title: Diaphragm Abnormalities in Patients with End-Stage Heart Failure: NADPH Oxidase Upregulation and Protein Oxidation.
abstract: Patients with heart failure (HF) have diaphragm abnormalities that contribute to disease morbidity and mortality. Studies in animals suggest that reactive oxygen species (ROS) cause diaphragm abnormalities in HF. However, the effects of HF on ROS sources, antioxidant enzymes, and protein oxidation in the diaphragm of humans is unknown. NAD(P)H oxidase, especially the Nox2 isoform, is an important source of ROS in the diaphragm. Our main hypothesis was that diaphragm from patients with HF have heightened Nox2 expression and p47phoxphosphorylation (marker of enzyme activation) that is associated with elevated protein oxidation. We collected diaphragm biopsies from patients with HF and brain-dead organ donors (controls). Diaphragm mRNA levels of Nox2 subunits were increased 2.5-4.6-fold over controls (p< 0.05). Patients also had increased protein levels of Nox2 subunits (p47phox, p22phox, and p67phox) and total p47phoxphosphorylation, while phospho-to-total p47phoxlevels were unchanged. The antioxidant enzyme catalase was increased in patients, whereas glutathione peroxidase and superoxide dismutases were unchanged. Among markers of protein oxidation, carbonyls were increased by ~40% (p< 0.05) and 4-hydroxynonenal and 3-nitrotyrosines were unchanged in patients with HF. Overall, our findings suggest that Nox2 is an important source of ROS in the diaphragm of patients with HF and increases in levels of antioxidant enzymes are not sufficient to maintain normal redox homeostasis. The net outcome is elevated diaphragm protein oxidation that has been shown to cause weakness in animals.
authors.affiliation: Department of Applied Physiology and Kinesiology, University of Florida Gainesville, FL, USA.
authors.forename: Bumsoo
authors.initials: B
authors.lastname: Ahn
authors.affiliation: Department of Applied Physiology and Kinesiology, University of Florida Gainesville, FL, USA.
authors.forename: Philip D
authors.initials: PD
authors.lastname: Coblentz
authors.affiliation: Department of Physical Therapy, University of Florida Gainesville, FL, USA.
authors.forename: Adam W
authors.initials: AW
authors.lastname: Beharry
authors.affiliation: Department of Applied Physiology and Kinesiology, University of Florida Gainesville, FL, USA.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Patel
authors.affiliation: Department of Physical Therapy, University of Florida Gainesville, FL, USA.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Judge
authors.affiliation: Department of Physiology, University of Kentucky Lexington, KY, USA.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Moylan
authors.affiliation: Division of Cardiothoracic Surgery, University of Alabama at Birmingham Birmingham, AL, USA.
authors.forename: Charles W
authors.initials: CW
authors.lastname: Hoopes
authors.affiliation: Division of Cardiothoracic Surgery, University of Toledo Medical Center Toledo, OH, USA.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Bonnell
authors.affiliation: Department of Applied Physiology and Kinesiology, University of Florida Gainesville, FL, USA.
authors.forename: Leonardo F
authors.initials: LF
authors.lastname: Ferreira
keywords: NOX2; carbonyls; diaphragm; inspiratory muscles; weakness