scholarly journals Time course of diaphragm function recovery after controlled mechanical ventilation in rats

2013 ◽  
Vol 115 (6) ◽  
pp. 775-784 ◽  
Author(s):  
Debby Thomas ◽  
Karen Maes ◽  
Anouk Agten ◽  
Leo Heunks ◽  
Richard Dekhuijzen ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Protein Synthesis ◽  
Time Course ◽  
Diaphragm Muscle ◽  
Initiation Factor ◽  
Diaphragm Function ◽  
Function Recovery ◽  
Phosphorylated Akt ◽  
Controlled Mechanical Ventilation ◽  
Fiber Dimensions

Controlled mechanical ventilation (CMV) is known to result in rapid and severe diaphragmatic dysfunction, but the recovery response of the diaphragm to normal function after CMV is unknown. Therefore, we examined the time course of diaphragm function recovery in an animal model of CMV. Healthy rats were submitted to CMV for 24–27 h ( n = 16), or to 24-h CMV followed by either 1 h (CMV + 1 h SB, n = 9), 2 h (CMV + 2 h SB, n = 9), 3 h (CMV + 3 h SB, n = 9), or 4–7 h (CMV + 4–7 h SB, n = 9) of spontaneous breathing (SB). At the end of the experiment, the diaphragm muscle was excised for functional and biochemical analysis. The in vitro diaphragm force was significantly improved in the CMV + 3 h SB and CMV + 4–7 h SB groups compared with CMV (maximal tetanic force: +27%, P < 0.05, and +59%, P < 0.001, respectively). This was associated with an increase in the type IIx/b fiber dimensions ( P < 0.05). Neutrophil influx was increased in the CMV + 4–7 h SB group ( P < 0.05), while macrophage numbers remained unchanged. Markers of protein synthesis (phosphorylated Akt and eukaryotic initiation factor 4E binding protein 1) were significantly increased (±40%, P < 0.001, and ±52%, P < 0.01, respectively) in the CMV + 3 h SB and CMV + 4–7 h SB groups and were positively correlated with diaphragm force ( P < 0.05). Finally, also the maximal specific force generation of skinned single diaphragm fibers was increased in the CMV + 4–7 h SB group compared with CMV (+45%, P < 0.05). In rats, reloading the diaphragm for 3 h after CMV is sufficient to improve diaphragm function, while complete recovery occurs after longer periods of reloading. Enhanced muscle fiber dimensions, increased protein synthesis, and improved intrinsic contractile properties of diaphragm muscle fibers may have contributed to diaphragm function recovery.

scholarly journals Time course of diaphragm function recovery after mechanical ventilation in an animal model

2011 ◽  
Vol 25 (S1) ◽  
Author(s):  
Debby Thomas ◽  
Karen Maes ◽  
Anouk Agten ◽  
Marc Decramer ◽  
Ghislaine Gayan‐Ramirez
Keyword(s):  
Mechanical Ventilation ◽  
Animal Model ◽  
Time Course ◽  
Diaphragm Function ◽  
Function Recovery

scholarly journals Paramyxovirus-Induced Shutoff of Host and Viral Protein Synthesis: Role of the P and V Proteins in Limiting PKR Activation

2007 ◽  
Vol 82 (2) ◽  
pp. 828-839 ◽  
Author(s):  
Maria D. Gainey ◽  
Patrick J. Dillon ◽  
Kimberly M. Clark ◽  
Mary J. Manuse ◽  
Griffith D. Parks
Keyword(s):  
Protein Synthesis ◽  
Hela Cells ◽  
Viral Protein ◽  
Time Course ◽  
Translation Initiation Factor ◽  
Host Protein ◽  
Initiation Factor ◽  
Viral Protein Synthesis ◽  
Viral Mrnas ◽  
V Protein

