Moderate Exercise Modulates Inflammatory Responses and Improves Survival in a Murine Model of Acute Pneumonia.

OBJECTIVES: An association between physical inactivity and worse outcome during infectious disease has been reported. The effect of moderate exercise preconditioning on the immune response during an acute pneumonia in a murine model was evaluated. SETTING: Laboratory experiments. SUBJECTS: C57BL6/j male mice. INTERVENTIONS: Six-week-old C57BL/6J mice were divided in two groups: an exercise group and a control group. In the exercise group, a moderate, progressive, and standardized physical exercise was applied for 8 weeks. It consisted in a daily treadmill training lasting 60 minutes and with an intensity of 65% of the maximal theoretical oxygen uptake. Usual housing recommendation were applied in the control group during the same period. After 8 weeks, pneumonia was induced in both groups by intratracheal instillation of a fixed concentration of a Klebsiella pneumoniae (5 × 103 colony-forming unit) solution. MEASUREMENTS AND MAIN RESULTS: Mice preconditioned by physical exercise had a less sever onset of pneumonia as shown by a significant decrease of the Mouse Clinical Assessment Severity Score and had a significantly lower mortality compared with the control group (27% vs. 83%; p = 0.019). In the exercise group, we observed a significantly earlier but transient recruitment of inflammatory immune cells with a significant increase of neutrophils, CD4+ cells and interstitial macrophages counts compared with control group. Lung tumor necrosis factor-α, interleukin (IL)-1ß, IL-6, and IL-10 were significantly decreased at 48 hours after pneumonia induction in the exercise group compared with the control group. CONCLUSIONS: In our model, preconditioning by moderate physical exercise improves outcome by reducing the severity of acute pneumonia with an increased but transient activation of the innate immune response.

Can selenium-enriched spirulina supplementation ameliorate sepsis outcomes in selenium-deficient animals?

In intensive care units, sepsis is the first cause of death. In this pathology, inflammation and oxidative status play a crucial role in patient outcomes. Interestingly, 92% of septic patients exhibit low selenium plasma concentrations (a component of antioxidant enzymes). Moreover, Spirulina platensis, a blue-green algae, demonstrated anti-inflammatory effects. In this context, the main purpose of our study was to analyze the effect of a selenium-enriched spirulina after a selenium deficiency on sepsis outcome in rats. Sixty-four rats were fed 12 weeks with a selenium-deficient food. After 8 weeks, rats were supplemented (via drinking water) for 4 weeks with sodium selenite (Se), spirulina (Spi), or selenium-enriched spirulina (SeSp). Sepsis was then induced by cecal ligature and puncture, and survival duration was observed. The plasma selenium concentration was measured by ICPMS. Expression of GPx1 and GPx3 mRNA was measured by RT-PCR. Blood parameters (lactates and HCO3- concentrations, pH, PO2 , and PCO2 ) were analyzed at 0, 1, and 2 h as well as inflammatory cytokines (IL-6, TNF-α, IL-10). Sodium selenite and SeSP supplementations restored plasma selenium concentration prior to sepsis. The survival duration of SeSP septic rats was significantly lower than that of selenium-supplemented ones. Gpx1 mRNA was increased after a selenium-enriched spirulina supplementation while Gpx3 mRNA levels remained unchanged. Furthermore, sodium selenite prevented sepsis-induced acidosis. Our results show that on a basis of a Se deficiency, selenium-enriched spirulina supplementations significantly worsen sepsis outcome when compared to Se supplementation. Furthermore, Se supplementation but not selenium-enriched spirulina supplementation decreased inflammation and restored acid-base equilibrium after a sepsis induction.

TGF-ß Pathway Inhibition Protects the Diaphragm From Sepsis-Induced Wasting and Weakness in Rat.

