The effect of advanced glycation end-products and aminoguanidine on TNF alpha production by rat peritoneal macrophages

Objective:To evaluate the effect of advanced glycation end-products (AGEs) and the inhibitor of their formation, aminoguanidine, on tumor necrosis fac tor-alpha (TNF alpha) production las a functional marker) by rat peritoneal macrophages (PM Phi). Design: Charles River rats underwent a daily intraperitoneal injection of p eritoneal dialysis solution [(PDS), 4.25 g/dL dextrose; Dialine, Travenol, Ashdod, Israel] for a 2-month period (group E). Another group of rats was s ubjected to the same protocol with the addition of 25 mg/kg aminoguanidine (group A). Three control groups were utilized: (1) rats that were injected daily with aminoguanidine only (group AO), (2) rats that were injected with Dulbecco's phosphate-buffered saline (group D), and (3) rats in which no i ntervention was carried out (group C). After 2 months, PM Phi were isolated from rat peritoneal effluent and their TNF alpha production measured by EL ISA in cell-free culture supernatants, in both the basal state and after 24 -hour stimulation with lipopolysaccharide (LPS). The concentrations of AGEs in peritoneal effluent were assayed and correlated to TNF alpha levels. PM Phi obtained from normal rats were then incubated for 24 hours with (1) th e peritoneal effluent of each of the above respective groups, with or witho ut LPS; (2) increasing concentrations of AGEs (0 - 250 mug/mL); and (3) inc reasing concentrations of aminoguanidine (0 - 7.5 mg/mL), and TNF alpha sec retion again determined. Results: After 2 months of daily intraperitoneal injection of PDS, in the b asal state, TNF alpha production was significantly higher in PM Phi, isolat ed from the peritoneal effluent groups (groups E, A, and AO) compared to co ntrols (group C). Following LPS stimulation, a further increase in TNFa sec retion was seen, with a significantly greater response in group AO versus g roups E, A, and D. Effluent AGEs were markedly elevated only in group E. No correlation was found between TNF alpha secretion by these PM Phi and the concentration of AGEs. On incubation with the respective peritoneal effluen ts (groups E, A, and AO), in both the basal and stimulated state,TNF alpha production by PM Phi, from normal rats was significantly enhanced compared to group C. Incubation with increasing concentrations of AGEs or aminoguani dine resulted in an increase of TNF alpha secretion by these PM Phi. Conclusions: Following intermittent intraperitoneal administration of gluco se-based PDS, rat PM Phi, are chronically activated, as evidenced by increa sed basal TNF alpha secretion. The peritoneal effluent of such treated anim als is capable of stimulating TNF alpha production by normal rat PM Phi. Th ese data suggest that glucose-based PDS acts as a primer of PM Phi, which r etain their ability to further stimulation by LPS. Although, in vitro, AGEs promote TNF alpha secretion by normal rat PM Phi, in vivo, their influence is probably modulated by other factors. Aminoguanidine has a specific indu cing effect on rat PM Phi, independent of glucose-based PDS.