Presence of a mobilizable intracellular pool of hepatocyte growth factor in human polymorphonuclear neutrophils.

Hepatocyte growth factor (HGF), a heparin-binding factor, is synthesized as a single-chain inactive precursor (pro-HGF), which is converted by proteolysis to an active heterodimer (mature HGF). HGF has pleiotropic activities and has been implicated in the regulation of mitogenesis, motogenesis, and morphogenesis of epithelial and endothelial cells. As polymorphonuclear neutrophils (PMNs) secrete numerous cytokines involved in the modulation of local inflammation, we investigated their ability to produce HGF. We found that HGF was stored in secretory vesicles and in gelatinase/specific granules. This intracellular stock was rapidly mobilized by degranulation when neutrophils were stimulated with phorbol myristate acetate or N-formylmethionyl-leucyl-phenylalanine. Cycloheximide did not affect the release of HGF. Moreover, HGF messenger RNA and protein expression was found in bone marrow myeloid cells, suggesting that HGF synthesis likely occurs during PMN maturation. In mature circulating PMNs, intracellular HGF was in the pro-HGF form, whereas the HGF secreted by degranulation was the mature form. Furthermore, PMNs pretreated with diisopropyl fluorophosphate only released the pro-HGF form, suggesting that PMN-derived serine protease(s) are involved in the proteolytic process. We also obtained evidence that secreted mature HGF binds PMN-derived glycosaminoglycans (probably heparan sulfate). These findings suggest that PMNs infiltrating damaged tissues may modulate local wound healing and repair through the production of HGF, a major mediator of tissue regeneration.

Polymorphonuclear neutrophils are a source of hepatocyte growth factor in patients with severe alcoholic hepatitis.

BACKGROUND/AIMS: Hepatocyte growth factor (HGF) is a pleiotropic cytokine involved in liver regeneration. Plasma HGF levels correlate with survival and hepatocyte proliferation in alcoholic hepatitis (AH). As AH is accompanied by inflammation, neutrophilia and polymorphonuclear neutrophil (PMN) infiltration of the liver, we postulated that PMN could be a source of HGF in such patients. METHODS: We studied 25 patients with severe AH in comparison with 20 alcoholic cirrhotic patients without AH and 20 healthy controls; the impact of a 28-day course of corticosteroids was evaluated in patients with AH. RESULTS: On day 0, HGF plasma and homogenized liver tissue levels were markedly increased in AH patients as compared to controls. The role of PMN in HGF production during AH was confirmed by a significantly higher ex-vivo HGF production capacity of lipopolysaccharide-stimulated blood PMN from AH patients relative to both control groups. Formyl-Methionyl-Leucyl-Phenylalanine-induced PMN release of HGF (degranulation conditions) was also higher in AH patients. In this setting, we found that HGF release by PMN ex vivo correlated strongly with HGF plasma levels, and that the degree of hepatic PMN correlated strongly with hepatic HGF levels. HGF plasma levels and ex-vivo HGF release by PMN were unaffected by steroid therapy. CONCLUSIONS: These findings suggest that, by releasing HGF, PMN could participate in liver regeneration during severe alcoholic hepatitis.

Hepatocyte growth factor is produced by blood and alveolar neutrophils in acute respiratory failure.

We tested the novel hypothesis that neutrophils in the lung or the airspaces may produce hepatocyte growth factor (HGF) in ventilated patients with acute respiratory failure. Neutrophils were purified from blood and bronchoalveolar lavage (BAL) fluid samples from 16 mechanically ventilated patients who underwent BAL for a diagnostic workup of ventilator-acquired pneumonia. Most of the patients had pneumonia (n = 11). Ten nonventilated patients served as controls. Both blood and BAL neutrophils released HGF in vitro. Basal HGF secretion by blood neutrophils from controls was 823 (666) pg x ml(-1) x 10(-7) neutrophils (median, 25th-75th percentile) and doubled to 1,730 (1,684-2,316) pg x ml(-1) x 10(-7) neutrophils (P = 0.001) with lipopolysaccharide (LPS) stimulation. Basal HGF secretion by blood neutrophils from patients was similar [956 (655-2,140) pg x ml(-1) x 10(-7) neutrophils, P = 0.4] and doubled with LPS stimulation [2,767 (2,165-3,688) pg x ml(-1) x 10(-7) neutrophils, P < 0.0001 vs. controls]. Alveolar neutrophils released HGF in vitro [653 (397-1,209) pg x ml(-1) x 10(-7) neutrophils]. LPS stimulation did not significantly increase the HGF release from alveolar neutrophils [762 (434-1,305) pg x ml(-1) x 10(-7) neutrophils]. BAL HGF positively correlated with the BAL neutrophil count (P = 0.01, R = 0.58). We conclude that blood and alveolar neutrophils from patients with acute respiratory failure can produce HGF, a mitogenic factor that may enhance the alveolar repair process.