Taurodeoxycholate ameliorates DSS-induced colitis in mice

BACKGROUND

Inflammatory bowel disease (IBD) is typically managed using medications such as 5-aminosalicylic acid (5-ASA), glucocorticoids, anti-TNFα Ab, or anti-IL-12/23 Ab. However, some patients do not respond well to these treatments or frequently experience relapses. Therefore, alternative therapeutic options are needed. Since the activation of the inflammasome is crucial to the pathogenesis of IBD, inhibiting the inflammasome may be beneficial for patients.

MATERIALS AND METHODS

We tested the efficacy of taurodeoxycholate (TDCA), which is a known G-protein coupled receptor 19 (GPCR19) agonist, in a mouse colitis model induced by dextran sodium sulfate (DSS).

RESULTS

In the mouse colitis model, TDCA prevented loss of body weight, shortening of the colon, production of pro-inflammatory cytokines, infiltration of pro-inflammatory cells, and mucosal ulceration in the colon. In vitro, TDCA inhibited the activation of NF-κB in bone marrow-derived macrophages (BMDMs) by activating the cAMP-PKA axis. TDCA downregulated the expression of purinergic receptor P2X7 (P2X7R) and enhanced the colocalization of P2X7R with GPCR19, and inhibited the Ca2+ mobilization of BMDMs when stimulated with ATP or BzATP, which plays a pivotal role in activating the NLRP3 inflammasome (N3I) via P2X7R. TDCA inhibited the oligomerization of NLRP3-ASC and downregulated the expression of NLRP3 and ASC, as well as suppressed the maturation of pro-caspase-1 and pro-IL-1β. TDCA also increased the percentage of M2 macrophages while decreasing the number of M1 macrophages, Th1, Th2, and Th17 cells in the colon.

CONCLUSION

TDCA ameliorated DSS-induced colitis in mice, possibly by inhibiting both the priming phase (via the GPCR19-cAMP-PKA-NF-κB axis) and the activation phase (via the GPCR19-P2X7R-NLRP3-Caspase 1-IL-1β axis) of N3I signaling.

CD115- monocytic myeloid-derived suppressor cells are precursors of OLFM4high polymorphonuclear myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) consist of monocytic (M-) MDSCs and polymorphonuclear (PMN-) MDSCs that contribute to an immunosuppressive environment in tumor-bearing hosts. However, research on the phenotypic and functional heterogeneity of MDSCs in tumor-bearing hosts and across different disease stage is limited. Here we subdivide M-MDSCs based on CD115 expression and report that CD115^- M-MDSCs are functionally distinct from CD115⁺ M-MDSCs. CD115^- M-MDSCs increased in bone marrow and blood as tumors progressed. Transcriptome analysis revealed that CD115^- M-MDSCs expressed higher levels of neutrophil-related genes. Moreover, isolated CD115^- M-MDSCs had higher potential to be differentiated into PMN-MDSCs compared with CD115⁺ M-MDSCs. Of note, CD115^- M-MDSCs were able to differentiate into both olfactomedin 4 (OLFM4)^hi and OLFM4^lo PMN-MDSCs, whereas CD115⁺ M-MDSCs differentiated into a smaller proportion of OLFM4^lo PMN-MDSCs. In vivo, M-MDSC to PMN-MDSC differentiation occurred most frequently in bone marrow while M-MDSCs preferentially differentiated into tumor-associated macrophages in the tumor mass. Our study reveals the presence of previously unrecognized subtypes of CD115^- M-MDSCs in tumor-bearing hosts and demonstrates their cellular plasticity during tumorigenesis.

GPCR19 Regulates P2X7R-Mediated NLRP3 Inflammasomal Activation of Microglia by Amyloid β in a Mouse Model of Alzheimer's Disease

Amyloid β (Aβ) and/or ATP activate the NLRP3 inflammasome (N3I) via P2X7R in microglia, which is crucial in neuroinflammation in Alzheimer’s disease (AD). Due to polymorphisms, subtypes, and ubiquitous expression of P2X7R, inhibition of P2X7R has not been effective for AD. We first report that taurodeoxycholate (TDCA), a GPCR19 ligand, inhibited the priming phase of N3I activation, suppressed P2X7R expression and P2X7R-mediated Ca⁺⁺ mobilization and N3I oligomerization, which is essential for production of IL-1β/IL-18 by microglia. Furthermore, TDCA enhanced phagocytosis of Aβ and decreased the number of Aβ plaques in the brains of 5x Familial Alzheimer’s disease (5xFAD) mice. TDCA also reduced microgliosis, prevented neuronal loss, and improved memory function in 5xFAD mice. The pleiotropic roles of GPCR19 in P2X7R-mediated N3I activation suggest that targeting GPCR19 might resolve neuroinflammation in AD patients.

