Functional significance of non-neuronal acetylcholine in skin epithelia

In recent years, the physiological role of non-neuronal acetylcholine (ACh) and its receptors (AChR) in epidermal physiology has been under intense investigation. However, little is known about the role of the non-neuronal cholinergic system in inflammatory skin diseases. We chose the clinically nicotine-dependent skin disease hidradenitis suppurativa (HS) as model to study the influence of long term nicotine ingestion on epidermal morphology and AChR expression. HS is a chronic inflammatory, disabling disease of unknown pathogenesis emerging from the pilosebaceous unit of the intertriginous areas. In order to correlate our findings to specific nicotine effects, we used the organotypical coculture system (OTC) and raised artificial epidermis in the presence of nicotine. After 12 days in culture control OTC showed a mature epithelium, while nicotine treated OTCs were significantly thicker. Using immunofluorescence analysis, nicotine treated OTCs produced significantly stronger immunoreactivity (IR) for the alpha3, M(3) and M(5) AChR antisera than control. In contrast, the alpha7 nAChR antiserum showed a slightly reduced IR in the granular layer and the alpha9 nAChR IR retracted to the lower suprabasal layers. In HS epidermis we found the strongest IR for all AChR around the follicular infundibulum while in the sinus epithelia it was only weak. In contrast to the nicotine treated OTC, the alpha7 nAChR IR in the hyperplastic HS epidermis was clearly extended to all living layers. Altogether we provide first hints for a causative role of the non-neuronal cholinergic system in the pathogenesis of HS by promoting infundibular epithelial hyperplasia and thus follicular plugging.     

T cell homing to epithelial barriers in allergic disease

Allergic inflammation develops in tissues that have large epithelial surface areas that are exposed to the environment, such as the lung, skin and gut. In the steady state, antigen-experienced memory T cells patrol these peripheral tissues to facilitate swift immune responses against invading pathogens. In at least two allergy-prone organs, the skin and the gut, memory T cells are programmed during the initial antigen priming to express trafficking receptors that enable them to preferentially home to these organs. In this review we propose that tissue-specific memory and inflammation-specific T cell trafficking facilitates the development of allergic disease in these organs. We thus review recent advances in our understanding of tissue-specific T cell trafficking and how regulation of T cell trafficking by the chemokine system contributes to allergic inflammation in mouse models and in human allergic diseases of the skin, lung and gut. Inflammation- and tissue-specific T lymphocyte trafficking pathways are currently being targeted as new treatments for non-allergic inflammatory diseases and may yield effective new therapeutics for allergic diseases.     

Scanning electron microscopy of the infundibulum, ampulla, and eggs of mice

The objective of the study reported here was to use scanning electron microscopy (SEM) to discover and describe the details of three-dimensional profiles and the natural (not surgically disturbed) topography/location of the infundibulum in the mouse. It will help new investigators to more quickly identify the infundibulum for successful transfer of microinjected eggs through a small opening into the oviduct/ampulla of pseudopregnant female mice for producing transgenic mice. Results of the study also illustrate the geographic orientation and natural topographic features of the ovary, infundibulum, ampulla, oviduct, and uterus. The presence of cilia on the surface of the crown foldings in the longitudinal section of the infundibular head stained with 1% toluidine blue provided direct evidence that evagination of the internal cilia of the infundibulum/oviduct results in formation of the infundibular crown. The new observation of the narrowing region of the infundibular head after surgical removal of the crown also suggests that formation of the infundibular crown may have resulted from the "evagination process" of internal cilia of the infundibulum/oviduct surface. The results also provide new evidence that the crown, terminal opening, and appearance of the left and the right infundibula of the same mouse differ.     

Phytomonas: Trypanosomatids Adapted to Plant Environments

Over 100 years after trypanosomatids were first discovered in plant tissues, Phytomonas parasites have now been isolated across the globe from members of 24 different plant families. Most identified species have not been associated with any plant pathology and to date only two species are definitively known to cause plant disease. These diseases (wilt of palm and coffee phloem necrosis) are problematic in areas of South America where they threaten the economies of developing countries. In contrast to their mammalian infective relatives, our knowledge of the biology of Phytomonas parasites and how they interact with their plant hosts is limited. This review draws together a century of research into plant trypanosomatids, from the first isolations and experimental infections to the recent publication of the first Phytomonas genomes. The availability of genomic data for these plant parasites opens a new avenue for comparative investigations into trypanosomatid biology and provides fresh insight into how this important group of parasites have adapted to survive in a spectrum of hosts from crocodiles to coconuts.     

