A critical role for muscle ring finger-1 in acute lung injury-associated skeletal muscle wasting.

RATIONALE: Acute lung injury (ALI) is a debilitating condition associated with severe skeletal muscle weakness that persists in humans long after lung injury has resolved. The molecular mechanisms underlying this condition are unknown. OBJECTIVES: To identify the muscle-specific molecular mechanisms responsible for muscle wasting in a mouse model of ALI. METHODS: Changes in skeletal muscle weight, fiber size, in vivo contractile performance, and expression of mRNAs and proteins encoding muscle atrophy-associated genes for muscle ring finger-1 (MuRF1) and atrogin1 were measured. Genetic inactivation of MuRF1 or electroporation-mediated transduction of miRNA-based short hairpin RNAs targeting either MuRF1 or atrogin1 were used to identify their role in ALI-associated skeletal muscle wasting. MEASUREMENTS AND MAIN RESULTS: Mice with ALI developed profound muscle atrophy and preferential loss of muscle contractile proteins associated with reduced muscle function in vivo. Although mRNA expression of the muscle-specific ubiquitin ligases, MuRF1 and atrogin1, was increased in ALI mice, only MuRF1 protein levels were up-regulated. Consistent with these changes, suppression of MuRF1 by genetic or biochemical approaches prevented muscle fiber atrophy, whereas suppression of atrogin1 expression was without effect. Despite resolution of lung injury and down-regulation of MuRF1 and atrogin1, force generation in ALI mice remained suppressed. CONCLUSIONS: These data show that MuRF1 is responsible for mediating muscle atrophy that occurs during the period of active lung injury in ALI mice and that, as in humans, skeletal muscle dysfunction persists despite resolution of lung injury.

Chitosan based titanium and iron oxide hybrid bio-polymeric nanocomposites as potential corrosion inhibitor for mild steel in acidic medium.

Biopolymer chitosan (CS), chitosan grafted acrylamide based titanium dioxide (CS-g-PAM/TiO2) and magnetite (CS-g-PAM/Fe3O4) hybrid nanocomposites have been synthesized through free radical graft co-polymerization and successfully validated as corrosion inhibitors for mild steel in 15 % HCl solution. The synthesized compounds have been characterized through FTIR, APC, XRD and TEM. The thermal stability of the nanocomposites was established by TGA. The anticorrosive performance was determined through gravimetric measurements and by electrochemical study. According to EIS technique it was observed that CS-g-PAM/TiO2 and CS-g-PAM/Fe3O4 showed maximum 97.19 % and 95.49 % efficiency respectively. Langmuir adsorption isotherm is obeyed in each case. The activation and adsorption parameters have been determined from isotherm study. FESEM and AFM confirmed better adsorption layer formed by composites over mild steel surface. The elemental composition of the metal samples was proved by the XPS investigation. DFT and ANOVA test further corroborates the experimental results.

A critical role for the protein apoptosis repressor with caspase recruitment domain in hypoxia-induced pulmonary hypertension.

BACKGROUND: Pulmonary hypertension (PH) is a lethal syndrome associated with the pathogenic remodeling of the pulmonary vasculature and the emergence of apoptosis-resistant cells. Apoptosis repressor with caspase recruitment domain (ARC) is an inhibitor of multiple forms of cell death known to be abundantly expressed in striated muscle. We show for the first time that ARC is expressed in arterial smooth muscle cells of the pulmonary vasculature and is markedly upregulated in several experimental models of PH. In this study, we test the hypothesis that ARC expression is essential for the development of chronic hypoxia-induced PH. METHODS AND RESULTS: Experiments in which cells or mice were rendered ARC-deficient revealed that ARC not only protected pulmonary arterial smooth muscle cells from hypoxia-induced death, but also facilitated growth factor-induced proliferation and hypertrophy and hypoxia-induced downregulation of selective voltage-gated potassium channels, the latter a hallmark of the syndrome in humans. Moreover, ARC-deficient mice exhibited diminished vascular remodeling, increased apoptosis, and decreased proliferation in response to chronic hypoxia, resulting in marked protection from PH in vivo. Patients with PH have significantly increased ARC expression not only in remodeled vessels but also in the lumen-occluding lesions associated with severe disease. CONCLUSIONS: These data show that ARC, previously unlinked to pulmonary hypertension, is a critical determinant of vascular remodeling in this syndrome.

Effects of acid aspiration-induced acute lung injury on kidney function.

Acute lung injury (ALI) in combination with acute kidney injury carries a mortality approaching 80% in the intensive care unit. Recently, attention has focused on the interaction of the lung and kidney in the setting of ALI and mechanical ventilation (MV). Small animal models of ALI and MV have demonstrated changes in inflammatory mediators, water channels, apoptosis, and function in the kidney early in the course of injury. The purpose of this investigation was to test the hypothesis that ALI and injurious MV cause early, measurable changes in kidney structure and function in a canine HCl aspiration model of ALI when hemodynamics and arterial blood gas tensions are carefully controlled. Intratracheal HCl induced profound ALI as demonstrated by increased shunt fraction and airway pressures compared with sham injury. Sham-injured animals had similar mean arterial pressure and arterial Pco(2) and HCO(3) levels compared with injured animals. Measurements of renal function including renal blood flow, urine flow, serum creatinine, glomerular filtration rate, urine albumin-to-creatinine ratio, and kidney histology scores were not different between groups. With maintenance of hemodynamic parameters and alveolar ventilation, ALI and injurious MV do not alter kidney structure and function early in the course of injury in this acid aspiration canine model. Kidney injury in large animal models may be more similar to humans and may differ from results seen in small animal models.

Sphingosine 1-phosphate rescues canine LPS-induced acute lung injury and alters systemic inflammatory cytokine production in vivo.

S1P has been demonstrated to protect against the formation of lipopolysaccharide (LPS)-induced lung edema when administered concomitantly with LPS. In the current study, we sought to determine the effectiveness of S1P to attenuate lung injury in a translationally relevant canine model of ALI when administered as rescue therapy. Secondarily, we examined whether the attenuation of LPS-induced physiologic lung injury after administration of S1P was, at least in part, caused by an alteration in local and/or systemic inflammatory cytokine expression. We examined 18, 1-year-old male beagles prospectively in which we instilled bacterial LPS (2-4 mg/kg) intratracheally followed in 1 h with intravenous S1P (85 microg/kg) or vehicle and 8 h of high-tidal-volume mechanical ventilation. S1P attenuated the formation of Q(s)/Q(t) (32%), and both the presence of protein (72%) and neutrophils (95%) in BAL fluid compared with vehicle controls. Although lung tissue inflammatory cytokine production was found to vary regionally throughout the LPS-injured lung, S1P did not alter the expression pattern. Similarly, BAL cytokine production was not altered significantly by intravenous S1P in this model. Interestingly, S1P potentiated the LPS-induced systemic production of 3 inflammatory cytokines, TNF-alpha (6-fold), KC (1.2-fold), and IL-6 (3-fold), without resulting in end-organ dysfunction. In conclusion, intravenous S1P reduces inflammatory lung injury when administered as rescue therapy in our canine model of LPS-induced ALI. This improvement is observed in the absence of changes in local pulmonary inflammatory cytokine production and an augmentation of systemic inflammation.