Sepsis is a frequent complication in patients in intensive care units (ICU). Diaphragm weakness, one of the most common symptoms observed, can lead to weaning problems during mechanical ventilation. Over the last couple of years, members of the transforming growth factor (TGF) ß family, such as myostatin, activin A, and TGF-ß1, have been reported to strongly trigger the activation of protein breakdown involved in muscle wasting. The aim of this study was to investigate the effect of TGF-ß inhibitor LY364947 on the diaphragm during chronic sepsis.Rats were separated into four groups exposed to different experimental conditions: Control group, Septic group, Septic group with inhibitor from day 0 (LY D0), and Septic group with inhibitor from day 1 (LY D1). Sepsis was induced in rats by cecal ligation and puncture, and carried out for 7 days.Chronic sepsis was responsible for a decrease in body weight, food intake and diaphragm's mass. The inhibitor was able to abolish diaphragm wasting only in the LY D1 group. Similarly, LY364947 had a beneficial effect on the diaphragm contraction only for the LY D1 group. SMAD3 was over-expressed and phosphorylated within rats in the Septic group; however, this effect was reversed by LY364947. Calpain-1 and -2 as well as MAFbx were over-expressed within individuals in the Septic group. Yet, calpain-1 and MAFbx expressions were decreased by LY364947.With this work, we demonstrate for the first time that the inhibition of TGF-ß pathway during chronic sepsis protects the diaphragm from wasting and weakness as early as one day post infection. This could lead to more efficient treatment and care for septic patients in ICU.

Relationship between baseline and post-bronchodilator interrupter resistance and specific airway resistance in preschool children.

BACKGROUND: The assessment of airway function in preschool children can be done using simple measurement techniques such as interrupter resistance (Rint) or specific airway resistance (sRaw). OBJECTIVE: The aim of the study was to assess the relationship and the agreement between Rint and sRaw baseline measurements expressed in z-score and bronchodilator response (BDR) in accordance with the latest reference equations and recommended procedures. METHODS: One hundred thirty children aged 3 to 6 years old, referred to our pediatric pulmonary function test unit for assessment of airway function were consecutively included. Children performed baseline and post-bronchodilator measurements of Rint and sRaw. RESULTS: One hundred twenty baseline measurements were obtained (98.7%) with both techniques. At baseline there was a strong correlation between Rint and sRaw z-score (r = 0.5, P < .01) despite the poor agreement (Cohen Kappa coefficient 0.09 [-0.08; 0.26]). The agreement for BDR was fair, with Cohen Kappa coefficient (95% IC) = 0.33 (0.13; 0.54). Children with poorly or partially controlled asthma had both higher baseline Rint and sRaw (P < .01), and higher post-bronchodilator mean change (P < .01), than children with well-controlled asthma. CONCLUSION: The poor agreement between the Rint and sRaw reference measurements demonstrates the lack of reliability of sole Rint or sRaw technique for airway obstruction diagnosis and the need to perform each technique concomitantly with BDR test. Other longitudinal and larger sample studies are needed to confirm the threshold value for a positive BDR, especially for sRaw.

The diaphragm is better protected from oxidative stress than hindlimb skeletal muscle during CLP-induced sepsis.

OBJECTIVES: The aim of this study was to determine whether non-lethal sepsis induced by cecal ligation and puncture (CLP) modulates oxidative damage and enzymatic antioxidant defenses in diaphragm and hindlimb skeletal muscles (soleus and Extensor Digitorus Longus (EDL)). METHODS: Female Wistar rats were divided into four experimental groups: (1) control animals, (2) animals sacrificed 2 hours or (3) 7 days after CLP, and (4) sham-operated animals. At the end of the experimental procedure, EDL, soleus, and diaphragm muscles were harvested and 4-hydroxynonenal (HNE)-protein adducts and protein carbonyl contents were examined in relation to superoxide dismutase and catalase expression and activities. RESULTS: We observed that both non-respiratory oxidative (i.e. soleus) and glycolytic skeletal muscles (i.e. EDL) are more susceptible to sepsis-induced oxidative stress than diaphragm, as attested by an increase in 4-HNE protein adducts and carbonylated proteins after 2 hours of CLP only in soleus and EDL. DISCUSSION: These differences could be explained by higher basal enzymatic antioxidant activities in diaphragm compared to hindlimb skeletal muscles. Together, these results demonstrate that diaphragm is better protected from oxidative stress than hindlimb skeletal muscles during CLP-induced sepsis.

Single Muscle Immobilization Decreases Single-Fibre Myosin Heavy Chain Polymorphism: Possible Involvement of p38 and JNK MAP Kinases.

