Validation of reference gene stability for miRNA quantification by reverse transcription quantitative PCR in the peripheral blood of patients with COVID-19 critical illness

The COVID-19 pandemic has created an urgency to study the host gene response that leads to variable clinical presentations of the disease, particularly the critical illness response. miRNAs have been implicated in the mechanism of host immune dysregulation and thus hold potential as biomarkers and/or therapeutic agents with clinical application. Hence, further analyses of their altered expression in COVID-19 is warranted. An important basis for this is identifying appropriate reference genes for high quality expression analysis studies. In the current report, NanoString technology was used to study the expression of 798 miRNAs in the peripheral blood of 24 critically ill patients, 12 had COVID-19 and 12 were COVID-19 negative. A list of potentially stable candidate reference genes was generated that included ten miRNAs. The top six were analyzed using reverse transcription quantitative polymerase chain reaction (RT-qPCR) in a total of 41 patients so as to apply standard computational algorithms for validating reference genes, namely geNorm, NormFinder, BestKeeper and RefFinder. There was general agreement among all four algorithms in the ranking of four stable miRNAs: miR-186-5p, miR-148b-3p, miR-194-5p and miR-448. A detailed analysis of their output rankings led to the conclusion that miR-186-5p and miR-148b-3p are appropriate reference genes for miRNA expression studies using PaxGene tubes in the peripheral blood of patients critically ill with COVID-19 disease.

S100B interaction with the receptor for advanced glycation end products (RAGE): a novel receptor-mediated mechanism for myocyte apoptosis postinfarction

RATIONALE

Post-myocardial infarction ventricular remodeling is associated with the expression of a variety of factors including S100B that can potentially modulate myocyte apoptosis.

OBJECTIVE

This study was undertaken to investigate the expression and function of S100B and its receptor, the receptor for advanced glycation end products (RAGE) in both postinfarction myocardium and in a rat neonatal myocyte culture model.

METHODS AND RESULTS

In a rat model of myocardial infarction following coronary artery ligation, we demonstrate in periinfarct myocytes, upregulation of RAGE, induction of S100B, and release into plasma with consequent myocyte apoptosis. Using a coimmunoprecipitation strategy, we demonstrate a direct interaction between S100B and RAGE. In rat neonatal cardiac myocyte cultures, S100B at concentrations > or = 50 nmol/L induced myocyte apoptosis, as evidenced by increased terminal DNA fragmentation, TUNEL, cytochrome c release from mitochondria to cytoplasm, phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and p53, increased expression and activity of proapoptotic caspase-3, and decreased expression of antiapoptotic Bcl-2. Transfection of a full-length cDNA of RAGE or a dominant-negative mutant of RAGE resulted in increased or attenuated S100B-induced myocyte apoptosis, respectively. Inhibition of ERK1/2 by U0126/PD-98059 or overexpression of a dominant negative p53 comparably inhibited S100B-induced myocyte apoptosis.

CONCLUSIONS

These results suggest that interaction of RAGE and its ligand S100B after myocardial infarction may play a role in myocyte apoptosis by activating ERK1/2 and p53 signaling. This receptor-mediated mechanism is uniquely amenable to therapeutic intervention.

Effects of the vasopeptidase inhibitor omapatrilat on peri- and postmyocardial infarction in Zucker lean rats

BACKGROUND

The vasopeptidase inhibitor omapatrilat improves insulin sensitivity and survival following myocardial infarction (MI). It also improves left ventricular (LV) remodelling following MI and reduces MI size.

OBJECTIVES

To determine whether improvement in LV remodelling and function is accompanied by a reduction in fetal gene expression of the contractile apparatus, and whether reduction in MI size is accompanied by an increase in the expression of the glucose transporter GLUT-4.

METHODS

Eighty-nine rats were pretreated for seven days with omapatrilat 20 mg/kg/day and 91 rats were left untreated. MI was induced in 180 Zucker lean male rats by ligating the left anterior descending coronary artery, and omapatrilat was given for another 38 days in the survivors. After 30 days, echocardiography was performed. At 38 days, hemodynamic measurements were performed, the rats were sacrificed and morphological measurements were done. Using quantitative reverse transcriptase-polymerase chain reaction, gene expression was measured in the LV using transcript levels.

