PD-L1 blockade attenuated sepsis-induced liver injury in a mouse cecal ligation and puncture model

Abstract

Liver plays a major role in hypermetabolism and produces acute phase proteins during systemic inflammatory response syndrome and it is of vital importance in host defense and bacteria clearance. Our previous studies indicated that programmed death-1 (PD-1) and its ligand programmed death ligand-1 (PD-L1) are crucial modulators of host immune responses during sepsis. Our current study was designed to investigate the role of PD-L1 in sepsis-induced liver injury by a mouse cecal ligation and puncture (CLP) model. Our results indicated that there was a significant increase of PD-L1 expression in liver after CLP challenge compared to sham-operated controls, in terms of levels of mRNA transcription and immunohistochemistry. Anti-PD-L1 antibody significantly alleviated the morphology of liver injury in CLP mice. Anti-PD-L1 antibody administration decreased ALT and AST release in CLP mice, decreased the levels of tumor necrosis factor (TNF)-α , interleukin (IL)-6, and IL-10 mRNA in liver after sepsis challenge. Thus, anti-PD-L1 antibody might have a therapeutic potential in attenuating liver injury in sepsis.

Figure 1

Immunohistochemical staining of liver tissues using anti-PD-L1 Abs. Representative patterns of expression of PD-L1 in liver tissues were shown in sham ((a) and (b)) and CLP mice ((c) and (d)). Positive cells were stained brown. The black arrows indicated PD-L1⁺ cells. Strong and widespread PD-L1 expression was examined as shown in panel (c) and (d), whereas sham groups showed undetectable signal. Original magnification ×200 for (a) and (c) and ×400 for (b) and (d).

Figure 2

PD-L1 mRNA was unregulated liver of septic mice livers versus Sham at 24 hours. n = 8 per each group. *P < 0.01 when mice with CLP were compared with mice from sham group. Bars represent the mean ± SD.

Figure 3

Morphological changes in liver 24 hours after CLP-induced sepsis in hematoxylin and eosin-stained section. Black squares in (a) were magnified into (b), (c), and (d). Spotty necrosis and infiltrations of inflammatory cells were observed in (b). Hepatocytes undergoing ballooning degeneration were observed in (c). Irregular central vein congestion were seen in (d). Original magnification was ×200 for (a) and ×400 for (b), (c), and (d).

Figure 4

Anti-PD-L1 antibody reverses morphology of liver injury induced by sepsis. Mice were administered anti-PD-L1 antibody (50 μg, i.p.). Liver specimens were sampled 24 hours after surgery. The liver tissue sections were stained with H and E. Black squares in (a) were magnified into (b), (c), and (d). Original magnification was ×200 for (a); ×400 for (b), (c), and (d).

Figure 5

Anti-PD-L1 antibody treatment improved liver function of septic mice. n = 8 per each group. *P < 0.01 when mice from CLP group were compared with mice from Sham group; ***P < 0.01 when mice from Anti-PD-L1 group were compared with mice from CLP group; **P > 0.05 when mice from Iso-type group were compared with mice from CLP group. Bars represent the mean ± SD.

Figure 6

Anti-PD-L1 antibody altered mRNA expression of IL-6, IL-10, and TNF-α in the liver of septic mice. Mice were administered anti-PD-L1 antibody (50 μg, i.p.). Liver specimens were sampled 24 hours after surgery. *P < 0.01 versus Sham, ***P < 0.01 versus CLP, **P = 0.7128 (IL-6), P = 0.8133 (IL-10), and P = 0.1228 (TNF-α) versus CLP. Bars represent the mean ± SD of eight mice for each group.