Sodium Butyrate Induces Apoptosis of Human Colon Cancer Cells by Modulating ERK and Sphingosine Kinase 2

Objective To investigate the role of extracellular signal-regulated kinase （ERK） in apoptosis of human colon cancer （HCT116） cells. Methods After the HCT116 cells were pretreated with specific ERK inhibitor （U0126） or specific siRNA and exposed to 10 mmol/L sodium butyrate （NaBT） for 24 h, their apoptosis was detected by flow cytometry, levels of SphK2 and ERK protein were measured by Western blot, and translocation of SphK2 was assayed by immunofluorescence microscopy. Results The U0126 and siRNAs specific for SphK2 blocked the export of SphK2 from nuclei to cytoplasm and increased the apoptosis of HCT116 cells following NaBT exposure. Over-expression of PKD decreased NaBT-induced apoptosis of HCT116 cells, which was reversed by U0126. Furthermore, transfection of HCT116 cells with constitutively activated PKD plasmids recovered the UO126-blocked export of SphK2. Conclusion ERK regulates the export of SphK2 and apoptosis of HCT116 cells by modulating PKD. Modulation of these molecules may help increase the sensitivity of colon cancer cells to the physiologic anti-colon cancer agent, NaBT.

Sphingosine-1-Phosphate Protects Against the Development of Cardiac Remodeling via Sphingosine Kinase 2 and the S1PR2/ERK Pathway

Objective:Cardiac remodeling is a common pathological change in various cardiovascular diseases and can ultimately result in heart failure.Thus,there is an urgent need for more effective strategies to aid in cardiac protection.Our previous work found that sphingosine-1-phosphate(S1P)could ameliorate cardiac hypertrophy.In this study,we aimed to investigate whether S1P could prevent cardiac fibrosis and the associated mechanisms in cardiac remodeling.Methods:Eight-week-old male C57BL/6 mice were randomly divided into a sham,transverse aortic constriction(TAC)or a TAC+S1P treatment group.Results:We found that S1P treatment improved cardiac function in TAC mice and that the cardiac fibrosis ratio in the TAC+S1P group was significantly lower and was accompanied by a decrease inα-smooth muscle actin(α-SMA)and collagen type I(COL I)expression compared with the TAC group.We also found that one of the key S1P enzymes,sphingosine kinase 2(SphK2),which was mainly distributed in cytoblasts,was downregulated in the cardiac remodeling case and recovered after S1P treatment in vivo and in vitro.In addition,our in vitro results showed that S1P treatment activated extracellular regulated protein kinases(ERK)phosphorylation mainly through the S1P receptor 2(S1PR2)and spurred p-ERK transposition from the cytoplasm to cytoblast in H9c2 cells exposed to phenylephrine.Conclusion:These findings suggest that SphK2 and the S1PR2/ERK pathway may participate in the anti-remodeling effect of S1P on the heart.This work therefore uncovers a novel potential therapy for the prevention of cardiac remodeling.

Sphingosine-1-phosphate signaling and the gut-liver axis in liver diseases

The liver is the central organ involved in lipid metabolism and the gastrointestinal(GI)tract is responsible for nutrient absorption and partitioning.Obesity,dyslipidemia and metabolic disorders are of increasing public health concern worldwide,and novel therapeutics that target both the liver and the GI tract(gut-liver axis)are much needed.In addition to aiding fat digestion,bile acids act as important signaling molecules that regulate lipid,glucose and energy metabolism via activating nuclear receptor,G protein-coupled receptors(GPCRs),Takeda G protein receptor 5(TGR5)and sphingosine-1-phosphate receptor 2(S1PR2).Sphingosine-1-phosphate(S1P)is synthesized by two sphingosine kinase isoforms and is a potent signaling molecule that plays a critical role in various diseases such as fatty liver,in-flammatory bowel disease(IBD)and colorectal cancer.In this review,we will focus on recent findings related to the role of S1P-mediated signaling pathways in the gut-liver axis.

Injectable cartilage matrix hydrogel loaded with cartilage endplate stem cells engineered to release exosomes for non-invasive treatment of intervertebral disc degeneration

Low back pain,mainly caused by intervertebral disc degeneration(IVDD),is a common health problem;however,current surgical treatments are less than satisfactory.Thus,it is essential to develop novel non-invasive surgical methods for IVDD treatment.Here,we describe a therapeutic strategy to inhibit IVDD by injecting hydrogels modified with the extracellular matrix of costal cartilage(ECM-Gels)that are loaded with cartilage endplate stem cells(CESCs).After loaded with CESCs overexpressing Sphk2(Lenti-Sphk2-CESCs)and injected near the cartilage endplate(CEP)of rats in vivo,ECM-Gels produced Sphk2-engineered exosomes(Lenti-Sphk2-Exos).These exosomes penetrated the annulus fibrosus(AF)and transported Sphk2 into the nucleus pulposus cells(NPCs).Sphk2 activated the phosphatidylinositol 3-kinase(PI3K)/p-AKT pathway as well as the intracellular autophagy of NPCs,ultimately ameliorating IVDD.This study provides a novel and efficient non-invasive combinational strategy for IVDD treatment using injectable ECM-Gels loaded with CESCs that express Sphk2 with sustained release of functional exosomes.

Bile acids as global regulators of hepatic nutrient metabolism

Bile acids(BA)are synthesized from cholesterol in the liver.They are essential for promotion of the absorption of lipids,cholesterol,and lipid-soluble vitamins from the intestines.BAs are hormones that regulate nutrient metabolism by activating nuclear receptors(farnesoid X receptor(FXR),pregnane X receptor,vitamin D)and G protein-coupled receptors(e.g.,TGR5,sphingosine-1-phosphate receptor 2(S1PR2))in the liver and intestines.In the liver,S1PR2 activation by conjugated BAs activates the extracellular signal-regulated kinase 1/2 and AKT signaling pathways,and nuclear sphingosine kinase 2.The latter produces sphingosine-1-phosphate(S1P),an inhibitor of histone deacetylases 1/2,which allows for the differential up-regulation of expression of genes involved in the metabolism of sterols and lipids.We discuss here the emerging concepts of the interactions of BAs,FXR,insulin,S1P signaling and nutrient metabolism.