Yoichi Itakura

Immunomodulatory Effects of Aged Garlic Extract

Using various kinds of models, we examined the effects of aged garlic extract (AGE) on immune functions. In the immunoglobulin (Ig)E-mediated allergic mouse model, AGE significantly decreased the antigen-specific ear swelling induced by picryl chloride ointment to the ear and intravenous administration of antitrinitrophenyl antibody. In the transplanted carcinoma cell model, AGE significantly inhibited the growth of Sarcoma-180 (allogenic) and LL/2 lung carcinoma (syngenic) cells transplanted into mice. Concomitantly, increases in natural killer (NK) and killer activities of spleen cells were observed in Sarcoma-180--bearing mice administered AGE. In the psychological stress model, AGE significantly prevented the decrease in spleen weight and restored the reduction of anti-SRBC hemolytic plaque-forming cells caused by the electrical stress. These studies strongly suggest that AGE could be a promising candidate as an immune modifier, which maintains the homeostasis of immune functions; further studies are warranted to determine when it is most beneficial.

Scavenging Effect of Aged Garlic Extract and its Constituents on Active Oxygen Species

The effect of aged garlic extract (AGE) and its major organosulphur constituents, S‐allylcysteine (SAC), S‐allylmercaptocysteine (SAMC) and alliin on active oxygen species were examined in an in vitro system. AGE and three compounds have demonstrated a scavenging effect on hydrogen peroxide, and also inhibited the chain oxidation induced by a hydrophilic radical initiator.

Antioxidant effects of fructosyl arginine, a Maillard reaction product in aged garlic extract.

The amino-carbonyl (Maillard) reaction of amino acids with sugars is a nonenzymatic browning reaction that takes place during the processing, cooking, and storage of foods. Maillard reaction products (MRPs) have been shown to possess interesting chemical and biological properties including antimutagenic and antioxidant activity. In this study, we determined the antioxidant effects of fructosyl arginine (Fru-Arg), a MRP in aged garlic extract. Low density lipoprotein (LDL) was incubated with Cu(2+) at 37 degrees C and 5% CO(2) for 24 hours, which resulted in an increase of thiobarbituric acid reactive substances (TBARS) indicating lipid peroxidation. Coincubation of Cu(2+) with Fru-Arg and LDL resulted in a significant inhibition of TBARS formation. Pulmonary artery endothelial cells (PAEC) were exposed to 0.1 mg/mL oxidized LDL (Ox-LDL) at 37 degrees C and 5% CO(2) for 24 hours. Lactate dehydrogenase (LDH) release, as an index of cell membrane damage, and TBARS were measured. Ox-LDL caused an increase of LDH release and TBARS formation. Pretreatment of PAEC with Fru-Arg inhibited these changes. Murine macrophages were incubated with Ox-LDL, and the release of peroxides was measured using a fluorometric assay. Ox-LDL caused an increased release of peroxides. Coincubation of macrophages with Fru-Arg and Ox-LDL inhibited the release of peroxides dose-dependently. In a cell free system, Fru-Arg was shown to scavenge hydrogen peroxide. These data suggest that Fru-Arg is a potent antioxidant, and thus may be useful for the prevention of atherosclerosis and other disorders associated with oxidative stress.

Immunomodulation and antitumor activities of Aged Garlic Extract.

We found that Aged Garlic Extract (AGE) could be a significant immuno-potentiator, and could exhibit anti-tumor activities through immune modulation. Consequently, AGE stimulated the proliferation of mouse spleen cells and the release of cytokines, such as IL-2, TNF-alpha and IFN-gamma, increased NK activities, and enhanced phagocytosis of peritoneal macrophages. AGE treatment also stimulated the reactivity of lymphocytes in response to cytokines or mitogens. AGE was far superior to PSK in IL-2 induction, but slightly inferior to PSK in nitric oxide induction. AGE, as effectively as PSK (Krestin), significantly inhibited the growth of Sarcoma-180 (allogenic) and LL/2 lung carcinoma (syngenic) cells transplanted into mice. Concomitantly, increases in NK and killer activities of spleen cells were observed in Sarcoma-180 bearing mice treated with AGE. These results strongly suggest that AGE is as effective as PSK, and could serve as a potent biological response modifier on NK cells and T lymphocytes, and subsequently inhibit the growth of transplanted tumors.

Prevention of psychological stress-induced immune suppression by aged garlic extract

We determined the effect of Aged Garlic Extract (AGE) on damage caused to immune function by a psychological stress using a communication box. After four days of a psychological stress, a decrease in spleen weight and spleen cells was observed in the psychological stress-exposed mice as compared normal mice (non-stress). AGE significantly prevented the decreases in spleen weight and cells. Additionally, AGE significantly prevented the reduction of hemolytic plaque-forming-cells in spleen cells and anti-SRBC antibody titer in serum caused by this psychological stress. Moreover, a reduction in NK activities was observed in the psychological stress-exposed mice as compared with normal mice (non-stress), whereas NK activities in the AGE administered mice were almost the same as normal mice (non-stress). These results indicate that psychological stress qualitatively and quantitatively impairs immune function, and that AGE is extremely useful for preventing psychologically-induced damage.

Anti-allergic effects of aged garlic extract.

To examine the effect of Aged Garlic Extract (AGE) on the function of mast cells and activated T lymphocytes, we adopted the in vitro histamine release system, the in vivo IgE mediated skin reaction system and the in vivo late phase reaction system. Consequently, at 1.25, 2.5, and 5.0% (v/v), AGE dose-dependantly inhibited the antigen specific histamine release by mouse anti-TNP monoclonal antibody and TNP-BSA hapten carrier complex against rat basophil cell line RBL-2H3 by 50, 80, and 90 percent, respectively. In the IgE mediated skin reaction system, repeated or single intragastric administration of AGE (10 ml/kg), decreased by 25-45% the antigen specific ear swelling which was induced by a picryl chloride ointment applied to the ear of mice also given an intravenous administration of anti-TNP antibody IgE ascites. In the late phase reaction system, repeated or single intragastric administration of AGE (10 ml/kg) suppressed by 45-55% the antigen specific ear swelling induced by a secondary challenge to the ear of mice given a picryl chloride ointment seven days prior. These results suggest that AGE application could modify, directly or indirectly, the function of mast cells, basophils and activated T lymphocytes which play a leading role in allergic cascade reactions including inflammation.

Effect of garlic and garlic preparations on physiological and psychological stress in mice

The effect of several kinds of garlic preparations such as raw garlic juice (RGJ), heated garlic juice (HGJ), processed garlic powder (PGP) and aged garlic extract (AGE) on both physiological and psychological stress were investigated using four stress models in mice: forced swimming test, mechanical treadmill running, immobilization stress test, and a cooling rewarming test. RGJ was shown to be effective only at a low dose in the forced swimming test, whereas the effect was reduced at a high dosage. HGJ and PGP demonstrated no antistress effects. In contrast, AGE was shown to be effective in all of the stress tests.