Estrogen attenuates lipopolysaccharide-induced nitric oxide production in macrophages partially via the nongenomic pathway

Causal association between body mass index and temporomandibular disorders: a bidirectional two-sample Mendelian randomization analysis

BACKGROUND

Observational studies have shown that body mass index (BMI) is highly correlated with the occurrence of temporomandibular disorders (TMDs). However, these studies failed to present a causal relationship. Thus, we aimed to performed a Mendelian randomization (MR) study to investigate causality between BMI and TMDs.

METHODS

We performed a two-sample bidirectional MR analysis using large-scale genome-wide association studies (GWAS). Data were obtained from a large-scale BMI dataset (N = 322,154), TMDs dataset (N = 134,280). The causal effects were estimated with inverse-variance weighted (IVW) method, MR Egger, weighted median. Sensitivity analyses were implemented with Cochran's Q test, MR-Egger intercept test, MR-PRESSO, leave-one-out analysis and the funnel plot.

RESULTS

In the forward MR analysis, a genetic prediction of low BMI was causally associated with a higher risk of TMDs (IVW OR: 0.575, 95% CI: 0.415-0.798, p: 0.001). Similar results were obtained using other complementary methods (MR Egger OR: 0.270, 95% CI: 0.104-0.698, p: 0.009; weighted median OR: 0.496, 95% CI: 0.298-0.826, p: 0.007). In the reverse MR results, TMDs was shown to have no significant effect on BMI (all p > 0.05). No pleiotropy and heterogeneity were detected in the bidirectional analysis (p > 0.05).

CONCLUSION

A lower BMI might be causally associated with increased risk of TMDs, supporting the importance of weight control for the prevention of TMDs. Clinicians should pay more attention to the low-BMI patients among those seeking medical advice due to temporomandibular joint discomfort.

Immunology of Pregnancy and Systemic Consequences

Pregnancy is an immunological paradox, with renowned Nobel Prize winning transplantation biologist Sir Peter Brian Medawar being the first to introduce this concept back in 1953. This concept considers how the maternal immune system can tolerate the developing fetus, which is 50% antigenically foreign to the uterus. There have been significant advances in our understanding of the immune system in regulating fertility, pregnancy and in complications of these, and what was once considered a paradox can be seen as a highly evolved system. Indeed, the complexity of the maternal-fetal interface along with our ever-advancing knowledge of immune cells and mediators means that we have a better understanding of these interactions, with gaps still present.  This chapter will summarise the key aspects of the role of the immune system at each stage of pregnancy and highlight the recent advances in our knowledge.

Moving beyond inclusion: Methodological considerations for the menstrual cycle and menopause in research evaluating effects of dietary nitrate on vascular function

Recent reports have acknowledged the underrepresentation of women in the field of dietary nitrate (NO₃^-) research. Undoubtedly, greater participation from women is warranted to clarify potential sex differences in the responses to dietary NO₃^- interventions. However, careful consideration for the effects of sex hormones - principally 17β-estradiol - on endogenous nitric oxide (NO) synthesis and dietary NO₃^- reductase capacity is necessary for improved interpretation and reproducibility of such investigations. From available literature, we present a narrative review describing how hormonal variations across the menstrual cycle, as well as with menopause, may impact NO biosynthesis catalyzed by NO synthase enzymes and NO₃^- reduction via the enterosalivary pathway. In doing so, we address methodological considerations related to the menstrual cycle and hormonal contraceptive use relevant for the inclusion of premenopausal women along with factors to consider when testing postmenopausal women. Adherence to such methodological practices may explicate the utility of dietary NO₃^- supplementation as a means to improve vascular function among women across the lifespan.

17β-estradiol protects sheep oviduct epithelial cells against lipopolysaccharide-induced inflammation in vitro

Estrogen has known anti-inflammatory effects, but the mechanism whereby 17β-estradiol (E2) protects oviduct sheep epithelial cells from inflammation remains unknown. In this study, we detected the E2 synthetase and E2 nuclear and membrane receptors in sheep oviducts, primarily in epithelial cells. Using lipopolysaccharide (LPS)-stimulated sheep oviduct epithelial cells as an in vitro inflammation model, we demonstrated that E2 attenuates the expression of inflammatory factors in a concentration-response manner. E2 also inhibited the LPS-stimulated phosphorylation of p38 MAPK and NF-κB p65 but did not reduce the phosphorylation of JNK and ERK 1/2. This attenuation was partially antagonized by an intracellular estrogen antagonist that was involved in genomic regulation and enhanced by a G protein-coupled estrogen receptor agonist that was involved in nongenomic cellular modulation. These results suggest that E2 has an inhibitory effect on LPS-induced oviduct epithelial cell inflammation in sheep, which is mediated by the downstream regulatory effects of estrogen receptors.

Bisphenol A and Phthalates Modulate Peritoneal Macrophage Function in Female Mice Involving SYMD2-H3K36 Dimethylation

