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Sympathetic Nervous System Mediates Cardiac Remodeling After Myocardial Infarction in a Circadian Disruption Model.

ABSTRACT: Background: Circadian rhythms have a considerable impact on the daily physiology of the heart, and their disruption causes pathology. Several studies have revealed that circadian disruption impaired cardiac remodeling after myocardial infarction (MI); however, the underlying brain-heart mechanisms remain unknown. We aim to discuss whether circadian disruption facilitates cardiac remodeling after MI by activating sympathetic nervous system. Methods: Rats were randomly divided into three groups: Sham group (Sham), MI group (MI), and MI+ circadian disruption group (MI+Dis); rats were treated with pseudorabies virus (PRV) injections for trans-synaptic retrograde tracing; rats were randomly divided into two groups: MI+ circadian disruption + Empty Vector+ clozapine N-oxide (CNO) (Empty Vector), and MI+ circadian disruption + hM4D(Gi)+ CNO [hM4D(Gi)]. Results: Circadian disruption significantly facilitated cardiac remodeling after MI with lower systolic function, larger left ventricular volume, and aggravated cardiac fibrosis. Cardiac sympathetic remodeling makers and serum norepinephrine levels were also significantly increased by circadian disruption. PRV virus-labeled neurons were identified in the superior cervical ganglion (SCG), paraventricular nucleus (PVN), and suprachiasmatic nucleus (SCN) regions. Ganglionic blockade via designer receptors exclusively activated by designer drugs (DREADD) technique suppressed the activity of sympathetic nervous system and significantly alleviated the disruption-related cardiac dysfunction. Conclusion: Circadian disruption adversely affected cardiac remodeling after MI possibly by activating sympathetic nervous system, and suppressing sympathetic activity can attenuate this disruption-related cardiac dysfunction.

SUBMITTER: Wang Y

PROVIDER: S-EPMC8032890 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background Ventricular arrhythmia after myocardial infarction is the most important risk factor for sudden cardiac death, which poses a serious threat to human health. As the correlation between autonomic nervous systemic dysfunction and heart rhythm abnormality has been gradually revealed, remedies targeting autonomic nervous system dysfunction, especially the sympathetic nerve, have emerged. Among them, renal denervation is noted for its powerful effect on the inhibition of sympathetic nerve activity. We aim to investigate whether renal denervation can reduce ventricular arrhythmia after myocardial infarction and thus decrease the risk of sudden cardiac death. In addition, we explore the potential mechanism with respect to nerve activity and remodeling. Methods and Results Twenty-four beagles were randomized into the control (n=4), renal denervation (n=10), and sham (n=10) groups. Permanent left anterior descending artery ligation was performed to establish myocardial infarction in the latter 2 groups. Animals in the renal denervation group underwent both surgical and chemical renal denervation. Compared with dogs in the sham group, dogs in the renal denervation group demonstrated attenuated effective refractory period shortening and inhomogeneity, flattened restitution curve, increased ventricular threshold, and decreased ventricular arrhythmia. Heart rate variability assessment, catecholamine measurement, and nerve discharge recordings all indicated that renal denervation could reduce whole-body and local tissue sympathetic tone. Tissue analysis revealed a significant decrease in neural remodeling in both the heart and stellate ganglion. Conclusions Surgical and chemical renal denervation decreased whole-body and local tissue sympathetic activity and reversed neural remodeling in the heart and stellate ganglion. Consequently, renal denervation led to beneficial remodeling of the electrophysiological characteristics in the infarction border zone, translating to a decrease in ventricular arrhythmia after myocardial infarction.

