Aldose reductase modulates acute activation of mesenchymal markers via the β-catenin pathway during cardiac ischemia-reperfusion

Cell type-specific regulation of the pentose phosphate pathway during development and metabolic stress-driven autoimmune diseases: Relevance for inflammatory liver, renal, endocrine, cardiovascular and neurobehavioral comorbidities, carcinogenesis, and aging

The pathogenesis of autoimmunity is incompletely understood which limits the development of effective therapies. New compelling evidence indicates that the pentose phosphate pathway (PPP) profoundly regulate lineage development in the immune system that are influenced by genetic and environmental factors during metabolic stress underlying the development of autoimmunity. The PPP provides two unique metabolites, ribose 5-phosphate for nucleotide biosynthesis in support of cell proliferation and NADPH for protection against oxidative stress. The PPP operates two separate branches, oxidative (OxPPP) and non-oxidative (NOxPPP). While the OxPPP functions in all organisms, the NOxPPP reflects adaptation to niche-specific metabolic requirements. The OxPPP primarily depends on glucose 6-phosphate dehydrogenase (G6PD), whereas transaldolase (TAL) controls the rate and directionality of metabolic flux though the NOxPPP. G6PD is essential for normal development but its partial deficiency protects from malaria. Although men and mice lacking TAL develop normally, they exhibit liver cirrhosis progressing to hepatocellular carcinoma. Mechanistic target of rapamycin-dependent loss of paraoxonase 1 drives autoimmunity and cirrhosis in TAL deficiency, while hepatocarcinogenesis hinges on polyol pathway activation via aldose reductase (AR). Accumulated polyols, such as erythritol, xylitol, and sorbitol, which are commonly used as non-caloric sweeteners, may act as pro-inflammatory oncometabolites under metabolic stress, such as TAL deficiency. The TAL/AR axis is identified as a checkpoint of pathogenesis and target for treatment of metabolic stress-driven systemic autoimmunity with relevance for inflammatory liver, renal and cardiovascular disorders, diabetes, carcinogenesis, and aging.

Aldose Reductase: An Emerging Target for Development of Interventions for Diabetic Cardiovascular Complications

Diabetes is a leading cause of cardiovascular morbidity and mortality. Despite numerous treatments for cardiovascular disease (CVD), for patients with diabetes, these therapies provide less benefit for protection from CVD. These considerations spur the concept that diabetes-specific, disease-modifying therapies are essential to identify especially as the diabetes epidemic continues to expand. In this context, high levels of blood glucose stimulate the flux via aldose reductase (AR) pathway leading to metabolic and signaling changes in cells of the cardiovascular system. In animal models flux via AR in hearts is increased by diabetes and ischemia and its inhibition protects diabetic and non-diabetic hearts from ischemia-reperfusion injury. In mouse models of diabetic atherosclerosis, human AR expression accelerates progression and impairs regression of atherosclerotic plaques. Genetic studies have revealed that single nucleotide polymorphisms (SNPs) of the ALD2 (human AR gene) is associated with diabetic complications, including cardiorenal complications. This Review presents current knowledge regarding the roles for AR in the causes and consequences of diabetic cardiovascular disease and the status of AR inhibitors in clinical trials. Studies from both human subjects and animal models are presented to highlight the breadth of evidence linking AR to the cardiovascular consequences of diabetes.

NR4A1 silencing protects against renal ischemia-reperfusion injury through activation of the β-catenin signaling pathway in old mice

Renal ischemia-reperfusion injury (IRI), a major cause of acute kidney injury as well as a contributor to a rapid kidney dysfunction and high mortality rates, is a complex yet not fully understood process. Investigation on the underlying molecular mechanism including the inflammation initiation and progression can help to have a better understanding of the disease, and thereby lead to a potential therapeutic approach. We established renal IRI mouse model groups differing in their ages. These renal IRI mice were treated either only with si-nuclear receptor subfamily 4, group A, member 1 (NR4A1) or together with si-β-catenin by tail vein injection to analyze the role of NR4A1 and β-catenin in the development of renal IRI. Serum creatinine (SCr) and blood urea nitrogen (BUN) levels were examined for renal function analysis. Levels of the apoptosis markers B-cell lymphoma-2 (Bcl-2), Bcl-2 associated protein X (Bax), and cleaved caspase-3 were determined. NR4A1 gene was up-regulated in the renal tissues of all mice with IRI, which showed a much higher level in the old mice with IRI. si-NR4A1 treatment resulted in reduced SCr and BUN levels and a decrease of cell apoptosis, indicated by lower expression of Bax and cleaved Caspase-3, while in contrast increased levels of Bcl-2 were detected. Interestingly, also the β-catenin level was increased by knockdown of NR4A1. Furthermore, si-β-catenin reversed the effect of knockdown of NR4A1, leading to aggravated renal function damage, severe pathological injury and increased apoptosis. Thus, silencing NR4A1 ameliorates renal IRI via β-catenin signaling pathway activation. Down-regulated NR4A1 confirms renoprotective properties against renal IRI via the activation of β-catenin signaling pathway in old mice.