Exercise does not ameliorate cardiac dysfunction in obese mice exposed to fine particulate matter.

BACKGROUND: Studies have demonstrated that exposure to fine particulate matter (PM2.5) is linked to cardiovascular disease (CVD), which is exacerbated in patients with pre-existing conditions such as obesity. In the present study, we examined cardiac function of obese mice exposed to PM2.5 and determined if mild exercise affected cardiac function. METHODS: Obese mice (ob/ob) (leptin deficient, C57BL/6J background) were exposed to either filtered air (FA) or PM2.5 at an average concentration of 32 µg/m3 for 6 h/day, 5 days/week for 9 months. Following exposure, mice were divided into four groups: (1) FA sedentary, (2) FA treadmill exercise, (3) PM2.5 sedentary, and (4) PM2.5 treadmill exercise and all mice were analyzed after 8 weeks of exercise training. RESULTS: Echocardiography showed increased left ventricular end systolic (LVESd) and diastolic (LVEDd) diameters in PM2.5 sedentary mice compared to FA sedentary mice. There was increased expression of ICAM1, VCAM and CRP markers in sedentary PM2.5 mice compared to FA mice. Both FA and PM2.5 exercised mice showed decreased posterior wall thickness in systole compared to FA sedentary mice, coupled with altered expression of inflammatory markers following exercise. CONCLUSION: Obese mice exposed to PM2.5 for 9 months showed cardiac dysfunction, which was not improved following mild exercise training.

Preconception Exposure to Fine Particulate Matter Leads to Cardiac Dysfunction in Adult Male Offspring.

Background Particulate matter (particles < 2.5 µm [ PM 2.5]) exposure during the in utero and postnatal developmental periods causes cardiac dysfunction during adulthood. Here, we investigated the potential priming effects of preconception exposure of PM 2.5 on cardiac function in adult offspring. Methods and Results Male and female friend leukemia virus b (FVB) mice were exposed to either filtered air ( FA ) or PM 2.5 at an average concentration of 38.58 µg/m3 for 6 hours/day, 5 days/week for 3 months. Mice were then crossbred into 2 groups: (1)  FA male× FA female (both parents were exposed to FA preconception) and, (2) PM 2.5male× PM 2.5female (both parents were exposed to PM 2.5 preconception). Male offspring were divided: (1) preconception FA (offspring born to FA exposed parents) and, (2) preconception PM 2.5 (offspring born to PM 2.5 exposed parents) and analyzed at 3 months of age. Echocardiography identified increased left ventricular end systolic volume and reduced posterior wall thickness, reduced %fractional shortening and %ejection fraction in preconception PM 2.5 offspring. Cardiomyocytes isolated from preconception PM 2.5 offspring showed reduced %peak shortening, -dL/dT, TPS 90 and slower calcium reuptake (tau). Gene and protein expression revealed modifications in markers of inflammation ( IL -6, IL -15, TNF α, NF қB, CRP , CD 26E, CD 26P, intercellular adhesion molecule 1, and monocyte chemoattractant protein-1) profibrosis (collagen type III alpha 1 chain), oxidative stress ( NOS 2), antioxidants (Nrf2, SOD , catalase), Ca2+ regulatory proteins ( SERCA 2a, p- PLN , NCX ), and epigenetic regulators (Dnmt1, Dnmt3a, Dnmt3b, Sirt1, and Sirt2) in preconception PM 2.5 offspring. Conclusions Preconception exposure to PM 2.5 results in global cardiac dysfunction in adult offspring, suggesting that abnormalities during development are not limited to the prenatal or postnatal periods but can also be determined before conception.

PM2.5 exposure in utero contributes to neonatal cardiac dysfunction in mice.

