Dysregulation of Krüppel-like Factor 2 and Myocyte Enhancer Factor 2D Drive Cardiac Microvascular Inflammation and Dysfunction in Diabetes

High Glucose Treatment Induces Nuclei Aggregation of Microvascular Endothelial Cells via the foxo1a-klf2a Pathway

BACKGROUND

Hyperglycemia is a major contributor to endothelial dysfunction and blood vessel damage, leading to severe diabetic microvascular complications. Despite the growing body of research on the underlying mechanisms of endothelial cell (EC) dysfunction, the available drugs based on current knowledge fall short of effectively alleviating these complications. Therefore, our endeavor to explore novel insights into the cellular and molecular mechanisms of endothelial dysfunction is crucial for the field.

METHODS

In this study, we performed a high-resolution imaging and time-lapse imaging analysis of the behavior of ECs in Tg(kdrl:ras-mCherry::fli1a:nGFP) zebra fish embryos upon high glucose treatment. Genetic manipulation and chemical biology approaches were utilized to analyze the underlying mechanism of high glucose-induced nuclei aggregation and aberrant migration of zebra fish ECs and cultured human ECs. Bioinformatical analysis of single-cell RNA-sequencing data and molecular biological techniques was performed to identify the target genes of foxo1a.

RESULTS

In this study, we observed that the high glucose treatment resulted in nuclei aggregation of ECs in zebra fish intersegmental vessels. Additionally, the aberrant migration of microvascular ECs in high glucose-treated embryos, which might be a cause of nuclei aggregation, was discovered. High glucose induced aggregation of vascular endothelial nuclei via foxo1a downregulation in zebra fish embryos. Then, we revealed that high glucose resulted in the downregulation of foxo1a expression and increased the expression of its direct downstream effector, klf2a, through which the aberrant migration and aggregation of vascular endothelial nuclei were caused.

CONCLUSIONS

High glucose treatment caused the nuclei of ECs to aggregate in vivo, which resembles the crowded nuclei of ECs in microaneurysms. High glucose suppresses foxo1a expression and increases the expression of its downstream effector, klf2a, thereby causing the aberrant migration and aggregation of vascular endothelial nuclei. Our findings provide a novel insight into the mechanism of microvascular complications in hyperglycemia.

MEF2C mitigates coronary artery lesions in Kawasaki disease by enhancing endothelial barrier function through KLF2 regulation

Coronary artery lesions constitute a significant complication of Kawasaki disease (KD) and represents one of the primary etiologies of acquired cardiovascular disease in pediatric populations. In the present study, we observed a downregulation of MEF2C expression in the whole blood of KD patients and in human coronary artery endothelial cells (HCAECs) during the pathophysiological progression of KD. Furthermore, transcriptomic data analysis, in conjunction with observations from HCAECs stimulated with KD serum, indicates that the downregulation of MEF2C in KD is correlated with increased inflammatory levels and the activation of inflammatory pathways. Overexpression of MEF2C has the potential to mitigate inflammation and apoptosis in HCAECs, whereas MEF2C knockdown exhibits contrary effects. Furthermore, MEF2C overexpression may alleviate inflammation and apoptosis in the coronary endothelium, attenuate abdominal aortic dilation, and prevent the decline of cardiac function in a CAWS-induced KD murine model. Mechanistically, MEF2C overexpression safeguards against KD-induced endothelial barrier disruption and the downregulation of endothelial junction proteins in coronary injury associated with KD. Additionally, through RNA sequencing, we identified that KLF2 might be involved in the MEF2C-mediated protection against coronary endothelial injury. Employing a gene interference methodology, we substantiated that MEF2C mitigates coronary artery injury in KD via KLF2-regulated endothelial barrier protection in HCAECs. These findings suggest that MEF2C could serve as a potential therapeutic target for the prevention and treatment of coronary lesions in KD.

