Type 2 diabetes mellitus (T2DM) is characterized by chronic low-grade systemic inflammation. Tissue infiltration by monocyte migration contributes to the pathogenesis of vascular complications in T2DM. We studied the role of intermediate-conductance Ca²⁺-activated K⁺ (K_Ca3.1) channels in the palmitic acid (PA)-induced migration of peripheral blood mononuclear cells (PBMCs) from T2DM patients and the influence of advanced glycation endproducts (AGEs). A total of 49 T2DM patients and 33 healthy subjects was recruited into this study. Using flow cytometry and Western blotting analysis as well as cell migration assay, we found that there was a significant decrease in frequency of T lymphocytes and monocytes in CD45⁺ leukocyte population. PA at 100 μM stimulated migration of PBMCs from T2DM individuals, which was inhibited by the specific K_Ca3.1 channel blocker TRAM-34 (1 μM). The PBMC migration was positively correlated with glycosylated hemoglobin A1 chain (HbA1c) level of T2DM patients, an indicator of AGEs, and PBMCs with higher level of HbA1c showed upregulated expression of toll-like receptor (TLR) 2/4 and K_Ca3.1 channels. In THP-1 cells, AGEs at 200 μg/ml increased protein expression of TLR 2/4 and K_Ca3.1 channels, and were synergistically involved in PA-induced migration through receptors of AGEs (RAGE)-mediated K_Ca3.1 upregulation. In conclusion, in PBMCs of T2DM patients, AGEs promotes PA-induced migration via upregulation of TLR2/4 and K_Ca3.1 channels.

BACKGROUND: Coronary microvascular hyperpermeability and the subsequent inflammation infiltration are the key early characteristics of pressure overload–induced myocardial injury. However, how changes in the coronary endothelial barrier function in response to cardiac pressure overload are less explored. Here, we investigated the specific role of S1PR1 (sphingosine-1-phosphate receptor type 1) on coronary endothelial permeability and the signaling pathways involved during pressure overload. METHODS: Mice with endothelial deletion of S1PR1 or MYPT1 (myosin phosphatase target subunit 1) were subjected to transverse aortic constriction. We also studied cultured human umbilical vein endothelial cells (ECs) in vitro. RESULTS: We found upregulated S1PR1 in cardiac ECs at 24 hours and 3 days after transverse aortic constriction, and EC-specific deletion of S1PR1 ( S1pr1 ^{Δ EC} ) led to coronary endothelial hyperpermeability, myocardial edema, and inflammatory infiltration in mice subjected to transverse aortic constriction. In cultured human umbilical vein ECs, silencing S1PR1 reduced total MYPT1 but increased phosphorylated MYPT1, and under TNF-α (tumor necrosis factor-α) stimulation led to MLC (myosin light chain) phosphorylation and actin cytoskeletal contraction. Although S1PR1-NFATc2 (Nuclear Factor of Activated T Cells 2) signaling was essential for maintaining MYPT1 expression, S1PR1 deficiency increased TRPV4 (transient receptor potential vanilloid 4) expression, enhancing extracellular Ca ²⁺ entry and MYPT1 phosphorylation. Mice with EC–specifically MYPT1-deficient ( Mypt1 ^{Δ EC} ) also showed coronary endothelial hyperpermeability, and treatment with the S1PR1 agonist FTY720 failed in alleviating the pathological effects. At 1 month post–transverse aortic constriction, both Mypt1 ^{Δ EC} and S1pr1 ^{Δ EC} mice displayed aggravated pathological cardiac remodeling. CONCLUSIONS: These findings suggest that the S1PR1-MYPT1 signaling is crucial for coronary endothelial permeability and myocardial microenvironmental homeostasis under pressure overload, targeting which may offer therapeutic potential for related heart diseases.