Sly, Laura M.

The chapter, "Generation and characterization of murine alternatively activated macrophages" was written by the listed authors including Shelley B. Weisser (Douglas College Faculty). Part of the "Methods in Molecular Biology (Methods and Protocols)" book series (MIMB, volume 946): For over 35 years, biological scientists have come to rely on the research protocols and methodologies in the critically acclaimed Methods in Molecular Biology series. The series was the first to introduce the step-by-step protocols approach that has become the standard in all biomedical protocol publishing. Each protocol is provided in readily-reproducible step-by step fashion, opening with an introductory overview, a list of the materials and reagents needed to complete the experiment, and followed by a detailed procedure that is supported with a helpful notes section offering tips and tricks of the trade as well as troubleshooting advice. These hallmark features were introduced by series editor Dr. John Walker and constitute the key ingredient in each and every volume of the Methods in Molecular Biology series. Tested and trusted, comprehensive and reliable, all protocols from the series are indexed in PubMed. <p> <p> Book "Basic Cell Culture Protocols": At some point in their careers, virtually every scientist and technician, as well as many medical professionals, regardless of their area of specialization have a need to utilize cell culture systems. Updating and significantly expanding upon the previous editions, Basic Cell Culture Protocols, Fourth Edition provides the novice cell culturist with sufficient information to perform the basic techniques, to ensure the health and identity of their cell lines, and to be able to isolate and culture specialized primary cell types. The intent of this extensive volume is to generate a valuable resource containing clear methodologies pertinent to current areas of investigation, rather than attempting to educate cell culturists on specific cell types or organ systems. Written in the highly successful Methods in Molecular Biology™, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols, and tips on troubleshooting and avoiding known pitfalls. Comprehensive and up-to-date, Basic Cell Culture Protocols, Fourth Edition compiles the essential techniques needed to approach this vital laboratory activity with full success. <p>Book Chapter: Macrophages play a key role in the innate immune response and help to direct the acquired immune response. Early in the innate immune response, they produce reactive oxygen species and pro-inflammatory cytokines and chemokines to drive inflammation and are referred to as “classically activated” or “killer” macrophages (M1). During the resolution phase of inflammation, they switch to what is known as an “alternatively activated” phenotype or “healer” macrophage (M2) and contribute to debris scavenging, angiogenesis, and wound healing. M1 macrophages are activated by treatment with IFNγ or LPS and M2 macrophages are activated by treatment with Th2 cytokines IL-4 or IL-13 and the M2 phenotype switch can be enhanced by IL-10. Macrophages can also be skewed during differentiation in vitro, and the resultant phenotype depends upon the cytokine provided to support their differentiation. In murine macrophages, MCSF promotes differentiation to an M1 phenotype, GM-CSF promotes differentiation to an M2 phenotype and IL-3 promotes differentiation into a profoundly M2 skewed phenotype. A defining feature of the phenotype of murine M1 versus M2 macrophages is how they metabolize L-arginine. In response to an inflammatory stimulus like LPS, M1 macrophages produce inducible nitric oxide synthase (iNOS) which uses L-arginine as a substrate to produce nitric oxide (NO). M2 macrophages constitutively produce the enzyme arginase I (argI), which sequesters L-arginine from iNOS and results in the production of ornithine and downstream polyamines and L-proline. M1 macrophages also produce relatively higher levels of pro-inflammatory IL-12 and lower levels of anti-inflammatory IL-10 relative to M2 macrophages. In this chapter, we describe in vitro derivation of polarized bone marrow macrophages and methods to analyze the resulting phenotype including Q-PCR, Western blotting, and enzyme assays to determine argI and iNOS expression and activity, as well as production of IL-12p40 and IL-10 and determination of IL-12/IL-10 ratios. Production of iNOS, NO, IL-12p40, and IL-10 are measured after treatment with LPS.

