A Src family kinase inhibitor improves survival in experimental acute liver failure associated with elevated cerebral and circulating vascular endothelial growth factor levels

Abstract

Background and aims Acute liver failure (ALF) is frequently complicated by cerebral edema, systemic inflammation and multi-organ dysfunction. Vascular endothelial growth factor (VEGF) may stimulate liver regeneration but can also be pro-inflammatory, activating endothelial cells and increasing permeability, actions mediated through Src kinase signalling. We therefore examined whether a Src inhibitor could have therapeutic potential in ALF. Methods Murine ALF was induced with azoxymethane. Liver pathology was graded by a blinded examiner and apoptosis quantified by immunohistochemistry. Cerebral VEGF expression was imaged using VEGF-GFP transgenic mice. Circulating and macrophage-secreted VEGF levels were measured. Experimental animals received a Src inhibitor or vehicle controls. Results VEGF was undetectable in normal plasma but reached a mean of 835pg/ml at grade III encephalopathy (p<0.001). Ammonia, lipopolysaccharide and interferon-gamma acted synergistically to enhance VEGF secretion by macrophages. Production of VEGF by cerebral cortical astrocytes increased with disease progression. Late treatment with inhibitors of Src or VEGF did not improve liver histology, encephalopathy or survival. However, early use of a Src kinase inhibitor significantly reduced hepatic injury, delayed encephalopathy and allowed 25% of mice to survive an otherwise lethal insult. Conclusion Systemic and cerebral VEGF levels are significantly elevated during experimental ALF and may be exacerbated by hyperammonemia and macrophage activation. Early use of a Src inhibitor reduced hepatocellular injury and enabled survival, indicating such agents may have some promise in the treatment of ALF.

Pharmacological inhibition of Src kinase protects against acute kidney injury in a murine model of renal ischemia/reperfusion

“…Nevertheless, we cannot exclude the possibility that Src kinase also causes renal injury through its effects on renal microvascular permeability. In this context, it has been demonstrated that Src mediates vascular endothelial permeability responses to TNF, reactive oxygen species, angiogenesis and vascular leakage [ 25 – 27 ]. Disruption of endothelial cell-cell contact [ 42 ] and alteration of cell-cell adhesion complexes [ 43 ] has also been observed in a model of ischemic AKI.…”

“…Paul et al first demonstrated that mice deficient in Src were resistant to ischemic injury, and administration of Src inhibitors PP1 or PP2 to wild-type animals reduced ischemic injury in the brain [ 22 – 24 ]; Weis et al showed that the genetic or pharmacological blockade of Src reduced edema and tissue injury following myocardial infarction [ 24 ]. Moreover, early use of a Src inhibitor reduced hepatocellular injury and enabled survival in a murine model of acute liver failure induced by azoxymethane [ 25 ]. Finally, Src tyrosine kinase inhibition prevents I/R-induced acute lung injury [ 26 ].…”

Morphological changes of cortical pyramidal neurons in hepatic encephalopathy

“…Hyperammonemia is also frequently complicated by systemic inflammation including increasing systemic and cerebral levels of vascular endothelial growth factor (VEGF), Tumor Necrosis Factor (TNF)-alpha and the interleukins (IL)-1beta and IL-6 [ 46 ]. The VEGF may stimulate liver regeneration but it can also be pro-inflammatory, activating endothelial cells and increasing permeability, actions mediated through Src kinase signaling [ 47 ]. These proinflammatory cytokines progress in parallel with the severity of astrocyte swelling [ 46 ].…”

Neuroinflammation in Hepatic Encephalopathy: Mechanistic Aspects

“…24,25 Additionally, activation of intracellular signaling systems, including c-fos, 26 mitogen-activated protein kinases, 26 protein kinase G, 27 Src kinase family, 28 ciliary neurotrophic factor, 26 and the transcription factors p53, 29 SP-1 26 and nuclear factor-kappaB (NF-kB) [30][31][32] have all been shown to be involved in the mechanism of ammonia neurotoxicity, particularly in neuroinflammation.…”