Chronic exposure to TiO2 micro- and nano particles: A biochemical and histopathological experimental study.

The aim of this work was to analyze the effects of long-term exposure to titanium dioxide (TiO2) micro- (MPs) and nanoparticles (NPs) (six and 12 months) on the biochemical and histopathological response of target organs using a murine model. Male Wistar rats were intraperitoneally injected with a suspension of TiO2 NPs (5 nm; TiO2-NP5 group) or MPs (45 µm; TiO2-NP5 group); the control group was injected with saline solution. Six and 12 months post-injection, titanium (Ti) concentration in plasma and target organs was determined spectrometrically (ICP-MS). Blood smears and organ tissue samples were evaluated by light microscopy. Liver and kidney function was evaluated using serum biochemical parameters. Oxidative metabolism was assessed 6 months post-injection (determination of superoxide anion by nitroblue tetrazolium (NBT) test, superoxide dismutase (SOD) and catalase (CAT), lipid peroxidation, and paraoxonase 1). Titanium (Ti) concentration in target organs and plasma was significantly higher in the TiO2-exposed groups than in the control group. Histological evaluation showed the presence of titanium-based particles in the target organs, which displayed no structural alterations, and in blood monocytes. Oxidative metabolism analysis showed that TiO2 NPs were more reactive over time than MPs (p < .05) and mobilization of antioxidant enzymes and membrane damage varied among the studied organs. Clearance of TiO2 micro and nanoparticles differed among the target organs, and lung clearance was more rapid than clearance from the lungs and kidneys (p < .05). Conversely, Ti concentration in plasma increased with time (p < .05). In conclusion, neither serum biochemical parameters nor oxidative metabolism markers appear to be useful as biomarkers of tissue damage in response to TiO2 micro- and nanoparticle deposits at chronic time points.

Systemic effect of TiO2 micro- and nanoparticles after acute exposure in a murine model.

The surface of a biomedical implant can be a potential endogenous source of release of microparticles (MPs) and nanoparticles (NPs) into the biological environment. In addition, titanium particles from exogenous sources can enter the body through inhalation, ingestion, or dermal contact. The aim of this work was to evaluate the biological response of the lung, liver, and kidneys to acute exposure to titanium dioxide (TiO2 ). Male Wistar rats were intraperitoneally injected with a suspension of 45 µm or 5 nm TiO2 particles. One month post-exposure, titanium concentration was determined spectrometrically (ICP-MS) in plasma and target organs. Blood smears and organ tissue samples were examined histopathologically, and oxidative metabolism was analyzed (superoxide anion by nitro blue tetrazolium (NBT) test; superoxide dismutase (SOD) and catalase (CAT); lipid peroxidation; paraoxonase 1). Liver (aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase) and kidney (urea, creatinine) function was evaluated using serum biochemical markers. Microchemical and histological analysis revealed the presence of particles, though no structural alterations, in TiO2 -exposed groups. NBT test showed an increase in the percentage of reactive cells and antioxidant enzyme consumption in lung samples in the 45 µm and 5 nm TiO2 -exposed groups. Only the 5 nm particles caused a decrease in SOD and CAT activity in the liver. No changes in renal oxidative metabolism were observed in either of the TiO2 -exposed groups. Determination of serum biochemical markers and analysis of oxidative metabolism are not early bioindicators of tissue damage caused by TiO2 MPs and NPs.

Changes in extrapulmonary organs and serum enzyme biomarkers after chronic exposure to Buenos Aires air pollution.

Urban air pollution is a serious environmental problem in developing countries worldwide, and health is a pressing issue in the megacities in Latin America. Buenos Aires is a megacity with an estimated moderate Air Quality Index ranging from 42 to 74 µg/m3. Exposure to Urban Air Particles from Buenos Aires (UAP-BA) induces morphological and physiological respiratory alterations; nevertheless, no studies on extrapulmonary organs have been performed. The aim of the present study was to explore the health effects of chronic exposure to UAP-BA (1, 6, 9, and 12 months) on the liver, heart, and serum risk biomarkers. BALB/c mice were exposed to UAP-BA or filtered air (FA) in inhalation chambers, and liver and heart histopathology, oxidative metabolism (superoxide dismutase, SOD; catalase, CAT; lipoperoxidation, TBARS), amino transaminases (AST, ALT) as serum risk biomarkers, alkaline phosphatase (ALP), paraxonase-1 (PON-1), and lipoprotein-associated phospholipase A2 (Lp-PLA2) were evaluated. Chronic exposure to real levels of UAP in Buenos Aires led to alterations in extrapulmonary organs associated with inflammation and oxidative imbalance and to changes in liver and heart risk biomarkers. Our results may reflect the impact of the persistent air pollution in Buenos Aires on individuals living in this Latin American megacity.

Chronic exposure to urban air pollution from Buenos Aires: the ocular mucosa as an early biomarker.

