Identification and experimental validation of KMO as a critical immune-associated mitochondrial gene in unstable atherosclerotic plaque.

BACKGROUND: The heightened risk of cardiovascular and cerebrovascular events is associated with the increased instability of atherosclerotic plaques. However, the lack of effective diagnostic biomarkers has impeded the assessment of plaque instability currently. This study was aimed to investigate and identify hub genes associated with unstable plaques through the integration of various bioinformatics tools, providing novel insights into the detection and treatment of this condition. METHODS: Weighted Gene Co-expression Network Analysis (WGCNA) combined with two machine learning methods were used to identify hub genes strongly associated with plaque instability. The cell-type identification by estimating relative subsets of RNA transcripts (CIBERSORT) method was utilized to assess immune cell infiltration patterns in atherosclerosis patients. Additionally, Gene Set Variation Analysis (GSVA) was conducted to investigate the potential biological functions, pathways, and mechanisms of hub genes associated with unstable plaques. To further validate the diagnostic efficiency and expression of the hub genes, immunohistochemistry (IHC), quantitative real-time polymerase chain reaction (RT-qPCR), and enzyme-linked immunosorbent assay (ELISA) were performed on collected human carotid plaque and blood samples. Immunofluorescence co-staining was also utilized to confirm the association between hub genes and immune cells, as well as their colocalization with mitochondria. RESULTS: The CIBERSORT analysis demonstrated a significant decrease in the infiltration of CD8 T cells and an obvious increase in the infiltration of M0 macrophages in patients with atherosclerosis. Subsequently, two highly relevant modules (blue and green) strongly associated with atherosclerotic plaque instability were identified. Through intersection with mitochondria-related genes, 50 crucial genes were identified. Further analysis employing least absolute shrinkage and selection operator (LASSO) logistic regression and support vector machine recursive feature elimination (SVM-RFE) algorithms revealed six hub genes significantly associated with plaque instability. Among them, NT5DC3, ACADL, SLC25A4, ALDH1B1, and MAOB exhibited positive correlations with CD8 T cells and negative correlations with M0 macrophages, while kynurenine 3-monooxygenas (KMO) demonstrated a positive correlation with M0 macrophages and a negative correlation with CD8 T cells. IHC and RT-qPCR analyses of human carotid plaque samples, as well as ELISA analyses of blood samples, revealed significant upregulation of KMO and MAOB expression, along with decreased ALDH1B1 expression, in both stable and unstable samples compared to the control samples. However, among the three key genes mentioned above, only KMO showed a significant increase in expression in unstable plaque samples compared to stable plaque samples. Furthermore, the expression patterns of KMO in human carotid unstable plaque tissues and cultured mouse macrophage cell lines were assessed using immunofluorescence co-staining techniques. Finally, lentivirus-mediated KMO silencing was successfully transduced into the aortas of high-fat-fed ApoE-/- mice, with results indicating that KMO silencing attenuated plaque formation and promoted plaque stability in ApoE-/- mice. CONCLUSIONS: The results suggest that KMO, a mitochondria-targeted gene associated with macrophage cells, holds promise as a valuable diagnostic biomarker for assessing the instability of atherosclerotic plaques.

Effect on hypoxia/reoxygenation-induced cardiomyocyte injury and Pink1/Parkin pathway.

Our study aimed to detect the effects of proprotein convertase subtilisin/kexin type 9 (PCSK9) on exacerbating cardiomyocyte hypoxia/reoxygenation (H/R) injury and the possible mechanism. A cell model of H/R was constructed. PCSK9 mRNA and protein levels were significantly upregulated during AC16 cardiomyocyte H/R. Flowmetry detection of apoptosis, as well as JC-1, confirmed that PCSK9 upregulation of autophagy levels was accompanied by apoptosis. Furthermore, in the H/R+si-PCSK9 group, the expression of autophagy-related protein LC3 decreased and P62 increased. At the same time, the presentation of the autophagic pathway Pink1/Parkin was also downregulated. In conclusion, in AC16 cardiomyocytes treated with H/R, PCSK9 expression and autophagy levels were increased; a possible molecular mechanism was the activation of the Pink1/Parkin pathway.

PCSK9 regulates myofibroblast transformation through the JAK2/STAT3 pathway to regulate fibrosis after myocardial infarction.

