Cardiomyocyte-specific RXFP1 overexpression protects against pressure overload-induced cardiac dysfunction independently of Relaxin

Heart failure (HF) prevalence is rising due to reduced early mortality and demographic change. Relaxin (RLN) mediates protective effects in the cardiovascular system through Relaxin-receptor 1 (RXFP1). Cardiac overexpression of RXFP1 with additional RLN supplementation attenuated HF in the pressure-overload transverse aortic constriction (TAC) model. Here, we hypothesized that robust transgenic RXFP1 overexpression in cardiomyocytes (CM) protects from TAC-induced HF even in the absence of RLN. Hence, transgenic mice with a CM-specific overexpression of human RXFP1 (hRXFP1tg) were generated. Receptor functionality was demonstrated by in vivo hemodynamics, where the administration of RLN induced positive inotropy strictly in hRXFP1tg. An increase in phospholamban-phosphorylation at serine 16 was identified as a molecular correlate. hRXFP1tg were protected from TAC without additional RLN administration, presenting not only less decline in systolic left ventricular (LV) function but also abrogated LV dilation and pulmonary congestion compared to WT mice. Molecularly, transgenic hearts exhibited not only a significantly attenuated fetal and fibrotic gene activation but also demonstrated less fibrotic tissue and CM hypertrophy in histological sections. These protective effects were evident in both sexes. Similar cardioprotective effects of hRXFP1tg were detectable in a RLN-knockout model, suggesting an alternative mechanism of receptor activation through intrinsic activity, alternative endogenous ligands or crosstalk with other receptors. In summary, CM-specific RXFP1 overexpression provides protection against TAC even in the absence of endogenous RLN. This suggests RXFP1 overexpression as a potential therapeutic approach for HF, offering baseline protection with optional RLN supplementation for specific activation.

Abstract P2100: Scalable Ultra-purification Of Adeno-associated Viral Vectors - A Novel Standard To Boost Transduction Efficacy And Potency For Cardiac Gene Therapy Development

Introduction: A high transduction efficacy and potency of AAV-based cardiac gene therapies is key for the clinical translation in which hereditary and acquired cardiac disorders will be targeted. As such, ultrapure vectors with superior biological and therapeutic capabilities are a must for these therapies.

Hypothesis: We hypothesized that our developed affinity chromatography (AC) based purification system will increase AAV recovery and - potency.

Methods: AAV vector production, AC based - or iodixanol density gradient (DG) based purification, Q-PCR, WB, EM, LC-MS/MS, P-loop

Results: Using the same vector input quantity, the AC-based purification enabled an approximately 13-fold greater vector genome copy (vgc) recovery than the DG-based purification. Mass spectrometry analysis demonstrated ultrapure AAV9 vectors as a result of an AC purification (AAV9 93.24% vs. 6,76% contaminants) whereas corresponding DG preparations resulted in highly contaminated vectors (AAV9 5.49% vs. 94,51% contaminants). Biological potency of AC- and DG-purified AAV9 vectors towards cardiac transduction were determined by systemic injections of 1·10 10 , 1·10 11 or 1·10 12 vgc of AAV9-EGFP in C57BL/6 mice (n=8 each group). AC-purified AAVs achieved a significantly higher cardiac transduction efficacy for every dosage assessed by comparative bulk myocardial DNA, RNA and protein level analysis after 2 weeks. Therapeutic potency was examined for a recently published novel target for chronic heart failure namely the RFXP1-RLN system. To this end, a dosage of 5·10 11 vgcs of either AC- or DG purified AAV9-RXFP1 vectors were systemically injected and the cardiac contractile performance increase was captured after 2 weeks in mice of both groups. Of note, 10 minutes after RLN administration, the rise in LV +dp/dt max. was already significantly greater in the AC- than the DG-vector treated group (AC: 13594+/-1972 vs. DC: 9822+/-801 mmHg/s; n=8 per group, p<0.01).