RESULTS

Treatment with omapatrilat resulted in improved early (24 h) and late (38 days) survival following MI (50% to 67%, P=0.023, and 44% to 59%, P=0.045, respectively). Omapatrilat treatment reduced MI size and resulted in beneficial ventricular remodelling as reflected by a reduction in cardiac dimensions by echocardiography, and LV and right ventricular hypertrophy, which resulted in borderline hemodynamic improvement. A large MI resulted in an increased expression of beta-myosin heavy chain, alpha-skeletal actin and atrial natriuretic peptide, and a decreased expression of GLUT-4. Omapatrilat treatment did not modify the expression of these genes.

CONCLUSIONS

The results suggest that the vasopeptidase inhibitor omapatrilat does not modify fetal gene expression of the contractile apparatus or the expression of GLUT-4 despite reducing cardiac hypertrophy and MI size.

S100A6 is a negative regulator of the induction of cardiac genes by trophic stimuli in cultured rat myocytes

S100A6 (calcyclin), a member of the S100 family of EF-hand Ca2+ binding proteins, has been implicated in the regulation of cell growth and proliferation. We have previously shown that S100B, another member of the S100 family, is induced postinfarction and limits the hypertrophic response of surviving cardiac myocytes. We presently report that S100A6 expression is also increased in the periinfarct zone of rat heart postinfarction and in cultured neonatal rat myocytes by treatment with several trophic agents, including platelet-derived growth factor (PDGF), the alpha1-adrenergic agonist phenylephrine (PE), and angiotensin II (AII). Cotransfection of S100A6 in cultured neonatal rat cardiac myocytes inhibits induction of the cardiac fetal gene promoters skeletal alpha-actin (skACT) and beta-myosin heavy chain (beta-MHC) by PDGF, PE, AII, and the prostaglandin F2alpha (PGF2alpha), induction of the S100B promoter by PE, and induction of the alpha-MHC promoter by triiodothyronine (T3). By contrast, S100B cotransfection selectively inhibited only PE induction of skACT and beta-MHC promoters. Fluorescence microscopy demonstrated overlapping intracellular distribution of S100B and S100A6 in transfected myocytes and in postinfarct myocardium but heterodimerization of the two proteins could not be detected by co-immunoprecipitation. We conclude that S100A6 may function as a global negative modulator of differentiated cardiac gene expression comparable to its putative role in cell cycle progression of dividing cells.

Inhibition of norepinephrine-induced cardiac hypertrophy in s100beta transgenic mice

We have recently reported that the Ca2+-binding protein S100beta was induced in rat heart after infarction and forced expression of S100beta in neonatal rat cardiac myocyte cultures inhibited alpha1-adrenergic induction of beta myosin heavy chain (MHC) and skeletal alpha-actin (skACT). We now extend this work by showing that S100beta is induced in hearts of human subjects after myocardial infarction. Furthermore, to determine whether overexpression of S100beta was sufficient to inhibit in vivo hypertrophy, transgenic mice containing multiple copies of the human gene under the control of its own promoter, and CD1 control mice were treated with norepinephrine (NE) (1.5 mg/kg) or vehicle, intraperitoneally twice daily for 15 d. In CD1, NE produced an increase in left ventricular/body weight ratio, ventricular wall thickness, induction of skACT, atrial natriuretic factor, betaMHC, and downregulation of alphaMHC. In transgenic mice, NE induced S100beta transgene mRNA and protein, but provoked neither hypertrophy nor regulated cardiac-specific gene expression. NE induced hypertrophy in cultured CD1 but not S100beta transgenic myocytes, confirming that the effects of S100beta on cardiac mass reflected myocyte-specific responses. These transgenic studies complement in vitro data and support the hypothesis that S100beta acts as an intrinsic negative regulator of the myocardial hypertrophic response.