Ample evidence suggests that environmental and occupational exposure to bisphenol A (BPA) and phthalate, two chemicals widely used in the plastics industry, disturbs homeostasis of innate immunity and causes inflammatory diseases. However, the underlying molecular mechanisms of these toxicants in the regulation of macrophage inflammatory functions remain poorly understood. In this study, we addressed the effect of chronic exposure to BPA or phthalate at levels relevant to human exposure, either in vitro or in vivo, on the inflammatory reprograming of peritoneal macrophages. Our studies revealed that BPA and phthalates adversely affected expression levels of the proinflammatory cytokines and mediators in response to lipopolysaccharide stimulation. Exposure to these toxicants also affected gene expression of scavenger receptors and phagocytic capacity of peritoneal macrophages. Our studies revealed that the epigenetic inhibitors differentially modulated target gene expression in these cells. Further analysis revealed that certain histone modification enzymes were aberrantly expressed in response to BPA or phthalate exposure, leading to alteration in the levels of H3K36 acetylation and dimethylation, two chromatin modifications that are critical for transcriptional efficacy and accuracy. Our results further revealed that silencing of H3K36-specific methyltransferase Smyd2 expression or inhibition of SMYD2 enzymatic activity attenuated H3K36 dimethylation and enhanced interleukin-6 and tumor necrosis factor-α expression but dampened the phagocytic capacity of peritoneal macrophages. In summary, our results indicate that peritoneal macrophages are vulnerable to BPA or phthalate at levels relevant to human exposure. These environmental toxicants affect phenotypic programming of macrophages via epigenetic mechanisms involving SMYD2-mediated H3K36 modification.

Tumor necrosis factor alfa and interleukin 1 alfa induced phosphorylation and degradation of inhibitory kappa B alpha are regulated by estradiol in endometrial cells

Objective:

When bound to the inhibitory kappa B (IкB) protein, the transcription factor nuclear factor kappa B (NF-кB) remains inactively in the cytoplasm. Activated NF-кB upregulates the gene expression of many chemokines including monocyte chemoattractant protein-1 and interleukin (IL)-8. We hypothesized that estrogen may regulate IкB phosphorylation and degradation thus influencing NF-кB-dependent gene expression. Regulation of chemokines by estrogen is different in uterine endometrial cells when compared to ectopic endometrial cells of endometriosis.

Materials and Methods:

We investigated the in vivo expression of IкB in normal endometrium and in eutopic and ectopic endometrium of women with endometriosis. We then studied in cultured endometrial cells to assess the effects of estradiol on IкB and NF-кB function.

Results:

Normal endometrium from mid-late proliferative phase revealed the strongest IкB immunoreactivity throughout the cycle (p<0.05). When compared to paired homologous eutopic endometrium, ectopic endometrium revealed significantly less immunoreactivity for IкB (p<0.05). Moreover, estradiol induced a decrease in tumor necrosis factor-and IL-1-induced IкB phosphorylation, and also decreased the levels of active-NF-кB (p<0.05).

Conclusion:

Our results support the conclusion that one pathway for estradiol-mediated NF-кB inhibition occurs through the down-regulation of IкB phosphorylation. We propose that the estradiol-induced regulation of IкB and consequent reduction in active-NF-кB may affect inflammatory responses in human endometrial cells.

S-Equol, a Major Isoflavone from Soybean, Inhibits Nitric Oxide Production in Lipopolysaccharide-Stimulated Rat Astrocytes Partially via the GPR30-Mediated Pathway

Cumulative evidence indicates that estrogen receptor (ER) agonists attenuate neuroinflammation. Equol, a major isoflavone from soybean, exhibits estrogen-like biological activity, but their effect on inflammatory response has not been well established. Here, we investigated the effect of S-equol on nitric oxide (NO) production, well-known inflammatory change in astrocytes stimulated by LPS. S-Equol attenuated LPS-induced NO production with a concomitant decrease in expression of inducible NO synthase (iNOS). S-Equol did not affect LPS-induced increase in intracellular ROS production. Intracellular ER blocker ICI 182.780 had no effect on S-equol-induced decrease in NO production. Addition of G-15, antagonist of G protein-coupled receptor 30 which is nongenomic ER and located on cell surface, partially recovered S-equol-induced attenuation of NO production. These findings suggest that attenuation of NO production by S-equol may mitigate LPS-induced neuroinflammation in astrocytes. S-Equol may exert a glioprotective effect, at least in part, via a nongenomic effect.

Assessment of leukocyte activity in mice devoid of the glucocorticoid receptor in the noradrenergic system (GRDBHCre)

Disturbances in brain monoamines, overactivity of the hypothalamo-pituitary adrenal (HPA) axis and pro-inflammatory tendency in the immune system are the key features of depressive disorders. Recently, several murine lines with mutations in glucocorticoid receptors (GRs) have been generated and these animals may be utilized for study depressive-like disorders. In the present study, we have investigated whether selective ablation of GRs in noradrenergic neurons affects functional properties of leukocytes and redirects them towards pro-inflammatory activity. Transgenic mice selectively devoid of GRs on noradrenergic cells were constructed using the Cre/loxP approach. Peritoneal leukocytes were collected from mutant and wild type (WT) animals of both sexes and were cultured in vitro for 24h both in basal conditions and after application of selected pro- or anti-inflammatory stimuli. Metabolic activity and adherence were measured in basal conditions. Nitric oxide (NO) synthesis and arginase (ARG) activity were assessed as the markers of functional status of the cells. Because adult mutant mice lack adrenal medulla and thereby peripheral adrenaline, we modulated pro- and anti-inflammatory culture conditions by addition of noradrenaline (10-6M). Finally, effects of in vivo pro-inflammatory challenge (with intraperitoneal administration of lipopolysaccharide) on properties of leukocytes were assessed 24h (in both sexes) and 48h later (in males only). The experiments indicated that selective ablation of GR in noradrenergic neurons did not affect fundamental properties of peritoneal leukocytes and exerted effects only under conditions of selected pro- or anti-inflammatory stimuli in vitro. Stronger response to pro-inflammatory stimulation in terms of NO synthesis and ARG activity may suggest pro-inflammatory tendency in mutant mice. In vivo inflammatory challenge failed to show any effect of GR ablation on selected parameters of leukocyte activity. Both in vitro studies and in vivo challenge revealed mainly sex-related differences in leukocyte activity.