The importance of interplays between NO and adhesion molecules in the regulation of liver cancer metastasis has been recognized and addressed in recent years [
10,
19,
20,
45]. The inducible murine hepatic microvascular adhesive and cytotoxic regulatory functions have been regulated by using LPS [
28,
30]. With enhanced local expression of VCAM-1 and ICAM-1 around B16F1 cell arrest sites in the liver, LPS significantly increased the retention of melanoma cells in the liver, especially in the terminal portal venule regions between 8 and 24 h after intramesenteric injection of melanoma cells [
30]. LPS also significantly increased the levels of iNOS expression and tumor cell induced-NO production at 8 h after administration and cell injection, and increased the rates of B16F1 cell apoptosis in the terminal portal venule region [
30]. These data have been interpreted to indicate that LPS stimulated a synergistic interaction by inducing both the hepatic endothelial adhesion molecule expression and NO release in the terminal portal venular regions, resulting in higher levels of tumor cell killing in this region in the liver [
30]. The dual roles of activated host liver endothelial cells in murine lymphoma metastatic process have also been reviewed [
16]. On one hand, upregulation of the expression of particular adhesion molecules is considered to lead to the increased tumor cell binding and stimulation of angiogenesis, and on the other hand, endothelial cells can contribute to host anti-metastatic responses by producing the cytotoxic molecule NO from arginine with the help of iNOS [
16]. Synergistic interactions between LFA-1/ICAM-1 and lymphoma progression phases with cytotoxic NO production have been described [
4]. Interactions between cytokine IL-18, VCAM-1, H
2O
2 and hepatic sinusoidal endothelial cells have also been demonstrated [
35]. Recombinant catalase administered
in vivo completely blocked the increase of VCAM-1 expression induced by B16M cell arrest in the liver, and blocked
in vitro B16M cell adhesion to sinusoidal lining cells isolated from B16M cell-injected mice [
35]. Incubation of hepatic endothelial cells with nontoxic concentrations of H
2O
2 directly enhanced VCAM-1-dependent B16M cell adhesion
in vitro without proinflammatory cytokine mediation [
35].
In addition to synergistic interactions between NO and adhesion molecules, their counteractive interactions have also been identified. NO reduces tumor cell adhesion to isolated rat postcapillary venules
in vitro [
66]. Anti-adhesive roles of constitutively produced NO in inhibiting leukocyte rolling and adhesion in the microcirculation have been described [
67,
68]. Oxidative stress in the liver can be caused by ischemia/reperfusion (I/R) injury when tumor cells entering the hepatic microcirculation obstruct hepatic sinusoids and temporarily occlude blood flow before the hepatic circulation is reestablished by either tumor cell death or invasion into the parenchyma [
8,
55]. The counteractive roles of NO with adhesion molecules, such as decreasing P-selectin and ICAM-1 mRNA expression, attenuating neutrophil accumulation and liver damage in hepatic ischemia/reperfusion injury have been reviewed [
69‐
71]. IL-10 has also been shown to inhibit hepatic I/R injury by inhibiting the upregulation of iNOS expression following I/R injury [
55]. The multifaceted roles and effects of NO and adhesion molecule interactions support the scenario that the host uses this flexible natural defensive mechanism to protect itself from a variety of disastrous oxidative injuries and tissue damages to the hepatic microvasculature.