Ubiquitin Urine Levels in Burn Patients

Abstract

Objective To determine whether urine ubiquitin levels are elevated after burns and to assess whether urine ubiquitin could be useful as a non-invasive biomarker for burn patients. Methods Forty burn patients (%TBSA: 20±22; modified Baux scores: 73±26) were included (control: 11 volunteers). Urine was collected in 2h-intervals for 72h, followed by 12h-intervals until discharge from the ICU. Ubiquitin concentrations were analyzed by ELISA and Western blot. Total protein was determined with a Bradford assay. Patient characteristics and clinical parameters were documented. Urine ubiquitin concentrations, renal ubiquitin excretion and excretion rates were correlated with patient characteristics and outcomes. Results Initial urine ubiquitin concentrations were 362±575 ng/mL in patients and 14±18 ng/mL in volunteers (p<0.01). Renal ubiquitin excretion on day-1 was 292.6±510.8 μg/24h and 21±27 μg/24h in volunteers (p<0.01). Initial ubiquitin concentrations correlated with modified Baux scores (r=0.46; p=0.02). Ubiquitin levels peaked at day 6 post-burn, whereas total protein concentrations and serum creatinine levels remained within the normal range. Total renal ubiquitin excretion and excretion rates were higher in patients with %TBSA ≥20 than with %TBSA <20, in patients who developed sepsis/MOF than in patients without these complications and in non-survivors vs. survivors. Conclusions Ubiquitin urine levels are significantly increased after burns. Renal ubiquitin excretion and/or excretion rates are associated with %TBSA, sepsis/MOF and mortality. Although these findings may explain previous correlations between systemic ubiquitin levels and outcomes after burns, the large variability of ubiquitin urine levels suggests that urine ubiquitin will not be useful as a non-invasive disease biomarker.

Sensitive ELISA-based detection method for the mitophagy marker p-S65-Ub in human cells, autopsy brain, and blood samples

“…Given its cellular origin, p-S65-Ub is either actively secreted, passively diffuses, or is released as the result of cell death and ultimately presents extracellularly in the plasma. Although we currently do not know the exact source, plasma concentrations of nonphosphorylated Ub have been found elevated in various diseases in the high picomolar to nanomolar range [55][56][57][58]. Here we show that p-S65-Ub is present and detectable and estimate that the absolute amount of in plasma as detected in our ELISA is in the femtomolar range.…”

Almost 50 Years of Monomeric Extracellular Ubiquitin (eUb)

“…Although studies of Ub have mainly been focused on its intracellular functions, there are several lines of evidence showing that extracellular (eUb) can also regulate different cellular processes. eUb is found at nanomolar concentrations in serum, cerebrospinal fluid (CSF), lung, alveolar lining fluid, and urine in normal individuals [ 13 ]. The increase in eUb levels in extracellular fluids has been observed in several human pathologies such as multiple sclerosis, Alzheimer’s disease, sepsis, and Parkinson’s disease, as well as in burn injury [ 13 , 14 , 15 , 16 , 17 , 18 ].…”

“…eUb is found at nanomolar concentrations in serum, cerebrospinal fluid (CSF), lung, alveolar lining fluid, and urine in normal individuals [ 13 ]. The increase in eUb levels in extracellular fluids has been observed in several human pathologies such as multiple sclerosis, Alzheimer’s disease, sepsis, and Parkinson’s disease, as well as in burn injury [ 13 , 14 , 15 , 16 , 17 , 18 ]. Although the function of eUb in such diseases has been suggested to lessen disease progression, its MoA has only partially been elucidated and it is currently under debate.…”