Development and homeostasis of the sebaceous gland

The important role of epidermal appendages especially the sebaceous gland has only recently been recognized. In particular, it has been convincingly shown that normal development and maintenance of the sebaceous gland are required for skin homeostasis since atrophic sebaceous glands and disturbances in sebaceous lipid composition result in major defects of the physiological barrier and maintenance of the skin. Consequently, it is important to unravel the signaling network controlling proper sebaceous lineage differentiation in mammalian skin and to understand the underlying mechanisms leading to severe skin diseases, including abnormal proliferation and differentiation of the gland, defects of the lipid metabolism and barrier, as well as sebaceous tumor formation. Over the last years, results from transgenic and knock out mouse models manipulating distinct signaling pathways in the skin as well as the detailed analysis of human sebaceous gland-derived cell lines provided new insights into crucial mediators balancing proliferation and differentiation of the sebaceous gland. Here, we discuss our current knowledge of in vivo mechanisms of sebaceous gland development, maintenance and disorders and highlight recent contributions to the field of sebaceous gland biology.     

Sperm transport and storage and its relation to the annual sexual cycle of the female red-sided garter snake,Thamnophis sirtalis parietalis

Female red-sided garter snakes (Thamnophis sirtalis parietalis) store sperm from both late-summer and spring matings. Before winter dormancy, sperm are stored in specialized furrows in the vaginal portion of the oviduct, 3–6 cm anterior to the vent. After 6 weeks in dormancy, the epithelial cells lining this vaginal region hypertrophy and stain strongly with periodic acid-Schiff (PAS). This PAS+ epithelial border sloughs and associates with sperm. These aggregations of PAS+ material, which will be referred to as carrier matrices, move anteriorly through the oviduct. After 20 weeks in dormancy, most sperm are found in specialized infundibular storage regions. Spring mating induces a rapid degeneration of winter-stored sperm. Stored sperm are evacuated from infundibular storage receptacles within 6 hours after mating. Yet sperm from the spring mating are not evident in the oviduct until 24 hours after mating. Carrier matrices begin to form at this time. At 48 hours after mating, sperm, often associated with carrier matrices, appear in the infundibulum. At 40 days after mating, most sperm have moved into infundibular storage receptacles. Evidence suggests that carrier matrices not only facilitate the transport of sperm anteriorly from vaginal to infundibular regions, but also function as nutritional stores.     

Nutrient Sensing by Histone Marks: Reading the Metabolic Histone Code Using Tracing,Omics, and Modeling

Several metabolites serve as substrates for histone modifications and communicate changes in the metabolic environment to the epigenome. Technologies such as metabolomics and proteomics have allowed us to reconstruct the interactions between metabolic pathways and histones. These technologies have shed light on how nutrient availability can have a dramatic effect on various histone modifications. This metabolism–epigenome cross talk plays a fundamental role in development, immune function, and diseases like cancer. Yet, major challenges remain in understanding the interactions between cellular metabolism and the epigenome. How the levels and fluxes of various metabolites impact epigenetic marks is still unclear. Discussed herein are recent applications and the potential of systems biology methods such as flux tracing and metabolic modeling to address these challenges and to uncover new metabolic–epigenetic interactions. These systems approaches can ultimately help elucidate how nutrients shape the epigenome of microbes and mammalian cells.     

Melanin-concentrating hormone and melanin-concentrating hormone receptors in mammalian skin physiopathology

To date, there is a dearth of evidence to support functions for melanin-concentrating hormone (MCH) and melanin-concentrating hormone receptors (MCH-R) in mammalian skin physiology including pigmentation, inflammation and immune responses and skin cell proliferation. Much research is therefore still needed to define the roles of the hormone and its receptors in mammalian skin. This will be a crucial step to identifying pathogenic mechanisms that may involve the MCH/MCH-R system in the context of inflammatory and autoimmune skin diseases as well as skin cancers. The following review summarizes the studies which have been carried out to examine the expression and function of MCH and MCH-R in mammalian skin. Recent findings with regard to humoral immune responses to the MCH-R1 in patients with the skin depigmenting disease vitiligo are also discussed.     