PURPOSE: Muscle contractile phenotype is affected during immobilization. Myosin heavy chain (MHC) isoforms are the major determinant of the muscle contractile phenotype. We therefore sought to evaluate the effects of muscle immobilization on both the MHC composition at single-fibre level and the mitogen-activated protein kinases (MAPK), a family of intracellular signaling pathways involved in the stress-induced muscle plasticity. METHODS: The distal tendon of female Wistar rat Peroneus Longus (PL) was cut and fixed to the adjacent bone at neutral muscle length. Four weeks after the surgery, immobilized and contralateral PL were dissociated and the isolated fibres were sampled to determine MHC composition. Protein kinase 38 (p38), extracellular signal-regulated kinases (ERK1/2), and c-Jun- NH2-terminal kinase (JNK) phosphorylations were measured in 6- and 15-day immobilized and contralateral PL. RESULTS: MHC distribution in immobilized PL was as follows: I = 0%, IIa = 11.8 ± 2.8%, IIx = 53.0 ± 6.1%, IIb = 35.3 ± 7.3% and I = 6.1 ± 3.9%, IIa = 22.1 ± 3.4%, IIx = 46.6 ± 4.5%, IIb = 25.2 ± 6.6% in contralateral muscle. The MHC composition in immobilized muscle is consistent with a faster contractile phenotype according to the Hill's model of the force-velocity relationship. Immobilized and contralateral muscles displayed a polymorphism index of 31.1% (95% CI 26.1-36.0) and 39.3% (95% CI 37.0-41.5), respectively. Significant increases in p38 and JNK phosphorylation were observed following 6 and 15 days of immobilization. CONCLUSIONS: Single muscle immobilization at neutral length induces a shift of MHC composition toward a faster contractile phenotype and decreases the polymorphic profile of single fibres. Activation of p38 and JNK could be a potential mechanism involved in these contractile phenotype modifications during muscle immobilization.

Effect of Induced Mild Hypothermia on Acid-Base Balance During Experimental Acute Sepsis in Rats.

The aim of this study was to determine the effect of induced mild hypothermia (34°C) on acid-base balance in septic rats. Twenty-eight male Sprague-Dawley rats median weight 306 g, range 251-333 g were used. After anesthesia and when the target temperature was reached (normothermia: 38°C or induced mild hypothermia: 34°C), sepsis was induced by cecal ligation and perforation. Measurements of cardiopulmonary parameters and blood samples were performed at T0h (occurring immediately after chirurgical procedures), T2h, T4h (at each temperature), and T6h (at 34°C only). Blood oxygen saturation, heart and respiratory rates, arterial blood pH, carbon dioxide partial pressure, sodium, potassium, chloride and calcium concentrations, hematocrit, blood lactate, tumor necrosis factor-α and interleukin-6 concentrations were measured on anesthetized rats. Other parameters such as bicarbonate concentration, hemoglobin concentration, base excess, and anion gap were estimated from measured parameters. Main results showed that an increase in both cytokines concentrations was observed in septic rats compared with sham rats. This increase was less marked at 34°C compared with 38°C. Moreover, sepsis induction led to a marked metabolic acidosis and hypothermia delayed this acidosis. Induced mild hypothermia delays the evolution of cytokines and metabolic acidosis during experimental sepsis.

Does induction time of mild hypothermia influence the survival duration of septic rats?

The relationship between hypothermia induction time and survival duration following sepsis was studied on 31 male Sprague-Dawley rats (median weight 311 g, range 260-356 g). After anesthesia and when the target temperature was reached (normothermia: 38°C or mild induced hypothermia: 34°C), sepsis was induced by cecal ligation and perforation. Five experimental groups were used. In groups 1 and 2, temperature of septic rats was maintained throughout the experiment at 38°C (seven rats) or 34°C (six rats), respectively. In groups 3, 4, and 5, septic rats (six per group) were maintained at 38°C for 1, 2, and 3 hours, respectively, and then placed in mild hypothermia (34°C). For each group, the survival duration was determined and blood samples were performed at the tail to measure tumor necrosis factor-α (TNF-α) plasma concentration. Whatever the experimental group, a decrease in temperature from 38°C to 34°C significantly increased the survival duration of septic rats compared with those maintained at 38°C throughout the experiment. The delay between the onset of sepsis and induction of hypothermia was also crucial. Thus, hypothermia induced after 1 hour of sepsis at 38°C significantly increased the survival duration of septic rats (12 hours 37 minutes±1 hour 4 minutes; group 3) compared with hypothermia induced after 3 hours of sepsis (8 hours 56 minutes±1 h 20 minutes; group 5). Moreover, except for group 5, survival duration improvement of septic rats observed in hypothermia was related to a lower increase of TNF-α plasma concentration compared with septic rats in normothermia. During sepsis, mild induced hypothermia significantly increased the survival duration of septic rats. The earlier hypothermia was applied, the longer the septic rats survived. According to these results, hypothermia may therefore provide the necessary time to apply a proper treatment.

