SUMMARYIn recent years, nitric oxide (NO), a gas previously considered to be a potentially toxic chemical, has been established as a diffusible universal messenger that mediates cell-cell communication throughout the body. Constitutive and inducible NO production regulate numerous essential functions of the gastrointestinal mucosa, such as maintenance of adequate perfusion, regulation of microvascular and epithelial permeability, and regulation of the immune response. Up-regulation of the production of NO via expression of inducible nitric oxide synthase (iNOS) represents part of a prompt intestinal antibacterial response; however, NO has also been associated with the initiation and maintenance of inflammation in human inflammatory bowel disease (IBD). Recent studies on animal models of experimental IBD have shown that constitutive and inducible NO production seems to be beneficial during acute colitis, but sustained up-regulation of NO is detrimental. This fact is also supported by studies on mice genetically deficient in various NOS isoforms. However, the mechanism by which NO proceeds from being an indispensable homeostatic regulator to a harmful destructor remains unknown. Furthermore, extrapolation of data from animal colitis models to human IBD is questionable. The purpose of this review is to update our knowledge about the role of this universal mediator and the enzymes that generate it in the pathogenesis of IBD.Keywords gut; inflammatory bowel diseases; nitric oxide synthase; nitric oxide NITRIC OXIDE SYNTHESIS AND CHEMISTRYNitric oxide (NO) is a free radical with moderate reactivity compared to other species, which gives rise to a multitude of organ-specific regulatory functions. NO is synthesized from the amino acid L-arginine (Fig. 1) by a family of enzymes generally referred to as the nitric oxide synthases (NOSs) (Fig. 2). The oxidation of a terminal nitrogen of the amino acid l-arginine produces NO and l-citrulline. Three isoforms have been identified: two are constitutively present in either neuronal (nNOS) or endothelial (eNOS) tissue and are termed constitutive NOS (cNOS), while a third isoform is expressed after induction by certain cytokines, microbes and bacterial products, and is thus called inducible nitric oxide synthase (iNOS).1 NO production by cNOS is low (nanomolar quantities) and short-lasting, being controlled by Ca 2+ -mobilizing agents in a very transient and highly controlled manner, and fully inhibited by calmodulin antagonists.2 In marked contrast, iNOS synthesizes NO in high (micromolar) amounts, it is regulated at the transcriptional level and is sensitive to inhibitors of DNA transcription and protein synthesis, such as actinomycin D and cycloheximide.3 NO production by iNOS is delayed by several hours following stimulation, but once induced is active for periods as long as 5 days. The delay between stimulation and enzyme generation suggests the requirement of de novo synthesis of a cofactor, e.g. tetrahydrobiopterin, 2 for maximal activity. The chemistry of NO provides a va...

Stem cells are a population of undifferentiated cells characterized by the ability to extensively proliferate (self-renewal), usually arise from a single cell (clonal), and differentiate into different types of cells and tissue (potent). There are several sources of stem cells with varying potencies. Pluripotent cells are embryonic stem cells derived from the inner cell mass of the embryo and induced pluripotent cells are formed following reprogramming of somatic cells. Pluripotent cells can differentiate into tissue from all 3 germ layers (endoderm, mesoderm, and ectoderm). Multipotent stem cells may differentiate into tissue derived from a single germ layer such as mesenchymal stem cells which form adipose tissue, bone, and cartilage. Tissue-resident stem cells are oligopotent since they can form terminally differentiated cells of a specific tissue. Stem cells can be used in cellular therapy to replace damaged cells or to regenerate organs. In addition, stem cells have expanded our understanding of development as well as the pathogenesis of disease. Disease-specific cell lines can also be propagated and used in drug development. Despite the significant advances in stem cell biology, issues such as ethical controversies with embryonic stem cells, tumor formation, and rejection limit their utility. However, many of these limitations are being bypassed and this could lead to major advances in the management of disease. This review is an introduction to the world of stem cells and discusses their definition, origin, and classification, as well as applications of these cells in regenerative medicine.

IntroductionRegenerative medicine and particular adult stem cells represent an alternative option with several fruitful therapeutic applications in patients suffering from chronic lung diseases including idiopathic pulmonary fibrosis (IPF). Nevertheless, lack of knowledge regarding the origin and the potential of mesenchymal stem cells (MSCs) to differentiate into fibroblasts has limited their use for the treatment of this dismal disease.Patients and methodsTo this end, we conducted a phase Ib, non-randomized, clinical trial to study the safety of three endobronchial infusions of autologous adipose derived stromal cells (ADSCs)-stromal vascular fraction (SVF) (0.5 million cells per kgr of body weight per infusion) in patients with IPF (n=14) of mild to moderate disease severity (forced vital capacity –FVC>50% predicted value and diffusion lung capacity for carbon monoxide-DLCO>35% of predicted value). Our primary end-point was incidence of treatment emergent adverse events within 12 months. Alterations of functional, exercise capacity and quality of life parameters at serial time points (baseline, 6 and 12 months after first infusion) were exploratory secondary end-points.ResultsNo cases of serious or clinically meaningful adverse events including short-term infusional toxicities as well as long-term ectopic tissue formation were recorded in all patients. Detailed safety monitoring through several time-points indicated that cell-treated patients did not deteriorate in both functional parameters and indicators of quality of life.ConclusionsThe clinical trial met its primary objective demonstrating an acceptable safety profile of endobronchially administered autologous ADSCs-SVF. Our findings accelerate the rapidly expanded scientific knowledge and indicate a way towards future efficacy trials.