Importance of microbial colonization of the gut in early life to the development of immunity

The mammalian gastrointestinal tract harbors a complex microbiota consisting of between 500 and 1000 distinct microbial species. Comparative studies based on the germ-free gut have provided clear evidence that the gut microbiota is instrumental in promoting the development of both the gut and systemic immune systems. Early microbial exposure of the gut is thought to dramatically reduce the incidence of inflammatory, autoimmune and atopic diseases further fuelling the scientific viewpoint, that microbial colonization plays an important role in regulating and fine-tuning the immune system throughout life. Recent molecular diversity studies have provided additional evidence that the human gut microbiota is compositionally altered in individuals suffering from inflammatory bowel disorders, suggesting that specific bacterial species are important to maintaining immunological balance and health. New and exciting insights into how gut bacteria modulate the mammalian immune system are emerging. However, much remains to be elucidated about how commensal bacteria influence the function of cells of both the innate and adaptive immune systems in health and disease.     

Advances in resolving the heterogeneity and dynamics of keratinocyte differentiation

The mammalian skin is equipped with a highly dynamic stratified epithelium. The maintenance and regeneration of this epithelium is supported by basally located keratinocytes, which display stem cell properties, including lifelong proliferative potential and the ability to undergo diverse differentiation trajectories. Keratinocytes support not just the surface of the skin, called the epidermis, but also a range of ectodermal structures including hair follicles, sebaceous glands, and sweat glands. Recent studies have shed light on the hitherto underappreciated heterogeneity of keratinocytes by employing state-of-the-art imaging technologies and single-cell genomic approaches. In this mini review, we highlight major recent discoveries that illuminate the dynamics and cellular mechanisms that govern keratinocyte differentiation in the live mammalian skin and discuss the broader implications of these findings for our understanding of epithelial and stem cell biology in general.     

Ubiquitin-dependent regulation of G protein-coupled receptor trafficking and signaling

G protein-coupled receptors (GPCRs) belong to one of the largest family of signaling receptors in the mammalian genome [1]. GPCRs elicit cellular responses to multiple diverse stimuli and play essential roles in human health and disease. GPCRs have important clinical implications in various diseases and are the targets of approximately 25–50% of all marketed drugs [2], [3]. Understanding how GPCRs are regulated is essential to delineating their role in normal physiology and in the pathophysiology of several diseases. Given the vast number and diversity of GPCRs, it is likely that multiple mechanisms exist to regulate GPCR function. While GPCR signaling is typically regulated by desensitization and endocytosis mediated by phosphorylation and β-arrestins, it can also be modulated by ubiquitination. Ubiquitination is emerging an important regulatory process that may have unique roles in governing GPCR trafficking and signaling. Recent studies have revealed a mechanistic link between GPCR phosphorylation, β-arrestins and ubiquitination that may be applicable to some GPCRs but not others. While the function of ubiquitination is generally thought to promote receptor endocytosis and endosomal sorting, recent studies have revealed that ubiquitination also plays an important role in positive regulation of GPCR signaling. Here, we will review recent developments in our understanding of how ubiquitin regulates GPCR endocytic trafficking and how it contributes to signal transduction induced by GPCR activation.     

Genome Editing by CRISPR/Cas9: A Game Change in the Genetic Manipulation of Protists

Genome editing by CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 (CRISPR‐associated gene 9) system has been transformative in biology. Originally discovered as an adaptive prokaryotic immune system, CRISPR/Cas9 has been repurposed for genome editing in a broad range of model organisms, from yeast to mammalian cells. Protist parasites are unicellular organisms producing important human diseases that affect millions of people around the world. For many of these diseases, such as malaria, Chagas disease, leishmaniasis and cryptosporidiosis, there are no effective treatments or vaccines available. The recent adaptation of the CRISPR/Cas9 technology to several protist models will be playing a key role in the functional study of their proteins, in the characterization of their metabolic pathways, and in the understanding of their biology, and will facilitate the search for new chemotherapeutic targets. In this work we review recent studies where the CRISPR/Cas9 system was adapted to protist parasites, particularly to Apicomplexans and trypanosomatids, emphasizing the different molecular strategies used for genome editing of each organism, as well as their advantages. We also discuss the potential usefulness of this technology in the green alga Chlamydomonas reinhardtii.     

New insights into Chlamydia intracellular survival mechanisms

Chlamydia sp. are responsible for a wide range of diseases of significant clinical and public health importance. In this review, we highlight how recent cellular and functional genomic approaches have significantly increased our knowledge of the pathogenic mechanisms used by these genetically intractable bacteria. As the extensive repertoire of chlamydial proteins that are translocated into the mammalian host is identified and characterized, a molecular understanding of how Chlamydiae co-opt host cellular functions and block innate immune pathways is beginning to emerge.     

