Clin Res Cardiol (2021) DOI DOI https://doi.org/10.1007/s00392-021-01843-w

Phosphatase nuclear targeting subunit PNUTS in inflammatory cardiomyopathy

V. Zirkenbach1, R. Öttl1, R. Ignatz1, M. Kaya1, N. Frey1, O. J. Müller2, Z. Kaya1

1Klinik für Innere Med. III, Kardiologie, Angiologie u. Pneumologie, Universitätsklinikum Heidelberg, Heidelberg; 2Klinik für Innere Medizin III, Schwerpunkt Kardiologie und Angiologie, Universitätsklinikum Schleswig-Holstein, Kiel;

Background: Myocarditis is an important cause of heart failure in young adults. It is characterized as inflammation of the heart muscle and treated with conservative therapy. However, some patients undergo acute heart failure, partially leading to death, which makes it necessary to understand the underlying pathomechanism. Our preliminary work indicates a potential for PNUTS (phosphatase nuclear targeting subunit) in inflammatory cardiomyopathy. PNUTS is part of the protein phosphatase 1 (PP1) and has an inhibitory effect on PP1. It directs PP1 into the nucleus. As part of the DNA damage response, PNUTS is targeted to damage sites during G2 checkpoint arrest. It was reported, that a PNUTS overexpression leads to an increased hypoxia-induced cell death with increased levels of Bax. The aim of the study was to investigate the role of PNUTS in inflammatory cardiomyopathy. Methods: 6-weeks-old A/JOla mice were transfected with AAV9-virus to overexpress PNUTS or eGFP as a control in the heart. To study the effect of PNUTS overexpression in our established model for experimental autoimmune myocarditis (EAM), we induced an EAM by immunization with TnI. Simultaneously, immunized mice were transfected two weeks earlier with either PNUTS-AAV or eGFP-AAV as control. Additionally, we used not TnI immunized mice as control which were also transfected with PNUTS-AAV and eGFP-AAV. The animals were administered three times with TnI or control buffer to induce a myocarditis. To evaluate heart function and inflammation score, ejection fraction was measured via echocardiography and inflammation score was quantified by histopathological staining. In Addition, hs-TnT levels were evaluated to detect myocardial damage. With this study design we investigated the additive effect on myocarditis. Results: As expected, a TnI immunization led to an inflammation in eGFP control transfected mice (20,5%, p=0,0042). This effect was even enhanced in PNUTS overexpressing mice (mean=43,25%, p=0,0090). This finding suggests that PNUTS promotes inflammation in the heart. Surprisingly, the sole overexpression of PNUTS in mice which were not immunized with TnI led to an inflammation (mean=22,75%, p=0,0090), whereas the eGFP control group showed no sign of inflammation (mean=0, p=0,0042). Additionally, hs-TnT levels were increased in PNUTS overexpressing mice treated in both TnI or CFA treated groups (mean=223,9 vs. mean =128), while there was measurable levels in control group expressing GFP treated with CFA (mean=0). These signs of inflammation are accompanied with a reduced ejection fraction in PNUTS overexpressing groups. Figure 1: Inflammation score of PNUTS or eGFP transfected mice. Inflammation score increased in both PNUTS groups with TnI or CFA immunization. The score was assessed by hematoxylin and eosin staining. Conclusion: This study shows that PNUTS overexpression in the model of EAM enhances inflammation in the heart. Additionally, our results indicate that PNUTS overexpression alone is able to induce a myocardial inflammation and heart failure.

https://dgk.org/kongress_programme/jt2021/aP844.html