Epigenetic regulation of miR-181c-5p in a cardiorenal mouse model with co-occurring thrombotic microangiopathy

Background

MiR-181c-5p is described to induce heart failure (HF), while its role in renal pathology and healthy mice is rather undetermined. Renal dysfunction is present in 40–60% of HF patients and associated with high morbidity and mortality rate.

Purpose

This study aims to investigate the role of miR-181c-5p in a new mouse model of metabolic cardiorenal disease (CRD). Our hypothesis states a protective effect of miR-181c-5p inhibition on HF development by regulation of Tgfbr1.

Methods

CRD was induced by feeding male C57BL/6J mice (n=20) a high-fat diet (HFD) and L-NAME in drinking water (5g/L) for 6 weeks, angiotensin-II was co-administered via osmotic minipumps (1000ng/kg/min) during the final 2 weeks. Healthy controls (n=16) were given normal chow and drinking water, and underwent sham-surgery. Mice were randomly assigned to weekly injections (40mg/kg) with miR-181c-5p antagomiR (INH) or scrambled control for the duration of the study. We assessed cardiac function (echocardiography, invasive hemodynamics), renal function (plasma creatinine), target expression (RT-qPCR), and histology.

Results

CRD animals showed mild systolic and diastolic cardiac dysfunction compared to healthy controls characterized by reduced dP/dt min (−4795±1164 vs −7728±1693 mmHg/s; p=0.01) and dP/dt max (6222±1069 vs 8706±1739 mmHg/s; p=0.038), and increased tau (9.88±3.09 vs 6.07±0.73 ms; p=0.02) with preserved ejection fraction (45±21 vs 51±8%; p=0.53). Histology shows cardiac fibrosis (2.5±0.3 vs 1.8±0.2% area; p=0.0004) and hypertrophy (0.11±0.03 vs 0.08±0.01g/cm; p=0.005). Renal dysfunction presents with kidney atrophy (0.07±0.006 vs 0.09±0.01g/cm; p=0.02), increased plasma creatinine (21±6 vs 10±5; p=0.01), renal fibrosis (0.26±0.22 vs 0.005±0.21% area; p=0.036) and glomerular abnormalities (glomerulosclerosis, hyperfiltration, mesangial matrix expansion, reduced podocyte number). CRD+INH animals had comparable cardiac phenotype to CRD (p>0.05), except a significantly reduced cardiac output compared to healthy controls (6±3 vs 18±3 μl/s; p=0.035). Their renal phenotype was exacerbated with elevated glomerular damage (26±3 vs 18±9; p=0.04) and significantly increased mortality rate (50%) (Kaplan-Meier p=0.01) compared to healthy controls (0%) or CRD (20%), associated with increased occurrence of tubular atrophy, endothelial swelling and systemic thrombotic microangiopathy (TMA) that manifested in kidney and the heart. RT-qPCR analysis identified Vegf as potential target of miR-181c-5p in kidney and showed significantly reduced levels of Tgfbr1 in cardiac tissue of CRD+INH mice.

Conclusion

This study demonstrates a detrimental effect of miR-181c-5p inhibition on renal function in a CRD mouse model, driven by glomerular damage and TMA through Vegf signaling. Despite identification of Tgfbr1 as potential target of miR-181c-5p in the heart, cardiac function was rather unaffected.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): University of Antwerp

Abstract P2047: Identification Of Selective Small-molecule ERBB4 Agonists With Cardioprotective Effects

Introduction: Morbidity and mortality of heart failure remain high, mandating new therapeutic approaches. The neuregulin-1 (NRG1)/ERBB4 axis is cardioprotective and an attractive target for treatment. Clinical trials with recombinant NRG1 are ongoing, but require intravenous administration, limiting applicability and efficacy.

Purpose: To develop selective small-molecule ERBB4 agonists with cardioprotective effects.

Methods: A high-throughput screening of 10,240 compounds (cpds) was performed on a ERBB4/ERBB4 dimerization assay. Hit cpds were co-administered with NRG1 or fluorescently labeled NRG1 to determine competitive binding. Selectivity, receptor phosphorylation, toxicity and metabolic stability were determined using Luminex RTK phosphoprotein, ERBB2/ERBB3 dimerization and adenylate kinase assays or LC-MS/MS. Apoptotic and hypertrophic effects of cpds (4-32μM) on cultured cardiomyocytes were studied after exposure to 100μM H 2 O 2 and 100nM angiotensin II (AngII). Antifibrotic effects (4-32μM) were studied on TGF-β-induced collagen synthesis in cultured human fibroblasts, and in mice (n=9-10/group) treated with AngII (1000 ng/kg/min) or cpd (83 μg/kg/h) using osmotic pumps.