Air pollution represents a major health problem in megacities, bringing about 8 million deaths every year. The aim of the study was to evaluate in vivo the ocular and respiratory mucosa biological response after chronic exposure to urban air particles from Buenos Aires (UAP-BA). BALB/c mice were exposed to UAP-BA or filtered air for 1, 6, 9, and 12 months. After exposure, histology, histomorphometry, and IL-6 proinflammatory cytokine level were evaluated in the respiratory and ocular mucosa. Total cell number and differential cell count were determined in the brochoalveolar lavage fluid. In the lung, chronic exposure to UAP-BA induced reduction of the alveolar space, polymorhonuclear cell recruitment, and goblet cell hyperplasia. In the ocular surface, UAP-BA induced an initial mucin positive cells rise followed by a decline through time, while IL-6 level increased at the latest point-time assayed. Our results showed that the respiratory and the ocular mucosas respond differently to UAP-BA. Being that lung and ocular mucosa diseases may be triggered and/or exacerbated by chronic exposure to urban air PM, the inhabitants of Buenos Aires whom are chronically exposed to environmental urban air pollution may be considered a subpopulation at risk. Based on our results, we propose the ocular mucosa as a reliable and more accessible surrogate for pulmonary mucosa environmental toxicity that might also serve as an earlier biomarker for air pollution adverse impact on health.

Oxidative stress response to air particle pollution in a rat nutritional growth retardation model.

Air pollution consisting of gases and particulate matter-(PM) represents a health problem in cities worldwide. However, air pollution does not impact equally all individuals, as children appear to be more vulnerable subpopulations. Air pollution and malnutrition are two distinct factors that have been associated with oxidative damage. Therefore, the interaction between environmental exposure and nutritional status in populations at risk needs to be explored. The aim of this study was to examine oxidative metabolism in lung, heart and liver in malnourished young rats exposed to residual oil fly ash (ROFA). A Nutritional Growth Retardation (NGR) model was developed in weanling male rats placed on a 20% restricted balanced diet for 4 weeks. Then, NGR and control rats were intranasally instilled with either ROFA (1mg/kg BW) or phosphate buffered saline (PBS). Twenty-four hr post-exposure lung, heart and liver were excised, and serum collected. ROFA induced lung and liver inflammation in control and NGR animals as evidenced by lung polymorphonuclear neutrophil (PMN) recruitment and alveolar space reduction accompanied by liver lymphocyte and binucleated hepatocyte level increase. In lung and liver, antioxidant defense mechanisms reduced lipoperoxidation. In contrast, only in NGR animals did ROFA exposure alter heart oxidative metabolism leading to lipid peroxidation. Although histological and biochemical tissue alterations were detected, no marked changes in serum liver and heart systemic biomarkers were observed. In conclusion, NGR animals responded differently to PM exposure than controls suggesting that nutritional status plays a key role in responsiveness to ambient air contaminants.

Increased nitric oxide production and gender-dependent changes in PPARα expression and signaling in the fetal lung from diabetic rats.

The fetal lung is affected by maternal diabetes. Nuclear receptor PPARα regulates nitric oxide (NO) overproduction in different tissues. We aimed to determine whether fetal lung PPARα expression is altered by maternal diabetes, and if there are gender-dependent changes in PPARα regulation of NO production in the fetal lung. Fetal lungs from control and diabetic rats were explanted on day 21 of gestation and evaluated for PPARα expression and NO production. Fetuses were injected with the PPARα ligand LTB(4) on days 19, 20 and 21, and the fetal lung explanted on day 21 to evaluate PPARα and the inducible isoform of NO synthase (iNOS). Besides, pregnant rats were fed with olive oil- and safflower oil-supplemented diets, enriched in PPAR ligands, for evaluation of fetal lung NO production and PPARα expression. We found reduced PPARα concentrations only in the lung from male fetuses from the diabetic group when compared to controls, although maternal diabetes led to NO overproduction in both male and female fetal lungs. Fetal activation of PPARα led to changes in lung PPARα expression only in female fetuses, although this treatment increased iNOS expression in both male and female fetuses in the diabetic group. Diets supplemented with olive oil and not with safflower oil led to a reduction in NO production in male and female fetal lungs. In conclusion, there are gender-dependent changes in PPARα expression and signaling in the fetal lung from diabetic rats, although PPARα activation prevents maternal diabetes-induced lung NO overproduction in both male and female fetuses.

Altered matrix metalloproteinases and tissue inhibitors of metalloproteinases in embryos from diabetic rats during early organogenesis.

Maternal diabetes increases the risks for embryo malformations. Matrix metalloproteinase-2 (MMP-2) and MMP-9 are two relevant MMPs for embryo development. Here, we addressed whether changes in these MMPs and in tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) and TIMP-2 are altered in embryos and decidua from type 1 diabetic rats during early organogenesis. Our results demonstrate MMP-2 and MMP-9 overactivities and overexpression, together with increases in lipid peroxidation and nitric oxide production in embryos and decidua from diabetic animals. There is a concomitant increase in the inhibitory activity of TIMP-1 and TIMP-2 in embryos and decidua, and an increase in protein expression of embryonic TIMP-1 and TIMP-2. In situ zymography demonstrated MMPs overactivities despite increased TIMPs in embryos and decidua in maternal diabetes during early organogenesis. This study reveals that maternal diabetes leads to profound alterations in MMPs/TIMPs balance during embryo organogenesis, the gestational period during which most malformations are induced.

