Abstract
Background. Human and murine studies suggest protein-calorie malnutrition (PCM) results in significant
host immunosuppression resulting in increased morbidity and mortality. Apoptosis has
been implicated as an important mediator in the immunosuppression observed in several
disease states. This study was designed to characterize macrophage apoptosis in a
murine model of PCM and investigate components that regulate the apoptotic process,
such as protein kinase C (PKC) and Bcl-2 activity. Methods. Swiss-Webster mice (n = 50) were randomly assigned to receive either a control (24%
protein) or a PCM diet (0% protein) for 7 days. Peritoneal macrophages were harvested
and detection of apoptosis was performed by terminal deoxy-transferase-mediated deoxyuridine
triphosphate (dUTP) nick-end labeling (TUNEL) and propidium iodide DNA staining under
baseline and pro-apoptotic conditions. Pro-apoptotic conditions included cells treated
with tumor necrosis factor-α (TNF-α) (10 ng/mL), interferon-γ (IFN-γ) (50 μ/mL), and
a combination of both agents. In addition, levels of PKC activity and expression of
Bcl-2 and p53 protein were measured. Results. Peritoneal macrophages from PCM mice had a significantly greater amount of apoptosis
at baseline and under stimulated conditions compared with controls. Levels of PCM
apoptosis were elevated at baseline by TUNEL staining compared with macrophages from
the control group (16.5% ± 1.4%, versus 4.5% ± 1.1%, P <.01). In addition, peritoneal macrophages from the malnourished animals were significantly
more susceptible to the apoptotic effect of TNF-α and the effects of INF-γ (27.3%
± 2.1% and 31% ± 1.4%) compared with control mice (5.5% ± 0.7% and 7.2% ± 0.5%, P <.01), respectively. Again, an increase in the baseline apoptosis rate was demonstrated
in peritoneal macrophages from PCM mice compared with control fed mice (13.2% ± 4.4%
versus 4.3% ± 3.1%, P <.01) as measured by propidium iodide staining. The combination of agents, TNF-α
and INF-γ, resulted in an additive apoptotic effect in the malnourished host compared
with the control animals (43.4% ± 4.7% versus 10.5% ± 2.2%, P <.01), respectively. Furthermore, there was a significant decrease in the mean total
PKC activity in the malnourished macrophages compared with results in controls (110,000
± 8000 versus 60,000 ± 4000 cpm, P <.01). Similar changes were also observed in PKC cytosolic and membrane activity
between both groups. In addition, Bcl-2 protein expression was significantly decreased
in PCM animals compared with control animals. Conclusions. Thus, peritoneal macrophages from PCM mice exhibit significantly greater levels of
apoptosis at baseline and when stimulated with pro-apoptotic agents compared with
controls. The propensity of macrophages from PCM mice to undergo apoptosis may be
attributable in part to decreased PKC activity and Bcl-2 protein expression. These
findings may help to explain the associated immune dysfunction observed in malnutrition.
(Surgery 2001;129:617-25.)
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Article info
Publication history
Accepted:
November 12,
2000
Footnotes
*Supported in part by grant R01DK43700-05A1 (JMD) and the Surgical Oncology Training Fellowship CA68971 (DER) from the National Institutes of Health.
**Reprint requests: John M. Daly, MD, Lewis Atterbury Stimson Professor and Chairman, Department of Surgery, New York Presbyterian Hospital-Cornell Campus and Weill Medical College of Cornell University, 525 E 68th St- F-739, New York, NY 10021.
*Surgery 2001;129:617-25.
Identification
Copyright
© 2001 Mosby, Inc. Published by Elsevier Inc. All rights reserved.
