Gi2 alpha protein deficiency: a model of inflammatory bowel disease

Update: Induction of Inflammatory Bowel Disease in Immunodeficient Mice by Injection of Naïve CD4+ T cells (T Cell Transfer Model of Colitis)

The intestinal inflammation induced by injection of naïve CD4+ T cells into lymphocyte-deficient hosts (more commonly known as the T cell transfer model of colitis) shares many features of idiopathic inflammatory bowel disease (IBD) in humans, such as epithelial cell hyperplasia, crypt abscess formation, and dense lamina propria lymphocyte infiltration. As such, it provides a useful tool for studying mucosal immune regulation as it relates to the pathogenesis and treatment of IBD in humans. In the IBD model described here, colitis is induced in Rag (recombination-activating gene)-deficient mice by reconstitution of these mice with naïve CD4+CD45RBhi T cells through adoptive T cell transfer. Although different recipient hosts of cell transfer can be used, Rag-deficient mice are the best characterized and support studies that are both flexible and reproduceable. As described in the Basic Protocol, in most studies the transferred cells consist of naïve CD4+ T cells (CD45RBhi T cells) derived by fluorescence-activated cell sorting from total CD4+ T cells previously purified using immunomagnetic negative selection beads. In a Support Protocol, methods to characterize colonic disease progression are described, including the monitoring of weight loss and diarrhea and the histological assessment of colon pathology. © 2024 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Induction of IBD in Rag-deficient mice by the transfer of naïve CD4+CD45RBhi T cells Support Protocol: Monitoring development of colitis.

Deletion of the α subunit of the heterotrimeric Go protein impairs cerebellar cortical development in mice

Go is a member of the pertussis toxin-sensitive Gi/o family. Despite its abundance in the central nervous system, the precise role of Go remains largely unknown compared to other G proteins. In the present study, we explored the functions of Go in the developing cerebellar cortex by deleting its gene, Gnao. We performed a histological analysis with cerebellar sections of adult mice by cresyl violet- and immunostaining. Global deletion of Gnao induced cerebellar hypoplasia, reduced arborization of Purkinje cell dendrites, and atrophied Purkinje cell dendritic spines and the terminal boutons of climbing fibers from the inferior olivary nucleus. These results indicate that Go-mediated signaling pathway regulates maturation of presynaptic parallel fibers from granule cells and climbing fibers during the cerebellar cortical development.

Glycoprotein A33 deficiency: a new mouse model of impaired intestinal epithelial barrier function and inflammatory disease

The cells of the intestinal epithelium provide a selectively permeable barrier between the external environment and internal tissues. The integrity of this barrier is maintained by tight junctions, specialised cell-cell contacts that permit the absorption of water and nutrients while excluding microbes, toxins and dietary antigens. Impairment of intestinal barrier function contributes to multiple gastrointestinal disorders, including food hypersensitivity, inflammatory bowel disease (IBD) and colitis-associated cancer (CAC). Glycoprotein A33 (GPA33) is an intestinal epithelium-specific cell surface marker and member of the CTX group of transmembrane proteins. Roles in cell-cell adhesion have been demonstrated for multiple CTX family members, suggesting a similar function for GPA33 within the gastrointestinal tract. To test a potential requirement for GPA33 in intestinal barrier function, we generated Gpa33^−/− mice and subjected them to experimental regimens designed to produce food hypersensitivity, colitis and CAC. Gpa33^−/− mice exhibited impaired intestinal barrier function. This was shown by elevated steady-state immunosurveillance in the colonic mucosa and leakiness to oral TRITC-labelled dextran after short-term exposure to dextran sodium sulphate (DSS) to injure the intestinal epithelium. Gpa33^−/− mice also exhibited rapid onset and reduced resolution of DSS-induced colitis, and a striking increase in the number of colitis-associated tumours produced by treatment with the colon-specific mutagen azoxymethane (AOM) followed by two cycles of DSS. In contrast, Gpa33^−/− mice treated with AOM alone showed no increase in sporadic tumour formation, indicating that their increased tumour susceptibility is dependent on inflammatory stimuli. Finally, Gpa33^−/− mice displayed hypersensitivity to food allergens, a common co-morbidity in humans with IBD. We propose that Gpa33^−/− mice provide a valuable model to study the mechanisms linking intestinal permeability and multiple inflammatory pathologies. Moreover, this model could facilitate preclinical studies aimed at identifying drugs that restore barrier function.

Highlighted Article: We show that GPA33, an intestine-specific cell surface protein, plays a role in the maintenance of intestinal barrier function and the prevention of intestinal pathologies such as food hypersensitivity, inflammatory bowel disease and colitis-associated cancer.

G(i)α proteins exhibit functional differences in the activation of ERK1/2, Akt and mTORC1 by growth factors in normal and breast cancer cells

Background

In a classic model, G_iα proteins including G_i1α, G_i2α and G_i3α are important for transducing signals from G_iα protein-coupled receptors (G_iαPCRs) to their downstream cascades in response to hormones and neurotransmitters. Our previous study has suggested that G_i1α, G_i2α and G_i3α are also important for the activation of the PI3K/Akt/mTORC1 pathway by epidermal growth factor (EGF) and its family members. However, a genetic role of these G_iα proteins in the activation of extracellular signal-regulated protein kinase 1 and 2 (ERK1/2) by EGF is largely unknown. Further, it is not clear whether these G_iα proteins are also engaged in the activation of both the Akt/mTORC1 and ERK1/2 pathways by other growth factor family members. Additionally, a role of these G_iα proteins in breast cancer remains to be elucidated.

Results

We found that Gi1/3 deficient MEFs with the low expression level of G_i2α showed defective ERK1/2 activation by EGFs, IGF-1 and insulin, and Akt and mTORC1 activation by EGFs and FGFs. Gi1/2/3 knockdown breast cancer cells exhibited a similar defect in the activations and a defect in in vitro growth and invasion. The G_iα proteins associated with RTKs, Gab1, FRS2 and Shp2 in breast cancer cells and their ablation impaired Gab1’s interactions with Shp2 in response to EGF and IGF-1, or with FRS2 and Grb2 in response to bFGF.

Conclusions

G_iα proteins differentially regulate the activation of Akt, mTORC1 and ERK1/2 by different families of growth factors. G_iα proteins are important for breast cancer cell growth and invasion.

Gαi2 signaling is required for skeletal muscle growth, regeneration, and satellite cell proliferation and differentiation

We have previously shown that activation of Gαi2, an α subunit of the heterotrimeric G protein complex, induces skeletal muscle hypertrophy and myoblast differentiation. To determine whether Gαi2 is required for skeletal muscle growth or regeneration, Gαi2-null mice were analyzed. Gαi2 knockout mice display decreased lean body mass, reduced muscle size, and impaired skeletal muscle regeneration after cardiotoxin-induced injury. Short hairpin RNA (shRNA)-mediated knockdown of Gαi2 in satellite cells (SCs) leads to defective satellite cell proliferation, fusion, and differentiation ex vivo. The impaired differentiation is consistent with the observation that the myogenic regulatory factors MyoD and Myf5 are downregulated upon knockdown of Gαi2. Interestingly, the expression of microRNA 1 (miR-1), miR-27b, and miR-206, three microRNAs that have been shown to regulate SC proliferation and differentiation, is increased by a constitutively active mutant of Gαi2 [Gαi2(Q205L)] and counterregulated by Gαi2 knockdown. As for the mechanism, this study demonstrates that Gαi2(Q205L) regulates satellite cell differentiation into myotubes in a protein kinase C (PKC)- and histone deacetylase (HDAC)-dependent manner.

