Cytostasis is required for IL-1 induced nitric oxide production in transformed hamster fibroblasts.
Interleukin-1 (IL-1) is known to inhibit proliferation in some tumor cells. This proinflammatory cytokine also induces nitric oxide production in a variety of cell types. In the present studies we determined if nitric oxide is involved in IL-1 induced growth inhibition in spontaneously transformed hamster embryonic fibroblasts (STHE cells). Both IL-1 alpha and IL-1 beta were found to stimulate nitric oxide production and to reduce 3H-thymidine (TdR) incorporation in high density cultures of STHE cells. However, maximal cytostasis was observed at least 24 h before significant amounts of nitric oxide accumulated in the cultures. In addition, doses of IL-1 which were too low to stimulate nitric oxide synthesis were effective in inducing cytostasis. Furthermore, in low density cultures of STHE cells, IL-1 inhibited DNA synthesis without inducing nitric oxide production. The nitric oxide synthase inhibitor NG-monomethyl-1-arginine (L-NMMA) had no effect on proliferation of cells plated at low density. In contrast, L-NMMA treatment resulted in a 40-60% reduction in IL-1 induced cytostasis in high density cultures. Neutralizing antibodies to IL-1 were found to completely block IL-1 induced cytostasis and nitric oxide production in cells plated at both densities. Although anti-IL-1 alpha and anti-IL-1 beta antibodies were highly specific and did not cross react, anti-tumor necrosis factor-alpha (TNF-alpha) antibody was able to partially suppress activation of STHE cells by both IL-1 alpha and IL-1 beta. These data suggest a potential involvement of endogenous TNF-alpha in IL-1 induced cytostasis and nitric oxide production. Exponentially growing STHE cells produced six-times less nitric oxide than non-proliferating cells. A ten-fold excess of 1-arginine was found to stimulate nitric oxide synthesis, an action that was independent of the rate of cellular proliferation. Taken together these data suggest that nitric oxide is not a major mediator of IL-1 induced cytostasis in STHE cells. Moreover, cytostasis appears to be required for nitric oxide synthesis in these cells.
Lavnikova
N
N
Rutgers University, Piscataway, New Jersey 08855-0789, USA.
Lakhotia
A
A
Patel
N
N
Prokhorova
S
S
Laskin
D L
DL
D000818:Animals; D001120:Arginine / Q000378:metabolism; D002455:Cell Division; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D002478:Cells, Cultured; D006224:Cricetinae; D016207:Cytokines / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D006131:Growth Inhibitors / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology*; D008647:Mesocricetus; D009569:Nitric Oxide / Q000096:biosynthesis*; D019323:omega-N-Methylarginine / Q000494:pharmacology
D016207:Cytokines; D006131:Growth Inhibitors; D007375:Interleukin-1; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D007213:Indomethacin