Fish oil alters T-lymphocyte proliferation and macrophage responses in Walker 256 tumor-bearing rats.
OBJECTIVE
We investigated the effect of the dietary ratio of omega-6 to omega-3 polyunsaturated fatty acids (PUFAs) from postweaning until adulthood on T-lymphocyte proliferation, T-lymphocyte subpopulations (helper and cytotoxic), and production of cytotoxic mediators by macrophages in tumor-bearing rodents.


METHODS
Weanling male Wistar rats received a normal low-fat (40 g/kg of diet) chow diet or a high-fat (300 g /kg) diet that included fish or sunflower oil or blends of fish and sunflower oils to yield omega-6:omega-3 PUFA ratios of approximately 6:1, 30:1, and 60:1 ad libitum. After 8 wk, 50% of rats in each group were inoculated with 1 mL of 2 x 10(7) Walker 256 cells. Fourteen days after tumor inoculation, animals were killed and lymphocytes and macrophages were obtained for study.


RESULTS
The diets richest in omega-6 PUFA resulted in higher proliferation of thymus, spleen, and gut-associated lymphocytes compared with the chow diet irrespective of tumor burden. In contrast, the fish oil diet resulted in lower proliferation of thymus and spleen lymphocytes compared with the chow diet. Diets rich in omega-6 PUFA decreased the proportion of CD8+ lymphocytes. In non-tumor-bearing and tumor-bearing rats, hydrogen peroxide production by macrophages was highest in rats that consumed diets high in omega-3 PUFAs. Superoxide and nitric oxide production were little affected by the dietary ratio of omega-6 to omega-3 PUFAs.


CONCLUSIONS
Dietary omega-6 and omega-3 PUFA contents alter immune function in non-tumor-bearing and tumor-bearing rats. The omega-3 PUFAs decreased T-cell proliferation but increased hydrogen peroxide production compared with omega-6 PUFAs. Decreased tumor growth and cachexia and increased survival previously reported for fish oil in Walker 256 tumor-bearing rats may be related to improved macrophage function rather than to improved T-cell function.
Department of Physiology, Federal University of Paraná, Paraná, Brazil.
Nathalia
N
Pizato
Sandro
S
Bonatto
Maressa
M
Piconcelli
Lauro M
LM
de Souza
Guilherme L
GL
Sassaki
Katya
K
Naliwaiko
Everson A
EA
Nunes
Rui
R
Curi
Philip C
PC
Calder
Luiz Claudio
LC
Fernandes
D000818:Animals; D002279:Carcinoma 256, Walker / Q000276:immunology / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D015525:Fatty Acids, Omega-3 / Q000008:administration & dosage / Q000494:pharmacology*; D043371:Fatty Acids, Omega-6 / Q000008:administration & dosage / Q000494:pharmacology*; D005395:Fish Oils / Q000008:administration & dosage / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism; D008213:Lymphocyte Activation; D008264:Macrophages / Q000187:drug effects / Q000276:immunology*; D008297:Male; D010938:Plant Oils / Q000008:administration & dosage / Q000494:pharmacology; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D000074242:Sunflower Oil; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*
D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D005395:Fish Oils; D010938:Plant Oils; D000074242:Sunflower Oil; D006861:Hydrogen Peroxide