Exosomes Derived from Glioma Cells under Hypoxia Promote Angiogenesis through Up-regulated Exosomal Connexin 43.

Glioblastoma multiform (GBM) is a highly aggressive primary brain tumor. Exosomes derived from glioma cells under a hypoxic microenvironment play an important role in tumor biology including metastasis, angiogenesis and chemoresistance. However, the underlying mechanisms remain to be elucidated. In this study, we aimed to explore the role of connexin 43 on exosomal uptake and angiogenesis in glioma under hypoxia. U251 cells were exposed to 3% oxygen to achieve hypoxia, and the expression levels of HIF-1α and Cx43, involved in the colony formation and proliferation of cells were assessed. Exosomes were isolated by differential velocity centrifugation from U251 cells under normoxia and hypoxia (Nor-Exos and Hypo-Exos), respectively. Immunofluorescence staining, along with assays for CCK-8, tube formation and wound healing along with a transwell assay were conducted to profile exosomal uptake, proliferation, tube formation, migration and invasion of HUVECs, respectively. Our results revealed that Hypoxia significantly up-regulated the expression of HIF-1α in U251 cells as well as promoting proliferation and colony number. Hypoxia also increased the level of Cx43 in U251 cells and in the exosomes secreted. The uptake of Dio-stained Hypo-Exos by HUVECs was greater than that of Nor-Exos, and inhibition of Cx43 by 37,43gap27 or lenti-Cx43-shRNA efficiently prevented the uptake of Hypo-Exos by recipient endothelial cells. In addition, the proliferation and total loops of HUVECs were remarkably increased at 24 h, 48 h, and 10 h after Hypo-Exos, respectively. Notably, 37,43gap27, a specific Cx-mimetic peptide blocker of Cx37 and Cx43, efficiently alleviated Hypo-Exos-induced proliferation and tube formation by HUVECs. Finally, 37,43gap27 also significantly attenuated Hypo-Exos-induced migration and invasion of HUVECs. These findings demonstrate that exosomal Cx43 contributes to glioma angiogenesis mediated by Hypo-Exos, and suggests that exosomal Cx43 might serve as a potential therapeutic target for glioblastoma.

HIF-1α promotes the proliferation and migration of pulmonary arterial smooth muscle cells via activation of Cx43.

The proliferation of pulmonary artery smooth muscle cells (PASMCs) is an important cause of pulmonary vascular remodelling in hypoxia-induced pulmonary hypertension (HPH). However, its underlying mechanism has not been well elucidated. Connexin 43 (Cx43) plays crucial roles in vascular smooth muscle cell proliferation in various cardiovascular diseases. Here, the male Sprague-Dawley (SD) rats were exposed to hypoxia (10% O2 ) for 21 days to induce rat HPH model. PASMCs were treated with CoCl2 (200 µM) for 24 h to establish the HPH cell model. It was found that hypoxia up-regulated the expression of Cx43 and phosphorylation of Cx43 at Ser 368 in rat pulmonary arteries and PASMCs, and stimulated the proliferation and migration of PASMCs. HIF-1α inhibitor echinomycin attenuated the CoCl2 -induced Cx43 expression and phosphorylation of Cx43 at Ser 368 in PASMCs. The interaction between HIF-1α and Cx43 promotor was also identified using chromatin immunoprecipitation assay. Moreover, Cx43 specific blocker (37,43 Gap27) or knockdown of Cx43 efficiently alleviated the proliferation and migration of PASMCs under chemically induced hypoxia. Therefore, the results above suggest that HIF-1α, as an upstream regulator, promotes the expression of Cx43, and the HIF-1α/Cx43 axis regulates the proliferation and migration of PASMCs in HPH.

Exosomal connexin 43 regulates the resistance of glioma cells to temozolomide.

