Sphingolipids: drivers of cardiac fibrosis and atrial fibrillation.

Sphingolipids (SLs) are vital constituents of the plasma membrane of animal cells and concurrently regulate numerous cellular processes. An escalating number of research have evinced that SLs assume a crucial part in the progression of tissue fibrosis, a condition for which no efficacious cure exists as of now. Cardiac fibrosis, and in particular, atrial fibrosis, is a key factor in the emergence of atrial fibrillation (AF). AF has become one of the most widespread cardiac arrhythmias globally, with its incidence continuing to mount, thereby propelling it to the status of a major public health concern. This review expounds on the structure and biosynthesis pathways of several pivotal SLs, the pathophysiological mechanisms of AF, and the function of SLs in cardiac fibrosis. Delving into the influence of sphingolipid levels in the alleviation of cardiac fibrosis offers innovative therapeutic strategies to address cardiac fibrosis and AF.

Hot Deformation Behavior and Processing Maps of 26CrMo7S Steel Used in Oil Exploration.

The hot deformation behavior and flow stress characteristics of experimental 26CrMo7S steel were analyzed using a thermal simulator under a range of conditions, including a strain rate range of 0.01~10 s-1, a temperature range of 850~1250 °C, and a maximum deformation amount of 70%. The Arrhenius constitutive model was built for the corresponding conditions, and the model's accuracy was verified through error analysis. Additionally, hot processing maps were constructed to analyze the processing zone of the steel under different hot deformation conditions. Finally, the microstructure of the processing zones was observed and verified using the electron backscattered diffraction (EBSD). The results indicate that the interaction of work hardening and dynamic softening influences the hot deformation behavior of 26CrMo7S steel. The Arrhenius constitutive equation with a value of the correlation coefficient (r = 0.99523) accurately predicts the flow behavior of 26CrMo7S steel under different strains. The optimal processing zone obtained with the hot processing maps is within a deformation range of 1010~1190 °C and a strain rate range of 0.01~10-1.5 s-1, and the obtained microstructure is in good agreement with the analysis results.

Phosphatidylethanolamine aggravates Angiotensin II-induced atrial fibrosis by triggering ferroptosis in mice.

As atrial fibrosis is the main feature of atrial structural remodeling, inhibiting atrial fibrosis is crucial to the prevention of atrial fibrillation (AF) progression. Research has shown the correlation between abnormal lipid metabolism and AF progression. However, the effect of specific lipids on atrial fibrosis remains unclear. In the present study, we applied ultra-high-performance lipidomics to analyze the lipid profiles in patients with AF and identify phosphatidylethanolamine (PE) as the differential lipid associated with AF. To detect the effect of the differential lipid on atrial fibrosis, we performed the intraperitoneal injection of Angiotensin II (Ang II) to mice to induce atrial fibrosis and supplemented PE in diets. We also treated atrial cells with PE to evaluate the cellular effect of PE. We found that PE supplementation aggravated atrial fibrosis and increased the expression of the fibrosis-related protein in vitro and in vivo. Moreover, we detected the effect of PE on the atrium. We found that PE increased oxidation products and regulated the expression of ferroptosis-related proteins, which could be alleviated by a ferroptosis inhibitor. PE increased peroxidation and mitochondrial damage in vitro, which promoted cardiomyocyte death induced by Ang II. Examination of protein expression in cardiomyocytes indicated that PE triggered ferroptosis and caused cell death to participate in myocardium fibrosis. In summary, our findings demonstrated the differential lipid profiles of AF patients and revealed the potential effect of PE on atrial remodelling, suggesting that inhibition of PE and ferroptosis might serve as a potential therapy to prevent AF progression.

MicroRNA-205-5p plays a suppressive role in the high-fat diet-induced atrial fibrosis through regulation of the EHMT2/IGFBP3 axis.

