Human Recombinant Vascular Endothelial Growth Factor Reduces Necrosis and Enhances Hepatocyte Regeneration in a Mouse Model of Acetaminophen Toxicity

Abstract

We reported previously that vascular endothelial growth factor (VEGF) was increased in acetaminophen (APAP) toxicity in mice and treatment with a VEGF receptor inhibitor reduced hepatocyte regeneration. The effect of human recombinant VEGF (hrVEGF) on APAP toxicity in the mouse was examined. In early toxicity studies, B6C3F1 mice received hrVEGF (50 g s.c.) or vehicle 30 min before receiving APAP (200 mg/kg i.p.) and were sacrificed at 2, 4, and 8 h. Toxicity was comparable at 2 and 4 h, but reduced in the APAP/hrVEGF mice at 8 h (p Ͻ 0.05) compared with the APAP/vehicle mice. Hepatic glutathione (GSH) and APAP protein adduct levels were comparable between the two groups of mice, with the exception that GSH was higher at 8 h in the hrVEGF-treated mice. Subsequently, mice received two doses (before and 10 h) or three doses (before and 10 and 24 h) of hrVEGF; alanine aminotransferase values and necrosis were reduced at 24 and 36 h, respectively, in the APAP/hrVEGF mice (p Ͻ 0.05) compared with the APAP/vehicle mice. Proliferating cell nuclear antigen expression was enhanced, and interleukin-6 expression was reduced in the mice that received hrVEGF (p Ͻ 0.05) compared with the APAP/ vehicle mice. In addition, treatment with hrVEGF lowered plasma hyaluronic acid levels and neutrophil counts at 36 h. Cumulatively, the data show that treatment with hrVEGF reduced toxicity and increased hepatocyte regeneration in APAP toxicity in the mouse. Attenuation of sinusoidal cell endothelial dysfunction and changes in neutrophil dynamics may be operant mechanisms in the hepatoprotection mediated by hrVEGF in APAP toxicity.Acetaminophen (APAP; C 8 H 9 NO 2 ) overdose is the most common cause of acute liver failure is the United States (Larson et al., 2005). N-acetylcysteine is the only available treatment of APAP overdose, but its efficacy is limited primarily to the initial, early stages of APAP toxicity. Currently, no other therapies exist for the management of APAP-induced liver failure, other than the management of coagulopathy and support of vital organ functions.Previous studies have shown that numerous proinflammatory and anti-inflammatory cytokines and chemokines are up-regulated in animal models of APAP toxicity, including interleukin (IL) 1␤, IL-6, IL-10, IL-13, macrophage inhibitory protein 2, and monocyte chemotactic protein 1 (Jaeschke, 2005). The role of cytokines and inflammation in APAP toxicity has been reviewed (Jaeschke, 2005), and the available data suggest that cytokines may play a role in the aggravation of cellular injury, but may also limit cell injury and initiate cell and organ repair processes (Hogaboam et al.,

Liver-Specific Deletion of Integrin-Linked Kinase in Mice Attenuates Hepatotoxicity and Improves Liver Regeneration After Acetaminophen Overdose

“…APAP overdose induced liver injury is one of the major causes of ALF in the western world contributing to almost 50% of the ALF cases (3). Studies show that increased liver regeneration is a key factor in inhibiting progression of injury and recovery from APAP overdose (5,8,18). Role of ECM or ILK mediated ECM signaling in liver injury and compensatory liver regeneration after APAP overdose is not known.…”

“…Liver injury after APAP overdose is also followed by compensatory liver regeneration, which is important for inhibition of progression of injury and final recovery (5). Various targets directed to attenuate liver injury or stimulate liver regeneration have been investigated in past to develop therapeutic strategy for APAP-induced ALF (5,8,18). …”

Liver sinusoidal endothelial cells and liver regeneration

“…Knockdown of hepatic VEGF with antisense oligonucleotides can exacerbate toxic injury to the liver (35), whereas infusion of VEGF can ameliorate toxic injury (44)(45)(46) and increases hepatocyte proliferation (38) and liver weight after partial hepatectomy (3,4). After both toxic injury and partial hepatectomy, hepatic VEGF has been shown to regulate each step of BM SPC recruitment to the liver: proliferation of BM SPCs, mobilization of BM SPCs to the circulation, engraftment of BM SPCs in the liver, and differentiation of BM SPCs to fenestrated LSECs lining the sinusoids (35) (Figure 3).…”

Microarchitecture of the liver: A Jigsaw puzzle

“…Shergill et al [6] showed that in a mouse model of liver regeneration post-hepatectomy, inhibition of VEGF and NOdependent angiogenesis did not impair liver regeneration. However, in a model of regeneration post-acetaminophen toxicity, Donahower et al [7] showed that the administration of recombinant VEGF reduced necrosis and enhanced hepatocyte regeneration. Thus, although there may be redundant pathways to stimulate vascular proliferation, this appears to be a key event in liver regeneration.…”

“…However, there are other factors that could play a role in organizing the microarchitecture of the liver. These include among others, the induction of endothelial cell proliferation by VEGF or NO [6,7], the production of Wingless (Wnt) and hedgehog (Hh) ligands by hepatocytes and liver sinusoidal cells [8], and the secretion of TGF-b, a negative regulator of hepatocyte proliferation [1]. In addition, EM produced could play a key role in harboring growth factors (i.e.…”