A. P. Bercz1, M. C. Morris1, F. Kassam1, R. Veile1, L. Friend1, R. Schuster1, T. A. Pritts1, A. T. Makley1, M. D. Goodman1 1University Of Cincinnati,Department Of Surgery, College Of Medicine,Cincinnati, OH, USA
Introduction: Ubiquitin carboxy-terminal hydroxylase L1 (UCH-L1) is specifically expressed by neurons and its release reflects the neuronal response to injury. In humans and murine models, UCH-L1 is elevated in serum and cerebrospinal fluid following traumatic brain injury (TBI), hypoxic encephalopathy, and intracerebral hemorrhage, but it is unknown whether UCH-L1 is specific to central nervous system injury. Our lab has recently demonstrated that UCH-L1 is significantly elevated in a murine polytrauma model, regardless of TBI. In this study, we hypothesized that UCH-L1 would function as a marker of peripheral nerve injury induced by extremity ischemia.
Methods: Mice were anesthetized mice with pentobarbital and the left femoral vessels isolated. Mice were then subjected to either femoral artery isolation alone (sham), femoral artery ligation, femoral vein ligation, femoral artery ligation after 60 minutes of controlled hemorrhagic shock followed by resuscitation with shed blood, or four hours of ischemia with a femoral artery clamp followed by reperfusion (I/R). Mice were sacrificed at 4, 24, or 72 hours after treatment. Serum was analyzed using enzyme-linked immunosorbent assays for UCH-L1, neuron specific enolase (NSE), and creatine kinase (CK), the latter two being known biomarkers of neuronal and muscle injury, respectively. The bilateral quadriceps muscles were harvested and analyzed using hematoxylin and eosin staining.
Results: UCH-L1 was significantly increased in the hemorrhagic shock/resuscitation group at 4 hours, compared to the sham, artery ligation, vein ligation, and I/R groups (Figure 1). No other groups had significant UCH-L1 elevations compared to Sham at 4 hours. In the setting of hemorrhagic shock, UCH-L1 elevation persisted through 72 hours. NSE was not as sensitive to these ischemic changes. CK was altered in a pattern similar to that of UCH-L1 in its temporal response profile and was significantly increased in the hemorrhagic shock/resuscitation group with respect to the other groups at 4 hours. Hematoxylin and eosin staining of the quadriceps revealed muscle necrosis in the hemorrhagic shock/resuscitation group only, demonstrated by increased inflammatory infiltrate surrounding enucleated fascicles.
Conclusion: The acute elevation of UCH-L1 in response to isolated, controlled hemorrhagic shock and resuscitation suggests that UCH-L1 is not specific for TBI or central nervous system injury. The lack of NSE elevation in response to femoral vessel ligation suggests that NSE may be a more specific biomarker for TBI than peripheral nerve injury. UCH-L1 may be utilized as an early marker of neuronal injury in the context of hemorrhagic shock, polytrauma, and isolated extremity ischemia.
