Identification of novel biomarkers for sepsis prognosis via urinary proteomic analysis using iTRAQ labeling and 2D-LC-MS/MS.
OBJECTIVE
Sepsis is the major cause of death for critically ill patients. Recent progress in proteomics permits a thorough characterization of the mechanisms associated with critical illness. The purpose of this study was to screen potential biomarkers for early prognostic assessment of patients with sepsis.


METHODS
For the discovery stage, 30 sepsis patients with different prognoses were selected. Urinary proteins were identified using isobaric tags for relative and absolute quantitation (iTRAQ) coupled with LC-MS/MS. Mass spec instrument analysis were performed with Mascot software and the International Protein Index (IPI); bioinformatic analyses were used by the algorithm of set and the Gene Ontology (GO) Database. For the verification stage, the study involved another 54 sepsis-hospitalized patients, with equal numbers of patients in survivor and non-survivor groups based on 28-day survival. Differentially expressed proteins were verified by Western Blot.


RESULTS
A total of 232 unique proteins were identified. Proteins that were differentially expressed were further analyzed based on the pathophysiology of sepsis and biomathematics. For sepsis prognosis, five proteins were significantly up-regulated: selenium binding protein-1, heparan sulfate proteoglycan-2, alpha-1-B glycoprotein, haptoglobin, and lipocalin; two proteins were significantly down-regulated: lysosome-associated membrane proteins-1 and dipeptidyl peptidase-4. Based on gene ontology clustering, these proteins were associated with the biological processes of lipid homeostasis, cartilage development, iron ion transport, and certain metabolic processes. Urinary LAMP-1 was down-regulated, consistent with the Western Blot validation.


CONCLUSIONS
This study provides the proteomic analysis of urine to identify prognostic biomarkers of sepsis. The seven identified proteins provide insight into the mechanism of sepsis. Low urinary LAMP-1 levels may be useful for early prognostic assessment of sepsis.


BACKGROUND
ClinicalTrial.gov NCT01493492.
Department of Respiratory Medicine, Hainan Branch of Chinese PLA General Hospital, Sanya, Hainan Province, China.
Longxiang
L
Su
Lichao
L
Cao
Ruo
R
Zhou
Zhaoxu
Z
Jiang
Kun
K
Xiao
Weijing
W
Kong
Huijuan
H
Wang
Jie
J
Deng
Bo
B
Wen
Fengji
F
Tan
Yong
Y
Zhang
Lixin
L
Xie
D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000652:urine; D002853:Chromatography, Liquid; D003936:Diagnosis, Computer-Assisted; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D051907:Lysosomal Membrane Proteins / Q000235:genetics / Q000652:urine*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D040901:Proteomics; D051137:Selenium-Binding Proteins / Q000235:genetics / Q000652:urine*; D018805:Sepsis / Q000175:diagnosis* / Q000235:genetics / Q000401:mortality / Q000652:urine*; D016019:Survival Analysis; D053719:Tandem Mass Spectrometry; D052118:Lysosomal-Associated Membrane Protein 1
D015415:Biomarkers; D051907:Lysosomal Membrane Proteins; D051137:Selenium-Binding Proteins; C489116:LAMP1 protein, human; D052118:Lysosomal-Associated Membrane Protein 1; C495175:SELENBP1 protein, human