Nobuyuki Marui

The effect of quercetin on cell cycle progression and growth of human gastric cancer cells

Quercetin, a flavonoid, is found in many plants, including edible fruits and vegetables. We examined the effects on cell growth of human malignant cells derived from the gastrointestinal tract and on cell cycle progression. Quercetin markedly inhibited the growth of human gastric cancer cells and the IC 50 value was 32–55 μM. DNA synthesis was suppressed to 14% of the control level by the treatment with 70 μM quercetin for 2 days. Furthermore, quercetin blocked cell progression from the G1 to the S phase.

Induction of heat shock proteins and their implication in protection against ethanol-induced damage in cultured guinea pig gastric mucosal cells

The induction of heat shock proteins in cultured guinea pig gastric mucosal cells was investigated to assess their role in gastric cytoprotection. In response to sublethal heat stress at 43 degrees C for 1 hour, the cells synthesized a 72-kilodalton protein and increased the synthesis of 74- and 90-kilodalton proteins, which were detected using gel electrophoresis after [35S]methionine labeling of the cells. Immunoblot analysis indicated that the 72- and 74-kilodalton proteins were members of the heat shock protein 70 family. Northern blot analysis showed the induction of a 2.6-kilobase messenger RNA of heat shock protein 70 gene only with heat treatment. Furthermore, with heat treatment, there was significant reduction of damage after ethanol treatment. This reduction was blocked with a protein synthesis inhibitor, cycloheximide, and was associated with inhibition of synthesis of heat shock proteins. These results strongly suggest that synthesis of heat shock proteins plays an important role in the intracellular mechanism of gastric protection against ethanol.

N-myc suppression and cell cycle arrest at G1 phase by prostaglandins

Effects of cyclopentenone prostaglandins, Δ12‐prostaglandin (PG) J2 and PGA2 on the expression of N‐myc in relation to the effects on cell cycle progression were investigated using human neuroblastoma cell line GOTO. Both PGs suppressed M‐myc expression within several hours prior to inducing G1 arrest. The N‐myc suppression with Δ12‐PGJ2 was continued but with PGA2 it was gradually released, followed by the release of G1 arrest. These results suggest that Δ12‐PGJ2 and PGA2 inhibit cell cycle progression in strong association with N‐myc suppression and Δ12‐PGJ2 is more potent and has a longer effect than PGA2.

Δ12-prostaglandin J2 mimics heat shock in inducing cell cycle arrest at G1 phase

Using a human neuroblastoma cell line GOTO, the effects of delta 12-prostaglandin (PG) J2 on the modulation of cell cycle progression and protein synthesis were examined in comparison with those caused by heat shock (HS). delta 12-PGJ2 induced G1 arrest, the peak of which was obtained at 24 h and continued for 72 h. HS was found to induce G1 arrest earlier than delta 12-PGJ2. Furthermore, sequential HS could maintain G1 arrest. delta 12-PGJ2 induced the synthesis of several heat shock proteins (HSPs) in a manner similar to HS. Using immunoblot analysis, HSP72 was detected prior to inducing G1 arrest and accumulated during the subsequent 72h. The content of HSP72 induced by HS also correlated well with the induction, release, and maintenance of G1 arrest. In addition, both delta 12-PGJ2 and HS induced HSP72 mRNA and simultaneously suppressed N-myc mRNA expression. These results suggest that delta 12-PGJ2 and HS regulate cell cycle progression of GOTO cells via similar mechanisms.

Studies on age-related functional changes in regulatory T cells and B cells involved in the autoantibody production of MRL/MpJ − + / + mice

Age-related changes in anti-DNA autoantibody production of MRL/MpJ- +/+ mice were investigated. In lipopolysaccharide (LPS)-stimulated cultures, spleen cells of the mice showed an age-related, marked increase in the ability to produce IgG class of the autoantibody after the age of 12 months, while they showed a tendency to decrease with age in the production of IgM class of the autoantibody. Serum levels of anti-DNA autoantibodies rose markedly in the IgG autoantibody but not in the IgM autoantibody after 12 months of age, which is well consistent with the observation in the LPS-stimulated cultures. T cell-depleted spleen cells, however, showed only a small increase with age in the IgG autoantibody productive ability. These results suggest that the age-associated increase in the IgG autoantibody production in the mice is under T-cell control. Age-associated changes in suppressor capacity in spleen cells of the mice were also investigated. Suppressive activity of the cells stimulated by 2-day incubation with concanavalin A (Con A) showed a clear increase as the donor age advanced, when assayed on the LPS-stimulated anti-DNA autoantibody production in vitro. The results indicate that, in MRL/MpJ-+/+ mice, suppressor capacity does not decline with age and is not related as a cause to the autoantibody production.

Effect of aging on induction of oral tolerance by intragastric administration of sheep red blood cells in mice

Fed SRBC induced oral tolerance in young C3H mice but not in the aged. An injection of SRBC via portal vein did not tolerize C3H mice. Gut associated local immune system seems to play a key role in induction of oral tolerance and the tolerance inducing function declines with aging. Mucosal immune system plays important roles in preventing invasion by viruses, bacteria, and other parasites. Oral injection of live virus generates local and systemic immunity (1). However, fed antigen often induces oral tolerance (2). Systemic immune system in mice shows age-associated resistance to tolerance induction by tolerogen via parenteral route (3). Here, we studied oral tolerance induction by SRBC in the systemic immune system of young and aged mice.