Biology subjects

Klinke, A.

Publications and source records attributed to Klinke, A..

4 recordsLinked to original sources

bioRxiv2024

Enhanced cardiac mitochondrial biogenesis by nitro-oleic acid remedies diastolic dysfunction in a mouse model of heart failure with preserved ejection fraction

Prevalence of heart failure with preserved ejection fraction (HFpEF) is increasing, while treatment options are inadequate. Hypertension and obesity-related metabolic dysfunctions contribute to HFpEF progression. Nitro-oleic acid (NO2-OA) impacts metabolic processes by improving glucose tolerance and adipocyte function. In this study, 4 week treatment with NO2-OA ameliorated diastolic dysfunction in a HFpEF mouse model induced by high-fat diet and inhibition of the endothelial nitric oxide synthase. A proteomic analysis of left ventricular tissue revealed, that one third of the identified proteins, mostly mitochondrial proteins, were upregulated in hearts of NO2-OA-treated HFpEF mice compared to controls and vehicle-treated HFpEF mice, which was confirmed by immunoblot. Activation of the 5-adenosine-monophosphate-activated-protein-kinase (AMPK) signaling pathway mediated an enhancement of mitochondrial biogenesis in hearts of NO2-OA-treated HFpEF mice. In cardiomyocytes under metabolic stress, NO2-OA increased mitochondrial protein level accompanied by enhanced oxidative phosphorylation. In conclusion, targeting mitochondrial integrity in HFpEF leads to improved diastolic function.

pathology↗

bioRxiv2023

Remodelling of the endothelial cell transcriptional program via paracrine and DNA-binding activities of MPO

Myeloperoxidase (MPO) is an enzyme that functions in host defence by catalysing the formation of reactive oxygen intermediates. Synthesized majorly by myeloid progenitor cell types and neutrophils, MPO is released into the vascular lumen during inflammation, where it may adhere and subsequently enter endothelial cells coating vascular walls. Here, we show that MPO actually enters the nucleus of these endothelial cells and binds chromatin independently of its enzymatic activity to cause changes in chromatin structure. At its binding sites, MPO drives chromatin decondensation, while enhancing condensation at flanking regions. We further show that MPO binds loci relevant for the activation of the endothelial-to- mesenchymal transition (EndMT) and the migratory potential of ECs. Finally, MPO interacts with the RNA- binding factor ILF3 affecting its relative abundance between cytoplasm and nucleus. This leads to ILF3:MPO- driven transcriptional and post-transcriptional regulation. Accordingly, MPO-knockout mice show reduced EC numbers at scars formed after myocardial infarction, indicating reduced neovascularization. In summary, we describe a non-enzymatic role for MPO in coordinating EndMT and controlling the fate of endothelial cells through direct chromatin binding and association with such co-factors as ILF3.

genomics↗

bioRxiv2022

Inhibition of myeloperoxidase prevents thoracic aortic aneurysm formation in Marfan mice

Marfan syndrome (MFS) is the most prevalent inherited connective tissue disorder, still remains uncurable, and is characterized by high mortality at early age driven by dissection and rupture of thoracic aortic aneurysms. MFS is caused by mutations in the fibrillin-1 gene and aberrant TGF{beta} signaling. Here we addressed whether myeloperoxidase (MPO), a leukocyte derived enzyme with potent matrix modulating properties also influences the aortic phenotype in MFS. MFS patients displayed increased circulating MPO levels compared to controls as well as marked aortic MPO deposition. In an MFS mouse model, MPO induced inflammatory endothelial activation and endothelial to mesenchymal transition which triggered aortic leukocyte recruitment. Moreover, MPO directly contributed to adverse extracellular matrix remodeling by promoting oxidative stress and nitration of proteins within the vascular wall. Genetic MPO deficiency and pharmacological MPO inhibition attenuated MFS-related aneurysm formation. We herein identify MPO as a critical mediator of MFS-related thoracic aortic aneurysm formation and - in the absence of any pharmacological treatment so far in this disease - a first anti-inflammatory target to modulate disease progression.

immunology↗

bioRxiv2018

Protein nitration is a physiological regulator of cardiac lactate dehydrogenase active site loop mobility and activity

Protein tyrosine nitration is a hallmark of oxidative stress related disease states, commonly detected as anti-nitrotyrosine immunoreactivity. The precise reactive oxygen sources, mechanisms of nitration as well as the modified target proteins and functional consequences, however, remain often unclear. Here we explore protein tyrosine nitration under basal conditions and find surprisingly physiologically nitrated proteins. Upon purifying a prominent physiologically nitrotyrosine immunopositive in hearts from mouse, rat and pig, we identify it as lactate dehydrogenase (LDH). Mechanistically, LDHs degree of basal nitration depended on two canonical sources, NO synthase (NOS) and myeloperoxidase (MPO), respectively. When validating the nitrated amino acid by MALDI-TOF mass spectrometry, we, surprisingly, located LDH nitration not to a tyrosine but the C-terminal tryptophan, Trp324. Molecular dynamics simulations suggested that Trp324 nitration restricts the interaction of the active site loop with the C-terminal -helix essential for activity. This prediction was confirmed by enzyme kinetics revealing an apparent lower Vmax of nitrated LDH, although yet unidentified concurrent oxidative modifications may contribute. Protein nitration is, thus, not a by definition disease marker but reflects also physiological signaling by eNOS/NO, MPO/nitrite and possibly other pathways. The commonly used assay of anti-nitrotyrosine immunoreactivity is apparently cross-reactive to nitrotryptophan requiring a reevaluation of the protein nitration literature. In the case of LDH, nitration of Trp324 is aggravated under cardiac metabolic stress conditions and functionally limits maximal enzyme activity. Trp324-nitrated LDH may serve both as a previously not recognized disease biomarker and possibly mechanistic lead to understand the metabolic changes under these conditions.

biochemistry↗