Modulation of adherence and chemotaxis of macrophages by norepinephrine. Influence of ageing

We evaluated the in vitro effect of norepinephrine (NE), over the range of concentrations between 10(-12) M and 10(-3) M, on adherence (to plastic surfaces) and chemotaxis (in a Boyden chamber) of peritoneal macrophages from BALB/c mice of different ages: young (12 weeks), adult (22 weeks), mature (48 weeks) and old (72 weeks). Increased adherence was induced by 10(-12) M of NE in macrophages from young, adult, mature and old mice. Also, 10(-9) M stimulated adherence in old animals, 10(-5) M in mature mice, and 10(-3) M in both young and old mices. With respect to chemotaxis, the low concentration of NE (10(-12) M) was stimulatory only in young and adult animals, higher concentrations (10(-5) M and 10(-7) M) were inhibitory for macrophages from mature and old animals, and the highest concentration of NE (10(-3) M) stimulated this capacity of macrophages only in young and mature animals. The conclusion is that while the mobility of macrophages to the focus of infection (i.e. chemotaxis) is stimulated by low concentrations of NE (10(-12), M) only in young-adult animals, this neurotransmitter induces a decline in this capacity in mature and old mice at high concentrations (10(-5) M - 10(-7) M). Also, macrophages from old animals have lost the capacity to respond to pharmacological (10(-3) M) concentrations of NE. The lower capacity of response to NE by macrophages from old animals possibly contributes to immunosenescence.