Central role of the gut epithelial barrier in the pathogenesis of chronic intestinal inflammation: lessons learned from animal models and human genetics

The gut mucosa is constantly challenged by a bombardment of foreign antigens and environmental microorganisms. As such, the precise regulation of the intestinal barrier allows the maintenance of mucosal immune homeostasis and prevents the onset of uncontrolled inflammation. In support of this concept, emerging evidence points to defects in components of the epithelial barrier as etiologic factors in the pathogenesis of inflammatory bowel diseases (IBDs). In fact, the integrity of the intestinal barrier relies on different elements, including robust innate immune responses, epithelial paracellular permeability, epithelial cell integrity, as well as the production of mucus. The purpose of this review is to systematically evaluate how alterations in the aforementioned epithelial components can lead to the disruption of intestinal immune homeostasis, and subsequent inflammation. In this regard, the wealth of data from mouse models of intestinal inflammation and human genetics are pivotal in understanding pathogenic pathways, for example, that are initiated from the specific loss of function of a single protein leading to the onset of intestinal disease. On the other hand, several recently proposed therapeutic approaches to treat human IBD are targeted at enhancing different elements of gut barrier function, further supporting a primary role of the epithelium in the pathogenesis of chronic intestinal inflammation and emphasizing the importance of maintaining a healthy and effective intestinal barrier.

A quantitative study of the mechanisms behind thymic atrophy in Gαi2-deficient mice during colitis development

Mice deficient for the G protein subunit Gαi2 spontaneously develop colitis, a chronic inflammatory disease associated with dysregulated T cell responses. We and others have previously demonstrated a thymic involution in these mice and an aberrant thymocyte dynamics. The Gαi2(-/-) mice have a dramatically reduced fraction of double positive thymocytes and an increased fraction of single positive (SP) thymocytes. In this study, we quantify a number of critical parameters in order to narrow down the underlying mechanisms that cause the dynamical changes of the thymocyte development in the Gαi2(-/-) mice. Our data suggest that the increased fraction of SP thymocytes results only from a decreased number of DP thymocytes, since the number of SP thymocytes in the Gαi2(-/-) mice is comparable to the control littermates. By measuring the frequency of T cell receptor excision circles (TRECs) in the thymocytes, we demonstrate that the number of cell divisions the Gαi2(-/-) SP thymocytes undergo is comparable to SP thymocytes from control littermates. In addition, our data show that the mature SP CD4(+) and CD8(+) thymocytes divide to the same extent before they egress from the thymus. By estimating the number of peripheral TREC(+) T lymphocytes and their death rate, we could calculate the daily egression of thymocytes. Gαi2(-/-) mice with no/mild and moderate colitis were found to have a slower export rate in comparison to the control littermates. The quantitative measurements in this study suggest a number of dynamical changes in the thymocyte development during the progression of colitis.

IEX-1 deficiency protects against colonic cancer

The immediate early response gene X-1 (IEX-1) is involved in regulation of various cellular processes including proliferation, apoptosis in part by controlling homeostasis of reactive oxygen species (ROS) at mitochondria. The present study shows reduced inflammatory responses and colorectal cancer in IEX-1 knockout (KO) mice treated with azoxymethane/dextran sulfate sodium (DSS). However, DSS induced worse colitis in RAG(-/-)IEX-1(-/-) double KO mice than in RAG and IEX-1 single KO mice, underscoring an importance of T cells in IEX-1 deficiency-induced protection against colon inflammation. Lack of IEX-1 promoted the differentiation of interleukin (IL)-17-producing T cells, concomitant with upregulation of Gαi2 expression, a gene that is well-documented for its role in the control of inflammation in the colon. In accordance with this, T-helper 17 (T(H)17) cell differentiation was compromised in the absence of Gαi2, and deletion of Gαi2 in T cells alone aggravated colon inflammation and colorectal cancer development after azoxymethane/DSS treatment. Null mutation of IEX-1 also enhanced both proliferation and apoptosis of intestinal epithelial cells (IEC) after injury. A potential impact of this altered IEC turnover on colon inflammation and cancer development is discussed. These observations provide a linkage of IEX-1 and Gαi2 expression in the regulation of T(H)17 cell differentiation and suggest a previously unappreciated role for IEX-1 in the control of colon epithelial homeostasis.

Early endothelial damage and increased colonic vascular permeability in the development of experimental ulcerative colitis in rats and mice

The role of endothelial damage and increased vascular permeability (VP) in the pathogenesis of ulcerative colitis (UC) has not been investigated. We examined using functional, morphologic, and molecular biologic studies whether and to what extent the endothelial barrier dysfunction precedes enhanced epithelial permeability (EP) and the development of mucosal lesions during the early stages of experimental UC. We showed that in rats with iodoacetamide (IA)-induced UC increased colonic VP occurs early (ie, 2.6-fold increase at 15 min, P<0.01) preceding changes in epithelial barrier permeability. EP was unchanged at 15 and 30 min after IA administration and was increased 1.9-fold at 1 h and 6.7-fold at 2 h (both P<0.001) after IA. In the dextran sodium sulfate-induced slowly developing UC, colonic VP was significantly increased in 2 days (P<0.05) and EP only in 4 days (P<0.05). Mucosal endothelial injury led to hypoxia (P<0.05) of colonic surface epithelial cells 30 min after IA administration that was associated with increased expressions of transcription factors hypoxia-inducible factor-1α and early growth response-1. Electron and light microscopy demonstrated areas of colonic mucosa with perivascular edema covered by intact layer of surface epithelial cells in both rat and mouse models of UC. This is the first demonstration in four models of UC that endothelial damage, increased colonic VP, perivascular edema, and epithelial hypoxia precede epithelial barrier dysfunction that is followed by erosions, ulceration, and inflammation in UC.

Animal models of colitis-associated carcinogenesis

Inflammatory bowel disease (IBD) is a group of chronic inflammatory disorders that affect individuals throughout life. Although the etiology and pathogenesis of IBD are largely unknown, studies with animal models of colitis indicate that dysregulation of host/microbial interactions are requisite for the development of IBD. Patients with long-standing IBD have an increased risk for developing colitis-associated cancer (CAC), especially 10 years after the initial diagnosis of colitis, although the absolute number of CAC cases is relatively small. The cancer risk seems to be not directly related to disease activity, but is related to disease duration/extent, complication of primary sclerosing cholangitis, and family history of colon cancer. In particular, high levels and continuous production of inflammatory mediators, including cytokines and chemokines, by colonic epithelial cells (CECs) and immune cells in lamina propria may be strongly associated with the pathogenesis of CAC. In this article, we have summarized animal models of CAC and have reviewed the cellular and molecular mechanisms underlining the development of carcinogenic changes in CECs secondary to the chronic inflammatory conditions in the intestine. It may provide us some clues in developing a new class of therapeutic agents for the treatment of IBD and CAC in the near future.

