Abstract
Background: Malnutrition impairs host immunity, resulting in high mortality and morbidity due to infections. Phosphorylation of protein tyrosine kinase (PTK) is a key step in the signaling of many cellular functions, including immune cell functions. Malnutrition may affect this signaling in response to surgical insults. The aim of this study was to examine the effects of PTK inhibition on mortality in ad libitum and in diet-restricted mice after cecal ligation and puncture (CLP). Moreover, tyrosine phosphorylation of peritoneal cells from these animals was evaluated. Methods: Survival study: Mice (n = 45) received chow, 146 g/kg per day (ad libitum) or 36.5 g/kg per day (diet-restricted), for 7 days. Two hours before CLP, one-half the mice in each group were given a tyrosine kinase inhibitor, AG 556 (3.0 mg/kg i.p.), and the others received vehicle. Survival was observed up to 7 days after CLP. Effects of AG 556 on survival with a lesser degree of malnutrition (chow 73 g/kg per day) were also examined (n = 41). Measurement of tyrosine phosphorylation: mice (n = 20) were assigned to the ad libitum and diet-restricted (chow 36.5 g/kg per day) groups. Peritoneal cells were harvested either before or 2 hours after glycogen injection. Glycogen treatment elicits polymorphonuclear neutrophil influx into the peritoneal cavity. The cells were incubated with or without N-formyl-methionyl-leucyl-phenylalanine (fMLP). Tyrosine phosphorylation in the cells was examined using flow cytometry, laser scanning cytometry, and Western blotting. Results: Diet restriction significantly reduced survival compared with the ad libitum group. AG 556 treatment decreased the survival of ad libitum, but not in diet-restricted mice in both survival experiments. Stimulation of peritoneal cells with fMLP increased tyrosine phosphorylation in the ad libitum group (23% increase before glycogen and 18% after glycogen), but not in the diet-restricted group (-9% before glycogen and 3% after glycogen). Conclusions: Inhibition of tyrosine kinase signaling impairs the ability of a well-nourished host to survive CLP—induced sepsis, while having no effects on survival in diet-restricted mice. Peritoneal cells from diet-restricted animals are unable to increase PTK phosphorylation in response to stimulation, which may be the mechanism underlying impaired host defense during malnutrition. (journal of Parenteral and Enteral Nutrition 25:291-298, 2001)
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