OBJECTIVE Caspase-1 is a component of the NALP3 inflammasome, a cytosolic multiprotein complex that mediates the processing of pro-inflammatory caspases and cytokines. The inflammasome represents the first line of defense against cellular stress and is a crucial component of innate immunity. Caspase-1 is the enzyme responsible for the cleavage and activation of interleukin-1β, which is a potent pro-inflammatory cytokine, and plays a central role in the mechanisms leading to labor (preterm and term) particularly in the context of intrauterine infection/inflammation. In addition, Caspase-1 cleaves IL-18 and IL-33. The objectives of this study were to determine whether there is a relationship between amniotic fluid concentrations of caspase-1 and gestational age, parturition (term and preterm) and intra-amniotic infection/inflammation (IAI). STUDY DESIGN A cross-sectional study was conducted including 143 pregnant women in the following groups: 1) mid-trimester of pregnancy (n=18); 2) term not in labor (n=25); 3) term in labor (n=28); 4) preterm labor (PTL) who delivered at term (n=23); 5) PTL without intra-amniotic infection and/or inflammation (IAI) who delivered preterm (n=32); 6) PTL with IAI who delivered preterm neonates (n=17). Caspase-1 concentrations in amniotic fluid were determined by a specific and sensitive immunoassay. Non-parametric statistics were used for analysis. RESULTS 1) Caspase-1 was detected in amniotic fluid of women at term, but in none of the mid-trimester samples; 2) Patients in labor at term had a significantly higher median amniotic fluid concentration of caspase-1 than women at term not in labor [term in labor: 10.5 pg/ml, range (0.0–666.0) vs. term not in labor: 5.99 pg/ml, range (0.0–237.4); p<0.05]; 3) Among patients with spontaneous PTL, those with intra-amniotic infection and/or inflammation [median 41.4 pg/ml; range: (0.00–515.00)] had a significantly higher median amniotic fluid caspase-1 concentration than those without intra-amniotic infection and/or inflammation who delivered preterm [median 0.0 pg/ml; range: (0.0–78.4)] and than those who delivered at term [median 0.0 pg/ml, range (0.00–199.5)], (p<0.001 for both comparisons). CONCLUSIONS 1) The presence and concentration of caspase-1 in the amniotic fluid varies as a function of gestational age; 2) Women with spontaneous labor at term had a higher median caspase-1 amniotic fluid concentration than women at term without labor. This suggests that the inflammasome may be activated in spontaneous parturition at term. Since most women with labor do not have intra-amniotic infection, we propose that cellular stress during labor accounts for activation of the inflammasome; 3) Preterm labor associated with infection/inflammation was also associated with a high concentration of caspase-1, suggesting that infection may induce caspase-1 production and activation of the inflammasome; 4) The sequential activation of the inflammasome and caspase-1, leading to interleukin-1β processing and secretion, is a candidate pathway leading...

Allele-specific DNA methylation (ASM) is well studied in imprinted domains, but this type of epigenetic asymmetry is actually found more commonly at non-imprinted loci, where the ASM is dictated not by parent-of-origin but instead by the local haplotype. We identified loci with strong ASM in human tissues from methylation-sensitive SNP array data. Two index regions (bisulfite PCR amplicons), one between the C3orf27 and RPN1 genes in chromosome band 3q21 and the other near the VTRNA2-1 vault RNA in band 5q31, proved to be new examples of imprinted DMRs (maternal alleles methylated) while a third, between STEAP3 and C2orf76 in chromosome band 2q14, showed non-imprinted haplotype-dependent ASM. Using long-read bisulfite sequencing (bis-seq) in 8 human tissues we found that in all 3 domains the ASM is restricted to single differentially methylated regions (DMRs), each less than 2kb. The ASM in the C3orf27-RPN1 intergenic region was placenta-specific and associated with allele-specific expression of a long non-coding RNA. Strikingly, the discrete DMRs in all 3 regions overlap with binding sites for the insulator protein CTCF, which we found selectively bound to the unmethylated allele of the STEAP3-C2orf76 DMR. Methylation mapping in two additional genes with non-imprinted haplotype-dependent ASM, ELK3 and CYP2A7, showed that the CYP2A7 DMR also overlaps a CTCF site. Thus, two features of imprinted domains, highly localized DMRs and allele-specific insulator occupancy by CTCF, can also be found in chromosomal domains with non-imprinted ASM. Arguing for biological importance, our analysis of published whole genome bis-seq data from hES cells revealed multiple genome-wide association study (GWAS) peaks near CTCF binding sites with ASM.