Faculty Bibliography

The large intestine is the site most commonly affected in inflammatory bowel diseases. However, the mechanism of T cell homing to the large intestine, which contributes to inflammation, had remained unclear. We show here that an orphan G-protein coupled receptor GPR15 controls the specific homing of T cells, particularly FOXP3+ regulatory T cells (Tregs), to the large intestine lamina propria (LILP). GPR15 expression is promoted by gut microbiota and TGF-beta1, but not by retinoic acid. GPR15-deficient mice had fewer Tregs in LILP and were prone to develop more severe inflammation in the large intestine, which was rescued by the transfer of GPR15-sufficient Tregs. Our findings thus indicate that GPR15 is a T cell homing receptor for LILP and that GPR15 plays a key role in maintaining gut immune homeostasis, largely by regulating the influx of Tregs. Our study also demonstrates that adaptive immune responses in the gut are functionally compartmentalized through the differential requirements for T cell homing to the small and large bowel

The contributions of TGF-beta signaling to cancer are complex but involve the inflammatory microenvironment as well as cancer cells themselves. In mice encoding a TGF-beta mutant that precludes its binding to the latent TGF-beta binding protein (Tgfb1-/C33S), we observed multiorgan inflammation and an elevated incidence of various types of gastrointestinal solid tumors due to impaired conversion of latent to active TGF-beta1. By genetically eliminating activators of latent TGF-beta, we further lowered the amount of TGF-beta, which enhanced tumor frequency and multiorgan inflammation. This model system was used to further investigate the relative contribution of TGF-beta1 to lymphocyte-mediated inflammation in gastrointestinal tumorigenesis. Toward this end, we generated Tgfb1-/C33S;Rag2-/- mice that lacked adaptive immune function, which eliminated tumor production. Analysis of tissue from Tgfb1-/C33S mice indicated decreased levels of P-Smad3 compared to wild type animals, whereas tissue from Tgfb1-/C33S;Rag2-/- mice had normal P-Smad3 levels. Inhibiting the inflammatory response normalized levels of IL-1beta and IL-6 and reduced tumor cell proliferation. Additionally, Tgfb1-/C33S;Rag2-/- mice exhibited reduced paracrine signaling in the epithelia, mediated by hepatocyte growth factor produced by gastric stroma. Together, our results indicate that many of the responses of the gastric tissue associated with decreased TGF-beta1 may be directly or indirectly affected by inflammatory processes, which accompany loss of TGF-beta1, rather than a direct effect of loss of the cytokine.

Pancreatic ductal adenocarcinoma (PDAC) is strikingly resistant to conventional therapeutic approaches. We previously demonstrated that the histone deacetylase-associated protein SIN3B is essential for oncogene-induced senescence in cultured cells. Here, using a mouse model of pancreatic cancer, we have demonstrated that SIN3B is required for activated KRAS-induced senescence in vivo. Surprisingly, impaired senescence as the result of genetic inactivation of Sin3B was associated with delayed PDAC progression and correlated with an impaired inflammatory response. In murine and human pancreatic cells and tissues, levels of SIN3B correlated with KRAS-induced production of IL-1alpha. Furthermore, evaluation of human pancreatic tissue and cancer cells revealed that Sin3B was decreased in control and PDAC samples, compared with samples from patients with pancreatic inflammation. These results indicate that senescence-associated inflammation positively correlates with PDAC progression and suggest that SIN3B has potential as a therapeutic target for inhibiting inflammation-driven tumorigenesis.

The "Discrimination" part of the OMERACT Filter asks whether a measure discriminates between situations that are of interest. "Feasibility" in the OMERACT Filter encompasses the practical considerations of using an instrument, including its ease of use, time to complete, monetary costs, and interpretability of the question(s) included in the instrument. Both the Discrimination and Reliability parts of the filter have been helpful but were agreed on primarily by consensus of OMERACT participants rather than through explicit evidence-based guidelines. In Filter 2.0 we wanted to improve this definition and provide specific guidance and advice to participants.

Promoters and enhancers establish precise gene transcription patterns. The development of functional approaches for their identification in mammalian cells has been complicated by the size of these genomes. Here we report a high-throughput functional assay for directly identifying active promoter and enhancer elements called FIREWACh (Functional Identification of Regulatory Elements Within Accessible Chromatin), which we used to simultaneously assess over 80,000 DNA fragments derived from nucleosome-free regions within the chromatin of embryonic stem cells (ESCs) and identify 6,364 active regulatory elements. Many of these represent newly discovered ESC-specific enhancers, showing enriched binding-site motifs for ESC-specific transcription factors including SOX2, POU5F1 (OCT4) and KLF4. The application of FIREWACh to additional cultured cell types will facilitate functional annotation of the genome and expand our view of transcriptional network dynamics.