Effect of induced mild hypothermia on two pro-inflammatory cytokines and oxidative parameters during experimental acute sepsis.

This study aimed to determine the effect of induced mild hypothermia (34°C) on the production of two cytokines (interleukin (IL-6) and tumor necrosis factor (TNF)alpha) and reactive nitrogen and oxygen species in plasma and the heart of acutely septic rats. After anesthesia and in conditions of normothermia (38°C) or mild hypothermia (34°C), acute sepsis was induced by cecal ligation and perforation. For each temperature three groups were formed: (1) baseline (blood sample collected at T0 hour), (2) sham (blood sample at T4 hours) and (3) septic (blood sample at T4 hours). At either temperature sepsis induced a significant increase in plasma IL-6, TNF-alpha and HO• concentration, compared with the sham groups (P≤0.016). Compared with the normothermic septic group, septic rats exposed to mild hypothermia showed a mild decrease in TNF-alpha concentration (104±50 pg/ml vs. 215±114 pg/ml; P>0.05) and a significant decrease in IL-6 (1131±402 pg/ml vs. 2494±691 pg/ml, P=0.038). At either temperature sepsis induced no enhancement within the heart of lipoperoxidation (malondialdehyde content) or antioxidant activities (superoxide dismutase and catalase). In conclusion, during acute sepsis, induced mild hypothermia appears to reduce some pro-inflammatory and oxidative responses. This may, in part, explain the beneficial effect of hypothermia on survival duration of septic rats.

Oxygen blood transport during experimental sepsis: effect of hypothermia*.

OBJECTIVES: The aim of this study was to highlight the link between induced hypothermia and increased survival duration as observed in the septic model developed by the laboratory. To reach this objective, survival duration and blood oxygen transport capacity were measured at two temperatures-38 °C (induced normothermia) and 34 °C (induced hypothermia)-in septic rats. DESIGN: A prospective, randomized, experimental animal study. SETTING: University laboratory. SUBJECTS: Forty-four male Sprague-Dawley rats (median weight, 232 g; range, 200-303 g). INTERVENTIONS: After anesthesia and obtention of the temperature goal, sepsis was induced by cecal ligation and perforation. MEASUREMENTS AND MAIN RESULTS: Sepsis induction led to death 5 hrs 11 mins ± 0 hr 36 mins after cecal ligation and perforation at 38 °C. At this temperature, significant changes in blood oxygen transport capacity were observed in septic rats; Hill number decreased from 2.36 ± 0.10 (baseline group) to 1.99 ± 0.17 (septic group) (p = .008) and oxygen-hemoglobin affinity decreased and P50 increased from 41.40 ± 2.4 Torr (baseline group) to 51.17 ± 14.07 Torr (septic group). Furthermore, in normothermia, a significant increase of creatinine and albumin plasmatic concentrations was observed 4 hrs after sepsis induction. Survival duration was significantly higher in induced hypothermia (7 hrs 22 mins ± 0 hr 12 mins at 34 °C) compared with induced normothermia. At 34 °C, no significant change in blood oxygen transport capacity was observed. In the same way, exposure to 34 °C induced no change in measured plasmatic parameters except an increase in albumin concentration in septic rats compared with the baseline group. CONCLUSIONS: Sepsis led to a decrease of both oxygen hemoglobin cooperativity and affinity at 38 °C. By contrast, no change in these parameters was observed when sepsis was induced during hypothermia. Taken together, these results could be interpreted in normothermia septic rats as an adaptive mechanism that could enhance the release of oxygen at the tissue level. Hypothermia by slowing down sepsis evolution could increase survival duration.