Conclusion: The data clearly promote AC-based AAV purification as a novel standard for cardiovascular basic and translational research. Higher consistency in results, higher therapeutic effects and superior biological potency can be expected from higher production yields of ultrapure AAVs even at lower vector dosages.

A consensus-based and readable extension of Linear Code for Reaction Rules (LiCoRR)

Systems glycobiology aims to provide models and analysis tools that account for the biosynthesis, regulation, and interactions with glycoconjugates. To facilitate these methods, there is a need for a clear glycan representation accessible to both computers and humans. Linear Code, a linearized and readily parsable glycan structure representation, is such a language. For this reason, Linear Code was adapted to represent reaction rules, but the syntax has drifted from its original description to accommodate new and originally unforeseen challenges. Here, we delineate the consensuses and inconsistencies that have arisen through this adaptation. We recommend options for a consensus-based extension of Linear Code that can be used for reaction rule specification going forward. Through this extension and specification of Linear Code to reaction rules, we aim to minimize inconsistent symbology thereby making glycan database queries easier. With a clear guide for generating reaction rule descriptions, glycan synthesis models will be more interoperable and reproducible thereby moving glycoinformatics closer to compliance with FAIR standards. Here, we present Linear Code for Reaction Rules (LiCoRR), version 1.0, an unambiguous representation for describing glycosylation reactions in both literature and code.

CaMKII activation participates in doxorubicin cardiotoxicity and is attenuated by moderate GRP78 overexpression

The clinical use of the chemotherapeutic doxorubicin (Dox) is limited by cardiotoxic side-effects. One of the early Dox effects is induction of a sarcoplasmic reticulum (SR) Ca²⁺ leak. The chaperone Glucose regulated protein 78 (GRP78) is important for Ca²⁺ homeostasis in the endoplasmic reticulum (ER)—the organelle corresponding to the SR in non-cardiomyocytes—and has been shown to convey resistance to Dox in certain tumors. Our aim was to investigate the effect of cardiac GRP78 gene transfer on Ca²⁺ dependent signaling, cell death, cardiac function and survival in clinically relevant in vitro and in vivo models for Dox cardiotoxicity.By using neonatal cardiomyocytes we could demonstrate that Dox induced Ca²⁺ dependent Ca²⁺ /calmodulin-dependent protein kinase II (CaMKII) activation is one of the factors involved in Dox cardiotoxicity by promoting apoptosis. Furthermore, we found that adeno-associated virus (AAV) mediated GRP78 overexpression partly protects neonatal cardiomyocytes from Dox induced cell death by modulating Ca²⁺ dependent pathways like the activation of CaMKII, phospholamban (PLN) and p53 accumulation. Most importantly, cardiac GRP78 gene therapy in mice treated with Dox revealed improved diastolic function (dP/dtmin) and survival after Dox treatment. In conclusion, our results demonstrate for the first time that Ca²⁺ dependent CaMKII activation fosters Dox cardiomyopathy and provide additional insight into possible mechanisms by which GRP78 overexpression protects cardiomyocytes from Doxorubicin toxicity.

G protein-coupled receptor kinase 2 promotes cardiac hypertrophy

The increase in protein activity and upregulation of G-protein coupled receptor kinase 2 (GRK2) is a hallmark of cardiac stress and heart failure. Inhibition of GRK2 improved cardiac function and survival and diminished cardiac remodeling in various animal heart failure models. The aim of the present study was to investigate the effects of GRK2 on cardiac hypertrophy and dissect potential molecular mechanisms. In mice we observed increased GRK2 mRNA and protein levels following transverse aortic constriction (TAC). Conditional GRK2 knockout mice showed attenuated hypertrophic response with preserved ventricular geometry 6 weeks after TAC operation compared to wild-type animals. In isolated neonatal rat ventricular cardiac myocytes stimulation with angiotensin II and phenylephrine enhanced GRK2 expression leading to enhanced signaling via protein kinase B (PKB or Akt), consecutively inhibiting glycogen synthase kinase 3 beta (GSK3β), such promoting nuclear accumulation and activation of nuclear factor of activated T-cells (NFAT). Cardiac myocyte hypertrophy induced by in vitro GRK2 overexpression increased the cytosolic interaction of GRK2 and phosphoinositide 3-kinase γ (PI3Kγ). Moreover, inhibition of PI3Kγ as well as GRK2 knock down prevented Akt activation resulting in halted NFAT activity and reduced cardiac myocyte hypertrophy. Our data show that enhanced GRK2 expression triggers cardiac hypertrophy by GRK2-PI3Kγ mediated Akt phosphorylation and subsequent inactivation of GSK3β, resulting in enhanced NFAT activity.

