J Cachexia Sarcopenia Muscle (2011) 2:181–188 DOI 10.1007/s13539-011-0037-3 ORIGINAL ARTICLE Decreased NADPH oxidase expression and antioxidant activity in cachectic skeletal muscle Melanie J. Sullivan-Gunn & Siun P. Campbell-O’Sullivan & Michael J. Tisdale & Paul A. Lewandowski Received: 22 February 2011 / Accepted: 27 July 2011 / Published online: 11 August 2011 # The Author(s) 2011. This article is published with open access at Springerlink.com Abstract Background Cancer cachexia is the progressive loss of skeletal muscle protein that contributes significantly to cancer morbidity and mortality. Evidence of antioxidant attenuation and the presence of oxidised proteins in patients with cancer cachexia indicate a role for oxidative stress. The level of oxidative stress in tissues is determined by an imbalance between reactive oxygen species production and antioxidant activity. This study aimed to investigate the superoxide generating NADPH oxidase (NOX) enzyme and antioxidant enzyme systems in murine adenocarcinoma tumour-bearing cachectic mice. Methods Superoxide levels, mRNA levels of NOX enzyme subunits and the antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidise (GPx) and catalase was measured in the skeletal muscle of mice with cancer and cancer cachexia. Protein expression levels of NOX enzyme subunits and antioxidant enzyme activity was also mea- sured in the same muscle samples. Results Superoxide levels increased 1.4-fold in the muscle of mice with cancer cachexia, and this was associated with M. J. Sullivan-Gunn : P. A. Lewandowski (*) School of Medicine, Deakin University, Geelong Campus, Geelong, VIC 3217, Australia e-mail: paul.lewandowski@deakin.edu.au S. P. Campbell-O’Sullivan School of Biomedical Sciences, Victoria University, Centre for Aging, Rehabilitation, Exercise and Sport, PO Box 14428, Melbourne 8001, Australia M. J. Tisdale School of Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK a decrease in mRNA of NOX enzyme subunits, NOX2, p40phox and p67phox along with the antioxidant enzymes SOD1, SOD2 and GPx. Cancer cachexia was also associated with a 1.3-fold decrease in SOD1 and 2.0-fold decrease in GPx enzyme activity. Conclusion Despite increased superoxide levels in cachectic skeletal muscle, NOX enzyme subunits, NOX2, p40phox and p67phox, were downregulated along with the expression and activity of the antioxidant enzymes. Therefore, the increased superoxide levels in cachectic skeletal muscle may be attributed to the reduction in the activity of endogenous antioxidant enzymes. Keywords Cancer cachexia . NADPH oxidase . ROS . O2− . Antioxidant . SOD 1 Introduction Cancer cachexia is a condition of progressive muscle wasting that develops as a secondary condition in response to tumour growth [1]. While cachexia develops in a wide range of pathologies including anorexia nervosa, acquired immunodeficiency syndrome, amyotrophic lateral sclerosis, congestive heart failure and various malignant cancers, cancer cachexia has been reported to develop at a faster rate than any other cachectic condition [1]. Approximately half of all patients with cancer experience cachexia and almost a third of mortalities are estimated to result from cachexia [2]. Tumour growth induces a specific catabolic response in skeletal muscle that causes the accelerated loss of protein, characterised by the significant loss of body weight [3]. Animal tumour models have been used to investigate cancer cachexia, developing up to 30% loss in body weight after tumour cell implantation. NMRI mice implanted with