Heterozygous bone morphogenetic protein receptor-II-knockout (BMPR2(+/-)) mice have a similar genetic trait like that in some idiopathic pulmonary arterial hypertension patients. To examine the effect of pulmonary endothelial injury in BMPR2(+/-) mice, we challenged the mice with two injections of monocrotaline combined with intratracheal instillation of replication-deficient adenovirus expressing 5-lipoxygenase (MCT+Ad5LO). After the challenge (1 wk), BMPR2(+/-) mice exhibited a doubling of right ventricular systolic pressure that was greater than that of wild-type mice and remained elevated for 3 wk before heart failure developed. Muscularization and thickening of small pulmonary arterioles was evident in the BMPR2(+/-) lungs at 2 wk after the challenge and became severe at 3 wk. Marked perivascular infiltration of T cells, B cells, and macrophages was associated with the remodeled vessels. Real-time PCR analysis showed that the expression of six endothelial cell markers in lung tissue was decreased to 20-40% of original levels at 1 wk after the challenge in both BMPR2(+/-) and wild-type mice and largely recovered in wild-type (50-80%) but not BMPR2(+/-) lungs (30-50%) at 3 wk after the challenge. Macrophage inflammatory protein-1alpha and fractalkine receptor expression doubled in BMPR2(+/-) compared with wild-type lungs. Expression of type I and type II BMP receptors, but not transforming growth factor-beta receptors, in the challenged BMPR2(+/-) and wild-type lungs showed a similar pattern of expression as that of endothelial markers. Apoptotic responses at 1 wk after MCT and Ad5LO challenge were also significantly greater in the BMPR2(+/-) lungs than the wild-type lungs. These data show that BMPR2(+/-) mice are more sensitive to MCT+Ad5LO-induced pulmonary hypertension than wild-type mice. Greater endothelial injury and an enhanced inflammatory response could be the underlying causes of the sensitivity and may work in concert with BMPR2 heterozygosity to promote the development of persistent pulmonary hypertension.
Purpose: We investigated the effects of chronic exposure to electronic cigarettes (e-cig) on myocardial infarct size and the size of the no-reflow zone in a rat model of both sexes. Methods and Results: Sprague Dawley rats (6 weeks old) were randomized to 4 exposure groups: (1) Purified air (n=16 male/16 female); (2) e-cig vapor with 15mg/mL nicotine (n=13 male/15 female); (3) e-cig vapor without nicotine (n=16 male/12 female); and (4) Standard nicotine-containing combustion cigarette smoke (n=16 male/16 female). All rats were exposed to inhalation exposure for 8 weeks, prior to being subjected to 30 minutes of left coronary artery occlusion followed by 3 hours of reperfusion. Two-way analysis of variance (that factors sex and treatment) demonstrated that chronic exposure to e-cig vapor (with or without nicotine) or to standard cigarettes did not alter myocardial infarct or no-reflow size compared to air. However, as shown in the figure, infarct size was significantly smaller (40.7 ± 2.7% vs 54.5 ± 2.6%; p=0.0004) and no-reflow size was smaller (18.1 ± 2.0% vs 26.8 ± 2.2%; p=0.0042) in female rats compared to male rats. Conclusions: Long-term e-cig exposure did not affect the cardiac sensitivity to ischemia/reperfusion injury in young rats. Female rats are more tolerance to ischemia/reperfusion injury than males. This sex difference phenomena was not observed in our previous study [Li et al. J Thromb Thrombolysis. 1995;2(3):221-225.] that examined the tolerance between males and females subjected to 90 mins of left coronary artery occlusion followed by 4 hours of reperfusion in 1-year-old SD rats and found the myocardial infarct size to be similar between the sexes. The different findings between the 2 studies may be due to the age difference (which implies possible hormonal effects in the younger rats) or different coronary artery occlusion and reperfusion times.
