Jennifer L. Owen

Abating colon cancer polyposis by Lactobacillus acidophilus deficient in lipoteichoic acid

An imbalance of commensal bacteria and their gene products underlies mucosal and, in particular, gastrointestinal inflammation and a predisposition to cancer. Lactobacillus species have received considerable attention as examples of beneficial microbiota. We have reported previously that deletion of the phosphoglycerol transferase gene that is responsible for lipoteichoic acid (LTA) biosynthesis in Lactobacillus acidophilus (NCK2025) rendered this bacterium able to significantly protect mice against induced colitis when delivered orally. Here we report that oral treatment with LTA-deficient NCK2025 normalizes innate and adaptive pathogenic immune responses and causes regression of established colonic polyps. This study reveals the proinflammatory role of LTA and the ability of LTA-deficient L. acidophilus to regulate inflammation and protect against colonic polyposis in a unique mouse model.

Macrophages and chemokines as mediators of angiogenesis

Accumulating evidence attests to the important roles of both macrophages and chemokines in angiogenesis. Tumor-associated macrophages or TAMS constitute the major fraction of tumor-infiltrating leukocytes and are recruited by a number of chemoattractants that are produced by the tumor and tumor-associated stroma. This heterogeneous cell population is activated by a variety of stimuli and becomes polarized to result in functionally different phenotypes regarding tumor progression. As opposed to classically activated or M1 macrophages that exhibit anti-tumor functions, most TAMS are considered to be of the alternatively activated or M2 phenotype, and express multiple cytokines, proteases, and chemokines that promote tumor angiogenesis. Chemokines also have disparate effects on angiogenesis regulation, as several members of the CXC and CC chemokine families are potent inducers of angiogenesis, while a subset of CXC chemokines are angiostatic. This review summarizes the current literature regarding the roles and modes of action of macrophage-derived chemokines as mediators of angiogenesis.

SIGNR3-dependent immune regulation by Lactobacillus acidophilus surface layer protein A in colitis

Intestinal immune regulatory signals govern gut homeostasis. Breakdown of such regulatory mechanisms may result in inflammatory bowel disease (IBD). Lactobacillus acidophilus contains unique surface layer proteins (Slps), including SlpA, SlpB, SlpX, and lipoteichoic acid (LTA), which interact with pattern recognition receptors to mobilize immune responses. Here, to elucidate the role of SlpA in protective immune regulation, the NCK2187 strain, which solely expresses SlpA, was generated. NCK2187 and its purified SlpA bind to the C‐type lectin SIGNR3 to exert regulatory signals that result in mitigation of colitis, maintenance of healthy gastrointestinal microbiota, and protected gut mucosal barrier function. However, such protection was not observed in Signr3−/− mice, suggesting that the SlpA/SIGNR3 interaction plays a key regulatory role in colitis. Our work presents critical insights into SlpA/SIGNR3‐induced responses that are integral to the potential development of novel biological therapies for autoinflammatory diseases, including IBD.

Epithelial CaSR deficiency alters intestinal integrity and promotes proinflammatory immune responses

The intestinal epithelium is equipped with sensing receptor mechanisms that interact with luminal microorganisms and nutrients to regulate barrier function and gut immune responses, thereby maintaining intestinal homeostasis. Herein, we clarify the role of the extracellular calcium‐sensing receptor (CaSR) using intestinal epithelium‐specific Casr −/− mice. Epithelial CaSR deficiency diminished intestinal barrier function, altered microbiota composition, and skewed immune responses towards proinflammatory. Consequently, Casr −/− mice were significantly more prone to chemically induced intestinal inflammation resulting in colitis. Accordingly, CaSR represents a potential therapeutic target for autoinflammatory disorders, including inflammatory bowel diseases.

New generation of oral mucosal vaccines targeting dendritic cells.

As most infectious organisms gain entry at mucosal surfaces, there is a great deal of interest in developing vaccines that elicit effective mucosal immune responses against pathogen challenge. Targeted vaccination is one of the most effective methods available to prevent and control infectious diseases. Mucosal vaccines can offer lower costs, better accessibility, needle free delivery, and a higher capacity for mass immunizations during pandemics. Both local mucosal immunity and robust systemic responses can be achieved through mucosal vaccination. Recent progress in understanding the molecular and cellular components of the mucosal immune system have allowed for the development of a novel mucosal vaccine platform utilizing specific dendritic cell-targeting peptides and orally administered lactobacilli to elicit efficient antigen specific immune responses against infections, including Bacillus anthracis in experimental models of disease.

Expression of the inflammatory chemokines CCL2, CCL5 and CXCL2 and the receptors CCR1–3 and CXCR2 in T lymphocytes from mammary tumor-bearing mice☆

Chemokines and their receptors have been studied in several solid tumor models as mediators of inflammation. In turn, inflammation has been implicated in the promotion and progression of tumors, and as such, chemokines have been proposed as novel molecular targets for chemotherapy. While the expression of these molecules has been described in tumor cells, endothelial cells, macrophages and neutrophils, less attention has been paid to the expression profile of these molecules by T lymphocytes in the periphery or infiltrating the tumor. Using the D1-DMBA-3 murine mammary adenocarcinoma model, we aimed to better characterize the differential expression of chemokines and/or their receptors in the host and in the tumor microenvironment, and specifically, in the T cells of tumor-bearing mice compared to normal control animals. We found that T lymphocytes from tumor-bearing mice express the pro-inflammatory chemokines, CCL2, CCL5 and CXCL2, as well as the chemokine receptors, CCR1, CCR2, CCR3 and CXCR2.

