Kupffer cell ablation attenuates cyclooxygenase-2 expression after trauma and sepsis

Prostaglandins, synthesized by cyclooxygenase (COX), play an important role in the pathophysiology of inflammation. Severe injuries result in immunosuppression, mediated, in part, by maladaptive changes in macrophages. Herein, we assessed Kupffer cell-mediated cyclooxygenase-2 (COX-2) expression on liver function and damage after trauma and sepsis.

To ablate Kupffer cells, Sprague Dawley rats were treated with gadolinium chloride (GdCl3) 48 and 24 h before experimentation. Animals then underwent femur fracture (FFx) followed 48 h later by cecal ligation and puncture (CLP). Controls received sham operations. After 24 h, liver samples were obtained, and mRNA and protein expression were determined by PCR, Western blot, and immunohistochemistry. Indocyanine-Green (ICG) clearance and plasma alanine aminotransferase (ALT) levels were determined to assess liver function and damage, respectively. One-way analysis of variance (ANOVA) with Student-Newman-Keuls test was used to assess statistical significance.

After CLP alone, FFx+CLP, and GdCl3+FFx+CLP, clearance of ICG decreased. Plasma ALT levels increased in parallel with severity of injury. Kupffer cell depletion attenuated the increased ALT levels after FFx+CLP. Femur fracture alone did not alter COX-2 protein compared with sham. By contrast, COX-2 protein increased after CLP and was potentiated by sequential stress. Again, Kupffer cell depletion abrogated the increase in COX-2 after sequential stress. Immunohistochemical data confirmed COX-2 positive cells to be Kupffer cells.

In this study, sequential stress increased hepatic COX-2 protein. Depletion of Kupffer cells reduced COX-2 and attenuated hepatocellular injuries. Our data suggest that Kupffer cell-dependent pathways may contribute to the inflammatory response leading to increased mortality after sequential stress.