Glioblastoma is the most common and aggressive brain tumor and it is characterized by a high mortality rate. Temozolomide (TMZ) is an effective chemotherapy drug for glioblastoma, but the resistance to TMZ has come to represent a major clinical problem, and its underlying mechanism has yet to be elucidated. In the present study, the role of exosomal connexin 43 (Cx43) in the resistance of glioma cells to TMZ and cell migration was investigated. First, higher expression levels of Cx43 were detected in TMZ­resistant U251 (U251r) cells compared with those in TMZ­sensitive (U251s) cells. Exosomes from U251s or U251r cells (sExo and rExo, respectively) were isolated. It was found that the expression of Cx43 in rExo was notably higher compared with that in sExo, whereas treatment with rExo increased the expression of Cx43 in U251s cells. Additionally, exosomes stained with dioctadecyloxacarbocyanine (Dio) were used to visualized exosome uptake by glioma cells. It was observed that the uptake of Dio­stained rExo in U251s cells was more prominent compared with that of Dio­stained sExo, while 37,43Gap27, a gap junction mimetic peptide directed against Cx43, alleviated the rExo uptake by cells. Moreover, rExo increased the IC50 of U251s to TMZ, colony formation and Bcl­2 expression, but decreased Bax and cleaved caspase­3 expression in U251s cells. 37,43Gap27 efficiently inhibited these effects of rExo on U251s cells. Finally, the results of the wound healing and Transwell assays revealed that rExo significantly enhanced the migration of U251s cells, whereas 37,43Gap27 significantly attenuated rExo­induced cell migration. Taken together, these results indicate the crucial role of exosomal Cx43 in chemotherapy resistance and migration of glioma cells, and suggest that Cx43 may hold promise as a therapeutic target for glioblastoma in the future.

Hydrogen sulfide is a novel gasotransmitter with pivotal role in regulating lateral root formation in plants.

Hydrogen sulfide (H 2S), the third gasotransmitter after nitric oxide (NO) and carbon monoxide (CO), is a critical neuromodulator in the pathogenesis of various diseases from neurodegenerative diseases to diabetes or heart failure. The crosstalk between NO and H 2S has been well established in mammalian physiology. In planta, NO is demonstrated to regulate lateral root formation by acting downstream of auxin. The recent reports revealed that H 2S is a novel inducer of lateral root (LR) formation by stimulating the expression of cell cycle regulatory genes (CCRGs), acting similarly with NO, CO, and IAA. Interestingly, during the initiation of lateral root primordia, IAA is a potent inducer of endogenous H 2S and CO, which is produced by L-cysteine desulfhydrase (LCD) and heme oxygenase-1 (HO-1), respectively. The increasing evidences suggest that H 2S-promoted LR growth is dependent on the endogenous production of CO. In addition, our results indicate that the H 2S signaling in the regulation of LR formation can be associated to NO and Ca 2+. In this addendum, we advanced a proposed schematic model for H 2S-mediated signaling pathway of plant LR development.

In site bioimaging of hydrogen sulfide uncovers its pivotal role in regulating nitric oxide-induced lateral root formation.

Hydrogen sulfide (H2S) is an important gasotransmitter in mammals. Despite physiological changes induced by exogenous H2S donor NaHS to plants, whether and how H2S works as a true cellular signal in plants need to be examined. A self-developed specific fluorescent probe (WSP-1) was applied to track endogenous H2S in tomato (Solanum lycopersicum) roots in site. Bioimaging combined with pharmacological and biochemical approaches were used to investigate the cross-talk among H2S, nitric oxide (NO), and Ca(2+) in regulating lateral root formation. Endogenous H2S accumulation was clearly associated with primordium initiation and lateral root emergence. NO donor SNP stimulated the generation of endogenous H2S and the expression of the gene coding for the enzyme responsible for endogenous H2S synthesis. Scavenging H2S or inhibiting H2S synthesis partially blocked SNP-induced lateral root formation and the expression of lateral root-related genes. The stimulatory effect of SNP on Ca(2+) accumulation and CaM1 (calmodulin 1) expression could be abolished by inhibiting H2S synthesis. Ca(2+) chelator or Ca(2+) channel blocker attenuated NaHS-induced lateral root formation. Our study confirmed the role of H2S as a cellular signal in plants being a mediator between NO and Ca(2+) in regulating lateral root formation.

[Construction and identification of eukaryotic expression plasmid expressing siRNA targeting USP22 gene].

OBJECTIVE: To construct eukaryotic expression plasmid expressing siRNA targeting ubiquitin specific peptidase 22 gene (USP22), and to investigate its effect on the growth of hepatoma carcinoma cells HepG2. METHODS: siRNA templates were synthesized based on USP22 mRNA sequence and cloned into vector Pmscv/Hyg/U6. The resulting recombinant was identified by restriction enzyme digestion and DNA sequencing. Recombinants were than transfected into HepG2 cells mediated by liposome. The USP22 protein and mRNA in HepG2 cells were detected by western blot and RT-PCR, respectively. The cellular growth activity was evaluated with MTT assay. RESULTS: Recombinant plasmid expressing siRNA targeting USP22 was successfully constructed. The down-regulated protein and mRNA level of USP22 and decreased cellular growth in HepG2 cells transfected with recombinant plasmid were observed. CONCLUSION: The eukaryotic expression vector for RNA interference USP22 gene is constructed successfully, which inhibits the expression of USP22 in HepG2 cells and suppresses cell proliferation.

