Titanium dioxide nanoparticles promote arrhythmias via a direct interaction with rat cardiac tissue

BackgroundIn light of recent developments in nanotechnologies, interest is growing to better comprehend the interaction of nanoparticles with body tissues, in particular within the cardiovascular system. Attention has recently focused on the link between environmental pollution and cardiovascular diseases. Nanoparticles <50 nm in size are known to pass the alveolar¿pulmonary barrier, enter into bloodstream and induce inflammation, but the direct pathogenic mechanisms still need to be evaluated. We thus focused our attention on titanium dioxide (TiO2) nanoparticles, the most diffuse nanomaterial in polluted environments and one generally considered inert for the human body.MethodsWe conducted functional studies on isolated adult rat cardiomyocytes exposed acutely in vitro to TiO2 and on healthy rats administered a single dose of 2 mg/Kg TiO2 NPs via the trachea. Transmission electron microscopy was used to verify the actual presence of TiO2 nanoparticles within cardiac tissue, toxicological assays were used to assess lipid peroxidation and DNA tissue damage, and an in silico method was used to model the effect on action potential.ResultsVentricular myocytes exposed in vitro to TiO2 had significantly reduced action potential duration, impairment of sarcomere shortening and decreased stability of resting membrane potential. In vivo, a single intra-tracheal administration of saline solution containing TiO2 nanoparticles increased cardiac conduction velocity and tissue excitability, resulting in an enhanced propensity for inducible arrhythmias. Computational modeling of ventricular action potential indicated that a membrane leakage could account for the nanoparticle-induced effects measured on real cardiomyocytes.ConclusionsAcute exposure to TiO2 nanoparticles acutely alters cardiac excitability and increases the likelihood of arrhythmic events

Corbicula fluminea ivasion in Lake Maggiore (Italy): population dynamics and comparison of dietary overlap with native mussels

The Asian clam, Corbicula fluminea (M?ller, 1774), was most likely introduced in 2007 in Lake Maggiore, the second largest and deepest lake in Italy. Spatial and temporal variations in abundance, biomass and population structure of C. fluminea at 5 sites, investigated since its first discovery in 2010, confirmed the well known ability of this species rapidly to spread in new recipient environments and to achieve densities of thousands per square meter. In few years Corbicula has colonized about one third of the lake littoral area and has become the dominant littoral benthic species in terms of abundance and biomass, creating the conditions for a competitive interaction for space and food with native mussels. Indeed, a comparison with previous data has evidenced a strong decline of the most abundant native mussel species (Unio mancus), whose actual density is reduced of about 75% after Corbicula invasion. Although native mussel depletion cannot be unequivocally attributed to Corbicula impact, the change in bivalve species dominance could lead to changes in the structure and function of the ecosystem. In spite of similar functional roles, unionids and C. fluminea are likely to differ in filtering efficiency and trophic niche. Therefore, understanding the role that both native and invasive species play in food-web structure and nutrient cycling is essential for predicting how the ecosystem might be altered. Our study aimed to: (i) explore the invasion dynamics of Corbicula in Lake Maggiore; (ii) compare the trophic roles of the native mussel U. mancus and C. fluminea through measurements of respective filtration rates and spectrum of food resources. Filtration rates were measured by the clearance method under different experimental conditions and over the whole diurnal cycle. Dietary composition and overlap were determined through the measurement of the elemental and stable isotopic compositions (&#948;13C and &#948;15N) of the respective tissues