TY - JOUR
T1 - Are free radicals involved in tumor promotion?
AU - Kozumbo, W. J.
AU - Trush, M. A.
AU - Kensler, T. W.
N1 - Funding Information:
Previously it was shown that lipophilic analogs of a free-radical scavenger, 2(3)-tert-butyl-4-hydroxyanisole (BHA), inhibit ornithine decarboxylase (ODC) activity which is induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in mouse epidermis. With regard to this antitumor-promoting effect, eight analogs of BHA (2-and 3-BHA, 2-t-butyl-I, 4-dimethoxybenzene methyl-BHA), t-butylhydroquinone (t-BHQ), p-hydroquinone (HQ), 4-hydroxyanisole, phenol and 2-t-butylphenol) are evaluated herein for their antioxidant capacities for scavenging superoxide anions (O~), of inhibiting lipid peroxidation and of inhibiting chemiluminescence (CL) in TPA-activated polymorphonuclear leukocytes (PMNs), an event associated with oxy-radical production. None of the analogs reacted with O~, while 2-and 3-BHA suppressed the formation of O~ by TPA-activated PMNs. T-BHQ underwent autoxidation in aqueous solution, reducing molecular oxygen and increasing the levels of O~ that were formed chemically, enzymatically and cellularly. However, all of the phenolic antioxidant analogs of BHA inhibited TPA-stimulated CL in PMNs and ascorbate-initiated lipid peroxidation, while methyl-BHA (a non-antioxidant analog) was inactive. The inhibitory activities of these analogs for lipid peroxidation were related to both their lipophilic and antioxidant properties and corresponded favorably with their inhibitory activities for TPA-induced ODC activities in mouse epidermis. On the other *Financial support was provided by NIH Grants ES00454 and CA 36380 and American Cancer Society Grant SIG-3. **To whom correspondence should be sent at: Swiss Institute for Experimental Cancer Research, CH-1066 Epalinges s/Lausanne, Switzerland. Abbreviations: 2(3)-BHA, 2(3)-tert-butyl-4-hydroxyanisole; methyl-BHA, 2-t-butyl-l,4-dimethoxybenzene; t-BHQ, t-butylhydroquinone; CL, chemiluminescence; CuDIPS, Cu(II)(3,5-diisopropylsalicylic acid)2; HQ, p-hydroquinone; ICs0, 50% inhibition; NBT, nitroblue tetrazolium; ODC, ornithine decarboxylase; PMN, polymorphonuclear leukocytes; TPA, 12-O-tetradecanoylphorbol-13-acetate.
PY - 1985
Y1 - 1985
N2 - Previously it was shown that lipophilic analogs of a free-radical scavenger, 2(3)-tert-butyl-4-hydroxyanisole (BHA), inhibit ornithine decarboxylase (ODC) activity which is induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in mouse epidermis. With regard to this antitumor-promoting effect, eight analogs of BHA (2- and 3-BHA, 2-t-butyl-1, 4-dimethoxybenzene methyl-BHA), t-butylhydroquinone (t-BHQ), p-hydroquinone (HQ), 4-hydroxyanisole, phenol and 2-t-butylphenol) are evaluated herein for their antioxidant capacities for scavenging superoxide anions (O2-, of inhibiting lipid peroxidation and of inhibiting chemiluminescence (CL) in TPA-activated polymorphonuclear leukocytes (PMNs), an event associated with oxy-radical production. None of the analogs reacted with O2-, while 2- and 3-BHA suppressed the formation of O2- by TPA-activated PMNs. T-BHQ underwent autoxidation in aqueous solution, reducing molecular oxygen and increasing the levels of O2- that were formed chemically, enzymatically and cellularly. However, all of the phenolic antioxidant analogs of BHA inhibited TPA-stimulated CL in PMNs and ascorbate-initiated lipid peroxidation, while methyl-BHA (a non-antioxidant analog) was inactive. The inhibitory activities of these analogs for lipid peroxidation were related to both their lipophilic and antioxidant properties and corresponded favorably with their inhibitory activities for TPA-induced ODC activities in mouse epidermis. On the other hand, inhibition of the CL response by these antioxidants was independent of their lipophilicity and compared less favorably with their capacities to antagonize phorbol ester-induced ODC activity. These results imply that lipophilic BHA analogs inhibit TPA-induced ODC activity by scavenging free radicals other than O2-. Furthermore, the fact that t-BHQ was the most potent inhibitor of CL, lipid peroxidation and ODC activity and simultaneously reduced molecular oxygen, suggests the possibility that O2- may act as a precursor to the formation of free radicals which are reactive with t-BHQ and more directly involved in the process of tumor promotion.
AB - Previously it was shown that lipophilic analogs of a free-radical scavenger, 2(3)-tert-butyl-4-hydroxyanisole (BHA), inhibit ornithine decarboxylase (ODC) activity which is induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in mouse epidermis. With regard to this antitumor-promoting effect, eight analogs of BHA (2- and 3-BHA, 2-t-butyl-1, 4-dimethoxybenzene methyl-BHA), t-butylhydroquinone (t-BHQ), p-hydroquinone (HQ), 4-hydroxyanisole, phenol and 2-t-butylphenol) are evaluated herein for their antioxidant capacities for scavenging superoxide anions (O2-, of inhibiting lipid peroxidation and of inhibiting chemiluminescence (CL) in TPA-activated polymorphonuclear leukocytes (PMNs), an event associated with oxy-radical production. None of the analogs reacted with O2-, while 2- and 3-BHA suppressed the formation of O2- by TPA-activated PMNs. T-BHQ underwent autoxidation in aqueous solution, reducing molecular oxygen and increasing the levels of O2- that were formed chemically, enzymatically and cellularly. However, all of the phenolic antioxidant analogs of BHA inhibited TPA-stimulated CL in PMNs and ascorbate-initiated lipid peroxidation, while methyl-BHA (a non-antioxidant analog) was inactive. The inhibitory activities of these analogs for lipid peroxidation were related to both their lipophilic and antioxidant properties and corresponded favorably with their inhibitory activities for TPA-induced ODC activities in mouse epidermis. On the other hand, inhibition of the CL response by these antioxidants was independent of their lipophilicity and compared less favorably with their capacities to antagonize phorbol ester-induced ODC activity. These results imply that lipophilic BHA analogs inhibit TPA-induced ODC activity by scavenging free radicals other than O2-. Furthermore, the fact that t-BHQ was the most potent inhibitor of CL, lipid peroxidation and ODC activity and simultaneously reduced molecular oxygen, suggests the possibility that O2- may act as a precursor to the formation of free radicals which are reactive with t-BHQ and more directly involved in the process of tumor promotion.
KW - Butylated hydroxyanisole
KW - Chemiluminescence
KW - Free radicals
KW - Lipid peroxidation
KW - Superoxide
KW - Tumor promotion
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U2 - 10.1016/S0009-2797(85)80163-0
DO - 10.1016/S0009-2797(85)80163-0
M3 - Article
C2 - 2992824
AN - SCOPUS:0021887981
SN - 0009-2797
VL - 54
SP - 199
EP - 207
JO - Chemico-Biological Interactions
JF - Chemico-Biological Interactions
IS - C
ER -