Plume-lithosphere interaction in the Comei Large Igneous Province: Evidence from two types of mafic dykes in Gyangze, south Tibet, China

Two suites of mafic dykes,T1193-A and T1194-A,outcrop in Gyangze area,southeast Tibet.They are in the area of Comei LIP and have indistinguishable field occurrences with two other dykes in Gyangze,T0902 dyke with 137.7±1.3 Ma zircon age and T0907 dyke with 142±1.4 Ma zircon age reported by Wang YY et al.(2016),indicating coeval formation time.Taking all the four diabase dykes into consideration,two different types,OIB-type and weak enriched-type,can be summarized.The“OIB-type”samples,including T1193-A and T0907 dykes,show OIB-like geochemical features and have initial Sr-Nd isotopic values similar with most mafic products in Comei Large Igneous Provinces(LIP),suggesting that they represent melts directly generated from the Kerguelen mantle plume.The“weak enriched-type”samples,including T1194-A and T0902 dykes,have REEs and trace element patterns showing withinplate affinity but have obvious Nb-Ta-Ti negative anomalies.They show uniform lowerεNd(t)values(−6‒−2)and higher 87Sr/86Sr(t)values(0.706‒0.709)independent of their MgO variation,indicating one enriched mantle source.Considering their closely spatial and temporal relationship with the widespread Comei LIP magmatic products in Tethyan Himalaya,these“weak enriched-type”samples are consistent with mixing of melts from mantle plume and the above ancient Tethyan Himalaya subcontinental lithospheric mantle(SCLM)in different proportions.These weak enriched mafic rocks in Comei LIP form one special rock group and most likely suggest large scale hot mantle plume-continental lithosphere interaction.This process may lead to strong modification of the Tethyan Himalaya lithosphere in the Early Cretaceous.

Anti-inflammatory and DNA Repair Effects of Astragaloside IV on PC12 Cells Damaged by Lipopolysaccharide

Objective This study aimed to establish a neural cell injury model in vitro by stimulating PC12 cells with lipopolysaccharide(LPS)and to examine the effects of astragaloside IV on key targets using high-throughput sequence technology and bioinformatics analyses.Methods PC12 cells in the logarithmic growth phase were treated with LPS at final concentrations of 0.25,0.5,0.75,1,and 1.25 mg/mL for 24 h.Cell morphology was evaluated,and cell survival rates were calculated.A neurocyte inflammatory model was established with LPS treatment,which reached a 50%cell survival rate.PC12 cells were treated with 0.01,0.1,1,10,or 100µmol/L astragaloside IV for 24 h.The concentration of astragaloside IV that did not affect the cell survival rate was selected as the treatment group for subsequent experiments.NOS activity was detected by colorimetry;the expression levels of ERCC2,XRCC4,XRCC2,TNF-α,IL-1β,TLR4,NOS and COX-2 mRNA and protein were detected by RT-qPCR and Western blotting.The differentially expressed genes(DEGs)between the groups were screened using a second-generation sequence(fold change>2,P<0.05)with the following KEGG enrichment analysis,RT-qPCR and Western blotting were used to detect the mRNA and protein expression of DEGs related to the IL-17 pathway in different groups of PC12 cells.Results The viability of PC12 cells was not altered by treatment with 0.01,0.1,or 1µmol/L astragaloside IV for 24 h(P>0.05).However,after treatment with 0.5,0.75,1,or 1.25 mg/mL LPS for 24 h,the viability steadily decreased(P<0.01).The mRNA and protein expression levels of ERCC2,XRCC4,XRCC2,TNF-α,IL-1β,TLR4,NOS,and COX-2 were significantly increased after PC12 cells were treated with 1 mg/mL LPS for 24 h(P<0.01);however,these changes were reversed when PC12 cells were pretreated with 0.01,0.1,or 1µmol/L astragaloside IV in PC12 cells and then treated with 1 mg/mL LPS for 24 h(P<0.05).Second-generation sequencing revealed that 1026 genes were upregulated,while 1287 genes were downregulated.The DEGs were associated with autophagy,TNF-α,interleukin-17,MAPK,P53,Toll-like receptor,and NOD-like receptor signaling pathways.Furthermore,PC12 cells treated with a 1 mg/mL LPS for 24 h exhibited increased mRNA and protein expression of CCL2,CCL11,CCL7,MMP3,and MMP10,which are associated with the IL-17 pathway.RT-qPCR and Western blotting analyses confirmed that the DEGs listed above corresponded to the sequence assay results.Conclusion LPS can damage PC12 cells and cause inflammatory reactions in nerve cells and DNA damage.astragaloside IV plays an anti-inflammatory and DNA damage protective role and inhibits the IL-17 signaling pathway to exert a neuroprotective effect in vitro.