mφ are heterogeneous in their functions, and although it is clear that inflammatory mφ contribute to inflammation in IBDs, multiple lines of evidence suggest that M2a mφ may offer protection during intestinal inflammation. In vivo SHIP‐deficient mouse mφ are M2a so SHIP‐deficient mice provide a unique genetic model of M2a mφ. Based on this, this study tested the hypothesis that SHIP‐deficient, M2a mφ protect mice from intestinal inflammation. The objectives were to compare the susceptibility of SHIP+/+ and SHIP−/− littermates with DSS‐induced intestinal inflammation and to determine whether protection was mφ‐mediated and whether protection could be transferred to a susceptible host. We have found that SHIP−/− mice are protected during DSS‐induced intestinal inflammation. SHIP−/− mice have delayed rectal bleeding and reduced weight loss, disruption of intestinal architecture, and immune cell infiltration during DSS‐induced colitis relative to their WT littermates. Using liposome depletion of mφ, we found that SHIP−/− mouse protection was indeed mφ‐mediated. Finally, we determined that SHIP−/− mφ‐mediated protection could be conferred to susceptible WT mice by adoptive transfer of M2a mφ derived ex vivo. This study supports our hypothesis by demonstrating that SHIP‐deficient, M2a mφ are protective in this murine model of acute intestinal inflammation. Adoptive transfer of M2a mφ to patients with IBDs offers a promising, new strategy for treatment that may be particularly useful in patients who are otherwise refractory to conventional therapies.

Alternatively activated or M2 macrophages have been reported to protect mice from intestinal inflammation, but the mechanism of protection has not been elucidated. In this study, we demonstrate that mice deficient in the p110δ catalytic subunit activity of class I phosphatidylinositol 3-kinase (PI3Kp110δ) have increased clinical disease activity and histological damage during dextran sodium sulfate (DSS) induced colitis. Increased disease severity in PI3Kp110δ-deficient mice is dependent on professional phagocytes and correlates with reduced numbers of arginase I+ M2 macrophages in the colon and increased production of inflammatory nitric oxide. We further demonstrate that PI3Kp110δ-deficient macrophages are defective in their ability to induce arginase I when skewed to an M2 phenotype with IL-4. Importantly, adoptive transfer of IL-4-treated macrophages derived from WT mice, but not those from PI3Kp110δ-deficient mice, protects mice during DSS-induced colitis. Moreover, M2 macrophages mediated protection is lost when mice are cotreated with inhibitors that block arginase activity or during adoptive transfer of arginase I deficient M2 macrophages. Taken together, our data demonstrate that arginase I activity is required for M2 macrophages mediated protection during DSS-induced colitis in PI3Kp110δ-deficient mice.

Intestinal fibrosis is a serious complication of Crohn's disease (CD) that can lead to stricture formation, which requires surgery. Mechanisms underlying intestinal fibrosis remain elusive because of a lack of suitable mouse models. Herein, we describe a spontaneous mouse model of intestinal inflammation with fibrosis and the profibrotic role of arginase I. The Src homology 2 domain–containing inositol polyphosphate 5′-phosphatase–deficient (SHIP –/–) mice developed spontaneous discontinuous intestinal inflammation restricted to the distal ileum starting at the age of 4 weeks. Mice developed several key features resembling CD, including inflammation and fibrosis. Inflammation was characterized by abundant infiltrating Gr-1–positive immune cells, granuloma-like immune cell aggregates that contained multinucleated giant cells, and a mixed type 2 and type 17 helper T-cell cytokine profile. Fibrosis was characterized by a thickened ileal muscle layer, collagen deposition, and increased fibroblasts at the sites of collagen deposition. SHIP –/– ilea had increased arginase activity and arginase I expression that was inversely proportional to nitrotyrosine staining. SHIP –/– mice were treated with the arginase inhibitor S-(2-boronoethyl)- l-cysteine, and changes in the disease phenotype were measured. Arginase inhibition did not affect the number of immune cell infiltrates in the SHIP –/– mouse ilea; rather, it reduced collagen deposition and muscle hyperplasia. These findings suggest that arginase activity is a potential target to limit intestinal fibrosis in patients with CD.