BACKGROUNDThe initial management of a poly-trauma patient requires evaluation for potential hemorrhage and ongoing monitoring to assess the efficacy of treatment and avoid complications related to massive blood loss. Certain serum protein levels may be altered in response to hemorrhagic shock, and may serve as useful biomarkers to guide diagnosis, prognosis, and therapeutics in traumatic hemorrhagic shock (HS). Treatment with valproic acid (VPA) has been shown to up-regulate various survival pathways and improve outcome. Here we determine whether these changes would result in altered serum biomarkers.METHODSWistar-Kyoto rats underwent hemorrhagic shock (60% blood loss) followed by treatment with or without VPA (300 mg/kg). Using surface enhanced laser desorption-time of flight mass spectrometry (SELDI or SELDI-TOF MS) technology, we screened serum samples obtained from five rats at different time points (baseline, post-hemorrhagic shock, and post-VPA treatment) in a lethal model of hemorrhagic shock (HS). Additionally, we used isobaric tag labeling for relative quantitation (iTRAQ) to identify potential biomarkers in the serum. Western blots were performed to validate iTRAQ-identified biomarker from independent serum samples, and to analyze protein biomarker levels in the intestine during hemorrhagic shock and treatment.RESULTSHS and treatment with VPA affected serum levels of many proteins. One such protein with a mass spectrum around 22.7 kDa was detected in all five rats. The same serum samples subjected to iTRAQ resulted in our identification of claudin-3, a 23 kDa tight junction protein. HS elevated serum claudin-3 protein levels, which was reversed by VPA treatment in a pattern similar to the SELDI-TOF MS studies. Further validation with independent serum and intestine samples from individual rats by Western blots confirmed that HS increased the protein level of claudin-3 in serum and decreased its level in the intestine. Treatment with VPA reversed the hemorrhagic shock-induced alteration in claudin-3 to sham levels.CONCLUSIONSHS causes an acute rise in serum claudin-3 protein levels and a concurrent decrease in intestinal claudin-3 protein expression. VPA treatment attenuates these alterations and stabilizes intestinal claudin-3 levels. Our results demonstrate for the first time that claudin-3 is a potential biomarker in HS and treatment.