OBJECTIVE: MicroRNAs (miRNAs) targeting has been revealed to be an appealing strategy for the treatment and management of atrial fibrillation (AF). In this research, we aimed to explore the mechanisms of miR-205-5p in reducing the high-fat diet (HFD)-induced atrial fibrosis through the EHMT2/IGFBP3 axis. METHODS: Expression levels of miR-205-5p, IGFBP3 and EHMT2 were determined in AF patients, cell fibrosis models and mouse atrial fibrosis models. Luciferase activity and RIP assays were performed to detect the binding between miR-205-5p and EHMT2, and ChIP assays were implemented to detect the enrichment of H3K9me2 and H3K4me3 in the promoter region of IGFBP3 in cells. The related experiments focusing on the inflammatory response, atrial fibrosis, mitochondrial damage, and metabolic abnormalities were performed to figure out the roles of miR-205-5p, IGFBP3, and EHMT2 in cell and mouse atrial fibrosis models. RESULTS: Low expression levels of miR-205-5p and IGFBP3 and a high expression of EHMT2 were found in AF patients, cell fibrosis models and mouse atrial fibrosis models. Upregulation of miR-205-5p reduced the expression of TGF-ß1, α-SMA, Col III and other fibrosis-related proteins. miR-205-5p overexpression targeted EHMT2 to regulate the methylation of H3 histones to promote IGFBP3 expression, which in turn affected the fibrosis of atrial muscle cells. In HFD-induced atrial fibrosis mice, upregulated miR-205-5p or elevated IGFBP3 alleviated atrial fibrosis, mitochondrial damage, and metabolic abnormalities. CONCLUSION: This study suggests that miR-205-5p attenuates HFD-induced atrial fibrosis via modulating the EHMT2/IGFBP3 axis. miR-205-5p alleviates high-fat diet-induced atrial fibrosis in mice via EHMT2/IGFBP3.

Profiling of miR-205/P4HA3 Following Angiotensin II-Induced Atrial Fibrosis: Implications for Atrial Fibrillation.

Objective: Atrial fibroblasts are the main component of atrial fibrosis. Data in previous studies proved the implication of miRNAs in AF progression and the association of miR-205 with cancer associated-fibroblasts, while no evidence supported the implication of miR-205 in atrial fibrosis. Therefore, this study aims to explore the effect and mechanism of miR-205/P4HA3 axis on atrial fibrosis. Methods: Angiotensin II (Ang II) was used to induce atrial fibrosis model in rats, which was verified by H&E staining and Masson staining. qRT-PCR and Western blot were applied to measure the expressions of miR-205, P4HA3, collagen I, and α-SMA. The rat atrial fibroblasts were isolated and then subjected to Ang II treatment or cell transfection for determination of cell biological functions using CCK-8, BrdU assay, TUNEL staining, and cell scratch assay. qRT-PCR and Western blot was applied to analyze the expressions of miR-205, P4HA3, collagen I, α-SMA, JNK, and p-JNK in atrial fibroblasts. Dual-luciferase reporter gene assay and RNA immune-precipitation experiment was employed to verify the binding relationship between miR-205 and P4HA3. Results: Ang II induced rats had disordered arrangement of atrial muscles with uneven nuclear sizes and necrotic atrial myocytes, and increased collagen deposition, in which elevated expressions of P4HA3, collagen I, and α-SMA as well as suppressed expression level of miR-205 were found. In vitro, Ang II treatment in atrial fibroblasts with overexpression of P4HA3 facilitated cellular migration and proliferation, with the induction of JNK signaling pathway. However, these trends were reversed after transfection with miR-205 mimic. P4HA3 is a target gene of miR-205. Conclusion: The miR-205/P4HA3 axis is implicated in atrial fibrosis by inhibition of rat fibroblast proliferation and migration and the inactivation of JNK signaling pathway.

Alterations of long non-coding RNA and mRNA profiles associated with extracellular matrix homeostasis and vascular aging in rats.

Vascular aging has been closely associated with various cardiovascular disorders; however, its molecular mechanism remains poorly understood. In our study, RNA sequencing was utilized to explore the expression profiles of long non-coding RNAs (lncRNAs) and mRNAs in the thoracic aortas of young (3 weeks) and old (16 weeks) rats. Functional categorization of differentially expressed mRNAs was evaluated using the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases, and lncRNA-microRNA-mRNA networks was constructed using Cytoscape software. In addition, three upregulated and three downregulated lncRNAs were further confirmed by quantitative reverse transcriptase-polymerase chain reaction. A total of 36 lncRNAs and 922 mRNAs were differential expression in the thoracic aortas of young and older rats. In addition, we found differentially expressed mRNAs that were enriched in multiple biological processes and signaling pathways associated with angiogenesis, such as extracellular matrix-receptor interaction and adenosine 3',5'-monophosphate-activated protein kinase (AMPK) signaling. Moreover, AABR07013558.1, AABR07014823.1, and AABR07031489.1 were upregulated and ABR07053849.3, AABR07067310.2, and AC111292.1 were downregulated in the thoracic aortas of older rats compared with the young ones. Therefore, our findings provide several potential lncRNAs and mRNAs and signaling pathways related to vascular aging, which provide new clue for underlying the improvement of vascular aging.

