Browsing by Author "Chingombe, Tsungai J."

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    Acute Exercise Activates Pulmonary eNOS and Lowers Pulmonary Pressure in Rats with Pulmonary Arterial Hypertension
    (Office of the Vice Chancellor for Research, 2013-04-05) Chingombe, Tsungai J.; Reddy, Jag; Fisher, Amanda; Presson, Robert G.; Lahm, Tim; Petrache, Irina; Brown, Mary Beth
    NO-dependent arterial relaxation is impaired in pulmonary arterial hypertension (PAH). Exercise may be beneficial in PAH, just as it is for systemic vascular disease, via upregulation of endothelial nitric oxide synthase (eNOS) expression and activity. However, exercise-induced cardiac stress in PAH could also promote detrimental RV inflammation. We investigated pulmonary pressure and eNOS, as well inflammatory indicators in the RV, following a single 45 min run bout at moderate intensity in a rat model of PAH. Male Sprague-Dawley rats received either monocrotaline to induce PAH, or saline, for healthy controls. A subset of PAH and healthy controls performed 4 wks of progressive TM familiarization (15-30min, 8-20 m/min) in preparation for their final 45 min run @ 75% of VO2max. Immediately following the run, RV systolic pressure was measured and RV and lung tissues were harvested and cryofixed. eNOS and phosphorylated (at Ser1177) eNOS (p-eNOS) was measured via immunoblotting in lung homogenates and expressed normalized to vinculin. Immunofluorescence for inflammatory markers CD45/68 in cryofixed RV sections evaluated the acute inflammatory response to exercise. MCT reduced VO2max and caused RV hypertrophy (expressed as RV/LV+septum) as consistent with this model. RVSP (normalized by systemic BP) was lower in PAH-Ex vs. unexercised PAH with no difference between exercised and unexercised controls. Greater p-eNOS was measured in PAH-Ex lung compared to unexercised PAH, with no difference between exercised and unexercised controls. PAH-Ex also tended to have greater pulmonary eNOS than their unexercised counterparts. No greater exercise-induced CD45/68 infiltration was observed in RV of PAH compared to that of controls. In rats with moderate MCT-induced PAH, a single exercise bout does not increase acute RV inflammation but lowers pulmonary pressure, possibly mediated in part via pulmonary eNOS activation.
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    The Effect of 17beta Estradiol on Glut1 Expression In The Right Ventricle Of Rats With Severe Pulmonary Hypertension
    (Office of the Vice Chancellor for Research, 2013-04-05) Taylor, Vanessa N.; Lahm, Tim; Cucci, Anthony; Petrache, Irina; Albrecht, Marjorie E.; Brown, Mary Beth; Chingombe, Tsungai J.; Gaidoo, Richard G.
    Pulmonary hypertension (PH) is a devastating disease that is characterized by a rise of blood pressure in the blood vessels of the lung. This puts significant strain on the right ventricle (RV) of the heart. If untreated, PH can lead to right heart failure and death. One of the hallmarks of right heart failure in PH is the development of cytoplasmic glycolysis in the cardiac muscle cells (myocytes) of the RV. This describes a compensatory process where glucose uptake into the mitochondria is inhibited, thereby leading to its conversion to lactate in the cytoplasm. Importantly, cytoplasmic glycolysis is associated with an increase in a protein called glucose transporter 1 (Glut 1). 17beta estradiol (E2) can ameliorate experimental PH, but its effects on RV glut 1 expression are not yet known. The aim of this project is to determine the RV expression of Glut 1 in a rat model of severe PH, and to investigate whether this is decreased by E2 treatment. We assessed Glut 1 via immunofluorescence staining in cryosections of RV tissue from control rats, untreated PH rats, and E2-treated PH rats. Cell nuclei were stained with DAPI (Diamidinophenyl-indole), cell membranes were stained with WGA (wheat germ agglutinin), and Glut1 was stained with a Glut1 antibody conjugated to a red immunofluorescent dye. Nuclei are stained blue; cell membranes are stained green. Glut 1 quantification occurs via visual inspection and determination of red staining via specific software (Metamorph). We were able to successfully establish the protocol for Glut1 staining. In pilot experiments, there was little Glut1 staining present in normal RVs, but we detected up-regulation of Glut 1 in the RV of animals with PH. Whether this is affected by E2 is currently under investigation.
