THU117 Lipocalin-2 As A Mediator Of Negative Affect After Sepsis
Authors: Yang Shany E , Johnston Colin , Laborc Klaudia , Kounelis-Wuillaume Savannah , Schwieterman Will , Hill Alice R , Spencer-Segal Joanna L 
Published: October 2023

Abstract
Disclosure: S.E. Yang: None. C. Johnston: None. K. Laborc: None. S. Kounelis-Wuillaume: None. W. Schwieterman: None. A.R. Hill: None. J.L. Spencer-Segal: None.
Sepsis is characterized by a life-threatening response to severe infection including systemic inflammation. Many sepsis survivors suffer long-term from a post-sepsis syndrome including prominent neuropsychiatric symptoms, but the mechanisms underlying these symptoms remain unknown. In mice, cecal ligation and puncture (CLP) is used to induce sepsis, which is then treated with antibiotics and fluids. Although mice successfully recover within a week, we observe long-lasting anxiety-like behaviors in C57BL/6J mice of both sexes up to 3 weeks post-CLP as shown by decreased time spent in the open areas of an elevated zero maze compared to SHAM mice (52.24±24.60 vs. 74.32±20.25 seconds; p&lt;0.05; n=12 CLP, n=18 SHAM), reminiscent of the symptoms seen in human sepsis survivors. To elucidate the mechanisms underlying anxiety-like behavior in CLP survivors, we performed bulk RNA-sequencing in hippocampal tissues 3 weeks after SHAM or CLP surgeries. We found that lipocalin-2 (LCN2), a key component of the innate immune response, was one of the most upregulated gene transcripts in the hippocampus after CLP (24.3-fold increase relative to SHAM). We also observed a significant increase in systemic LCN2 protein levels in plasma samples 3 weeks after CLP compared to SHAM (1246±1902.62 vs. 77.53±59.09 ng/mL; p&lt;0.001; n=30 CLP, n=39 SHAM). To identify the cellular source of lcn2 mRNA upregulation, we performed RNAscope in hippocampal tissues and found that lcn2 mRNA expression is similar between SHAM and CLP mice in CA1 hippocampal neurons, and highly abundant in TEK+ endothelial cells after CLP (0.43±0.18 vs. 0.25±0.05 relative optical density; p&lt;0.05; n=8 CLP, n=20 SHAM) suggesting that endothelial cells are the major source of LCN2 upregulation after CLP. To investigate the role of LCN2 as a hormonal mediator of negative affect in sepsis, we administered recombinant LCN2 (rLCN2) once a day for 7 days via subcutaneous injections in both male and female mice and assessed affect and memory using the open field test, the elevated zero maze and the novel objection recognition test. While vehicle and rLCN2-injected female mice showed no significant differences in behavior, rLCN2-injected male mice exhibited anxiety-like behaviors as indicated by a significant decrease in the time spent in the center of an open field compared to vehicle-injected controls (48.25±18.62 vs. 65.87±14.76 seconds; p&lt;0.05; n=9 per group). This difference was not caused by locomotion deficits as the mean total distance travelled was similar between groups. Overall, our results demonstrate that LCN2 is a hormone produced in excess by endothelial cells in sepsis survivors, and that chronic rLCN2 administration was sufficient to induce anxiety-like behaviors in male mice but not female mice. Taken together, our data suggest that LCN2 is a novel endocrine mediator of post-sepsis syndrome.
Presentation: Thursday, June 15, 2023