Eruptive furunculosis following the soak and smear regimen

The 'soak and smear' regimen is a highly effective method for localised topical therapy employed by dermatologists for widespread inflammatory skin conditions. The regimen involves application of topical medication under occlusion after soaking in water. Complications from this treatment method are rare. We present a case of multiple, generalised methicillin-resistant Staphylococcus aureus (MRSA)-positive furuncles arising in a patient as an unexpected consequence of therapy. The case highlights an unanticipated risk of a commonly employed treatment amid an epidemic of MRSA in the community.

Neutrophilic urticaria with systemic inflammation: a case series

IMPORTANCE

Predominantly neutrophilic infiltrates are seen in a subset of patients with urticaria. The lesions tend to be less itchy and poorly responsive to standard therapy, including antihistamines. We describe 2 patients having neutrophilic urticaria with systemic inflammation (NUSI) without known connective tissue disorder or malignancy. We propose the term NUSI to help classify a previously undefined multisystemic inflammatory entity likely mediated by interleukin 1 (IL-1).

OBSERVATIONS

Patient 1, a 47-year-old woman, was seen with urticaria and associated night sweats, fevers, and polyarticular arthritis. Acute-phase reactants were elevated with worsening of symptoms. Initial treatment with a combination of topical and systemic corticosteroids, antihistamines, and immunosuppressants was unsuccessful. A 100% clinical resolution was achieved with anakinra, an IL-1 receptor antagonist. Patient 2, a 24-year-old woman, was seen with urticaria and associated joint pain and swelling. Initial treatment included a combination of antihistamines, colchicine, and dapsone. Only colchicine provided moderate benefit but was stopped because of significant gastrointestinal tract discomfort. Anakinra was initiated; the patient achieved 100% control while receiving daily therapy.

CONCLUSIONS AND RELEVANCE

The diagnosis of NUSI is important to consider in patients who are seen with antihistamine-resistant urticaria in combination with systemic inflammatory symptoms. Interleukin 1 blockade is a viable option for therapy.

Paced respiratory sinus arrhythmia as an index of cardiac parasympathetic tone during varying behavioral tasks

This study addresses a number of unresolved issues regarding the employment of respiratory sinus arrhythmia as an index of tonic parasympathetic cardiac control in psychophysiological investigations. These questions include the following: (1) Does respiratory sinus arrhythmia reflect cardiac vagal tone under conditions in which alterations in parasympathetic control are expected to be mild to moderate? (2) Are variations in human respiratory sinus arrhythmia that occur in response to varying behavioral demands independent of beta-adrenergic effects on the heart? (3) To what extent do typical experimental tasks apparently affect tonic cardiac vagal control? Twelve healthy male subjects were administered a joint alpha- and beta-adrenoreceptor pharmacological blocker on one day and a placebo on another (balanced across subjects). On both days, respiratory sinus arrhythmia and heart period were monitored during a number of different experimental tasks while subjects continuously paced their respiration. Results indicated that respiratory sinus arrhythmia, under controlled respiratory conditions, is uninfluenced by variations in sympathetic activity, and provides a reasonably sensitive index of cardiac vagal tone, even when alterations in parasympathetic tone are not large. Furthermore, our findings suggest that cardiac vagal tone is responsive to varying behavioral demands and may interact in different ways with beta-adrenergic mechanisms.