OBJECTIVE: Exposure of fine particulate matter (PM2.5) to pregnant dams has been shown to be strongly associated with adverse cardiovascular outcomes in offspring at adulthood, however, effects evident during neonatal periods are unclear. We designed this study to examine cardiac function of neonatal mice (14 days old) exposed to in utero PM2.5. METHODS: Pregnant FVB female mice were exposed either to filtered air (FA) or PM2.5 at an average concentration of 91.78 µg/m3 for 6 h/day, 5 days/wk (similar to exposure in a large industrial area) throughout the gestation period (21 days). After birth, animals were analyzed at day 14 of life. RESULTS: Fourteen day old mice exposed to PM2.5 during the in utero period demonstrated decreased fractional shortening (%FS, 41.1 ± 1.2% FA, 33.7 ± 1.2% PM2.5, p < 0.01) and LVEDd (2.87 ± 0.08 mm FA, 2.58 ± 0.07 mm PM2.5, p < 0.05) compared to FA exposed mice. Contractile kinetics and calcium transients in isolated cardiomyocytes from PM2.5 exposed mice illustrated reduced peak shortening (%PS, 16.7 ± 0.5% FA, 14.7 ± 0.4% PM2.5, p < 0.01), negative contractile velocity (-dL/dT, -6.91 ± 0.3 µm/s FA, -5.46 ± 0.2 µm/s PM2.5, p < 0.001), increased time to relaxation 90% (TR90, 0.07 ± 0.003 s FA, 0.08 ± 0.004 s PM2.5, p < 0.05), decreased calcium transient amplitude (Δ340/380, 33.8 ± 3.4 FA, 29.5 ± 2.8 p.m.2.5) and slower fluorescence decay rate (τ, 0.72 ± 0.1 s FA, 1.16 ± 0.15 s PM2.5, p < 0.05). Immunoblotting studies demonstrated alterations in expression of Ca2+ handling proteins- SERCA-2A, p-PLN, NCX and CaV1.2 in hearts of 14 day old in utero PM2.5 exposed mice compared to FA exposed hearts. CONCLUSION: PM2.5 exposure during the critical in utero period adversely affects the developing mouse fetus leading to functional cardiac changes that were evident during the very early (14 days) stages of adolescence. These data demonstrated that exposure to PM2.5 during the gestation period significantly impacts cardiovascular outcomes early in life.

In vitro particulate matter exposure causes direct and lung-mediated indirect effects on cardiomyocyte function.

Particulate matter (PM) exposure induces a pathological response from both the lungs and the cardiovascular system. PM is capable of both manifestation into the lung epithelium and entrance into the bloodstream. Therefore, PM has the capacity for both direct and lung-mediated indirect effects on the heart. In the present studies, we exposed isolated rat cardiomyocytes to ultrafine particulate matter (diesel exhaust particles, DEP) and examined their contractile function and calcium handling ability. In another set of experiments, lung epithelial cells (16HBE14o- or Calu-3) were cultured on permeable supports that allowed access to both the basal (serosal) and apical (mucosal) media; the basal media was used to culture cardiomyocytes to model the indirect, lung-mediated effects of PM on the heart. Both the direct and indirect treatments caused a reduction in contractility as evidenced by reduced percent sarcomere shortening and reduced calcium handling ability measured in field-stimulated cardiomyocytes. Treatment of cardiomyocytes with various anti-oxidants before culture with DEP was able to partially prevent the contractile dysfunction. The basal media from lung epithelial cells treated with PM contained several inflammatory cytokines, and we found that monocyte chemotactic protein-1 was a key trigger for cardiomyocyte dysfunction. These results indicate the presence of both direct and indirect effects of PM on cardiomyocyte function in vitro. Future work will focus on elucidating the mechanisms involved in these separate pathways using in vivo models of air pollution exposure.

Losartan treatment attenuates tumor-induced myocardial dysfunction.

UNLABELLED: Fatigue and muscle wasting are common symptoms experienced by cancer patients. Data from animal models demonstrate that angiotensin is involved in tumor-induced muscle wasting, and that tumor growth can independently affect myocardial function, which could contribute to fatigue in cancer patients. In clinical studies, inhibitors of angiotensin converting enzyme (ACE) can prevent the development of chemotherapy-induced cardiovascular dysfunction, suggesting a mechanistic role for the renin-angiotensin-aldosterone system (RAAS). In the present study, we investigated whether an angiotensin (AT) 1-receptor antagonist could prevent the development of tumor-associated myocardial dysfunction. METHODS AND RESULTS: Colon26 adenocarcinoma (c26) cells were implanted into female CD2F1 mice at 8weeks of age. Simultaneously, mice were administered Losartan (10mg/kg) daily via their drinking water. In vivo echocardiography, blood pressure, in vitro cardiomyocyte function, cell proliferation assays, and measures of systemic inflammation and myocardial protein degradation were performed 19days following tumor cell injection. Losartan treatment prevented tumor-induced loss of muscle mass and in vitro c26 cell proliferation, decreased tumor weight, and attenuated myocardial expression of interleukin-6. Furthermore, Losartan treatment mitigated tumor-associated alterations in calcium signaling in cardiomyocytes, which was associated with improved myocyte contraction velocity, systolic function, and blood pressures in the hearts of tumor-bearing mice. CONCLUSIONS: These data suggest that Losartan may mitigate tumor-induced myocardial dysfunction and inflammation.