Project description:AimsRetinoic acid receptor-related orphan nuclear receptor ?t (ROR?t) is a transcriptional factor responsible for IL-17-producing T-cell differentiation. Although it was demonstrated that ROR?t plays essential roles in the onset of autoimmune myocarditis, pathophysiological significance of ROR?t in cardiac remodeling after myocardial infarction (MI) remains to be fully elucidated.Methods and resultsMI was generated by ligating coronary artery. The expression of ROR?t and IL-17A transcripts increased in murine hearts after MI. Additionally, immunohistochemical staining revealed that ROR?t-expressing cells infiltrated in the border zone after MI. Flow cytometric analysis showed that ROR?t-expressing cells were released from the spleen at day 1 after MI. Though ROR?t-expressing cells in spleen expressed ??TCR or CD4, ??TCR+ cells were major population of ROR?t-expressing cells that infiltrated into post-infarct myocardium. To address the biological functions of ROR?t-expressing cells in infarcted hearts, we used mice with enhanced GFP gene heterozygously knocked-in at ROR?t locus (ROR?t+/- mice), which physiologically showed reduced expression of ROR?t mRNA in thymus. Kaplan-Meier analysis showed that MI-induced mortality was higher in ROR?t+/- mice than wild-type (WT) mice. Masson's trichrome staining demonstrated that cardiac injury was exacerbated in ROR?t+/- mice 7 days after MI (Injured area: ROR?t+/-; 42.1±6.5%, WT; 34.0±3.7%, circumference of injured myocardium: ROR?t+/-; 61.8±4.8%, WT; 49.6±5.1%), accompanied by exacerbation of cardiac function (fractional shortening: ROR?t+/-; 32.9±2.9%, WT; 38.3±3.6%). Moreover, immunohistochemical analyses revealed that capillary density in border zone was significantly reduced in ROR?t+/- mice after MI, compared with WT mice, associated with the reduced expression of angiopoietin 2. Finally, the mRNA expression of ROR?t, IL-17A, IL-17F and IL-23 receptor (IL-23R) mRNA and protein expression of IL-10 were decreased in ROR?t+/- hearts.ConclusionsHeterozygous deletion of ROR?t gene resulted in aggravated cardiac remodeling, accompanied by reduced capillary density, after MI, suggesting that ROR?t-expressing cells contribute to tissue repair in infarcted myocardium.

Project description:BackgroundInformation on the role of intermittent fasting (IF) on pathologic cardiac remodeling is scarce. We compared the effects of IF before and after myocardial infarction (MI) on rat cardiac remodeling and survival.MethodsWistar rats were intermittently fasted (food available every other day) or fed ad libitum for 12 weeks and then divided into three groups: AL - fed ad libitum; AL/IF - fed AL before MI and IF after MI; and IF - fed IF before and after MI. Echocardiogram was performed before MI and 2 and 12 weeks after surgery. Isolated hearts were evaluated in Langendorff preparations.ResultsBefore surgery, body weight (BW) was lower in IF than AL. Final BW was lower in AL/IF and IF than AL. Perioperative mortality did not change between AL (31.3%) and IF (27.3%). Total mortality was lower in IF than AL. Before surgery, echocardiographic parameters did not differ between groups. Two weeks after surgery, MI size did not differ between groups. Twelve weeks after MI, left ventricular (LV) diastolic posterior wall thickness was lower in AL/IF and IF than AL. The percentage of variation of echocardiographic parameters between twelve and two weeks showed that MI size decreased in all groups and the reduction was higher in IF than AL/IF. In Langendorff preparations, LV volume at zero end-diastolic pressure (V0; AL: 0.41 ± 0.05; AL/IF: 0.34 ± 0.06; IF: 0.28 ± 0.05 mL) and at 25 mmHg end-diastolic pressure (V25; AL: 0.61 ± 0.05; AL/IF: 0.54 ± 0.07; IF: 0.44 ± 0.06 mL) was lower in AL/IF and IF than AL and V25 was lower in IF than AL/IF. V0/BW ratio was lower in IF than AL and LV weight/V0 ratio was higher in IF than AL. Myocyte diameter was lower in AL/IF and IF than AL (AL: 17.3 ± 1.70; AL/IF: 15.1 ± 2.21; IF: 13.4 ± 1.49 μm). Myocardial hydroxyproline concentration and gene expression of ANP, Serca 2a, and α- and β-myosin heavy chain did not differ between groups.ConclusionIntermittent fasting initiated before or after MI reduces myocyte hypertrophy and LV dilation. Myocardial fibrosis and fetal gene expression are not modulated by feeding regimens. Benefit is more evident when intermittent fasting is initiated before rather than after MI.

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Sympathetic Nervous System Mediates Cardiac Remodeling After Myocardial Infarction in a Circadian Disruption Model.

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