Plasma from septic shock patients induces loss of muscle protein

Hieronymus WH van Hees,Floris Leenders,Rogier Donders,Johannes G van der Hoeven,Willem-Jan M Schellekens,Leo MA Heunks,Jan Zoll,PN Richard Dekhuijzen,Marianne Linkels

doi:10.1186/cc10475

Hieronymus WH van Hees, Floris Leenders + Show 7 more

Open Access

https://doi.org/10.1186/cc10475

Copy DOI

Abstract

IntroductionICU-acquired muscle weakness commonly occurs in patients with septic shock and is associated with poor outcome. Although atrophy is known to be involved, it is unclear whether ligands in plasma from these patients are responsible for initiating degradation of muscle proteins. The aim of the present study was to investigate if plasma from septic shock patients induces skeletal muscle atrophy and to examine the time course of plasma-induced muscle atrophy during ICU stay.MethodsPlasma was derived from septic shock patients within 24 hours after hospital admission (n = 21) and healthy controls (n = 12). From nine patients with septic shock plasma was additionally derived at two, five and seven days after ICU admission. These plasma samples were added to skeletal myotubes, cultured from murine myoblasts. After incubation for 24 hours, myotubes were harvested and analyzed on myosin content, mRNA expression of E3-ligase and Nuclear Factor Kappa B (NFκB) activity. Plasma samples were analyzed on cytokine concentrations.ResultsMyosin content was approximately 25% lower in myotubes exposed to plasma from septic shock patients than in myotubes exposed to plasma from controls (P < 0.01). Furthermore, patient plasma increased expression of E3-ligases Muscle RING Finger protein-1 (MuRF-1) and Muscle Atrophy F-box protein (MAFbx) (P < 0.01), enhanced NFκB activity (P < 0.05) and elevated levels of ubiquitinated myosin in myotubes. Myosin loss was significantly associated with elevated plasma levels of interleukin (IL)-6 in septic shock patients (P < 0.001). Addition of antiIL-6 to septic shock plasma diminished the loss of myosin in exposed myotubes by approximately 25% (P < 0.05). Patient plasma obtained later during ICU stay did not significantly reduce myosin content compared to controls.ConclusionsPlasma from patients with septic shock induces loss of myosin and activates key regulators of proteolysis in skeletal myotubes. IL-6 is an important player in sepsis-induced muscle atrophy in this model. The potential to induce atrophy is strongest in plasma obtained during the early phase of human sepsis.

Highlights

intensive care unit (ICU)-acquired muscle weakness commonly occurs in patients with septic shock and is associated with poor outcome
The current study adds to these earlier observations as we show that plasma from septic shock patients increases ubiquitinated myosin levels and activates Muscle RING Finger protein-1 (MuRF-1) and MAFBx in skeletal myotubes
In line with that study, we found that Muscle Atrophy F-box protein (MAFbx) expression diminished after Day 2 on the ICU and followed a similar trend as interleukin 6 (IL-6), which in turn is inversely related to myosin content

Summary

Introduction

ICU-acquired muscle weakness commonly occurs in patients with septic shock and is associated with poor outcome. Tiao et al [6] found that in septic rats, skeletal muscle protein breakdown van Hees et al Critical Care 2011, 15:R233 http://ccforum.com/content/15/5/R233 was increased due to enhanced activity of the proteolytic ubiquitin-proteasome pathway. It is unknown whether ligands in human septic plasma can activate the ubiquitin-proteasome pathway and induce loss of myosin. This is of relevance as it will help to understand the importance of systemic components compared to intrinsic muscle factors, such as disuse, in sepsis-induced muscle atrophy. We explored the relation between myosin loss and plasma levels of inflammatory cytokines

Objectives

Methods

Results

Conclusion