ABSTRACT The paramyxovirus simian virus 5 (SV5) establishes highly productive persistent infections of epithelial cells without inducing a global inhibition of translation. Here we show that an SV5 mutant (the P/V-CPI− mutant) with substitutions in the P subunit of the viral polymerase and the accessory V protein also establishes highly productive infections like wild-type (WT) SV5 but that cells infected with the P/V-CPI− mutant show an overall shutdown of both host and viral translation at late times postinfection. Reduced host and viral protein synthesis with the P/V-CPI− virus was not due to lower levels of mRNA or caspase-dependent apoptosis and correlated with phosphorylation of the translation initiation factor eIF-2α. WT SV5 was a poor activator of the eIF-2α kinase protein kinase R (PKR). By contrast, the P/V-CPI− mutant induced PKR phosphorylation, which correlated with the time course of translation inhibition but was independent of interferon signaling. In HeLa cells that expressed the PKR inhibitor influenza A virus NS1 or reovirus sigma3, the rate of host protein synthesis at late times after infection with the P/V-CPI− mutant was restored to ∼50% that of control HeLa cells. By contrast, the rates of P/V-CPI− viral protein synthesis in HeLa cells expressing NS1 or sigma3 were dramatically enhanced, between 5- and 20-fold, while levels of viral mRNA were increased only slightly (NS1-expressing cells) or remained constant (sigma3-expressing cells). Similar results were found using HeLa cells where PKR levels were reduced due to knockdown by small interfering RNA. Expression of either the WT P or the WT V protein from the genome of the P/V-CPI− mutant resulted in lower levels of PKR activation and rates of host and viral protein synthesis that closely matched those seen with WT SV5. Despite higher rates of translation, cells infected with the V- or P-complemented virus accumulated viral mRNAs to lower levels than that seen with the parental P/V-CPI− mutant. We present a model in which the paramyxovirus P/V gene products limit induction of PKR by limiting the synthesis of aberrant viral mRNAs and double-stranded RNA and thus prevent the shutdown of translation by a mechanism that differs from that of other PKR inhibitors such as NS1 and sigma3.

Time course changes in signaling pathways and protein synthesis in C2C12 myotubes following AMPK activation by AICAR

2006 ◽  
Vol 291 (1) ◽  
pp. E80-E89 ◽  
Author(s):  
David L. Williamson ◽  
Douglas R. Bolster ◽  
Scot R. Kimball ◽  
Leonard S. Jefferson
Keyword(s):  
Protein Synthesis ◽  
Signaling Pathway ◽  
Time Course ◽  
Mrna Translation ◽  
Mapk Signaling ◽  
Mtor Signaling ◽  
Initiation Factor ◽  
C2c12 Myotubes ◽  
Ampk Activation ◽  
Ampk Phosphorylation

The role of the AMP-activated kinase (AMPK) as a metabolic sensor in skeletal muscle has been far better characterized for glucose and fat metabolism than for protein metabolism. Therefore, the studies presented here were designed to examine the effects of 5-aminoimidazole-4-carboxamide-1-β-d-ribonucleoside (AICAR)-induced AMPK signaling on effector mechanisms of mRNA translation and protein synthesis in cultures of C2C12 myotubes. The findings show that, following AICAR (2 mM) treatment, AMPK phosphorylation was increased within 15 min and remained elevated throughout a 60-min time course. In association with the increase in AMPK phosphorylation, global rates of protein synthesis declined to 90, 70, and 63% of the control values at the 15-, 30-, and 60-min time points, respectively. By 60 min, polysomes disaggregated into free ribosomal subunits, suggesting an inhibition of initiation of mRNA translation. However, phosphorylation of eukaryotic elongation factor 2 was increased at 15 and 30 min but then declined to control values by 60 min, suggesting a transient inhibition of translation elongation. The decline in protein synthesis and changes in mRNA translation were associated with a repression of the mammalian target of rapamycin (mTOR) signaling pathway, as indicated by increased association of Hamartin with Tuberin, increased association of regulatory associated protein of mTOR with mTOR, and dephosphorylation of the downstream targets ribosomal protein S6 kinase-1 and eukaryotic initiation factor 4E-binding protein-1. They were also associated with activation of the MAPK signaling pathway, as indicated by increased phosphorylation of MEK1/2 and ERK1/2 and the downstream target eIF4E. Overall, the data support the conclusion that AICAR-induced AMPK activation suppresses protein synthesis through concurrent repression of mTOR signaling and activation of MAPK signaling, the combination of which modulates transient changes in the initiation and elongation phases of mRNA translation.

scholarly journals Intracellular signaling pathways regulating net protein balance following diaphragm muscle denervation