[Effect of intracoronary injection with xuesaitong in treating post-PCI slow-reflow phenomenon in patients with ST-segment elevation myocardial infarction].

OBJECTIVE: To evaluate the effect and safety of Xuesaitong (XST, a Panax Notoginseng extract preparation) via intracoronary injection for treating post-PCI slow-reflow phenomenon in patients with ST-segment elevation myocardial infarction (STEMI) and its impact on patients' prognosis. METHODS: Thirty-nine STEMI patients who suffered from post-PCI slow-reflow after received percutaneous transluminal coronary angioplasty or stenting were assigned to two groups, 20 patients in the treated group and 19 in the control group. Intracoronary administering of 10 mL (0.5 mg) tirofiban and 400 mg XST were given to the treated group through guiding catheter, and followed with 36 h continuous intravenous dripping of tirofiban 10 mL/h and 400 mg XST in 250 mL of saline for dripping, while to the control group, the same intracoronary administering and intravenous dripping of tirofiban but without XST was given. The treatment was implemented for two days. Patients' coronary flow was assessed by the TIMI frame count method (TFC) at 1 min, 5 min and 10 min after injection; and the changes of ST-segment in 2 h, and incidence of bleeding in 48 h after medication were recorded. All patients were followed-up for 6 months to observe the incidence of cardiovascular events. RESULTS: Before the medication, the TIMI flow grade and the TFC in the treated group and the control group showed insignificantly statistical difference between groups (P > 0.05). After medication, 11 patients (55%) in the treated group and 8 patients (42%) in the control group with their blood flow reaching TIMI grade 3; the TFC decreased at 1, 5 and 10 min to 57.6 +/- 12.6, 46.1 +/- 9.3, 49.8 +/- 10.9 in the treated group and to 69.3 +/- 16.1, 61.2 +/- 15.3, 63.7 +/- 18.3 in the control group; and the 2 h ST segment fallback in them was 1.85 +/- 0.31 mm and 1.40 +/- 0.21 mm respectively, showing that the coronary blood flow in both groups were improved significantly after medication but the improvement in the former was better than in the latter group (P < 0.05). No case of death occurred in the hospitalization period. Results of 6-month follow-up study showed that the incidence of major adverse cardiac events, including angina pectoris, myocardial infarction, heart failure and cardiac death, was 33% in treated group and 44% in the control group, showing insignificant difference between groups (P > 0.05). CONCLUSION: Concomitant coronary injection with tirofiban and XST is more effective than that with tirofiban alone in improving the coronary blood flow and shows no increasing on the incidence of hemorrhagic complication.

[Preparation of a monoclonal antibody against methyl jasmonate and quantification of jasmonic acid in florets of wheat and Italian ryegrass].

A monoclonal antibody (McAb) against methyl jasmonate (MeJA) was prepared and characterized. The McAb, J2-4B, was derived from an immunogen in which the C1-COOH of jasmonic acid (JA) was conjugated to the -NH2 of keyhole limpet hemocyanin (KLH). The McAb showed a higher recognition ability to methyl esters of JA than to its free acids. The integrity of a pentenyl in JA molecule was necessary for the recognition of McAb. Hydrogenation at C-9 and C-10 (dihydrojasmonic acid, 2H-JA) or eliminating the methyl group at C-12 (JAS-25) significantly abolished the binding force of JA molecule with the McAb. Some structural or functional analogues or precursor of JA, such as cucurbic acid, theobroxide, coronatine, and linolenic acid, could not be recognized by the McAb. The McAb has been used to set up a competitive enzyme-linked immunosorbent assay (ELISA) with a linearity range from 2.06 to 500 pmol of MeJA. Using this method, the fluctuations of JA content in florets during anthesis of wheat and Italian ryegrass were analyzed. Results showed that JA level increased obviously as the florets approaching to opening, arrived at a "peak" value at full opening and decreased sharply afterwards.