Age Impairs Soluble Guanylyl Cyclase Function in Mouse Mesenteric Arteries

Endothelial dysfunction (ED) comes with age, even without overt vessel damage such as that which occurs in atherosclerosis and diabetic vasculopathy. We hypothesized that aging would affect the downstream signalling of the endothelial nitric oxide (NO) system in the vascular smooth muscle (VSM). With this in mind, resistance mesenteric arteries were isolated from 13-week (juvenile) and 40-week-old (aged) mice and tested under isometric conditions using wire myography. Acetylcholine (ACh)-induced relaxation was reduced in aged as compared to juvenile vessels. Pretreatment with L-NAME, which inhibits nitrix oxide synthases (NOS), decreased ACh-mediated vasorelaxation, whereby differences in vasorelaxation between groups disappeared. Endothelium-independent vasorelaxation by the NO donor sodium nitroprusside (SNP) was similar in both groups; however, SNP bolus application (10−6 mol L−1) as well as soluble guanylyl cyclase (sGC) activation by runcaciguat (10−6 mol L−1) caused faster responses in juvenile vessels. This was accompanied by higher cGMP concentrations and a stronger response to the PDE5 inhibitor sildenafil in juvenile vessels. Mesenteric arteries and aortas did not reveal apparent histological differences between groups (van Gieson staining). The mRNA expression of the α1 and α2 subunits of sGC was lower in aged animals, as was PDE5 mRNA expression. In conclusion, vasorelaxation is compromised at an early age in mice even in the absence of histopathological alterations. Vascular smooth muscle sGC is a key element in aged vessel dysfunction.

Coronary Large Conductance Ca2+-Activated K+ Channel Dysfunction in Diabetes Mellitus

Diabetes mellitus (DM) is an independent risk of macrovascular and microvascular complications, while cardiovascular diseases remain a leading cause of death in both men and women with diabetes. Large conductance Ca2+-activated K+ (BK) channels are abundantly expressed in arteries and are the key ionic determinant of vascular tone and organ perfusion. It is well established that the downregulation of vascular BK channel function with reduced BK channel protein expression and altered intrinsic BK channel biophysical properties is associated with diabetic vasculopathy. Recent efforts also showed that diabetes-associated changes in signaling pathways and transcriptional factors contribute to the downregulation of BK channel expression. This manuscript will review our current understandings on the molecular, physiological, and biophysical mechanisms that underlie coronary BK channelopathy in diabetes mellitus.

Alternative Splicing: A Key Mediator of Diabetic Vasculopathy

Cardiovascular disease is the leading cause of death amongst diabetic individuals. Atherosclerosis is the prominent driver of diabetic vascular complications, which is triggered by the detrimental effects of hyperglycemia and oxidative stress on the vasculature. Research has extensively shown diabetes to result in the malfunction of the endothelium, the main component of blood vessels, causing severe vascular complications. The pathogenic mechanism in which diabetes induces vascular dysfunction, however, remains largely unclear. Alternative splicing of protein coding pre-mRNAs is an essential regulatory mechanism of gene expression and is accepted to be intertwined with cellular physiology. Recently, a role for alternative splicing has arisen within vascular health, with aberrant mis-splicing having a critical role in disease development, including in atherosclerosis. This review focuses on the current knowledge of alternative splicing and the roles of alternatively spliced isoforms within the vasculature, with a particular focus on disease states. Furthermore, we explore the recent elucidation of the alternatively spliced QKI gene within vascular cell physiology and the onset of diabetic vasculopathy. Potential therapeutic strategies to restore aberrant splicing are also discussed.

­PlGF Regulates Angiopoietin-1 and Tie-2 Expression in Human Retinal Endothelial Cell-Pericyte Cocultures and iPSC-Derived Vascular Organoids through VEGFR1

Placental growth factor (PlGF) and Angiopoietin (Ang)-1 are two angiogenic factors that play vital roles in vascular cell growth and stabilization. The present study's objective is to examine PlGF's regulation of Ang-1 and its Tie-2 receptor expression in human vascular cells and vasculature. We exploited the cocultures of human primary retinal endothelial cells (HREC) and pericytes (HRP) and the blood vessel or vascular organoids derived from human-induced pluripotent stem cells (iPSC) as experimental models. In the HREC-HRP cocultures, PlGF blockage upregulated the expressions of Ang-1 and Tie-2 in an antibody dose-dependent manner. Upregulation of Ang-1 and Tie-2 by PlGF blockade did not occur in HREC and HRP monocultures but only in HREC-HRP cocultures, indicating the interactions of the two cell types. VEGFR1 inhibition diminished Ang-1 and Tie-2 upregulation caused by PlGF blockade and reduced pericyte variability in high glucose conditions. In the iPSC-derived vascular organoids (VO), PlGF, Ang-1, and Ang-2 were expressed mainly by perivascular cells. Bioinformatics analysis of RNA sequencing data revealed that diabetes-mimicking conditions upregulated PlGF and Ang-2 expressions in the VO cultures. PlGF blockade upregulated Ang-1 and Tie-2 expression and promoted pericyte coverage and association with ECs in the VO. Together, the data suggest that PlGF regulates Ang-1 and Tie-2 expression in part through VEGFR1, which is involved in vascular cell function and stabilization. The findings may help design new therapeutic interventions for diabetic vasculopathy, such as diabetic macular edema and proliferative diabetic retinopathy, by targeting PlGF and Ang signaling pathways.

