Effect of recombinant human keratinocyte growth factor (rHuKGF) on the immunopathogenesis of intestinal graft-vs.-host disease induced without a preconditioning regimen.

We studied the effect of rHuKGF on acute, lethal graft- vs.-host disease (GVHD) in the C57BL/6-->(C57BL/6 X DBA/2)F(1)-hybrid model. rHuKGF-treated recipients did not develop intestinal GVHD despite elevated levels of intestinal NO and TNF alpha, did not develop endotoxemia, and did not die. LPS augmented serum TNF alpha release and intestinal NO production, but did not induce intestinal epithelial cell apoptosis, a phenomenon associated with acute GVHD. These data suggest that KGF prevents the development of acute lethal GVHD by protecting epithelial cell injury mediated by TNF-alpha, NO, and other potential cytotoxic factors. We noted a moderate reduction in intestinal KGFR mRNA expression in untreated GVH mice on day 8, when IFN-gamma mRNA levels were highest. This reduction in KGFR mRNA levels was not seen in recipients of IFN-gamma gene knockout grafts, suggesting that IFN-gamma may be involved in reducing KGFR mRNA expression in the intestine. A similar reduction in intestinal KGFR mRNA expression was also seen in rHuKGF-treated recipients, suggesting that rHuKGF does not mediate its protective effect by maintaining KGFR at control levels. KGF-treatment also redirected the cytokine response in acute GVH mice from Th1 to a mixed pattern of both Th1 and Th2 cytokines. This was associated with histopathologic changes resembling chronic GVHD.

The role of interferon-gamma, nitric oxide and lipopolysaccharide in intestinal graft-versus-host disease developing in F1-hybrid mice.

(C57BL/6 x DBA/2)F1-hybrid mice injected with lymphoid cells from wild-type, C57BL/6 donors develop acute, lethal graft-versus-host disease (GVHD) in which the intestine is a major target. In its destructive phase intestinal GVHD is characterized by apoptosis of intestinal crypt epithelial cells and the development of endotoxaemia. Injection of as little as 10 microg endotoxin is lethal in mice with acute GVHD, and associated with the release of large amounts of tumour necrosis factor-alpha (TNF-alpha) into the serum. To explore the role of interferon-gamma (IFN-gamma) in the pathogenesis of intestinal GVHD we used IFN-gamma gene knockout (gko) mice as donors. Recipients of grafts from these donors did not develop intestinal GVHD and, unlike recipients of wild-type grafts, did not die when injected with lipopolysaccharide (LPS). We also found that injection 10 microg LPS into recipients of wild-type grafts induced apoptosis of intestinal epithelial crypt cells and was associated with a burst of nitric oxide production in the intestine. Administration of N(omega)nitro L-arginine methyl ester blocked this response. In contrast, LPS did not induce either intestinal epithelial cell apoptosis or increased nitric oxide production in recipients of IFN-gamma gko grafts. These findings indicate that donor-derived IFN-gamma is instrumental for the development of intestinal GVHD. In a previous study we showed that recipients of IFN-gamma gko grafts develop high levels of LPS-induced TNF-alpha release. When our current data are viewed in the context of this observation, they suggest that intestinal epithelial cell apoptosis in the parent-->F1-hybrid model of acute GVHD is mediated primarily by nitric oxide rather than TNF-alpha, and that this depends on donor-derived IFN-gamma.

Arrest of B16 melanoma cells in the mouse pulmonary microcirculation induces endothelial nitric oxide synthase-dependent nitric oxide release that is cytotoxic to the tumor cells.

Metastatic cancer cells seed the lung via blood vessels. Because endothelial cells generate nitric oxide (NO) in response to shear stress, we postulated that the arrest of cancer cells in the pulmonary microcirculation causes the release of NO in the lung. After intravenous injection of B16F1 melanoma cells, pulmonary NO increased sevenfold throughout 20 minutes and approached basal levels by 4 hours. NO induction was blocked by N(G)-nitro-L-arginine methyl ester (L-NAME) and was not observed in endothelial nitric oxide synthase (eNOS)-deficient mice. NO production, visualized ex vivo with the fluorescent NO probe diaminofluorescein diacetate, increased rapidly at the site of tumor cell arrest, and continued to increase throughout 20 minutes. Arrested tumor cells underwent apoptosis with apoptotic counts more than threefold over baseline at 8 and 48 hours. Neither the NO signals nor increased apoptosis were seen in eNOS knockout mice or mice pretreated with L-NAME. At 48 hours, 83% of the arrested cells had cleared from the lungs of wild-type mice but only approximately 55% of the cells cleared from eNOS-deficient or L-NAME pretreated mice. eNOS knockout and L-NAME-treated mice had twofold to fivefold more metastases than wild-type mice, measured by the number of surface nodules or by histomorphometry. We conclude that tumor cell arrest in the pulmonary microcirculation induces eNOS-dependent NO release by the endothelium adjacent to the arrested tumor cells and that NO is one factor that causes tumor cell apoptosis, clearance from the lung, and inhibition of metastasis.