Towards a molecular risk map--recent advances on the etiology of inflammatory bowel disease

Recent advances have enabled a comprehensive understanding of the genetic architecture of inflammatory bowel disease (IBD) with over 30 identified and replicated disease loci. The pathophysiological consequences of disease gene variants in Crohn disease and ulcerative colitis, the two main subentities of IBD, so far are only understood on the single disease gene level, yet complex network analyses linking the individual risk factors into a molecular risk map are still missing. In this review, we will focus on recent pathways and cellular functions that emerged from the genetic studies (e.g. innate immunity, autophagy) and delineate the existence of shared (e.g. IL23R, IL12B) and unique (e.g. NOD2 for CD) risk factors for the disease subtypes. Ultimately, the defined molecular profiles may identify individuals at risk early in life and may serve as a guidance to administer personalized interventions for causative therapies and/or early targeted prevention strategies. Due to this comparatively advanced level of molecular understanding in the field, IBD may represent precedent also for future developments of individualized genetic medicine in other polygenic disorders in general.

Colitis-associated colorectal cancer driven by T-bet deficiency in dendritic cells

We previously described a mouse model of ulcerative colitis linked to T-bet deficiency in the innate immune system. Here, we report that the majority of T-bet(-/-)RAG2(-/-) ulcerative colitis (TRUC) mice spontaneously progress to colonic dysplasia and rectal adenocarcinoma solely as a consequence of MyD88-independent intestinal inflammation. Dendritic cells (DCs) are necessary cellular effectors for a proinflammatory program that is carcinogenic. Whereas these malignancies arise in the setting of a complex inflammatory environment, restoration of T-bet selectively in DCs was sufficient to reduce colonic inflammation and prevent the development of neoplasia. TRUC colitis-associated colorectal cancer resembles the human disease and provides ample opportunity to probe how inflammation drives colorectal cancer development and to test preventative and therapeutic strategies preclinically.

Global survey of protein expression during gonadal sex determination in mice

The development of an embryo as male or female depends on differentiation of the gonads as either testes or ovaries. A number of genes are known to be important for gonadal differentiation, but our understanding of the regulatory networks underpinning sex determination remains fragmentary. To advance our understanding of sexual development beyond the transcriptome level, we performed the first global survey of the mouse gonad proteome at the time of sex determination by using two-dimensional nanoflow LC-MS/MS. The resulting data set contains a total of 1037 gene products (154 non-redundant and 883 redundant proteins) identified from 620 peptides. Functional classification and biological network construction suggested that the identified proteins primarily serve in RNA post-transcriptional modification and trafficking, protein synthesis and folding, and post-translational modification. The data set contains potential novel regulators of gonad development and sex determination not revealed previously by transcriptomics and proteomics studies and more than 60 proteins with potential links to human disorders of sexual development.

RNAi methodologies for the functional study of signaling molecules

RNA interference (RNAi) was investigated with the aim of achieving gene silencing with diverse RNAi platforms that include small interfering RNA (siRNA), short hairpin RNA (shRNA) and antisense oligonucleotides (ASO). Different versions of each system were used to silence the expression of specific subunits of the heterotrimeric signal transducing G-proteins, G alpha i2 and G beta 2, in the RAW 264.7 murine macrophage cell line. The specificity of the different RNA interference (RNAi) platforms was assessed by DNA microarray analysis. Reliable RNAi methodologies against the genes of interest were then developed and applied to functional studies of signaling networks. This study demonstrates a successful knockdown of target genes and shows the potential of RNAi for use in functional studies of signaling molecules.

Alterations in myeloid dendritic cell innate immune responses in the Galphai2-deficient mouse model of colitis

BACKGROUND

The G protein alpha subunit type-2 (Galpha(i)2)-deficient mouse develops inflammatory bowel disease (IBD) with increased severity in mice on a 129SvEv (129) background compared to the C57BL/6 (B6) background. Since dendritic cells (DCs) are key cells of innate immunity, we determined whether Galpha(i)2(-/-) DCs have functional defects, influenced by strain background, that predispose to IBD.

METHODS

By breeding these strains to homozygosity for the first time, it became possible to study innate immunity in this animal model with more precision than ever before. Immature DCs were generated using bone marrow monoblasts cultured in the presence of GM-CSF (BMDCs), DC subsets sorted and responses to TLR9 activation were assayed.

RESULTS

In contrast to Galpha(i)2(-/-) B6, Galpha(i)2(-/-) 129 mice display accelerated onset and increased severity of colitis, abnormal mucosal DC distribution, accompanied by preponderance for Th1 and Th17-associated gut cytokine expression. TLR9 activation of BMDCs induces sustained p38 MAPK activation and greater Th1- and Th17-type cytokine secretion in both strains of Galpha(i)2-deficient compared to wildtype BMDCs. However, only B6 Galpha(i)2(-/-) BMDCs concomitantly produces IL-10 while Galpha(i)2(-/-) 129 BMDCs do not.

CONCLUSIONS

Loss of Galpha(i)2 promotes a Th1/Th17 phenotype and relative IL-10 insufficiency in Galpha(i)2(-/-) 129 BMDCs may account for the striking difference in disease.

Induction of TNBS colitis in mice

The animal model described in this unit is one of several that have been used to study the immunopathogenesis of inflammatory bowel disease. The model employs the use of 2,4,6-trinitrobenzenesulfonic acid (TNBS), which induces severe colonic inflammation when administered intrarectally in SJL/J mice. The colitis which results from this procedure presents clinical and histopathological findings that resemble those seen in Crohn's disease. The unit describes the critical parameters needed for successful induction of TNBS-colitis as well methods for monitoring and grading disease levels. A support protocol for isolating lamina propria mononuclear cells from mouse colons is also included.

Time course of neural and contractile disturbances in a rat model of colitis induced by Trichinella spiralis

Colitis induced by Trichinella spiralis in rat induces alterations in the spontaneous motor pattern displayed by circular colonic muscle [Auli, M., Fernandez, E., 2005. Characterization of functional and morphological changes in a rat model of colitis induced by T. spiralis. Digestive Diseases and Sciences 50(8), 1432-1443]. We examined the temporal relationship between the severity of inflammation and the altered contractility of the underlying circular muscle as well as the role of NANC inhibitory pathways in the disruption of the motility pattern. Colitis was induced by intrarectal administration of T. spiralis larvae. Responses to acetylcholine (ACh) and increased extracellular potassium as well as the effect of tetrodotoxin (TTX, 1 microM), N-nitro-l-arginine (L-NOARG, 1 mM) and apamin (1 microM) were determined in vitro in the organ bath with circular muscle strips from sham-infected and infected rats at days 2-30 postinfection (PI). Microelectrode recordings were performed to study the putative changes in electrical activity of colonic smooth muscle cells. Responses to ACh and KCl were decreased at all days PI compared to sham. Intracellular calcium depletion had a greater inhibitory effect in inflamed tissue (6-14 PI). The effect of TTX, L-NOARG and apamin on the spontaneous contractions was found to be altered in all infected rats, i.e. their effects were transient and milder. Inflamed tissue showed lower resting membrane potential and a decreased duration of inhibitory junction potentials induced by electrical stimulation. These data suggest that the decreased contractility of colonic circular smooth muscle induced by the intrarectal T. spiralis infection results from the impairment of the excitation-contraction coupling, from a persistent hyperpolarization of smooth muscle cells and from impaired NANC inhibitory neurotransmission.

