Differential effects of nordihydroguaiaretic acid (NDGA) on b-cell subsets: Reversal of NDGA-induced antibody suppression by cyclic GMP is subset specific

Abstract

Nordihydroguaiaretic acid (4,4′-[2,3-dimethyl tetramethylene]-dipyrocatechol) (NDGA), a reportedly specific lipoxygenase inhibitor, suppressed the in vitro murine plaque-forming cell (PFC) response to a thymus-dependent (TD) antigen, and the two subclasses of thymus-independent (TI) antigens, TI1 and TI2, at a final concentration of 33 μM. Suppression kinetics were inconsistent with those observed in previous experiments for other lipoxygenase inhibitors, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), in that BHA and BHT exert suppression early in the 5-day PFC culture system, whereas NDGA suppressed through the 96th h of the 120 h culture period. The sulfhydryl-protective agent 2-mercaptoethanol (2ME) protected both the TD and TI responses. Dibutyryl cyclic GMP (dbcGMP) failed to restore NDGA-suppressed TD and TI1 PFC responses but restored the TI2 response when added at 0-, 24-, 48-, 72-, and 96-h at concentrations of 1–2 mM. NDGA inhibited lipopolysaccharide- (LPS-) induced increases in murine splenocyte cyclic GMP (cGMP) levels, and dbcGMP failed to accelerate the onset of the TI2 PFC response appreciably. The results of these and other laboratory studies indicated that NDGA may not be a specific inhibitor of lipoxygenase. Furthermore, the B-cell subset responding to TI2 antigens may be separated from the TD- and TI1-responding subsets because of the ability of dbcGMP to restore NDGA-suppressed TI2 responses but not the TD or TI1 response. The results suggest a fundamental difference in the biochemical pathways of B-cell subsets, and that cGMP metabolism in some cells may be linked to specific protein synthesis.