Deepa Subramaniyan

Contrasting actions of diesel exhaust particles on the pulmonary and cardiovascular systems and the effects of thymoquinone

BACKGROUND AND PURPOSE Acute exposure to particulate air pollution has been linked to acute cardiopulmonary events, but the underlying mechanisms are uncertain.

Protective Effect of Curcumin on Pulmonary and Cardiovascular Effects Induced by Repeated Exposure to Diesel Exhaust Particles in Mice

Particulate air pollution has been associated with increased risk of cardiopulmonary diseases. However, the underlying mechanisms are not fully understood. We have previously demonstrated that single dose exposure to diesel exhaust particle (DEP) causes lung inflammation and peripheral thrombotic events. Here, we exposed mice with repeated doses of DEP (15µg/animal) every 2nd day for 6 days (a total of 4 exposures), and measured several cardiopulmonary endpoints 48 h after the end of the treatments. Moreover, the potential protective effect of curcumin (the yellow pigment isolated from turmeric) on DEP-induced cardiopulmonary toxicity was assessed. DEP exposure increased macrophage and neutrophil numbers, tumor necrosis factor α (TNF α) in the bronchoalveolar lavage (BAL) fluid, and enhanced airway resistance to methacoline measured invasively using Flexivent. DEP also significantly increased plasma C-reactive protein (CRP) and TNF α concentrations, systolic blood pressure (SBP) as well as the pial arteriolar thrombosis. It also significantly enhanced the plasma D-dimer and plasminogen activator inhibitor-1 (PAI-1). Pretreatment with curcumin by oral gavage (45 mg/kg) 1h before exposure to DEP significantly prevented the influx of inflammatory cells and the increase of TNF α in BAL, and the increased airway resistance caused by DEP. Likewise, curcumin prevented the increase of SBP, CRP, TNF α, D-dimer and PAI-1. The thrombosis was partially but significantly mitigated. In conclusion, repeated exposure to DEP induced lung and systemic inflammation characterized by TNFα release, increased SBP, and accelerated coagulation. Our findings indicate that curcumin is a potent anti-inflammatory agent that prevents the release of TNFα and protects against the pulmonary and cardiovascular effects of DEP.

Short-Term Systemic Effects of Nose-Only Cigarette Smoke Exposure in Mice: Role of Oxidative Stress

Background/Aims: Long–term cigarette smoking (CS) is a major risk factor for respiratory and cardiovascular diseases, and is also known to adversely affect other organs. However, data on the systemic effects of short-term CS exposure (STCSE) are scarce. Presently, using a nose-only exposure system, we evaluated the systemic effects of STCSE in mice. Methods: We assessed the effects of CS generated by 9 consecutive cigarettes per day for 4 days in a nose-only exposure system on cardiovascular, hepatic and renal endpoints evaluated on day 5 in mice. Control mice were exposed to air only. Results: CS significantly increased systolic blood pressure and decreased total nitric oxide plasma concentration. Circulating platelets and erythrocyte numbers were also increased. However, STCSE did not significantly increase thrombosis in pial arterioles and venules. STCSE significantly raised plasma alanine aminotransferase and gamma glutamyl transpeptidase activities, but did not affect urea or creatinine concentrations. Interestingly, while STCSE enhanced the production of reactive oxygen species in heart and kidney and lipid peroxidation in heart, liver and kidneys, it also enhanced the antioxidant activity of superoxide dismutase, probably indicating that STCSE causes adaptive reactions to counterbalance the potentially damaging action of oxygen radicals induced by STCSE. Conclusion: These results suggest that STCSE causes blood pressure increase, hepatotoxicity and oxidative stress in the heart, liver and the kidneys. These data provide information on the initial steps leading to the systemic effects of STCSE, a stage at which the diseases may likely be reversed.

