Vitamin A and retinoic acid in T cell-related immunity.
ABSTRACT Interest in vitamin A as a regulator of immune function goes back to the early 1900s. Recently, several lines of evidence have converged to show that retinoic acid (RA), a major oxidative metabolite of vitamin A, plays a key role in the differentiation of T cell subsets, the migration of T cells into tissues, and the proper development of T cell-dependent antibody responses. This review discusses evidence from experimental studies that RA promotes the differentiation of regulatory T cells, which help to suppress inflammatory reactions, and plays a significant role in normal mucosal immunity by modulating T cell activation and regulating cell trafficking. RA also promotes antibody responses to T cell-dependent antigens. Conversely, in a state of vitamin A deficiency, inflammatory T cell reactions may be inadequately opposed and therefore become dominant. Although data from human studies are still needed, the framework now developed from studies in mice and rat models suggests that adequate vitamin A status, whether derived from ingestion of preformed retinol or β-carotene, is important for maintaining a proper balance of well-regulated T cell functions and for preventing excessive or prolonged inflammatory reactions.
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ABSTRACT: Limbal epithelial stem cells are the likely progenitor cells of OSSN.•UV radiation causes DNA damage via dimers, photoimmunosuppression and reactivates latent HPV.•HPV E6 inhibits p53 tumour suppressor gene allowing DNA-damaged cells past the G1-S checkpoint of the cell cycle.•HPV E7 inhibits pRB gene antitranscription at G1 so infected cells keep replicating.•HIV, photoimmunosuppression and vitamin A deficiency impair tumour surveillance.Experimental Eye Research 10/2014; · 3.02 Impact Factor
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ABSTRACT: The meninges forms a critical epithelial barrier, which protects the central nervous system (CNS), and therefore its prompt reconstruction after CNS injury is essential for reducing neuronal damage. Meningeal cells migrate into the lesion site after undergoing an epithelial-mesenchymal transition (EMT) and repair the impaired meninges. However, the molecular mechanisms of meningeal EMT remain largely undefined. Here we show that TGF-β1 and retinoic acid (RA) released from the meninges, together with oxygen tension, could constitute the mechanism for rapid meningeal reconstruction. AKAP12 is an effector of this mechanism, and its expression in meningeal cells is regulated by integrated upstream signals composed of TGF-β1, RA and oxygen tension. Functionally, AKAP12 modulates meningeal EMT by regulating the TGF-β1-non-Smad-SNAI1 signalling pathway. Collectively, TGF-β1, RA and oxygen tension can modulate the dynamic change in AKAP12 expression, causing prompt meningeal reconstruction after CNS injury by regulating the transition between the epithelial and mesenchymal states of meningeal cells.Nature Communications 09/2014; 5:4952. · 10.74 Impact Factor
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ABSTRACT: Vitamin A or retinol which is the natural precursor of several biologically active metabolites can be considered the most multifunctional vitamin in mammals. Its deficiency is currently, along with protein malnutrition, the most serious and common nutritional disorder worldwide. It is necessary for normal embryonic development and postnatal tissue homeostasis, and exerts important effects on cell proliferation, differentiation and apoptosis. These actions are produced mainly by regulating the expression of a variety of proteins through transcriptional and non-transcriptional mechanisms. Extracellular matrix proteins are among those whose synthesis is known to be modulated by vitamin A. Retinoic acid, the main biologically active form of vitamin A, influences the expression of collagens, laminins, entactin, fibronectin, elastin and proteoglycans, which are the major components of the extracellular matrix. Consequently, the structure and macromolecular composition of this extracellular compartment is profoundly altered as a result of vitamin A deficiency. As cell behavior, differentiation and apoptosis, and tissue mechanics are influenced by the extracellular matrix, its modifications potentially compromise organ function and may lead to disease. This review focuses on the effects of lack of vitamin A in the extracellular matrix of several organs and discusses possible molecular mechanisms and pathologic implications.Nutrients 11/2014; 6(11):4984-5017. · 3.15 Impact Factor