Study on the Colon Specific Delivery of Prednisolone Using Chitosan Capsules

In this study, we examined the effectiveness of chitosan capsules for the colon-specific delivery of prednisolone in rats. We also evaluated the effectiveness and side effects of prednisolone using chitosan capsules compared with the conventional dosage form (gelatin capsules). We found a significant increase in the concentration of prednisolone in the large intestinal mucosa when prednisolone was administered orally using chitosan capsules, as compared with the case using gelatin capsules. On the other hand, the plasma concentrations of prednisolone after oral administration using chitosan capsules were much lower than those in the case of gelatin capsules. We also assessed the effectiveness of prednisolone for the healing of trinitrobenzene sulfonic acid-induced colitis by measuring myeloperoxidase (MPO) activity and colon wet weight/body weight (C/B) ratio. MPO activities and C/B ratios were significantly reduced when prednisolone was administered orally using chitosan capsules, in comparison with the case of gelatin capsules. Moreover, the weight of the thymus, which is an index of the side effects of prednisolone, markedly decreased after oral administration of prednisolone using gelatin capsules, whereas its weight did not change as much when prednisolone was administered orally using chitosan capsules. These findings indicate that chitosan capsules might be useful for the colon-specific delivery of prednisolone and its enhanced effectiveness for the healing of colitis in rats. Moreover, chitosan capsules might be also effective in reducing the side effects of prednisolone due to its decreased intestinal transfer to the systemic circulation.

Signaling through Galphai2 protein is required for recruitment of neutrophils for antibody-mediated elimination of larval Strongyloides stercoralis in mice

The heterotrimeric guanine nucleotide-binding protein Galphai2 is involved in regulation of immune responses against microbial and nonmicrobial stimuli. Galphai2-/- mice have a selectively impaired IgM response consistent with a disorder in B cell development yet have augmented T cell effector function associated with increased production of IFN-gamma and IL-4. The goal of the present study was to determine if a deficiency in the Galphai2 protein in mice would affect the protective immune response against Strongyloides stercoralis, which is IL-4-, IL-5-, and IgM-dependent. Galphai2-/- and wild-type mice were immunized and challenged with S. stercoralis larvae and analyzed for protective immune responses against infection. Galphai2-/- mice failed to kill the larvae in the challenge infection as compared with wild-type mice despite developing an antigen-specific Th2 response characterized by increased IL-4, IL-5, IgM, and IgG. Transfer of serum collected from immunized Galphai2-/- mice to naïve wild-type mice conferred passive protective immunity against S. stercoralis infection thus confirming the development of a protective antibody response in Galphai2-/- mice. Differential cell analyses and myeloperoxidase assays for quantification of neutrophils showed a significantly reduced recruitment of neutrophils into the microenvironment of the parasites in immunized Galphai2-/- mice. However, cell transfer studies demonstrated that neutrophils from Galphai2-/- mice are competent in killing larvae. These data demonstrate that Galphai2 signaling events are not required for the development of the protective immune responses against S. stercoralis; however, Galphai2 is essential for the recruitment of neutrophils required for host-dependent killing of larvae.

Localization and variable expression of G alpha(i2) in human endometrium and Fallopian tubes

BACKGROUND

Heterotrimeric G proteins take part in membrane-mediated cell signalling and have a role in hormonal regulation. This study clarifies the expression and localization of the G protein subunit G alpha(i2) in the human endometrium and Fallopian tube and changes in G alpha(i2) expression in human endometrium during the menstrual cycle.

METHODS

The expression of G alpha(i2) was identified by Polymerase chain reaction (PCR), and localization confirmed by immunostaining. Cyclic changes in G alpha(i2) expression during the menstrual cycle were evaluated by quantitative real-time PCR.

RESULTS

We found G alpha(i2) to be expressed in human endometrium, Fallopian tube tissue and in primary cultures of Fallopian tube epithelial cells. Our studies revealed enriched localization of G alpha(i2) in Fallopian tube cilia and in endometrial glands. We showed that G alpha(i2) expression in human endometrium changes significantly during the menstrual cycle, with a higher level in the secretory versus proliferative and menstrual phases (P < 0.05).

CONCLUSIONS

G alpha(i2) is specifically localized in human Fallopian tube epithelial cells, particularly in the cilia, and is likely to have a cilia-specific role in reproduction. Significantly variable expression of G alpha(i2) during the menstrual cycle suggests G alpha(i2) might be under hormonal regulation in the female reproductive tract in vivo.

Pleiotropic phenotype of a genomic knock-in of an RGS-insensitive G184S Gnai2 allele

Signal transduction via guanine nucleotide binding proteins (G proteins) is involved in cardiovascular, neural, endocrine, and immune cell function. Regulators of G protein signaling (RGS proteins) speed the turn-off of G protein signals and inhibit signal transduction, but the in vivo roles of RGS proteins remain poorly defined. To overcome the redundancy of RGS functions and reveal the total contribution of RGS regulation at the Galpha(i2) subunit, we prepared a genomic knock-in of the RGS-insensitive G184S Gnai2 allele. The Galpha(i2)(G184S) knock-in mice show a dramatic and complex phenotype affecting multiple organ systems (heart, myeloid, skeletal, and central nervous system). Both homozygotes and heterozygotes demonstrate reduced viability and decreased body weight. Other phenotypes include shortened long bones, a markedly enlarged spleen, elevated neutrophil counts, an enlarged heart, and behavioral hyperactivity. Heterozygous Galpha(i2)(+/G184S) mice show some but not all of these abnormalities. Thus, loss of RGS actions at Galpha(i2) produces a dramatic and pleiotropic phenotype which is more evident than the phenotype seen for individual RGS protein knockouts.

Formation of B and T cell subsets require the cannabinoid receptor CB2

A recent and surprising body of research has linked changes in immune function to biologic and therapeutic targeting of cannabinoid receptors, which prototypically respond to delta-9 tetrahydrocannabinol. The peripheral cannabinoid receptor CB2 is highly expressed in immune cell types (macrophages, dendritic cells, and B cells), and pharmacologically alters their cytokine production and responsiveness. Accordingly, cannabinoid agonists can powerfully alter susceptibility to certain microbial infections, atherosclerosis, and cancer immunotherapy. What is unknown is the physiologic role of natural levels of endocannabinoids and their receptors in normal immune homeostasis. Galphai2-/- mice are deficient in the formation of certain B and T cell subsets and are susceptible to immune dysregulation, notably developing inflammatory bowel disease. A key issue is the identity of the Gi-coupled receptors relevant to this Galphai2-signaling pathway. We find that mice deficient in CB2, the Gi-coupled peripheral endocannabinoid receptor, have profound deficiencies in splenic marginal zone, peritoneal B1a cells, splenic memory CD4+ T cells, and intestinal natural killer cells and natural killer T cells. These findings partially phenocopy and extend the lymphocyte developmental disorder associated with the Galphai2-/- genotype, and suggest that the endocannabinoid system is required for the formation of T and B cell subsets involved in immune homeostasis. This noncompensatable requirement for physiologic function of the endocannabinoid system is novel. Because levels of endocannabinoids are highly restricted microanatomically, local regulation of their production and receptor expression offers a new principle for regional immune homeostasis and disease susceptibility, and extends and refines the rationale for CB2-targeted immunotherapy in immune and inflammatory diseases.

Environment as a Critical Factor for the Pathogenesis and Outcome of Gastrointestinal Disease: Experimental and Human Inflammatory Bowel Disease and Helicobacter-Induced Gastritis

Environmental factors play an important role in the manifestation, course, and prognosis of diseases of the gastrointestinal tract such as inflammatory bowel disease (IBD) and Helicobacter pylori-induced gastritis. These two disease complexes were chosen for a discussion of the contribution of environmental factors to the disease outcome in humans and animal models. Dissecting complex diseases like IBD and Helicobacter-induced gastritis has shown that the outcome of disease depends on the allelic constellation of a host and the microbial and physical environments. Host alleles predisposing to a disease in one genomic and/or environmental milieu may not be deleterious in other constellations; on the other hand, microbes can have different effects in different hosts and under different environmental conditions. The impact of the complex interaction between host genetics and environmental factors, particularly microflora, also underlines the importance of a defined genetic background and defined environments in animal studies and is indicative of the difficulties in analyzing complex diseases in humans.