Background— Ischemic cardiomyopathy is the major cause of heart failure and a significant cause of morbidity and mortality. The degree of left ventricular dysfunction in this setting is often out of proportion to the amount of overtly infarcted tissue, and how decreased delivery of oxygen and nutrients leads to impaired contractility remains incompletely understood. The Prolyl Hydroxylase Domain-Containing Protein (PHD) prolyl hydroxylases are oxygen-sensitive enzymes that transduce changes in oxygen availability into changes in the stability of the hypoxia-inducible factor transcription factor, a master regulator of genes that promote survival in a low-oxygen environment. Methods and Results— We found that cardiac-specific PHD inactivation causes ultrastructural, histological, and functional changes reminiscent of ischemic cardiomyopathy over time. Moreover, long-term expression of a stabilized hypoxia-inducible factor α variant in cardiomyocytes also led to dilated cardiomyopathy. Conclusion— Sustained loss of PHD activity and subsequent hypoxia-inducible factor activation, as would occur in the setting of chronic ischemia, are sufficient to account for many of the changes in the hearts of individuals with chronic coronary artery disease.
We tested the hypothesis that therapeutic hypothermia (TH) improves survival and blunts inflammation in rats undergoing experimental hemorrhagic shock. Rats were randomized to TH (n = 16) or normothermia (n = 15). Hemorrhagic shock was induced by withdrawing blood to a fixed mean blood pressure (MBP) of 30 mmHg for 30 minutes followed by reinfusion of shed blood for the next 30 minutes. TH (target 32°C) was started at 5 minutes after MBP reached 30 mmHg and was maintained throughout blood volume resuscitation. In the normothermic control group, body temperature was maintained at 37°C during the procedure. Rats were allowed to recover for 6 weeks. TH significantly improved survival: 4 of 15 (26.7%) rats in the normothermic group and 11 of 16 (68.8%; p = 0.032) rats in the TH group survived 6 weeks. Recovery of MBP during the resuscitation phase was significantly improved and left ventricular fractional shortening was markedly increased in the TH group compared with the normothermic group. Brain infarction was observed in 3 of 4 surviving rats (75%) in normothermic group, and in only 1 of the 11 surviving rats (9%) in TH group. The neutrophil-to-lymphocyte ratio was lower in TH group (0.20 ± 0.02) compared with the normothermic group (0.32 ± 0.03; p = 0.003). TH influenced the levels of blood gases and blood counts, favoring hypothermia over control. TH significantly improved long-term survival and blunted the inflammatory response in experimental hemorrhagic shock.
Abstract The effect of electronic cigarette (E-cig) vaping on cardiac and vascular function during the healing phase of myocardial infarction (MI), and post-MI remodeling was investigated. Sprague Dawley rats were subjected to left coronary artery ligation to induce MI. One week later, rats were randomized to receive either 12 weeks of exposure to purified air ( n = 37) or E-cig vapor (15 mg/ml of nicotine) ( n = 32). At 12 weeks, cardiac and vascular function, and post-MI remodeling were assessed. Baseline blood flow in the femoral artery did not differ between groups, but peak reperfusion blood flow was blunted in the E-cig group (1.59 ± 0.15 ml/min) vs. the air group (2.11 ± 0.18 ml/min; p = 0.034). Femoral artery diameter after reperfusion was narrower in the E-cig group (0.54 ± 0.02 mm) compared to the air group (0.60 ± 0.02 mm; p = 0.023). Postmortem left ventricular (LV) volumes were similar in the E-cig (0.69 ± 0.04 ml) and air groups (0.73 ± 0.04 ml; p = NS); and myocardial infarct expansion index did not differ between groups (1.4 ± 0.1 in E-cig group versus 1.3 ± 0.1 in air group; p = NS). LV fractional shortening by echo did not differ between groups at 12 weeks (E-cig at 29 ± 2% and air at 27 ± 1%; p = NS). Exposure to E-cig during the healing phase of MI was associated with altered vascular function with reduced femoral artery blood flow and diameter at reperfusion, but not with worsened LV dilation or worsened cardiac function.
