Exercise preconditioning prevents left ventricular dysfunction and remodeling in monocrotaline-induced pulmonary hypertension

Acute sleep deprivation (ASD) and cardioprotection: Impact of ASD on oxytocin-mediated sympathetic nervous activation preceding myocardial infarction

INTRODUCTION

This study explored how acute sleep deprivation (ASD) before myocardial ischemia influences oxytocin release from paraventricular (PVN) neurons and its correlation with sympathetic nervous system (SNS) activity post-acute sleep loss, impacting subsequent left ventricular (LV) remodeling following myocardial infarction (MI).

METHODS

The study was conducted in two phases: induction of ASD, inducing MI, blood sampling, euthanizing animals and collecting their heart and brain for histological and gene expression evaluations. The animals in first and second phase were euthanized 24 h and 14 days after MI, respectively.

RESULTS

Pre-MI ASD, accompanied by increased serum epinephrine levels within 24 h of MI, upregulated oxytocin and cFos expression in the PVN. Also, pre-MI ASD resulted in decreased serum PAB levels 14 days post-MI (P < 0.001). While notable echocardiographic changes were seen in MI versus sham groups, ASD demonstrated protective effects. This was evidenced by reduced infarct size, elevated TIMP1, MMP2, and MMP9 in the LV of SD + MI animals versus MI alone (P < 0.05). Additionally, histological analysis showed reduced LV fibrosis in pre-MI ASD subjects (P < 0.05).

CONCLUSION

Our study supports the notion that activation of oxytocin neurons within the PVN subsequent to ASD interacts with autonomic centers in the central nervous system. This enhanced sympathetic outflow to the heart prior to MI triggers a preconditioning response, thereby mediating cardioprotection through decreased oxidative stress biomarkers and regulated extracellular matrix (ECM) turnover.

Combined physical training protects the left ventricle from structural and functional damages in experimental pulmonary arterial hypertension

BACKGROUND

Under the adverse remodeling of the right ventricle and interventricular septum in pulmonary arterial hypertension (PAH) the left ventricle (LV) dynamics is impaired. Despite the benefits of combined aerobic and resistance physical trainings to individuals with PAH, its impact on the LV is not fully understood.

OBJECTIVE

To test whether moderate-intensity combined physical training performed during the development of PAH induced by MCT in rats is beneficial to the LV's structure and function.

METHODS

Male Wistar rats were divided into two groups: Sedentary Hypertensive Survival (SHS, n = 7); and Exercise Hypertensive Survival (EHS, n = 7) to test survival. To investigate the effects of combined physical training, another group of rats were divided into three groups: Sedentary Control (SC, n = 7); Sedentary Hypertensive (SH, n = 7); and Exercise Hypertensive (EH, n = 7). PAH was induced through an intraperitoneal injection of MCT (60 mg/kg). Echocardiographic evaluations were conducted on the 22nd day after MCT administration. Animals in the EHS and EH groups participated in a combined physical training program, alternating aerobic (treadmill running: 50 min, 60% maximum running speed) and resistance (ladder climbing: 15 climbs with 1 min interval, 60% maximum carrying load) exercises, one session/day, 5 days/week for approximately 4 weeks.

RESULTS

The physical training increased survival and tolerance to aerobic (i.e., maximum running speed) and resistance (i.e., maximum carrying load) exertions and prevented reductions in ejection fraction and fractional shortening. In addition, the physical training mitigated oxidative stress (i.e., CAT, SOD and MDA) and inhibited adverse LV remodeling (i.e., Collagen, extracellular matrix, and cell dimensions). Moreover, the physical training preserved the amplitude and velocity of contraction and hindered the reductions in the amplitude and velocity of the intracellular Ca2+ transient in LV single myocytes.

CONCLUSION

Moderate-intensity combined physical training performed during the development of MCT-induced PAH in rats protects their LV from damages to its structure and function and hence increases their tolerance to physical exertion and prolongs their survival.

Exercise-induced myocardial hypertrophy preconditioning promotes fibroblast senescence and improves myocardial fibrosis through Nrf2 signaling pathway

This study aims to investigate how exercise-induced myocardial hypertrophy preconditioning affects cardiac fibroblasts in the context of myocardial fibrosis, a chronic disease that can cause cardiac arrhythmia and heart failure. Heart failure was induced in male C57BL/6 mice via Transverse aortic constriction, and some mice were given swimming exercise before surgery to test the effects of exercise-induced myocardial hypertrophy preconditioning on myocardial fibrosis. Myocardial tissue was evaluated for fibrosis, senescent cells, and apoptotic cells. Myocardial fibroblasts from rats were cultured and treated with norepinephrine to induce fibrosis which were then treated with si-Nrf2 and analyzed for markers of fibrosis, senescence, apoptosis, and cell proliferation. Exercise-induced myocardial hypertrophy preconditioning reduced myocardial fibrosis in mice, as shown by decreased mRNA expression levels of fibrosis-related indicators and increased cell senescence. In vitro data indicated that norepinephrine (NE) treatment increased fibrosis-related markers and reduced apoptotic and senescent cells, and this effect was reversed by pre-conditioning in PRE+NE group. Preconditioning activated Nrf2 and downstream signaling genes, promoting premature senescence in cardiac fibroblasts and tissues isolated from preconditioned mice. Moreover, Nrf2 knockdown reversed proapoptotic effects, restored cell proliferation, reduced senescence-related protein expression, and increased oxidative stress markers and fibrosis-related genes, indicating Nrf2's crucial role in regulating oxidative stress response of cardiac fibroblasts. Exercise-induced myocardial hypertrophy preconditioning improves myocardial fibrosis which is Nrf2-dependent, indicating the protective effect of hypertrophy preconditioning. These findings may contribute to the development of therapeutic interventions to prevent or treat myocardial fibrosis.

