Aging alters the production of iNOS, arginase and cytokines in murine macrophages

W.M.S.C. Tamashiro,E.H. Costa,C.A. Cecílio,D.L. Gabriel,P.U. Simioni

doi:10.1590/s0100-879x2011000700010

Abstract

The limited amount of information on the primary age-related deficiencies in the innate immune system led us to study the production of inducible nitric oxide synthase (iNOS), arginase, and cytokines in macrophages of young (8 weeks old) and old (72 weeks old) female BALB/c mice. We first evaluated iNOS and arginase inducers on peritoneal (PMΦ) and bone marrow-derived (BMMΦ) macrophages of young BALB/c and C57BL/6 mice, and then investigated their effects on macrophages of old mice. Upon stimulation with lipopolysaccharide (LPS), resident and thioglycolate-elicited PMΦ from young mice presented higher iNOS activity than those from old mice (54.4%). However, LPS-stimulated BMMΦ from old mice showed the highest NO levels (50.1%). Identical NO levels were produced by PMΦ and BMMΦ of both young and old mice stimulated with interferon-γ. Arginase activity was higher in resident and elicited PMΦ of young mice stimulated with LPS (48.8 and 32.7%, respectively) and in resident PMΦ stimulated with interleukin (IL)-4 (64%). BMMΦ of old mice, however, showed higher arginase activity after treatment with IL-4 (46.5%). In response to LPS, PMΦ from old mice showed the highest levels of IL-1α (772.3 ± 51.9 pg/mL), whereas, those from young mice produced the highest amounts of tumor necrosis factor (TNF)-α (937.2 ± 132.1 pg/mL). Only TNF-α was expressed in LPS-treated BMMΦ, and cells from old mice showed the highest levels of this cytokine (994.1 ± 49.42 pg/mL). Overall, these results suggest that macrophages from young and old mice respond differently to inflammatory stimuli, depending on the source and maturity of the cell donors.

Highlights

Aging is accompanied by a reduced efficiency of the immune system, compromising the general health of older individuals [1,2,3]
The peritoneal and bone marrow-derived macrophages were cultured for 48 h with LPS, IFN-γ and IL-4, alone or in combination. inducible form of nitric oxide synthase (NOS) (iNOS) activity was measured on the basis of nitrite accumulation in the culture supernatants, and arginase activity was determined by measuring arginine-derived urea in the cell extracts
Arginase activity was already present in the non-stimulated macrophages, since extracts obtained from these cells were able to convert L-arginine to urea (Figure 1, Panels B and D)

Summary

Introduction

Aging is accompanied by a reduced efficiency of the immune system, compromising the general health of older individuals [1,2,3]. Nitric oxide (NO) is a toxic gas produced by the action of the enzyme family nitric oxide synthase (NOS), which converts L-arginine to citrulline and NO [6,7]. Cytokines such as interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α), as well as bacterial lipopolysaccharide (LPS), are responsible for the expression of an inducible form of NOS (iNOS) and the generation of large amounts of NO in neutrophils and macrophages [8,9,10,11,12]. NO reacts with superoxide anion to form peroxynitrite, a potent oxidizing molecule that contributes to tissue injury during inflammatory processes [13]

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Conclusion