Exacerbation of thrombotic events by diesel exhaust particle in mouse model of hypertension

Several epidemiological studies have shown that acute exposure to particulate air pollution is associated with increases in cardiovascular morbidity and mortality, and that these effects are especially exacerbated among individuals with pre-existing compromised cardiovascular function such as hypertension. This study was undertaken to determine the cardiovascular effect of diesel exhaust on TO mice made hypertensive by implanting osmotic minipump infusing angiotensin II or vehicle (control). On day 13, the animals were intratracheally instilled with either DEP (15 μg/mouse) or saline. 24 h later, pulmonary exposure to DEP had significantly decreased the systolic blood pressure (SBP) in hypertensive (HT) mice (P<0.01), but not in normotensive (NT) mice. The number of leukocytes and red blood cells, and the plasma interleukin 6 concentration in plasma, however, were not affected in any of the animals. The PaO₂ was decreased, and PaCO₂ increased in DEP-treated HT mice compared to NT mice treated with DEP (P<0.05). The number of circulating platelets was significantly increased in DEP-treated HT versus saline-treated HT and DEP-treated NT mice. Moreover, in NT mice, DEP exposure induced a prothrombotic effect in pial arterioles compared with saline-treated NT mice (P<0.05). Interestingly, in DEP-treated HT mice, the prothrombotic events were significantly aggravated compared with saline-treated HT and DEP-treated NT mice. The direct addition of DEP (0.1-1 μg/ml) to untreated mouse blood significantly induced in vitro platelet aggregation in a dose-dependent fashion, and these effects were more pronounced in blood of HT mice. In vitro exposure to DEP (0.25-1 μg/ml) led to activated intravascular coagulation, an effect that was confirmed by a shortening of both the activated partial thromboplastin time (aPTT) and the prothrombin time (PT). The effect of DEP on aPTT was potentiated in the plasma of HT mice. It can be concluded that the thrombotic events caused by DEP are exacerbated by hypertension in mice. Our findings, therefore, provide a possible plausible explanation for the cardiovascular morbidity and mortality accompanying urban air pollution.

Evaluation of the pulmonary effects of short-term nose-only cigarette smoke exposure in mice

Much is known about the chronic effects of cigarette smoke (CS) on lung function and inflammation and development of chronic obstructive pulmonary disease. However, the underlying pathophysiological mechanisms related to the short-term exposure to CS are not fully understood. Here, we assessed the effect of CS generated by nine consecutive cigarettes per day for four days in a nose-only exposure system on airway resistance measured using forced oscillation technique, lung inflammation and oxidative stress in BALB/c mice. Control mice were exposed to air. Mice exposed to CS showed a significant increase of neutrophils and lymphocytes numbers in bronchoalveolar lavage (BAL). The total protein and endothelin levels in BAL fluid were significantly augmented suggesting an increase of alveolar-capillary barrier permeability. Similarly, airway resistance was significantly increased in the CS group compared with controls. Furthermore, reactive oxygen species and lipid peroxidation levels in lung tissue were significantly increased. The antioxidant activities of reduced glutathione, glutathione S transferase and superoxide dismutase were all significantly increased following CS exposure, indicating that CS could trigger adaptive responses that counterbalance the potentially damaging activity of oxygen radicals induced by CS exposure. In conclusion, our data indicate that short-term nose-only exposure to CS causes lung inflammation and increase of airway resistance mediated at least partly through the oxidative stress.

Airway resistance, inflammation and oxidative stress following exposure to diesel exhaust particle in angiotensin II-induced hypertension in mice

Exposure to particulate matter is a risk factor for respiratory and cardiovascular diseases. However, the mechanisms underlying these effects are not well understood. Here, we compared the impact of diesel exhaust particles (DEP) on airway resistance, inflammation and oxidative stress in normal mice, or mice made hypertensive by implanting osmotic minipump infusing angiotensin II. On day 13 after the onset of infusion, angiotensin II induced significant increase in heart rate (P<0.05) and systolic blood pressure (P<0.0001). On the same day, mice were intratracheally instilled with either DEP (15 μg/mouse) or saline. Twenty-four hour later, the measurement of airway reactivity to methacholine (0-10mg/ml) in vivo by a forced oscillation technique showed a significant and dose dependent increase in airway resistance in normotensive mice exposed to DEP compared to those exposed to saline. In hypertensive mice, there was no difference in airway resistance in DEP versus saline exposed mice. However, following exposure to DEP, airway resistance significantly increased in normotensive versus hypertensive mice. Bronchoalveolar lavage (BAL) fluid analysis showed a significant increase in macrophage numbers in normotensive mice exposed to DEP compared to those exposed to saline, and to hypertensive mice exposed to DEP. Neutrophil numbers were significantly increased in both normotensive and hypertensive mice exposed to DEP compared with their respective control groups. Superoxide dismutase activity was significantly decreased following DEP exposure in both normotensive and hypertensive mice compared to their respective controls. However, total proteins, a marker for increase of epithelial permeability, and malondialdehyde, a reflection of lipid peroxidation, were only increased in normotensive mice exposed to DEP. Therefore, our data suggest that DEP do not aggravate airway resistance and inflammation in angiotensin II-induced hypertensive mice. On the contrary, at the dose of DEP and time point investigated, airway resistance, inflammation and oxidative stress are increased in normotensive compared to hypertensive mice.

