Kidney Ischemia-Reperfusion Elicits Acute Liver Injury and Inflammatory Response

Abstract

Ischemia-reperfusion (IR) is a common risk factor that causes acute kidney injury (AKI). AKI is associated with dysfunction of other organs also known as distant organ injury. The liver function is often compromised in patients with AKI and in animal models. However, the underlying mechanisms are not fully understood. Inflammatory response plays an important role in IR-induced tissue injury. Although increased proinflammatory cytokines have been detected in the kidney and the distant organs after renal IR, their original sources remain uncertain. In the present study, we investigated the acute effect of renal IR on hepatic inflammatory cytokine expression and the mechanism involved. Sprague-Dawley rats that were subjected to renal IR (ischemia for 45 min followed by reperfusion for 1 h or 6 h) had increased plasma levels of creatinine, urea, and transaminases, indicating kidney and liver injuries. There was a significant increase in the expression of proinflammatory cytokine mRNA (MCP-1, TNF-α, IL-6) in the kidney and liver in rats with renal IR. This was accompanied by a significant increase in proinflammatory cytokine protein levels in the plasma, kidney, and liver. Activation of a nuclear transcription factor kappa B (NF-κB) was detected in the liver after renal IR. The inflammatory foci and an increased myeloperoxidase (MPO) activity were detected in the liver after renal IR, indicating hepatic inflammatory response and leukocyte infiltration. These results suggest that renal IR can directly activate NF-κB and induce acute production of proinflammatory cytokines in the liver. Renal IR-induced hepatic inflammatory response may contribute to impaired liver function and systemic inflammation.

Keywords: acute kidney injury; inflammation; ischemia-reperfusion; kidney; liver.

Figure 1

Effect of kidney ischemia-reperfusion on kidney function. The left kidney of rats was subjected to 45 min ischemia followed by 1 hour (1 h) or 6 hours (6 h) of reperfusion (IR). As a control, rats were subjected to a sham-operation without inducing ischemia (Sham). Plasma creatinine (A) and urea nitrogen (B) were measured. Results are expressed as mean ± SE (n = 5 for each group). *p < 0.05 when compared with the value obtained from the sham-operated group.

Figure 2

Effect of kidney ischemia-reperfusion on histological change in the kidney. The left kidney of rats was subjected to 45 min ischemia followed by 1 hour (1 h) or 6 hours (6 h) of reperfusion (IR). As a control, rats were subjected to a sham-operation without inducing ischemia (Sham). The histological structure of kidney was examined by hematoxylin and eosin (H&E) staining and analyzed at ×200 magnification. Kidneys of the IR group showed tubular necrosis (arrowheads), interstitial congestion of red blood cells (arrow), and glomerulus enlargement compared with the Sham group (scale bar = 100 μm).

Figure 3

Effect of kidney ischemia-reperfusion on liver function. The left kidney of rats was subjected to 45 min ischemia followed by 1 hour (1 h) or 6 hours (6 h) of reperfusion (IR). As a control, rats were subjected to a sham-operation without inducing ischemia (Sham). Plasma alanine transaminase (ALT) (A) and aspartate aminotransferase (AST) (B) were measured. Results are expressed as mean ± SE (n = 5 for each group). *p < 0.05 when compared with the value obtained from the sham-operated group.

Figure 4

Effect of kidney ischemia-reperfusion on cytokine protein levels in the kidney, liver, and plasma. The left kidney of rats was subjected to 45 min ischemia followed by 6 hours (6 h) of reperfusion (IR). As a control, rats were subjected to a sham-operation without inducing ischemia (Sham). The protein expressions of MCP-1, TNF-α, and IL-6 were measured in the kidney (A), liver (B), and plasma (C) by using ELISA. For reference, the cytokine levels in the sham group were MCP-1 (kidney 3.9 ng/g tissue, liver 100 pg/g tissue, plasma 13.63 ng/ml), TNF-α (kidney 200 ng/g tissue, liver 41 pg/g tissue, plasma 1.2 pg/ml), IL-6 (kidney 3.2 ng/g tissue, liver 1,880 pg/g tissue, plasma 1.8 pg/ml). Results are expressed as fold change to the Sham (n = 5 for each group). *p < 0.05 when compared with the value obtained from the sham-operated group.

Figure 5

Effect of kidney ischemia-reperfusion on cytokine mRNA expression in the kidney. The left kidney of rats was subjected to 45 min ischemia followed by 1 hour (1 h) or 6 hours (6 h) of reperfusion (IR). As a control, rats were subjected to a sham-operation without inducing ischemia (Sham). The mRNA expressions of TNF-α (A), IL-6 (B), and MCP-1 (C) were determined in the kidney by a real-time PCR analysis. Results are expressed as fold change to the Sham (n = 5 for each group). *p < 0.05 when compared with the value obtained from the sham-operated group.

Figure 6

Effect of kidney ischemia-reperfusion on cytokine mRNA expression in the liver. The left kidney of rats was subjected to 45 min ischemia followed by 1 hour (1 h) or 6 hours (6 h) of reperfusion (IR). As a control, rats were subjected to a sham-operation without inducing ischemia (Sham). The mRNA expression of TNF-α (A), IL-6 (B), and MCP-1 (C) was determined in the liver by a real-time PCR analysis. Results are expressed as fold change to the Sham (n = 5 for each group). *p < 0.05 when compared with the value obtained from the sham-operated group.

Figure 7

The DNA binding activity of NF-κB in the liver. The left kidney of rats was subjected to 45 min ischemia followed by 1 hour (1 h) or 6 hours (6 h) of reperfusion (IR). As a control, rats were subjected to a sham-operation without inducing ischemia (Sham). Liver nuclear proteins were prepared. The DNA binding activity of NF-κB in the liver was determined by EMSA. Histone H3 was determined by Western immunoblotting analysis and used as an internal control. Results are expressed as fold change to the Sham (n = 5 for each group). *p < 0.05 when compared with the value obtained from the sham-operated group.

Figure 8

Effect of kidney ischemia-reperfusion on pathohistological change of the liver. The left kidney of rats was subjected to 45 min ischemia followed by 1 hour (1 h) or 6 hours (6 h) of reperfusion (IR). As a control, rats were subjected to a sham-operation without inducing ischemia (Sham). The histological structure of liver was examined by hematoxylin and eosin (H&E) staining (magnification ×200). Arrows point to inflammatory foci (scale bar = 100 μm).

Figure 9

Effect of kidney ischemia-reperfusion on myeloperoxidase activity in the liver. The left kidney of rats was subjected to 45 min ischemia followed by 1 hour (1 h) and 6 hours (6 h) of reperfusion (IR). As a control, rats were subjected to a sham-operation without inducing ischemia (Sham). The myeloperoxidase (MPO) activity were determined in the liver. Results are expressed as fold change to the Sham. Results are expressed as mean ± SE (n = 4–5 for each group). *p < 0.05 when compared with the value obtained from the sham-operated group.