Glucal-conjugated sterols as novel vascular leakage blocker: Structure–activity relationship focusing on the C17-side chain

GPR30-driven fatty acid oxidation targeted by ginsenoside Rd maintains mitochondrial redox homeostasis to restore vascular barrier in diabetic retinopathy

Blood-retinal barrier (BRB) breakdown, a pivotal contributor to multiple retinal vascular diseases, manifests as a progressive increase in vascular permeability induced by various pathological stimuli. The functional plasticity of retinal endothelial cells can be intricately shaped by metabolic alteration. However, little is known about the mechanisms through which endothelial metabolic disorders trigger the dissolution of inter-vascular junctions and the selective approaches to targeting metabolic homeostasis. Herein, we identify AMPK-associated fatty acid oxidation (FAO) inhibition as a critical driver of vascular barrier dysfunction via exacerbating redox imbalance. Pharmacological facilitation of FAO by ginsenoside Rd (Rd) suppresses BRB collapse and other secondary retinal damage in diabetic retinopathy (DR). Mechanistically, Rd targets GPR30 to phosphorylate AMPK via the PKA-LKB1-AMPK kinase cascade. The AMPK activation induced by Rd revitalizes hyperglycemia-compromised FAO, and then sustains mitochondrial NADPH regeneration by emphasis on IDH2 at various levels, including substrate supply, transcription, and post-translational modifications. Therefore, Rd alleviates the disruption of BRB integrity driven by mitochondrial oxidative stress, with the vasculoprotection of Rd diminished by GPR30 knockdown and pharmacological attenuation of AMPK. These findings collectively reveal the previously-unanticipated role of endothelial FAO in heightened retinal vascular leakage, and highlight the potential translational application of GPR30 agonism with Rd to mitigate barrier dysfunction, providing a metabolic regulatory therapeutic strategy for DR.

Ginsenoside Rk1 improves endothelial function in diabetes through activating peroxisome proliferator-activated receptors

Ginsenoside Rk1, one kind of ginsenoside, is a minor ginsenoside found in Panax ginseng and used as traditional Chinese medicine for centuries. It exhibits anti-tumor and anti-aggregation effects. However, little research has been done on its effect on endothelial function. This study investigated whether ginsenoside Rk1 improved endothelial dysfunction in diabetes and the underlying mechanisms in vivo and in vitro. Male C57BL/6 mice were fed with a 12 week high-fat diet (60% kcal % fat), whereas treatment groups were orally administered with ginsenoside Rk1 (10 and 20 mg per kg per day) in the last 4 weeks. Aortas isolated from C57BL/6 mice were induced by high glucose (HG; 30 mM) and co-treated with or without ginsenoside Rk1 (1 and 10 μM) for 48 h ex vivo. Moreover, primary rat aortic endothelial cells (RAECs) were cultured and stimulated by HG (44 mM) to mimic hyperglycemia, with or without the co-treatment of ginsenoside Rk1 (10 μM) for 48 h. Endothelium-dependent relaxations of mouse aortas were damaged with elevated oxidative stress and downregulation of three isoforms of peroxisome proliferator-activated receptors (PPARs), PPAR-α, PPAR-β/δ, and PPAR-γ, as well as endothelial nitric oxide synthase (eNOS) phosphorylation due to HG or high-fat diet stimulation, which also existed in RAECs. However, after the treatment with ginsenoside Rk1, these impairments were all ameliorated significantly. Moreover, the vaso-protective and anti-oxidative effects of ginsenoside Rk1 were abolished by PPAR antagonists (GSK0660, GW9662 or GW6471). In conclusion, this study reveals that ginsenoside Rk1 ameliorates endothelial dysfunction and suppresses oxidative stress in diabetic vasculature through activating the PPAR/eNOS pathway.

Ultrasound accelerated synthesis of O-alkylated hydroximides under solvent- and metal-free conditions

A novel, sustainable, environmentally friendly, high substrate scope, efficient, solvent-free and metal catalyst-free method for the cross-dehydrogenative coupling (CDC) reaction between N-hydroxyphthalimide (NHPI) and benzyl/ether compounds is described. This coupling reaction proceeds through ultrasound acceleration. Compared to conventional heating conditions, the use of ultrasound techniques not only improves the reaction efficiency and enhances the reaction rate but also minimizes the side reactions.

Ginsenoside Rk1 suppresses pro-inflammatory responses in lipopolysaccharide-stimulated RAW264.7 cells by inhibiting the Jak2/Stat3 pathway

The saponin ginsenoside Rk1 is a major compound isolated from ginseng. Ginsenoside Rk1 has been reported to have anti-inflammatory and anti-tumor properties and to be involved in the regulation of metabolism. However, the effect and mechanism of anti-inflammatory action of ginsenoside Rk1 has not been fully clarified. We investigated whether ginsenoside Rk1 could suppress the inflammatory response in lipopolysaccharide-stimulated RAW264.7 macrophages and to explore its mechanism of the action. RAW264.7 cells were treated with LPS (1 μg·mL^-1) in the absence or the presence of Ginsenoside Rk1 (10, 20, and 40 μmol·L^-1). Then the inflammatory factors were tested with Griess reagents, ELISA, and RT-PCR. The proteins were analyzed by Western blotting. Ginsenoside Rk1 inhibited lipopolysaccharide-induced expression of nitric oxide (NO), interleukin (IL)-6, IL-1β, tumor necrosis factor (TNF)-α, and monocyte chemotactic protein (MCP)-1. Ginsenoside Rk1 inhibited the lipopolysaccharide-stimulated phosphorylation of NF-κB and janus kinase (Jak)2 and signal transducer and activator of transcription (Stat)3 at Ser727 and Tyr705. These data suggested that ginsenoside Rk1 could inhibit expression of inflammatory mediators and suppress inflammation further by blocking activation of NF-κB and the Jak2/Stat3 pathway in LPS-stimulated RAW264.7 cells.