Results: We identified 8 similar pyrimidine derivatives inducing ERBB4/ERBB4 dimerization (Emax 9-33% relative to NRG1, EC50 6E-6 to 2E-7M). Competition assays indicated allosteric receptor binding and potentiation of NRG1-induced ERBB4 receptor dimerization, up to 2.7 fold (P<0.0001). Six were non-toxic and induced ERBB4 phosphorylation, but ERBB1, ERBB2 or ERBB3 phosphorylation remained unaffected and cpds did not induce ERBB2/ERBB3 dimerization, showing ERBB4 selectivity. Cpds showed a t1/2 of 170min in human liver microsomes. Cpds attenuated hypertrophic and apoptotic effects of AngII or H 2 O 2 (P<0.05), and decreased collagen upregulation in vitro (P<0.05). In vivo , a selected cpd attenuated AngII-induced myocardial interstitial fibrosis (-76±26%, P<0.01), and cardiac Col1a1, Col3a1 (-64±22%; -71±25%, P<0.01) and Nppa (-77±22%, P<0.01) mRNA expression.

Conclusion: We identified selective novel pyrimidine derivative small-molecule ERBB4 agonists with cardioprotective effects in vitro and in vivo .

Abstract P3094: Mir-181c-5p As Detrimental Player In A Mouse Model Of Cardiorenal Syndrome With Thrombotic Microangiopathy

Background: MiR-181c-5p is described to induce heart failure (HF), while its role in renal pathology is undetermined. Renal dysfunction is present in 40-60% of HF patients and associated with poor prognosis. This study is the first of its kind to investigate the role of miR-181c-5p in a mouse model of cardiorenal disease (CRD). Our hypothesis states a protective effect of miR-181c-5p inhibition on HF development.

Methods: CRD was induced by feeding male C57BL/6J mice (n=20) a high-fat diet (HFD) and L-NAME in drinking water (5g/L) for 6 weeks, angiotensin-II was co-administered via osmotic minipumps (1000ng/kg/min) during the final 2 weeks. Healthy controls (n=16) underwent sham-surgery. Mice were randomly assigned to weekly injections (40mg/kg) with miR-181c-5p antagomiR (INH) or scrambled control for the duration of the study. We assessed cardiac function (echocardiography, hemodynamics), renal function (plasma creatinine), target expression (RT-qPCR), and histology.

Results: CRD animals showed mild systolic and diastolic cardiac dysfunction compared to healthy controls, with cardiac fibrosis (2.5±0.3 vs 1.8±0.2% area; p=0.0004) and hypertrophy (0.11±0.03 vs 0.08±0.01g/cm; p=0.005). Renal dysfunction presents with kidney atrophy (0.07±0.006 vs 0.09±0.01g/cm; p=0.02), increased plasma creatinine (21±6 vs 10±5; p=0.01), renal fibrosis (0.26±0.22 vs 0.005±0.21 % area; p=0.036) and glomerular abnormalities (glomerulosclerosis, hypertrophy/atrophy, mesangial matrix expansion, reduced podocyte number). CRD+INH animals had comparable cardiac phenotype to CRD (p>0.05). Their renal phenotype was exacerbated with elevated glomerular damage (26±3 vs 18±9;p=0.04) and significantly increased mortality rate (50%) (Kaplan-Meier p=0.01) compared to healthy controls (0%) or CRD (20%), associated with increased occurrence of tubular atrophy, endothelial swelling and systemic thrombotic microangiopathy (TMA). qPCR analysis identified Vegf as potential target of miR-181c-5p.

Conclusion: This study demonstrates a detrimental effect of miR-181c-5p inhibition on renal function in a CRD mouse model, driven by glomerular damage and TMA through Vegf signaling. Cardiac function was unaffected.

Abstract P2087: ERBB4-Selective And Sustained Activation By NRG1 Attenuates Atrial Fibrosis And Fibrillation

Introduction: Atrial fibrillation (AF) results from electrical and structural remodeling of the atria, in which inflammation and fibrosis play an important role. Current therapy is limited to antiarrhythmic drugs and ablations, but does not target the structural problem. Recent studies showed that neuregulin-1 (NRG1), an epidermal growth factor family member, has anti-fibrotic and anti-inflammatory effects in the myocardium.

Purpose: To test the effects of JK07, a NRG1 antibody fusion comprising an ERBB3 antagonistic antibody which selectively signals through ERBB4 preferentially over ERBB3, on atrial fibrosis and AF inducibility.

