Role of endothelin ETA receptors in sepsis-induced mortality, vascular leakage, and tissue injury in rats

The role of endothelin ETA receptors in sepsis-induced mortality and edema formation was evaluated with a selective antagonist ABT-627 [2-(4-methoxyphenyl)-4-(1,3-benzodioxol-5-yl)-1-(N,N-di(n-butyl)amino carbonylmethyl)-pyrrolidine-3-carboxylic acid]. Sprague-Dawley rats received saline (control group), Escherichia coli endotoxin (10 mg/kg, sepsis group) or infusion of ABT-627 prior and immediately after saline and endotoxin injection. Mortality, edema formation (wet/dry ratios), and multiple tissue injury (indicated by serum concentrations of creatinine, urea, bilirubin, creatine kinase, lactate dehydrogenase, and aspartate aminotransferase) were monitored within 5 h. Endotoxin injection elicited 64% mortality, significantly augmented edema formation in liver, heart, lung, and kidney, and raised serum levels of tissue injury markers. Pretreatment with ABT-627 completely reversed endotoxin-induced mortality, significantly attenuated wet/dry ratios of the heart, liver, and kidney, but not lungs, and reduced serum levels of creatine kinase, creatinine, aspartate aminotransferase, and lactate dehydrogenase, but not that of urea and bilirubin. These results suggest that endothelin ET A receptors play a significant role in promoting mortality, edema formation (except in the lungs), and tissue injury in animals with severe sepsis

The effect of level of contraction on the electromyographic power spectrum of the diaphragm in pigs

We investigated the relationship between the frequency components of myoelectric power spectra of the diaphragm and the level of diaphragmatic contraction in seven anaesthetized spontaneously breathing pigs. Electromyographic activity of the costal and crural portions of the diaphragm were recorded with fish-hook electrodes and the frequency-power spectra during inspiration were computed and expressed in terms of centroid frequency (fc). Diaphragmatic force was indirectly assessed as transdiaphragmatic pressure (Pdi) which was measured with balloon-catheter systems placed in the abdomen and oesophagus. The relationships between Pdi and costal and crural fc were assessed during brief (2 min) and incremental increases in diaphragmatic contraction, achieved by gradual occlusion of the inspiratory line of the breathing circuit. When Pdi was increased to 128, 191, 287 and 421% of the value measured during unobstructed breathing, costal and crural fc rose significantly in all animals because of an increase in the power of high-frequency components and a decline in the power of low-frequency components. Both costal and crural fc returned to control values within 5 min of the release of inspiratory occlusion. Our results indicate that the level of contraction is an important determinant of the diaphragmatic myoelectric power spectrum and should be taken into consideration when using power spectral analysis to diagnose diaphragmatic mechanical failure

Effect of NO synthase inhibition on cardiovascular and pulmonary dysfunction in a porcine short-term model of endotoxic shock

In a porcine model of endotoxic shock, we evaluated the circulatory and respiratory effects of NO synthase (NOS) blockade. Twenty anaesthetised pigs were divided into three groups and studied for 240 min after induction of endotoxic shock with lipopolysaccharides of Escherichia coli (LPS). After 180 min of endotoxic shock, one group (n = 6) received aminoguanidine, another group (n = 6) received N(G)-nitro-L -arginine methyl ester (L -NAME) and a third group (n = 8) received only LPS. A sham group (n = 3) was also studied. LPS decreased systemic arterial pressure and cardiac output (CO) and increased mean pulmonary arterial pressure (MPAP), pulmonary vascular resistance (PVR) and heart rate. Significant changes were also observed in compliance (-18.4%) and resistance (+33.6%) of the respiratory system. Aminoguanidine did not modify LPS-dependent effects, while, after L -NAME, a significant increase in MPAP, PVR and SVR and a decrease in CO were observed. In conclusion, aminoguanidine does not play a significant cardiocirculatory and pulmonary role in the short-term dysfunction of endotoxic shock, while L -NAME has a detrimental effect on haemodynamics, suggesting a protective role of constitutive NO production at vascular level during the early stages of endotoxaemia

Differential regulation of myofibrillar proteins in skeletal muscles of septic mice

