Urinary trypsin inhibitor: anti-inflammatory effects in septic mice and molecular insights in bacterial lipoprotein-induced THP-1 cells

Introduction:
Excessive release of inflammatory cytokines in severe infections significantly contributes to the onset and progression of sepsis, a condition linked to elevated mortality rates in intensive care units. However, the lack of effective sepsis treatment strategies remains a significant challenge in critical care medicine. The use of anti-inflammatory agents against sepsis has advantages. Urinary trypsin inhibitor (UTI), a serine protease inhibitor obtained from the urine of healthy males, finds broad application in patients with inflammatory conditions such as shock, pancreatitis, and trauma. This investigation aimed to examine the impact and underlying mechanism of UTI in mice with sepsis and THP-1 cells stimulated by bacterial lipoprotein (BLP).

Material and methods:
C57BL/6J mice were divided into the control, sham operation, cecal ligation and puncture (CLP), and UTI + CLP groups. Histological staining was performed to assess heart and lung injury. Transmission electron microscopy was performed to analyze myocardial mitochondrial injury. The creatine kinase-myoglobin binding and aspartate aminotransferase isoenzyme were detected by evaluating heart injury. Serum interleukin 1β (IL-1β) levels were identified using enzyme-linked immunosorbent assay. Human monocyte-derived THP-1 cells were cultured and divided into the control, BLP, and BLP + UTI (10, 100, 1000 U/ml, respectively) groups. Cell supernatant and extracted proteins from cultured cells treated at different UTI concentrations (10, 100, and 1000 U/ml) were collected to evaluate the tumor necrosis factor α (TNF-α) and IL-1β levels using enzyme-linked immunosorbent assay. Western blot analysis was executed to evaluate the level of expression of nuclear factor kappa B (NF-κB), phosphorylated-IκB, IκB, phosphorylated protein 38, and protein 38.

Results:
The CLP group exhibited elevated levels of creatine kinase-myoglobin binding, aspartate aminotransferase, and IL-1β. However, after the administration of UTI, these levels decreased. UTI treatment proved effective in improving inflammatory injury in the heart and lung tissues in septic mice. Furthermore, it reduced the release of inflammatory cytokines in THP-1 cells stimulated by BLP. Additionally, treatment with UTI decreased the activity of NF-κB and upregulated the protein expression levels of phosphorylated-IκB and phosphorylated protein 38 in THP-1 cells induced by BLP.

Conclusions:
UTI can effectively inhibit BLP-induced activation of the NF-κB/IκB and protein 38/ mitogen-activated protein kinase signaling pathways, thereby suppressing the inflammatory response and improving sepsis.