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    Effect of Exercise on Right Ventricle Inflammation in a Rat Model of Severe Monocrotaline-Induced Pulmonary Arterial Hypertension
    (Office of the Vice Chancellor for Research, 2015-04-17) Chingombe, Tsungai J.; Lahm, Tim; Brown, Mary Beth
    Pulmonary arterial hypertension (PAH) is a devastating disease of progressive remodeling of small and mid-size pulmonary arteries that leads to elevated pulmonary pressure. The work of the right heart is increased due to the elevated pulmonary pressures and can lead to maladaptive cardiac wall hypertrophy, right heart failure and then eventually death. Whether exercise-induced cardiac stress also promotes detrimental right ventricle (RV) inflammation in PAH has not been thoroughly examined. The purpose of this study is to determine if treadmill exercise at low relative intensity in a rat model of severe PAH without promoting greater RV inflammation. Adult male Sprague- Dawley rats were injected with monocrotaline (60mg/kg, subcutaneously, n=14) or saline (healthy controls, n=4). RV tissue was obtained from these rats following a 6 week, 5 times/week treadmill training program at a low intensity of 50% of measured aerobic capacity (VO2max) and compared to tissue obtained from sedentary counterparts. RV immunofluorescent staining for CD45, a lymphocyte marker, was performed to evaluate the inflammatory response due to chronic exercise training. The experiment is still underway and the expected result is that there is no greater exercised induced RV inflammation in PAH rats compared to healthy rats.
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    EFFECT OF TREADMILL RUNNING ON CARDIAC AND SKELETAL MUSCLE METABOLISM AND RIGHT VENTRICLE INFLAMMATION IN RATS WITH PULMONARY ARTERIAL HYPERTENSION
    (Office of the Vice Chancellor for Research, 2012-04-13) Chingombe, Tsungai J.; Lahm, Tim; Reddy, Jag; Fisher, Amanda; Petrache, Irina; Brown, Mary Beth
    It has been suggested that a shift from oxidative to non-oxidative (glycolytic) metabolism promotes a right ventricle (RV) and skeletal muscle dysfunction in patients with pulmonary arterial hypertension (PAH), contributing to their reduced exercise tolerance. Exercise training may ameliorate this glycolytic switch in PAH as it does for other cardiopulmonary diseases. However, whether exercise-induced cardiac stress also promotes detrimental RV inflammation in PAH has not yet been thoroughly examined. We hypothesized that exercise training will promote a shift back towards the more efficient oxidative metabolism in cardiac and skeletal muscle of PAH rats and that 45 minutes of exercise at a prescribed moderate intensity will not promote greater RV inflammation in PAH rats. Tissues were obtained from monocrotaline-induced PAH and healthy control rats immediately following a 45 min treadmill run (75% VO2max) that concluded a 4 week treadmill familiarization/running program (15-45 min, 4x/wk). A group of unexercised PAH and healthy rats served as sedentary controls. Immunofluorescent staining (IF) for inflammatory markers CD45 (lymphocytes) and CD68 (macrophages) in cryofixed RV sections were used to assess the acute inflammatory response to exercise. In fixed soleus and RV sections, IF for the glucose transporter Glut1, and for capillary marker CD31, were used as indicators of glycolytic metabolism and tissue capillarization, respectively. Data thus far indicates no greater acute exercise-induced RV inflammation in PAH rats compared to healthy rats. We observed higher expression of Glut1 and lower capillarization in the RV and soleus of PAH rats, indicative of a shift toward greater dependency on non-oxidative metabolism. However, since Glut1 levels for exercised rats were measured in tissue harvested immediately following a run bout, evaluation of a chronic training effect on Glut1 expression is potentially confounded by the acute exercise effect and therefore remains to be investigated in a follow-up study.
