Suppressing Syndecan-1 Shedding to Protect Against Renal Ischemia/Reperfusion Injury by Maintaining Polarity of Tubular Epithelial Cells

RBT-1, a "preconditioning" agent, mitigates syndecan-1 shedding in patients undergoing "on pump" cardiac surgery and following experimental AKI

During systemic stress, syndecan-1 (SDC-1) shedding into plasma results, implying endothelial damage. RBT-1, a "preconditioning" agent, has been shown to mitigate postoperative complications following cardiac surgeries. This study assessed whether RBT-1 preconditioning attenuated SDC-1 shedding in these patients, implying a vascular protective effect. Patients (n, 112) were randomized to receive low-dose RBT-1, high-dose RBT-1, or placebo 24-48 h prior to surgery. Plasma samples were obtained before and 2 days postsurgery and assayed for SDC-1 (ELISA). To gain further insights, male CD-1 mice were subjected to acute renal injuries, and RBT-1's impact on plasma SDC-1 increases, vascular/aortic stress responses (NGAL/KIM-1/IL-6 gene induction), and two vascular cytoprotective pathways (Nrf2; ferritin) were assessed. Baseline plasma SDC-1 levels did not differ between patient groups. The placebo group developed an approximate 50% plasma SDC-1 (ng/mL) increase (p, 0.012). Conversely, no significant SDC-1 increases were seen in the RBT-1 treatment groups. Experimental injury markedly increased plasma SDC-1 concentrations, and these were significantly blunted by RBT-1 preconditioning. RBT-1 also mitigated AKI-induced aortic NGAL/KIM-1/IL-6 mRNA increases, activated aortic Nrf2, and increased vascular ferritin levels. RBT-1 preconditioning diminishes SDC-1 release and upregulates vascular ferritin and Nrf2. Hence, RBT-1 preconditioning can confer select vasoprotective effects.

Syndecan-1 shedding destroys epithelial adherens junctions through STAT3 after renal ischemia/reperfusion injury

Adherens junctions between tubular epithelial cells are disrupted in renal ischemia/reperfusion (I/R) injury. Syndecan-1 (SDC-1) is involved in maintaining cell morphology. We aimed to study the role of SDC-1 shedding induced by renal I/R in the destruction of intracellular adherens junctions. We found that SDC-1 shedding was increased while the expression of E-cadherin was decreased. This observation was accompanied by the activation of STAT3 in the kidneys. Inhibiting the shedding of SDC-1 induced by I/R could alleviate this effect. Mild renal I/R could induce more severe renal injury, lower E-cadherin expression, damaged cell junctions, and activated STAT3 in knockout mice with the tubule-specific deletion of SDC-1 mice. The results in vitro were consistent with those in vivo. Inhibiting the shedding of SDC-1 could alleviate the decreased expression of E-cadherin and damage of cell adherens junctions through inhibiting the activation of STAT3 during ischemic acute kidney injury.

Extracellular matrix-induced signaling pathways in mesenchymal stem/stromal cells

The extracellular matrix (ECM) is a crucial component of the stem cell microenvironment, or stem-cell niches, and contributes to the regulation of cell behavior and fate. Accumulating evidence indicates that different types of stem cells possess a large variety of molecules responsible for interactions with the ECM, mediating specific epigenetic rearrangements and corresponding changes in transcriptome profile. Signals from the ECM are crucial at all stages of ontogenesis, including embryonic and postnatal development, as well as tissue renewal and repair. The ECM could regulate stem cell transition from a quiescent state to readiness to perceive the signals of differentiation induction (competence) and the transition between different stages of differentiation (commitment). Currently, to unveil the complex networks of cellular signaling from the ECM, multiple approaches including screening methods, the analysis of the cell matrixome, and the creation of predictive networks of protein-protein interactions based on experimental data are used. In this review, we consider the existing evidence regarded the contribution of ECM-induced intracellular signaling pathways into the regulation of stem cell differentiation focusing on mesenchymal stem/stromal cells (MSCs) as well-studied type of postnatal stem cells totally depended on signals from ECM. Furthermore, we propose a system biology-based approach for the prediction of ECM-mediated signal transduction pathways in target cells. Video Abstract.

Magnesium Lithospermate B Protects Against Cisplatin-Induced Acute Kidney Injury via Alleviating Mitochondrial Dysfunction

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