In vitro effects of exercise on the heart.

Pathologic and physiologic factors acting on the heart can produce consistent pressure changes, volume overload, or increased cardiac output. These changes may then lead to cardiac remodeling, ultimately resulting in cardiac hypertrophy. Exercise can also induce hypertrophy, primarily physiologic in nature. To determine the mechanisms responsible for each type of remodeling, it is important to examine the heart at the functional unit, the cardiomyocyte. Tests of individual cardiomyocyte function in vitro provide a deeper understanding of the changes occurring within the heart during hypertrophy. Examination of cardiomyocyte function during exercise primarily follows one of two pathways: the addition of hypertrophic inducing agents in vitro to normal cardiomyocytes, or the use of trained animal models and isolating cells following the development of hypertrophy in vivo. Due to the short lifespan of adult cardiomyocytes, a proportionately scant amount of research exists involving the direct stimulation of cells in vitro to induce hypertrophy. These attempts provide the only current evidence, as it is difficult to gather extensive data demonstrating cell growth as a result of in vitro physical stimulation. Researchers have created ways to combine skeletal myocytes with cardiomyocytes to produce functional muscle cells used to repair pathologic heart tissue, but continue to struggle with the short lifespan of these cells. While there have been promising findings regarding the mechanisms that surround cardiac hypertrophy in vitro, the translation of in vitro findings to in vivo function is not consistent. Therefore, the focus of this review is to highlight recent studies that have investigated the effect of exercise on the heart, both in vitro and in vivo.

Early life exposure to air pollution induces adult cardiac dysfunction.

Exposure to ambient air pollution contributes to the progression of cardiovascular disease, particularly in susceptible populations. The objective of the present study was to determine whether early life exposure to air pollution causes persistent cardiovascular consequences measured at adulthood. Pregnant FVB mice were exposed to filtered (FA) or concentrated ambient particulate matter (PM2.5) during gestation and nursing. Mice were exposed to PM2.5 at an average concentration of 51.69 µg/m(3) from the Columbus, OH region for 6 h/day, 7 days/wk in utero until weaning at 3 wk of age. Birth weight was reduced in PM2.5 pups compared with FA (1.36 ± 0.12 g FA, n = 42 mice; 1.30 ± 0.15 g PM2.5, n = 67 P = 0.012). At adulthood, mice exposed to perinatal PM2.5 had reduced left ventricular fractional shortening compared with FA-exposed mice (43.6 ± 2.1% FA, 33.2 ± 1.6% PM2.5, P = 0.001) with greater left ventricular end systolic diameter. Pressure-volume loops showed reduced ejection fraction (79.1 ± 3.5% FA, 35.5 ± 9.5% PM2.5, P = 0.005), increased end-systolic volume (10.4 ± 2.5 µl FA, 39.5 ± 3.8 µl PM2.5, P = 0.001), and reduced dP/dt maximum (11,605 ± 200 µl/s FA, 9,569 ± 800 µl/s PM2.5, P = 0.05) and minimum (-9,203 ± 235 µl/s FA, -7,045 ± 189 µl/s PM2.5, P = 0.0005) in PM2.5-exposed mice. Isolated cardiomyocytes from the hearts of PM2.5-exposed mice had reduced peak shortening (%PS, 8.53 ± 2.82% FA, 6.82 ± 2.04% PM2.5, P = 0.003), slower calcium reuptake (τ, 0.22 ± 0.09 s FA, 0.26 ± 0.07 s PM2.5, P = 0.048), and reduced response to ß-adrenergic stimulation compared with cardiomyocytes isolated from mice that were exposed to FA. Histological analyses revealed greater picro-sirius red-positive-stained areas in the PM2.5 vs. FA group, indicative of increased collagen deposition. We concluded that these data demonstrate the detrimental role of early life exposure to ambient particulate air pollution in programming of adult cardiovascular diseases and the potential for PM2.5 to induce persistent cardiac dysfunction at adulthood.

Adverse perinatal environment contributes to altered cardiac development and function.