2011 ◽  
Vol 300 (2) ◽  
pp. C318-C327 ◽  
Author(s):  
Heather M. Argadine ◽  
Carlos B. Mantilla ◽  
Wen-Zhi Zhan ◽  
Gary C. Sieck
Keyword(s):  
Protein Synthesis ◽  
Protein Degradation ◽  
Nuclear Translocation ◽  
Glycogen Synthase ◽  
Diaphragm Muscle ◽  
Initiation Factor ◽  
Protein Balance ◽  
Downstream Effector ◽  
Ampk Phosphorylation ◽  
Net Protein

Unilateral denervation (DNV) of rat diaphragm muscle increases protein synthesis at 3 days after DNV (DNV-3D) and degradation at DNV-5D, such that net protein breakdown is evident by DNV-5D. On the basis of existing models of protein balance, we examined DNV-induced changes in Akt, AMP-activated protein kinase (AMPK), and ERK½ activation, which can lead to increased protein synthesis via mammalian target of rapamycin (mTOR)/p70S6 kinase (p70S6K), glycogen synthase kinase-3β (GSK3β), or eukaryotic initiation factor 4E (eIF4E), and increased protein degradation via forkhead box protein O (FoxO). Protein phosphorylation was measured using Western analyses through DNV-5D. Akt phosphorylation decreased at 1 h and 6 h after DNV compared with sham despite decreased AMPK phosphorylation. Both Akt and AMPK phosphorylation returned to sham levels by DNV-1D. Phosphorylation of their downstream effector mTOR (Ser2481) did not change at any time point after DNV, and phosphorylated p70S6K and eIF4E-binding protein 1 (4EBP1) increased only by DNV-5D. In contrast, ERK½ phosphorylation and its downstream effector eIF4E increased 1.7-fold at DNV-1D and phosphorylated GSK3β increased 1.5-fold at DNV-3D ( P < 0.05 for both comparisons). Thus, following DNV there are differential effects on protein synthetic pathways with preferential activation of GSK3β and eIF4E over p70S6K. FoxO1 nuclear translocation occurred by DNV-1D, consistent with its role in increasing expression of atrogenes necessary for subsequent ubiquitin-proteasome activation evident by DNV-5D. On the basis of our results, increased protein synthesis following DNV is associated with changes in ERK½-dependent pathways, but protein degradation results from downregulation of Akt and nuclear translocation of FoxO1. No single trigger is responsible for protein balance following DNV. Protein balance in skeletal muscle depends on multiple synthetic/degradation pathways that should be studied in concert.

scholarly journals Effects of controlled and pressure support mechanical ventilation on rat diaphragm muscle

2012 ◽  
Vol 27 (2) ◽  
pp. 109-116 ◽  
Author(s):  
André de Sá Braga Oliveira ◽  
Lívia Bandeira Costa ◽  
Thiago de Oliveira Assis ◽  
Diógenes Luís da Mota ◽  
Eduardo Ériko Tenório de França ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Pressure Support ◽  
Muscular Atrophy ◽  
Diaphragm Muscle ◽  
Control Group ◽  
Cross Sectional ◽  
Significant Difference ◽  
Controlled Mechanical Ventilation ◽  
To Receive ◽  
Pressure Controlled

PURPOSE: The objective of this study was to analyze the effects of Pressure Controlled Ventilation mode (PCV-C) and PSV mode in diaphragm muscle of rats. METHODS: Wistar rats (n=18) were randomly assigned to the control group or to receive 6 hours of PCV and PSV. After this period, animals were euthanized and their diaphragms were excised, frozen in liquid nitrogen and stored in at -80º C for further histomorphometric analysis. RESULTS: Results showed a 15% decrease in cross-sectional area of muscle fibers on the PCV-C group when compared to the control group (p<0.001) and by 10% when compared to the PSV group (p<0.05). Minor diameter was decreased in PCV-C group by 9% when compared with the control group (p<0.001) and by 6% when compared to the PSV group (p<0.05). When myonuclear area was analyzed, a 16% decrease was observed in the PCV-C group when compared to the PSV group (p<0.05). No significant difference between the groups was observed in myonuclear perimeter (p>0.05). CONCLUSION: Short-term controlled mechanical ventilation seems to lead to muscular atrophy in diaphragm fibers. The PSV mode may attenuate the effects of VIDD.

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