Induction of S100b in myocardium: an intrinsic inhibitor of cardiac hypertrophy

Cardiac hypertrophy induced by pressure overload and following myocardial infarction entails regulation of myocardial gene expression, recapitulating an embryonic phenotype, including activation of fetal beta-myosin heavy chain and skeletal alpha-actin. Progressive hypertrophy and alterations in gene expression may contribute to myocardial failure. Although signaling pathways that contribute to hypertrophy development have been identified, intrinsic cardiac regulators that limit hypertrophic response have not been determined. The beta subunit of S100 protein is induced in the myocardium of human subjects and an experimental rat model following myocardial infarction. Forced S100 beta expression in neonatal rat cardiac myocyte cultures and high level expression of S100 beta in transgenic mice hearts inhibit cardiac hypertrophy and the associated phenotype by modulating protein kinase C-dependent pathways. S100 beta expression is probably a component of the myocyte response to trophic stimulation that serves as a negative feedback mechanism to limit cellular growth and the associated alterations in gene expression.

The role of action potential prolongation and altered intracellular calcium handling in the pathogenesis of heart failure

Action potential prolongation is a common finding in human heart failure and in animal models of cardiac hypertrophy. The mechanism of action potential prolongation involves altered expression of a variety of depolarising and hyperpolarising currents in the myocardium. In particular, decreased density of the transient outward potassium current seems to play a prominent role, regardless of species, precipitating factors or the severity of hypertrophy. The decreased density of the transient outward current appears to be caused by reduced transcription of Kv4.2 and Kv4.3 and may be caused in part by an inhibitory effect of alpha-adrenoceptor stimulation. During the early stage of the disease process, action potential prolongation may increase the amplitude of the intracellular calcium transient, causing positive inotropy. We argue therefore, that action prolongation may be a compensatory response which may acutely support the compromised cardiac output. In severe hypertrophy and end-stage heart failure however, despite continued action potential prolongation, the amplitude of the calcium transient becomes severely reduced. The mechanism underlying this event appears to involve reduced expression of calcium handling proteins, and these late events may herald the onset of failure. At present the events leading to the late changes in calcium handling are poorly understood. However, chronic activation of compensatory mechanisms including action potential prolongation may trigger these late events. In the present article we outline a hypothesis which describes a potential role for action potential prolongation, and the associated elevation in the levels of intracellular calcium, in maladaptive gene expression and the progression toward cardiac failure.

S100beta inhibits alpha1-adrenergic induction of the hypertrophic phenotype in cardiac myocytes

In an experimental rat model of myocardial infarction, surviving cardiac myocytes undergo hypertrophy in response to trophic effectors. This response involves gene reprogramming manifested by the re-expression of fetal genes, such as the previously reported isoform switch from adult alpha- to embryonic beta-myosin heavy chain. We now report the transient re-expression of a second fetal gene, skeletal alpha-actin in rat myocardium at 7 days post-infarction, and its subsequent down-regulation coincident with the delayed induction of S100beta, a protein normally expressed in brain. In cultured neonatal rat cardiac myocytes, co-transfection with an S100beta-expression vector inhibits a pathway associated with hypertrophy, namely, alpha1-adrenergic induction of beta-myosin heavy chain and skeletal alpha-actin promoters mediated by beta-protein kinase C. The induction of beta-myosin heavy chain by hypoxia was similarly blocked by forced expression of S100beta. Our results suggest that S100beta may be an intrinsic negative regulator of the hypertrophic response of surviving cardiac myocytes post-infarction. Such negative regulators may be important in limiting the adverse consequences of unchecked hypertrophy leading to ventricular remodeling and dysfunction.

Reduced glutathione modulates the arachidonic acid induced coronary reactions

Coronary flow was recorded from spontaneously beating isolated perfused hearts of rats and guinea pigs. Arachidonic acid (AA), in single bolus doses, produced a fast short lasting coronary constriction followed by a slow developing but persisting vasodilation. These reactions (biphasic type) were characteristic of the guinea pig heart. In about 50% of the rat hearts the vasoconstrictor action predominated while the biphasic response was obtained in the rest of the experiments. Pretreatment of rats with aspirin prevented the responses to AA in the isolated heart. The administration of reduced glutathione (GSH) (about 1 mM to the rat or 0.5-0.75 mM to the guinea pig hearts) produced a marked development and (or) enhancement of the vasodilator action of AA. Repeated or single large doses of AA produced a change of pattern of responses from biphasic to constrictor type; the addition of GSH restored the vasodilator phase. Since GSH directs the endoperoxide metabolism towards the synthesis of prostaglandin E2 (PGE2), we postulate that the coronary dilatation of resistance vessels produced by AA would be due to a great extent to PGE2.