Epidemiological observations report an association between intrauterine growth restriction (IUGR) and cardiovascular diseases. Systemic maternal inflammation is the most common stress during pregnancy, leading to IUGR. We hypothesized that perinatal inflammation and hyperoxygenation induce discernible alterations in cardiomyocyte contractility and calcium signaling, causing early cardiac dysfunction. Pregnant C3H/HeN mice were injected with LPS or saline on embryonic day 16. Newborn mice were placed in 85% O2 or room air (RA) for 14 days. Pups born to LPS-injected dams had reduced birth weight. Echocardiographic measurements revealed that in vivo LV function was compromised in LPS/O2 mice as early as 3 days of life. Isolated cardiomyocytes from LPS/O2 mice at day 14 exhibited decreased sarcomere fractional shortening, along with decreased time-to-90% peak shortening. Calcium transient amplitude was greatest in LPS/O2 mice. SERCA2a mRNA and protein levels were increased and phospholamban mRNA levels were decreased in LPS/O2 mice. Phosphorylation of phospholamban was increased, along with Sorcin mRNA levels in LPS/O2 mice. Combined exposure to perinatal inflammation and hyperoxia resulted in growth restriction, in vivo and in vitro cardiac dysfunction, coinciding with humans and animal models of cardiac dysfunction. Expression of calcium handling proteins during the neonatal period was similar to that observed during fetal stages of development. Our data suggest that perinatal inflammation and hyperoxia exposure alter fetal development, resulting in early cardiac dysfunction.

Cardiovascular remodeling in response to long-term exposure to fine particulate matter air pollution.

BACKGROUND: Air pollution is a pervasive environmental health hazard that occurs over a lifetime of exposure in individuals from many industrialized societies. However, studies have focused primarily on exposure durations that correspond to only a portion of the lifespan. We therefore tested the hypothesis that exposure over a considerable portion of the lifespan would induce maladaptive cardiovascular responses. METHODS AND RESULTS: C57BL/6 male mice were exposed to concentrated ambient particles <2.5 µm (particulate matter, PM or PM(2.5)) or filtered air (FA), 6 h/d, 5 d/wk, for 9 months. Assessment of cardiac contractile function, coronary arterial flow reserve, isolated cardiomyocyte function, expression of hypertrophic markers, calcium handling proteins, and cardiac fibrosis were then performed. Mean daily concentrations of PM(2.5) in the exposure chamber versus ambient daily PM(2.5) concentration at the study site were 85.3 versus 10.6 µg/m(3) (7.8-fold concentration), respectively. PM(2.5) exposure resulted in increased hypertrophic markers leading to adverse ventricular remodeling characterized by myosin heavy chain (MHC) isoform switch and fibrosis, decreased fractional shortening (39.8 ± 1.4 FA versus 27.9 ± 1.3 PM, FS%), and mitral inflow patterns consistent with diastolic dysfunction (1.95 ± 0.05 FA versus 1.52 ± 0.07 PM, E/A ratio). Contractile reserve to dobutamine was depressed (62.3 ± 0.9 FA versus 49.2 ± 1.5 PM, FS%) in response to PM(2.5) without significant alterations in maximal vasodilator flow reserve. In vitro cardiomyocyte function revealed depressed peak shortening (8.7 ± 0.6 FA versus 7.0 ± 0.4 PM, %PS) and increased time-to-90% shortening (72.5 ± 3.2 FA versus 82.8 ± 3.2 PM, ms) and re-lengthening (253.1 ± 7.9 FA versus 282.8 ± 9.3 PM, ms), which were associated with upregulation of profibrotic markers and decreased total antioxidant capacity. Whole-heart SERCA2a levels and the ratio of α/ß-MHC were both significantly decreased (P<0.05) in PM(2.5)-exposed animals, suggesting a switch to fetal programming. CONCLUSIONS: Long-term exposure to environmentally relevant concentrations of PM(2.5) resulted in a cardiac phenotype consistent with incipient heart failure.

Particulate matter exposure exacerbates high glucose-induced cardiomyocyte dysfunction through ROS generation.

