ß-hydroxybutyrate suppresses NLRP3 inflammasome-mediated placental inflammation and lipopolysaccharide-induced fetal absorption.

The immune system contributes to the regulation of pregnancy, and the disruption of well-controlled immune functions leads to pregnancy complications. Recently, the nucleotide-binding oligomerization domain, leucine-rich repeat-, and pyrin domain-containing 3 (NLRP3) inflammasome mechanisms [(a protein complex of NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and caspase-1)] have been reported to play roles in controlling placental inflammation involved in pregnancy pathologies. The ketone body ß-hydroxybutyrate (BHB) can suppress NLRP3 inflammasome activation and improve various inflammatory diseases. Therefore, we hypothesized that BHB could suppress activation of the NLRP3 inflammasome in the placenta, resulting in the improvement of pregnancy complications. In human placental tissue culture, treatment with BHB suppressed the secretion levels of inflammatory cytokines, such as interleukin (IL)-1ß, IL-6, and IL-8, but did not affect the mRNA expression levels of NLRP3 inflammasome-associated factors. Treatment with BHB reduced IL-1ß secretion and the amount of mature IL-1ß protein induced by lipopolysaccharide (LPS) stimulation in the placenta. In human trophoblast cells, BHB reduced ASC and activated-caspase-1 expression, resulting in the inhibition of IL-1ß secretion. To investigate the effect of BHB during pregnancy, we used an animal model of LPS (100 µg/kg intraperitoneally [i.p.] on gestational day 14)-induced pregnancy complications. Administration of BHB (100 mg/kg i.p.) clearly suppressed the absorption rate and IL-1ß production in the placenta induced by LPS in pregnant mice. Moreover, LPS-induced pregnancy abnormalities were improved in NLRP3-deficient mice. These findings suggest that BHB play a role in reducing placental inflammation and pregnancy complications via inhibition of NLRP3 inflammasome activation.

Advanced maternal age induces fetal growth restriction through decreased placental inflammatory cytokine expression and immune cell accumulation in mice.

Advanced maternal age is a risk factor for female infertility, and placental dysfunction is considered one of the causes of pregnancy complications. We investigated the effects of advanced maternal aging on pregnancy outcomes and placental senescence. Female pregnant mice were separated into three groups: young (3 months old), middle (8-9 months old), and aged (11-13 months old). Although the body weights of young and middle dams gradually increased during pregnancy, the body weight of aged dams only increased slightly. The placental weight and resorption rate were significantly higher, and live fetal weights were reduced in a maternal age-dependent manner. Although mRNA expression of senescence regulatory factors (p16 and p21) increased in the spleen of aged dams, mRNA expression of p16 did not change and that of p21 was reduced in the placenta of aged dams. Using a cytokine array of proteins extracted from placental tissues, the expression of various types of senescence-associated secretory phenotype (SASP) factors was decreased in aged dams compared with young and middle dams. The aged maternal placenta showed reduced immune cell accumulation compared with the young placenta. Our present results suggest that models using pregnant mice older than 8 months are more suitable for verifying older human pregnancies. These findings suggest that general cellular senescence programs may not be included in the placenta and that placental functions, including SASP production and immune cell accumulation, gradually decrease in a maternal age-dependent manner, resulting in a higher rate of pregnancy complications.

Palmitic acid activates NLRP3 inflammasome and induces placental inflammation during pregnancy in mice.

Maternal obesity is one of the major risk factors for pregnancy complications and is associated with low-grade chronic systemic inflammation due to higher levels of pro-inflammatory cytokines such as interleukin (IL)-1ß. Pregnant women with obesity have abnormal lipid profiles, characterized by higher levels of free fatty acids, especially palmitic acid (PA). Previously, we reported that PA stimulated IL-1ß secretion via activation of NLRP3 inflammasome in human placental cells. These observations led us to hypothesize that higher levels of PA induce NLRP3 inflammasome activation and placental inflammation, resulting in pregnancy complications. However, the effects of PA on NLRP3 inflammasome during pregnancy in vivo remain unclear. Therefore, PA solutions were administered intravenously into pregnant mice on day 12 of gestation. Maternal body weight was significantly decreased and absorption rates were significantly higher in PA-injected mice. The administration of PA significantly increased IL-1ß protein and the mRNA expression of NLRP3 inflammasome components (NLRP3, ASC, and caspase-1) within the placenta. In murine placental cell culture, PA significantly stimulated IL-1ß secretion, and this secretion was suppressed by a specific NLRP3 inhibitor (MCC950). Simultaneously, the number of macrophages/monocytes and neutrophils, together with the mRNA expression of these chemokines increased significantly in the placentas of PA-treated mice. Treatment with PA induced ASC assembling and IL-1ß secretion in macrophages, and this PA-induced IL-1ß secretion was significantly suppressed in NLRP3-knockdown macrophages. These results indicate that transient higher levels of PA exposure in pregnant mice activates NLRP3 inflammasome and induces placental inflammation, resulting in the incidence of absorption.

Factors determining species displacement of related predatory mite species (Acari: Phytoseiidae).

Neoseiulus womersleyi (Acari: Phytoseiidae) used to be the dominant species in fruit-tree orchards throughout Japan, but starting in the 1990s, N. womersleyi began to be displaced by Neoseiulus californicus in central and southwestern Japan. The present study was conducted to examine factors explaining the displacement of N. womersleyi by N. californicus. First, we confirmed under laboratory conditions that N. californicus could exclude N. womersleyi if they initially coexisted in a 1:1 ratio. During a 2-h continuous observation period, none of the heterospecific pairs had copulated and after 5 days together with heterospecific males, none of the females had laid eggs. When these females were placed with conspecific males, normal numbers of offspring were produced. Moreover, conspecific matings were not substantially disturbed in the presence of heterospecific males or females. Total fecundity was significantly lower in N. womersleyi than in N. californicus, but their r m values did not differ from each other. On the other hand, the frequency of intraguild predation by N. californicus on N. womersleyi was significantly higher than vice versa. From these results, we concluded that not reproductive interference nor differential female fecundity but asymmetrical intraguild predation seemed to explain the competitive exclusion of N. womersleyi by N. californicus.

Identification and characterization of an increased glycoprotein in aging: age-associated translocation of cathepsin D.

We found that 14 N-glycosylated proteins were accumulated in the rat cerebral cortex cytosolic fraction in the aging process by a comparative study with two-dimensional gel electrophoresis and concanavalin A staining. All proteins had high mannose and/or hybrid-type N-glycans, as indicated by the fact that they were sensitive to endoglycosidase H digestion. Three of these cytosolic glycoproteins were identified as cathepsin D, a lysosomal protease, by tryptic digestion and nano liquid chromatography electrospray ionization quadrupole time of flight mass spectrometry. The increase of cytosolic cathepsin D during aging was not due to lysosomal membrane disruption, as shown by the fact that the activities of beta-hexosaminidase and beta-glucuronidase, other lysosomal enzymes, did not increase in the cytosolic fraction. Although the total amount of cathepsin D increased during aging, the amount of cathepsin D in the microsomal fraction did not change, indicating a selective increase of cytosolic cathepsin D. This phenomenon was also observed in the hippocampus, cerebellum, kidney, liver, and spleen. Based on these results, we propose that cytosolic cathepsin D is a new biomarker of aging.