Cell Therapy for Critical Limb Ischemia: Advantages, Limitations, and New Perspectives for Treatment of Patients with Critical Diabetic Vasculopathy

Purpose of Review To provide a highlight of the current state of cell therapy for the treatment of critical limb ischemia in patients with diabetes. Recent Findings The global incidence of diabetes is constantly growing with consequent challenges for healthcare systems worldwide. In the UK only, NHS costs attributed to diabetic complications, such as peripheral vascular disease, amputation, blindness, renal failure, and stroke, average £10 billion each year, with cost pressure being estimated to get worse. Although giant leaps forward have been registered in the scope of early diagnosis and optimal glycaemic control, an effective treatment for critical limb ischemia is still lacking. The present review aims to provide an update of the ongoing work in the field of regenerative medicine. Recent advancements but also limitations imposed by diabetes on the potential of the approach are addressed. In particular, the review focuses on the perturbation of non-coding RNA networks in progenitor cells and the possibility of using emerging knowledge on molecular mechanisms to design refined protocols for personalized therapy. Summary The field of cell therapy showed rapid progress but has limitations. Significant advances are foreseen in the upcoming years thanks to a better understanding of molecular bottlenecks associated with the metabolic disorders.

Exploring the Protective Effect of ShenQi Compound on Skeletal Muscle in Diabetic Macrovasculopathy Mice

Objective: ShenQi compound (SQC) is a traditional herbal formula, which has been used to treat Type 2 diabetes mellitus (T2DM) and complications for years. The aim of this study was to explore the preventive and protective effects of SQC recipe on the skeletal muscle of diabetic macrovasculopathy mice, which provides a theoretical basis for the clinical use of this formula. Methods: We evaluated the effect of SQC in a diabetic vasculopathy mouse model by detecting a series of blood indicators (blood glucose, lipids and insulin) and performing histological observations. Meanwhile, we explored the molecular mechanism of SQC treatment on skeletal muscle by genome expression profiles. Results: The results indicated that SQC could effectively improve blood glucose, serum lipids (total cholesterol (TC), Triglyceride (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C)) and insulin (INS) levels in diabetic vasculopathy mice, as well as alleviating skeletal muscle tissue damage for diabetic macrovasculopathy. Meanwhile, compared with rosiglitazone, SQC showed a better effect on blood glucose fluctuation. Moreover, the gene microarray analysis indicated that SQC might improve T2DM by affecting biological functions related to cell death and cell adhesion. Moreover, 7 genes (Celsr2, Rilpl1, Dlx6as, 2010004M13Rik, Anapc13, Gm6097, Ddx39b) might be potential therapeutic targets of SQC. Conclusion: All these results indicate that SQC is an effective preventive and protective drug for skeletal muscle in diabetic macrovasculopathy, and could alleviate skeletal muscle tissue damage through affecting biological functions related to cell death and cell adhesion.

HIF-transcribed p53 chaperones HIF-1α

Chronic hypoxia is associated with a variety of physiological conditions such as rheumatoid arthritis, ischemia/reperfusion injury, stroke, diabetic vasculopathy, epilepsy and cancer. At the molecular level, hypoxia manifests its effects via activation of HIF-dependent transcription. On the other hand, an important transcription factor p53, which controls a myriad of biological functions, is rendered transcriptionally inactive under hypoxic conditions. p53 and HIF-1α are known to share a mysterious relationship and play an ambiguous role in the regulation of hypoxia-induced cellular changes. Here we demonstrate a novel pathway where HIF-1α transcriptionally upregulates both WT and MT p53 by binding to five response elements in p53 promoter. In hypoxic cells, this HIF-1α-induced p53 is transcriptionally inefficient but is abundantly available for protein-protein interactions. Further, both WT and MT p53 proteins bind and chaperone HIF-1α to stabilize its binding at its downstream DNA response elements. This p53-induced chaperoning of HIF-1α increases synthesis of HIF-regulated genes and thus the efficiency of hypoxia-induced molecular changes. This basic biology finding has important implications not only in the design of anti-cancer strategies but also for other physiological conditions where hypoxia results in disease manifestation.