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    Exercise Training Improves Cardiac and Skeletal Muscle Metabolism in Rats with Pulmonary Arterial Hypertension
    (Office of the Vice Chancellor for Research, 2013-04-05) Gaidoo, Richard G.; Crist, Jacob; Little, Nathaniel; Chingombe, Tsungai J.; Fisher, Amanda; Presson, Robert G.; Lahm, Tim; Petrache, Irina; Brown, Mary Beth
    In patients with pulmonary arterial hypertension (PAH), a shift from oxidative to glycolytic metabolism promotes right ventricular (RV) and skeletal muscle dysfunction that contributes to reduced exercise tolerance. As seen for other cardiopulmonary diseases, exercise training (ExT) may ameliorate this glycolytic switch in PAH and improve exercise capacity. The purpose of this research is to investigate ExT in a rat model of PAH on markers of glycolytic and oxidative metabolism in RV and skeletal muscle. Male Sprague-Dawley rats received monocrotaline (MCT, 40 mg/kg, s.q.) to induce PAH (n= 13), or saline, for healthy controls (n=5). After 2 wks, with MCT-induced PAH established, 6 wks of treadmill (TM) ExT was initiated for a subset of PAH animals (PAH-ExT, n= 6) and healthy controls (CON-ExT, n=3). ExT runs progressed up to 60 min at mild relative intensity, 50% of maximal aerobic capacity (VO2max). VO2max was assessed at baseline, in pre-training and post-training TM testing via analysis of expired gases. Abundance of Glut-1, a marker of glycolytic metabolism, was evaluated in cryosections of RV and soleus with immunofluorescent (IF) staining and quantification. Data are presented as mean±SE. MCT-ExT rats maintained aerobic capacity over 6 wks better than sedentary counterparts (MCT-SED)(VO2max= -134±109 vs. -521±129 ml/kg/hr, p=0.04) and was not different than CON-ExT (-201±31 ml/kg/hr, p=0.82). A lower abundance of Glut-1 was observed in both RV and soleus myocytes of PAH-ExT rats (MPI= 10.9 ±0.9 for RV; 13.7±0.8 for soleus) compared to PAH-SED rats (15.7±2.4, p=0.05, for RV; 17.4±1.4, p=0.04, for soleus) and was similar to CON-ExT rats (13.0±2.2, p=0.33, for RV; 9.0±2.3, p=0.26, for soleus), indicative of a shift toward greater dependency on oxidative metabolism. Exercise training attenuates functional decline following MCT administration in rats. Preservation of aerobic capacity may be explained by promotion of more efficient RV and skeletal muscle mitochondrial substrate utilization.
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    Investigating Skeletal Muscle Metabolic Adaptations underlying Aerobic Fitness Gains Following High Intensity Interval Training in a Rat Model of Pulmonary Arterial Hypertension
    (Office of the Vice Chancellor for Research, 2015-04-17) Talley, Mary; Novack, Rachel; Chingombe, Tsungai J.; Lahm, Tim; Petrache, Irina; Brown, Mary Beth
    Rationale: In patients with pulmonary arterial hypertension (PAH) a shift from oxidative to a less efficient non-oxidative (glycolytic) metabolism in skeletal muscle is believed to contribute to the reduced exercise tolerance hallmark of the disease. As seen for other cardiopulmonary diseases, exercise training (ExT) may ameliorate this “glycolytic switch” in PAH and improve exercise capacity. Previous studies in this lab showed an improved metabolic profile of skeletal muscle in PAH rats following an ExT protocol of continuous running at moderate relative intensity, 60 minutes at 75% of maximal aerobic capacity (VO2Max). High intensity interval training (HIIT) has been shown in healthy individuals as well as in patients with cardiovascular disease to promote favorable cardiac and skeletal muscle adaptations and greater improvements in aerobic capacity versus customary continuous training. This study tests the hypothesis in a PAH rat model that HIIT will result in preserved aerobic capacity and a greater attenuation of skeletal muscle glycolytic shift than that observed with continuous moderate intensity exercise. Methods: Male Sprague-Dawley rats received either monocrotaline (MCT, 40 mg/kg, s.q.) to induce PAH (n= 8), or saline, for healthy controls (n=4). After 2 wks, with MCT-induced PAH wellestablished, 6 wks of treadmill HIIT was initiated for a subset of PAH animals (PAH-ExT, n= 6) and healthy controls (CON-ExT, n=2). The HIIT runs were alternated between 2 to 3 minutes of high intensity exercise (85% VO2max reserve) and active recovery intervals between 2 to 3 minutes (10 m/min, 0 incline) VO2max was assessed at baseline, and in pre-training and post-training via analysis of expired gases during incremental treadmill running. Preliminary results: MCT-induced decrement in VO2max was attenuated by HIIT. Abundance of membrane glucose transporter Glut-1, a marker of glycolytic metabolism, is currently being evaluated in soleus cryosections with immunofluorescent staining. Findings are being compared to historical data for PAH and healthy rats from a study protocol that differed only by training approach-continuous instead of HIIT.