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Background-Nitric oxide (NO) synthesis and inducible nitric oxide synthase (iNOS) expression are increased in colonic biopsy specimens from patients with ulcerative colitis, but the cellular source of NO production is not known. Aims-To examine the distribution of iNOS in human colonic mucosa and to explore the ability of T lymphocyte derived cytokines to regulate iNOS expression and activity in human colonic epithelial cells. Methods-iNOS expression was examined using immunohistochemistry in colonic biopsy samples from 12 patients with ulcerative colitis and three with infectious colitis and compared with 10 normal controls. In vitro iNOS expression and activity were determined in HT-29 cell cultures; nitrite levels were measured using a fluorescent substrate, iNOS mRNA expression by northern blot analysis, and iNOS protein expression by western blot analysis. Results-No iNOS expression was detected (10 of 10) in non-inflamed mucosa derived from normal controls. In 11 of 12 cases of newly diagnosed ulcerative colitis, iNOS protein was expressed in the epithelial cells, while no other positive cells were found in the lamina propria. Similar iNOS labelling was found in colonic biopsy samples from patients with infectious colitis in the acute phase, but when re-examined in samples from patients in total remission, no iNOS staining was observed. Both interleukin (IL)-13 and IL-4, but not IL-10, are potent inhibitors of iNOS expression and activity induced by an optimal combination of cytokines, namely IL-1 , tumour necrosis factor and interferon . Conclusions-The data suggest that the epithelium is the major source of iNOS activity in ulcerative colitis and that IL-13 and IL-4 may act as intrinsic regulators of NO generation in intestinal inflammation.

The intestinal microflora is a large bacterial community that colonizes the gut, with a metabolic activity equal to an organ and various functions that affect the physiology and pathology of the host's mucosal immune system. Intestinal bacteria are useful in promotion of human health, but certain components of microflora, in genetically susceptible individuals, contribute to various pathological disorders, including inflammatory bowel disease. Clinical and experimental observations indicate an imbalance in protective and harmful microflora components in these disorders. Manipulation of gut flora to enhance its protective and beneficial role represents a promising field of new therapeutic strategies of inflammatory bowel disease. In this review, we discuss the implication of gut flora in the intestinal inflammation that justifies the role of probiotics and prebiotics in the prevention and treatment of inflammatory bowel disease and we address the evidence for therapeutic benefits from their use in experimental models of colitis and clinical trials.

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Gemcitabine, a drug with established efficacy against a number of solid tumors, has therapeutic limitations due to its rapid metabolic inactivation. The aim of this study was the development of an innovative strategy to produce a metabolically stable analogue of gemcitabine that could also be selectively delivered to prostate cancer (CaP) cells based on cell surface expression of the Gonadotropin Releasing HormoneReceptor (GnRH-R). The synthesis and evaluation of conjugated molecules, consisting of gemcitabine linked to a GnRH agonist, is presented along with results in androgen-independent prostate cancer models. NMR and ligand binding assays were employed to verify conservation of microenvironments responsible for binding of novel GnRH-gemcitabine conjugates to the GnRH-R. In vitro cytotoxicity, cellular uptake and metabolite formation of the conjugates were examined in CaP cell lines. Selected conjugates were efficacious in the in vitro assays with one of them, namely GSG, displaying high antiproliferative activity in CaP cell lines along with significant metabolic and pharmacokinetic advantages in comparison to gemcitabine. Finally, treatment of GnRH-R positive xenografted mice with GSG, showed a significant advantage in tumor growth inhibition when compared to gemcitabine. 3 IntroductionDespite advancements in methods for early cancer detection and improved insights into the molecular mechanisms and treatment options, advanced prostate cancer (CaP) remains a major health problem for the aging man. 1,2 Hormonal therapy is usually the first line of defense for CaP treatment by using drugs that lead to chemical castration, suppression of testosterone and dihydrotestosterone (DHT) biosynthesis. 3,4 The hormonal ablation approach has been achieved successfully using agonist (through desensitization) or antagonist analogue drugs, of the native Gonadotropin Releasing Hormone (GnRH). These drugs exert their effects primarily on the pituitary gland through the GnRH-R by lowering gonadotropins and downstream gonadal sex steroids. Nevertheless, in many cases after treatment, following initial tumor regression, CaP progresses to an androgen-independent state with poor prognosis, which presents a major challenge for the physician and the patient. 3,[5][6][7][8][9][10] Research on the GnRH-R has shown that its expression is not confined solely to the pituitary but that is also present in several other tissues such as prostate, breast 11-13 and the GnRH-R level of expression along with cell context is critical for cell responses to either agonist or antagonist drugs of the receptor. 14 It is also well established that GnRH-R gene expression is upregulated in patients with androgenindependent CaP, making the GnRH-R an attractive target for the design of novel and specific therapeutics. 15 A modern approach to improve conventional chemotherapy is by direct targeting of chemotherapeutic agents to cancer cells in order to enhance the tumoricidal effect and reduce peripheral toxicity of a specific drug. Linking chemo...