Methods: Atrial samples were harvested from male rats (Wistar Han, 10 weeks old), cut into small pieces (1-2mm 2 ) and kept in low serum medium in the presence or absence of JK07 (5nM). Col1a1 and Col3a1 mRNA was quantified after 24-72 hours. AF inducibility was tested in a first AF model in which male mice (C57BL/6N, 12-15 weeks old) were treated with angiotensin-II (Ang-II, 4 weeks, osmotic mini-pumps, 3000 ng/kg/min), and in a second AF model in which mice were fed with a high fat diet (HFD, 8 weeks, 60% Kcal fat) inducing severe weight gain (56±3% increase compared to 23±4% with regular chow). In both models, AF inducibility was tested by 5 runs of programmed electrical stimulation (PES) with a trans-jugular octapolar catheter. AF inducibility (% mice inducible by ≥3 PES-runs) and duration of PES-induced AF (AF duration) were recorded. Mice were randomized for treatment with vehicle or JK07 (2x/week, 1mg/kg, IV, n=5-7/group).

Results: In cultured atrial samples, Col1a1 and Col3a1 mRNA expression gradually increased up to 2-3 fold over 3 days. JK07 robustly attenuated this effect by 59±17% (p<0.05). In mice, both Ang-II and HFD significantly increased AF inducibility and AF duration. In Ang-II mice, JK07 attenuated AF inducibility (from 57% to 20%) and AF duration (from 33.3 ± 15.1 to 1.5 ± 1s). In HFD mice, JK07 significantly attenuated AF inducibility (from 57% to 0%) and AF duration (from 10.9±3.2s to 0.76±0.5s, p<0.05).

Conclusions: These results show anti-fibrotic effects by selective ERBB4 stimulation with JK07 in atrial tissue in vitro, together with AF-preventive effects in two unrelated mouse models.

ERBB4 and Multiple MicroRNAs That Target ERBB4 Participate in Pregnancy-Related Cardiomyopathy

BACKGROUND

Peripartum cardiomyopathy (PPCM) is a life-threatening disease in women without previously known cardiovascular disease. It is characterized by a sudden onset of heart failure before or after delivery. Previous studies revealed that the generation of a 16-kDa PRL (prolactin) metabolite, the subsequent upregulation of miR-146a, and the downregulation of the target gene Erbb4 is a common driving factor of PPCM.

METHODS

miRNA profiling was performed in plasma of PPCM patients (n=33) and postpartum-matched healthy CTRLs (controls; n=36). Elevated miRNAs in PPCM plasma, potentially targeting ERBB4 (erythroblastic leukemia viral oncogene homolog 4), were overexpressed in cardiomyocytes using lentiviral vectors. Next, cardiac function, cardiac morphology, and PPCM phenotype were investigated after recurrent pregnancies of HZ (heterozygous) cardiomyocyte-specific Erbb4 mice (Erbb4^F/+ αMHC-Cre⁺, n=9) with their age-matched nonpregnant CTRLs (n=9-10).

RESULTS

Here, we identify 9 additional highly conserved miRNAs (miR-199a-5p and miR-199a-3p, miR-145a-5p, miR-130a-3p, miR-135a-5p, miR-221-3p, miR-222-3p, miR-23a-3p, and miR19b-3p) that target tyrosine kinase receptor ERBB4 and are over 4-fold upregulated in plasma of PPCM patients at the time of diagnosis. We confirmed that miR-146a, miR-199a-5p, miR-221-3p, miR-222-3p, miR-23a-3p, miR-130a-5p, and miR-135-3p overexpression decreases ERBB4 expression in cardiomyocytes (-29% to -50%; P<0.05). In addition, we demonstrate that genetic cardiomyocyte-specific downregulation of Erbb4 during pregnancy suffices to induce a variant of PPCM in mice, characterized by left ventricular dilatation (postpartum second delivery: left ventricular internal diameter in diastole, +19±7% versus HZ-CTRL; P<0.05), increased atrial natriuretic peptide (ANP) levels (4-fold increase versus HZ-CTRL mice, P<0.001), decreased VEGF (vascular endothelial growth factor) and VE-cadherin levels (-33±17%, P=0.07; -27±20%, P<0.05 versus HZ-CTRL), and histologically enlarged cardiomyocytes (+20±21%, versus HZ-CTRL, P<0.05) but without signs of myocardial apoptosis and inflammation.

CONCLUSIONS

ERBB4 is essential to protect the maternal heart from peripartum stress. Downregulation of ERBB4 in cardiomyocytes induced by multiple miRNAs in the peripartum period may be crucial in PPCM pathophysiology. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT00998556.

