Estrogen stimulates female biliary epithelial cell interleukin-6 expression in mice and humans.

UNLABELLED: Females are more susceptible than males to several biliary tract diseases. Interleukin-6 (IL-6) is critical to triggering autoimmune reactions and contributes substantially to biliary epithelial cell (BEC) barrier function and wound repair, and estrogen differentially regulates IL-6 expression in various cell types. We hypothesized that estrogen might stimulate BEC IL-6 production. Exposure to physiologic levels of estradiol, in vitro, increased female mouse BEC (mBEC) IL-6 messenger RNA (mRNA) and protein expression, but either inhibited or had no effect on male mBECs. Female mBECs expressed higher concentrations of estrogen receptor-alpha (ERalpha) mRNA and protein and were also more dependent on estradiol for survival, in vitro. In vivo, elevated estrogen during estrous cycling in mice, and estrogen treatment of mice harboring an ERalpha(+) human cholangiocarcinoma resulted in increased BEC IL-6 mRNA and tumor viability, respectively. Both responses could be blocked by an ERalpha antagonist. Human cholangiocarcinoma cell lines differentially expressing ERalpha were treated with specific ERalpha and ERbeta agonists/antagonists to further test the relationship between estrogen stimulation, ERalpha expression, and IL-6 production. Results show that ERalpha, and not the underlying BEC sex, was responsible for estrogen-induced IL-6 production. Estrogen-induced proliferation of ERalpha-expressing cholangiocarcinoma was blocked by anti-IL-6 antibodies, indicating that at least some of the estrogen-trophic effects are mediated via IL-6. Finally, an association between ERalpha, IL-6, and phosphorylated signal transducer and activator of transcription 3 (pSTAT3) signaling was shown in female-predominant polycystic livers using immunohistochemical analyses, including multiplex quantum dot labeling. CONCLUSION: Estrogens stimulate IL-6 production in non-neoplastic female BECs and in neoplastic BECs expressing ERalpha. An association between these signaling pathways was demonstrated for female-predominant polycystic livers and might also influence autoimmune hepatitis, primary biliary cirrhosis, and cholangiocarcinogenesis.

Gut-derived commensal bacterial products inhibit liver dendritic cell maturation by stimulating hepatic interleukin-6/signal transducer and activator of transcription 3 activity.

UNLABELLED: Intraorgan dendritic cells (DCs) monitor the environment and help translate triggers of innate immunity into adaptive immune responses. Liver-based DCs are continually exposed, via gut-derived portal venous blood, to potential antigens and bacterial products that can trigger innate immunity. However, somehow the liver avoids a state of perpetual inflammation and protects central immune organs from overstimulation. In this study, we tested the hypothesis that hepatic interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) activity increases the activation/maturation threshold of hepatic DCs toward innate immune signals. The results show that the liver nuclear STAT3 activity is significantly higher than that of other organs and is IL-6-dependent. Hepatic DCs in normal IL-6 wild-type (IL-6(+/+)) mice are phenotypically and functionally less mature than DCs from IL-6-deficient (IL-6(-/-)) or STAT3-inhibited IL-6(+/+) mice, as determined by surface marker expression, proinflammatory cytokine secretion, and allogeneic T-cell stimulation. IL-6(+/+) liver DCs produce IL-6 in response to exposure to lipopolysaccharide (LPS) and cytidine phosphate guanosine oligonucleotides (CpG) but are resistant to maturation compared with IL-6(-/-) liver DCs. Conversely, exogenous IL-6 inhibits LPS-induced IL-6(-/-) liver DC maturation. IL-6/STAT3 signaling influences the liver DC expression of toll-like receptor 9 and IL-1 receptor associated kinase-M. The depletion of gut commensal bacteria in IL-6(+/+) mice with oral antibiotics decreased portal blood endotoxin levels, lowered the expression of IL-6 and phospho-STAT3, and significantly increased liver DC maturation. CONCLUSION: Gut-derived bacterial products, by stimulating hepatic IL-6/STAT3 signaling, inhibit hepatic DC activation/maturation and thereby elevate the threshold needed for translating triggers of innate immunity into adaptive immune responses. Manipulating gut bacteria may therefore be an effective strategy for altering intrahepatic immune responses.

Production of alpha 1,3-galactosyltransferase-deficient pigs.

The enzyme alpha1,3-galactosyltransferase (alpha1,3GT or GGTA1) synthesizes alpha1,3-galactose (alpha1,3Gal) epitopes (Galalpha1,3Galbeta1,4GlcNAc-R), which are the major xenoantigens causing hyperacute rejection in pig-to-human xenotransplantation. Complete removal of alpha1,3Gal from pig organs is the critical step toward the success of xenotransplantation. We reported earlier the targeted disruption of one allele of the alpha1,3GT gene in cloned pigs. A selection procedure based on a bacterial toxin was used to select for cells in which the second allele of the gene was knocked out. Sequencing analysis demonstrated that knockout of the second allele of the alpha1,3GT gene was caused by a T-to-G single point mutation at the second base of exon 9, which resulted in inactivation of the alpha1,3GT protein. Four healthy alpha1,3GT double-knockout female piglets were produced by three consecutive rounds of cloning. The piglets carrying a point mutation in the alpha1,3GT gene hold significant value, as they would allow production of alpha1,3Gal-deficient pigs free of antibiotic-resistance genes and thus have the potential to make a safer product for human use.

Immature and mature CD8alpha+ dendritic cells prolong the survival of vascularized heart allografts.

CD8alpha+ and CD8alpha- dendritic cells (DCs) arise from committed bone marrow progenitors and can induce or regulate immune reactivity. Previously, the maturational status of CD8alpha-(myeloid) DCs has been shown to influence allogeneic T cell responses and allograft survival. Although CD8alpha+ DCs have been implicated in central tolerance and found to modulate peripheral T cell function, their influence on the outcome of organ transplantation has not been examined. Consistent with their equivalent high surface expression of MHC and costimulatory molecules, sorted mature C57BL/10J (B10; H2(b)) DCs of either subset primed naive, allogeneic C3H/HeJ (C3H; H2(k)) recipients for Th1 responses. Paradoxically and in contrast to their CD8alpha- counterparts, mature CD8alpha+ B10 DCs given systemically 7 days before transplant markedly prolonged B10 heart graft survival in C3H recipients. This effect was associated with specific impairment of ex vivo antidonor T cell proliferative responses, which was not reversed by exogenous IL-2. Further analyses of possible underlying mechanisms indicated that neither immune deviation nor induction of regulatory cells was a significant contributory factor. In contrast to the differential capacity of the mature DC subsets to affect graft outcome, immature CD8alpha+ and CD8alpha- DCs administered under the same experimental conditions significantly prolonged transplant survival. These observations demonstrate for the first time the innate capacity of CD8alpha+ DCs to regulate alloimmune reactivity and transplant survival, independent of their maturation status. Mobilization of such a donor DC subset with capacity to modulate antidonor immunity may have significant implications for the therapy of allograft rejection.