Taurodeoxycholate Increases the Number of Myeloid-Derived Suppressor Cells That Ameliorate Sepsis in Mice

Bile acids (BAs) control metabolism and inflammation by interacting with several receptors. Here, we report that intravenous infusion of taurodeoxycholate (TDCA) decreases serum pro-inflammatory cytokines, normalizes hypotension, protects against renal injury, and prolongs mouse survival during sepsis. TDCA increases the number of granulocytic myeloid-derived suppressor cells (MDSCLT) distinctive from MDSCs obtained without TDCA treatment (MDSCL) in the spleen of septic mice. FACS-sorted MDSCLT cells suppress T-cell proliferation and confer protection against sepsis when adoptively transferred better than MDSCL. Proteogenomic analysis indicated that TDCA controls chromatin silencing, alternative splicing, and translation of the immune proteome of MDSCLT, which increases the expression of anti-inflammatory molecules such as oncostatin, lactoferrin and CD244. TDCA also decreases the expression of pro-inflammatory molecules such as neutrophil elastase. These findings suggest that TDCA globally edits the proteome to increase the number of MDSCLT cells and affect their immune-regulatory functions to resolve systemic inflammation during sepsis.

A multifunctional core-shell nanoparticle for dendritic cell-based cancer immunotherapy

Dendritic cell-based cancer immunotherapy requires tumour antigens to be delivered efficiently into dendritic cells and their migration to be monitored in vivo. Nanoparticles have been explored as carriers for antigen delivery, but applications have been limited by the toxicity of the solvents used to make nanoparticles, and by the need to use transfection agents to deliver nanoparticles into cells. Here we show that an iron oxide-zinc oxide core-shell nanoparticle can deliver carcinoembryonic antigen into dendritic cells while simultaneously acting as an imaging agent. The nanoparticle-antigen complex is efficiently taken up by dendritic cells within one hour and can be detected in vitro by confocal microscopy and in vivo by magnetic resonance imaging. Mice immunized with dendritic cells containing the nanoparticle-antigen complex showed enhanced tumour antigen specific T-cell responses, delayed tumour growth and better survival than controls.

CD14 but not MD2 transmit signals from DAMP

Both pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) activate antigen-presenting cells, often through the same pattern recognition receptors (PRR), such as Toll-like receptors (TLR). The TLR4-CD14-MD2 and TLR2-CD14 complexes have been shown to play a role in the recognition of lipopolysaccharide (LPS) and peptidoglycan (PG), respectively. Since many DAMPs have also been known to activate TLR2 or TLR4 pathways, we dissected the role of each molecule in the receptor complexes (TLR2-D14-MD2) responding to DAMP (necrotic cells) or PAMP (LPS and PG). CD14 played a significant role in the activation of NF-kappaB in response to necrotic cells in the presence or absence of TLR2. However, MD2 did not play a significant role in NF-kappaB activation by necrotic cells. Intriguingly, MD2 did play a significant role in activating NF-kappaB by PG in the presence of TLR2-CD14. Compared with CD14(pos) B6 mice, CD14(neg) B6 mice showed delayed production of IL12p40 in response to necrotic cells in vivo. Microarray analysis showed that various pro-inflammatory genes of peritoneal cells were regulated in response to necrotic cells, in a CD14-dependent manner. The CD14 appears to recognize necrotic cells in addition to LPS, PG, apoptotic cells, and lipids, suggesting that CD14 might be a universal adaptor for DAMP and PAMP. On the contrary, MD2 recognizes only exogenous PAMP, when complexed with TLR2-CD14 or TLR4-CD14. Taken together, MD2 appears to discriminate between DAMP and PAMP.

Current status of protein chip development in terms of fabrication and application

Sequencing of the human genome revealed that more than 30 000 genes encode proteins comprising the human proteome. "Proteomics" can be defined as a field of research studying proteins in terms of their function, expression, structure, modification and their interaction in physiological and in pathological states. The concentration, modification and interaction of proteins in cells, plasma, and in tissues are crucial in determining the phenotype of living organisms. Although fluctuation of protein concentration is essential to maintain homeostasis, protein expression levels are also pathognomonic features. Estimating protein concentration by analyzing the quantity of mRNA in cells through conventional technologies, such as DNA chips, does not provide precise values since the half-life and translation efficacy of mRNA is variable. In addition, polypeptides undergo post-translational modification. For these reasons, novel techniques are needed to analyze multiple proteins simultaneously using protein microarrays. In the near future, protein chips may allow construction of complete relational databases for metabolic and signal transduction pathways. This article reviews the current status of technologies for fabricating protein microarrays and their applications.