Experimental models of inflammatory bowel disease reveal innate, adaptive, and regulatory mechanisms of host dialogue with the microbiota

There are now many experimental models of inflammatory bowel disease (IBD), most of which are due to induced mutations in mice that result in an impaired homeostasis with the intestinal microbiota. These models can be clustered into several broad categories that, in turn, define the crucial cellular and molecular mechanisms of host microbial interactions in the intestine. The first of these components is innate immunity defined broadly to include both myeloid and epithelial cell mechanisms. A second component is the effector response of the adaptive immune system, which, in most instances, comprises the CD4+ T cell and its relevant cytokines. The third component is regulation, which can involve multiple cell types, but again particularly involves CD4+ T cells. Severe impairment of a single component can result in disease, but many models demonstrate milder defects in more than one component. The same is true for both spontaneous models of IBD, C3H/HeJBir and SAMPI/Yit mice. The thesis is advanced that 'multiple hits' or defects in these interacting components is required for IBD to occur in both mouse and human.

Organizing a mucosal defense

Gastrointestinal associated lymphoid tissue can be divided into loosely organized effector sites, which include the lamina propria and intraepithelial lymphocytes, and more organized structures, such as mesenteric lymph nodes (LNs), Peyer's patches (PPs), isolated lymphoid follicles, and cryptopatches (CPs). These organized structures in the gastrointestinal tract have been hypothesized to play the role of primary lymphoid organ, supporting the extrathymic development of T lymphocytes (CPs), secondary lymphoid organs involved in the induction of the mucosal immune response (PPs), and tertiary lymphoid structures whose function is still under debate (isolated lymphoid follicles). The most widely studied lymphoid structure found in the small intestine is the PP. PPs are secondary lymphoid structures, and their development and function have been extensively investigated. However, single lymphoid aggregates resembling PPs have been also described in humans and in the murine small intestines. These isolated lymphoid follicles have both germinal centers and an overlying follicle-associated epithelium, suggesting that they also can function as inductive sites for the mucosal immune response. This review compares and contrasts the development and function of the four main organized gastrointestinal lymphoid tissues: CPs, isolated lymphoid follicles, PPs, and mesenteric LNs.

Impaired TGF-beta responses in peripheral T cells of G alpha i2-/- mice

Null mutation of heterotrimeric G protein alpha2 inhibitory subunit (Galphai2) induces Th1-skewed hyperimmune responses in the colon, leading to chronic colitis and the development of colonic adenocarcinoma. However, the underlying molecular mechanisms and cellular basis, in particular, for the role of Galphai2 in regulating immune responses, are poorly understood. We show here that peripheral T cells from Galphai2-deficient mice do not respond normally to the inhibitory effects of TGF-beta on proliferation and cytokine production, revealing a previously unappreciated cross-talk between these two signaling pathways. Lack of Galphai2 resulted in decreased phosphorylation of Smad2 and Smad3 in T cells at the basal levels as well as at the late but not early phase of TGF-beta stimulation, which appears to be ascribed to differential expression of neither cell surface TGF-beta receptors nor Smad7. The altered phosphorylation of Smad proteins involves phospholipase C-mediated signaling, a downstream signaling molecule of Galphai2, because phospholipase C inhibitors could restore Smad2 and Smad3 phosphorylation in Galphai2(-/-) T cells at levels comparable to that in wild-type T cells. Moreover, adoptive transfer of Galphai2-deficient T cells into immunocompromised mice rendered an otherwise resistant mouse strain susceptible to trinitrobenzesulfonic acid-induced colitis, suggesting that an impaired response of Galphai2-deficient T cells to TGF-beta may be one of the primary defects accounting for the observed colonic Th1-skewed hyperimmune responses. These findings shed new lights on the molecular and cellular basis of how Galphai2 down-regulates immune responses, contributing to the maintenance of mucosal tolerance.

Murine models of ulcerative colitis

Ulcerative colitis (UC) is an inflammatory bowel disease of unknown etiology limited to the large intestine. The disease is prevalent in industrial societies and is associated with specific ethnic populations. A number of murine models, each focused on distinct aspects of the disease process, were developed over the past 20 years to further our understanding of the pathogenesis of UC. These models have been and remain our best resource for the study of the disorder as a result of their homology to human UC and the ease in which they can be manipulated and examined. This review examines and distills what has been leamed from these models and how this information is related back to human UC.

Mouse models for the study of Crohn's disease

Crohn's Disease (CD) is a chronic inflammatory bowel disease (IBD) that can affect any portion of the gastrointestinal tract and can cause significant morbidity. A variety of animal models of both acute and chronic intestinal inflammation have been developed to investigate disease pathogenesis and novel treatment modalities. These include chemically induced, genetically manipulated and immune-mediated models of gut inflammation, each of which possesses similarities to human IBD and offers unique advantages for studying specific aspects of disease pathogenesis. However, the majority of these models are characterized by colitis and, unlike human CD, do not involve the small intestine. More recently, murine models of chronic ileal inflammation have been characterized that spontaneously develop and closely resemble human CD with regard to disease location, histologic features and clinical response to therapy. Two mouse models of experimental ileitis will be discussed in this review: the TNF DeltaARE and SAMP1/YitFc strains. Studies using these new models might provide important insight into the pathogenesis of human CD and test the efficacy of potential therapies to treat this devastating disease.

Overexpression of wild-type Galpha(i)-2 suppresses beta-adrenergic signaling in cardiac myocytes

The role of Galpha(i)-2 overexpression in desensitization of beta-adrenergic signaling in heart failure is controversial. An adenovirus-based approach was used to investigate whether overexpression of Galpha(i)-2 impairs beta-adrenergic stimulation of adenylyl cyclase (AC) activity and cAMP levels in neonatal rat cardiac myocytes (NRCM) and cell shortening of adult rat ventricular myocytes (ARVM). Infection of NRCM with Ad5Galpha(i)-2 increased Galpha(i)-2 by 50-600% in a virus dose-dependent manner. Overexpression was paralleled by suppression of GTP- and isoprenaline-stimulated AC by 10-72% (P<0.001) in a PTX-sensitive manner. Isoprenaline-stimulated shortening of Ad5Galpha(i)-2-infected ARVM was attenuated by 34% (P<0.01). Ad5Galpha(i)-2/GFP (Galpha(i)-2, green fluorescent protein; bicistronic) was constructed to monitor transfection homogeneity and target Galpha(i)-2 overexpression to levels found in heart failure. At Galpha(i)-2 levels of 93% above control, isoprenaline-stimulated AC activity and cAMP levels were reduced by 17% and 40% (P<0.02), respectively. Beta1- and beta2-adrenergic stimulation was reduced similarly. Our results suggest that (a) the Galpha(i)-2 system exhibits tonic inhibition of stimulated AC in cardiac myocytes, (b) Galpha(i)-2-mediated inhibition is concentration-dependent and occurs at Galpha(i)-2 levels seen in heart failure, and (c) Galpha(i)-2-mediated inhibition affects both beta1- and beta2-adrenergic stimulation of AC. The data argue for an important, independent role of the Galpha(i)-2 increase in heart failure.