Venous thrombosis and obesity: from clinical needs to therapeutic challenges

Weight bias and stigma have limited the awareness of the systemic consequences related to obesity. As the narrative evolves, obesity is emerging as a driver and enhancer of many pathological conditions. Among these, the risk of venous thromboembolism (VTE) is a critical concern linked to obesity, ranking as the third most common cardiovascular condition. Obesity is recognized as a multifactorial risk factor for VTE, influenced by genetic, demographic, behavioral, and socio-economic conditions. Despite established links, the exact incidence of obesity related VTE in the general population remains largely unknown. The complexity of distinguishing between provoked and unprovoked VTE, coupled with gaps in obesity definition and assessment still complicates a tailored risk assessment of VTE risk. Obesity reactivity, hypercoagulability, and endothelial dysfunction are driven by the so-called 'adiposopathy'. This state of chronic inflammation and metabolic disturbance amplifies thrombin generation and alters endothelial function, promoting a pro-thrombotic environment. Additionally, the inflammation-induced clot formation-also referred to as 'immunothrombosis' further exacerbates VTE risk in people living with obesity. Furthermore, current evidence highlights significant gaps in the management of obesity related VTE, particularly concerning prophylaxis and treatment efficacy of anticoagulants in people living with obesity. This review underscores the need for tailored therapeutic approaches and well-designed clinical trials to address the unique challenges posed by obesity in VTE prevention and management. Advanced research and innovative strategies are imperative to improve outcomes and reduce the burden of VTE in people living with obesity.

Krüppel-like factor 2 is an endoprotective transcription factor in diabetic kidney disease

Diabetic kidney disease (DKD) is a microvascular complication of diabetes, and glomerular endothelial cell (GEC) dysfunction is a key driver of DKD pathogenesis. Krüppel-like factor 2 (KLF2), a shear stress-induced transcription factor, is among the highly regulated genes in early DKD. In the kidney, KLF2 expression is mostly restricted to endothelial cells, but its expression is also found in immune cell subsets. KLF2 expression is upregulated in response to increased shear stress by the activation of mechanosensory receptors but suppressed by inflammatory cytokines, both of which characterize the early diabetic kidney milieu. KLF2 expression is reduced in progressive DKD and hypertensive nephropathy in humans and mice, likely due to high glucose and inflammatory cytokines such as TNF-α. However, KLF2 expression is increased in glomerular hyperfiltration-induced shear stress without metabolic dysregulation, such as in settings of unilateral nephrectomy. Lower KLF2 expression is associated with CKD progression in patients with unilateral nephrectomy, consistent with its endoprotective role. KLF2 confers endoprotection by inhibition of inflammation, thrombotic activation, and angiogenesis, and thus KLF2 is considered a protective factor for cardiovascular disease (CVD). Based on similar mechanisms, KLF2 also exhibits renoprotection, and its reduced expression in endothelial cells worsens glomerular injury and albuminuria in settings of diabetes or unilateral nephrectomy. Thus KLF2 confers endoprotective effects in both CVD and DKD, and its activators could potentially be developed as a novel class of drugs for cardiorenal protection in diabetic patients.

Correction: Samak et al. Dysregulation of Krüppel-like Factor 2 and Myocyte Enhancer Factor 2D Drive Cardiac Microvascular Inflammation and Dysfunction in Diabetes. Int. J. Mol. Sci. 2023, 24, 2482

In the original publication [...].

The Molecular and Biological Function of MEF2D in Leukemia

Myocyte enhancer factor 2 (MEF2) is a key transcription factor (TF) in skeletal, cardiac, and neural tissue development and includes four isoforms: MEF2A, MEF2B, MEF2C, and MEF2D. These isoforms significantly affect embryonic development, nervous system regulation, muscle cell differentiation, B- and T-cell development, thymocyte selection, and effects on tumorigenesis and leukemia. This chapter describes the multifaceted roles of MEF2 family proteins, covering embryonic development, nervous system regulation, and muscle cell differentiation. It further elucidates the contribution of MEF2 to various blood and immune cell functions. Specifically, in B-cell precursor acute lymphoblastic leukemia (BCP-ALL), MEF2D is aberrantly expressed and forms a fusion protein with BCL9, CSF1R, DAZAP1, HNRNPUL1, and SS18. These fusion proteins are closely related to the pathogenesis of leukemia. In addition, it specifically introduces the regulatory effect of MEF2D fusion protein on the proliferation and growth of B-cell acute lymphoblastic leukemia (B-ALL) cells. Finally, we detail the positive feedback loop between MEF2D and IRF8 that significantly promotes the progression of acute myeloid leukemia (AML) and the importance of the ZMYND8-BRD4 interaction in regulating the IRF8 and MYC transcriptional programs. The MEF2D-CEBPE axis is highlighted as a key transcriptional mechanism controlling the block of leukemic cell self-renewal and differentiation in AML. This chapter starts with the structure and function of MEF2 family proteins, specifically summarizing and analyzing the role of MEF2D in B-ALL and AML, mediating the complex molecular mechanisms of transcriptional regulation and exploring their implications for human health and disease.