Functional assessment of genetic variants located in the promoter of SHP1 (NR0B2)

Microbiome, bile acids, and obesity: How microbially modified metabolites shape anti-tumor immunity

Bile acids (BAs) are known facilitators of nutrient absorption but recent paradigm shifts now recognize BAs as signaling molecules regulating both innate and adaptive immunity. Bile acids are synthesized from cholesterol in the liver with subsequent microbial modification and fermentation adding complexity to pool composition. Bile acids act on several receptors such as Farnesoid X Receptor and the G protein-coupled BA receptor 1 (TGR5). Interestingly, BA receptors (BARs) are expressed on immune cells and activation either by BAs or BAR agonists modulates innate and adaptive immune cell populations skewing their polarization toward a more tolerogenic anti-inflammatory phenotype. Intriguingly, recent evidence also suggests that BAs promote anti-tumor immune response through activation and recruitment of tumoricidal immune cells such as natural killer T cells. These exciting findings have redefined BA signaling in health and disease wherein they may suppress inflammation on the one hand, yet promote anti-tumor immunity on the other hand. In this review, we provide our readers with the most recent understanding of the interaction of BAs with the host microbiome, their effect on innate and adaptive immunity in health and disease with a special focus on obesity, bariatric surgery-induced weight loss, and immune checkpoint blockade in cancer.

OATP1B3-1B7, a novel organic anion transporting polypeptide, is modulated by FXR ligands and transports bile acids

Organic anion transporting polypeptide (OATP) 1B3-1B7 (LST-3TM12) is a member of the OATP1B [solute carrier organic anion transporter (SLCO) 1B] family. This transporter is not only functional but also expressed in the membrane of the smooth endoplasmic reticulum of hepatocytes and enterocytes. OATP1B3-1B7 is a splice variant of SLCO1B3 in which the initial part is encoded by SLCO1B3, whereas the rest of the mRNA originates from the gene locus of SLCO1B7. In this study, we not only showed that SLCO1B3 and the mRNA encoding for OATP1B3-1B7 share the 5' untranslated region but also that silencing of an initial SLCO1B3 exon lowered the amount of SLCO1B3 and of SLCO1B7 mRNA in Huh-7 cells. To validate the assumption that both transcripts are regulated by the same promoter we tested the influence of the bile acid sensor farnesoid X receptor (FXR) on their transcription. Treatment of Huh-7 and HepaRG cells with activators of this known regulator of OATP1B3 not only increased SLCO1B3 but also OATP1B3-1B7 mRNA transcription. Applying a heterologous expression system, we showed that several bile acids interact with OATP1B3-1B7 and that taurocholic acid and lithocholic acid are OATP1B3-1B7 substrates. As OATP1B3-1B7 is located in the smooth endoplasmic reticulum, it may grant access to metabolizing enzymes. In accordance are our findings showing that the OATP1B3-1B7 inhibitor bromsulphthalein significantly reduced uptake of bile acids into human liver microsomes. Taken together, we report that OATP1B3-1B7 transcription can be modulated with FXR agonists and antagonists and that OATP1B3-1B7 transports bile acids.NEW & NOTEWORTHY Our study on the transcriptional regulation of the novel organic anion transporting polypeptide (OATP) 1B3-1B7 concludes that the promoter of solute carrier organic anion transporter (SLCO) 1B3 governs SLCO1B3-1B7 transcription. Moreover, the transcription of OATP1B3-1B7 can be modulated by farnesoid X receptor (FXR) agonists and antagonists. FXR is a major regulator in bile acid homeostasis that links OATP1B3-1B7 to this physiological function. Findings in transport studies with OATP1B3-1B7 suggest that this transporter interacts with the herein tested bile acids.

Mechanisms of Inflammation in Neutrophil-Mediated Skin Diseases

Neutrophil-mediated skin diseases, originally named neutrophilic dermatoses (NDs), are a group of conditions due to an altered neutrophil recruitment and activation, characterized by polymorphic cutaneous manifestations with possible internal organ involvement. Although a number of diseases are included in this setting, the two prototypic forms are pyoderma gangrenosum (PG) and Sweet's syndrome (SS) which usually present with skin ulcers and plaque-type lesions, respectively. They have central features significantly overlapping with autoinflammatory conditions which manifest as repeated episodes of tissue inflammation. However, in contrast to appropriate inflammatory responses to insults or to autoimmune disease, there is an absence of identifiable pathogens, autoantibodies, or autoreactive lymphocytes. The recognition of monogenic autoinflammatory diseases which can present with NDs has led to study several genes involved in autoinflammation in NDs. Based on discovering of a number of mutations involving different autoinflammatory genes, neutrophil-mediated skin diseases are nowadays regarded as a spectrum of polygenic autoinflammatory conditions. Although disease mechanisms have not yet been completely elucidated, NDs are recognized as diseases involving dysfunctional cellular signaling mediated by pathways mainly related to inflammasome and IL-1 with the contributory role of IL-17 and other effector molecules. The precise elucidation of the above-mentioned pathologic mechanisms may pave the way to tailored treatments for patients with different neutrophil-mediated skin diseases.