Exogenous myristoylated-G(i2)alpha subunits of GTP-binding proteins are mitogens following their internalization by astrocytes in culture

Heterotrimeric GTP-binding proteins (G proteins) are involved in the coupling of a variety of cell surface receptors to different intracellular signalling pathways, some of which take part in the regulation of growth by affecting cell proliferation and/or differentiation. In cultured astrocytes, many receptors of neuropeptides and hormones are coupled to the heterotrimeric G(i) proteins which regulate the mitogen-activated protein kinase (MAPK/ERK) cascade through both the Galpha and Gbetagamma subunits. We have previously reported that functionally active recombinant myr-G(i2)alpha subunits added to such cultures are internalised and distributed within the plasma membrane and cytosol as well as in the nuclei of dividing astrocytes. Here we show that astrocytes proliferate dose-dependently in response to exogenous myr-G(i2)alpha subunits. Concentrations of 100 pM-30 nM myr-G(i2)alpha caused more than 2.5-fold increase of [3H]thymidine incorporation over basal levels. Other classes of myr-Galpha subunits, such as G(i3)alpha or G(o)alpha, induced a much lower proliferative effect. The addition of G(i1)alpha subunits to the cultures produced no change, indicating the selectivity of this effect. Even though myr-G(i2)alpha subunits are internalised by the cells regardless of their guanine nucleotide-bound state, much less [3H]thymidine incorporation was observed in the presence of GDPbetaS-myr-G(i2)alpha or GTPgammaS-myr-G(i2)alpha. Further, the fluorescent labelling was dissimilarly distributed, the signal being concentrated in the nucleus and perinuclear regions of the astrocytes. Selective disassembly of caveolae impaired both myr-G(i2)alpha internalisation and DNA induction. Together, these data reveal a proliferative effect of myr-G(i2)alpha subunits in astrocytes, and provide evidence for the incorporation of exogenous myr-G(i2)alpha subunits into the mitogen cascade activated by neurotransmitters or growth factors. The fact that Galpha proteins can enter cells is particularly interesting because options for delivering functional proteins into cells are limited. Thus, these proteins may have clinical applications for compensating deficits in the transduction mechanisms associated with several neurological diseases, or as a non-invasive membrane traversing carriers.

The immunology of mucosal models of inflammation

In recent years the status of the inflammatory bowel diseases (IBDs) as canonical autoimmune diseases has risen steadily with the recognition that these diseases are, at their crux, abnormalities in mucosal responses to normally harmless antigens in the mucosal microflora and therefore responses to antigens that by their proximity and persistence are equivalent to self-antigens. This new paradigm is in no small measure traceable to the advent of multiple models of mucosal inflammation whose very existence is indicative of the fact that many types of immune imbalance can lead to loss of tolerance for mucosal antigens and thus inflammation centered in the gastrointestinal tract. We analyze the immunology of the IBDs through the lens of the murine models, first by drawing attention to their common features and then by considering individual models at a level of detail necessary to reveal their individual capacities to provide insight into IBD pathogenesis. What emerges is that murine models of mucosal inflammation have given us a road map that allows us to begin to define the immunology of the IBDs in all its complexity and to find unexpected ways to treat these diseases.

Heterotrimeric G protein signaling: role in asthma and allergic inflammation

Asthma and rhinitis are pathophysiologic conditions associated with a prototypical allergic response to inhaled allergens consisting of both neuromechanical and inflammatory components. Heptahelical receptors that bind guanosine triphosphate-binding proteins (G proteins), referred to as G protein-coupled receptors (GPCRs), have been intimately linked with asthma and allergic inflammation for many years. G protein signaling mediates responses throughout the immune, nervous, and muscular systems that might contribute to the pathogenesis of allergic processes and asthma. For example, GPCR agonists or antagonists are used as therapies for asthma either by promoting airway smooth muscle relaxation (beta2 adrenergic receptor agonists) or by inhibiting inflammation in the nasal mucosa and airways (cysteinyl leukotriene receptor antagonists). The focus of this review is to explore how downstream signaling cascades elicited by GPCR activation contribute to the allergic phenotype and the mechanism by which pharmaceuticals alter signaling to generate a therapeutic effect. We also discuss physiologic modulators of G protein signaling, such as regulator of G protein signaling proteins and G protein receptor kinases, inasmuch as they represent potential new therapeutic targets in the treatment of atopy and other inflammatory conditions.

Immunological basis of inflammatory bowel disease: role of the microcirculation

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the intestine and/or colon of unknown etiology in which patients suffer from severe diarrhea, rectal bleeding, abdominal pain, fever, and weight loss. Active episodes of IBD are characterized by vasodilation, venocongestion, edema, infiltration of large numbers of inflammatory cells, and erosions and ulcerations of the bowel. It is becoming increasingly apparent that chronic gut inflammation may result from a dysregulated immune response toward components of the normal intestinal flora, resulting in a sustained overproduction of proinflammatory cytokines and mediators. Many of these Th1 and macrophage-derived cytokines and lipid metabolites are known to activate microvascular endothelial cells, thereby promoting leukocyte recruitment into the intestinal interstitium. This review discusses the basic immune mechanisms involved in the regulation of inflammatory responses in the gut and describes how a breakdown in this protective response initiates chronic gut inflammation.

Helicobacter bilis infection accelerates and H. hepaticus infection delays the development of colitis in multiple drug resistance-deficient (mdr1a-/-) mice

mdr1a-deficient mice lack P-glycoprotein and spontaneously develop colitis with age. Helicobacter spp. are gram-negative organisms that have been associated with colitis in certain mouse strains, but Helicobacter spp. have been excluded as contributing to the spontaneous colitis that develops in mdr1a-/- mice. We wished to determine whether infection with either H. bilis or H. hepaticus would accelerate the development of inflammatory bowel disease (IBD) in mdr1a-/- mice. We found that H. bilis infection induced diarrhea, weight loss, and IBD in mdr1a-/- mice within 6 to 17 weeks post-inoculation and before the expected onset of spontaneous IBD. Histopathology of H. bilis-induced IBD included crypt hyperplasia, inflammatory cell infiltrates, crypt abscesses, and obliteration of normal gut architecture. Reverse transcription-polymerase chain reaction and Taqman analysis from colonic tissue showed increased transcripts for interferon-gamma and interleukin-10 from H. bilis-infected colitic mdr1a-/- mice. Additionally, mesenteric lymph nodes had increased cellularity with expansion of CD4+ and CD8+ T cells and B cells and increased proliferation to soluble H. bilis antigens with elaboration of interferon-gamma, tumor necrosis factor-alpha and interleukin-10. In contrast, H. hepaticus infection of mdr1a-/- mice did not accelerate disease but rather delayed the onset of spontaneous colitis which was milder in severity. mdr1a-/- mice infected with Helicobacter spp. may provide a useful tool to explore the pathogenesis of microbial-induced IBD in a model with a presumed epithelial cell "barrier" defect.

Distinct inflammatory mechanisms mediate early versus late colitis in mice

BACKGROUND & AIMS

Progression from the acute to chronic phase of inflammatory bowel disease cannot be easily evaluated in patients and has not been characterized in animal models. We report a longitudinal study investigating changes in the mucosal immune response in an experimental model of colitis.

METHODS

Severity of colitis, body mass, stool consistency and blood content, serum amyloid A, and tissue histology were examined in interleukin (IL)-10-deficient mice over 35 weeks. The corresponding production of IL-12, IL-18, interferon gamma, tumor necrosis factor alpha, IL-4, and IL-13 by lamina propria mononuclear cells in the inflamed intestine was measured. Administration of neutralizing antibody to IL-12 at distinct times during disease progression permitted evaluation of its therapeutic potential.

