stopped. Prior heat shock also attenuated the elevation of W/D of lung weight (5.19 +/- 0.40) and the increase in BAL protein (371 +/- 69 mg/l) in air embolism group. Our results showed that the occurrence of DCS after rapid decompression is associated with increased expression of a stress protein (HSP70) and that prior heat shock exposure attenuates the air bubble-induced lung injury. These results suggest that bubble formation in tissues activates a stress response and that stress preconditioning attenuates lung injury on subsequent stress, which may be the mechanism responsible for diving acclimatization.