RESUMEN
Despite intensive media coverage and international regulations, man-made persistent organic pollutants such as dioxins represent a serious environmental and health threat. Their detection by sophisticated chromatography technologies is highly complex, impeding the constant monitoring of food or environmental samples. This limitation has fostered the development of generations of bioassays exploiting the molecular function of the aryl hydrocarbon receptor (AhR), which binds toxic compounds and directly activates the transcription of target genes. Here, we review the rich panel of available AhR-dependent bioassays and propose a novel classification based on the source of AhR, which can either be endogenously produced by cell types or tissues naturally responsive to dioxins, or exogenously introduced into a wide range of cellular contexts. In both cases, in vitro and in vivo strategies have been engineered to monitor the formation of molecular complexes, and the activation of direct downstream targets or reporter genes. We evaluate and compare bioassays based on exogenous and endogenous AhR proteins and discuss their specific challenges, strengths and opportunities for futures applications. Undoubtedly, the dynamic field of AhR-dependent bioassays will keep providing new and original strategies to help protect human health and ecosystems from persistent organic pollutants.
Asunto(s)
Bioensayo/métodos , Dioxinas/análisis , Receptores de Hidrocarburo de Aril/metabolismo , Contaminantes Químicos del Agua/análisis , Animales , HumanosRESUMEN
Osteogenesis is the fundamental process by which bones are formed, maintained and regenerated. The osteoblasts deposit the bone mineralized matrix by secreting large amounts of extracellular proteins and by allowing the biochemical conditions for the nucleation of hydroxyapatite crystals. Normal bone formation requires a tight control of osteoblastic activity, and therefore, osteoblasts represent a major focus of interest in biomedical research. Several crucial features of osteogenesis can be readily recapitulated using murine, avian and fish primary and immortalized osteoblastic cultures. Here, we describe a novel and straightforward in vitro culture of primary osteoblasts from the amphibian Xenopus tropicalis, a major vertebrate model organism. X. tropicalis osteoblasts can readily be extracted from the frontoparietal bone of pre-metamorphosing tadpole skulls by series of gentle protease treatments. Such primary cultures efficiently proliferate and can conveniently be grown at room temperature, in the absence of CO2, on a variety of substrates. X. tropicalis primary osteoblasts express well-characterized genes known to be active during osteogenesis of teleost fish, chick, mouse and human. Upon differentiation, such cultures mineralize and activate DMP1, an osteocyte-specific gene. Importantly, X. tropicalis primary osteoblasts can be efficiently transfected and respond to the forced activation of the bone morphogenetic protein pathway by increasing their nuclear levels of phospho-Smad. Therefore, this novel primary culture is amenable to experimental manipulations and represents a valuable tool for improving our understanding of the complex network of molecular interactions that govern vertebrate bone formation.