Sepsis elicits skeletal muscle atrophy as a result of decreased total protein synthesis and/or increased total protein degradation. It is unknown how and whether sepsis differentially affects the expression of specific myofibrillar proteins in respiratory and limb muscles. In this study, we measured the effects of sepsis myofibrillar mRNAs and their corresponding protein levels in the diaphragm (DIA) and tibialis anterior (TA) muscles in a murine cecal ligation and perforation (CLP) model of sepsis. Male mice (C57/BL6j) underwent CLP-induced sepsis. Sham-operated mice were subjected to the same surgical procedures, except for CLP. Mice were euthanized 24, 48, or 96 h postsurgery. Transcript and protein levels of autophagy-related genes, ubiquitin E3 ligases, and several myofibrillar genes were quantified. Sepsis elicited transient fiber atrophy in the DIA and prolonged atrophy in the TA. Atrophy was coincident with increased autophagy and ubiquitin E3 ligase expression. Myosin heavy chain isoforms decreased at 24 h in the DIA and across the time-course in the TA, myosin light chain isoforms decreased across the time-course in both muscles, and troponins T and C as well as tropomyosin decreased after 24 and 48 h in both the DIA and TA. α-Actin and troponin I were unaffected by sepsis. Sepsis-induced decreases in myofibrillar protein levels coincided with decreased mRNA expressions of these proteins, suggesting that transcriptional inhibition is involved. We hypothesize that sepsis-induced muscle atrophy is mediated by decreased transcription and enhanced degradation of specific myofibrillar proteins, including myosin heavy and light chains, troponin C, troponin T, and tropomyosin. © 2019 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society

Role of poly-(ADP-ribose) synthetase in lipopolysaccharide-induced vascular failure and acute lung injury in pigs

PURPOSE: To assess the contribution of poly (adenosine 5'-diphosphate ribose) synthetase (PARS) to the development of bacterial lipopolysaccharide (LPS)-induced acute lung injury and vascular failure in pigs. MATERIALS AND METHODS: Four groups of anesthetized, paralyzed, and mechanically ventilated domestic white pigs. Group 1 served as control, whereas Escherichia coli LPS (20 microg/kg/h) was continuously infused in group 2. Group 3 received 20 mg/kg injection of 3-aminobenzamide (a selective inhibitor of PARS activity) 15 minutes before LPS infusion. Only 3-aminobenzamide and not LPS was injected in group 4. All animals were examined for 180 minutes. Systemic and pulmonary hemodynamics and lung mechanics were measured during the experimental period. Lung wet/dry ratio, bronchoalveolar lavage (BAL) protein levels and cell counts and lung nitrotyrosine (footprint of peroxynitrite) immunostaining were also measured in a few animals. RESULTS: LPS infusion evoked a progressive decline in systemic arterial pressure, a small increase in cardiac output, and biphasic elevation of pulmonary arterial pressure. Lung compliance declined progressively, whereas lung and total respiratory resistance rose significantly after LPS infusion. Prominent nitrotyrosine immunostaining was detected around small airways and pulmonary endothelium of LPS-infused animals. No significant changes in lung wet/dry ratio and BAL protein levels and cell counts were produced by LPS infusion. Pretreatment with 3-aminobenzamide did not alter the systemic and pulmonary hemodynamic responses to LPS infusion but eliminated the rise in pulmonary and total respiratory resistance. CONCLUSIONS: We concluded that PARS activation plays an important role in the changes of lung mechanics associated with LPS-induced acute lung injury but had no role in vascular failur

Angiogenesis-related factors in skeletal muscles of COPD patients: Roles of angiopoietin-2

The role of angiogenesis factors in skeletal muscle dysfunction in patients with chronic obstructive pulmonary disease (COPD) is unknown. The first objective of this study was to assess various pro- and antiangiogenic factor and receptor expressions in the vastus lateralis muscles of control subjects and COPD patients. Preliminary inquiries revealed that angiopoietin-2 (ANGPT2) is overexpressed in limb muscles of COPD patients. ANGPT2 promotes skeletal satellite cell survival and differentiation. Factors that are involved in regulating muscle ANGPT2 production are unknown. The second objective of this study was to evaluate how oxidants and proinflammatory cytokines influence muscle-derived ANGPT2 expression. Angiogenic gene expressions in human vastus lateralis biopsies were quantified with low-density real-time PCR arrays. ANGPT2 mRNA expressions in cultured skeletal myoblasts were quantified in response to proinflammatory cytokine and H2O2 exposure. Ten proangiogenesis genes, including ANGPT2, were significantly upregulated in the vastus lateralis muscles of COPD patients. ANGPT2 mRNA levels correlated negatively with forced expiratory volume in 1 s and positively with muscle wasting. Immunoblotting confirmed that ANGPT2 protein levels were significantly greater in muscles of COPD patients compared with control subjects. ANGPT2 expression was induced by interferon-γ and -β and by hydrogen peroxide, but not by tumor necrosis factor. We conclude that upregulation of ANGPT2 expression in vastus lateralis muscles of COPD patients is likely due to oxidative stress and represents a positive adaptive response aimed at facilitating myogenesis and angiogenesis. Copyright © 2013 the American Physiological Society