Interaction of diesel exhaust particles with human, rat and mouse erythrocytes in vitro.

Inhaled ultrafine (nano) particles can translocate into the bloodstream and interact with circulatory cells causing systemic and cardiovascular events. To gain more insight into this potential mechanism, we studied the interaction of diesel exhaust particles (DEP) with human, rat and mouse erythrocytes in vitro. Incubation of erythrocytes with DEP (1, 10 or 100 µg/ml) for 30 min caused the highest hemolytic effect (up to 38%) in rats, compared to small but significant hemolysis in mice (up to 2.5%) and humans (up to 0.7%). Transmission electron microscopy of erythrocytes revealed the presence of variable degrees of ultrafine (nano)-sized aggregates of DEP either internalized and/or adsorbed onto the erythrocytes in the three species. A significant amount of DEP was found in rat and mouse (but not human) erythrocytes. Lipid erythrocyte susceptibility to in vitro peroxidation measured by malondialdehyde showed a significant and dose-dependent increase in erythrocytes of rats, but not humans or mice. Unlike in human erythrocytes, total antioxidant status (TAS) and superoxide dismutase (SOD) activity in rats were significantly and dose- dependently decreased. In mouse erythrocytes, DEP caused a decreased in SOD (at 10 µg/ml) and TAS (at 100 µg/ml) activities. In conclusion, DEP caused species–dependent erythrocyte hemolysis and oxidative stress, and were either taken up and/or adsorbed onto the red blood cells. Rat (and to a lesser degree mouse) erythrocytes were susceptible to DEP. Human erythrocytes showed the highest resistance to the observed effects. These species difference should be noted when using rats and mice blood as models for humans.

Influence of experimental type 1 diabetes on the pulmonary effects of diesel exhaust particles in mice

Epidemiologically, exposure to particulate air pollution is associated with increases in morbidity and mortality, and diabetics are especially vulnerable to effects of particles. This study was carried out to determine the respiratory effect of diesel exhaust particles (DEP; 0.4mg/kg) on mice rendered diabetic by the injection of streptozotocin or vehicle (control). Four weeks following induction of diabetes, the animals were intratracheally instilled (i.t.) with DEP (0.4mg/kg) or saline. 24h later, the measurement of airway reactivity to methacholine in vivo by a forced oscillation technique showed a significant and dose-dependent increase in airway resistance in non-diabetic mice exposed to DEP versus non-diabetic mice exposed to saline. Similarly, the airway resistance was significantly increased in diabetic mice exposed to DEP versus diabetic mice exposed to saline. Nevertheless, there was no difference in the airway resistance between diabetic and non-diabetic mice after i.t. administration of DEP. Following DEP administration there were neutrophil polymorphs infiltration of pulmonary interalveolar septae and the alveolar spaces with many macrophages containing DEP in both diabetic and non-diabetic mice. Interestingly, apoptotic cells were only found in the examined lung sections from diabetic mice exposed to DEP. Total proteins and albumin concentrations in bronchoalveolar lavage (BAL) fluid, markers for increase of epithelial permeability, were significantly increased in diabetic mice exposed to DEP compared to saline-treated diabetic and DEP-treated non diabetic mice. Superoxide dismutase activity and reduced glutathione concentration in BAL were significantly decreased in diabetic mice exposed to DEP compared to saline-treated diabetic and DEP-treated non diabetic mice. Moreover, tumor necrosis factor α (TNFα) concentrations were significantly increased in diabetic mice exposed to DEP compared to saline-treated diabetic and DEP-treated non diabetic mice. We conclude that, at the dose and time point investigated, DEP equally increased airway resistance and caused infiltration of inflammatory cells in the lung of both diabetic and non-diabetic mice. However, the occurrence of oxidative stress, the presence lung apoptotic cells and the increase of total proteins, albumin and TNFα in BAL fluid were only seen in DEP-exposed diabetic mice suggesting an increased respiratory susceptibility to particulate air pollution.