Activated peritoneal macrophages inhibit the proliferation of rat ascites hepatoma AH-130 cells via the production of tumor necrosis factor-α and nitric oxide

Objective: To study the effect of peritoneal macrophages on tumor cell proliferation, we cultured ascites hepatoma AH-130 cells with unstimulated, or lipopolysaccharide (LPS)- or interleukin (IL)-2-stimulated rat peritoneal macrophages, and examined the proliferation of AH-130 cells.¶Materials and Methods: Rat peritoneal macrophages isolated from male Wistar rats were co-cultured with AH-130 cells in the absence or presence of LPS or IL-2. After incubation, proliferation of AH-130 cells was analyzed using flow cytometry. In addition, the levels of tumor necrosis factor (TNF)-α and nitric oxide (NOx, nitrate + nitrite) in the culture supernatants were measured. Furthermore, anti-TNF-α antibody (10 μg/ml) and nitric oxide synthase inhibitor, NG-monomethyl-L-arginine (L-NMMA, 100 μM) were added to the co-culture, and their effect on AH-130 cell proliferation was examined.¶Results: When AH-130 cells were co-cultured with unstimulated peritoneal macrophages, proliferation of AH-130 cells was not affected. In contrast, when AH-130 cells were co-cultured with peritoneal macrophages in the presence of LPS (0.1-20 μg/ml) or IL-2 (1-200 U/ml), proliferation of AH-130 cells was dose-dependently suppressed by LPS or IL-2. Moreover, LPS- or IL-2-stimulation increased the levels of TNF-α and NOx in the supernatants of AH-130 cell and macrophage co-culture, although LPS and IL-2 did not induce TNF-α and NOx production by AH-130 cells incubated without macrophages. Interestingly, anti-TNF-α antibody and L-NMMA significantly inhibited the suppression of AH-130 cell proliferation by LPS- or IL-2-stimulated macrophages (p<0.05). Furthermore, exogenously added recombinant rat TNF-α (0.26-1300 ng/ml) or NO donor (GSNO, S-nitroso-L-glutathione) (0.1-10 mM) dose-dependently suppressed the proliferation of AH-130 cells in the absence of macrophages.¶Conclusion: Together these observations suggest that when peritoneal macrophages are activated by LPS and IL-2, they suppress the proliferation of ascites hepatoma AH-130 cells via the production of TNF-α and nitric oxide.¶