High concentration magnesium inhibits extracellular matrix calcification and protects articular cartilage via Erk/autophagy pathway.

The significant cytopathological changes of osteoarthritis are chondrocyte hypertrophy, proteoglycan loss, extracellular matrix (ECM) calcification, and terminally, the replacement of cartilage by bone. Meanwhile, magnesium ion (Mg2+ ), as the second most abundant divalent cation in the human body, has been proved to inhibit the ECM calcification of hBMSCs (human bone marrow stromal cells), hVSMCs (Human vascular smooth muscle cells), and TDSCs (tendon-derived stem cells) in vitro studies. The ATDC5 cell line, which holds chondrocyte characteristics, was used in this study as an in vitro subject. We found that Mg2+ can efficiently suppress the ECM calcification and downregulate both hypertrophy and matrix metalloproteinase-related genes. Meanwhile, Mg2+ inhibits the formation of autophagy by inhibiting Erk phosphorylation signaling and lowers the expression of LC3, and eventually effectively reduces the formation of ECM calcification in vitro. In this study, we also used destabilization of the medial meniscus (DMM)-induced osteoarthritis (OA) animal model to further confirm the protective effect of Mg2+ on articular cartilage. Compared with the control group (saline-injected), continuous intra-articular magnesium chloride (MgCl2 ) injection can significantly alleviate the severity of cartilage calcification in OA animal model. Immunofluorescence staining also revealed that saline-injected DMM group had a higher positive rate of LC3 expression in cartilage chondrocytes, compared with MgCl2 -injected DMM group. In general, Mg2+ can significantly downregulate the hypertrophic gene Runx2, MMP13, and Col10α1, upregulate the chondrogenic genes Sox9 and Col1α1, inhibit the Erk phosphorylation signaling, reduce the expression of autophagy protein LC3, and effectively inhibit the ECM calcification of ATDC5. In vivo study also proved that intra-articular injection of Mg2+ protected knee cartilage by inhibiting the autophagy formation.

Unfractionated Heparin Alleviates Human Lung Endothelial Barrier Dysfunction Induced by High Mobility Group Box 1 Through Regulation of P38-GSK3ß-Snail Signaling Pathway.

BACKGROUND/AIMS: The high mobility group box 1 (HMGB1) has been regarded as an important inflammatory mediator. Previous studies showed the involvement of HMGB1 protein in the dysfunction of endothelial barrier function during acute lung injury. However, the molecular mechanism remains unclear. METHODS: In this study, we used recombinant human HMGB1 (rhHMGB1) and HMGB1 plasmid to treat human pulmonary microvascular endothelial cell (HPMECs). We examined endothelial permeability by measuring TEER value and HRP flux. Western blot and real-time PCR were used to examined change of endothelial-to-mesenchymal transition (EndoMT) markers and related pathways. Immunofluorescence was used to examine localization and expression of ZO-1 and VE-cadherin. SB203580.was used to block p38 pathway. Unfractionated heparin (UFH) and RAGE siRNA were also used to antagonize the effect of HMGB1. RESULTS: We showed that HMGB1 induced EndoMT with downregulation of ZO-1 and VE-cadherin at both mRNA and protein levels in HPMECs. We also demonstrated that HMGB1 upregulated endothelial permeability by measuring TEER value and HRP flux. Moreover, HMGB1 activated p38/GSK3ß/Snail signaling pathway and treatment with p38 inhibitor SB203580 abolished its biological effects. In addition, we found that UFH was able to reverse the effect of HMGB1 on EndoMT and endothelial permeability through inhibition of p38 signaling in a dose-dependent manner. We discovered that RAGE, a membrane receptor of HMGB1, transduced p38/Snail pathway to EndoMT. RAGE siRNA inhibited the effect of HMGB1 induced EndoMT in HPMECs. CONCLUSION: The present study demonstrated that HMGB1 induced EndoMT through RAGE receptor and p38/GSK3ß/Snail pathway. While UFH antagonized HMGB1 and maintained the integrity of the endothelial barrier through p38 inhibition.

[The role of mitochondrial permeability transition pore in the occurrence of septic myocardial depression].

OBJECTIVE: Sepsis is defined as life-threatening organ dysfunction caused by a dys-regulated host response to infection and septic myocardial depression (SMD) is a common complication. Pathogenesis of SMD is complicated and there is lack of specific treatment. Mitochondrial damage is an important pathological basis of SMD, and mitochondrial permeability transition pore (MPTP) plays an important role in maintaining the normal structure and function of the mitochondria. The change of MPTP during sepsis is summarized in this review so as to reveal the significant mechanism of MPTP in the occurrence of SMD.

Magnesium inhibits the calcification of the extracellular matrix in tendon-derived stem cells via the ATP-P2R and mitochondrial pathways.

Tendon calcification has been widely regarded by researchers to result from the osteogenic differentiation of Tendon-Derived Stem Cells (TDSCs) and ectopic mineralization caused by the calcification of cellular matrix. Recent studies have revealed a correlation between the Mg(2+)/Ca(2+) balance and the degeneration or calcification of tendon tissues. Furthermore, the ATP-P2X/P2Y receptor pathway has been shown to play a decisive role in the process of calcification, with calcium exportation from mitochondria and calcium oscillations potentially representing the cohesive signal produced by this pathway. Our previous study demonstrated that matrix calcification is inhibited by magnesium. In this study, we examined the effects of extracellular Mg(2+) on the deposition of calcium phosphate matrix and cellular pathways in TDSCs. The suppression of the export of calcium from mitochondria has also been detected. We found that a high concentration of extracellular Mg(2+) ([Mg(2+)]e) inhibited the mineralization of the extracellular matrix in TDSCs and that 100 µM ATP reversed this inhibitory effect in vitro. In addition, the spontaneous release of ATP was inhibited by high [Mg(2+)]e levels. A high [Mg(2+)]e suppressed the expression of P2X4, P2X5 and P2X7 and activated the expression of P2Y1, P2Y2, P2Y4 and P2Y14. The interaction between Mg(2+) and Ca(2+) is therefore contradictory, Mg(2+) inhibits mitochondrial calcium concentrations, meanwhile it reverses the opening of mPTP that is induced by Ca(2+). JC-1 staining verified the protective effect of Mg(2+) on mitochondrial membrane potential and the decrease induced by Ca(2+). Taken together, these results indicate that high [Mg(2+)]e interferes with the expression of P2 receptors, resulting in decreased extracellular mineralization. The balance between Mg(2+) and Ca(2+) influences mitochondrial calcium exportation and provides another explanation for the mechanism underlying matrix calcification in TDSCs.