Training programs in preclinical studies. The example of pulmonary hypertension. Systematic review and meta-analysis

Background

Exercise and cardiopulmonary exercise testing are essential in the evaluation of physiological, biochemical, and molecular responses in the experimental studies on chronic diseases such as diabetes, heart failure and hypertension. The exercise tolerance and seem to be a valuable contribution to the experiments that are performed in animal models of pulmonary hypertension (PH), as well. The current survey uses detailed quantitative analyses to assess the advantages of exercise training programs performed in preclinical studies based on outcomes such as exercise capacity, cardiopulmonary hemodynamics, and mortality.

Methods

Articles were identified through search engines in the online electronic databases Pubmed/Medline, Web of Science following the PRISMA Protocol. Studies conducted between 1991 and 2022 without language restrictions were included in this study. Heterogeneity was assessed using the Cochrane Q-test and I2 test statistics. Subgroup analysis was employed with evidence of heterogeneity. Quality assessment was carried out using SYRCLE’s risk of bias tool for animal studies. Publication bias across studies was determined using the funnel plot and Egger’s regression test statistic.

Results

The available protocols typically included treadmill running, swimming, and voluntary wheel running with a different series of intensities, times and durations; these were also used in studies examining the efficacy of chronic training programs. In 66 interventions, PH induction reduced exercise endurance by half compared to healthy subjects, while exposure to tested medical agents normalized exercise capacity. The other 58 interventions demonstrated the advantages of various exercise training programs for PH. Induction of PH reduced exercise endurance by half compared to healthy subjects (R = 0.52; 0.48 − 0.55 95%CI; P<0.0001; I2 = 98.9%), while the exposure to tested medical agents normalized exercise capacity (R = 1.75; 1.61 − 1.91 95%CI; P<0.0001; I2 = 97.8%).

Conclusion

Despite a wide spectrum of study protocols to measure exercise endurance in animals with PH, there is a significant correlation between worsening of exercise-related parameters and PH development, manifested by alterations in haemodynamic and remodeling parameters. Familiarization with exercise, training program schedule, method used for PH induction, or detailed training parameters such as slope, exercise intensity or individualization, can influence the final outcome. This in turn can impact on the diversity and reproducibility of results being obtained in particular experimental studies.

O Treinamento Físico Resistido Atenua as Disfunções Ventriculares Esquerdas em Modelo de Hipertensão Arterial Pulmonar

Fundamento

A hipertrofia e a dilatação do ventrículo direito observadas na hipertensão arterial pulmonar (HAP) prejudicam a dinâmica do ventrículo esquerdo (VE) achatando o septo interventricular.

Objetivo

Investigar se o treinamento físico resistido (TFR) de intensidade baixa a moderada é benéfico para funções contráteis do VE e de cardiomiócitos em ratos durante o desenvolvimento de HAP induzida por monocrotalina (MCT).

Métodos

Foram usados ratos Wistar machos (Peso corporal: ~ 200 g). Para avaliar o tempo até o possível surgimento de insuficiência cardíaca (ou seja, ponto de desfecho), os ratos foram divididos em dois grupos, hipertensão com sedentarismo até a insuficiência (HSI, n=6) e hipertensão com treinamento até a insuficiência (HTI, n=6). Para testar os efeitos do TFR, os ratos foram divididos entre grupos de controle sedentários (CS, n=7), hipertensão com sedentarismo (HS, n=7) e hipertensão com treinamento (HT, n=7). A HAP foi induzida por duas injeções de MCT (20 mg/kg, com um intervalo de 7 dias). Os grupos com treinamento foram submetidos a um protocolo de TFR (subir escadas; 55-65% da máxima carga carregada), 5 dias por semana. A significância estatística foi definida em p <0,05.

Resultados

O TFR prolongou o ponto de desfecho (~25%), melhorou a tolerância ao esforço físico (~55%) e atenuou as disfunções de contratilidade de VE e de cardiomiócitos promovidas pela MCT preservando a fração de ejeção e o encurtamento fracional, a amplitude do encurtamento, e as velocidades de contração e relaxamento nos cardiomiócitos. O TFR também preveniu os aumentos de fibrose e colágeno tipo I no ventrículo esquerdo causados pela MCT, além de manter as dimensões de miócitos e colágeno tipo III reduzidas por MCT.

Conclusão

O TFR de intensidade baixa a moderada é benéfico para funções contráteis de VE e cardiomiócitos em ratos durante o desenvolvimento de HAP induzida por MCT.