PPARα agonists regulate lipid metabolism and nitric oxide production and prevent placental overgrowth in term placentas from diabetic rats.

Maternal diabetes impairs fetoplacental metabolism and growth. Peroxisome proliferator-activated receptor α (PPARα) is a nuclear receptor capable of regulating lipid metabolism and inflammatory pathways. In this study, we analyzed whether placental and fetal PPARα activation regulates lipid metabolism and nitric oxide (NO) production in term placentas from diabetic rats. Diabetes was induced by neonatal streptozotocin administration. On day 21 of pregnancy, placentas from control and diabetic rats were cultured in the presence of PPARα agonists (clofibrate and leukotriene B(4) (LTB(4))) for further evaluation of levels, synthesis, and peroxidation of lipids as well as NO production. Besides, on days 19, 20, and 21 of gestation, fetuses were injected with LTB(4), and the placentas were explanted on day 21 of gestation for evaluation of placental weight and concentrations of placental lipids, lipoperoxides, and NO metabolites. We found that placentas from diabetic rats showed reduced PPARα concentrations. They presented no lipid overaccumulation but reduced lipid synthesis, parameters negatively regulated by PPARα activators. Lipid peroxidation and NO production, increased in placentas from diabetic rats, were negatively regulated by PPARα activators. Fetal PPARα activation in diabetic rats does not change placental lipid concentrations but reduced placental weight and NO production. In conclusion, PPARα activators regulate lipid metabolism and NO production in term placentas from diabetic rats, an activation that regulates placental growth and can partly be exerted by the developing fetus.

Activation of the nuclear receptor PPARα regulates lipid metabolism in foetal liver from diabetic rats: implications in diabetes-induced foetal overgrowth.

BACKGROUND: peroxisome proliferator-activated receptor α (PPARα) is a crucial regulator of liver lipid metabolism. As maternal diabetes impairs foetal lipid metabolism and growth, we aimed to determine whether PPARα activation regulates lipid metabolism in the foetal liver from diabetic rats as well as foetal weight and foetal liver weight. METHODS: diabetes was induced by neonatal streptozotocin administration (90 mg/kg). For ex vivo studies, livers from 21-day-old foetuses from control and diabetic rats were explanted and incubated in the presence of PPARα agonists (clofibrate and leukotriene B(4) ) for further evaluation of lipid levels (by thin layer chromatography and densitometry), de novo lipid synthesis (by (14) C-acetate incorporation) and lipid peroxidation (by thiobarbituric reactive substances evaluation). For in vivo studies, foetuses were injected through the uterine wall with leukotriene B(4) on days 19, 20 and 21 of gestation. On day 21 of gestation, foetal liver concentrations of lipids and lipoperoxides were evaluated. RESULTS: foetuses from diabetic rats showed increased body weight and liver weight, as well as accumulation of triglycerides and cholesteryl esters, increased de novo lipid synthesis and lipid peroxidation in the liver when compared to controls. Ex vivo studies showed that PPARα ligands reduced both the concentrations and synthesis of the lipid species studied and lipid peroxidation in the foetal liver from diabetic rats. In vivo experiments showed that leukotriene B(4) reduced the concentrations of triglycerides, cholesteryl esters and phospholipids, as well as lipid peroxidation, foetal weight and foetal liver weight in diabetic rats. CONCLUSIONS: PPARα activation regulates the impaired foetal liver lipid metabolism, prevents hepatomegaly and reduces foetal overgrowth induced by maternal diabetes.

Carbaprostacyclin, a PPARdelta agonist, ameliorates excess lipid accumulation in diabetic rat placentas.

AIMS: Maternal diabetes impairs placental development and metabolism. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear receptors relevant in metabolic homeostasis. We investigated the concentrations of PPARdelta and its endogenous agonist prostacyclin (PGI2), as well as the effects of carbaprostacylin (cPGI(2,) a PPARdelta agonist) on lipid metabolism in placentas from control and streptozotocin-induced diabetic rats on day 13.5 of gestation. MAIN METHODS: The placentas were explanted to evaluate PPARdelta expression and PGI2 concentrations, and cultured with cPGI2 for further analysis of lipid metabolism (concentrations and (14)C-acetate derived synthesis of triglycerides, cholesteryl esters, phospholipids, cholesterol and free fatty acids; release of glycerol and lipid peroxidation). KEY FINDINGS: Reduced PGI2 concentrations were found in the placentas from diabetic rats when compared to controls. cPGI2 additions reduced the concentrations and synthesis of several lipid species, increased lipid catabolism and reduced lipid peroxidation in the placenta. These effects were more marked in diabetic tissues, which presented alterations in the lipid metabolic parameters evaluated. cPGI2 additions increased placental PPARdelta and acyl-CoA oxidase expression, which are changes possibly involved in the catabolic effects observed. SIGNIFICANCE: The present study reveals the capability of cPGI2 to regulate placental lipid metabolism and PPARdelta expression, and suggests that preserving appropriate PGI2 concentrations in the placenta may help to metabolize maternal derived lipid overload in diabetic gestations.