Integrative analysis of differentially expressed genes and miRNAs predicts complex T3-mediated protective circuits in a rat model of cardiac ischemia reperfusion

Abstract

Thyroid hormone (T3) dyshomeostasis in the cardiac ischemia-reperfusion (IR) setting negatively impacts on mitochondria function and extracellular matrix remodeling. The modulation of cardiac miRNAs may represent the underlying molecular mechanisms, but a systems biology perspective investigating this critical issue in depth is still lacking. A rat model of myocardial IR, with or without an early short-term T3-replacement, was used to predict putative T3-dependent miRNA-gene interactions targeted to mitochondria quality control and wound healing repair. As evidenced by mRNA and miRNA expression profiling, the T3 supplementation reverted the expression of 87 genes and 11 miRNAs that were dysregulated in the untreated group. In silico crossing and functional analysis of the T3-associated differentially expressed transcripts, identified a signature of interconnected miRNA-gene regulatory circuits that confer resistance to noxious cascades of acute stress. In this network the T3-down-regulated Tp53, Jun and Sp1 transcription factors emerge as critical nodes linking intrinsic cell death and oxidative stress pathways to adverse remodeling cascades. The data presented here provide a novel insight into the molecular basis of T3 cardioprotection in the early post-IR phase and highlight the contribution of a previously unappreciated complex T3-regulatory network that may be helpful in translating T3 replacement into clinical practice.

T3 Critically Affects the Mhrt/Brg1 Axis to Regulate the Cardiac MHC Switch: Role of an Epigenetic Cross-Talk

“…The experimental design included an in vivo exploratory investigation on established rat models of hyperthyroidism and acute myocardial ischemia and reperfusion (IR), followed by an in vitro validation study on neonatal rat cardiomyocytes (NRCM). The left ventricle samples used in the in vivo study were collected during previous works [ 16 , 17 , 18 ]. NRCM were obtained from rat pups as described below.…”

“…At the end of the experimental procedure, the left ventricle was immediately frozen. Myocardial ischemia/reperfusion (IR) was induced in 2–3-month-old Wistar rats by 30 min ischemia followed by unrestrained reperfusion for 3 d or 14 d. Following IR after 24 h, rats showing a low T3 state were randomly allocated to receive 48 h infusion of saline (IR group) or T3 at the replacement dose of 3 μg/kg/die (IRT3 group) [ 17 , 18 ]. The choice of infusing T3 instead of T4 was dictated by the notion that under condition of low T3 syndrome the tissue local modulation of the activity of different isoforms of deiodinases seems to favor the conversion of T4 into rT3 (metabolically inactive form) rather than T3 (metabolically active form) [ 19 ].…”

“…miRNA target prediction was performed by using the online miRWalk2.0 tool ( ). To find putative miRNA binding sites within the Brg1 complete sequence, previously reported T3-regulated miRNAs were used as input [ 17 ] and the search was restricted to miRNAs that were predicted to target both human and rat Brg1 with a binding score > 85% (see Table S3 ).…”

The current debate over treatment of subclinical hypothyroidism to prevent cardiovascular complications

“…In this regard, the thyroid hormones play a significant role in regulating multiple components of the MQC by improving mitochondrial biogenetics and maintaining cell function. In this regard, recent studies have indicated that T3 is involved in the mitochondrial biogenesis and protein import and provides protection in ischemic heart disease 38,39 . In the model of ischemia reperfusion (IR), low T3 impacts negatively on the mitochondrial function and also has a negative effect on the extracellular matrix remodelling 38,39 .…”

“…In this regard, recent studies have indicated that T3 is involved in the mitochondrial biogenesis and protein import and provides protection in ischemic heart disease 38,39 . In the model of ischemia reperfusion (IR), low T3 impacts negatively on the mitochondrial function and also has a negative effect on the extracellular matrix remodelling 38,39 . With respect to HF in patients with SCH, studies have shown that the myocardium is very sensitive to thyroid hormones and any disturbance in the circulating hormone levels can lead to HF secondary to decreased cardiac output from the systolic and diastolic myocardial dysfunction 40 .…”