RESUMEN
<p><b>OBJECTIVE</b>To explore the effects of the exogenous and endogenous reactive nitrogen metabolites (RNM) as NK cell inhibitors on NK cell-mediated killing of K562 cells and the influence of Tiopronin (TIP), glutamylcysteinylglycine (GSH) and histamine dihydrochloride (DHT) as RNM scavengers on reversing the suppressing effect of RNM.</p><p><b>METHODS</b>The exogenous ONOO(-) was administered in the NK+K562 culture system, then the RNM scavengers were added in the NK+K562+ONOO(-) culture system, respectively. The concentrations of RNM, TNF-beta and IFN-gamma, K562 cell inhibition rate (KIR) and the percentage of living NK cells were examined. IL-2+PHA were used as monocyte (MO) activators in the culture system of MO+NK+K562. Then TIP, GSH and DHT were administered and the parameters of NK cell activity were analyzed.</p><p><b>RESULTS</b>After exogenous ONOO(-) was administered in NK+K562 culture system, the percentage of living NK cells was decreased from (93.17 +/- 2.57)% to (71.87 +/- 1.02)% (P < 0.01) and KIR was decreased from (67.47 +/- 2.64)% to (43.44 +/- 2.87)% (P < 0.01). When TIP, GSH and DHT were administered into the systems, the percentage of living NK cells was increased to (91.13 +/- 3.67)% (P < 0.05), (88.03 +/- 1.46)% (P < 0.05), (73.60 +/- 2.76)% (P > 0.05), respectively; KIR was increased to (61.58 +/- 1.89)% (P < 0.05), (60.68 +/- 2.07)% (P < 0.05) and (45.26 +/- 3.31)% (P > 0.05), respectively. When IL-2/PHA were administered in the NK+K562+MO culture system, RNM products was increased from (82.10 +/- 6.60) micromom/L to (193.65 +/- 5.95) micromom/L(P < 0.01);KIR was decreased from (90.64 +/- 3.06)% to (61.29 +/- 2.22)% (P < 0.01). When the TIP, GSH and DHT were administered in the systems, RNM products were decreased to (91.32 +/- 6.81) micromom/L (P < 0.05), (84.66 +/- 5.99) micromom/L (P < 0.05) and (188.92 +/- 5.00) micromom/L (P > 0.05), respectively; KIR was increased to (84.31 +/- 4.56)%(P < 0.05), (81.65 +/- 3.09)% (P < 0.05) and (72.20 +/- 4.10)% (P < 0.05), respectively.</p><p><b>CONCLUSION</b>NK Cell-mediated killing of K562 cells can be suppressed by exogenous and endogenous RNM administration. Both of TIP and GSH can protect NK cells by scavenging RNM and enhance the antineoplasmic activity of NK cells.</p>