Cardiac fibrosis is pivotal in the progression of numerous cardiovascular diseases. This phenomenon is hallmarked by an excessive deposition of ECM protein secreted by myofibroblasts, leading to increased myocardial stiffness. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease that belongs to the proprotein-converting enzyme family. It has emerged as a viable therapeutic target for reducing plasma low-density lipoprotein cholesterol. However, the exact mechanism via which PCSK9 impacts cardiac fibrosis remains unclear. In the present research, an increase in circulating PCSK9 protein levels was observed in individuals with myocardial infarction and rat models of myocardial infarction. Moreover, the inhibition of circulating PCSK9 in rats was found to reduce post-infarction fibrosis. In vitro experiments further demonstrated that overexpression of PCSK9 or stimulation by extracellular PCSK9 recombinant protein enhanced the transformation of cardiac fibroblasts to myofibroblasts. This process also elevated collagen Ⅰ, and Ⅲ, as well as α-SMA protein levels. However, these effects were countered when co-incubated with the STAT3 inhibitor S3I-201. This study suggests that PCSK9 may function as a novel regulator of myocardial fibrosis, primarily via the JAK2/STAT3 pathway.

PCSK9 Knockdown Can Improve Myocardial Ischemia/Reperfusion Injury by Inhibiting Autophagy.

This study investigates the effect and mechanism of proprotein convertase subtilisin/Kexin type 9 (PCSK9) on myocardial ischemia-reperfusion injury (MIRI) and provides a reference for clinical prevention and treatment of acute myocardial infarction (AMI). We established a rat model of myocardial ischemia/reperfusion (I/R) and AC16 hypoxia/reoxygenation (H/R) model. A total of 48 adult 7-week-old male Sprague-Dawley rats were randomly assigned to three groups (n = 16): control, I/R, and I/R + SiRNA. In I/R and I/R + siRNA groups, myocardial ischemia was induced via occlusion of the left anterior descending branch (LAD) of the coronary artery in rats in I/R group for 30 min and reperfused for 3 days. To assess the myocardial injury, the rats were subjected to an electrocardiogram (ECG), cardiac function tests, cardiac enzymes analysis, and 2,3,5-triphenyl tetrazolium chloride (TTC)/Evan Blue (EB) staining. Meanwhile, differences in the expression of autophagy-level proteins and Bcl-2/adenovirus E1B 19-kDa interacting protein (Bnip3) signaling-related proteins were determined by protein blotting. In vitro and in vivo experimental studies revealed that siRNA knockdown of PCSK9 reduced the expression of autophagic protein Beclin-1, light chain 3 (LC3) compared to normal control-treated cells and control-operated groups. Simultaneously, the expression of Bnip3 pathway protein was downregulated. Furthermore, the PCSK9-mediated small interfering RNA (siRNA) group injected into the left ventricular wall significantly improved cardiac function and myocardial infarct size. In ischemic/hypoxic circumstances, PCSK9 expression was dramatically increased. PCSK9 knockdown alleviated MIRI via Bnip3-mediated autophagic pathway, inhibited inflammatory response, reduced myocardial infarct size, and protected cardiac function.

Influence of static electric field on cognition in mice.

With the rapid development of high voltage direct current transmission, the possibility of health effects associated with static electric field (SEF) has caused wide public concern. To examine the effects of long-lasting, full-body exposure to SEF on cognition, Institute of Cancer Research mice were exposed to SEF for 35 d. The intensities of SEF in experimental group I (EG-I), experimental group II (EG-II) and control group (CG) were 2.30∼15.40 kV/m, 9.20∼21.85 kV/m and 0 kV/m, respectively. The performance in learning and memory of mice were tested by Morris water maze (MWM) on days 2∼6, 16∼20 and 30∼34 during the exposure period. The concentrations of hippocampal amino acid neurotransmitters were evaluated on days 7, 21 and 35. Results showed that the latency in the MWM test had no significant difference among the EG-I, EG-II and CG (P > 0.05) during the exposure period. The percentage of time spent in the target quadrant was significantly decreased in the EG-II on day 34 during the exposure period (P < 0.05), whereas the percentage of time spent in the opposite quadrant increased markedly (P < 0.01). The glutamate and gamma-aminobutyric acid concentrations showed no significant differences among the EG-I, EG-II and CG (P > 0.05) during the exposure period. These results indicated that long-lasting, full-body exposure to SEF with certain intensity would not cause significant influence on learning ability, but it might associate with memory impairment of receptors. Meanwhile, this effect of memory impairment was dose-dependent and not causally linked to the glutamate and gamma-aminobutyric acid levels in the hippocampus.