RESULTS

The clinical manifestations and intestinal inflammation delineated an early phase of colitis (10-24 weeks), characterized by a progressive increase in disease severity, followed by a late phase (>25 weeks), in which chronic inflammation persisted indefinitely. Lamina propria mononuclear cells from mice with early disease synthesized progressively greater quantities of IL-12 and interferon gamma, whereas production of both cytokines dramatically declined and returned to pre-disease levels in the late phase of colitis. Consistent with this pattern, neutralizing antibody to IL-12 reversed early, but not late, disease. In contrast, IL-4 and IL-13 production increased progressively from pre- to early to late disease.

CONCLUSIONS

Colitis that develops in IL-10-deficient mice evolves into 2 distinct phases. IL-12 plays a pivotal role in early colitis, whereas its absence and the synthesis of IL-4 and IL-13 in late disease indicate that other immune mechanisms sustain chronic inflammation.

Molecular cloning of a Bacteroides caccae TonB-linked outer membrane protein identified by an inflammatory bowel disease marker antibody

Commensal enteric bacteria are a required pathogenic factor in inflammatory bowel disease (IBD), but the identity of the pertinent bacterial species is unresolved. Using an IBD-associated pANCA monoclonal antibody, a 100-kDa protein was recently characterized from an IBD clinical isolate of Bacteroides caccae (p2Lc3). In this study, consensus oligonucleotides were designed from 100-kDa peptides and used to identify a single-copy gene from the p2Lc3 genome. Sequence analysis of the genomic clone revealed a 2,844-bp (948 amino acid) open reading frame encoding features typical of the TonB-linked outer membrane protein family. This gene, termed ompW, was detected by Southern analysis only in B. caccae and was absent in other species of Bacteroides and gram-negative coliforms. The closest homologues of OmpW included the outer membrane proteins SusC of Bacteroides thetaiotaomicron and RagA of Porphyromonas gingivalis. Recombinant OmpW protein was immunoreactive with the monoclonal antibody, and serum anti-OmpW immunoglobulin A levels were elevated in a Crohn's disease patient subset. These findings suggest that OmpW may be a target of the IBD-associated immune response and reveal its structural relationship to a bacterial virulence factor of P. gingivalis and periodontal disease.

Th1-type responses mediate spontaneous ileitis in a novel murine model of Crohn's disease

We describe here the immunologic characterization of a new mouse strain, SAMP1/Yit, which spontaneously develops a chronic intestinal inflammation localized to the terminal ileum. The resulting ileitis bears a remarkable resemblance to human Crohn's disease. This strain of mice develops discontinuous, transmural inflammatory lesions in the terminal ileum with 100% penetrance by 30 weeks of age. The intestinal inflammation is characterized by massive infiltration of activated CD4+ and CD8alpha(+)TCRalphabeta(+) T cells into the lamina propria and is accompanied by a dramatic decrease in the intraepithelial lymphocyte CD8alpha(+)TCRgammadelta(+)/CD8alpha(+)TCRalphabeta(+) ratio. The results of adoptive transfer experiments strongly suggest that CD4+ T cells that produce a Th1-like profile of cytokines, e.g., IFN-gamma and TNF, mediate the intestinal inflammation found in SAMP1/Yit mice. In addition, pretreatment of adoptive transfer recipients with a neutralizing anti-TNF antibody prevents the development of intestinal inflammation, suggesting that TNF plays an important role in the pathogenesis of intestinal inflammation in this model. To our knowledge, these data provide the first direct evidence that Th1-producing T cells mediate intestinal inflammation in a spontaneous animal model of human Crohn's disease.

Regulation of interleukin-12 production by G-protein-coupled receptors

G-protein-coupled receptors have long been known to play a critical role in the recruitment and migration of leukocytes to areas of inflammation. This review will focus, however, on emerging data that G-protein-coupled receptors can modulate cytokine production by antigen-presenting cells including interleukin-12 and tumor necrosis factor-alpha and may therefore play a significant role in the regulation of innate and acquired immunity.

Lessons from genetically engineered animal models XI. Novel mouse models to study pathogenic mechanisms of Crohn's disease

Crohn's Disease (CD) affects more than 500,000 individuals in the United States and represents the second most common chronic inflammatory disorder after rheumatoid arthritis. Although major advances have been made in defining the basic mechanisms underlying chronic intestinal inflammation, the precise etiopathogenesis of CD remains unknown. We have recently characterized two novel mouse models of enteritis that express a CD-like phenotype, namely the TNF DeltaARE model of tumor necrosis factor (TNF) overexpression and the SAMP1/Yit model of spontaneous ileitis. The unique feature of these models is that they closely resemble CD for location and histopathology. These genetically manipulated new models of intestinal inflammation offer a powerful tool to investigate potential causes of human disease and may allow the development of novel disease-modifying therapeutic modalities for the treatment of CD.

Absence of GNAI2 codon 179 oncogene mutations in inflammatory bowel disease

The human GNAI2 gene coding for G protein, Galphai2, is located on chromosome 3p21 in proximity to the region where an inflammatory bowel disease (IBD) locus has been suggested. Galphai2-deficient mice develop a lethal diffuse colitis that resembles human ulcerative colitis (UC) and frequently progresses to colon adenocarcinoma. Furthermore, the human GNAI2 gene is subject to point mutations at certain positions, including three at codon 179, all of which have been reported in human endocrine tumors. In order to evaluate the possible involvement of this gene in IBD pathogenesis, we have examined GNAI2 codon 179 sequences in 28 familial IBD patients, including 13 UC, 15 Crohn's disease (CD), and 7 patients with colon cancer/dysplasia, from 12 multiplex IBD families. The wildtype codon 179, CGC for arginine, plus the first G of the codon 180 engender a sequence recognizable by the enzyme BstUI. Mutations, therefore, can result in the abrogation of BstUI digestion of polymerase chain reaction (PCR) products containing the codon 179. Using the PCR-restriction fragment length polymorphism technique, all 28 IBD patients, including those with colon cancer, and 14 non-IBD family members show a BstUI-cleavable PCR-banding pattern indicating the presence of wildtype codon 179. We conclude that, in the familial IBD and colon cancer/dysplasia patients studied, there is no detectable mutation in the codon 179 of the GNAI2 gene.

The GTP-binding protein G(ialpha) translocates to kinetochores and regulates the M-G(1) cell cycle transition of Swiss 3T3 cells

The receptor-generated signals that are responsible for driving the cell cycle are incompletely characterised in mammalian cells. It is clear, however, that the cellular messenger systems that stimulate DNA synthesis and mitosis are separable. These are interwoven with biochemical checkpoints that ensure that processes, such as chromosomal replication and microtubule attachment to duplicated chromosomes, are complete before the following phase of the cell cycle is initiated. In some cells, activation of DNA synthesis by factors such as LPA and serum has been shown to require the GTP-binding protein G(i). We have found that G(i) plays an additional role in mitosis activated by both 7-transmembrane receptors and tyrosine kinase receptors, and that this involves the translocation of the alpha-subunit of G(i) (G(ialpha)) to the nucleus. Here we show by confocal microscopy that G(ialpha)migrates to the nucleus near the onset of mitosis in serum-activated Swiss 3T3 cells and binds to the kinetochore region of replicated chromosomes. Inhibition of G(i) function with pertussis toxin had no effect on the induction of DNA synthesis by serum, but cell proliferation was inhibited. Flow cytometric analysis showed that this resulted from retardation of the transition through mitosis and into G(1). Additionally, pertussis toxin impaired the activity of p34(cdc2), a cyclin-dependent kinase involved in the transition from M-phase to G(1), but not the S-phase cyclin, cyclin E. These data show that the G-protein G(i) has a key role in the regulation of mitosis in fibroblasts.