Pancreatic cancer is one of the most lethal cancers worldwide. No effective screening methods exist, and available treatment modalities do not effectively treat the disease. Inflammatory conditions such as pancreatitis represent a well-known risk factor for pancreatic cancer development. Yet only in the past 2 decades has pancreatic cancer been recognized as an inflammation-driven cancer, and the precise mechanisms underlying the pathogenic role of inflammation are beginning to be explored in detail. A substantial amount of preclinical and clinical evidence suggests that bacteria are likely to influence this process by activating immune receptors and perpetuating cancer-associated inflammation. The recent explosion of investigations of the human microbiome have highlighted how perturbations of commensal bacterial populations can promote inflammation and promote disease processes, including carcinogenesis. The elucidation of the interplay between inflammation and microbiome in the context of pancreatic carcinogenesis will provide novel targets for intervention to prevent and treat pancreatic cancer more efficiently. Further studies toward this direction are urgently needed.

Salt stress is a widespread phenomenon, limiting plant performance in large areas around the world. Although various types of plant sodium/proton antiporters have been characterized, the physiological function of NHD1 from Arabidopsis thaliana has not been elucidated in detail so far. Here we report that the NHD1-GFP fusion protein localizes to the chloroplast envelope. Heterologous expression of AtNHD1 was sufficient to complement a salt-sensitive Escherichia coli mutant lacking its endogenous sodium/proton exchangers. Transport competence of NHD1 was confirmed using recombinant, highly purified carrier protein reconstituted into proteoliposomes, proving Na(+) /H(+) antiport. In planta NHD1 expression was found to be highest in mature and senescent leaves but was not induced by sodium chloride application. When compared to wild-type controls, nhd1 T-DNA insertion mutants showed decreased biomasses and lower chlorophyll levels after sodium feeding. Interestingly, if grown on sand and supplemented with high sodium chloride, nhd1 mutants exhibited leaf tissue Na(+) levels similar to those of wild-type plants, but the Na(+) content of chloroplasts increased significantly. These high sodium levels in mutant chloroplasts resulted in markedly impaired photosynthetic performance as revealed by a lower quantum yield of photosystem II and increased non-photochemical quenching. Moreover, high Na(+) levels might hamper activity of the plastidic bile acid/sodium symporter family protein 2 (BASS2). The resulting pyruvate deficiency might cause the observed decreased phenylalanine levels in the nhd1 mutants due to lack of precursors.

Objective. To determine the actions of lithium chloride (LiCl) on catabolic events in articular chondrocytes and cartilage degradation after interleukin (IL)-1beta(beta) treatment and after surgically induced osteoarthritis (OA) in mice. Methods. The expression levels of catabolic genes in human articular chondrocytes treated with LiCl followed by IL-1beta were determined by real time PCR. To understand the mechanism of how LiCl affects catabolic events in articular chondrocytes after IL-1beta treatment, the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappaB) was determined using luciferase reporter assays, and the activities of mitogen-activated protein kinases (MAPK) and signal transducer and activator of transcription 3 (Stat3) signaling pathway were determined by immunoblot analysis of total cell lysates. Mouse femoral head explant cultures treated with IL-1beta and a surgically induced OA mouse model were used to determine the effect of LiCl on proteoglycan loss and cartilage degradation. Results. LiCl treatment resulted in decreased catabolic marker mRNA levels and activation of NF-kappaB, p38 MAPK, and Stat3 signaling in IL-1beta -treated chondrocytes. Furthermore, LiCl directly inhibited IL-6-stimulated activation of Stat3 signaling. Consequently, loss of proteoglycan and cartilage destruction in LiCl-treated knee joints 8 weeks after OA-induced surgery or in LiCl-treated femoral head explants after IL-1beta treatment were markedly reduced compared to vehicle-treated joints or explants. Conclusion. LiCl reduced catabolic events in IL-1beta -treated human articular chondrocytes and cartilage destruction in IL-1beta -treated mouse femoral head explants and in surgically induced OA mouse models via the inhibition of NF-kappaB, p38 and Stat3 signaling pathway activities. (c) 2014 American College of Rheumatology.