Donor heart preservation with hypoxic-conditioned medium-derived from bone marrow mesenchymal stem cells improves cardiac function in a heart transplantation model.

BACKGROUND: In heart transplantation, donor hearts inevitably suffer from ischemia/reperfusion (I/R) injury, which leads to primary graft dysfunction and affects patients' survival rate. Bone marrow mesenchymal stem cells (BMSCs) have been reported to attenuate myocardial I/R injury via their paracrine effects, which can be enhanced by hypoxic preconditioning. We hypothesized that the donor heart preservation with hypoxic conditioned medium (CdM) derived from BMSCs would improve post-transplant graft function. METHODS: Normoxic or hypoxic CdM were isolated from rat BMSCs cultured under normoxic (20% O2) or hypoxic (1% O2) condition. Donor hearts were explanted; stored in cardioplegic solution supplemented with either a medium (vehicle), normoxic CdM (N-CdM), or hypoxic CdM (H-CdM); and then heterotopically transplanted. Antibody arrays were performed to compare the differences between hypoxic and normoxic CdM. RESULTS: After heart transplantation, the donor heart preservation with normoxic CdM was associated with a shorter time to return of spontaneous contraction and left ventricular systolic diameter, lower histopathological scores, higher ejection fraction, and fractional shortening of the transplanted hearts. The cardioprotective effects may be associated with the inhibition of apoptosis and inflammation, as reflected by less TUNEL-positive cells and lower levels of plasma proinflammatory cytokines (interleukin-1ß, interleukin-6, tumor necrosis factor-α) and cardiac troponin I in the N-CdM group compared with the vehicle group. These therapeutic effects can be further enhanced by hypoxic preconditioning. Antibody arrays revealed that nine proteins were significantly increased in hypoxic CdM compared with normoxic CdM. Furthermore, compared with vehicle and N-CdM groups, the protein levels of PI3K and p-Akt/Akt ratio in the transplanted hearts significantly increased in the H-CdM group. However, no significant difference was found in the phosphorylation of Smad2 and Smad3 for the donor hearts among the three groups. CONCLUSIONS: Our results indicate that the cardioplegic solution-enriched with hypoxic CdM can be a novel and promising preservation solution for donor hearts.

Machine perfusion of donor heart with normothermic blood versus hypothermic HTK in preserving coronary endothelium in a porcine model of DCD.

BACKGROUND: Both machine perfusion (MP) of donor hearts with autologous blood and crystalloid perfusates have advantages and disadvantages. Currently, which of the aforementioned preservation strategies can better preserve the coronary endothelium has not yet been determined. We aim to compare the impact of hypothermic continuous MP with histidine-tryptophan-ketoglutarate (HTK) solution versus normothermic continuous MP with autologous blood on coronary endothelium in a porcine ex vivo model of donation following circulatory death (DCD). METHODS: DCD pigs underwent circulatory arrest via asphyxiation followed by 30-minute warm ischemia time. Donor hearts were preserved with either hypothermic MP with HTK solution (MP + HTK group; 4 ℃; n=6), or normothermic MP with blood (MP + blood group; 37 ℃; n=6) for 4 hours. After 2-hour ex vivo reperfusion, the assessment of endothelial-dependent (Edep) and -independent (Eind) relaxation of coronary artery, histopathological analysis, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay were performed. RESULTS: Preservation of DCD hearts with MP + Blood strategy significantly improved both Edep and Eind vasorelaxation of coronary artery compared with MP + HTK strategy (maximum relaxation to bradykinin: MP + HTK 80.9%±2.6% vs. MP + Blood 91.9%±1.9%, P<0.001; maximum relaxation to sodium nitroprusside: MP + HTK 97.1%±1.0% vs. MP + Blood 99.8%±0.2%, P<0.05). MP + Blood strategy significantly decreased nitrotyrosine but increased intercellular adhesion molecule-1 immunoreactivity in the coronary artery. The number of TUNEL-positive cells in MP + Blood group were significantly fewer compared with MP + HTK group. CONCLUSIONS: Compared with MP + HTK strategy, MP + Blood strategy significantly alleviates coronary endothelial dysfunction during donor heart preservation. This protective effect is associated with the inhibition of apoptosis and nitro-oxidative stress in coronary artery.