Potential involvement of ubiquitin-proteasome system dysfunction associated with oxidative stress in the pathogenesis of sickle cell disease.

The ubiquitin-proteasome system (UPS) is an important intracellular proteolytic pathway responsible for the degradation of proteins and oxidative damage; hence it plays a central role in maintaining homeostasis of red blood cells (RBCs). The present study investigated the levels of polyubiquitination, the function of proteasomes and effect of hydroxycarbamide (HC) therapy in RBCs from sickle cell disease (SCD) patients. Polyubiquitinated proteins were found to be elevated in untreated SCD (UT-SCD) patients compared to those in HC-treated SCD patients (HC-SCD) and controls. Activities of ß1 and ß2 subunits were a little higher in UT-SCD patients, and much higher proteolytic activities were observed in all three subunits (ß1, ß2 and ß5) of RBCs in HC-SCD patients compared to those of UT-SCD patients and controls, although the protein levels of these subunits remained approximately the same. It is notable that, despite HC therapy, some patients showed persistent complications and accumulation of polyubiquitinated proteins. The enhanced proteasomal activity among HC-treated patients might remove the polyubiquitinated protein and could be one of the important mechanisms of therapeutic action. These findings could be useful to understand the pathophysiology of SCD and its clinical heterogeneity and identify a suitable therapeutic target for the better management of these patients.

Discovery and identification of serum biomarkers of Wilms' tumor in mice using proteomics technology.

BACKGROUND: Wilms' tumor (nephroblastoma) is a cancer of the kidneys that occurs typically in children and rarely in adults. Early diagnosis is very important for the treatment and prognosis of the disease. The aim of our study was to discover and identify potential non-invasive and convenient biomarkers for the diagnosis of Wilms' tumor. METHODS: Nude mice were used to construct a Wilms' tumor model by injecting nephroblastoma cells into their bilateral abdomen. We collected 94 serum samples from mice consisting of 45 samples with Wilms' tumor and 49 controls. The serum proteomic profiles of the samples were analyzed via surface-enhanced laser desorption/ionization time-of-flight mass spectrometry. The candidate biomarkers were purified by high-performance liquid chromatography, identified by liquid chromatography-mass spectrometry, and validated using ProteinChip immunoassays. RESULTS: We finally retrieved two differential proteins (m/z 4509.2; 6207.9), which were identified as apolipoprotein A-II and polyubiquitin, respectively. The expression of apolipoprotein A-II was higher in the Wilms' tumor group than in the control group (P < 0.01). By contrast, the expression of polyubiquitin was lower in the Wilms' tumor group than in the control group. CONCLUSION: Apolipoprotein A-II and polyubiquitin may be used as potential biomarkers for nephroblastoma in children, and the analysis of apolipoprotein A-II may help diagnose and treat Wilms' tumor.