Colonic Immune Suppression, Barrier Dysfunction, and Dysbiosis by Gastrointestinal Bacillus anthracis Infection

Gastrointestinal (GI) anthrax results from the ingestion of Bacillus anthracis. Herein, we investigated the pathogenesis of GI anthrax in animals orally infected with toxigenic non-encapsulated B. anthracis Sterne strain (pXO1+ pXO2−) spores that resulted in rapid animal death. B. anthracis Sterne induced significant breakdown of intestinal barrier function and led to gut dysbiosis, resulting in systemic dissemination of not only B. anthracis, but also of commensals. Disease progression significantly correlated with the deterioration of innate and T cell functions. Our studies provide critical immunologic and physiologic insights into the pathogenesis of GI anthrax infection, whereupon cleavage of mitogen-activated protein kinases (MAPKs) in immune cells may play a central role in promoting dysfunctional immune responses against this deadly pathogen.

Induction of intestinal pro-inflammatory immune responses by lipoteichoic acid

BackgroundThe cellular and molecular mechanisms of inflammatory bowel disease are not fully understood; however, data indicate that uncontrolled chronic inflammation induced by bacterial gene products, including lipoteichoic acid (LTA), may trigger colonic inflammation resulting in disease pathogenesis. LTA is a constituent glycolipid of Gram-positive bacteria that shares many inflammatory properties with lipopolysaccharide and plays a critical role in the pathogenesis of severe inflammatory responses via Toll-like receptor 2. Accordingly, we elucidate the role of LTA in immune stimulation and induced colitis in vivo.MethodsTo better understand the molecular mechanisms utilized by the intestinal microbiota and their gene products to induce or subvert inflammation, specifically the effect(s) of altered surface layer protein expression on the LTA-mediated pro-inflammatory response, the Lactobacillus acidophilus s urface l ayer p rotein (Slp) genes encoding SlpB and SlpX were deleted resulting in a SlpB- and SlpX- mutant that continued to express SlpA (assigned as NCK2031).ResultsOur data show profound activation of dendritic cells by NCK2031, wild-type L. acidophilus (NCK56), and purified Staphylococcus aureus-LTA. In contrary to the LTA-deficient strain NCK2025, the LTA-expressing strains NCK2031 and NCK56, as well as S. aureus-LTA, induce pro-inflammatory innate and T cell immune responses in vivo. Additionally, neither NCK2031 nor S. aureus-LTA supplemented in drinking water protected mice from DSS-colitis, but instead, induced significant intestinal inflammation resulting in severe colitis and tissue destruction.ConclusionsThese findings suggest that directed alteration of two of the L. acidophilus NCFM-Slps did not ameliorate LTA-induced pro-inflammatory signals and subsequent colitis.

The role of the calcium-sensing receptor in gastrointestinal inflammation.

The gastrointestinal (GI) tract must balance the extraction of energy and metabolic end-products from ingested nutrition and resident gut microbes and the maintenance of a symbiotic relationship with this microbiota, with the ability to mount functional immune responses to pathogenic organisms to maintain GI health. The gut epithelium is equipped with bacteria-sensing mechanisms that discriminate between pathogenic and commensal microorganisms and regulate host responses between immunity and tolerance. The epithelium also expresses numerous nutrient-sensing receptors, but their importance in the preservation of the gut microbiota and immune homeostasis remains largely unexplored. Observations that a deficiency in the extracellular calcium-sensing receptor (CaSR) using intestinal epithelium-specific receptor knockout mice resulted in diminished intestinal barrier integrity, altered composition of the gut microbiota, modified expression of intestinal pattern recognition receptors, and a skewing of local and systemic innate responses from regulatory to stimulatory, may change the way that this receptor is considered as a potential immunotherapeutic target in gut homeostasis. These findings suggest that pharmacologic CaSR activators and CaSR-based nutrients such as calcium, polyamines, phenylalanine, tryptophan, and oligo-peptides might be useful in conditioning the gut microenvironment, and thus, in the prevention and treatment of disorders such as inflammatory bowel disease (IBD), infectious enterocolitis, and other inflammatory and secretory diarrheal diseases. Here, we review the emerging roles of the CaSR in intestinal homeostasis and its therapeutic potential for gut pathology.

Partial cytogenetic response with toceranib and prednisone treatment in a young dog with chronic monocytic leukemia.

Treatment of chronic monocytic leukemia (CMoL) in dogs has traditionally consisted of hydroxyurea. The use of tyrosine kinase inhibitors has been proposed as a treatment option for dogs with CMoL but has never been reported. We report a case of CMoL in a young dog that achieved clinical remission with treatment with the tyrosine kinase inhibitor toceranib and prednisone.