Regulatory T cells and inflammatory bowel disease

Recent studies have identified interleukin 10 as a differentiation factor for a novel subset of immune suppressive regulatory T cells. Here, Hervé Groux and Fiona Powrie discuss the role that these cells play in the regulation of immune responses to enteric antigens and suggest that a deficiency in these cells might be involved in the pathogenesis of inflammatory bowel disease.

Physiological regulation of G protein-linked signaling

Heterotrimeric G proteins in vertebrates constitute a family molecular switches that transduce the activation of a populous group of cell-surface receptors to a group of diverse effector units. The receptors include the photopigments such as rhodopsin and prominent families such as the adrenergic, muscarinic acetylcholine, and chemokine receptors involved in regulating a broad spectrum of responses in humans. Signals from receptors are sensed by heterotrimeric G proteins and transduced to effectors such as adenylyl cyclases, phospholipases, and various ion channels. Physiological regulation of G protein-linked receptors allows for integration of signals that directly or indirectly effect the signaling from receptor-->G protein-->effector(s). Steroid hormones can regulate signaling via transcriptional control of the activities of the genes encoding members of G protein-linked pathways. Posttranscriptional mechanisms are under physiological control, altering the stability of preexisting mRNA and affording an additional level for regulation. Protein phosphorylation, protein prenylation, and proteolysis constitute major posttranslational mechanisms employed in the physiological regulation of G protein-linked signaling. Drawing upon mechanisms at all three levels, physiological regulation permits integration of demands placed on G protein-linked signaling.

Autoimmune intestinal pathology induced by hsp60-specific CD8 T cells

Due to their ubiquitous distribution and high degree of structural similarity, heat shock proteins (hsp) are potential target antigens in autoimmune diseases. Here, we describe induction of intestinal inflammation following transfer of hsp60-reactive CD8 T cells into mice. Inflammatory reactions were MHC class I dependent and developed primarily in the small intestine. IFN gamma and TNF alpha, as well as gut-derived hsp60, were elevated at sites of T cell infiltration. Intestinal lesions were drastically reduced in mice lacking receptors for TNF alpha. Pathology also developed in germ-free mice, indicating recognition of host-derived hsp60 by CD8 T cells. This report demonstrates that CD8 T cells with defined antigen specificity cause intestinal inflammation, emphasizing a link between infection and autoimmune disease.

Colitis-Inducing Potency of CD4+ T Cells in Immunodeficient, Adoptive Hosts Depends on Their State of Activation, IL-12 Responsiveness, and CD45RB Surface Phenotype

We studied the induction, severity, and rate of progression of inflammatory bowel disease (IBD) induced in SCID mice by the adoptive transfer of low numbers of the following purified BALB/c CD4+ T cell subsets: 1) unfractionated, peripheral, small (resting), or large (activated) CD4+ T cells; 2) fractionated, peripheral, small, or large, CD45RBhigh or CD45RBlow CD4+ T cells; and 3) peripheral IL-12-unresponsive CD4+ T cells from STAT-4-deficient mice. The adoptive transfer into SCID host of comparable numbers of CD4+ T cells was used to assess the colitis-inducing potency of these subsets. Small CD45RBhigh CD4+ T lymphocytes and activated CD4+ T blasts induced early (6–12 wk posttransfer) and severe disease, while small resting and unfractionated CD4+ T cells or CD45RBlow T lymphocytes induced a late-onset disease 12–16 wk posttransfer. SCID mice transplanted with STAT-4−/− CD4+ T cells showed a late-onset IBD manifest &gt;20 wk posttransfer. In SCID mice with IBD transplanted with IL-12-responsive CD4+ T cells, the colonic lamina propria CD4+ T cells showed a mucosa-seeking memory/effector CD45RBlow Th1 phenotype abundantly producing IFN-γ and TNF-α. In SCID mice transplanted with IL-12-unresponsive STAT-4−/− CD4+ T cells, the colonic lamina propria, mesenteric lymph node, and splenic CD4+ T cells produced very little IFN-γ but abundant levels of TNF-α. The histopathologic appearance of colitis in all transplanted SCID mice was similar. These data indicate that CD45RBhigh and CD45RBlow, IL-12-responsive and IL-12-unresponsive CD4+ T lymphocytes and lymphoblasts have IBD-inducing potential though of varying potency.

Murine mentors: transgenic and knockout models of surgical disease

OBJECTIVE

Transgenic and knockout technologies have emerged from the "molecular biology revolution" as unprecedented techniques for manipulating gene function in intact mice. The goals of this review are to outline the techniques of creating transgenic and knockout mice, and to demonstrate their use in elucidation of the molecular mechanisms underlying common surgical diseases.

SUMMARY BACKGROUND DATA

Gain of gene function is created by transgenic technology, whereas gene function is ablated using gene knockouts. Each technique has distinctive applications and drawbacks. A unique feature of genetically manipulated mice is that combinatorial genetic experiments can be executed that precisely define the functional contribution of a gene to disease progression. Transgenic and knockout mouse models of wound healing, cardiovascular disease, transplant immunology, gut motility and inflammatory bowel disease, and oncology are beginning to illuminate the precise molecular regulation of these diseases. Transgenic technology has also been extended to larger mammals such as pigs, with the goal of using genetic manipulation of the xenogenic immune response to increase the availability of transplant organs. Continual refinements in gene manipulation technology in mice offer the opportunity to turn genes on or off at precise time intervals and in particular tissues, according to the needs of the investigator. Ultimately, investigation of disease development and progression in genetically manipulated mammals may delineate new molecular targets for drug discovery and provide novel platforms for drug efficacy screens.

CONCLUSIONS

Emulation of human disease and therapy using genetically manipulated mammals fulfills a promise of molecular medicine: fusion of molecular biochemistry with "classical" biology and physiology. Surgeons have unique skills spanning both worlds that can facilitate their success in this expanding arena.

The anatomical basis of intestinal immunity

The lymphoid tissues associated with the intestine are exposed continuously to antigen and are the largest part of the immune system. Many lymphocytes are found in organised tissues such as the Peyer's patches and mesenteric lymph nodes, as well as scattered throughout the lamina propria and epithelium of the mucosa itself. These lymphocyte populations have several unusual characteristics and the intestinal immune system is functionally and anatomically distinct from other, peripheral compartments of the immune system. This review explores the anatomical and molecular basis of these differences, with particular emphasis on the factors which determine how the intestinal lymphoid tissues discriminate between harmful pathogens and antigens which are beneficial, such as food proteins or commensal bacteria. These latter antigens normally provoke immunological tolerance, and inappropriate responses to them are responsible for immunopathologies such as food hypersensitivity and inflammatory bowel disease. We describe how interactions between local immune cells, epithelial tissues and antigen-presenting cells may be critical for the induction of tolerance and the expression of active mucosal immunity. In addition, the possibility that the intestine may act as an extrathymic site for T-cell differentiation is discussed. Finally, we propose that, under physiological conditions, immune responses to food antigens and commensal bacteria are prevented by common regulatory mechanisms, in which transforming growth factor beta plays a critical role.