Hypoxic cardiac fibroblasts from failing human hearts decrease cardiomyocyte beating frequency in an ALOX15 dependent manner

Abstract

A common denominator for patients with heart failure is the correlation between elevated serum levels of proinflammatory cytokines and adverse clinical outcomes. Furthermore, lipoxygenase-induced inflammation is reportedly involved in the pathology of heart failure. Cardiac fibroblasts, which are abundant in cardiac tissue, are known to be activated by inflammation. We previously showed high expression of the lipoxygenase arachidonate 15 lipoxygenase (ALOX15), which catalyzes the conversion of arachidonic acid to 15-hydroxy eicosatetraenoic acid (15-HETE), in ischemic cardiac tissue. The exact roles of ALOX15 and 15-HETE in the pathogenesis of heart failure are however unknown. Biopsies were collected from all chambers of explanted failing human hearts from heart transplantation patients, as well as from the left ventricles from organ donors not suffering from chronic heart failure. Biopsies from the left ventricles underwent quantitative immunohistochemical analysis for ALOX15/B. Gene expression of ALOX enzymes, as well as 15-HETE levels, were examined in cardiac fibroblasts which had been cultured in either hypoxic or normoxic conditions after isolation from failing hearts. After the addition of fibroblast supernatants to human induced pluripotent stem cell-derived cardiomyocytes, intracellular calcium concentrations were measured to examine the effect of paracrine signaling on cardiomyocyte beating frequency. While ALOX15 and ALOX15B were expressed throughout failing hearts as well as in hearts from organ donors, ALOX15 was expressed at significantly higher levels in donor hearts. Hypoxia resulted in a significant increase in gene and protein expression of ALOX15 and ALOX15B in fibroblasts isolated from the different chambers of failing hearts. Finally, preconditioned medium from hypoxic fibroblasts decreased the beating frequency of human cardiomyocytes derived from induced pluripotent stem cells in an ALOX15-dependent manner. In summary, our results demonstrate that ALOX15/B signaling by hypoxic cardiac fibroblasts may play an important role in ischemic cardiomyopathy, by decreasing cardiomyocyte beating frequency.

Human intracardiac SSEA4+CD34 cells show features of cycling, immature cardiomyocytes and are distinct from Side Population and C-kit+CD45- cells

“…The study was approved by the local ethics committee at the University of Gothenburg (#436–15, #596–11) and carried out in accordance with the Helsinki Declaration as revised 2013. Biopsy material from some of the patients were also used in other previously published studies or unpublished studies due to the limited supply of biopsy material [ 24 – 26 ]. No organs/tissues were procured from prisoners.…”

Mechanism and potential treatment of the “no reflow” phenomenon after acute myocardial infarction: role of pericytes and GPR39

“…The reduction in no reflow is also associated with a reduction in infarct size. Furthermore, we show that cultured primary mouse heart pericytes from GPR39-KO mice and WT mice treated with a specific GPR39 antagonist show a markedly reduced calcium response to 15-HETE, a vasoconstrictor that is released during myocardial ischemia (42)(43)(44) and could play an important role in the pathogenesis of myocardial necrosis.…”

“…GPR39 is not expressed in endothelial cells (41). Clinical data indicate that 15-HETE is increased in the hearts of patients with ischemic heart disease (42) probably in response to oxidant exposure (43), and this elevation is associated with adverse cardiac effects (44). Thus, it appears that GPR39 could be the mechanism that senses ischemic conditions and engages vascular mechanisms that reduce nutrient blood flow.…”

Beyond Family: Modeling Non-hereditary Heart Diseases With Human Pluripotent Stem Cell-Derived Cardiomyocytes

“…A recent hEHT I/R model showed for the first time in human cells the cardioprotective effect of ischemic preconditioning and efficacy of one out of three proposed cardioprotection treatments for reperfusion injury (Chen and Vunjak-Novakovic, 2019). Nevertheless, similar hEHTs generated by pure hPSC-CM populations are limited in their maturation potential (Park et al, 2019) and limit the study of the complex bidirectional crosstalk of multiple cell types, important during ischemic stress via paracrine signaling (Sandstedt et al, 2018;Sebastiao et al, 2019Sebastiao et al, , 2020 and neurohormonal stimulation. The latter can be effectively modeled solely with hEHTs, as 2D cultures lack or display functionally impaired a β-adrenergic signaling cascades (Jung et al, 2016;Uzun et al, 2016;Trieschmann et al, 2019), despite being able to form functional sympathetic neurojunctions (Sakai et al, 2017).…”