The S4-S5 linker of KCNQ1 channels forms a structural scaffold with the S6 segment controlling gate closure

In vivo, KCNQ1 α-subunits associate with the β-subunit KCNE1 to generate the slowly activating cardiac potassium current (I(Ks)). Structurally, they share their topology with other Kv channels and consist out of six transmembrane helices (S1-S6) with the S1-S4 segments forming the voltage-sensing domain (VSD). The opening or closure of the intracellular channel gate, which localizes at the bottom of the S6 segment, is directly controlled by the movement of the VSD via an electromechanical coupling. In other Kv channels, this electromechanical coupling is realized by an interaction between the S4-S5 linker (S4S5(L)) and the C-terminal end of S6 (S6(T)). Previously we reported that substitutions for Leu(353) in S6(T) resulted in channels that failed to close completely. Closure could be incomplete because Leu(353) itself is the pore-occluding residue of the channel gate or because of a distorted electromechanical coupling. To resolve this and to address the role of S4S5(L) in KCNQ1 channel gating, we performed an alanine/tryptophan substitution scan of S4S5(L). The residues with a "high impact" on channel gating (when mutated) clustered on one side of the S4S5(L) α-helix. Hence, this side of S4S5(L) most likely contributes to the electromechanical coupling and finds its residue counterparts in S6(T). Accordingly, substitutions for Val(254) resulted in channels that were partially constitutively open and the ability to close completely was rescued by combination with substitutions for Leu(353) in S6(T). Double mutant cycle analysis supported this cross-talk indicating that both residues come in close contact and stabilize the closed state of the channel.

Conserved negative charges in the N-terminal tetramerization domain mediate efficient assembly of Kv2.1 and Kv2.1/Kv6.4 channels

Voltage-gated potassium (Kv) channels are transmembrane tetramers of individual alpha-subunits. Eight different Shaker-related Kv subfamilies have been identified in which the tetramerization domain T1, located on the intracellular N terminus, facilitates and controls the assembly of both homo- and heterotetrameric channels. Only the Kv2 alpha-subunits are able to form heterotetramers with members of the silent Kv subfamilies (Kv5, Kv6, Kv8, and Kv9). The T1 domain contains two subdomains, A and B box, which presumably determine subfamily specificity by preventing incompatible subunits to assemble. In contrast, little is known about the involvement of the A/B linker sequence. Both Kv2 and silent Kv subfamilies contain a fully conserved and negatively charged sequence (CDD) in this linker that is lacking in the other subfamilies. Neutralizing these aspartates in Kv2.1 by mutating them to alanines did not affect the gating properties, but reduced the current density moderately. However, charge reversal arginine substitutions strongly reduced the current density of these homotetrameric mutant Kv2.1 channels and immunocytochemistry confirmed the reduced expression at the plasma membrane. Förster resonance energy transfer measurements using confocal microscopy showed that the latter was not due to impaired trafficking, but to a failure to assemble the tetramer. This was further confirmed with co-immunoprecipitation experiments. The corresponding arginine substitution in Kv6.4 prevented its heterotetrameric interaction with Kv2.1. These results indicate that these aspartates (especially the first one) in the A/B box linker of the T1 domain are required for efficient assembly of both homotetrameric Kv2.1 and heterotetrameric Kv2.1/silent Kv6.4 channels.

Kv2.1 and silent Kv subunits underlie the delayed rectifier K+ current in cultured small mouse DRG neurons

Silent voltage-gated K(+) (K(v)) subunits interact with K(v)2 subunits and primarily modulate the voltage dependence of inactivation of these heterotetrameric channels. Both K(v)2 and silent K(v) subunits are expressed in the mammalian nervous system, but little is known about their expression and function in sensory neurons. This study reports the presence of K(v)2.1, K(v)2.2, and silent subunit K(v)6.1, K(v)8.1, K(v)9.1, K(v)9.2, and K(v)9.3 mRNA in mouse dorsal root ganglia (DRG). Immunocytochemistry confirmed the protein expression of K(v)2.x and K(v)9.x subunits in cultured small DRG neurons. To investigate if K(v)2 and silent K(v) subunits are underlying the delayed rectifier K(+) current (I(K)) in these neurons, K(v)2-mediated currents were isolated by the extracellular application of rStromatoxin-1 (ScTx) or by the intracellular application of K(v)2 antibodies. Both ScTx- and anti-K(v)2.1-sensitive currents displayed two components in their voltage dependence of inactivation. Together, both components accounted for approximately two-thirds of I(K). A comparison with results obtained in heterologous expression systems suggests that one component reflects homotetrameric K(v)2.1 channels, whereas the other component represents heterotetrameric K(v)2.1/silent K(v) channels. These observations support a physiological role for silent K(v) subunits in small DRG neurons.

Possible inadvertent subdural block following attempted stellate ganglion blockade

A case is reported of suspected inadvertent subdural block following attempted stellate ganglion blockade for relief of cervicobrachial pain in a patient suffering from reflex sympathetic dystrophy. Possible complications due to neuraxial spread of local anaesthetics while performing a cervicothoracic ganglion blockade are considered.