Bendavia (Ben), a mitochondria‐targeting peptide, protects mitochondrial function by enhancing bioenergetics under conditions of oxidative stress, thus inhibiting ROS formation. We hypothesized that Ben therapy would benefit post‐myocardial infarction (MI) cardiac function and remodeling in rats. At 2 hours after left coronary ligation, rats were randomized to receive Ben that was delivered subcutaneously by an Alzet Osmotic Pump (3 mg/kg/day, n=28) or water (n=26). Six weeks later, scar circumference assessed by histology and expressed as percentage of total left ventricular (LV) circumference, was significantly smaller in the Ben group (39.7 ± 2.2 %) versus the water group (47.4 ± 2.5 %, p=0.024). Post‐mortem LV volume was 9.6% smaller in the Ben group (p=0.019). LV fractional shortening by echo was significantly greater in the Ben group (28.8 ± 1.7 %) than in the water group (23.8 ± 1.8 %, p=0.047). LV stroke volume was greater in the Ben group (0.257 ± 0.008 ml) versus the water group (0.231 ± 0.008 ml, p=0.029), and LV ejection fraction assessed by LV ventriculography was greater with Ben (55.3 ± 1.4%) versus water (49.3 ± 1.4%, p=0.005). Ben treatment reversed the down‐regulated expression of mitochondrial energy metabolism‐related genes at the noninfarcted infarct border assessed by PCR array. Chronic Ben therapy improved post‐MI cardiac function, prevented stretching of the scar and adverse remodeling in rats. Grant Funding Source : Supported by Stealth Peptides, Inc., Newton, Mass.
Background: Our research group recently observed that therapeutic hypothermia (TH) compared with normothermia improved long-term survival in an experimental model of hemorrhagic shock. The effect of TH on blood counts, blood gases and chemistries during the early phase of recovery from hemorrhagic shock are unknown. Therefore, the purpose of the present study was to examine the effects of TH on blood parameters in the early phase of resuscitation from hemorrhagic shock. Methods and results: Sprague Dawley rats (both genders) were randomly assigned to TH (n= 16) or normothermia group (n= 15). Rats were anesthetized with intraperitoneal ketamine and xylazine. After heparinizing, hemorrhagic shock was induced by withdrawing blood to a fixed mean blood pressure (MBP) of 30 mmHg for 30 minutes and then shed blood was reinfused. TH was started 5 minutes after MBP reached 30 mmHg. Core temperature was maintained at ~ 32 °C until blood volume was fully restored, after which the rats were allowed to warm back to normal temperature. In the normothermia group, body temperature was maintained at ~ 37°C. Arterial blood samples were collected 1 hour after resuscitation with shed blood. We found that pO2 (partial pressure of oxygen) was significantly higher in TH group versus the normothermic group. The rats in normothermic group had significantly elevated potassium, chloride and lactate levels and more negative base excess compared to rats that in TH group (Table). The neutrophil was lower in the TH group; the lymphocyte (%) was higher in the TH group. There were no significantly differences in pH, pCO2, sodium, calcium or glucose between the normothermia and TH groups. Conclusions: pO2 remained normal and levels of potassium, chloride, lactate and neutrophil were lower in TH group. These results may contribute to the protective effect of TH during hemorrhagic shock.
Hypothermia is known to protect against ischemia/reperfusion (I/R) injury, however, the mechanisms underlying its cardiac protective effect are poorly understood. A major mechanism of I/R injury is the inflammatory response. We therefore hypothesized that therapeutic hypothermia reduces the inflammatory response following I/R injury in rat hearts. Rats were randomized to normothermic or hypothermia groups and subjected to 1 hour coronary artery occlusion and 48 hours reperfusion. Hypothermia was initiated 2 minutes after the onset of coronary artery occlusion to a core temperature of 32°C, and then allowed to rewarm. After 48 hours, blue dye was injected to separate the risk zone and non-risk zone. Heart samples were collected from shams, Risk/normothermia, Risk/hypothermia, Non-risk/normothermia and Non-risk/hypothermia. qRT-PCR analysis showed that MCP1, IL6, TGFb1 and TNFa gene expression were significantly increased by 90.87 fold, p<0.0001, 177.58 fold, p<0.0001, 17.57 fold, p<0.0001 and 7.34 fold, p<0.0001, respectively, in the Risk/normothermia vs sham. Hypothermia significantly decreased the gene expression of MCP1 (p=0.01) and showed a trend of lowering IL6 (p=0.052), TGFb1 and TNFa (p=0.09) expression levels (Figure). We conclude that hypothermia decreases inflammation gene expression, which may have contributed to the preservation of cardiac structure and function. qRT-PCR analysis for MCP1, TGFβ1, TNFα and 116 (n=6 in each group). All data were normalized to β-actin and presented relative to the sham group. *p<0.05 vs. sham # p<0.05 vs. Risk/normothermia. qRT-PCR analysis for MCP1, TGFβ1, TNFα and 116 (n=6 in each group). All data were normalized to β-actin and presented relative to the sham group. *p<0.05 vs. sham # p<0.05 vs. Risk/normothermia.
