Protective Effects Of Fisetin Against Listeria Monocytogenes Induced Abortion In Mice

Listeria monocytogenes(L. monocytogenes) is the only causative agent of listeriosis, which can cause a disease with a high mortality(about 25%). The facultative intracellular bacterial pathogen Listeria monocytogenesis, a gram-positive bacterial rod, has the ability to cross the intestinal, placental and blood-brain barriers. So L. monocytogenes can cause severe and life- threatening infections, particularly in pregnancy leading to intrauterine fetal death, abortion, pretermbirth, or a neonatal infection. Very few pathogens are capable of placental and fetal infections. Those that can include some parasites such as Toxoplasma gondii and Plasmodium falciparum, and some bacterias, such as Chlamydia psittaci, Coxiella burnetti, and L.monocytogenes. It is unclear that how does L. monocytogenes can cross bloodplacental barriers, and it is tough to cure the disease. There is accumulating experimental evidence that that L.monocytogenes infection during pregnancy has been associated with an unregulated cell death and inflammation in placenta, and these conditions can result in fetal death and abortion. Recently, the increasing emergence of antibiotic resistant L. monocytogenes coupled with poor antibiotic penetration limits the treatment options for this bacterial infection. So people need to take the better measures to dissolve it. In our lab, we focus on the virulence factors of L.monocytogenes. And we found that a key feature of L. monocytogenes is its ability to evade host immune recognition via Listeriolysin O(LLO). LLO, a pore- forming cytolysin, is a most important virulence factor involved in the intracellular growth and survival of L. monocytogenes. It can allow bacteria to lyse the host vacuole membrane and escapes into the cytoplasm where free bacteria spread intracellularly and from cell to cell. L. monocytogenes mutant with a hly deletion(Δhly) results in the loss of hemolytic activity and lead to the inability to escape from the bacterial vacuole. Thus, the mutant failed to invade the mouse infection model.n the previous study, we have reported that FSN effectively blocked L. monocytogenes virulence by interfering with LLO oligomerization. On the basis of previous experiment, our study further demonstrates that FSN treatment can significantly inhibit L. monocytogenes induced abortion in pregnant mice. So pregnant mice were injected intravenously with L. monocytogenes EGD and hly deletion(EGDΔhly) strains at day 14.5 of gestation, followed by fisetin admistration subcutaneously. Forty-two hours after infection, the fetus, fetoplacental unit, and uterine tissue were harvested and homogenized. We found approximately 80% of pregnant mice can result in spontaneous abortion within 42 hours. However, similar infections with the Δhly mutant failed to cause abortion during the same experimental duration, and FSN effectively inhibited L. monocytogenes induced abortion. CFUs were determined from serial dilutions of the samples, plated on BHI agar plates. We found that the CFUs of FSN-treated group was significan lower than the CFUs in the L. monocytogenes group. Histologic examination of the placental labyrinthine zone was performed, Cell degeneration, numerous spotty necroses, and the accumulation of bacteria in the tissues were evident. But FSN-treated group displayed only minor inflammatory lesions. In summary, our animal model provide sufficient evidence to validate that FSN can significantly inhibit abortion in pregnant mice with L.monocytogenes infection. To further confirm the effects of FSN in trophoblast cell after L.monocytogenes infection, we used the Be Wo trophoblast cells model. The results indicated that FSN can markedly reduce bacterial intracellular replication and cell death in vitro. The mechanisms may be that FSN can effectively block L. monocytogenes virulence by interfering with LLO oligomerization.Chinese Medicine is very vital for our country, which is handed down from generation to generation. There is an accumulating evidence that Chinese medicine becomes more useful for difficult miscellaneous diseases, especially flavonoid extracted from Chinese medicine with multiply biological activities, little side effects and low drug resistance characteristics. Fisetin, belongs to flavonoid, has been reported to exert broad biological activities. In this study, our finding strongly suggest that FSN may be a latent therapeutics agent for L.monocytogenes induced abortion and will provide an important experimental basis for the effective therapeutics agent against bacterial infection.