The lymphatic vasculature in disease

Blood vessels form a closed circulatory system, whereas lymphatic vessels form a one-way conduit for tissue fluid and leukocytes. In most vertebrates, the main function of lymphatic vessels is to collect excess protein-rich fluid that has extravasated from blood vessels and transport it back into the blood circulation. Lymphatic vessels have an important immune surveillance function, as they import various antigens and activated antigen-presenting cells into the lymph nodes and export immune effector cells and humoral response factors into the blood circulation. Defects in lymphatic function can lead to lymph accumulation in tissues, dampened immune responses, connective tissue and fat accumulation, and tissue swelling known as lymphedema. This review highlights the most recent developments in lymphatic biology and how the lymphatic system contributes to the pathogenesis of various diseases involving immune and inflammatory responses and its role in disseminating tumor cells.     

NF-κB in the regulation of epithelial homeostasis and inflammation

The IκB kinase/NF-κB signaling pathway has been implicated in the pathogenesis of several inflammatory diseases. Increased activation of NF-κB is often detected in both immune and non-immune cells in tissues affected by chronic inflammation, where it is believed to exert detrimental functions by inducing the expression of proinflammatory mediators that orchestrate and sustain the inflammatory response and cause tissue damage. Thus, increased NF-κB activation is considered an important pathogenic factor in many acute and chronic inflammatory disorders, raising hopes that NF-κB inhibitors could be effective for the treatment of inflammatory diseases. However, ample evidence has accumulated that NF-κB inhibition can also be harmful for the organism, and in some cases trigger the development of inflammation and disease. These findings suggested that NF-κB signaling has important functions for the maintenance of physiological immune homeostasis and for the prevention of inflammatory diseases in many tissues. This beneficial function of NF-κB has been predominantly observed in epithelial cells, indicating that NF-κB signaling has a particularly important role for the maintenance of immune homeostasis in epithelial tissues. It seems therefore that NF-κB displays two faces in chronic inflammation: on the one hand increased and sustained NF-κB activation induces inflammation and tissue damage, but on the other hand inhibition of NF-κB signaling can also disturb immune homeostasis, triggering inflammation and disease. Here, we discuss the mechanisms that control these apparently opposing functions of NF-κB signaling, focusing particularly on the role of NF-κB in the regulation of immune homeostasis and inflammation in the intestine and the skin.     

The protective roles of NLRP6 in intestinal epithelial cells

The evolution of chronic inflammatory diseases is thought to be due to a combination of host genetic variations and environmental factors that include the alteration of intestinal flora, termed “dysbiosis.” The intestinal mucosal barrier includes a chemical barrier and physical barrier that have important roles in protecting the intestine against inflammatory injury. The chemical barrier includes antimicrobial peptides (AMPs), and the physical barrier includes a mucous layer, a monolayer of intestinal epithelial cells and cell junctions. The intestinal mucosal barrier is not a static barrier, but rather, it strongly interacts with the gut microbiome and cells of the immune system. Correct expression of AMPs, together with mucus and balanced epithelial cell proliferation, prevents the occurrence of disease. NLRP6, a member of the nucleotide‐binding domain, leucine‐rich repeat‐containing (NLR) innate immune receptor family, participates in the progression of intestinal inflammation and enteric pathogen infections. It has become apparent in recent years that NLRP6 is important in disease pathogenesis, as it responds to internal ligands that lead to the release of AMPs and mucus, thus regulating the regeneration of intestinal epithelial cells. This review summarizes the activation of NLRP6 and its protective role in the intestinal epithelial cell.     

FGF-dependent midline-derived progenitor cells in hypothalamic infundibular development

The infundibulum links the nervous and endocrine systems, serving as a crucial integrating centre for body homeostasis. Here we describe that the chick infundibulum derives from two subsets of anterior ventral midline cells. One set remains at the ventral midline and forms the posterior-ventral infundibulum. A second set migrates laterally, forming a collar around the midline. We show that collar cells are composed of Fgf3(+) SOX3(+) proliferating progenitors, the induction of which is SHH dependent, but the maintenance of which requires FGF signalling. Collar cells proliferate late into embryogenesis, can generate neurospheres that passage extensively, and differentiate to distinct fates, including hypothalamic neuronal fates and Fgf10(+) anterior-dorsal infundibular cells. Together, our study shows that a subset of anterior floor plate-like cells gives rise to Fgf3(+) SOX3(+) progenitor cells, demonstrates a dual origin of infundibular cells and reveals a crucial role for FGF signalling in governing extended infundibular growth.