Diabetes mellitus and fine particulate matter from diesel exhaust (DEP) are both important contributors to the development of cardiovascular disease (CVD). Diabetes mellitus is a progressive disease with a high mortality rate in patients suffering from CVD, resulting in diabetic cardiomyopathy. Elevated DEP levels in the air are attributed to the development of various CVDs, presumably since fine DEP (<2.5 µm in diameter) can be inhaled and gain access to the circulatory system. However, mechanisms defining how DEP affects diabetic or control cardiomyocyte function remain poorly understood. The purpose of the present study was to evaluate cardiomyocyte function and reactive oxygen species (ROS) generation in isolated rat ventricular myocytes exposed overnight to fine DEP (0.1 µg/ml), and/or high glucose (HG, 25.5 mM). Our hypothesis was that DEP exposure exacerbates contractile dysfunction via ROS generation in cardiomyocytes exposed to HG. Ventricular myocytes were isolated from male adult Sprague-Dawley rats cultured overnight and sarcomeric contractile properties were evaluated, including: peak shortening normalized to baseline (PS), time-to-90% shortening (TPS(90)), time-to-90% relengthening (TR(90)) and maximal velocities of shortening/relengthening (±dL/dt), using an IonOptix field-stimulator system. ROS generation was determined using hydroethidine/ethidium confocal microscopy. We found that DEP exposure significantly increased TR(90), decreased PS and ±dL/dt, and enhanced intracellular ROS generation in myocytes exposed to HG. Further studies indicated that co-culture with antioxidants (0.25 mM Tiron and 0.5 mM N-Acetyl-L-cysteine) completely restored contractile function in DEP, HG and HG+DEP-treated myocytes. ROS generation was blocked in HG-treated cells with mitochondrial inhibition, while ROS generation was blocked in DEP-treated cells with NADPH oxidase inhibition. Our results suggest that DEP exacerbates myocardial dysfunction in isolated cardiomyocytes exposed to HG-containing media, which is potentially mediated by various ROS generation pathways.

Myocardial dysfunction in an animal model of cancer cachexia.

AIMS: Fatigue is a common occurrence in cancer patients regardless of tumor type or anti-tumor therapies and is an especially problematic symptom in persons with incurable tumor disease. In rodents, tumor-induced fatigue is associated with a progressive loss of skeletal muscle mass and increased expression of biomarkers of muscle protein degradation. The purpose of the present study was to determine if muscle wasting and expression of biomarkers of muscle protein degradation occur in the hearts of tumor-bearing mice, and if these effects of tumor growth are associated with changes in cardiac function. MAIN METHODS: The colon26 adenocarcinoma cell line was implanted into female CD2F1 mice and skeletal muscle wasting, in vivo heart function, in vitro cardiomyocyte function, and biomarkers of muscle protein degradation were determined. KEY FINDINGS: Expression of biomarkers of protein degradation were increased in both the gastrocnemius and heart muscle of tumor-bearing mice and caused systolic dysfunction in vivo. Cardiomyocyte function was significantly depressed during both cellular contraction and relaxation. SIGNIFICANCE: These results suggest that heart muscle is directly affected by tumor growth, with myocardial function more severely compromised at the cellular level than what is observed using echocardiography.

Right ventricular remodeling in restrictive ventricular septal defect.

Restrictive ventricular septal defect (rVSD) presents with little/no hemodynamic aberrations despite a patent septal defect. Clinically, these patients are observed with the hope that the defect will functionally close over time without the need for surgical repair and development of heart failure. Without evidence supporting a definitive therapeutic strategy, rVSD patients may have increased risk of a poor outcome. We tested the hypothesis that rVSD results in subclinical RV diastolic dysfunction and molecular remodeling. Five pigs underwent surgical rVSD creation. Echocardiography, hemodynamics, myocyte contractility experiments, and proteomics/Western blot were performed 6-weeks post-rVSD and in controls. *p<0.05. LV and RV hemodynamics in rVSD were comparable to controls. The tricuspid valve early/late diastolic inflow velocity ratio (TV E/A ratio) decreased from 1.6+/-0.05 in controls to 1.0+/-0.08* in rVSD, indicating RV diastolic dysfunction. rVSD RV myocytes showed abnormalities in contraction (departure velocity (Vd) -51%*, Vd time +55%*) and relaxation (return velocity (Vr) -50%*, Vr time +62%*). Mitochondrial proteins (fatty acid, TCA cycle) increased 2-fold*, indicating heightened RV work. Desmin protein upregulated 285%* in rVSD RV myocardium, suggesting cytoskeletal remodeling. rVSD causes RV diastolic dysfunction, myocyte functional impairment, and mitochondrial/cytoskeletal protein upregulation in our model. Desmin upregulation may hinder sarcomeric organization/relaxation, representing a key subclinical early marker for future RV dysfunction. TV E/A measurements are a non-invasive modality to assess rVSD patients for diastolic dysfunction. Translational research applications may lead to fundamental changes in the clinical management of rVSD by providing evidence for early repair of the defect.